Federal Motor Vehicle Safety Standards No. 121; Air Brake Systems

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

Christopher J. Bonanti
Federal Register
September 9, 2011

[Federal Register Volume 76, Number 175 (Friday, September 9, 2011)]
[Proposed Rules]
[Pages 55859-55865]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-23043]



[[Page 55859]]

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571


Federal Motor Vehicle Safety Standards No. 121; Air Brake Systems

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

ACTION: Denial of Petition for Rulemaking.

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SUMMARY: This Notice denies the petition for rulemaking from William B. 
Trescott, in which the petitioner requested that the National Highway 
Traffic Safety Administration (NHTSA) vacate Federal Motor Vehicle 
Safety Standard (FMVSS) No. 121, Air Brake Systems by removing 
requirements for antilock brake systems (ABS) for newly-manufactured 
vehicles equipped with air-brake systems; or that the agency require a 
driver-controllable switch that would allow the driver to deactivate 
the ABS on air-braked vehicles; or that the agency require the 
automatic deactivation of ABS on air braked vehicles when the vehicles 
are traveling at speeds greater than 55 mph. The petitioner claims that 
an agency report shows that ABS on tractor-trailers increases fatal 
crash involvements, and also that ABS allows incompetent truck drivers 
to drive trucks. The agency reviewed these claims and found them to be 
without merit, and concludes that the agency report cited by the 
petitioner does not support the conclusion that safety would be 
improved by allowing ABS to be deactivated. Rather, the data supports 
the conclusion that removing ABS from trucks would result in an 
increase in crashes.

FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may contact 
Mr. Jeffrey Woods, Office of Crash Avoidance Standards, NHTSA, 1200 New 
Jersey Avenue, SE., Washington, DC 20590 (Telephone: 202-366-6206) 
(FAX: 202-366-7002). For legal issues, you may contact Mr. David 
Jasinski, Office of the Chief Counsel, NHTSA, 1200 New Jersey Avenue, 
SE., Washington, DC 20590 (Telephone: 202-366-2992) (Fax: 202-366-
3820).

SUPPLEMENTARY INFORMATION: 

Table of Contents

I. Trescott Petition
II. Summary of the ABS Effectiveness Study Results
III. ABS Requirements
IV. Agency Analysis of the Petition
V. Agency Decision

I. Trescott Petition

    On October 27, 2010, the agency received a petition for rulemaking 
from William B. Trescott of Bay City, Texas, requesting that FMVSS No. 
121, Air Brake Systems, either be vacated entirely or amended to 
require one of two options regarding antilock brake systems that are 
required for air-braked vehicles. The first option would be to require 
automatic deactivation of the antilock brake system (ABS) when vehicles 
are travelling at speeds faster than 55 mph, and the second option 
would be to require an ABS deactivation switch to allow the driver to 
disable the ABS. The petition cited data from a recent NHTSA report, 
``The Effectiveness of ABS in Heavy Truck Tractors and Trailers,'' \1\ 
and stated that it showed no statistically significant benefits of ABS 
in reducing fatal truck crashes. The petition stated that the best 
estimate of a reduction in all crash types by having ABS on the tractor 
was only three percent, and that ABS increased overall fatalities by 
one percent. The petition cited several tables in the report describing 
both reductions and increases in certain types of crashes. For example, 
the petition cited Table 2, Reduction in response group crashes based 
on tractor and trailer ABS equipment, Florida state data, of the report 
which summarized state data from Florida showing a 30 percent decrease 
in single vehicle rollover crashes for tractors and trailers equipped 
with ABS, and a 21 percent increase in two vehicle front-to-rear 
crashes with the truck as the striking vehicle for tractors and 
trailers equipped with ABS. From Table 4, Reduction in response group 
crashes on wet roads based on tractor and trailer ABS equipment, 
Florida state data, the petition cited the 67 percent reduction in 
jackknife crashes on wet roads for tractors and trailers equipped with 
ABS. The petition stated that there is no doubt that ABS prevents 
jackknife crashes.
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    \1\ Report No. DOT HS 811 339, July 2010, available at http://www-nrd.nhtsa.dot.gov/Pubs/811339.pdf.
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    The petition cited specific roadway type, speed, and locality data 
that are contained in the report as follows. Table 17, Number of 
crashes and reduction for ABS-equipped tractors according to type of 
locality and speed of road, FARS data, indicates an 11 percent increase 
in fatal crashes on rural, high-speed roads for ABS-equipped tractors, 
while the data in Table 18, Number of crashes and reduction for ABS-
equipped tractors on roads that are not high-speed, FARS data, show 
fatal crash reductions of 23 percent on all roads that are not high 
speed for tractors with ABS. Table 19, Number of crashes and reduction 
for ABS-equipped tractors on roads that are rural and high-speed 
according to whether the road is an interstate or not, FARS data, shows 
an eight percent increase in fatal crashes on rural interstate roads 
for ABS-equipped tractors, and a three percent decrease in fatal 
crashes on other non-interstate rural high speed roads for ABS-equipped 
tractors. Table 20, Crash reductions for all crash mechanisms by 
locality and road type, FARS, shows a 30 percent increase in fatal, 
two-vehicle rear impact crashes with the truck as the striking vehicle, 
for tractors equipped with ABS on rural interstate highways. On the 
basis of these data, the petition stated that long-haul truckers who 
operate primarily in rural areas should disable their ABS and the 
agency should issue a recall order to that effect. However, the recall 
order should not apply to drivers who operate primarily in urban areas, 
and further, it may be safest for truckers to turn off their ABS when 
exceeding 55 mph and to leave it on the rest of the time.
    The petition stated that an unintended consequence of preventing 
jackknife crashes through the use of ABS is that incompetent drivers, 
who prior to the introduction of ABS would have been fired for the 
occurrence of a jackknife, were instead being retained and subsequently 
their continued driving resulted in increases in other types of 
crashes. The petition cited a 29 percent increase in two-vehicle rear 
end crashes on wet or icy roads with the truck as the striking vehicle, 
from Table 4, Reduction in response group crashes on wet roads based on 
tractor and trailer ABS equipment, Florida state data, for tractors and 
trailers equipped with ABS, as an example of incompetent truck driver 
retention. The petition also cited a 21 percent increase in single 
vehicle crash truck occupant fatalities in 1997, the same year that ABS 
was mandated on newly-manufactured tractors, and concluded that this 
increase in fatalities was an unintended side effect of less qualified 
drivers being hired that was made possible by ABS. The petition 
reasoned that trucking fleets realized cost savings because ABS reduced 
truck tire damage during panic stops, which thereby allowed the fleets 
to hire less qualified drivers who were subsequently involved in more 
crashes.

[[Page 55860]]

II. Summary of the ABS Effectiveness Study Results

    The agency's study on the effectiveness of ABS on tractors and 
trailers included a statistical analysis of crash data from seven 
states for fatal and non-fatal crashes that occurred between 1998 and 
2007 (data for all of these years were not used or were not available 
for every state), and from the Fatality Analysis Reporting System 
(FARS) for fatal crashes that occurred between 1998 and 2008 from all 
fifty states. All states provided the vehicle identification number 
(VIN) or the model year data for the tractors so that the model year of 
the tractor could be determined, while only two states for which 
trailer ABS was evaluated (Florida and North Carolina) included the VIN 
or the model year for the trailers. For all of the crashes, the data 
were limited to a tractor towing one trailer; thus tractors not towing 
a trailer (bobtail tractors) or tractors towing multiple trailers were 
not included in the analysis. Tractors of model year 1998 or newer were 
assumed to have ABS while those of model year 1996 or older were 
assumed not to have ABS. Model year 1997 was excluded since the ABS 
requirements in FMVSS No. 121 became effective on March 1, 1997, and 
therefore a model year 1997 tractor may or may not have been equipped 
with ABS. Similarly, trailers of model year 1999 or newer were assumed 
to have ABS, while those of model year 1997 or older were assumed not 
to have ABS, and model year 1998 trailers were excluded from the 
analysis, since the trailer ABS requirements became effective on March 
1, 1998.
    Limitations of the study included the overall small vehicle 
population for tractor-trailers (compared to light vehicles for which 
there are many more vehicles on the road) and the limited amount of 
crash data from the seven-state sample (27,777 total crashes). 
Additionally, all model years of vehicles prior to the ABS effective 
date were assumed not to have ABS, which did not account for an unknown 
number of vehicles that were voluntarily equipped with ABS prior to the 
effective date. Also, there was no way to discern whether the vehicles 
equipped with ABS had been properly maintained so that the ABS was 
functional at the time of the crash; both of these factors would result 
in underestimation of the ABS effectiveness. As described above, only 
two states had information on trailer model year, so the main focus of 
the analysis was on the effectiveness of tractor ABS.
    The crashes, in which tractor-trailers were involved in either 
single vehicle crashes or multiple vehicle crashes, were divided into 
control and response groups that both contained tractors and trailers 
with and without ABS. The crash types for the control group were those 
in which ABS should not have been influential in the crash outcome, 
including crash involved tractor-trailers that were moving slowly, 
parking or unparking, backing up, impacted in the rear, etc. The crash 
types for the response group were those in which ABS should have been 
influential either by helping the driver to maintain control of the 
vehicle or by contributing to improved stopping distance. Response 
group single vehicle crash types included run-off-road collisions with 
fixed objects; collisions with animals, pedestrians, or bicycles; 
jackknife crashes, etc. Response group multi-vehicle crashes included 
those in which the truck was the striking vehicle in rear-end crashes 
or the truck was the at-fault vehicle in any other type of crash 
involving other vehicles. Differences in control group and response 
group crashes were used to determine ABS effectiveness as evidenced by 
reductions or increases in crashes among the response group, and 
statistical measures were provided to determine the statistical 
significance of the results.
    The primary findings of the analysis are summarized as follows:
     The best estimate of a reduction by ABS on the tractor 
unit in all levels of police-reported crashes for air-braked tractor-
trailers is three percent, based on crash data from seven states and 
controlling for the age of the tractor at the time of the crash. This 
represents a statistically significant six percent reduction in crashes 
in which ABS is assumed to be potentially influential, relative to a 
control group, of about the same number of crashes, in which ABS was 
likely to be irrelevant.
     In fatal crashes, there was a non-significant two percent 
reduction in crash involvement, resulting from a four percent reduction 
in crashes in which ABS should have been potentially influential. 
External factors of roadway urbanization and speed, and ambient 
lighting, were accounted for in the final estimates.
     Among the types of crashes that ABS influences, there is a 
large reduction in jackknife crashes, off-road truck rollovers, and at-
fault involvements in crashes with other vehicles, except in rear-end 
crashes. Counteracting was an increase in the number of involvements in 
crashes with animals, pedestrians, or bicyclists and, only in fatal 
crashes, two-vehicle rear-end crashes with the truck as the striking 
vehicle.
    The first stage of the analysis considered ABS on both the tractors 
and the trailers. For the Florida data, the reduction in response group 
crashes was a statistically significant 14 percent for ABS-equipped 
tractors when towing either ABS-equipped trailers or non-ABS-equipped 
trailers.\2\ The largest crash reductions associated with ABS on the 
tractor or trailer were among single-vehicle tractor-trailer crashes 
and particularly jackknife crashes (statistically significant 
reductions of 76 percent for ABS tractors with non-ABS trailers, and 65 
percent for ABS tractors with ABS trailers). Crashes with pedestrians, 
bicycles, and animals increased, although this result was not 
statistically significant. For multi-vehicle crashes, increases were 
seen for rear-end crashes with the tractor as the striking vehicle when 
tractors with ABS were compared to those without, while decreases in 
other tractor-at-fault crashes were seen for the ABS tractors. These 
sub-group results were statistically significant while the overall 
results for all multi-vehicle crashes (a five percent reduction for ABS 
tractors with non-ABS trailers, and a one percent increase for ABS 
tractors with ABS trailers) were not statistically significant.
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    \2\ See Table 2: Reduction in response group crashes based on 
tractor and trailer ABS equipment, Florida state data.
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    When the Florida data were limited to wet roadways (with the road 
surface coded as wet, slippery, or icy), the reductions in crashes for 
ABS tractors were even higher: 26 percent when operated with non-ABS-
equipped trailers, and 23 percent when operated with ABS-equipped 
trailers, both statistically significant.\3\ These results suggested 
that ABS is more effective on wet roads than on dry roads, noting that 
comparison data were not always statistically significant but 
nevertheless showed an overall trend. When the North Carolina data (the 
other State providing trailer model year) were also considered, the 
tractor ABS was still seen to be the most influential in overall crash 
reductions, although the crash data sample was small. The amount of 
available data from both Florida and North Carolina was found to be 
insufficient to draw further conclusions about the effects of ABS on 
the trailers.
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    \3\ See Table 4: Reduction in response group crashes on wet 
roads based on tractor and trailer ABS equipment, Florida state 
data.
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    An initial analysis of the state data for all levels of crash 
severity (property damage only, or resulting in an injury or

[[Page 55861]]

a fatality) for the seven states showed reductions in response group 
crashes for ABS-equipped tractors ranging between 10 percent and 17 
percent for each state.\4\ Results by crash type were typically similar 
in magnitude and in the same direction (reductions or increases in 
crashes) for each state. The largest percentage reductions for ABS 
tractors were for jackknife crashes, followed by single-vehicle run-
off-road rollovers and other types of single-vehicle crashes (both on-
road and off-road). Reductions in multi-vehicle crashes were also seen 
across the states, with only Florida data showing an increase in rear-
end crashes with the truck as the striking vehicle. Substantial 
increases were seen for single vehicle crashes with animals, 
pedestrians, and bicyclists, although these results were not 
statistically significant and the number of crashes was small.
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    \4\ See Table 11: Reduction in response group crashes for 
various crash mechanisms, summary of seven States.
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    However, the age differences between the ABS and non-ABS tractors 
were found to have biased the results because the non-ABS tractors were 
at least two years older than the ABS-equipped tractors. Additional 
analyses of the state data were conducted on an age-restricted subset 
of the crash data for overlapping tractor ages at the time of the crash 
for both ABS tractors and non-ABS tractors. Since varying years of 
state data were used, the tractor age varied between three and ten 
years at the time of the crash depending on the state (e.g., between 
three to ten years for Florida, and eight to nine years for North 
Carolina).
    The results of the age-restricted state data still showed crash 
reductions for the ABS tractors in each of the seven states, but the 
reductions were smaller than those seen from the unrestricted data set 
and there were few results that were statistically significant.\5\ The 
ABS tractors in the response group of crashes showed crash reductions 
ranging between three percent and 10 percent for each state in 
comparison with the control group, and similar to the results in the 
unrestricted data set, single vehicle jackknife crashes had the largest 
reductions of all the crash types, followed by single-vehicle 
rollovers. Increases were seen in five states for crashes with animals, 
pedestrians, and bicyclists, and in three states for two-vehicle rear 
end crashes with ABS tractors as the striking vehicle. Considering the 
total crash population for the combined response and control groups, 
ABS tractors were associated with overall crash reductions of between 
two percent and six percent for each state.
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    \5\ See Table 27: Reductions in all crash mechanisms, age-
restricted State data.
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    A similar analysis was conducted using 50-state FARS data from 1998 
to 2008 with a data set of 30,275 crashes. The analysis considered 
tractors towing one trailer, but only the effectiveness of tractor ABS 
was considered since trailer model year information was not available. 
Comparisons were conducted similarly to those in the state data 
analysis, with a control group consisting of crash types in which ABS 
would not be considered to have an influence, and a response group in 
which ABS could be considered to have an influence in the crash. The 
response and control groups included both ABS tractors and non-ABS 
tractors.
    The initial FARS results found that the ABS tractors in the 
response group had an overall two percent increase in crashes compared 
to non-ABS tractors, although these results were not statistically 
significant.\6\ In single-vehicle crashes, there was a reduction in 
run-off-road crashes with rollover and single-vehicle jackknife crashes 
for the ABS tractors. However, there was an increase in run-off-road 
crashes without rollover and crashes with pedestrians, animals, and 
bicyclists. A few of the subgroup results were statistically 
significant, but the overall results were not.
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    \6\ See Table 15: Reduction in response group crashes for 
various crash mechanisms, FARS data.
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    In two-vehicle rear end crashes with the truck as the striking 
vehicle, a 44 percent increase was seen for the ABS tractors. However, 
there was an eight percent reduction in other multi-vehicle crashes in 
which the truck was the at-fault vehicle. Since there were many more 
multi-vehicle crashes that are in the ``other,'' non-rear-end crash 
category, the net result was a non-significant one percent increase in 
overall multi-vehicle crashes for the ABS tractors. In addition, the 
ABS tractors were found to have a slightly higher percentage of crashes 
occurring on wet roadways (18 percent of crashes occurring on wet 
roadways) compared to the non-ABS tractors (16 percent of crashes 
occurring on wet roadways), which was contrary to what was seen in the 
analysis of the state data.
    The FARS data were then segregated by roadway locality and speed, 
and the results showed that reductions in crashes for the ABS tractors 
occurred on non-high-speed roadways (both rural and non-rural), while 
the increases occurred on high speed roadways (mainly rural, with only 
a slight increase on non-rural roads).\7\ Further segregation showed 
that the increases occurring on high speed roads were on interstate 
highways, although these results were not statistically significant.\8\ 
When overall results were compared among four categories of road 
locality and type, the only statistically significant result was a 24 
percent decrease among ABS tractors for all road types that were not 
high speed (including both single-vehicle and multi-vehicle 
crashes).\9\ Furthermore, when individual crash types were reviewed 
within these data, a 43 percent overall increase in rear-end crashes 
with an ABS tractor as the striking vehicle, considering all roadways, 
was considered questionable because it was more negative than seen for 
any individual road locality and speed type. Therefore, adjustments 
were made in the final estimates for tractor ABS effectiveness in fatal 
crashes.
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    \7\ See Table 17: Number of crashes and reduction for ABS-
equipped tractors according to type of locality and speed of road, 
FARS data.
    \8\ See Table 19: Number of crashes and reduction for ABS-
equipped tractors on roads that are rural and high-speed according 
to whether the road is an interstate or not, FARS data.
    \9\ See Table 20: Crash reductions for all crash mechanisms by 
locality and road type, FARS.
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    The analysis found that the type of road locality, travel speed, 
and ambient lighting condition (daylight or non-daylight) were 
influential in the fatal crash data. The data were then weighted to 
account for these influences and the final estimates for tractor ABS 
effectiveness and confidence intervals were derived.\10\ The result was 
a four percent reduction among all ABS tractor response group crashes, 
although this result was not statistically significant. Single vehicle 
crashes among ABS tractors were reduced by five percent (not 
statistically significant) with the largest reductions in the run-off-
road with subsequent rollover (statistically significant) and jackknife 
crash types (not statistically significant). The results also showed an 
increase in crashes with pedestrians, animals, and bicycles. ABS 
tractors had an overall five percent reduction in fatal multi-vehicle 
crashes (not statistically significant) with a nine percent reduction 
(statistically significant) in multi-vehicle crashes with the tractor 
at fault, and a ten percent increase (not statistically significant) in 
rear end crashes with the tractor as the striking vehicle. Tractor age 
was not found to be influential in the FARS data. Therefore, there was 
no need to conduct an age-restricted analysis of these data.
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    \10\ See Table 23: Final weighted estimate of tractor ABS 
effectiveness from FARS.

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[[Page 55862]]

III. ABS Requirements

    During the rulemaking in the 1990's to require ABS on air-braked 
heavy vehicles (and, concurrently, to require ABS on medium and heavy 
trucks and buses equipped with hydraulic brakes), the agency solicited 
public comments and input on how the ABS requirements would be 
implemented, including a definition of ABS, ABS equipment requirements 
for different vehicle types, and ABS road tests to set pass-fail 
performance criteria for tractors, trucks, and buses. An advanced 
notice of proposed rulemaking (ANPRM) was published on June 8, 1992 
\11\ outlining the agency's general approach to include heavy vehicle 
ABS requirements, followed by a notice of proposed rulemaking (NPRM) on 
September 28, 1993 \12\ that included more detailed information along 
with an agency proposal for the regulatory text to include the ABS 
requirements in FMVSS No. 121. The agency was not aware of any reason 
to consider including an ABS on-off switch to allow the drivers to 
deactivate ABS during the rulemaking, and the heavy vehicles that were 
available with ABS at that time did not include any ABS on-off 
switches. None of the public comments or petitions for rulemaking 
submitted during the rulemaking requested that ABS disabling switches 
be provided.
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    \11\ 57 FR 24212.
    \12\ 58 FR 50738.
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    On May 1, 1998, the agency issued an interpretation letter in 
response to an inquiry from Navistar International (Navistar) regarding 
air-braked vehicles that are equipped with an all-wheel drive (AWD) 
system that is selectable by the driver. Under this scenario, the 
vehicles are normally operated in two-wheel drive mode, and the AWD 
mode is selectable by the driver for severe service, off-road 
operation. Navistar asked if the ABS on such vehicles needed to be 
fully operational when the vehicle is in the AWD mode. The agency's 
letter stated that there is no exception in FMVSS No. 121 to permit the 
ABS to be disabled when AWD has been selected, although the ABS 
operation could be modified to better suit off-road conditions, as can 
be found in construction, logging, or mining operations for example. 
The requirements in S6, Test conditions, in FMVSS No. 121 specify that 
during road tests for the braking system, a vehicle equipped with an 
interlocking axle system or a front wheel drive system which is engaged 
and disengaged by the driver is tested with such system disengaged.
    The practical effect of this agency interpretation letter is that 
during a stopping distance test, the vehicle must comply with the 
stopping distance requirements and meet the wheel lockup provisions 
specified in the standard, and during a stability and control test the 
vehicle must remain in the 12-foot-wide lane during a full brake 
application in at least three out of four test runs, with the ABS fully 
functional and, if so equipped, a front drive axle or an interaxle 
locking system disengaged via the driver controls. However, when either 
a front drive axle or interaxle locking system is engaged by the 
driver, additional wheel lockup could be provided to meet operational 
needs. An example of this is a logging truck descending a steep grade 
on a muddy road at very low speeds, where some wheel lockup is needed 
to restrict the forward motion of the vehicle by allowing a wedge of 
mud to build up in front of the tires. Thus, a vehicle manufacturer can 
activate a modified ABS algorithm based upon the driver engaging the 
controls for an interaxle locking system or front wheel drive system as 
such needs are identified by the vehicle manufacturer. To date, the 
provisions already contained in FMVSS No. 121 permit modified ABS 
operation, without the need for an ABS on-off switch.

IV. Agency Analysis of the Petition

    The purpose of requiring ABS on medium and heavy vehicles, 
including tractors and trailers, is to improve vehicle control and 
stability during panic braking. During normal driving, drivers brake 
lightly and no wheel lockup occurs. However, when faced with an 
imminent crash situation, drivers may apply the brakes by making a full 
brake pedal application, which can result in wheel lockup at one or 
more wheels on a vehicle. Since locked wheels cannot provide the 
lateral force needed to maintain directional control or to permit the 
driver to steer the vehicle around an obstacle, a loss-of-control 
situation occurs. A jackknife can occur if the tractor's drive axle 
wheels are locked and the tractor rotates about its center of gravity 
(often until it makes contact with a trailer being towed), or if the 
locked wheels on the trailer cause it to swing out of its travel lane. 
Both a jackknifed tractor and a trailer that has swung out of its lane 
can crash into other vehicles, skid off the road and strike roadside 
objects, or rollover. ABS keeps the wheels from locking up; thus 
lateral control of the vehicle is retained so the vehicle stays in its 
lane and the driver can also execute a steering maneuver to try and 
avoid a crash.
    The March 10, 1995 final rule on heavy vehicle ABS included an 
appendix that provided details on heavy vehicle braking systems, tire 
characteristics related to lateral force and longitudinal force 
generation relative to wheel lockup, and explained why braking-related 
wheel lockup causes loss-of-control crashes on heavy vehicles.\13\ 
Also, it describes why heavy vehicles are more prone to braking-related 
wheel lockup compared to light vehicles. Since heavy vehicle brakes are 
sized to stop the vehicle in the fully-loaded condition, they are over-
braked (a brake imbalance condition) on the drive axles or trailer 
axles when operated in a lightly-loaded condition. The ratio of the 
weight of a loaded truck to the weight of an unloaded truck is 
considerably greater than the comparable loaded-to-unloaded weight 
ratio of a light vehicle. All of the physical conditions discussed in 
the appendix are still true today and thus removing ABS would result in 
the described loss of control conditions and a subsequent increase in 
crashes related to loss of control.
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    \13\ 60 FR 13259.
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    However, since the ABS final rule was published, the agency 
published a final rule on July 27, 2009, which requires shorter 
stopping distances for truck tractors.\14\ The availability of improved 
foundation brakes for tractors, including more powerful S-cam drum 
brakes and air disc brakes, enabled the agency to reduce both the 
loaded and unloaded stopping distance requirements for newly 
manufactured tractors by 30 percent (starting with most tractors 
manufactured on or after August 1, 2011), compared to the existing 
FMVSS No. 121 tractor stopping distance requirements. The agency 
estimated that once all tractors are equipped with improved foundation 
brakes (which will take a considerable number of years as new tractors 
are phased into the national fleet), the safety benefits will be 227 
fewer fatalities, 300 fewer serious injuries, and $205M in reduced 
property damage each year. The new stopping distance requirements in 
the unloaded condition are particularly relevant to ABS. The old 
requirement of stopping within 335 feet for an unloaded (bobtail) 
tractor from 60 mph was a considerably long distance because, during 
compliance tests, the test driver needed to carefully modulate (apply 
and release) the brake pedal or only make a very light brake pedal 
application to keep the drive axle wheels from locking up during the 
stop. However, now that tractors are required to be equipped

[[Page 55863]]

with ABS, the test driver can simply make a hard brake application and 
the ABS prevents wheel lockup on the drive axle wheels. Thus, the new 
stopping distance of 235 feet can be readily achieved without the 
danger of losing control of the tractor due drive wheel lockup. The ABS 
plays an important role in achieving shorter stopping distances on 
tractors, because it allows higher brake torques to improve a loaded 
tractor's stopping distance, yet also provides for shorter stopping 
distances in the unloaded condition without wheel lockup. Removing ABS 
from tractors, or permitting it to be disabled, would not allow 
reductions in stopping distance to be safely achieved without 
compromising the ability of the driver to maintain full directional 
control of the tractor under all loading and road conditions.
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    \14\ 74 FR 37122.
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    In terms of on-the-road stopping distance performance of tractor-
trailers, ABS may also improve the stopping distance compared to a 
driver's best effort on a non-ABS brake system, particularly if the 
vehicle is not loaded optimally or if the roadway is slippery. For 
example, a tractor-trailer that is half-loaded with the load placed 
only in the forward half of the trailer would first experience trailer 
wheel lockup during hard braking if there was no ABS on the tractor or 
trailer. In order to prevent the trailer from swinging out of the lane, 
the driver would need to modulate the brake pedal to alternate between 
a momentary trailer wheel lockup condition, and an unlocked trailer 
wheel condition. However, if the tractor and trailer both were equipped 
with ABS, then the driver could apply the brakes with a higher pressure 
to take advantage of the greater tire traction available on the 
heavier-loaded tractor drive axles, and the ABS would prevent the 
trailer wheels from locking up. Thus, ABS allows the driver to use the 
peak amount of friction available at each wheel position even though 
the load at each wheel may vary greatly.
    Under ideal loading conditions, such as a fully loaded tractor-
trailer on dry pavement, a highly skilled test driver may be able to 
achieve the shortest possible stopping distance without activating the 
ABS system by braking the vehicle so that the brake pressure is just 
below the threshold of wheel lockup. However, on the highways when 
faced with an imminent crash threat, drivers often make a full brake 
application, thus engaging the ABS if any wheels are prone to lockup or 
going into a jackknife or trailer swing on vehicles without ABS. In 
summary, we believe that trucks equipped with ABS have improved 
stopping distance compared to non-ABS trucks when lightly-loaded, and 
particularly on wet or slippery roads. ABS also provides the driver 
with an increased level of confidence that he/she can make a hard brake 
application in crash-threatening situations and still be able to 
maintain directional control of the vehicle.
    The agency reviewed the crash data that were cited in the petition 
as the basis for requesting to either vacate FMVSS No. 121, or 
requiring an on-off switch or automatic disabling of the ABS on heavy 
vehicles at speeds greater than 55 mph. The petition stated that the 
agency's report on the ABS effectiveness on tractors and trailers 
showed no statistically significant benefits in reducing fatal truck 
crashes and that the best estimate of a reduction in all types of 
crashes by having ABS on the tractor was only three percent. The 
petition stated that ABS increased overall fatalities by one percent. 
The agency finds that the overall three percent crash reduction for the 
data from the seven states correctly reflects the findings in the 
report, with overall crash reductions ranging between two percent and 
six percent for each state. Considering the response group of crashes 
in which ABS was possibly influential in the crash, the reductions in 
all crash types for ABS tractors ranged between three and ten percent 
for the seven states, with a median value of six percent, when compared 
to a control group of vehicles involved in crashes in which ABS would 
not be likely to be influential.
    However, the one percent increase in fatal crashes for ABS tractors 
cited in the petition is from Table 15, Reduction in response group 
crashes for various crash mechanisms, FARS data. However, as described 
in the report, those initial FARS results were found to have influences 
of road locality and speed category, and ambient lighting condition. 
Thus, the results in Table 23, Final weighted estimate of tractor ABS 
effectiveness from FARS, have been adjusted for control group exposure 
for roadway type and lighting condition, and indicated an overall four 
percent reduction in fatal crashes. The confidence intervals of -0.7 
percent to 9.0 percent fell short of statistical significance, and 
therefore it is not an unequivocal confirmation of fatality reduction 
for tractor ABS. But, the results for the state data and the FARS data 
both showed reductions in crashes for tractor ABS and this result leads 
the agency to conclude that ABS is an effective safety system. We 
therefore disagree with the statement in the petition that ABS on heavy 
trucks increases fatal crashes; overall, the analysis shows crash 
reductions for both fatal and non-fatal crashes.
    The petition addresses the effectiveness study's findings on the 
effect of ABS in selected subgroups of crashes. The agency notes that 
examination of subgroups is typically an important component of the 
agency's evaluations. Nevertheless, when the data are limited, as in 
this case, the results for the various subgroups typically comprise a 
wide range of positive and negative results, and some of the outlying 
results may even achieve statistical significance. However, without 
additional confirmation from other sources, it is not clear if such 
results are meaningful. They should be considered secondary to the 
overall effectiveness rating.
    The petition cited the subgroup of two-vehicle rear end crashes 
with the truck as the striking vehicle in Table 20, Crash reductions 
for all crash mechanisms by locality and road type, FARS, where a 30 
percent increase in rear end crashes among ABS tractors is shown for 
roads that are interstate (high speed) and rural. Here again, the 
petition cites the unweighted FARS results, and the agency considers 
the values for the weighted FARS data in Table 23 to be more 
representative of the highway usage for tractors with ABS. The Table 23 
results indicated a non-statistically significant 10 percent increase 
in two-vehicle rear end crashes with the truck as the striking vehicle.
    However, this single data result does not convince the agency that 
there would be any potential safety benefit to disabling the ABS at 
speeds greater than 55 mph, allowing drivers to disable the ABS, or 
removing ABS altogether on heavy vehicles. The aggregate of all fatal 
crash data shows a trend of tractor ABS reducing fatal crashes. Six of 
the crash subgroups also reflect reductions in crashes among ABS 
tractors, and two subgroups show increases among ABS tractors. The 
petition did not address specifically how ABS could be contributing to 
increases in fatal rear end crashes with the tractor as the striking 
vehicle, other than the unsubstantiated indirect effect of motor 
carriers retaining less qualified drivers to drive ABS-equipped 
tractors.
    Furthermore, the state data results in Table 27, Reductions in all 
crash mechanisms, age-restricted State data, indicated that four states 
showed a reduction in two-vehicle rear end crashes with the truck as 
the striking vehicle among the ABS tractors, and three states showed 
increases in these crashes among the ABS tractors. The median value was 
a one percent reduction in rear end crashes for the

[[Page 55864]]

ABS tractors. The agency concludes that the evaluation does not present 
clear evidence of an overall increase in rear-end crashes among the ABS 
tractors, but in fact presents some evidence to the contrary.
    In summary, since ABS improves vehicle control and stability and 
may have improved stopping distance performance during panic braking 
and under other circumstances, the agency is not able to explain why 
the crash data show an increase in fatal rear end crashes among the ABS 
tractors with the truck as the striking vehicle. The state data for all 
types of crashes involving tractor-trailers show decreases in rear end 
crashes among the ABS tractors in four states while three states show 
an increase in rear end crashes among the ABS tractors. The answer may 
not be related to ABS at all. However, the crash data provided no 
insight into possible relationships between the data and ABS 
performance in rear end crashes.
    The petition stated that ``antilock brakes reduce rollovers by 
preventing truckers from steering to avoid hitting cars'' and alluded 
that this prevention of steering control caused an increase in rear end 
crashes with the ABS tractors as the striking vehicle. However, the 
agency finds that ABS prevents wheel lockup during braking so that 
steering control is maintained. Therefore, because trucks without ABS 
would not have steering control when the wheels are locked in a panic 
braking situation, the agency believes that they would be more likely 
candidates to strike leading vehicles than tractors equipped with ABS. 
The agency concludes that the petition incorrectly stated that tractor-
trailers equipped with ABS do not have steering control; in fact they 
have improved steering control compared to tractor-trailers without 
ABS. We note, however, that if the ABS is not maintained in proper 
working order, it would not provide the improved steering control as 
designed. That is one reason that a crash data analysis on the basis of 
year of vehicle manufacture contains some uncertainty regarding the 
effectiveness of ABS, as was noted in the report.
    The petition stated that drivers operating in rural areas should 
disable their ABS, while drivers operating in urban areas should not. 
The agency does not believe that it is valid to apply the subgroup 
results from the data analysis in reaching conclusions about whether 
ABS should be disabled on roads because of their locality. ABS operates 
identically on either type of road. There is no technical justification 
included in the petition explaining how disabling the ABS would reduce 
crashes, other than the concept that more highly skilled drivers would 
be required to be hired to drive trucks. The agency believes that 
disabling the ABS on heavy vehicles would result in an increase in 
crashes, based upon the overall results of the ABS effectiveness study. 
The only technical justification that the agency is aware of for 
disabling ABS to increase braking performance is to increase wheel 
lockup on loose surface roads under severe, off-road conditions. We 
note that this has already been addressed by vehicle manufacturers 
without the need to completely disable the ABS.
    The petition stated that the agency's study was unable to explain 
the 21 percent increase in single vehicle trucker fatalities observed 
in 1997 when ABS was mandated, and speculated that this was not 
directly caused by ABS itself, but due to an unintended side effect of 
hiring less qualified drivers since ABS reduces the cost of tire damage 
from lockup of the truck's wheels during panic stops. The agency has 
not previously analyzed this yearly increase in truck occupant 
fatalities, and this issue was not investigated in the agency's ABS 
effectiveness study. However, we have reviewed the data and reached the 
following conclusions. Table 10, Vehicle Occupants Killed in Large 
Truck Crashes by Vehicle Type, 1975-2008, of the Federal Motor Carrier 
Safety Administration report Large Truck and Bus Crash Facts 2008,\15\ 
does indicate that total truck occupant fatalities in single-vehicle 
truck crashes increased from 412 in 1996 to 499 in 1997. The agency 
attributes this mainly due to year-to-year variability in the data (and 
to a lesser extent, a five percent increase in truck miles travelled 
from 1996 to 1997 \16\), and does not believe it has any direct or 
indirect relationship to ABS. The overall trend for truck occupant 
fatalities (considering truck occupant fatalities in both single-
vehicle and multi-vehicle fatal crashes) is a reduction from a range of 
950 to 1400 truck occupant fatalities each year in the late 1970's, to 
a range of 600 to 750 truck occupant fatalities each year in the late 
1990's. Considering that total vehicle miles travelled by trucks and 
the number of registered trucks both increased greatly over that time 
frame, the rate of truck occupant fatalities per 100 million miles of 
vehicles travelled by trucks decreased greatly (see, for example, Table 
13, Combination Truck Fatal Crash Statistics, 1975-2008, in the Large 
Truck and Bus Crash Facts 2008 report).
---------------------------------------------------------------------------

    \15\ Report No. FMCSRA-RRA-10-043, March 2010, available at: 
http://www.fmcsa.dot.gov/facts-research/LTBCF2008/Index-2008LargeTruckandBusCrashFacts.aspx.
    \16\ See Table 13: Combination Truck Fatal Crash Statistics, 
1975-2008, and Table 14: Single-Unit Truck Crash Statistics, 1975-
2008, of the FMCSA 2008 Large Truck and Bus Crash Facts report.
---------------------------------------------------------------------------

    Furthermore, the effective date of March 1, 1997 for truck tractors 
to be equipped with ABS only applied to newly-manufactured tractors, 
which would have only made up a small percentage of the total number of 
tractors on the road by the end of 1997. We do not have production 
figures for 1997 tractors but assuming that ABS-equipped tractor 
production was on the order of 100,000 units manufactured between March 
1, 1997 and December 31, 1997, they would have constituted less than 
six percent of the 1,790,000 registered combination trucks on the road 
in 1997 (plus an additional small unknown percentage of tractors also 
on the road that were already voluntarily equipped with ABS prior to 
March 1, 1997). There were few ABS-equipped tractors on the road in 
1997 so any positive (or potentially negative) safety effects of ABS 
would have been minimal during the first year of the ABS mandate for 
tractors. Thus the agency cannot attribute any ABS effects to the 
unusual increase in truck occupant fatalities that occurred in 1997.
    As to the premise in the petition that the presence of ABS on heavy 
vehicles causes less-qualified truck drivers to be retained by motor 
carriers, when those drivers would otherwise have had their employment 
terminated due to a tractor jackknife crash that could occur with a 
non-ABS equipped tractor, the agency has no data, nor did the 
petitioner provide any, to support this claim. However, we believe that 
it is unlikely that the presence of ABS on a tractor by itself causes 
less-qualified truck drivers to be hired or retained. Truck driving has 
many professional aspects including driver physical qualifications; 
commercial driver's license requirements, including an air brake 
endorsement to operate air-braked trucks; and the Federal regulations 
that govern the loading and securing of cargo, vehicle inspections and 
maintenance.
    The petition stated that the petitioner's own calculations showed 
that ABS probably saved the lives of 12 percent of truckers in 1998, 16 
percent in 1999, and 5 percent in 2000. Here again, the agency believes 
that while tractors on the road were increasingly equipped with ABS as 
new vehicles entered service after March 1, 1997, there were still many 
trucks on the road that were not ABS equipped during those years. The 
details of the petitioner's analysis were not included

[[Page 55865]]

in the petition for review so it was not possible for the agency to 
determine what assumptions were made as to how many trucks on the road 
were equipped with ABS. In summary, the petition claims that ABS 
contributed to reductions in truck occupant fatalities during three 
years (1998 through 2000) but also contributed to increases in truck 
occupant fatalities in the first year (1997). The agency study of ABS 
effectiveness did not specifically address how ABS contributed to truck 
occupant safety (due to the limited amount of available crash data it 
only reviewed overall increases and reductions in crashes), but since 
ABS prevents tractor-trailers from losing control under a variety of 
circumstances the agency believes it is likely that it has reduced 
injuries and fatalities among truck occupants.

V. Agency Decision

    The agency has reviewed the petition and is denying it. The agency 
does not plan to initiate rulemaking or other actions to consider 
removing ABS from heavy vehicles, to consider requiring an on-off 
switch for the driver to disable the ABS, or to consider requiring the 
automatic disabling of ABS at speeds greater than 55 mph. The 
petitioner has not demonstrated that a safety need exists, which would 
justify removing or disabling ABS on heavy vehicles, or to vacate FMVSS 
No. 121 or the ABS requirements contained in it. The safety-need basis 
of the petition included citations of the agency's study on the 
effectiveness of ABS on tractor-trailers, and a claim that ABS has 
allowed less-skilled truck drivers to operate trucks. However, citing a 
subgroup of FARS data where there was an increase in fatal rear-end 
crashes among ABS tractors on a particular type of roadway (i.e., high-
speed rural highways) does not prove by itself, or provide sufficient 
evidence, that a safety problem with ABS exists. We note that state 
data indicated reductions in rear-end crashes for ABS tractors in four 
states and increases in rear-end crashes for ABS tractors in three 
states. The crash data were not sufficiently detailed, or consistently 
conclusive, to present clear evidence that ABS causes an increase in 
rear-end crashes when it is installed on tractors.
    The petition cited a slight increase in overall fatal crashes among 
ABS tractors, but when those data were weighted to account for the 
effects of road type and lighting condition, the results indicated an 
overall reduction in fatal crashes. Although this result was not 
statistically significant, possibly due to the limited amount of 
available crash data, the results of the study indicated that ABS is 
effective in reducing all crashes, with quite possibly a similar effect 
on fatal crashes. Beyond these data that were cited in the petition, 
there was the claim that ABS allows incompetent truck drivers to 
operate trucks. The agency concludes that while there are variations in 
levels of experience of truck drivers, they all must meet the same 
qualifications to drive trucks. We do not believe that ABS somehow 
allows incompetent drivers to drive trucks. The agency notes that, 
since the ABS final rule was published in 1995, only one ABS 
functionality problem has been identified related to some trucks 
operating in severe, off-road conditions. This problem has been 
resolved by using a modified ABS algorithm to provide an additional 
amount of wheel lockup at very low vehicle speeds. The vehicle 
manufacturers can incorporate this feature as needed by switching to a 
modified ABS wheel slip algorithm when a front drive axle or interaxle 
locking system is engaged by the driver. The agency is not aware of any 
other functionality problems with heavy vehicle ABS that would justify 
disabling it. We conclude that the petition has not demonstrated that 
there is a safety need or other technical reason that would justify 
disabling the ABS at highway speeds under any circumstances.

    Issued: September 2, 2011.
Christopher J. Bonanti,
Associate Administrator for Rulemaking.
[FR Doc. 2011-23043 Filed 9-8-11; 8:45 am]
BILLING CODE 4910-59-P