[Federal Register Volume 66, Number 3 (Thursday, January 4, 2001)]
[Proposed Rules]
[Pages 968-999]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-136]



[[Page 967]]

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Part III





Department of Transportation





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National Highway Traffic Safety Administration



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49 CFR Part 571



Federal Motor Vehicle Safety Standards; Head Restraints; Proposed Rule

  Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / 
Proposed Rules  

[[Page 968]]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2000-8570]
RIN 2127-AH09


Federal Motor Vehicle Safety Standards; Head Restraints

AGENCY: National Highway Traffic Safety Administration (NHTSA), DOT.

ACTION: Notice of proposed rulemaking.

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SUMMARY: Consistent with this agency's policy of seeking to adopt those 
regulatory requirements that produce the highest benefits at reasonable 
costs, this document proposes to upgrade the standard for head 
restraints for passenger cars and for light multipurpose vehicles, 
trucks and buses. The proposal would establish higher minimum height 
requirements for head restraints, and add a requirement limiting 
backset, i.e., the distance between a person's head and his or her head 
restraint. The proposal would also extend the requirement for head 
restraints to rear outboard designated seating positions; establish new 
strength requirements for head restraints; and place limits on the size 
of gaps and openings in head restraints. In addition, it would modify 
the dynamic compliance test and amend test procedures. The proposal 
would harmonize the standard with the counterpart regulation of the 
Economic Commission for Europe (ECE) to an extent, but would set 
different requirements for head restraint width and gap measurement for 
adjustable restraints. Further, it would add two requirements not found 
in the ECE regulation, i.e., one for backset and one for adjustment 
retention locks. The goal of these proposed changes is to improve the 
protection that head restraints provide in rear-end collisions.
    This document also proposes that before compliance with the 
upgraded requirements becomes mandatory on the first September 1, three 
years following publication of the final rule, the manufacturers could 
chose to comply with any of three sets of requirements: the existing 
requirements of Standard 202, the ECE regulation, or the upgraded 
requirements of Standard 202. The proposal to allow compliance with the 
ECE regulation during the interim responds to a petition for rulemaking 
by the American Automobile Manufacturers Association (AAMA) and the 
Association of International Automobile Manufacturers (AIAM) requesting 
that we consider the benefits of complying with the European regulation 
to be at least equivalent to those of complying with the existing 
requirements of Standard 202.

DATES: You should submit your comments early enough to ensure that 
Docket Management receives them not later than March 5, 2001.

ADDRESSES: You should mention the docket number of this document in 
your comments and submit your comments in writing to: Docket 
Management, Room PL-401, 400 Seventh Street, SW., Washington, DC, 
20590. Comments may also be submitted to the docket electronically by 
logging onto the Dockets Management System website at http://dms.dot.gov. Click on ``Help & Information'' or ``Help/Info'' to obtain 
instructions for filing the document electronically.
    You may call Docket Management at 202-366-9324. You may visit the 
Docket from 10 a.m. to 5 p.m., Monday through Friday.

FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may contact 
Louis Molino of the Office of Safety Performance Standards, Vehicle 
Crashworthiness Standards, Light Duty Vehicle Division, NPS-11, (Phone: 
202-366-2264; fax: 202-366-4329; E-mail: [email protected]).
    For legal issues, you may contact Otto Matheke of the Office of 
Chief Counsel, NCC-20, (Phone: 202-366-5263; Fax 202-366-3820).
    You may send mail to both of these officials at the National 
Highway Traffic Safety Administration, 400 Seventh St., SW., 
Washington, DC, 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. The Safety Problem
II. Background
    A. Studies of Head Restraint Effectiveness
    B. December 1996 Request for Comments
    C. AIAM/AAMA Petition
III. Overview of Proposal
IV. Proposed Upgraded Requirements
    A. Height Requirements
    B. Backset Requirement
    C. Height Adjustment Retention Requirement
    D. Rear Outboard Seating Positions
    E. Removability of Head Restraints
    F. Head Restraint Configuration Requirements
    1. Width
    2. Gaps
    G. Energy Absorption
    H. Test Procedures
    1. Displacement Test Procedure
    2. Dynamic Sled Test Procedure
V. Interim Compliance Options Before Upgraded Requirements Become 
Mandatory
VI. Benefits
VII. Costs
VIII. Effective Date
IX. Rulemaking Analyses and Notices
X. Submission of Comments
XI. Proposed Regulatory Text

I. The Safety Problem

    Whiplash injuries, a set of common symptoms involving the soft 
tissues of the head, neck and spine, are believed to be associated with 
rapid motion of the head and neck relative to the torso in a crash. 
Symptoms of pain in the head, neck, shoulders, and arms may be present 
along with damage to muscles, ligaments and vertebrae, but in many 
cases lesions are not evident. The onset of symptoms may be delayed and 
may only last a few hours; however, in some cases, effects of the 
injury may last for years or be permanent. The relatively short-term 
symptoms are associated with muscle and ligament trauma, while the 
long-term ones are associated with nerve damage.\1\
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    \1\ Summary of the highlights of Traffic Safety and Auto 
Engineering Stream, World Congress on Whiplash-Associated Disorders, 
February 1999, Vancouver, Canada http://www.whiplash99.org/highlights/index.htm.
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    Although whiplash injuries can occur in any kind of crash, they 
occur most often in rear-end collisions. When a vehicle is struck from 
behind, typically several things occur in quick succession to an 
occupant of that vehicle. First, from the occupant's frame of 
reference, the back of the seat moves forward into his or her torso, 
straightening the spine and forcing the head to rise vertically. 
Second, as the occupant's body is pushed forward by the seat, the 
unrestrained head tends to lag behind. This causes the neck to change 
shape, first taking on an S-shape and then bending backward. Third, the 
forces on the neck accelerate the head, which catches up with--and, 
depending on the seat back stiffness and if the occupant is using a 
shoulder belt, passes--the restrained torso. This motion of the head, 
which is like the lash of a whip, gives the resulting neck injuries 
their popular name. However, at what point in this motion the injury 
occurs is still a matter of debate.
    We estimate from National Analysis Sampling System (NASS) data that 
between 1988 and 1996, 805,581 whiplash injuries (non-contact 
Abbreviated Injury Scale (AIS) 1 neck) occurred annually in all crashes 
in passenger cars (PCs), and in LTV's (light trucks, multipurpose 
passenger vehicles and vans). The average cost (excluding property 
damage) of such an injury is $6,485, resulting in a total annual cost 
of $5.2 billion.

[[Page 969]]

    The potential for whiplash injuries is influenced by the ability of 
several aspects of vehicle design, including vehicle structure, seats 
and head restraints, to absorb and control crash forces. In addition to 
integral and adjustable head restraints, which are designed to maintain 
their position relative to the seat back during a crash, several 
manufacturers have recently introduced new seat and head restraint 
designs that allow the head restraints to actively move closer to the 
occupant's head during a rear impact of the vehicle. Volvo has 
introduced a system it has labeled as WHIPS (Whiplash Head Impact 
Protection System) in which the seat back recliner is designed to give 
a controlled rearward motion of the seat back relative to the seat base 
in a rear impact--allowing the torso to move backward. In the first 
phase the seat back translates rearward for the purpose of reducing 
relative motion of the seat back--reducing relative motion of the head 
and torso and allowing the head to move closer to the head restraint. 
The second phase involves rearward folding of the seat back, with the 
center of motion in the recliner. This reduces acceleration of the 
occupant while absorbing energy. Saab has incorporated an active and 
adjustable head restraint into the front seat backs of its 9-3 and 9-5 
models. Known as the Saab Active Head Restraint System, it moves the 
head restraint forward and upward as the seat occupant moves backward 
during and after a rear impact. Model year 2000 Infiniti I30s, Buick 
LeSabres and Pontiac Bonnevilles also have active front seat head 
restraints. The Insurance Institute for Highway Safety (IIHS) has 
attempted to determine the potential contributions of the advanced 
seats like the Volvo seat and of active head restraints through dynamic 
testing of those designs. More information on these tests is discussed 
in the Background section of this document. Two suppliers, TRW and 
Breed Siemens Restraint Systems, are each in the process of developing 
an inflatable head restraint that is activated in rear impacts.
    This notice focuses on the potential for reducing whiplash through 
requiring improvements in head restraints. A historical examination of 
head restraint standards in this country indicates that the focus has 
been the prevention of neck hyperextension (the rearward movement of 
the head and neck over a large range of motion relative to the torso), 
as opposed to controlling lesser amounts of head and neck movement in a 
crash. The predecessor to Federal Motor Vehicle Safety Standard 202 
(Standard 202) was General Services Administration (GSA) Standard 515/
22, which applied to vehicles purchased by the U.S. Government and went 
into effect on October 1, 1967. GSA 515/22 required that the top of the 
head restraint achieve a height 700 mm (27.5 inches) above the H-point. 
The H-point is defined by a test machine placed in the vehicle seat 
(SAE J826, July 1995). From the side, the H-point represents the pivot 
point between the torso and upper leg portions of the test machine. It 
can be thought of, roughly, as the hip joint of a 50th percentile male 
occupant viewed laterally. Also in 1967, research using staged 48.3 kph 
(30 mph) crashes concluded that a head restraint 711 mm (28 inches) 
above the H-point was adequate to prevent neck hyperextension of a 95th 
percentile male.\2\ Standard 202, which became effective on January 1, 
1969, required that head restraints be at least 700 mm (27.5 inches) 
above the seating reference point or limit the relative angle between 
the head and the torso to 45 degrees or less during a dynamic test.
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    \2\ Severy et al. (1968) Backrest and Head Restraint Design for 
Rear-End Collision Protection. SAE 680029.
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    Current research indicates that whiplash may occur as a result of 
head and neck movements insufficient to cause hyperextension. Low speed 
staged impacts indicate that mild whiplash symptoms can occur without 
exceeding the normal range of motion.\3\ Other research shows that 70.8 
kph (44 mph) impacts can be sustained without injury if no relative 
motion occurs between the head and torso.\4\ A Volvo study reported 
that, when vehicle occupants involved in rear crashes had their heads 
against the head restraint during impact, no injury occurred.\5\ The 
same study related a rear impact simulation computer model to actual 
crash data and identified the rate of volume change in the cervical 
spinal canal as a possible predictor of whiplash injury. Other 
predictors identified were neck shear force, neck tensile force and 
head angular acceleration. A study of Volvo vehicles involved in rear 
impacts showed that a significant increase in injury duration occurred 
when the occupant's head was more than 100 mm (4 inches) away from the 
head restraint at the time of the rear impact.\6\
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    \3\ McConnell et al. (1995) Human Head and Neck Kinematics After 
Low Velocity Rear-End Impacts--Understanding ``Whiplash.'' SAE 
952724.
    \4\ Mertz and Patrick (1967) Investigation of the Kinematics and 
Kinetics of Whiplash. Proceedings of the 11th STAPP Car Crash 
Conference, pp. 267-317.
    \5\ Jacobsson et al. (1994) Analysis of Head and Neck Responses 
in Rear End Impacts--A New Human-Like Model. Volvo Car Corporation 
Safety Report.
    \6\ Olsson et al. (1990) An In-depth Study of Neck Injuries in 
Rear-end Collisions. IRCOBI, pp. 269-280.
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    Although there seems to be no clear consensus in the biomechanics 
community about the mechanism for whiplash injuries, several hypotheses 
have been proposed based on investigations using animals, volunteers, 
and human surrogates. Animal research at Chalmers University suggests 
that rapid head/neck motion, within the normal range, can cause spinal 
canal pressures to damage nerve ganglia.\7\ Other studies have 
attributed whiplash injuries to damage to the highly innervated 
cervical facet joints. Researchers at the Medical College of Wisconsin 
propose that local compression in the lower cervical spine and sliding 
along the facet joint may cause the excitation of local pain fibers, 
micro-damage to the cartilage plates and squeezing of the synovial 
space in the facet joints.\8\ Similarly, a study performed in Japan 
using cineradiography (x-ray motion pictures) on human volunteers to 
study vertebral motion, hypothesized that the upward ramping of the 
torso due to the straightening of the natural spine lordotic curvature 
causes compression of the cervical spine and an unnatural S-shape of 
the cervical spine.\9\ At the mid-portion of this unnatural S-shape, 
large rotations may occur which stretch the ligaments or damage the 
facet joint.
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    \7\ Svensson et al. (1993) Pressure Effects in the Spinal Canal 
During Whiplash Extension Motion: A Possible Cause of Injury to the 
Cervical Spinal Ganglia. IRCOBI, pp. 189-200.
    \8\ Yoganandan et al. (1998) Biomechanical Assessment of 
Whiplash. In: Frontiers in Head and Neck Trauma: Clinical and 
Biomechanical, pp. 344-373.
    \9\ Kaneoka and Ono (1998) Human Volunteer Studies on Whiplash 
Injury Mechanisms. In: Frontiers in Head and Neck Trauma: Clinical 
and Biomechanical, pp. 313-325.
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    In 1995, the National Highway Traffic Safety Administration (NHTSA) 
performed a survey of the relative position of occupants' heads and 
head restraints on 282 vehicles. The survey examined relative position 
of the head to the restraint, how the head restraint was adjusted and 
if the head restraint could potentially have been adjusted higher. The 
tops of 59 percent of adjustable and 77 percent of integral head 
restraints were at or above the occupant's ear--a point equivalent to 
the head center of gravity. NHTSA also estimated the backset of these 
head restraints--the horizontal distance from the back of the 
occupant's head to the head restraint. Sixty-nine percent of adjustable 
head restraints and 77

[[Page 970]]

percent of integral head restraints had a backset of less than 100 mm 
(4 inches). When combined height and backset position was assessed, 53 
percent of adjustable and 70 percent of integral head restraints were 
both above the ear and less than 100 mm (4 inches) from the head. Half 
of adjustable head restraints were left in the lowest adjustable 
position and three quarters of these could have been raised to decrease 
whiplash potential by bringing the head restraint higher in relation to 
the occupant's head height.
    The continued persistence of whiplash injuries indicates that 
Standard 202 should be revised. The current state of knowledge 
indicates that limiting hyperextension of the neck does not prevent the 
occurrence of whiplash and that controlling even smaller amounts of 
rapid head and neck movement relative to the torso would be more 
effective. The current regulation requires a head restraint height of 
700 mm (27.5 inches) to prevent hyperextension and has been shown to 
accomplish this for occupants as large as 95th percentile males. 
However, the current regulation has no lower limit on head restraint 
position. Therefore, if an adjustable head restraint is not raised to 
the 700 mm (27.5 inch) level, hyperextension may be more likely for 
some occupants. Additionally, if an existing head restraint is not 
designed to exceed the current height requirement and to also limit 
backset distance, it will not be capable of controlling small amounts 
of head and neck movement relative to the torso for many occupants. 
These factors may be playing a large role in the persistence of 
whiplash. NHTSA has tentatively concluded that an upgrade to Standard 
202 is required to foster further gains in neck injury protection in 
rear impacts.

II. Background

A. Studies of Head Restraint Effectiveness

    Since January 1, 1969, passenger cars have been required by 
Standard 202 to have head restraints in the front outboard seating 
positions. Head restraints must either (a) be at least 700 mm (27.5 
inches) above the seating reference point in their highest position and 
not deflect more than 100 mm (4 inches) under a 373 Nm (3,300 inch-
pounds) moment, or (b) limit the relative angle of the head and torso 
of a 95th percentile dummy to not exceed 45 degrees when exposed to an 
8 g acceleration. Standard 202 was extended to light trucks and vans 
under 10,000 pounds, effective September 1, 1991.
    In 1982, NHTSA assessed the performance of head restraints 
installed pursuant to Standard 202 and reported that integral head 
restraints are 17 percent effective at reducing neck injuries in rear 
impacts and adjustable head restraints are 10 percent effective at 
doing so. The difference was due to integral head restraints being 
higher with respect to the occupant's head than adjustable head 
restraints, which were normally left down.
    IIHS evaluated and rated head restraints in 1995, 1997 and 1999. In 
1998, in conjunction with the State Farm Insurance Company (State 
Farm), IIHS compared the conclusions from the 1995 and 1997 evaluations 
to crash data.\10\ In the 1997 evaluation, the head restraints of 214 
1997 model year (MY) vehicles were rated based on their position 
relative to the 50th percentile male head. The restraints were ranked 
according to the prevailing view of the biomechanics community that 
head restraints that are in close proximity, both horizontally and 
vertically, to the center of gravity of the head are more effective. 
The vertical reference value used in the evaluation of each head 
restraint was the distance from the top of the head to the head's 
center of gravity. The vertical reference measurement of 90 mm (3.5 
inches) was taken from the 50th percentile adult male dummy drawing 
produced by the University of Michigan. The height of a head restraint 
was rated as ``marginal'' if the restraint's top was 90  10 
mm (3.5  0.4 inches) below the top of the head form. The 
vertical rating was ``good'' if the distance from the top of the head 
form to the top of the restraint was less than 60 mm (2.36 inches) 
(i.e., the top of the head restraint was at least 30 mm (1.2 inches) 
above the head's center of gravity).
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    \10\ This study is summarized in the May 22, 1999 edition of 
IIHS' Status Reports (http://www.hwysafety.org).
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    The reference value used to evaluate backset, 100 mm (4 inches), 
was based on a 1990 study showing a statistical relationship between 
the backset larger than 100 mm (4 inches) and the duration of neck 
symptoms. The backset of a restraint was rated as ``marginal'' if the 
horizontal distance between the head form and restraint was 100 
 10 mm (4  0.4 inches). The backset was rating 
as ``good'' if the distance was less than 70 mm (2.8 inches). A 
restraint's overall rating was the lower of the height and backset 
scores. The results of the IIHS study and the rating criteria are 
presented in Table 1.

                                    Table 1.--1999 IIHS Head Restraint Study
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                                       Number of                 Distance down from top
             IIHS rating                vehicles     Percent            of head                  Backset
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Good................................           10          5.4  60 mm (2.36 in.) or      70 mm (2.76 in.) or
                                                                 less.                    less.
Acceptable..........................           50         26.9  60-80 mm (2.36-3.15      70-90 mm (2.76-3.54
                                                                 in.).                    in.).
Marginal............................           60         32.3  80-100 mm (3.15-3.94     90-110 mm (3.54-4.33
                                                                 in.).                    in.)
Poor................................           66         35.5  100 mm (3.94 in.) or     110 mm (4.33 in.) or
                                                                 greater.                 greater.
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      Total.........................          186          100
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    Scores were reduced for adjustable head restraints since IIHS 
contends that field observations have shown that they typically are not 
adjusted properly. Adjustable head restraints without locks were 
evaluated based on their lowest and most rearward position of 
adjustment. For adjustable head restraints with locks, IIHS rated the 
restraint according to its locked position, but downgraded the rating 
by one category based on data establishing that few users properly 
adjust head restraints.
    Because of variations in the shapes of head restraints, it is not 
possible to accurately correlate head restraint height as measured by 
IIHS and the height as measured by the method in Standard 202. The IIHS 
method evaluates head restraint height by

[[Page 971]]

measuring the difference in vertical height between the top of a 
special (50th percentile male) head form mounted on a standard H-point 
machine and the top of the head restraint. The Standard 202 method 
measures along the torso line (which has an angle  with 
respect to the vertical--see Figure A) from the H-point on the vehicle 
seat to the point at which the torso line intersects with the upper 
surface of the head restraint. Assuming an idealized head restraint 
shape, a simple relationship between the two measurement methods can be 
developed as shown in Figure A. The dimension of this figure assume a 
torso angle () of 25 degrees from the vertical and a distance 
from the H-point to the top of the head of 755 mm (29.7 inches). Figure 
B is a graphical depiction of how head restraints of 700 mm (27.5 
inches), 750 mm (29.5 inches) and 800 mm (31.5 inches) fare with 
respect to the IIHS dimensional rating technique. For any backset up to 
70 mm (2.8 inches), the 800 mm (31.5 inches) high head restraint is 
always rated ``good.'' A 700 mm (27.5 inches) high head restraint can 
never be rated better than ``poor'' for any backset. A 750 mm (29.5 
inch) high head restraint is ``good'' for backsets up to 30 mm (1.2 
inches) and ``acceptable'' for backsets up to 73 mm (2.9 inches).
[GRAPHIC] [TIFF OMITTED] TP04JA01.000


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[GRAPHIC] [TIFF OMITTED] TP04JA01.001

    The 1998 joint State Farm-IIHS study compared the ratings applied 
in the 1995 and 1997 IIHS evaluations to actual whiplash claims. The 
new study, based on detailed analyses of more than 5,000 State Farm 
claims involving midsize cars struck in the rear by other vehicles, 
indicates that head restraints rated ``good'' in the 1995 and 1997 IIHS 
evaluations offered better protection in real-world crashes than those 
rated ``poor.'' According to the State Farm-IIHS study, drivers in cars 
with head restraints rated ``good'' by IIHS are 24 percent less likely 
to suffer neck injuries in rear-end crashes than drivers with head 
restraints rated ``poor.'' Percentages of drivers with neck injuries 
ranged from 22 percent of those with ``good'' head restraints to 27 
percent of those with ``poor'' head restraints. The State Farm-IIHS 
study also found that female drivers have higher neck injury rates 
overall than male drivers--30 percent versus 23 percent, but that the 
likelihood of neck injury was 36 percent lower among female drivers 
with ``good'' head restraints than among females with ``poor'' 
restraints. Among male drivers, the State Farm-IIHS study found that 
the risk reduction was 10 percent with ``good'' head restraints. 
However, it should be noted that there were a limited number of 
``good'' head restraints in the study (3 vehicles, all Volvos). Thus, 
the results are not conclusive.
    The State Farm-IIHS study appears to verify that higher head 
restraints that are also closer to the back of an occupant's head 
(i.e., have less backset) reduce the risk of whiplash. The study also 
found measurable improvement as the ratings increased between head 
restraints in the four categories established by IIHS--poor, marginal, 
acceptable and good. The State Farm-IIHS study does not, however, allow 
for analysis of the virtues of increases in height with no change in 
backset or reductions in backset independent of changes in height. 
Further, the IIHS methodology accounted for the fact that adjustable 
restraints are often not placed in their highest and closest position, 
resulting in only integral restraints being rated as ``good.''
    IIHS reported in its 1999 head restraint evaluation that it 
dynamically tested two advanced head restraint designs and applied the 
Chalmers University NIC criterion to the results. These were moving 
rigid barrier to full vehicle impacts at barrier speed of 24 kph (15 
mph). IIHS tested the Saab Active Head Restraint System and the Volvo 
WHIPS seat. The two designs had significantly lower NIC values than 
even ``good'' non-deploying designs.

B. December 1996 Request for Comments

    In 1996, NHTSA issued a Technical Report entitled, ``Head 
Restraints--Identification of Issues Relevant to Regulation, Design and 
Effectiveness.'' This report identified and examined issues related to 
the biomechanics of neck injury, whiplash rates, occupant and head 
restraint positioning and the state of contemporary and future head 
restraint designs. On December 19, 1996, NHTSA published a document in 
the Federal Register (61 FR 66992) alerting the public to the existence 
of the report and that the agency was interested in obtaining 
information and comments about the performance of head restraints and 
potential modifications to Standard 202. The December 1996 document 
contained questions regarding:

[[Page 973]]

    (1) The effectiveness of current designs and the potential for 
improvements to reduce injury;
    (2) The adequacy of Standard 202's height requirements and the 
efficacy of new requirements such as backset and adjustable head 
restraint locks;
    (3) The continued need for and possible changes to the existing 
dynamic test procedure;
    (4) Potential conflicts between visibility and revised head 
restraint requirements;
    (5) Whether NHTSA should harmonize its regulations with ECE 
requirements;
    (6) Whether changes to Standard 202 should be synchronized with 
changes to Standard 207, Seating Systems; and
    (7) The costs of whiplash injury in the United States and the costs 
and benefits of modifying Standard 202.
    The agency received comments from four manufacturers (Volkswagen, 
Toyota, Volvo, and Ford), three safety advocacy organizations 
(Consumers Union (CU), Advocates for Highway Safety (Advocates) and 
IIHS), one equipment manufacturer, Cerviguard, one insurance company, 
Insurance Corporation of British Columbia (ICBC), and the Chalmers 
University of Technology (Chalmers).
    None of the respondents submitting comments stated that current 
head restraint designs were sufficiently effective at preventing neck 
injuries. While Ford indicated that current ``designs have been shown 
to be effective at reducing the risk of neck injuries in vehicle 
crashes,'' it also stated that improved designs will require additional 
research and testing. Chalmers, ICBC, CU and Advocates stated that they 
believed current head restraint designs were not sufficiently 
protective against neck injuries. None of the commenters stated that 
the current required height for head restraints of 700 mm (27.5 inches) 
is sufficient. IIHS, whose comments were submitted prior to the 
completion of the 1998 State Farm-IIHS report, referred to its 1995 and 
1997 studies of head restraints. These studies, based on an examination 
of the head restraint positions relative to the head, concluded that 
the majority of head restraints were inadequate. According to IIHS, 
only 2.3 percent of 1997 vehicles evaluated had ``good'' head 
restraints, thus indicating that the current dimensional requirements 
are not sufficient.
    Advocates indicated that most head restraint designs allow too much 
backset and that this should be limited to ``considerably'' less than 
four inches. CU stated that head restraints should have a minimum 
height of 737 mm (29 inches) to 762 mm (30 inches), but should be able 
to adjust even higher. Advocates urged the agency to require adjustable 
head restraints to lock in position, considering this ``a crucial 
aspect of restraint design and performance.'' It stated that it 
believes many of the current designs allow vertical collapse of the 
head restraints in rear crashes especially when the top of the head 
restraint is below the head's C.G. Chalmers and CU also endorsed 
adjustable head restraints having locks. Toyota said it believes that, 
at a minimum, the vertical adjustment should lock.
    In reference to changes to test procedures, Chalmers stated that a 
dynamic test procedure is a necessity for new designs known as 
``active'' head restraints. These head restraints move forward and/or 
higher in a crash. Chalmers also stated that this test should use a 
Rear Impact Dummy (RID) neck (developed by Chalmers) mounted on a 
Hybrid III dummy. The RID neck was developed at Chalmers because they 
thought the Hybrid III neck was too stiff in the midsagittal plane. 
Advocates, Toyota and Cervigard also expressed concern about the 
biofidelity of the Hybrid III neck. Volvo advised ``that the present 8g 
alternate standard in Standard 202 should be deleted and no new dynamic 
performance standard should be adopted until more knowledgeable injury 
mechanisms have been acquired and until relevant test procedures and 
improved test dummies have been developed.'' This would include a 
change to the dummy spine as well as the neck.
    Comments on the impact of potential changes to head restraint 
requirements included concerns about effectiveness and degradation in 
visibility. Volvo stated that head restraint designs may not be optimal 
for occupant protection because manufacturers must also consider 
occupant comfort and visibility through the vehicle from the rear. 
Advocates noted that increasing the protective value of head restraints 
will be affected by comfort considerations as well as lateral and rear 
visibility issues. Chalmers said it believes that head restraints which 
are ``actively positioned during impact, would solve both the problems 
of visibility and injury prevention.''
    The comments also indicated support for harmonizing Standard 202 
with Economic Commission for Europe (ECE) Regulation 25.\11\ Advocates 
favored harmonization, but said that the modified Standard 202 must go 
further. The organization said it believes the agency should 
investigate the merits of requiring head restraints in rear seats, as 
is required by ECE 25. However, it also mentions that this might 
conflict with tethered child safety seats and rear window visibility. 
CU recommended harmonization with ECE 25 as a move towards the goal of 
improving head restraints. This includes the provision for head 
restraints in the rear seats. However, it also endorsed other changes 
to the standard. Volkswagen endorsed harmonization with ECE Commission 
Directive 96/37/EC which combines ECE 25 (Head Restraints) and ECE 17 
(Seats). Toyota stated that if the agency raises the required height 
for head restraints, it should match ECE 25. Volvo asked that NHTSA 
simply ``monitor'' the European standard. Ford stated that it 
``strongly supports harmonization with other world regulations to 
promote world trade, providing it does not compromise safety or the 
integrity of the vehicle.'' It supported modification of Standard 202 
on this basis.
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    \11\ Economic Commission for Europe (ECE) Regulation 25--Uniform 
Provisions Concerning the Approval of Head Restraints (HeadRests), 
Whether or Not Incorporated in Vehicle Seats is similar to Standard 
202 in that the same strength/displacement test procedure and 
performance values are required. The head restraint height is 
measured in the same way by both regulations, but the required 
heights differ. ECE 25 specifies that head restraints he higher than 
the current version of Standard 202. In addition, the current ECE 25 
requires all forward facing outboard seats to have head restraints.
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    Most of the commenters also favored coordinating changes to 
Standard 202 with changes to Standard 207 on the basis that seat and 
head restraint performance are closely linked because the longitudinal 
stiffness of a seat back will have an impact on the relative movement 
of the head and torso in the event of a crash. Chalmers indicated that 
their dynamic test proposal inherently coordinates changes to Standards 
202 and 207. Advocates said that it believes coordinating the head 
restraint standard with any seat back standard is worthy of exploration 
and urged NHTSA to give explicit attention to the relationship between 
head restraints and integrated seat/head restraint systems. Volvo 
stated that in the short term no change should be made to either 
Standard 202 or 207 until more research has been done. At the same 
time, it provided information on its Whiplash Protection Study (WHIPS) 
in which Volvo modified its standard seat to optimize it for whiplash 
protection.
    Only one commenter, ICBC, submitted data on the costs of whiplash 
and the benefits of reducing whiplash

[[Page 974]]

injuries. ICBC stated that 45,437 British Columbians suffered whiplash 
in 1996. Since the population of British Columbia is about 1 percent of 
the U.S. population, extrapolating this figure to the U.S. would imply 
that there were 4,543,700 whiplash injuries in the U.S. during 1996. 
This figure is more than five times NHTSA's estimate of the number of 
whiplash injuries in the U.S. ICBC estimates that each whiplash costs 
$8,199 U.S. If this figure were multiplied by the number of 
extrapolated injuries, this would suggest a total cost of $37 billion 
U.S. That is more than seven times greater than NHTSA's estimate. NHTSA 
does not know why the number of whiplashes estimated from the ICBC 
figures are so much higher than the NHTSA estimate. While the agency 
has not examined the methodology used by ICBC to calculate its 
estimate, it is possible that the number of insurance reported 
whiplashes may overstate the actual incidence of injury.\12\ The 
agency's whiplash estimate is based on crash data generated by police 
reported crashes where one or all of the vehicles involved are towed 
away from the scene. Since many whiplashes occur in crashes where no 
vehicle is towed and no police report is made, a correction factor was 
used to adjust the estimate for these non-towed crashes.
---------------------------------------------------------------------------

    \12\ NHTSA observes that the 1998 State Farm-IIHS study revealed 
that the overall neck injury rate in Michigan, the study's only no-
fault state, was 13 percent compared with 26 percent in other 
states, without no-fault liability systems. This suggest that the 
availability of fault-based compensation systems may lead to higher 
reported rates of whiplash.
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C. AIAM/AAMA Petition

    On August 13, 1997, the American Automobile Manufacturers 
Association (AAMA) and the Association of International Automobile 
Manufacturers (AIAM) submitted a joint petition for rulemaking 
requesting that NHTSA consider the possibility of amending five safety 
standards so that these standards would be ``functionally equivalent'' 
to corresponding ECE standards. The petition defined ``functional 
equivalence'' through comparison with harmonization:

    A harmonized regulation would contain and define either (1) a 
single set of performance requirements that a vehicle could be 
``certified'' to and sold anywhere in the world or (2) common test 
conditions and procedures, common test devices and measurement 
techniques, and common test criteria limits. A functionally 
equivalent regulation may have any number of ``technical'' 
differences but would provide an equivalent level of real world 
performance despite these differences.

    The petition did not offer any further illumination of what 
``technical'' differences may exist between two regulatory schemes that 
are ``functionally equivalent.'' The AAMA/AIAM petition implies that 
two standards should be considered as functionally equivalent if they 
are similar and offer equivalent levels of performance.
    AAMA/AIAM indicated that the European standards, ECE 17 and ECE 
17.04,\13\ differ from Standard 202 in the requirements for the height 
and width of head restraints, the energy absorption characteristics of 
the front surface of restraints and in the requirement for rear head 
restraints. The petition requested that NHTSA amend S4.3 of its 
standard to require that the top of a fully extended head restraint be 
not less than 800 mm above the seating reference point and that the top 
of a head restraint, when adjusted to its lowest adjustment position, 
be not less than 750 mm above the seating reference point. The addition 
of these proposed amendments, in AAMA/AIAM's view, would make Standard 
202 functionally equivalent to the European regulations. Further, AAMA/
AIAM requested that a new provision be added to Standard 202 indicating 
that head restraints meeting the requirements of ECE 17.05 or ECE 25.04 
or EEC 74/408 be deemed to have met the requirements of Standard 202. 
In order to accommodate the product cycles of their members, AAMA/AIAM 
suggested that the upgraded Standard 202 have an effective date of 
September 1, 2004.
---------------------------------------------------------------------------

    \13\ The European regulations, EEC 74/408, as amended by 
Directive 96/37/EC, promulgated by the European Union, and ECE 
17.04, established by the UN Economic Commission for Europe (ECE), 
apply to vehicles with a seating capacity of nine passengers or 
less. These regulations, which principally govern seats and seating 
systems, are identical to each other. ECE 25, which applies to head 
restraints, is incorporated into ECE 17.04. Therefore, for the 
purposes of head restraints, ECE 17.04 and ECE 25 may be considered 
to be one and the same.
---------------------------------------------------------------------------

III. Overview of Proposal

    NHTSA is proposing a series of amendments to upgrade Standard 202 
to improve the protection provided to occupants. The agency anticipates 
that these amendments will provide safety benefits in all crashes. 
However, we are limiting our benefits analysis to rear end collisions 
only. These new requirements would require that head restraints, when 
adjusted to their lowest possible adjustment position, be at least 50 
mm (2 inches) higher than they are currently required to be. (Note: 
This proposal is presented in the International System of Units (SI) 
with the English Units conversion provided in parenthesis for 
convenience. A final rule will be presented in only SI units.) It would 
also require front seat head restraints to be able to achieve a height 
100 mm (4 inches) higher than currently required, and lock in this 
adjustment position as well as lock at the highest adjustment position. 
Rear seat head restraints would also be required to lock in the highest 
adjustment position. Head restraints would also be subject to a new 
requirement limiting the amount of backset, i.e., distance between the 
back of an occupant's head and the front of the head restraint, to 50 
mm (2 inches). NHTSA is also proposing that head restraints be required 
in the rear outboard seating positions. These upgraded requirements 
appear in the portion of the regulatory text which would apply to 
vehicles manufactured after the first occurrence of September 1, three 
years after publication of the final rule.
    The agency proposal for upgrading Standard 202 would harmonize 
Standard 202 with the requirements for head restraints in ECE 
Regulation 25 in some respects. The proposed height requirements are 
identical to those in ECE 25. The agency proposal also contains 
provisions establishing performance criteria for energy absorption by 
the front surface of head restraints. Finally, as amended, Standard 202 
would require rear seat head restraints.
    However, the proposal would set different requirements for head 
restraint width and gap measurement for adjustable restraints than 
those found in ECE 25. Further, it would add requirements for backset 
and adjustment retention locks. It would also include a dynamic 
compliance option not found in ECE 25. In the current and proposed 
Standard 202, compliance may be measured in one of two ways. The first 
way is to meet all static dimension and strength requirements, while 
the second way is to meet a dynamic test. The proposal would modify the 
required level of performance in the dynamic compliance option to 
reflect the proposed height and backset requirements.
    Prior to the first occurrence of September 1, three years after 
publication of the final rule on which compliance with the upgraded 
requirements becomes mandatory, the manufacturers would be given the 
option of complying with any of three different sets of requirements: 
the existing requirements of Standard 202, the existing requirements of 
ECE 25, or the upgraded requirements of Standard 202. Consistent with 
other recent

[[Page 975]]

amendments to our Safety Standards, the compliance option would have to 
be selected prior to certification of the vehicle, and the selection 
could not be changed thereafter.

IV. Proposed Upgraded Requirements

A. Height Requirements

    Standard 202 currently requires that all head restraints be capable 
of achieving a height where the top of the head restraint must be at 
least 700 mm (27.5 inches) above the seating reference point measured 
parallel to the torso reference line. For vehicles produced on or after 
the first occurrence of September 1, three years after publication of 
the final rule, NHTSA proposes to change this requirement to 800 mm 
(31.5 inches) above the H-point for front seat head restraints. The 
proposal adds a lower limit on all required head restraints including 
those in the rear outboard seats, requiring that head restraints may 
not be less than 750 mm (29.5 inches) above the H-point. Therefore, 
under the proposal, front integral head restraints must have a minimum 
height of 800 mm (31.5 inches) and front adjustable head restraints 
must be capable of achieving a height of at least 800 mm (31.5 inches) 
and cannot be adjusted below 750 mm (29.5 inches). Rear integral 
restraints must have a minimum height of 750 mm (29.5 inches) and rear 
adjustable head restraints must not be adjustable to a height below 750 
mm (29.5 inches). Research indicates that, for many occupants, in order 
to prevent hyperextension or lesser movements of the head and neck in 
relation to the torso that result in injury, head restraints must be 
higher than currently required by Standard 202 and close to the rear of 
the head.
    The proposed alterations in the height requirements are intended to 
prevent whiplash injuries by requiring that head restraints be high 
enough to limit the movement of the head and neck, even if such 
movements do not result in hyperextension of the neck. The persistence 
of whiplash injuries in current vehicles indicates that current designs 
are not preventing whiplash injuries from occurring. Research has led 
to the conclusion that prevention of hyperextension alone does not stop 
whiplash from occurring. Since a 700 mm (27.5 inch) high head restraint 
is capable of preventing hyperextension in many occupants, it seems 
likely that the persistence of whiplash may be the result of the 
inability of current head restraints to be positioned to sufficiently 
limit relative head and neck motion in the normal range of motion. 
Research conducted since the implementation of the current height 
requirement has shown that head restraints should be at least as high 
as the center of gravity (C.G.) of the occupant's head to adequately 
control motion of the head and neck relative to the torso. This does 
not mean that there would be no additional benefits for a head 
restraint with a height greater than the height of the head C.G. 
However, this is likely to be controlled by other factors such as 
backset, head restraint shape and the underlying structure of the head 
restraint under the upholstery. Therefore, the head restraint height 
relative to the head C.G. height will be used here as an indication of 
the adequacy of the proposed height dimension.
    A 750 mm (29.5 inch) high head restraint would have a height above 
the C.G. of a 50th percentile male if the backset were 125 mm (5 
inches) or less, and assuming a head C.G. 105 mm from the top of the 
head (See Figure B). The difference in erect seating height between a 
50th and 95th percentile male is 58 mm (2.3 inches). The size of most 
adult heads is essentially the same. The difference between the base of 
the neck and the top of the head of a 50th and 95th percentile male is 
only 6 mm (0.2 inches). Therefore it is reasonable to assume that the 
vertical dimensions from the top of the head to the C.G. is nearly the 
same at 105 mm (4.1 inches). A 95th percentile male with a torso angle 
of 25 degrees will have the top and C.G. of the head 53 mm (2.1 inches) 
higher than a 50th percentile male.
    It is also reasonable to assume that the back of the 95th and 50th 
percentile male heads are essentially aligned vertically with each 
other. Therefore, they would have the same distance from a head 
restraint with a flat vertical face. This is because the longer torso 
of the 95th male would tend to place it closer to the head restraint 
and the larger lower back and buttocks would push the H-point away from 
the back of the seat, resulting in no net change in backset (see Figure 
C). These assumptions about backset are consistent with the agency's 
laboratory observations and a 1998 Experimental Safety of Vehicles 
(ESV) Conference paper by Toyota.
    Based on these assumptions, a 750 mm (29.5 inch) high head 
restraint would be as high as the 95th percentile male head C.G. if the 
backset were 13 mm (0.5 inches) or less (see Figure D). It would be 17 
mm (0.7 inches) below the 95th percentile male head C.G. at 50 mm of 
backset. A 800 mm (31.5 inch) high head restraint would be as high as 
the 95th percentile male C.G. if the backset were 133 mm (5.3 inches) 
or less. It would be 38 mm (1.5 inches) above the 95th percentile male 
head C.G. at 50 mm of backset.
    The proposal for the front seat of requiring head restraints to be 
capable of achieving an 800 mm height and have a backset no greater 
than 50 mm should assure that the top of the head restraint is above 
the head C.G. of virtually all front seat occupants. The proposal for 
front and rear seats requiring a minimum height of 750 mm and backset 
no greater than 50 mm will provide head restraints higher than the head 
C.G. of about 86 percent of the adult males (assuming a normal 
distribution of height). The C.G. height of a 99th percentile female 
reclined at 25 degrees is about 19 mm below a 750 mm (29.5 inches) high 
head restraint at a 50 mm (2 inch) backset. Therefore, this will 
provide head restraints higher than the head C.G. of nearly all adult 
females and 93 percent of all adults. In term of the rear seat target 
population, this proposal will cover an even higher percentage of rear 
seat occupants than it would of the entire population of occupants. 
This is because more children occupy the rear seats and larger 
occupants rarely sit in the rear where there is generally less room.

[[Page 976]]

[GRAPHIC] [TIFF OMITTED] TP04JA01.002


[[Page 977]]


[GRAPHIC] [TIFF OMITTED] TP04JA01.003

    The recent State Farm-IIHS study also suggests that head restraints 
that are higher in relation to the head center of gravity and closer to 
the back of the head provide greater protection against whiplash. The 
agency notes that head restraints rated ``good'' by IIHS--integral 
restraints with a height less than 60 mm (2.36 inches) below the top to 
the head and within 70 mm of the rear of the head--reduced the 
likelihood of whiplash by 36 percent in females and 10 percent in 
males. Figure B shows that an 800 mm (31.5 inches) high head restraint 
is likely to be high enough to be rated as ``good'' at all backsets 
within the ``good'' range. NHTSA believes that the proposed requirement 
for backset, in conjunction with the proposed height requirements, 
would lead to a significant improvement in safety.
    Although the agency tentatively concludes that its proposed 800 mm 
(31.5 inches) height requirement would offer significant benefits for 
people taller than 50th percentile males, the agency wishes to know if 
additional safety benefits could be realized by requiring head 
restraints to be capable of achieving a somewhat greater height. 
Therefore, NHTSA requests comments on:

    1. The marginal benefits and costs of requiring head restraints 
to be capable of achieving a height greater than the one proposed in 
this notice.
    2. Other issues that may be raised by a height requirement 
greater than the proposed one, including those associated with the 
potential effects on visibility, seat adjustability and compliance 
with other safety standards, e.g., Standard 201, ``Head Protection 
in Interior Impact.''

B. Backset Requirement

    NHTSA is also proposing to add, for vehicles produced on or after 
the first occurrence of September 1, three years after publication of 
the final rule, a backset requirement of no more than 50 mm (2 inches) 
for front and rear head restraints. The consensus of the biomechanics 
community is that the backset dimension has an important influence on 
the forces felt by the neck and the length of time a person is disabled 
by injury. This judgment is based on testing, computer modeling and 
real world crash data. As far back as 1967, Mertz and Patrick showed 
that loading on the head during a rear impact is minimized by reducing 
the initial separation between the head restraint and head. With the 
head initially against the head restraint, a volunteer test subject 
endured a 71 kph (44 mph) rear impact without discomfort. Research 
presented at the 1990 International Research Council on the 
Biomechanics of Impact (IRCOBI) examined 25 rear impacts involving 33 
occupants of Volvo cars. The study results showed a statistically 
significant increase in neck injury duration when there was more than 
100 mm (4 inches) of backset. A 1994 study conducted by Volvo found 
additional potential injury reduction as the backset approaches zero, 
allowing no relative motion between the head and torso upon rear 
impact. IIHS, in its studies of head restraints, considered a backset 
of 70 mm (2.8 inches) or less to be ``good.''
    NHTSA has tentatively concluded that adding a requirement 
specifying a limit on backset would result in reduced angular 
displacement between the head and torso in a crash. One method the 
agency used to assess the potential benefits of a backset limit was 
through a computer modeling study in which the backset dimension was 
defined as the distance between two vertical lateral

[[Page 978]]

planes; one plane passing through the rearmost point on the headform 
and the other passing through the forwardmost part of the head 
restraint at its centerline. A seat model intended to represent a 1986-
1994 Pontiac Grand Am was used with the head restraint positioned in 21 
different configurations with varying heights and backsets. The vehicle 
seat, as modeled, was relatively stiff in the longitudinal direction in 
comparison to those currently on the market. Another set of data was 
generated with the hinge joint kept completely rigid. This was intended 
to simulate a rear seat that has its seat back structure rigidly 
attached to the vehicle body, such as is the case for many passenger 
cars. A model of a Hybrid III 50th percentile male was the seat 
occupant.
    For both seat stiffnesses, no head-to-torso angular rotation was 
greater than 2 degrees for head restraints above 750 mm (29.5 inches) 
and backsets 50 mm (2 inches) and closer. At backsets up to 100 mm (4 
inches), all head-to-torso angular rotations were less than 21 degrees 
for head restraints above 750 mm (29.5 inches). At a backset of 150 mm 
(6 inches), head rotations of 27 and 44 degrees occurred at head 
restraint heights of 750 mm (29.5) and 800 mm (31.5 inches), 
respectively.
    The computer modeling indicates that the lowest head-to-torso 
rotation value was seen when the backset was approximately 50 mm (2 
inches). NHTSA tentatively concludes that this amount of backset is 
appropriate for all outboard seating positions.
    The agency understands that there are differences in the way 
occupants adjust and sit in seats and that the backset measurement 
device being used may not capture this variety completely since it 
attempts to represent the head position of a 50th percentile male in a 
seat with a 25 degree inclination from the vertical. A steeper seat 
back inclination will further reduce the backset.
    The agency also believes that physical differences in seat design 
may contribute to seat performance. In fact, National Automotive 
Sampling Systems (NASS) crash data indicate that the whiplash rate for 
rear seat occupants is significantly lower than that of front seat 
occupants. One explanation may be that many rear seats are often 
configured differently than front seats and frequently do not have 
adjustable backs. Adjustable seat backs allow wide variations in 
location of the head restraint relative to the user as the seatback 
angle changes through the range of adjustment.
    In making the backset proposal, the agency has attempted to balance 
the need for both occupant safety and comfort while considering 
potential misadjustment. The agency believes the backset requirement is 
practicable--the majority of occupants should comfortably fit in seats 
with a 50 mm (2 inch) backset and it is well within the capability of 
manufacturers to produce seats with this backset.
    The agency measured 14 MY 1999 vehicles and found that the front 
seats of the Toyota Camry, Chevy C1500, Chevy S10, Saab 9-5, and Chevy 
Malibu had backsets within the proposed 50 mm (2 inch) limit. Saab 9-5 
rear seats also meet that proposal. For the entire fleet of new 
vehicles, we estimate that front seats are an average of 23 mm (0.9 
inches) away from meeting the proposal and rear seats are an average of 
47 mm (1.8 inches) away from the proposal. These fleet estimates were 
derived by using the sales weighted averages of the 14 MY 1999 vehicles 
measured. More details can be found in the PEA for this proposed rule.
    Further, based on IIHS' rating of head restraints in MY 1999 
vehicles, it appears that there are at least some models in all classes 
of vehicles that already meet or come close to meeting the proposed 
backset limit. As noted above, IIHS rates the backset of a vehicle's 
head restraints as good if it is not more than 70 mm (2.6 inches). 
According to IIHS, cars with head restraints rated good overall (i.e., 
both backset and height) include the BMW Z3 Coupe, Saab 9-3 and 9-5, 
Volkswagen New Beetle (some seat options), and Volvo C70/S70/V70 and 
S80 models. Among pickups, the Chevrolet S10 and GMC Sonoma have good 
restraints. And among utility vehicles, the Chevrolet Blazer (some seat 
options) and Mitsubishi Montero earn good ratings.
    Nonetheless, NHTSA solicits comments on whether this proposed 
backset limitation is appropriate. In particular, the agency seeks 
information and comments on:

    3. Whether limiting backset to 50 mm (2 inches) is sufficient to 
prevent excessive relative motion between the occupant's head and 
torso. Does 50 mm (2 inches) of backset provide sufficient head 
clearance and comfort for most occupants?
    4. Would it be appropriate to allow a greater maximum backset 
(e.g., 100 mm (4 inches)) while requiring that head restraints with 
more than 50 mm (2 inches) of backset be adjustable so that backset 
can be reduced to 50 mm (2 inches)? Please provide data on the 
amount of safety disbenefit that would be associated with allowing a 
backset of 75 or 100 mm (3 or 4 inches), instead of 50 mm (2 
inches).

    NHTSA is proposing that compliance with the backset requirement be 
measured through use of the ICBC Head Restraint Measuring Device. Under 
the proposed rule, all outboard seat head restraints must have a 
backset of not more than 50 mm (2 inches). This 50 mm (2 inches) 
backset must not be exceeded at any height between 750-800 mm (29.5-
31.5 inches). Although no height adjustment beyond 750 mm (29.5 inches) 
is required for rear seats, if these higher height positions exist, 
backset must be limited to 50 mm (2 inches). Figure E is a graph of the 
zones of adjustment for front and rear head restraints relative to the 
head C.G. of a 50th and 95th percentile male dummy. These positions are 
based on the assumptions stated in Section IV.A., Height Requirements 
and shown in Figures C and D.

[[Page 979]]

[GRAPHIC] [TIFF OMITTED] TP04JA01.004

    The agency believes that the ICBC measuring device is an 
appropriate tool for measuring backset. However, the agency solicits 
comments on:

    5. Other devices that may be used to perform the same function 
as the ICBC device and whether such devices would be more 
appropriate.

    NHTSA observes that the ECE 25 requirements do not include a 
specification for backset. The agency believes, however, that the 
proposed backset requirement, which the agency believes offers 
significant safety benefits, would not prevent manufacturers from 
producing designs meeting ECE 25.
    Both the height and backset measurements are accomplished through 
the use of the SAE J826 manikin (June 1992) or H-point machine. The 
positioning procedure for this device is explicitly defined in SAE J826 
in order to maximize repeatability. This in turn maximizes the 
repeatability of the height and backset measurements.

C. Height Adjustment and Backset Limit Retention Requirements

    The agency is also proposing, for vehicles produced on or after the 
first occurrence of September 1, three years after publication of the 
final rule, that performance requirements for adjustable head 
restraints be added to Standard 202 which are intended to assure that 
the front head restraints remain locked in specific positions. A 1982 
NHTSA study found that the effectiveness of integral head restraints 
was greater than adjustable head restraints. The study concluded that 
this difference in effectiveness was due, in part, to adjustable head 
restraints not being properly positioned. Although one reason for 
improper positioning is a lack of understanding on the part of the 
occupant on where to place the head restraint, it also could be due to 
the head restraint's moving out of position either during normal 
vehicle use or in a crash. Adjustment locks can mitigate this problem 
by helping to retain the adjusted position. IIHS has also been critical 
of adjustable head restraints, especially when they do not provide 
locks, in their evaluation of head restraints. This criticism has 
manifested itself in that IIHS, in its rating of head restraints, 
automatically gave adjustable restraints a lower rating on the 
assumption that these restraints would not be properly adjusted. In 
addition, it only evaluated adjustable head restraints without locks in 
their lowest position. In comments on the agency's 1996 technical 
report, Advocates stated that adjustable restraints should be required 
to lock. Toyota also stated that, at a minimum, head restraints should 
lock vertically.
    The modifications to the existing height requirements and the 
addition of a backset requirement that are now being proposed are 
expected to improve the performance of all adjustable head restraints. 
The performance of adjustable head restraints may be further improved 
if steps are taken to ensure that a restraint remains in position after 
it has been set by the user.
    In making this proposal, the agency has no desire to require 
specific methods for adjustment and locking. A typical adjustable head 
restraint design allows manual adjustment by sliding the head restraint 
in and out of the seat back on posts attached to the head restraint. 
Position locking is achieved by notches in the shaft allowing for a 
detent mechanism. There are also powered adjustable head restraints 
which are infinitely adjustable within a specific range. When the 
adjustment mechanism is inactive, the head restraint is, in effect, 
locked in position. Under the

[[Page 980]]

current proposal, these and other locking methods would be permissible 
as long as the performance criteria below are met.
    Therefore, we are proposing that adjustable head restraints for the 
front outboard seating positions must maintain their height (i.e., 
lock) in several height positions under application of a downward 
force. In addition to locking at a position of not less than 800 mm 
(31.5 inches), they must also lock at the highest adjustment positions. 
It may be that, for some designs, the highest position is at 800 mm 
(31.5 inches). Adjustable head restraints for the rear outboard seating 
positions must lock at the highest position of adjustment above 750 mm 
(29.5 inches), if this position exists. In addition to locking at these 
specified positions of height adjustment, both front and rear head 
restraints must be capable of retaining the minimum height of 750 mm 
(29.5 inches) under application of a downward force.
    The height position retention requirements must be met at any 
backset position of adjustment. The agency believes that this is 
important for designs which adjust vertically as well as rotate for 
backset adjustment. Although there may be no backset position more than 
50 mm (2 inches), a change in the backset position may change the 
height of the head restraint.
    We are also proposing to adopt the following backset retention 
requirement. Under application of a rearward moment, with the head 
restraint adjusted to 800 mm (31.5 inches) for front outboard seats and 
750 mm (29.5 inches) for rear outboard seats, the head restraint must 
maintain any position of backset adjustment.
    The agency believes that the proposed height and backset position 
retention requirements are very comprehensive and that requirements for 
other positions than those mentioned above are unnecessary and would 
not result in significant additional safety benefits. The agency notes, 
however, that manufacturers would not be precluded from providing 
additional lockable positions within the range of the head restraint's 
adjustment.
    The proposed height adjustment retention lock and backset limiter 
compliance tests begin by applying a small initial load to the head 
restraint. A headform is used to apply the load and a reference 
position is recorded. The head form reference position is measured with 
this load applied to eliminate variability associated with the soft 
upholstery of the head restraint. A larger load is then applied through 
the headform to test the locking mechanism. Finally, the load is then 
reduced to the initial value and the head form is checked against its 
initial position. In order to comply, the locking and limiter 
mechanisms must not have allowed the headform to have moved more than 
10 mm (0.4 inches) from the initial reference position. First, to test 
the vertical lock, a load is of 500 N (112 pounds) is applied 
vertically downward. Then, to test the backset limiter, a force is 
applied sufficient to generate a 373 Nm moment (3,300 inch-pounds) 
perpendicular and rearward to the torso reference line about the H-
point. A force of approximately 500 N (112 pounds) is required to 
generate this moment. The agency has reviewed upper neck shear loading 
from 33 rigid moving barrier, rear impact (48 kph (30 mph)) FMVSS 301 
tests and found the average maximum load caused by the head being 
loaded in the forward direction with respect to the torso is 351 N 
(78.9 pounds). This direction of shear load is a good indicator of head 
restraint loading on the head and, therefore, head loading on the head 
restraint. Thus, the 373 Nm (3,300 inch-pounds) rearward moment and 500 
N (112) downward force are representative of the peak loads likely to 
be encountered in moderate to severe rear impacts.
    NHTSA remains concerned, however, that while the addition of the 
proposed locking and limiter requirements will help ensure that 
properly adjusted head restraint remain in position, the requirements 
cannot do anything to ensure that adjustable head restraints are 
actually put in that position in the first place. The agency requests 
comments on:

    6. The appropriateness of the load values used to assess the 
position retention capability of head restraints. Should other 
height and adjustment positions such as a mid-height position be 
tested and/or required?
    7. Do vehicle users understand how to properly adjust head 
restraints? If not, should manufacturers be required to provide 
information on this subject to consumers in the vehicle owner's 
manual or elsewhere?
    8. The extent to which misadjustment of head restraints is due 
to the absence of adjustment retention locks versus intentional 
misadjustment by occupants.
    9. Do vehicle users intentionally misadjust head restraints for 
reasons related to comfort, visibility, or other factors?
    10. Are adjustable head restraints with adjustment retention 
locks significantly less likely to be misadjusted than ones without 
such locks?
    11. Would equipping restraints with locks discourage 
misadjustment? If not, should other requirements be adopted to 
address the problem of misadjustment? The agency has previously 
addressed issues of misuse, non-use and adjustment in several 
contexts, including manual seat belts and child seats. Would the 
measure adopted in these contexts be appropriate with respect to 
head restraints?
    12. What would the costs and benefits be of requiring that the 
height of front seat head restraints be fixed at 800 mm (31.5 
inches) or at some other single height? What would the costs and 
benefits be of adopting such a fixed head restraint requirement for 
rear seat head restraints?

D. Rear Outboard Seating Positions

    In addition to modifying requirements for head restraints for front 
outboard seating positions, NHTSA is also proposing to add head 
restraint requirements for rear outboard seating positions for vehicles 
produced on or after the first September 1 that occurs three years 
after publication of the final rule. The agency has tentatively 
concluded that the addition of head restraints for these seating 
positions would reduce whiplash injuries to rear seat occupants and 
harmonize Standard 202 with the ECE 25 head restraint requirements. 
Data obtained from NASS for non-rollover towaway rear crashes for 
passenger cars and LTV's for the years 1988 through 1996 shows that 
there were 5,440 whiplash injuries reported annually for occupants of 
rear outboard seating positions.
    The whiplash rate (number of occupants with whiplash divided by the 
number in crashes) for these seating positions is less than that for 
front outboard seating positions, but is still significant. The reasons 
for a lower rear seat whiplash rate are not clear, but probably cannot 
be attributed solely to the fact that rear seat occupants are on 
average shorter than front seat occupants. Occupants may sit 
differently in rear seats--their posture may place the head closer to 
the head restraint and reduce or eliminate backset. Although rear seat 
head restraints are on average 33 mm (1.3 inches) lower than front seat 
head restraints, the reason for the relatively low occurrence of 
whiplash in rear seats may be the existing configuration of rear seats 
and rear seat head restraints.
    NHTSA is proposing that rear outboard seat head restraints must 
have a minimum height of 750 mm (29.5 inches) above the H-point. As 
noted above in the backset requirement section, the rear outboard head 
restraints must also meet backset requirements and have a backset of 50 
mm (2 inches) or less.
    NHTSA sampled the head restraint heights and backsets of 12 1999 MY 
vehicles which had front and rear head restraints. Three of the 
vehicles had rear seats of sufficient height and one vehicle met the 
backset limit proposed

[[Page 981]]

for rear seats. One of the twelve vehicles would meet both the height 
and backset proposal.
    The agency's proposal to require head restraints in the rear 
outboard seating positions is, in part, based on a philosophy that 
commonly used seating positions should offer similar levels of 
protection to their occupants. This philosophy has guided the agency in 
requiring a test dummy to be placed in the rear seat for the dynamic 
performance test in FMVSS 214; Side Impact Protection, and in the 
provision of FMVSS 208; Occupant Crash Protection, requiring lap/
shoulder seat belts to be installed in forward facing rear outboard 
seating positions. In establishing the FMVSS 208 and 214 requirements 
for both front and rear seats, we realized that, because of the 
significantly lower rear seat occupancy rates, the ratio of cost to 
benefit was inherently higher than similar front seating position 
requirements. In this case, there are again lesser safety benefits from 
rear seat head restraint protection because of lower rear seat 
occupancy rates. However, when people are sitting in the rear seat, 
they will gain safety benefits from improved head restraints.
    Assessment of the relative merits of requiring enhanced protection 
for rear seats must also reflect the fact that NHTSA has recommended 
that all children 12 and under sit in the rear. Given that we have 
provided this advice to parents, NHTSA feels particularly obligated to 
provide similar levels of protection in the rear. Older children are 
large enough to benefit from a rear seat head restraint particularly in 
family vehicles with bench type seats such as minivans and SUVs. Also, 
rear seat occupancy should rise as more children sit there, thereby 
increasing the at-risk population and the corresponding benefits of 
rear seat head restraints. For these reasons, we have decided to 
propose upgrading whiplash protection in outboard rear seats 
notwithstanding lower cost-effectiveness for improved head restraints 
at those positions. NHTSA is especially interested in public comments 
on this approach.
    The agency is not proposing to require front or rear center seat 
head restraints because of significant costs, much higher cost per 
equivalent fatality than outboard positions, and visibility concerns. 
The combined total cost of front and rear center seats head restraints 
would be $52 million (front) + $94 million (rear) = $146 million. We 
estimate that this substantial investment would result in reducing the 
annual number of whiplash injuries in the front center seat by 440 and 
in the rear center seat by 1,276. The combination of these cost and 
benefit figures would be a cost per equivalent life saved (at 7 percent 
discount) of $52 million for front center seat head restraints, based 
on the effectiveness for increasing the height of head restraints and 
assuming no benefit for backset. For rear center seat head restraints, 
the cost would be $33 million. For both front and rear center seats 
combined, the cost per equivalent life saved would be $38 million. All 
of those figures are much higher than the cost per equivalent life 
saved for front outboard seats ($3 million) and that for rear outboard 
seats ($9 million).
    Finally, having center seat head restraints limits to some extent 
the driver's ability to see following traffic using the inside rearview 
mirror. When a vehicle is in reverse, front and rear center head 
restraints limit visibility when the driver turns his/her head to back 
up. In addition, a front center seat head restraint can limit vision 
through the right side second seat window when the driver is 
considering a lane change maneuver to the right. The agency can not 
quantify these potential losses in visibility, nor the potential impact 
that this loss in visibility could have on safety.
    The agency is aware of rear seat head restraint designs which have 
the goal of lessening the rearview obstruction. Some designs provide 
open areas in the head restraint so the driver can see through them. 
Other head restraints fold out of the way into non-use positions. The 
agency's current proposal does not contain any requirements to 
specifically compensate for the potential rearview obstruction. 
However, the agency is proposing language in S4.3 which will allow for 
folding or retractable head restraints for rear seats if they meet 
specific criteria. If such a head restraint is adjusted to a non-use 
position, i.e., any position in which its minimum height is less than 
that proposed in this document or in which its backset is more than 
that proposed in this document, it must give the occupant an 
unambiguous physical cue that the head restraint is not properly 
positioned by altering the normal torso angle of the occupant or it 
must automatically return to a position where it would comply with all 
provisions of the regulation when the seat is occupied. To determine if 
the head restraint in a non-use position alters the torso angle of an 
occupant, the SAE J826 manikin is placed in the seat position. The 
torso angle of the manikin when the head restraint is in a non-use 
position must be at least 10 degrees closer to the vertical than when 
the head restraint is in a normal use position. Alternately, if the 
head restraint is designed to return automatically from a non-use 
position to a normal use position, this must occur when a 5th female 
and 50th male Hybrid III test dummy in placed in the seating position.
    The agency would like commenters to address the issues surrounding 
rear seat head restraints and their impact on rearward visibility. 
Specifically, the agency would like to know the following:

    13. Are data available related to safety risks, if any, 
associated with decreased visibility caused by rear seat head 
restraints?
    14. Should the agency place specific design requirements on rear 
seat head restraints to compensate for any potential visibility 
losses?
    15. Should Standard 202 allow rear head restraints to have non-
use positions? If so, how should such positions be defined and 
limited?
    16. Are the proposed requirements for non-use positions 
sufficiently objective? Are they sufficient to alert occupants that 
the head restraint is not in a normal use position?
    17. Given the lesser safety from rear seat head restraint 
protection because of lower rear seat occupancy rates, and given the 
visibility issues, should the agency limit the application of any 
final rule to front seating positions?

    An additional concern raised by the required installation of 
outboard rear seat head restraints is the impact of such restraints on 
child restraints that use top mounted tether straps. The agency notes 
that tethered child restraint requirements have just been instituted in 
the United States and have been required for some time in Canada and 
Australia--where vehicles with rear head restraints are relatively 
common. Inquiries to Transport Canada, NHTSA's Canadian counterpart, 
indicate that interference between rear head restraints and child seat 
tethers has not posed significant problems. NHTSA also wishes to point 
out that on March 5, 1999, the agency published the final rule for 
Standard 225, ``Child Restraint Anchorage System'' (64 FR 10785). The 
standard requires an independent system which has two lower anchorages, 
and one upper anchorage. Each lower anchorage includes a rigid round 
rod or bar onto which a hook, a jaw-like buckle or other connector can 
be snapped. The bars will be located near the intersection of the 
vehicle seat cushion and seat back. The upper anchorage will be a ring-
like object to which the upper tether of a child restraint system can 
be attached.
    In its examination of the potential for interference between 
tethers and rear seat head restraints conducted prior to the issuance 
of that final rule, the agency agreed that compatibility

[[Page 982]]

problems between the tether and rear seat head restraints could occur 
in some situations but concluded that this did not present an 
unsurmountable design problem. NHTSA concluded that ``Y'' shaped tether 
strap designs that encircle the head restraint might be used where the 
tether could not pass over or under the head restraint. Furthermore, as 
the final rule amending Standard 213, ``Child Restraint Systems,'' 
requires the use of a fixture for testing tether strength, 
manufacturers should be able to identify and correct for potential 
compatibility problems between the tether system and head restraints.
    Nonetheless, the agency solicits comments on the following:

    18. Are there potential safety concerns caused by interference 
between rear seat head restraints and child seat tethers?
    19. The existence or significance of test data showing whether 
passing the top tether over the top of the head restraint or 
underneath an adjustable head restraint has any effect on head 
excursion or lateral stability of a child restraint.

E. Removability of Head Restraints

    The agency is aware that some current head restraints, both front 
and rear, can be manually removed solely by hand (i.e., without the 
assistance of any hand held object). Such a design is not currently 
prohibited by Standard 202. The agency believes strongly that all 
occupied outboard seats should have a properly positioned head 
restraint in place. However, for seats which are often unoccupied, 
which is usually the case for rear seats, there may be a potential 
benefit to allow head restraints to be removable for the sake of 
increasing a driver's field of view towards the rear. The proposed rule 
would prohibit removable head restraints in the front seats, but would 
not prohibit removable head restraints in the rear seats. The agency 
believes that a rear seat which has its head restraint removed gives a 
strong visual cue to a prospective occupant unlike a head restraint 
which may be in a subtle non-use position. Front seats must be designed 
so that they cannot be removed solely by hand.

    20. Should Standard 202 continue to allow any head restraints to 
be removable by hand? If so, should this be limited to rear seat 
head restraints?
    21. Should there be some type of indicator to warn a prospective 
occupant that the head restraint has been removed, or is the visual 
cue of a seat without a head restraint sufficient?

F. Head Restraint Configuration Requirements

1. Width
    NHTSA has tentatively concluded that the requirements for head 
restraints on vehicles produced on or after the first occurrence of 
September 1, three years after publication of the final rule, should 
maintain the existing width requirements contained in Standard 202. 
These provisions require that head restraints be at least 170 mm (6.7 
inches) wide on single seats and 254 mm (10 inches) wide on bench 
seats. The agency believes that doing otherwise will degrade the level 
of safety currently available. Occupants seated on bench seats are 
freer than occupants of single seats to position themselves so that 
they are not directly in front of the head restraint. This is 
especially true if they do not use their seat belts--a concern that is 
more relevant in the United States than in Europe. Thus, the head 
restraint needs to be wider to assure that, in the event of a crash, 
the head restraint will be positioned behind an occupant's head.
    This proposal differs from the ECE 25 regulations in specifying a 
different width requirement for bench seats than for other seats. As 
noted above, the agency is concerned that because seats other than 
bucket seats, i.e., bench and split bench seats, are more widely used 
in the United States than in Europe, Standard 202 should dictate 
different width requirements than those found in ECE 25.
2. Gaps
    NHTSA is proposing the addition of maximum gap requirements for 
head restraint designs incorporating openings within the perimeter of 
the restraint. Gaps may be provided to allow for sight through the head 
restraint. However, gaps which are too large may defeat the purpose of 
the head restraint by allowing the head to displace too far before 
contact with the head restraint. The agency used ECE 25 as a model for 
the gap requirement in the NPRM. The agency proposal for integral 
restraints allows a maximum 60 mm (2.36 inches) gap in the head 
restraint and an identical maximum gap between the head restraint and 
seat. For height adjustable head restraints, 60 mm (2.36 inches) gaps 
are allowed in the head restraint. When adjustable head restraints are 
in their lowest position they must have some position of backset 
adjustment where the gap between the seat and head restraint is less 
than 25 mm (1 inch). However, this gap cannot be greater than 60 mm 
(2.36 inches). The agency believes that a 25 mm (1 inch) gap 
requirement between the seat and head restraint would essentially 
require the seat back to provide the travel stop for head restraint 
adjustment downward. This would eliminate significant discontinuities 
between the seat back and head restraint when the head restraint is in 
its lowest position, which may be a benefit to short occupants. The 
maximum 60 mm (2.36 inches) gap between the seat back and head 
restraint when the head restraint is in the lowest adjustment position 
is allowed in anticipation of designs that have rotational backset 
adjustment. It may not be possible for this type of design to meet the 
25 mm (1 inch) limit in all rotational positions.
    Finally, it should be noted that the gap requirements would place 
no limit on the size of the gap between the seat back and head 
restraint that is produced when the head restraint is raised. The 
establishment of such a limit would eliminate from the market place 
most existing adjustable head restraints. The agency anticipates that 
occupants will not adjust their head restraints such that the rear 
portion of their head would be between the top of the seat and bottom 
of the head restraint. Nonetheless, the agency would like comments on 
this issue.
    For harmonization purposes, NHTSA notes that the proposed gap 
requirements are identical to the ECE 25 specifications with two 
exceptions. First, the proposed NHTSA limit on the distance between the 
head restraint and the seat when the head restraint is in its lowest 
position applies only at a single position of backset adjustment. The 
ECE requirement does not contemplate head restraints that may be 
adjustable for backset and simply allows no more than a 25 mm (1 inch) 
gap. Second, the ECE standard allows an alternate compliance option of 
application of a load to the gap area rather than limiting the gap to 
60 mm (2.36 inches). The agency assumes that the concept behind this 
option is that if pushing on the gap area with a head form does not 
cause deflection of more than 102 mm (4 inches), the gap is acceptable. 
The agency sees no need for permitting this alternate method of 
compliance.

    22. The agency requests comments on the need for a requirement 
limiting the gap between the lower edge of an adjustable head 
restraint and the seat to 25 mm (1 inch) when the restraint is in 
its lowest position.
    23. NHTSA requests comments on whether 60 mm (2.36 inches) is an 
appropriate value for the maximum size of the gap between a seat and 
the lower edge of an integral head restraint and the maximum 
allowable gap in any head restraint.
    24. The agency also requests comments on whether a limit should 
be placed on the gap

[[Page 983]]

between adjustable head restraints and the seat back when the head 
restrain is in a raised position.

G. Energy Absorption

    For vehicles produced on or after the first occurrence of September 
1, three years after publication of the final rule, the agency is also 
proposing an energy absorption requirement specifying that when the 
front of the head restraint is impacted by a head form at a velocity of 
24.1 kilometers per hour (15 mph), the deceleration of the head form 
must not exceed 80g continuously for more than 3 milliseconds. The 
impactor would be a free-motion head form with a 6.8 kg (15 pound) 
mass. The proposal would require the head restraint to comply in any 
position of adjustment. The area of the head restraint subject to 
impact in the compliance test would differ depending on the seat 
configuration. The proposal limits this area to within 70 mm (2.8 
inches) of the head restraint vertical centerline for single seats, but 
increases the impact area to within 105 mm (4.1 inches) of the 
centerline for bench seats because of the potential for occupants to be 
seated farther from the centerline in bench seats. The point of impact 
must be at least 635 mm (25 inches) above the H-point.
    The agency proposal is similar, but not identical, to the 
requirements of ECE 25. ECE 25 requires the use of a pendulum impactor. 
The agency's proposal specifies the use of a free-motion head form 
impactor. NHTSA believes the results from a pendulum or head form 
impactor would be the same. In order to increase the level of 
harmonization with ECE 25, the agency is not at this time proposing the 
use of the free-motion head form in Part 572 Subpart L. This head form 
is required for upper interior impacts in Standard 201; Occupant 
Protection in Interior Impacts. The Part 572(L) head form has a 4.5 kg 
mass (10 pound) rather than a 6.8 kg (15 pound) mass. However the mass 
and impact speed of the head form in ECE 25 and being proposed here are 
the same as required by Section 5 of Standard 201.
    The agency proposal also differs from ECE 25 in the dimensions of 
the area of impact. ECE 25 specifies a single size for the impact area 
regardless of the seat configuration. As bench seating is more common 
in vehicles produced for the North American market, the agency believes 
that the variance between the two regulations is justified.
    The proposal also contains a minimum radius of curvature 
requirement for the front surface of the head restraint. In order to 
protect rear seat occupants from injuries caused by impact with the 
head restraint in frontal crashes and all occupants in rollovers or 
similar crashes, any part of the head restraint outside of the impact 
zone for the energy absorption requirement must not have a radius 
smaller than 5 mm (0.2 inches) unless it can pass the energy absorption 
requirement. This requirement is intended to eliminate potential 
sources of high pressure contacts between occupants and head 
restraints. NHTSA is not aware of any surfaces on current head 
restraint designs that have such a small radius of curvature and 
believes that most, if not all, would be in compliance. Nonetheless, 
NHTSA is proposing this requirement in the interest of increasing the 
level of harmonization with ECE 25.

    25. The agency requests comment on the need for the requirement 
for limiting the radius of curvature outside of the impact zone to 
no less than 5 mm (0.2 inches).
    26. NHTSA would also like comments whether the Part 572 Subpart 
L free-motion head form should be proposed rather than the head form 
in the current proposal which more closely harmonizes with ECE 25.

H. Test Procedures

1. Displacement Test Procedure
    The agency is also proposing changes to the existing displacement 
test procedure contained in Standard 202. In this procedure, the head 
restraint's ability to resist deflection is measured by applying a load 
to the back pan of the seat and applying a load to the head restraint 
after the load on the back pan of the seat is released. A 102 mm (4 
inch) displacement is allowed with a 373 Nm (3,300 inch-pounds) moment 
applied. The applied load is then increased until the seat or seat back 
fails or the load reaches 890 N (200 pounds) and the head restraint 
withstands this load.
    The proposal modifies this test procedure to require that the back 
pan of the seat and the head restraint be subjected to simultaneous 
loading. The agency proposal also removes the current standard's 
provision allowing seats or seat backs to fail when the head restraint 
is subjected to the 890 N (200 pounds) load. Lastly, the proposal 
modifies the existing test procedure to clarify the direction of the 
loads placed on the restraint, seat and seat back. The proposal 
maintains the 4 inch displacement limit. The exact SI conversion to 102 
mm is used rather than rounding the value to 100 mm because it is an 
existing requirement.
    Data provided by the AAMA and AIAM indicate that loading the seat 
back pan and the head restraint at the same time results in a more 
severe test. These data were contained in a petition submitted to the 
agency in support of harmonizing the existing Standard 202 test with 
the ECE 25 test. AAMA/AIAM provided data from one 1998 model year 
vehicle seat that showed a 64 mm (2.5 inch) displacement for the 
Standard 202 method and a 89 mm (3.5 inch) displacement for the ECE 
method. NHTSA's review of the AAMA/AIAM data indicates that the AAMA/
AIAM position appears to be correct. Because the back pan position is 
maintained while the head restraint is loaded, some amount of load may 
be applied through the back pan to the seat. This load, along with the 
load applied to the head restraint, results in the total applied seat 
moment and contributes to head restraint deflection. Thus, the head 
restraint deflection may be greater than if the back pan load is 
removed before application of the head restraint load. The agency 
believes that applying loads to both the back pan and the head 
restraint simultaneously better reflects the stresses that occur in 
rear end crashes.
    This change, if adopted, will harmonize the Standard 202 
displacement test procedure with that contained in the ECE 25 
regulation. In both test procedures, the back pan of the SAE J826 test 
device is used to apply a 373 Nm (3,300 inch-pounds) moment to the seat 
back. Currently, the difference in the two test procedures is that 
Standard 202 specifies that the back pan load is removed before 
application of the moment to the head restraint and ECE 25 specifies 
that the back pan position is maintained while the head restraint 
moment is applied.
    Additional text has been added to the displacement test procedure 
to clarify the direction of loading on the head restraint and seat 
back. The proposal would require that the back pan be constrained so 
that as pressure is applied, it rotates about the H-point and the 
moment producing force, which is initially perpendicular to the torso 
line, rotates with the back pan. However, the proposal also would 
require that the moment-producing force on the head restraint initially 
be applied perpendicular to the displaced torso reference line and that 
the orientation be maintained with respect to the ground throughout the 
testing.
    Finally, the existing displacement procedure allows the seat back 
to fail without consequence under application of 890 N (200 pounds) to 
the head restraint. Yet, from the perspective of an occupant, if the 
head restraint is displaced during loading, the consequences may be 
equally severe regardless of the reason for the

[[Page 984]]

displacement. Therefore, the NPRM removes the allowance for seat back 
failure. The head restraint must be able to apply a resistive force of 
890 N (200 pounds) to the load applying head form. If the head 
restraint is displaced out of the path of the head form prior to 
achievement of the 890 N (200 pounds) load, the head restraint has 
failed, regardless of whether failure was due to weakness in the seat 
or the head restraint components.
2. Dynamic Sled Test Procedure
    The agency is also proposing changes to the existing Standard 202 
dynamic test option. Currently, Standard 202's dynamic compliance 
option specifies that the seat structure must be accelerated such that 
the acceleration pulse lies between two half sine waves. The lower 
boundary half sine wave is represented by the expression a = 78 
Sin(t/80) and the upper boundary is represented by a = 94 
Sin(t/96), where t is in milliseconds and a has the units of 
m/s 2. Figure F shows these sled pulse boundaries along with 
the target sled pulse between them (represented by a = 86 
Sin(t/88)). It can be seen from this figure that at the 
beginning of the pulse there is very little area in the corridor. NHTSA 
believes that as a practical matter the existing corridor cannot be 
met. For this reason, a new sled pulse corridor has been developed. Its 
dimensions are derived from a scaled down corridor now used in the 
FMVSS 208 sled test procedure. The new corridor is wider than the 
existing corridor until about 40 ms and narrower from about 60 ms on. 
However, the target sled pulse remains the same.
    In addition to modifying the corridor shape, we have revised the 
test procedure to specify that the vehicle, instead of simply the seat, 
is mounted on the sled. The agency believes this is necessary because 
both front and rear seats are now required to have head restraints and 
could be dynamically tested. This also simplifies the test setup 
because the dummies are required to be restrained by a Type 2 belt 
which is often attached to the B-pillar. The agency believes existing 
sled designs can stay within the specified acceleration corridor with a 
vehicle mounted to them. Finally, SAE J211/1 (March 1995) has been 
referenced to indicate the use of channel filter class (CFC) 60 for 
data processing.
[GRAPHIC] [TIFF OMITTED] TP04JA01.005

    The agency is also proposing to alter the performance requirements 
for the dynamic compliance test option due to the proposal's alteration 
of the existing head restraint height requirements. The current dynamic 
test accelerates a seat loaded with a 95th percentile dummy to an 8g 
half sine acceleration pulse over 80 ms. In order to pass this test, 
the dummy neck must not rotate rearward with respect to the torso more 
than 45 degrees. The 45 degree performance limit was developed such 
that a 700 mm (27.5 inch) high head restraint would pass the dynamic 
test.
    The proposal also alters the specifications for one aspect of the 
seating procedure for the dynamic test. Standard 202 currently 
specifies that the test device shall be secured by a Type 1 seat belt 
in the design seating position of each designated seating position with 
a head restraint. The proposal changes

[[Page 985]]

this requirement by substituting a Type 2 seat belt for a Type 1. This 
change is being instituted to more accurately reflect current 
requirements for the installation of Type 2 belts in outboard seating 
positions.
    If the agency's proposal did not alter the dummy head rotation 
requirement, manufacturers could pass the standard using the dynamic 
test with 700 mm (27.5 inch) high head restraints even though the new 
proposed minimum height requirement is 750 mm (29.5 inches). To avoid 
this, we are proposing to alter the dynamic test procedure and injury 
criteria for front outboard seating positions so that when the 95th 
percentile male test dummy is used, only head restraints at least 800 
mm (31.5 inches) high with a maximum 50 mm (2 inch) backset could pass. 
We are also proposing requirements using a 50th percentile male test 
dummy at all outboard seating positions.
    In their comments to the agencies 1996 Technical Report discussed 
in Section II.B, Volvo favored the elimination of the dynamic test 
option. It believed that there was insufficient knowledge about injury 
mechanisms and that test dummies needed to be improved. However, Volvo 
has developed a seat design to specifically reduce whiplash injuries, 
indicating that it believes that it has enough knowledge to change the 
way it designs seats. In their comments to the Technical Report, 
Chalmers supported a dynamic test using either a BioRID or Hybrid III 
dummy and suggested that the Neck Injury Criterion (NIC) be used to 
evaluate performance. Chalmers also believes a dynamic test procedure 
is needed to measure the performance of active head restraints.
    There are several reasons why the agency does not wish to eliminate 
the dynamic compliance option. Some of these became apparent when NHTSA 
proposed deleting this option in 1995. In October 1995, under the 
``Regulatory Reinvention Initiative,'' the agency published an NPRM 
which proposed to eliminate the dynamic options because it believed 
neither manufacturers nor the agency used this option to determine 
compliance. Comments on the Reinvention NPRM by vehicle manufacturers 
favored deleting the options, but Advocates and recreational vehicle 
(RV) manufacturers and a seat supplier opposed the deletion because it 
would limit compliance options.
    IIHS wanted to keep the dynamic test because not having it might 
limit the development of active head restraint systems designed to 
deploy upon rear impact. For example, as noted above, the Saab 9-5 is 
equipped with active head restraints which operate by use of a 
lever.\14\ We measured a head restraint in a MY 1999 model 9-5 to 
determine its height and backset. It meets the current height 
requirement by 95 mm (3.8 inches). Therefore, there is no need for the 
manufacturer to certify to the current dynamic compliance option. 
However, the current design would not meet the requirements in this 
proposal by 6 mm (0.3 inches). However, if the proposed requirements 
were in place, the manufacturer could choose to certify to the dynamic 
compliance option.
---------------------------------------------------------------------------

    \14\ The Saab active head restraint is purely mechanical. When 
the vehicle is struck from the rear (at speeds equivalent to 16 km/h 
or greater in a crash involving a barrier), the driver and front 
seat passenger's bodies move rearward into the seat cushion. A 
padded pressure plate is moved rearward as a result, and through a 
linkage moves the head restraint upwards and forward to support the 
head. The precise activation of the system is determined by the 
force with which the driver or passenger's back is propelled against 
the backrest, the magnitude of the crash forces and the occupant's 
weight.
---------------------------------------------------------------------------

    NHTSA believes that the dynamic test option should be retained and 
upgraded. The dynamic test option provides the means to assess the many 
seat design parameters which affect whiplash reduction. However, as it 
is clear that limiting hyperextension alone does not prevent whiplash 
injury, the agency proposes to modify the dynamic test procedure by 
adopting new performance values of relative head-to-torso rearward 
rotation for determining compliance with Standard 202. The proposed 
performance requirement for front seating positions is a maximum of 12 
degrees of relative head-to-torso rotation with the 50th percentile 
dummy and a maximum of 20 degrees of head-to-torso rotation with a 95th 
percentile dummy. For rear seating positions no more than 12 degrees of 
head-to-torso rotation is permissible with a 50th percentile dummy as 
the measurement device. The current standard allows head-to-torso 
rotation of 45 degrees with a 95th percentile dummy for the front 
seating positions and does not regulate the rear seating positions.
    The proposed values were selected to be consistent with the height 
and backset requirements in the proposed static compliance option. The 
head restraints would need to comply at any position of height and 
backset adjustment when the 50th percentile dummy is used in the front 
and rear seats. The manufacturer would have the option of selecting a 
single height position for the 95th percentile dummy in the front 
seats. The key testing parameters associated with each seating position 
are shown in Table 3.

        Table 3.--Proposed Testing Parameters for Each Seating Position for the Dynamic Compliance Option
----------------------------------------------------------------------------------------------------------------
                                                             Rotation           Head restraint adjustment
         Seating position                 Dummy size          limit    -----------------------------------------
                                                              (deg.)          Backset               Height
----------------------------------------------------------------------------------------------------------------
Front.............................  50th male............           12  Any................  Any
Front.............................  95th male............           20  Any................  One *
Rear..............................  50th male............           12  Any................  Any
----------------------------------------------------------------------------------------------------------------
* Position selected at the manufacturer's option.

    The criteria were developed primarily through sled testing of a 
modified production vehicle seat. A preliminary report on the 
experimental results is available in the docket for this notice. The 
seat used was not optimized to limit head rotation, but was modified to 
allow positioning of the head restraint to specified locations and 
stiffened to eliminate seat back rotation with respect to the seat 
base. Stiffening of the seat back was believed to create a worst case 
situation for head rotation. Table 4 shows the rearward angular head-
to-torso rotation of a 50th and 95th percentile Hybrid III dummy when 
exposed to a sled acceleration such that the change in velocity was 
about 20--25 percent greater than that in both the current and proposed 
regulation. Rotation was not measured beyond 200

[[Page 986]]

milliseconds because the dummy torso has rebounded away from the seat 
at that point in time. The backset values listed were as measured by 
the ICBC device prior to testing.

 Table 4.--50th and 95th Percentile Male Hybrid III Dummy Maximum Head-to-Torso Rotation (deg.) as a Function of
                                        Head Restraint Backset and Height
----------------------------------------------------------------------------------------------------------------
                                                                       Backset
                                   -----------------------------------------------------------------------------
              Height                      0 mm (0 in.)              50 mm (2 in.)            100 mm (4 in.)
                                   -----------------------------------------------------------------------------
                                        50th         95th         50th         95th         50th         95th
----------------------------------------------------------------------------------------------------------------
750 mm (29.5 in.).................           11         * 25           18           45           41           61
800 mm (31.5 in.).................         * 13         * 20           23           34           44          56
----------------------------------------------------------------------------------------------------------------
* Maximum value prior to 200 ms after start of acceleration.

    The sled test data for the 50th percentile dummy show that the 750 
mm (29.5 inches) high head restraint had lower head rotation than the 
800 mm (31.5 inches) high restraint. This may have been because of the 
shape of the head restraint caused the dummy head to contact the head 
restraint above the rearmost portion of the head. Thus, the tested head 
restraint was more optimally fit to the 50th percentile dummy head when 
positioned at a height of 750 mm (29.5 inches). This phenomenon 
illustrates why the proposed regulation would also specify the use of a 
95th percentile male dummy. If only the 50th dummy were specified, 
complying head restraints could have heights of no more than 750 mm 
(29.5 inches). This would be inconsistent with the static height 
requirement of 800 mm (31.5 inches) for front seats. The agency 
believes that compliance with performance requirements with both the 
50th and 95th percentile dummies is needed to assure that all occupants 
in the front seating positions up to and including the tallest are 
protected. To be consistent with the rear seat static requirement, 
where only a minimum height of 750 mm (29.5 inches) required, only the 
50th percentile dummy is specified for rear seat dynamic compliance.
    Based on the sled testing, the agency believes that head restraints 
800 mm (31.5 inches) high with a backset of 50 mm (2 inches) could 
restrict head-to-torso rearward rotation of a 95th percentile dummy to 
20 degrees in the proposed dynamic test. Similarly, head restraint at 
least 750 mm (29.5 inch) high with a 50 mm (2 inch) backset could 
restrict head-to-torso rearward rotation of a 50th percentile dummy to 
12 degrees. The proposed performance values are as shown in Table 3.
    In selecting performance criteria for the dynamic compliance 
option, the agency's goal was to provide a level of safety similar to 
that provided by the static requirements and provide a method of 
compliance appropriate for both static and active head restraint 
designs. Although the modified seat tested by the agency had greater 
head-to-torso rotation than the proposed performance values in some of 
the head restraint positions that are proposed for the static 
compliance option, the agency believes these test data provide insight 
into the worst case head-to-torso rotation at each head restraint 
position tested. As stated above, this was partially due to the rigid 
nature of the seat back, which provided very firm restraint to the 
dummy torso and therefore accentuated the effect of any gap between the 
dummy head and the head restraint. It was also due to the sled pulse 
velocity change being 20-25 percent greater than the target of 17.3 kph 
in about the same time period. Finally, the method used to attach the 
head restraint to the seat back, which in some situations allowed 
significant movement of the head restraint when in contact with the 
dummy head, added to head-to-torso rotation. As an example of this 
movement, when the 95th male dummy was tested at the 800 mm (31.5 inch) 
high and 50 mm (2 inch) backset head restraint position, the dummy head 
rotated an additional 10 degrees after the head restraint began to 
deform due to contact with the dummy head. A similar situation occurred 
at the 750 mm (29.5 inch) high and 50 mm (2 inch) backset head 
restraint position when the 50th percentile dummy was tested. 
Therefore, the agency believes that it would be practicable for 
manufacturers to achieve head-to-torso rotations below those proposed 
when tested within the proposed acceleration corridor.
    The agency plans to perform additional sled tests before the 
publication of the final rule to assure that the head rotation 
performance values selected are appropriate.
    The agency considered performance criteria other than head rotation 
for the dynamic compliance options. These included Nij, 
which is a combination of upper neck moments and forces introduced in 
the Advanced Air Bag Rulemaking (Docket NHTSA-98-4405); NIC, which was 
developed by Chalmers University and has been used by IIHS in testing 
active head restraints; and individual values of force, moment and 
acceleration. In the absence of generally accepted injury criteria 
specifically applicable to whiplash injuries, the agency must still 
assume that a head restraint's ability to prevent whiplash is primarily 
due to its ability to prevent the rearward translation and rotation of 
the occupant's head with respect to the torso. The sled tests showed 
that rearward head rotation seemed to correlate to head restraint 
position. Other biomechnics researchers have found a similar 
correlation and used head-to-torso rotations for the evaluation of 
whiplash injury.\15\ Such a correlation indicates there are similar 
safety benefits between the dynamic and static requirements of the 
proposed regulation. The agency is willing to reconsider the dynamic 
performance criteria when more advanced whiplash injury criteria become 
available.
---------------------------------------------------------------------------

    \15\ Geigl et al. (1994) The Movement of Head and Cervical Spine 
During Rear-end Impact. IRCOBI, pp 127-137.
---------------------------------------------------------------------------

    The agency requests comments on:

    27. Are the performance criteria and values tentatively selected 
for the dynamic performance option the most appropriate criteria and 
values?
    28. Should a limit also be placed on forward head rotation or 
neck loading so that any potential negative effects of active head 
restraints would be minimized?

    In the current standard the dynamic test procedure specifies only a 
95th percentile dummy, but not the specific type. This proposal 
rectifies this ambiguity by proposing the use of the Hybrid III 50th 
and 95th percentile dummy. The 95th percentile male dummy is not 
currently incorporated in 49 CFR Part 572, Anthropomorphic Test

[[Page 987]]

Devices. However, we anticipate issuing an NPRM to incorporate this 
dummy into 49 CFR Part 572 within 12 to 18 months, which will probably 
be several years prior to the proposed effective date of the upgraded 
Standard 202.
    The positioning procedure for the 95th Hybrid III dummy is 
essentially the same as for the 50th Hybrid III except for the 
positioning of dummy's H-point in reference to the seat H-point. The 
offset specified is 9 mm (0.35 inches) above and 15 mm (0.60 inches) 
forward of the seat H-point.
    NHTSA is aware of criticism that the 50th percentile Hybrid III 
neck lacks sufficient biofidelity to be a useful tool for rear impact 
testing and, since it is likely to be very similar in design, the same 
criticism could be extended to the 95th percentile dummy neck. NHTSA is 
also aware of a newly developed test device, BioRID,\16\ which purports 
to more accurately models the human neck, and of a recent paper by Ford 
(SAE 973342) which argues that the 50th percentile Hybrid III neck is 
sufficiently biofidelic in the rearward direction. The agency is likely 
to revisit both the dynamic performance values and the proposed test 
device as more advanced dummies are developed and as injury criteria 
based on human studies achieve broader consensus. The agency would like 
commenters to address the following issues related to the test dummy 
selected for the dynamic compliance option:
---------------------------------------------------------------------------

    \16\ BioRID stands for Biofidelic Rear Impact Dummy. It was 
developed by a consortium of Chalmers University of Technology in 
Sweden, Autoliv, Saab and Volvo to help safety engineers evaluate 
the relative motion of the head and torso in rear crashes. BioRID 
has a flexible spine with 24 vertebra-like segments, the same number 
as in the human spine. It has joints that allow for forward and 
backward movement of the head, and integrates spring-loaded cables 
that simulate the action of human neck muscles. Its spine is said to 
interact with vehicle seats in a more humanlike way than the Hybrid 
III's rigid spine. Further, its neck is capable of producing the S-
shape observed in human necks during rear crashes.

    29. Should the agency consider the use of the 5th percentile 
female in addition to the 50th and 95th percentile male dummies in 
the dynamic test or is it reasonable to assume that designs which 
are adequate for the 50th and 95th males will be adequate for the 
5th female?
    30. Which advanced dummy neck designs should be considered for 
future use in the dynamic test and are they likely to be available 
prior to the effective date of the proposal?

    Currently, the dynamic compliance test option requires only that 
the head rotation criteria be met. The agency is now proposing that, in 
addition to head rotation, a Head Injury Criterion (HIC) (15 ms) limit 
of 150 must not be exceeded. We are proposing a 15 ms HIC window to be 
consistent with the new HIC criterion in Standard 208. The HIC level of 
150 is associated with a 1.1 to 4.3 percent probability of moderate 
(MAIS 2+) head injury. It is the agency's view that inclusion of this 
requirement would serve as an equivalent to the 80g energy absorption 
limit found in the static test option.
    NHTSA has tentatively concluded that the addition of the HIC 
requirement to the dynamic compliance option would not place an undue 
burden on manufacturers while ensuring that head restraints certified 
to this option have adequate impact absorption characteristics. The HIC 
values measured in sled testing of a modified production vehicle seat 
are shown in Table 5. The greatest HIC value in Table 5 is for the 50th 
percentile dummy with a head restraint position of 50 mm (2 inches) of 
backset and 750 mm (29.5 inches) of height. This HIC of 157 exceeds the 
proposed limit of 150. However, the sled pulse for this test had a 
velocity change of 4.3 kph (25 percent) greater than the proposed 
velocity change of 17.3 kph and, as mentioned previously the head 
restraint was not optimized in any way. The agency believes that for a 
more optimally designed head restraint tested within the proposed 
acceleration corridor the 150 HIC limit can be met without great 
difficulty and is needed to provide assurance that head restraints will 
be sufficiently padded.

    31. The agency solicits comments on the proposed HIC 15 limit of 
150. Should a different upper limit be specified? Should a 36 ms 
window be used? If so, should the maximum allowable HIC value be 
increased?


 Table 5.--50th and 95th Percentile Male Hybrid III Dummy Maximum Head-to-Torso Rotation (deg.) as a Function of
                                        Head Restraint Backset and Height
----------------------------------------------------------------------------------------------------------------
                                                                       Backset
                                   -----------------------------------------------------------------------------
              Height                      0 mm (0 in.)              50 mm (2 in.)            100 mm (4 in.)
                                   -----------------------------------------------------------------------------
                                        50th         95th         50th         95th         50th         95th
----------------------------------------------------------------------------------------------------------------
750 mm (29.5 in.).................           11         * 25           18           45           41           61
800 mm (31.5 in.).................         * 13         * 20           23           34           44           56
----------------------------------------------------------------------------------------------------------------

    The agency believes that head restraints certified to the dynamic 
compliance option should also be required to meet the head restraint 
width provisions proposed for the static test. These provisions require 
that head restraints be at least 170 mm (6.7 inches) wide on single 
seats and 254 mm (10 inches) wide on bench seats. The agency notes that 
because the motion of the sled used in the dynamic test is unimodal--in 
a single longitudinal direction--the proposed test would not address 
the performance of head restraints in off-axis impacts.
    The proposed width requirements are the only dimensional criteria 
offered for inclusion in the dynamic test option. The agency believes 
that the gap limits proposed in the static test option are not 
necessary, as head rotation limits would be exceeded if gap sizes were 
excessive. NHTSA is, however, soliciting comments relating to certain 
aspects of the proposed dynamic test option:

    32. Is the head restraint width requirement appropriate for the 
dynamic compliance option? Should any of the other dimensional 
requirements used in the static test option be inserted into the 
dynamic test requirements?

V. Interim Compliance Options Before Upgraded Requirements Become 
Mandatory

    The August 13, 1997 petition submitted by AAMA/AIAM urged NHTSA to 
consider compliance with European head restraint regulations to be 
functionally equivalent to compliance with the current Standard 202. 
There are three European regulations applicable to head restraints--EEC 
96/37/EU, promulgated by the European Union, and ECE 17.05, and ECE 
25.04, both issued by the Economic Commission for Europe. Of these 
three regulations, both 96/37/EU

[[Page 988]]

and ECE 17.05 are applicable to seats and seat backs, but incorporate 
the head restraint provisions found in ECE 25. Each establishes a 
performance requirement for energy absorption which is slightly more 
stringent than that now in Standard 202. Further, the requirements for 
height, allowable gaps, rear seat head restraints, energy absorption 
and the procedure for rearward displacement testing are identical to 
those now being proposed by NHTSA for incorporation in Standard 202. 
However, the agency's proposal contains backset requirements and 
adjustment retention lock provisions not found in the European 
regulations and retains the existing minimum width provisions currently 
incorporated into Standard 202. The European regulations also do not 
contain a separate width requirement for bench seats found in the 
current version of Standard 202 and specify a slightly smaller minimum 
width for head restraints for non-bench seats.
    NHTSA's policies and procedures for evaluating the functional 
equivalence of foreign safety standards are contained in Appendix B of 
49 CFR Part 553, the agency's rulemaking procedures, published in the 
Federal Register on May 13, 1998 (63 FR 26508). Under the policy and 
procedures enunciated in that final rule, a determination by this 
agency that a foreign standard is functionally equivalent to a 
counterpart U.S. standard is dependent upon this agency's concluding 
that the functional performance or safety benefits associated with 
compliance with the foreign standard is at least as great as those 
associated with the current U.S. standard.
    The first step in the procedures is the determination of whether 
the U.S. regulation and the foreign directive are intended to address 
the same safety problem. In the instant case, ECE 25 and Standard 202 
are intended to address neck and other injuries to occupants in rear 
impacts. Having identified both standards as addressing the same safety 
need, the agency then performed further analysis.
    Under the agency's procedures, the next step in evaluating 
functional equivalence is a comparison of the requirements, test 
conditions and test procedures found in the two standards. If the 
differences between the two standards are not insignificant, the next 
step involves the examination of the real world safety data to examine 
the relative benefits of the two standards. If this safety data show 
the foreign standard offers greater benefits, the agency will begin 
rulemaking to upgrade the U.S. standard to the level of the foreign 
standard or beyond. If the real world data show the performance of the 
two standards to be equal, the agency may initiate rulemaking to add 
the foreign standard as an alternative means of compliance.
    NHTSA recognizes that the differences in requirements, test 
conditions, and test procedures between the U.S. regulation and the ECE 
25 may have safety consequences. Therefore, the agency must make some 
effort to compare the relative benefits and effectiveness of each 
regulation. The preferred means of determining if foreign standard 
produces at least as much benefit are real world crash data from some 
vehicles meeting one standard and from other vehicles meeting the other 
standard.
    When an attempt was made to examine crash data to compare the 
relative benefits of Standard 202 and ECE 25, NHTSA determined that the 
crash data available relating to the actual performance of ECE 25 was 
not sufficient to allow the agency to draw any meaningful conclusions. 
Similarly, the agency has determined that since ECE 25 and Standard 202 
compliance data are primarily dimensional in nature, these data are not 
useful in comparing the relative safety benefits of each.
    Completion of this initial phase of data analysis placed NHTSA at a 
major decision point in the functional equivalence process (i.e., Are 
there sufficient data to assess the functional equivalency of the two 
standards? If not, could additional research be conducted to generate 
data?). Rather than embarking on a research program of its own, the 
agency surveyed existing biomedical and safety research to determine if 
this information could be used to assess the relative merits of ECE 25 
and the existing provisions of Standard 202.
    As noted above, there is a general consensus in the safety and 
biomedical community that head restraints that are both higher and 
closer to the head offer increased protection against whiplash injuries 
in rear impacts. ECE 25 specifies a greater minimum height which is 50 
mm (2 inches) greater than the height that must currently be achieved 
in Standard 202. That difference suggests that compliance with ECE 25 
provides greater safety benefits than the existing provisions of 
Standard 202. Also, the maximum height that must be achieved in ECE 25 
is 100 mm (4 inches) greater than that required by Standard 202. ECE 25 
differs from the existing version of Standard 202 in ways other than 
height requirements. Standard 202 currently does not require head 
restraints for rear seating positions or contain any requirements for 
energy absorption. ECE 25 contains requirements for energy absorption 
and applies to head restraints in rear seating positions.
    Therefore, the agency has tentatively concluded that ECE 25 offers 
greater safety benefits than the existing version of Standard 202 under 
the functional equivalence process defined in Part 553, Appendix B. 
Therefore, the agency is proposing that in the period between 90 days 
following the publication of any final rule that is derived from this 
proposal and the first occurrence of September 1, three years after 
publication of the final rule (the date on which new cars must meet the 
upgraded Standard 202 requirements), manufacturers may certify their 
vehicles using the existing ECE 25 requirements, with one exception. 
Standard 202 now requires that restraints on vehicles equipped with 
bench seats must be at least 254 mm (10 inches) wide and other seats 
must have head restraints that are 171 mm (6.75 inches) wide while ECE 
25 specify a 170 mm (6.70 inch) minimum width for all head restraints. 
The agency has tentatively concluded that the continued use of bench 
and split bench seats in vehicles manufactured for the U.S. market 
makes it necessary maintain this portion of FMVSS 202.
    The agency is not simply proposing that compliance with ECE 25 be 
considered to be the equivalent of compliance with the existing version 
of Standard 202 but is also proposing an upgrade to Standard 202. The 
proposed upgrade to Standard 202 requires the agency to make a second 
functional equivalence assessment comparing ECE 25 to the new Standard 
202. As outlined above, the agency's functional equivalence assessment 
in this case has, due to the lack of European crash and compliance test 
data, focused on existing research regarding the performance of head 
restraints in reducing whiplash injuries.
    The backset, vertical adjustment retention, and existing bench seat 
head restraint width requirements proposed for the upgrade to Standard 
202 do not have counterparts in the European regulations. In performing 
its functional equivalence assessment, NHTSA found that current 
research indicates that these requirements are important factors in the 
safety performance of head restraints. If those new requirements were 
adopted, ECE 25 could no longer be said to be equivalent to the 
upgraded Standard. Accordingly, we are not proposing to allow 
compliance with

[[Page 989]]

ECE 25 as an option after the upgraded requirements go into effect.

VI. Benefits

    In support of this rulemaking action, the agency has prepared a 
Preliminary Economic Assessment (PEA) which contains a thorough 
analysis of both the benefits and the costs of the changes this 
document proposes for Standard 202. The analysis contained in the PEA 
estimates that full implementation of the proposed changes would result 
in, on an annual basis, 9,575 fewer whiplash injuries for front seat 
occupants and 4,672 fewer whiplash injuries for rear seat occupants, 
providing a total of 14,247 fewer whiplash injuries for both front and 
rear seating positions in rear impacts.
    NHTSA estimates from National Automotive Sampling System (NASS) 
data that, between 1988 and 1996, there were 805,581 occupants with 
whiplash injuries (non-contact AIS 1 neck injuries) annually in the 
outboard seating positions of passenger cars (PCs), light trucks, and 
vans (LTVs) in police reported and unreported towaway and non-towaway 
nonrollover impacts. However, since the agency believes head restraints 
will have their greatest effectiveness in rear impacts, the benefits 
analysis will be restricted to that crash mode only. Based on this same 
1988 to 1996 NASS data, the average number of whiplash injuries in rear 
impacts annually was 272,088. The number of vehicles with head 
restraints in the rear outboard seats has increased dramatically over 
the last several years. An estimated 41 percent of the MY 1999 fleet 
have rear seat head restraints and 20 percent have no rear seat. 
Because of the increase in the numbers of rear seat head restraints, it 
is estimated that for the 1999 model year the total population of 
whiplash injures will be 270,815 (251,035 front seat occupant injuries 
and 19,780 rear seat occupant injuries).
    The average economic cost (excluding property damage) of a whiplash 
injury in a rear impact, in 1998 dollars, is estimated to be $6,485, 
resulting in a total annual cost of approximately $1.75 billion for 
272,088 whiplash injuries. The $6,485 estimate is based on the 
assumption that the maximum injury per occupant is an AIS 1 injury. The 
agency believes that this is a reasonable assumption because very few 
occupants in the rear impact crashes used to develop our estimate had 
injuries higher than AIS 1. Further, in such impacts, a whiplash injury 
is likely to be the most costly AIS 1 injury and the longest lasting 
one.
    The characteristics of adjustable head restraints and their use 
have changed as well. A 1982 survey of adjustable head restraints 
indicated that at the lowest position in the range of adjustment, the 
lowest head restraint was 635 mm (25 inches) high. In a survey 
conducted for this rulemaking, the agency determined that, at the 
lowest position of adjustment, the lowest head restraint observed had a 
height of 712 mm (28 inches). Therefore, the lowest adjustment height 
for these restraints has increased by three inches. Examination of 
survey data for the highest position of adjustment indicates that 
adjustable head restraints are also 40 mm (1.6 inches) higher now at 
the uppermost range of adjustment than they were in 1982. At the lowest 
observed position, contemporary adjustable restraints are now 13 mm (.5 
inches) lower than integral restraints observed in 1982.
    Adjustable restraints are not only higher now than they were in 
1982, but they are also more likely to be properly adjusted. While the 
majority of adjustable head restraints are still not properly adjusted, 
agency data indicates that 47 percent of current head restraints are 
properly positioned as opposed to 27 percent in 1982.
    The agency believes that about 30 percent of all occupants involved 
in towaway rear impacts receive a whiplash injury. However, injury 
rates do not appear to vary significantly between integral and 
adjustable head restraints. The changes in head restraint 
configurations and use discussed above may explain why. The data 
available for front and rear head restraints combined are not 
sufficient to make statistically valid comparisons between restraint 
and vehicle types. This data indicated that the average whiplash injury 
rate for passenger cars with integral head restraints (31.75 per 
hundred occupants in towaway rear impacts) was higher than the whiplash 
injury rate (27.99 per hundred) for adjustable head restraints. For 
LTVs, the data indicated that the average whiplash rate (30.57 per 
hundred) for adjustable head restraints was slightly higher than the 
whiplash injury rate (30.53 per hundred) for integral head restraints. 
Comparing integral restraints by vehicle type shows that the injury 
rate for cars (31.75 per hundred) exceeds that for trucks (30.53 per 
hundred) while for adjustable head restraints, the rate for cars is 
lower (27.99 per hundred) than it is for trucks (30.57 per hundred).
    Two sets of data were statistically significant for front occupants 
only and indicate that integral restraints are performing differently 
in cars and trucks and in trucks depending on occupant height. For 
shorter occupants of front outboard seats, the injury rate for trucks 
with integral restraints was much lower (17.14 per hundred) than the 
rate for cars (37.94 per hundred). When comparing short drivers with 
taller drivers in trucks with integral restraints, the taller drivers 
were injured at a much greater rate (56.71 per hundred) than the 
shorter (17.14 per hundred). This may indicate that integral head 
restraints in trucks are better positioned to perform well in 
preventing injury to short drivers and not as well in protecting tall 
drivers. Estimates of annual whiplash injury rates by vehicle and 
restraint type are shown in Table 6.

  Table 6.--Whiplash Rates for Nonrollover Rear Impacts 1988-1996 NASS
                   Annualized Data in Towaway Crashes
------------------------------------------------------------------------
 
------------------------------------------------------------------------
                    Front and Back Outboard Occupants
------------------------------------------------------------------------
Vehicle Type:                                     Integral    Adjustable
    Car......................                         31.75        27.99
    Truck....................                         30.53        30.57
Head Restraint Type:                                   Car:       Truck:
    Integral.................                         31.75        30.53
    Adjustable...............                         27.99        30.57
------------------------------------------------------------------------
                           Front Outboard Only
------------------------------------------------------------------------
Vehicle Type:                  Occupant           Integral    Adjustable
                                Height:
    Car......................      Short......        37.94        31.00

[[Page 990]]

 
    Car......................      Tall.......        35.72        28.04
Vehicle Type:                  Head Restraint      Short         Tall
                                Type:
    Car......................      Integral...        37.94        35.72
    Car......................      Adjustable.        31.00        28.04
Vehicle Type:                  Occupant           Integral    Adjustable
                                Height:
    Truck....................      Short......        17.14        20.65
    Truck....................      Tall.......        56.71        30.19
Vehicle Type:                  Head Restraint        Short:        Tall:
                                Type:
    Truck....................      Integral...        17.14       *56.71
    Truck....................      Adjustable.        20.65        30.19
Head Restraint Type:           Occupant             Car         Truck
                                Height:
    Integral.................      Short......        37.94       *17.14
    Integral.................      Tall.......        35.72        56.71
    Adjustable...............      Short......        31.00        20.65
    Adjustable...............      Tall.......        28.04       30.19
------------------------------------------------------------------------
* Difference is significant at 0.05.

    NHTSA estimates that the present fleet of vehicles has an average 
front seat outboard head restraint maximum height of 768 mm (30.2 
inches), which is 32 mm (1.3 inches) less than the proposed minimum 
height capability of 800 mm (31.5 inches). As outlined in the PEA, the 
agency believes that raising the height of the front seat outboard head 
restraint from the present average to 800 mm (31.5 inches) will result 
in a 1.1 percentage point increase in effectiveness for all rear impact 
injuries and a 1.83 percentage point increase for whiplash injuries 
alone.
    In examining the effectiveness of the proposed changes, the agency 
considered the differences between integral and adjustable head 
restraints. For integral head restraints and those adjustable head 
restraints properly adjusted in the fully up position (which the agency 
estimates would be 53 percent of such restraints), the average increase 
in effectiveness would be a 1.68 percentage points. For the remaining 
percentage of adjustable head restraints, the 47 percent that would be 
adjusted in the lowest adjustment position, we estimated that the 
proposed minimum height of 750 mm (29.5 inches) would result in a 3.50 
percentage point increase in effectiveness for all rear impact injuries 
and 5.83 percentage point increase in effectiveness for whiplash 
injuries.
    Calculating the benefits of the proposed requirements for rear seat 
head restraints poses several challenges. The baseline heights of rear 
seats are different than those of front seats. In addition, rear seats 
are less frequently occupied. When they are occupied, the occupant is 
often a child. The present fleet also includes vehicles with and 
without rear seat head restraints.
    Agency survey data indicate that, in vehicles with rear seat head 
restraints, the average lowest head restraint height is 653 mm (25.7 
inches), which is 97 mm (3.8 inches) lower than the proposed minimum 
height of 750 mm (29.5 inches). In models with rear seat adjustable 
head restraints, the average head restraint height is 655 mm (25.8 
inches) and the average seatback height in vehicles without rear seat 
head restraints is 650 mm (25.6 inches). As outlined in the PEA, an 
increase in head restraint height from 25.7 inches to the 29.5 inches 
for front seats would increase effectiveness by 12.35 percentage 
points. After correcting for the different occupancy rates and occupant 
heights in rear seats, the average effectiveness for the rear seat 
would be 13 percent.
    Taking into account the differing degrees of effectiveness for each 
type of head restraint available for front seat occupants, i.e., 
integral, adjustable in the highest position, and adjustable in the 
lowest position, the agency estimates that the increase in minimum head 
restraint height for integral head restraints would result in 1,588 
fewer injuries per year. For adjustable head restraints adjusted to the 
highest position, it is anticipated that the proposed increase in 
minimum height would result in 1,959 fewer front seat occupant injuries 
per year. Reductions in injuries for adjustable head restraints in the 
lowest position would be 6,028 front seat occupant injuries annually. 
The total reduction in injuries attributable to the proposed front seat 
head restraint requirements would be 9,575 fewer injuries per year.
    For the rear seat, the proposed head restraint requirement, which 
would require head restraints to be installed at locations where they 
were not previously required, would result in 4,642 fewer injuries per 
year.
    Adding the benefits from the rear seat requirements to those 
calculated for the front seat results in rear impact crashes alone a 
total reduction of 14,247 whiplash injuries each year.
    The agency has not prepared an analysis of the potential benefits 
of two other new requirements contained in this proposal--the backset 
requirement and the adjustment lock requirement. It should be noted 
that while there is a general consensus among safety researchers that a 
smaller backset will result in a reduction of injuries, NHTSA has not 
yet developed a methodology for quantitatively assessing this benefit. 
Similarly, the benefits of adding a height locking requirement have 
also not been calculated. The agency has not determined how many 
vehicles in the current fleet have height locks for their head 
restraints. Therefore, a baseline for calculating benefits has not been 
developed. Further, the benefits of such locks will depend entirely on 
the rate at which they are employed. As NHTSA does not have access to 
such data at this time, no estimation of the benefits of the height 
lock requirement has been prepared.

VII. Costs

    In estimating the costs of the proposed requirements, the agency 
relied on a 1992 NHTSA tear down study of a variety of vehicles. As 
outlined in the PEA, this study, adjusted to 1998 dollar values, 
revealed that the sales weighted average cost of integral head 
restraints is $30.12 per restraint. The same analysis applied to 
adjustable head restraints indicated an average cost of $29.13 per 
restraint. The average cost for both adjustable and integral is $29.44 
per restraint. As the proposal contains provisions requiring that head 
restraints be higher than the existing ones in the front and rear 
seats, we used data from the 1992 study also to calculate the cost per 
inch of head restraint. Using the same tear-down study and 
distinguishing between

[[Page 991]]

integral and adjustable head restraints, the agency calculated a cost 
per inch of $1.40 for integral head restraints and $1.46 per inch for 
adjustable head restraints. As these calculations indicated little 
difference in cost between integral and adjustable head restraints, the 
agency estimated that the sales weighted average cost per inch of head 
restraints for all restraints, in 1998 dollars, was $1.54. In 
determining the overall cost of compliance with the proposed 
regulations both in situations where existing head restraints must be 
raised or a head restraint must be added to the rear seat, we have 
tentatively concluded that an average cost of $1.54 per additional inch 
of head restraint height is appropriate.
    To evaluate the cost of the proposed minimum height requirements, 
NHTSA assumed that the cost increase associated with this new 
requirement is the cost of increasing the highest head restraint 
position up to 800 mm (31.5 inches) in the front seat or to 750 mm 
(29.5 inches) in the rear seat. As we believe that the cost of head 
restraints would be very similar for adjustable and integral head 
restraints, we assume that the true cost would be to raise the highest 
height of the head restraint and that changes in design, at no 
additional variable cost, could be accomplished to comply with the 
minimum height requirements.
    The agency believes that the backset requirements would not add 
cost to the vehicle. There would be some redesign costs to both 
increase the height and reduce the backset, but the agency believes 
that the backset requirement is a design change that could be 
implemented at the same time as height is increased, with no increase 
in head restraint cost.
    Light vehicle sales in the U.S. totaled 15.55 million units in 
1998. There were 8.14 million car sales and 7.40 million truck sales in 
the U.S. in 1998. All of these vehicles would be required to have 
higher front seat head restraints. The cost of raising front seat head 
restraints would be $4.21 per vehicle, resulting in a fleet cost of 
$65.5 million. In regard to rear seats without head restraints, raising 
the seat back to create an integral restraint would cost $12.34 per 
vehicle, resulting in a fleet cost of $74.8 million. Raising the rear 
seat head restraints in vehicles already equipped with rear head 
restraints costs $3.61 per vehicle, resulting in a fleet cost of $19.6 
million. There would be a small cost to add locking mechanisms to those 
head restraints that do not currently have such mechanisms. Our studies 
indicate that approximately half of the existing fleet with adjustable 
head restraints has locking mechanisms. Adding locking mechanisms to 
the rest of the fleet with adjustable head restraints at a cost of 
$0.15 per vehicle is projected to result in costs of $3.3 million for 
front seat restraints and $2.6 million for rear seats for a combined 
total is $5.9 million. The total estimated costs of the vehicle changes 
that would be required by this proposal would be $160.5 million ($65.5 
million for the front seat and $95.0 million for the rear seat).

VIII. Effective Date

    As noted above, the agency is proposing two amended versions of 
Standard 202. The first version would become effective 90 days after 
issuance of the final rule. It would allow three options for 
compliance. The first option would be compliance with the requirements 
of the existing Standard 202. The second option would allow 
manufacturers to comply with the requirements of ECE 25 as supplemented 
by the current width requirements. The third option would allow 
manufacturers to comply with the new upgraded Standard 202 
requirements, which would apply to vehicles manufactured on or after 
the first occurrence of September 1, three years after the publication 
of the final rule, before that date. Between the effective date of the 
final rule and August 31, 2004, manufacturers may choose one of the 
foregoing three options when certifying their vehicles. However, the 
election of the option used by the manufacturer in certifying the 
vehicle, including the choice between the static and dynamic test 
options, must be made at or before the time of certification, and the 
manufacturer may not thereafter rely on any other test option to 
establish compliance.
    The agency is proposing that compliance with the upgraded version 
of the standard become mandatory on the first occurrence of September 
1, three years after publication of the final rule. NHTSA believes that 
this date will provide manufacturers with sufficient leadtime to 
redesign seats and seating systems in production vehicles and to 
incorporate new elements of head restraint design in new models.

IX. Rulemaking Analyses and Notices

A. Executive Order 12866 and DOT Regulatory Policies and Procedures

    NHTSA has considered the impact of this rulemaking action under 
Executive Order 12866 and the Department of Transportation's regulatory 
policies and procedures. This rulemaking document was reviewed by the 
Office of Management and Budget under Executive Order 12866, 
``Regulatory Planning and Review.'' The rulemaking action has been 
determined to be economically significant. NHTSA is placing in the 
public docket a Preliminary Economic Assessment (PEA) describing the 
costs and benefits of this rulemaking action. The costs and benefits 
are summarized earlier in this document.

B. Regulatory Flexibility Act

    NHTSA has considered the effects of this rulemaking action under 
the Regulatory Flexibility Act (5 U.S.C. 601 et seq.) I hereby certify 
that the proposed amendment would not have a significant economic 
impact on a substantial number of small entities.
    The proposed rule would affect motor vehicle manufacturers, 
alterers, and seating manufacturers.
    NHTSA estimates that there are only about four small passenger car 
and light truck manufacturers in the United States. These manufacturers 
serve a niche market. The agency believes that small manufacturers 
manufacture less than 0.1 percent of total U.S. passenger car and light 
truck production per year.
    There are about 30 seating manufacturers in the U.S. Many of these 
are small businesses. The proposed rule would affect these small 
businesses by changing the requirements for head restraints. Raising 
the height of and integral seat or of an adjustable head restraint is 
not a new or novel idea. The agency does not believe that this will 
have a significant impact on these manufacturers.
    NHTSA notes that final stage vehicle manufacturers and alterers 
could also be affected by this proposal. Many final stage manufacturers 
and alterers install supplier constructed seating systems in vehicles 
they produce. The proposal would not have any significant effect on 
final stage manufacturers or alterers, however, since the seats they 
purchase should be tested and certified by the seat manufacturer.
    Small organizations and small governmental units would not be 
significantly affected since the potential cost impacts associated with 
this proposed action should only slightly affect the price of new motor 
vehicles.
    For the reasons discussed above, the small entities that would most 
likely be affected by this proposal are small vehicle manufacturers, 
seating manufacturers, final stage manufacturers and alterers.
    The agency believes, further, that the economic impact on these 
manufacturers would be small. While the small vehicle manufacturers 
would face additional compliance costs, the

[[Page 992]]

agency believes that seating manufacturers would likely provide much of 
the engineering expertise necessary to meet the new requirements. 
Raising the height of a head restraint is not a new or novel 
engineering task. However, doing so for many makes and models at the 
same time could present a challenge. The agency also notes that, in the 
unlikely event that a small vehicle manufacturer or alterer did face 
substantial economic hardship, it could apply for a temporary exemption 
for up to three years. See 49 CFR Part 555. It could subsequently apply 
for a renewal of such an exemption. However, the agency requests 
comments concerning:

    32. The economic impact of the proposed rule on small vehicle 
manufacturers, seating manufacturers, final stage manufacturers and 
vehicle alterers.

    Additional information concerning the potential impacts of the 
proposed requirements on small entities is presented in the PEA.

C. National Environmental Policy Act

    NHTSA has analyzed this proposal for the purposes of the National 
Environmental Policy Act. The agency has determined that implementation 
of this action would not have any significant impact on the quality of 
the human environment.

D. Executive Order 13132 (Federalism)

    The agency has analyzed this rulemaking in accordance with the 
principles and criteria contained in Executive Order 13132 and has 
determined that it does not have sufficient federalism implications to 
warrant consultation with State and local officials or the preparation 
of a federalism summary impact statement. The final rule has no 
substantial effects on the States, or on the current Federal-State 
relationship, or on the current distribution of power and 
responsibilities among the various local officials.

E. Unfunded Mandates Act

    The Unfunded Mandates Reform Act of 1995 requires agencies to 
prepare a written assessment of the costs, benefits and other effects 
of proposed or final rules that include a Federal mandate likely to 
result in the expenditure by State, local or tribal governments, in the 
aggregate, or by the private sector, of more than $100 million annually 
(adjusted for inflation with base year of 1995). This assessment is 
included in the PEA.

F. Civil Justice Reform

    This proposal would not have any retroactive effect. Under 49 
U.S.C. 21403, whenever a Federal motor vehicle safety standard is in 
effect, a State may not adopt or maintain a safety standard applicable 
to the same aspect of performance which is not identical to the Federal 
standard, except to the extent that the state requirement imposes a 
higher level of performance and applies only to vehicles procured for 
the State's use. 49 U.S.C. 21461 sets forth a procedure for judicial 
review of final rules establishing, amending or revoking Federal motor 
vehicle safety standards. That section does not require submission of a 
petition for reconsideration or other administrative proceedings before 
parties may file suit in court.

G. National Technology Transfer and Advancement Act

    Under the National Technology Transfer and Advancement Act of 1995 
(NTTAA)(Public Law 104-113), ``all Federal agencies and departments 
shall use technical standards that are developed or adopted by 
voluntary consensus standards bodies, using such technical standards as 
a means to carry out policy objectives or activities determined by the 
agencies and departments.'' This action proposes to modify performance 
requirements for head restraints to allow, on an interim basis, 
compliance with either U.S. or ECE requirements. After the end of the 
interim period, head restraints must comply with the proposed U.S. 
requirements. Certain technical standards developed by the Society of 
Automotive Engineers (SAE) and other bodies have been incorporated into 
this proposal but the overall need for safety precludes, in NHTSA's 
view, the adoption of such voluntary standards as a substitute for this 
proposal.

H. Paperwork Reduction Act

    This rule does not contain any collection of information 
requirements requiring review under the Paperwork Reduction Act of 1995 
(Public Law 104-13).

X. Submission of Comments

How Can I Influence NHTSA's Thinking on This Proposed Rule?

    In developing this proposal, we tried to address the concerns of 
all our stakeholders. Your comments will help us improve this rule. We 
invite you to provide different views on options we propose, new 
approaches we haven't considered, new data, how this proposed rule may 
affect you, or other relevant information. We welcome your views on all 
aspects of this proposed rule, but request comments on specific issues 
throughout this notice. We grouped these specific requests near the end 
of the sections in which we discuss the relevant issues. Your comments 
will be most effective if you follow the suggestions below:
     Explain your views and reasoning as clearly as possible.
     Provide solid technical and cost data to support your 
views.
     If you estimate potential costs, explain how you arrived 
at the estimate.
     Tell us which parts of the proposal you support, as well 
as those with which you disagree.
     Provide specific examples to illustrate your concerns.
     Offer specific alternatives.
     Refer your comments to specific sections of the proposal, 
such as the units or page numbers of the preamble, or the regulatory 
sections.
     Be sure to include the name, date, and docket number with 
your comments.

How Do I Prepare and Submit Comments?

    Your comments must be written and in English. To ensure that your 
comments are correctly filed in the Docket, please include the docket 
number of this document in your comments.
    Your comments must not be more than 15 pages long. (49 CFR 553.21). 
We established this limit to encourage you to write your primary 
comments in a concise fashion. However, you may attach necessary 
additional documents to your comments. There is no limit on the length 
of the attachments.
    Please submit two copies of your comments, including the 
attachments, to Docket Management at the address given above under 
ADDRESSES.
    Comments may also be submitted to the docket electronically by 
logging onto the Dockets Management System website at http://dms.dot.gov. Click on ``Help & Information'' or ``Help/Info'' to obtain 
instructions for filing the document electronically.

How Can I Be Sure That My Comments Were Received?

    If you wish Docket Management to notify you upon its receipt of 
your comments, enclose a self-addressed, stamped postcard in the 
envelope containing your comments. Upon receiving your comments, Docket 
Management will return the postcard by mail.

How Do I Submit Confidential Business Information?

    If you wish to submit any information under a claim of 
confidentiality, you

[[Page 993]]

should submit three copies of your complete submission, including the 
information you claim to be confidential business information, to the 
Chief Counsel, NHTSA, at the address given above under FOR FURTHER 
INFORMATION CONTACT. In addition, you should submit two copies, from 
which you have deleted the claimed confidential business information, 
to Docket Management at the address given above under ADDRESSES. When 
you send a comment containing information claimed to be confidential 
business information, you should include a cover letter setting forth 
the information specified in our confidential business information 
regulation. (49 CFR Part 512.)

Will the Agency Consider Late Comments?

    We will consider all comments that Docket Management receives 
before the close of business on the comment closing date indicated 
above under DATES. To the extent possible, we will also consider 
comments that Docket Management receives after that date. If Docket 
Management receives a comment too late for us to consider it in 
developing a final rule (assuming that one is issued), we will consider 
that comment as an informal suggestion for future rulemaking action.

How Can I Read the Comments Submitted by Other People?

    You may read the comments received by Docket Management at the 
address given above under ADDRESSES. The hours of the Docket are 
indicated above in the same location.
    You may also see the comments on the Internet. To read the comments 
on the Internet, take the following steps:
    (1) Go to the Docket Management System (DMS) Web page of the 
Department of Transportation (http://dms.dot.gov/).
    (2) On that page, click on ``search.''
    (3) On the next page (http://dms.dot.gov/search/), type in the 
four-digit docket number shown at the beginning of this document. 
Example: If the docket number were ``NHTSA-1998-1234,'' you would type 
``1234.'' After typing the docket number, click on ``search.''
    (4) On the next page, which contains docket summary information for 
the docket you selected, click on the desired comments. You may 
download the comments. However, since the comments are imaged 
documents, instead of word processing documents, the downloaded 
comments are not word searchable.
    Please note that even after the comment closing date, we will 
continue to file relevant information in the Docket as it becomes 
available. Further, some people may submit late comments. Accordingly, 
we recommend that you periodically check the Docket for new material.

Plain Language

    Executive Order 12866 and the President's memorandum of June 1, 
1998, require each agency to write all rules in plain language. 
Application of the principles of plain language includes consideration 
of the following questions:
     Have we organized the material to suit the public's needs?
     Are the requirements in the rule clearly stated?
     Does the rule contain technical language or jargon that 
isn't clear?
     Would a different format (grouping and order of sections, 
use of headings, paragraphing) make the rule easier to understand?
     Would more (but shorter) sections be better?
     Could we improve clarity by adding tables, lists, or 
diagrams?
     What else could we do to make the rule easier to 
understand?
    If you have any responses to these questions, please include them 
in your comments on this proposal.

List of Subjects in 49 CFR Part 571

    Imports, Motor vehicle safety, Motor vehicles.
    In consideration of the foregoing, it is proposed that 49 CFR part 
571 be amended as follows:

PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS

    1. The authority citation for part 571 of title 49 would be revised 
to read as follows:

    Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.50.

    2. Section 571.202 would be revised to read as follows:


Sec. 571.202  Standard No. 202; Head restraints.

    S1. Purpose and scope. This standard specifies requirements for 
head restraints to reduce the frequency and severity of neck injury in 
rear-end and other collisions.
    S2. Application. This standard applies to passenger cars, and to 
multipurpose passenger vehicles, trucks and buses with a GVWR of 4,536 
kg (10,000 pounds) or less manufactured before [Insert a date which is 
the first occurrence of September 1, three years after publication of 
the final rule].
    S3. Definitions.
    Head restraint means a device that limits rearward displacement of 
a seated occupant's head relative to the occupant's torso.
    S4. Requirements.
    S4.1 Each passenger car must comply with, at the manufacturer's 
option, either S4.3, S4.4 or S4.5 of this section.
    S4.2 Each truck, multipurpose passenger vehicle and bus with a GVWR 
of 4,536 kg (10,000 pounds) or less must comply with, at the 
manufacturer's option, either S4.3, S4.4 or S4.5 of this section.
    S4.3 Except for school buses, a head restraint that conforms to 
either S4.3 (a) or (b) of this section must be provided at each 
outboard front designated seating position. For school buses, a head 
restraint that conforms to either S4.3 (a) or (b) of this section must 
be provided for the driver's seating position.
    (a) It must, when tested in accordance with S5.1 of this section, 
limit rearward angular displacement of the head reference line to 45 
degrees from the torso reference line; or
    (b) It must, when adjusted to its fully extended design position, 
conform to each of the following--
    (1) When measured parallel to torso line, the top of the head 
restraint must not be less than 700 mm above the seating reference 
point;
    (2) When measured either 64 mm below the top of the head restraint 
or 635 mm above the seating reference point, the lateral width of the 
head restraint must be not less than--
    (i) 254 mm for use with bench-type seats; and
    (ii) 171 mm for use with individual seats;
    (3) When tested in accordance with S5.2 of this section, any 
portion of the head form in contact with the head restraint must not be 
displaced to more than 102 mm perpendicularly rearward of the displaced 
extended torso reference line during the application of the load 
specified in S5.2(c) of this section; and
    (4) When tested in accordance with S5.2 of this section, the head 
restraint must withstand an increasing load until one of the following 
occurs:
    (i) Failure of the seat or seat back; or,
    (ii) Application of a load of 890N.
    S4.4 Except for school buses, a head restraint that conforms to 
S4.4 (a) and (b) of this section must be provided at each outboard 
front designated seating position. For school buses, a head restraint 
that conforms to S4.4 (a) and (b) of this section must be provided for 
the driver's seating position.

[[Page 994]]

    (a) The head restraint must comply with paragraphs 6.1 through 
6.6.3, 6.8 through 6.10, 7, and 8 of the following English language 
version of the Economic Commission for Europe Regulation 25: E/ECE/324-
E/ECE/TRANS/505/Rev.1/Add.24/Rev.1, as amended by E/ECE/324-E/ECE/
TRANS/505/Rev.1/Add.24/Rev.1/Corr.1, E/ECE/324-E/ECE/TRANS/505/Rev.1/
Add.24/Rev.1/Amend.1, and E/ECE/324-E/ECE/TRANS/505/Rev.1/Add.24/Rev.1/
Amend.2. (A copy of paragraphs 2, 6.1 through 6.6.3 and 6.8 through 
6.10, 7, and 8 may be reviewed at the DOT Docket Management Facility, 
U.S. Department of Transportation, Room PL-01, 400 Seventh Street, SW., 
Washington, DC 20590-0001. Copies of E/ECE/324-E/ECE/TRANS/505, Rev.1/
Add.24/Rev.1/Amend.2, 16 April 1997 may be obtained from the ECE 
Internet site at http://www.unece.org/trans/main/wp29/wp29regs.html or 
by writing to the United Nations, Conference Services Division, 
Distribution and Sales Section, Office C.115-1, Palais des Nations, CH-
1211, Geneva 10, Switzerland); and
    (b) The head restraint must meet the width requirements specified 
in S4.3(b)(2) of this section.
    S4.5 Head restraints that comply with the requirements of 
Sec. 571.202a of this part, becoming effective on [Insert a date which 
is the first occurrence of September 1, three years after publication 
of the final rule], must be provided at each outboard designated 
seating position.
    S4.6 Whenever this standard provides an option for compliance the 
manufacturer must select the option no later than the time it certifies 
the vehicle and may not thereafter select a different option for the 
vehicle.
    S5. Demonstration procedures.
    S5.1 Compliance with S4.3(a) of this section is demonstrated in 
accordance with the following with the head restraint in its fully 
extended design position:
    (a) On the exterior profile of the head and torso of a dummy having 
the weight and seated height of a 95th percentile adult male with an 
approved representation of a human, articulated neck structure, or an 
approved equivalent test device, establish reference lines by the 
following method:
    (1) Position the dummy's back on a horizontal flat surface with the 
lumbar joints in a straight line.
    (2) Rotate the head of the dummy rearward until the back of the 
head contacts the same flat horizontal surface in paragraph (a)(1) of 
S5.1 of this section.
    (3) Position the SAE J-826 two-dimensional manikin's back against 
the flat surface in S5.1(a)(1) of this section, alongside the dummy 
with the h-point of the manikin aligned with the h-point of the dummy.
    (4) Establish the torso line of the manikin as defined in SAE 
Aerospace-Automotive Drawing Standards, sec. 2.3.6, P.E1.01, September 
1963.
    (5) Establish the dummy torso reference line by superimposing the 
torso line of the manikin on the torso of the dummy.
    (6) Establish the head reference line by extending the dummy torso 
reference line onto the head.
    (b) At each designated seating position having a head restraint, 
place the dummy, snugly restrained by a Type 2 seat belt, in the 
manufacturer's recommended design seated position.
    (c) During forward acceleration applied to the structure supporting 
the seat as described in this paragraph, measure the maximum rearward 
angular displacement between the dummy torso reference line and head 
reference line. When graphically depicted, the magnitude of the 
acceleration curve must not be less than that of a half-sine wave 
having the amplitude of 78 m/s2 and a duration of 80 
milliseconds and not more than that of a half-sine wave curve having an 
amplitude of 94 m/s2 and a duration of 96 milliseconds.
    S5.2 Compliance with S4.3(b) of this section is demonstrated in 
accordance with the following with the head restraint in its fully 
extended design position:
    (a) Place a test device, having the back plan dimensions and torso 
line (centerline of the head room probe in full back position), of the 
three dimensional SAE J826 manikin, at the manufacturer's recommended 
design seated position.
    (b) Establish the displaced torso reference line by applying a 
rearward moment of 373 Nm moment about the seating reference point to 
the seat back through the test device back pan located in paragraph 
S5.2(a) of this section.
    (c) After removing the back pan, using a 165 mm diameter spherical 
head form or cylindrical head form having a 165 mm diameter in plan 
view and a 152 mm height in profile view, apply, perpendicular to the 
displaced torso reference line, a rearward initial load 64 mm below the 
top of the head restraint that will produce a 373 Nm moment about the 
seating reference point.
    (d) Gradually increase this initial load to 890 N or until the seat 
or seat back fails, whichever occurs first.
* * * * *
    3. On [Insert a date which is the first occurrence of September 1, 
three years after publication of the final rule], Sec. 571.202(a) would 
be added to read as follows:


Sec. 571.202(a)  Standard 202; Head restraints.

    S1. Purpose and scope. This standard specifies requirements for 
head restraints to reduce the frequency and severity of neck injury in 
rear-end and other collisions.
    S2. Application. This standard applies to passenger cars, and to 
multipurpose passenger vehicles, trucks and buses with a GVWR of 4526 
kg (10,000 pounds) or less.
    S3. Definitions.
    Backset means the minimum horizontal distance between the rear of a 
representation of the head of a seated 50th percentile male occupant 
and the head restraint.
    Head restraint means a device that limits rearward displacement of 
a seated occupant's head relative to the occupant's torso.
    Height means the distance from the H-point to a point measured 
parallel to the torso reference line defined by the three dimensional 
SAE J826 (July 1995) manikin.
    Top means the point on the head restraint with the greatest height.
    S4. Requirements.
    S4.1 Except as provided in S4.3 of this section, each vehicle must 
comply with S4 of this section.
    S.4.2 Performance levels. In vehicles other than school buses, a 
head restraint that conforms to either S4.2(a) or (b) of this section 
must be provided at each outboard designated seating position. In 
school buses, a head restraint that conforms to either S4.2(a) or (b) 
of this section must be provided for the driver's seating position.
    (a) Dynamic performance and width. Each head restraint must conform 
to the following--
    (1) When tested in accordance with S5.1 of this section, during a 
forward acceleration of the dynamic test platform described in S5.1(a), 
the head restraint must--
    (i) Limit the rearward angular displacement between the dummy's 
head and torso to 12 degrees for the 50th percentile male dummy in 
front and rear seating positions and 20 degrees for the 95th percentile 
male dummy in front seating positions; and
    (ii) Limit HIC to 150, when calculated in accordance with the 
following formula:
[GRAPHIC] [TIFF OMITTED] TP04JA01.006


[[Page 995]]


    Where the term a is the resultant head acceleration expressed as a 
multiple of g (the acceleration of gravity), and t1 and t2 are any two 
points in time during the impact which are separated by not more than a 
15 millisecond time interval; and
    (2) The head restraint must have the lateral width specified in 
S4.2(b)(3) of this section.
    (b) Dimensional and static performance. Each head restraint must 
conform to each of paragraphs S4.2(b) (1) through (12) of this section:
    (1) Minimum height capability. When measured in accordance with 
S5.2(a) of this section, the top of head restraints in front seating 
positions must be capable of being positioned at a height not less than 
800 mm (31.5 inches).
    (2) Minimum height limit. When measured in accordance with S5.2(b) 
of this section, the top of the head restraint must have a height not 
less than 750 mm (29.5 inches) in any position of adjustment.
    (3) Width. When measured 64  3 mm (2.5  0.1 
inches) below the top of the head restraint, the lateral width of the 
head restraint must be not less than--
    (i) 254 mm (10 inches), in the case of head restraints on bench-
type seats; and
    (ii) 171 mm (6.75 inches), in the case of head restraints on 
individual seats.
    (4) Backset. When measured in accordance with S5.2(c) of this 
section, the head restraint backset must be not more than 50 mm (1.97 
inches), with the top of adjustable head restraints in any height 
position of adjustment between 750 mm (29.5 inches) and 800 mm (31.5 
inches).
    (5) Gaps. Except as provided in S4.2(b)(6) of this section, when 
measured in accordance with S5.3 of this section using the described 
head form, there must not be any gap greater than 60 mm (2.36 inches) 
in the front surface of the head restraint or between the front surface 
of the head restraint and the front surface of the seat.
    (6) Gaps. For adjustable head restraints, when measured in 
accordance with S5.3 of this section using the described head form, 
there must be no gap greater than 25 mm (1 inch) between the front 
surface of the head restraint and the front surface of the seat.
    (7) Energy absorption. When the front surface of the head restraint 
is impacted in accordance with S5.4 of this section by the described 
head form at any velocity up to and including 24.1 kilometers per hour 
(15 mph), the deceleration of the head form must not exceed 785 m/s\2\ 
(80g) continuously for more than 3 milliseconds.
    (8) Radius of curvature. Any portion of the front surface of the 
seat or head restraint that has a height greater than 635 mm (25 
inches) and that is outside of the impact area described in S5.4(c) of 
this section must either have a radius of curvature of not less than 5 
mm (0.2 inches) or meet the requirement of S4.2(b)(7) of this section 
when tested outside the impact area.
    (9) Height retention. When tested in accordance with S5.5 of this 
section, the lowest portion of the described head form must return to 
within 10 mm (0.4 inches) of its initial reference position after 
application of at least a 500 N (112 pound) load and reduction of the 
load to 50  1 N (11.2  0.2 pounds).
    (10) Displacement. When tested in accordance with S5.6(a) through 
(f) of this section, the rearmost portion of the described head form 
must not be displaced to more than 102 mm (4 inches) perpendicularly 
rearward of the displaced extended torso reference line during the 
application of a 373  7.5 Nm (3,300  66 inch-
pounds) moment about the H-point.
    (11) Backset retention. When tested in accordance with S5.6 of this 
section, the rearmost portion of the described head form must return to 
within 10 mm (0.39 inches) of its initial reference position after 
application of a 373  7.5 Nm (3,300  66 inch-
pounds) moment about the H-point and reduction of the moment to 37 
 0.7 Nm (327  6.5 inch-pounds).
    (12) Strength. When tested in accordance with S5.6 of this section, 
the head restraint must provide a resistance to the test device of at 
least 890 N (200 pounds).
    S4.3 Folding or retracting head restraints for unoccupied seats. A 
rear seat head restraint may be adjustable by folding or retracting to 
a position in which its minimum height is less than that specified in 
S4.2(b)(2) of this section or in which its backset is more than that 
specified in S4.2(b)(4) of this section. In any such position, the head 
restraint must meet either S4.3(a) or (b) of this section.
    (a) The head restraint must automatically return to a position in 
which its height is not less than that specified in S4.2(b)(2) of this 
section and its backset is not more than that specified in S4.2(b)(4) 
of this section when a test dummy representing a 5th percentile female 
is positioned in the seat and when a test dummy representing 50th 
percentile male is positioned in the seat and the midsagittal plane of 
the test dummy is aligned within 15 mm (0.6 inches) of the head 
restraint centerline; or
    (b) The head restraint must, when tested in accordance with S5.7 of 
this section, cause the torso reference line angle to be at least 10 
degrees closer to vertical than when the head restraint is in any 
position of adjustment in which its height is not less than that 
specified in S4.2(b)(2) of this section and its backset is not more 
than that specified in S4.2(b)(4) of this section.
    S4.4 Removability of head restraints. A front seat head restraint 
must not be removable from the seat solely by hand. A rear seat head 
restraint may be removable from the seat solely by hand.
    S4.5 Compliance option selection. Whenever this standard provides 
an option for compliance, the manufacturer must select the option not 
later than the time it certifies the vehicle and may not thereafter 
select a different option for the vehicle.
    S5. Procedures. Demonstrate compliance with S4.2 and S4.3 of this 
section with any adjustable lumbar support adjusted to its rearwardmost 
nominal design position in forward facing seats and its forwardmost 
nominal design position in rear facing seats. Except for S5.1 of this 
section, if the seat back is adjustable, it shall be set at an initial 
inclination position closest to 25 degrees from the vertical, as 
measured by the three dimensional SAE J826 manikin (July 1995) equipped 
with the ICBC Head Restraint Measuring Device (available from the 
Insurance Corporation of British Columbia, 151 West Esplanade, North 
Vancouver, BC V7M 3H9, Canada. www.icbc.com). The order of test 
performance is S5.7 and S5.1 to S5.6 of this section, in numerical 
order.
    S5.1 Procedures for dynamic performance. Demonstrate compliance 
with S4.2(a) of this section in accordance with S5.1(a) though (i) of 
this section with the head restraints in any backset position of 
adjustment. For all seating positions demonstrate compliance with a 
50th percentile male Hybrid III test dummy specified in 49 CFR part 
572, subpart E. For front seating positions demonstrate compliance with 
a 95th percentile male Hybrid III test dummy specified in 49 CFR part 
572. When testing with the 95th percentile dummy demonstrate compliance 
with the head restraint at one height position of adjustment, at the 
option of the manufacturer. When testing with the 50th percentile 
demonstrate compliance with the head restraint at any height position 
of adjustment.
    (a) Mount the vehicle on a dynamic test platform at the vehicle 
attitude set forth in S13.3 of Sec. 571.208 of this part, so that the 
longitudinal centerline of the

[[Page 996]]

vehicle is parallel to the direction of the test platform travel and so 
that movement between the base of the vehicle and the test platform is 
prevented. Instrument the platform with an accelerometer and data 
processing system having a frequency response of channel class 60 as 
specified in the Society of Automotive Engineers (SAE) Recommended 
Practice J211/1, March 1995. Position the accelerometer sensitive axis 
parallel to the direction of test platform travel.
    (b) Remove the tires, wheels, battery, fluids, and all unsecured 
components. Remove or rigidly secure the engine, transmission, axles, 
exhaust, vehicle frame, etc. in order to assure that all points on the 
acceleration vs. time plot measured by an accelerometer on the floor 
pan fall within the corridor described in Figure 1 and Table 1.
    (c) Place any moveable windows in the fully open position.
    (d) At each outboard designated seating position, place the test 
dummy with the seat adjusted as specified in S8.1.2 through S8.1.3 of 
Sec. 571.208 of this part. Prior to placing the Type 2 seat belt around 
the test dummy, exercise the seat belt retractor(s) three times to 
remove slack.
    (e) Dress and adjust each test dummy as specified in S8.1.8.2 
through S8.1.8.3 of Sec. 571.208 of this part.
    (f) Position each test dummy as specified in S10.1 through S10.3 of 
Sec. 571.208 of this part and S7.1 through S7.4 of Sec. 571.214 of this 
part, except for the following:
    (1) If it is not possible to position the test dummy so that the 
midsagittal plane is aligned within 15 mm (0.6 inches) of the head 
restraint centerline, follow the positioning procedure in S7.1 through 
S7.4 of Sec. 571.214 of this part.
    (2) The H-point of the 95th percentile male test dummy coincides 
within 13 mm (0.5 inches) in the vertical dimension and 13 mm (0.5 
inches) in the horizontal dimension of a point 9 mm (0.4 inches) above 
and 15 mm (0.6 inches) forward of the H-point of the seat.
    (g) Accelerate the dynamic test platform such that it experiences a 
forward velocity change of 17.3  0.6 kph (10.8  
0.37 mph) and all of the points on the acceleration vs. time curve fall 
within the corridor described in Figure 1 and Table 1. Measure the 
maximum rearward angular displacement between the head and torso of 
each dummy.
    (h) Calculate the angular displacement from the output of 
instrumentation placed in the torso and head of the test dummy and an 
algorithm capable of determining the relative angular displacement to 
within one degree and conforming to the requirements for a 600 Hz 
channel class as specified in SAE Recommended Practice J211/1 (March 
1995). No data generated after 200 ms from the beginning of the forward 
acceleration are used in determining angular displacement.
    (i) Calculate the HIC from the output of instrumentation placed in 
the head of the test dummy using the equation in S4.2(a)(1)(ii) of this 
section and conforming to the requirements for a 1000 Hz channel class 
as specified in SAE Recommended Practice J211/1 (March 1995). No data 
generated after 200 ms from the beginning of the forward acceleration 
are used in determining angular displacement.
    S5.2 Procedures for height and backset. Demonstrate compliance with 
S4.2(b)(1), (2), and (4) of this section in accordance with S5.2(a) 
through (c) of this section.
    (a) For adjustable head restraints in front seating positions, 
adjust the top of the head restraint to its highest position and 
measure the height. For all other head restraints in front seating 
positions, measure the height.
    (b) For adjustable head restraints, adjust the top of the head 
restraint to its lowest position and measure the height. For all other 
head restraints, measure the height.
    (c) For adjustable head restraints, adjust the head restraint so 
that its top is at any height between 750 mm (29.5 inches) and 800 mm 
(31.5 inches) and to the maximum backset position at that height, and 
measure the backset. For all other head restraints, measure the 
backset.
    S5.3 Procedures for measuring gaps. Demonstrate compliance with 
S4.2(b)(5) and (6) of this section in accordance with the requirements 
of S5.3(a) through (c) of this section. For adjustable head restraints, 
demonstrate compliance with the head restraint adjusted to its minimum 
height position. Demonstrate compliance with S4.2(b)(5) of this section 
at any backset position of adjustment. Demonstrate compliance with 
S4.2(b)(6) of this section at one backset position of adjustment, at 
the option of the manufacturer.
    (a) The area of measurement is anywhere on the front surface of the 
head restraint or seat with a height greater than 540 mm (21.3 inches) 
and within a distance of the head restraint vertical centerline of--
    (1) 127 mm (5 inches) for bench-type seats; and
    (2) 85 mm (3.4 inches) for individual seats.
    (b) Place a 165  2 mm (6.5  0.1 inches) 
diameter spherical head form against any gap such that only two points 
of contact are made. The surface roughness of the head form is less 
than 1.6 m, root mean square.
    (c) Determine the gap dimension by measuring the straight line 
distance between the two contact points, as shown in Figures 2 and 3.
    S5.4 Procedures for energy absorption. Demonstrate compliance with 
S4.2(b)(7) of this section in accordance with S5.4(a) through (e) of 
this section, with the seatback rigidly fixed and adjustable head 
restraints in any height and backset position of adjustment.
    (a) Propel a semispherical head form with a 165  2 mm 
(6.5  0.1 inches) diameter and a surface roughness of less 
than 1.6 m, root mean square, into the head restraint. The 
head form and associated base have a combined mass of 6.8  
0.05 kg (15  0.1 pound).
    (b) Instrument the head form with an acceleration sensing device 
whose output is recorded in a data channel that conforms to the 
requirements for a 600 Hz channel class as specified in SAE Recommended 
Practice J211/1 (March 1995). The axis of the acceleration sensing 
device coincides with the geometric center of the head form and the 
direction of impact.
    (c) At the time of launch, the longitudinal axis of the head form 
is within 2 degrees of being horizontal and parallel to the vehicle 
longitudinal axis. The direction of travel is rearward.
    (d) The headform travels freely through the air along the path 
described in S5.4(b) of this section not less than 25 mm (1 inch) 
before making contact with the head restraint.
    (e) Impact the front surface of the seat or head restraint at any 
point with a height greater than 635 mm (25 inches) and within a 
distance of the head restraint vertical centerline of--
    (1) 105 mm (4.1 inches) for bench-type seats; and
    (2) 70 mm (2.8 inches) for individual seats.
    S5.5 Procedures for height retention. Demonstrate compliance with 
S4.2(b)(9) of this section in accordance with S5.5 (a) through (d) of 
this section.
    (a) Adjust adjustable head restraints so that the top of the head 
restraint is at any of the following height positions at any backset 
position--
    (1) For front seating positions--
    (i) The highest position;
    (ii) Not less than, but closest to 800 mm (31.5 inches);
    (iii) Not less than, but closest to 750 mm (29.5 inches); and
    (2) For rear seating positions--

[[Page 997]]

    (i) The highest position; and
    (ii) Not less than, but closest to 750 mm (29.5 inches).
    (b) Establish the head form initial reference position by applying 
a vertical downward load of 50 N  1 (11.2  0.2 
pounds) to the top of the head restraint at the head restraint 
centerline using a 165  2 mm (6.5  0.1 inch) 
diameter spherical head form with a surface roughness of less than 1.6 
m, root mean square.
    (c) Increase the load at the rate of 250  50 N/minute 
(50.6  10 pounds/minute) to at least 500 N (112 pounds) and 
maintain this load level for not less than 5 seconds.
    (d) Reduce the load at the rate of 250  50 N/minute 
(50.6  11.2 pounds/minute) to 50  1 N (11.2 
 0.22 pounds) and determine the head form position with 
respect to its initial reference position.
    S5.6 Procedures for displacement, backset retention and strength. 
Demonstrate compliance with S4.2(b)(10) through (12) of this section in 
accordance with S5.6(a) through (h) of this section. The angular 
orientation of the load vectors generating the specified moments on the 
head restraint are initially within 2 degrees of a vertical plane 
parallel to the vehicle longitudinal centerline and do not deviate more 
than 2 degrees from their initial orientation.
    (a) Adjust adjustable head restraints so that the top of the head 
restraint is at the height not less than, but closest to--
    (1) 800 mm (31.5 inches) for front seating positions; and
    (2) 750 mm (29.5 inches) for rear seating positions;
    (b) Adjust adjustable head restraints to any backset position;
    (c) Place a test device, having the back pan dimensions and torso 
line (vertical centerline), when viewed laterally, of the head room 
probe in full back position, of the three dimensional SAE J826 manikin, 
in the seat;
    (d) Establish the displaced torso reference line by creating a 
rearward moment of 373  7.5 Nm (3,300  66 inch-
pounds) about the H-point by applying a force to the seat back through 
the test device back pan located as specified in S5.6(c) of this 
section at the rate of 187  37 Nm/minute (1,655 
 327 inch-pounds/minute). The initial location on the back 
pan of the moment generating force vector has a height of 290 mm 
 13 mm (11.4  0.5 inches). Apply the force 
vector normal to the torso line and maintain it within 2 degrees of a 
vertical plane parallel to the vehicle longitudinal centerline. 
Constrain the back pan to rotate about the H-point. Rotate the force 
vector direction with the back pan;
    (e) Maintain the position of the test device back pan as 
established in S5.6(d) of this section. Using a 165  2 mm 
(6.5  0.1 inch) diameter spherical head form with a surface 
roughness of less than 1.6 m, root mean square, establish the 
head form initial reference position by applying, perpendicular to the 
displaced torso reference line, a rearward initial load on the head 
restraint centerline 65  3 mm (2.6  0.1 inches) 
below the top of the head restraint that will produce a 37  
0.7 Nm (327  6.5 inch-pounds) moment about the H-point;
    (f) Increase this initial load at the rate of 187  37 
Nm/minute (1,655  327 inch-pounds/minute) until a 373 
 7.5 Nm (3,300  66 inch-pound) moment about the 
H-point is produced. Maintain the load level producing that moment for 
not less than 5 seconds and then determine the head form position with 
respect to the displaced torso reference line;
    (g) Reduce the load at the rate of 187  37 Nm/minute 
(1655  327 inch-pounds/minute) until a 37  0.7 
Nm (327  6.5 in-pound) moment about the H-point is 
produced. While maintaining the load level producing that moment, 
determine the head form position with respect to its initial reference 
position; and
    (h) Increase the load at the rate of 250  50 N/minute 
(50.6  10 pounds/minute) to at least 890 N (200 pounds) and 
maintain this load level for not less than 5 seconds.
    S5.7 Procedures for folding or retracting head restraints for 
unoccupied rear seats. Demonstrate compliance with S4.3(b) of this 
section in accordance with S5.7(a) through (d) of this section:
    (a) Place the head restraint into any position meeting the 
requirements of S4.2 of this section;
    (b) Measure the torso reference line angle with the three 
dimensional SAE J826 manikin;
    (c) Fold or retract the head restraint to any position in which its 
minimum height is less than that specified in S4.2(b)(2) of this 
section or in which its backset is more than that specified in 
S4.2(b)(4) of this section; and
    (d) Again measure the torso reference line angle.

[[Page 998]]

[GRAPHIC] [TIFF OMITTED] TP04JA01.007


         Table 1.--Sled Pulse Corridor Reference Point Locations
------------------------------------------------------------------------
                                                           Acceleration
            Reference  point                time  (ms)       (m/s\2\)
------------------------------------------------------------------------
A.......................................               0              10
B.......................................              28              94
C.......................................              60              94
D.......................................              92               0
E.......................................               4               0
F.......................................            38.5              80
G.......................................            49.5              80
H.......................................              84               0
------------------------------------------------------------------------


[[Page 999]]

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[GRAPHIC] [TIFF OMITTED] TP04JA01.009


    Issued on December 22, 2000.
Stephen R. Kratzke,
Associate Administrator for Safety Performance Standards.
[FR Doc. 01-136 Filed 1-3-01; 8:45 am]
BILLING CODE 4910-59-P