Federal Motor Vehicle Safety Standards; Roof Crush Resistance |
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Topics: National Highway Traffic Safety Administration, Federal Motor Vehicle Safety Standards
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Barry Felrice
Federal Register
December 27, 1994
[Federal Register: December 27, 1994]
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DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. 94-97; Notice 01]
RIN 2127-AF40
Federal Motor Vehicle Safety Standards; Roof Crush Resistance
AGENCY: National Highway Traffic Safety Administration (NHTSA) DOT.
ACTION: Request for comments.
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SUMMARY: Ford Motor Company (Ford) and the Recreation Vehicle Industry
Association (RVIA) have each submitted petitions asking NHTSA to
clarify some provisions in the roof crush resistance standard.
Specifically, both these petitioners suggested changes to the current
specifications for placing the load plate on vehicles during compliance
testing, particularly vehicles with sloped aerodynamic roofs or raised
roofs. NHTSA has granted both of these petitions.
This notice 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 together with the petitions in
deciding what regulatory changes, if any, may be appropriate for the
roof crush resistance standard.
DATES: Comments on this notice must be received by NHTSA no later than
February 10, 1995.
ADDRESSES: Comments should refer to the docket and notice number shown
in the heading of this notice and be submitted to: NHTSA Docket
Section, Room 5109, 400 Seventh Street, SW., Washington, DC 20590.
Docket hours are 9:30 a.m. to 4 p.m. Monday through Friday.
FOR FURTHER INFORMATION CONTACT:
Dr. Glen Rains, Office of Vehicle Safety Standards, NRM-14, NHTSA, 400
Seventh Street, SW., Washington, DC 20590. Dr. Rains can be reached by
telephone at (202) 366-5277.
SUPPLEMENTARY INFORMATION:
Background
Standard No. 216 (49 CFR 571.216) sets forth roof crush resistance
requirements that must be met by passenger cars, trucks, buses, and
multipurpose passenger vehicles with a GVWR of 6000 pounds or less. The
purpose of the standard, as stated in S2 of the standard, is ``to
reduce deaths and injuries due to the crushing of the roof into the
passenger compartment in rollover accidents.''
Standard No. 216 seeks to achieve this purpose by requiring
vehicles to be certified as complying with a performance test in which
a load of 1\1/2\ times the unloaded vehicle weight (up to a maximum of
5000 pounds for passenger cars) is applied to the vehicle roof by means
of a rigid unyielding block whose lower surface consists of a flat
rectangle 30 inches wide and 72 inches long.
During the test, the plate is required to be positioned so that:
(1) When viewed from the side of the test vehicle, the test plate
is angled 5 deg. toward the front of the vehicle;
(2) When viewed from the front of the test vehicle, the test plate
is angled 25 deg. below the horizontal on the side of the vehicle to
which the test plate is applied; and
(3) The initial contact point of the test plate with the test
vehicle roof is 10 inches from the forwardmost point of the test plate.
The test plate orientation and placement are illustrated in Figure
1 of Standard No. 216.
These requirements were initially proposed in a notice published on
January 6, 1971 (36 FR 3) and are patterned after the specifications in
the Society of Automotive Engineers (SAE) Standard J374. At that time,
most vehicle roofs were less rounded than today's designs, and there
were no raised-roof vehicles to be tested. Thus, the specifications for
positioning the test plate ensured that it would be positioned to
measure the roof's strength in the A-pillar region and to ensure that
the strength was sufficient to prevent sudden collapse of the roof
above the A-pillars and front seating areas during rollovers.
Petitions
A. RVIA
RVIA recently submitted a petition asking that vans, motor homes
and other multipurpose passenger vehicles, trucks, and buses that have
raised roofs and that are now subject to Standard No. 216 be tested
according to the requirements of Standard No. 220, School Bus Rollover
Protection. Standard No. 220 subjects vehicles to the same force on the
roof as does Standard No. 216 (1\1/2\ times the unloaded vehicle
weight), but the force is applied differently. The test plate used in
Standard No. 220 is larger than the 30 x 72 inch plate used in Standard
No. 216. In addition, instead of concentrating the load in the vicinity
of the A-pillars the test load is evenly distributed over the entire
roof in Standard No. 220.
RVIA used the following arguments to support its petition:
(1) There are several van conversions currently produced with
raised roofs that are subject to Standard No. 216. Such vehicles
include conversions of the Plymouth Voyager, Doge Caravan, Chrysler
Town & Country, Chevrolet Astro, and GMC Safari minivans. Because of
the raised roof configuration, the load plate for the test cannot be
placed according to the specified procedure in the standard.
(2) Since the original vehicles, prior to conversion that raises
the roof, have been certified as complying with Standard No. 216, the
A-pillar strength will have already been demonstrated. Testing to
Standard No. 220 after raising the roof would then test the strength of
the entire roof structure.
B. Ford
Ford recently submitted a petition focused on what it believes is
an anomaly with the current positioning procedures for the test plate
in Standard No. 216. Ford indicated that several of its models with
aerodynamic roof designs have roof slopes greater than 5 deg. at the
forward edge of the roof. The test plate is required to be angled
5 deg. of the forward edge of the roof. The effect of the slope on
these aerodynamic roof designs is that the initial point of contact
between the roof and the test plate is moved several inches behind the
A-pillar when the test plate is positioned according to the current
placement procedure. Ford believes this rearward movement of the
initial contact point is contrary to the agency's intent when it
initially promulgated the standard.
Ford argued that additional support for this argument can be found
in S6.2 of Standard No. 216, which specifies the test plate should be
applied by ``(o)rient(ing) the test device as shown in Figure 1 * * *''
Figure 1 clearly shows the test plate is applied at the front corner of
the roof. Thus, for vehicles with sloped, aerodynamic roofs, there is a
conflict between Figure 1, which positions the test plate forward of
the leading edge of the roof, and S6.2(d), which specifies that the
test plate should be positioned with reference to the initial point of
contact, even if that point is rearward of the leading edge of the
roof. Ford acknowledged that NHTSA has addressed this conflict in an
October 3, 1980 interpretation, in which the agency said that the
language of S6.2(d) should be used to position the test plate, even if
that means the test plate will not be forward of the A-pillar or the
roof's leading edge. Ford indicated that it has followed this
interpretation, but it does not believe that such an interpretation
results in improved roof crush performance when vehicles are in use on
the public roads.
Ford asked in its petition that S6.2(d) of Standard No. 216 be
amended to specify that the leading edge of the test plate should
always be placed over the leading edge of the vehicle roof. Ford
proposed the following language:
The initial contact point, or center of the initial contact
area, is on the longitudinal centerline of the device. A plane
perpendicular to the lower surface of the test device and 25 mm
rearward of the front edge of the lower surface passes through the
rearmost point of the opening in the body structure for the
windshield.
Agency Response to the Petitions
NHTSA believes that both of these petitions raise issues that
should be examined further. RVIA believes the requirement to move the
test plate rearward of the A-pillar on conversion vans with raised
roofs imposes needless and significant burdens on second-stage
manufacturers. Ford believes the requirement to move the test plate
rearward of the A-pillar on vehicles with aerodynamic roofs is contrary
to the agency's original intent and results in a less stringent test of
the A-pillars' strength. both of these are relevant issues.
Accordingly, the agency has granted both the RVIA and Ford petitions.
NHTSA is now conducting a research program to investigate the test
methods described in these petitions and to see if the current test
procedures are suitable for vehicles with raised or contour roofs, or
if some changed test procedures are needed.
The fact that the agency has granted these petitions does not mean
that the requirements of the standard will necessarily be modified.
NHTSA has undertaken to investigate this issue more carefully and,
after the conclusion of this investigation, will decide whether it
should propose any modifications to the test procedure. In the
meantime, manufacturers must continue to certify their vehicles for
compliance according to the existing requirements of Standard No. 216
unless and until some modified requirements are in place.
Further, the fact that the agency has granted these petitions does
not mean that NHTSA agrees with all that is said in these petitions.
For instance, the RVIA petition asks that Standard No. 220 test for
roof crush resistance be substituted for the current Standard No. 216
test for roof crush resistance. NHTSA is concerned that such a
substitution could result in a less stringent test over the front
seating positions, or may not be appropriate to evaluate the strength
of the pillars for crush resistance. Standard No. 220 was developed for
school buses and it assesses the roof crush protection afforded for the
entire seating area. It does this by using a test procedure that loads
the entire roof structure, including A-, B-, and any other pillars in
the vehicle.
By way of contrast, Standard No. 216 is applicable to smaller
vehicles. Front seat occupants experience the vast majority of deaths
and injuries in these vehicles. To address this, a test procedure was
developed to assess the roof crush protection afforded to front seat
occupants. The test procedure concentrates the load in the vicinity of
one of the A-pillars to simulate the most severe impact condition that
a pillar would experience in a rollover crash.
It appears, then, that substituting the Standard No. 220 test for
raised roof vehicles instead of the Standard No. 216 test, would trade
off increased roof crush protection for rear seat occupants in those
vehicles, with diminished protection for front seat occupants. However,
there is no supporting information in the RIVA petition that quantifies
either how much protection front seat occupants might lose or how much
protection rear seat occupants might gain from this substitution. The
agency will examine this carefully in its research before deciding
whether to consider any change to the current test requirements.
In addition, RVIA suggested that the strength of the A-pillars in
the vehicle that is converted by its members would be demonstrated by
the original vehicle manufacturer's certification for the vehicle that
complied with Standard No. 216. The agency is not convinced at this
point that this conclusion is valid because the agency has no data to
prove or disprove that the roof strength in the area of the A-pillars
is affected by raised roof conversions. RVIA provided no such data in
its petition in support of their claim.
In its petition, Ford did provide some test data, although they
were very limited. Ford provided roof crush test results for two
prototypes of a new vehicle design. In one, the test plate was
positioned according to the current Standard No. 216 procedures. In the
second, the front edge of the test plate was positioned 100 mm behind
the front corner of the roof (closer to the A-pillar structure). The
test results from the latter procedure produced a peak force that was
49 percent higher than the peak force produced using the current
positioning procedure, within 5 inches of crush. When following
Standard No. 216 test procedures, the test plate was positioned 150 mm
behind the windshield opening, completely missing the A-pillar and
leading edge of the roof.
Ford's petition indicates that its proposed change to the language
of S6.2(d) would consistently locate the test place one inch forward of
the rearmost edge of the front windshield opening, thereby reducing
test variability and ensuring that the test plate is positioned ahead
of the roof's leading edge. NHTSA notes that while this would position
the test plate over the leading edge of the roof, it would not
necessarily load the roof at the rearmost windshield opening. Ford's
proposed change retained the same test plate angles currently specified
in Standard No. 216, which means the initial contact point for the test
plate on the roof would be the same as at present. In other words, it
appears to NHTSA that Ford's proposal would ensure the consistent
orientation of the test plate over the front of the roof, but would not
ensure that area of the roof would be tested. Further, the agency is
uncertain whether the proposed test plate positioning one inch forward
of the rearmost edge of the front windshield opening would be an
improved test for all vehicles with uncommon roof shapes or whether it
would reduce the stringency of the current test procedure.
Areas in Which the Public's Ideas and Information Are Requested
The agency is interested in comments on the changes requested in
both the Ford and RVIA petitions. Therefore, the agency is seeking from
all interested parties comments on the two proposals along with any
available test data to substantiate or refute those proposals. The
agency is also interested in other ways to accommodate aerodynamically
sloped and raised roof vehicles. For instance, should the angles at
which the test plate is applied and/or the size and shape of the test
plate itself be changed? If the plate size were reduced or if the plate
shape were changed to circular, the test plate could be placed over the
A-pillar region on raised roof vehicles.
Standard No. 216 currently provides that the test plate shall be
angled 5 deg. toward the front of the vehicle, when viewed from the
side of the test vehicle. This angle could be changed sufficiently to
ensure the test plate would contact the A-pillar region, with the new
angle based on an analysis of real world crashes and roof geometries.
The agency is also interested in any other approaches the public
might wish to suggest in this area. As always, the most helpful
comments will be those that set forth data to substantiate the position
taken in the comment. NHTSA would like to alert commenters that the
agency will not propose any changes to Standard No. 216 test procedures
until the agency is satisfied that data and analysis show the changes
will not reduce real world safety protection for vehicle occupants.
Submission of Comments
Interested persons are invited to submit comments in response to
this request for comments. It is 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 15-page limit. This limitation is intended to encourage
commenters to state their positions and arguments concisely.
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 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. 30111, 30168, delegations of authority at
49 CFR 1.50 and 49 CFR 501.8.
Issued on December 20, 1994.
Barry Felrice,
Associate Administrator for Rulemaking.
[FR Doc. 94-31739 Filed 12-23-94; 8:45 am]
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