level would correspond to structural roof contact rather than interior
trim components coming loose. This was consistent with comments from
DaimlerChrysler and GM that used a force load approach as a reliable
method of identifying head contact and removing the uncertainty of
random interior trim contact.
---------------------------------------------------------------------------

    \25\ See report Two-Sided Roof Crush Testing Analysis placed in
the docket with this notice.
---------------------------------------------------------------------------

    Our test experience with the simpler HPF proved to be repeatable in
the tests and easier than using the Hybrid III dummy itself during the
test.
    We believe specification of the HPF appropriately addresses
commenters' concerns regarding variability with regard to locating the
dummy's head. With the HPF rigidly fixed to the vehicle, we also
believe this addresses the concerns of manufacturers, such as Porsche,
which alter the attitude of the vehicle with respect to the load press
when conducting roof crush tests.
    Because head contact is defined as a load on the headform, the test
result is more objective/repeatable, and not sensitive to incidental
contact with interior surfaces that may disengage during testing.
    We disagree with comments from manufacturers that recommended the
removal of the roof's interior trim prior to testing in order to
simplify the procedure. The agency's headroom analysis established a
correlation between injuries and head contact with a NASS-CDS roof
component when the injury source was the A-Pillar, B-Pillar, front or
rear header, roof rail or the roof itself. These interior surfaces are
considered interior trim. We believe they should be factored in when
considering the available headroom in the test. By defining head
contact as occurring when a 222 N (50 pound) load is applied to the
headform, we are addressing concerns about incidental contact with
trim. This definition of head contact also addresses concerns about
possible conflicts with the intent of FMVSS No. 201U, with respect to
concerns with incidental contact. If the headform experiences a 222 N
(50 pound) load, the contact is not incidental and there is a safety
issue related to available headroom.
    We also disagree with comments from manufacturers recommending that
the head contact device be a headform on a stand located at a position
specified by the manufacturer and not a crash test dummy or a headform
located based on SAE J826 manikin (OSCAR) location. The HPF test
procedure (as would a test procedure using a test dummy) measures head
contact in the vehicle being tested. However, the approach of using a
headform on a stand located at a position specified by the manufacturer
would not necessarily represent the actual vehicle build.
    We note that the SAE J826 mannequin has long been incorporated in
NHTSA's safety standards for purposes of determining the H-point
location. Issues concerning the accuracy of measurements using this
device and the HRMD were addressed at length in our rulemaking
upgrading our head restraints standard. Manufacturers can address
concerns about different trim and seating options by factoring in the
location where the headform (and also the head of a typical average
size male occupant) will be under those different options.
    Definition of head contact:
    As noted above, the Alliance stated that possible use of a 222 N
(50 pound) contact criterion has not been supported

by any scientific data. Public Citizen expressed concern that defining
head contact with the HPF by means of force-deflection criteria would
result in a significant number of front seat occupants suffering head
and neck injuries.
    We note that the load as defined is not intended to be an injury
criterion, for which one would expect supporting scientific data, but
is instead simply an objective way of defining head contact and
avoiding treating incidental contact with loose trim as head contact.
Our testing has shown, on average, once physical contact between the
interior roof trim and the headform occurred resulting in the onset of
a load on the headform, the platen traveled 6 mm (0.24 inches) prior to
the load reaching 220 N (50 pounds). Therefore, we do not expect
increased head and neck injuries from this approach. Moreover,
retention of the current platen travel requirement will also prevent
such increased injuries. We selected the 222 N (50 pound) contact
criterion based on comments from GM and DaimlerChrysler and our own
testing experience.
    Possible Reduced Stringency:
    IIHS, LSMM and Public Citizen expressed concern that if the platen
travel requirement were not retained in addition to adopting the
headroom criterion, adoption of the proposed headroom criterion would
represent a decrease in stringency for the standard's performance
criterion. This is not an issue since we are retaining the platen
travel requirement.
    Possible more restrictive requirements. We disagree with commenters
which recommended that the agency reduce the platen travel requirement
to 76.3 mm (3 inches).
    On average, the vehicles the agency has tested have reached the
maximum SWR in 90 mm (3.5 inches) of platen travel. A requirement for
reduced platen travel would represent an increase in stringency and, in
many respects, would be similar to a requirement for a higher SWR. We
note that the agency has already been considering the possibility of a
higher SWR, as well as two-sided test requirement, which would also
increase stringency. We have not conducted testing to analyze the
appropriateness of applying a 3 inch platen travel requirement to all
vehicles. However, we believe the other issues we have considered
ensure an appropriate level of stringency.
    We also do not agree with commenters recommending the use of the
95th percentile dummy (or equivalent HPF) for measuring head contact.
Restricting headroom to a 95th percentile occupant is similar to
limiting the platen displacement to 76.3 mm (3 inches) in increasing
stringency. As indicated above, we believe the other issues we have
considered ensure an appropriate level of stringency. Moreover, we
believe that the relationship between vehicle headroom and occupant
size is insignificant in most cases. It is likely that taller front
seat occupants adjust the seat positions to prevent uncomfortable
proximity to the roof such as by lowering the seat cushion bottom,
increasing the seat back angle and/or adjusting the seat position
further rearward.
    Low roofline vehicles: In the NPRM, we discussed possible concerns
with vehicles that have relatively little available headroom when the
50th percentile adult male dummy is positioned properly in the seat.
Vehicles with these aerodynamically sloped roofs will hereafter be
referred as ``low roofline vehicles.'' We stated that we were concerned
that, in some limited circumstances, the headroom between the head of a
50th percentile male dummy and the interior headliner is so small that
even minimal deformation resulting from the application of the required
force would lead to test failure. NHTSA requested comments on whether
any additional or substitute requirements would be appropriate for low
roofline vehicles in order to make the standard practicable.
    Several commenters, including DaimlerChrysler, Ford, Porsche,
Mitsubishi Motors R&D of America, Inc. (Mitsubishi) and Hyundai America
Technical Center, Inc. (Hyundai), provided comments on low roofline
vehicles. The commenters recommended that the requirements be limited
to 127 mm (5 inches) of deflection for a load of 2.5 SWR in order to
minimize the negative impact on continued availability of this type of
vehicle if the agency were to adopt a headroom requirement.
DaimlerChrysler stated that the proposed standard was not reasonable,
practicable and appropriate for these types of motor vehicles as
required by the Motor Vehicle Safety Act. It further stated that the
agency had not demonstrated in the NPRM or the PRIA, the feasibility of
going beyond 1.5 times the UVW in roof strength without head contact
for vehicles with steeply raked windshields and reduced headroom.
    DaimlerChrysler suggested its recommendation would be applicable to
the Chrysler Crossfire, Dodge Viper, and McLaren Mercedes models and
successors, which are generally designed with a steeply raked
windshield and a low roofline for reduced frontal area and low drag. It
further stated that this modified requirement should also apply to
other kinds of vehicles, such as any two-seater that is designed with a
more aggressively raked windshield. DaimlerChrysler recommended that
vehicles of this type could be identified or defined based on a set of
characteristics such as the Static Stability Factor (SSF) (e.g.,
>=1.4), NCAP rollover rating (e.g., >=4 stars), height-to-width ratio
(e.g., <=0.75), windshield rake angle, vehicle height, etc.
    Ford stated that low roofline vehicles are not the only vehicles
that have problems with limited headform clearance. It stated that
vehicles that may be considered as ``high roofline'' can also have
limited headform-to-roof clearance due to interior package design.
Based on the interior package design of a particular vehicle,
regardless of roof line characteristics, the critical dimension
(distance between the outboard side of dummy's headform and the roof
side rail trim) can be minimal. Mitsubishi commented that headform-to-
roof clearance is a concern for not only low roofline vehicles but may
be more generically classified as being an issue for limited headroom
vehicles.
    Porsche expressed concern that low roofline vehicles have less
opportunity for enhanced roof structures because the focus on
performance and aerodynamics virtually eliminates the option of taller
pillar supports.
    Hyundai stated it will be challenging for low roofline vehicles and
particularly two door coupe vehicles to meet the upgraded standard
because of the lack of headroom and the possibility the B-pillar may
not be loaded because it is further away from the A-pillar compared to
a sedan. It requested that the agency define a low roofline vehicle to
explicitly include two-door coupe vehicles in the definition. It also
requested that these types of vehicles be allowed to meet the current
requirements until it can be demonstrated that practicability with the
upgrade is feasible.
    Based on its analysis, the agency believes the requirements it is
adopting will not create new problems for low roofline vehicles. In our
most recent two-sided research program, the agency tested a 2006
Chrysler Crossfire, a vehicle identified as a low roofline vehicle.
During the first-side test, the vehicle had a peak SWR of 2.9 at 97 mm
(3.85 inches) of platen displacement. Head contact based upon our
criteria (222 N load on the headform) occurred at 107 mm (4.21 inches)
of platen travel. This showed the maximum SWR was reached prior to head
contact. On the

second side, the Crossfire reached a 2.7 SWR prior to head contact at
135 mm (5.31 inches) of platen travel.
    The agency tested another low roofline vehicle, the 2007 Scion tC.
This vehicle achieved a maximum SWR of 4.6 on the first side at 113.3
mm (4.46 inches) of platen travel. Head contact occurred at 119 mm
(4.68 inches) of platen travel. On the second side, the Scion achieved
a 4.1 SWR prior to head contact at 95.0 mm (3.74 inches) of platen
travel. From these tests we believe it is feasible and practicable for
smaller vehicles with less initial headroom to meet the requirements.
Since both are two-door vehicles, we disagree with Hyundai's assertion
that two-door vehicles pose an unreasonable challenge.
    We agree with Ford's observations that some vehicles that may
appear to be ``high roofline'' vehicles, but may experience head
contact in less platen travel than a ``low roofline'' vehicle. The 2007
Buick Lucerne, a large full size vehicle reached a maximum SWR of 2.3
at a platen displacement of 110 mm (4.33 inches). The vehicle did not
reach the proposed SWR of 2.5. In this test, platen travel at head
contact was less than the Crossfire. Therefore, the arguments being
made for excluding low roofline vehicles may not be unique to low
roofline vehicles. Ford's comments also illustrate the difficulty in
identifying what is or is not a low roofline vehicle.
    DaimlerChrysler suggested SSF or other vehicle parameters could be
used to define low roofline vehicles and exclude them from the headroom
requirement. However, we believe that this exclusion is not warranted
based on our testing. Moreover, we are concerned about the safety
impact of unnecessarily excluding vehicles from the upgraded
requirements.
6. Leadtime and Phase-In
    NHTSA proposed that manufacturers be required to comply with the
new requirements three years after the issuance of the final rule. At
that time, based upon vehicle testing, we estimated that 68 percent of
the current fleet already complied with the proposed roof strength
criteria. We anticipated the proposal would not require fleet-wide roof
structural changes and believed the manufacturers had engineering and
manufacturing resources to meet the new requirements within that
timeframe.
    In commenting on the NPRM, vehicle manufacturers and their
associations argued that additional leadtime was needed, and that a
significantly greater portion of the fleet would require redesign than
estimated by the agency. The Alliance, Ford and GM stated that
approximately 60 percent of their fleets would need to be redesigned,
and Hyundai commented that 75 percent of its vehicles would need
changes to comply with the requirements.
    Toyota, Ford, GM, Hyundai, Nissan and DaimlerChrysler stated that
the agency underestimated the necessary modifications to vehicle design
and manufacturing challenges that must be overcome to comply with the
proposal. Ford, GM, DaimlerChrysler, and Toyota stated that the
challenges are especially true for heavier vehicle over 2,722 kg (6,000
pounds) GVWR which have not been required to meet FMVSS No. 216.
    GM and Ford stated that they rely on outside suppliers for advanced
high strength material and currently there is an insufficient supply
base for high strength steel. They also cited significant manufacturing
challenges that must be overcome to adapt ultra high strength steel to
the mass production environment. They argued that leadtime with a
phase-in is necessary to permit growth in the supply base and allow the
manufacturers to resolve manufacturability issues for high volume
production requirements.
    The vehicle manufacturers generally requested a 3-year leadtime
followed by a multi-year phase-in. Most supported a minimum 3-year
phase-in. GM requested a 4-year phase-in period, and DaimlerChrysler
requested a 5-year phase-in only for vehicles over 3,855 kg (8,500
pounds). The AIAM requested compliance credits for an early phase in,
while the Alliance, Ford and Mitsubishi requested carryforward credits.
The AIAM and Ferrari requested that small volume manufacturers be
permitted to comply at the end of the phase-in due to compliance
difficulties, long product cycles and cost penalties associated with
running structural changes to vehicle programs.
    In commenting on the SNPRM, the Alliance reiterated points made in
its comment on the NPRM, stating that the final rule needs to provide
at least three years initial leadtime followed by a multi-year phase-in
with carryforward credits. It stated that additional time is needed if
the agency adopted the proposed head contact criterion, a two-side test
requirement, or an SWR higher than 2.5. Ford suggested that if the
agency adopted a more stringent requirement than the one it focused on
in the NPRM, that vehicles meeting a 2.5 SWR/one-sided test requirement
earn compliance credits before and during the phase-in.
Agency Decision/Response
    After carefully considering the comments and available information,
and for the reasons discussed below, we have decided to adopt different
implementation schedules for vehicles with a GVWR of 2,722 kilograms
(6,000 pounds) or less, i.e., the vehicles currently covered by FMVSS
No. 216, and those with a higher GVWR. The implementation schedules we
are adopting are as follows:
    Passenger cars, multipurpose passenger vehicles, trucks and buses
with a GVWR of 2,722 kilograms (6,000 pounds) or less. We are adopting
a phase-in of the upgraded roof crush resistance requirements for these
vehicles. The phase-in requirement for manufacturers of these vehicles
(with certain exceptions) is as follows:

--25 percent of the vehicles manufactured during the period from
September 1, 2012 to August 31, 2013;
--50 percent of the vehicles manufactured during the period from
September 1, 2013 to August 31, 2014;
--75 percent of the vehicles manufactured during the period from
September 1, 2014 to August 31, 2015;
--100 percent of light vehicles manufactured on or after September 1,
2015.

    Credits may be earned during the phase-in, i.e., beginning
September 1, 2012, and carried forward through August 31, 2015.
    Small volume manufacturers are not subject to the phase-in but must
meet the requirements beginning on September 1, 2015. Vehicles produced
in more than one stage and altered vehicles must meet the upgraded
requirements beginning September 1, 2016.
    Multipurpose passenger vehicles, trucks and buses with a GVWR
greater than 2,722 kilograms (6,000 pounds) and less than or equal to
4,536 kilograms (10,000 pounds). All of these vehicles must meet the
requirements beginning September 1, 2016,\26\ with the following
exceptions. Vehicles produced in more than one stage and altered
vehicles must meet the requirements beginning September 1, 2017.
---------------------------------------------------------------------------

    \26\ If heavier vehicles are designed to meet the new
requirements early, their production volumes are not to be included
when calculating the light vehicle fleet phase-in percent
compliance. The phase-in schedule for the two fleets are separate.
---------------------------------------------------------------------------

    Our rationale for this implementation schedule is as follows.
    As discussed in the FRIA, a significantly larger proportion of the
vehicle fleet will require changes than estimated at the time of the
NPRM. This

would be true even for a 2.5 SWR/one-sided test requirement, and the
proportion is higher for the 3.0 SWR/two-sided requirement. We
therefore agree that a combination of approximately three years
leadtime plus a multi-year phase-in is appropriate.
    In developing the implementation schedule, we have considered costs
and benefits. The vast majority of the benefits of the rule come from
vehicles with a GVWR of 2,722 kilograms (6,000 pounds) and less. Of the
135 fatalities that will be prevented each year, 133 will come from
these lighter vehicles. Moreover, the lighter vehicles are generally
redesigned more often than the heavier vehicles. Also, manufacturers
are familiar with designing and testing the lighter vehicles to meet
the current FMVSS No. 216 requirements.
    In order to implement the upgraded requirements in a cost effective
manner, we believe it is appropriate to provide approximately three
years of leadtime coupled with a 25 percent/50 percent/75 percent/100
percent phase-in for the lighter vehicles, and longer leadtime for the
heavier vehicles. The benefits for the heavier vehicles are relatively
small, and approximately seven years leadtime will generally permit
manufacturers to improve roof strength at the same time they redesign
these vehicles for other purposes.
    While vehicle manufacturers made varying recommendations for the
specific provisions of a phase-in, the phase-in we are adopting for
lighter vehicles is within the general range of those recommendations.
We recognize that manufacturers argued that longer leadtime should be
provided for requirements more stringent than a 2.5 SWR/one-sided test
requirement. However, while the 3.0 SWR/two-sided test requirement will
increase the number of vehicles requiring redesign and the specific
countermeasures that are needed, we believe that approximately three
years of leadtime coupled with a 25 percent/50 percent/75 percent/100
percent phase-in provides sufficient time for manufacturers to make
these changes. We note that the vehicles likely to present the greatest
design challenges under our proposal were the ones with a GVWR above
2,722 kilograms (6,000 pounds), for which we are providing longer
leadtime and a lower SWR requirement. Vehicle manufacturers have not
provided persuasive evidence that longer leadtime is needed, or that a
less stringent requirement should be established for an initial period.
    We believe that providing for carry forward credits during the
phase-in, but not the earning of advance credits prior to the beginning
of the phase-in, balances encouraging early compliance and manufacturer
flexibility with also encouraging manufacturers to continue to improve
roof strength during the years of the phase-in.
    As with a number of other rulemakings, we are establishing special
requirements for small volume manufacturers and for vehicles produced
in more than one stage and altered vehicles.
    Given the leadtime needed for manufacturers to redesign their
vehicles to meet the upgraded roof crush requirements, we find good
cause for the compliance dates included in this document.

b. Aspects of the Test Procedure

1. Tie-down Procedure
    In the NPRM, we proposed to revise the vehicle tie-down procedure
in order to improve test repeatability. Specifically, we proposed to
specify that the vehicle be secured with four vertical supports welded
or fixed to both the vehicle and the test fixture. If the vehicle
support locations are not metallic, a suitable epoxy or an adhesive
could be used in place of welding. Under the proposal, the vertical
supports would be located at the manufacturers' designated jack points.
If the jack points were not sufficiently defined, the vertical supports
would be located between the front and rear axles on the vehicle body
or frame such that the distance between the fore and aft locations was
maximized. If the jack points were located on the axles or suspension
members, the vertical stands would be located between the front and
rear axles on the vehicle body or frame such that the distance between
the fore and aft locations was maximized. All non-rigid body mounts
would be made rigid to prevent motion of the vehicle body relative to
the vehicle frame.
    We explained that we believed this method of securing the vehicle
would increase test repeatability. Welding the support stands to the
vehicle would reduce testing complexity and variability of results
associated with the use of chains and jackstands. We also stated that
we believed that using the jacking point for vertical support
attachment is appropriate because the jacking points are designed to
accommodate attachments and withstand certain loads without damaging
the vehicle.
Comments
    Commenters on the proposed tie-down procedure included the
Alliance, DaimlerChrysler, Ford, GM, Toyota, AIAM, Mr. Chu, Hyundai and
BMW Group (BMW). A number of commenters agreed with the agency's
intention to revise the tie-down procedure for the quasi-static test to
improve test repeatability. However, manufacturers raised specific
concerns about the proposed procedure. AIAM, Mr. Chu, Hyundai and BMW
alternatively recommended retention of the current tie-down procedure.
Advocates and SAFE supported the revised tie-down procedure because it
has the potential to ensure less vehicle movement during testing.
    Ford suggested that the proposed tie-down procedure can cause
localized, unrealistic floor pan deformations that can reduce the
measured strength of the roof. The Alliance, DaimlerChrysler, Ford, GM
and Toyota recommended providing one vehicle support per vehicle
pillar. However, they recommended placing the support along the sill,
as opposed to the jack points, since they stated that jack points are
not designed to withstand the forces generated during a roof crush
test. The commenters suggested that this would minimize unwanted body
displacement by providing a direct load path during testing which the
proposal does not address. For body-on-frame vehicles, DaimlerChrysler
also recommended support of the vehicle frame, in addition to the
pillar supports, to further prevent sag of the body. In the event that
the agency adopts the practice of supporting the body at the pillars,
the Alliance, GM, and BMW also requested that a minimum area of support
be provided to avoid concentrated loading.
    The Alliance, BMW and Ford also had concerns about welding supports
to the vehicle body. The commenters stated that welding could decrease
the material properties of the body reducing the measured roof
strength, and welding might not be practical or possible for non-
ferrous or composite materials. BMW alternatively recommended clamping
instead of welding, citing concerns about welding certain materials and
the possibility of failure of the sills due to the welding. Ford
recommended contacting the manufacturer for instructions about welding
aluminum sills, if the agency proceeded with the welding protocol.
    AIAM, Mr. Chu, Hyundai and Nissan recommended maintaining the
existing procedure that supports the entire length of the sill in order
to reduce complexities and unwanted body deformation with the tie-down
proposal. Nissan suggested supporting the wheelbase at the sill flange
pinch welds between the two channels that grab the

pinch weld on the bottom of the sill. The side sill flange would be
constrained to prevent transverse body movement when tested. Hyundai
recommended that the current procedure be permitted at the
manufacturer's option since it believes the revised tie down procedure
is burdensome. DaimlerChrysler and Toyota also recommended continuous
mounting along the sills suggesting this would prevent unwanted body
deformation at the jack point locations.
    For vehicles without B-pillars, the Alliance, Ford, and GM
recommended that a support be placed at the seam between the doors as
if a pillar existed between the doors. The Alliance stated that doors
connected without a pillar often have reinforcements to compensate for
the structure that would be afforded by a pillar if it were part of the
vehicle design, and therefore, the joint between the doors will act as
one of the direct load paths from the roof to the rocker. Without a
support at the door joint, the Alliance suggested that the roof
strength cannot be accurately measured in these types of vehicles.
Agency Response
    As part of analyzing the comments on the proposed tie-down
procedure for the quasi-static test, the agency conducted analytical
simulations using a finite element model on a late model Ford
Explorer.\27\ First the agency performed an analysis of the proposed
procedure where the vehicle was supported at the jack locations. Two
additional models were also developed to evaluate supporting the
vehicle body under the pillars and continuously along the length of the
body sill, as the commenters suggested.
---------------------------------------------------------------------------

    \27\ See report, Finite Element Simulation of FMVSS No. 216 Test
Procedures, placed in the docket with this notice.
---------------------------------------------------------------------------

    The Ford Explorer was modeled because it is a body-on-frame \28\
vehicle, and according to the comments, the proposed procedure would
not accurately evaluate the roof strength of that type of vehicle. The
first Explorer tie-down model followed the NPRM procedure where the
vehicle was supported at its jack point locations. This was along the
frame mounted inward of the vehicle body sill in the case of the
Explorer. The analysis showed that the NPRM procedure produced
compression of the body-to-frame rubber body mounts. We believe this
tie-down simulation did not accurately evaluate the strength of the
roof because the body was not isolated in the simulation. The loading
of the body mounts is also unrealistic in a rollover. The results were
consistent with Ford's comment that suggested supporting a vehicle by
its frame at the body mount locations could cause floor pan deformation
and thereby reduce the measured strength of the roof.
---------------------------------------------------------------------------

    \28\ A body-on-frame vehicle is constructed by attaching a
vehicle body to a rigid frame which supports the drivetrain. At the
attachment points, rubber body mounts are used to isolate the body
from vibration.
---------------------------------------------------------------------------

    The results of the other simulations (vehicle secured under the
pillars and vehicle secured along the rocker/sill) showed higher roof
strength than the NPRM procedure. There was nearly a 7 percent increase
in roof strength within 127 mm (5 inches) of platen travel when the
vehicle's body was supported under the pillars compared to the NPRM
procedure. The simulation results using the continuous sill support
tie-down showed a 3 percent increase in roof strength compared to the
NPRM procedure. Overall, in both simulations, the body sag in the floor
pan did not appear to be a concern and produced a more realistic
loading of the roof. The load-deformations curves were also similar,
whereas the results from the simulation using the NPRM tie-down
procedure diverged early in the analysis at approximately 18,000 N or
0.8 SWR.
    We note that the full sill tie-down procedure generated a lower
peak force when compared to the vehicle supported under the pillars.
The simulation for the full sill tie-down procedure did not include any
constraints for the Explorer's frame. However, when the vehicle body
was supported under each pillar, a number of vertical supports were
added to support the mass of the frame. This could explain the slight
difference in the maximum strength of the roof. However, we believe the
difference is negligible.
    After considering the comments and the computer simulations, we
decided, for purposes of fleet testing, to revise the tie-down
procedure to support the vehicle continuously under the sill. We
believe this approach further reduces any variability compared to the
Alliance recommendation because the entire wheelbase of the vehicle is
supported and not just under each pillar. Also, the peak force
difference in the computer models was not a significant issue because
both methods addressed the commenters' main concern of inappropriate
floor pan deformation. For body-on-frame vehicles, additional supports
would be placed under the frame as this constraint was not included in
the computer simulation and might account for the difference in peak
force. The full sill tie-down procedure is consistent with the existing
FMVSS No. 216 requirement supported by AIAM, Mr. Chu, Hyundai, and
Nissan.
    For the fleet testing,\29\ the vehicle's sill at the body flange
weld was fully supported along the wheelbase between two box tubes and
securely fixed into place with high strength epoxy. For body-on-frame
vehicles, additional supports were placed under the frame to reduce
body sag created by an unsupported frame, as recommended by
DaimlerChrysler. Epoxy was selected in response to the Alliance, BMW
and Ford's comments that welding may adversely alter the vehicle's
structure prior to testing. We believe the epoxy will not alter the
material properties of the vehicle structure or cause complications for
sills made of non-ferrous or composite materials. The revised test
procedure provided support for each of the vehicle pillars and provided
a stable load path when tested, consistent with the recommendations by
the Alliance, DaimlerChrysler, Ford, GM and Toyota. Also, by supporting
the vehicle along the wheelbase, which includes the door seam for
vehicles without a B-pillar (the joint between the doors), a
reactionary surface is provided for the applied load when tested,
addressing the Alliance, GM and Ford's concerns.
---------------------------------------------------------------------------

    \29\ See report, Two-Sided Roof Crush Strength Analysis, placed
in the docket of this notice.
---------------------------------------------------------------------------

    During our evaluation of the tie-down procedure,\30\ dial
indicators were placed at the sill below the vehicle's pillars on the
opposite side of the platen travel to check for vehicle displacement
during the test. The tie-down procedure showed on average less than a
millimeter (0.04 inches) of body displacement at all measurement
locations, parallel to the direction of platen motion for both unibody
and body-on-frame vehicles. For comparison, the agency also tested a
Buick Lacrosse that was rigidly supported along the entire wheelbase
and compared the result to another Lacrosse test where the sill was
supported along the wheelbase only at 152.4 mm (6 inch) increments. The
Lacrosse was also supported under the pillars, as recommended by the

Alliance. The results showed that the body displacement was lower for
the full sill tie-down when compared to the results where the sill was
only partially supported.
---------------------------------------------------------------------------

    \30\ The agency measured the sill displacement at three
locations along the wheelbase on the side opposite to the force
application on the roof, for 13 vehicles. Ten of the tests were
single-sided and three were two-sided. The sill displacement ranged
from 0 to 2.3 mm (0.09 inches). The VW Jetta achieved the highest
SWR level at 5.7 in this data set and experienced almost no sill
movement. In the three two-sided tests in this series, conducted
with the Subaru Tribeca and two Buick Lacrosses, the agency did not
observe any significant difference in sill displacement on the
second side compared to the first.
---------------------------------------------------------------------------

    After considering the comments and in light of the testing and
simulations, we are adopting the revised tie-down procedure, where the
vehicle is supported at the sill, along the entire wheelbase. This
procedure reduces vehicle displacement, more accurately measures the
strength of the roof, and is more robust than the procedure recommended
by the Alliance and its members. Furthermore, the revised test
procedure addresses the comments to the NPRM because it supports the
vehicle pillars during testing and reduces the likelihood of vertical
and horizontal translation of the body.
    We note that, in light of the fact that the test procedure is
consistent with the current FMVSS No. 216 test procedure while
providing improved clarity, the agency has adopted it for use in
current FMVSS No. 216 \31\ compliance tests. This procedure has been
used for 19 fiscal year 2007 and 2008 OVSC compliance tests.
---------------------------------------------------------------------------

    \31\ TP-216-05 Laboratory Test Procedure for FMVSS No. 216,
November 16, 2006.
---------------------------------------------------------------------------

2. Platen Angle and Size
    In the NPRM, we did not propose to change the test device
orientation or the size of the test plate. However, we included a
discussion of comments related to test device orientation and size that
we had received in response to the October 2001 RFC.
    Under the current test procedure specified in FMVSS No. 216, the
test plate is tilted forward at a 5-degree pitch angle, along its
longitudinal axis, and rotated 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 size of 762 mm (30 inches) wide by 1,829
mm (72 inches) long is designed to load the roof over the occupant
compartment. The edges of the test plate are positioned based on fixed
points on the vehicle's roof. The forward edge of the plate is
positioned 254 mm (10 inches) forward of the forwardmost point on the
roof, including the windshield trim. We note that, as discussed later
in this document, there is a secondary test procedure for certain
vehicles with raised roofs or altered roofs, which we proposed to
eliminate.
Comments
    The agency received numerous comments and recommendations to change
the platen test angle and size. A number of the comments were from
safety advocacy groups. Some commenters recommending a 2-sided test
requirement recommended that we use different criteria for the two
tests.
    Consumers Union cited comments it had made on the agency's 2001 RFC
and the agency's discussion in the NPRM. That commenter noted that it
had recommended that the agency modify the test plate load and size. It
stated that it continues to believe that the current plate load and
size does not reflect real-world rollover conditions. Consumers Union
stated that it believes that more of the roof crush force is absorbed
by the A-pillar than accounted for by the current or proposed
procedure. It recommended that the agency conduct additional studies
concerning this issue.
    IIHS commented that testing roof crush strength at multiple load
angles would add to the meaningfulness of the quasi-static test
requirement that NHTSA currently specifies. However, it also stated
that in the absence of a range of plate angles, any distinct test angle
choice should be supported by evidence that such an angle is
representative of a significant percentage of real-world rollovers.
    Various commenters recommended that the agency change the platen
pitch in ways they believe would better reflect the more aggressive
loading angles that are frequently sustained in real-world rollover
crashes, particularly for SUVs and pickups. The general recommendation
was to increase the pitch angle of the platen to 10 degrees because
commenters believed the proposed 5 degree pitch is not realistic.
    CAS stated that the pitch angle must be increased to at least 10
degrees to emulate actual rollovers where damage to front fenders is
testimony to the fact that in a rollover, the pitch angles are this
high. Advocates suggested that vehicles be evaluated at different
platen angles, up to and including 10 degrees pitch x 45 degrees roll.
    Mr. Chu suggested a series of procedures he believed would best
address the plate angle issue. His 6-step procedure would test each
front corner of the roof three times, with the roll angle of the plate
maintained at 25 degrees, and the pitch angle from 5 to 10 degrees.
    Consumers Union and Mr. Friedman encouraged the agency to consider
the use of a smaller platen in order to load the A-Pillar and not
extensively load the B-pillar. Mr. Friedman submitted two-sided test
data published in a recent technical publication using a smaller platen
301 mm (11.8 inches) wide by 610 mm (24 inches) long and at different
pitch and roll angles.\32\ The commenter stated that the smaller plate
more aggressively loads the A-pillar. It showed the roof achieved a
lower SWR on the second side by as much as 40-70 percent compared to
the current FMVSS No. 216 procedure.
---------------------------------------------------------------------------

    \32\ Friedman D., et al., ``Result From Two Sided Quasi-Static
(M216) and Repeatable Dynamic Rollover Test (JRS) Relative to FVMSS
216 Tests,'' 20th ESV Conference, Lyon, France, 2007.
---------------------------------------------------------------------------

Agency Response
    After carefully considering the comments, we have decided to
maintain the current platen size and the pitch and roll angle. We note
that many of the issues raised by the commenters were ones that were
also raised in comments on the 2001 RFC.
    Prior to issuing the NPRM, the agency conducted a test series to
evaluate alternative platen angles using the FMVSS No 216 platen.\33\ A
finite element study was first conducted to evaluate a range of platen
configurations and to select appropriate conditions for testing. NHTSA
tested four vehicle pairs using 5 degree x 25 degree and 10 degree x 45
degree platen angles. The peak SWR from these tests did not demonstrate
a consistent pattern between the two test conditions. For two vehicle
models, the 10 degree x 45 degree tests generated a higher peak SWR,
whereas, the 10 degree x 45 degree tests generated a lower peak SWR in
the others. Therefore, the test results were inconclusive.
---------------------------------------------------------------------------

    \33\ See Docket NHTSA 2005-22143-57: Load Plate Angle
Determination and Initial Fleet Evaluation.
---------------------------------------------------------------------------

    To help evaluate the comments submitted in the NPRM docket, the
agency extended the previous finite element studies to evaluate
alternative platen angles in conjunction with a smaller platen.\34\ The
finite element model of a 1997 Dodge Caravan was used to evaluate two-
sided simulations with a 5 degree x 25 degree orientation on the first
side and a 10 degree x 45 degree orientation on the second side. The
reduction in peak SWR for using a 10 degree x 45 degree platen angle on
a second side test was 18.7 percent. The 18 percent reduction in peak
SWR, while significant, is much less than the 40 to 70 percent shown in
the test results submitted to the docket. The results were also in line
with our two-sided vehicle test results using the 5 degree x 25 degree
platen orientation for both sides. On average there was an 8.7 percent
reduction of strength on the second side compared to the first.
Furthermore, we found an average

difference of approximately 7.1 percent lower peak force for the second
side in vehicles under 2,722 kilograms (6,000 pounds) GVWR and 14.9
percent lower peak force for the second side in vehicles over 2,722
kilograms (6,000 pounds) GVWR.
---------------------------------------------------------------------------

    \34\ See, Finite Element Simulation of FMVSS No. 216 Test
Procedures, placed in the docket with this notice.
---------------------------------------------------------------------------

    To evaluate how a smaller platen affects roof strength
measurements, the agency also conducted simulations with a smaller 305
x 610 mm (12 x 24 inch) platen using a 10 degree x 45 degree platen
angle on a Dodge Caravan model. The results showed an approximate six
percent decrease in peak force compared to our baseline results with a
larger platen using the same configuration. However, the simulations
showed the potential for platen edge-to-roof contact. Since the platen-
to-roof contact is intended to be a surrogate for vehicles rolling on
the ground, localized loading from the platen edge can cause
unrealistic loading conditions. Therefore, the results demonstrated how
a smaller platen localized the stress on the A-pillar, reducing the
measured strength during the evaluation, but the crush deformation does
not appear to represent real-world crash results.
    Many of the commenters assumed that a higher pitch angle leads to a
more demanding test procedure and also assumed it is more reflective of
real world rollovers, particularly for pickups and SUVs. However, only
limited anecdotal evidence (based on interpretation of crash photos)
was provided to support these conclusions. Due to the extremely complex
and chaotic nature of rollover crashes, it is impossible for any one
test to fully replicate all of the loading forces that occur in all
real-world crashes. However, we believe the platen size and pitch/roll
angles proposed and currently incorporated in the standard produce roof
crush damage patterns that are representative of the crash damage
patterns observed in real-world crashes.\35\ The use of the smaller
platen would result in edge contact and unrealistic buckling of the
roof. We did not propose to alter these parameters in the NPRM or
SNPRM.
---------------------------------------------------------------------------

    \35\ See Docket NHTSA 2005-22143-56: Roof Crush Analysis Using
1997-2001 NASS Case Review, 2004.
---------------------------------------------------------------------------

    We are also not persuaded by commenters that recommended varying
the pitch and roll angle in a two-sided test. As discussed above, the
agency conducted analytical simulations varying the platen angles.
Based on the similarity of the post test damage pattern in that
research, there was not sufficient evidence to justify changing the
load plate configuration from our current protocol. We are further not
persuaded by CFIR, Mr. Chu, and LSSM comments to require testing on
both sides with a smaller platen size. Analytical simulations \36\
conducted by the agency using a Dodge Caravan showed that a smaller
platen is sensitive to positioning and can result in edge contact. As a
result, a smaller test plate can produce unrealistic contact with the
roof and highly localized loading, inconsistent with real world
rollover crashes. CFIR's finding of a 40-70 percent reduction in roof
strength for the second side tests it conducted may be attributed to
its smaller platen adding unrealistic stress on the roof.
---------------------------------------------------------------------------

    \36\ See, Finite Element Simulation of FMVSS No. 216 Test
Procedures, placed in the docket with this notice.
---------------------------------------------------------------------------

3. Testing Without Windshields and/or Other Glazing in Place
    We did not propose to change the current FMVSS No. 216 procedure
and test the vehicle without the windshield or side windows in place.
In the NPRM, we stated:

    The agency believes that windshields provide some structural
support to the roof even after the windshield breaks because the
force-deflection plots in some of the recent test vehicles (e.g.,
Ford Explorer, Ford Mustang, Toyota Camry, Honda CRV) show little or
no drop off in force level after the windshield integrity was
compromised. Further examination of real-world crashes indicates
that the windshield rarely separates from the vehicle, and
therefore, does provide some crush resistance. Because NHTSA
believes that the vehicle should be tested with all structural
components that would be present in a real-world rollover crash, we
decline to propose testing without the windshield or other glazing.
70 FR 49238.

    A number of commenters, including ones from safety advocacy groups,
questioned the contribution of the windshield to the overall strength
of the roof and generally recommended the windshield be removed prior
to the test. Advocates, Boyle, et al., CFIR, Consumers Union,
DVExperts, IIHS, Public Citizens, Penn Engineering, and Perrone
commented that windshields often break in a rollover, and stated that
the agency should not specify a test procedure with windshields in
place. Consumers Union expressed concern about aftermarket windshield
installation and the unquantifiable strength of the windshield in a
crash. The Engineering Institute (EI) and Mr. Hauschild recommended
that if the agency maintains the 2.5 SWR requirement then the
windshield should be removed. Mr. Slavik stated he conducted tests
which confirm that on some vehicles, damage to the windshield
significantly reduces the force and energy required to produce an
incremental amount of intrusion.
    Technical Services recommended that the side window glass should be
required to be preserved during testing to improve vehicle rollover
performance. Xprts and Mr. Friedman also recommended that the side
windows should not be permitted to fail during the test. Both
commenters referenced Volvo's internal criteria and suggested that
tempered glass windows can remain intact.
    ARCCA, Consumer Union, Specialty Equipment Market Association
(SEMA) and Hyundai raised concerns with regard to vehicles equipped
with sunroofs. ARCCA and Consumers Union suggested vehicles equipped
with sunroofs meet the roof crush requirements. Hyundai noted that
vehicles equipped with sunroofs have reduced headroom compared with
those without sunroofs. SEMA requested the agency ensure aftermarket
sunroofs be permitted because they are installed inside the roof's
perimeter cage.
Agency Response
    After considering the comments, we decline to change the current
test procedure in which the windshield and side windows remain in place
during FMVSS No. 216 tests. We also disagree with the recommendation
that the agency require side windows to be preserved during test. The
agency was not presented with new information showing windshield
breakage in a rollover significantly contributed to a reduction in roof
strength.
    We have examined the post crash windshield status for 1997-2006
NASS investigated rollover crashes with greater than one quarter turn.
The majority of the windshields were coded as either ``in place and
cracked'' or ``in place and holed.'' Less than 10 percent of weighted
incidents indicate the windshield is ``out of place.''
    While Mr. Slavik stated he conducted testing, the agency was not
provided data to evaluate. He asserted that there is anecdotal
acknowledgement by some manufacturers that the windshield provides
upwards of 30 percent of the measured roof strength. We note that that
the agency's testing showed that windshield breakage has not been a
factor in the maximum strength of the roof for some vehicles.\37\ The
peak load continued to increase after windshield breakage in the
testing of the 2003 Ford Focus, 2003 Chevrolet Cavalier, and 2002
Nissan Xterra. In the case of the

Cavalier, the windshield did not contribute to a decrease in strength
until 170 mm (6.7 inches) of platen travel.
---------------------------------------------------------------------------

    \37\ See NHTSA-2005-22143-0049: Roof Crush Research: Phase 3--
Expanded Fleet Evaluation.
---------------------------------------------------------------------------

    The windshield is a structural element for some vehicles, and we
continue to believe that vehicles should be tested with all structural
components that would be present in a real-world rollover crash. We
declined to propose testing without the windshield or other glazing for
that reason, and we are not persuaded that there is sufficient
justification to revise our position.
    The agency also wanted to ascertain the influence of sunroofs on
roof strength. The Scion tC, Cadillac SRX and Ford Edge were tested
with large panoramic sunroofs. The glass panel sunroof in the Scion tC
shattered during the two-sided test, yet the glass panel in the SRX did
not fail during the single-sided only test. After review of the load-
deformation curves for both vehicles, the test results showed the
effect of the sunroof was insignificant to the overall strength of the
roof. In the case of the Scion tC, at the point when the sunroof glass
broke during the first side test, there was no change in the platen
load. In the case of the Ford Edge, the rear glass panel of the sun
roof failed in the second-sided test; however, the front glass panel
over the front row occupants remained intact. This occurred well after
125 mm of platen travel. As a result, we believe it is practicable for
vehicles with sunroofs (including large panoramic roofs) to meet the
requirements and we do not foresee this upgrade inhibiting aftermarket
sunroofs mounted within the roof structure.
    In response to Consumers Union, the possibility exists that
aftermarket windshield installations may not perform to OEM standards.
However, we do not believe this possibility justifies changing roof
strength requirements for all new vehicles.
    Xprts and Mr. Friedman recommended a requirement that the side
windows not break during the roof strength test. The agency
investigated the contribution of side windows to the strength of the
roof structure. Our testing showed that side window breakage is
directly correlated to platen displacement with limited effect on the
strength of the roof. In reviewing the load-deformation curves at the
point where the side glass breaks, there is no measurable drop in load
of the roof and it generally occurs well after the peak strength of the
roof has been reached.\38\ For completeness, the agency also assessed
the impact of rear window breakage. The rear windows broke well after
peak strength was reached and generally past 127 mm (5 inches) of
platen travel. The breakage of the rear window glass resulted in a
slight drop in the strength of the roof particularly in pick-up trucks
where the vertical glass is loaded by the test device and can add some
strength. Overall, the impact of the side and rear glass had little
impact on the strength of the roof. We also note that such a
requirement is outside the scope of notice of the proposal.
---------------------------------------------------------------------------

    \38\ Ibid.
---------------------------------------------------------------------------

4. Deletion of Secondary Plate Positioning Procedure
    In the NPRM, we proposed to apply the primary plate procedure for
all vehicles, removing the secondary plate procedure that applies to
some raised and altered roof vehicles. We explained that the secondary
plate positioning procedure produces rear edge plate loading onto the
roof of some raised and altered roof vehicles that may cause excessive
deformation uncharacteristic of real-world rollover crashes. Because an
optimum plate position cannot be established for all roof shapes, the
testing of some raised and altered roof vehicles will result in loading
the roof rearward of the front seat area. We stated that we believe
this is preferable to edge contact because edge contact produces
localized concentrated forces upon the roof typically resulting in
excessive shear deformation of a small region. We also stated that we
believe that removing the secondary plate position would make the test
more objective and practicable.
    Advocates was the only commenter on this issue and opposed
eliminating the secondary plate positioning. It stated that reverting
back to the primary plate position for aerodynamic roof vehicles would
induce unrealistic loads in that the proportion of force applied to the
roof is excessively concentrated over the B-pillars. It stated that as
a consequence, test conditions and roof response to plate loading can
be substantially different than the loading that actually occurs in
real-world rollovers of these vehicles where the A-pillars receive a
proportionately greater force. Advocates suggested this is crucial
because some vehicles with severely sloped A-pillars are candidates for
A-pillar collapse in rollover crashes and the percentage of new
vehicles with severely raked A-pillars and aerodynamically sloped roofs
has increased each year since their use began in the early to mid-
1990s.
Agency Response
    After considering Advocates' comment, we have decided to remove the
secondary plate procedure. We do not agree that the FMVSS No. 216
platen size and positioning produces unrealistic loading of aerodynamic
roofs. This issue was considered in the 1999 final rule (64 FR 22567)
where the agency adopted a revised platen positioning procedure to
reduce the likelihood of unrealistic loading on vehicles with rounded
roofs. The agency's recent testing of modern vehicles has shown the
current plate positioning procedure does distribute the load between
the A- and B-pillars. Generally, the plate's initial point of contact
with the roof is slightly behind the A-pillar including the Volvo XC90
which had a large amount of curvature to the roof in the test area
compared to most vehicles tested.
    However, we continue to believe that edge contact induced by the
secondary plate procedure results in unrealistic loading specifically
when the roof is raised or altered. In some circumstances, the plate
will essentially punch through the sheetmetal instead of loading the
roof structure. We also do not believe vehicles with steeply raked A-
pillars are common architectures for raised and altered roof vehicles.
Vans with more upright A-pillars are generally modified to have their
roofs raised or altered. We are not aware of such changes to
traditional passenger cars with steeply raked A-pillars.
5. Removal of Roof Components
    FMVSS No. 216 currently specifies removal of roof racks prior to
platen positioning or load application. We did not propose to change
this provision.
    Xprts recommended that the roof be tested as the vehicle is to be
sold, with roof racks or other equipment in place. That commenters
stated that removal of roof racks prior to conducting the roof crush
test eliminates a typical roof failure mode. It states that roof rack
mountings initiate buckling of the roof, increasing the risk of
occupant injury from roof panel buckling.
    After considering this comment, we decline to change the current
test procedure. No data were provided by Xprts to support its
contention that roof racks result in a typical roof failure mode and
thereby increase the risk of occupant injury from roof panel buckling.
We reviewed several NASS-CDS cases \39\ of utility vehicles with roof
racks that had undergone rollover crashes. Our review did not support
the contention that the presence of a roof rack initiated buckling of
the roof and increased the risk of occupant injury. There was also no
general trend

concerning injury severity and presence of a roof rack in the reviewed
cases.
---------------------------------------------------------------------------

    \39\ Photographs collected from NASS-CDS Case Query Page. NASS-
CDS cases examined: 100121, 102005185, 146004985, 161005827,
656500082, 471300143, and 129005218.
---------------------------------------------------------------------------

    We further reviewed our fatal hardcopy case files \40\ and could
not identify a single case where the roof rack appeared to aggravate
the deformation of the roof structure.
---------------------------------------------------------------------------

    \40\ See Docket Number NHTSA 2005-22143-56: Roof Crush Analysis
Using 1997-2001 NASS Case Review.
---------------------------------------------------------------------------

6. Tolerances
    In response to comments from the Alliance and Chrysler LLC, we are
adding several tolerances in the regulatory text to help improve test
repeatability. We note that platen angles are measured from the
horizontal and not from the vehicle's frame of reference. Measuring
platen angles with respect to the ground is more objective than using
the test vehicle's frame of reference because the latter would
introduce manufacturing variability. We note that we are not including
a specification concerning platen overshoot on the first side test
since we will not conduct compliance tests beyond the specified SWR.
    We decline to add a calibration procedure for the test device or to
make changes relating to load application rate or to add platen
material specifications. The basic FMVSS No. 216 test procedure has
been used for many years, and the commenters did not provide persuasive
evidence that changes are needed in these areas. As to platen
materials, we believe the current specification for a rigid unyielding
block is sufficient.

c. Requirements for Multi-Stage and Altered Vehicles

    For vehicles manufactured in two or more stages,\41\ other than
vehicles incorporating chassis-cabs,\42\ we proposed to give
manufacturers the option of certifying to either the existing roof
crush requirements of FMVSS No. 220, School Bus Rollover Protection, or
the new roof crush requirements of FMVSS No. 216. FMVSS No. 220 uses a
horizontal plate, instead of the angled plate of Standard No. 216.
---------------------------------------------------------------------------

    \41\ Vehicles manufactured in two or more stages are assembled
by several independent entities with the ``final stage''
manufacturer in most cases assuming the ultimate responsibility for
certifying the completed vehicle.
    \42\ Under 49 CFR Sec.  567.3, chassis-cab means an incomplete
vehicle, with a completed occupant compartment, that requires only
the addition of cargo-carrying, work-performing, or load-bearing
components to perform its intended functions.
---------------------------------------------------------------------------

    As explained in the NPRM, multi-stage vehicles are aimed at a
variety of niche markets, most of which are too small to be serviced
economically by single stage manufacturers. Some multi-stage vehicles
are built from chassis-cabs that, by definition, have a completed
occupant compartment. A chassis-cab's roof is an integral part of its
body structure surrounding the seats for the occupants. Other vehicles
are built using incomplete vehicles that do not have a completed
occupant compartment. These include a van cutaway, which consists of
the frame, drive train, steering, suspension, brakes, axles, and the
front body section of a van that has no body structure behind the two
front seats. Another example is a stripped chassis. A final stage
manufacturer would typically complete the occupant compartments of
these incomplete vehicles by adding body components to produce a truck
(e.g., work truck) or multipurpose passenger vehicle (e.g., motor
home).
    In developing our proposal, we considered whether the proposed
standard would be appropriate for the type of motor vehicle for which
it would be prescribed. We stated that we believed it was appropriate
to consider incomplete vehicles, other than those incorporating
chassis-cabs, as a vehicle type subject to different regulatory
requirements. We anticipated that final stage manufacturers using
chassis cabs to produce multi-stage vehicles would be in position to
take advantage of ``pass-through certification'' of chassis-cabs, and
therefore did not believe the option of alternative compliance with
FMVSS No. 220 was appropriate.
    We noted that while we believed that the requirements in FMVSS No.
220 have been effective for school buses, we were concerned that they
may not be as effective for other vehicle types. As noted above, the
FMVSS No. 216 test procedure results in roof deformations that are
consistent with the observed crush patterns in the real world for light
vehicles. Because of this, we explained that our preference would be to
use the FMVSS No. 216 test procedure for light vehicles. We believed,
however, that this approach would fail to consider the practicability
problems and special issues for multi-stage manufacturers.
    We stated that in these circumstances, we believed that the
requirements of FMVSS No. 220 appeared to offer a reasonable avenue to
balance the desire to respond to the needs of multi-stage manufacturers
and the need to increase safety in rollover crashes. Several states
already require ``para-transit'' vans and other buses, which are
typically manufactured in multiple stages, to comply with the roof
crush requirements of FMVSS No. 220. These states include Pennsylvania,
Minnesota, Wisconsin, Tennessee, Michigan, Utah, Alabama, and
California. We tentatively concluded that these state requirements show
the burden on multi-stage manufacturers for evaluating roof strength in
accordance with FMVSS No. 220 is not unreasonable, and applying FMVSS
No. 220 to these vehicles would ensure that there are some requirements
for roof crush protection where none currently exist.
Comments
    We received comments concerning requirements for multi-stage and
altered vehicles from Advocates, NTEA, NMEDA and RVIA.
    Advocates stated that it opposes permitting FMVSS No. 220 as an
alternative for multi-stage vehicles. It claimed that FMVSS No. 220 is
a ``weak'' standard whose effects on roof strength in actual rollover
crashes are mostly unknown.
    NTEA recommended that all multi-stage vehicles be excluded from
roof crush resistance requirements. It stated that manufacturers of
non-chassis-cab vehicles will not be able to conduct the tests or
perform engineering analysis to ensure conformance to FMVSS No. 220.
NTEA also disagreed with the assumption that the presence of state
requirements for FMVSS No. 220 compliance demonstrates that final stage
manufacturers can actually comply. It stated that the ability of school
bus and para-transit bus manufacturers to comply with FMVSS No. 220
does not reflect the ability of typical final stage manufacturers to
comply with FMVSS No. 220.
    NTEA also stated it is impractical for the agency to assume
manufacturers of multi-stage vehicles built on chassis-cabs will be
able to use pass-through certification for compliance. That
organization stated that these type of vehicles are generally unique
and built to customer specifications. It also raised a concern that
some manufacturers of chassis-cabs may not provide the necessary
specifications for the final stage manufacturer to rely on pass-through
certification as it applies to roof strength. It argued that the final
stage manufacturer would therefore be responsible for conducting costly
analysis and testing to verify compliance with FMVSS No. 216.
    NMEDA expressed concern that the FMVSS No. 220 option would only be
available for multi-stage vehicles. It asked that the FMVSS No. 220
option be extended to raised or altered roof vehicles. To encompass the
modifiers in the proposed upgrade to FMVSS No. 216, NMEDA asked that a
vehicle roof that is altered after first retail sale be considered in
compliance if it meets the requirements of FMVSS No. 216 or

FMVSS No. 220. NMEDA also stated that raising a roof increases the
available headroom and that the roof therefore can crush more before
there is any contact with an occupants head. NMEDA requested the agency
account for the additional headroom beyond the original vehicle's
headroom in establishing any requirement.
    RVIA supported our proposal to permit FMVSS No. 220 as an option
for small motor homes as this would allow manufacturers to address the
unique issues concerning such specialized vehicles built in two or more
stages.
Agency Response
    After carefully considering the comments and as explained below, we
are providing a FMVSS No. 220 option for multi-stage vehicles, except
those built on chassis-cab incomplete vehicles, and for vehicles which
are changed in certain ways to raise the height of the roof. For
example, a van may be altered by replacing its roof with a taller
structure (referred to as a raised roof) to better accommodate a person
in a wheelchair. We are also excluding a narrow category of multi-stage
vehicles from FMVSS No. 216 altogether, multi-stage trucks built on
incomplete vehicles other than chassis cabs.
    In discussing the issues raised by commenters, we begin by
addressing the comment of Advocates. That organization opposed
permitting FMVSS No. 220 as an alternative for multi-stage vehicles
because it believes that FMVSS No. 220 is not sufficiently stringent
and that its effects on actual rollover crashes are mostly unknown.
    As we discussed in the NPRM, we believe the requirements in FMVSS
No. 220 have been effective for school buses, but we are concerned that
they may not be as effective for other vehicle types. We explained that
our preference would be to use the FMVSS No. 216 test procedure for
light vehicles, but that this approach would fail to consider the
practicability problems and special issues for multi-stage
manufacturers.
    Advocates did not provide analysis or data addressing the special
circumstances faced by multi-stage manufacturers, or explain why it
believes these manufacturers can certify compliance of their vehicles
to FMVSS No. 216. Therefore, that commenter has not provided a basis
for us to take a different position than we took in the NPRM.
    We next turn to the issues raised by NTEA. As a general matter, we
believe that it is neither necessary nor would it be appropriate to
exclude all multi-stage vehicles from roof crush resistance
requirements. The purpose of FMVSS No. 216 is to improve occupant
safety in the event of a rollover. If a multi-stage vehicle is involved
in a rollover, the vehicle's roof strength will be an important factor
in providing occupant protection. Therefore, while we seek to address
the special needs and circumstances of multi-stage manufacturers, we
decline to provide any blanket exclusion for all multi-stage vehicles.
We will address the issues raised by that commenter separately for
multi-stage vehicles built on chassis-cab incomplete vehicles, multi-
stage trucks with a GVWR greater than 2,722 kilograms (6,000 pounds)
not built on a chassis cab and not built on an incomplete vehicle with
a full exterior van body, and other multi-stage vehicles not built on
chassis cabs.
    Multi-stage vehicles built on chassis-cab incomplete vehicles.
    A chassis-cab is an incomplete vehicle, with a completed occupant
compartment, that requires only the addition of cargo-carrying, work-
performing, or load-bearing components to perform its intended
functions. As such, chassis-cabs have intact roof designs. Chassis-cabs
are based on vehicles that are sold as complete vehicles, e.g., medium
and full size pickup trucks, so their roof structure will be designed
to meet the upgraded requirements of FMVSS No. 216.
    After considering the comments of NTEA, we believe that final stage
manufacturers can rely on the incomplete vehicle documents (IVD) for
pass-through certification of compliance with FMVSS No. 216 for
vehicles built using chassis cabs. To do this, final stage
manufacturers will need to remain within specifications contained in
the IVD. Since the stringency of FMVSS No. 216 is dependent on a
vehicle's unloaded vehicle weight, the final stage manufacturer would
need to remain within the specification for unloaded vehicle weight. If
they did not, the roof would not likely have the strength to comply
with FMVSS No. 216. Also, final stage manufacturers will need to avoid
changes to the vehicle that would affect roof strength.
    We note that some changes made by final stage manufacturers could
affect the ability to conduct an FMVSS No. 216 test, e.g., for a truck,
the addition of a cargo box structure higher than the occupant
compartment, which could interfere with the placement of the FMVSS No.
216 test device. To address this concern, we are including a
specification in the final rule that such structures are removed prior
to testing. (They are still counted as part of a vehicle's unloaded
weight.)
    Multi-stage trucks with a GVWR greater than 2,722 kilograms (6,000
pounds) not built on a chassis cab and not built on an incomplete
vehicle with a full exterior van body.
    We have decided to exclude from FMVSS No. 216 a very limited group
of multi-stage trucks with a GVWR greater than 2,722 kilograms (6,000
pounds), ones not built on a chassis cab and ones not built on an
incomplete vehicle with a full exterior van body. We note that some
incomplete vehicles with a full exterior van body might not be included
in the definition of chassis-cab but would still have an intact roof
design.
    For the reasons discussed in the previous section, final stage
manufacturers can rely on the IVD for pass-through certification of
compliance with FMVSS No. 216 for vehicles built using chassis cabs.
For multi-stage trucks built on an incomplete vehicle with a full
exterior van body, the manufacturer can rely on either the IVD for
pass-through certification of compliance with FMVSS No. 216, or use the
FMVSS No. 220 option. Since the incomplete vehicle will have an intact
roof design and will be similar to ones sold as non-multi-stage
vehicles, the roof will have been designed to comply with FMVSS No.
216. Therefore, it is likely that the final stage manufacturer can pass
through FMVSS No. 216 certification. Since the vehicle at issue will be
based on an incomplete vehicle with a full exterior van body, the FMVSS
No. 220 procedure is likely to also be an appropriate one for the final
stage vehicle.
    We are concerned, however, that for other multi-stage trucks, e.g.,
van cutaways, there may be practicability problems for final stage
manufacturers. Because the incomplete vehicle will not have an intact
roof and because the strength of the roof may be dependent on the
structure to be added by the final stage manufacturer, the incomplete
vehicle manufacturer may not provide IVD or similar information that
would permit pass-through certification. Moreover, the design of the
completed truck may be such that it is not possible to test the vehicle
to FMVSS No. 216 (due to interference with the FMVSS test device) or
inappropriate for testing with FMVSS No. 220. As noted earlier, the
FMVSS No. 220 test was designed for school buses and uses a horizontal
plate over the driver and passenger compartment instead of the angled
plate of Standard No. 216. This test may not be appropriate for a truck
with a cargo box that is higher than the occupant compartment.
    Given these practicability issues, we have decided to exclude this
limited

group of multi-stage trucks from the requirements of FMVSS No. 216.
    Other multi-stage vehicles not built on chassis cabs.
    For other multi-stage vehicles not built on chassis cabs, we
continue to believe, for the reasons discussed in the NPRM, that
permitting FMVSS No. 220 as an option is a reasonable way to balance
the desire to respond to the needs of multi-stage manufacturers and the
need to increase safety in rollover crashes. As we noted, several
states already require ``para-transit'' vans and other buses, which are
typically manufactured in multiple stages, to comply with the roof
crush requirements of FMVSS No. 220. We also note that RVIA supported
our proposal.
    Multi-stage vehicles and complete vehicles with a GVWR greater than
2,722 kilograms (6,000 pounds) which have been changed by raising their
original roof.
    In response to the comments of NMEDA, we agree that the FMVSS No.
220 option should be available to multi-stage and complete vehicles
with a GVWR greater than 2,722 kilograms (6,000 pounds) which have been
changed by raising their original roof.
    In considering this issue, we note that in 1999 the agency
published a final rule (64 FR 22567) that was in part in response to an
RVIA petition to allow vans, motor homes and other multipurpose
vehicles with raised roofs the option to certify to FMVSS No. 220. The
RVIA had argued first that since raised roof vehicles would have met
FMVSS No. 216 requirements prior to modification of their roofs, the A-
Pillar strength has already been demonstrated. Second, RVIA had claimed
that the modifications usually do not affect the roof strength near the
A-pillar. RVIA believed that the FMVSS No 220 test procedure could be
used to test the strength of the entire modified vehicle roof without
repeating the FMVSS No. 216 certification test. In the final rule, we
stated that we disagreed with RVIA's analysis that concluded FMVSS No.
220 is comparable to FMVSS No. 216 and is preferable for testing
vehicles with raised or modified roofs. We stated that that the agency
stood by its tentative conclusions stated in the NPRM that the FMVSS
No. 220 test is less stringent than FMVSS No. 216 for testing the
appropriate roof area.
    In considering the issues raise by NMEDA, we note that the
discussion we included in the 1999 final rule was in the context of the
version of FMVSS No. 216 that existed at that time. The standard was
applicable to vehicles with a GVWR of 2,722 kilograms (6,000 pounds) or
less. Here we are discussing vehicles with a GVWR greater than 2,722
kilograms (6000 pounds).
    We believe that practicability issues arise for vehicles with a
GVWR greater than 2,722 kilograms (6,000 pounds) whose roofs are
raised. Moreover, we believe that the FMVSS No. 220 option is
appropriate for the ``para-transit'' vans and buses. The FMVSS No. 220
option will help ensure that these occupants are afforded a level of
protection that is currently not required. We are not providing this
option to vehicles with raised roofs and a GVWR of less than or equal
to 2,722 kilograms (6,000 pounds).
    We believe that the practicability issues for vehicle alterers
which raise roofs on the vehicles at issue are comparable to those of
final stage manufacturers. An alterer may raise a roof on a vehicle
that was originally certified to FMVSS No. 216. We believe that
permitting alterers which raise roofs on these vehicles the option of
certifying to FMVSS No. 220 balances potential practicability issues
with the need to increase safety in rollovers.
    The FMVSS No. 220 130 mm (5.1 inches) limit of platen travel
established at the point of contact with the raised roof is consistent
with FMVSS No. 216 requirements. As discussed elsewhere in this
document, we are maintaining the current platen travel requirement as
well as adding a headroom requirement in FMVSS No. 216. Therefore, even
if a roof is raised and the manufacturer or alterer selects the FMVSS
No. 220 option, we believe the platen travel requirement should be the
same, even if there is additional headroom.
    In arguing for an alternative requirement in this area, NMEDA
raised a concern about higher center of gravity. NMEDA surveyed its
members to obtain, amongst a number of things, an estimate of the
height of raised roofs. It found that some raised roofs can be as high
as 762 mm (30 inches). It was concerned about the resulting center of
gravity's effect on rollover propensity of these vehicles.
    We note that in raising the roof of a vehicle, a final stage
manufacturer or alterer will likely increase the center of gravity of
the vehicle, independent of any roof crush resistance requirements. We
believe that it is important that manufacturers carefully analyze the
impacts of their changes, and choose appropriate vehicles for such
modifications. We also believe that if final stage manufacturers or
alterers raise the roof of a vehicle, it is still necessary that the
vehicle have appropriate roof strength to provide protection in
potential rollovers.
    As to NMEDA's specific recommendation, we believe that organization
has not demonstrated a need for a different requirement in this area.
According to that organization, the typical height of a raised roof is
356-406 mm (14-16 inches). Its members have designed raised roofs that
meet FMVSS No. 220, and FMVSS No. 216 as amended will permit this
option. In addition, vans which are typically altered or modified in
this manner will have an electronic stability control system as
standard equipment. Also, different vehicles can be used for higher
raised roofs, i.e., those with dual rear wheels. We note that the GVWR
of those vehicles is greater than 4,536 kg (10,000 pounds) and FMVSS
No. 216 would not apply.

d. Other Issues

1. Convertibles and Open Bodied Vehicles
    Convertibles are excluded from the requirements of FMVSS No. 216.
In the NPRM, we sought to clarify the definition and scope of exclusion
for convertibles.
    We explained that FMVSS No. 216 does not define the term
``convertible.'' We noted, however, that S3 of 49 CFR 571.201 defines
convertibles as vehicles whose A-pillars are not joined with the B-
pillars (or rearmost pillars) by a fixed, rigid structural member. In a
previous rulemaking, NHTSA stated that ``open-body type vehicles'' \43\
are a subset of convertibles and are therefore excluded from the
requirements of FMVSS No. 216.\44\
---------------------------------------------------------------------------

    \43\ An open-body type vehicle is a vehicle having no occupant
compartment top or an occupant compartment top that can be installed
or removed by the user at his convenience. See Part 49 CFR 571.3.
    \44\ See 56 FR 15510 (April 17, 1991).
---------------------------------------------------------------------------

    We stated in the NPRM that we had reassessed our position with
respect to ``open-body type vehicles.'' Specifically, we believed that
we were incorrect in stating that ``open-body type vehicles'' are a
subset of convertibles because some open-body type vehicles do not fall
under the definition of convertibles in S3 of FMVSS No. 201. We cited
the example of a Jeep Wrangler, which we believed to have a rigid
structural member that connects the A-pillars to the B-pillars.
    We stated in the NPRM that we believe that ``open-body type
vehicles are capable of offering roof crush protection over the front
seat area.'' Accordingly, we proposed to limit the exclusion of
convertibles from the requirements of FMVSS No. 216 to only those
vehicles whose A-pillars are not

joined with the B-pillars, thus providing consistency with the
definition of a convertible in S3 of FMVSS No. 201. We proposed to add
the definition of convertibles contained in S3 of 49 CFR Sec.  571.201
to the definition section in FMVSS No. 216.
Comments
    The agency received comments on this issue from Advocates, the
Alliance, AIAM, BMW, DaimlerChrysler, Ferrari and Porsche. Vehicle
manufacturers supported continuing to exclude convertibles from the
requirements; however they raised some concerns with regard to the
proposed definition. The Alliance commented that there is no evidence
that it is practicable for convertibles or open body vehicles to
comply.
    DaimlerChrysler disagreed with the agency's position that the
Wrangler is not a convertible. It claimed that the Wrangler does not
have an A-pillar, since the structure is not rigid and is hinged to
fold down. Further, that company stated that the padded tube connecting
the windshield frame and the sport bar is not rigid because it is
attached with easily-removable screws.
    Several commenters addressed the proposed definition of
convertible. Ferrari suggested that the definition of convertible
include ``above the window opening light lowermost point.'' AIAM
recommended two changes: to add ``not permanently joined'' and to make
it clear that the referenced connection is ``above the lowest point of
the side window opening.'' This would lead to the following complete
definition: ``A convertible is a vehicle whose A-pillars are not
permanently joined with the B-pillars (or rearmost pillars) by a fixed,
rigid structural member above the lowest point of the window opening.''
DaimlerChrysler suggested changing the convertible definition to
``vehicles with folding tops or removable hardtops with A-pillars not
joined to the B-pillars (or rearmost pillars) or joined with removable
parts to the B-pillars (or rearmost pillars).''
    Advocates disagreed with excluding convertibles from FMVSS No. 216
and stated further that the agency should establish rollover
requirements for convertibles that limit ejections and head and neck
injuries.
Agency Response
    After considering the comments, we are adopting the proposed
definition of convertible for the final rule and we are continuing to
exclude convertibles within that definition from the FMVSS No. 216
requirements. This includes retractable hard top convertibles. We
believe that to establish a roof crush requirement on vehicles that do
not have a permanent roof structure would not be practical from a
countermeasure perspective. A convertible roof would have to be strong
enough to pass the quasi-static test, yet flexible enough to fold into
the vehicle. Since we are not aware of any such designs, we do not
agree with Advocates on this point. We also note that new rollover and
ejection requirements for convertibles are outside the scope of this
rulemaking.
    On the issue of open-body vehicles, we agree with DaimlerChrysler
that the agency misidentified the Wrangler as an open-body vehicle in
the NPRM when it should have been considered a convertible (since the
A-pillar is not rigid and fixed to the B-pillar or other rearmost
pillar). At the time, we were unaware that the windshield and support
bars were designed to be disassembled.
    Our position on open-body vehicles has not changed. Under the new
definition, open-body vehicles will be subject to FMVSS No. 216, since
they are capable of offering roof crush protection over the front seat
area. We note, however, that given DaimlerChrysler's comment about the
Jeep Wrangler, we are not aware of other vehicles currently available
for sale that are considered open-body vehicles.
    We disagree with the Alliance's assertion that it is not
practicable for open-body vehicles to meet the requirements of FMVSS
No. 216. We believe that if a vehicle otherwise similar to the Wrangler
had roof supports that are fixed (as in a roll cage), it should be
capable of providing protection to the occupants as required by today's
final rule.
    We are also not making the changes to the proposed definition of
convertible suggested by some commenters. The definition proposed was
previously adopted in FMVSS No. 201 (62 FR 16725), and the agency
believes the applicability is the same and is unaware of any concerns.
Furthermore, we do not believe further specificity is warranted given
our revised position on the Wrangler. We believe our discussion in the
NPRM concerning the Wrangler may have caused confusion. We also do not
agree that there is a need to specify that convertibles have folding
hardtops or removable hardtops. These roof systems are not intended as
significant structural elements but are designed primarily to provide
protection from inclement weather, improve theft protection and are
generally offered as a luxury item. These types of roof systems are
also designed of lighter weight materials, such as aluminum or
composites, for ease of folding and storage within the vehicle or
removal by the consumer. and we believe consumers readily recognize
they will afford the occupants limited protection in a rollover.
2. Vehicles Without B-Pillars
    In the NPRM, we did not specifically discuss vehicles that are
designed without B-pillars. At the time we were unaware of any
technical concerns the manufacturers might have with these vehicle, to
meet the proposed requirements.
    Ford identified a number of design challenges for vehicles without
B-pillars. That company's concerns were focused on pickup trucks
without B-pillars that have a GVWR of 3,856 kilograms (8,500 pounds) or
more. These vehicles have a front-forward opening and a rear-rearward
opening side door configuration that latch together without a fixed,
structural B-pillar. Ford expressed concern that there is no direct
load path to resist the platen during testing and as a result, there
are significant design and manufacturing issues that must be addressed
while avoiding a major incremental weight penalty. Ford did not make
any specific recommendations.
Agency Response
    We agree with Ford's analysis that certain vehicles without B-
pillars may raise additional technical challenges compared to other
vehicles, particularly for heavier vehicles. However, based upon our
fleet testing, we believe that a structure can be designed at the joint
between the doors that acts as a surrogate B-pillar to resist roof
displacement during testing. We note that the Alliance's comments on
how the proposed tie-down procedure adversely affects vehicles without
B-pillars reinforce this view. The revised tie-down procedure for the
final rule will aid vehicles without B-pillars in complying since
support will be placed along the complete body sill.
    NHTSA tested two vehicles without B-pillars, the 2004 Chevrolet
Silverado HD and 2005 Nissan Frontier. This testing confirmed that the
load can be successfully transferred to the joint between adjacent
doors where a B-pillar would be in a conventional vehicle design. The
Silverado did not meet the 2.5 SWR proposed in the NPRM, but it did
exceed 1.5. The Frontier achieved a peak SWR of almost 4.0 within the
allocated platen displacement.
    While we appreciate the challenges manufacturers will incur to meet
the new requirements, we believe the upgrade is feasible for vehicles
without B-pillars. We note that one of the

reasons we are providing a phase-in is to permit manufacturers
additional time to make the design changes needed to enable some of the
more challenging vehicles to comply with the requirements of the final
rule.
3. Heavier Vehicles With a High Height to Width Aspect Ratio
    The Alliance and Mercedes-Benz USA requested that vehicles with a
GVWR above 3,856 kilograms (8,500 pounds) GVWR and a height to width
aspect ratio greater than 1.2 be permitted to certify to FMVSS No. 220
as an option or, at a minimum, use the larger platen specified for
FMVSS No. 220. They argued that the FMVSS No. 216 platen results in
unrealistic roof deformation for these particular vehicles.
Agency Response
    While we have considered this comment, we believe that the
commenters have not provided persuasive evidence that a special
requirement is needed for these vehicles. While we did observe edge
contact in our testing of the Sprinter, it was not of a nature that
prevents compliant designs. We note that the 1.5 SWR we are adopting
for vehicles within this weight range reduces possible concerns in this
area.
4. Active Roofs
    Autoliv North America (Autoliv) stated that the quasi-static test
procedure does not have a provision for active roof structure systems.
Active roof structures are being developed to provide added stiffness
during an actual rollover event. The effectiveness of such a system may
be transient, deployed during a rollover initiation and lasting only as
long as required to reduce intrusion. The quasi-static test specifies a
deformation rate of not more than 13 millimeters per second with the
total time for crush not to exceed 120 seconds. According to Autoliv,
the duration of this test may exceed the time in which certain active
roof structures can be effective.
Agency Response
    We are not aware of the near term implementation or effectiveness
of active roof structure technology. In developing performance
requirements, we seek to develop ones that are appropriate for, and do
not unnecessarily discourage, new technologies. However, our ability to
do this is dependent on the amount of information we have. We do not
have sufficient information at this time to indicate the quasi-static
test will prevent implementation of active roof systems.
5. Whether an Additional SNPRM Is Needed
    Several commenters argued that the agency's January 2008 SNPRM did
not provide sufficient information about the alternatives we were
considering and that an additional SNPRM should be published.
    Public Citizen claimed that the January 2008 SNPRM failed to
provide enough information for meaningful public comment. It stated
that the agency did not spell out the explicit safety benefits of
mandating a two-sided test, or how using the one-sided test would meet
the statutory requirement relating to roof strength for driver and
passenger sides. Public Citizen argued that a new SNPRM is needed.
    Advocates claimed that the January 2008 SNPRM offered several
regulatory alternatives without support from a cost-benefits analysis.
That commenter stated that this denied the public an opportunity to
evaluate the agency's comparative estimates of costs and benefits
before submitting comments. Advocates argued that the SNPRM did not
fulfill agency's obligation to present the public with the regulatory
alternatives it is considering.
    The AIAM stated that it believes there would not be a fair
opportunity for public comment on a two-sided test requirement without
an opportunity of review of revised cost-benefit analysis.
Agency Response
    We reject the commenters' arguments that the agency did not provide
a meaningful opportunity for comment. In conjunction with the August
2005 NPRM, the agency's PRIA included an assessment of the 2.5 and 3.0
SWR alternatives. As discussed above, in our January 2008 SNPRM, we
asked for public comment on a number of issues that might affect the
content of the final rule, including possible variations in the
proposed requirements. We also announced the release of the results of
various vehicle tests conducted since the proposal. In the SNPRM, we
noted that we had been carefully analyzing the numerous comments we had
received on the NPRM, as well as the various additional vehicle tests,
including both single-side tests and two-sided tests, conducted since
the NPRM. We invited comments on how the agency should factor the new
information into its decision. We noted that while the NPRM focused on
a specified force equivalent to 2.5 times the unloaded vehicle weight,
the agency could adopt a higher or lower value for the final rule. We
explained, with respect to two-sided vehicle testing, that we believed
there was now sufficient available information for the agency to
consider a two-sided requirement as an alternative to the single-sided
procedure described in the NPRM. We stated that we planned to evaluate
both the single-sided and two-sided testing alternatives for the final
rule and requested comments that would help us reach a decision on that
issue.
    While the agency did not provide complete new cost-benefits
analyses to accompany the SNPRM, we included a detailed discussion in
the SNPRM of how estimated impacts of the final rule would be changed
by a number of relevant factors. See 73 FR 5488-5490. These factors
included the pass/fail rate of the vehicle fleet, the impact of the ESC
standard on potential benefits, revised cost and weight estimates, two-
sided testing implications, and other factors.
    Thus, in the NPRM and SNPRM, we provided detailed information
concerning the alternatives we were considering and the relevant
issues. We also note that both Public Citizen and Advocates supported a
two-sided test requirement, the alternative we are adopting in today's
rule.
6. Rear Seat Occupants
    As a general comment to the NPRM, the Advocates raised a concern
that the quasi-static platen test is not applicable to rear seat
occupants including small children seated in the rear.
Agency Response
    We note that the large size of the FMVSS No. 216 platen covers the
rear seat in most vehicles to help ensure protection for rear seat
occupants. We believe that one of the countermeasures that vehicle
manufacturers will use to meet the upgraded roof strength requirements
is strengthening the B-pillars. In terms of possible benefits to small
children, belted occupant injuries sustained due to rollover roof crush
are to the head, neck, and face from contact with roof structures.
Appropriately restrained children are generally not tall enough to
sustain such injuries.
7. New Car Assessment Program (NCAP)
    Several commenters suggested that the agency develop a 5-star
rating system concerning roof strength for our NCAP program to provide
the public with information on roof strength and to encourage
manufacturers to improve the roof strength of their vehicles.

Agency Response
    The purpose of this rulemaking is to upgrade our roof strength
standard. The issue of whether roof strength might be addressed in some
way in our NCAP program would be considered separately in the context
of that program.
8. Possible Energy Requirement
    We did not propose an energy requirement in the NPRM but indicated
that we would welcome comments on an energy absorption test that had
previously been suggested by SAFE and Syson-Hille and Associates
(Syson).
Agency Response
    We received several comments. We appreciate the information
provided in the comments but note that we are not considering
rulemaking in this area.
9. Advanced Restraints
    In the NPRM, we presented a summary of our advanced restraints
research and requested comments in this area.
Agency Response
    While advanced restraints are not part of this rulemaking, the
agency is continuing research in this area and appreciates the comments
that were provided.

VII. Costs and Benefits

    At the time of the NPRM, the agency prepared a PRIA describing the
estimated costs and benefits of the proposal. While the agency did not
provide complete new cost-benefits analyses to accompany the SNPRM, we
included a detailed discussion in the SNPRM of how estimated impacts of
the final rule would be changed by a number of relevant factors. See 73
FR 5488-5490. These factors included the pass/fail rate of the vehicle
fleet, the impact of the ESC standard on potential benefits, revised
cost and weight estimates, two-sided testing implications, and other
factors.
    Many commenters addressed the PRIA and the later discussion of
these impacts included in the SNPRM. Among other things, commenters
addressed the target population, the pass/fail rate of the current
fleet, cost and weight impacts, and estimates of benefits.
    The agency addresses the comments concerning its analysis of costs
and benefits in detail in the FRIA. In this document, we summarize the
agency's estimates of costs and benefits and discuss the comments
concerning target population and roof crush as a cause of injury.

a. Conclusions of the FRIA

    The conclusions of the FRIA can be summarized as follows:
    Countermeasures
    The agency believes that manufacturers will meet this standard by
strengthening reinforcements in roof pillars, by increasing the gauge
of steel used in roofs, and/or by using higher strength materials. The
agency believes that pressure to improve fuel economy in vehicles,
driven by more stringent Corporate Average Fuel Economy (CAFE)
standards as well as by market forces, together with safety
considerations, will provide a strong incentive for manufacturers to
achieve increased roof strength through use of light weight materials
and stronger roof designs initiated during the redesign cycle. The
agency believes that the phase-in schedule provided in this rule will
allow manufacturers to establish such designs in an efficient manner.
The agency estimates that about 82 percent of all current passenger car
and light truck models with GVWRs less than 2,722 kilograms (6,000
pounds) will need changes to meet the 3.0 SWR requirement, and that 40
percent of vehicles over 2,722 kilograms (6,000 pounds) GVWR will need
changes to meet the 1.5 SWR requirement.
    Benefits
    The agency estimates that the changes in FMVSS No. 216 will prevent
135 fatalities and 1,065 nonfatal injuries annually.
    Costs
    The design changes made to comply with higher test load
requirements will add both cost and weight to the vehicle. This will
increase the initial purchase price and will increase lifetime fuel
usage costs.
    Taking account of both the costs of design changes and lifetime
fuel usage costs, the agency estimates that compliance with the
upgraded roof strength standard will increase lifetime consumer costs
by $69-$114 per affected vehicle. Redesign costs are expected to
increase affected vehicle prices by an average of about $54. Added
weight is estimated to increase the lifetime cost of fuel usage by $15
to $62 for an average affected vehicle. The range in fuel costs
reflects different discount rate assumptions of 7% and 3%, as well as a
range of assumptions regarding the ability of manufacturers to
incorporate advanced weight saving technology into their redesigned
fleet. Total consumer costs are expected to range from $875 million to
$1.4 billion annually.
    Cost Effectiveness and Net Benefits
    Cost effectiveness is a measure of the economic investment that is
required to prevent a fatality. The cost effectiveness of this rule was
estimated under both 3% and 7% discount rate assumptions for each
alternative. Nonfatal injuries were translated into fatality
equivalents based on comprehensive valuations that included both
economic impacts and valuations of lost quality of life. To reflect the
present value of benefits that would be experienced over the vehicle's
useful life, the resulting equivalent fatalities were discounted over
the vehicle's life based on annual exposure to crash involvement as
measured by annual miles traveled. The 135 fatalities and 1,065
nonfatal injuries that will be prevented translate into 190 equivalent
fatalities, which are valued at 156 equivalent fatalities under a 3%
discount rate, and 125 equivalent fatalities under a 7% discount rate.
When compared to total costs, the results indicate that the new
standard will cost from $6.1 million to $9.8 million per equivalent
life saved.
    Net benefits represent the difference between total costs and the
total monetary value of benefits. DOT's guidance specifies a value of
$5.8 million as the value of a statistical life (VSL), with a range of
uncertainty covering $3.2 million to $8.4 million. The monetary value
of benefits was estimated by assigning a value of $6.1 million to each
equivalent fatality prevented. This value includes the $5.8 million VSL
plus approximately $300,000 of economic savings to represent the
comprehensive societal benefit from preventing a fatality. This means
that the standard would be considered to result in net benefits only if
the cost per equivalent life saved was below $6.1 million.
    Net benefits represent the difference between total costs and the
total monetary value of benefits. The monetary value of benefits was
estimated by assigning a value of $6.1 million to each equivalent
fatality prevented. This value consists of a value per statistical life
saved (VSL) of $5.8 million plus $300,000 in economic costs prevented.
For the 3.0/1.5 load requirements of the final rule, the net impact
would range from a net benefit of $6 million to a net loss of $458
million. Using an alternate comprehensive value of $8.7 million (which
consists of a VSL of $8.4 million plus $300,000 in economic savings),
the standard could result in a net benefit of $388 million to a net
loss of $151 million. Using an alternate comprehensive value of $3.5
million (which consists of a VSL of $3.2 million plus $300,000 in
economic savings), the standard could result in a net loss ranging from
$376 million to $824

million. These impacts are disproportionately influenced by the
relatively large contributions to costs and small contributions to
benefits from vehicles over 6,000 lbs. GVWR. Nearly all alternatives
covering vehicles from 6,001 to 10,000 lbs. GVWR yield net losses
rather than net savings to society.
    The following table summarizes the cost and benefits of this final
rule.

                    Table 2--Cost and Benefit Summary
------------------------------------------------------------------------

------------------------------------------------------------------------
Total Cost.............................  $875 to $1,391 million.
Cost per Affected Vehicle..............  $69 to $114.
Benefits...............................  135 fatalities, 1,065 injuries,
                                          190 equivalent fatalities.
Cost per Equivalent Life Saved.........  $6.1million to $9.8 million.
Net Benefits...........................  $6 million to -$458.
------------------------------------------------------------------------

b. Comments

Target Population
    The agency received numerous comments concerning the target
population. CAS and Advocates argued that improving roof strength would
impact ejection and that mitigated ejections should therefore be
included in the agency's benefit calculations. Advocates also argued
that rear seat occupants should be covered by the revised standard.
SAFE argued that roof crush increases the likelihood of glass fracture
and vehicle structure deformation, thereby increasing the possibility
of ejection. It also argued that roof crush reduces the effectiveness
of restraint systems, decreases the effectiveness of rollover air
curtains, and decreases the ability of occupants to be extricated from
the vehicle. The Xprts disagreed with several of NHTSA's target
population restrictions. It stated that ejected occupants, rear seat
occupants, and children under 12 should be included. It also argued
that roof crush can cause thoracic and spinal injuries, and that upper
extremity injuries from ejection through side windows should also be
included. Many of these arguments were repeated in a separate
submission by CFIR signed by one of the Xprts authors. Consumers Union
and Public Citizen also argued that stronger roofs would reduce
ejections and better maintain the performance of other safety features
such as safety belts, air bags, and door locks. Public Citizen also
argued that unbelted occupants would benefit from stronger roofs.
    Agency response. We begin our response by noting that Table 1, set
forth earlier in this document, shows a breakdown of the target
population that could potentially benefit from roof crush improvements.
    To examine the inclusion of different categories of injuries in the
target population, the agency has conducted several analyses of
ejections in rollovers. The first study was a statistical analysis
examining the relationship between intrusion and ejection. In this
study,\45\ Strashny examined 36 different Probit models examining
belted cases, unbelted cases, complete ejections, all ejections
(including both complete and partial ejection), continuous models,
dichotomous models, adjusted models based on both quarter turns and
roof exposures, as well as unadjusted models. In all, there were 18
models for complete ejections and 18 for all ejections. Strashny found
that there was no significant relationship between the level of
intrusion and the probability of complete ejection in any of the 18
full ejection models. For all ejections, which include partial
ejections, he found some level of significance for 8 of the 18 models,
indicating that a minority of the models found a possibility that some
partial ejections might be influenced by stronger roofs. However, 12 of
the models found no statistically significant relationship between
intrusion and all ejections. We note that partial ejections that meet
the other inclusion criteria are a part of the target population for
this rulemaking.
---------------------------------------------------------------------------

    \45\ Strashny, Alexander, ``The Role of Vertical Roof Intrusion
in Predicting Occupant Ejection,'' National Center for Statistics
and Analysis, 2009.
---------------------------------------------------------------------------

    The agency then conducted a detailed examination of all fatal
complete ejection cases that were excluded from the target population.
A panel of three NHTSA safety engineers independently examined each
case to determine whether (a) for ejections through open doors, there
was deformation in the door latch area where the root cause could be
directly attributed to roof crush, and (b) for ejections through
windows, if the broken glass through which the occupant was ejected was
directly related to deformation of the roof rather than dynamic crash
impulse loads or side window/door to ground contact. The panel
concluded that there were no cases that met either of these criteria.
Therefore, based on these findings and Strashny's finding of no
statistically significant correlation between intrusion and ejection
probability, all cases of total ejection were excluded from the target
population unless their MAIS level injury occurred inside the vehicle
prior to ejection.
    For occupants who were unbelted but not fully ejected, we could not
establish a relationship between roof crush injuries and the magnitude
of roof crush. Strashny analyzed the relationship between intrusion and
injuries to unbelted occupants and found no significant correlation.
This is not unexpected because unbelted occupants essentially become
flying objects inside vehicles as they roll over, and head injuries can
occur at multiple interior locations. Therefore, only belted occupants
are included in the target population.
    Regarding the other categories of injuries noted in the comments,
partially ejected occupants were already included in the target
population, and the agency has decided to include rear seat occupants
in the target population. We note that B pillar strength upgrades were
included in all of our finite element countermeasure analyses, and this
support also provides protection for rear occupants. Moreover, vehicle
schematics submitted by both industry and contractors indicate that
some design solutions contemplated for increased roof strength include
not only stronger A- and B-pillars but also a stronger B- to C-pillar
load path to resist platen movement. Such solutions may benefit rear
seat occupants as well as front seat occupants. The agency has also
decided to include belted children in the target population.
Roof Crush as a Cause of Injury
    A number of commenters including GM, Ford, Nissan, and SAFE stated
that the statistical correlation Strashny found between roof intrusion
and injury does not establish a causal relationship between roof
deformation and injury. SAFE stated that the studies by both Rains and
Strashny merely suggest that there is a relationship. SAFE stated that
`` * * * when you compare rollover accidents that have significant
roof/pillar deformation with other rollover

accidents that have very little or no roof/pillar deformation, you are
not comparing similar accidents with respect to roof-to-ground impact
severity. Just the fact that two vehicles are in a rollover with
greater than 2 quarter turns does not mean they are in the same or even
similar impact severities.'' SAFE also noted an earlier study (matched
pair comparison project) in which production and roll bar-equipped
vehicles were tested where the comprehensive forces measured on test
dummies were similar regardless of the vehicle roof crush. Ford stated
that ``The amount of roof deformation is only an indication of the
severity of the impact between the roof and the ground * * *.'' GM
stated that ``Observations of injury occurrence at the end of a
rollover collision reveal nothing regarding the relationship of roof
deformation, roof strength, or roof strength-to-weight ratio injury
causation.'' Nissan stated that deformation and injury severity are
both independently associated with roof impact severity.
Agency Response
    The agency agrees that as a general principle, a statistical
correlation does not in itself prove that a causal relationship exists.
However, the Strashny study was designed with a strict focus to only
include injury scenarios where the intruding roof was the injury
source. The study compared cases where there was intrusion to cases
where there was no intrusion and found that as intrusion increases, the
probability of, and severity of injury also increases. The study
controlled for crash severity using quarter turns, which is the best
available metric for rollover severity. Contrary to SAFE's contention,
the study does not compare crashes over 2 quarter turns as a group.
Rather, it compares only crashes of similar severity as defined by each
iterative quarter turn exposure. Thus, a vehicle that experienced 3
quarter turns would only be compared to other vehicles that experienced
3 quarter turns. SAFE's and Ford's arguments appear to imply that any
difference in roof intrusion must be due to a difference in impact
severity rather than roof strength or design, whereas the Strashny
study, by controlling for quarter turns, attempts to minimize
differences due to impact severity. Further, the study included only
belted cases which minimized the impact of ``diving'' as an injury
cause.
    There are logical reasons to believe that a collapsing roof that
strikes an occupant's head at the nearly instantaneous impact velocity
experienced when structures deform might cause serious injury. These
types of injuries were documented by Rechnitzer and Lane in a detailed
investigation of 43 rollover crashes.\46\ The agency believes that the
statistically significant relationship between roof intrusion and
belted occupant injury found in the Strashny study indicates not just a
suggestion, but a probability that increasing roof strength reduces
injuries.
---------------------------------------------------------------------------

    \46\ Rechnutzer, George and Lane, John, ``Rollover Crash Study,
Vehicle Design and Occupant Injuries'', Monash University, 1994.
---------------------------------------------------------------------------

    Regarding the SAFE matched pair comparison project, the agency
notes that the dummy necks used in the tests were not biofidelic. They
are rigid structures that do not allow for the normal bending that
occurs in the human spine. The agency believes that lateral bending
plays an important role in determining the degree of injury sustained
by humans in rollovers, and does not view these results as an adequate
assessment of injury in humans during rollover crashes.

VIII. Rulemaking Analyses and Notices

a. Executive Order 12866 (Regulatory Planning and Review) and DOT
Regulatory Policies and Procedures

    The agency has considered the impact of this rulemaking action
under Executive Order 12866 and the Department of Transportation's
regulatory policies and procedures. This rulemaking is economically
significant and was reviewed by the Office of Management and Budget
under E.O. 12866, ``Regulatory Planning and Review.'' The rulemaking
action has also been determined to be significant under the
Department's regulatory policies and procedures. The FRIA fully
discusses the estimated costs and benefits of this rulemaking action.
The costs and benefits are summarized in section VII of this preamble,
supra.

b. Regulatory Flexibility Act

    The Regulatory Flexibility Act of 1980, as amended, requires
agencies to evaluate the potential effects of their proposed and final
rules on small businesses, small organizations and small governmental
jurisdictions. I hereby certify that this rule will not have a
significant economic impact on a substantial number of small entities.
Small organizations and small governmental units will not be
significantly affected since the potential cost impacts associated with
this action will not significantly affect the price of new motor
vehicles.
    The rule directly affects motor vehicle manufacturers, second stage
or final manufacturers, and alterers. The majority of motor vehicle
manufacturers would not qualify as a small business. There are six
manufacturers of passenger cars that are small businesses.\47\ These
manufacturers, along with manufacturers that do not qualify as a small
business, are already required to comply with the current requirements
of FMVSS No. 216 for vehicles with a GVWR of 2,722 kilograms (6,000
pounds) or less. Improving performance as necessary to meet the
upgraded requirements, and for the requirements for heavier light
vehicles, can be achieved by means including strengthening
reinforcements in roof pillars, by increasing the gauge of steel used
in roofs and by using higher strength materials.
---------------------------------------------------------------------------

    \47\ Fisker, Mosler, Panoz, Saleen, Standard Taxi, Tesla.
---------------------------------------------------------------------------

    All of these small manufacturers could be affected by the upgraded
requirements. However, the economic impact upon these entities will not
be significant for the following reasons.
    (1) Potential cost increases are very small compared to the price
of the vehicles being manufactured and can be passed on to the
consumer.
    (2) Some of the vehicles manufactured by these small businesses are
convertibles not subject to this requirement.
    (3) The rule provides several years leadtime, and small volume
manufacturers are given the option of waiting until the end of the
phase-in (until September 1, 2015) to meet the upgraded requirements
for lighter vehicles. All manufacturers are given until September 1,
2016 to meet the requirements for the heavier light vehicles.
    Most of the intermediate and final stage manufacturers of vehicles
built in two or more stages and alterers have 1,000 or fewer employees.
Some of these companies already are required to comply with the current
requirements of FMVSS No. 216 for vehicles with a GVWR of 2,722
kilograms (6,000 pounds) or less. We have included several provisions
in the final rule to address the special needs of multi-stage
manufacturers and alterers. While the number of these small businesses
potentially affected by this rule is substantial, the economic impact
upon these entities will not be significant for the following reasons:
    (1) We are providing a FMVSS No. 220 option for multi-stage
vehicles, except those built on chassis-cab incomplete vehicles, and
for vehicles

which are changed in certain ways to raise the height of the roof. This
aspect of our rule affords significant economic relief to small
businesses, some of which are already required by States to certify to
the requirements of FMVSS No. 220.
    (2) Small businesses using chassis cabs will be in position to take
advantage of ``pass-through certification,'' and therefore are not
expected to incur any additional expenditures.
    (3) We are excluding a narrow category of multi-stage vehicles from
FMVSS No. 216 altogether, multi-stage trucks built on incomplete
vehicles other than chassis cabs.
    (4) Some of the vehicles manufactured by these small businesses are
convertibles.
    (5) Final stage manufacturers and alterers can wait until one year
after the end of the phase-in to meet the new requirements.
    Accordingly, there will not be a significant economic impact on
small businesses, small organizations, or small governmental units by
these amendments. For these reasons, the agency has not prepared a
regulatory flexibility analysis.

c. Executive Order 13132 (Federalism)

    NHTSA has examined today's final rule pursuant to Executive Order
13132 (64 FR 43255, August 10, 1999) and concluded that no additional
consultation with States, local governments or their representatives is
mandated beyond the rulemaking process. The agency has concluded that
the rule does not have federalism implications because the rule does
not have ``substantial direct effects on the States, on the
relationship between the national government and the States, or on the
distribution of power and responsibilities among the various levels of
government.''
    Further, after careful consideration of the public comments and
further analysis of the issues, NHTSA concludes that no consultation is
needed to discuss the preemptive effect of today's rule. NHTSA's safety
standards can have preemptive effect in at least two ways. First, the
National Traffic and Motor Vehicle Safety Act contains an express
preemption provision: ``When a motor vehicle safety standard is in
effect under this chapter, a State or a political subdivision of a
State may prescribe or continue in effect a standard applicable to the
same aspect of performance of a motor vehicle or motor vehicle
equipment only if the standard is identical to the standard prescribed
under this chapter.'' 49 U.S.C. 30103(b)(1). It is this statutory
command that unavoidably preempts non-identical State legislative and
administrative law, not today's rulemaking, so consultation would be
unnecessary.
    Second, the Supreme Court has recognized the possibility of implied
preemption: State requirements imposed on motor vehicle manufacturers,
including sanctions imposed by State tort law, can stand as an obstacle
to the accomplishment and execution of a NHTSA safety standard. When
such a conflict is discerned, the Supremacy Clause of the Constitution
makes the State requirements unenforceable. See Geier v. American Honda
Motor Co., 529 U.S. 861 (2000). For the reasons explained below, the
agency has reconsidered the tentative position presented in the NPRM
and does not currently foresee any potential State tort requirements
that might conflict with today's final rule.
    In the NPRM, NHTSA considered the objectives of the proposed roof
crush resistance upgrade in the context of the agency's overall
rollover plan and addressed whether there might be specific conflicts
between the standard and anticipated State tort law. The agency opined
on the possibility that certain State tort law actions might conflict
with an improved Federal roof crush resistance standard and that those
conflicts could result in those actions being determined by a court to
be impliedly preempted. It presented the following tentative
conclusions:
     Overall, safety would best be promoted by the careful
balance it had struck in the proposal among a variety of considerations
and objectives regarding rollover safety.
     The proposal to upgrade roof crush resistance was a part
of a comprehensive plan for reducing the serious risk of rollover
crashes and the risk of death and serious injury in those crashes. The
objective of the proposal was to increase the requirement for roof
crush resistance only to the extent that it can be done without
creating too much risk of negatively affecting vehicle dynamics and
rollover propensity. Excessively increasing current roof crush
resistance requirements could lead vehicle manufacturers to add weight
to vehicle roof and pillars, thereby raising the vehicle center of
gravity (CG) and increasing rollover propensity.
     Some methods of improving roof crush resistance are
costlier than others and the resources diverted to increasing roof
strength using one of the costlier methods could delay or even prevent
vehicle manufacturers from equipping their vehicles with advanced
vehicle technologies for reducing rollovers.
     Either a broad State performance requirement for levels of
roof crush resistance greater than those proposed or a narrower
requirement mandating that increased roof strength be achieved by a
particular specified means, could frustrate the agency's objectives by
upsetting the balance between efforts to increase roof strength and
reduce rollover propensity.
     Based on this conflict analysis, if the proposal were
adopted as a final rule, all conflicting State common law requirements,
including rules of tort law, would be subject to being found to be
impliedly preempted.
1. Public Comments About NHTSA's Tentative Views on Conflict and
Preemption
    Vehicle manufacturers and one legal advocacy organization strongly
supported the view that an upgraded roof crush standard would conflict
with and therefore impliedly preempt State rules of tort law imposing
more stringent requirements than the one ultimately adopted by NHTSA.
    Consumer advocacy groups, members of Congress and State officials,
trial lawyers, consultants and members of academia, and private
individuals strongly opposed our view that there could be conflict. The
opposing letters from State officials included one signed by 27 State
Attorneys General and the National Conference of State Legislatures.
    A summary of the primary arguments of the commenters on each side
follows:
A. Primary Arguments for the Existence of Conflict
     There is a limit to the increases in roof crush resistance
or stiffening that can practicably be achieved across the fleet without
introducing unacceptable risk of undesirable effects, such as increases
in the height of the center of gravity of the vehicle or diverting
resources away from other promising advanced vehicle technologies for
reducing rollovers.
     Small additions of weight and small changes in center of
gravity height will, based on NHTSA's analysis presented in Appendix A
of the PRIA, have large consequences on the level of rollover risk and
risk of associated fatalities and injuries. Moreover, the weight
impacts of meeting requirements at different SWR levels are greater
than estimated by the agency in the PRIA.
     There is a conflict between the agency's comprehensive
rollover policy and some state common law rules related to roof
strength. Any state

common law rule that would purport to impose a duty to design vehicles'
roofs to meet a more stringent strength requirement has the potential,
as a practical matter, to result in a reduction in vehicle stability
(as measured by average SSF), at least for some vehicle models in the
fleet. Such a result would undercut NHTSA's overall rollover mitigation
policy that has been developed to balance the competing goals of
preventing rollover crashes in the first place and of reducing the risk
of injury when such crashes nevertheless occur.
     The creation of a patchwork of different State roof crush
resistance requirements across the country would not contribute toward
achievement of an appropriate balancing of roof strength and rollover
propensity.
     Being required to devote resources to increasing roof
strength using one of the costlier methods could delay or even prevent
manufacturers from installing advanced vehicle technologies for
reducing rollovers.
     The agency should also be concerned about another
potential safety conflict, in the area of vehicle compatibility, as the
addition of weight increases the chances of vehicle mass mismatch in a
collision.
B. Primary Arguments Against the Existence of Conflict
     NHTSA's claims that a more stringent standard could result
in increased vehicle weight and decreased stability are not supported
by the record.
     Manufacturers can strengthen roofs by a variety of means
without significantly increasing weight, and advanced steels and other
lightweight materials can be used to strengthen roofs without a weight
increase.
     NHTSA's data show that increases in roof structural
strength will not have a physically measurable influence on CG height.
Production of vehicles that exceed the NHTSA standard would enhance the
safety objectives of that standard.
     NHTSA did not provide any examples of vehicles with
elevated rollover risk due to weight added to the roof. An examination