[Federal Register Volume 66, Number 204 (Monday, October 22, 2001)]
[Proposed Rules]
[Pages 53376-53385]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-26560]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-1999-5572; Notice 2]
RIN 2127-AG51


Federal Motor Vehicle Safety Standards; Roof Crush Resistance

AGENCY: National Highway Traffic Safety Administration (NHTSA), 
Department of Transportation.

ACTION: Request for comments.

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SUMMARY: This notice is a request for comments to assist NHTSA in 
upgrading the requirements of Federal Motor Vehicle Safety Standard No. 
216, ``Roof Crush Resistance,'' to reduce injuries and fatalities in 
passenger cars, pickup trucks, vans and multipurpose passenger vehicles 
resulting from roof intrusion during rollover crashes. It asks the 
public for its views and comments on what changes, if any, are needed 
to the roof crush resistance standard. NHTSA will consider all such 
comments in deciding what regulatory changes, if any, may be 
appropriate for upgrading the standard. Concerns presented in a 
petition for rulemaking from the law firm R. Ben Hogan, Smith and 
Alspaugh requesting that dynamic testing be used to validate the 
strength of vehicle roof structures, instead of the current quasi-
static procedure, are also addressed in this notice.

DATES: Comments on this notice must be received no later than December 
6, 2001.

ADDRESSES: You may submit your comments in writing to: Docket 
Management, Room PL-401, 400 Seventh Street, SW., Washington, DC 20590. 
Alternatively, you may submit your comments electronically by logging 
onto the Docket Management System (DMS) website at http://dms.dot.gov. 
Click on ``Help & Information'' or ``Help/Info'' to view instructions 
for filing your comments electronically. Regardless of how you submit 
your comments, you should mention the docket number of this document.

FOR FURTHER INFORMATION CONTACT: The following persons at the National 
Highway Traffic Safety Administration, 400 Seventh Street, SW., 
Washington, DC, 20590: For technical and policy issues: Mr. Maurice 
Hicks, Office of Crashworthiness Standards, NPS-11, telephone (202) 
366-6345, facsimile (202) 366-4329, electronic mail: 
[email protected] For legal issues: Ms. Nancy Bell, Office of 
the Chief Counsel (202-366-2992), facsimile (202) 366-3820, electronic 
mail: [email protected]

SUPPLEMENTARY INFORMATION: You may read the materials placed in the 
docket for this notice (e.g., the comments submitted in response to 
this notice by other interested persons) by going to the DMS at the 
street address given above under ADDRESSES. The hours of the DMS are 
indicated above in the same location.
    You may also read the materials on the Internet. To do so, take the 
following steps:
    (1) Go to the Web page of the Department of Transportation DMS 
(http://dms.dot.gov/).
    (2) On that page, click on ``search'' near the top of the page or 
scroll down to the words ``Search the DMS Web'' and click on them.

[[Page 53377]]

    (3) On the next page (http://dms.dot.gov/search/), scroll down to 
``Docket Number'' and type in the four-digit docket number shown in the 
title at the beginning of this notice. After typing the docket number, 
click on ``search.''
    (4) On the next page (``Docket Summary Information''), which 
contains docket summary information for the materials in the docket you 
selected, scroll down to ``search results'' and click on the desired 
materials. You may download the materials.

Table of Contents

I. Background
    A. Current Requirements
    B. Safety Problem
    C. Evaluation of Roof Crush Testing
    D. Previous Agency Roof Crush Rulemaking
II. Agency Roof Crush Research
    A. Vehicle Testing
    B. Analytical Research
III. Discussion of Issues
    A. Current Test Procedure
    B. Alternative Dynamic Tests
    C. Limiting Headroom Reduction
IV. Submission of Comments

I. Background

A. Current Requirements

    In the early 1970's, the National Highway Traffic Safety 
Administration (NHTSA) was responsible for the United States becoming 
the first country in the world to address deaths and serious injures 
associated with vehicle roof crush. Federal Motor Vehicle Safety 
Standard (FMVSS) No. 216, ``Roof Crush Resistance,'' became effective 
on September 1, 1973. This standard established strength requirements 
for the roof structure over the front occupants of passenger cars with 
a gross vehicle weight rating (GVWR) of 6,000 pounds or less. The 
purpose of the standard is to reduce deaths and injuries due to 
crushing of the roof into the passenger compartment area in rollover 
crashes. Since 1973, Canada and Saudi Arabia have adopted roof crush 
standards that have the same requirements as Standard No. 216. We are 
not aware that any other country has adopted a roof crush standard, and 
know that both Europe and Japan do not have any such requirements.
    Since inception, the roof crush standard has been amended, 
extending its requirements to passenger cars, trucks, buses, and 
multipurpose passenger vehicles with a GVWR of 2722 kilograms (6,000 
pounds) or less (55 FR 15510, April 17, 1991). The standard was also 
amended to modify the test device placement procedure to accommodate 
vehicles with raised and highly sloped (aerodynamic) roof structures 
(64 FR 22567, April 27, 1999).
    The test procedure currently used to evaluate compliance with the 
standard involves securing a vehicle on a rigid horizontal surface, 
placing a flat steel rectangular plate on the vehicle's roof, and using 
the plate to apply 1.5 times the unloaded weight of the vehicle (up to 
a maximum of 22,240 N, or 5,000 pounds, for passenger cars) onto the 
roof structure. During the test, the plate is angled and positioned to 
simulate vehicle-to-ground contact on the roof over the front seat 
area.\1\ To achieve this contact, the plate is tilted forward at a 5-
degree angle, along its longitudinal axis, and tilted outward at a 25-
degree angle, along its lateral axis, so that the plate's outboard side 
is lower than its inboard side. The test plate's edges are also 
positioned with respect to fixed locations on the vehicle's roof, 
depending upon the roof slope, to ensure that the plate stresses the 
roof over the front seat area. Compliance with the standard is achieved 
if the vehicle's roof prevents the test plate from moving downward more 
than 127 mm (5 inches).
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    \1\ The roof over the front seat area means the portion of the 
roof, including windshield trim, forward of a transverse plane 
passing through a point 162 mm rearward of the seating reference 
point of the rearmost front outboard seating position.
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B. Safety Problem

    Roof intrusion and roof contact injury are common factors in 
rollovers. Based upon crash data in NHTSA's National Automotive 
Sampling System (NASS) for 1995-1999, rollover crashes are the most 
dangerous collision type for light duty vehicles, measured by the 
ratios of fatal and serious injuries to the number of occupants 
involved in towaway crashes. Table 1 shows the ratios and the number of 
fatalities and serious injuries in light duty vehicle towaway crashes 
by crash type.

 Table 1.--Annual Average Number of Fatal and Serious Occupant Injuries in Towaway Crashes by Crash Type in the
                                    1995-1999 NASS and FARS Crash Databases*
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                                                                  Fatalities per     Fatal and     Injuries per
           Crash type                  Total        Fatalities         total          serious          total
                                     occupants                       occupants       injuries        occupants
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Rollover........................         418,371          10,149          0.0243          27,057          0.0647
Frontal.........................       2,921,864          12,384          0.0042          62,536          0.0214
Side............................       1,359,538           8,169          0.0060          33,610          0.0247
Rear............................         467,559           1,023          0.0022           2,701          0.0058
Other...........................          36,978             432          0.0117             580          0.0157
    Totals......................       5,204,309          32,157          0.0062         126,484          0.0243
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* Adjusted for unknowns

    From NASS, it is estimated that an annual average of 253,000 light 
vehicle rollovers resulted in towaway crashes. Eighty-one percent 
(205,000) of these rollovers are in single-vehicle crashes, and 87 
percent (178,000) occurred after the vehicle left the roadway. 
According to the 1999 Fatality Analysis Reporting System (FARS), 10,149 
people were killed in light vehicle rollovers. This includes 8,345 
occupants who were killed in single-vehicle rollovers. Eighty percent 
of these people were unrestrained and 64 percent were ejected 
(including 53 percent who were completely ejected). FARS shows that 55 
percent of light vehicle occupant fatalities in single-vehicle crashes 
involved rollover. The proportion differs greatly by vehicle type: 46 
percent of passenger car occupant fatalities in single-vehicle crashes 
involved rollover, compared to 63 percent for pickup trucks, 60 percent 
for vans, and 78 percent for multipurpose passenger vehicles. The 
higher proportion for pickup, vans, and sports utility vehicles may be 
attributed to their higher center of gravity compared to passenger 
cars.
    The FARS and NASS data were further analyzed to determine the 
various causes and distribution of rollover injury. NASS data from 
1988-1999 were used in the analysis, and thus provide slightly 
different estimates of

[[Page 53378]]

rollover serious injury from those presented in Table 1. The NASS data 
were adjusted and prorated to account for unknown data relating to 
ejection, roof intrusion, roof contact injury, and belt use. Fatality 
estimates from the NASS sample were adjusted to agree with the 10,149 
rollover fatalities in the 1999 FARS. As shown in Figure 1, this 
analysis resulted in an estimate of 16,227 seriously injured occupants 
in light vehicle rollover, where serious injury was defined as an 
Abbreviated Injury Scale (AIS) \2\ rating of at least 3. An estimated 
26,376 vehicle occupants sustain serious or fatal injury due to 
rollover annually. Over half of these are ejected, and about 13,000 are 
occupants who remain in the vehicle. In 7,460 cases, at least one 
injury was due to roof contact, and roof intrusion was present for 
6,934 (93%) of those. Over half (3,734) of those sustaining injury with 
the occurrence of roof intrusion were belted. Thus, roof crush 
intrusion is estimated to occur, and potentially contribute to serious 
or fatal occupant injury, in about 26% (6,934/26,376) of the rollover 
crashes.
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    \2\ The Abbreviated Injury Scale is a method of classifying 
injuries. It is a six level scale, with higher levels associated 
with more serious injury. AIS 1 is assigned to minor injuries; AIS 3 
injuries include serious lacerations, breaks, and concussions; AIS 6 
represents currently untreatable, fatal injuries.
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BILLING CODE 4910-59-P

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[GRAPHIC] [TIFF OMITTED] TP22OC01.000

BILLING CODE 4910-59-C

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    A study by Partyka \3\ examining light duty vehicle crashes that 
required towing found that roof intrusion occurs in approximately 10 
percent of all crashes. The study showed that eighty percent of 
rollover crashes, with two or more vehicle quarter turn rolls, involved 
vertical roof intrusion (which included the roof top, roof side rails 
and front/rear headers). It is noted that the first quarter turn occurs 
when the vehicle flips from the upright position (wheels on the 
roadway) to either side of the vehicle, and the second quarter turn 
occurs when the vehicle flips from its side to the roof that is in 
contact with the roadway/ground. Other meaningful findings from the 
study showed that vertical roof intrusion was present in a larger 
percentage of pickups (12.9%) and sport utility vehicles (13.7%) than 
in passenger cars (6.3%) in towaway crashes.
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    \3\ Partyka, Susan C., ``Roof Intrusion and Occupant Injury in 
Light Passenger Vehicle Towaway Crashes,'' NHTSA Docket No. 88-06-
GR, 1992.
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    Observing only drivers in rollover crashes with vertical roof 
intrusion, the study concluded that 15 percent of drivers are injured 
by roof intrusion. It was also found that the roof itself was the most 
frequently reported source of roof injury and the head was the body 
part most frequently injured by these contacts. Further, 89 percent of 
roof-injured drivers received their most serious injuries from the 
roof.
    According to NASS, roof contact and the severity of rollover injury 
is greatly influenced by belt usage. Eighty-nine percent of unbelted 
ejected occupants receive their most severe injury from ejection (based 
on NASS annual averages from 1988-1997). Consequently, preventing 
ejection is the most important means for reducing injury to unbelted 
occupants. Roof crush intrusion is an additional injury source for 
unbelted occupants, although generally only a minor contributor. Roof 
intrusion is present in the majority of cases, but is only the leading 
cause of injury in less than 10 percent of unbelted rollover cases.
    Partyka's study found that eliminating injuries caused by roof 
intrusion might not reduce overall injury severity of non-ejected 
unbelted occupants. It showed that severe injuries received by unbelted 
rollover occupants are more frequently caused by ejection or vehicle 
interior components rather than from the roof structure. Thus, unbelted 
occupants will gain little, if any, safety benefit from changes to the 
roof crush standard. By contrast, belted rollover occupants usually 
receive their most severe injury by contacting the roof structure.
    The methods for preventing roof contact, by limiting the occupant's 
movement or by limiting roof intrusion (through improved roof strength 
or roof reinforcements), and the predicted benefits (lives saved and 
injuries prevented), have been debated for many years. There are a 
number of possible factors that influence the type of outcomes and the 
severity of injury for belted occupants in rollover crashes. These 
factors include the occupant's initial position and motion while in the 
rollover event, seatbelt tension or/slack, the deformation and velocity 
of intruding vehicle components (i.e., the roof, side rails and A/B-
pillars), and severity of the crash. Additionally, most crash 
databases, including the NASS Crashworthiness Database System (CDS), do 
not provide sufficient information to separate and identify the 
contribution of each of these and other factors. For example, most 
crash databases only record whether seat belts are worn, not whether 
they were worn properly. In addition, belt slack and any subsequent 
vertical excursion of the occupant cannot be determined. Of particular 
interest is the timing of occupant to roof contact and any roof 
intrusion that may occur. Crash investigations cannot distinguish 
between occupant travel off the seat towards the roof, and head to roof 
contact from roof intrusion.
    In summary, unbelted occupants in rollover crashes are primarily 
injured by ejection from the vehicle, which is fatal in about half the 
cases. Belted occupants in rollover crashes are primarily injured by 
roof contact and by contacts with other components within the vehicle's 
interior. Roof contact for belted occupants in rollover crashes is 
usually non-fatal, but the severity of the injury is only directly 
related to the level of roof intrusion in severe cases of intrusion. In 
less severe cases, the severity of injury is related to other vehicle 
and occupant factors. A discussion of the relationship between these 
factors and injury severity is presented in the following section.

C. Evaluation of Roof Crush Testing

    In November 1989, NHSTA published an Evaluation Report concerning 
FMVSS No. 206, Door Locks and Door Retention Components (49 CFR 
571.206) and FMVSS No. 216.\4\ This report specifically evaluated the 
safety effectiveness and benefits of improvements to door locks and 
roof structures in passenger cars.\5\
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    \4\ Charles J. Kahane, PhD, January 1989, DOT HS 807 489.
    \5\ The report was developed in response to Executive Order 
12291, which provided for Government-wide review of existing major 
Federal regulations.
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    The objectives of the evaluation were to determine if there were 
actual benefits (lives saved, injuries prevented, damage avoided and 
costs of safety equipment installed in production vehicles) in 
connection with FMVSS Nos. 206 and 216 for passenger car occupants. 
More specifically, the evaluation examined these standards in the 
context of the overall trend in fatality risk of unbelted occupants of 
passenger cars of model years 1963-82 in rollover crashes. However, 
because FMVSS Nos. 206 and 216 were not the only vehicle factors which 
affected fatality risk in rollover crashes during the 1963-82 periods, 
a major task of the evaluation was to study the overall fatality trend 
and identify what changes were due to improved door locks and roof 
crush strength, as opposed to other vehicle factors.
    Based on examinations of rollover trends as well as more detailed 
analyses of vehicle changes in the fleet, the principal rollover 
findings and conclusions of the analysis were as follows:
    (1) By influencing changes during the 1970's in vehicle design 
(true hardtops were restyled as pillared hardtops or sedans), the 
implementation of the standard saved an estimated 110 lives per year 
for vehicles manufactured from 1963-1982.
    (2) True hardtops have approximately 15 percent higher risk of a 
non-ejection fatality in a rollover crash than pillared cars of the 
same size and exposure pattern.
    (3) Narrower, lighter, shorter cars have higher rollover rates than 
wide, heavy, long ones under the same crash conditions. During 1970-82, 
as the market shifted from large domestic cars to downsized, subcompact 
or imported cars, the fleet became more rollover prone. That may have 
been partly offset by increases in the track width of some imported 
cars after 1977. The net effect of all car changes since 1970 is an 
increase of approximately 1340 rollover fatalities per year.
    (4) The fatality or injury rate per 100 rollover crashes is not a 
valid measure of crashworthiness in comparisons of cars of different 
sizes. Cars that tend to roll over easily (small, narrow cars) do so in 
crashes of intrinsically low severity. These rollovers have low injury 
rates. Larger cars would not roll over at all in those circumstances. 
When

[[Page 53381]]

larger cars do roll over, it is typically in more severe crashes, which 
are more likely to result in injuries. Hence, the fatality rate per 100 
rollover crashes may well be lower for small cars, even if they are 
less crashworthy, simply because they are more likely to experience a 
rollover crash.
    The Kahane study has not been updated to examine the post-1982 
fleet, particularly as it has shifted to a greater percentage of light 
trucks, vans, and sport utility vehicles. Consequently, the 
effectiveness of the changes made to FMVSS No. 216 in 1991, extending 
the requirements to pickup trucks and multipurpose passenger vehicles 
with a GVWR of 6,000 pounds or less, has not been assessed.
    Various researchers \6\ have found that comparing the results from 
FMVSS No. 216's compliance testing directly to the severity of injury 
in rollover crashes involving occupants with roof contact injuries only 
had meaningful relationships after intrusion reached extensive levels. 
Other researchers support this conclusion. An analysis by Friedman \7\ 
on rollover crash data from the 1982-1983 NASS data files showed that 
the injury risk in rollover accidents increased dramatically only when 
intrusion in the proximity of the occupant exceeds a Collision 
Deformation Classification (CDC) \8\ extent of 3. A CDC value of 3 
usually denotes vertical deformation about half the distance from the 
roof to the bottom of the side door window. Digges and Klisch \9\ found 
similar findings when examining 161 rollover cases from the 1988-1989 
NASS data. It was noted that when CDC extent values approached 4 or 5 
(5 denotes the location of the bottom of the side door window), 5 
percent of non-ejected occupants were fatalities and intrusion was 
approximately 12 to 15 inches (for the studied vehicles); however, when 
the CDC extent values were below the top of the side door window, at 
CDC 6 or 7, 20 percent of the occupants received fatal injuries.
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    \6\ Moffatt Edward A. and Padmanaban, Jeya, ``The Relationship 
Between Vehicle Roof Strength and Occupant Injury in Rollover Crash 
data,'' 39th Annual Proceedings: AAAM, Oct 1995.
    \7\ Friedman, Donald and Keith D. Friedman, ``Roof Collapse and 
the Risk of Severe Head and Neck Injury,'' Paper No. 91-S6-0-11, 
13th Experimental Safety Vehicle Conference, Paris, France, 1991.
    \8\ The Collision Deformation Classification (CDC), defined in 
SAE J224, is a means of classifying the extent of vehicle 
deformation caused by vehicle accidents on the highway by direction, 
size of the area and extent of the damage.
    \9\ Digges, Kennerly and Steven Klisch, ``Crashworthiness 
Effectiveness in Rollover Crashes,'' Final Report, Task II (DTRS-57-
90-c-00092), Washington, DC, 1992.
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    However, these findings became confounded by other limitations 
existing within the data investigations. In particular, researchers 
acknowledged that both the severity of the roof crush and the severity 
of injury were possibly related to the severity of the crash. Partyka 
\3\ concluded that there are two important limitations with the results 
of most data analysis. First, most investigators did not attempt to 
determine whether intrusion increased the frequency or the severity of 
injury, that is, whether the roof intrusion is something more than 
merely a reflection of crash severity. If it is merely a reflection of 
crash severity, one generally expects higher severity injuries in 
higher severity crashes. It should be noted that there is no widely 
accepted measure of crash severity in rollover crashes. A measure of 
crash severity would allow fair comparison of injury rates in similar 
crash exposures of occupants with and without roof intrusion.
    Second, occupant contacts with vehicle interior components are 
reported only if they cause injury. Therefore, it is not possible to 
estimate how often occupants contact intruding surfaces without injury 
when estimating injury rates for these contacts or comparing them to 
rates for non-intruding surfaces. On the other hand, occupant contact 
with interior vehicle components can produce injury even when there is 
no intrusion, and preventing roof intrusion may not always prevent 
injury from contact. Thus, it is important to determine if roof crush 
and injury are both associated with impact severity.
    In an attempt to determine the relationship between limiting roof 
intrusion, by rollcaged/reinforced roofs, and injury severity measured 
using unbelted Hybrid III anthropomorphic test dummies, Orlowski, et 
al.,\10\ conducted full vehicle dolly rollover tests (as defined in 
FMVSS No. 208, ``Frontal Occupant Protection'') measuring dummy 
movement and head and neck loads with intrusion. They concluded that 
roof strength was not an important factor in the mechanics of head/neck 
injuries in rollover collisions for unbelted occupants. There were no 
significant differences in dummy kinematics or any reduction in head 
injury severity resulting for roof reinforcements.
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    \10\ Orlowski, KF, RT Bundorf, and EA Moffat, ``Rollover Crash 
Test--The influence of Roof Strength on Injury Mechanics,'' SAE 
Paper No. 851734, Society of Automotive Engineers, Warrendale, PA, 
1985.
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    In 1990, Orlowski, et al.,\11\ conducted similar research using 
lap/shoulder belted Hybrid III dummies in dynamic dolly rollover tests 
and inverted vehicle drop tests. This research was conducted to 
evaluate the relationship between roof strength and injury severity 
when restraints are used. Comparisons were made on the basis of the 
dummy axial neck loads resulting from rollover tests in production and 
reinforced roof vehicles. The analysis also attempted to understand the 
factors that influence neck loads under these conditions. For these 
analyses, Orlowski found similarities between the results of dynamic 
drop and rollover tests. Particularly, in both tests, the dummies in 
the reinforced roof vehicles indicated a lower number of potentially 
injurious impacts and a lower average neck load than the dummies in the 
production vehicles. However, for tests that could be compared on the 
basis of similar roof-to-ground impact conditions (i.e., drop and 
rollover conditions), Orlowski found that there was no increase in the 
level of protection in the reinforced roof vehicles over the production 
roof vehicles. He concluded that roof strength might not be a factor 
influencing injury. Orlowski also found that roof deformation never 
caused the dummy to be compressed between the roof and the seat. He 
observed that all of the dummy neck loads resulted from ``diving'' type 
impacts where the head stops the torso momentum and compresses the 
neck, with a magnitude proportional to the impact velocity. Orlowski 
stated that, at best, the absence of deformation may only benefit 
belted occupants if it results in the belted occupant not contacting 
the roof.
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    \11\ Bahling GS, RT Bunforf, GS Kaspzyk, EA Moffat, KF Orlowski, 
and JE Stocke, ``Rollover and Drop Tests: The Influence of Roof 
Strength on Injury Mechanics Using Belted Dummies,'' SAE Paper No. 
902314, Society of Automotive Engineers, Warrendale, PA, 1990.
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D. Previous Agency Roof Crush Rulemaking

    On April 17, 1991, NHTSA published a final rule amending FMVSS No. 
216 to extend its requirements to multipurpose passenger vehicles, 
trucks, and buses with a gross vehicle weight rating (GVWR) of 6,000 
pounds or less (56 FR 15510). NHTSA explained that we were extending 
FMVSS No. 216 to light trucks because of the increased use of light 
trucks as passenger vehicles and the need to ensure that those vehicles 
offer safety protection comparable to that offered passenger car 
occupants. This final rule adopted the same test requirement and 
procedure as those for passenger cars, except there is

[[Page 53382]]

no 5,000 pound maximum limit on the test force. This test force is 
applied to either side of the forward edge of the vehicle. This 
amendment became effective on September 1, 1994.
    In 1991, Congress mandated NHTSA to assess rulemaking on rollover 
occupant protection as a part of the Intermodal Surface Transportation 
Efficiency Act (ISTEA). ISTEA required NHTSA to initiate rulemaking to 
address the problems of rollover crashes. In response to that mandate, 
NHTSA published an advance notice of proposed rulemaking (ANPRM) (57 FR 
242, January 3, 1991) that summarized the statistics and research in 
rollover crashes, sought answers to several questions about vehicle 
stability and rollover crashes, and outlined possible regulatory and 
other approaches to reduce rollover casualties. NHTSA also published a 
report to Congress \12\ that detailed agency efforts in these areas.
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    \12\ ``Rollover Prevention and Roof Crush'', April 1992, DOT 
Docket No. NHTSA-1999-5572.
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    During the development of the ANPRM and after receiving and 
analyzing comments to the ANPRM, it became apparent that no single type 
of rulemaking could solve all, or even a majority of, the problems 
associated with rollover. This view was strengthened by the agency's 
review and analysis of comments on the ANPRM. To emphasize this 
conclusion and inform the public further about the complicated nature 
of the light duty vehicle rollover problem, the agency released a 
document titled, ``Planning Document for Rollover Prevention and Injury 
Mitigation,'' at a Society of Automotive Engineers (SAE) meeting on 
rollover on September 23, 1992. The Planning Document gave an overview 
of the rollover problem and a list of alternative actions that NHTSA 
was examining to address the problem. Activities described in the 
document were: crash avoidance research on vehicle measures for 
rollover resistance, research on antilock brake effectiveness, 
rulemaking on upper interior padding to prevent head injury, research 
into improved roof crush resistance to prevent head and spinal injury, 
research on improved side window glazing and door latches to prevent 
occupant ejection, and consumer information to alert people to the 
severity of rollover crashes and the benefits of safety seat belt use 
in this type of crash. NHTSA published a notice announcing the 
availability of the Planning Document and requesting comments (57 FR 
44721, September 29, 1992).
    In May 1996, NHTSA issued the ``Status Report for Rollover 
Prevention and Injury Mitigation'' (NHTSA 1996-1811-2). This document 
updated the progress of the programs discussed in the Planning 
Document.
    On May 6, 1996, the agency received a petition for rulemaking from 
R. Ben Hogan, Smith and Alspaugh, PC, a law firm. Hogan commented that 
the current static requirements in FMVSS No. 216 bear no relationship 
to real world rollover crash conditions and therefore should be 
replaced with a more realistic test such as the inverted vehicle drop 
test defined in the Society of Automotive Engineers (SAE) Standard 
J996. This request coincided with agency research testing that was 
being conducted using the inverted drop test procedure. The petitioner 
also requested that NHTSA require ``roll cages'' to be standard in all 
cars as requested by some commenters responding to the January 3, 1992, 
ANPRM on rollover occupant protection. NHTSA granted this petition on 
January 8, 1997, because we believed that the inverted drop testing had 
merit for further agency consideration.
    On April 27, 1999, NHTSA published a final rule relating to the 
test procedure in FMVSS No. 216 (64 FR 22567). Prior to the amendments 
made by the final rule, the existing procedure resulted in certain 
vehicles with rounded roofs (e.g., the Ford Taurus) being tested with 
the test plate positioned too far rearward on the vehicle roof. In this 
position, the plate did not test the roof over the front occupants. In 
addition, this position created the potential for contact between the 
front edge of the test plate and the roof, allowing the plate to 
penetrate the roof along the leading edge of the plate. Similarly, in 
following this procedure for vehicles with raised, irregularly-shaped 
roofs (such as some vans with roof conversions), the initial contact 
point on the roof may not be above the front occupants, but on the 
raised rear portion of the roof, behind those occupants. In both of 
these cases, the positioning of the plate relative to the initial 
contact point on the roof, instead of relative to a fixed location on 
the roof, resulted in too much variability in the plate positioning and 
reduced test repeatability.
    This final rule addressed the problem of rounded roofs by 
specifying a new primary test procedure for all vehicles except those 
with certain modified roof configurations. Under the new procedure, the 
test plate is to be positioned so that the front edge of the plate is 
254 mm (10 inches) in front of the forwardmost point of the roof. 
Positioned in this way, the front edge of the plate will always project 
slightly forward of the roof instead of contacting it. The rule 
addressed the problem for vehicles with raised or modified roofs by 
specifying that if following the primary test procedure results in an 
initial point of contact that is rearward of the front seats, a second 
procedure would be used to position and orient the plate as specified 
for the primary procedure, except that the plate is moved forward such 
that its rearward edge is positioned at the rear of the roof over the 
front seat area.
    Until October 25, 2000, vehicle manufacturers also had the option 
of using the standard's original test plate placement procedure (as 
established in 1973) for multipurpose vehicles, trucks and buses that 
have a raised or altered roof, instead of the primary or secondary 
procedures defined above (65 FR 4579, January 31, 2000). The original 
procedure positioned the plate with respect to its initial point of 
contact with the roof. The initial point of contact was established by 
angling the plate as required for the first procedure and then lowering 
it horizontally until it contacted the roof. After establishing the 
initial contact point on the vehicle, the test plate was moved upwards, 
and positioned as specified in the first procedure, except the plate's 
forward edge was positioned 254 mm forward of the initial point of 
contact with the vehicle. This position was allowed to make testing 
possible for raised roof vehicles that experience contact with the 
plate's rearward edge when testing to the second procedure.\13\
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    \13\ Currently, the agency is assessing whether to re-allow this 
option or to add/modify the placement procedure to address the 
petitions for reconsideration dated June 11, 1999, from Ford and the 
Recreational Vehicle Industry Association (see DOT Docket 99-5572).
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II. Agency Roof Crush Research

    NHTSA has undertaken a comprehensive research program to find ways 
to protect occupants better in rollover crashes. The roof crush 
research has taken the form of both vehicle testing and analytical 
research.

A. Vehicle Testing

    NHTSA has conducted an extensive vehicle-testing program to 
evaluate rollover crashes. The research has consisted of: (1) full 
vehicle dynamic rollover testing (as defined in FMVSS No. 208, 
``Frontal Occupant Protection''); (2) computer modeling; (3) inverted 
vehicle drop test (as defined in the SAE Recommended Practice J996); 
and (4) modified FMVSS No. 216 testing with comparisons to inverted 
drop testing. The following paragraphs summarize the findings of these 
activities.

[[Page 53383]]

    A series of full-scale dynamic rollover tests has been conducted by 
NHTSA to evaluate a range of crash situations, injury mechanisms, and 
safety countermeasures. NHTSA designed a rollover test cart that was 
similar to the FMVSS 208 dolly rollover cart, but was elevated four 
feet vertically and the vehicle's angular momentum could be initiated 
using pneumatic cylinders. These tests were designed to produce severe 
roof intrusion, and to study occupant kinematics and injury mechanisms. 
The severity of this test condition, however, made it difficult to 
discriminate between good and bad performing roof structures. While the 
test program provided valuable insight into occupant kinematics and 
injury mechanisms, the occupant kinematics were inherently 
unrepeatable. As a result, it was determined that the development of an 
improved roof crush standard based on dynamic rollover testing was not 
feasible.\14\ \15\
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    \14\ Segal, D. and Kamholz, L., ``Development of a General 
Rollover Test Device'', DOT Report HS-807-587 September 1983.
    \15\ Stultz, John C., ``Modifications to the NHTSA General 
Purpose Rollover Test Device'', Transportation Research Center of 
Ohio, January 1989.
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    The agency also contracted with Pioneer Engineering and later EASi 
Engineering to design and test a reinforced roof structure for a Nissan 
pickup.\16\ The Nissan pickup was chosen since several rollover tests 
had previously been conducted with this vehicle. Modification involved 
the use of high strength steel reinforcements and foam filler material 
in the roof header, side rails and A and B-pillars. It was found that 
substantial reduction in roof intrusion could be achieved by 
reinforcing the roof. However, the severity of the full-scale dynamic 
rollover test made it difficult to prevent all intrusion.
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    \16\ Design Modification for a 1989 Nissan Pick-up--Final 
Report. 1991. NHTSA/USDOT. DOT HS 807 925, NTIS, Springfield, 
Virginia, 22161.
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    NHTSA also began investigating other possible test procedures for 
upgrading FMVSS No. 216. One such procedure was the inverted vehicle 
drop test, defined in SAE J996\17\, which has been noted to produce 
deformation patterns similar to what is observed in rollover tests and 
real-world collisions.\18\ After evaluating a series of dynamic drop 
tests, NHTSA concluded that this procedure had merit in its usage, 
realism and repeatability in evaluating roof crush. However, the 
disadvantage to this approach is that it does not introduce the complex 
rolls and ground/vehicle interaction of a full-scale rollover test. The 
dynamic drop test also involves a difficult procedure for suspending 
the vehicle and turning it over. While the dynamic drop test would be 
more repeatable than a full-scale rollover test, it would not be as 
repeatable as the existing FMVSS No. 216 static test.
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    \17\ The Inverted Drop Test in SAE J996 involves suspending the 
vehicle upside down at specified roll and pitch angles, and at a 
specified height above the ground. The vehicle is then allowed to 
free-fall and provide roof crush upon contact with the ground.
    \18\ Michael J. Leigh and Donald T. Willke, ``Upgraded Rollover 
Roof Crush Protection: Rollover Test and NASS Case Analysis,'' 
Docket NHTSA-1996-1742-18, June 1992.
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    Additional testing was then conducted using a modified FMVSS No. 
216 test with increased loads to produce more extensive roof crush (254 
mm (10 inches) and 381 mm (15 inches), instead of the 127 mm (5 inches) 
requirement in the standard).\19\ In order to achieve the more 
extensive roof crush levels, forces ranging up to twice that required 
by Standard No. 216 were necessary. The objective of the study was to 
determine the correlation between roof crush performance measured by 
the modified 216 test and the dynamic inverted drop test. A series of 
tests comparing quasi-static roof loading versus dynamic roof loading 
was conducted to determine how static and dynamic tests can be 
correlated, and if static test results can be used to predict the 
dynamic behavior of the roof structure.
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    \19\ Glen C. Rains and Mike Van Voorhis, ``Quasi Static and 
Dynamic Roof Crush Testing'', DOT HS 808-873, 1999.
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    It is noted that a statistical analysis of the findings showed the 
modified FMVSS No. 216 procedure results strongly correlated with the 
dynamic results of inverted drop tests (correlation coefficient of 
0.94). This correlation was based on energy equivalence between the 
results of the two sets of tests. To further validate the relationship 
(energy equation), additional vehicle testing was performed using the 
modified 216 test. The energy equation was then used to predict the 
dynamic performance of the same vehicle types drop tested at two 
different heights. The energy equation from the modified 216 deviated 
from the two dynamic drop heights by no more than about 15 percent.

B. Analytical Research

    NHTSA conducted an analytical study to explore the relationship 
between roof intrusion and the severity of injury. To evaluate the 
relationship between injury, occupant parameters and belt slack, the 
agency conducted a comparative study \20\ using the NASS CDS. This 
study evaluated belted rollover occupants who did and did not receive 
head injuries from roof contact to determine if headroom reduction \21\ 
was related to the risk of head injury in rollovers. For the analysis, 
pre-crash and post-crash headroom for 155 rollover involved belted 
occupants in the 1988-1992 NASS data was determined using information 
in the American Automobile Manufacturers Association manuals, and NASS 
reported occupant height and vehicle roof intrusion measurements. 
Examining the severity of head injuries with the pre-crash and post-
crash headroom led to the following conclusions:
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    \20\ Kanianthra, Joseph and Rains, Glen, ``Determination of the 
Significance of Roof Crush on Head and Neck Injury to Passenger 
Vehicle Occupants in Rollover Crashes,'' SAE Paper 950655, Society 
of Automotive Engineers, Warrendale, PA, 1994.
    \21\ Headroom reduction was defined as the decrease in the 
vertical space between the interior of the roof and the top of the 
occupant's head.
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    (1) Headroom reduction (pre- versus post-crash) by more than 70% 
substantially increased the risk of head injury from roof contact.
    (2) Head injury increased when the post crash headroom was less 
than the original headroom. Also, as the severity of the injury 
increased, the percentage of cases with no remaining headroom 
increased.
    (3) When the intrusion exceeded the original headroom, the 
percentage of injured occupants was 1.8 times the percentage of 
uninjured occupants.
    (4) The average percent of headroom reduction for injured occupants 
was more than twice that of uninjured occupants.

III. Discussion of Issues

    This section discusses a range of issues and presents a series of 
questions for public comment to aid the agency in evaluating the 
current roof crush standard and whether further action by the agency is 
warranted. These issues and questions are grouped according to the 
following areas: (1) Current test procedure; (2) alternative dynamic 
tests; and (3) limiting headroom reduction.

A. Current Test Procedure

    1. Agency analysis of crash data indicates that injury levels did 
not progressively increase with roof intrusion until severe amounts of 
intrusion were established. In addition, vehicles that perform well in 
roof crush tests do not appear to better protect occupants from more 
severe roof intrusion in real world crashes. Are there more appropriate 
ways than the current FMVSS No. 216 test procedure to measure roof 
intrusion that would

[[Page 53384]]

better relate to injury severity in rollover crashes? If so, please 
identify the appropriate metric. Is it possible to evaluate the more 
appropriate metric with the current test procedure? If so, please 
explain how. If not, please describe the test procedure that should be 
used to evaluate the appropriate performance and provide any data that 
show the repeatability, practicability, and objectivity of the 
alternative test procedure.
    2. Are FMVSS No. 216's testing procedures, particularly the test 
plate load requirement and plate angles, adequate for simulating real 
world rollover conditions? If not, please identify more appropriate 
testing parameters and explain the basis for the belief that this 
parameter is more appropriate.
    3. Beginning in the mid-1990's, the composition of the light duty 
vehicle fleet has been drastically changing with an increasing 
proportion of this fleet consisting of light trucks. This has been 
accompanied by increases in GVWR for some of these vehicles. In the 
past, vehicles with a GVWR of more than 6,000 pounds were typically 
used for commercial applications as work vehicles. However, today's 
larger light trucks, particularly sport utility vehicles, are now 
typically used as an everyday means for personal transportation. 
Currently, the requirements of FMVSS No. 216 are not applicable to many 
of these vehicles because they exceed 6,000 pounds GVWR. Is it 
appropriate for NHTSA to propose extending the applicability of FMVSS 
No. 216 to vehicles with a 10,000 pounds GVWR?
    4. FMVSS No. 216's test load application is not representative of 
dynamic roof crush rates in real-world rollovers. Our standard 
currently applies the load at a rate of 13 mm per second, which is far 
less than the loading rate in a real-world rollover. However, agency 
research demonstrates that static loading in the current standard and 
dynamic loading in inverted drop tests can be correlated by use of a 
dynamic equivalency factor/equation. Is such a factor appropriate for 
equating static and dynamic roof intrusion? If so, is it appropriate or 
necessary for the agency to conduct further research into finding 
appropriate dynamic conditions through inverted vehicle drop testing 
before proceeding with a proposal? Or, is it more appropriate for the 
agency to accept the current static loading as ``good enough,'' based 
on the correlation already found, and proceed with a proposal based on 
what we now know?

B. Alternative Dynamic Tests

    5. As mentioned above, the current standard uses a quasi-static 
rate of load application that is not representative of real-world 
dynamic roof intrusion. Full vehicle dynamic testing is most 
representative of real-world rollover conditions. However, it has been 
difficult to attain repeatable results when testing vehicles. Factors 
such as the orientation/altitude of the vehicle at the initiation of 
the rollover, the tolerance of the speed of the vehicle and test cart 
before roll initiation and the method of initiating the roll cause 
variability in testing. To date, the agency has evaluated two dynamic 
tests to better simulate real-world rollovers. This includes: (1) the 
full vehicle rollover test (as defined in FMVSS No. 208, ``Frontal 
Occupant Protection''); and (2) an inverted vehicle drop test (as 
defined in the Society of Automotive Engineers Recommended Practice 
J996).\22\
    a. Is it appropriate to consider using the FMVSS No. 208 dynamic 
rollover procedure for testing vehicles and, if so, are there any means 
of reducing/eliminating the test variability resulting from dynamic 
conditions?
    b. With regard to SAE J996, should the agency require inverted drop 
testing as requested by R. Ben Hogan and Associates? Have manufacturers 
or others evaluated the drop angle conditions for inverted drop tests? 
What complications with the test have manufacturers experienced? (In 
agency testing, certain vehicles experienced complications in testing 
at the angles prescribed within J996, whereas ground contact with the 
hood or top of the front quarter panel occurred prior to, or just 
after, contact with the roof structure, resulting in less energy being 
imparted to the roof structure.) Also, have manufacturers or others 
evaluated the effects of different drop heights? If so, what attempts 
have been made to equate drop height to real-world deformation or 
injury severity?
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    \22\ The inverted vehicle drop test, defined in the Society of 
Automotive Engineers Recommended Practice J996, provides a 
repeatable means of dynamically testing roof crush. The agency has 
conducted numerous tests to evaluate its performance. However, very 
little research has been done by NHTSA, and we are not aware of 
research by others, to relate the results in SAE J996 to real-world 
rollover condition and performance. Also, there is no certainty that 
the test parameters (defined in J996) relate to real-world 
conditions.
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    6. Have any other dynamic rollover test procedures been evaluated 
by manufacturers or other interested parties? Have manufacturers or 
other parties assessed any new criteria for experimental dynamic 
rollover tests? Have manufacturers or other parties performed dynamic 
rollover testing using dummies? If so, what injury criteria do 
manufacturers or other parties use to assess performance in that 
dynamic test?

C. Limiting Headroom Reduction

    7. Agency research analysis demonstrates that limiting the 
reduction of headroom between the occupant's head and the roof reduces 
injuries in rollovers. More specifically, this research shows a 
moderate correlation between post crash headroom elimination and the 
severity of injury to the head, neck or face resulting from roof 
contact. However, this benefit only exists for belted occupants.
    Can limiting headroom reduction offer quantifiable benefits for 
unbelted occupants in rollover crashes? Are there quantifiable benefits 
for belted occupants in rollover crashes where roof intrusion does not 
exceed the top of the occupant's head?
    8. If NHTSA were to incorporate a headroom limitation in a 
compliance procedure, either as percentage of the original cabin 
environment or an absolute crush requirement based upon maintaining 
room over the head of an anthropomorphic dummy, what would be an 
appropriate limitation and would there be any problems associated with 
such a requirement? Should different limitations be made to accommodate 
different size occupants?

IV. Submission of Comments

    Interested persons are invited to submit comments in response to 
this request for comments. For easy reference, the agency has 
consecutively numbered its questions. NHTSA requests that commenters 
respond to each question by these numbers and provide all relevant 
factual information of which they are aware to support their conclusion 
or opinions, including but not limited to statistical data and 
estimated cost and benefits, and the source of such information. It is 
also requested, but not required, that 10 copies be submitted.
    All comments must not exceed 15 pages in length (49 CFR 553.21). 
Necessary attachments may be appended to these submissions without 
regard to the length limitation. This limitation is intended to 
encourage commenters to state their positions and arguments as 
concisely as possible.
    If a commenter wishes to submit certain information under a claim 
of confidentiality, three copies of the complete submission, including 
purportedly confidential business information, should be submitted to 
the

[[Page 53385]]

NHTSA Chief Counsel, Room 5219, 400 Seventh Street, SW., Washington DC 
20590, and seven copies from which the purportedly confidential 
information has been deleted should be submitted to the Docket Section 
at the street address given above. A request for confidentiality should 
be accompanied by a cover letter setting forth the information 
specified in the agency's confidential business information regulation 
(49 CFR Part 512).
    Comments on this notice will be available for inspection in the 
docket. NHTSA will continue to file relevant information as it becomes 
available in the docket after the closing date. Those persons desiring 
to be notified upon receipt of their written comments in the Docket 
Section should enclose, in the envelope with their comments, a self 
addressed stamped postcard. Upon receipt, the docket supervisor will 
return the postcard by mail.

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

    Issued on: October 16, 2001.
Stephen R. Kratzke,
Associate Administrator for Safety Performance Standards.
[FR Doc. 01-26560 Filed 10-19-01; 8:45 am]
BILLING CODE 4910-59-P