[Federal Register Volume 64, Number 122 (Friday, June 25, 1999)]
[Notices]
[Pages 34309-34310]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-16165]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration
[Docket No. NHTSA 99-5862; Notice 1]


General Motors Corp.; Receipt of Application for Determination of 
Inconsequential Noncompliance

    General Motors Corporation (GM) of Warren, Michigan, has applied to 
be exempted for the notification and remedy requirements of 49 U.S.C. 
Chapter 301 ``Motor Vehicle Safety'' because of a noncompliance with, 
Federal Motor Vehicle Safety Standard (FMVSS) No. 208, ``Occupant Crash 
Protection.'' The basis of the application is that the noncompliance is 
inconsequential to motor vehicle safety. GM has filed an appropriate 
report pursuant to 49 CFR part 573, ``Defect and Noncompliance 
Information Reports.''
    This notice of receipt of an application is published under 49 
U.S.C. 30118 and 30120 and does not represent any agency decision or 
other exercise of judgment concerning the merits of the application.

Description of Noncompliance

    On February 2, 1999, NHTSA tested a 1999 Chevrolet Tahoe to the 
performance requirements of S13 of FMVSS No. 208 Alternative unbelted 
test for vehicles manufactured before September 1, 2001. The test was 
conducted at the Transportation Research Center of Ohio and the right 
front passenger Anthropomorphic Test Dummy (ATD) registered a neck 
extension moment of 67 Nm. This value exceeds the maximum limit of 57 
Nm specified by S13.2(b) of the standard.
    In response to the test failure, GM conducted an investigation to 
understand the subject test results and to determine the cause of the 
resultant neck extension moment of 67 Nm. After examining all the 
relevant information and conducting additional tests, GM estimates that 
50 percent of the 1999 model year (MY) Chevrolet and GMC 
C/K vehicles manufactured between September 1, 1998 and May 5, 1999, 
may produce similar results if all the subject vehicles were subjected 
to the 30 mph Sled Test in accordance with S13.1 of FMVSS No. 208.

Supporting Information as Submitted by GM

    There were 279,132 subject vehicles manufactured between 
September 1, 1998 and May 5, 1999, with right front passenger 
restraint systems that may not consistently meet the neck extension 
moment prescribed in S13.2(b) of the standard. A neck extension 
moment is produced during the test as a result of the reaction to 
forces acting on the head in such a way as to rotate the head 
rearward at the top of the neck. GM's analysis indicates that, due 
to test and/or product variations, approximately 50 percent of the 
right front passenger air bags could contribute to ATD kinematics 
that could allow the passenger ATD to exceed the 57 Nm neck 
extension value limit.
    The prescribed Sled Test pulse is of a longer duration than a 
typical 30 mph rigid barrier pulse for the subject vehicles (125 
msec versus approximately 80 msec). Because of this, the air bag 
must stay inflated longer during a test using the sled pulse to 
allow the unbelted ATD's torso energy to dissipate over a longer 
time period. Two design interventions involving the air bag system 
could be used to address this. It would be possible to increase the 
gas output into the deploying bag by adding more propellant to the 
inflator. However, this would be counter to the reasons the agency 
permitted less forceful air bags, and for the FMVSS 208 Sled Test 
being allowed as an alternative test method with an unbelted, 50th 
percentile ATD. The intent of the Sled Test provision, and the 
ongoing rulemaking to address air bag aggressivity, is to allow and 
encourage less aggressive air bag inflators in motor vehicles to 
reduce the inflation induced injury risks to out-of-position small 
adults and children.
    A second possible approach is to reduce the venting capacity of 
the air bag. By reducing the venting capacity, the inflation gas is 
retained in the bag for a longer period of time resulting in bag 
pressure being retained over a longer period. GM test results 
(provided to NHTSA-OVSC in USG 3433; Part 5, dated May 7, 1999) 
consistently provided neck extension moments well below the 57 Nm 
limit when conducted with air bags having each of the two vent holes 
reduced from a 60 mm diameter to a 30 mm diameter. Considering all 
these resultant test values and the consistency of the neck 
extension measurements from these tests, GM implemented this vent 
size change in the subject vehicle production to further assure 
compliance. The implementation of this change was completed in GM's 
vehicle production facilities on May 5, 1999.
    GM has examined the effect on motor vehicle safety involved in 
this noncompliance and the appropriateness of field action. This 
evaluation utilizes the total of 279,132 1999 MY Chevrolet and GMC 
C/K vehicles that were manufactured between September 1, 1998 and 
May 5, 1999 with the right front passenger air bag systems in 
question and very conservative estimates for the remainder of the 
analysis's multipliers. Approximately 50 percent of the subject 
vehicles, or 139,566 vehicles, may have a passenger air bag that 
could contribute to ATD kinematics that could allow the passenger 
ATD to exceed the 57 Nm neck extension requirement if tested to the 
S13 requirements of the standard. Projecting 5,700 deployments per 1 
million car years for a 10 year vehicle life cycle, a total of 7,960 
deployments can be expected. It is anticipated that one third of 
these deployments (2,653) would have a right front passenger 
present. Using the recognized current national seat belt use rate of 
70 percent, 30 percent (or 796 occupants) of these deployments may 
involve an unbelted occupant. Approximately 20 percent of the 
deployments would be at a crash pulse similar to or more severe than 
used for the FMVSS 208 Sled Test, resulting in the potential that 
159 of the passengers may be involved in such a deployment. Assuming 
60 percent of these passengers are the same size or larger than the 
50th percentile male ATD, 95 right front occupants could be large 
enough that sufficient torso energy may not be dissipated to meet 
the specific neck extension requirement of the standard.
    The risk of neck injury to these 95 occupants can be estimated 
using the neck extension moment injury risk curve submitted to the 
agency during the referenced rulemaking and provided as Attachment 
A. It was also provided as Figure 4 of Attachment C--Proposal for 
Dummy Response Limits for FMVSS 208 Compliance Testing--in the AAMA 
response S98-13 to Docket No. NHTSA 98-4405; Notice 1 dated December 
17, 1998. The risks of an AIS3 neck injury for the 50th 
percentile adult male experiencing a neck extension moment of 57 Nm 
(current FMVSS 208 requirement) and 67 Nm (measured during the 
subject agency enforcement test) for both a relaxed and tensed 
occupant are given in Table 1. Also shown are the estimated number 
of the 95 occupants who may experience an AIS3 neck 
injury.

[[Page 34310]]



 Table 1.--Injury Risk Value for an AIS3 Neck Injury of Neck Extension Moments for No Muscle Tone and
                   for 80 Percent Muscle Tone Measured With the 50th Percentile Adult Male ATD
----------------------------------------------------------------------------------------------------------------
                                                     % Risk of AIS3 Neck      Potential number of
                                                                 Injury               occupants with AIS3 neck injury
                                       moment (Nm)                                  ----------------------------
                                                     No muscle tone    80% muscle                     80% muscle
                                                                          tone       No muscle tone      tone
----------------------------------------------------------------------------------------------------------------
MVSS Req'mt........................              57             0.8            0.09       <1 (0.76)     0 (0.09)
TRC Test...........................              67             2.2            0.3         2 (2.09)     0 (0.29)
----------------------------------------------------------------------------------------------------------------

    Therefore, if corrective action is not implemented for the 
279,132 subject vehicles, the increase in the estimated number of 
occupants that may be exposed to an AIS3 neck injury 
would be no more than one occupant, but more likely would be close 
to zero depending on the degree of muscle tone involved. The reason 
this increase is so small is that the current FMVSS 208 neck 
extension moment limit of 57 Nm is an extremely conservative limit. 
This value corresponds to only a 0.8 percent risk of an 
AIS3 neck injury with no muscle tone assumed and only a 
0.09 percent risk if 80 percent muscle tone is assumed.
    As part of the aforementioned ongoing rulemaking, the agency is 
currently considering the AAMA recommendation that an injury risk 
level of 5 percent be used for setting regulated injury criteria 
limits. This includes the recommendation that the neck extension 
limit be set at a 5 percent risk of an AIS3 neck injury. 
For out-of-position occupant measurements with the 50th percentile 
male ATD, this would be a 77 Nm limit without consideration for 
muscle tone, and the neck extension limit for in-position occupants 
would be 96 Nm considering 80 percent muscle tone. For either case, 
the resultant 67 Nm measurement from the agency's test is 
substantially below these recommended limits.
    These recommended neck extension limits of 77 and 96 Nm are also 
exceptionally conservative compared to the risk level associated 
with brain injury that is currently comprehended in FMVSS 208. The 
current head injury criteria (HIC) limit of 1000 allows for a 16 
percent risk of an AIS4 brain injury. Furthermore, the 
current FMVSS 208 injury criteria for chest displacement and femur 
loads are regulated at even higher risk levels than HIC. In fact, 
the rigid barrier test methods prescribed in FMVSS 208 for both 
belted and unbelted ATDs currently include these HIC, chest 
displacement and femur injury criteria, but do not currently specify 
any of the neck criteria associated with the Sled Test.
    The current neck extension limit of 57 Nm is a very conservative 
limit, especially when compared to the current HIC, chest 
displacement and femur load limits required by FMVSS 208. Because of 
this and because of no more that one occupant and possible zero 
occupants may be at risk of an AIS  3 neck injury if 
corrective action is not implemented for 279,132 subject vehicles, 
GM believes this noncompliance is inconsequential as it relates to 
motor vehicle safety. Therefore, GM requests the affected vehicles 
be exempted from the recall and remedy provisions of Section 30120 
of the Safety Act.
    The agency is aware that significant controversy continues with 
regard to the injury criteria currently specified for the neck. This 
is a continuing topic of discussion between the agency and others in 
the ongoing rulemaking regarding air bag related injuries and 
fatalities to unbelted and out-of-position occupants. These ongoing 
rulemaking discussions support GM's belief that the current limit of 
57 Nm for the specified neck extension criteria is well below the 
level necessary to meet the need for motor vehicle safety.

    Interested persons are invited to submit written data, views and 
arguments on the petition of GM, described above. Comments should refer 
to the Docket Number and be submitted to: Docket Management, Room PL-
401, 400 Seventh Street, SW, Washington, DC 20590. It is requested that 
two copies be submitted.
    All comments received before the close of business on the closing 
date indicated below will be considered. The application and supporting 
materials, and all comments received after the closing date will also 
be filed and will be considered to the extent practicable. When the 
application is granted or denied, the Notice will be published in the 
Federal Register pursuant to the authority indicated below.
    Comment closing date: July 26, 1999.

(49 U.S.C. 30118, 30120; delegations of authority at 49 CFR 1.50 and 
49 CFR 501.8)

    Issued on: June 21, 1999.
L. Robert Shelton,
Associate Administrator for Safety Performance Standards.
[FR Doc. 99-16165 Filed 6-24-99; 8:45 am]
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