[Federal Register Volume 66, Number 128 (Tuesday, July 3, 2001)]
[Proposed Rules]
[Pages 35179-35193]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-16659]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 575

[Docket No. NHTSA-2001-9663]


Consumer Information Regulations; Federal Motor Vehicle Safety 
Standards; Rollover Resistance

AGENCY: National Highway Traffic Safety Administration (NHTSA), DOT.

ACTION: Request for comments.

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SUMMARY: This notice announces NHTSA's plans to evaluate a number of 
driving maneuver tests for rollover resistance in accordance with the 
requirements of the TREAD Act. The agency will develop a dynamic test 
on rollovers of light motor vehicles for a consumer information 
program, and seeks comments on the subject of dynamic rollover testing 
and our approach to developing meaningful consumer information.

DATES: Comment Date: Comments must be received by August 17, 2001.

ADDRESSES: All comments should refer to Docket No. NHTSA-2001-9663 and 
be submitted to: Docket Management, Room PL-401, 400 Seventh Street, 
SW, Washington, D.C. 20590. Docket hours are 10 a.m. to 5 p.m. Monday 
through Friday.
    For public comments and other information related to previous 
notices on this subject, please refer to DOT Docket Nos. NHTSA-2000-
6859 and 8298 also available on the web at http://dms.gov/search, and NHTSA Docket No. 91-68; Notice 3, NHTSA Docket, 
Room 5111, 400 Seventh Street, SW, Washington, DC 20590. The NHTSA 
Docket hours are from 9:30 am to 4 pm Monday through Friday.

FOR FURTHER INFORMATION CONTACT: For technical questions you may 
contact Patrick Boyd, NPS-23, Office of Safety Performance Standards, 
National Highway Traffic Safety Administration, 400 Seventh Street, SW, 
Washington, DC 20590. Mr. Boyd can be reached by phone at (202) 366-
6346 or by facsimile at (202) 493-2739.

SUPPLEMENTARY INFORMATION:

    I. Safety Problem.

[[Page 35180]]

    II. Background.
    III. Preparatory Activity.
    IV. Difficulties Common to Various Dynamic Rollover Tests Using 
Driving Maneuvers.
    V. Path-Following Driving Maneuver Tests.
    A. CU Double Lane Change.
    B. VDA Double Lane Change.
    C. Open-Loop Pseudo-Double Lane Change.
    D. Path-Corrected Limit Lane Change.
    VI. Open Loop Fishhook Maneuvers--Defined Steering Tests.
    VII. Dynamic Tests Other Than Driving Maneuvers.
    A. Centrifuge Test.
    B. Driving Maneuver Simulation.
    VIII. Solicitation of Comments.
    IX. Rulemaking Analyses and Notices.
    X. Submission of Comments.

I. Safety Problem

    Rollover crashes are complex events that reflect the interaction of 
driver, road, vehicle, and environmental factors. We can describe the 
relationship between these factors and the risk of rollover using 
information from the agency's crash data programs. We limit our 
discussion here to light vehicles, which consist of (1) passenger cars 
and (2) multipurpose passenger vehicles and trucks under 4,536 
kilograms (10,000 pounds) gross vehicle weight rating.\1\
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    \1\ For brevity, we use the term ``light trucks'' in this 
document to refer to vans, minivans, sport utility vehicles (SUVs) 
and pickup trucks, under 4,536 kilograms (10,000 pounds) gross 
vehicle weight rating. NHTSA has also used the term ``LTVs'' to 
refer to the same vehicles.
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    According to the 1999 Fatality Analysis Reporting System (FARS), 
10,140 people were killed as occupants in light vehicle rollover 
crashes, including 8,345 killed in single-vehicle rollover crashes. 
Eighty percent of the people who died in single-vehicle rollover 
crashes were not using a seat belt, and 64 percent were partially or 
completely ejected from the vehicle (including 53 percent who were 
completely ejected). FARS shows that 55 percent of light vehicle 
occupant fatalities in single-vehicle crashes involved a rollover 
event. The proportion differs greatly by vehicle type: 46 percent of 
passenger car occupant fatalities in single-vehicle crashes involved a 
rollover event, compared to 63 percent for pickup trucks, 60 percent 
for vans, and 78 percent for sport utility vehicles (SUVs).
    Using data from the 1995-1999 National Automotive Sampling System 
(NASS) Crashworthiness Data System (CDC), we estimate that 253,000 
light vehicles were towed from a police-reported rollover crash each 
year (on average), and that 27,000 occupants of these vehicles were 
seriously injured (defined as an Abbreviated Injury Scale (AIS) rating 
of at least AIS 3).\2\ Of these 253,000 light vehicle rollover crashes, 
205,000 were the result of a single vehicle crash. (The present 
rollover resistance ratings estimate the risk of rollover if a vehicle 
is involved in a single vehicle crash.) Sixty-five percent of those 
people who suffered a serious injury in single-vehicle tow-away 
rollover crashes were not using a safety belt, and 50 percent were 
partially or completely ejected (including 41 percent who were 
completely ejected). Estimates from NASS-CDC indicate that 81 percent 
of tow-away rollovers occurred in single-vehicle crashes, and that 87 
percent (178,000) of the single-vehicle rollover crashes occurred after 
the vehicle left the roadway. An audit of 1992-96 NASS-CDC data showed 
that about 95 percent of rollovers in single vehicle crashes were 
tripped by mechanisms such as curbs, soft soil, pot holes, guard rails, 
and wheel rims digging into the pavement, rather than by tire/road 
interface friction as in the case of untripped rollover events.
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    \2\ A broken hip is an example of an AIS 3 injury.
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    According to the 1995-1999 NASS-General Estimates System (GES) 
data, 57,000 occupants annually received injuries rated as K or A on 
the police KABCO injury scale in rollover crashes. (The police KABCO 
scale calls ``A'' injuries ``incapacitating,'' but their actual 
severity depends on local reporting practice. An ``incapacitating'' 
injury may mean that the injury was visible to the reporting officer or 
that the officer called for medical assistance. A ``K'' injury is 
fatal.) The data indicate that 205,000 single-vehicle rollover crashes 
resulted in 46,000 K or A injuries. Fifty-four percent of those with K 
or A injury in single-vehicle rollover crashes were not using a seat 
belt, and 20 percent were partially or completely ejected from the 
vehicle (including 18 percent who were completely ejected). Estimates 
from NASS-GES indicate that 16 percent of light vehicles in police-
reported single-vehicle crashes rolled over. The estimated risk of 
rollover differs by light vehicle type: 13 percent of cars and 14 
percent of vans in police-reported single-vehicle crashes rolled over, 
compared to 24 percent of pickup trucks and 32 percent of SUVs. The 
percent of all police reported crashes for each vehicle type that 
resulted in rollover was 1.6 percent for cars, 2.0 percent for vans, 
3.7 percent for pickup trucks and 5.1 percent for SUVs as estimated by 
NASS-GES.

II. Background

    In a June 1, 2000 notice (65 FR 34998), NHTSA announced its 
intention to include consumer information ratings for rollover 
resistance of passenger cars and light trucks in its New Car Assessment 
Program (NCAP). NCAP has provided comparative consumer information on 
vehicle performance in frontal and side impact crashes for many years. 
About 22 percent of passenger car occupants killed in crashes are 
killed in rollover crashes, as compared with more than 70 percent 
killed in frontal and side crashes combined. In the case of light 
trucks, however, about as many occupants are killed in rollover crashes 
as in frontal and side crashes combined. NHTSA proposed a rating system 
based on the Static Stability Factor (SSF) which is the ratio of one 
half the track width to the center of gravity height.
    SSF was chosen over vehicle maneuver tests because it represents 
the first order factors that determine vehicle rollover resistance in 
the 95 percent of rollovers that are tripped. Driving maneuver tests 
represent on-road untripped rollover crashes which are about 5 percent 
of the total. Other reasons for selecting the SSF measure are: driving 
maneuver test results are greatly influenced by SSF; the SSF is highly 
correlated with actual crash statistics; it can be measured accurately 
and explained to consumers; and changes in vehicle design to improve 
SSF are unlikely to degrade other safety attributes.
    The industry comments to the June 2000 notice were that SSF was too 
simple because it did not include the effects of suspension 
deflections, tire traction and electronic stability control (ESC) and 
that the influence of vehicle factors on rollover risk was so slight 
that vehicles should not be rated for rollover resistance. In the 
conference report dated October 23, 2000 of the FY2001 DOT 
Appropriation Act, Congress permitted NHTSA to move forward with the 
rollover rating proposal and directed the agency to fund a National 
Academy of Sciences' study on vehicle rollover ratings. The study 
topics are ``whether the static stability factor is a scientifically 
valid measurement that presents practical, useful information to the 
public including a comparison of the static stability factor test 
versus a test with rollover metrics based on dynamic driving conditions 
that may induce rollover events.''
    The Consumers Union (CU) commented to the June 2000 notice that 
although SSF is a useful predictor of tripped rollover, it should be 
used in

[[Page 35181]]

conjunction with a dynamic stability test using vehicle maneuvers to 
better predict the risk of untripped rollovers. CU also believes that 
NHTSA underestimated the incidence of on-road untripped rollover by 
relying upon 1992-1996 data.
    Section 12 of the ``Transportation Recall, Enhancement, 
Accountability and Documentation (TREAD) Act of November 2000'' 
reflects CU's concern. It directs the Secretary to ``develop a dynamic 
test on rollovers by motor vehicles for a consumer information program; 
and carry out a program conducting such tests. As the Secretary 
develops a [rollover] test, the Secretary shall conduct a rulemaking to 
determine how best to disseminate test results to the public.'' The 
rulemaking and test program must be carried out by November 1, 2002. 
This notice is part of NHTSA's work to satisfy the requirements of 
Section 12 of the TREAD Act.
    NHTSA responded to these and other technical comments to the June 
2000 notice in a January 12, 2001 notice (66 FR 3388) and announced the 
agency's decision to use the SSF as a measure, along with publishing 
the initial rollover resistance ratings. As of April 2001, the agency 
has added the rollover resistance ratings of 104 vehicles to the 
frontal and side crash ratings given by NCAP (see www.nhtsa.dot.gov/hot/rollover/ for ratings, vehicle details and explanatory 
information).
    NHTSA awarded a grant to the National Academy of Sciences for its 
study of vehicle rollover ratings on December 15, 2000 and its first 
public meeting on the subject took place on April 11 and 12, 2001. A 
second open meeting will allow for consideration of alternatives to SSF 
for rating vehicles, and presentations on consumer information and risk 
communication. At a closed meeting the NAS committee will finalize its 
draft report. The study will conclude with the required report to 
Congress.

III. Preparatory Activity

    In response to the TREAD Act, NHTSA met with the Alliance of 
Automobile Manufacturers, Nissan, Toyota, Ford, Consumers Union (CU), 
Automotive Testing, Inc. (an independent test lab), MTS Systems Corp., 
the University of Michigan Transportation Research Institute (UMTRI), 
Daimler-Chrysler, BMW, Volkswagen and Volvo to gather information on 
possible approaches for dynamic rollover tests. These parties made 
specific suggestions about approaches to dynamic testing of vehicle 
rollover resistance. In addition, recent NHTSA research summarized in 
the report entitled ``An Experimental Examination of Selected Maneuvers 
That May Induce On-Road Untripped, Light Vehicle Rollover--Phase II of 
NHTSA's 1997-1998 Vehicle Rollover Research Program'' \3\ is relevant 
to the development of a dynamic rollover test suitable for inclusion in 
our consumer information program.
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    \3\ Available at http://www-nrd.nhtsa.dot.gov/vrtc/ca/rollover.htm.
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    This notice identifies a variety of dynamic rollover tests that we 
have chosen to evaluate in our research program and what we believe to 
be their potential advantages and disadvantages. It also discusses 
other possible approaches we considered but decided not to pursue. 
Table 1 summarizes the advantages and disadvantages we anticipate for 
the various approaches prior to research which will increase our 
understanding. We invite public comment on our decisions, on our 
observations and on the general subject of rollover resistance testing 
for consumer information.
    Track testing using the maneuvers discussed in this notice began in 
April 2001 at NHTSA's Vehicle Research and Test Center in East Liberty, 
Ohio. We intend to publish a second notice in early 2002 presenting a 
tentative dynamic rollover test procedure chosen on the basis of this 
research and the comments to today's notice. We will review the 
comments to today's notice expeditiously and may revise the test 
development research based on the comments. A final notice responding 
to the comments to the second notice, presenting the final dynamic 
rollover test procedure, and containing an initial set of rollover 
resistance ratings will be published in October 2002.
    The test vehicles chosen for the evaluation of potential maneuver 
tests are the 2001 Ford Escape (without electronic stability control 
(ESC \4\)), the 2001 Chevrolet Blazer (without ESC), the 2001 Toyota 
4Runner (with and without ESC enabled) and the 1999 Mercedes ML-320 
(with and without ESC enabled). They represent the significant range of 
static stability factors that characterize today's SUVs. They also 
include two ESC systems with possible differences in operation. The 
vehicles will be tested in a base load configuration with driver, 
instruments and outriggers, in a second configuration with a roof load 
to reduce SSF by .05, and in other load configurations intended to 
influence handling. The loads will be positioned so as to change one 
coordinate of the c.g. location without influencing the other two. For 
example, in the second load configuration, about 200 pounds will be 
secured to the roof in a position that maintains the fore-aft and side-
to-side location of the c.g. but raises it enough to cause a reduction 
of 0.05 in the SSF (while also increasing the vehicle's mass moments of 
inertia).
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    \4\ ESC is a safety system that can apply the brake at one or 
more wheels automatically to keep the yaw rate of the vehicle 
proportional to its speed and lateral acceleration. For example, 
braking the outside front wheel can correct the heading of a vehicle 
beginning to oversteer (spin out).
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    The test vehicles will be equipped with special wheel force sensors 
at each wheel during some of the evaluation of potential maneuver 
tests. They will provide better information for our evaluation of how 
these vehicles react to different characteristics of the candidate test 
maneuvers. Wheel force measurements will determine absolutely when two 
wheel lift occurs. Also, they will allow us to measure the degree of 
load transfer during runs that do not cause wheel lift, a capability 
not possible in our previous research. The sensors also can reveal 
possible interactions between vertical and lateral wheel forces that 
maneuvers may produce in some vehicles.

IV. Difficulties Common to Various Dynamic Rollover Tests Using 
Driving Maneuvers

    We considered some methods of dynamic testing for rollover 
resistance that did not use driving maneuvers, but decided to 
concentrate our research on driving maneuver tests for the reasons 
discussed in Section VII. However, driving maneuver tests share some 
significant difficulties in comparison to laboratory tests. Since they 
directly represent a deadly type of crash, the safety of test drivers 
will always be a concern, even though drivers will be belted and 
outriggers will be used in most circumstances. Outriggers are the usual 
means of minimizing the chance of an actual rollover crash during a 
test, but they also introduce problems. If an outrigger digs into the 
pavement, it can cause the vehicle to ``pole vault'' resulting in an 
even worse rollover crash. The weight of the outrigger(s) may change 
the vehicle's c.g. location and will increase its mass moments of 
inertia, placing restraints on the natural desire to overdesign the 
outriggers for safety. The mounting of the outrigger can also influence 
vehicle handling by changing its structural stiffness. We will choose 
outriggers designed to the best contemporary practices and evaluate 
their effect on maneuver test results.
    Maneuver tests are expensive. Besides the labor involved in 
performing the maneuvers and interpreting the results,

[[Page 35182]]

the test methods require that each test vehicle be custom fitted with 
costly precision instruments, onboard computers, probably an array of 
special steering and braking controls, and possibly telemetry. The 
wheel force transducers included in these developmental tests are not 
expected to be necessary for routine tests in a consumer information 
program, but there may be a need for less intrusive means of load 
transfer monitoring. Frequent tire changes, adding to cost and labor, 
are necessary in maneuver tests because tire shoulder wear can 
significantly influence force generation. Part of this research will 
define the need for tire changes in the selected maneuver in routine 
consumer information testing. Finally, damage to the vehicles as a 
result of the tests or the installation of equipment is a cost factor.
    The use of driving maneuver tests to rate rollover resistance 
presents some questions beyond test methodology, danger and expense. A 
high statistical correlation based on a large sample of police reports 
of rollover crashes was possible for the present ratings based on SSF 
because SSF is a good predictor of tripped rollovers, in particular, 
and the preponderance of rollovers in state crash reports are tripped. 
As part of NHTSA' s dynamic maneuver test program in 1997 and 1998, we 
tried to correlate the performance of the test vehicles on various 
maneuvers to their rates of on-road untripped rollover crashes. We 
found that it is not possible to obtain sufficient data, even on high 
volume vehicles, to determine a correlation between maneuver test 
outcome and untripped rollover involvement. The only data base we are 
aware of that contains data identifying untripped rollover crashes is 
NHTSA's NASS-CDS. However, only about 4300 crashes of all types 
(frontal, side, rear and rollover) are researched in depth each year 
for inclusion in this data base and only about ten of those cases are 
untripped rollovers.\5\ The NASS-CDS data base is usually used with 
weighting factors for different types of crashes to represent national 
trends. However, the number of observations is too small to support 
make/model correlations between maneuver test results and real-world 
untripped rollover rates.
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    \5\ 1998-1999 NASS-CDS annual averages.
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    Some of the 17 states in NHTSA's State Data System (SDS) data base 
\6\ attempt to distinguish between on-road and off-road rollover 
crashes. While it seems inviting to use on-road rollover as a surrogate 
for untripped rollover, this is not strictly accurate. Most on-road 
rollovers occur when the vehicle is tripped by road surface 
irregularities or the wheel rim digging into the pavement.\7\ Also, 
police may code a rollover crash as ``on-road'' because the vehicle was 
found at rest on the roadway. The designation ``on-road'' does not 
necessarily mean that the roll initiation occurred on the roadway.
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    \6\ A collection of data from the police accident reports (PARs) 
of 17 participating states. This data is limited to what was 
recorded by the responding officer(s) at the time of the crash.
    \7\ ``Analysis of Untripped Rollovers''; Calspan Corporation for 
American Automobile Manufacturer's Association and Association of 
International Automobile Manufacturers; May 15, 1998, and ``NASS 
Rollover Study Evaluation Report''; NHTSA National Center for 
Statistics and Analysis; August 1998.
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    The correlation, by make/model, of performance in a maneuver test 
to the rate of all rollovers would be highly dependent on the degree to 
which good performance in the driving maneuver test is the result of 
low c.g. height, large track width and other factors which also 
increase resistance to tripped rollovers. Optimization of tire 
properties and ESC operation for a particular maneuver test would 
likely decrease this level of correlation over time if effective ways 
of improving test performance are developed that do not improve the 
tripped rollover resistance of vehicles. Therefore, it is unlikely that 
the choice of any particular maneuver test or tests can be justified on 
the basis of the correlation of the test results to real-world rollover 
rates. This situation makes the resemblance of the chosen maneuver test 
or tests to documented crash scenarios even more important.
    Ratings based on driving maneuvers may be complex and hard to 
communicate to the public because the usual rollover criterion of two 
wheel lift can be at odds with the handling capability of the vehicle. 
In a path following maneuver, the test is terminated when the vehicle 
can no longer follow the path. For example, consider a vehicle that 
cannot negotiate the path beyond 38 mph, but it departs the path before 
it achieves two wheel lift. Consider a second vehicle that can follow 
the path at 45 mph but lifts the inside tires three inches off the 
pavement. Which vehicle should be rated higher? Departing the roadway, 
as the first vehicle would seem likely to do more often than the second 
vehicle, can expose a vehicle to a high risk of tripped rollover.
    ESC was originally designed to keep the vehicle headed in the 
direction desired by the driver rather than to plow-out (understeer) or 
to spin-out (oversteer) in a limit cornering situation by using one or 
more brakes to help turn the vehicle to the correct heading. ESC cannot 
increase the maximum traction, and consequently prevent a vehicle from 
leaving the road, if the vehicle is going too fast. ESC may help 
drivers regain control rather than overreact in situations like an 
abrupt ``road-edge recovery'' where there is sufficient traction to 
recover. In this way, ESC has the potential to reduce the number of 
single vehicle crashes that turn into tripped rollovers. However, ESC 
can be programmed to work in many other ways. In one way, it can apply 
the brakes automatically to slow the vehicle at a selected value of 
lateral acceleration or at a similar criterion. While this is a 
plausible safety strategy, it has the potential to overwhelm the other 
aspects of vehicle behavior measured in a maneuver test. In most 
maneuver tests, the vehicle is steered through the maneuver while 
coasting because any attempt to keep a steady throttle position tends 
to make the tests less repeatable. Even in a short maneuver, the 
vehicle scrubs off some speed. For example, a vehicle entering a short 
maneuver coasting at 50 mph is likely to exit at 45 mph or less. 
However, with braking intervention programed into the ESC, a vehicle 
could easily slow to 25 mph during the test. While both vehicles would 
be rated on their entry speed, the ESC vehicle may be going much slower 
at the critical part of the maneuver. It is possible that maneuver 
tests could simply result in segregating vehicles with automatic brake 
intervention from those without it. Automatic brake intervention may 
produce some safety benefits. NHTSA believes, however, that the vast 
majority of drivers also apply the brakes in difficult situations, 
regardless of whether the vehicle has automatic brake intervention. 
Thus, a maneuver test conducted while coasting could reward this type 
of ESC design excessively. NHTSA expects that most drivers would brake 
during similar maneuvers, and that automatic brake intervention would 
make less difference in real driving than during tests in which drivers 
are not permitted to brake.
    Important environmental conditions also will influence the results 
of any driving maneuver test for rollover ratings. The pavement 
friction of even a dedicated test area does not remain constant. There 
is a cycle of polishing and weathering during periods of use and 
disuse, and a possible temperature effect on pavement friction. The 
usual method of determining pavement friction is a locked wheel braking 
test conducted at a constant 40 mph using

[[Page 35183]]

a ``skid trailer'' with a water nozzle to wet the surface immediately 
ahead of the skidding tire. The pavement friction coefficient generated 
by this test is called the ``skid number''. General Motors has reported 
that moderate differences in skid number, even when measured without 
pavement wetting, do not correspond well to differences in lateral 
force generated by vehicles on different pavements. Our planned test 
program includes hot weather and cold weather testing as well as tests 
conducted on different surfaces at three to date undetermined test 
facilities. The result we hope for is a definition of a minimum 
friction level for a valid test as tracked by tests using a control 
vehicle.
    Not every vehicle is tested each year in the new car assessment 
program. The results for vehicles without substantial changes tested in 
previous years are carried over to represent vehicles of the current 
model year. The test results, and the resulting rollover ratings, from 
the previous year might not be comparable to the new year's results if 
there were significant differences in pavement friction.

V. Path-Following Driving Maneuver Tests

    The driving maneuver tests for rollover resistance that have 
received the most publicity over the years are the ``emergency double 
lane change'' of Consumer Reports magazine and the European ``moose 
test.'' The first test was the basis of criticism by Consumer Reports 
that the 1988 Suzuki Samurai and the 1996 Isuzu Trooper were ``not 
acceptable.'' The ``moose test'' was used by a European auto magazine 
to demonstrate that the 1998 Mercedes-Benz A Class minicar could 
experience on-road untripped rollover in a similar maneuver. We 
classify both tests as path following tests to distinguish them from 
another type of maneuver tests in which explicit steering inputs are 
required without reference to the path they cause the vehicle to take. 
We will evaluate both the CU double lane change (CU is the publisher of 
Consumer Reports) and a version of the moose test recommended by 
Daimler-Chrysler. We will also evaluate the use of mathematical path 
correction and an automated steering controller \8\ to improve these 
driving maneuver tests.
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    \8\ The automated steering controller was referred to as a 
``Programmable Steering Machine'' in our June 1, 2000 notice (65 FR 
34998).
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A. CU Double Lane Change

    The CU double lane change short course (figure 1) was developed in 
order to replicate an unintentional rollover experienced by a Consumer 
Reports staff member driving a Suzuki Samurai. It consists of a 70-
foot-long, 8-foot-wide entrance lane that is centered in a 12-foot-wide 
first (right) lane, a 50-foot-long area to make the first lane change 
(to the left), a set of gate cones at this 50-foot mark that are 12 
feet apart (with the right cone three feet into the left lane), a 60-
foot-long area to make the second lane change back to the right lane, 
and a 12-foot-wide exit lane. The test driver steers the vehicle 
through the course at successively higher entry speeds until the 
vehicle either plows out, spins out, or tips up. The vehicle is 
coasting through the maneuver. The driver does not apply the brakes, 
and driver releases the throttle 35 feet into the 70 foot entrance 
lane.
    An advantage of the CU double lane change is its face validity, 
that is, drivers can imagine a situation in which they may try to make 
a similar maneuver. However, NHTSA believes that there are good 
arguments that simply braking without steering or braking and steering 
with an ABS equipped vehicle are better strategies to avoid the 
hypothetical object in the road that is the basis of the CU test. In 
addition, it is hard to find actual crashes that resemble the test. 
Nevertheless, driving through a tight double lane change without wheel 
lift is probably a good representation of what the public expects of a 
personal vehicle.
    An important part of the double lane change is the immediate 
steering reversal necessary to get back in the right lane after 
steering sharply into the left lane to avoid the hypothetical object in 
the roadway. This steering reversal allows the energy stored in the 
suspension springs during the left steer and the roll momentum of the 
sprung mass when that energy is released at the steering reversal to 
add to the load transfer caused by the sharp right steer. The dynamics 
of the steering reversal are not included in SSF, Tilt Table Ratio, or 
even the J-turn maneuver (see 65 FR 34998 for details about these 
rollover resistance metrics). So this aspect of the double lane change 
better represents the dynamics that may result in an untripped 
rollover.
    However, if the only criterion for success in a double lane change 
maneuver is whether or not two-wheel lift can be made to occur, any 
vehicle will pass such a test if equipped with tires of sufficiently 
low traction or with chassis tuning that produces the same effect. In 
this case, the vehicle will simply run off the desired path at a speed 
and lateral acceleration too low to produce two-wheel lift. On the 
other hand, an inherent advantage of path-following maneuvers like the 
double lane change is that the maximum speed through the maneuver can 
be used as part of the vehicle score to reward good handling and avoid 
creating a rollover resistance rating with incentives for reduced 
handling and braking performance. Like all the driving maneuvers we are 
considering, the CU double lane change also has the advantage of 
displaying the operation of electronic stability control systems.
    The foremost disadvantage of the CU double lane change is that 
differences in driving style can strongly influence the test results. 
The time history of the steering wheel angle may vary considerably for 
runs of the same vehicle at the same speed (figure 2). Tests in which 
the driver starts the steering movements earlier seem to produce a 
moderately smaller initial left steer and a much smaller amount of 
right steer after passing through the offset gate. The steering 
reversal (from maximum left steer to maximum right steer) can vary 
significantly at the same test speed, and the runs with a greater 
steering reversal appear more likely to produce two-wheel lift. For 
example, during CU tests of the Isuzu Trooper, one driver ran the 
course at 37.5 mph with a left steer of 183 degrees followed by a right 
steer of 216 degrees (399 degree steering reversal) and did not knock 
down the course boundary cones or experience two-wheel lift. Another 
driver ran the same course at 37.5 mph using an initial left steer of 
191 degrees followed by a right steer of 388 degrees (579 degree 
steering reversal) and experienced two-wheel lift.
    Another potential disadvantage of the double lane change maneuver 
is the possibility that the course layout may cause the steering 
reversal and roll momentum effect to be more critical for some vehicles 
than for others. The course originally used by Consumer Reports had the 
offset gate forcing the lane change positioned 60 feet from the end of 
the entrance lane and also 60 feet from beginning of the exit lane. 
When the publication tried to replicate its staff member's rollover 
crash of a Suzuki Samurai, it found that shortening the distance from 
the end of the entrance lane to the offset gate by 10 feet and moving 
the offset gate three feet further to the left made two wheel lift of 
the Samurai more likely. This suggests that tuning of the course to the 
vehicle may be necessary to create a worst case condition and that a 
course tuned to one vehicle may not be the worst case for another 
vehicle to which it is compared.

[[Page 35184]]

B. VDA Double Lane Change

    The VDA Double Lane Change is a variant of the ``moose test'' used 
by a Scandinavian automotive magazine. It was developed by the German 
Alliance of Automotive Industry (VDA) to minimize the influence of 
driving style on the original moose test for use as an industry 
standard rollover and handling test procedure. As a double lane change 
maneuver, it is identical in concept to the CU test, and it is useful 
to contrast the two maneuvers.
    The method VDA used to minimize driver influence was to reduce the 
lane and gate widths and tie these parameters to the width of the test 
vehicle. Using the VDA course (figure 3) for a 70 inch wide vehicle 
(typical of the most popular SUVs and mid-sized cars) the widths of the 
entrance lane, offset gate, and exit lane are 7.25 feet, 9.12 feet and 
9.9 feet, respectively, compared with 8 feet, 12 feet and 12 feet for 
the same components of the CU double lane change course. The distance 
from the end of the entrance lane to the beginning of the offset gate 
is 44.3 feet rather than 50 feet for the CU test, and the distance from 
the end of the offset gate to the beginning of the exit lane is only 41 
feet, compared to 60 feet for the CU test. There is also a difference 
in the amount of offset of the left lane gate. In the CU test, the 
inside of the gate is offset 5 feet to the left of the inside of the 
entrance lane and 3 feet to the left of the exit lane (because the exit 
lane is 4 feet wider than the entrance lane). In the VDA test, the left 
edges of the entrance and exit lanes are in line, and right edge of the 
offset gate is 3.3 feet to the left.
    The fundamental difference between the CU and VDA courses is that 
while the vehicle has to pass through a gate comprised of two cones 
marking a 12 foot left lane width in the CU test, it has to traverse a 
36-foot-long by 9.12-foot-wide left lane in the VDA test before turning 
right to re-enter the right lane. The VDA test is more like a single 
lane change to the left immediately followed by a second single lane 
change to the right and does not have as sharp a steering reversal as 
the CU double lane change test. In both tests, the vehicle begins to 
coast about 35 feet before the end of the entrance lane.
    The VDA double lane change shares with the CU test the advantage of 
face validity, but the VDA test would appear to be less subject to 
variability in driving style. It also uses a rating criteria that 
implicitly rewards good handling. It is scored by the maximum entry 
speed of the vehicle's clean runs along with a notation of the limiting 
event: understeer, oversteer or two-wheel lift. Like all the other 
maneuver tests we are considering, it has the advantage of displaying 
the operation of ESC systems, but the entry speed criteria may 
disproportionately favor ESC systems with simple brake intervention.
    Efforts to reduce driver variability may also introduce problems. 
The least serious problem is that narrow lanes may make the course so 
hard to follow that imprecise driving rather than actual oversteer or 
understeer may cause collisions with the course marking cones. Daimler-
Chrysler reports that expert drivers can negotiate the course at about 
4 mph faster than average drivers. It is unclear whether this is due to 
expert steering strategy optimizing the vehicle path for lower peak 
lateral acceleration even within the reduced boundaries or simply to 
better ability to judge cone position and control vehicle position. If 
this problem exists, simply allowing the driver more tries at a given 
speed may be all that is necessary to determine whether vehicle 
handling is really the limiting factor.
    The more serious potential problem is the use of a 36 foot long 
left lane, rather than just a gate to drive around. It potentially 
removes the roll momentum effect associated with the sharp steering 
reversals. While this effect increases the variability of CU test 
results due to differences in driving style, it also reveals rollover 
propensities that would not likely show up in a test like the J-turn.
    Assuming that the VDA double lane change does not suppress the 
potential effects of unfavorable roll momentum, it also shares the 
question of steering reversal timing with the CU test. Namely, does the 
course layout present a worst case timing in which roll momentum 
reinforces the side to side load transfer at peak lateral acceleration 
for some vehicles but not for others?

C. Open-Loop Pseudo-Double Lane Change

    In its 1997-1998 rollover research, NHTSA made use of an automated 
steering controller to achieve highly repeatable J-turn and fish hook 
maneuvers. As discussed above, the potential problems of double lane 
change tests are the lack of repeatability caused by variations in 
driving style and the possibility that a course producing worst case 
roll momentum for one vehicle may not do so for the next vehicle. We 
will attempt to solve these problems by using the steering controller 
in a non-path following maneuver approximating a double lane change.
    The idea is to use steering rates and magnitudes typical of driver-
controlled CU tests, but to use the automated controller for 
repeatability. Separate circular path tests of each vehicle would be 
done to relate lateral acceleration to steering angle in the linear 
range. This information would be used to tailor the steering angles for 
the pseudo-double lane change to the steering ratio and wheelbase of 
each test vehicle. The steering controller would also tailor the course 
for the worst case roll momentum for each vehicle. Body roll rate 
feedback would be used to time the first steering reversal left to 
right and also the second steering reversal right to straight ahead.
    This is not a maneuver established in literature or in practice. It 
is little more than a concept now. Its potential drawback is that the 
maneuver may stray too far from an actual double lane change to retain 
any face validity. Also, it is unclear if the advantage of a simple 
speed and limit circumstance score would remain applicable to a double 
lane change performed in this manner.

D. Path-Corrected Limit Lane Change

    From a vehicle manufacturer's prospective, the double lane change 
maneuver is a good test to evaluate a vehicle's limit handling 
behavior, because it is a realistic maneuver and it allows engineers to 
simultaneously evaluate the three main behaviors that affect limit 
handling safety (responsiveness, lateral stability and rollover 
resistance). However, lane changes are driver-dependent (meaning 
vehicle performance is heavily influenced by how the driver drives the 
vehicle) and their rating scales are usually subjective (meaning based 
on driver expert evaluation rather than on measured data). To solve 
this problem, Ford Motor Company has developed Path-Corrected Limit 
Lane Change (PCLLC). It is claimed to be a driver-independent, 
objective way to run limit handling lane changes. First, vehicles are 
run through a series of maneuvers much like the CU double lane change 
except that a range of course lengths and degrees of lane offsets are 
used to measure their responses to steering inputs in a range of 
frequencies. The data is then normalized mathematically to show how 
each of those vehicles would have performed had they followed precisely 
the same paths in the lane change. This is what ``Path-Correction'' 
means, and this normalization reduces the driver influence in the 
maneuver.
    PCLLC is a proprietary technique, and the details have not been 
reported publicly by Ford. Ford is allowing

[[Page 35185]]

NHTSA to evaluate this technique under a confidentiality agreement. 
NHTSA will run Ford's specified suite of vehicle characterization tests 
using its own vehicles and test track with Ford's assistance in 
instrumenting the vehicles for the measurements required for the 
mathematical path corrections. Ford will explain the theory of the 
mathematical corrections to NHTSA, and perform the corrections on 
NHTSA's vehicle test data in a confidential report. If NHTSA decides to 
propose this technique as the best way of accomplishing the dynamic 
rollover tests required by the TREAD Act, it expects that Ford will 
release it from the confidentiality agreement so that the test 
procedure can be proposed in detail in our next notice early in 2002.
    We view PCLLC as a mathematical technique which allows the 
construction of ``perfect test runs'' for an objective comparison of 
vehicles from a suite of similar test runs which expose each vehicle to 
a range of speeds, steering frequencies, rates and amplitudes. It looks 
like a good approach to overcoming the disadvantages discussed earlier 
for the more conventional driver controlled lane change maneuver tests. 
Driving style variability would clearly be eliminated, and it appears 
that this technique can construct a number of standard paths to examine 
the question of how many courses are necessary for a fair evaluation of 
the roll momentum effect for vehicles with different properties.
    NHTSA has envisioned that PCLLC could be used as a way of producing 
the equivalent of a CU double lane change test with every vehicle 
following exactly the same geometric path up to the point that it 
either has two-wheel lift or can no longer maintain the prescribed path 
as a result of limit understeer or oversteer. Under this idea, the 
rating criteria could be speed and the limiting circumstance (plow, 
spin or two wheel lift) as with the Daimler-Chrysler recommendation, 
with the possibility of greater rating complexity if more than one test 
course were required.
    However, it is not clear whether the PCLLC technique can be used 
this way and whether this would be the best way to use it. Ford is 
looking at many different vehicle handling metrics and cited three 
examples. Responsiveness could be represented by a delay time from 
steering input to yaw response evaluated on a path corrected to the 
same time history of yaw angle for each vehicle. Lateral stability 
could be characterized by rear tire slip angle on a path corrected to 
equal lateral acceleration for each vehicle. Untripped rollover 
resistance could be characterized by the degree of side to side load 
transfer evaluated on a path representing the maximum lateral 
acceleration capacity of the vehicle (considering such factors as 
practical limits on steering angle and rate and limit oversteer). Since 
the vehicle characterization runs are performed with ESC operating, the 
results should reflect its influence in the same way as other driving 
maneuver tests.

VI. Open Loop Fishhook Maneuvers--Defined Steering Tests

    The fishhook maneuver was originally developed by Toyota Motor 
Corporation as a maneuver with a strong roll momentum effect and a 
simple steering regime that would be fairly repeatable by test drivers. 
The maneuver requires the driver to steer as quickly as possible 270 
degrees of steering wheel angle, and then to steer 870 degrees in the 
opposite direction as quickly as possible (figure 4). At less than 
limit speed runs, the vehicle's path resembles a fishhook shape (figure 
5), but the actual path is immaterial to the scoring. The maneuver is 
repeated in each direction of initial steering and at increasing speed 
until two-wheel lift or loss of control occurs, or until preset maximum 
speed for test driver safety is reached. Toyota also added pulse 
braking \9\ to make the maneuver more likely to induce two-wheel lift 
if the vehicle under test would not lift wheels without braking. The 
lateral acceleration at two-wheel lift (LAR) is Toyota's figure of 
merit for this maneuver.
---------------------------------------------------------------------------

    \9\ Pulse braking is a short hard brake application that creates 
a transient increase in lateral acceleration upon release.
---------------------------------------------------------------------------

    NHTSA's 1997-98 research program made use of two variations on the 
Toyota ``fishhook'' maneuver theme. Since these tests are described by 
the steering input without regard for different paths taken by 
different vehicles, they are considered ``open-loop''. They were also 
perfect candidates for NHTSA's goal of using an automated steering 
controller for precise repeatability for maximum objectivity. NHTSA's 
tests did not use pulse braking because we were concerned that pulse 
braking tests were not merely a more stringent level of the basic 
fishhook, but a test of different vehicle dynamics. In one version, the 
steering rate was set at 750 degrees per second for all vehicles and 
the dwell time \10\ between steering reversals was ``tuned'' for each 
vehicle to resemble half a sine wave at what we thought was the roll 
natural frequency of each vehicle. In the other variation, we attempted 
to represent a road edge recovery maneuver by setting the initial steer 
angle to 7.5 degrees of the road wheels (to represent the front tire 
slip angle possible when a vehicle mounts a four inch pavement height 
above the road shoulder), using a constant 0.5 second dwell time and a 
more moderate steering rate of 500 steering wheel degrees per second. 
The first maneuver was generally more severe than the second. It was 
configured to represent a steering frequency of 0.5 Hz, which was the 
roll natural frequency assumed for most vehicles because our attempts 
at measuring roll natural frequency were thwarted by vehicle suspension 
damping. However, some of the vehicles responded with greater load 
transfer to the seemingly gentler ``road-edge recovery'' fishhook which 
used a different steering frequency. This suggests the possible 
importance of roll momentum timing.
---------------------------------------------------------------------------

    \10\ Dwell time is the short time internval of less than one 
second between the initial steering angle (shown as negative angle 
in Figure 4) and larger steering movement in the reverse direction.
---------------------------------------------------------------------------

    Open loop fishhook maneuver tests are like the mirror image of the 
double lane change tests because their principle advantages and 
disadvantages are reversed. Aided by a steering controller, driving 
style differences are absolutely eliminated. These maneuvers also 
present the best possibility for tuning the maneuver to the roll 
characteristics of each test vehicle, thereby eliminating the suspicion 
that the steering frequency of a fixed double lane change makes the 
test inherently more stringent for some vehicles than others. However, 
the fishhook maneuver has much less face validity than the double lane 
change maneuver. Even the ``road edge recovery'' version of the 
fishhook does not look, to a ordinary driver, like a maneuver he or she 
would ever be called upon to make.
    There is another disadvantage to open loop tests. Because the 
vehicle path does not matter, two-wheel lift can be prevented simply by 
using tires of sufficiently low traction or chassis tuning that 
produces the same effect. Unless an open loop test is accompanied by 
other tests of specific handling properties, it could have the perverse 
effect of encouraging manufacturers to sacrifice handling and braking 
to make superficial refinements to improve a rollover rating. Also, 
improvements in a rollover rating gained by special original equipment 
tire properties may be negated when the tires are replaced later in the 
life of the vehicle.
    NHTSA will evaluate three types of fishhook maneuvers. In one 
maneuver the counter steer will be limited to about 500 to 600 degrees, 
rather than

[[Page 35186]]

870, because the large countersteer is thought to scrub off so much 
speed that it reduces the severity of the maneuver. Also, instead of a 
fixed 270 degree initial steer, a steering wheel angle derived from the 
steering angle causing a fixed lateral acceleration, in the linear 
range, will be chosen to put vehicles with differences in steering gear 
ratio and wheelbase on an equal footing. A fixed steering rate of 720 
degrees per second and a fixed time from the beginning of steering to 
its return to zero angle during countersteer will be used.
    In the second fishhook, the timing of the steering reversal will be 
based on roll rate feedback. The worse case roll momentum effect is 
expected when the start of the steering reversal coincides with the 
instant of maximum roll angle resulting from the first steer. We expect 
to use an approximate zero reading of a roll rate sensor to indicate 
maximum roll angle and trigger the countersteer by the automatic 
steering controller.
    The third variation will use a counter steer timing technique 
suggested by Nissan (figure 6). In this method, the first part of the 
fishhook is studied separately prior to the fishhook test maneuvers in 
order to define the worst case dwell time. This is done by running a 
step steer maneuver (the same as a J turn) at the same steering rate 
and maximum angle as the first steering movement of the fishhook. The 
roll rate is measured to determine the time of the maximum roll angle 
of the second oscillation. Nissan believes that the most severe 
fishhook for each vehicle is the one in which the lateral acceleration 
zero crossing during countersteering in the fishhook occurs at the 
second oscillation peak time as measured in the J turn maneuver. The 
dwell time from initial steer to countersteer would be adjusted 
accordingly. The theoretical basis for Nissan's observation on fishhook 
severity is not obvious. Nissan's belief is based on experimental 
studies during which dwell time was varied. Its technique appears to 
produce a countersteer timing similar to that produced by roll rate 
feedback.
    As mentioned above, fishhook tests contain no inherent 
disincentives for rollover resistance strategies that sacrifice 
handling. NHTSA is considering adding some objective measure of 
handling ability to any fishhook test used for consumer information. We 
are considering a steering response time test possibly based on a J-
turn (step steer) and a maximum lateral acceleration test based on 
either a constant steer input with slowly increasing speed regime or a 
constant speed with slowly increasing steer regime. We are concerned, 
however, that even this limited NHTSA definition of handling may 
produce undesirable trade-offs of less measurable aspects of vehicle 
handling when manufacturers design to the test. We are particularly 
interested in comments on how likely it is that vehicle manufacturers 
would make such trade-offs to ``beat'' the test.

VII. Dynamic Tests Other Than Driving Maneuvers

    NHTSA also considered two dynamic tests that did not involve 
driving maneuvers, namely the centrifuge test and driving maneuver 
simulation using computational models. Both of these tests have the 
major benefit of being independent of pavement friction, whereas the 
problem of pavement friction variation is perhaps the most vexing issue 
common to all the driving maneuver tests discussed above. However, we 
decided not to include these tests in our research plan under TREAD for 
the reasons explained below.

A. Centrifuge Test

    The test device for the centrifuge test is similar in concept to a 
merry-go-round. A person seated at the edge of the merry-go-round feels 
a lateral force pushing him or her away from the spinning surface that 
increases with the rotational speed of the merry-go-round. The 
centrifuge device test (figure 7) consists of an arm attached to a 
powered vertical shaft. At the end of the arm is a horizontal platform 
upon which the test vehicle is parked. As the vertical shaft rotates, 
the parked vehicle is subjected to a lateral acceleration that can be 
precisely controlled and measured. The basic measurement is the lateral 
acceleration at which the parked vehicle experiences two-wheel lift. 
The outside tires are restrained by a low curb so the measurement is 
independent of surface friction, and the vehicle is tethered to prevent 
excessive wheel lift. This test method was suggested by the University 
of Michigan Transportation Research Institute (UMTRI) both in comments 
to our notice about the present rollover resistance ratings and more 
recently in the context of the TREAD Act. The test method is directed 
primarily at tripped rollover, which UMTRI noted accounts for all but a 
small percentage of rollovers.
    The centrifuge test has many advantages. It can produce 
measurements which are accurate, repeatable and economical in labor 
costs. It includes the effects of tire and suspension deflections, and 
its measurements would be expected to correlate well with the actual 
rollover rates of vehicles, because those statistics are largely driven 
by tripped rollovers. The centrifuge test is arguably more accurate 
than SSF in evaluating tripped rollover resistance because it evaluates 
the outward c.g. movement as a result of suspension and tire 
deflections. Its basic measurement of a vehicle, lateral acceleration 
at two-wheel lift, is roughly 15 percent less than the vehicle's SSF 
with about a +/-5 percent range to cover extremes in roll stiffness.
    Despite these advantages, we did not choose to investigate the 
centrifuge test under the TREAD Act. Improvements in centrifuge test 
performance can be made by suspension changes that degrade handling. 
The best performance in the centrifuge test (and in the closely related 
but less accurate tilt table test) occurs when the front and rear 
inside tires lift from the platform at the same time. The tuning of the 
relative front/rear suspension roll stiffness to accomplish this will 
cause the vehicle to oversteer more than most manufacturers would 
otherwise desire. We do not want to tempt manufacturers to make this 
kind of trade-off. Further, we understood the intention behind TREAD to 
be that NHTSA should give the American public information on 
performance in a driving maneuver that would evaluate the performance 
of new technologies like ESC. The centrifuge test would not do so.

B. Driving Maneuver Simulation

    Computational models that simulate test maneuvers are used by 
vehicle manufacturers to assess handling and rollover performance of 
vehicle designs prior to building prototypes, and to evaluate the 
effect of suspension changes in prototypes and production vehicles. 
They present a potential solution to the safety, repeatability and 
pavement surface variability of real driving maneuver tests. 
Unfortunately, simulations now also carry enough disadvantages to 
disqualify their use for rollover resistance ratings. The various 
models used by different manufacturers produce different results, 
especially in simulating limit maneuvers. There is no agreement among 
manufacturers on a single model sufficient for this purpose. The time 
and cost of measuring the vehicle properties necessary for a limit 
maneuver model exceed that of running a real driving maneuver test. 
Validation testing of a model is necessary and greatly resembles the 
real tests the model hoped to avoid. Testing of the operation of ESC is 
problematic because the algorithms are often proprietary at the 
supplier level and not well known by the vehicle manufacturers. Given 
these difficulties, NHTSA has concluded that it is extremely unlikely

[[Page 35187]]

they could be resolved in time for us to use computer modeling for the 
information we must provide to the American public beginning in 
November 2002.

VIII. Solicitation of Comments

    NHTSA solicits general and specific comments on the subject of the 
development of a dynamic test for vehicle rollover resistance. We also 
wish to bring the following specific questions to the attention of 
commenters:
    1. NHTSA has decided to devote its available time and resources 
under the TREAD Act to develop a dynamic test for rollover based on 
driving maneuver tests. Is this the best approach to satisfy the intent 
of Congress in the time allotted? Are there additional maneuvers that 
NHTSA should be evaluating? Which maneuver or combination of maneuvers 
do you believe is the best for rollover rating? Are these other 
approaches well enough developed and validated that they could be 
implemented 18 months from now?
    2. How should NHTSA address the problem of long term and short term 
variations in pavement friction in conducting comparative driving 
maneuver tests of vehicle rollover resistance for a continuing program 
of consumer information?
    3. Some ESC systems presently have two functions. One is yaw 
stability which uses one or more brakes to keep the vehicle headed in 
the right direction in a limit maneuver, and the other is simple brake 
intervention in excess of the braking required for yaw stability. It is 
expected that the presence of a brake intervention function in ESC will 
have a large effect on the rating of vehicles because the average speed 
through a given test maneuver for vehicles having this function will be 
much less than for vehicles without it (even if equipped with ESC for 
yaw stability) under the usual test protocols of coasting through 
maneuvers and using the entry speed as the test speed. Is the value 
given to the brake intervention function of ESC as opposed to the yaw 
stability function by potential rollover rating tests commensurate with 
its safety value to consumers? Please provide all the data and 
reasoning that support your view. Should NHTSA measure the vehicle 
speed at the completion of the maneuver as well as vehicle speed at 
entry?
    4. If open-loop (defined steering input) maneuvers are used to 
determine whether a vehicle is susceptible to two wheel lift as a 
result of severe steering actions, superficial changes that reduce tire 
traction or otherwise reduce vehicle handling (but prevent wheel lift) 
would be rewarded the same as more fundamental or costly improvements. 
The same is true of closed loop (path following) maneuvers that use 
wheel lift as the sole criterion. Should measures of vehicle handling 
be reported so that consumers can be aware of possible trade-offs. What 
indicators of vehicles handling would be appropriate to measure and how 
should this consumer information be reported?
    5. What criteria should NHTSA use to select the best vehicle 
maneuver test for rollover resistance? Should the maneuver that has the 
greatest chance of producing two wheel lift in susceptible vehicles be 
chosen regardless of its resemblance to driving situations? Is it more 
important that the maneuver resemble an emergency maneuver that 
consumers can visualize? How important is objectivity and 
repeatability?

IX. Rulemaking Analyses and Notices

Executive Order 12866

    This request for comment was not reviewed under Executive Order 
12866 (Regulatory Planning and Review). Agency actions to develop tests 
for NHTSA's New Car Assessment Program are not rulemaking actions 
because the program does not impose requirements on any party.

X. Submission of Comments

A. How Can I Influence NHTSA's Thinking on This Document?

    In developing this document, we tried to address the concerns of 
all our stakeholders. Your comments will help us improve this notice. 
We invite you to provide different views on options we propose, new 
approaches we have not considered, new data, how this document may 
affect you, or other relevant information. We welcome your views on all 
aspects of this document, but request comments on specific issues 
throughout this document. Your comments will be most effective if you 
follow the suggestions below:
     Explain your views and reasoning as clearly as possible.
     Provide solid technical and cost data to support your 
views.
     If you estimate potential costs, explain how you arrived 
at the estimate.
     Tell us which parts of this document you support, as well 
as those with which you disagree.
     Provide specific examples to illustrate your concerns.
     Offer specific alternatives.
     Refer your comments to specific sections of this document.
     Be sure to include the name, date, and docket number with 
your comments.

B. How Do I Prepare and Submit Comments?

    Your comments must be written and in English. To ensure that your 
comments are correctly filed in the Docket, please include the docket 
number of this document in your comments.
    Your comments must not be more than 15 pages long. (49 CFR 553.21). 
We established this limit to encourage you to write your primary 
comments in a concise fashion. However, you may attach necessary 
additional documents to your comments. There is no limit on the length 
of the attachments.
    Please submit two copies of your comments, including the 
attachments, to Docket Management at the address given above under 
ADDRESSES.
    Comments may also be submitted to the docket electronically by 
logging onto the Dockets Management System website at http://dms.dot.gov. Click on ``Help & Information'' or ``Help/Info'' to obtain 
instructions for filing the document electronically.

C. How Can I Be Sure That My Comments Were Received?

    If you wish Docket Management to notify you upon its receipt of 
your comments, enclose a self-addressed, stamped postcard in the 
envelope containing your comments. Upon receiving your comments, Docket 
Management will return the postcard by mail.

D. How Do I Submit Confidential Business Information?

    If you wish to submit any information under a claim of 
confidentiality, you should submit three copies of your complete 
submission, including the information you claim to be confidential 
business information, to the Chief Counsel, NHTSA, at the address given 
above under FOR FURTHER INFORMATION CONTACT. In addition, you should 
submit two copies, from which you have deleted the claimed confidential 
business information, to Docket Management. When you send a comment 
containing information claimed to be confidential business information, 
you should include a cover letter setting forth the information 
specified in our confidential business information regulation. (49 CFR 
Part 512.)

[[Page 35188]]

E. Will the Agency Consider Late Comments?

    We will consider all comments that Docket Management receives 
before the close of business on the comment closing date indicated 
above under DATES. To the extent possible, we will also consider 
comments that Docket Management receives after that date. However, late 
comments will not likely be able to influence our testing program. We 
encourage commenters to respond as soon as possible since the testing 
described in this notice is already underway. If Docket Management 
receives a comment too late for us to consider it in completing our 
test program developing a proposal on dynamic rollover performance, we 
will consider that comment as an informal suggestion for future 
enhancements to our rollover program.

F. How Can I Read the Comments Submitted by Other People?

    You may read the comments received by Docket Management at the 
address given above under ADDRESSES. The hours of the Docket are 
indicated above in the same location.
    You may also see the comments on the Internet. To read the comments 
on the Internet, take the following steps:
    (1) Go to the Docket Management System (DMS) Web page of the 
Department of Transportation (http://dms.dot.gov/).
    (2) On that page, click on ``search.''
    (3) On the next page (http://dms.dot.gov/search/), type in the 
four-digit docket number shown at the beginning of this document. 
Example: If the docket number were ``NHTSA-1998-1234,'' you would type 
``1234.'' After typing the docket number, click on ``search.''
    (4) On the next page, which contains docket summary information for 
the docket you selected, click on the desired comments. You may 
download the comments. Although the comments are imaged documents, 
instead of word processing documents, the ``pdf'' versions of the 
documents are word searchable.
    Please note that even after the comment closing date, we will 
continue to file relevant information in the Docket as it becomes 
available. Further, some people may submit late comments. Accordingly, 
we recommend that you periodically check the Docket for new material.

G. Plain Language

    Executive Order 12866 requires each agency to write all rules in 
plain language. Application of the principles of plain language 
includes consideration of the following questions:
     Have we organized the material to suit the public's needs?
     Are the requirements in the rule clearly stated?
     Does the rule contain technical language or jargon that is 
not clear?
     Would a different format (grouping and order of sections, 
use of headings, paragraphing) make the rule easier to understand?
     Would more (but shorter) sections be better?
     Could we improve clarity by adding tables, lists, or 
diagrams?
     What else could we do to make the rule easier to 
understand?
    If you have any responses to these questions, please include them 
in your comments on this document.

    Issued on June 27, 2001.
Stephen R. Kratzke,
Associate Administrator for Safety Performance Standards.

Table 1.--Summary of Anticipated Advantages and Disadvantages for 
Possible Dynamic Rollover Tests

    Note: The extent to which many of these anticipated attributes 
are realized will not be known until the completion of the resesarch 
project.

1. Path Following Driving Maneuver Tests

A. CU Double Lane Change
    Anticipated advantages: Familiar to the public, represents a real 
maneuver, considers roll momentum, use of speed as criteria implicitly 
rewards good handling, demonstrates action of ESC.
    Anticipated disadvantages: Poor repeatability due to large driver 
influence, use of wheel lift as main criterion invites trade-offs in 
tire traction, may operate at a worst case suspension frequency for 
some vehicles but not others.
B. VDA/ISO/Moose Test
    Anticipated advantages: Like CU but with less room for driver 
variability through tight cone placement, represents a real maneuver, 
use of speed as criteria implicitly rewards good handling, demonstrates 
action of ESC.
    Anticipated disadvantages: Driver influence is reported to be still 
on the order of 4 mph, tight lane widths may test driver ability as 
much a vehicle handling, more like 2 back to back single lane changes--
may not include roll momentum, may operate at a worst case suspension 
frequency for some vehicles but not others (course adjustments for 
wheelbase mentioned).
C. Open Loop Pseudo-Double Lane Change (Concept for Automating the CU 
to the Extent Possible Using a Automated Steering Controller)
    Anticipated advantages: Eliminates repeatability issues due to 
driver influences, attempts to represent a real maneuver, considers 
roll momentum, may use roll feedback to find worst case steering timing 
for each vehicle, use of speed as criteria implicitly rewards good 
handling? demonstrates action of ESC.
    Anticipated disadvantages: Exists only as a concept--may prove to 
be entirely impractical, use of wheel lift as main criterion invites 
trade-offs in tire traction, failure to replicate a realistic path 
would devalue face validity and speed criterion, may be difficult to 
develop with available resources.
D. Ford Path Corrected Limit Lane Change
    Anticipated advantages: Objective and repeatable, can it 
``perfect'' the double lane change? considers roll momentum, 
demonstrates action of ESC.
    Anticipated disadvantages: Suggested criteria requires handling 
definition and still may reward poor tire traction as it currently 
operates, rollover resistance is rated on different paths for different 
vehicles.

2. Open Loop ( Defined Steering) Fishhook Maneuver Tests (With Several 
Steering Timing Ideas To Be Evaluated)

    Anticipated advantages: Performed by automated steering controller 
for maximum objectivity and repeatability, considers roll momentum and 
seeks worst case for every vehicle, demonstrates action of ESC.
    Anticipated disadvantages: Lacks face validity of lane change 
maneuvers, actual paths may differ widely between vehicles, needs 
separate handling criteria because poor tire traction is otherwise 
rewarded.

3. Dynamic Tests Other Than Driving Maneuvers--Not Planned for 
Evaluation

A. Centrifuge
    Advantages: A ``perfection'' of the well known tilt table, 
expandable to test performance at road perturbations, accounts for 
suspension and tire deflections (unlike SSF), can represent tripped 
rollover (like SSF), accurate, repeatable and relatively cheap 
measurements.
    Disadvantages: Suspension optimization for centrifuge test score 
can degrade handling (unlike SSF), not be perceived as ``dynamic 
enough'' for TREAD requirements, does not demonstrate action of ESC.

[[Page 35189]]

B. Mathematic Simulation
    Advantages: Objective and repeatable, solves pavement friction 
issues, any maneuver is possible.
    Disadvantages: Cost of vehicle characterization even greater than 
for maneuver tests, ESC algorithms proprietary and possibly not known 
to vehicle mfgr., no universally accepted mathematic model.

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[FR Doc. 01-16659 Filed 7-2-01; 8:45 am]
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