[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="">3 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]
BILLING CODE 4910-59-P
