Document ID: NHTSA-2015-0056-0001
Agency: nhtsa
Document Type: Rule
Title: Federal Motor Vehicle Safety Standards: Electronic Stability Control Systems for Heavy Vehicles
Posted Date: 2015-06-23T04:00Z

[Federal Register Volume 80, Number 120 (Tuesday, June 23, 2015)]
[Rules and Regulations]
[Pages 36049-36110]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-14127]

[[Page 36049]]

Vol. 80

Tuesday,

No. 120

June 23, 2015

Part II

Department of Transportation

-----------------------------------------------------------------------

National Highway Traffic Safety Administration

-----------------------------------------------------------------------

49 CFR Part 571

Federal Motor Vehicle Safety Standards; Electronic Stability Control 
Systems for Heavy Vehicles; Final Rule

  Federal Register / Vol. 80 , No. 120 / Tuesday, June 23, 2015 / Rules 
and Regulations  

[[Page 36050]]

-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2015-0056]
RIN 2127-AK97

Federal Motor Vehicle Safety Standards; Electronic Stability 
Control Systems for Heavy Vehicles

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

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This document establishes a new Federal Motor Vehicle Safety 
Standard No. 136 to require electronic stability control (ESC) systems 
on truck tractors and certain buses with a gross vehicle weight rating 
of greater than 11,793 kilograms (26,000 pounds). ESC systems in truck 
tractors and large buses are designed to reduce untripped rollovers and 
mitigate severe understeer or oversteer conditions that lead to loss of 
control by using automatic computer-controlled braking and reducing 
engine torque output.
    In 2018, we expect that, without this rule, about 34 percent of new 
truck tractors and 80 percent of new buses affected by this final rule 
would be equipped with ESC systems. We believe that, by requiring that 
ESC systems be installed on the rest of truck tractors and large buses, 
this final rule will prevent 40 to 56 percent of untripped rollover 
crashes and 14 percent of loss-of-control crashes. As a result, we 
expect that this final rule will prevent 1,424 to 1,759 crashes, 505 to 
649 injuries, and 40 to 49 fatalities at $0.1 to $0.6 million net cost 
per equivalent life saved, while generating positive net benefits.

DATES: The effective date of this rule is August 24, 2015. The 
incorporation by reference of certain publications listed in the rule 
is approved by the Director of the Federal Register as of August 24, 
2015.
    Petitions for reconsideration: Petitions for reconsideration of 
this final rule must be received not later than August 7, 2015.

ADDRESSES: Petitions for reconsideration of this final rule must refer 
to the docket and notice number set forth above and be submitted to the 
Administrator, National Highway Traffic Safety Administration, 1200 New 
Jersey Avenue SE., Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: For technical issues, you may contact 
Patrick Hallan, Office of Crash Avoidance Standards, by telephone at 
(202) 366-9146, and by fax at (202) 493-2990. For legal issues, you may 
contact David Jasinski, Office of the Chief Counsel, by telephone at 
(202) 366-2992, and by fax at (202) 366-3820. You may send mail to both 
of these officials at the National Highway Traffic Safety 
Administration, 1200 New Jersey Avenue SE., Washington, DC 20590.

SUPPLEMENTARY INFORMATION: 

Table of Contents

I. Executive Summary
II. Statutory Authority
III. Background
IV. Safety Need
    A. Heavy Vehicle Crash Problem
    B. Contributing Factors in Rollover and Loss-of-Control Crashes
    C. NTSB Safety Recommendations
    D. Motorcoach Safety Plan
    E. International Regulation
V. Summary of the May 2012 NPRM
VI. Overview of the Comments
VII. Key Differences Between the Final Rule and the NRPM
VIII. ESC Requirement
    A. Whether To Require Stability Control
    B. Whether To Require ESC or RSC
    C. Definition of ESC
    D. Technical Documentation
IX. Vehicle Applicability and Phase-In
    A. Trucks
    1. Summary of the NPRM
    2. Exclusions From ESC Requirement
    3. Single-Unit Trucks
    4. Compliance Dates
    B. Buses
    1. Summary of the NPRM
    2. Buses Built on Truck Chassis
    (a) Summary of NPRM
    (b) Summary of Comments
    (c) NHTSA's Response to Comments
    3. Hydraulic-Braked Buses
    4. School Buses
    5. Transit Buses
    6. Minimum Seating Capacity and Seating Configuration
    7. Compliance Dates
    8. Class 3 Through 6 Buses
    C. Retrofitting
X. Performance Testing
    A. NHTSA's Proposed Performance Tests
    1. Characterization Test--SIS
    2. Roll and Yaw Stability Test--SWD
    3. Lateral Displacement
    B. Comments on SIS and SWD Maneuvers
    C. Alternative Maneuvers Considered in the NPRM
    D. Comments on Alternative Test Maneuvers
    E. NHTSA Examination and Testing of EMA Maneuvers
    F. Roll Stability Performance Test--J-Turn Test
    1. Rationale for Using J-Turn Test
    2. Test Procedure and Performance Requirements
    3. System Responsiveness
    4. Engine Torque Reduction
    5. Roll Stability Performance Requirements
    G. Yaw Stability
    H. Understeer
XI. Test Conditions and Equipment
    A. Outriggers
    B. Automated Steering Machine
    C. Anti-Jackknife System
    D. Control Trailer
    E. Sensors
    F. Ambient Conditions
    G. Road Test Surface
    H. Vehicle Test Weight
    I. Tires
    J. Mass Estimation Drive Cycle
    K. Brake Conditioning
    L. Compliance Options
    M. Data Collection
    XII. ESC Disablement
    A. Summary of Comments
    B. Response to Comments
XIII. ESC Malfunction Detection, Telltale, and Activation Indicator
    A. ESC Malfunction Detection
    B. ESC Malfunction Telltale
    C. Combining ESC Malfunction Telltale With Related Systems
    D. ESC Activation Indicator
XIV. Benefits and Costs
    A. Target Crash Population
    B. System Effectiveness
    1. Summary of the NPRM
    2. Summary of Comments and Response
    (a) ATRI Study
    (b) Bendix Study
    3. Effectiveness Estimate
    C. Benefits Estimates
    1. Safety Benefits
    2. Monetized Benefits
    D. Cost Estimate
    Truck Tractors
    Large Buses
    E. Cost Effectiveness
    F. Comparison of Regulatory Alternatives
XV. Regulatory Analyses and Notices
    A. Executive Order 12866, Executive Order 13563, and DOT 
Regulatory Policies and Procedures
    B. Regulatory Flexibility Act
    C. Executive Order 13132 (Federalism)
    D. Executive Order 12988 (Civil Justice Reform)
    E. Protection of Children From Environmental Health and Safety 
Risks
    F. Paperwork Reduction Act
    G. National Technology Transfer and Advancement Act
    H. Unfunded Mandates Reform Act
    I. National Environmental Policy Act
    J. Incorporation by Reference
    K. Regulatory Identifier Number (RIN)
    L. Privacy Act

I. Executive Summary

    This final rule establishes a new Federal Motor Vehicle Safety 
Standard (FMVSS) No. 136, Electronic Stability Control Systems for 
Heavy Vehicles, to reduce rollover and loss of directional control of 
truck tractors and large buses. The standard requires that truck 
tractors and certain large buses with a gross vehicle weight rating 
(GVWR) of greater than 11,793 kilograms (26,000 pounds) to be equipped 
with an electronic stability control (ESC) system that meets the 
equipment and performance criteria of the standard. ESC systems use 
engine torque control and computer-controlled

[[Page 36051]]

braking of individual wheels to assist the driver in maintaining 
control of the vehicle and maintaining its heading in situations in 
which the vehicle is becoming roll unstable (i.e., wheel lift 
potentially leading to rollover) or experiencing loss of control (i.e., 
deviation from driver's intended path due to understeer, oversteer, 
trailer swing or any other yaw motion leading to directional loss of 
control). In such situations, intervention by the ESC system can assist 
the driver in maintaining control of the vehicle, thereby preventing 
fatalities and injuries associated with vehicle rollover or collision.
    This final rule is made pursuant to the authority granted to NHTSA 
under the National Traffic and Motor Vehicle Safety Act (``Motor 
Vehicle Safety Act''). Under 49 U.S. C. Chapter 301, Motor Vehicle 
Safety (49 U.S. C. 30101 et se.), the Secretary of Transportation is 
responsible for prescribing motor vehicle safety standards that are 
practicable, meet the need for motor vehicle safety, and are stated in 
objective terms. The responsibility for promulgation of Federal motor 
vehicle safety standards is delegated to NHTSA. This rulemaking also 
completes NHTSA's rulemaking pursuant to a directive in the Moving 
Ahead for Progress in the 21st Century Act (MAP-21) that the Secretary 
consider requiring stability enhancing technology on motorcoaches.\1\
---------------------------------------------------------------------------

    \1\ Pub. L. 112-141 (July 6, 2012).
---------------------------------------------------------------------------

    There have been two types of stability control systems developed 
for heavy vehicles. A roll stability control (RSC) system is designed 
to prevent rollover by decelerating the vehicle using braking and 
engine torque control. The other type of stability control system is 
ESC, which includes all of the functions of an RSC system plus the 
ability to mitigate severe oversteer or understeer conditions by 
automatically applying brake force at selected wheel-ends to help 
maintain directional control of a vehicle. To date, ESC and RSC systems 
for heavy vehicles have been developed for air-braked vehicles. Truck 
tractors and buses covered by today's final rule make up a large 
proportion of air-braked heavy vehicles and a large proportion of the 
heavy vehicles involved in both rollover crashes and total heavy 
vehicle crashes.
    As a result of the data analysis research, we determined that ESC 
systems can be 40 to 56 percent effective in reducing first-event 
untripped rollovers and 14 percent effective in eliminating loss-of-
control crashes caused by severe oversteer or understeer conditions. 
This estimate is based on an update of the estimate presented in a 2011 
research note analyzing the effectiveness of ESC systems discussed in 
the Final Regulatory Impact Analysis (FRIA) accompanying this final 
rule.\2\
---------------------------------------------------------------------------

    \2\ See Wang, Jing-Shiam, ``Effectiveness of Stability Control 
Systems for Truck Tractors'' (January 2011) (DOT HS 811 437); Docket 
No. NHTSA-2010-0034-0043.
---------------------------------------------------------------------------

    The agency considered requiring truck tractors and large buses to 
be equipped with RSC systems. When compared to the ESC requirement in 
this final rule, RSC systems would cost less than ESC systems, be 
slightly more cost-effective, but would produce net benefits that are 
much lower than the net benefits from this final rule. This is because 
RSC systems are less effective at preventing rollover crashes and much 
less effective at preventing loss-of-control crashes. We also 
considered requiring trailers to be equipped with RSC systems. However, 
this alternative would save many fewer lives, would not be cost-
effective, and would not result in net benefits.
    This final rule requires ESC systems to meet both definitional 
criteria and performance requirements. It is necessary to include 
definitional criteria and require compliance with them because 
developing separate performance tests to cover the wide array of 
possible operating ranges, roadways, and environmental conditions would 
be impractical. The definitional criteria are consistent with those 
recommended by SAE International and used by the United Nations (UN) 
Economic Commission for Europe (ECE), and similar to the definition of 
ESC in FMVSS No. 126, the agency's stability control standard for light 
vehicles. This definition describes an ESC system for heavy vehicles as 
one that will enhance both the roll and yaw stability of a vehicle 
using a computer-controlled system that can receive inputs such as the 
vehicle's lateral acceleration and yaw rate, and use the information to 
apply brakes individually, including trailer brakes, and modulate 
engine torque.
    This final rule is applicable to all new typical three-axle truck 
tractors manufactured on or after August 1, 2017. We believe that two 
years of lead time is sufficient for these vehicles to be equipped with 
ESC, given that this is a common platform for which ESC systems are 
readily available today. We are allowing four years of lead time for 
all other truck tractors. These vehicles include two-axle vehicles, 
which have been more recently required to satisfy new, reduced minimum 
stopping distance requirements, and severe-service tractors, for which 
we believe two additional years of lead time is necessary to design and 
test ESC systems.
    This final rule is applicable to buses over 14,969 kilograms 
(33,000 pounds) GVWR manufactured more than three years after the date 
of this final rule. Although we proposed a two-year lead time for buses 
in the NPRM, the Motorcoach Enhanced Safety Act mandates that new 
rules, including stability enhancing technology, be applicable to all 
buses manufactured more than three years after publication of a final 
rule. However, for buses with a GVWR greater than 11,793 kilograms 
(26,000 pounds) but not more than 14,969 kilograms (33,000 pounds), we 
believe that three years of lead time is not feasible. Some of these 
buses include vehicles with body-on-frame construction and hydraulic 
brakes, for which ESC system availability is not as widespread. 
Therefore, we are allowing four years of lead time for buses with a 
GVWR greater than 11,793 kilograms (26,000 pounds) but not more than 
14,969 kilograms (33,000 pounds). We believe that including buses with 
body-on-frame construction and hydraulic brakes in this final rule will 
spur development of ESC systems for other hydraulic-braked vehicles, 
including vehicles with a GVWR of greater than 4,536 kilograms (10,000 
pounds) but not more than 11,793 kilograms (26,000 pounds), which are 
not covered by this rulemaking.
    We have chosen an alternative performance test to demonstrate an 
ESC system's ability to mitigate roll instability to what was proposed. 
After considering the public comments and conducting additional track 
testing, we have determined that a 150-foot-radius J-turn test maneuver 
is an efficient means to ensure vehicles maintain roll stability. Like 
the test maneuver in the NPRM, the J-turn test maneuver is among those 
available to manufacturers to demonstrate compliance with the UNECE 
mandate for ESC on trucks and buses.
    The J-turn test maneuver, based on an alternative test discussed in 
the NPRM, involves accelerating to a constant speed on a straight 
stretch of high-friction track before entering into a 150-foot radius 
curve. After entering the curve, the driver attempts to maintain the 
lane. At a speed that is at up to 1.3 times the speed at which the ESC 
system activates, but in no case below 48.3 km/h (30 mph), an ESC 
system must activate the vehicle's service brakes to slow the vehicle's 
speed to 46.7 km/h (29 mph) within 3 seconds

[[Page 36052]]

after entering the curve and 45.1 km/h (28 mph) within 4 seconds after 
entering the curve. Additional J-turn tests are conducted to ensure 
that an ESC system is able to reduce engine torque.
    The performance metric for the J-turn (reduction in forward speed) 
is easy to obtain and serves as a proxy for absolute lateral 
acceleration. Lateral acceleration on a fixed-radius curve is a 
function of forward velocity. On a 150-foot radius curve, a forward 
speed of 48.3 km/h (30 mph) corresponds to a lateral acceleration of 
approximately 0.4g. Based on prior NHTSA testing, we have found that 
0.4g represents the margin of lateral stability on a typical fully 
loaded truck tractor with the loads having a high center of gravity 
(CG). That is, lateral acceleration levels greater than 0.4g (or 
forward speeds on a 150-foot radius curve of greater than 48.3 km/h (30 
mph)) on a typical truck tractor are likely to lead to lateral 
instability, wheel lift, and possible rollover. However, lateral 
acceleration levels less than 0.4g (or forward speeds on a 150-foot 
radius curve of less than 48.3 km/h (30 mph)) on a typical truck 
tractor are unlikely to lead to lateral instability, wheel lift, and 
rollover.
    This final rule includes a requirement proposed in the NPRM that an 
ESC system be able to mitigate yaw instability. This requirement is 
similar to one proposed in the NPRM, and adopted in this final rule, 
requiring an ESC system be able to mitigate understeer. However, this 
final rule does not include any performance test to evaluate the 
ability of an ESC system to mitigate yaw instability. Although the NPRM 
included the sine with dwell (SWD) maneuver to test both roll and yaw 
instability, we have decided not to include it in this final rule. The 
SWD maneuver is only a partial test of the ability to mitigate yaw 
instability. It tests an ESC system's ability to mitigate loss of 
control resulting from oversteer conditions, but not its ability to 
mitigate understeer, which is the most common loss-of-control scenario 
for heavy vehicles. NHTSA has been unable to develop a test for 
understeer mitigation. As argued by many commenters, performing the SWD 
maneuver entails substantial time and instrumentation burdens. We do 
not believe that this additional time and cost is justified solely to 
test an ESC system's ability to mitigate yaw instability caused by 
oversteer conditions when a majority of the benefits of this final rule 
are derived from rollover prevention and the majority of benefits 
attributed to prevented loss-of-control crashes in heavy vehicles are 
derived from understeer mitigation, which would not have been tested in 
the SWD maneuver. However, we are continuing to examine possible yaw 
performance maneuvers, including the SWD maneuver, to test yaw 
stability performance in the future.
    The decision to adopt the J-turn test maneuver as the performance 
test in this final rule has caused us to reconsider test conditions and 
equipment. However, many aspects of testing remain identical to the 
proposal. For example, we will conduct performance testing on a high-
friction surface. We believe that the potential for variance in surface 
friction on a low-friction surface may introduce variabilities in ESC 
testing that may lead to inconsistent results. We are still equipping 
all test vehicles with outriggers and truck tractors with anti-
jackknife systems for the safety of test drivers.
    On the other hand, many proposed aspects of testing had to be 
modified to accommodate the J-turn test maneuver. Because the J-turn 
test maneuver is a path-following maneuver, we are not using a steering 
wheel controller that was proposed in the NPRM. We noted potential 
variabilities in the proposed specification for the control trailer. 
However, because the performance metric for the J-turn test maneuver is 
different than the proposed SWD requirements, those variabilities 
identified in the NPRM that were related to the SWD maneuver are no 
longer relevant. We have modified the loading condition to load the 
vehicle to its GVWR because that is the most severe test condition with 
the J-turn test maneuver. Finally, the number of sensors used in 
testing is substantially reduced because the vehicle's actual lateral 
acceleration throughout the maneuver does not need to be measured.
    We have considered comments on the issue of allowing ESC system 
disablement. This final rule does not allow the driver to disable the 
ESC system at speeds higher than 20 km/h (12.4 mph), which we have 
defined as the minimum speed at which an ESC system must operate. Many 
of the comments we received arguing in favor of allowing ESC system 
disablement were, in fact, arguing for disablement of traction control 
to allow a vehicle to start moving on certain surfaces with low 
friction such as on snow, ice, or off-road conditions. However, we do 
not believe that an ESC system would prevent a heavy vehicle from 
moving in these circumstances. Rather, we believe that manufacturers 
may wish to disable an automatic traction control system to allow the 
vehicle to move. NHTSA does not require traction control systems, nor 
does NHTSA prohibit the installation of an on/off switch for a traction 
control system. We understand that traction control systems are related 
to ESC systems in that they can control engine torque output and 
activate the brakes on individual wheel ends. However, we do not find 
these arguments to be a compelling reason to allow an ESC system 
deactivation switch or automatic deactivation of ESC systems at speeds 
above 20 km/h (12.4 mph).
    This final rule requires that an ESC system be able to detect a 
malfunction and provide a driver with notification of a malfunction by 
means of a telltale. This requirement is similar to the malfunction 
detection and telltale requirements for light vehicles in FMVSS No. 
126. After considering public comments, we have changed the vehicle 
depicted on the telltale to better represent the profile of a 
combination vehicle or bus rather than a passenger car.
    Based on the agency's effectiveness estimates, this final rule will 
prevent 1,424 to 1,759 crashes per year resulting in 505 to 649 
injuries and 40 to 49 fatalities. This final rule will also result in 
significant monetary savings as a result of the prevention of property 
damage and travel delays.
    Without this final rule, we project that, in 2018, manufacturers 
would have equipped 33.9 percent of truck tractors with ESC systems, 
21.3 percent of truck tractors would be equipped with RSC systems, and 
80.0 percent of large buses would be equipped with ESC systems. Based 
on the agency's cost teardown study, the average ESC system cost is 
estimated to be $585 for truck tractors and $269 for large buses. The 
incremental cost of installing an ESC system in place of an RSC system 
on a truck tractor is estimated to be $194. Based upon the agency's 
estimate that 150,000 truck tractors and 2,200 buses covered by this 
final rule will be manufactured annually, the agency estimates the 
total technology cost of this final rule to be approximately $45.6 
million.
    This final rule is highly cost effective and beneficial. The net 
benefits of this final rule are estimated to range from $412 to $525 
million at the 3 percent discount rate and $312 to $401 million at the 
7 percent discount rate. The agency estimates that this rule will 
result in societal economic savings resulting from preventing crashes, 
reducing congestion, and preventing property damage, such that the net 
cost of this final rule range from $3.6 to $12.3 million at a 3 percent 
discount rate and from $12.3 to $19.2 million at 7 percent discount 
rate. As a result, the net cost per equivalent life saved ranges

[[Page 36053]]

from $0.1 to $0.3 million at the 3 percent discount rate and from $0.3 
to $0.6 million at the 7 percent discount rate. The costs and benefits 
of this rule are summarized in Table 1.

                                      Table 1--Estimated Annual Cost, Benefits, and Net Benefits of the Final Rule
                                                              [In millions of 2013 dollars]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                             Societal                          Total         Cost per
                                                           Vehicle costs     economic       VSL savings      monetized      equivalent     Net benefits
                                                                              savings                         savings       live saved
--------------------------------------------------------------------------------------------------------------------------------------------------------
At 3% Discount..........................................           $45.6     $33.3-$42.1       $424-$528       $458-$571       $0.1-$0.3       $412-$525
At 7% Discount..........................................            45.6       26.4-33.3         332-413         358-446         0.3-$.6         312-401
--------------------------------------------------------------------------------------------------------------------------------------------------------

II. Statutory Authority

    NHTSA is issuing this final rule under the National Traffic and 
Motor Vehicle Safety Act (``Motor Vehicle Safety Act''). Under 49 
U.S.C. Chapter 301, Motor Vehicle Safety (49 U.S.C. 30101 et seq.), the 
Secretary of Transportation is responsible for prescribing motor 
vehicle safety standards that are practicable, meet the need for motor 
vehicle safety, and are stated in objective terms. ``Motor vehicle 
safety'' is defined in the Motor Vehicle Safety Act as ``the 
performance of a motor vehicle or motor vehicle equipment in a way that 
protects the public against unreasonable risk of accidents occurring 
because of the design, construction, or performance of a motor vehicle, 
and against unreasonable risk of death or injury in an accident, and 
includes nonoperational safety of a motor vehicle.'' ``Motor vehicle 
safety standard'' means a minimum performance standard for motor 
vehicles or motor vehicle equipment. When prescribing such standards, 
the Secretary must consider all relevant, available motor vehicle 
safety information. The Secretary must also consider whether a standard 
is reasonable, practicable, and appropriate for the types of motor 
vehicles or motor vehicle equipment for which it is prescribed and the 
extent to which the standard will further the statutory purpose of 
reducing traffic accidents and associated deaths. The responsibility 
for promulgation of Federal motor vehicle safety standards is delegated 
to NHTSA.
    On July 6, 2012, President Obama signed MAP-21, which incorporated 
in Subtitle G the ``Motorcoach Enhanced Safety Act of 2012.'' Section 
32703(b)(3) of the Act states that, not later than two years after the 
date of enactment of the Act, the Secretary shall consider requiring 
motorcoaches to be equipped with stability enhancing technology, such 
as electronic stability control and torque vectoring, to reduce the 
number and frequency of rollover crashes of motorcoaches. The Secretary 
was directed to prescribe regulations that address stability enhancing 
technology if the Secretary determines that such standards meet the 
requirements and considerations set forth in subsections (a) and (b) of 
49 U.S.C. 30111. These requirements are discussed in the preceding 
paragraph.
    The Motorcoach Enhanced Safety Act directs the Secretary to 
consider various other motorcoach rulemakings, in provided timeframes, 
related to safety belts,\3\ improved roof support standards, advanced 
glazing standards and other portal improvements to prevent partial and 
complete ejection of motorcoach passengers, tire pressure monitoring 
systems, and tire performance standards. The Act also includes 
provisions on fire research, interior impact protection, enhanced 
seating designs, and collision avoidance systems, and the consideration 
of rulemaking based on such research. There also are provisions in the 
Motorcoach Enhanced Safety Act relating to improved oversight of 
motorcoach service providers, including enhancements to driver 
licensing and training programs and motorcoach inspection programs.
---------------------------------------------------------------------------

    \3\ Pursuant to the Motor Vehicle Safety Act and the Motorcoach 
Enhanced Safety Act, NHTSA published a final rule requiring lap/
shoulder seat belts for each passenger seating position on all new 
over-the-road buses, and in new buses other than over-the-road buses 
with a GVWR greater than 11,793 kilograms (26,000 pounds) beginning 
on November 26, 2016. 78 FR 70415 (Nov. 25, 2013).
---------------------------------------------------------------------------

    In section 32702, ``Definitions,'' of the Motorcoach Enhanced 
Safety Act, the Act states at section 32702(6) that ``the term 
`motorcoach' has the meaning given the term `over-the-road bus' in 
section 3038(a)(3) of the Transportation Equity Act for the 21st 
Century (TEA-21) (49 U.S.C. 5310 note), but does not include a bus used 
in public transportation provided by, or on behalf of, a public 
transportation agency; or a school bus, including a multifunction 
school activity bus.'' Section 3038(a)(3) states: ``The term `over-the-
road bus' means a bus characterized by an elevated passenger deck 
located over a baggage compartment.''
    Under section 32703(e)(1) of the Motorcoach Enhanced Safety Act, 
any regulation prescribed in accordance with section 32703(b) (and 
several other subsections) shall apply to all motorcoaches manufactured 
more than three years after the date on which the regulation is 
published as a final rule, take into account the impact to seating 
capacity of changes to size and weight of motorcoaches and the ability 
to comply with State and Federal size and weight requirements, and be 
based on the best available science.
    Prior to enactment of the Motorcoach Enhanced Safety Act, the 
agency's May 23, 2012 NPRM proposed requiring truck tractors and large 
buses with a GVWR of greater than 11,793 kg (26,000 lb.) to be equipped 
with stability enhancing technology. Thus, the agency had already 
considered requiring motorcoaches to have stability enhancing 
technology, and had proposed requiring the same, prior to the enactment 
of the Motorcoach Enhanced Safety Act.
    The agency does not interpret the Motorcoach Enhanced Safety Act on 
its own as a mandate to require stability enhancing technology on over-
the-road buses. With respect to rollover crash avoidance, section 
32703(b)(3) of the Motorcoach Enhanced Safety Act directs the agency to 
``consider requiring'' stability enhancing technology such as 
electronic stability control or torque vectoring on over-the-road 
buses. However, the agency was also directed in section 32703(b) to 
prescribe a regulation if the Secretary determines that such standards 
meet the requirements and considerations for issuing a motor vehicle 
safety standard under the Motor Vehicle Safety Act. The Motorcoach 
Enhanced Safety Act does not provide independent statutory authority to 
require stability enhancing technologies on over-the-road buses.\4\

[[Page 36054]]

Thus, any mandate requiring stability enhancing technology pursuant to 
the Motorcoach Enhanced Safety Act is dependent on satisfying the 
considerations and requirements of the Motor Vehicle Safety Act.
---------------------------------------------------------------------------

    \4\ In contrast, the Motorcoach Enhanced Safety Act specifically 
mandated that the agency prescribe regulations requiring safety 
belts to be installed at each designated seating position on all 
over-the-road buses.
---------------------------------------------------------------------------

    In issuing this final rule, we took into account the considerations 
of section 32703(e)(1) of the Motorcoach Enhanced Safety Act regarding 
the implementation of regulations prescribed in accordance with 
subsection (b)(3). Unlike subsection (b)(3), subsection (e)(1) does not 
use permissive language. Because this final rule is issued in 
accordance with subsection (b)(3), we believe the considerations 
regarding the application of regulations in subsection (e)(1) must be 
addressed in this rulemaking. Nonetheless, because the Motorcoach 
Enhanced Safety Act contains no independent statutory authority in 
support of a mandate for stability enhancing technology, the 
considerations in subsection (e)(1) are constrained by the agency's 
authority to issue standards under the Motor Vehicle Safety Act. 
Therefore, where the considerations in subsection (e)(1) conflict with 
any requirements and considerations set forth in subsections (a) and 
(b) of 49 U.S.C. 30111, the requirements of the Motor Vehicle Safety 
Act supersede the Motorcoach Enhanced Safety Act.\5\
---------------------------------------------------------------------------

    \5\ See section IX.B below for such a finding with respect to 
the application of this final rule to buses with a GVWR of 14,969 
kilograms (33,000 pounds) or less.
---------------------------------------------------------------------------

    This final rule is practicable, meets a need for motor vehicle 
safety, and is stated in objective terms. With respect to the 
considerations of the Motorcoach Enhanced Safety Act, we believe that 
Congress intended that a final rule based on the 2012 NPRM would 
complete the rulemaking proceeding specified in section 32703(b)(3) of 
the Act. Electronic stability control will reduce the number and 
frequency of rollover crashes of motorcoaches. This rulemaking is based 
on the best available science. Further, we have considered the impact 
to seating capacity and changes to size and weight of motorcoaches, and 
we believe that this rule will have no effect on these considerations. 
ESC systems will add less than 10 pounds of additional weight to over-
the-road buses.\6\
---------------------------------------------------------------------------

    \6\ ``Report: Cost and Weight Analysis of Electronic Stability 
Control (ESC) and Roll Stability Control for Heavy Trucks,'' Docket 
No. NHTSA-2011-0066-0034.
---------------------------------------------------------------------------

    Although the Motorcoach Enhanced Safety Act also suggested torque 
vectoring as a possible technology to consider requiring on 
motorcoaches, we did not propose requiring torque vectoring in the May 
2012 NPRM, and it is beyond the scope of this rulemaking proceeding. 
Even if it was within scope to require torque vectoring, the agency 
would not do so in this rulemaking. The agency's understanding of 
torque vectoring is that it is a technology that allows a vehicle's 
differential or brakes to vary the power supplied to the drive axle 
wheel end. In contrast, ESC systems activate the vehicle's service 
brakes to vary the braking on each wheel end combined with the ability 
to reduce engine torque (which reduces power on drive axle wheel ends). 
In the May 2012 NPRM, we noted that, all things being equal, a vehicle 
entering a curve at a higher speed is more likely to roll over than a 
vehicle entering a curve at a lower speed.\7\ Once a vehicle is about 
to enter a curve at a high enough speed that would generate sufficient 
lateral acceleration to cause a possible rollover, the most effective 
manner to vary the individual wheel speeds in an attempt to prevent the 
rollover is primarily through the activation of a vehicle's service 
brakes along with the decrease in engine power and the use of engine 
braking. Torque vectoring systems that are differential-based would not 
provide adequate braking power and would be less effective than ESC at 
slowing a vehicle down to allow it to maneuver a curve without rolling 
over. Likewise, brake-based torque vectoring systems would be less 
effective than ESC for braking in a curve. In brake-based systems, the 
inside wheels are braked during cornering in order to prevent any loss 
of traction, which could result because there is less weight on those 
wheel during cornering. ESC provides braking to both the inside and 
outside wheels of the vehicle resulting in better brake performance.
---------------------------------------------------------------------------

    \7\ 77 FR 30771.
---------------------------------------------------------------------------

III. Background

    In the NPRM, we provided a detailed explanation of how rollovers 
occur, how stability control technologies such as roll stability 
control and electronic stability control function and reduce rollover, 
examples of situations in which stability control systems may not be 
effective, and the differences between stability enhancing technology 
on light vehicles and heavy vehicles.\8\ This section is a summary of 
that information.
---------------------------------------------------------------------------

    \8\ 77 FR 30771-74.
---------------------------------------------------------------------------

    A turning maneuver initiated by the driver's steering input results 
in a vehicle response that can be broken down into two phases. As the 
steering wheel is turned, the displacement of the front wheels 
generates a slip angle at the front wheels and a lateral force is 
generated. That lateral force leads to vehicle rotation, and the 
vehicle starts rotating about its center of gravity. Then, the 
vehicle's yaw causes the rear wheels to experience a slip angle. That 
causes a lateral force to be generated at the rear tires, which causes 
vehicle rotation. All of these actions establish a steady-state turn in 
which lateral acceleration and yaw rate are constant. In combination 
vehicles, which typically consist of a tractor towing a trailer, an 
additional phase is the turning response of the trailer, which is 
similar to, but slightly delayed, when compared to the turning response 
of the tractor.
    If the lateral forces generated at either the front or the rear 
wheels exceed the friction limits between the road surface and the 
tires, the result will be a vehicle loss-of-control in the form of 
severe understeer (loss of traction at the steer tires) or severe 
oversteer (loss of traction at the rear tires). In a combination 
vehicle, a loss of traction at the trailer wheels would result in the 
trailer swinging out of its intended path. Conversely, rollover 
conditions occur on a vehicle when high lateral forces are generated at 
the tires from steering or sliding and result in a vehicle lateral 
acceleration that exceeds the rollover threshold of the vehicle.
    High lateral acceleration is one of the primary causes of 
rollovers. Figure 1 depicts a simplified untripped rollover condition. 
As shown, when the lateral force (i.e., lateral acceleration) is 
sufficiently large and exceeds the roll stability threshold of the 
tractor-trailer combination vehicle, the vehicle will roll over. Many 
factors related to the drivers' maneuvers, heavy vehicle loading 
conditions, vehicle handling characteristics, roadway design, and road 
surface properties would result in various lateral accelerations and 
influences on the rollover propensity of a vehicle. For example, given 
other factors are equal, a vehicle entering a curve at a higher speed 
has a higher lateral acceleration and, as a result, is more likely to 
roll than a vehicle entering the curve at a lower speed. Also, 
transporting a high-CG load would increase the rollover probability 
more than transporting a relatively lower CG load.

[[Page 36055]]

[GRAPHIC] [TIFF OMITTED] TR23JN15.008

    Stability control technologies help a driver maintain directional 
control and help to reduce roll instability. Two types of heavy vehicle 
stability control technologies have been developed. One such technology 
is roll stability control or RSC. RSC systems are available for truck 
tractors and for trailers. A tractor-based RSC system consists of an 
electronic control unit (ECU) that is mounted on a vehicle and 
continually monitors the vehicle's speed and lateral acceleration based 
on an accelerometer, and estimates vehicle mass based on engine torque 
information.\9\ The ECU continuously estimates the roll stability 
threshold of a vehicle, which is the lateral acceleration above which a 
combination vehicle will roll over. When the vehicle's lateral 
acceleration approaches the roll stability threshold, the RSC system 
intervenes. Depending on how quickly the vehicle is approaching the 
estimated rollover threshold, the RSC system intervenes by one or more 
of the following actions: Decreasing engine power, using engine 
braking, applying the tractor's drive-axle brakes, or applying the 
trailer's brakes. When RSC systems apply the trailer's brakes, they use 
a pulse modulation protocol to prevent wheel lockup because tractor 
stability control systems cannot currently detect whether or not the 
trailer is equipped with ABS.
---------------------------------------------------------------------------

    \9\ RSC systems are not presently available for large buses.
---------------------------------------------------------------------------

    An RSC system can reduce rollovers, but is not designed to help to 
maintain directional control of a truck tractor. Nevertheless, RSC 
systems may provide some additional ability to maintain directional 
control in some scenarios, such as in a low-center-of-gravity scenario, 
where an increase in a lateral acceleration may lead to yaw instability 
rather than roll instability.
    In comparison, a trailer-based RSC system has an ECU mounted on the 
trailer, which typically monitors the trailer's wheel speeds, the 
trailer's suspension to estimate the trailer's loading condition, and 
the trailer's lateral acceleration. A trailer-based RSC system works 
similarly to a tractor-based system. However, a trailer-based RSC 
system can only apply the trailer brakes to slow a combination vehicle, 
whereas a tractor-based RSC system can apply brakes on both the tractor 
and trailer.
    The other type of stability control systems available for truck 
tractors and large buses is an ESC system. An ESC system incorporates 
all of the inputs of an RSC system. However, it also has two additional 
sensors to monitor a vehicle for loss of directional control, which may 
result due to either understeer or oversteer. The first additional 
sensor is a steering wheel angle sensor, which senses the driver's 
steering input.10 11 The other is a yaw rate sensor, which 
measures the actual turning movement of the vehicle. These system 
inputs are monitored by the system's ECU, which estimates when the 
vehicle's directional response begins to deviate from the driver's 
steering command, either by oversteer or understeer. An ESC system 
intervenes to restore directional control by taking one or more of the 
following actions: Decreasing engine power, using engine braking, 
selectively applying the brakes on the truck tractor to create a 
counter-yaw moment to turn the vehicle back to its steered direction, 
or applying the brakes on the trailer. An ESC system enhances the RSC 
functions because it has the added information from the steering wheel 
angle and yaw rate sensors, as well as more braking power because of 
its additional capability to apply the tractor's steer axle brakes.\12\
---------------------------------------------------------------------------

    \10\ Because ESC systems must monitor steering inputs from the 
tractor, ESC systems are not available for trailers.
    \11\ Some RSC systems also use a steering wheel angle sensor, 
which allows the system to identify potential roll instability 
events earlier.
    \12\ This is a design strategy to avoid the unintended 
consequences of applying the brakes on the steering axle without 
knowing where the driver is steering the vehicle.
---------------------------------------------------------------------------

    Figure 2 illustrates the oversteering and understeering conditions. 
While Figure 2 may suggest that a particular vehicle loses control due 
to either oversteer or understeer, it is quite possible that a vehicle 
could require both understeering and oversteering interventions during 
progressive phases of a complex crash avoidance maneuver such as a 
double lane change.

[[Page 36056]]

[GRAPHIC] [TIFF OMITTED] TR23JN15.009

    Understeering. The left side of Figure 2 shows a truck tractor 
whose driver has lost directional control during an attempt to drive 
around a right curve. The ESC system momentarily applies the right rear 
brake, creating a clockwise rotational force, to turn the heading of 
the vehicle back to the correct path. It will also reduce engine power 
to gently slow the vehicle and, if necessary, apply additional brakes 
(while maintaining the uneven brake force to create the necessary yaw 
moment).
    Oversteering. The right side of Figure 2 shows that the truck 
tractor whose driver has lost directional control during an attempt to 
drive around a right curve. In a vehicle equipped with ESC, the system 
immediately detects that the vehicle's heading is changing more quickly 
than appropriate for the driver's intended path (i.e., the yaw rate is 
too high). To counter the clockwise rotation of the vehicle, it 
momentarily applies the left front brake, thus creating a counter-
clockwise counter-rotational force and turning the heading of the 
vehicle back to the correct path. It will also reduce engine power to 
gently slow the vehicle and, if necessary, apply additional brakes 
(while maintaining the uneven brake force to create the necessary yaw 
moment). The ESC activation can be so subtle that the driver does not 
perceive the need for steering corrections.
    A stability control system will not prevent all rollover and loss-
of-control crashes. A stability control system has the capability to 
prevent many untripped on-road rollovers and first-event loss-of-
control events. Nevertheless, there are real-world situations in which 
stability control systems may not be as effective in avoiding a 
potential crash. Such situations include:
     Off-road maneuvers in which a vehicle departs the roadway 
and encounters a steep incline or an unpaved surface that significantly 
reduces the predictability of the vehicle's handling
     Entry speeds that are much too high for a curved roadway 
or entrance/exit ramp
     Cargo load shifts or liquid sloshing within the trailer 
during a steering maneuver
     Vehicle tripped by a curb or other roadside object or 
barrier
     Truck rollovers that are the result of collisions with 
other motor vehicles
     Inoperative antilock braking systems--the performance of 
stability control systems depends on the proper functioning of ABS
     Brakes that are out-of-adjustment or other defects or 
malfunctions in the ESC, RSC, or brake system.
     Maneuvers during tire tread separation or sudden tire 
deflation events.
    On April 6, 2007, the agency published a final rule that 
established FMVSS No. 126, Electronic Stability Control Systems, which 
requires all passenger cars, multipurpose passenger vehicles, trucks 
and buses with a GVWR of 4,536 kg (10,000 lb.) or less to be equipped 
with an electronic stability control system beginning in model year 
2012.\13\ The system must be capable of applying brake torques 
individually at all four wheels, and must comply with the performance 
criteria established for stability and responsiveness when subjected to 
the sine with dwell steering maneuver test. For light vehicles, the 
focus of the FMVSS No. 126 is on addressing yaw instability, which can 
assist the driver in preventing the vehicle from leaving the roadway, 
thereby preventing fatalities and injuries associated with crashes 
involving tripped rollover, which often occur when light vehicles run 
off the road. The standard does not include any equipment or 
performance requirements for roll stability.
---------------------------------------------------------------------------

    \13\ 72 FR 17236.
---------------------------------------------------------------------------

    The dynamics of light vehicles and heavy vehicles differ in many 
respects. First, on light vehicles, the yaw stability threshold is 
typically lower than the roll stability threshold. This means that a 
light vehicle making a crash avoidance maneuver, such as a lane change 
on a dry road, is more likely to reach its yaw stability threshold and 
lose directional control before it reaches its roll stability threshold 
and rolls over. On a heavy vehicle, however, the roll stability 
threshold is lower than the yaw stability threshold in most operating 
conditions, primarily because of its higher center-of-gravity 
height.\14\ As a result, there is a greater propensity for a heavy 
vehicle, particularly in a loaded condition, to roll during a severe 
crash avoidance maneuver or when negotiating a curve, than to become 
yaw unstable, as compared with light vehicles.
---------------------------------------------------------------------------

    \14\ One instance where a heavy vehicle's yaw stability 
threshold might be higher than its roll stability threshold is in an 
unloaded condition on a low-friction road surface.
---------------------------------------------------------------------------

    Second, a tractor-trailer combination unit is comprised of a power 
unit and one or more trailing units with one or more articulation 
points. In contrast, although a light vehicle may occasionally tow a 
trailer, a light vehicle is usually a single rigid unit. The tractor 
and the trailer have different center-of-gravity heights and different 
lateral acceleration threshold limits for rollover. A combination 
vehicle rollover frequently begins with the trailer where the rollover 
is initiated by trailer wheel lift.
    Third, due to greater length, mass, and mass moments of inertia of 
heavy vehicles, they respond more slowly to steering inputs than do 
light vehicles. The longer wheelbase of a heavy vehicle, compared with 
a light vehicle, results in a slower response time, which gives the 
stability control system the opportunity to intervene and prevent 
rollovers.
    Finally, the larger number of wheels on a heavy vehicle, as 
compared to a light vehicle, makes heavy vehicles less

[[Page 36057]]

likely to become yaw unstable on dry road surface conditions.

IV. Safety Need

A. Heavy Vehicle Crash Problem

    This section presents data on the safety problem associated with 
rollover and loss of control of heavy vehicles. The information has 
been updated from similar information contained in the NPRM. For the 
specific target population used to support the agency's system 
effectiveness and estimated benefits, see Section XIV.
    The Traffic Safety Facts 2012 reports that tractor trailer 
combination vehicles are involved in about 72 percent of the fatal 
crashes involving large trucks, annually.\15\ According to FMCSA's 
Large Truck and Bus Crash Facts 2011, these vehicles had a fatal crash 
involvement rate of 1.46 crashes per 100 million vehicle miles traveled 
during 2011, whereas single-unit trucks had a fatal crash involvement 
rate of 1.00 crashes per 100 million vehicle miles traveled.\16\ 
Combination vehicles represent about 24 percent of large trucks 
registered but travel 61 percent of the large truck miles, annually. 
Traffic tie-ups resulting from loss-of-control and rollover crashes 
also contribute to in millions of dollars of lost productivity and 
excess energy consumption each year.
---------------------------------------------------------------------------

    \15\ DOT HS 812 032, available at http://www-nrd.nhtsa.dot.gov/Pubs/812032.pdf.
    \16\ FMCSA-RRA-13-049 (Oct. 2013), available at http://www.fmcsa.dot.gov/sites/fmcsa.dot.gov/files/docs/LargeTruckandBusCrashFacts2011.pdf.
---------------------------------------------------------------------------

    According to Traffic Safety Facts 2012, the overall crash problem 
for tractor trailer combination vehicles in that year was approximately 
180,000 crashes, 42,000 of which involve injury. The overall crash 
problem for single-unit trucks is nearly as large--in 2012, there were 
approximately 154,000 crashes, 35,000 of which were injury crashes. 
However, the fatal crash involvement for truck tractors is much higher. 
In 2011, there were 2,736 fatal combination truck crashes and 1,066 
fatal single-unit truck crashes.
    The rollover crash problem for combination trucks is much greater 
than for single-unit trucks. In 2011, there were approximately 8,000 
crashes involving combination truck rollover and 5,000 crashes 
involving single-unit truck rollover. As a percentage of all crashes, 
combination trucks are involved in rollover crashes at a higher rate 
compared to single-unit trucks. Approximately 4.6 percent of all 
combination truck crashes were rollovers, but 3.2 percent of single-
unit truck crashes were rollovers. Combination trucks were involved in 
3,000 injury crashes and 373 fatal crashes, and single-unit trucks were 
involved in 3,000 injury crashes and 194 fatal crashes.
    According to FMCSA's Large Truck and Bus Crash Facts 2011, cross-
country intercity buses were involved in 39 of the 242 fatal bus 
crashes in 2011. The bus types presented in the crash data include 
school buses, cross-country intercity buses, transit buses, van-based 
buses, and other buses. From 2002 to 2011, cross-country intercity 
buses, on average, accounted for approximately 12 percent of all buses 
involved in fatal crashes, whereas transit buses and school buses 
accounted for 34 percent and 40 percent, respectively, of all buses 
involved in fatal crashes. However, most of the transit bus and school 
bus crashes are not rollover or loss-of-control crashes that ESC 
systems are capable of preventing. Fatal rollover and loss-of-control 
crashes are a subset of these crashes.
    There are many more fatalities in buses with a GVWR greater than 
11,793 kg (26,000 lb.) compared to buses with a GVWR between 4,536 kg 
and 11,793 kg (10,000 lb. and 26,000 lb.).\17\ In the 10-year period 
between 2000 and 2009, there were 42 fatalities on buses with a GVWR 
between 4,536 kg and 11,793 kg (10,000 lb. and 26,000 lb.) compared to 
209 fatalities on buses with a GVWR greater than 11,793 kg (26,000 
lb.). Among buses with a GVWR of greater than 11,793 kg (26,000 lb.), 
over 70 percent of the fatalities were cross-country intercity bus 
occupants, ``other buses,'' and ``unknown buses.'' \18\ Thus, although 
these buses are only involved in 12 percent of fatal crashes involving 
buses, they represent the majority of fatalities from bus crashes.
---------------------------------------------------------------------------

    \17\ This data was taken from the FARS database and was 
presented in the final rule requiring that seat belts be installed 
on certain buses. See 78 FR 70415, 70423-26 (Nov. 25, 2013).
    \18\ The FARS database has five bus body type categories: (1) 
Cross-country/intercity bus, (2) transit bus, (3) school bus, (4) 
other bus, and (5) unknown bus. Transit bus and school bus body 
types were excluded from the analysis because they are easily 
recognized and categorized as such by crash investigators and those 
coding the FARS data. Thus, those vehicles are unlikely to be 
miscoded as other buses.
---------------------------------------------------------------------------

    Furthermore, the size of the rollover crash problem for cross-
country intercity buses is greater than in other buses. According to 
FARS data from 2000 to 2009, there were 114 occupant fatalities as a 
result of rollover events on cross-country intercity buses, ``other 
buses,'' and ``unknown buses'' with a GVWR of greater than 11,793 kg 
(26,000 lb.), which represents 55 percent of bus fatalities on those 
bus types.

B. Contributing Factors in Rollover and Loss-of-Control Crashes

    Many factors related to heavy vehicle operation, as well as factors 
related to roadway design and road surface properties, can cause heavy 
vehicles to become yaw unstable or to roll. Listed below are several 
real-world situations in which stability control systems may prevent or 
lessen the severity of such crashes.
     Speed too high to negotiate a curve--The entry speed of 
vehicle is too high to safely negotiate a curve. When the lateral 
acceleration of a vehicle during a steering maneuver exceeds the 
vehicle's roll or yaw stability threshold, a rollover or loss of 
control is initiated. Curves can present both roll and yaw instability 
issues to these types of vehicles due to varying heights of loads (low 
versus high, empty versus full) and road surface friction levels (e.g., 
wet, dry, icy, snowy).
     Road design configuration--Some drivers may misjudge the 
curvature of ramps and not brake sufficiently to negotiate the curve 
safely. This includes driving on ramps with decreasing radius curves as 
well as operating on curves and ramps with improper signage. A vehicle 
traveling on a curve with a decrease in super-elevation (banking) at 
the end of a ramp where it merges with the roadway causes an increase 
in vehicle lateral acceleration, which may increase even more if the 
driver accelerates the vehicle in preparation to merge.
     Sudden steering maneuvers to avoid a crash--The driver 
makes an abrupt steering maneuver, such as a single- or double-lane-
change maneuver, or attempts to perform an off-road recovery maneuver, 
generating a lateral acceleration that is sufficiently high to cause 
roll or yaw instability. Maneuvering a vehicle on off-road, unpaved 
surfaces such as grass or gravel may require a larger steering input 
(larger wheel slip angle) to achieve a given vehicle response, and this 
can lead to a large increase in lateral acceleration once the vehicle 
returns to the paved surface. This increase in lateral acceleration can 
cause the vehicle to exceed its roll or yaw stability threshold.
     Loading conditions--A loss of yaw stability due to severe 
over-steering is more likely to occur when a vehicle is in a lightly 
loaded condition and has a lower center-of-gravity height than it would 
have when fully loaded. Heavy vehicle rollovers are much more likely to 
occur when the vehicle is in a fully loaded condition, which results in 
a high center of gravity for the vehicle.

[[Page 36058]]

Cargo placed off-center in the trailer may result in the vehicle being 
less stable in one direction than in the other. It is also possible 
that improperly secured cargo can shift while the vehicle is 
negotiating a curve, thereby reducing roll or yaw stability. Sloshing 
can occur in tankers transporting liquid bulk cargoes, which is of 
particular concern when the tank is partially full because the vehicle 
may experience significantly reduced roll stability during certain 
maneuvers.
     Road surface conditions--The road surface condition can 
also play a role in the loss of control a vehicle experiences. On a 
dry, high-friction asphalt or concrete surface, a tractor trailer 
combination vehicle executing a severe turning maneuver is likely to 
experience a high lateral acceleration, which may lead to roll or yaw 
instability. However, a similar maneuver performed on a wet or slippery 
road surface is not as likely to experience the high lateral 
acceleration because of less available tire traction. Hence, the 
vehicle is more likely to be yaw unstable than roll unstable.

C. NTSB Safety Recommendations

    The National Transportation Safety Board (NTSB) has issued several 
safety recommendations relevant to ESC systems on heavy and other 
vehicles. One is H-08-15, which addresses ESC systems and collision 
warning systems with active braking on commercial vehicles. 
Recommendations H-11-07 and H-11-08 specifically address stability 
control systems on commercial motor vehicles and buses with a GVWR 
above 10,000 pounds. Two other safety recommendations, H-01-06 and H-
01-07, relate to adaptive cruise control and collision warning systems 
on commercial vehicles and are indirectly related to ESC on heavy 
vehicles because these technologies require the ability to apply brakes 
without driver input.
     H-08-15: Determine whether equipping commercial vehicles 
with collision warning systems with active braking \19\ and electronic 
stability control systems will reduce commercial vehicle accidents. If 
these technologies are determined to be effective in reducing 
accidents, require their use on commercial vehicles.
---------------------------------------------------------------------------

    \19\ Active braking involves using the vehicle's brakes to 
maintain a certain, preset distance between vehicles.
---------------------------------------------------------------------------

     H-11-07: Develop stability control system performance 
standards for all commercial motor vehicles and buses with a gross 
vehicle weight rating greater than 10,000 pounds, regardless of whether 
the vehicles are equipped with a hydraulic or pneumatic brake system.
     H-11-08: Once the performance standards from Safety 
Recommendation H-11-07 have been developed, require the installation of 
stability control systems on all newly manufactured commercial vehicles 
with a GVWR greater than 10,000 pounds.

D. Motorcoach Safety Plan

    In November 2009, the U.S. Department of Transportation Motorcoach 
Safety Action Plan was issued.\20\ Among other things, the Motorcoach 
Safety Action Plan includes an action item for NHTSA to assess the 
safety benefits for stability control on large buses and develop 
objective performance standards for these systems.\21\ Consistent with 
that plan, NHTSA made a decision to pursue a stability control 
requirement for large buses.
---------------------------------------------------------------------------

    \20\ See supra, note 6.
    \21\ Id. at 28-29.
---------------------------------------------------------------------------

    In March 2011, NHTSA issued its latest Vehicle Safety and Fuel 
Economy Rulemaking and Research Priority Plan (Priority Plan).\22\ The 
Priority Plan describes the agency plans for rulemaking and research 
for calendar years 2011 to 2013. The Priority Plan includes stability 
control on truck tractors and large buses, and states that the agency 
plans to develop test procedures for a Federal motor vehicle safety 
standard on stability control for truck tractors, with the 
countermeasures of roll stability control and electronic stability 
control, which are aimed at addressing rollover and loss-of-control 
crashes.
---------------------------------------------------------------------------

    \22\ See Docket No. NHTSA-2009-0108-0032.
---------------------------------------------------------------------------

E. International Regulation

    The United Nations (UN) Economic Commission for Europe (ECE) 
Regulation 13, Uniform Provisions Concerning the Approval of Vehicles 
of Categories M, N and O with Regard to Braking, has been amended to 
include Annex 21, Special Requirements for Vehicles Equipped with a 
Vehicle Stability Function. Annex 21's requirements apply to trucks 
with a GVWR greater than 3,500 kg (7,716 lb.), buses with a seating 
capacity of 10 or more (including the driver), and trailers with a GVWR 
greater than 3,500 kg (7,716 lb.). Trucks and buses are required to be 
equipped with a stability system that includes rollover control and 
directional control, while trailers are required to have a stability 
system that includes only rollover control. The directional control 
function must be demonstrated in one of eight tests, and the rollover 
control function must be demonstrated in one of two tests. For 
compliance purposes, the ECE regulation requires a road test to be 
performed with the function enabled and disabled, or as an alternative, 
accepts results from a computer simulation. No test procedure or pass/
fail criterion is included in the regulation, but it is left to the 
discretion of the Type Approval Testing Authority in agreement with the 
vehicle manufacturer to show that the system is functional. The 
implementation date of Annex 21 was 2012 for most vehicles, with a 
phase-in based on the vehicle type.

V. Summary of the May 2012 NPRM

    Since 2006, the agency has been involved in testing truck tractors 
and large buses with stability control systems. To evaluate these 
systems, NHTSA sponsored studies of crash data in order to examine the 
potential safety benefits of stability control systems. NHTSA and 
industry representatives separately evaluated data on dynamic test 
maneuvers. At the same time, the agency launched a three-phase testing 
program to improve its understanding of how stability control systems 
in truck tractors and buses work and to develop dynamic test maneuvers 
to challenge roll propensity and yaw stability. By combining the 
studies of the crash data with the testing data, the agency is able to 
evaluate the potential effectiveness of stability control systems for 
truck tractors and large buses.
    The agency conducted a three-phase testing program for truck 
tractors and large buses that was described at length in the NPRM and 
in published reports in order to develop one or more test maneuvers to 
ensure that ESC systems can reduce vehicle instability. As a result of 
the agency's testing program and the test data received from industry, 
the agency was able to develop reliable and repeatable test maneuvers 
that could demonstrate a stability control system's ability to prevent 
rollover and loss of directional control among the varied 
configurations of truck tractors and buses in the fleet.
    After considering and evaluating several test maneuvers, the agency 
proposed using two test maneuvers for performance testing: The slowly 
increasing steer (SIS) maneuver and the sine with dwell (SWD) maneuver. 
The SIS maneuver is a characterization maneuver used to determine the 
amount of steering input required by the SWD maneuver. By determining 
the relationship between a vehicle's steering wheel angle and the 
lateral acceleration,

[[Page 36059]]

the SIS maneuver normalizes the severity of the SWD maneuver. The SIS 
maneuver was also proposed to be used to ensure that the system has the 
ability to reduce engine torque.
    Using a steering wheel angle derived from the SIS maneuver, the 
agency proposed conducting the sine with dwell maneuver. The SWD test 
maneuver challenges both roll and yaw stability by subjecting the 
vehicle to a sinusoidal input. This maneuver would be repeated for two 
series of test runs (first in the counterclockwise direction and then 
in the clockwise direction) at several target steering wheel angles 
from 30 to 130 percent of the angle derived in the SIS maneuver.
    We proposed measuring, recording, and processing lateral 
acceleration, yaw rate, and engine torque data derived from the SIS and 
SWD maneuvers to determine four performance metrics: Lateral 
acceleration ratio (LAR), yaw rate ratio (YRR), lateral displacement, 
and engine torque reduction. The LAR and YRR metrics ensure that the 
system reduces lateral acceleration and yaw rate, respectively, after 
an aggressive steering input, thereby preventing rollover and loss of 
control, respectively. The lateral displacement metric ensures that the 
stability control system is not set to intervene solely by making the 
vehicle nonresponsive to driver input. The engine torque reduction 
metric ensures that the system has the capability to automatically 
reduce engine torque in response to high lateral acceleration and yaw 
rate conditions.
    The agency also considered several test maneuvers based on its own 
work and that of industry. In particular, the agency's research 
included both a J-turn maneuver and a ramp steer maneuver (RSM) for 
evaluating roll stability. The J-turn maneuver is a path-following 
maneuver where a vehicle is driven on a test course consisting of a 
straight lane followed by a fixed radius curve. The steering wheel 
angle is determined by the driver making adjustments and corrections to 
maintain the fixed path. In the RSM maneuver, a vehicle is driven at a 
constant speed and a steering wheel input that is based on the steering 
wheel angle derived from the SIS maneuver. The steering wheel angle is 
then held for a period of time before it is returned to zero. In both 
the J-turn and RSM maneuvers, a stability control system acts to reduce 
lateral acceleration, and thereby wheel lift and roll instability, by 
applying selective braking. A vehicle without a stability control 
system being tested with these maneuvers would exhibit high levels of 
lateral acceleration and potentially experience wheel lift or rollover.
    The NPRM also set forth the test conditions that the agency would 
use to ensure safety and demonstrate sufficient performance. All 
vehicles were proposed to be tested using outriggers for the safety of 
the test driver. The agency proposed using an automated steering 
controller for the RSM, SIS, and SWD maneuvers to ensure reproducible 
and repeatable test execution performance. The agency proposed testing 
truck tractors with an unbraked control trailer to eliminate the effect 
of the trailer's brakes on testing. The agency also proposed a test to 
ensure that system malfunction is detected.
    The NPRM proposed that a final rule would take effect for most 
truck tractors and applicable buses produced two years after 
publication of a final rule. We stated that two years of lead time 
would be necessary to ensure sufficient availability of stability 
control systems from suppliers of these systems and to complete 
necessary engineering on all vehicles. For three-axle tractors with one 
drive axle, tractors with four or more axles, and severe service 
tractors, we proposed allowing two years of additional lead time. We 
stated this additional time would be necessary to develop, test, and 
equip these vehicles with ESC systems. Although the agency has 
statutory authority to require retrofitting of in-service truck 
tractors, trailers, and large buses, the agency did not propose to 
require retrofitting, but sought comment on its feasibility, given the 
integrated aspects of a stability control system.

VI. Overview of the Comments

    This section presents a brief overview of the comments received in 
response to the NPRM. The comments are addressed in detail in the 
section related to the subject of the comment. However, those comments 
that merely advocated the adoption or rejection of the proposal or some 
aspect thereof without any underlying explanation are not addressed 
further.
    We also conducted a public hearing on July 24, 2012 in Washington, 
D.C.\23\ Summaries of the oral testimony and a transcript of the 
hearing are both available in the docket.\24\ Although we have 
considered the public hearing testimony as if it was a written comment 
received in the docket, much of the testimony was duplicated in the 
written comments. We have discussed public hearing testimony below only 
where that testimony was not reflected in written comments received by 
the agency.
---------------------------------------------------------------------------

    \23\ Notice of the hearing was published in the Federal Register 
on July 2, 2012. 77 FR 39206.
    \24\ Summaries of the oral testimony provided by the presenters 
are contained in Docket No. NHTSA-2012-0065-0049. A transcript of 
the public hearing is contained in Docket No. NHTSA-2012-0065-0056.
---------------------------------------------------------------------------

    In addition to the comments received at the public hearing, we 
received written comments from 43 individuals or entities. The 
commenters represented wide-ranging interests, including individuals, 
truck drivers, truck fleet operators, vehicle component manufacturers, 
truck and bus manufacturers, and safety advocacy organizations. The 
identity of the 46 commenters, their self-identified interest or 
affiliation, if given, where the comments can be located in the docket 
are cited in Table 2.\25\
---------------------------------------------------------------------------

    \25\ Three commenters presented comments only at the public 
hearing.

   Table 2--List of Commenters and Location of Comments in the Docket
------------------------------------------------------------------------
            Commenter                          Docket Number
------------------------------------------------------------------------
Vehicle Manufacturers:
Blue Bird Body Company (Blue       NHTSA-2012-0065-0034
 Bird).
Daimler Trucks North America LLC   NHTSA-2012-0065-0028
 (Daimler).
EvoBus GmbH......................  NHTSA-2012-0065-0027
Fire Apparatus Manufacturer's      NHTSA-2012-0065-0014
 Association.
Navistar, Inc....................  NHTSA-2012-0065-0039
Schneider National Inc.            NHTSA-2012-0065-0033
 (Schneider).
Temsa Global (Temsa).............  NHTSA-2012-0065-0019
Truck & Engine Manufacturers       NHTSA-2012-0065-0044
 Association (EMA).
Volvo Group......................  NHTSA-2012-0065-0031

[[Page 36060]]

 
Component Manufacturers:
Bendix Commercial Vehicle Systems  NHTSA-2012-0065-0046
                                   NHTSA-2012-0065-0048
                                   NHTSA-2012-0065-0055
Heavy Duty Brake Manufacturers     NHTSA-2012-0065-0041
 Council (HDBMC).
Meritor WABCO....................  NHTSA-2012-0065-0035
Robert Bosch LLC (Bosch).........  NHTSA-2012-0065-0036
Drivers and Fleet Operators:
American Trucking Associations,    NHTSA-2012-0065-0016
 Inc. (ATA), including report of   NHTSA-2012-0065-0030
 the American Transportation       NHTSA-2012-0065-0057
 Research Institute (ATRI).
Associated Logging Contractors--   NHTSA-2012-0065-0042
 Idaho.
John Boyle.......................  NHTSA-2012-0065-0017
Jim Burg, James Burg Trucking      NHTSA-2012-0065-0056 (public hearing)
 Company.
John H. Hill, The Hill Group.....  NHTSA-2012-0065-0056 (public hearing)
Alexander J. MacDonald...........  NHTSA-2012-0065-0005
National Ready Mixed Concrete      NHTSA-2012-0065-0038
 Association.
National School Transportation     NHTSA-2012-0065-0037
 Association.
Owner-Operator Independent         NHTSA-2012-0065-0024
 Drivers Association (OOIDA).
Skagit Transportation Inc........  NHTSA-2012-0065-0006
Bob Waterman.....................  NHTSA-2012-0065-0052
Safety Organizations:
AAA Public Affairs (AAA).........  NHTSA-2012-0065-0043
Advocates for Highway and Auto     NHTSA-2012-0065-0047
 Safety (Advocates).
American Highway Users Alliance..  NHTSA-2012-0065-0040
Commercial Vehicle Safety          NHTSA-2012-0065-0050
 Alliance (CVSA).
Consumers Union..................  NHTSA-2012-0065-0053
Insurance Institute for Highway    NHTSA-2012-0065-0021
 Safety (IIHS).
Kentucky Injury Prevention and     NHTSA-2012-0065-0007
 Research Center.
National Association for Pupil     NHTSA-2012-0065-0023
 Transport (NAPT).
National Transportation Safety     NHTSA-2012-0065-0015
 Board (NTSB).
Road Safe America................  NHTSA-2012-0065-0004
Other Organizations and Private
 Individuals:
American Association for Justice   NHTSA-2012-0065-0020
 (AAJ).
American Trauma Society..........  NHTSA-2012-0065-0009
Justin C. Barriault..............  NHTSA-2012-0065-0010
Robert M. Chin...................  NHTSA-2012-0065-0011
Jerry R. Curry...................  NHTSA-2012-0065-0018
Jerry J. Evans...................  NHTSA-2012-0065-0003
Fried Rogers Goldberg, LLC.......  NHTSA-2012-0065-0025
Nadya V. Gerber..................  NHTSA-2012-0065-0012
The Martec Group, Inc. (Martec)..  NHTSA-2012-0065-0051
Mercatus Center at George Mason    NHTSA-2012-0065-0022
 University (Mercatus).
Josh A. Sullivan.................  NHTSA-2012-0065-0013
Hon. Betty Sutton................  NHTSA-2012-0065-0056
                                   (public hearing)
------------------------------------------------------------------------

VII. Key Differences Between the Final Rule and the NRPM

    This section summarizes the significant differences between the 
NPRM and this final rule. Less significant changes are noted in the 
appropriate sections of the preamble.
    The most significant change between the NPRM and the final rule is 
that the agency has chosen an alternative performance test maneuver to 
demonstrate an ESC system's ability to maintain vehicle stability. 
After considering public comments and conducting additional track 
testing, we have adopted a 150-foot J-turn maneuver as the performance 
test maneuver in this final rule. In the NPRM, we proposed using a 
slowly increasing steer (SIS) maneuver as a characterization maneuver 
and a sine with dwell (SWD) maneuver as a roll and yaw performance 
maneuver. The 150-foot J-turn test maneuver is discussed in the NPRM 
and is a variation of an alternative test maneuver proposed in the 
NPRM.
    Because the 150-foot J-turn test maneuver only tests an ESC 
system's ability to mitigate roll instability and the agency lacks any 
alternative test maneuver to test an ESC system's ability to mitigate 
yaw instability, this final rule does not include a performance test to 
evaluate yaw instability. However, this final rule carries forward the 
requirement that an ESC system be capable of mitigating yaw 
instability.
    The 150-foot J-turn maneuver also uses a different performance 
metric than the SWD maneuver. The SWD maneuver's performance criteria 
were the change in lateral acceleration and yaw rate through the 
maneuver. In this final rule, we are using a simpler metric--reduction 
in forward speed.
    The change in performance test maneuver has also led to changes in 
the test conditions and equipment. Because the test maneuver in this 
final rule is conducted over a fixed path, rather than fixed steering 
used for the SWD maneuver, an automated steering wheel controller will 
not be used for the J-turn maneuver. We have also modified the

[[Page 36061]]

loading condition for vehicles to test them at GVWR. We have also 
reduced the instrumentation requirements in light of the simpler 
performance metric.

VIII. ESC Requirement

A. Whether to Require Stability Control

    In the May 2012 NPRM, the agency proposed to require that all truck 
tractors and certain buses with a GVWR of more than 11,793 kg (26,000 
lb.) to be equipped with ESC. The agency preliminarily found that the 
proposed standard met the need for motor vehicle safety.\26\ That 
finding was based upon the safety problem discussed in the NPRM and 
summarized in section IV above.\27\ Moreover, the agency found that 
requiring ESC systems on truck tractors and certain large buses would 
be cost-effective.\28\
---------------------------------------------------------------------------

    \26\ 77 FR 30788.
    \27\ 77 FR 30769-71.
    \28\ 77 FR 30791.
---------------------------------------------------------------------------

    We received many comments addressing the general question of 
whether stability control systems should be required on truck tractors 
and large buses. Several commenters questioned the need for a stability 
control mandate on truck tractors and certain large buses and 
recommended against adopting a final rule requiring any type of 
stability control system. A consistent theme in many of the comments 
received from private individuals was also expressed in the comment 
from Yankee Trucks. These commenters argued that the decision to 
include ESC should be decided by the vehicle's end user.
    Other commenters such as Mercatus and OOIDA were concerned that 
NHTSA failed to look at alternative methods to improve motor vehicle 
safety problems caused by rollover and loss-of-control crashes. 
Mercatus suggested that NHTSA failed to look at driver fatigue 
detection, road condition sensors, improved safety procedures, or 
driver training, which might be less costly. OOIDA highlighted driver 
training, enforcement of traffic laws, driver incentives, improved 
crashworthiness, and road signage as alternative ways to deal with the 
rollover problem. Several other commenters highlighted driver training 
and accountability related to both driving and vehicle loading as 
alternative methods that could prevent rollover and loss-of-control 
crashes. The Boyle Brothers, OOIDA, and several individual commenters 
both noted that stability control systems would not prevent crashes 
caused by driving too fast for conditions. Both Mercatus and OOIDA 
believe that alternative measures are less costly than a stability 
control mandate at preventing rollover and loss-of-control crashes.
    Individual commenters, many of whom identified themselves as truck 
drivers, also questioned the safety of stability control systems and 
their ability to prevent crashes. One commenter believes that stability 
control systems are unsafe based on personal experience because it 
often engaged the service brakes in curves. Another commenter was 
concerned that drivers would become too dependent on stability control 
systems and cause them to drive through curves faster with the system 
than without.
    OOIDA and many individual commenters were concerned about the total 
cost of the rule and whether the benefits justified the costs. 
Relatedly, several commenters raised concerns that stability control 
systems would add complexity to the brake system by requiring 
additional parts, and thus, higher repair costs. Yankee Trucks also 
raised concerns that if a stability control system malfunctions, ABS 
would also not function. OOIDA claimed that a stability control 
requirement would cause drivers and truck companies to keep existing 
vehicles in service longer or even go out of business due to the added 
costs of stability control and other regulatory mandates.
    Some commenters also expressed concerns that stability control 
technologies could have negative effects on safety. For example, 
individual commenters questioned whether it was safe to have stability 
control systems braking the vehicle automatically in wet conditions or 
on curves. Associated Logging Contractors opposed a mandate because it 
believes that a stability control requirement may cause safety issues 
on forest roads, which are different from highways.
    Commenters from a wide variety of backgrounds supported a stability 
control mandate. These organizations include organizations such as Road 
Safe America, the Kentucky Injury Prevention and Research Center, the 
American Trauma Society, the American Association for Justice, 
Advocates, the American Highway Users Alliance, AAA, the Commercial 
Vehicle Safety Alliance, and Consumers Union. Business associations 
representing brake suppliers (HDBMC), truck manufacturers (EMA), and 
truck fleet operators (ATA) all supported a stability control mandate. 
Brake suppliers such as Bosch, Bendix, and Meritor WABCO also supported 
a stability control mandate. Individual truck and bus manufacturers who 
commented also such as Daimler, Volvo, and Navistar supported a 
stability control mandate. Some motor carriers who commented also 
supported a stability control mandate. The NTSB and a former Member of 
Congress, Betty Sutton, both supported a stability control mandate. 
Many individual commenters also supported a stability control mandate.
    Although these commenters come from varied backgrounds, their 
reasons for supporting a stability control mandate were generally 
consistent. Commenters supporting a mandate generally cited research 
from NHTSA, the manufacturing industry, and others regarding the 
effectiveness of stability control systems, and their ability to 
prevent rollover and loss-of-control crashes and save lives. IIHS, for 
example, cited its own research suggesting that having ESC systems on 
all truck tractors could prevent as many as 295 fatal crashes each 
year. Some individual commenters also cited personal experience with 
stability control systems. John Hill observed that the cost of a 
stability control system on a vehicle is comparable to the cost to the 
government of a single compliance review of a motor carrier's safety 
practices. These commenters generally agreed that the benefits of a 
stability control mandate far exceed its costs.
    After considering all public comments, the agency is proceeding 
with adopting FMVSS No. 136 to require all truck tractors and certain 
large buses with a GVWR of more than 11,793 kg (26,000 lb.) to have 
stability control systems. This decision is largely driven by the data 
before the agency. In developing the proposal, the agency analyzed 
crash data to identify risks not addressed in existing FMVSSs. These 
safety risks include rollover and loss-of-control crashes that are 
caused by many factors including traveling at a speed too high to 
negotiate a curve, sudden steering maneuvers to avoid a crash, loading 
conditions, road surface conditions, and road design configuration. The 
agency's research, described at length in the NPRM, shows that 
stability control technologies could prevent crashes in these 
situations.
    With respect to the comments suggesting that vehicles braking 
during a curve or on wet conditions could have adverse safety 
consequences, we observe that an ESC system is designed to slow the 
vehicle in a curve in order to reduce the lateral acceleration and 
allow the operator to maintain roll and yaw control of the vehicle only 
in situations where instability is imminent. After careful qualitative 
and quantitative assessment, we have concluded that requiring stability

[[Page 36062]]

control systems will improve the overall safety of the vehicle.
    Regarding other possible improvements to reduce crashes, we do not 
disagree that many of the suggestions regarding driver training, 
enforcements, and crashworthiness of trucks and buses could improve 
motor vehicle safety and (except for the latter) reduce vehicle 
rollover and loss-of-control crashes. However, driver training and 
enforcement of traffic safety laws are outside of NHTSA's regulatory 
authority under the Safety Act. Moreover, the commenters advocating 
these alterative means to address the safety problem did not provide 
data to support their conclusions that their alternatives would be less 
costly or more cost-effective than a stability control mandate. 
Although the issues related to costs and benefits will be addressed 
more specifically in section XIV below, the agency has concluded that 
requiring ESC systems on truck tractors and certain large buses is 
cost-effective and the most effective means to address the safety 
problem identified in this rulemaking.

B. Whether to Require ESC or RSC

    The agency proposed to require that truck tractors and large buses 
be equipped with ESC systems rather than RSC systems. An ESC system is 
capable of all of the functions of an RSC system. In addition, an ESC 
system has the additional ability to detect yaw instability, provide 
braking at front wheels, and detect the steering wheel angle. These 
additions, as demonstrated by NHTSA's testing, allow an ESC system to 
have better rollover prevention performance than an RSC system in 
addition to the yaw instability prevention component. This is because 
the steering wheel angle sensor allows the ESC system to anticipate 
changes in lateral acceleration based upon driver input and to 
intervene with engine torque reduction or selective braking sooner, 
rather than waiting for the lateral acceleration sensors to detect 
potential instability.
    The NPRM stated that mandating ESC systems rather than RSC systems 
will prevent more crashes, injuries, and fatalities. The additional 
benefits from ESC systems can be attributed to both the ESC's system's 
ability to intervene sooner and its ability to prevent yaw instability 
that would lead to loss-of-control crashes.
    The NPRM stated that mandating ESC systems rather than RSC systems 
will result in higher initial costs to manufacturers. Moreover, while 
our benefit and cost estimates led to the preliminary conclusion that 
mandating RSC systems would be more cost-effective than mandating ESC 
systems, mandating ESC systems would result in higher net benefits.
    Several commenters agreed with NHTSA's proposal to require ESC 
systems rather than RSC systems. Jerry Curry and Bendix specifically 
mentioned that ESC systems should be required instead of RSC systems. 
Mr. Curry and IIHS also commented that RSC systems would not be the 
best platform to use when considering future technological advances. 
John Hill similarly observed that ESC systems have the potential to 
support future collision avoidance and crash mitigation technologies. 
Mr. Hill also observed that loss-of-control crashes can be difficult to 
identify and classify. Road Safe America, Mr. MacDonald, and AAA said 
the agency should require ESC equipment on truck tractors and buses. 
IIHS and Jim Burg recommended requiring ESC systems over RSC systems 
because loss-of-control collisions can be reduced using ESC systems. 
Volvo, while not expressly advocating for an ESC mandate, stated that 
it had investigated the use of RSC systems, but found they were unable 
to provide stability control in a wide range of driving conditions and 
environments that its customers operate.
    In its comment, Bendix stated that an ESC system has an 
effectiveness that is 31% greater than a RSC system. Bendix also 
commented that ESC systems provide ``more information about what the 
vehicle is doing'' because these systems include two additional 
sensors. Bendix also said that ESC systems provide more effective 
interventions through selective application of all available vehicle 
brakes.
    Other commenters supported RSC as a minimum requirement rather than 
ESC. Schneider, for example, asserted that it considered purchasing 
vehicles with ESC system, but determined that ESC systems would provide 
a negligible benefit at substantially higher costs when compared to 
RSC. ATA also asserted that marginal benefit of ESC over RSC is not 
justified by the added cost based on current information. ATA cited the 
variability of the truck-tractor industry in four areas: (1) Private 
trucking vs. for-hire companies; (2) the size of loads; (3) the type of 
truck and trailer being used (e.g., box, van, refrigerated, liquid and 
bulk tankers); and by operation (e.g., agricultural, long haul, short 
haul, over size, overweight, etc.). ATA believes this diversity may 
warrant choosing ESC or RSC depending on the individual vehicle.
    Both Schneider and ATA cited a study by the American Transportation 
Research Institute (ATRI) that surveyed stability control technology 
used in the trucking industry. This study collected crash and financial 
data from the trucking industry, including information regarding 
whether the vehicle was equipped with an ESC system, an RSC system, or 
no stability control system at all. The sample included 135,712 trucks, 
of which 68,647 had RSC systems, 39,529 had ESC systems, and 27,536 had 
no stability control systems. The study included unit costs of 
stability systems, average annual miles per tractor, the total number 
of safety incidents (including rollover crashes), and the average cost 
of each incident. The crash analysis concluded that industry-wide 
installation of RSC systems would result in fewer rollover, jackknife, 
and tow/stuck crashes compared to industry-wide installation of ESC 
systems.
    NHTSA agrees with those commenters recommending ESC systems instead 
of RSC systems. However, we are not relying on the assertions of Mr. 
Curry, Mr. Hill and IIHS that ESC systems provide a better platform for 
future technological advances. We believe the justification for ESC 
systems is satisfied using benefits estimates for today's ESC systems, 
without having to consider possible future advances such as forward 
collision mitigation systems. Similarly, we are not relying on Bendix's 
assessment of ESC system effectiveness. While Bendix's analysis of the 
effectiveness of ESC and RSC systems is addressed in more detail in 
section XIV below, we believe that our own analysis based on an 
effectiveness study conducted by University of Michigan Transportation 
Research Institute (UMTRI) and Meritor WABCO is a more accurate 
assessment of the effectiveness of ESC and RSC systems. Although both 
NHTSA and Bendix reached the conclusion that ESC systems will be more 
effective than RSC systems at preventing rollover crashes, we believe 
that Bendix's method of determining system effectiveness is arbitrarily 
biased in favor of ESC systems.
    Regarding ATA's assertion of the variability of trucks, we agree 
that truck tractors are varied and that some of those variations affect 
vehicle stability. However, we believe that variability justifies 
choosing to require ESC systems rather than RSC systems. In particular, 
ATA observed that trucks carry various loads, implying that certain 
kinds of loads may be more suited to ESC systems whereas other

[[Page 36063]]

loads may only require RSC systems to achieve equal effectiveness. 
However, the nature of the trucking industry is such that a truck 
tractor may end up towing many different types of trailers in its 
lifetime, including flatbed trailers, box trailers, and tanker 
trailers. A vehicle manufacturer is unlikely to know at the time of a 
vehicle's production whether a specific truck tractor is going to be 
carrying loads that are more likely to cause a rollover or loss-of-
control crash because the load has a high center of gravity or has the 
potential to slosh. The only way to ensure that the vehicles that ATA 
believes would perform better with ESC systems is to require all truck 
tractors to be equipped with ESC systems.
    The ATRI study will be addressed more specifically in the benefits 
and costs discussion in section XIV below and in the FRIA accompanying 
this final rule. However, for the purpose of determining whether to 
require ESC systems or RSC systems, the ATRI study's suggestion that 
RSC systems would be more beneficial than ESC systems reflects the 
specific truck carriers they studied, but does not necessarily 
constitute a representative sample of the truck fleet. ATRI's 
conclusion is contrary to NHTSA's own findings that ESC systems are 
more effective and have greater net benefits than RSC systems. First, 
as explained above, ESC systems contain all of the functions of RSC 
systems, plus have additional sensors such as a steering wheel angle 
sensor, to allow a system to intervene based on a predicted rise in 
lateral acceleration rather than waiting for the lateral acceleration 
to rise. Second, ESC systems have the capability to braking all of the 
vehicle's axles, whereas an RSC system is generally unable to brake the 
steering axle of the vehicle. Third, although NHTSA's own research 
found that one RSC system performed as well or slightly better than an 
ESC system under certain conditions, we attributed the performance 
difference to that particular RSC system being programmed to brake more 
aggressively than the ESC system on the same vehicle.\29\ For these 
reasons, we conclude that the ATRI study is not representative of the 
entire trucking industry or the performance of ESC systems compared to 
RSC systems.
---------------------------------------------------------------------------

    \29\ 77 FR 30779.
---------------------------------------------------------------------------

    Based on the foregoing, this final rule will require that truck 
tractors and certain buses be equipped with ESC systems rather than RSC 
systems. As discussed in section XIV below, RSC systems are less 
beneficial than ESC systems in reducing rollover crashes and much less 
beneficial in addressing loss-of-control crashes. Although RSC systems 
are slightly more cost beneficial than ESC systems, ESC systems provide 
substantially higher net benefits because ESC systems will prevent many 
more crashes.\30\ NHTSA has concluded that the additional safety 
benefits of ESC systems in both rollover and loss-of-control crashes 
justify the additional cost of ESC systems compared to RSC systems.
---------------------------------------------------------------------------

    \30\ Cost-effectiveness is measured in terms of lower cost per 
equivalent life saved. For more discussion of the costs and benefits 
of this rule see Section XIV, below, and the Final Regulatory Impact 
Analysis accompanying this final rule, which has been placed in the 
docket.
---------------------------------------------------------------------------

C. Definition of ESC

    The NPRM included definitional criteria in the proposed regulatory 
text. We reasoned that, relying solely on performance-based tests 
without mandating any specific equipment may require a battery of tests 
to cover the complete operating range of the vehicle. Given the wide 
array of possible configurations and operating ranges for heavy 
vehicles, the agency did not believe it was practical to develop 
performance tests that address the full range of possibilities and 
remain cost-effective. Accordingly, the agency proposed to include 
definitional criteria in the NPRM, which included equipment that would 
be required as part of a compliant ESC system.\31\ We note that, when 
developing the ESC requirement for light vehicles, the agency chose to 
include such a requirement in FMVSS No. 126.
---------------------------------------------------------------------------

    \31\ Similar requirements exist in the light vehicle ESC 
requirements. See 49 CFR 571.126, S4.
---------------------------------------------------------------------------

    SAE International has a Recommended Practice on Brake Systems 
Definitions-Truck and Bus, J2627 (Aug. 2009), which includes a 
definition of Electronic Stability Control and Roll Stability Control. 
SAE International's definition of an ESC system requires that a system 
have an electronic control unit that considers wheel speed, yaw rate, 
lateral acceleration, and steering angle and that the system must 
intervene and control engine torque and auxiliary brake systems to 
correct the vehicle's path.
    The UN ECE Regulation 13 definition for the electronic stability 
control system, promulgated in Annex 21, includes the following 
functional attributes for directional control: Sensing yaw rate, 
lateral acceleration, wheel speeds, braking input and steering input; 
and the ability to control engine power output. For vehicles with 
rollover control, the functions required by the stability control 
include: Sensing lateral acceleration and wheel speeds; and the ability 
to control engine power output.
    In developing a definition for ESC, the agency reviewed the 
functional attributes contained in SAE J2627 and the requirements of 
Annex 21 of UN ECE Regulation 13, and incorporated parts of both of 
definitions the NPRM. The proposed definition was similar in wording to 
the definition from FMVSS No. 126, which specifies certain features 
that must be present, that ESC be capable of applying all the brakes 
individually on the vehicle, and that it have a computer using a 
closed-loop algorithm to limit vehicle oversteer and understeer when 
appropriate. Unlike the light vehicle standard, which focuses on yaw 
stability, the NPRM proposed to require a stability control system that 
also helps to mitigate roll instability conditions.
    Furthermore, the proposed definition required that the ESC system 
must be operational during all phases of driving, including 
acceleration, coasting, deceleration, and braking, except when the 
vehicle is below a low-speed threshold where loss of control or 
rollover is unlikely. According to information the agency obtained from 
vehicle manufacturers and ESC system suppliers, the low speed threshold 
for a stability control system is 10 km/h (6.2 mph) for yaw stability 
control and 20 km/h (12.4 mph) for roll stability control. For the 
purposes of the NPRM, the agency set a single threshold of 20 km/h 
(12.4 mph) as the speed below which ESC is not required to be 
operational.
    The benefit of an ESC system is that it will reduce vehicle 
rollovers and loss of control under a wide variety of vehicle 
operational and environmental conditions. However, the performance 
tests in the NPRM would only evaluate ESC system performance under very 
specific conditions. To ensure that a vehicle is equipped with an ESC 
system that met the proposed definition, we proposed that vehicle 
manufacturers make available to the agency documentation that would 
enable NHTSA to ascertain that the system includes the components and 
performs the functions of an ESC system.
    Meritor WABCO, HDBMC, and Bendix recommended a change to the 
definition of an ESC system. Where the definition required that the 
system both augment vehicle directional stability and enhance rollover 
stability by applying and adjusting brake torques, the commenters 
recommended that the words ``having the capability of'' be added to 
each instance. Bendix also recommended that each instance of

[[Page 36064]]

``brake torque'' should be changed to ``deceleration torque.''
    We agree with the commenters' recommendation to change the 
requirement that ESC systems augment vehicle directional stability and 
enhance rollover stability by ``applying and adjusting vehicle brake 
torques'' to ``having the capability of applying and adjusting vehicle 
brake torques.'' The wording in the NPRM could be construed to require 
brake torques to be applied simultaneously at each wheel position for 
correcting yaw moment or reduce lateral acceleration. This was not our 
intention. Rather, we intended to require that brake torque at each 
wheel position be capable of being applied and adjusted individually. 
In analogous portions of the ESC system definition, we use the words 
``has a means,'' which is similar in meaning to ``capable.''
    However, we are not making Bendix's suggested change of the term 
``brake torque'' to ``deceleration torque.'' We are not sure that 
Bendix's suggested language would be functionally different than the 
proposal and cannot see how it adds clarity. We are specifically 
interested in requiring that systems be capable of controlling the 
brakes independently at each wheel end on at least one front and at 
least one rear axle of the vehicle.
    Bendix also recommended a change to the requirement that the system 
enhance vehicle directional stability by applying and adjusting the 
vehicle brake torques. Bendix requested that NHTSA clarify that the 
``vehicle'' referred to in this requirement is the truck tractor or bus 
and not the trailer. That is, Bendix wanted to ensure that the trailer 
is omitted from the vehicle directional stability requirements. Bendix 
noted that the requirements regarding the system's ability to control 
trailer brakes is addressed elsewhere.
    We agree with Bendix's recommendation. It was not our intention to 
include trailers in the requirement that vehicles be capable of 
maintaining directional stability. Bendix is correct that there could 
to be some confusion with the proposed requirement because a trailer is 
also a motor vehicle and consequently, the proposed requirement that 
vehicles have the capability to maintain directional stability and the 
roll stability may be misinterpreted to apply to a trailer. Therefore, 
we have revised the ESC definition to specify that truck tractors and 
buses must have the means to apply and adjust vehicle brake torques on 
at least one front and at least one rear axle.
    Regarding the definitional criteria for mass estimation, Meritor 
WABCO, HDBMC, and Bendix suggested an addition to the requirement that 
a system have a means to estimate the vehicle (or combination vehicle) 
mass. The commenters request that NHTSA include language allowing a 
system to automatically obtain the vehicle's mass.
    NHTSA is not making the suggested change. The suggested change 
would require a system to have a means to estimate or automatically 
obtain vehicle mass. We do not believe there is a manner in which to 
automatically obtain the vehicle's mass short of weighing it on a 
scale. Any other calculation of the vehicle's mass is an estimate. We 
note that the means for obtaining the vehicle's mass is not prescribed. 
The requirement is necessary to ensure that the ESC system is capable 
of using the vehicle mass data in the closed-loop algorithm of its 
computer to apply and adjust the vehicle brake torques for enhancing 
rollover stability and inducing correcting yaw moment. Adding 
``automatically obtain'' to the definition does not improve or clarify 
the requirement to have a means of estimating vehicle mass.
    In summary, NHTSA continues to believe that the definitional 
criteria, including required equipment and system capabilities, are 
necessary to ensure that ESC systems perform as they are intended and 
as they currently perform. These criteria are objective in terms of 
explaining to manufacturers what type of performance is required and 
the minimal equipment necessary for that purpose.

D. Technical Documentation

    The NPRM proposed requiring that the vehicle manufacturer provide a 
system diagram that identifies all ESC system hardware; a written 
explanation, with logic diagrams included, describing the ESC system's 
basic operational characteristics; and a discussion of the pertinent 
inputs to the computer and how its algorithm uses that information to 
prevent rollover and limit oversteer and understeer. Because the 
proposed definition for ESC systems on truck tractors included the 
capability to provide brake pressure to a towed vehicle, the agency 
proposed requiring that, as part of the system documentation, the 
manufacturer include the information that shows how the tractor 
provides brake pressure to a towed trailer under the appropriate 
conditions.
    Volvo questioned the need for manufacturers to submit technical 
documentation to NHTSA, stating that NHTSA has relied on the 
manufacturer's certification that the system meets the FMVSSs. HDBMC 
and Bendix requested confirmation that this technical documentation 
would be considered proprietary information and would not be released 
to the public. Finally, Bendix was concerned about the acceptance 
criteria for the evaluation of the submitted technical documentation. 
Bendix stated that there was no objective acceptance criteria in the 
proposed standard and recommended that the agency add acceptance 
criteria.
    Upon consideration of the comments, we have decided to remove from 
the regulatory text references to specific documentation that NHTSA 
would request from manufacturers. However, NHTSA's Office of Vehicle of 
Safety Compliance often requests, as part of its testing to verify 
compliance with the FMVSSs, certain information from manufacturers. For 
example, NHTSA may ask how a manufacturer's system meets the definition 
of an ``ESC System'' set forth in this final rule. Information such as 
the technical documentation that was listed in the regulatory text of 
the NPRM may be included in or responsive to such a request. Of course, 
a manufacturer's inability to demonstrate that its system meets the 
definition of an ``ESC System'' could lead to a finding of 
noncompliance with S5.1 of FMVSS No. 136.

IX. Vehicle Applicability and Phase-In

A. Trucks

1. Summary of the NPRM
    Vehicles with a GVWR greater than 10,000 pounds include a large 
variety of vehicles ranging from medium duty pickup trucks to different 
types of single-unit trucks, buses, trailers and truck tractors. 
Vehicles with a GVWR of greater than 10,000 pounds are divided into 
Classes 3 through 8. Class 7 vehicles are those with a GVWR greater 
than 11,793 kilograms (26,000 pounds) and up to 14,969 kilograms 
(33,000 pounds), and Class 8 vehicles are those with a GVWR greater 
than 14,969 kilograms (33,000 pounds).
    About 85 percent of truck tractors sold annually in the U.S. are 
air-braked three-axle (6x4) tractors with a front axle that has a GAWR 
of 14,600 pounds or less and with two rear drive axles that have a 
combined GAWR of 45,000 pounds or less, which we will refer to as 
``typical 6x4 tractors.'' Other truck tractors, including two-axle 
(4x2) tractors, tractors with four or more axles, and severe service 
tractors, represent about 15 percent of the truck-tractor market in the 
U.S.
    In the NPRM, the agency proposed that truck tractors with a GVWR 
greater

[[Page 36065]]

than 11,793 kilograms (26,000 pounds) would be required to have ESC 
systems. The agency did not propose requiring stability control systems 
on trailers, primarily because trailer-based RSC systems were 
determined by the agency research to be much less effective than 
tractor-based RSC or ESC systems in preventing rollover. Trailer-based 
RSC systems are capable of applying braking only on the trailer's 
brakes. Tractor-based systems can command more braking authority by 
using both the tractor and trailer brakes. As a result, trailer-based 
RSC systems do not appear to provide additional safety benefits when 
used in combination with tractor-based RSC or ESC systems. In addition, 
the typical service life of a trailer is 20 to 25 years compared with 
about 8 to 10 years for a truck tractor. Because new tractors are added 
to the U.S. fleet at a faster rate than new trailers, the safety 
benefits from stability control systems would be achieved at a faster 
rate by requiring stability control systems to be installed on a 
tractor.
    Our proposed rule also excluded certain types of low-volume, highly 
specialized vehicle types. In these cases, the vehicle's speed 
capability does not allow it to operate at speeds where roll or yaw 
instability is likely to occur. These exclusions were drawn from FMVSS 
No. 121, Air brake systems, which exclude any vehicle equipped with an 
axle that has a gross axle weight rating of 29,000 pounds or more; any 
truck or bus that has a speed attainable in two miles of not more than 
33 mph; and any truck that has a speed attainable in two miles of not 
more than 45 mph, an unloaded vehicle weight that is not less than 95 
percent of its GVWR, and no capacity to carry occupants other than the 
driver and operating crew.
2. Exclusions From ESC Requirement
    The Fire Apparatus Manufacturers' Association (FAMA) was generally 
supportive of the rule. However, they stated that the rule would not be 
feasible if it is interpreted to apply to a Tractor Drawn Aerial 
Apparatus. As FAMA explained, this apparatus is a combination vehicle 
used for firefighting, which are used in many large urban fire 
departments. The distinguishing feature of this vehicle is that it has 
two drivers, one in the truck tractor and one in the trailer. FAMA 
believes that an ESC algorithm on such a vehicle would be very complex 
because it would need to consider two steering wheels rather than one. 
FAMA suggested that NHTSA exclude from a final rule any combination 
vehicle that requires more than one operator to steer it.
    The agency is not adding the exclusion suggested by FAMA. Although 
FAMA stated that its vehicles would not be subject to the exclusion of 
vehicles with an axle having a gross axle weight rating of 29,000 
pounds or more, it is not clear that this or other exclusions do not 
apply. Moreover, absent specific information that more fully explains 
why an exclusion is necessary and not overly broad, NHTSA cannot agree 
that an exclusion for all combination vehicles that require more than 
one operator to steer it is necessary.
    Furthermore, the scope of the exclusion suggested by FAMA is not 
consistent with the scope of the rule. Specifically, this final rule, 
like the NPRM, applies to truck tractors, not trailers. However, the 
suggested exclusion would apply to combination vehicles, which include 
both a truck tractor and a trailer. That is, the presence of a trailer 
would form the basis for the exclusion. If this exclusion was added to 
the final rule, then the basis for the exclusion would be dependent on 
the trailer that is attached to the vehicle. This would be confusing 
and unnecessarily complicate enforcement.
    Finally, FAMA has not articulated why its vehicles cannot be 
equipped with ESC systems. Because the ESC requirement applies only to 
the truck tractor, the system would only need to take account of one 
steering wheel input. There would be no requirement that the vehicle 
respond to any inputs from the trailer. Moreover, NHTSA would conduct 
compliance testing of the truck tractor using the control trailer 
specified in the test procedure, not a trailer with a steering wheel.
    Several commenters suggested that the agency reduce the scope of 
the ESC requirement. EMA requested that NHTSA exclude all severe duty 
trucks from the scope of a final rule. It reasoned that manufacturers 
offer multiple configurations of truck tractors with different 
wheelbases, axle, and suspension combinations. Furthermore, it claimed 
that manufacturers often build only a few vehicles in each 
configuration and in some cases of severe duty trucks, may only build a 
single vehicle in a particular configuration.
    The agency is not excluding severe duty trucks as EMA suggests. 
Currently, manufacturers are able to produce products in small volumes 
that meet all the requirements of the Federal Motor Vehicle Safety 
Standards (FMVSS). The addition of the ESC rule will not unduly burden 
the manufacturers with regard to their small volume products. EMA's 
actions related to this rulemaking support this conclusion. For 
example, EMA provided test data to the agency after performing multiple 
test maneuvers with severe duty trucks equipped with ESC systems. EMA 
also included the test results from the severe duty trucks to form its 
recommended test criteria for an alternate roll stability test.
    Meritor WABCO requested NHTSA to add the words ``pneumatically 
braked'' to the definitions of truck tractors and buses in the ESC 
rule. Similarly, EMA recommended that NHTSA include the ESC 
requirements within FMVSS No. 121 rather than in a separate standard.
    We are not expressly limiting the scope of the final rule to air 
braked vehicles. Although Class 8 vehicles typically use pneumatic or 
air brakes, Class 7 vehicles vary between either air or hydraulic 
brakes. The scope of the NPRM includes all truck tractors and Class 7 
and 8 buses, which showed the greatest rollover problem of all the 
buses according to our research. In order to address the safety problem 
with these classes of buses, the ESC rule must include both air and 
hydraulic brakes. Limiting the scope of this rulemaking to air braked 
vehicles could provide an incentive for some manufacturers to equip 
vehicles with hydraulic brakes rather than air brakes to circumvent an 
ESC system requirement.
3. Single-Unit Trucks
    The agency did not propose to include single-unit trucks with a 
GVWR over 4,536 kg (10,000 pounds). Several commenters recommended 
expanding the scope of the rule to include straight trucks. Skagit, 
NTSB, IIHS, and NAPT all suggested that ESC should be mandated on all 
commercial vehicles greater than 10,000 pounds GVWR, including straight 
trucks. Advocates recommended that NHTSA should consider the FMCSA 
study stating the number of fatalities by single-unit trucks, based on 
data from 2008, are 1,147 each year. Bosch stated that the rule should 
be expanded to cover all vehicles over 10,000 pounds GVWR vehicles, 
including hydraulic-braked vehicles, because this segment accounts for 
a large number of commercial and load bearing vehicles on the U.S. 
roads. Bosch claims that a mandate with a phase-in period is needed to 
facilitate industry development of ESC systems on these vehicles. On 
the other hand, Bendix recommended that ``[t]he decision by the agency 
regarding if and when to consider rulemaking on single-unit trucks 
should be based on the same

[[Page 36066]]

level of research undertaken for tractor and coach.''
    We are not expanding the scope of this rulemaking to include 
single-unit trucks. We believe that a level of research closer to what 
we had to support the NPRM for truck tractors and large buses is 
necessary before NHTSA would propose to mandate ESC on all single-unit 
trucks. After publishing the NPRM, we began a research and testing 
program to study the safety benefits and performance criteria of ESC 
systems on single-unit trucks. The research is not yet complete. 
Furthermore, as we stated in the NPRM, the complexity of the single-
unit truck population and the limited crash data available present a 
significant challenge to determining the effectiveness of stability 
control on these vehicles. At this time, we will not include single-
unit trucks in the ESC rule. However, we believe including buses with 
hydraulic brakes in this final rule will spur development of ESC 
systems for other hydraulic-braked vehicles, including trucks with a 
GVWR of greater than 4,536 kilograms (10,000 pounds) but not more than 
11,793 kilograms (26,000 pounds).
4. Compliance Dates
    The agency proposed that all new typical 6x4 truck tractors would 
be required to meet the proposed standard beginning two years after a 
final rule is published. Because there are currently only two suppliers 
of truck tractor and large bus stability control systems, Bendix and 
Meritor WABCO, we reasoned that the industry would require lead time to 
ensure that the necessary production stability control systems are 
available to manufacturers. NHTSA also proposed a two-year lead time 
for two-axle tractors.
    For severe service tractors and tractors with four axles or more, 
which represent about 5 percent of annual truck tractor sales, the 
agency believed additional lead time was necessary to develop, test, 
and equip these vehicles with a stability control system. Therefore, we 
proposed to require that severe service tractors and other atypical 
tractors be equipped with ESC systems beginning four years after the 
final rule is published.
    Four commenters addressed the compliance dates for trucks proposed 
by the NPRM. Daimler requested an additional lead time for ESC 
implementation because it said that it only has RSC systems developed 
on some models and needs more time to design and validate ESC on all of 
its models.
    In its comment, EMA mentioned that this ESC rule should align with 
the implementation dates of the new FMVSS No. 121 stopping distance 
requirements to give manufacturers the opportunity to refine the 
braking systems prior to the implementation of this ESC rule. EMA said 
it is impractical for manufacturers to certify compliance tests using 
the tests in the NPRM for all typical 6x4 tractors within 2 years of 
the final rule. Moreover, EMA said that tractors with four or more 
axles and severe service tractors have not been evaluated using the 
tests in the NPRM and likely would need additional lead time. However, 
EMA did not specify how much additional lead time was necessary. 
Finally, EMA and Bendix recommended including two-axle tractors in the 
longer lead time period because it appears to be an error.
    In contrast, HDBMC stated its belief that the suppliers of ESC 
systems are prepared to meet the anticipated deployment demands by the 
implementation dates proposed.
    We recognize the recent changes to the stopping distance 
requirements in FMVSS No. 121 affected truck tractors. Truck tractors, 
other than three-axle truck tractors, were recently subjected to the 
reduced stopping distance changes that went into effect on August 1, 
2013. Manufacturers of these truck tractors were given two additional 
years beyond the timeframe for three-axle truck tractors to comply with 
the amendments to FMVSS No. 121. We agree with Daimler and EMA that at 
least four years of lead time is warranted for all truck tractors other 
than typical 6x4 tractors (three-axle truck tractors with a front axle 
that has a GAWR of 6,622 kg (14,600 pounds) or less and with two rear 
drive axles that have a combined GAWR of 20,412 kg (45,000 pounds) or 
less). Although HDMA said that its member companies are ready to supply 
brake components by the implementation dates proposed, we realize that 
truck tractor manufacturers need extra time to integrate the ESC 
systems into their products and to perform the necessary testing to 
ensure compliance. In addition, manufacturers recently made brake 
system changes to these models of truck tractors in order to comply 
with the new requirements in the FMVSS No. 121 amendments. We recognize 
that ESC systems must be integrated into the brake systems, and we 
expect that manufacturers may need to modify the brake systems for a 
second time.

B. Buses

1. Summary of the NPRM
    The NPRM proposed that certain buses would be required to be 
equipped with ESC systems. The applicability of the proposal to buses 
mirrored the applicability of the agency's proposal that certain large 
buses be equipped with seat belts.\32\ The proposal for seat belts was 
applicable to buses with a gross vehicle weight rating (GVWR) of 11,793 
kilograms (26,000 pounds) or greater, 16 or more designated seating 
positions (including the driver), and at least 2 rows of passenger 
seats that are rearward of the driver's seating position and are 
forward-facing or can convert to forward-facing without the use of 
tools.'' That proposal excluded school buses and urban transit buses 
sold for operation in urban transportation along a fixed route with 
frequent stops. The agency proposed a very similar applicability in the 
NPRM for this rulemaking.\33\ We believed that the proposal encompassed 
the category of ``cross-country intercity buses'' represented in the 
FARS and FMCSA data (identified in section II.A above) that had a 
higher involvement of crashes that ESC systems are capable of 
preventing.
---------------------------------------------------------------------------

    \32\ 75 FR 50958 (Aug. 18, 2010).
    \33\ The primary difference is that the ESC proposal was not 
made applicable to buses with a GVWR of exactly 11,793 kilograms 
(26,000 pounds) in order to exclude Class 6 vehicles from the 
proposal.
---------------------------------------------------------------------------

2. Buses Built on Truck Chassis
(a) Summary of NPRM
    The agency tested three air-braked buses, all of which had a GVWR 
over 14,969 kg (33,000 lb.) (Class 8). Nevertheless, the agency 
included Class 7 buses (buses with a GVWR of more than 11,793 kg 
(26,000 lb.) but not greater than 14,969 kg (33,000 lb.). We reasoned 
that, although many Class 7 buses are built on chassis similar to those 
of single-unit trucks for which ESC has not been widely developed, and 
we are not aware of any Class 7 bus that is equipped or currently 
available with ESC. Class 7 buses represent less than 20 percent of the 
market. Although the agency was not aware of any Class 7 bus currently 
available with ESC, we were aware that stability control systems are 
available on a limited number of Class 8 single-unit trucks, such as 
concrete trucks, refuse trucks, and other air-braked trucks, and that 
the same technology could be developed for use on Class 7 buses, which 
we believed were also air-braked vehicles. We also believed that the 
manufacturers of Class 7 buses would need additional lead time to have 
the ESC systems developed, tested and installed on their vehicles. 
Hence, for large buses, the agency proposed an effective date of two 
years after the final rule is published,

[[Page 36067]]

primarily to accommodate manufacturers of Class 7 buses.
    However, we sought comment on the feasibility of including Class 7 
buses that are built on chassis similar to those of single-unit trucks 
within two years. We noted that, although we believed that Class 7 
buses were primarily air braked and that ESC systems were readily 
available for air-braked buses, system availability for any hydraulic-
braked buses that may be covered may be more limited. We requested 
that, if hydraulic-braked buses were covered by the proposal, 
commenters address manners in which hydraulic-braked buses may be 
differentiated for exclusion or a different phase-in period.
(b) Summary of Comments
    Several commenters raised issues related to the NPRM's definition 
for large buses. EMA and Navistar commented that the ``large bus'' 
definition should not include commercial buses, which are buses greater 
than 11,793 kg (26,000 lb.), but are not traditional intercity buses. 
They claimed that many of these buses are built on truck chassis and 
are different than the Class 8 buses tested by NHTSA. They stated that 
these buses are built in multiple stages by multiple manufacturers, 
which would make compliance certification difficult.
    According to Navistar, NHTSA did not ``reach out'' to Navistar 
regarding its commercial buses because it claimed NHTSA was not aware 
of its Class 8 commercial buses from the sole fact that they were not 
specifically mentioned in list of bus manufacturers included in the 
NPRM.
    In its comments, EMA opined that non-motorcoach buses with a GVWR 
over 11,793 kg (26,000 lb.) are more closely related to single-unit 
trucks. It also commented that some of the same issues related to 
requiring ESC systems on single-unit trucks are also present for large 
buses.
    EMA stated that consistent with the Motorcoach Enhanced Safety Act 
(part of MAP-21), it considered the term ``motorcoach'' to have the 
same meaning as ``over-the-road-bus,'' which ``means a bus 
characterized by an elevated passenger deck located over a baggage 
compartment.'' \34\ EMA and Daimler also commented that a 
``motorcoach'' has some, if not all, of the following attributes: a 
GVWR greater than 33,000 pounds (Class 8); air disc brakes; passenger 
deck floor more than 45 inches above the ground; rear engine 
configuration; monocoque \35\ construction; 40 or more passenger seats; 
no provisions for standee passengers; and one passenger entrance and 
exit door. EMA asserted that NHTSA did not study ESC on other non-
motorcoach buses, and therefore, the rule should not apply to those 
buses.
---------------------------------------------------------------------------

    \34\ The rulemaking requirements of the Motorcoach Enhanced 
Safety Act are addressed in section II above.
    \35\ Monocoque means a type of vehicular construction in which 
the body is combined with the chassis as a single unit.
---------------------------------------------------------------------------

(c) NHTSA's Response to Comments
    NHTSA is not changing the general applicability of the ESC 
requirement to buses. As we stated in the NPRM, we intended the 
applicability of the ESC requirement to buses to be similar to the 
applicability of the agency's requirement that buses have seat belts at 
each passenger seating position. In both rulemakings, the target 
vehicles were high occupancy buses associated with a known fatality and 
injury risk. The buses typically carried a large number of passengers 
and were operated at highway speeds. We examined the involvement of 
high occupancy buses in fatal crashes over a 10-year period (FARS data 
files, for the NPRM, 1999-2008). In this examination of high occupancy 
bus data, we inspected crash data for buses with a GVWR greater than 
4,536 kg (10,000 lb.). We analyzed the construction type and various 
attributes of the vehicles. The 2000-2009 FARS data show that for buses 
over 4,536 kg (10,000 lb.), there were 49 passenger fatalities in buses 
with a GVWR less than 11,793 kg (26,000 lb.), but there were 209 in 
buses with a GVWR greater than 11,793 kg (26,000 lb.).
    Moreover, MAP-21, which was enacted after publication of the NPRM, 
requires the Secretary to consider requiring ESC systems on certain 
large buses if the Secretary determines that such a requirement is 
consistent with the requirements of the Motor Vehicle Safety Act. We 
believe that mandating ESC systems on the buses covered by the NPRM, 
subject to some minor changes discussed below, is consistent with those 
requirements. That is, this standard is practicable, meets the need for 
motor vehicle safety, and may be stated in objective terms. We believe 
that ESC systems are currently available for must buses covered by this 
final rule and can be developed for the others. Moreover, the safety 
problem discussed in Section IV.D above highlights the rollover problem 
in buses with a GVWR greater than 11,793 kg (26,000 lb.).
    NHTSA has decided to adopt the proposal to require all buses with a 
GVWR over 11,793 kg (26,000 lb.), subject to some modified exclusions 
for school buses, transit buses, and perimeter seating buses. In 
Section V.B.1 of the NPRM, NHTSA mentioned the rationale for not 
including a requirement for ESC on single-unit trucks with a GVWR over 
4,536 kilograms (10,000 pounds) at this time.\36\ The rationale was 
primarily based on the differences between truck tractors and single-
unit trucks; it was not intended and did not mention the differences 
between buses built on truck chassis and buses built with monocoque 
construction. Although the NPRM stated that single-unit trucks as a 
whole are more complex and diverse than truck tractors, this does not 
necessarily apply to buses built on truck chassis. Among the different 
bodies that could be assembled on a truck chassis, a bus body presents 
a degree of complexity and diversity that is substantially less than 
the other truck bodies. For example, a bus body presents a scenario 
where center-of-gravity height and cargo type are more easily 
calculated because the bus is limited to transporting people and their 
luggage rather than varied cargo. The chassis supplier for a bus would 
be more likely to have knowledge of critical vehicle design parameters 
that affect ESC calibration.
---------------------------------------------------------------------------

    \36\ 77 FR 30789.
---------------------------------------------------------------------------

    NHTSA reviewed various definitions used in motorcoach safety 
legislation including the ``over-the-road bus'' definition in TEA-21 
that was referenced in MAP-21. Similar to the final rule requiring seat 
belts on certain buses, we are not limiting the applicability of the 
ESC requirement to TEA-21's definition of over-the-road buses.\37\ We 
believe that the definitions referring to over-the-road buses or over-
the-road bus service are too narrow, because a number of intercity 
transport buses involved in fatal crashes were body-on-chassis buses 
that lacked an elevated passenger deck over a baggage compartment. 
Further, definitions based on the intended use of the vehicle could 
pose difficulties for manufacturers and dealers, because the intended 
use of a vehicle might not be known at the time of vehicle manufacture 
or sale. We want to make sure as reasonably possible that the buses we 
most wanted to affect (high-capacity buses associated with known 
fatality and injury risks) would meet the ``motorcoach'' safety 
standards, without having to depend on the state of knowledge of 
persons in the manufacturing and distribution chain about the 
prospective use of the bus.
---------------------------------------------------------------------------

    \37\ 78 FR 70429.
---------------------------------------------------------------------------

    Currently, there is no common Departmental or industry definition 
of ``motorcoach.'' FMCSA does not have a

[[Page 36068]]

definition for motorcoach in its regulations, but it considers a 
``motorcoach'' to be an over-the-road bus. As noted above, over-the-
road buses are a subset of the buses NHTSA believes should be regulated 
as ``motorcoaches,'' encompassing a part of but not enough of the heavy 
bus safety problem we seek to address.
    We reviewed the underlying chassis structure of high-occupancy 
vehicles involved in fatal crashes. Some had a monocoque structure with 
a luggage compartment under the elevated passenger deck (``over-the-
road buses''). However, an elevated passenger deck over a baggage 
compartment was not an element common to the buses involved in fatal 
intercity transport. In FARS data for buses with a GVWR greater than 
11,793 kg (26,000 lb.), 36 percent of the fatalities were in the other 
bus and unknown bus categories, i.e., not in the over-the-road bus 
category. Some buses were built using body-on-chassis configurations.
    We believe that body-on-chassis configurations are newer entrants 
into the motorcoach services market. They appear to be increasing in 
number. A cursory review of the types of buses being used in the 
Washington, DC area for motorcoach services showed that traditional 
motorcoaches are generally used for fixed-route services between major 
metropolitan areas. However, for charter, tour, and commuter 
transportation from outlying areas, many bus types are used. Some are 
of monocoque structure, while others are of body-on-chassis structure.
    The agency tested Class 8 buses, those with a GVWR greater than 
14,969 kg (33,000 lb.), because these buses have larger dimensions and 
masses than Class 7 buses, and it places them on the most severe end of 
the spectrum. The performance criteria were created based on the 
testing of the larger Class 8 buses, and the agency has made a reasoned 
determination that the criteria are applicable for Class 7 buses, as 
well. If a Class 8 bus with a larger GVWR can pass the minimum 
performance criteria for ESC systems, a Class 7 bus with a smaller GVWR 
can reasonably be required to meet the same criteria.
    Despite the fact that some of these buses are built in multiple 
stages by multiple manufacturers, the agency does not agree that 
compliance with the ESC standard will be very difficult. Presently, 
manufacturers building buses in various stages must provide an 
incomplete vehicle document (49 CFR part 568) to subsequent 
manufacturers listing each standard that applies. One example of a 
standard that must be documented is FMVSS No. 121, Air Brake Systems. A 
number of factors such as GVWR, GAWR, and any other specific conditions 
given by the manufacturer must be considered when determining if a bus 
will be compliant with the braking requirements after it is built. 
Likewise, the agency expects manufacturers to give similar conditions 
of final manufacture under which the manufacturer specifies that the 
completed vehicle will conform to the ESC standard. The agency 
considers that burden of bus manufacturers to comply with the ESC rule 
will not be more difficult than the current burden of complying with 
the air brake requirements in FMVSS No. 121.
3. Hydraulic-Braked Buses
    In the NPRM, we requested comment on manners in which hydraulic-
braked buses may be differentiated, such as by exclusion or a different 
phase-in period for the ESC rule. Six commenters provided statements 
about hydraulic-braked buses and how they should be excluded. 
Specifically, Blue Bird opposes an ESC mandate on hydraulic-braked 
buses with a GVWR of 36,200 pounds and less. It also commented that the 
agency should wait until ESC systems are developed and fully evaluated 
for hydraulic-braked medium or heavy buses and not include hydraulic-
braked buses as part of the ESC rule at this time. Blue Bird, Daimler, 
Meritor WABCO, Navistar, and EMA all commented that they are not aware 
of any ESC systems available for hydraulic-braked buses covered by the 
NPRM. Meritor WABCO recommended that NHTSA exclude vehicles that are 
not ``pneumatically braked.'' Finally, both Daimler and EMA stated that 
they want the ESC regulation to extend only to motorcoaches over 33,000 
pounds.
    NHTSA has no convincing evidence to exclude hydraulic-braked buses 
from this ESC rule. The NPRM proposed to require ESC on both Class 7 
and Class 8 buses. The mandate in the Motorcoach Enhanced Safety Act 
makes no differentiation between Class 7 and Class 8 buses. In order to 
address the rollover and loss-of-control safety problems with these 
classes of buses, the ESC rule must include both air and hydraulic 
brakes.
    Based on feedback received from the commenters, we recognize that 
Class 7 buses are composed of both air- and hydraulic-braked vehicles. 
We recognize that manufacturers who produce large buses equipped with 
hydraulic-powered brakes might need extra time to ensure the proper 
integration between the ESC system and the vehicle's chassis, engine, 
and braking system. Rather than exclude hydraulic-braked buses from the 
rule entirely, NHTSA will extend the compliance date for buses that may 
be equipped with hydraulic brakes. NHTSA acknowledges that ESC systems 
are still in development for large buses with hydraulic-braked buses, 
and therefore, manufacturers and suppliers need additional time to 
implement this new technology. However, whether the bus is equipped 
with air brakes or hydraulic brakes, we expect the performance 
requirements to apply because they are based on the stability of the 
bus as defined by its attributes such as geometry, mass, inertia, and 
center-of-gravity height. There is a negligible change in these 
attributes between an air-braked and a hydraulic-braked bus.
4. School Buses
    Six commenters recommended that NHTSA include a requirement that 
school buses be equipped with ESC systems in the final rule. Consumers 
Union commented that ESC technology should be required for school buses 
in order to set a precedent for future crash avoidance technologies. 
Martec recommended that ESC be required on all buses because it claims 
that ``large school buses satisfy multiple criteria described by NHTSA 
in its 2011-2013 Rulemaking and Research Priority Plan: the addition of 
ESC/RSC to school buses would offer large safety benefits, would apply 
to high-occupancy vehicles, and would apply to a vulnerable 
population--children.'' Skagit, NTSB, and IIHS all want ESC to be 
mandated on all buses greater than 10,000 lb., including school buses.
    Conversely, Daimler and NSTA both agreed that NHTSA not include 
school buses in a final rule mandating ESC systems on large buses. NSTA 
asserted that, if school buses were subject to an ESC mandate, the 
costs to purchase school buses would increase. NSTA is concerned that 
the added costs would reduce the number of school buses on the road, 
and, consequently, reduce the number of children riding buses to 
school. NTSA claims that students riding school buses are eight times 
safer than riding in the family vehicle because school buses travel at 
lower speeds and largely in residential areas.
    As in the NPRM, we are excluding school buses from the ESC 
requirement. Each NHTSA rulemaking must address a present safety need 
and be justified by present safety benefits. We cannot accept Consumers 
Union's recommendation to do rulemaking now based on speculative 
benefits of ESC systems on school buses. According to FARS data between 
2000 and 2009, among the large buses, more than 70%

[[Page 36069]]

of fatalities on large buses with a GVWR greater than 11,793 kg (26,000 
lb.) were related to cross-country intercity bus crashes. Similarly, we 
stated in the NPRM that FMCSA's Large Truck and Bus Crash Facts 2008 
indicates that most of the school bus crashes are not rollover or loss-
of-control crashes that ESC systems are capable of preventing. For 
these reasons, we will not require school buses to be equipped with ESC 
at this time.
    Navistar, EMA, and Daimler requested that the school bus exclusion 
extend into its line of school bus derivatives. Navistar and EMA 
reasoned that some commercial buses are built on truck chassis. Because 
of their similarities to school buses, they reasoned that those buses 
should be exempted from the ESC rule. According to Daimler, school bus 
derivatives are vehicles built with hydraulic brakes, and no ESC system 
is available on these types of hydraulic brakes in the market today.
    We disagree with Daimler, EMA, and Navistar that the school bus 
exception should extend to other buses that are similar or 
``derivatives'' as Daimler stated. If the commenters' reasoning was 
adopted, any manufacturer could offer a school bus version of a 
particular bus model and claim that the school bus exception should 
apply because of the artificially created similarities. This would 
create an unintended loophole for the ESC requirement and potentially 
undermine the rule.
5. Transit Buses
    The NPRM proposed to exclude from the ESC system requirements urban 
transit buses sold for operation in urban transportation along a fixed 
route with frequent stops. EMA and Volvo suggested that we exclude 
certain buses based on the intended use of the vehicle in public 
transit. Volvo requested that the agency base the exclusion on the 
Federal Transit Administration's (FTA) bus procurement guidelines. 
Volvo suggested excluding ``urban transit buses which may be used on 
suburban express service and general service on urban arterial streets 
along a fixed route with frequent stops.'' Similarly, EMA suggested 
adding to the exclusion for transit buses ``urban transit buses used in 
suburban express service.'' Conversely, Volvo stated during the public 
hearing that it was practical and technologically feasible to equip its 
urban buses with ESC, but it did not want to do so because it did not 
perceive a safety need.
    The Motorcoach Enhanced Safety Act excludes from its mandate to 
consider requiring ESC systems on large buses a bus used in public 
transportation provided by, or on behalf of, a public transportation 
agency. However, as we explained in the previous section regarding 
school buses, an exclusion based on the intended use of the vehicle 
could pose difficulties for manufacturers and dealers, because the 
intended use of a vehicle might not be known at the time of vehicle 
manufacture or sale. Consequently, we will not adopt the recommendation 
suggested by EMA and Volvo to exclude urban transit buses used in 
suburban express service.
    The final rule requiring seat belts at all passenger seating 
position on certain buses noted that commenters on that NPRM were 
troubled that the proposed transit bus exclusion was not sufficiently 
clear. To make the definition more clear, the final rule made 
clarifications that we believe are also warranted in this final rule 
requiring ESC systems on certain buses.\38\ First, we made the 
regulatory text clearer in describing a ``transit bus'' by referring to 
a structural feature (a stop-request system) that buses must have to be 
a ``transit bus.'' A ``stop-request system'' means a vehicle-integrated 
system for passenger use to signal to a vehicle operator that a stop is 
requested. Second, we expanded the description of a transit bus by 
recognizing that a transit bus could be sold for public transportation 
provided not only by, but also on behalf of, a State or local 
government, for example, by a contractor.
---------------------------------------------------------------------------

    \38\ 78 FR 70438.
---------------------------------------------------------------------------

    Finally, we made clear that over-the-road buses, as defined by TEA-
21, do not qualify as ``transit buses,'' even if the over-the-road bus 
has a stop-request system or is sold for public transportation provided 
by or on behalf of a State or local government. This final 
clarification ensures both that a manufacturer cannot integrate a 
simple stop-request system on any bus and make it subject to the 
transit bus exclusion. We recognize that any over-the-road bus used for 
public transportation provided by or on behalf of a State or local 
government is likely to be used as a commuter express bus that would 
carry large numbers of passengers over long distances at highway 
speeds. However, this use case is similar to the use of over-the-road 
buses by private companies in intercity service.
6. Minimum Seating Capacity and Seating Configuration
    The NPRM also excluded buses that had fewer than 16 designated 
seating positions (DSPs), including the driver. This reference was 
included in the seat belt NPRM based on FMCSA's definition of a 
``commercial motor vehicle,'' for purposes of FMCSA's commercial 
driver's license requirements.\39\ In the final rule, however, NHTSA 
noted that FMCSA's regulations state that buses with a GVWR greater 
than 11,793 kg (26,000 lb.) are commercial vehicles under the 
commercial driver's license regulations, regardless of the number of 
DSPs. Accordingly, that exclusion was removed from the final rule.\40\
---------------------------------------------------------------------------

    \39\ 75 FR 50969.
    \40\ 78 FR 70433.
---------------------------------------------------------------------------

    EMA and Daimler suggested that the rule exclude all buses with 
fewer than 40 passenger seats, which they imply would exclude buses 
that are not considered ``motorcoaches.'' However, neither EMA nor 
Daimler included any explanation for why 40 passenger seats is an 
appropriate cutoff for an ESC system requirement, and we can perceive 
none. We do not believe that a minimum number of passenger seats would 
serve to include or exclude buses that are being driven at long 
distances or at highway speeds.
    The NPRM also proposed to exclude buses with fewer than two rows of 
passenger seats that are rearward of the driver's seating position and 
are forward-facing or can convert to forward-facing without the use of 
tools. This reference was included in the large bus seat belt NPRM to 
distinguish buses with perimeter seating such as those used to 
transport passengers in airports between the terminal and locations 
such as a rental car facility or long term parking.\41\ These buses 
typically have a single forward-facing row of seats in the back of the 
vehicle and seats along one or both sides of the bus. These buses 
typically carry people for a relatively short period, often transport 
standees, generally accommodate baggage and other items, and are 
designed for rapid boarding and alighting. These buses were excluded 
because we believed they would be used for relatively short distances 
on set routes, which are not widely exposed to general traffic.
---------------------------------------------------------------------------

    \41\ 78 FR 70434.
---------------------------------------------------------------------------

    In the seat belt final rule, the agency simplified the exclusion by 
defining these vehicles as perimeter seating buses and excluding them 
from the seat belt requirement rather than specifying the number of 
rows and seats that a bus has. Second, we referred to the maximum 
number of forward-facing DSPs that the vehicle may have rather than the 
number of ``rows'' it may have. We made this change because there is no 
definition of ``row'' generally

[[Page 36070]]

applicable to the FMVSSs and it was difficult to define ``row'' for the 
purpose of excluding perimeter-seating buses using plain language. 
Thus, we defined a ``perimeter-seating bus'' as a bus with 7 or fewer 
DSPs rearward of the driver's seating position that are forward-facing 
or can convert to forward-facing without the use of tools, and excluded 
perimeter-seating buses from the seat belt requirement.\42\
---------------------------------------------------------------------------

    \42\ See 78 FR 70434-35.
---------------------------------------------------------------------------

    We believe that this exclusion is similarly applicable to the ESC 
system requirement, and we are adopting in this final rule the 
simplified language used in the seat belt final rule. A perimeter-
seating bus typically carries people for short distances on set routes 
and is often less exposed to general traffic than transit buses. 
However, consistent with the Motorcoach Enhanced Safety Act, we are not 
excluding from the ESC system requirement perimeter-seating buses that 
are also over-the-road buses. Some of these buses may include vehicles 
often referred to as ``limo buses'' or ``party buses.'' These vehicles 
may also be used as touring or entertainment buses with eating and 
sleeping accommodations that are used by celebrities and entertainers 
on tour. We expect that these types of buses will be used for intercity 
travel and driven at highway speeds.
7. Compliance Dates
    The NPRM proposed that buses meet the ESC system requirements two 
years after publication of a final rule implementing the proposal. 
Although we did not receive any comments specifically addressing the 
compliance date for large buses, the Motorcoach Enhanced Safety Act 
specifically states that a stability enhancing requirement shall apply 
to all motorcoaches manufactured more than 3 years after the date on 
which the regulation is published as a final rule. Based on the 
Congressional determination that any enhancing stability technology 
rulemaking shall apply to all over-the-road buses manufactured more 
than 3 years after the final rule is published, we will allow bus 
manufacturers that amount of time inasmuch as a three-year lead time is 
practical.
    With respect to Class 7 buses, the agency has determined that a 
three-year compliance date is not practical. The scope of this final 
rule includes buses that are hydraulic-braked. We recognize the 
manufacturers of hydraulic-braked buses will likely require extra time 
to ensure system availability and that the ESC system is properly 
integrated with the vehicle. Based on the comments received from the 
bus industry, Class 7 buses are equipped with both air and hydraulic 
brakes. Rather than differentiate between brake systems of the Class 7 
buses, we believe it would be better to base the compliance date 
requirements on GVWR. This will also address the concerns of 
manufacturers of buses built on truck chassis, for which ESC systems 
may not currently be equipped. We believe that at least four years of 
lead time are necessary to ensure that suppliers have ESC systems 
available for hydraulic-braked large buses. Accordingly, this final 
rule allows Class 7 bus manufacturers four years of lead time before 
the requirements of this final rule become applicable.
8. Class 3 Through 6 Buses
    Some of the commenters recommended that we expand the scope to 
include mid-size buses which are typically built on single-unit truck 
frames. Skagit, NTSB, IIHS, NAPT, Advocates, and Bosch all suggested 
that ESC should be mandated on all buses greater than 10,000 pounds. 
The NTSB estimated that 11,600 mid-size buses (buses with a GVWR 
between 10,000 pounds and 26,000 pounds) are produced each year. 
Advocates recommended that NHTSA should consider the NTSB 
recommendation that all buses over 10,000 pounds GVWR should be 
equipped with stability control systems. Bosch stated that the agency 
should develop a performance standard to cover vehicles in Classes 3 
through 7 with hydraulic brakes because this segment accounts for a 
large number of commercial and load bearing vehicles on the U.S. roads. 
Bosch claims that a standard with a phase-in period is needed to 
facilitate industry development of ESC systems for these vehicles. 
Bosch also cites Annex 21 of UN ECE Regulation 13, which requires ESC 
on buses operating in the European Union.
    We are not expanding the scope of this rule to include vehicles 
with a GVWR of 11,793 kilograms (26,000 pounds) or less. After 
publishing the NPRM, we began a research program to study the safety 
benefits and performance criteria of ESC systems on single-unit trucks, 
which includes mid-size buses. The research is not yet complete on 
single-unit trucks or smaller buses. However, we believe including 
buses with hydraulic brakes in this final rule will spur development of 
ESC systems for other hydraulic-braked vehicles, including buses with a 
GVWR of greater than 4,536 kilograms (10,000 pounds) but not more than 
11,793 kilograms (26,000 pounds).

C. Retrofitting

    NHTSA considered proposing to require retrofitting of in-service 
truck tractors, trailers, and large buses with stability control 
systems. The Secretary has the statutory authority to promulgate safety 
standards for ``commercial motor vehicles and equipment subsequent to 
initial manufacture.'' \43\ The Secretary has delegated authority to 
NHTSA to promulgate safety standards for commercial motor vehicles and 
equipment subsequent to initial manufacture when the standards are 
based upon and similar to an FMVSS promulgated, either simultaneously 
or previously, under chapter 301 of title 49, U.S.C.\44\ Additionally, 
the Federal Motor Carrier Safety Administration (FMCSA) is authorized 
to promulgate and enforce vehicle safety regulations, including those 
aimed at maintaining commercial motor vehicles so they continue to 
comply with the safety standards applicable to commercial motor 
vehicles at the time they were manufactured.
---------------------------------------------------------------------------

    \43\ See Motor Carrier Safety Improvement Act of 1999, section 
101(f), Pub. L. 106-159 (Dec. 9, 1999).
    \44\ See 49 CFR 1.50(n).
---------------------------------------------------------------------------

    Although the NPRM did not propose requiring truck tractors, 
trailers, or large buses to be equipped with stability control systems 
``subsequent to initial manufacture,'' we requested public comment on 
several issues related to retrofitting in-service truck tractors, 
trailers, and buses:
     The extent to which a proposal to retrofit in-service 
vehicles with stability control systems would be complex and costly 
because of the integration between a stability control system and the 
vehicle's chassis, engine, and braking systems.
     The changes necessary to an originally manufactured 
vehicle's systems that interface with a stability control system, such 
as plumbing for new air brake valves and lines and a new electronic 
control unit for a revised antilock brake system.
     The additional requirements that would have to be 
established to ensure that stability control components are at an 
acceptable level of performance for a compliance test, given the 
uniqueness of the maintenance condition for vehicles in service, 
particularly for items such as tires and brake components that are 
important for ESC performance.
     The original manufacture date of vehicles that should be 
subject to any retrofitting requirements.

[[Page 36071]]

     Whether the performance requirements for retrofitted 
vehicles should be less stringent or equally stringent as for new 
vehicles, and, if less stringent, the appropriate level of stringency.
     The cost of retrofitting a stability control system on a 
vehicle, which we believe would exceed the cost of including stability 
control on a new vehicle.
    Several commenters addressed issues related to retrofitting in-
service vehicles with ESC systems. We received comments both favoring 
and opposing retrofitting.
    Road Safe America, NTSB, and Advocates supported a requirement for 
ESC to be retrofitted to existing heavy vehicles. Road Safe America 
recommended that RSC systems be retrofitted on all existing truck 
trailers. NTSB cited its recommendation that RSC systems be retrofitted 
on in-use cargo tank trailers. In its comments, Advocates said that 
there should be a retrofit requirement to install ESC systems on all 
in-service vehicles. Advocates stated that the failure to require 
retrofitting could significantly delay fleet penetration of ESC systems 
because of the extended service life of the affected vehicles.
    Many more commenters were opposed to a retrofit requirement for ESC 
systems. IIHS stated that ESC systems should not be required to be 
retrofitted at this time, but that the agency should explore the 
feasibility creating a requirement in the future. American Highway 
Users requested that there should be no retrofit requirements for 
existing vehicles in order to incorporate ESC systems and would oppose 
any efforts to implement a retrofit requirement. In its comment, ATA 
did not support a retrofit requirement for ESC systems because it 
claims there is an average of a 4-5 year turnover for a majority of 
Class 7 and Class 8 tractors. Volvo commented that there should not be 
a retrofit of trucks because the changes to the vehicle are too 
significant, and there is no way to assure the quality of the retrofit.
    Meritor WABCO stated that there should not be a retrofit of 
vehicles because, as a system supplier, it does not offer an ESC system 
retrofit option. Meritor WABCO also specified that ESC systems must be 
engineered and validated for each vehicle model and parts must be 
added, which would be difficult to do on in-service vehicles. Meritor 
WABCO further stated that an ESC system requires a steering wheel angle 
sensor, which is difficult to design for in-service vehicles. Meritor 
WABCO also expressed concern about the possibility of incomplete or 
incorrect retrofit installations if retrofits are required.
    The National Ready Mix Concrete Association argued that there 
should not be an ESC system retrofit requirement on single-unit trucks 
or truck tractors because retrofit costs will be higher on existing 
trucks than installations on new trucks. They further stated that a 
variety of improvised techniques are needed when doing retrofit 
installations, and these techniques result in higher maintenance costs. 
They were also concerned that a retrofitted system would not work on 
some older trucks because of unworkable truck designs and interference 
with safety and electronic features.
    HDBMC stated that there should be no retrofit requirement because 
retrofitting of ESC systems is impractical and difficult. HDBMC cited 
the challenges of ESC system retrofitting, which include: (1) 
Compatibility of the vehicle; (2) computer hardware and software 
issues; (3) issues with new component installation; (4) vehicle 
downtime to make the conversion; (5) testing and validation; and (6) 
further unknown variables.
    EMA asserted that it would be unsafe to implement a retrofit 
requirement because ESC systems are not currently installed over 
existing components. EMA also believes that aftermarket facilities do 
not have the capability to design, test, and implement ESC systems. EMA 
stated that rotational sensors, yaw rate, and lateral accelerometers 
must be mounted close to the vehicle's center of yaw rotation, or 
complex calculations must be used to compensate for any deviations in 
the mounting. Finally, EMA commented that the necessary components for 
an ESC system do not exist for older vehicle models.
    Bendix commented that it had, for the purposes of research and 
development, retrofitted ESC to more than 25 vehicles. Bendix estimated 
that retrofitting in-service vehicles would take between 80 and 120 
person-hours for installation because each installation would have to 
be customized and there would be little or no OEM support.
    After considering the public comments, NHTSA has decided not to 
include a retrofit requirement in this final rule. NHTSA recognizes 
that the costs and safety risks of mandating an ESC system retrofit may 
exceed the benefits. Those commenters supporting an ESC system retrofit 
did not provide any information to mitigate issues such as: (1) The 
complexity and cost to retrofit in-service vehicles with ESC systems; 
(2) the changes necessary to integrate the ESC system to the vehicle's 
chassis, engine, and braking system; (3) the changes necessary on the 
in-service vehicle to interface with the ESC system such as plumbing 
for new air brake valves and lines and a new electronic control unit 
for the ABS system; and (4) the additional requirements for in-service 
vehicles considering the uniqueness of the maintenance condition of the 
tire and brake components. Considering that the potential safety risks 
and certain high costs associated with a requirement to retrofit in-
service vehicles with ESC systems greatly exceed the benefits, NHTSA 
has not included a retrofit requirement in this final rule.

X. Performance Testing

A. NHTSA's Proposed Performance Tests

    The agency's research initially focused on a variety of maneuvers 
that we could use to evaluate the roll stability performance and the 
yaw stability performance of truck tractors and large buses. Several of 
these maneuvers were also tested by industry and some of them are 
allowed for use in testing for compliance to the UN ECE stability 
control regulation. The agency's goal was to develop one or more 
maneuvers that showed the most promise as repeatable and reproducible 
roll and yaw performance tests for which objective pass/fail criteria 
could be developed. Based on the agency's own testing and the results 
from industry-provided test data, two stability performance tests were 
proposed to evaluate ESC systems on truck tractors and large buses--the 
SIS test and the SWD test.
1. Characterization Test--SIS
    The agency proposed using the slowly increasing steer maneuver 
(SIS) as a characterization test to determine the unique dynamic 
characteristics of a vehicle. This maneuver would allow the agency to 
determine the relationship between the steering wheel angle and lateral 
acceleration of a vehicle. Also as part of the SIS characterization 
test, the ability of the ESC system to reduce engine torque is 
determined. During each of the SIS maneuvers, ESC activation is 
confirmed by verifying that the system automatically reduces the driver 
requested engine torque output. The NPRM proposed that, for each of the 
SIS maneuver test runs, the commanded engine torque and the driver 
requested torque signals must diverge at least 10 percent for 1.5 
seconds after the beginning of ESC system activation. This test

[[Page 36072]]

demonstrates that the ESC system has the capability to reduce engine 
torque, as required in the functional definition. The vehicles that the 
agency tested were all able to meet this proposed performance level.
2. Roll and Yaw Stability Test--SWD
    In the NPRM, we proposed using the sine with dwell maneuver (SWD) 
to test the ability of an ESC system to mitigate conditions that would 
lead to rollover or loss of control. Conceptually, the steering profile 
of this maneuver is similar to that expected to be used by real drivers 
during some crash avoidance maneuvers. As the agency found in the light 
vehicle ESC research program, the severity of the SWD maneuver makes it 
a rigorous test, while maintaining steering rates within the 
capabilities of human drivers. We believed that the maneuver is severe 
enough to produce rollover or vehicle loss-of-control without a 
functioning ESC system on the vehicle.
    The agency's test program was able to develop test parameters for 
the SWD maneuver so that both roll stability and yaw stability could be 
evaluated using a single loading condition and test maneuver. 
Previously, the SWD maneuver had typically been used to evaluate only 
the yaw instability of a vehicle. NHTSA evaluated several loading 
conditions and found that a loading condition of 80 percent of the 
tractor's GVWR enabled us to evaluate both the yaw and roll stability 
control of the ESC system.
    For a truck tractor, the agency would conduct the SWD test with the 
truck tractor coupled to an unbraked control trailer and loaded with 
ballast directly over the kingpin. The combination vehicle would be 
loaded to 80 percent of the tractor's GVWR. For a bus, the vehicle is 
loaded with a 68 kilogram (150 pound) ballast in each of the vehicle's 
designated seating positions, which would bring the vehicle's weight to 
less than its GVWR. The test vehicles were proposed to be equipped with 
outriggers to prevent the trailer from rolling over in case the ESC 
system does not function properly.
    The SWD test would be conducted at a speed of 72 km/h (45 mph). An 
automated steering machine would be used to initiate the steering 
maneuver. Each vehicle is subjected to two series of test runs. One 
series uses counterclockwise steering for the first half-cycle, and the 
other series uses clockwise steering for the first half-cycle. The 
steering amplitude for the initial run of each series is 0.3A, where A 
is the steering wheel angle determined from the SIS maneuver. In each 
of the successive test runs, the steering amplitude would be increased 
by increments of 0.1A until a steering amplitude of 1.3A or 400 
degrees, whichever is less, is achieved. Upon completion the test runs, 
the agency would conduct post-processing of the yaw rate and lateral 
acceleration data to determine the lateral acceleration ratio, yaw rate 
ratio, and lateral displacement, as discussed below.
    The lateral acceleration ratio (LAR) is a performance metric 
developed to evaluate the ability of a vehicle's ESC system to prevent 
rollovers. Lateral acceleration is measured on a bus or a tractor and 
corrected for the vehicle's roll angle. As a performance metric, the 
lateral acceleration value is normalized by dividing it by the maximum 
lateral acceleration that was determined at any time between 1.0 
seconds after the beginning of steering and the completion of steering. 
The two proposed performance criteria are described below:
     A vehicle must have a LAR of 30 percent or less 0.75 
seconds after completion of steer.
     A vehicle must have a LAR of 10 percent or less at 1.5 
seconds after completion of steer.
    The yaw rate ratio (YRR) is a performance metric used to evaluate 
the ability of a vehicle's ESC system to prevent yaw instability. The 
YRR expresses the lateral stability criteria for the sine with dwell 
test to measure how quickly the vehicle stops turning, or rotating 
about its vertical axis, after the steering wheel is returned to the 
straight-ahead position. The lateral stability criterion, expressed in 
terms of YRR, is the percent of peak yaw rate that is present at 
designated times after completion of steer. This performance metric is 
identical to the metric used in the light vehicle ESC system 
performance requirement in FMVSS No. 126. The two proposed performance 
criteria are described below:
     A vehicle must have a YRR of 40 percent or less 0.75 
seconds after completion of steer.
     A vehicle must have a YRR of 15 percent or less at 1.5 
seconds after completion of steer.
3. Lateral Displacement
    Lateral displacement is a performance metric used to evaluate the 
responsiveness of a vehicle, which relates to its ability to steer 
around objects. Stability control intervention has the potential to 
significantly increase the stability of the vehicle in which it is 
installed. However, we believe that these improvements in vehicle 
stability should not come at the expense of poor lateral displacement 
in response to the driver's steering input.
    A hypothetical way to pass a stability control performance test 
would be to make either the vehicle or its stability control system 
intervene simply by making the vehicle poorly responsive to the speed 
and steering inputs required by the test. An extreme example of this 
potential lack of responsiveness would occur if an ESC system locked 
both front wheels as the driver begins a severe avoidance maneuver that 
might lead to vehicle rollover. Front wheel lockup would create an 
understeer condition in the vehicle, which would result in the vehicle 
plowing straight ahead and colliding with an object the driver was 
trying to avoid. It is very likely that front wheel lockup would reduce 
the roll instability of the vehicle since the lateral acceleration 
would be reduced. This is clearly, however, not a desirable compromise.
    Because a vehicle that simply responds poorly to steering commands 
may be able to meet the stability criteria proposed in the NPRM, a 
minimum responsiveness criterion was also proposed for the SWD test. 
The proposed lateral displacement criterion was that a truck tractor 
equipped with stability control must have a lateral displacement of 
2.13 meters (7 feet) or more at 1.5 seconds from the beginning of 
steer, measured during the sine with dwell maneuver. For a bus, the 
proposed performance criterion is a lateral displacement of 1.52 meters 
(5 feet) or more at 1.5 seconds after the beginning of steer. The 
lateral displacement criteria is less for a bus because a large bus has 
a longer wheelbase than a truck tractor and higher steering ratio, 
which makes it less responsive than a truck tractor.

B. Comments on SIS and SWD Maneuvers

    The agency received many comments, particularly from 
representatives of ESC system, truck tractor, and bus manufacturers 
specifically addressing the slowly increasing steer and sine with dwell 
maneuvers proposed in the NPRM. The comments raised issues regarding 
the relevance of the SWD and SIS tests, the amount of space required to 
perform the test, and the automated steering machine.
    Daimler Trucks North America (DTNA), the ATA, and Navistar claimed 
the SWD was not representative of a real-world maneuver. EMA stated the 
no manufacturer to date was using the SWD maneuver to test and validate 
an ESC system. Navistar claimed the standard width of a highway lane 
does not allow room for the SWD maneuver

[[Page 36073]]

to be completed. EMA shared Navistar's belief that a driver of a truck 
tractor would require 6 to 8 lanes of road width to perform a SWD 
maneuver on a roadway, and the SWD test is unlike any maneuver likely 
to occur on public roads.
    DTNA asserted that the SWD test fails to provide adequate pass/fail 
criteria as an ESC performance test. Similarly, Volvo stated that the 
SWD performance test criteria is impractical and unnecessary because 
there are established validation test methods available and in use.
    DTNA, Navistar, and EMA suggested that tuning the ESC system to 
pass the SWD test could compromise the system performance. Navistar 
reasoned that focusing on the SWD test would diminish the amount of 
design work done to optimize ESC performance for other conditions. 
Navistar also speculated that some ESC systems may not comply with the 
SWD test and may require a lengthy research and development plan to 
redesign the systems. On the other hand, Bendix Commercial Vehicle 
Systems (Bendix) assured the agency that tractors equipped with the 
current Bendix ESC systems could pass the proposed SWD and SIS tests.
    DTNA and EMA alleged that there would be additional burdens and 
restrictions on manufacturers caused by a SWD performance test. DTNA 
stated that manufacturers have a burden to conduct extensive ESC 
testing because of the lack of experience with the SWD test. EMA 
claimed that heavy vehicle options would be restricted to ensure 
compliance with the SWD test. Neither commenter provided details to 
support its claims.
    We also received comments on the amount of space required to 
conduct SIS and SWD tests. According to Navistar, EMA, and Bendix, the 
SWD and SIS tests require a large area in order to perform the tests. 
Navistar, EMA, DTNA, Volvo, and the HDBMC claimed that the 
Transportation Research Center (TRC) in Ohio is the only test facility 
large enough to perform the SWD and SIS tests. Based on this belief, 
they assume an increase in the number of manufacturers using TRC will 
limit the test facility availability. Bendix provided data and 
calculations to support its recommendation for the test area dimensions 
needed to safely perform the SIS and SWD tests. According to Bendix, 
the SIS test needs an area of 176 m (563.2 ft.) by 151 m (483.2 ft.), 
and the SWD test needs a smaller area of 112 m (358.4 ft.) by 58 m 
(185.6 ft.). Bendix further argued that the ESC performance tests 
should be portable, meaning that any test facility that can run FMVSS 
No. 121 tests should be able to run FMVSS No. 136 tests.
    In the NPRM, we proposed using a steering machine to provide the 
steering wheel inputs for the vehicles during the SIS and SWD tests. 
Advocates recommended that the SWD and SIS tests should be required 
along with an automated steering machine. However, Bendix, Volvo, and 
EMA expressed concern regarding the steering machine and the 
capabilities of a vehicle's steering system to perform the SWD 
maneuver. Bendix stated that the steering robot specified in the NPRM 
is inadequate and suggested that more research needs to be done to find 
a steering controller more suited for large vehicles. According to 
Volvo, the same steering machine requirements as those found in FMVSS 
No. 126 would not be sufficient for heavy vehicles. EMA and Bendix 
expressed concerns that the SWD requires steering inputs that approach 
the limit of what a human being can accomplish. EMA also claims the SWD 
test exceeds the capacity of power steering systems on some tractors, 
which affects the results of the SWD and exposes the driver to safety 
risks.
    Commenters also addressed the costs of conducting the proposed SIS 
and SWD tests. ATA and EMA stated that the proposed SWD test would be 
costly because of the logistics and preparation costs to test at TRC. 
Navistar said that a new facility would need to be built to conduct the 
SWD tests at an estimated cost of $4 to 6 million plus additional costs 
for maintenance and repair of the facility.
    Meritor WABCO, EMA, and Volvo provided estimates regarding the 
costs and burden of conducting the SWD test. Meritor WABCO commented 
that the tests are too costly and estimated the costs to be in excess 
of $28,000 per tractor. EMA claimed the SWD is too expensive because 
heavy vehicles have many variations, small volumes, and typically 
testing is performed on saleable vehicles. EMA estimated that each 
truck tractor manufacturer would need to run 50 to 80 tests for its 6x4 
tractors causing a high cost for the SWD testing, which is spread out 
over a low production volume of heavy vehicles. EMA further commented 
that manufacturers might have to redesign steering systems to comply in 
order to perform the SWD tests, which would further increase the costs. 
Additionally, EMA claims NHTSA did not test any severe service tractors 
using SWD testing, and the sample of truck tractors NHTSA tested was 
too narrow to support the proposal. Further EMA criticized NHTSA's test 
program for using only one control trailer and one test facility. Volvo 
alleged that the proposed performance tests could potentially damage 
test vehicles, and some manufacturers conduct assurance tests on 
customer vehicles.

C. Alternative Maneuvers Considered in the NPRM

    We considered other test maneuvers besides the SIS and SWD tests in 
the NPRM. The SWD maneuver was chosen in the NPRM over other maneuvers 
because our research demonstrated that it has the most optimal set of 
characteristics, including the severity of the test, repeatability and 
reproducibility of results, and the ability to address rollover, 
lateral stability, and responsiveness. However, we left within the 
scope of the NPRM several other test maneuvers that could be used to 
test an ESC system's ability to mitigate instability.
    With respect to rollover instability mitigation, we discussed the 
ramp steer maneuver (RSM) and J-turn maneuver. The two tests are 
similar in that both maneuvers require the tested vehicle to be driven 
at a constant speed and then the vehicle is turned in one direction for 
a certain period of time. The test speed and the severity of the turn 
are designed to cause a test vehicle to approach or exceed its roll 
stability threshold such that, without a stability control system, the 
vehicle would exhibit signs of roll instability. Both tests would be 
performed with the tractor loaded to its GVWR. Furthermore, we do not 
expect a vehicle that could pass one test to fail the other.
    The most notable difference between the J-turn and the RSM 
maneuvers is that the J-turn is a path-following maneuver. That is, it 
is performed on a fixed path curve. In contrast, the RSM maneuver is a 
non-path-following maneuver that is performed with a fixed steering 
wheel input determined for each vehicle. For example, during the 
agency's and EMA's testing, the J-turn maneuver was performed on a 150-
foot radius curve. In contrast, the RSM is performed based on a 
steering wheel angle derived from the SIS test. We expect that, with 
the RSM, the radius of the curve would be close to the fixed radius 
used in the J-turn maneuver. However, in the RSM, the vehicle would be 
steered with a steering controller and the driver would not have to 
make adjustments and corrections to steering to maintain the fixed 
path.
    We included both maneuvers in our roll stability testing. We also 
included possible performance metrics. For the

[[Page 36074]]

RSM, these performance metrics were included in the preamble to the 
NPRM. For the J-turn maneuver, the performance metrics were included in 
materials supporting the NPRM that were placed in the docket.\45\
---------------------------------------------------------------------------

    \45\ See ``Tractor Semi-Trailer Stability Objective Performance 
Test Research--Roll Stability,'' Docket No. NHTSA-2010-0034-0009 
Pages xiv, 18, 22-27, 35.
---------------------------------------------------------------------------

    When comparing the J-turn to the RSM in the NPRM, the agency 
considered the RSM to be a preferable test maneuver because the RSM 
maneuver can be performed with an automated steering wheel controller. 
Because the J-turn is a path-following maneuver, a test driver must 
constantly make adjustments to the steering input for the vehicle to 
remain in the lane throughout the test maneuver. Moreover, driver 
variability could be introduced from test to test based upon minor 
variations in the timing of the initial steering input and the position 
of the test vehicle in the lane.
    In addition, the RSM appeared to be more consistent because it 
involves a fixed steering wheel angle rather than a fixed path. There 
is negligible variability based on the timing of the initial steering 
input because the test is designed to begin at the initiation of 
steering input, rather than the vehicle's position on a track. 
Moreover, an automated steering wheel controller can more precisely 
maintain the required steering wheel input than a driver can. 
Therefore, we tentatively concluded that the RSM is more consistent and 
more repeatable than the J-turn, which is critical for agency 
compliance testing purposes.
    Notwithstanding the above observations, we recognized that many 
manufacturers perform NHTSA's compliance tests in order to certify that 
their vehicles comply with NHTSA's safety standards. We also recognize 
that, over time, manufacturers are likely to use other methods such as 
simulation, modeling, etc., to determine compliance with Federal Motor 
Vehicle Safety Standards. In this regard, we observed that, because the 
J-turn and the ramp steer maneuvers are so similar, manufacturers may 
be able to determine compliance with a stability control standard by 
using the J-turn maneuver even if the agency ultimately decided to use 
the RSM for compliance testing. Thus, if a manufacturer sought to 
certify compliance based upon performance testing, a manufacturer would 
not necessarily need to perform compliance testing with an automated 
steering controller.
    The RSM would use a similar, but not identical lateral acceleration 
ratio performance metric to evaluate roll stability. As with the SWD 
maneuver, the LAR used in the RSM would indicate that the stability 
control system is applying selective braking to lower lateral 
acceleration experienced during the steering maneuver. In the SWD 
maneuver, the LAR is the ratio of the lateral acceleration at a fixed 
point in time to the peak lateral acceleration during the period from 
one second after the beginning of steer to the completion of steer. In 
contrast, the LAR metric we would use for the RSM would be the ratio of 
the lateral acceleration at a fixed point in time to the lateral 
acceleration at the end of ramp input, which is the moment at which the 
steering wheel angle reaches the target steering wheel angle for the 
test. Also, in contrast to the SWD maneuver, the LAR measurements for 
the RSM would be taken at a time when the steering wheel is still 
turned. This means that, although the SWD maneuver is a more dynamic 
steering maneuver, the LAR criteria for the RSM would be greater than 
the LAR criteria for the SWD maneuver. The performance criteria for the 
RSM would depend on whether fixed-rate steering or fixed-time steering 
input is used.
    In a March 2012 submission given to the agency prior to the 
publication of the NPRM, which was revised with additional details in 
April 2012, EMA suggested that NHTSA use different test speeds and 
performance criteria for the J-turn maneuver.\46\ EMA suggested that a 
test speed that is 30 percent greater than the minimum speed at which 
the ESC system intervenes with engine, engine brake, or service brake 
control. Instead of measuring LAR, EMA suggested that, during three out 
of four runs, the vehicle would be required to decelerate at a minimum 
deceleration rate. NHTSA has conducted testing on variations of this 
EMA maneuver, and we suggested that we would conduct further testing. 
We requested comments on EMA's suggested test procedure and performance 
criteria for the J-turn maneuver.
---------------------------------------------------------------------------

    \46\ Docket No. NHTSA-2010-0034-0032; Docket No. NHTSA-2010-
0034-0040.
---------------------------------------------------------------------------

    After evaluating several maneuvers on different surfaces, the 
agency was unable to develop any alternative performance-based dynamic 
yaw test maneuvers that were repeatable enough for compliance testing 
purposes. Bendix described two maneuvers intended to evaluate the yaw 
stability of tractors.\47\ However, neither of these test maneuvers was 
developed to a level that would make them suitable for the agency to 
consider using as yaw performance tests.
---------------------------------------------------------------------------

    \47\ These tests are discussed in section IV.E.3. See Docket No. 
NHTSA-2010-0034-0037 and Docket No. NHTSA-2010-0034-0038.
---------------------------------------------------------------------------

    In July 2009, EMA provided research information on several yaw 
stability test maneuvers.\48\ One of these maneuvers was the SWD on dry 
pavement that is similar to what was proposed in the NPRM. The second 
maneuver was a SWD maneuver conducted on wet Jennite. The third 
maneuver was a ramp with dwell maneuver on wet Jennite.\49\ EMA did not 
provide any test data on the last two maneuvers. Thus, we considered 
them to be concepts rather than fully developed maneuvers that we could 
consider using for yaw stability testing.
---------------------------------------------------------------------------

    \48\ Docket No. NHTSA-2010-0034-0035.
    \49\ This ramp with dwell maneuver is the same one identified by 
Bendix referenced in the prior paragraph and in section IV.E.3.
---------------------------------------------------------------------------

    We received no other alternative yaw performance tests from 
industry until EMA's submission of data in late 2010.\50\ EMA suggested 
using a wet Jennite drive through test maneuver demonstrated yaw 
performance in a curve on a low friction surface. The maneuver is based 
upon a maneuver the agency currently conducts on heavy vehicles to 
verify stability and control of antilock braking systems while braking 
in a curve. As part of the test, a vehicle is driven into a 500-foot 
radius curve with a low-friction wet Jennite surface at increasing 
speeds to determine the maximum drive-through speed at which the driver 
can keep the vehicle within a 12-foot lane. As with the J-turn, we are 
concerned about the repeatability of this test maneuver because of 
variability in the wet Jennite test surface and the drivers' difficulty 
in maintaining a constant speed and steering input in the curve.
---------------------------------------------------------------------------

    \50\ Docket No. NHTSA-2010-0034-0022; Docket No. NHTSA-2010-
0034-0023.
---------------------------------------------------------------------------

    In a March 2012 submission, which was revised with additional 
details in April 2012, EMA provided information about another yaw 
stability test along with additional information on the J-turn 
maneuver.\51\ This maneuver simulates a single lane change on a wet 
roadway surface. It is be conducted within a 3.7 meter (12 foot) wide 
path. The roadway condition is be a wet, low friction surface such as 
wet Jennite with a peak coefficient of friction of 0.5. The other test 
conditions (i.e., road conditions, burnish procedure, liftable axle 
position, and initial brake temperatures) are similar to those proposed 
in the NPRM. In this

[[Page 36075]]

maneuver, the truck enters the path at progressively higher speeds to 
establish the minimum speed at which the ESC system intervenes and 
applies the tractor's brakes. The maneuver is then be repeated four 
times at that speed with the vehicle remaining within the lane at all 
times during the maneuver. EMA suggests, as a performance criterion, 
that during at least three of the four runs, the ESC system must 
provide a minimum level (presently unspecified) of differential 
braking. At the NPRM phase, the agency had not had an opportunity to 
conduct testing of this maneuver, but we expressed an intention to 
determine whether this is a viable alternative yaw stability test. The 
agency requested comment on all aspects of EMA's yaw stability test 
discussed in its March and April 2012 submissions, including the test 
conditions, test procedure, and possible performance criteria that 
would allow the agency to test both trucks and buses with this 
maneuver.
---------------------------------------------------------------------------

    \51\ Docket No. NHTSA-2010-0034-0032; Docket No. NHTSA-2010-
0034-0040.
---------------------------------------------------------------------------

D. Comments on Alternative Test Maneuvers

    Seven commenters (Daimler, Volvo, Meritor WABCO, Navistar, HDMA, 
EMA, and Bendix) recommended that NHTSA adopt alternative dynamic 
performance test maneuvers instead of the SIS and SWD. These 
alternative maneuvers were either described in the NPRM or included in 
comments submitted in response to the NPRM.
    EMA submitted a comment including general test conditions for a J-
turn maneuver to test roll stability and a single lane change on a wet 
surface to test yaw stability. In a later submission, EMA provided 
actual test information and suggested performance criteria based on 
data gathered at two different test facilities using 10 different truck 
tractors. Daimler, Meritor WABCO, HDMA, EMA, and Bendix supported 
adopting EMA's J-turn test maneuver as the performance test requirement 
for testing roll stability.
    The J-turn maneuver described in EMA's submissions uses a test 
course with straight lane connected to a 45.7-meter (150-foot) radius, 
a lane width of 3.7 meters (12 feet), and a surface coefficient of 0.9. 
The test speed of the maneuver is determined by driving a vehicle on 
the test course and identifying the minimum vehicle speed that causes 
the ESC system to apply the service brakes. That speed is the reference 
speed. The vehicle is then driven on the test course, entering the 
curve at 1.3 times the reference speed. The deceleration rate is 
determined from a time starting at when the ESC system activates the 
service brakes. The brakes are considered to be activated when at least 
35 kPa (5 psi) is observed at the service brakes. EMA recommended that 
four test runs be performed and that the deceleration rate must be at 
least 0.91 m/s\2\ (3.0 ft./s\2\) in three of the four test runs.
    With respect to the SWD test in the agency's proposal, EMA stated 
that the SWD maneuver is nearly identical to the maneuver used in FMVSS 
No. 126. However, in FMVSS No. 126, NHTSA stated that the maneuver was 
only used to test yaw stability, not roll stability. EMA observed that 
heavy vehicles are different from light vehicles because they have 
higher centers of gravity and are more likely to roll over than to lose 
directional control. Because the SWD test does not test roll stability 
on light vehicles, EMA reasoned that the maneuver should not be used to 
test roll stability on heavy vehicles.
    Regarding yaw testing, EMA disagreed with NHTSA's assessment in the 
NPRM that low friction surfaces such as wet Jennite may be too variable 
to conduct ESC testing, citing NHTSA's use of wet Jennite in testing 
air brake performance in FMVSS No. 121. EMA recommended using a test 
course with an overall length of 58.5 meters (192 feet). The vehicle 
proceeds into the maneuver in a 3.1-meter (10-foot) wide entrance lane. 
A steering maneuver is made within 28 meters (92 feet), and the vehicle 
completes the maneuver by entering a second 3.7-meter (12-foot) wide 
departure lane with a length of 15.2 meters (50 feet). The coefficient 
of friction of the road surface is 0.5. The maneuver is similar to a 
single lane change on a wet surface test. The test is conducted at a 
speed that is 1.6 km/h (1 mph) greater than the reference speed 
determined in the rollover maneuver. The vehicle is driven on the test 
course for four test runs at the test speed and the brake pressure is 
measured at opposite wheel ends. EMA recommended that a differential 
brake pressure of at least 69 kPa (10 psi) in three of the four test 
runs as a minimum performance requirement.
    Daimler, HDMA, EMA, and Bendix recommended that NHTSA adopt the 
single lane change maneuver described in EMA's comment for testing yaw 
stability, if the test is workable. Otherwise, they recommended 
removing performance requirements related to yaw stability, leaving 
only an equipment definition requiring yaw stability performance.
    Other commenters had similar views on yaw testing. For example, 
Meritor WABCO recommended that NHTSA should wait to test yaw stability 
until it could develop a new yaw stability test. Bendix submitted test 
data and criteria using a ramp with dwell maneuver, which it suggested 
could be used for testing both the roll and yaw stability of a vehicle. 
IIHS did not endorse a particular performance test, but made a general 
statement that there should be a requirement of performance tests for 
ESC.
    Furthermore, EMA agrees with NHTSA's assessment that it is 
difficult to test for understeer control. EMA believes that the 
reasoning for not testing understeer control in FMVSS No. 126 can be 
carried over to heavy vehicle ESC. In that rulemaking, NHTSA concluded 
that the understeer prevention requirement that was included in the 
system capability requirements was objective, even without a 
performance test.\52\
---------------------------------------------------------------------------

    \52\ 72 FR 17261 (Apr. 6, 2007).
---------------------------------------------------------------------------

E. NHTSA Examination and Testing of EMA Maneuvers

    In response to the March and April 2012 submission from EMA and 
additional data submitted to the agency in June 2012 and November 2012 
after the issuance of the NPRM containing results of additional tests 
discussed by EMA, the agency conducted its own testing in 2013 using 
EMA's suggested rollover performance maneuver.\53\ The results of this 
testing are summarized in the reports: (1) ``2013 Tractor Semitrailer 
Stability Objective Performance Test Research--150-Foot Radius J-Turn 
Test Track Research;'' (2) ``Stability Control System Test Track 
Research with a 2014 Prevost X3-45 Passenger Motorcoach;'' and (3) 
``Stability Control System Test Track Research with a 2014 Van Hool 
CX45 Passenger Motorcoach.'' \54\ This section provides a summary of 
these reports.
---------------------------------------------------------------------------

    \53\ Docket No. NHTSA-2010-0034-0032; Docket No. NHTSA-2010-
0034-0040; Docket No. NHTSA-2012-0065-0059; Docket No. NHTSA-2012-
0065-0060.
    \54\ Docket No. NHTSA-2012-0065-0062; Docket No. NHTSA-2012-
0065-0063; Docket No. NHTSA-2012-0065-0064.
---------------------------------------------------------------------------

    These reports do not address the yaw stability performance maneuver 
suggested by EMA to test yaw stability. EMA's lane change maneuver test 
is performed on a wet level surface with a peak friction coefficient of 
0.5. NHTSA's past test results with this test surface and similar 
performance maneuvers has shown that ESC systems have the capability to 
improve vehicle yaw and roll stability performance on low friction 
surfaces. However, vehicle handling characteristics dictated the 
performance of the vehicle on low friction surfaces. Test data revealed 
that, depending on whether the tractor

[[Page 36076]]

understeered or oversteered with respect to the trailer, the ESC system 
behavior changed. Under such varying behaviors, measures of performance 
that were investigated could not be standardized to capture the 
benefits of an ESC system over the whole range of vehicles tested. We 
have concluded that objective performance tests for ESC using a low 
friction surface requires additional data analysis, maneuver design, 
and test procedure development, which would require further delaying 
this final rule with no assurance that an acceptable maneuver on a low-
friction surface could be developed. Therefore, we have not further 
tested EMA's suggested yaw performance maneuver. We may investigate 
this maneuver in the future.
    The main objective of NHTSA's truck-tractor testing was to gain 
additional experience with a the 150-foot radius J-turn maneuver 
procedures suggested by EMA and to collect test track performance data 
on air braked truck tractors equipped with stability control system. 
The agency conducted tests on three class 8 air-braked truck tractors 
and two control trailers. The three trucks used were a 2006 
Freightliner 6x4 equipped with separate RSC and ESC systems, a 2006 
Volvo 6x4 equipped with an ESC system, and a 2011 Mack 4x2 equipped 
with an ESC system.
    The test procedures were derived from those EMA submitted in April 
2012, which the agency placed in the docket with the NPRM.\55\ The test 
course consisted of a 12-foot wide curved lane with a 150-foot radius 
measured from the center of the lane and a peak surface friction 
coefficient of 0.9. The curved lane formed a semicircle, and a straight 
lane used for bringing the vehicle up to speed was oriented 
tangentially at both ends of the curved lane. This allowed the same 
test course to be used in both a clockwise and counterclockwise 
orientation. The agency placed cones at every 11.25 degrees of arc 
angle to mark the inner and outer lane boundaries.
---------------------------------------------------------------------------

    \55\ Docket No. NHTSA-2010-0034-0040.
---------------------------------------------------------------------------

    Prior to testing, the test tractors were loaded to the GVWR by 
attaching them to one of the two unbraked control trailers used for 
testing. The remaining test conditions (i.e., road surface friction, 
ambient temperature conditions, burnish procedure, liftable axle 
conditions) largely mirrored those specified in FMVSS No. 121 for 
testing air brakes, which also generally mirrored the test conditions 
set forth in the NPRM.
    The test driver maneuvered the test vehicle into the straight lane 
and approached the curve, then traveled through the 180 degrees of arc 
in the curve. The driver attempted to steer the vehicle in such a 
manner that it stayed in the lane throughout the maneuver. The brake 
pressure was measured at each wheel end and was monitored using a 
computer. All maneuvers were conducted in one direction, and then the 
entire procedure was completed in the opposite direction, so that 
vehicles were tested both clockwise and counterclockwise independently. 
The test sequence was repeated for each of the test vehicles and, for 
the Freightliner, repeated separately with the ESC and RSC systems 
enabled.
    Each test was conducted at a specified entrance speed, with a 
tolerance of +/-1 mph, which the driver would reach and maintain prior 
to entering the curve. The test driver released the throttle two or 
more seconds after the stability control system intervened with either 
torque reduction or brake application. However, it was discovered that 
it was easier for the test driver to control speed if throttle was 
maintained until the stability control system reduced the vehicle's 
forward speed by 2 to 3 mph.
    Initially, vehicles were tested with an entrance speed of 20 mph. 
Additional test runs were conducted at entrance speeds increased 
incrementally by 1 mph until a reference speed could be determined. The 
reference speed was the speed at which the stability system intervened 
with at least 5 psi of service brake pressure. Additional tests were 
conducted at speeds incremented by 1 mph until the target test speed 
was reached, which was 130 percent of the reference speed. Four 
additional test runs were conducted at the target test speed.
    Near the end of testing, the agency conducted four additional test 
runs at the reference speed, during which the test driver fully 
depressed the accelerator pedal after crossing the start gate. The 
purpose of this testing was to evaluate the stability control system's 
ability to reduce driver-commanded engine torque.
    Following this procedure, the agency determined reference speeds 
and target test speeds for each test vehicle connected to each of the 
control trailers and run in each direction. All vehicles tested had the 
ESC systems intervene at entrance speeds not greater than 30 mph. The 
results are summarized in the following table.

                         TABLE 3--Reference Speed, Target Test Speed, and Lane Violations Observed During 150-foot J-turn Tests
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                        Reference speed (mph)           Target test speed  (mph) [Reference    Lane violations observed
                                              ----------------------------------------              Speed x 1.3]                at or below the target
                                    Control                                           ---------------------------------------         test speed
            Tractor                 trailer                                                                                  ---------------------------
                                               Counter- clockwise       Clockwise      Counter- clockwise      Clockwise        Counter-
                                                                                                                                clockwise     Clockwise
--------------------------------------------------------------------------------------------------------------------------------------------------------
Freightliner 6x4 ESC...........             1  28................  28................  36................  36...............             0             0
                                            2  27................  28................  35................  36...............             0             0
Freightliner 6x4 RSC...........             1  30................  26................  39................  34...............             2             0
                                            2  Not Tested........  Not Tested........  Not Tested........  Not Tested.......             -             -
Mack 4x2 ESC...................             1  25................  24................  33................  31...............             0             0
                                            2  25................  24................  33................  31...............             0             0
Volvo 6x4 ESC..................             1  26................  26................  34................  34...............             0             0
                                            2  26................  25................  34................  33...............             0             0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    EMA suggested, as the performance metric, that the ESC system 
decelerate the vehicle at a rate greater than 3 ft./s \2\ during three 
of four test runs at an entrance speed of 130 percent of the reference 
speed. In addition to evaluating EMA's suggested performance metric, 
the agency considered additional performance

[[Page 36077]]

metrics for evaluating roll stability performance. In its roll 
stability test development, the agency had considered lateral 
acceleration and forward speed as possible roll stability performance 
metrics.\56\
---------------------------------------------------------------------------

    \56\ See Docket No. NHTSA-2010-0034-0009.
---------------------------------------------------------------------------

    NHTSA's past test track research showed that tractors pulling 
trailers with high centers-of-gravity have a high probability of 
rolling over in a 150-foot radius curve when speeds exceeded 30 
mph.\57\ Tractors equipped with ESC systems, driven under the same 
scenario, were slowed down by the ESC systems and consequently, roll 
instability was mitigated. These observations guided comparisons in 
performance and allowed the agency to develop speed-based performance 
metrics relative to the entrance to the 150-foot curve. Specific speed 
thresholds can be established as a performance metric.
---------------------------------------------------------------------------

    \57\ See ``Tractor Semi-Trailer Stability Objective Performance 
Test Research--Roll Stability,'' Docket No. NHTSA-2010-0034-0009; 
``Tractor Semitrailer Stability Objective Performance Test 
Research--Yaw Stability,'' Docket No. NHTSA-2010-0034-0046.
---------------------------------------------------------------------------

    In the agency's testing using a high center-of-gravity load, roll 
instability (wheel lift) was first observed in tests generating 
approximately 0.4g of lateral acceleration at the tractor's center of 
gravity. Wheel lift was generally observed between 3 and 4 seconds 
after the steering input, which is when 0.4g of lateral acceleration 
was sustained. Based on these observations, the agency set the tractor 
lateral acceleration thresholds for roll stability during the 150-foot 
J-turn maneuver at a maximum of 0.375 g at 3.0 seconds after the 
vehicle crossed the start gate and 0.350 g at 4.0 seconds after the 
vehicle crossed the start gate.
    However, because the radius of the curved portion of the track is 
fixed, these lateral acceleration thresholds can be related to speed 
thresholds using the formula A=V\2\/R, where A is the lateral 
acceleration, V is the vehicle's forward speed, and R is the radius of 
the curve. Inserting the specified lateral acceleration levels and the 
radius of the curve, the agency's lateral acceleration thresholds 
converted to maximum speed thresholds of 29 mph and 28 mph at 3.0 and 
4.0 seconds, respectively.
    Each tractor and stability control system tested exceeded EMA's 
suggested 3 ft./s\2\ minimum deceleration test criteria. Each tractor 
and stability control system tested also exceeded NHTSA's speed and 
lateral acceleration thresholds.

F. Roll Stability Performance Test--J-Turn Test

1. Rationale for Using J-Turn Test
    NHTSA has decided to substitute the J-turn maneuver in place of the 
SIS and SWD maneuvers as the performance test for an ESC system. The J-
turn test will be used to evaluate the roll stability of a vehicle. 
Likewise, the J-turn will also be used to ensure that the ESC system 
reduces engine torque to the wheels. Because the J-turn is conducted on 
a fixed curve, longitudinal velocity (speed) directly correlates to 
lateral acceleration. NHTSA has determined that the J-turn test is the 
most cost-effective and least burdensome alternative that achieves the 
objectives of the ESC rule. Moreover, the roll stability mitigation 
performance requirements associated with the J-turn maneuver are 
comparable to the minimum performance requirements associated with the 
SWD maneuver proposed in the NPRM.
    To be clear, however, the agency rejects much of the criticism of 
the SWD maneuver in the comments from truck manufacturers. Although we 
are abandoning the proposed SIS and SWD maneuver in favor of a J-turn 
maneuver to test roll stability in this final rule, NHTSA still 
considers the SWD test to be a viable test to measure the minimum 
performance of an ESC system on a heavy vehicle.
    We do not agree with the commenters' assertions about the relevance 
of the SWD maneuver. The lack of voluntary adoption of the SWD test by 
vehicle manufacturers does not, by itself, make the SWD test 
irrelevant.
    Likewise, the comments regarding the width of public roads and how 
the maneuver is not likely to occur on public roads are inapposite. The 
purpose of the performance test is to determine the minimum performance 
requirements of ESC systems using an objective and repeatable test. The 
fact that the SWD test will not be performed on public roads and must 
be performed on a test track, which can be 6 to 8 lanes of public road 
width or larger, is not by itself a persuasive argument that the test 
is irrelevant.
    Nor does the agency agree with the commenters suggesting that 
additional design work would be necessary in order for vehicles to meet 
SWD performance requirement. None of the commenters suggesting 
additional design work was necessary submitted information to justify 
the assertion. Moreover, Bendix, a system supplier, asserted that 
current ESC systems could pass the proposed SWD test. NHTSA's own 
testing using two typical 6x4 tractors each equipped with ESC systems 
consistently met the proposed performance requirements using the SWD 
test. In addition, no commenter submitted supporting information 
describing any specific design compromises that would occur as a result 
of complying with the SWD test.
    Likewise, the agency does not characterize the testing of saleable 
vehicles as an unnecessary cost increase. Contrarily, performing the 
tests on saleable vehicles, as opposed to manufacturing a vehicle 
solely for testing purposes, reduces the amount of cost to a 
manufacturer. The manufacturers have provided no basis for their 
assertions that they could not resell vehicles after conducting SWD 
tests. Although they have asserted that the vehicles may be damaged 
during testing, NHTSA has not experienced any vehicle damage during its 
own testing. In response to Volvo's claim of potential damage to 
vehicles being tested, the agency recognizes that any performance test, 
if done unsafely, could potentially damage the vehicle being tested.
    Nevertheless, NHTSA believes the J-turn test maneuver is more 
efficient than the SWD test for assessing the roll instability 
mitigation of ESC systems. The J-turn test can demonstrate roll 
stability using only a single test. There is no need to analyze and 
extrapolate data between two separate test maneuvers as there is using 
the SIS and SWD tests. This will allow the agency to complete a 
compliance test more quickly using the J-turn than using the SIS and 
SWD tests.
    We did not receive any estimate from EMA or its members regarding 
the costs to perform the J-turn test. However, EMA and its members did 
not object to the cost of its suggested performance test, nor did any 
commenter discuss the difference in cost of the J-turn test versus the 
SWD and SIS tests. Instead, the agency received a recommendation from 
dozens of commenters to adopt the J-turn test. The agency estimates 
that it would cost approximately $13,400 per truck tractor and $20,100 
per large bus to conduct the full series of J-turn test maneuvers 
contained in this final rule.
    We also note that the J-turn maneuver is similar to the Ramp Steer 
Maneuver (RSM), which was discussed at length in the NPRM. Both 
maneuvers use a test course with a straight lane connected to a curved 
lane. However, the RSM maneuver is an open loop type test, uses an 
automated steering controller, and requires conducting an SIS maneuver 
to determine the appropriate steering wheel angle for testing. The J-
turn is a path-following maneuver and the vehicle is steered by the 
driver. We have

[[Page 36078]]

chosen a path-following maneuver over the fixed-steering RSM because of 
track space concerns regarding the SIS maneuver. We believe that the 
amount of track space necessary to conduct the SIS maneuver may only be 
available at one or two test facilities in the United States. While one 
of these facilities is readily available to NHTSA for compliance 
testing purposes, we recognize that manufacturers may wish to test 
their own vehicles as part of their compliance certification.
    We emphasize that the adoption of the J-turn maneuver should not in 
any way diminish the roll stability performance we have observed from 
ESC systems. The performance criteria associated with the J-turn test 
maneuver in this final rule have been chosen to ensure a level of roll 
instability mitigation performance similar to that required to satisfy 
the SWD maneuver. Although the test is conducted at a lower speed, the 
radius of the curve will increase lateral acceleration to a level that 
would generate roll instability in vehicles without ESC systems. We 
believe that all large trucks and buses equipped with current 
generation ESC systems will meet the minimum performance requirements 
just as we believe they would have met the minimum performance 
requirements associated with the SWD maneuver. Therefore, we do not 
believe that the use of a different test maneuver will change the 
expected performance of ESC systems.
    We also observe that, like the sine with dwell maneuver, the J-turn 
maneuver that is one of the demonstration tests in Annex 21 of UN ECE 
Regulation 13. If a manufacturer chooses the J-Turn test as a 
demonstration test to show compliance with Annex 21 and can achieve the 
performance criteria established in this final rule, then there would 
be compatibility between the performance tests of FMVSS No. 136 and UN 
ECE Regulation 13.
    NTSB provided comments indicating that rollover performance 
standards should be measured by static rollover stability. NHTSA does 
not agree with the NTSB's suggestion. NHTSA developed test methods that 
could evaluate an ESC system's performance dynamically. The goal is to 
create a measure of performance that will ensure that an ESC system 
could prevent a rollover. A static stability test would not measure how 
an ESC system reduces lateral acceleration to reduce untripped 
rollovers.
2. Test Procedure and Performance Requirements
    The J-turn test procedure developed based on EMA's suggestion is a 
sequential procedure in which the test vehicle is repeatedly driven 
through a 150-foot radius curve. The test is conducted on the same test 
course and is generally performed in the manner suggested by EMA with 
only minor changes added to test lateral responsiveness and to test the 
ESC system's ability to reduce engine output. We have also modified the 
minimum performance criteria to use forward speed rather than 
deceleration rate. We found that using deceleration rate as a minimum 
performance criteria would not address vehicle wheel lift and 
subsequent rollover, especially when the vehicle has a load with a high 
center-of-gravity. EMA's suggestion only measures the braking rate, but 
it does not measure the ESC system's capability to lower vehicle 
lateral acceleration to an acceptable threshold.
    A diagram of the curve is included in the regulatory text to 
clarify any ambiguities in the description of the course. Although the 
lane markings are depicted with dots on the figure, there is no 
specification for how the lane is marked. It may, for example, be 
marked with cones or painted lines. Although the figure depicts a 
counter-clockwise layout, the test is conducted in both directions.
    The start gate is placed at the point of the test course where the 
straight lane section intersects with the curved section of the lane. 
An end gate is placed on the curved portion of the lane at 120 degrees 
of arc angle from the start gate. It will take a test vehicle more than 
4 seconds to pass through the end gate. Therefore, all of the necessary 
data will be collected by that point.
    For truck tractors, the lane width is 3.7 meters (12 feet) for both 
the straight section and curved section of the course. However, large 
buses require additional lane width on the curved section of the course 
because buses have longer wheelbases, which make it substantially more 
difficult to maintain a narrower lane within the curve. The large buses 
that the agency tested did not physically fit in the curved section of 
the 12-foot lane because of their long wheelbases. During testing, the 
rear wheels of the buses departed the lane even at very low entrance 
speeds because of the geometry of the buses, not because of a lack of 
stability. Therefore, for buses, the lane width on the curved section 
of the course is 4.3 meters (14 feet).
    Each is subjected to multiple J-turn test runs with a test speed 
starting at 32 km/h (20 mph) and increased in 1.6 km/h (1 mph) 
increments until ESC service brake activation is observed. The test 
driver will not apply the service brakes or the engine exhaust braking 
during the maneuver. For air-braked vehicles, ESC service brake 
activation occurs when the ESC system causes the pressure in the 
service brake system to reach at least 34 kPa (5 psi) for a continuous 
duration of at least 0.5 second. For vehicles with hydraulic brakes, 
ESC service brake application occurs when the ESC system causes the 
pressure in the service brake system to reach at least 172 kPa (25 psi) 
for a continuous duration of at least 0.5 second. This speed is 
considered the Preliminary Reference Speed. This procedure is conducted 
separately using clockwise and counterclockwise steering.
    The J-turn maneuver is then repeated four times at the Preliminary 
Reference Speed to confirm that this is the speed at which ESC service 
brake activation occurs. To do this, four test runs are performed and 
ESC service brake application is verified. If ESC service brake 
application is verified, this speed is considered the Reference Speed. 
If ESC service brake activation does not occur during at least two of 
the four test runs, the Preliminary Reference Speed is incremented by 
1.6 km/h (1 mph) and ESC service brake application is again verified. 
Again, the Reference Speed is determined for both the clockwise and 
counterclockwise direction.
    Once the Reference Speed is determined, the ESC system's ability to 
reduce engine torque is verified. Two series of four test runs (one 
series clockwise, the other series counterclockwise) are conducted at 
the Reference Speed. During these maneuvers, the driver will fully 
depress the accelerator pedal after entering the curve and throughout 
the curve. NHTSA will verify that the engine torque output is less than 
the driver-requested output. This ensures that the driver's attempt to 
accelerate the vehicle does not override the ESC service brake 
application and verifies the system's ability to mitigate instability 
by reducing engine torque.
    Thereafter, the vehicle is subjected to multiple series of test 
runs (both clockwise and counterclockwise) at an entrance speed up to a 
maximum test speed, which is up to 1.3 times the Reference Speed, but 
no less than 48 km/h (30 mph). At a speed between 48 km/h (30 mph) and 
the maximum test speed, the vehicle is subjected to eight maneuvers, 
during which ESC service brake activation is verified. The vehicle must 
be able to meet the roll stability

[[Page 36079]]

performance criteria discussed below at any speed between 48 km/h (30 
mph) and the maximum test speed.
3. System Responsiveness
    The NPRM described the need for a lateral displacement performance 
metric because of the possibility of a manufacturer making the vehicle 
poorly responsive to the speed and steering inputs required by the SWD 
test. The risk of poor lateral displacement in response to the driver's 
steering input was mitigated by a minimum responsiveness criterion. 
Although the SWD test is being replaced with the J-turn test, we still 
need to account for vehicle responsiveness. The nature of the J-turn 
test provides two criteria for ensuring vehicle responsiveness: 
Maintaining the lane within the fixed radius curve and a minimum test 
speed.
    The first responsiveness criterion is the requirement that the 
vehicle maintain the lane during at least six of eight runs in the roll 
performance test series or at least two of four runs in any other test 
series. This requirement ensures that, during J-turn test runs at 
increasing speeds, the ESC system actually activates before the vehicle 
becomes unstable. We are not imposing this requirement for each test 
run within a series to account for driver variability and possible 
driver error in conducting the maneuver. Absent driver error, we do not 
expect any vehicle equipped with current-generation ESC systems to 
leave the lane during any J-turn test.
    The other responsiveness criterion in this final rule is the 
minimum vehicle entry speed of 48 km/h (30 mph) for the roll 
performance test. This will discourage a manufacturer from designing a 
system that will intervene only at very low speeds, thus artificially 
decreasing the speed at which the vehicle will enter the curve during 
the roll performance test.
4. Engine Torque Reduction
    As proposed in the NPRM, there must be at least a 10 percent 
reduction in engine torque when measured 1.5 seconds after the 
activation of the ESC system. The percent reduction is measured between 
the actual engine torque output and the driver-requested torque input. 
This measurement was to be taken during the slowly increasing steer 
maneuver. However, now that the agency has adopted the J-turn test as 
its performance test, the SIS test is no longer necessary.
    Accordingly, the agency has modified the engine torque reduction 
test in the NPRM so that it can be used with the J-turn test. The 
reference speed, which is the lowest test speed at which the ESC system 
activated the vehicle's service brakes, is determined as part of the J-
turn test sequence. An additional two test series (one using clockwise 
steering and the other using counterclockwise steering) are conducted 
after the reference speed is calculated. The driver then fully 
depresses the accelerator pedal after the vehicle crosses the start 
gate. After ESC activation occurs, data is collected to determine the 
difference between the actual engine torque output and the driver 
requested torque. After analyzing research data from the J-turn 
testing, we have determined that the ESC system must reduce the driver 
requested engine torque by at least 10 percent for at least 0.5 second 
during the time period between 1.5 seconds after the vehicle passes the 
start gate and when it travels through the end gate. We are not 
considering reduced engine torque before 1.5 seconds after the vehicle 
crosses the start gate (and the driver fully depresses the accelerator 
pedal) because our testing has shown that there is a lag between when 
the operator of the vehicle requests full throttle and when the vehicle 
responds by providing full throttle.
5. Roll Stability Performance Requirements
    Based on NHTSA's research, for a typical combination vehicle, an 
ESC system must reduce the heavy vehicle's lateral acceleration to less 
than 0.4g to prevent wheel lift and possible vehicle rollover.\58\ 
NHTSA considered how to measure lateral acceleration during the J-turn 
maneuver. However, lateral acceleration is a function of longitudinal 
velocity. Using the equation A=V\2\/R, where A is lateral acceleration, 
V is longitudinal velocity, and R is the radius of the curve, when 
driven in a fixed radius curve, with a 45.7-meter (150-foot) radius, 
0.4g of lateral acceleration would be achieved at a forward velocity of 
approximately 48 km/h (30 mph). That is, at speeds below 30 mph, a 
vehicle would generate less than 0.4g of lateral acceleration and would 
be unlikely to roll over. This was confirmed in the agency's testing, 
where the test vehicles remained stable at speeds below 30 mph.
---------------------------------------------------------------------------

    \58\ See 77 FR 30776-78.
---------------------------------------------------------------------------

    NHTSA track testing has shown that the minimum test speed for 
effectively testing the ESC system is 48 km/h (30 mph). However, where 
the ESC system activates at a speed such that 1.3 times the minimum 
activation speed is greater than 48 km/h (30 mph), the vehicle may be 
tested at a speed up to 1.3 times the minimum activation speed. A 
multiplication factor of 1.3 will be used to ensure that ESC systems 
operate over a range of speeds. A factor of 1.3 allows the vehicle's 
ESC system to reach a level where maximum brake force is applied by the 
system, and, as a result, ensures the ESC system reduces the 
longitudinal velocity and lateral acceleration of the vehicle are below 
the threshold values. At factors below 1.3, our testing has shown that 
ESC systems have not yet achieved their maximum braking force. At 
factors above 1.3, we have concerns about the safety of testing because 
the ESC systems have achieved their maximum braking force and the 
lateral acceleration of the vehicle could remain high.
    In contrast, using a performance requirement such as EMA's 
suggested minimum deceleration metric provides no assurance that the 
deceleration will be sufficient to prevent rollover. For example, using 
EMA's suggested procedure, if a vehicle is able to enter a curve at a 
relatively high rate of speed before an ESC system activates, the 
performance requirement will be more stringent than if a system is 
tuned to activate at lower rates of speed. Particularly, if a test is 
conducted at an entrance speed of less than 48 km/h (30 mph), the 
system's ability to prevent rollover is not challenged because the 
vehicle is unlikely to experience lateral forces that have the 
potential to cause instability, even if the vehicle was not equipped 
with an ESC system.
    We considered, but rejected, using the lateral acceleration ratio, 
which was the proposed performance criteria for both the SWD maneuver 
and the alternative RSM, rather than the reduction in absolute lateral 
acceleration. Using the J-turn maneuver, it was sufficient to ensure 
that the absolute lateral acceleration was below the threshold for 
wheel lift after the vehicle has begun its turn. Furthermore, unlike 
the SWD and RSM maneuver where the beginning of steer can be 
determined, the beginning of the J-turn maneuver occurs when the 
vehicle crosses the start gate. At this point, the lateral acceleration 
of the vehicle is zero or close to zero because the vehicle is 
traveling in a straight line. After the vehicle crosses the start gate, 
the driver has some discretion for steering the vehicle and maintaining 
the lane. The low initial lateral acceleration and the driver variation 
both make the lateral acceleration ratio an inappropriate performance 
metric for the J-Turn test. Instead, we found that reduction in the 
absolute lateral acceleration of a vehicle, which on a fixed curve is a 
function of velocity, was sufficient to determine the performance

[[Page 36080]]

of an ESC system with respect to roll stability control.
    Thus, the minimum performance requirement to demonstrate roll 
stability performance in this final rule is expressed in terms of a 
vehicle's forward speed (longitudinal velocity) at two points in time. 
The specific requirements are:
     The longitudinal velocity measured at 3.0 seconds after 
vehicle passes through the start gate to the J-turn maneuver must not 
exceed 47 km/h (29 mph).

     The longitudinal velocity measured at 4.0 seconds after 
vehicle passes through the start gate to the J-turn maneuver must not 
exceed 45 km/h (28 mph).

NHTSA's research indicates than an ESC system's ability to maintain an 
absolute lateral acceleration below the criteria would provide an 
acceptable probability that the vehicle would remain stable and that a 
level of absolute lateral acceleration above the criteria would result 
in a high probability of the vehicle becoming unstable.

G. Yaw Stability

    NHTSA has decided to defer research on the yaw maneuver suggested 
by EMA, the single lane change on a wet surface test. EMA did not 
provide any data showing how its performance criterion (differential 
brake pressure) measures the capability of the ESC system to prevent 
yaw instability. Moreover, EMA submitted data showing that at least 
three of its tested vehicles failed to meet the criteria. NHTSA would 
need to further research the EMA maneuver and determine adequate 
performance metrics. More data is needed to create criteria that 
represent appropriate stability thresholds by showing an acceptable 
probability that the vehicle would remain stable if the ESC system 
maintains those criteria.
    The SWD maneuver was designed to test the ESC system's ability to 
prevent yaw instability by measuring how quickly the vehicle stops 
turning, or rotating about its vertical axis, after the steering wheel 
is returned to the straight-ahead position. The vehicle that continues 
to turn or rotate about its vertical axis under these conditions is 
most likely experiencing oversteer, which is what ESC is designed to 
prevent. EMA's data does not show how its yaw maneuver will adequately 
test the ESC system's capabilities to prevent oversteer. Likewise, the 
Bendix test, a ramp with dwell maneuver, will not be examined by NHTSA 
at this time for yaw stability testing. In order to create a 
performance test, NHTSA would need to do further research on the Bendix 
maneuver and determine adequate performance metrics.
    We are also concerned that the maneuver is conducted on a low-
friction wet Jennite surface. EMA stated that it disagrees with the 
statement in the NPRM that low-friction surfaces such as wet Jennite 
are too variable to make them unusable for ESC testing. EMA believes 
that the use of wet Jennite in FMVSS No. 121 for air-brake testing 
makes wet Jennite suitable for ESC testing. However, we remain 
concerned about the potential for variability in surface friction on a 
wet Jennite surface for ESC system testing.
    To date, we have found that only the SWD maneuver proposed in the 
NPRM is suitable for testing yaw stability, and even that test is 
limited to testing oversteer. As discussed above, we have decided not 
to conduct compliance tests on vehicles using the SWD because of the 
substantial time and instrumentation burden associated with the SWD 
maneuver. We do not believe that this additional time and cost is 
justified solely to test yaw stability when a majority of the benefits 
of this final rule are derived from rollover prevention. Moreover, the 
SWD maneuver would only test oversteer mitigation of yaw instability, 
whereas understeer is the primary type of yaw instability that we 
observed in our testing. However, we are continuing to examine possible 
yaw performance maneuvers, including the SWD maneuver and the lane 
change maneuver suggested by EMA to test yaw stability control 
performance in the future.

H. Understeer

    As we stated in the NPRM, the agency has no performance test to 
evaluate how the ESC responds when understeer is induced. The technique 
used by a stability control system for mitigating wheel lift, excessive 
oversteer or understeer conditions is to apply unbalanced wheel braking 
so as to generate moments (torques) to reduce lateral acceleration and 
to correct excessive oversteer or understeer. However, for a vehicle 
experiencing excessive understeer, if too much oversteering moment is 
generated, the vehicle may oversteer and spin out with obvious negative 
safety consequences. In addition, excessive understeer mitigation acts 
like an anti-roll stability control where it momentarily increases the 
lateral acceleration the vehicle can attain. Hence, too much understeer 
mitigation can create safety problems in the form of vehicle spin out 
or rollover.
    During the testing to develop FMVSS No. 126 for light vehicles, the 
agency concluded that understanding both what understeer mitigation can 
and cannot do is complicated, and that there are certain situations 
where understeer mitigation could potentially produce safety 
disbenefits if not properly tuned. Therefore, the agency decided to 
enforce the requirements to meet the understeer criterion included in 
the ESC definition using a two-part process. First, the requirement to 
meet definitional criteria ensured that all had the hardware needed to 
limit vehicle understeer. Second, the agency required manufacturers to 
make available engineering documentation to NHTSA upon request to show 
that the system is capable of addressing vehicle understeer.
    Based on the agency's experience from the light vehicle ESC 
rulemaking and the lack of a suitable test to evaluate understeer 
performance, the agency did not propose a test for understeer to 
evaluate ESC system performance for truck tractors and large buses. The 
agency sought comment on the lack of an understeer test.
    Advocates stated in its comment that there should be a compliance 
test for understeer performance. It said the ESC equipment requirement 
for understeer is not enough to ensure sufficient performance to 
mitigate understeer conditions.
    While we agree with the Advocates goal of having an understeer 
test, we have not been able to develop a test that safely challenges an 
ESC system's ability to mitigate understeer. Moreover, we believe the 
definitional criteria are robust enough to ensure that an ESC system 
will reduce loss-of-control crashes in both understeer and oversteer 
conditions.

XI. Test Conditions and Equipment

A. Outriggers

    Throughout the agency's research program, truck tractors and buses 
were equipped with outrigger devices to prevent vehicle rollover. 
During the program, the agency encountered many instances of wheel lift 
and outrigger contact with the ground indicating that it was probable 
that rollover could occur during testing. Over many years of research 
of ESC systems, it has been proven that outriggers are essential to 
ensure driver safety and to prevent vehicle and property damage during 
NHTSA's compliance testing. Although NHTSA conducted some of its 
testing with ESC systems disabled, thereby increasing the need for 
outriggers, outriggers are still necessary as a safety

[[Page 36081]]

measure during testing of vehicles equipped with an ESC system in case 
the system fails to activate.
    The agency proposed that outriggers be used on all truck tractors 
and buses tested. We believe that outrigger influence on heavy vehicles 
is minimal because of the higher vehicle weight and test load. To 
reduce test variability and increase the repeatability of the test 
results, the agency proposed to specify a standard outrigger design for 
the outriggers that will be used for compliance testing. The agency 
used this same approach in FMVSS No. 126 for compliance testing of 
light vehicle ESC systems. The agency also made available the detailed 
design specifications by reference to a design document located in the 
agency public docket.
    For truck tractors, the document detailing the outrigger design to 
be used in testing has been placed in a public docket.\59\ This 
document provides detailed construction drawings, specifies materials 
to be used, and provides installation guidance. For truck tractor 
combinations, the outriggers are mounted on the trailer. The outriggers 
are mounted mid-way between the center of the kingpin and the center of 
the trailer axle (in the fore and aft direction of travel), which is 
generally near the geometric center of the trailer. They will be 
centered geometrically from side-to-side and bolted up under the 
traditional flatbed control trailer. Total weight of the outrigger 
assembly, excluding the mounting bracket and fasteners required to 
mount the assembly to the flatbed trailer, is less than 2,500 pounds. 
The bulk of the mass is for the mounting bracket which is located under 
the trailer near the vehicle's lateral and longitudinal center of 
gravity so that its inertial effects are minimized. The width of the 
outrigger assembly is 269 inches and the contact wheel to ground plane 
height is adjustable to allow for various degrees of body roll. A 
typical installation on a flatbed type trailer involves clamping and 
bolting the outrigger mounting bracket to the main rails of the 
flatbed.
---------------------------------------------------------------------------

    \59\ Docket No. NHTSA-2010-0034-0010.
---------------------------------------------------------------------------

    The NPRM proposed that the outrigger design have a maximum weight 
of 726 kg (1,600 lb.). However, the agency raised the weight limit of 
the outriggers used for testing to accommodate the use of older and 
heavier outrigger designs. This final rule raises the maximum weight of 
the outriggers to 1,134 kg (2,500 lb.).
    For buses, the outrigger installations will not be as 
straightforward as the outrigger installations on the control trailers, 
and the NPRM solicited comments on bus outrigger designs. This is 
because outriggers cannot be mounted under the flat structure, but 
instead must extend through the bus. NHTSA used outriggers on the three 
large buses tested during its research program and will use outriggers 
for testing buses for compliance with this rule. The agency plans to 
use the same outrigger arms of the standard outrigger design that it 
plans to use for truck tractor testing. Therefore, the size, weight, 
and other design characteristics will be similar.
    The location and manner of mounting the outriggers on buses cannot 
be identical to truck tractors. Nonetheless, there are a limited number 
of large bus manufacturers, which results in a limited number of unique 
chassis structural designs. Also, the agency understands that large bus 
structural designs do not change significantly from year-to-year. We 
believe that once outrigger mounts have been constructed for several 
different bus designs, those mountings can be modified and reused 
during subsequent testing. The agency has, in the document described 
above, provided additional engineering design drawings and further 
installation guidelines for installing the standard outrigger assemble 
to large buses.

B. Automated Steering Machine

    The NPRM proposed using an automated steering machine be used for 
the test maneuvers on the truck tractors and large buses in an effort 
to achieve highly repeatable and reproducible compliance test results. 
In the SWD maneuver, the steering must follow an exact sinusoidal 
pattern over a three-second time period. For the SWD maneuver, each 
test vehicle is subjected to as many 22 individual test runs all 
requiring activation at a specific vehicle speed, each of which will 
require a different peak steering wheel angle and corresponding 
steering wheel turning rate.
    However, the agency has chosen the J-turn maneuver for the 
performance test. Although the SWD test requires a fixed steering wheel 
angle, the J-turn test is a path-following maneuver. This means a 
steering controller will not be required for the J-turn test because 
the driver provides the steering wheel input in order to keep the 
vehicle within the lane during the test maneuver.
    Because the driver must attempt to keep the vehicle within the lane 
width, he has some discretion on the steering wheel angle and the 
position of the vehicle within the lane as the vehicle crosses the 
start gate. Depending on the experience and technique of the driver, 
the vehicle may have a steering wheel angle that is varied by the time 
the vehicle crosses the start gate. This variance is tolerable because 
we do not expect that it will be difficult for a professional test 
driver to maintain the vehicle lane. Nevertheless, to ensure that 
variability in testing does not affect vehicle compliance, the 
performance requirements need only be satisfied during two out of four 
runs of a test series (or six out of eight runs of the final series).

C. Anti-Jackknife System

    The agency proposed using an anti-jackknife system when testing 
truck tractors. An anti-jackknife system prevents the trailer from 
striking the tractor during testing in the event that a jackknife event 
occurs during testing. This would prevent damage to the tractor that 
may occur during testing. We do not believe that the use of an anti-
jackknife system will affect test results, nor have we observed any 
damage to test vehicles, including vehicle finishes, caused by anti-
jackknife cables.
    The agency proposed using cables to limit the angle of articulation 
between the truck tractor and trailer, and set a minimum angle of 45 
degrees because setting the cables too tight could artificially help 
the ESC system maintain control during testing. However, if the angle 
of articulation is set too low the turning radius of the combination 
vehicle decreases to a point where maneuverability of the vehicle 
becomes an issue. A vehicle with too low of a turning radius would not 
be able to drive through the J-turn test course. Therefore, we must to 
set a minimum articulation angle for the jackknife system that ensures 
safety during testing, but is not too low such that it would affect 
test results. However, our testing has shown that 45 degrees is too 
high of an angle for a 4x2 truck tractor, because the trailer could 
still contact the truck tractor. Therefore agency is specifying 30 
degrees as the minimum articulation angle in this final rule, which is 
sufficient to provide safety during the testing of all truck tractors.

D. Control Trailer

    The agency proposed using a control trailer to evaluate the 
performance of a truck tractor in the loaded condition. In FMVSS No. 
121, the agency specifies the use of an unbraked control trailer for 
compliance testing purposes. An unbraked control trailer minimizes the 
effect of the trailer's brakes when testing the braking performance of 
a tractor in

[[Page 36082]]

its loaded condition. Nevertheless, in the NPRM, we identified 
potential variability in the control trailer that affected the 
repeatability of SWD testing and asked for comments on how the control 
trailer may be specified to prevent variability.\60\
---------------------------------------------------------------------------

    \60\ There were three specifications, not set forth in control 
trailer specifications in FMVSS No. 121, that the agency identified 
that might affect SWD test performance and prevent repeatable, 
consistent test results using different control trailers. First, the 
track width of the control trailer is not specified. Second, the 
center of gravity of the control trailer is not specified. Third, 
the center of gravity of the load in FMVSS No. 121 testing is only 
specified to be less than 24 inches above the top of the tractor's 
fifth wheel.
---------------------------------------------------------------------------

    Navistar and EMA commented on a specific truck tractor that 
satisfied the proposed SWD criteria with the ESC system disabled. We 
believe this is ``Vehicle J'' that was identified in the NPRM. NHTSA 
conducted its own testing on ``Vehicle J'' using a different control 
trailer. In contrast to EMA's test results, NHTSA's testing showed that 
Vehicle J became laterally unstable with the ESC system disabled.
    Volvo, EMA, Advocates, and Bendix commented on the control trailer 
specifications. Volvo asserted that further specifications need to be 
made for the control trailer because trailer configuration greatly 
affects compliance of the SWD test. EMA stated that the control 
trailer's track width, deck height, ballast, suspension, tires and 
torsional stiffness affect the SWD test results, and small variations 
in the control trailer influence the SWD testing. EMA further indicated 
that would not be practical to build trailers with stricter design 
specifications in order to perform SWD tests and obtain consistent 
results. Conversely, Advocates and Bendix recommended that the agency 
add new specifications and tighten up existing requirements in order to 
reduce the variability in testing. Advocates recommended specifying 
track width, trailer CG height, and load CG height in the standard 
because it would minimize variation in testing.
    Other than soliciting comments in the NPRM, the agency did not 
investigate whether variations in the control trailer significantly 
affect the results of the SWD maneuver. However, the agency has not 
further modified the specifications of the control trailer. Rather, we 
believe that, by using the J-turn maneuver rather than the SWD 
maneuver, any potential test variability caused by different control 
trailers is ameliorated. The agency's research shows that, because the 
performance metric is vehicle speed rather than lateral acceleration 
ratio, the effect that the control trailer has on the lateral 
acceleration is negligible. The sole consideration in the performance 
criteria in this final rule is speed reduction, which has not been 
observed to be affected by variations in the control trailer.
    We note that Volvo, EMA, and Bendix recommended the adoption of the 
J-turn test, which is one of the alternative tests discussed in the 
NPRM. None of the commenters supporting adoption of the J-turn test 
raised issues regarding variability in the control trailer with the J-
turn maneuver. Rather, their comments regarding control trailer 
variability were limited to the SWD test maneuver.
    Further, the agency conducted J-turn testing using two different 
control trailers. We did not find any relevant differences in the ESC 
system performance of the truck tractors when connected to different 
control trailers. We believe, based on our testing and the lack of 
comments related to the control trailer in the J-turn maneuver, that 
the potential for variability identified in the NPRM related to the 
control trailer was limited to the SWD maneuver. We conclude that the 
factors identified in the NPRM will have no effect on the performance 
of vehicles using the J-turn maneuver.
    Volvo also commented that the control trailer specified in FMVSS 
No. 121 will not work with four or more axle tractors such as 8x6 truck 
tractor's because the trailer's fifth wheel position causes 
interference between the tractor frame and trailer frame. NHTSA has 
considered this comment and believes that there is merit in Volvo's 
assertion. A control trailer at the length specified in the NPRM of 
6550  150 mm (258  6 in) may be too short to 
test vehicles with four or more axles. In this final rule, we are 
changing the specified length of the control trailer to allow for 
testing with a longer trailer. We are specifying that truck tractors 
will be tested with a control trailer that is between 6400 mm and 7010 
mm (252 in and 276 in), inclusive. However, for truck tractors with 
four or more axles, at the manufacturer's option, NHTSA will test with 
a control trailer with a length up to 13,208 mm (520 in). We do not 
believe that using a control trailer longer than that specified in the 
proposal would cause variability in testing.

E. Sensors

    The vehicle speed is measured with a non-contact GPS-based speed 
sensor. Accurate speed data is required to ensure that the SWD maneuver 
is executed at the required 72.4  1.6 km/h (45.0  1.0 mph) test speed. Sensor outputs are available to allow the 
driver to monitor vehicle speed.

F. Ambient Conditions

    The ambient temperature range specified in other FMVSSs for outdoor 
brake performance testing is 0 [deg]C to 38 [deg]C (32[emsp14][deg]F to 
100[emsp14][deg]F). However, when the agency proposed a range of 0 
[deg]C to 40 [deg]C (32[emsp14][deg]F to 104[emsp14][deg]F) for FMVSS 
No. 126, the issue of tire performance at near freezing temperatures 
was raised. The agency understood that near freezing temperatures could 
impact the variability of compliance test results. As a result, the 
agency increased the lower bound of the temperature range to 7 [deg]C 
(45[emsp14][deg]F) to minimize test variability at lower ambient 
temperatures. For the same reasons, the NPRM proposed an ambient 
temperature range of 7 [deg]C to 40 [deg]C (45[emsp14][deg]F to 
104[emsp14][deg]F) for testing.
    In their comments, Meritor WABCO, EMA, and Bendix recommended 
changes to the minimum ambient temperature allowed for testing. The 
three commenters requested that the minimum temperature for performance 
tests to be reduced. Meritor WABCO recommended a minimum temperature of 
2 [deg]C (35[emsp14][deg]F). Both EMA and Bendix recommended a minimum 
temperature of 0 [deg]C (32[emsp14][deg]F). EMA asserted that the 
minimum temperature of 7 [deg]C (45[emsp14][deg]F) proposed in the NPRM 
reduces the amount of time available to test vehicles during the year. 
We agree that a minimum test temperature of 7 [deg]C (45[emsp14][deg]F) 
restricts the agency's ability to test for compliance in certain areas 
of the United States, including NHTSA's Vehicle Research and Test 
Center in Ohio. Thus, we are lowering the minimum testing temperature 
to 2 [deg]C (35[emsp14][deg]F). We believe this change will have a 
negligible effect on the outcome of performance testing.
    EMA further recommended that the upper limit be decreased from 40 
[deg]C (104[emsp14][deg]F) to 38 [deg]C (100[emsp14][deg]F) to match 
the FMVSS No. 121 ambient temperature specifications. We are not 
adopting this suggestion to match the temperature specifications in 
FMVSS No. 121. EMA gave no reason other than consistency with FMVSS No. 
121 for adopting this change. Allowing for a larger temperature range 
for testing ESC systems does not have any effect on the agency's 
ability to conduct consecutive FMVSS No. 121 and FMVSS No. 136 tests 
because the FMVSS No. 121 testing is conducted at an ambient 
temperature of not greater than 38 [deg]C (100[emsp14][deg]F). Thus, 
compliance testing will be conducted at any temperature between 2 
[deg]C (35[emsp14][deg]F) and 40 [deg]C (104[emsp14][deg]F). The agency 
proposed a maximum wind speed for conducting the compliance testing of 
no greater

[[Page 36083]]

than 5 m/s (11 mph). This is the same value specified for testing 
multi-purpose passenger vehicles (MPVs), buses, and trucks under FMVSS 
No. 126. This is also the same value used for compliance testing for 
FMVSS No. 135, Light Vehicle Brake Systems.
    As for other ambient conditions, Bendix recommended that the 
maximum wind speed be raised from 11 mph (5 m/s) to 22 mph (10 m/s). 
Bendix did not specify any rationale for wanting the increase in the 
allowable wind speed. The agency sees no reason to increase the wind 
speed at this time.

G. Road Test Surface

    The NPRM proposed that the SWD maneuver be executed on a high 
friction surface with a peak friction coefficient (PFC) of 0.9, which 
is typical of a dry asphalt surface or a dry concrete surface. As in 
other standards where the PFC is specified, we proposed that the PFC be 
measured using an ASTM E1136 standard reference test tire in accordance 
with ASTM Method E1337-90, at a speed of 64.4 km/h (40 mph), without 
water delivery. We proposed incorporating these ASTM provisions into 
the standard.
    Although we have changed the performance test maneuver, we have not 
changed the specifications for the road test surface. The J-turn 
maneuver is conducted on a high friction surface with a PFC of 0.9. 
Thus, we are incorporating the relevant ASTM provisions into this 
standard.
    Bendix recommended adding a restriction that there be no ice or 
snow buildup on the test track surface. NHTSA has not adopted this 
suggested change. We believe that the surface PFC specification of 0.9 
already ensures that the test track will be free of snow and ice.

H. Vehicle Test Weight

    The agency proposed that truck tractors be tested with the combined 
weight of the truck tractor and control trailer be equal to 80 percent 
of the tractor's GVWR. To achieve this load condition, we proposed that 
the tractor be loaded with the fuel tanks filled to at least 75 percent 
capacity, test driver, test instrumentation, and ballasted control 
trailer with outriggers. The center of gravity of all ballast on the 
control trailer was proposed to be located directly above the kingpin. 
When possible, load distribution on non-steer axles will be in 
proportion to the tractor's respective axle GAWRs. Load distribution 
will be adjusted by altering fifth wheel position, if adjustable. In 
the case where the tractor's fifth wheel cannot be adjusted so as to 
avoid exceeding a GAWR, ballast will be reduced so that axle load 
equals specified GAWR, maintaining load proportioning as close as 
possible to specified proportioning.
    In its comments, EMA recommended changing the loading requirements 
from 80 percent of the truck tractor's GVWR to 100 percent of the truck 
tractor's GVWR requirements. EMA wanted this loading condition because 
it is used in FMVSS No. 121 testing, and it would eliminate the burden 
of changing the vehicle's load when going from FMVSS No. 121 testing to 
FMVSS No. 136 testing.
    In light of the change to the J-turn maneuver, we have determined 
that the vehicle should be tested at its GVWR rather than 80 percent of 
the truck tractor's GVWR. The agency proposed SWD testing at 80 percent 
of GVWR because it was determined that such a weight would enable the 
agency to evaluate both roll and yaw stability with a single maneuver. 
The J-turn maneuver is designed to evaluate only roll stability, and 
testing the vehicle at its GVWR is the most severe configuration for 
the maneuver. Thus, the agency can use the same loading condition that 
it uses for FMVSS No. 121 testing.
    EMA also suggested removing the proposed test condition that the 
fuel tank be 75 percent full. EMA reasoned that high fuel volume is 
dangerous for testing. Also, EMA observed that a 75% fuel filling 
condition is not included in FMVSS No. 121.
    Regarding the fuel tank filling, NHTSA specifies the 75 percent 
fuel level in FMVSS No. 126 for testing light vehicles. The goal of the 
fuel level specification in FMVSS No. 126 was to ensure consistent 
vehicle test weights for the performance tests. With the adoption of 
the J-turn maneuver, NHTSA did not find any evidence of varying fuel 
levels affecting the results of the ESC performance tests. Therefore, 
NHTSA agrees with EMA and will remove the specification of a minimum 
fuel tank level.
    The agency proposed that liftable axles be in the down position for 
testing. This was because we proposed to conduct our performance test 
in a loaded condition. Although the NPRM proposed to load the truck 
tractor to 80 percent of its GVWR, we believed that a truck tractor 
would operate with liftable axles in the down position. In the final 
rule, we are testing vehicles at GVWR. Consequently, we will test 
vehicles equipped with liftable axles in the down position. This is 
consistent with the test conditions for testing fully loaded air braked 
vehicles under FMVSS No. 121.
    For testing buses, the agency proposed loading the vehicle to a 
simulated multi-passenger configuration. For this configuration the bus 
would be loaded with the fuel tanks filled to at least 75 percent 
capacity, test driver, test instrumentation, outriggers and simulated 
occupants in each of the vehicle's designated seating positions. The 
simulated occupant loads would be obtained by securing 68 kilograms 
(150 pounds) of ballast in each of the test vehicle's designated 
seating positions without exceeding the vehicle's GVWR and GAWR. The 68 
kilogram (150 pound) occupant load was chosen because that is the 
occupant weight specified for use by the agency for evaluating a 
vehicle's load carrying capability under FMVSS Nos. 110 and 120. During 
loading, if any rating is exceeded the ballast load would be reduced 
until the respective rating or ratings are no longer exceeded.
    In the final rule, we have removed the specification that the 
ballast consists of water dummies. We do not believe that it is 
necessary to specify the type of ballast in the test procedure. We note 
that, for truck tractors, the type of ballast that is loaded on the 
control trailer is not specified. We do not believe, especially in 
light of the change to the J-turn test, that the type of ballast used 
(whether it is water, sand, or some other ballast) would have an effect 
on the ESC system's ability to lower the vehicle's forward speed.
    Unlike in the NPRM, this final rule specifies that buses are tested 
at its GVWR. This is the most severe loading condition for testing 
buses using the J-turn test maneuver. The NPRM specified that buses 
would be tested with a simulated full passenger load, without any cargo 
other than test equipment. We have increased the testing load, which 
makes the load condition consistent with the loading NHTSA uses to test 
FMVSS No. 121 compliance. We have added specification to the loading 
procedure to allow for the vehicle to be loaded to GVWR. First, 
simulated passengers are loaded. Next, ballast is added to the lowest 
baggage compartment. If the bus does not have a baggage compartment or 
additional ballast is needed because the baggage compartment is loaded 
to capacity, ballast is added to the floor of the passenger compartment 
to load the bus to its GVWR. During loading, if any axle rating is 
exceeded, the ballast is reduced in the reverse order it is loaded 
until the GVWR or GAWR of any axle is no longer exceeded.

[[Page 36084]]

I. Tires

    We proposed testing the vehicles with the tires installed on the 
vehicle at time of initial vehicle sale. The agency's compliance test 
programs generally evaluate new vehicles with new tires. Therefore, we 
proposed that a new test vehicle have less than 500 miles on the 
odometer when received for testing.
    For testing, the agency proposed that tires be inflated to the 
vehicle manufacturer's recommended cold tire inflation pressure(s) 
specified on the vehicle's certification label or the tire inflation 
pressure label. We will not change the vehicle's tires during testing 
unless test vehicle tires are damaged before or during testing. We did 
not propose using inner tubes for testing because we have not seen any 
tire debeading in any test.
    Before executing any test maneuvers, the agency proposed to 
condition tires to wear away mold sheen and achieve operating 
temperatures. To begin the conditioning the test vehicle would be 
driven around a circle 46 meters (150 feet) in radius at a speed that 
produces a lateral acceleration of approximately 0.1g for two clockwise 
laps followed by two counterclockwise laps.
    EMA asserted that there should be no requirement for testing using 
the tires installed on the vehicle at the time of initial sale. 
According to EMA, sometimes a test vehicle is used for certifying 
compliance, but sometimes a vehicle that is later sold to a customer is 
tested. Further, EMA notes that heavy truck manufacturers often offer 
hundreds of different tire options for their customers. EMA notes that 
different tires would change the road adhesion and cornering stiffness, 
potentially affecting test results.
    Finally, EMA recommended using language from FMVSS No. 121 for the 
tire inflation procedure specified by manufacturer for the vehicle's 
GVWR, instead of the procedure proposed in the NPRM, which is to use 
the vehicle's certification label or tire inflation pressure label. EMA 
reasoned that the actual tires installed on the vehicle may differ from 
the specifications given on the label.
    First, inasmuch as EMA is referring to the tires used for 
certifying compliance, we note that our regulations do not specify how 
manufacturers certify compliance. We recognize that some manufacturers 
do wish to base their certification of compliance on a vehicle's 
performance in NHTSA's test maneuvers. However, there is no obligation 
for manufacturer's to conduct NHTSA's compliance test for any vehicle, 
much less for every possible tire combination. For instance, 
manufacturers currently certify that their vehicles meet the minimum 
stopping distance and ABS requirements of FMVSS No. 121. They must 
satisfy those requirements for any vehicle-tire combination that is 
sold. That is, manufacturers have an obligation to certify compliance 
with all applicable standards in whatever configuration that tires are 
delivered to customers. We expect that manufacturers design their ESC 
systems to account for any potential differences in tires that might be 
installed on the vehicle at the time of initial sale.
    However, with respect to the tire inflation pressure at which 
testing will be conducted, we agree with EMA that we should not use the 
inflation pressure specified on the vehicle's certification or tire 
information labels. As EMA observes, a heavy truck may be sold with 
many different tire combinations. However, nothing requires that all of 
those combinations be listed on the certification or tire information 
label.\61\ However, multiple combinations may be listed on the label. 
Thus, we are removing from the regulatory text the reference to the 
vehicle's certification or tire information label and merely specifying 
that the tires' inflation pressure will be the inflation pressure 
specified for the GVWR of the vehicle.
---------------------------------------------------------------------------

    \61\ In fact, S5.1.2 of FMVSS No. 120, the standard that 
provides for tire information labeling on vehicles over 10,000 
pounds GVWR, expressly contemplates that a vehicle may be sold with 
a tire size designation that is not listed on the tire information 
label.
---------------------------------------------------------------------------

    Regarding tire conditioning, Bendix requested clarification of 
whether the presence of a tire conditioning procedure means that the 
vehicle must be equipped with new tires. Bendix also recommended that 
the agency remove this section about the removal of mold sheen because 
by performing the brake conditioning test procedure, the same result is 
likely to be achieved.
    To clarify, the agency is not specifying that new tires must be 
installed prior to the ESC testing. However, in the event the vehicle 
has not been driven prior to testing (for example, a FMVSS No. 121 
compliance test has not been performed), we do not believe that the 
brake burnishing procedure is sufficient to wear away any mold sheen on 
the tire prior to ESC testing. Therefore, the requirement to perform 
four laps is necessary for the consistency and repeatability of the ESC 
tests. We do not believe that this procedure is especially burdensome, 
even if the mold sheen was removed during prior testing.

J. Mass Estimation Drive Cycle

    Both truck tractors and large buses experience large variations in 
payload mass, which affects a vehicle's roll and yaw stability 
thresholds. To adjust the activation thresholds for these variations, 
stability control systems estimate the mass of the vehicle after 
ignition cycles, periods of static idling, and other driving scenarios. 
To estimate the mass, these systems require a period of initial 
driving.
    The agency proposed including a mass estimation drive cycle as a 
part of pre-test conditioning. To complete this drive cycle the test 
vehicle is accelerated to a speed of 64 km/h (40 mph), and then, by 
applying the vehicle brakes, decelerated at 0.3g to 0.4g to a stop.
    Meritor WABCO requested that the mass estimation drive cycle 
procedure be made manufacturer-specific. That is, Meritor WABCO 
requested that the procedure be changed to specify that NHTSA would 
contact the ESC system supplier for a mass estimation procedure.
    Although we specified a mass estimation procedure in the NPRM, that 
procedure is based on current ESC system designs. We recognize that 
system designs could change or new suppliers could enter the market 
with different designs that estimate vehicle mass differently. Thus, we 
accept Meritor WABCO's request that NHTSA not specify a mass estimation 
cycle.
    However, we do not agree with Meritor WABCO's suggestion that NHTSA 
contact the ESC system supplier for the mass estimation cycle. It is 
the vehicle's manufacturer that is ultimately responsible for 
certifying compliance with the FMVSSs. Thus, we believe it is the 
vehicle's manufacturer, not the ESC system supplier, who should be 
responsible for supplying NHTSA with the mass estimation cycle 
procedure. Thus, we expect that the vehicle manufacturer will be able 
to provide the mass estimation cycle procedure to NHTSA upon request in 
advance of any compliance testing.

K. Brake Conditioning

    Heavy vehicle brake performance is affected by the original 
conditioning and temperatures of the brakes. We believe that 
incompletely burnished brakes and excessive brake temperatures can have 
an effect on ESC system test results, particularly in the rollover 
performance testing, because a hard brake application may be needed for 
the foundation brakes to reduce speed to prevent rollover.
    The agency proposed that the burnish procedure specified in S6.1.8 
of FMVSS

[[Page 36085]]

No. 121 be conducted prior to ESC system testing. The burnish procedure 
is performed by conducting 500 brake snubs \62\ between 40 mph and 20 
mph at a deceleration of 10 fps\2\. If the vehicle has already 
completed testing to FMVSS No. 121, the agency did not propose to 
repeat the full burnishing procedure. Instead, the brakes are 
conditioned for ESC system testing with 40 snubs. The agency proposed 
that the brake temperatures be in the range of 65 [deg]C to 204 [deg]C 
(150[emsp14][deg]F to 400[emsp14][deg]F) at the beginning of each test 
maneuver. We also proposed that the brake temperature be measured by 
plug-type thermocouples installed on all brakes and that the hottest 
brake be used for determining whether cool-down periods required.
---------------------------------------------------------------------------

    \62\ A snub is a brake application where the vehicle is not 
braked to a stop but to a lower speed.
---------------------------------------------------------------------------

    We received no comment on the burnishing procedure and are adopting 
the proposed procedure in this final rule, with two exceptions. First, 
in the NPRM, we proposed to repeat the FMVSS No. 121 burnish procedure 
at the manufacturer's option. However, in this final rule, we have 
removed the option. Rather, we are merely specifying that a burnish 
procedure similar to the one in FMVSS No. 121 be completed prior to 
testing. Furthermore, rather than referencing FMVSS No. 121, we have 
included the entire burnishing in FMVSS No. 136 to avoid the need to 
cross-reference between Standards. Second, we have altered the metric 
conversion of 150[emsp14][deg]F from 65 [deg]C to 66 [deg]C to be more 
accurate.
    In the NPRM, the agency suggested, as a general rule, that a new 
test vehicle have less than 500 miles on the odometer when received for 
testing. EMA commented on this suggestion, requesting that there be no 
odometer requirements on a test vehicle. EMA believes that this 
requirement may require transporting the test vehicle by hauling it on 
a trailer to the test site if the test site is located far away from 
the place of manufacture. NHTSA agrees with EMA that it is not feasible 
to require that a test vehicle have less than 500 miles on its odometer 
prior to testing. This is particularly true in light of the burnishing 
procedure, which could itself require 500 miles of driving. Thus, the 
final rule does not have a mileage requirement for test vehicles.

L. Compliance Options

    Both Bendix and Volvo requested clarification of the proposed 
regulatory text specifying compliance options. That provision would 
require that a manufacturer identify which compliance option was 
selected for compliance test purposes and provide that information to 
the agency upon request. Bendix and Volvo raised this issue because 
they did not believe that any of the proposed requirements offered 
manufacturers any compliance options to choose from.
    In this final rule, we are giving manufacturers a compliance option 
with respect to the length of the control trailer used for testing 
truck tractors. As discussed in section XI.D, manufacturers of truck 
tractors with four or more axles may, at the manufacturer's option, 
have testing conducted with a longer control trailer. Thus, we are 
retaining the language requiring manufacturers to specify compliance 
options prior to agency testing.

M. Data Collection

    In the NPRM, we proposed that the collection of data from the 
vehicle, such as engine torque output and driver-requested torque, come 
from the SAE J1939 communication data link. Bendix requested that NHTSA 
change the collection procedure to specify that the data come from the 
vehicle controller area network (CAN) bus, which is a more generic 
reference instead of specifically requiring a SAE J1939 data link. The 
CAN bus is what allows a vehicle's electronic control units and other 
devices to communicate with each other. SAE J1939 is a recommended 
practice to standardize vehicle communications. Bendix believes that 
citing SAE J1939 specifically may have the effect of limiting vehicle 
design in the future.
    We agree with Bendix that the reference to SAE J1939 should be 
changed to a more generic reference. This will allow future 
technological advances regarding in-vehicle communications, including 
the adoption of new industry recommended practices. Accordingly, we are 
specifying that data be collected from the vehicle's communication 
network or CAN bus.
    Bendix also commented upon the filtering of engine torque data 
received from an analog signal. Bendix noted that data from an SAE 
J1939 compliant communication network is digital data. However, because 
we are removing the references to SAE J1939 in response to Bendix's 
comment, we are not changing the procedure for filtering analog data 
signals because recognize that some communication systems could use 
analog signals.

XII. ESC Disablement

A. Summary of Comments

    In the NPRM, the agency considered allowing a control for the ESC 
to be disabled by the driver. Because, heavy vehicles currently 
equipped with ESC systems do not include on/off controls for ESC that 
allow a driver to deactivate or adjust the ESC system, the agency did 
not propose allowing an on/off switch for ESC systems. The agency 
sought public comment on the need to allow an on/off switch, and asked 
that commenters specifically address why manufacturers might need such 
a switch and how manufacturers would implement a switch in light of the 
ABS requirements.
    Temsa and Advocates opposed allowing the disablement of the ESC 
system. They stated that the ESC system should not be allowed to be 
deactivated by a switch because the driver may inadvertently forget to 
reactivate the system.
    In contrast, Daimler, Volvo, Meritor WABCO, HDBMC, Associated 
Logging, EMA, and Bendix recommended that we allow the ESC systems to 
be disabled. The commenters asserted that the ESC system may need to be 
disabled in certain conditions such as slippery roads in snow and mud, 
off-road operation, and when using snow chains on the tires.
    Daimler stated in its comment that the current ESC and traction 
control systems are interlinked, and the disablement of traction 
control will disable ESC systems. Daimler asserted that disabling 
traction control may be necessary in conditions such as starting from 
rest on sloped ground, driving on slippery roads, and using snow 
chains. HDBMC also asserted that ESC disablement is needed for gaining 
traction in snow and mud and to provide optimum performance when using 
snow chains. Meritor WABCO similarly referred to the need for the 
ability to change the control scheme of the ESC system to allow for 
deep snow and mud.
    In contrast, Bendix stated that its ESC system is tuned for both 
on-road and mild off-road conditions. However, Bendix suggested that 
different vehicle tuning may be necessary for severe off-road 
conditions.
    Regarding the absence of ESC disablement on current truck tractors, 
EMA also suggested that some small volume tractors are more likely to 
need to have an ESC disablement function for off-road operation and 
claimed that at least one manufacturer had equipped a vehicle with such 
a switch to temporarily disable ESC. Further, EMA

[[Page 36086]]

suggested that ESC disablement functions are not prevalent because 
large fleet customers have been purchasing ESC systems.
    HDMBC recommended that vehicles that have a switch to disable ESC 
systems be equipped with a lamp indicating that the ESC system is off 
similar to the ESC Off telltale in FMVSS No. 126. In its comment, 
Meritor WABCO suggested that the ESC malfunction lamp should be 
constantly illuminated if ESC is deactivated.
    Meritor WABCO, HDBMC, Bendix, EMA, and Volvo also suggested that 
vehicles be allowed to automatically disable their ESC systems under 
certain conditions. Meritor WABCO claimed that all-wheel drive is an 
example of when ESC should automatically be disabled. HDBMC, EMA, and 
Bendix said there should be the ability to automatically disable ESC 
system for certain applications such as all-wheel drive and truck 
tractors with multiple steering axles. Volvo asserted that, while it 
has no plans to offer an ESC on/off switch, it recognizes that some 
customers may want to convert a truck tractor to a truck. Volvo 
believes that it may be preferable to allow an ESC off switch rather 
than having converters disabling the ESC system during a conversion.
    In its comment, Bendix also recommended changing the minimum speed 
at which an ESC system is required to operate from 20 km/h (12.4 mph) 
to 25 km/h (15.5 mph) to accommodate the wide variation of tires sizes, 
tone ring tooth counts, and production tolerances. Bendix said the 
higher speed threshold is necessary based on wheel-speed sensor signal 
strength and antilock braking system functionality.

B. Response to Comments

    This final rule does not allow a function to disable an ESC system 
at speeds where ESC systems are required to operate.
    First, we address the integration between traction control systems 
and ESC systems. Both systems use the vehicle's brake control system to 
accomplish different goals. Traction control reduces engine power and 
applies braking to a spinning drive wheel in order to transfer torque 
to the other drive wheel on the axle. This function is used to allow a 
vehicle to move forward in certain conditions where wheel spin may 
otherwise prevent forward movement. In contrast, ESC systems are 
designed to maintain roll and yaw stability rather than facilitate 
forward movement.
    While we agree that traction control may need to be disabled in 
slippery conditions such as snow or mud or other off-road conditions, 
the commenters do not explain why ESC functions must be disabled in 
those circumstances. Although ESC may share components with traction 
control, the requirements for ESC are independent of those for traction 
control. As explained above, ESC mitigates roll and yaw instability of 
the vehicle by reducing lateral acceleration and maintaining 
directional control, respectively. Although traction control provides 
mobility in starting on slippery surfaces, it does not improve lateral 
stability beyond what ESC provides through braking and reduction in 
engine torque. Likewise, traction control does not improve yaw 
stability by providing directional control. Traction control provides 
no further assistance when lateral or yaw instability is detected.
    Furthermore, we are not requiring the ESC system to activate at 
extremely low vehicle speeds, which is when the vehicle would be 
starting from rest. This concern may be remedied by optimizing traction 
control, and a manufacturer has the option to activate traction control 
or allow deactivation of traction control at any vehicle speed. If the 
disablement of traction control also disables the ESC system, then the 
disablement function is prohibited from disabling ESC functionality at 
speeds above the minimum speed ESC systems are required to operate. 
This means that the ESC system must automatically reactivate once the 
vehicle reaches the minimum speed at which the ESC system is required 
to operate.
    Some of the commenters asserted the need for ESC disablement on 
vehicles with all-wheel-drive or multi-steering axles. In FMVSS No. 
126, we allow the ESC to be disabled on light vehicles for certain 
four-wheel drive modes. None of the commenters asserted any 
similarities that truck tractors and large buses have with light 
vehicles regarding enhanced traction modes such as four-wheel drive 
low. Therefore, we do not believe any exceptions should be made for 
all-wheel drive vehicles because there was insufficient data submitted 
to justify an exception for heavy vehicles.
    With regard to vehicles with multiple steering axles, we received 
no specific information about the vehicle operation and why vehicle 
with multiple steer axles should be allowed to have their ESC systems 
disabled either by switch or automatically. Without any information, 
the agency cannot justify an exception.
    Regarding off-road use, Bendix and Meritor WABCO discussed ESC 
tuning differences between on-road and off-road uses in their comments. 
However, neither supplier provided detailed reasons for why ESC system 
disablement would be beneficial when used in off-road circumstances. In 
contrast, Bendix said the off-road situations need ESC disablement at 
low speeds and different ESC tuning is expected.
    Regarding Volvo's assertion that an ESC disablement switch may be 
preferable to converters disabling ESC during a conversion of a vehicle 
from a truck tractor to a truck, we do not believe that this limited 
circumstance justifies an ESC disablement switch. Volvo was not 
specific on the nature of the conversion it was referring to and why 
the ESC system would need to be disabled.
    Bendix suggested that a switch could be allowed to disable an ESC 
system below a maximum speed of 25 mph. Bendix believes that this would 
allow for maneuverability in slippery conditions such as mud or snow. 
Relatedly, Bendix suggested that the minimum ESC operational speed be 
raised from the proposed 20 km/h (12.4 mph) to 25 km/h (15.5 mph).
    After considering the comments, we are not raising the minimum 
speed at which an ESC system must operate. We proposed the minimum 
operating speed of 20 km/h (12.4 mph) based on information we obtained 
from vehicle manufacturers and ESC system suppliers, including Bendix. 
As we stated in the NPRM, the low speed thresholds of ESC systems were 
10 km/h (6.2 mph) for yaw stability control and 20 km/h (12.4 mph) for 
roll stability control. We believed that setting a single low speed 
threshold was preferable because yaw and roll stability functions are 
intertwined. Bendix's recommendation for increasing the minimum speed 
criteria presents new information to the agency. We also observe that 
the proposed minimum speed threshold is the same as UN ECE Regulation 
13. Instead of raising the minimum activation speed, at which an ESC 
system must operate, manufacturers may wish to disable the traction 
control system, where disabling traction control does not cause the ESC 
system to be in a malfunction state, without compromising the 
effectiveness of an ESC system. However, once a vehicle reaches a 
forward speed of 20 km/h (12.4 mph), the ESC system is required to be 
functional to prevent roll and yaw instability. We believe that changes 
to the traction control system operation will mitigate the concerns 
raised by the commenters regarding

[[Page 36087]]

system operability in slippery or off-road conditions.
    Finally, we also sought and received comments on how a manufacturer 
would implement an ESC disablement switch. Because we have decided not 
to allow ESC disablement above the minimum speed at which ESC is 
required to operate, we need not address these comments in this final 
rule.

XIII. ESC Malfunction Detection, Telltale, and Activation Indicator

A. ESC Malfunction Detection

    The NPRM proposed that that vehicles would be required to be 
equipped with an indicator lamp, mounted in front of and in clear view 
of the driver, which would be activated whenever there is a malfunction 
that affects the generation or transmission of control or response 
signals in the vehicle's ESC system. Heavy vehicles presently equipped 
with ESC generally do not have a dedicated ESC malfunction lamp. 
Instead, they share that function with the mandatory ABS malfunction 
indicator lamp or the traction control activation lamp. The agency 
proposed requiring a separate ESC malfunction lamp because it would 
alert the driver to the malfunction condition of the ESC and would help 
to ensure that the malfunction is corrected at the earliest 
opportunity.
    The ESC malfunction telltale would be required to remain 
illuminated continuously as long as the malfunction exists whenever the 
ignition locking system is in the ``On'' (``Run'') position. The 
proposal required that ESC malfunction telltale extinguish after the 
malfunction has been corrected.
    The NPRM also included a test that would allow the engine to be 
running and the vehicle to be in motion as part of the diagnostic 
evaluation. The agency proposed simulating several possible 
malfunctions to ensure the system and corresponding malfunction 
telltale provides the required warning to the vehicle operator, such as 
by disconnecting the power source to an ESC system component or 
disconnecting an electrical connection to or between ESC system 
components. After a malfunction has been simulated and identified by 
the system, the system would be restored to normal operation. The 
engine is started and the malfunction telltale is checked to ensure it 
has cleared.
    We received no adverse comments on the requirement that an ESC 
system malfunction be displayed to the driver, nor did we receive 
comments on the test procedure for ensuring malfunction detection. 
Therefore, we are adopting these requirements as proposed in the NPRM.

B. ESC Malfunction Telltale

    The NPRM proposed requiring that an ESC malfunction lamp provide a 
warning to the driver when one or more malfunctions that affect the 
generation of control or response signals in the vehicle's electronic 
stability control system is detected. Specifically, the ESC malfunction 
telltale would be required to be mounted in the driver's compartment in 
front of and in clear view of the driver and be identified by the 
symbol shown for ``ESC Malfunction Telltale'' or the specified words or 
abbreviations listed in Table 1 of FMVSS No. 101, Controls and 
displays. FMVSS No. 101 includes a requirement for the telltale symbol, 
or abbreviation, and the color required for the indicator lamp to show 
a malfunction in the ESC system.
    The agency proposed that the symbol and color used to identify ESC 
malfunction should be standardized with the symbol used on light 
vehicles. The symbol established in FMVSS No. 126 is the International 
Organization for Standardization (ISO) ESC symbol, designated J.14 in 
ISO Standard 2575. The symbol shows the rear of a vehicle trailed by a 
pair of ``S'' shaped skid marks, shown below in Figure 3. The 
malfunction telltale is displayed in the color yellow, which 
communicates the malfunction of a system that does not require 
immediate correction. The agency found that the ISO J.14 symbol and 
close variations were the symbols used by the greatest number of light 
vehicle manufacturers that used an ESC symbol before the requirement 
was established. Furthermore, FMVSS No. 126 allows, as an option, the 
use of the text ``ESC'' in place of the telltale symbol. This same 
option was proposed in the NPRM for heavy vehicles.
[GRAPHIC] [TIFF OMITTED] TR23JN15.010

    In addition to the ESC malfunction telltale being used to warn the 
driver of a malfunction in the ESC, the telltale is also used as a 
check of lamp function during vehicle start-up. We believe that the ESC 
malfunction telltale should be activated as a check of lamp function 
either when the ignition locking system is turned to the ``On'' 
(``Run'') position whether or not the engine is running. This function 
provides drivers with the information needed to ensure that the ESC 
system is operational before the vehicle is driven. It also provides 
Federal and State inspectors with the means to determine the 
operational status of the ESC system during a roadside safety 
inspection.
    In the regulatory text of the NPRM, we proposed requiring that the 
ESC malfunction telltale illuminate only when a malfunction exists. 
However, we also required that the telltale illuminate as a check of 
lamp function. These two requirements may be read as inconsistent with 
each other. We have added language to this final rule to clarify that 
the check of lamp function is an exception to the requirement that the 
telltale only illuminate in the event of a system malfunction.
    Meritor WABCO commented on the operation of the light and said that 
the ESC malfunction lamp should be continuously illuminated if there is 
a malfunction in the ESC system. We agree with Meritor WABCO. The 
requirement that the indicator lamp be continuously illuminated if 
there is a malfunction in the ESC system was included in the proposed 
standard and is included in this final rule.
    Bendix recommended a change that would allow a malfunction lamp to

[[Page 36088]]

remain illuminated until either the system self-resets with an ignition 
cycle or a recommended diagnostic tool can be used to clear faults. 
Bendix states that in some cases of faults, their systems are not 
guaranteed to self-reset upon correction.
    We are not adopting Bendix's suggested change to allow that the 
telltale remain illuminated until a diagnostic tool can be used to 
reset a fault. If a diagnostic tool can be used to remedy a fault 
without an ignition cycle, there is nothing prohibiting the malfunction 
telltale from being extinguished. However, we cannot include in the 
malfunction lamp requirements the ability for the telltale to remain 
illuminated, even after a malfunction may have been corrected, until a 
diagnostic tool can be used. The purpose of the requirement that the 
malfunction lamp extinguish upon an ignition cycle after correction of 
the problem is that the system should be able to detect both a 
malfunction and a correction without the use of external tools. The 
malfunction lamp should not extinguish until the fault is actually 
corrected.
    We also received comments regarding the ESC system malfunction 
telltale itself. Temsa commented that there should be the option to use 
the text of ``ESC'' on the malfunction indicator. Temsa reasoned that 
this would be more user-friendly. This option was included in the NPRM 
and is included in this final rule.
    We received several comments on the depiction of the vehicle in the 
telltale. Daimler referred to ECE Regulation 13, which citing ISO 2575, 
allows the vehicle shape to be changed to better represent the true 
exterior shape of a given vehicle. Daimler also stated that it uses a 
heavy truck or bus symbol on its European systems and it may result in 
an increased cost if the symbol depicting a passenger car was required 
in the U.S. Daimler asserted that the discretion to choose the vehicle 
outline should be left to the manufacturer. Similarly ATA and Volvo 
recommended that the telltale should depict the rear of a truck tractor 
above the ``S'' shaped skid marks.
    In response, we acknowledge desire of the industry to most 
accurately depict the type of vehicle being displayed on the ESC system 
malfunction telltale. We believe that requiring a symbol depicting the 
rear end of a trailer or bus above the ``S'' skid marks will satisfy 
the concerns of the manufacturers without causing any confusion 
regarding the identification of the telltale. We are including in the 
allowable telltales for this Standard trailer and bus symbols drawn 
from ISO 2575. We have chosen to depict the rear outline of a trailer 
rather than a truck because it is a better depiction of the usual rear 
view of a combination vehicle. The symbols are depicted in Figure 4 
below.
[GRAPHIC] [TIFF OMITTED] TR23JN15.011

C. Combining ESC Malfunction Telltale With Related Systems

    In its comment, CVSA supported NHTSA's proposal to require a 
separate ESC malfunction telltale, without which the end user would not 
know if the system is operating. Further, CVSA reasoned that an 
anticipated Federal Motor Carrier Safety Administration (FMCSA) rule 
would require commercial vehicles with ESC systems be free of any 
indicated ESC faults.
    Volvo supported combining the ESC malfunction indicator with a 
malfunction indicator for a traction control system. Volvo reasoned 
that a malfunction in the traction control system would be likely to 
also constitute a malfunction in the ESC system. In a simplified fault 
representation system submitted by Volvo, 17 out of 18 faults in a 
traction control system were also ESC system faults that would 
presumably trigger the ESC malfunction indicator. Volvo reasoned that 
having separate lamps for traction control and ESC system faults could 
confuse a driver and diminish the importance of addressing the fault.
    Likewise, EMA noted that the current industry practice is to 
combine the malfunction indicator lamp for the ESC and traction control 
systems. EMA also observed that traction control and ESC systems share 
similar components and, thus, tend to fail simultaneously. EMA stated 
that by mandating separate traction control and ESC malfunction lamps, 
NHTSA would be unnecessarily requiring investment of resources to 
change the instrument cluster. EMA stated that in FMVSS No. 126, NHTSA 
permits light vehicles to use the ESC malfunction indicator to signal 
malfunctions in related systems such as traction control. EMA requested 
that NHTSA provide similar flexibility.
    Bendix similarly observed that the current industry practice is to 
combine ESC and traction control system malfunction indicators and that 
having a third lamp for traction control system malfunctions is 
unnecessary. Bendix also stated that the interconnected nature of 
traction control and ESC systems means that a failure in one system is 
likely to be a failure in the other system.
    In response, the agency must first correct what appears to be a 
common misconception shared by the commenters advocating that a 
separate traction control malfunction indicator should not be required. 
Currently, NHTSA has no performance requirements for traction control 
systems and no requirement that a traction control system malfunction 
generate a telltale visible to the driver. Thus, to require an ESC-only 
telltale does not necessarily require separate telltales for ESC system 
malfunctions and traction control system malfunctions. In fact, as the 
comments demonstrate, nearly all traction control system malfunctions 
would also be ESC system malfunctions and will require an ESC system 
malfunction telltale to illuminate. For those limited circumstances 
where a traction control system malfunction is not simultaneously an 
ESC system malfunction, the manufacturer could

[[Page 36089]]

display the malfunction to the driver in any manner that is not 
contrary to FMVSS No. 101 or not display the malfunction at all.

D. ESC Activation Indicator

    The agency requested comment on whether there is a safety need for 
an ESC activation indicator. We received four comments on the issue.
    Daimler stated that UN ECE Regulation 13 requires an ESC activation 
indicator and that the U.S. should allow such an indicator. Daimler 
reasoned that the driver would benefit from indication of the 
activation of an ESC system because it may allow him to realize that a 
more cautious driving style may be appropriate. Moreover, Daimler 
argued that it would not be advantageous to have contrary requirements 
in the U.S. and Europe.
    Volvo and Bendix stated that it currently provides ESC system 
activation indication by flashing the malfunction lamp during system 
interventions. Both Volvo and Bendix requested that NHTSA not preclude 
the use of system activation indicators. EMA similarly requested 
flexibility for manufacturers to allow system activation indicators.
    Based on the comments, NHTSA is allowing, but not requiring, the 
use of the ESC malfunction telltale in a flashing mode to indicate ESC 
operation. Furthermore, we are expressly excluding this function from 
the requirement that the malfunction telltale only illuminate if there 
is an ESC system malfunction. We believe that allowing an activation 
indicator will give manufacturers flexibility to inform drivers when 
the ESC system is activating. However, we are not requiring such an 
indicator because we do not believe, nor do we have any data to 
suggest, that drivers with activation indicators will perform better 
than drivers who are given no indicator. This is consistent with the 
agency's decision to allow, but not require, activation indicators on 
light vehicles.

XIV. Benefits and Costs

    This section addresses the benefits and costs of the rule, 
including estimates of ESC system effectiveness and the size of the 
crash population. We also address public comments related to these 
issues. Much of the information in this section is derived from the 
Final Regulatory Impact Analysis (FRIA) associated with this final 
rule, which has been placed in the docket.

A. Target Crash Population

    The initial target crash population for estimating benefits 
includes all crashes resulting in occupant fatalities, MAIS 1 and above 
nonfatal injuries, and property damage only crashes that were the 
result of either (a) first-event untripped rollover crashes and (b) 
loss-of-control crashes (e.g., jackknife, cargo shift, avoiding, 
swerving) that involved truck tractors or large buses and might be 
prevented if the subject vehicle were equipped with a stability control 
system.
    We updated the estimates from the NPRM which used the 2006-2008 
Fatality Analysis Reporting System (FARS) and General Estimate System 
(GES) to used 2006-2012 FARS and GES data. The FARS data were used for 
evaluating fatal crashes and the GES data were used for evaluating 
nonfatal crashes. The updated crash data showed a lower number of 
rollover crashes and injuries from rollover crashes compared to the 
NPRM, but a higher number of fatalities from rollover crashes. 
Conversely, there are a higher overall number of loss-of-control 
crashes and injuries resulting from those crashes compared to the NPRM, 
but a lower number of fatalities from loss-of-control crashes. The 
estimated number of crashes, fatalities, injuries, and deaths that make 
up the initial target population are summarized in the following table.

     Table 4--Initial Target Crashes, MAIS Injuries, and Property Damage Only Vehicle Crashes by Crash Type
----------------------------------------------------------------------------------------------------------------
                   Crash type                         Crashes       Fatalities       Injuries           PDO
----------------------------------------------------------------------------------------------------------------
Rollover........................................           4,577             122           1,957           2,510
Loss of control.................................           6,266             184           1,510           5,351
                                                 ---------------------------------------------------------------
    Total.......................................          10,843             306           3,467           7,861
----------------------------------------------------------------------------------------------------------------
Source: 2006-2012 FARS, 2006-2012 GES.
PDO: property damage only.

    The 2006-2012 crash data were then adjusted to take account of the 
estimated ESC and RSC system installation rates in model year 2018. To 
determine the number of crashes that could be prevented by requiring 
that ESC systems be installed on new truck tractors, the agency had to 
consider two subsets of the total crash population--those vehicles that 
would not be equipped with stability control systems (Base 1 
population) and those vehicles that would be equipped with RSC systems 
(Base 2 population). The Base 1 population will benefit fully from this 
final rule. However, the Base 2 population will benefit only from the 
incremental increased effectiveness of ESC systems over RSC systems.
    Based upon manufacturer production estimates, about 26.2 percent of 
truck tractors manufactured in model year 2012 were equipped with ESC 
systems and 16.0 percent were equipped with RSC systems. We also 
estimate that 80 percent of large buses subject to this final rule are 
equipped with ESC systems. Based upon historical rates of increase of 
installation of ESC and RSC systems, from 2013 to 2018 (which is the 
base model year for the cost and benefit analysis), we expect the rate 
of ESC system installation to increase by approximately 15 percent 
annually and the rate of RSC system installation to increase by about 5 
percent annually. Thus, by 2018, we expect that 33.9 percent of 
vehicles would be equipped with ESC systems and 21.3 percent of 
vehicles would be equipped with ESC systems. We would not expect that 
the installation rate on buses would change substantially before 2018. 
Adjusting the initial target crash populations using these estimates, 
the agency was able to estimate the Base 1 and Base 2 populations and 
the projected target crash population (Base 1 + Base 2) expressed in 
the following table.

[[Page 36090]]

     Table 5-Projected Crashes, MAIS Injuries, and Property Damage Only Vehicle Crashes by Crash Type, Crash
                              Severity, Injury Severity, and Vehicle Type for 2018
----------------------------------------------------------------------------------------------------------------
                   Crash type                         Crashes       Fatalities       Injuries           PDO
----------------------------------------------------------------------------------------------------------------
                                                     Base 1
----------------------------------------------------------------------------------------------------------------
Rollover........................................           2,099              56             898           1,151
Loss of Control.................................           2,813              83             678           2,403
                                                 ---------------------------------------------------------------
    Total.......................................           4,912             139           1,576           3,554
----------------------------------------------------------------------------------------------------------------
                                                     Base 2
----------------------------------------------------------------------------------------------------------------
Rollover........................................             998              27             426             547
Loss of Control.................................           1,337              39             322           1,142
                                                 ---------------------------------------------------------------
    Total.......................................           2,335              66             748           1,689
----------------------------------------------------------------------------------------------------------------
                                  Base 1 + Base 2 (Projected Target Population)
----------------------------------------------------------------------------------------------------------------
Rollover........................................           3,097              83           1,324           1,698
Loss of Control.................................           4,150             122           1,000           3,545
                                                 ---------------------------------------------------------------
    Total.......................................           7,247             205           2,324           5,243
----------------------------------------------------------------------------------------------------------------
Source: 2006-2012 FARS, 2006-2012 GES.
PDO: property damage only.

    The agency has also examined the same crash data sources for large 
buses. Based upon this examination, the agency estimates that an 
average of two target rollover and three loss-of-control crashes that 
would be affected by ESC systems occur annually. The small number of 
crashes combined with the high projected voluntary ESC system 
installation rate causes the benefits resulting from this final rule 
attributable to buses to be very small. Therefore, the benefits 
estimates for buses are not further presented and the benefits of this 
final rule are assumed to be the benefits derived only from truck 
tractors.

B. System Effectiveness

1. Summary of the NPRM
    As we stated in the NPRM, direct data that would show the 
effectiveness of stability control systems is not available because 
stability control technology on heavy vehicles is relatively new. 
Accordingly, the effectiveness rates presented in the NPRM were built 
upon from three earlier studies: (1) A 2008 study on RSC that was 
conducted by American Transportation Research Institute and sponsored 
by the Federal Motor Carrier Safety Administration (FMCSA),\63\ (2) a 
2009 study that was conducted by UMTRI and Meritor WABCO and sponsored 
by NHTSA,\64\ and (3) The 2011 NHTSA Research Note.\65\ The 
effectiveness rates from the first two studies were based on computer 
simulation results, expert panel assessments of available crash data, 
input from trucking fleets that had adopted the technology, and 
research experiments. The third study refined the effectiveness that 
was established in the second study.
---------------------------------------------------------------------------

    \63\ Murray, D., Shackelford S., House, A., Analysis of Benefits 
and Costs of Roll Stability Control Systems, FMCSA-PRT-08-007 
October 2008.
    \64\ Woodrooffe, J., Blower, D., and Green, P., Safety Benefits 
of Stability Control Systems for Tractor-Semitrailers, DOT HS 811 
205, October 2009.
    \65\ Docket No. NHTSA-2010-0034-0043.
---------------------------------------------------------------------------

    None of these studies derived the effectiveness from a statistical 
analysis of real-world crashes. Such statistical analyses require a 
comparison of vehicles with and without the technology. This is not 
feasible because ESC and RSC penetration in the national fleet of truck 
tractors is still small. ESC and RSC are relatively new technologies 
that have only been installed on a small percentage of new tractors 
over the past few years.
2. Summary of Comments and Response
    ATA, Schneider, OOIDA, EMA, Bendix, and Martec commented on the 
agency's effectiveness estimates. ATA, Schneider, and OOIDA all relied 
upon a study by the American Transportation Research Institute entitled 
``Roll Stability Systems: Cost Benefit Analysis of Roll Stability 
Control Verses Electronic Stability Control Using Empirical Crash 
Data.'' EMA and OOIDA both criticized the use of simulation and expert 
analysis data as a substitute for real-world data. OOIDA asserted that 
the ATRI study represented real-world data that did not support 
requiring vehicles to have ESC systems. EMA asserted that, with so many 
trucks on the road currently equipped with stability control systems, 
real-world data ought to be available. Martec presented a rebuttal to 
the ATRI study. Bendix conducted its own ESC and RSC system 
effectiveness study using a method similar to that used by NHTSA.
(a) ATRI Study
    ATRI's study concluded that equipping vehicles with RSC systems 
would result in fewer rollover, jackknife, and tow/struck crashes 
compared to ESC systems. The ATRI study used crash data, miles 
traveled, and financial information that they collected through their 
survey of 14 large and mid-size motor carriers. Of these carriers, 81.5 
percent were in the truckload sector, 10.0 percent were in the less-
than-truckload sector, and 8.5 percent were in the specialized sector. 
The ATRI sample included 135,712 trucks; of these trucks, 68,647 
(50.6%) were equipped with RSC systems, 39,529 (29.1%) with ESC 
systems, and 27,536 (20.3%) with no stability control systems. Using 
the data received, ATRI calculated the crash rate per 100 million miles 
traveled, the crash cost per 1,000 miles traveled, and annual benefits 
and crash costs for three truck groups: Those with ESC systems, those 
with RSC systems, and those with no stability control systems. The 
group with no stability control systems served as the baseline to 
compare the other two groups. ATRI concluded that, if their sample is 
consistent with the industry as whole, RSC would result in fewer

[[Page 36091]]

rollover, jackknife, and tow/struck crashes than ESC. RSC also would 
provide greater benefits and lower installation costs than ESC.
    Martec was asked by Bendix to evaluate the ATRI's study. Martec 
asserted that the methods employed by ATRI do not meet basic standards 
found in the global market research industry. Martec stated that, 
because the methods ATRI employed in its study were inadequate, the 
results cannot be used to draw any meaningful conclusions about the 
overall trucking industry's experience with stability control systems 
or the analysis of the costs and benefits of individual technologies as 
sold into the marketplace.
    Martec reached four conclusions regarding ATRI's study. First, 
ATRI's study demonstrated confirmation bias by elaborating on its 
hypotheses and stating that the results of its research will be used to 
``inform responses'' to a proposed NHTSA mandate. Second, ATRI's study 
lost objectivity by not collecting all evidence in a controlled and 
systematic way so that the results can be replicated and validated by 
other researchers and by not making an attempt to assure that its 
sample of fleets was random. Third, ATRI's study is biased due to 
disproportionate sampling that is not representative of the industry. 
Fourth, ATRI's study lacks the necessary statistical tests to address 
the uncertainty of the statistics.
    We largely agree with Martec's conclusions regarding the ATRI 
study. Based in these concerns, we conclude that it is inappropriate to 
use ATRI's results to calculate the benefits and the cost-effectiveness 
of ESC and RSC systems.
    ATRI's sample is subjected to self-selection bias. When soliciting 
data, ATRI revealed the research hypothesis in their data request form, 
as shown in Appendix A of the ATRI report: ``ATRI's Research Advisory 
Committee hypothesized that, while ESC has more crash mitigation 
sensors than RSC systems, the higher per-unit cost of ESC may not make 
it as `cost-effective' as RSC.'' Furthermore, in the survey form, ATRI 
stated that its research is intended to inform responses to NHTSA's 
NPRM, which proposed to mandate ESC systems on all new equipment two 
years after the rule goes into effect.
    By revealing the hypothesis and the very specific intention of 
survey, ATRI potentially biased the participants' responses in favor of 
RSC systems. Carriers who have strong opinions in favor of RSC systems 
over ESC systems may have been more willing to respond than those who 
did not respond. We believe that this happened given that trucks with 
RSC systems (50.6 percent) and ESC systems (29.1 percent) are 
substantially overrepresented in the ATRI's sample. The self-reporting 
bias is further evidenced by the lack of accurate representation of 
trucking industry and counterintuitive crash rate outcome. Based on 
ATRI's data, the respondents skewed towards the truckload sector (e.g., 
dry van, refrigerated, flatbed, intermodal container, and end-dump 
carriers) compared to the overall industry and thus does not represent 
the truck industry as a whole. Therefore, ATRI's results may not be 
attributed to the effects of RSC systems and ESC systems, but rather to 
the sample bias from self-reporting.
    The quality of the self-reporting is also questionable, as 
evidenced by the crash rates per 100 million miles traveled as shown in 
Table 1 of ATRI's report. The report states that trucks equipped with 
ESC systems had higher rollover and jackknife crash rates than trucks 
equipped with RSC systems. Given that ESC systems include all of the 
functionality of an RSC system, that ESC systems have additional 
braking capability, and that ESC has substantially more effect on loss-
of-control crashes, these rates are illogical. These illogical results 
most likely can be explained by the impact of self-selection in the 
sample.\66\
---------------------------------------------------------------------------

    \66\ The results may also reflect that the RSC systems could be 
tuned to be more sensitive to allow them to brake more aggressively. 
We noted this possibility in the NPRM.
---------------------------------------------------------------------------

    ATRI used control and comparison methodology to examine RSC and 
ESC. In its approach, ATRI used the trucks without stability control as 
the control group and compared the crash rates of trucks equipped with 
ESC and RSC systems to those of the control group. For this approach, 
controlling confounding factors (i.e., factors other than the 
technologies of interest that would influence the crash rates) is 
critical in order to draw valid conclusions. There is no indication 
that ATRI investigated whether the three groups have similar 
characteristics. For example, if the majority of trucks in the control 
group were specialty trucks and specialty trucks were prone to rollover 
crashes while the ESC and RSC groups were overrepresented by a 
different truck sector that would prone to loss-of-control crashes, 
then the ATRI results are not valid to address the difference between 
ESC and RSC.
    ATRI acknowledged that there are some confounding factors that were 
not controlled for. However, ATRI did not try to identify these factors 
and examine the effects of these factors. Examining the confounding 
factors is essential to the validity of the analysis. With these 
concerns, the agency believes that it is inappropriate to use ATRI's 
results to support this final rule.
    There are no other sources of real-world data available to NHTSA 
that discriminate between crashes involving heavy vehicles equipped 
with stability control systems and those that do not. The UMTRI study, 
which includes case reviews and simulation, which has been reviewed and 
slightly modified by NHTSA, represents the best estimate available to 
the agency regarding the effectiveness of stability control systems.
(b) Bendix Study
    Bendix stated that, based on over 30 years of experience on 
commercial vehicle dynamic, braking, and stability control systems, the 
agency's assessment of the effectiveness of ESC systems is 
conservative. Bendix reviewed the 159 cases that were used as the basis 
for the agency's effectiveness estimates and re-rated ESC and RSC 
system effectiveness based on its experience. Furthermore, Bendix 
identified some of these 159 cases that were not stability-control 
relevant and included additional cases that agency did not identify as 
relevant. Based upon these changes and Bendix's own estimates of ESC 
and RSC system effectiveness, Bendix concluded that ESC systems are 31 
percent greater than RSC systems. The gap is much wider that the 6 to 7 
percent estimated by NHTSA. Table 6 shows the effectiveness from 
Bendix's analysis and those estimated by NHTSA in the NPRM.

[[Page 36092]]

                  Table 6--Effectiveness Comparison Between Bendix's Analysis and NHTSA's NPRM
----------------------------------------------------------------------------------------------------------------
                                                    Bendix                              NHTSA's NPRM
                                   -----------------------------------------------------------------------------
                                      Overall      Rollover       LOC        Overall      Rollover       LOC
----------------------------------------------------------------------------------------------------------------
ESC...............................           78           83           69        28-36        40-56           14
RSC...............................           47           58           26        21-30        37-53            3
Difference........................           31           25           43          6-7            3           12
----------------------------------------------------------------------------------------------------------------

    The agency believes that Bendix's method of determining system 
effectiveness is biased in favor of ESC systems. Prior to issuing the 
NPRM, the agency had shared its concerns with Bendix's assignment of 
effectiveness at two meetings. The agency identified four issues.
    First, for many rollover crashes, Bendix assigned a significant 
higher effectiveness to ESC systems compared to RSC systems. Based on 
the agency's understanding of ESC and RSC system functions to prevent 
rollover crashes, the agency's engineers did not believe the difference 
between ESC and RSC would be as pronounced as Bendix had estimated. 
Second, Bendix assigned a relatively high effectiveness for RSC systems 
against loss-of-control crashes. However, the agency's testing suggests 
that RSC systems would have a small effect on loss-of-control crashes. 
Third, although Bendix categorized some of the cases addressed by NHTSA 
as not relevant, Bendix still assigned effectiveness for those cases. 
This seems contradictory. Finally, Bendix included additional cases 
that were not included by NHTSA and UMTRI. However, these cases 
included truck types that are not covered by the NPRM or this final 
rule. Thus, while we commend Bendix for undertaking the review that 
NHTSA and UMTRI undertook to review individual crash cases, we cannot 
agree with the conclusion that ESC systems are substantially more 
effective that RSC systems at preventing rollover crashes.
3. Effectiveness Estimate
    In this final rule, we are generally using the effectiveness 
estimate used the NPRM, which was derived from 2011 research note. 
However, we have made two modifications. First, we have included an 
additional loss-of-control crash type (non-collision single-vehicle 
jackknife crashes) that should have been included in the PRIA. Second, 
because we added an additional loss-of-control crash type, we have 
reweighted the ratio of rollover to loss-of-control crashes. However, 
these modifications have not substantially changed the effectiveness 
rates for ESC and RSC systems from the rates presented in the NPRM. As 
shown in Table 7, ESC systems are considered to be 3 percent more 
effective than RSC systems at reducing rollover crashes and 12 percent 
more effective at reducing loss-of-control crashes.

   Table 7--Effectiveness Rates for ESC and RSC by Target Crash Types
------------------------------------------------------------------------
            Technology               Overall      Rollover       LOC
------------------------------------------------------------------------
ESC..............................        25-32        40-56           14
RSC..............................        17-24        37-53            2
------------------------------------------------------------------------

    Although the J-turn performance test does not measure an ESC 
system's ability to prevent loss-of-control crashes resulting from yaw 
instability, the equipment requirement ensures some level of yaw 
stability performance. Our assessment for yaw stability control 
performance is based on the ability of current generation ESC systems 
to prevent yaw instability, just as our assessment for roll stability 
performance (which does have an associated performance test) is based 
on the ability of current generation ESC systems to prevent roll 
instability.

C. Benefits Estimates

1. Safety Benefits
    The crash benefits of this final rule were derived by multiplying 
the projected target population, including fatalities, injuries, and 
property damage only crashes by the effectiveness rate for both 
rollover and loss-of-control crashes. The benefits estimate for 
rollover crashes are presented as a range because the ESC effectiveness 
rate is a range. In contrast, there is only one estimate of benefits 
for loss-of-control crashes. Table 8 presents the benefits of this 
final rule. As shown in that table, this final rule will prevent 1,424 
to 1,759 crashes, 40 to 49 fatalities, and 505 to 649 injuries.

                                       Table 8--Benefits of the Final Rule
----------------------------------------------------------------------------------------------------------------
                   Crash type                         Crashes       Fatalities       Injuries           PDO
----------------------------------------------------------------------------------------------------------------
Rollover........................................       870-1,205           23-32         372-516         476-661
LOC.............................................             554              17             133             473
                                                 ---------------------------------------------------------------
    Total.......................................     1,424-1,759           40-49         505-649       949-1,134
----------------------------------------------------------------------------------------------------------------

2. Monetized Benefits
    ESC systems are crash avoidance systems. Preventing a crash not 
only saves lives and reduces injuries, but it also provides tangible 
benefits associated with the reduction in crashes. These benefits 
include savings from medical care, emergency services, insurance 
administration, workplace costs, legal costs, congestion, property 
damage, and productivity. We have broken down these benefits into those 
that are injury related and those that are non-injury related. Of the 
listed

[[Page 36093]]

benefits, congestion and property damage reduction are non-injury-
related benefits, and the others are injury-related benefits. These 
benefits are estimated based upon periodic examinations of the economic 
impact of vehicle crashes. The most recent analysis was completed in 
2014.\67\
---------------------------------------------------------------------------

    \67\ Blincoe, L. J., Miller, T. R., Zaloshnja, E., & Lawrence, 
B. A., The economic and societal impact of motor vehicle crashes, 
2010, (May 2014) (DOT HS 812 013).
---------------------------------------------------------------------------

    We have also monetized benefits in terms of the value of a 
statistical life (VSL), which represents individuals' willingness to 
pay to reduce the risk of dying. These benefits include the value of 
quality of life, household productivity, and after-tax wages. These 
benefits are realized through the life of the vehicle and must be 
discounted to reflect their value at the time of purchase.
    June 2014 guidance from the Department's Office of the Secretary 
sets forth guidance for the treatment of VSL in regulatory 
analysis.\68\ This guidance establishes a VSL of $9.2 million for 
analyses based on 2013 economics and a 1.18 percent annual adjustment 
rate for the VSL for the next 30 years. The VSL is adjusted to reflect 
real increases in VSL that are likely to occur in the future as 
consumers become economically better off in real terms over time.
---------------------------------------------------------------------------

    \68\ 2014 Office of the Secretary memorandum on the ``Guidance 
on Treatment of the Economic Value of a Statistical Life in U.S. 
Department of Transportation Analyses--2014 Adjustment., June 13, 
2014'' http://www.dot.gov/regulations/economic-values-used-in-analysis
---------------------------------------------------------------------------

    Using this guidance applied to the prevention of crashes resulting 
in fatalities, injuries, and property damage only, the following 
undiscounted monetized benefits of this final rule are estimated.

       Table 9--Undiscounted Monetized Benefits of the Final Rule
                             [2013 Dollars]
------------------------------------------------------------------------
                                                Low            High
------------------------------------------------------------------------
Societal Economic Savings for                $27,013,989     $34,526,917
 Crashworthiness........................
Congestion and Property Damage..........      14,234,540      17,566,251
Societal Economic Savings Total.........      41,248,529      52,093,168
VSL.....................................     484,836,271     603,762,776
                                         -------------------------------
    Total Monetized Savings.............     526,084,800     655,855,944
------------------------------------------------------------------------

D. Cost Estimate

    In the NPRM, we relied upon data received from manufacturers to 
estimate the costs of implementing the proposal to require ESC systems 
on truck tractors and large buses. Based upon these submissions, NHTSA 
calculated that the average cost of an ESC system for both truck 
tractors and buses was $1,160 and the average cost of an RSC system was 
$640. Based on our estimates that 150,000 truck tractors and 2,200 
buses would be covered by the proposal, and the estimates of 2012 ESC 
and RSC system adoption in the fleet, we estimated that the total cost 
of the proposal would be $113.6 million in 2010 economics. Furthermore, 
we estimated that the proposed SIS and SWD test maneuvers would cost 
approximately $15,000 per test to run, assuming availability of test 
facilities, tracks, and vehicles.
    We received specific a comment on the costs of ESC system from 
Bendix. Bendix stated that they did not see a correlation between the 
cost differential estimated in the PRIA and those from Bendix to its 
OEM customers. Bendix did not specify their cost differential. However, 
Bendix stated that when ESC was mandated, they believed the cost would 
be in the lower end of estimates. Thus, the net benefits of ESC would 
be further increased.
    After publishing the NPRM, the agency published a cost teardown 
study for ESC and RSC systems for heavy trucks to assess the required 
components and their unit costs. The results were published in a report 
titled, ``Cost and Weight Analysis of Electronic Stability Control and 
Roll Stability Control for Heavy Trucks,'' on October 25, 2012.\69\ The 
study looked at the incremental costs of equipping vehicles with ESC 
and RSC systems over a baseline of ABS by looking at one truck equipped 
only with ABS, two truck tractors equipped with RSC, one truck tractor 
equipped with ESC, and one large bus equipped with ESC. The following 
table shows the components and the cost of each component on the five 
vehicles that were examined.
---------------------------------------------------------------------------

    \69\ See Docket No. NHTSA-2011-0066-0034.
    \70\ The cost teardown study is in 2011 economics, and it was 
revised to 2013 economics using an implicit price deflator 
(1.033=106.588/103.199).

                                         Table 10--Component Cost Estimates for Baseline ABS and Four Stability Technology Systems in 2013 Dollars \70\
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                        ABS WABCO tractor      RSC Bendix tractor             RSC WABCO tractor                 ESC Bendix large bus                  ESC WABCO tractor
                                            baseline        ------------------------------------------------------------------------------------------------------------------------------------
                                    ------------------------
                                      component     total     component     total     component           total           component           total           component           total
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Wheel Speed Sensor.................      $11.85      $47.40           X           X           X  X.....................           X  X.....................           X  X
Wheel Speed Cables.................        5.32       21.28           X           X           X  X.....................           X  X.....................           X  X
Dual Modulator Valves..............      284.82      569.64           X           X           X  X.....................           X  X.....................           X  X
Modulator Valve Cables.............       10.50       42.00           X           X           X  X.....................           X  X.....................           X  X
ECU................................       90.05       90.05           X           X           X  X.....................           X  X.....................           X  X
Delta ECU *........................  ..........  ..........       37.80       37.80       50.36  50.36.................       37.80  37.80.................       43.58  43.58
Solenoid Valves....................  ..........  ..........       29.20       58.40       29.20  58.40.................       29.20  58.40.................       29.20  87.60
Solenoid Valve Cables..............  ..........  ..........        9.58       19.16        9.58  19.16.................        9.58  19.16.................        9.58  28.74
Lateral Accelerometer..............  ..........  ..........       49.74       49.74  ..........  In ECU................  ..........  In Yaw Sensor.........  ..........  In ESC Module

[[Page 36094]]

 
Modulator Valve (for trailer)**....  ..........  ..........      197.82      197.82      197.82  197.82................  ..........  ......................      197.82  197.82
Modulator Valve Cables (for          ..........  ..........       10.50       10.50       10.50  10.50.................  ..........  ......................       10.50  10.50
 trailer).
Yaw Rate Sensor....................  ..........  ..........  ..........  ..........  ..........  ......................       51.38  51.38.................  ..........  In ESC Module
Pressure Sensor....................  ..........  ..........  ..........  ..........  ..........  ......................        2.14  6.42..................        2.14  6.42
Pressure Sensor Cable..............  ..........  ..........  ..........  ..........  ..........  ......................       10.12  30.36.................       10.12  30.36
Steering Angle Sensor..............  ..........  ..........  ..........  ..........  ..........  ......................       29.50  29.50.................       29.50  29.50
ESC Module.........................  ..........  ..........  ..........  ..........  ..........  ......................  ..........  ......................       85.48  85.48
ESC Module Cable...................  ..........  ..........  ..........  ..........  ..........  ......................  ..........  ......................       28.86  28.86
Baseline ABS Cost..................  ..........      770.37  ..........  ..........  ..........  ......................  ..........  ......................  ..........  .......................
Incremental Costs Above Baseline     ..........  ..........  ..........      373.42  ..........  336.24................  ..........  233.02................  ..........  548.86
 ABS.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* Delta ECU is an incremental cost estimate over the cost of WABCO Tractor Baseline ABS ECU.
** Modulator Valve for trailer is added as a component in Bendix Tractor RSC, Meritor-WABCO Tractor RSC and Meritor-WABCO Tractor ESC since it is required to be installed in trailers in the
  final rule.

    Furthermore, the installation of an ESC system requires a 
technician to tune a system for each vehicle. We estimate that it will 
take one hour of labor to perform this task at the cost of $33.40. 
Additionally, this final rule requires the installation of a telltale 
lamp using specific symbols or text. We estimate the cost of this lamp 
and associated wiring at $2.96. Thus, we estimate the total cost for 
installing an ESC system to be $585.22 on truck tractors and $269.38 on 
large buses. We have averaged the two estimates of the cost to install 
an RSC system, which is $391.19.\71\ We note that this estimate 
generally corresponds to the lower end of the cost estimate in the 
FRIA, which is consistent with Bendix's comment.
---------------------------------------------------------------------------

    \71\ Unlike in the NPRM, the cost of installing an ESC system on 
a bus is considered to be substantially less than on a truck 
tractor. This is because an ESC system on a bus is not required to 
control a trailer's brakes.

   Table 11--Summary of ESC and RSC System Unit Cost Estimates in 2013
                                 Dollars
------------------------------------------------------------------------
 
------------------------------------------------------------------------
ESC.....................................................         $585.22
RSC.....................................................          391.19
ESC Incremental over RSC................................          194.03
------------------------------------------------------------------------

    We have also examined the effect of increased costs on vehicle 
sales. We expect that the cost of ESC systems is relatively small 
compared to the estimated average cost of a truck tractor of $110,000. 
We expect that this cost will be passed on to purchasers of truck 
tractors and large buses. Those purchasers have indicated that truck 
operating costs represent about 21 percent of total operating costs, 
and that the elasticity of demand for truck freight is approximately -
1.174. Thus, we believe that the increased costs of truck tractors 
related to this final rule will reduce truck tractor sales by 101 units 
per year. We expect that this rule will have even less of an impact on 
the sales of large buses, because the average cost of a bus affected by 
this rule is approximately $400,000.
    Based on our assumptions regarding costs and the estimates of ESC 
and RSC system penetration in the market in 2018, we expect that this 
final rule will result in a total cost of $45.6 million. The costs are 
set forth in Tables 12 and 13. This total cost is based upon 21.3 
percent of truck tractors sold annually upgrading from RSC systems to 
ESC systems, 44.8 percent of truck tractors sold annually without 
stability control systems installing ESC systems, and 20.0 percent of 
large buses sold annually without stability control systems installing 
ESC systems.

                                     Table 12--Total Cost of the Final Rule
                                                    [2013 $]
----------------------------------------------------------------------------------------------------------------
                                                                             Technology Upgrade Needed
                                                                 -----------------------------------------------
                                                                                  Upgrade RSC to
                                                                       None             ESC             ESC
----------------------------------------------------------------------------------------------------------------
Truck Tractors:
    % Needing Improvements......................................           33.9%           21.3%           44.8%
    150,000 Sales Estimated.....................................          50,850          31,950          67,200
    Costs per Affected Vehicle..................................               0         $194.03         $585.22
                                                                 -----------------------------------------------
        Total Costs.............................................               0          $6.2 M         $39.3 M
Large Buses:
    % Needing Improvements......................................             80%              0%             20%
    2,200 Sales Estimated.......................................           1,760               0             440
    Costs per Affected Vehicle..................................               0              NA         $269.38
                                                                 -----------------------------------------------
        Total Costs.............................................               0            $0 M          $0.1 M
----------------------------------------------------------------------------------------------------------------
M: million.

[[Page 36095]]

                   Table 13--Summary of Vehicle Costs
                                [2013 $]
------------------------------------------------------------------------
                                              Average
                                           vehicle costs    Total costs
------------------------------------------------------------------------
Truck Tractors..........................         $303.50         $45.5 M
Large Buses.............................           53.90           0.1 M
                                         -------------------------------
    Total...............................          299.90          45.6 M
------------------------------------------------------------------------

    The agency estimates that the cost of executing the J-turn test 
maneuvers will be $13,400 per truck tractor and $20,100 per large bus, 
assuming access is available to test facilities, tracks, and vehicles. 
The costs include preparation, brake burnish test, and other 
miscellaneous preparations and required equipment. Table 14 presents 
these estimated costs. In addition, for comparison purpose, the table 
also includes the costs for SWD maneuver that was proposed in the 
NPRM.\72\
---------------------------------------------------------------------------

    \72\ We have revised the estimated SWD maneuver costs from the 
PRIA. In the PRIA, the estimated cost for SWD is $15,000 which 
included $10,000 for preparing for and executing the maneuvers, 
$2,000 for executing FMVSS No. 121 brake burnish test, and $3,000 
for other miscellaneous preparations and required equipment.

                              Table 14--Estimated Compliance Test Cost per Vehicle
                                                    [2013 $]
----------------------------------------------------------------------------------------------------------------
                                                              J-Turn                            SWD
                   Cost Items                    ---------------------------------------------------------------
                                                      Tractor        Large Bus        Tractor        Large Bus
----------------------------------------------------------------------------------------------------------------
(1) Preparing for and executing the test               $8,400.00      $12,800.00      $10,800.00      $14,700.00
 maneuvers,.....................................
(2) Executing brake burnish test, and...........        2,600.00        3,600.00        2,600.00        3,600.00
(3) Other miscellaneous preparations and                2,400.00        3,700.00        3,400.00        4,800.00
 required equipment such as.....................
    (a) Brake conditioning between maneuvers,
    (b) Jackknife cable maintenance,
    (c) ballast loading, and
    (d) Post data processing, i.e., LAR and
     Torque reduction process
                                                 ---------------------------------------------------------------
        Sum.....................................       13,400.00       20,100.00       16,800.00       23,100.00
----------------------------------------------------------------------------------------------------------------

E. Cost Effectiveness

    Safety benefits can occur at any time during the vehicle's 
lifetime. Therefore, the benefits are discounted at both 3 and 7 
percent to reflect their values in 2013 dollars, as reflected in Table 
15. Table 15 also shows that the net cost per equivalent life saved 
from this final rule range from $0.1 to $0.3 million at a 3 percent 
discount rate and from $0.3 to $0.6 million at a 7 percent discount 
rate. The net benefits of this final rule are estimated to range from 
$412 to $525 million at a 3 percent discount rate and from $312 to $401 
million at a 7 percent discount rate.

                    Table 15--Summary of Cost-Effectiveness and Net Benefits by Discount Rate
                                                    [2013 $]
----------------------------------------------------------------------------------------------------------------
                                                            3% Discount                     7% Discount
                                                 ---------------------------------------------------------------
                                                        Low            High             Low            High
----------------------------------------------------------------------------------------------------------------
Fatal Equivalents...............................              40              50              32              40
Societal Economic Savings for Crashworthiness...     $21,816,498     $27,883,938     $17,288,953     $22,097,227
Congestion and Property Damage..................      11,495,815      14,186,504       9,110,106      11,242,401
Total Societal Economic Savings (1).............      33,312,313      42,070,442      26,399,059      33,339,628
VSL.............................................     424,352,045     528,442,215     331,681,943     413,040,877
Total Monetized Savings (2).....................     457,664,358     570,512,657     358,081,002     446,380,505
Vehicle Costs *.................................      45,644,570      45,644,570      45,644,570      45,644,570
Net Costs (3)...................................      12,332,257       3,574,128      19,245,511      12,304,942
Net Cost Per Fatal Equivalent (4)...............         308,306          71,483         601,422         307,624
Net Benefits (5)................................     412,019,788     524,868,087     312,436,432     400,735,935
----------------------------------------------------------------------------------------------------------------
* Vehicle costs are not discounted, since they occur when the vehicle is purchased, whereas benefits occur over
  the vehicle's lifetime and are discounted back to the time of purchase.
(1) = Societal Economic Savings for Crashworthiness + VSL Savings.
(2) = Societal Economic Savings + VSL.
(3) = Vehicle Costs - Total Societal Economic Savings.
(4) = Net Costs/Fatal Equivalents.
(5) = VSL - Net Costs.

[[Page 36096]]

F. Comparison of Regulatory Alternatives

    The agency considered two alternatives to this final rule. The 
first alternative was requiring RSC systems be installed on all newly 
manufactured truck tractors and buses covered by this final rule. The 
second alternative was requiring RSC systems be installed on all newly 
manufactured trailers.
    Regarding the first alternative, requiring RSC systems be installed 
on truck tractors and large buses, our research has concluded that RSC 
systems are less effective than ESC systems. An RSC system is only 
slightly less effective at preventing rollover crashes than an ESC 
system, but it is much less effective at preventing loss-of-control 
crashes. However, RSC systems are estimated to cost less than ESC 
systems. Furthermore, only approximately 44.8% of truck tractors will 
be required to install RSC systems based on data regarding 
manufacturers' plans and the agency's estimates of ESC and RSC system 
adoption rates between 2012 and 2018.
    A summary of the cost effectiveness of RSC systems is set forth in 
Table 16. When comparing this alternative to this final rule, requiring 
RSC systems rather than ESC systems would be slightly more cost 
effective. However, this alternative would save fewer lives and have 
lower net benefits than this final rule. Consequently, the agency has 
rejected this alternative.

                    Table 16--Summary of Cost-Effectiveness and Net Benefits by Discount Rate
                               Alternative 1--Requiring Tractor-Based RSC Systems
                                                    [2013 $]
----------------------------------------------------------------------------------------------------------------
                                                            3% Discount                     7% Discount
                                                 ---------------------------------------------------------------
                                                        Low            High             Low            High
----------------------------------------------------------------------------------------------------------------
Fatal Equivalents...............................              25              35              20              28
Societal Economic Savings--Crashworthiness......     $14,708,167     $20,700,276     $11,655,804     $16,404,380
Congestion and Property Damage..................       6,694,636       9,378,093       5,305,308       7,431,871
Total Societal Economic Savings (1).............      21,402,803      30,078,369      16,961,112      23,836,251
VSL.............................................     260,249,473     363,828,274     203,416,130     284,375,367
Total Monetized Savings (2).....................     281,652,276     393,906,643     220,377,242     308,211,618
Vehicle Costs *.................................      26,406,495      26,406,495      26,406,495      26,406,495
Net Costs (3)...................................       5,003,692      -3,671,874       9,445,383       2,570,244
Net Cost Per Fatal Equivalent (4)...............         200,148             N/A         472,269          91,794
Net Benefits (5)................................     255,245,781     367,500,148     193,970,747     281,805,123
----------------------------------------------------------------------------------------------------------------
* Vehicle costs are not discounted, since they occur when the vehicle is purchased, whereas benefits occur over
  the vehicle's lifetime and are discounted back to the time of purchase.
(1) = Societal Economic Savings - Crashworthiness + VSL Savings.
(2) = Societal Economic Savings + VSL.
(3) = Vehicle Costs - Total Societal Economic Savings; Cost per equivalent life saved is not presented where the
  alternative results in negative net cost because there would be no cost per equivalent life saved.
(4) = Net Costs/Fatal Equivalents.
(5) = VSL - Net Costs.

    The second alternative considered was requiring trailer-based RSC 
systems to be installed on all newly manufactured trailers. Trailer-
based RSC systems are only expected to prevent rollover crashes. Based 
on 2006-2012 GES data, 98 percent of the target truck-tractor crashes 
involve truck tractors with trailers attached. Therefore, the base 
crash population is 98 percent of Base 1 discussed above.
    As discussed in the NPRM, it became apparent during testing that 
trailer-based stability control systems were less effective than 
tractor-based systems because trailer-based systems could only control 
the trailer's brakes. Based upon the agency's testing of trailer-based 
RSC systems using a 150-foot J-turn test maneuver, the benefits of 
trailer-based RSC systems in preventing rollover are about 17.6 percent 
of tractor-based ESC systems, corresponding to an effectiveness rate of 
7 to 10 percent.
    The agency estimates that about 217,000 new trailers are 
manufactured each year. Further, based on information from 
manufacturers, the agency estimates that a trailer-based RSC system 
costs $400 per trailer. Available data indicates that as much as 5 
percent of the current annual production of trailers comes with RSC 
systems installed. Assuming all new trailers would be required to 
install RSC, the cost of this alternative is estimated to be $74.7 
million.
    Table 17 sets forth a summary of the cost effectiveness of trailer-
based RSC systems. Because the operational life of a trailer 
(approximately 45 years) is much longer than that of a truck tractor, 
it would take longer for trailer-based RSC systems to fully penetrate 
the fleet than it would for any tractor-based system. Therefore, when 
the benefits of trailer-based RSC systems are discounted at a 3 and 7 
percent rate, there is a much higher discount factor. As can be seen in 
Table 17, this results in this alternative having negative net benefits 
and a high cost per life saved. Also, this alternative would have no 
effect on buses. Accordingly, the agency has rejected this alternative.

                    Table 17--Summary of Cost-Effectiveness and Net Benefits by Discount Rate
                               Alternative 2--Requiring Trailer-Based RSC Systems
                                                    [2013 $]
----------------------------------------------------------------------------------------------------------------
                                                            3% Discount                     7% Discount
                                                 ---------------------------------------------------------------
                                                        Low            High             Low            High
----------------------------------------------------------------------------------------------------------------
Fatal Equivalents...............................               3               3               2               2

[[Page 36097]]

 
Societal Economic Savings--Crashworthiness......      $1,571,042      $2,036,588      $1,057,467      $1,370,825
Congestion and Property Damage..................         684,213         938,236         460,543         631,526
Total Societal Economic Savings (1).............       2,255,255       2,974,824       1,518,010       2,002,351
VSL.............................................      30,196,954      39,659,995      19,696,851      25,869,398
Total Monetized Savings (2).....................      32,452,209      42,634,819      21,214,861      27,871,749
Vehicle Costs *.................................      74,734,800      74,734,800      74,734,800      74,734,800
Net Costs (3)...................................      72,479,545      71,759,976      73,216,790      72,732,449
Net Cost Per Fatal Equivalent (4)...............      24,159,848      23,919,992      36,608,395      36,366,225
Net Benefits (5)................................     -42,282,591     -32,099,981     -53,519,939     -46,863,051
----------------------------------------------------------------------------------------------------------------
* Vehicle costs are not discounted, since they occur when the vehicle is purchased, whereas benefits occur over
  the vehicle's lifetime and are discounted back to the time of purchase.
(1) = Societal Economic Savings - Crashworthiness + VSL Savings.
(2) = Societal Economic Savings + VSL.
(3) = Vehicle Costs - Total Societal Economic Savings; negative means benefits are greater than the cost.
(4) = Net Costs/Fatal Equivalents.
(5) = VSL - Net Costs.

XV. Regulatory Analyses and Notices

A. Executive Order 12866, Executive Order 13563, and DOT Regulatory 
Policies and Procedures

    NHTSA has considered the impact of this rulemaking action under 
Executive Order 12866, Executive Order 13563, and the Department of 
Transportation's regulatory policies and procedures. This rulemaking is 
considered economically significant and was reviewed by the Office of 
Management and Budget under E.O. 12866, ``Regulatory Planning and 
Review.'' The rulemaking action has also been determined to be 
significant under the Department's regulatory policies and procedures. 
NHTSA has placed in the docket a Final Regulatory Impact Analysis 
(FRIA) describing the benefits and costs of this rulemaking action. The 
benefits and costs are summarized in section XIV of this preamble.
    Consistent with Executive Order 13563 and to the extent permitted 
under the Vehicle Safety Act, we have considered the cumulative effects 
of the new regulations stemming from NHTSA's 2007 ``NHTSA's Approach to 
Motorcoach Safety'' plan, DOT's 2009 Motorcoach Safety Action Plan, and 
the Motorcoach Enhanced Safety Act, and have taken steps to identify 
opportunities to harmonize and streamline those regulations. By 
coordinating the timing and content of the rulemakings, our goal is to 
expeditiously maximize the net benefits of the regulations (by either 
increasing benefits or reducing costs or a combination of the two) 
while simplifying requirements on the public and ensuring that the 
requirements are justified. We seek to ensure that this coordination 
will also simplify the implementation of multiple requirements on a 
single industry.
    NHTSA's Motorcoach Safety Action Plan identified four priority 
areas--passenger ejection, rollover structural integrity, emergency 
egress, and fire safety. There have been other initiatives on large bus 
performance, such as ESC systems--an action included in the DOT plan--
and an initiative to update the large bus tire standard.\73\ In 
deciding how best to initiate and coordinate rulemaking in these areas, 
NHTSA examined various factors including the benefits that would be 
achieved by the rulemakings, the anticipated vehicle designs and 
countermeasures needed to comply with the regulations, and the extent 
to which the timing and content of the rulemakings could be coordinated 
to lessen the need for multiple redesign and to lower overall costs. 
After this examination, we decided on a course of action that 
prioritized the goal of reducing passenger ejection and increasing 
frontal impact protection because many benefits could be achieved 
expeditiously with countermeasures that were readily available (using 
bus seats with integral seat belts, which are already available from 
seat suppliers) and whose installation would not significantly impact 
other vehicle designs. Similarly, we have also determined that an ESC 
rulemaking presents relatively few synchronization issues with other 
rules, because the vehicles at issue already have the foundation 
braking systems needed for the stability control technology and the 
additional equipment necessary for an ESC system are sensors that are 
already available and that can be installed without significant effect 
on other vehicle systems. Further, we estimate that 80 percent of the 
affected buses already have ESC systems. We realize that a rollover 
structural integrity rulemaking, or an emergency egress rulemaking, 
could involve more redesign of vehicle structure than rules involving 
systems such as seat belts, ESC, or tires.\74\ Our decision-making in 
these and all the rulemakings outlined in the ``NHTSA's Approach to 
Motorcoach Safety'' plan, DOT's Motorcoach Safety Action Plan, and the 
Motorcoach Enhanced Safety Act will be cognizant of the timing and 
content of the actions so as to simplify requirements applicable to the 
public and private sectors, ensure that requirements are justified, and 
increase the net benefits of the resulting safety standards.
---------------------------------------------------------------------------

    \73\ 75 FR 60037 (Sept. 29, 2010).
    \74\ The initiative on fire safety is in a research phase. 
Rulemaking resulting from the research will not occur in the near 
term.
---------------------------------------------------------------------------

B. Regulatory Flexibility Act

    Pursuant to the Regulatory Flexibility Act (5 U.S.C. 601 et seq., 
as amended by the Small Business Regulatory Enforcement Fairness Act 
(SBREFA) of 1996), whenever an agency is required to publish a notice 
of rulemaking for any proposed or final rule, it must prepare and make 
available for public comment a regulatory flexibility analysis that 
describes the effect of the rule on small entities (i.e., small 
businesses, small organizations, and small governmental jurisdictions). 
The Small Business Administration's

[[Page 36098]]

regulations at 13 CFR part 121 define a small business, in part, as a 
business entity ``which operates primarily within the United States.'' 
(13 CFR 121.105(a)). No regulatory flexibility analysis is required if 
the head of an agency certifies the rule will not have a significant 
economic impact on a substantial number of small entities. SBREFA 
amended the Regulatory Flexibility Act to require Federal agencies to 
provide a statement of the factual basis for certifying that a rule 
will not have a significant economic impact on a substantial number of 
small entities.
    NHTSA has considered the effects of this final rule under the 
Regulatory Flexibility Act. I certify that this final rule will not 
have a significant economic impact on a substantial number of small 
entities. This final rule will directly impact manufacturers of truck-
tractors, large buses, and stability control systems for those 
vehicles. It will indirectly affect purchasers of new truck-tractors 
and large buses, which include both fleets and owner-operators. NHTSA 
believes the entities directly affected by this rule do not qualify as 
small entities. Inasmuch as some second-stage manufacturers of certain 
body-on-frame buses that are subject to this final rule are small 
businesses, this final rule will not substantially affect those small 
businesses. The small manufacturers that may be affected by this rule 
are final stage manufacturers that purchase incomplete vehicles from 
other large manufacturers and complete the manufacturing process. The 
incomplete vehicle manufacturers, which we do not believe are small 
businesses, typically certify compliance with all braking-related 
standards and we believe ESC would be included among those. The sole 
effect on the final stage manufacturers is a marginal increase in the 
cost of incomplete vehicles due to the addition of ESC systems. This 
additional cost is very small relative to the average cost of buses 
subject to this final rule ($200,000 to $500,000), and the costs would 
likely ultimately be passed on to the final purchaser.

C. Executive Order 13132 (Federalism)

    NHTSA has examined this final rule pursuant to Executive Order 
13132 (64 FR 43255, August 10, 1999) and concluded that no additional 
consultation with States, local governments or their representatives is 
mandated beyond the rulemaking process. The agency has concluded that 
the rulemaking will not have sufficient federalism implications to 
warrant consultation with State and local officials or the preparation 
of a federalism summary impact statement. The final rule will not have 
``substantial direct effects on the States, on the relationship between 
the national government and the States, or on the distribution of power 
and responsibilities among the various levels of government.''
    NHTSA rules can preempt in two ways. First, the National Traffic 
and Motor Vehicle Safety Act contains an express preemption provision: 
When a motor vehicle safety standard is in effect under this chapter, a 
State or a political subdivision of a State may prescribe or continue 
in effect a standard applicable to the same aspect of performance of a 
motor vehicle or motor vehicle equipment only if the standard is 
identical to the standard prescribed under this chapter. 49 U.S.C. 
30103(b)(1). It is this statutory command by Congress that preempts any 
non-identical State legislative and administrative law addressing the 
same aspect of performance.
    The express preemption provision described above is subject to a 
savings clause under which ``[c]ompliance with a motor vehicle safety 
standard prescribed under this chapter does not exempt a person from 
liability at common law.'' 49 U.S.C. 30103(e). Pursuant to this 
provision, State common law tort causes of action against motor vehicle 
manufacturers that might otherwise be preempted by the express 
preemption provision are generally preserved. However, the Supreme 
Court has recognized the possibility, in some instances, of implied 
preemption of such State common law tort causes of action by virtue of 
NHTSA's rules, even if not expressly preempted. This second way that 
NHTSA rules can preempt is dependent upon there being an actual 
conflict between an FMVSS and the higher standard that would 
effectively be imposed on motor vehicle manufacturers if someone 
obtained a State common law tort judgment against the manufacturer, 
notwithstanding the manufacturer's compliance with the NHTSA standard. 
Because most NHTSA standards established by an FMVSS are minimum 
standards, a State common law tort cause of action that seeks to impose 
a higher standard on motor vehicle manufacturers will generally not be 
preempted. However, if and when such a conflict does exist--for 
example, when the standard at issue is both a minimum and a maximum 
standard--the State common law tort cause of action is impliedly 
preempted. See Geier v. American Honda Motor Co., 529 U.S.C. 861 
(2000).
    Pursuant to Executive Order 13132 and 12988, NHTSA has considered 
whether this rule could or should preempt State common law causes of 
action. The agency's ability to announce its conclusion regarding the 
preemptive effect of one of its rules reduces the likelihood that 
preemption will be an issue in any subsequent tort litigation.
    To this end, the agency has examined the nature (e.g., the language 
and structure of the regulatory text) and objectives of this rule and 
finds that this rule, like many NHTSA rules, prescribes only a minimum 
safety standard. As such, NHTSA does not intend that this rule preempt 
state tort law that would effectively impose a higher standard on motor 
vehicle manufacturers than that established by this rule. Establishment 
of a higher standard by means of State tort law would not conflict with 
the minimum standard announced here. Without any conflict, there could 
not be any implied preemption of a State common law tort cause of 
action.

D. Executive Order 12988 (Civil Justice Reform)

    With respect to the review of the promulgation of a new regulation, 
section 3(b) of Executive Order 12988, ``Civil Justice Reform'' (61 FR 
4729; Feb. 7, 1996), requires that Executive agencies make every 
reasonable effort to ensure that the regulation: (1) clearly specifies 
the preemptive effect; (2) clearly specifies the effect on existing 
Federal law or regulation; (3) provides a clear legal standard for 
affected conduct, while promoting simplification and burden reduction; 
(4) clearly specifies the retroactive effect, if any; (5) specifies 
whether administrative proceedings are to be required before parties 
file suit in court; (6) adequately defines key terms; and (7) addresses 
other important issues affecting clarity and general draftsmanship 
under any guidelines issued by the Attorney General. This document is 
consistent with that requirement.
    Pursuant to this Order, NHTSA notes as follows. The issue of 
preemption is discussed above. NHTSA notes further that there is no 
requirement that individuals submit a petition for reconsideration or 
pursue other administrative proceedings before they may file suit in 
court.

E. Protection of Children From Environmental Health and Safety Risks

    Executive Order 13045, ``Protection of Children from Environmental 
Health and Safety Risks'' (62 FR 19855, April 23, 1997), applies to any 
rule that: (1) is determined to be ``economically significant'' as 
defined under Executive

[[Page 36099]]

Order 12866, and (2) concerns an environmental, health, or safety risk 
that the agency has reason to believe may have a disproportionate 
effect on children. If the regulatory action meets both criteria, the 
agency must evaluate the environmental health or safety effects of the 
planned rule on children, and explain why the planned regulation is 
preferable to other potentially effective and reasonably feasible 
alternatives considered by the agency.
    This document is part of a rulemaking that is not expected to have 
a disproportionate health or safety impact on children. Consequently, 
no further analysis is required under Executive Order 13045.

F. Paperwork Reduction Act

    Under the Paperwork Reduction Act of 1995 (PRA), a person is not 
required to respond to a collection of information by a Federal agency 
unless the collection displays a valid OMB control number. There is not 
any information collection requirement associated with this final rule.

G. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act (NTTAA) requires NHTSA to evaluate and use existing voluntary 
consensus standards in its regulatory activities unless doing so would 
be inconsistent with applicable law (e.g., the statutory provisions 
regarding NHTSA's vehicle safety authority) or otherwise impractical. 
Voluntary consensus standards are technical standards developed or 
adopted by voluntary consensus standards bodies. Technical standards 
are defined by the NTTAA as ``performance-based or design-specific 
technical specification and related management systems practices.'' 
They pertain to ``products and processes, such as size, strength, or 
technical performance of a product, process or material.''
    Examples of organizations generally regarded as voluntary consensus 
standards bodies include ASTM International, SAE International (SAE), 
and the American National Standards Institute (ANSI). If NHTSA does not 
use available and potentially applicable voluntary consensus standards, 
we are required by the Act to provide Congress, through OMB, an 
explanation of the reasons for not using such standards.
    This final rule requires truck tractors and large buses to have 
electronic stability control systems. In the definitional criteria, the 
agency adapted the criteria based on the light vehicle ESC rulemaking, 
which was based on (with minor modifications) SAE Surface Vehicle 
Information Report on Automotive Stability Enhancement Systems J2564 
JUN2004 that provides an industry consensus definition of an ESC 
system. In addition, SAE International has a Recommended Practice on 
Brake Systems Definitions--Truck and Bus, J2627 AUG2009 that has been 
incorporated into the agency's definition.
    The agency based the performance requirement (with modifications) 
on SAE Surface Vehicle Recommended Practice J266 JAN96, Steady-State 
Directional Control Test Procedures for Passenger Cars and Light 
Trucks. UN ECE Regulation 13 also allows the J-Turn test maneuver as 
one option to be used for demonstrating proper function of an ESC 
system.
    The agency has also incorporated by reference two ASTM standards in 
order to provide specifications for the road test surface. These are: 
(1) ASTM E1136-93 (Reapproved 2003), ``Standard Specification for a 
Radial Standard Reference Test Tire,'' and (2) ASTM E1337-90 
(Reapproved 2008), ``Standard Test Method for Determining Longitudinal 
Peak Braking Coefficient of Paved Surfaces Using a Standard Reference 
Test Tire.''

H. Unfunded Mandates Reform Act

    Section 202 of the Unfunded Mandates Reform Act of 1995 (UMRA) 
requires federal agencies to prepare a written assessment of the costs, 
benefits, and other effects of proposed or final rules that include a 
Federal mandate likely to result in the expenditure by State, local, or 
tribal governments, in the aggregate, or by the private sector, of more 
than $100 million annually (adjusted for inflation with base year of 
1995). Before promulgating a rule for which a written statement is 
needed, section 205 of the UMRA generally requires the agency to 
identify and consider a reasonable number of regulatory alternatives 
and adopt the least costly, most cost-effective, or least burdensome 
alternative that achieves the objectives of the rule. The provisions of 
section 205 do not apply when they are inconsistent with applicable 
law. Moreover, section 205 allows the agency to adopt an alternative 
other than the least costly, most cost-effective, or least burdensome 
alternative if the agency publishes with the final rule an explanation 
of why that alternative was not adopted.
    This final rule will not result in any expenditure by State, local, 
or tribal governments or the private sector of more than $100 million, 
adjusted for inflation.

I. National Environmental Policy Act

    NHTSA has analyzed this rulemaking action for the purposes of the 
National Environmental Policy Act. The agency has determined that 
implementation of this action will not have any significant impact on 
the quality of the human environment.

J. Incorporation by Reference

    As discussed earlier in the relevant portions of this document, we 
are incorporating by reference various materials into the Code of 
Federal Regulations in this rulemaking. The standards we are 
incorporating are:
     ASTM E1136-93 (Reapproved 2003), ``Standard Specification 
for a Radial Standard Reference Test Tire,'' approved March 15, 1993.
     ASTM E1337-90 (Reapproved 2008), ``Standard Test Method 
for Determining Longitudinal Peak Braking Coefficient of Paved Surfaces 
Using a Standard Reference Test Tire,'' approved June 1, 2008.
    Under 5 U.S.C. 552(a)(1)(E), Congress allows agencies to 
incorporate by reference materials that are reasonably available to the 
class of persons affected if the agency has approval from the Director 
of the Federal Register. As a part of that approval process, the 
Director of the Federal Register (in 1 CFR 51.5) directs agencies to 
discuss (in the preamble) the ways that the materials we are 
incorporating by reference are reasonably available to interested 
parties. Further the Director requires agencies to summarize the 
material that they are incorporating [proposing to incorporate] by 
reference.
    NHTSA has worked to ensure that standards being considered for 
incorporation by reference are reasonably available to the class of 
persons affected. In this case, those directly affected by incorporated 
provisions are NHTSA and parties contracting with NHTSA to conduct 
testing of new vehicles. New vehicle manufacturers may also be affected 
to the extent they wish to conduct NHTSA's compliance test procedures 
on their own vehicles. These entities have access to copies of 
aforementioned standards through ASTM International for a reasonable 
fee. These entities have the financial capability to obtain a copy of 
the material incorporated by reference.
    Other interested parties in the rulemaking process beyond the class 
affected by the regulation include members of the public, safety 
advocacy groups, etc. Such interested parties can access the standard 
by obtaining a copy from the aforementioned standards development 
organizations.

[[Page 36100]]

    Interested parties may also access the standards through NHTSA or 
the National Archives and Records Administration (NARA). All approved 
material is available for inspection at NHTSA, 1200 New Jersey Avenue 
SE., Washington, DC 20590, and at the National Archives and Records 
Administration (NARA). For information on the availability of this 
material at NHTSA, contact NHTSA's Office of Technical Information 
Services, phone number (202) 366-2588. For information on the 
availability of this material at NARA, call (202) 741-6030, or go to: 
http://www.archives.gov/federal-register/cfr/ibr-locations.html.
    Finally, we have also described and summarized the materials that 
we are incorporating by reference in this document to give all 
interested parties an effective opportunity to comment. The materials 
were previously discussed in section XI.G.

K. Regulatory Identifier Number (RIN)

    The Department of Transportation assigns a regulation identifier 
number (RIN) to each regulatory action listed in the Unified Agenda of 
Federal Regulations. The Regulatory Information Service Center 
publishes the Unified Agenda in April and October of each year. You may 
use the RIN contained in the heading at the beginning of this document 
to find this action in the Unified Agenda.

L. Privacy Act

    Anyone is able to search the electronic form of all comments 
received into any of our dockets by the name of the individual 
submitting the comment (or signing the comment, if submitted on behalf 
of an association, business, labor union, etc.). You may review DOT's 
complete Privacy Act Statement in the Federal Register published on 
April 11, 2000 (65 FR 19477-78).

List of Subjects in 49 CFR Part 571

    Imports, Incorporation by reference, Motor vehicle safety, Motor 
vehicles, Rubber and rubber products, Tires.
    Regulatory Text
    In consideration of the foregoing, we amend 49 CFR part 571 as 
follows:

PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS

0
1. The authority citation for part 571 continues to read as follows:

    Authority:  49 U.S.C. 322, 30111, 30115, 30166 and 30177; 
delegation of authority at 49 CFR 1.95.

0
2. Revise paragraphs (d)(33) and (34) of Sec.  571.5 to read as 
follows:

Sec.  571.5  Matter incorporated by reference.

* * * * *
    (d) * * *
    (33) ASTM E1136-93 (Reapproved 2003), ``Standard Specification for 
a Radial Standard Reference Test Tire,'' approved March 15, 1993, into 
Sec. Sec.  571.105; 571.121; 571.122; 571.126; 571.135; 571.136; 
571.139; 571.500.
    (34) ASTM E1337-90 (Reapproved 2008), ``Standard Test Method for 
Determining Longitudinal Peak Braking Coefficient of Paved Surfaces 
Using a Standard Reference Test Tire,'' approved June 1, 2008, into 
Sec. Sec.  571.105; 571.121; 571.122; 571.126; 571.135; 571.136; 
571.500.
* * * * *

0
3. Revise Table 1 of Sec.  571.101 to read as follows:

Sec.  571.101  Standard No. 101; Controls and displays.

[[Page 36101]]

[GRAPHIC] [TIFF OMITTED] TR23JN15.012

[[Page 36102]]

[GRAPHIC] [TIFF OMITTED] TR23JN15.013

[[Page 36103]]

[GRAPHIC] [TIFF OMITTED] TR23JN15.014

[[Page 36104]]

[GRAPHIC] [TIFF OMITTED] TR23JN15.015

[[Page 36105]]

[GRAPHIC] [TIFF OMITTED] TR23JN15.016

* * * * *

0
4. Revise the heading of Sec.  571.126 to read as follows:

Sec.  571.126  Standard No. 126; Electronic stability control systems 
for light vehicles.

* * * * *

0
5. Add Sec.  571.136 to read as follows:

Sec.  571.136  Standard No. 136; Electronic stability control systems 
for heavy vehicles.

    S1 Scope. This standard establishes performance and equipment 
requirements for electronic stability control (ESC) systems on heavy 
vehicles.
    S2 Purpose. The purpose of this standard is to reduce crashes 
caused by rollover or by directional loss-of-control.
    S3 Application. This standard applies to the following vehicles:
    S3.1 Truck tractors with a gross vehicle weight rating of greater 
than 11,793 kilograms (26,000 pounds). However, it does not apply to:
    (a) Any truck tractor equipped with an axle that has a gross axle 
weight rating of 13,154 kilograms (29,000 pounds) or more;
    (b) Any truck tractor that has a speed attainable in 3.2 km (2 
miles) of not more than 53 km/h (33 mph); and
    (c) Any truck tractor that has a speed attainable in 3.2 km (2 
miles) of not more than 72 km/h (45 mph), an unloaded vehicle weight 
that is not less than 95 percent of its gross vehicle weight rating, 
and no capacity to carry occupants other than the driver and operating 
crew.
    S3.2 Buses with a gross vehicle weight rating of greater than 
11,793 kilograms (26,000 pounds). However, it does not apply to
    (a) School buses;
    (b) Perimeter-seating buses;
    (c) Transit buses;
    (d) Any bus equipped with an axle that has a gross axle weight 
rating of 13,154 kilograms (29,000 pounds) or more; and
    (e) Any bus that has a speed attainable in 3.2 km (2 miles) of not 
more than 53 km/h (33 mph.)
    S4 Definitions.
    Ackerman Steer Angle means the angle whose tangent is the wheelbase 
divided by the radius of the turn at a very low speed.
    Electronic stability control system or ESC system means a system 
that has all of the following attributes:
    (1) It augments vehicle directional stability by having the means 
to apply and adjust the vehicle brake torques individually at each 
wheel position on at least one front and at least one rear axle of the 
truck tractor or bus to induce correcting yaw moment to limit vehicle 
oversteer and to limit vehicle understeer;
    (2) It enhances rollover stability by having the means to apply and 
adjust the vehicle brake torques individually at each wheel position on 
at least one front and at least one rear axle of the truck tractor or 
bus to reduce lateral acceleration of a vehicle;
    (3) It is computer-controlled with the computer using a closed-loop 
algorithm to induce correcting yaw moment and enhance rollover 
stability;
    (4) It has a means to determine the vehicle's lateral acceleration;
    (5) It has a means to determine the vehicle's yaw rate and to 
estimate its side slip or side slip derivative with respect to time;
    (6) It has a means to estimate vehicle mass or, if applicable, 
combination vehicle mass;
    (7) It has a means to monitor driver steering inputs;
    (8) It has a means to modify engine torque, as necessary, to assist 
the driver in maintaining control of the vehicle and/or combination 
vehicle; and
    (9) When installed on a truck tractor, it has the means to provide 
brake pressure to automatically apply and modulate the brake torques of 
a towed trailer.
    ESC service brake application means the time when the ESC system 
applies a service brake pressure at any wheel for a continuous duration 
of at least 0.5 second of at least 34 kPa (5 psi) for air-braked 
systems and at least 172 kPa (25 psi) for hydraulic-braked systems.
    Initial brake temperature means the average temperature of the 
service brakes on the hottest axle of the vehicle immediately before 
any stability control system test maneuver is executed.
    Lateral acceleration means the component of the vector acceleration 
of a point in the vehicle perpendicular to the vehicle x-axis 
(longitudinal) and parallel to the road plane.
    Oversteer means a condition in which the vehicle's yaw rate is 
greater than the yaw rate that would occur at the vehicle's speed as 
result of the Ackerman Steer Angle.
    Over-the-road bus means a bus characterized by an elevated 
passenger deck located over a baggage compartment, except a school bus.
    Peak friction coefficient or PFC means the ratio of the maximum 
value of braking test wheel longitudinal force to the simultaneous 
vertical force occurring prior to wheel lockup, as the

[[Page 36106]]

braking torque is progressively increased.
    Perimeter-seating bus means a bus with 7 or fewer designated 
seating positions rearward of the driver's seating position that are 
forward-facing or can convert to forward-facing without the use of 
tools and is not an over-the-road bus.
    Side slip or side slip angle means the arctangent of the lateral 
velocity of the center of gravity of the vehicle divided by the 
longitudinal velocity of the center of gravity.
    Snub means the braking deceleration of a vehicle from a higher 
speed to a lower speed that is greater than zero.
    Stop-request system means a vehicle-integrated system for passenger 
use to signal to a vehicle operator that they are requesting a stop.
    Transit bus means a bus that is equipped with a stop-request system 
sold for public transportation provided by, or on behalf of, a State or 
local government and that is not an over-the-road bus.
    Understeer means a condition in which the vehicle's yaw rate is 
less than the yaw rate that would occur at the vehicle's speed as 
result of the Ackerman Steer Angle.
    Yaw Rate means the rate of change of the vehicle's heading angle 
measure in degrees per second of rotation about a vertical axis through 
the vehicle's center of gravity.
    S5 Requirements. Each vehicle must be equipped with an ESC system 
that meets the requirements specified in S5 under the test conditions 
specified in S6 and the test procedures specified in S7 of this 
standard.
    S5.1 Required Equipment. Each vehicle to which this standard 
applies must be equipped with an electronic stability control system, 
as defined in S4.
    S5.2 System Operational Capabilities.
    S5.2.1 The ESC system must be operational over the full speed range 
of the vehicle except at vehicle speeds less than 20 km/h (12.4 mph), 
when being driven in reverse, or during system initialization.
    S5.2.2 The ESC must remain capable of activation even if the 
antilock brake system or traction control is also activated.
    S5.3 Performance Requirements.
    S5.3.1 Lane Keeping During Reference Speed Determination. During 
each series of four consecutive test runs conducted at the same 
entrance speed as part of the test procedure to determine the 
Preliminary Reference Speed and the Reference Speed (see S7.7.1), the 
wheels of the truck tractor or bus must remain within the lane between 
the start gate (0 degrees of radius arc angle) and the end gate (120 
degrees of radius arc angle) during at least two of the four test runs.
    S5.3.2 Engine Torque Reduction. During each series of four 
consecutive test runs for the determination of engine torque reduction 
(see S7.7.2), the vehicle must satisfy the criteria of S5.3.2.1 and 
S5.3.2.2 during at least two of the four test runs.
    S5.3.2.1 The ESC system must reduce the driver-requested engine 
torque by at least 10 percent for a minimum continuous duration of 0.5 
second during the time period from 1.5 seconds after the vehicle 
crosses the start gate (0 degree of radius arc angle) to when it 
crosses the end gate (120 degrees of radius arc angle).
    S5.3.2.2 The wheels of the truck tractor or bus must remain within 
the lane between the start gate (0 degrees of radius arc angle) and the 
end gate (120 degrees of radius arc angle).
    S5.3.3 Roll Stability Control Test. During each series of eight 
consecutive test runs for the determination of roll stability control 
(see S7.7.3) conducted at the same entrance speed, the vehicle must 
satisfy the criteria of S5.3.3.1, S5.3.3.2, S5.3.3.3, and S5.3.3.4 
during at least six of the eight consecutive test runs.
    S5.3.3.1 The vehicle speed measured at 3.0 seconds after vehicle 
crosses the start gate (0 degrees of radius arc angle) must not exceed 
47 km/h (29 mph).
    S5.3.3.2 The vehicle speed measured at 4.0 seconds after vehicle 
crosses the start gate (0 degrees of radius arc angle) must not exceed 
45 km/h (28 mph).
    S5.3.3.3 The wheels of the truck tractor or bus must remain within 
the lane between the start gate (0 degrees of radius arc angle) and the 
end gate (120 degrees of radius arc angle).
    S5.3.3.4 There must be ESC service brake activation.
    S5.4 ESC Malfunction Detection. Each vehicle must be equipped with 
an indicator lamp, mounted in front of and in clear view of the driver, 
which is activated whenever there is a malfunction that affects the 
generation or transmission of control or response signals in the 
vehicle's electronic stability control system.
    S5.4.1 Except as provided in S5.4.3 and S5.4.6, the ESC malfunction 
telltale must illuminate only when a malfunction exists and must remain 
continuously illuminated for as long as the malfunction exists, 
whenever the ignition locking system is in the ``On'' (``Run'') 
position.
    S5.4.2 The ESC malfunction telltale must be identified by the 
symbol shown for ``Electronic Stability Control System Malfunction'' or 
the specified words or abbreviations listed in Table 1 of Standard No. 
101 (Sec.  571.101).
    S5.4.3 The ESC malfunction telltale must be activated as a check-
of-lamp function either when the ignition locking system is turned to 
the ``On'' (``Run'') position when the engine is not running, or when 
the ignition locking system is in a position between the ``On'' 
(``Run'') and ``Start'' that is designated by the manufacturer as a 
check-light position.
    S5.4.4 The ESC malfunction telltale need not be activated when a 
starter interlock is in operation.
    S5.4.5 The ESC malfunction telltale lamp must extinguish at the 
next ignition cycle after the malfunction has been corrected.
    S5.4.6 The manufacturer may use the ESC malfunction telltale in a 
flashing mode to indicate ESC operation.
    S6 Test Conditions. The requirements of S5 must be met by a vehicle 
when it is tested according to the conditions set forth in the S6, 
without replacing any brake system part or making any adjustments to 
the ESC system except as specified. On vehicles equipped with automatic 
brake adjusters, the automatic brake adjusters will remain activated at 
all times.
    S6.1 Ambient Conditions.
    S6.1.1 The ambient temperature is any temperature between 2 [deg]C 
(35[emsp14][deg]F) and 40 [deg]C (104[emsp14][deg]F).
    S6.1.2 The maximum wind speed is no greater than 5 m/s (11 mph).
    S6.2 Road Test Surface.
    S6.2.1 The tests are conducted on a dry, uniform, solid-paved 
surface. Surfaces with irregularities and undulations, such as dips and 
large cracks, are unsuitable.
    S6.2.2 The road test surface produces a peak friction coefficient 
(PFC) of 0.9 when measured using an American Society for Testing and 
Materials (ASTM) E1136-93 (Reapproved 2003) standard reference test 
tire, in accordance with ASTM Method E 1337-90 (Reapproved 2008), at a 
speed of 64.4 km/h (40 mph), without water delivery (both documents 
incorporated by reference, see Sec.  571.5).
    S6.2.3 The test surface has a consistent slope between 0% and 1%.
    S6.2.4 J-Turn Test Maneuver Test Course. The test course for the J-
Turn test maneuver is used for the Reference Speed Test in S7.7.1, the 
Engine Torque Reduction Test in S7.7.2, and the Roll Stability Control 
Test in S7.7.3.

[[Page 36107]]

    S6.2.4.1 The test course consists of a straight entrance lane with 
a length of 22.9 meters (75 feet) tangentially connected to a curved 
lane section with a radius of 45.7 meters (150 feet) measured from the 
center of the lane.
    S6.2.4.2 For truck tractors, the lane width of the test course is 
3.7 meters (12 feet). For buses, the lane width of the test course is 
3.7 meters (12 feet) for the straight section and is 4.3 meters (14 
feet) for the curved section.
    S6.2.4.3 The start gate is the tangent point on the radius (the 
intersection of the straight lane and the curved lane sections) and is 
designated as zero degrees of radius of arc angle. The end gate is the 
point on the radius that is 120 degrees of radius arc angle measured 
from the tangent point.
    S6.2.4.4 Figure 1 shows the test course with the curved lane 
section configured in the counter-clockwise steering direction relative 
to the entrance lane. The course is also arranged with the curved lane 
section configured in the clockwise steering direction relative to the 
entrance lane. The cones depicted in Figure 1 defining the lane width 
are positioned solely for illustrative purposes.
[GRAPHIC] [TIFF OMITTED] TR23JN15.017

    S6.3 Vehicle Conditions.
    S6.3.1 The ESC system is enabled for all testing, except for the 
ESC malfunction test (see S7.8).
    S6.3.2 All vehicle openings (doors, windows, hood, trunk, cargo 
doors, etc.) are in a closed position except as required for 
instrumentation purposes.
    S6.3.3 Test Weight.
    S6.3.3.1 Truck Tractors. A truck tractor is loaded to its GVWR by 
coupling it to a control trailer (see S6.3.5). The tractor is loaded 
with the test driver, test instrumentation, and an anti-jackknife 
system (see S6.3.8).
    S6.3.3.2 Buses. A bus is loaded with ballast (weight) to its GVWR 
to simulate a multi-passenger and baggage configuration. For this 
configuration the bus is loaded with test driver, test instrumentation, 
outriggers (see S6.3.6), ballast, and a simulated occupant in each of 
the vehicle's designated seating positions. The simulated occupant 
loads are attained by securing 68 kilograms (150 pounds) of ballast in 
each of the test vehicle's designated seating positions. If the 
simulated occupant loads result in the bus being loaded to less than 
its GVWR, additional ballast is added to the bus in the following 
manner until the bus is loaded to its GVWR without exceeding any axle's 
GAWR: First, ballast is added to the lowest baggage compartment; 
second, ballast is added to the floor of the passenger compartment. If 
the simulated occupant loads result in the GAWR of any axle being 
exceeded or the GVWR of the bus being exceeded, simulated occupant 
loads are removed until the vehicle's GVWR and all axles' GAWR are no 
longer exceeded.
    S6.3.4 Transmission and Brake Controls. The transmission selector 
control is in a forward gear during all maneuvers. A vehicle equipped 
with an engine braking system that is engaged and disengaged by the 
driver is tested with the system disengaged.
    S6.3.5 Control Trailer.
    S6.3.5.1 The control trailer is an unbraked, flatbed semi-trailer 
that has a single axle with a GAWR of 8,165 kg (18,000 lb.). The 
control trailer has a length of at least 6,400 mm (252 inches), but no 
more than 7,010 mm (276

[[Page 36108]]

inches), when measured from the transverse centerline of the axle to 
the centerline of the kingpin (the point where the trailer attaches to 
the truck tractor). At the manufacturer's option, truck tractors with 
four or more axles may use a control trailer with a length of more than 
7,010 mm (276 inches), but no more than 13,208 mm (520 inches) when 
measured from the transverse centerline of the axle to the centerline 
of the kingpin.
    S6.3.5.2 The location of the center of gravity of the ballast on 
the control trailer is directly above the kingpin. The height of the 
center of gravity of the ballast on the control trailer is less than 
610 mm (24 inches) above the top of the tractor's fifth-wheel hitch 
(the area where the truck tractor attaches to the trailer).
    S6.3.5.3 The control trailer is equipped with outriggers (see 
S6.3.6).
    S6.3.5.4 A truck tractor is loaded to its GVWR by placing ballast 
(weight) on the control trailer which loads the tractor's non-steer 
axles. The control trailer is loaded with ballast without exceeding the 
GAWR of the trailer axle. If the tractor's fifth-wheel hitch position 
is adjustable, the fifth-wheel hitch is adjusted to proportionally 
distribute the load on each of the tractor's axle(s), according to each 
axle's GAWR, without exceeding the GAWR of any axle(s). If the fifth-
wheel hitch position cannot be adjusted to prevent the load from 
exceeding the GAWR of the tractor's axle(s), the ballast is reduced 
until the axle load is equal to or less than the GAWR of the tractor's 
rear axle(s), maintaining load proportioning as close as possible to 
specified proportioning.
    S6.3.6 Outriggers. Outriggers are used for testing each vehicle. 
The outriggers are designed with a maximum weight of 1,134 kg (2,500 
lb.), excluding mounting fixtures.
    S6.3.7 Tires. The tires are inflated to the vehicle manufacturer's 
specified pressure for the GVWR of the vehicle.
    S6.3.8 Truck Tractor Anti-Jackknife System. A truck tractor is 
equipped with an anti-jackknife system that allows a minimum 
articulation angle of 30 degrees between the tractor and the control 
trailer.
    S6.3.9 Special Drive Conditions. A vehicle equipped with an 
interlocking axle system or a front wheel drive system that is engaged 
and disengaged by the driver is tested with the system disengaged.
    S6.3.10 Liftable Axles. A vehicle with one or more liftable axles 
is tested with the liftable axles down.
    S6.3.11 Initial Brake Temperature. The initial brake temperature of 
the hottest brake for any performance test is between 66 [deg]C 
(150[emsp14][deg]F) and 204 [deg]C (400[emsp14][deg]F).
    S6.3.12 Thermocouples. The brake temperature is measured by plug-
type thermocouples installed in the approximate center of the facing 
length and width of the most heavily loaded shoe or disc pad, one per 
brake. A second thermocouple may be installed at the beginning of the 
test sequence if the lining wear is expected to reach a point causing 
the first thermocouple to contact the rubbing surface of a drum or 
rotor. The second thermocouple is installed at a depth of 0.080 inch 
and located within 1.0 inch circumferentially of the thermocouple 
installed at 0.040 inch depth. For center-grooved shoes or pads, 
thermocouples are installed within 0.125 inch to 0.250 inch of the 
groove and as close to the center as possible.
    S6.4 Selection of Compliance Options. Where manufacturer options 
are specified, the manufacturer must select the option by the time it 
certifies the vehicle and may not thereafter select a different option 
for the vehicle. Each manufacturer shall, upon request from the 
National Highway Traffic Safety Administration, provide information 
regarding which of the compliance options it has selected for a 
particular vehicle or make/model.
    S7 Test Procedure. S7.1 Tire Inflation. Inflate the vehicle's tires 
as specified in S6.3.7.
    S7.2 Telltale Lamp Check. With the vehicle stationary and the 
ignition locking system in the ``Lock'' or ``Off'' position, activate 
the ignition locking system to the ``On'' (``Run'') position or, where 
applicable, the appropriate position for the lamp check. The ESC system 
must perform a check-of-lamp function for the ESC malfunction telltale, 
as specified in S5.4.3.
    S7.3 Tire Conditioning. Condition the tires to wear away mold sheen 
and achieve operating temperature immediately before beginning the J-
Turn test runs. The test vehicle is driven around a circle 150 feet (46 
meters) in radius at a speed that produces a lateral acceleration of 
approximately 0.1g for two clockwise laps followed by two 
counterclockwise laps.
    S7.4 Brake Conditioning and Temperature. Conditioning and warm-up 
of the vehicle brakes are completed before and monitored during the 
execution of the J-Turn test maneuver.
    S7.4.1 Brake Conditioning. Condition the brakes in accordance with 
S7.4.1.1 and S7.4.1.2.
    S7.4.1.1 Prior to executing the J-Turn test maneuver, the vehicle's 
brakes are burnished as follows: With the transmission in the highest 
gear appropriate for a speed of 64 km/h (40 mph), make 500 snubs 
between 64 km/h (40 mph) and 32 km/h (20 mph) at a deceleration rate of 
0.3g, or at the vehicle's maximum deceleration rate if less than 0.3g. 
After each brake application accelerate to 64 km/h (40 mph) and 
maintain that speed until making the next brake application at a point 
1.6 km (1.0 mile) from the initial point of the previous brake 
application. If the vehicle cannot attain a speed of 64 km/h (40 mph) 
in 1.6 km (1.0 mile), continue to accelerate until the vehicle reaches 
64 km/h (40 mph) or until the vehicle has traveled 2.4 km (1.5 miles) 
from the initial point of the previous brake application, whichever 
occurs first. The brakes may be adjusted up to three times during the 
burnish procedure, at intervals specified by the vehicle manufacturer, 
and may be adjusted at the conclusion of the burnishing, in accordance 
with the vehicle manufacturer's recommendation.
    S7.4.1.2 Prior to executing the performance tests in S7.7, the 
brakes are conditioned using 40 brake application snubs from a speed of 
64 km/h (40 mph) to a speed of 32 km/h (20 mph), with a target 
deceleration of approximately 0.3g. After each brake application, 
accelerate to 64 km/h (40 mph) and maintain that speed until making the 
next brake application at a point 1.6 km (1.0 mile) from the initial 
point of the previous brake application.
    S7.4.2 Brake Temperature. Prior to testing or any time during 
testing, if the hottest brake temperature is above 204[deg]C 
(400[emsp14][deg]F) a cool down period is performed until the hottest 
brake temperature is measured within the range of 66[deg]C-204[deg]C 
(150[emsp14][deg]F-400[emsp14][deg]F). Prior to testing or any time 
during testing, if the hottest brake temperature is below 66[deg]C 
(150[emsp14][deg]F) individual brake stops are repeated to increase any 
one brake temperature to within the target temperature range of 
66[deg]C-204[deg]C (150[emsp14][deg]F-400[emsp14][deg]F) before a test 
maneuver is performed.
    S7.5 Mass Estimation Cycle. Perform the mass estimation procedure 
for the ESC system according to the manufacturer's instructions. This 
procedure will be repeated if an ignition cycle occurs or is needed at 
any time between the initiation and completion of S7.7.
    S7.6 ESC System Malfunction Check. Check that the ESC system is 
enabled by ensuring that the ESC malfunction telltale is not 
illuminated.
    S7.7 J-Turn Test Maneuver. The truck tractor or bus is subjected to 
multiple series of test runs using the J-Turn test maneuver. The truck 
tractor or bus

[[Page 36109]]

travels through the course by driving down the entrance lane, crossing 
the start gate at the designated entrance speed, turning through the 
curved lane section, and crossing the end gate, while the driver 
attempts to keep all of the wheels of the truck tractor or bus within 
the lane.
    S7.7.1 Reference Speed Test. The vehicle is subjected to J-Turn 
test maneuvers to determine the Reference Speed for each steering 
direction. The Reference Speeds are used in S7.7.2 and S7.7.3.
    S7.7.1.1 Preliminary Reference Speed Determination. The vehicle is 
subjected to two series of test runs using the J-Turn test maneuver at 
increasing entrance speeds. One series uses clockwise steering, and the 
other series uses counterclockwise steering. The entrance speed of a 
test run is the 0.5 second average of the raw speed data prior to any 
ESC system activation of the service brakes and rounded to the nearest 
1.0 mph. During each test run, the driver attempts to maintain the 
selected entrance speed throughout the J-Turn test maneuver. For the 
first test run of each series, the entrance speed is 32 km/h  1.6 km/h (20 mph  1.0 mph) and is incremented 1.6 
km/h (1.0 mph) for each subsequent test run until ESC service brake 
application occurs or any of the truck tractor's or bus's wheels 
departs the lane. The vehicle entrance speed at which ESC service brake 
application occurs is the Preliminary Reference Speed. The Preliminary 
Reference Speed is determined for each direction: Clockwise steering 
and counter-clockwise steering. During any test run, if any of the 
wheels of the truck tractor or bus depart the lane at any point within 
the first 120 degrees of radius arc angle, the test run is repeated at 
the same entrance speed. If any of the wheels of the truck tractor or 
bus depart the lane again, then four consecutive test runs are repeated 
at the same entrance speed (1.6 km/h (1.0 
mph)).
    S7.7.1.2 Reference Speed Determination. Using the Preliminary 
Reference Speed determined in S7.7.1.1, perform two series of test runs 
using the J-Turn test maneuver to determine the Reference Speed. The 
first series consists of four consecutive test runs performed using 
counter-clockwise steering. The second series consists of four 
consecutive test runs performed using clockwise steering. During each 
test run, the driver attempts to maintain a speed equal to the 
Preliminary Reference Speed throughout the J-Turn test maneuver. The 
Reference Speed is the minimum entrance speed at which ESC service 
brake application occurs for at least two of four consecutive test runs 
of each series conducted at the same entrance speed (within 1.6 km/h (1.0 mph)). The Reference Speed is 
determined for each direction: clockwise steering and counter-clockwise 
steering. If ESC service brake application does not occur during at 
least two test runs of either series, the Preliminary Reference Speed 
is increased by 1.6 km/h (1.0 mph), and the procedure in this section 
is repeated.
    S7.7.2 Engine Torque Reduction Test. The vehicle is subjected to 
two series of test runs using the J-Turn test maneuver at an entrance 
speed equal to the Reference Speed determined in S7.7.1.2. One series 
uses clockwise steering, and the other series uses counter-clockwise 
steering. Each series consists of four test runs with the vehicle at an 
entrance speed equal to the Reference Speed and the driver fully 
depressing the accelerator pedal from the time when the vehicle crosses 
the start gate until the vehicle reaches the end gate. ESC engine 
torque reduction is confirmed by comparing the engine torque output and 
driver requested torque data collected from the vehicle communication 
network or CAN bus. During the initial stages of each maneuver the two 
torque signals with respect to time will parallel each other. Upon ESC 
engine torque reduction, the two signals will diverge when the ESC 
system causes a commanded engine torque reduction and the driver 
depresses the accelerator pedal attempting to accelerate the vehicle.
    S7.7.2.1 Perform two series of test runs using the J-Turn test 
maneuver at the Reference Speed determined in S7.7.1.2 (1.6 
km/h (1.0 mph)). The first series consists of four 
consecutive test runs performed using counter-clockwise steering. The 
second series consists of four consecutive test runs performed using 
clockwise steering. During each test run, the driver fully depresses 
the accelerator pedal from the time when the vehicle crosses the start 
gate until the vehicle reaches the end gate.
    S7.7.2.2 During each of the engine torque reduction test runs, 
verify the commanded engine torque and the driver requested torque 
signals diverge according to the criteria specified in S5.3.2.1.
    S7.7.3 Roll Stability Control Test. The vehicle is subjected to 
multiple series of test runs using the J-Turn test maneuver in both the 
clockwise and the counter-clockwise direction.
    S7.7.3.1 Before each test run, the brake temperatures are monitored 
and the hottest brake is confirmed to be between 66 [deg]C 
(150[emsp14][deg]F) and 204 [deg]C (400[emsp14][deg]F). If the hottest 
brake temperature is not between 66 [deg]C (150[emsp14][deg]F) and 204 
[deg]C (400[emsp14][deg]F), the brake temperature is adjusted in 
accordance with S7.4.2.
    S7.7.3.2 During each test run, the driver will release the 
accelerator pedal after the ESC system has slowed vehicle by more than 
4.8 km/h (3.0 mph) below the entrance speed.
    S7.7.3.3 The maximum test speed is the greater of 130 percent of 
the Reference Speed (see S7.7.1.2) or 48 km/h (30 mph). The maximum 
test speed is determined for each direction: clockwise steering and 
counter-clockwise steering.
    S7.7.3.4 For each series of Roll Stability Control test runs, the 
vehicle will perform eight consecutive test runs at the same entrance 
speed, which is any speed between 48 km/h (30 mph) and the maximum test 
speed determined according to S7.7.3.3.
    S7.7.3.5 Upon completion of testing, post processing is done as 
specified in S7.9.
    S7.8 ESC Malfunction Detection.
    S7.8.1 Simulate one or more ESC malfunction(s) by disconnecting the 
power source to any ESC component, or disconnecting any electrical 
connection between ESC components (with the vehicle power off). When 
simulating an ESC malfunction, the electrical connections for the 
telltale lamp(s) are not disconnected.
    S7.8.2 With the vehicle initially stationary and the ignition 
locking system in the ``Lock'' or ``Off'' position, activate the 
ignition locking system to the ``Start'' position and start the engine. 
Place the vehicle in a forward gear and accelerate to 48  8 
km/h (30  5 mph). Drive the vehicle for at least two 
minutes including at least one left and one right turning maneuver and 
at least one service brake application. Verify that, within two minutes 
of attaining this speed, the ESC malfunction indicator illuminates in 
accordance with S5.4.
    S7.8.3 Stop the vehicle, deactivate the ignition locking system to 
the ``Off'' or ``Lock'' position. After a five-minute period, activate 
the vehicle's ignition locking system to the ``Start'' position and 
start the engine. Verify that the ESC malfunction indicator again 
illuminates to signal a malfunction and remains illuminated as long as 
the engine is running until the fault is corrected.
    S7.8.4 Deactivate the ignition locking system to the ``Off'' or 
``Lock'' position. Restore the ESC system to normal operation, activate 
the ignition system to the ``Start'' position and start the engine. 
Verify that the telltale has extinguished.
    S7.9 Post Data Processing.

[[Page 36110]]

    S7.9.1 Raw vehicle speed data is filtered with a 0.1 second running 
average filter.
    S7.9.2 The torque data collected from the vehicle communication 
network or CAN bus as a digital signal does not get filtered. The 
torque data collected from the vehicle communication network or CAN bus 
as an analog signal is filtered with a 0.1-second running average.
    S7.9.3 The activation point of the ESC engine torque reduction is 
the point where the measured driver demanded torque and the engine 
torque first begin to deviate from one another (engine torque decreases 
while the driver requested torque increases) during the Engine Torque 
Reduction Test. The torque values are obtained directly from the 
vehicle communication network or CAN bus. Torque values used to 
determine the activation point of the ESC engine torque reduction are 
interpolated.
    S7.9.4 The time measurement for the J-Turn test maneuver is 
referenced to ``time zero'', which is defined as the instant the center 
of the front tires of the vehicle reach the start gate, the line within 
the lane at zero degrees of radius arc angle. The completion of the 
maneuver occurs at the instant the center of the front tires of the 
vehicle reach the end gate, which is the line within the lane at 120 
degrees of radius arc angle.
    S7.9.5 Raw service brake pressure measurements are zeroed 
(calibrated). Zeroed brake pressure data are filtered with 0.1 second 
running average filters. Zeroed and filtered brake pressure data are 
dynamically offset corrected using a defined ``zeroed range''. The 
``zeroing range'' is defined as the 0.5 second time period prior to 
``time zero'' defined in S7.9.4.
    S8 Compliance Dates. Vehicles that are subject to this standard 
must meet the requirements of this standard according to the 
implementation schedule set forth in S8.
    S8.1 Buses.
    S8.1.1 All buses with a gross vehicle weight rating of greater than 
14,969 kilograms (33,000 pounds) manufactured on or after June 24, 2018 
must comply with this standard.
    S8.1.2 All buses manufactured on or after August 1, 2019 must 
comply with this standard.
    S8.2 Trucks.
    S8.2.1 All three-axle truck tractors with a front axle that has a 
GAWR of 6,622 kilograms (14,600 pounds) or less and with two rear drive 
axles that have a combined GAWR of 20,412 kilograms (45,000 pounds) or 
less manufactured on or after August 1, 2017 must comply with this 
standard.
    S8.2.2 All truck tractors manufactured on or after August 1, 2019 
must comply with this standard.

    Issued on June 3, 2015, in Washington, DC, under authority 
delegated in 49 CFR 1.95 and 501.5.
Mark R. Rosekind,
Administrator.
[FR Doc. 2015-14127 Filed 6-22-15; 8:45 am]
 BILLING CODE 4910-59-P