Federal Motor Vehicle Safety Standards No. 121; Air Brake Systems, 55859-55865 [2011-23043]
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Federal Register / Vol. 76, No. 175 / Friday, September 9, 2011 / Proposed Rules
DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety
Administration
49 CFR Part 571
Federal Motor Vehicle Safety
Standards No. 121; Air Brake Systems
National Highway Traffic
Safety Administration (NHTSA), DOT.
AGENCY:
Denial of Petition for
Rulemaking.
ACTION:
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 newlymanufactured 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.
SUMMARY:
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).
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FOR FURTHER INFORMATION CONTACT:
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
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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.
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
1 Report No. DOT HS 811 339, July 2010,
available at https://www-nrd.nhtsa.dot.gov/Pubs/
811339.pdf.
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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 ABSequipped 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 newlymanufactured 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.
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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 sevenstate 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.
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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 nonsignificant 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,
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only in fatal crashes, two-vehicle rearend 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 nonABS-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 multivehicle 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.
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.
An initial analysis of the state data for
all levels of crash severity (property
damage only, or resulting in an injury or
2 See Table 2: Reduction in response group
crashes based on tractor and trailer ABS equipment,
Florida state data.
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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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 singlevehicle crashes (both on-road and offroad). 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.
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 agerestricted subset of the crash data for
overlapping tractor ages at the time of
the crash for both ABS tractors and nonABS 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 twovehicle rear end crashes with ABS
tractors as the striking vehicle.
Considering the total crash population
for the combined response and control
4 See Table 11: Reduction in response group
crashes for various crash mechanisms, summary of
seven States.
5 See Table 27: Reductions in all crash
mechanisms, age-restricted State data.
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groups, ABS tractors were associated
with overall crash reductions of
between two percent and six percent for
each state.
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 singlevehicle 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.
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 atfault vehicle. Since there were many
more multi-vehicle crashes that are in
the ‘‘other,’’ non-rear-end crash
category, the net result was a nonsignificant 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
6 See Table 15: Reduction in response group
crashes for various crash mechanisms, FARS data.
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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.
The analysis found that the type of
road locality, travel speed, and ambient
lighting condition (daylight or nondaylight) 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.
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.
10 See Table 23: Final weighted estimate of tractor
ABS effectiveness from FARS.
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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.
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 twowheel 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.
11 57
12 58
FR 24212.
FR 50738.
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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-ofcontrol 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.
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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 brakingrelated wheel lockup compared to light
vehicles. Since heavy vehicle brakes are
sized to stop the vehicle in the fullyloaded 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.
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
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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.
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 halfloaded 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
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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
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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
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ABS tractors. The agency concludes that
the evaluation does not present clear
evidence of an overall increase in rearend 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 tractortrailers 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
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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 singlevehicle 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
15 Report No. FMCSRA–RRA–10–043, March
2010, available at: https://www.fmcsa.dot.gov/factsresearch/LTBCF2008/Index2008LargeTruckandBusCrashFacts.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.
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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).
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 ABSequipped 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
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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 safetyneed 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 lessskilled 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., highspeed 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
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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
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric
Administration
50 CFR Part 660
RIN 0648–BB27
Fisheries Off West Coast States;
Notice of Availability for Secretarial
Amendment 1 to the Pacific Coast
Groundfish Fishery Management Plan
National Marine Fisheries
Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA),
Commerce.
ACTION: Availability of Secretarial
amendment to a fishery management
plan; request for comments.
AGENCY:
NMFS has prepared
Secretarial Amendment 1 to the Pacific
Coast Groundfish Fishery Management
Plan (FMP). Secretarial Amendment 1
would modify the FMP to add an
SUMMARY:
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overfished species rebuilding plan for
petrale sole and revise existing
overfished species rebuilding plans. In
addition, Secretarial Amendment 1
would modify the default proxy values
for FMSY and BMSY as they apply to the
flatfish species, including petrale sole;
and the harvest control rule policies.
Finally the amendment makes nonsubstantive changes and updates factual
information.
DATES: Comments on Secretarial
Amendment 1 must be received on or
before November 8, 2011.
ADDRESSES: You may submit comments
on this document, identified by NOAA–
NMFS 2011–0207, by any of the
following methods:
• Electronic Submission: Submit all
electronic public comments via the
Federal e-Rulemaking Portal https://
www.regulations.gov. To submit
comments via the e-Rulemaking Portal,
first click the ‘‘submit a comment’’ icon,
then enter NOAA–NMFS 2011–0207 in
the keyword search. Locate the
document you wish to comment on
from the resulting list and click on the
‘‘Submit a Comment’’ icon on the right
of that line.
• Mail: William W. Stelle, Jr.,
Regional Administrator, Northwest
Region, NMFS, 7600 Sand Point Way
NE., Seattle, WA 98115–0070, Attn:
Sarah Williams.
• Fax: 206–526–6736, Attn: Sarah
Williams.
Instructions: Comments must be
submitted by one of the above methods
to ensure that the comments are
received, documented, and considered
by NMFS. Comments sent by any other
method, to any other address or
individual, or received after the end of
the comment period, may not be
considered. All comments received are
a part of the public record and will
generally be posted for public viewing
on https://www.regulations.gov without
change. All personal identifying
information (e.g., name, address, etc.)
submitted voluntarily by the sender will
be publicly accessible. Do not submit
confidential business information, or
otherwise sensitive or protected
information. NMFS will accept
anonymous comments (enter ‘‘N/A’’ in
the required fields if you wish to remain
anonymous). Attachments to electronic
comments will be accepted in Microsoft
Word or Excel, WordPerfect, or Adobe
PDF file formats only.
FOR FURTHER INFORMATION CONTACT:
Sarah Williams (Northwest Region,
NMFS), phone: 206–526–4646; fax:
206–526–6736; and e-mail:
sarah.williams@noaa.gov.
SUPPLEMENTARY INFORMATION:
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[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.
-----------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\1\ Report No. DOT HS 811 339, July 2010, available at https://www-nrd.nhtsa.dot.gov/Pubs/811339.pdf.
---------------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\2\ See Table 2: Reduction in response group crashes based on
tractor and trailer ABS equipment, Florida state data.
---------------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\3\ See Table 4: Reduction in response group crashes on wet
roads based on tractor and trailer ABS equipment, Florida state
data.
---------------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\4\ See Table 11: Reduction in response group crashes for
various crash mechanisms, summary of seven States.
---------------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\5\ See Table 27: Reductions in all crash mechanisms, age-
restricted State data.
---------------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\6\ See Table 15: Reduction in response group crashes for
various crash mechanisms, FARS data.
---------------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\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.
---------------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\10\ See Table 23: Final weighted estimate of tractor ABS
effectiveness from FARS.
---------------------------------------------------------------------------
[[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.
---------------------------------------------------------------------------
\11\ 57 FR 24212.
\12\ 58 FR 50738.
---------------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\13\ 60 FR 13259.
---------------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\14\ 74 FR 37122.
---------------------------------------------------------------------------
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).
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\15\ Report No. FMCSRA-RRA-10-043, March 2010, available at:
https://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.
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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