[Federal Register Volume 61, Number 109 (Wednesday, June 5, 1996)]
[Proposed Rules]
[Pages 28550-28560]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-14145]
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DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. 91-68; Notice 5]
RIN 2127-AC64
Federal Motor Vehicle Safety Standards; Rollover Prevention
AGENCY: National Highway Traffic Safety Administration (NHTSA), DOT.
ACTION: Denial of petitions for reconsideration.
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SUMMARY: This notice announces the denial of petitions for
reconsideration of the agency's decision to terminate rulemaking to
develop a vehicle rollover stability standard.
FOR FURTHER INFORMATION CONTACT: The following persons at the National
Highway Traffic Safety Administration, 400 Seventh Street, S.W.,
Washington, D.C. 20590:
For non-legal issues: Gayle Dalrymple, Office of Crash Avoidance
Standards, telephone (202) 366-5559, facsimile (202) 366-4329.
For legal issues: Steve Wood, Office of the Chief Counsel, NCC-20,
telephone (202) 366-2992, facsimile (202) 366-3820.
SUPPLEMENTARY INFORMATION:
I. 1994 Notice Terminating Rulemaking on a Vehicle Rollover
Stability Standard
On June 28, 1994, NHTSA published a notice in the Federal Register
announcing two agency actions: (1) the termination of rulemaking to
develop a Federal Motor Vehicle Safety Standard on vehicle rollover
stability; and (2) the proposal of a consumer regulation for labeling
vehicles with rollover stability information. (59 FR 33254)
In the portion of the 1994 notice terminating rulemaking, the
agency examined the suitability of using a variety of vehicle stability
metrics 1 as a basis for a rollover standard. NHTSA concluded that
two such metrics, tilt table angle (TTA) 2 and critical sliding
velocity (CSV),3 can each separately account for approximately
half of the variability in rollover risk in single vehicle accidents
remaining after considering driver, roadway, and environmental factors.
NHTSA stated:
1 A vehicle stability metric is a measured vehicle
characteristic that is analyzed to determine whether it is related
to a vehicle's likelihood of rollover involvement.
2 The tilt table test involves placing the vehicle on a
platform which is then tilted about an axis parallel to the
vehicle's longitudinal axis. TTA is the angle at which the last tire
on the upper side of the platform loses contact with the platform
and the vehicle begins to fall off the platform. This metric is
influenced by changes in a vehicle's mass, center of gravity height,
track width, and suspension movement, all of which are physically
related to rollover stability.
3 Critical sliding velocity includes the roll moment of
inertia as well as the various static factors included in tilt table
angle. CSV is calculated from an equation which can be found in the
June 28, 1994 notice, as corrected on July 26, 1994 (59 FR 38038).
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The suitability of a vehicle safety standard based on rollover
stability depends on the importance of rollover stability, as
represented by a vehicle metric, relative to other rollover
influences, such as vehicle handling properties, vehicle condition,
the nature of the roadway and shoulder terrain, and driver behavior.
The agency sought to determine whether vehicle stability metrics are
significant variables in a statistical model of the risk of
rollover. If they are, then a standard regulating stability might be
justified, depending on the results of a comparison of benefits and
costs for such a standard.
After analyzing a number of static and dynamic rollover metrics,
the agency concluded that two vehicle metrics, tilt table angle and
critical sliding velocity, can account for about 50 percent of the
variability in rollover risk in single vehicle accidents, after
considering driver, roadway, and environmental factors. (Rollover
risk is the number of single vehicle rollovers involving a
particular make/model divided by the number of single vehicle
crashes of all types involving the same make/model.) This
statistical analysis was conducted on all light duty vehicles
treated as a group. However, analysis of accident data indicated
that certain subgroups of light duty vehicles are more likely to
roll over than other subgroups. For example, sport utility vehicles
and compact pickup trucks tend to be the most likely vehicles to
roll over. Large passenger cars tend to be the least likely to roll
over.
59 FR 33254, at 33258.
While NHTSA concluded that the two vehicle stability metrics were
of some value in estimating the likelihood that a single vehicle
accident involving a particular model of vehicle would result
[[Page 28551]]
in a rollover, the agency emphasized that analyses also ``show that
other factors in addition to those analyzed are affecting rollover
risk.'' (Id., at 33260) As the agency noted, ``[t]he suitability of a
vehicle safety standard based on rollover stability depends on the
importance of rollover stability, as represented by a vehicle metric,
relative to other rollover influences, such as vehicle handling
properties, vehicle condition, the nature of the roadway and shoulder
terrain, and driver behavior.'' (Id., at 33258) In other words, the
issue was not simply whether there is a statistical relationship, but
also whether that relationship is strong enough, considering other
influences, so that improvements in the stability metrics, especially
relatively small improvements, would generate benefits commensurate
with the costs. If the relationship is not sufficiently strong, even
significant changes in the stability metrics may be overwhelmed by the
other influences and thus fail to cause a significant change in
rollover experience.
The agency concluded that while each of the stability metrics has
some causal relationship to the potential for rollover and a
statistical relationship to real-world rollover frequency, a standard
based on either of the metrics would yield measurable benefits only if
it required that the metrics be increased to an extent that would
impose excessive costs and necessitate radically redesigning one or
more types of light trucks.4 The agency reached this conclusion
after examining the merits of establishing a single rollover standard
for all light duty vehicles (i.e., passenger cars and light trucks).
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\4\ The term ``light trucks'' includes sport utility vehicles,
vans, and pickup trucks with a gross vehicle weight rating of 4,536
kilograms (10,000 pounds) or less.
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With respect to a single standard, the agency stated:
The agency also determined that, considering the costs and
benefits involved, proposing a safety standard specifying a single
minimum stability value for both cars and light trucks could not be
justified. While light trucks have lower stability measurements than
cars do, the greatest number of rollover-related deaths and injuries
occur in passenger cars because of their larger population size.
Therefore, if the agency wished to set a stability minimum high
enough to realize significant reductions in the number of fatalities
in all light duty vehicles, it would have to set the minimum above
the stability number of most light trucks. The costs of such a
standard, in terms of the cost of vehicle redesign and the loss of
consumer-desired attributes, were determined to be very high, as
entire classes of light trucks would probably need to be
substantially redesigned to meet such a standard. This redesign
could result in the elimination of some vehicle types, e.g., sport
utility vehicles, as they are known today.
Id., at 33258.
To avoid such drastic consequences for light trucks, the agency
considered whether it would be appropriate to set one standard for cars
and separate standards for various classes of light trucks.5 NHTSA
concluded that it was not appropriate. Since its analysis of the
ability of the two vehicle stability metrics to account for the
variability in rollover risk in single vehicle accidents was conducted
on all light duty vehicles as a group, the agency examined the ability
of the metrics to account for variability within individual subgroups
of those vehicles. Regarding the results of that examination, NHTSA
stated:
\5\ Id., at 33258.
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[I]t was necessary to determine whether either of the stability
metrics exhibited sufficiently high levels of correlation to assure
the agency that a requirement applying to only one class of vehicle
would be expected to reduce the incidence of rollovers for vehicles
in that class. * * * [T]he agency found that the statistical
correlations of the metrics with rollover accident data within a
class of vehicles was not so consistent as for all vehicles grouped
together. This weakening of the predictive ability of the metric is,
to some extent, the result of the smaller range of the metric within
any class of vehicles together with the inherent variability in the
data. Based on this analysis, and the general analysis of costs and
benefits discussed later, the agency determined that proposing a
standard specifying one minimum stability value for cars and others
for various classes of light trucks could not be justified.
Id., at 33528.
II. Petitions for Reconsideration of Decision To Terminate
Rulemaking
In July 1994, the agency received two petitions for reconsideration
of its decision to terminate rulemaking on a rollover stability
standard. One petition was submitted by Advocates for Highway and Auto
Safety and the Insurance Institute for Highway Safety (Advocates/IIHS)
and the other by Randall and Sandy Vance, Doug White, and Robert and
Glenda Cammack (Vance, et al.). Both petitions asked NHTSA to
reconsider its decision to terminate rulemaking to establish a minimum
standard for vehicle rollover stability. The Vance et al. petition
expressed general disagreement with that decision, while the Advocates/
IIHS petition identified detailed points of disagreement. For this
reason, unless otherwise specified, references below to ``the
petition'' or ``the petitioners'' are references to the Advocates/IIHS
petition.
While the petitioners made numerous contentions, they focused on
four general areas: the character of a reasonable rollover standard,
the agency's statistical analysis of how a standard could be selected,
the agency's benefit calculations, and the agency's statements
concerning cost burden to the manufacturing industry. The following is
a summary of the more important contentions addressed in this notice
and the appendix to this notice:
NHTSA should have more thoroughly considered establishing
separate standards for separate classes of vehicles.
To achieve a better relationship between costs and
benefits, NHTSA should have considered the alternative of setting a
standard for the most rollover-prone vehicles within one or more of the
following groups: sport utility vehicles (SUVs), vans, and pickup
trucks.
Compact SUVs 6 are the most rollover prone group of
light duty vehicles.
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\6\ The vehicles considered compact SUVs in NHTSA's analysis
were: Ford Explorer, Chevy S10 Blazer, Jeep Cherokee, Jeep Wrangler,
Toyota 4-Runner, Nissan Pathfinder, Geo Tracker, GMC S-15 Jimmy
(essentially a twin of the Blazer), Isuzu Trooper, Isuzu Rodeo,
Suzuki Sidekick (essentially a twin of the Tracker), Mazda Navaho
(essentially a twin of the 4WD Explorer), Mitsubishi Montero, Isuzu
Amigo, and Suzuki Samurai.
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Minor vehicle changes (e.g., suspension changes) could be
used to achieve stability improvements at reasonable cost.
NHTSA did not provide any factual support for its
assertion that there are serious safety problems associated with
improving vehicle stability metrics through suspension changes.
NHTSA did not explain the nature and extent of the major
design changes that it said were necessary to meet any stability
metric, nor how much such changes would cost.
The level of projected benefits of a rollover standard was
understated by the agency because it:
used average class values in lieu of model specific
rollover accident data for the rollover experience of some vehicle
models;
used inappropriate statistical measures; and
viewed rollover prevention as accident mitigation instead
of accident prevention.
Although Congress did not mandate the issuance of a
rollover stability standard, it expected that such a standard would be
issued.
Contrary to NHTSA's position, the statute governing the
agency's vehicle
[[Page 28552]]
safety rulemaking readily permits the elimination of a class of
vehicles widely accepted in the marketplace.
The agency may not consider the policy concerns underlying
the Regulatory Flexibility Act without preparing a regulatory
flexibility analysis.
III. Response To Petitions for Reconsideration
In response to the petitions, the agency has reconsidered its
decision to terminate rulemaking on a rollover stability standard. As
explained below, the agency is, on reconsideration, reaffirming that
decision.
The petitions raise several points that are not disputed by NHTSA;
however, they do not compel the conclusion that NHTSA should establish
a rollover standard based on vehicle stability metrics. For example,
the agency agrees that single vehicle rollover is a significant safety
problem. NHTSA also agrees that the two vehicle stability metrics are
useful in estimating the likelihood that a single vehicle accident
involving a particular model of vehicle will result in a rollover.
Finally, the agency agrees that it is appropriate in determining
the desirability of a rollover standard to consider a rollover standard
regulating vehicles in the most rollover-prone groups. While the 1994
notice focused primarily on the approach of a single standard for all
light duty vehicles, the agency did analyze separate standards for
separate classes of vehicles. The notice explained that the predictive
ability of the vehicle stability metrics decreased as the vehicle
population was divided into smaller groups. As noted above, the agency
concluded that ``a standard specifying one minimum stability value for
cars and others for various classes of light trucks could not be
justified.'' (Id., at 33257). Since the petitioners suggest issuing a
rollover standard regulating the most rollover-prone vehicles, NHTSA
has focused on such an approach in responding to the petitions for
reconsideration. The agency agrees with the petitioners that, in
theory, the comparatively high rollover rate of compact SUVs makes a
standard regulating that group of vehicles appear more likely to
generate benefits commensurate with its costs than would a standard
regulating any other group of vehicles.
These areas of agreement are insufficient, however, to lead the
agency to the conclusion reached by petitioners. To the contrary, the
agency's detailed analysis below of a rollover stability standard based
on TTA or CSV demonstrates that the costs and other impacts of such a
standard manifestly outweigh the estimated but uncertain benefits.
A general response to the petitioners' arguments appears below.
Certain issues are covered in greater detail in the Appendix to this
notice.
IV. Rationale for Reaffirming Decision To Terminate
A. Summary
Following its examination of the arguments raised by the
petitioners, the agency has revisited and, in some respects expanded,
its rationale for terminating rulemaking on a vehicle stability
standard. The agency again concludes that it is not appropriate to
establish a vehicle rollover stability standard based on a vehicle
stability metric.
If a stability standard were set at a level that would require only
minor vehicle changes in order for the affected models to achieve
compliance, the standard would not produce any safety benefits. Minor
vehicle changes, which consist predominately of suspension changes,
would not produce significant improvements in the vehicle stability
metrics and would not be likely to result in any reductions in
fatalities and injuries.\7\ Moreover, there is reason to conclude that
such suspension changes would, in fact, produce negative safety side
effects.
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\7\ As noted above, the agency stated in the 1994 notice that a
standard limited in its application to a vehicle subgroup (e.g.,
sport utility vehicles) is particularly unlikely to reduce
fatalities and injuries given the weaker statistical relationships
between the stability metrics and the rollover involvement for
vehicle subgroups. (Id., at 33528)
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If a stability standard were set high enough to require significant
improvements in the vehicle stability metrics, it would necessitate
full vehicle redesigns and major vehicle changes. However, the safety
benefits of such changes would nevertheless be relatively modest.
Moreover, the overall costs and loss of consumer choice resulting from
full vehicle redesigns involving major vehicle changes would be
substantial and excessive. On balance, the potential for improved
vehicle safety associated with such improvements in the vehicle
stability metrics is not sufficiently large to justify such redesigns.
B. Vehicle Changes To Increase Vehicle Stability Metrics
There are two general categories of vehicle changes that would
increase the vehicle stability metrics (TTA and CSV). One consists of
relatively minor vehicle changes (i.e., suspension changes); the other,
of major vehicle changes (i.e., widening the vehicle track and lowering
the center of gravity) that could only be achieved through full
redesign of the vehicle. The petitioners appear to believe that a
vehicle can be redesigned so it will be significantly less likely to
roll over, that the means for accomplishing this will be ``invisible''
to the consumer, and that the vehicle will look and function as it did
before the redesign. As discussed below, redesigning a vehicle to
significantly reduce its likelihood of rolling over necessarily
involves making fundamental changes in the vehicle's dimensions (making
it wider, longer, lower, heavier) and compromising its utility to
consumers (e.g., by reducing its fuel efficiency, ground clearance,
load-carrying capacity, off-road capability, or driveability on snowy
roads).
1. Minor Vehicle Changes To Increase Vehicle Stability Metrics
Minor vehicle changes have very little effect on the vehicle
stability metrics. Moreover, they do not result in net safety
improvements.
As the petitioners correctly point out, the Preliminary Regulatory
Evaluation (PRE) for the 1992 Advance Notice of Proposed Rulemaking
(ANPRM) suggested that there were grounds for optimism about the
ability of minor vehicle changes, such as suspension tuning, to affect
stability metrics and improve rollover stability. (57 FR 242; January
3, 1992) However, after reviewing the comments on the 1992 ANPRM, the
agency concluded in the 1994 notice that minor vehicle changes could
not, in fact, significantly affect the vehicle stability metrics.
Comments from Advocates itself,\8\ as well as Ford and General Motors,
on the ANPRM indicate that suspension changes result in very little
improvement in rollover stability.
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\8\ In commenting on the ANPRM, Advocates indicated that it did
not share the agency's optimism at that time about the desirability
of relying on suspension changes to improve rollover stability
metrics. Advocates commented that the selection of TTR as the
parameter to be regulated would ``permit a manufacturer to attempt
manipulation of other stability-related elements of the vehicle's
design, such as its suspension, in order to secure a barely passing
tilt- table score.'' It also expressed concern that the agency ``may
be already tending towards selection of TTRs [see footnote 12] that
will not move the industry towards safer overall vehicle designs,
particularly with regard to wheelbase, width, length, and center of
gravity height, but rather will encourage the perpetuation of the
status quo designs especially with regard to very small cars, small
pickups, and SUVs that will continue to show high rollover
propensities.''
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Moreover, vehicle rollover stability is not the same as vehicle
handling and control. Some measures that improve
[[Page 28553]]
TTA or CSV do not necessarily result in improved directional control
and stability. Available information suggests that directional control
and stability would be adversely affected as a result of relying upon
suspension changes to make small increases in the vehicle stability
metrics. This information was supplied in comments from Advocates,
Ford, and General Motors on the ANPRM expressing concern with the side
effects of suspension changes to improve TTA.
For example, Ford used a computer simulation of a compact pickup
truck to evaluate the effect of a series of suspension changes on
directional stability and side-to-side load transfer in cornering.
(Docket 91-68-N01-21) Ford evaluated substantial suspension changes,
including a 30 percent increase in spring rates, removal of stabilizer
bars, and a change in the front suspension roll center by 1.5 inches.
It also examined a ride height change that would lower the center of
gravity by 0.5 inch. Ford noted that, in general, tuning a suspension
system such that both the front and rear tires lift from the tilt table
simultaneously would maximize the TTA. However, this optimization
requires either decreasing the front roll stiffness (by removing the
front stabilizer bar), or increasing the rear roll stiffness (by using
a 30 percent greater rear spring rate). The simulation showed that,
among the suspension changes examined by Ford, these two changes made
the greatest improvements in TTA (an increase of 0.62 and 0.55 degrees,
respectively). However, these changes were also shown to alter
directional stability toward oversteer (i.e., these changes tend to
make a vehicle turn more sharply than a driver intends). Ford's
simulation showed that other suspension changes, such as an increase in
front spring rate or a decrease in front roll center height, could
increase TTA (to a lesser degree than those mentioned above), while
altering directional stability toward understeer (i.e., these changes
tend to make a vehicle turn less sharply that a driver intends). The
only minor change mentioned by Ford in its comment which improved TTA
without influencing directional stability was lowering the vehicle c.g.
height by 0.5 inch, resulting in only a 0.17 degree increase in TTA.
Based on its consideration of such comments, the agency concludes
that suspension changes would not produce significant improvements in
rollover stability and would have the potential to cause undesirable
changes in directional stability and handling, which in turn could lead
to an increase in crashes. In view of this conclusion, the agency has
not examined whether those changes could be made at a reasonable cost,
since they are unlikely to yield net safety benefits.
2. Major Vehicle Changes To Increase Vehicle Stability Metrics
Thus, significant improvements to the vehicle stability metrics
could be achieved only through making major changes to the vehicle
chassis and body to increase the track width and/or lower the center of
gravity. These major changes would require full vehicle redesigns that
substantially change the parameters affecting vehicle stability
metrics. The necessary extent of such redesigns is illustrated in the
following example. Given that the center of gravity height for a
typical compact SUV 9 is 27 inches, to raise its TTA (42.9
degrees) to that of the typical full- size SUV (46.4 degrees), it would
be necessary to increase the track width (i.e., the distance between
the left and right tires on an axle) more than 6 inches. Further, such
a track width increase would require a corresponding wheelbase (i.e.,
the distance between the front and rear axles) lengthening of 10 inches
to retain the braking stability of the smaller SUV. As noted later in
the sections regarding cost and impact on consumer choice, such
modifications would eliminate most of the compact SUVs as they
currently exist, converting the typical compact SUV into a full-size
SUV.
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\9\ A ``typical compact SUV'' and a ``typical full-size SUV''
are hypothetical vehicles with the average TTA and dimensions of all
the vehicles in their class.
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Citing the example of the GMC Jimmy, which was redesigned for 1995,
petitioners argued that vehicle manufacturers can gradually redesign
their compact SUVs so as to increase their vehicle stability. The
petitioners presented an article from Automotive News stating that the
new Jimmy is longer, lower, and wider than its predecessor.10 The
petitioners further attributed to the new Jimmy ``a chassis
modification that can result in better stability metrics and in lower
rollover crash rates.'' 11
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\10\ Advocates/IIHS petition, attachment 2.
11 Advocates/IIHS petition, page 18.
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NHTSA draws a very different lesson than do petitioners from the
example of the Jimmy. In the agency's view, the petitioners
underestimate the extent to which the parameters affecting a vehicle's
stability metrics must be changed to significantly improve those
metrics. As explained below, the overall lessons of the new Jimmy are
that even a significant partial redesign of a vehicle will change its
vehicle stability metrics little in the absence of major changes to the
vehicle's c.g. height and track width, and that even minor changes in
those parameters may come at the cost of adversely affecting other
attributes desired by consumers. For example, the new Jimmy is heavier
and more costly than the prior model.
The agency agrees that the vehicle stability metrics of the new
Jimmy are likely to be somewhat better than those of the old Jimmy.
Although the agency has no TTA or CSV data on the new design, its lower
body height and wider track suggest that it has a slightly better TTA
than its predecessor and its longer, wider, and heavier body suggests
that it may have a greater roll moment of inertia and, therefore, a
slightly greater CSV.
However, the increases in the Jimmy's vehicle stability metrics are
likely to be very small. The reason is that the changes made to the
parameters affecting those metrics were relatively minor. Although the
changes increased the size and weight of the Jimmy, the magnitude of
those changes fell short of the levels needed to make a significant
improvement in its TTA or CSV. The body height of the 2WD model was
reduced by 1.6 inches, but the associated reduction in center of
gravity height is likely to be much less, since the location of the
engine, drive train, suspension, and passenger accommodation component
masses remained unchanged. The height reduction of the 4WD model was
only 0.8 inches. Likewise, the body width was increased by 2.4 inches,
but the front and rear track widths of the 4WD model were increased
less: 1.6 and 1.0 inches, respectively. The 2WD model track width
increases were even less: 0.9 inch at the front and 0.5 inch at the
rear.
Taken together, these changes to the Jimmy's parameters affecting
the rollover stability metrics are very minor compared to the ones
described above as being necessary for a typical compact SUV to achieve
a TTA of 46.4 degrees. Thus, these changes predict at best a very small
improvement in TTA or CSV.
The impact of such small improvements in vehicle stability metrics
on rollover risk is unknown. Since this is a new model for 1995,
neither NHTSA nor the petitioners have data on the rollover experience
of the new Jimmy. There is no way to know at this time if the changes
will actually lead to a reduced risk of rollover.
C. Benefits of Improvements in Vehicle Stability Metrics
NHTSA's 1994 notice estimated that the benefits of a rollover
standard requiring a TTA of 46.4 degrees for all light duty vehicles
included a modest
[[Page 28554]]
amount of benefits for compact SUVs. The agency's estimate that 63
fatalities and 61 serious injuries might be prevented for all light
duty vehicles included the prevention of 31 fatalities and 22 serious
injuries for compact SUVs. The potential compact SUV benefits were
predominately attributable to those particular compact SUV models that
would require significant changes in track width and/or center of
gravity height to achieve the required TTA.
As part of its review of the petitions, the agency recomputed its
estimate of the benefits of making significant design changes in order
to raise the TTR 12 of compact SUVs to 1.05,13 using data
that were not available for some makes and models when the analysis was
done for the 1994 notice.14 The agency estimates that, using the
more current data and certain optimistic assumptions (discussed below),
22 serious injuries and 32 fatalities might be prevented annually if
all new compact SUVs were redesigned to the extent necessary so that
each vehicle in that class had a TTR of 1.05 and if all existing
compact SUVs with a lower TTR were retired from the vehicles-in-use
fleet. The potential benefits for a rollover stability standard are
computed by considering:
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12 TTR is the tangent of TTA. In its analysis prior to
the 1994 notice, the agency used TTR. Because TTA is an easier
concept to depict on labels for the general public, the agency
proposed the use of TTA rather than TTR for the vehicle label under
a consumer information regulation that was proposed in the 1994
notice. NHTSA used TTA throughout the 1994 notice for that reason.
However, NHTSA has not converted the TTR values to TTA values when
discussing its statistical and benefits analyses in this document.
13 A TTR of 1.05 is the equivalent of a TTA of 46.4
degrees. On page 33261 of the 1994 notice, the agency explained
that, if the agency were to adopt a rollover stability standard
applicable to all vehicles, a TTA of 46.4 degrees was the highest
practicable standard. The agency explained that a TTA of 46.4
degrees is representative of the average full-size SUV. Since the
design changes to increase TTA to that level would cause a compact
SUV to approach the size of full-size SUVs, establishing any higher
standard, whether for all vehicles or for compact SUVs alone, would
lead to the virtual elimination of compact SUVs as that class
currently exists.
14 The recomputation was performed using the same
procedures used for the 1994 estimates and explained in detail in
the document ``Potential Reductions in Fatalities and Injuries in
Single Vehicle Rollover Crashes as a Result of a Minimum Rollover
Stability Standard.'' That document is in Docket 91-68; Notice 3.
However, while the procedures were the same, an expanded set of data
(the number of rollover accidents and single vehicle accidents) were
used in the recomputation to increase its accuracy. The use of the
new data adequately addresses the petitioners' concerns about the
agency's use in the 1994 notice of weighted averages for models for
which there was insufficient data to determine the actual rollover
rate.
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(1) The reduction of rollovers per single vehicle accident (RO/SVA)
predicted for increases in TTR;
(2) The number of single vehicle accidents experienced by vehicles
that would need to be altered in order to comply with the standard; and
(3) The degree of harm mitigation (in the number of fatalities and
serious injuries) as a result of rollover prevention given that a
single vehicle accident has occurred.
The following table, corresponding to Table 1 of the document
``Potential Reductions in Fatalities and Injuries in Single Vehicle
Rollover Crashes as a Result of a Minimum Rollover Stability
Standard,'' contains the results of this latest computation. For an
explanation of the headings and entries in the table, see that
document.
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Est % Projected AIS3 + Fatality
MY 1991 1986-88 5 1986-90 of Est AIS3 Est RO/SVA @ reduction reduction
Compact SUV make model Drive production TTR state SVA/RV Michigan compact + fatalities min TTR @ min TTR @ min TTR
RO/SVA SUV ROs injuries 1.05 1.05 1.05
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Vehicle A.................................... 2 WD*\15\ 65,515 0.88 **\16\0.0068 **0.359 6 39 28 0.270 9.6 6.9
4 WD 184,554 0.88 **0.0068 **0.359 16 110 79 0.270 27.2 19.5
Vehicle B.................................... 2 WD 29,480 0.95 0.0103 0.342 4 25 18 0.280 4.6 3.3
4 WD 93,866 0.99 **0.0102 0.27 9 63 45 0.244 6.1 4.4
Vehicle C.................................... 2 WD* 19,920 1.08 0.0091 0.317 2 14 10 ........... ......... .........
4 WD 101,541 1.08 0.0091 0.317 11 71 51 ........... ......... .........
Vehicle D.................................... 2 WD 0 ........... ............ ......... ....... ........ .......... ........... ......... .........
4 WD 46,478 1.03 0.0163 0.273 8 50 36 0.263 1.8 1.3
Vehicle E.................................... 2 WD* 4,892 1.01 0.0211 0.362 1 9 7 0.338 0.6 0.4
4 WD 39,989 1.01 0.0211 0.362 11 74 53 0.338 4.9 3.5
Vehicle F.................................... 2 WD* 3,555 0.93 **0.0215 **0.315 1 6 4 0.258 1.1 0.8
4 WD 35,945 0.93 **0.0215 **0.315 9 59 42 0.258 10.8 7.7
Vehicle G.................................... 2 WD 0 ........... ............ ......... ....... ........ .......... ........... ......... .........
4 WD 30,702 0.978 ............ 0.394 5 31 22 0.348 3.6 2.6
Vehicle H.................................... 2 WD 6,479 0.95 0.0114 0.259 1 5 3 0.219 0.7 0.5
4 WD 23,515 0.99 **0.0123 0.252 3 18 13 0.228 1.7 1.2
Vehicle I.................................... 2 WD 0 ........... ............ ......... ....... ........ .......... ........... ......... .........
4 WD 26,776 0.98 ............ **0.481 5 33 24 0.427 3.7 2.7
Vehicle J.................................... 2 WD* 740 0.947 ............ ......... 0 1 0 0.281 0.1 0.1
4 WD 23,870 0.947 ............ ......... 3 20 15 0.281 3.3 2.1
Vehicle K.................................... 2 WD* 1,257 0.978 ............ 0.407 0 2 1 0.360 0.2 0.1
4 WD 10,492 0.978 ............ 0.407 2 13 10 0.360 1.6 1.1
Vehicle L.................................... 2 WD 0 ........... ............ ......... ....... ........ .......... ........... ......... .........
4 WD 11,404 0.88 **0.0068 **0.359 1 7 5 0.270 1.7 1.2
Vehicle M.................................... 2 WD 0 ........... ............ ......... ....... ........ .......... ........... ......... .........
4 WD 10,616 0.93 ............ ......... 1 9 7 0.274 1.7 1.2
Vehicle N.................................... 2 WD* 5,011 1.016 ............ ......... 1 4 3 0.315 0.2 0.2
4 WD 2,818 1.016 ............ ......... 0 2 2 0.315 0.1 0.1
Vehicle O.................................... 2 WD* 832 1.04 ............ ......... 0 1 1 0.329 0.0 0.0
4 WD 3,546 1.04 ............ ......... 0 3 2 0.329 0.1 0.0
[[Page 28555]]
Weighted Averge.............................. ............................. .......... ........... 0.01049 0.335 ....... ........ .......... ........... ......... .........
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Total \17\............................. ............................. 783,783 ........... ............ ......... 100 669 480 ........... 85.0 61.0
Total \18\............................. ............................. .......... ........... ............ ......... ....... ........ .......... ........... 22.0 32
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\15\ An ``*'' in this column indicates that the agency lacked sufficient data for the 2WD version of the model. For these models, the agency assumed that the 2WD version had the same TTR and
the same rollover rate as the 4WD version.
\16\ An ``**'' in this column and in the next one indicates that 1988-91 Michigan accident data were used instead of the data indicated by the column heading.
\17\ The serious injury and fatality reduction figures in this row are the benefits that might result if the standard prevented not only a rollover, but also an accident of any type.
\18\ The serious injury and fatality reduction figures in this row are the benefits that might result if the standard prevented a rollover, but still allowed an injury-causing accident of some
type to occur after the vehicle left the road. The injury and fatality figures in this row were derived by multiplying the figures in the row immediately above by a mitigation factor of 26
percent for injuries and 52 percent for fatalities. For further details on these factors, see section 3 of the Appendix to this notice.
There are two optimistic assumptions incorporated in the
computation process for both the original and new estimates: \19\
---------------------------------------------------------------------------
\19\ The agency made these assumptions because limitations in
available data made it impossible to use more precise values. When
making these assumptions, the agency took an optimistic approach so
as to present the prospects of a vehicle stability standard in the
best possible light.
---------------------------------------------------------------------------
The number of rollover injuries and fatalities prevented
will be proportional to the number of rollovers prevented; and
The fatality and injury rates of the late 1980's will be
representative of future rates.
The effect of these optimistic assumptions is that these new
estimates, like the 1994 estimates based on the same assumptions, may
in fact overstate the actual benefits, i.e., the number of fatalities
and injuries likely to be prevented by improving the TTR of compact
SUVs to 1.05.
The first assumption assumes that the rollover accidents that would
be prevented as a result of requiring an increase in TTR would have the
same fatality and injury rates as rollover accidents in general. There
is reason to believe that this would not be the case. The likelihood of
fatalities and serious injuries in rollover accidents is heavily skewed
toward crashes involving more than one quarter turn. Data show that
light truck rollover crashes involving only a single quarter turn have
about one-third the fatality rate of the average rollover. This
difference in likelihood of harm is significant if moderately improving
TTR would not be equally likely to prevent a multiple quarter-turn
rollover as a single quarter-turn rollover. NHTSA believes that it is
more likely that the prevented rollovers would tend to be the lowest
energy rollovers, i.e., the single quarter-turn rollovers. At best,
improving TTR would only slightly mitigate the more severe rollovers.
Thus, by assuming that rollovers prevented by an improvement in TTR
would be average rollovers instead of the least severe rollovers, the
agency is overstating the benefits obtainable from such an improvement.
Had the agency based its benefit estimates on the fatality rate of
rollovers involving a single quarter turn, the estimated number of
prevented fatalities would have been about 11 instead of 32.
The second assumption, that the fatality and injury rate in
rollovers will remain constant, is likely to overstate the benefits of
a vehicle stability standard since, if recent trends continue, future
increases in safety belt use, as a result of Federal, state, and local
efforts, can reasonably be expected to reduce the overall harm from
rollover accidents. As belt use increases, rollover casualties
decrease, even if the number of rollover crashes remains constant.
Consequently, even with liberal assumptions and using the most
current and complete database available, NHTSA estimates that a
rollover stability standard requiring compact SUVs to achieve the same
TTR (1.05) as the typical full-size SUV would prevent 22 serious
injuries and 32 fatalities annually. While precise quantification is
impossible, the agency believes, for the reasons stated above, that the
actual level of safety benefits would be significantly lower.
D. Costs of Improvements in Vehicle Stability Metrics
The substantial vehicle redesigns necessary to enable many existing
compact SUVs to achieve a TTR of 1.05 and produce the estimated
reductions in fatalities and injuries discussed above would have
substantial negative impacts, both in terms of reduced consumer choice
and unmet preferences and in terms of increases in manufacturer and
consumer costs.\20\ As noted above, the only way to achieve significant
increases in TTR is to increase the track width and/or lower the center
of gravity. Increasing track width or lowering the center of gravity,
using conventional, commonly used designs and production methods, would
necessarily, and significantly, increase vehicle size and weight. For
NHTSA, in effect, to require compact SUVs to approach the size and
weight of full-size SUVs would run counter to consumer preferences that
have led to the existing fleet of compact SUVs. The strength of those
preferences is demonstrated by the fact that compact SUVs outsold full-
size SUVs by a margin of six to one in 1994, the latest year for which
the agency has sales data.\21\ The Ford Explorer, the compact SUV model
with the lowest TTR and therefore the compact SUV which would be most
affected by any minimum standard, is the best-selling SUV and is the
ninth most popular make/model of all car and truck models combined.
---------------------------------------------------------------------------
\20\ As explained in the Appendix, NHTSA made two cost
estimates. The first was based on the assumption that compact SUVs
needing a TTR increase of more than 0.06 would require a full
vehicle redesign. The second was based on the assumption that only
compact SUVs needing a TTR increase of more than 0.04 would require
such a redesign.
\21\ Model year 1994 sales data from Automotive News 1995 Market
Data Book, Crain Communications, Detroit, Michigan, May 24, 1995.
All light trucks--6,097,787 vehicles.
Compact SUVs--21.9% of light trucks, or 1,335,415 vehicles.
Full-size SUVs--3.6% of light trucks, or 219,520 vehicles.
---------------------------------------------------------------------------
Upsizing compact SUVs so as to eliminate much of the size and
weight difference between those vehicles and full-size SUVs also might
have a significant adverse affect on the
[[Page 28556]]
production and sales of SUVs. The body of the average full-size SUV is
currently about 10 inches wider than that of the average compact SUV,
and the track width is about 9 inches greater. The 6-inch increase in
track width necessary to bring the TTR of compact SUVs up to that of
full-size SUVs (assuming no increase in c.g. height) would remove much
of those differences between compact SUVs and full-size SUVs. Given the
admonition in the legislative history of the National Traffic and Motor
Vehicle Safety Act against eliminating vehicle types (see the
discussion in section D of the Appendix to this notice), such a
dramatic potential impact on the design of compact SUVs and on the
market for those vehicles must be carefully weighed.
In addition to impacts on consumer choice and sales, there are
substantial monetary costs associated with redesigning those compact
SUVs that would need significant increases in TTR to meet a standard of
1.05.\22\ The agency estimated those costs using confidential cost data
submitted by domestic automobile manufacturers during the course of
several agency rulemaking proceedings to establish light truck
Corporate Average Fuel Economy (CAFE) standards. The estimated consumer
cost of bringing all such new compact SUVs into compliance with such a
standard is between $310 million and $335 million, depending on which
of two assumptions is made about the vehicles that would require a full
vehicle redesign. A detailed discussion of the method used to estimate
these costs is included in the Appendix to this notice.
---------------------------------------------------------------------------
\22\ As demonstrated by Table 1, the vast majority of the
measurable benefits from such a standard would come from
improvements to these fully redesigned vehicles, instead of those
vehicles that would need only lesser changes to comply with the
standard.
---------------------------------------------------------------------------
The agency believes that the foregoing estimate of the costs of a
rollover standard requiring compact SUVs to achieve a minimum TTR of
1.05 is understated. Those estimates do not include the incremental
costs of material and labor involved in the manufacture of a larger
vehicle. In addition, the estimates do not include any costs for
vehicles that would only need minor changes, instead of a full vehicle
redesign, to comply with the standard. NHTSA has not attempted to
calculate those costs because the benefits of the standard are already
outweighed by the initial cost estimate.
The agency recognizes that providing a lengthy leadtime period
would reduce the costs of compliance to the extent that manufacturers
were able to make their compliance efforts coincide with their normal
model changeover timetable. However, providing additional leadtime
would do nothing to reduce the adverse impacts on consumer preferences.
Further, an extended lead time would not affect the costs of additional
labor or materials.
VI. Conclusion
The discussion above and in the Appendix demonstrates that even a
standard applicable only to compact SUVs, the vehicle type that the
petitioners characterize as one of the two ``most rollover-prone
vehicle types,'' 23 would generate substantial adverse impacts on
manufacturers and consumers, both in terms of monetary costs and in
loss of consumer choice, that would outweigh the benefits of such a
standard. There is no reason to believe that a standard that would
mandate significant increases in TTR/TTA or CSV for any other vehicle
type or group of vehicle types would be any more cost beneficial.
---------------------------------------------------------------------------
23 Advocates/IIHS petition, page 12.
---------------------------------------------------------------------------
Accordingly, NHTSA reaffirms its decision to terminate this
rulemaking without proposing a rollover stability performance standard.
Issued on May 31, 1996.
Barry Felrice,
Associate Administrator for Safety Performance Standards.
Appendix
The Advocates/IIHS petition contained many detailed technical
arguments. Responses to the more significant ones are provided in
this appendix.
A. The Benefits Estimate
1. Replacing Weighted Averages With Actual Rollover Data Now Available
Makes No Appreciable Change in the Estimate
The petitioners criticized the benefit estimates made by the
agency in connection with the 1994 notice because, for those vehicle
models for which the agency lacked sufficient rollover accident
data, it used the average of the rollover per single vehicle
accident rate (RO/SVA) of the class of vehicles to which that make
and model belonged, weighted by the 1991 production of each make and
model for which the agency had RO/SVA. The benefits were calculated
using the TTRs of 1991 makes and models and the accident records of
1991 makes and models (and identical vehicles from prior model
years) to represent a hypothetical future fleet.1
---------------------------------------------------------------------------
1 A detailed discussion of the method can be found in
``Potential Reductions in Fatalities and Injuries in Single Vehicle
Rollover Crashes as a Result of a Minimum Rollover Stability
Standard'' in Docket 91-68, Notice 3.
---------------------------------------------------------------------------
The petitioners pointed out that the average TTR for vehicles
for which the agency did not have adequate RO/SVA data was lower
than the average TTR of vehicles for which it had RO/SVA data, and
therefore claimed that use of weighted averages was inappropriate.
The petitioners' criticism concerning the use of weighted averages
as substitutes for missing data was focused particularly on the use
of those averages for the large number of vehicles in the
hypothetical future fleet that were represented by the Ford
Explorer. The agency had no RO/SVA or single vehicle accident
involvement rate (SVA/RV) data for the Ford Explorer and certain
other vehicles at the time of the notice because they were either
recently introduced or comparatively low production volume models.
The petitioners argued that a higher rollover rate should have been
used for vehicles like the Explorer which have a lower TTA than the
vehicles from which the weighted average was derived.
It is not appropriate to assume that a higher than average
rollover rate is appropriate for the Explorer or the other vehicles
simply based on their having a lower than average TTA. The data
demonstrate that the order of vehicle models ranked according to TTA
is not the same as the order of models ranked according to rollover
rate. See Table 1 in the accompanying notice of denial of petitions
for reconsideration. Thus, although two different vehicle models may
have the same TTA, they may not necessarily have the same rollover
rate. Likewise, a vehicle model with a TTA lower than that of
another model may nevertheless have a lower rollover rate, and vice
versa.
Accordingly, the agency has not assumed a higher rollover rate
for those models for which sufficient rollover data are lacking.
However, the agency has responded to the petitioners' concern about
the use of weighted averages in connection with the 1994 notice by
replacing those averages, where possible, with rates based on actual
rollover accident data that became available after that notice was
prepared.
Where sufficient, the 1988--1991 Michigan accident data were
used to calculate the rollover rate figures for models for which
data were previously missing. Following the practice of previous
analyses, the agency used the accident data to calculate rollover
rates only for makes and models which had at least 25 single vehicle
accidents. Actual rollover rates (RO/SVA) from Michigan were added
for the 4WD Ford Explorer, Nissan Pathfinder, and Isuzu Trooper, and
actual single vehicle accident rates (SVA/RV) were added for the 4WD
Ford Explorer, the 4WD S10 Blazer, the Nissan Pathfinder, and the
4WD GMC S15 Jimmy. The 4WD Explorer data were used for the nearly
identical, but low production volume, Mazda Navajo.
There were still some models for which the agency lacked
sufficient actual make and model accident data. For most of these
models, while the agency lacked sufficient data for the 2WD versions
of those models, it had sufficient data for the more numerous 4WD
versions. In these instances, the agency assumed that the rates for
the 2WD versions were identical to the rates for the 4WD versions of
the same make and model, instead of calculating rates based on
weighted averages. New weighted averages
[[Page 28557]]
were computed on the basis of the expanded data and were used only
where sufficient specific data remained unavailable for a particular
model. The instances in which the agency computed new weighted
averages were limited. Weighted averages of RO/SVA and SVA/RV were
used for less than 10 percent and 19 percent, respectively, of the
example population of compact SUVs. See Table 1.
Using actual rollover data wherever available, the agency
recomputed the benefit estimates for compact SUVs. Substitution of
the new rollover rates produced very little change in the estimate
of the numbers of fatalities and serious injuries that might be
prevented if a rollover stability standard were adopted for compact
SUVs. Replacing the weighted averages used in the 1994 notice with
rates based on accident data for particular makes and models changed
the result of the analysis very little, i.e., by less than four
percent. This may be seen by comparing the estimates of the benefits
that would be obtained if preventing a rollover meant preventing an
accident altogether. Those benefits were estimated to be 83 serious
injuries and 59 fatalities in the 1994 notice. They have been
recomputed to be 85 serious injuries and 61 fatalities, based on the
new accident data and less reliance on weighted averages. See Table
1.
2. Accident Mitigation, Not Accident Prevention, Is the Proper Measure
of Benefits
Since an accident would still occur in the vast majority of
instances in which a rollover is prevented, the agency reduced those
figures accordingly using an accident mitigation factor. The
resulting new benefit estimate is 22 serious injuries and 32
fatalities.
The petitioners criticized the agency for making the same
adjustment to the benefits in the 1994 notice. Then, as now, NHTSA
assumed that the benefits would come from accident mitigation
instead of accident prevention. It was appropriate for the agency to
assume that the benefits would be in terms of accident mitigation
since over 90 percent of all single vehicle rollovers are off-road,
tripped rollovers, i.e., rollovers that occur when a vehicle leaves
the roadway sideways, encounters a tripping mechanism, and rolls.
Since a vehicle is running off the road in a tripped rollover
situation, such a vehicle will still likely crash into some off-road
object even if the vehicle is prevented from rolling over after it
leaves the road. If a rollover can be prevented in that situation,
then the resulting accident will most likely be one of lower
severity than if a rollover had occurred because rollovers tend to
be more severe than non-rollover accidents. The primary benefits
from a rollover stability standard would result from preventing the
more severe form of off-road accident.
3. A Single Accident Mitigation Factor, Not Separate Factors for
Individual Vehicle Types, Is the Proper Basis for Measuring Benefits
The petitioners also criticized the agency for using a single
accident mitigation factor (52 percent) for fatalities across the
board instead of computing separate factors for different types of
vehicles. In support of their argument for the use of different
factors, they noted that rollover accidents account for 80 percent
of the fatalities of the occupants of compact SUVs in single vehicle
accidents. Based on this, the petitioners concluded that rollovers
in compact SUVs are four times as deadly as non-rollover accidents,
and therefore the agency should have used a mitigation factor of 75
percent for compact SUVs.
The agency rejects the petitioners' argument. A mitigation
factor based on ratios of absolute numbers of fatalities, instead of
on fatality rates, is incorrect unless the same number of occupants
were exposed to rollover accidents and non-rollover accidents. If
the exposure is not the same, then it is impossible to determine the
extent to which the ratio reflects the difference in accident
exposure versus a difference in accident severity. Further, the
issue of a difference in accident severity is not just a matter of
the difference in severity of a rollover accident and a non-rollover
accident at the same speed. It is also a matter of possible
differences in speed. For example, it is necessary to determine
whether the consequences of 60 mph rollovers are being compared to
those of 30 mph non-rollover accidents. Finally, it is also
necessary to examine whether apparent differences between vehicle
groups are a result of differences in crashworthiness, or just a
consequence of smaller sample sizes.
The agency's use of a single mitigation factor for fatalities
takes these considerations into account. NHTSA considered the number
of occupants exposed to rollover and non-rollover single vehicle
accidents as well as the number of fatalities for each accident
type. It also considered the speed limit of the road as a rough
indication of the severity of the accident.
As a first step in determining the mitigation factor, NHTSA
compared the overall fatality rate of rollover accidents to the
overall fatality rate of non-rollover accidents, based on single
vehicle accidents of all cars and light trucks without consideration
of accident severity. The fatality rate of rollover accidents was
slightly more than twice that of non-rollovers, suggesting a 52
percent mitigation factor.
Next, the agency computed a series of relative fatality rates
(with and without rollover), comparing only accidents occurring on
roads with the same range of posted speed limits (25 mph or less;
30-35 mph; 40-50 mph; 55-65 mph). While the accident data do not
indicate the actual accident speed, grouping by speed limit acts as
a rough control on accident severity, because it restricts accident
groups to the same kinds of roads, even though the actual range of
crash speeds may significantly exceed the range of posted speed
limits for a particular group of accidents. The relative fatality
rate for each road speed limit group were added and then averaged.
The result was the same 52 percent mitigation factor for fatalities.
Using the same process led to a mitigation factor of 26 percent for
serious injuries.
In addition, even if the agency were to use different mitigation
factors for different vehicle types, their use would not result in
dramatic changes in benefit estimates. For compact SUVs, the 75
percent mitigation factor suggested by the petitioners would result
in a fatality reduction of 46 rather than the 32 calculated by the
agency. This difference is 0.15 percent of the 9,000 annual rollover
fatalities. Using the estimates prepared for the 1994 notice, for
the entire light duty vehicle fleet, the use of different mitigation
factors resulted in predicting 71, instead of the agency's 63, lives
saved from requiring a TTR of 1.05. This is a difference of 0.089
percent.
B. The Cost Estimate
The petitioners criticized the agency for failing to provide any
costs for the vehicle changes that would be necessary to meet a
minimum rollover stability standard. The agency concluded in the
1994 notice that a large number of vehicles would require
fundamental full redesigns to meet a minimum stability standard.
Because the agency was aware of the magnitude of costs involved in
vehicle redesigns, it was apparent that the costs and other impacts
would substantially exceed the benefits. NHTSA did not, however,
provide a quantification of those costs and other impacts.
To demonstrate the validity of its conclusion about the costs
and other impacts, the agency has conducted a rough cost analysis
for this notice as set forth below.2 To estimate the compliance
costs for those vehicles which would have to be fully redesigned to
make the substantial changes necessary to comply with a minimum
stability standard, the agency used confidential cost data submitted
by domestic automobile manufacturers during the course of several
agency rulemaking proceedings for light truck Corporate Average Fuel
Economy (CAFE) standards. These data are manufacturer estimates of
the costs of full redesigns of compact SUVs that would have been
necessary if the CAFE standards had been set at certain levels.
These submissions include estimates of investment costs for a
redesigned vehicle model, but do not include material and labor
costs for the manufacture of the vehicle. NHTSA believes a full
vehicle redesign for rollover stability purposes would necessitate
similar investment costs. Accordingly, it is appropriate to use the
investment cost figures from the CAFE program to estimate the
investment costs for vehicles which would require a full redesign to
comply with a rollover stability standard.
---------------------------------------------------------------------------
\2\ As explained below, the agency did not calculate all costs
of a standard because it determined that one category of those
costs, the investment costs for vehicles requiring major changes,
would by itself exceed the benefits of a standard.
---------------------------------------------------------------------------
The CAFE submissions include investment cost data for five
models of compact SUVs. Since the specific raw data are
confidential, they cannot be set forth here or otherwise publicly
released. To convert those data into a form in which the original
data can not be determined, the agency divided the per model data by
the applicable manufacturer's estimated average annual production
capacity and then divided by the number of
[[Page 28558]]
years of the vehicle's design cycle life.3 The per-vehicle cost
estimates for these five vehicle design cycle lives were then
averaged to arrive at the estimate used in this analysis. The
individual per-vehicle cost estimates range from $317.37 to $532.37
and the average is $416.77. Since these costs are costs to the
manufacturer, they were adjusted to represent costs to the consumer
by dividing them by 0.75, a standard factor used by the agency in
its vehicle rulemaking in estimating consumer costs from
manufacturer's wholesale costs. The resulting estimated average
consumer cost per vehicle resulting from the redesign of a compact
SUV is $555.69.
---------------------------------------------------------------------------
3 Since the submissions were made in 1986, 1989, 1993,
and 1994, submissions for years prior to 1994 were adjusted to 1994
dollars using the implicit gross domestic product deflator as
calculated by the Bureau of Economic Analysis.
---------------------------------------------------------------------------
The agency then determined the number of vehicles that would
need vehicle redesigns to comply with a vehicle rollover stability
standard requiring a minimum TTR of 1.05. Based on available data,
the agency believes at least some models would have to be fully
redesigned to achieve TTR increases of more than 0.04, and that
almost all models would have to be fully redesigned to achieve at
TTR increase of 0.06. The agency determined next that 558,756
vehicles would need to be fully redesigned if the threshold for
having to make a full redesign were 0.06 and 603,637 vehicles would
need to be fully redesigned if the threshold were 0.04. Multiplying
these numbers of vehicles by the $555.69 per vehicle investment cost
estimate, the agency estimated that the total investment costs of a
standard requiring a TTR of 1.05 would be $310,495,121 to
$335,435,044.
The agency believes that this range of estimated costs of a
rollover standard requiring compact SUVs to achieve a minimum TTR of
1.05 is understated. As noted earlier, these cost estimates do not
include estimates of the incremental costs of material and labor
involved in the manufacture of the vehicle. Since vehicles would
need significant increases in track width, and attendant increases
in wheelbase, they would be generally larger and heavier. As a
result, the agency concludes that there would be significant
increases in the costs of material and labor involved in the
manufacture of such vehicles. In addition, these cost estimates do
not include any costs for vehicles which could comply with the
standard by changes that are less than a full vehicle redesign.
C. Objections to the Statistical Tools Used by the Agency in
Reaching Its Decision
The petitioners asserted that the agency did not use the
``typical'' statistical measure, the deviance statistic, to judge
the adequacy of the logistic regression models used by the agency in
its analyses of the relationship of TTA to RO/SVA, and the
importance of the vehicle stability metrics. The petitioners also
objected to the agency's use of two statistical measures, R2
and the C-statistic. Finally, the petitioners questioned the
agency's reliance on data from the State of Michigan.
Although the agency did not use the deviance statistic to judge
the adequacy of the logistic regression models, the agency did use a
mathematically equivalent measure, the likelihood statistic (-
2*ln(likelihood)). Using that measure permitted the agency to
compare the effect of adding variables (specifically the vehicle
stability metrics) to the hypothesized models. Detailed discussions
of the agency's analyses are found in the Technical Assessment Paper
(TAP) (Docket 91-68-N01-03) and the Addendum to the Technical
Assessment Paper (Docket 91-68-N03-02) which were placed in NHTSA's
docket. The TAP and the Addendum present analyses using five
measures: the C-statistic, R2, the percentage change in
R2, the likelihood statistic, and the variables' chi-square. It
is true that the deviance statistic was not reported because the
computer software the agency used to conduct this analysis, SAS
Institute's PROC LOGIST, does not include the deviance statistic as
one of the model diagnostics. However, the agency does not believe
that this affects the general conclusions regarding the importance
of the vehicle stability metrics.
NHTSA believes that it may help to explain this issue in non-
statistical terms. The petitioners' argument amounts to a complaint
that the agency described various glasses of water in terms of how
much water is in the glass, instead of in terms of how much water
could be added to the glass. In either case, the capacity of the
glass is the same. If the capacity is known, and if either the
amount of water or the amount of unused capacity is known, the other
amount can be derived.
Similarly, the deviance statistic preferred by the petitioners
describes how much of the variability 4 in the regression model
is left to be explained. The likelihood statistic, which the agency
used, describes how much of the variability in the model is
explained. In either case, the total variability to be explained is
the same. If, as the agency's analysis showed, the addition of TTR
to the model decreased the value of the likelihood statistic, the
deviance statistic would have increased by the same amount. Using
either measure would lead to the same conclusion about the value of
TTR.
---------------------------------------------------------------------------
4 Variability is the difference between what the
statistical model predicts and actual accident records.
---------------------------------------------------------------------------
The petitioners also assert that the use of R2 was
inappropriate because it is not weighted, i.e., it does not reflect
the number of single vehicle accidents for each vehicle make and
model. The petitioners also state that R2 is sensitive to
extreme values. The agency's use of R2 was described fully on
page 5-66 of the TAP. The agency agrees, as explained in the TAP,
that there are limitations to the use of R2. As also explained
in the TAP, R2 was used as an approach to providing the types
of descriptive statistics of model fit with which more people are
familiar, and not to provide a mathematically rigorous assessment of
model fit. The agency's use of R2 was an attempt to make the
explanation of the analysis understandable to a wider audience, and
was not the sole basis of the agency's decision.
The petitioners' assertions of problems with the use of the C-
statistic are not applicable to the C-statistic as used by the
agency. In an attempt to support their assertions, the petitioners
pointed to an example of how the C-statistic can ``misbehave''
presented on page 146 of Hosmer and Lemeshow.5 The agency's use
of the C-statistic is not the same as that in Hosmer and Lemeshow's
example. That example simply uses a classification table with an
arbitrary cut point to determine, e.g., whether an actual rollover
was predicted to be a rollover. The C-statistic employed by NHTSA
measured the concordance between all possible pairs of observations,
taking one from the actual rollover population and one from the
actual non-rollover population. The C-statistic represents the
percentage of those pairs (which number literally in the millions)
for which the actual rollover had a higher predicted probability
than the actual non-rollover's predicted probability (of rolling
over), minus one-half the number of ties. There is no arbitrary
cutoff point. In addition, the agency's decision was not based on a
single statistical measure. The agency analyzed the data with a
number of statistical measures, all of which pointed to the same
conclusions. Accordingly, the agency remains confident in its
results.
---------------------------------------------------------------------------
5 D.W. Hosmer and S. Lemeshow, Applied Logistic
Regression, Wiley Interscience, New York, 1989.
---------------------------------------------------------------------------
Finally, the petitioners' objection to the agency's reliance on
Michigan data for performing the statistical regressions instead of
using the data from the other four states was based on their concern
that the agency did not examine the extent to which the state is
anomalous because of its generally flat topography. The petitioners
stated that this could lead to a lower proportion of rollovers per
single vehicle accident than the other states in the data base. The
agency relied on Michigan data because they included a large number
of available observations, and were based on a low reporting
threshold and more refined accident reporting variables. The agency
did examine whether the rollover rate in this state was anomalous,
and as stated on page 13 of the Addendum, discovered that ``(t)he
rollover rate in Michigan is near the midpoint of the range for all
five states studied.'' The examination of the relative rollover
rates of the five different states was fully explained in the TAP on
pages 59-65.
D. Legal Arguments
The petitioners also addressed the implications of the
Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA)
(P.L. 102-240), the National Traffic and Motor Vehicle Safety Act of
1966 (the Safety Act) (P.L. 89-563),6 and the Regulatory
Flexibility Act (P.L. 96-354) for rulemaking concerning a vehicle
stability standard. The petitioners also argue that the decision not
to issue a rollover standard is judicially reviewable.7
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6 After the publication of the termination notice, the Safety
Act was codified in volume 49 of the United States Code. Any cites
to provisions of the Safety Act have been updated to reflect the
codification.
7 The agency agrees with the petitioners that this
termination is ``final agency action'' for the purposes of judicial
review.
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[[Page 28559]]
The petitioners begin by citing the provision in ISTEA that
required NHTSA to initiate rulemaking concerning a rollover
standard. The petitioners acknowledge that Congress did not mandate
the issuance of a final rule in this area.
Although the petitioners make this concession, it bears
emphasizing how clearly ISTEA and its legislative history
demonstrate that in each instance in which Congress mandated that
the agency initiate vehicle safety rulemaking, it clearly specified
whether the agency had the discretion to decide not to issue a final
rule. In sections 2502-3 of ISTEA, Congress specified that the
agency was to initiate rulemaking regarding five different areas of
vehicle safety performance. With respect to one area, upper interior
head impact protection, Congress specified that rulemaking would be
considered completed only when a final rule was issued. However,
with respect to the other four areas, including rollover, Congress
did not mandate the issuance of a final rule. It expressly provided
that rulemaking on rollover and the other three areas would be
considered completed either when the agency issued a final rule or
when the agency decided, after considering public comments, not to
issue a final rule. The Conference Report on ISTEA emphasized the
discretion which it had reserved to the agency. The conferees said,
with reference to the mandated rulemaking on rollover, ``the
conferees do not predetermine the outcome of [this rulemaking]. The
[NHTSA] is free to conclude the rulemaking in any manner consistent
with the APA and the 1966 Act'' (H. Conf. Rep. 404, 102d Cong., 1st
Sess., at 397 (1991)). Thus, Congress made no judgment in ISTEA
about the ultimate merits of issuing a final rule on rollover.
Instead, Congress provided NHTSA with the latitude to decide that a
rollover standard should not be issued if, in the agency's judgment,
the facts did not warrant such issuance. The agency's conclusion
that such a regulation would not have sufficient benefits to justify
its cost is an ample and proper basis for a decision not to issue a
final rule.
Although the petitioners concede that Congress did not require
the agency to issue a final rule on rollover, they assert that
Congress ``expected the agency to set some form of stability-
enhancing regulation.'' 8 As authority for that assertion, they
cite the legislative history of the Department of Transportation and
Related Agencies Appropriations Act of 1995. (P.L. 104-59) The
Senate committee report on that Act contended that NHTSA had
``effectively abandoned efforts at developing a performance standard
for improved rollover protection.''
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\8\ Advocates/IIHS petition, page 41.
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The 1995 Appropriation Act legislative history is inapposite
here and lacks any possible binding effect. Since that history
pertains to a different statute, it carries no weight in the
interpretation of NHTSA's duties under ISTEA. NHTSA notes further
that the language cited by the petitioners is part of a discussion
expressing concern about the agency's delay in publishing some of
the ISTEA rulemakings. The discussion does not express any
expectation about the substantive outcome of agency rulemaking on
rollover, but does express an expectation that NHTSA will complete
the remaining ISTEA rulemakings expeditiously. Finally, even if the
Senate committee had specifically expressed an expectation
concerning the outcome of the rollover rulemaking, that expectation
would not impose a binding obligation on NHTSA unless Congress
coupled that expectation with a mandate to issue a final rule on
rollover and enacted that mandate into law. See Center for Auto
Safety v. Peck, 751 F.2d 1336, at 1351 (D.C. Cir. 1985). Congress
did not do so. Instead, it expressly decided not to mandate the
issuance of a final rule on that subject.
The petitioners argued that neither the Safety Act nor the
Regulatory Flexibility Act provide any legal grounds for terminating
rulemaking on a vehicle stability standard. The petitioners quoted
statements in the 1994 notice that 49 U.S.C. Sec. 30111(b)(3) would
preclude NHTSA from mandating any stability requirement that is
``incompatible with certain types of vehicles,'' and that a
stability requirement ``could raise concerns'' under the Regulatory
Flexibility Act. (59 FR 33254, 33263) They interpreted these
statements as implying that the agency believed it was prohibited
from issuing any standard that might require ``the radical redesign
of the characteristics [of] many, and in some cases all, vehicles of
certain classes * * * and possibly even the elimination of certain
classes of vehicles as they are known today.'' The petitioners
countered with alternative propositions, arguing that NHTSA has
authority to eliminate whole classes of vehicles, and that, even if
NHTSA does not have such authority, it failed to consider a less
demanding regulatory approach such as setting different standards
for separate vehicle types which would not require all vehicles in a
class to be altered. The petitioners argued also that NHTSA cannot
rely on the Regulatory Flexibility Act when the agency did not
prepare any analysis of the impacts of a standard on small entities.
The primary bases for the agency's decision to terminate
rulemaking on a vehicle stability standard are the limited safety
benefits, and the excessive costs and market disruption of such a
standard, regardless of whether that standard applies to all light
duty vehicles or to particular class such as compact SUVs. The 1994
notice discussed the high costs of a standard that specifies a
single performance level which was applicable to all light duty
vehicles and was high enough to require the full redesign of at
least some passenger cars. As explained previously, the agency
concluded that such a standard would have costs and other impacts
which outweighed its benefits. NHTSA similarly concludes that the
costs and other impacts of a standard applicable to compact SUVs
would far outweigh its benefits. Logically, if a standard for the
most rollover-prone light duty vehicles would fail this basis test,
it follows that a standard for other groups of light duty vehicles
would not be justified.
It should be noted that neither 49 U.S.C. 30111(b)(3) nor the
Regulatory Flexibility Act impose an absolute legal bar to a minimum
stability standard. The agency is not foreclosing any possibility of
further rulemaking. As stated above, NHTSA might reinitiate
rulemaking in this area if information becomes available
demonstrating the cost effectiveness of a minimum stability
standard.
However, the Safety Act does place limits on the agency's
rulemaking authority. The agency lacks authority to eliminate entire
classes of vehicles. This interpretation reflects the language of 49
U.S.C. 30111(b)(3) and its legislative history. 49 U.S.C.
30111(b)(3) states:
When prescribing a motor vehicle safety standard under this
chapter, the Secretary shall * * * consider whether a proposed
standard is reasonable, practicable, and appropriate for the
particular type of motor vehicle or item of motor vehicle equipment
for which it is prescribed.
The Senate Report accompanying the 1966 Safety Act explained
this provision as follows:
In determining whether any proposed standard is ``appropriate''
for the particular type of motor vehicle or item of motor vehicle
equipment for which it is prescribed, the committee intends that the
[NHTSA] will consider the desirability of affording consumers
continued wide range of choices in the selection of motor vehicles.
Thus it is not intended that standards will be set which will
eliminate or necessarily be the same for small cars or such widely
accepted models as convertibles and sports cars, so long as all
motor vehicles meet basic minimum standards.
(S. Rep. 1301, 89th Cong., 2d Sess., at 6 (1966))
Given this legislative history, NHTSA cannot mandate a stability
requirement so incompatible with the most fundamental
characteristics which define a class of vehicles that implementing
the requirement would cause the elimination of that class. As an
example, the agency noted in the 1994 notice that sport utility
vehicles have features (high ground clearance and narrow track
width) to facilitate off-road use and use on snowy roads. The agency
would not have the authority to set a performance level so stringent
that no vehicles could have these features. This is neither a
radical, nor a new interpretation of the agency's authority. NHTSA
is not suggesting, as the petitioners suggest, that the agency lacks
any authority to issue a standard that requires significant change
to all vehicles in a class. In fact, there are many examples of the
agency using its authority to require changes to all vehicles in a
particular class. Those changes did not, however, eliminate as a
practical matter any recognized classes of vehicles.
Petitioners incorrectly suggested that the agency had a duty
under the Regulatory Flexibility Act to prepare a regulatory
flexibility analysis in connection with either the 1994 notice or
the ANPRM which preceded it. NHTSA did not ``fail'' to prepare any
required report. That Act mandates the preparation of analyses in
connection with notices of proposed rulemaking and final rules only.
NHTSA believes that the Regulatory Flexibility Act was a
relevant concern in
[[Page 28560]]
considering the possibility of proposing a stability standard
applicable to all light duty vehicles because multistage
manufacturers, especially van converters, which are often small
business entities, could be affected by such a standard. NHTSA is
not suggesting that that Act would prevent the issuance of such a
standard or that the concerns about impacts on small manufacturers
were insurmountable regardless of what approach is taken by the
agency in setting the standard. In fact, a standard limited to
compact SUVs would essentially eliminate those impacts because few,
if any, of those vehicles are produced by multistage or other small
manufacturers.
F. NHTSA's Alleged Lack of a Comprehensive Rollover Program
The petitioners characterized NHTSA's identification of seven
separate measures as part of a comprehensive agency plan to address
rollovers as simply ``a chronicle of ongoing or prospective crash
reduction programs that are not aimed uniquely at mitigating
rollover losses.'' The petition went on to complain that some of the
measures ``may never come to fruition,'' and that others have not
been specifically tailored by the agency to address the rollover
problem. The petitioners concluded by stating their belief that
NHTSA's comprehensive program for rollover is really an attempt to
try to persuade the public that the agency is taking action on
rollover safety, notwithstanding the termination of the vehicle
stability rulemaking.
The agency believes that the question of whether the activities
comprising its comprehensive rollover program uniquely address
rollover safety is irrelevant if those activities effectively
address that issue. If NHTSA can take actions, such as issuing a
standard, that significantly reduces the deaths and injuries that
occur in rollover crashes, it should make no difference whether that
reduction is achieved by means that also reduce deaths and injuries
in other types of crashes. The agency agrees that there is a
possibility that some of the regulatory initiatives announced by the
agency as part of its rollover program involve proposals that may
never become final rules. However, this possibility exists with any
regulatory initiative. The agency cannot foretell the nature of the
public comments that it will receive or prejudge the outcome of its
analyses of comments and other information obtained during the
rulemaking process. NHTSA included those initiatives in its rollover
program because preliminary evaluations of those initiatives
indicate that they are promising avenues for addressing rollovers.
The agency will pursue these initiatives expeditiously and
conscientiously. For example, since the 1994 notice was published,
NHTSA has published a final rule to extend the current requirements
for side door latches to rear door latches. (60 FR 50124) This rule
is an attempt to reduce the number of ejections from the rear door
of vehicles, thus reducing injuries and fatalities. Based on data
for years 1988-1992, NHTSA estimates that 147 occupants were fatally
ejected from the rear door of vehicles. Forty two percent of those
fatalities occurred in rollover accidents.
One of the specific initiatives singled out for criticism by
petitioners was the upgrade of Standard 201 to reduce head impact
injuries. The petitioners objected to its inclusion in NHTSA's
comprehensive rollover plan because the proposed compliance impact
speeds ``are often less than those [speeds] responsible for the very
high rate of severe head trauma that is suffered by occupants in
rollover crashes.'' The final rule upgrading Standard No. 201 was
published on August 16, 1995. (60 FR 43031) Even if the petitioners
were correct, the essential fact remains that the final rule will
make substantial reductions in rollover fatalities and injuries. The
agency estimated that 244-334 fatalities and 189-273 serious
injuries would be averted in rollovers as a result of that rule.
Authority: 49 U.S.C. 322, 30111, 30115, 30117 and 30166;
delegation of authority at 49 CFR 1.50 and 501.8.
[FR Doc. 96-14145 Filed 5-31-96; 4:38 pm]
BILLING CODE 4910-59-P
