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Federal Motor Vehicle Safety Standards; Roof Crush Resistance

American Government Special Collections Reference Desk

American Government Topics:  National Highway Traffic Safety Administration, Federal Motor Vehicle Safety Standards

Federal Motor Vehicle Safety Standards; Roof Crush Resistance

Barry Felrice
Federal Register
December 27, 1994

[Federal Register: December 27, 1994]


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.


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.

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.



    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.



    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 

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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