[Federal Register Volume 91, Number 122 (Friday, June 26, 2026)]
[Proposed Rules]
[Pages 38593-38612]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-12981]
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DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. NHTSA-2026-0728]
RIN 2127-AN00
Federal Motor Vehicle Safety Standards; Modernization of FMVSS
No. 135 To Accommodate ADS-Equipped Vehicles
AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).
ACTION: Notice of proposed rulemaking.
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SUMMARY: NHTSA is proposing to amend Federal Motor Vehicle Safety
Standard (FMVSS) No. 135, ``Light vehicle brake systems.'' The proposed
modifications would distinguish how regulations apply to vehicles with
and without manually operated driving controls. The proposed
modifications would clarify definitions, telltale requirements,
performance requirements, and test procedures in the standard and
remove sections that are no longer relevant. The stopping distance
performance requirements, which address the primary safety purpose of
the standard, would still apply to all subject vehicles. This
rulemaking would remove unnecessary regulatory burdens and costs
without detriment to vehicle safety.
DATES: Comments should be submitted no later than July 27, 2026.
ADDRESSES: You may submit comments identified by the docket number in
the heading of this document through any of the following methods:
Electronic Submissions: Go to the Federal eRulemaking
Portal at http://www.regulations.gov. Follow the online instructions
for submitting comments.
Fax: (202) 493-2251.
Mail or Hand Delivery: Docket Management, U.S. Department
of Transportation, 1200 New Jersey Avenue SE, West Building, Suite W58-
213, Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through
Friday, except on Federal holidays. To be sure someone is there to help
you, please call (202) 366-9826 or (202) 366-9317 before coming.
Instructions: All submissions must include the agency name and
docket number for this notice. Note that all comments received will be
posted without change to http://www.regulations.gov, including any
personal information provided. Please see the Privacy Act heading
below.
[[Page 38594]]
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) or you may visit https://www.transportation.gov/privacy.
Docket: For access to the docket to read background documents or
comments received, go to http://www.regulations.gov or the street
address listed above. Follow the online instructions for accessing the
dockets via internet.
Confidential Business Information: If you claim that any of the
information in your comment (including any additional documents or
attachments) constitutes confidential business information within the
meaning of 5 U.S.C. 552(b)(4) or is protected from disclosure pursuant
to 18 U.S.C. 1905, please see the detailed instructions given under the
Public Participation heading of the SUPPLEMENTARY INFORMATION section
of this document.
FOR FURTHER INFORMATION CONTACT: For technical issues, you may contact
Ms. Lina Valivullah, Office of Automation Safety; Telephone: 202-366-
1810; Email: [email protected]; Facsimile: 202-493-2739. For
legal issues, you may contact Mr. David Jasinski, NHTSA Office of the
Chief Counsel, Email: [email protected]. The mailing address of
these officials is: National Highway Traffic Safety Administration,
1200 New Jersey Avenue SE, Washington, DC 20590.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Executive Summary
II. Background
III. Proposed Changes
a. Brake Controls and Test Specifications
b. Telltales and Indicators
c. Parking Brake Requirements
IV. Request for Comment
V. Rulemaking Analyses and Notices
VI. Public Participation
I. Executive Summary
This rulemaking is intended primarily to modernize Federal Motor
Vehicle Safety Standard No. 135, ``Light vehicle brake systems,'' to
apply the standard's performance requirements to vehicles equipped with
Automated Driving Systems (ADS) that do not have manually operated
driving controls. Though these vehicles currently are not available for
consumer purchase, there is considerable testing, development, and
validation of these vehicles, as well as localized deployment by
manufacturers and rideshare operators. Vehicle automation technology
has the potential to reduce roadway crashes and fatalities while
increasing mobility. As the technology is still maturing and many of
the potential benefits are yet to be realized, NHTSA is engaging in a
process to modernize existing FMVSS to remove unnecessary barriers to
technological innovation while ensuring motor vehicle safety is not
compromised.
In this document, NHTSA proposes to amend FMVSS No. 135 to clarify
the requirements and test procedures for vehicles with and without
manually operated driving controls, while retaining the existing
requirements for stopping distance. NHTSA proposes to revise the
current requirements that all light vehicles contain hand- or foot-
operated brake controls, removing those requirements for vehicles
designed never to be operated by a human. For vehicles without manually
operated driving controls, the agency proposes application of existing
performance requirements through alternative test procedures. The
proposed changes also include language modifications, corrections of
typographical errors, and removal of outdated information to clarify
the braking performance requirements for all subject vehicles. NHTSA is
not proposing changes to any stopping distance requirements in FMVSS
No. 135. Regardless of the manner of brake control application, the
brake systems must be capable of safely stopping the vehicle, as
already required by the standard. This rulemaking would remove
unnecessary regulatory burdens and costs with no negative impact to
vehicle safety. For ADS-equipped vehicles that contain manually
operated driving controls, the existing requirements of the standard
would still apply.
Importantly, this proposal is intended to remove unintended design
barriers that exist in FMVSS No. 135 and maintain existing brake
performance requirements for designs that are newly enabled. The
proposal would ensure that ADS-equipped vehicles without manually
operated driving controls can stop within an appropriate distance once
brake controls are actuated. However, whether the vehicle's brakes are
actuated appropriately given a specific driving scenario is an
independent question relating to ADS performance. To this end, NHTSA is
in the process of developing safety performance tests for ADS-equipped
vehicles, which would be implemented in a separate standard. As with
any ADS-equipped vehicle, NHTSA will not hesitate to use its strong and
broad defect enforcement authority to address unsafe ADS performance if
the proposal is finalized.
II. Background
This proposed rule is intended primarily to address ADS-equipped
vehicles that do not have manually operated driving controls. An ADS
commonly is considered to be a combination of hardware and software
that can perform all real-time operational and tactical functions
required to operate a vehicle on a sustained basis \1\--functions
traditionally performed by a human driver using manually operated
driving controls. As defined in part 571.3 and used throughout this
document, manually operated driving controls means a system of
controls: (i) used by an occupant for real-time, sustained, manual
manipulation of the motor vehicle's heading (steering) and/or speed
(accelerator and brake); and (ii) positioned such that they can be used
by an occupant, regardless of whether the occupant is actively using
the system to manipulate the vehicle's motion. In an ADS-equipped
vehicle designed to be operated only by an ADS, manually operated
driving controls are not inherently necessary. Further, in an ADS-
operated vehicle, the inclusion of a manually operated driving control
that directly overrides ADS operation could pose a safety risk through
intentional or unintentional misuse by a vehicle passenger. A vehicle
occupant that is a passenger, not a driver, should also not be expected
to perform driver functions such as engaging the parking brake.
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\1\ See, e.g., SAE J3016_202104; Tex. Transp. Code Sec.
545.451.
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NHTSA has published prior Federal Register notices requesting
comment, proposing changes, and updating existing regulations to
address vehicle automation. These notices include a request for comment
(RFC), ``Removing Regulatory Barriers for Vehicles with Automated
Driving Systems,'' published on February 13, 2018,\2\ and a subsequent
advance notice of proposed rulemaking (ANPRM) with the same title
published on May 28, 2019.\3\ The RFC posed questions about identifying
and addressing regulatory barriers for vehicles that lack traditional
manual controls or have unconventional seating. The ANPRM focused on
the challenges of testing and verifying compliance for vehicles without
traditional manual controls. A separate notice of proposed
[[Page 38595]]
rulemaking (NPRM), ``Occupant Protection for Automated Driving
Systems,'' \4\ was published on March 30, 2020, with the corresponding
final rule, ``Occupant Protection for Vehicles with Automated Driving
Systems,'' published on March 30, 2022.\5\ The rulemaking focused on
crashworthiness standards for ADS-equipped vehicles without manual
driving controls, revising definitions and updating occupant protection
standards to exclude vehicles specifically designed not to contain any
occupants. The 2022 final rule also established the definition in 49
CFR 571.3 for manually operated driving controls. On December 3, 2020,
NHTSA published an ANPRM titled, ``Framework for Automated Driving
Systems,'' to discuss and request comment on the manner in which the
agency would define, assess, and manage objectively the safety of ADS
performance while ensuring the needed flexibility to enable further
innovation.\6\ The ANPRM included recognition of a phased approach to
addressing ADS safety including NHTSA's modernization of the FMVSS for
ADS-equipped vehicles without traditional manual driving controls.
Earlier this year, NHTSA published three NPRMs proposing to amend FMVSS
No. 102, ``Transmission shift position sequence, starter interlock, and
transmission braking effect;'' FMVSS Nos. 103 and 104, ``Windshield
defrosting and defogging systems'' and ``Windshield wiping and washing
systems;'' and FMVSS No. 110, ``Tire selection and rims and motor home/
recreation vehicle trailer load carrying capacity information for motor
vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less;'' to
eliminate unnecessary barriers to vehicles without manually operated
driving controls in furtherance of these modernization efforts.\7\
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\2\ 83 FR 6148.
\3\ 84 FR 24433.
\4\ 85 FR 17624.
\5\ 87 FR 18560.
\6\ 85 FR 78058.
\7\ 91 FR 12532, 91 FR 12537, and 91 FR 16172, respectively.
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NHTSA proposes amendments to the existing requirements to allow
ADS-equipped vehicles that do not contain manually operated driving
controls, and therefore cannot be driven by a human occupant, to be
certified under FMVSS No. 135. ADS-equipped vehicles without manually
operated driving controls currently face regulatory barriers presented
by requirements for manual controls such as a foot-operated service
brake pedal, which is unnecessary for operation of the vehicle by the
ADS. Some ADS-equipped vehicles do have manually operated driving
controls, especially if converted from a conventional vehicle or if
equipped with controls only for specialized use. NHTSA maintains that
any vehicle equipped with manually operated driving controls must
continue to meet all existing safety requirements associated with
manual controls, regardless of whether the vehicle is equipped with an
ADS.
General updates and corrections to the regulatory text are also
discussed in this document. The final rule establishing FMVSS No. 135,
``Passenger car brake systems,'' was published on February 2, 1995,\8\
to harmonize passenger vehicle braking requirements with international
standards. The new standard replaced the application of FMVSS No. 105,
``Hydraulic brake systems,'' to passenger cars. At that time, brake
standards were written to provide flexibility for vehicles with and
without antilock brake systems. Over time, sections of the standard
have become superfluous. The standard also was written with verbiage
for telltales that is not in line with current usage. In addition, on
September 30, 1997, a final rule was published expanding the
application of FMVSS No. 135 to multi-purpose passenger vehicles,
trucks, and buses with a gross vehicle weight rating (GVWR) of 3,500
kilograms (7,716 pounds) or less. The revised Code of Federal
Regulations (CFR) as of October 1, 1997, contained typographical errors
for some test requirements in FMVSS No. 135, specifically pedal force
and initial brake temperatures, which were not corrected in subsequent
versions of the CFR. The regulatory text amendments in this document
include plain language edits for clarity, corrections to typographical
errors, and removal of sections that are no longer relevant.
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\8\ 60 FR 6411.
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III. Proposed Changes
a. Brake Controls and Test Specifications
Background
FMVSS No. 135, ``Light vehicle brake systems,'' specifies
requirements for service brake and parking brake systems in passenger
cars, multi-purpose passenger vehicles, trucks, and buses with a GVWR
of 3,500 kilograms (7,716 pounds) or less. The purpose of the standard
is to ensure safe braking performance under normal and emergency
driving conditions. Brake performance is evaluated using the vehicle's
stopping distance, which is defined as the distance traveled by a
vehicle from the point of application of force to the brake control to
the point at which the vehicle reaches a full stop. FMVSS No. 135
currently requires service brakes to be activated by means of a foot
control. It requires control of the parking brake to be independent of
the service brake control and to be either a hand or foot control. In
addition, the standard includes wheel lockup sequence and adhesion
utilization requirements for vehicles without an antilock brake system
(ABS). The standard applies to passenger cars manufactured on or after
September 1, 2000, and to multi-purpose passenger vehicles, trucks and
buses with a GVWR of 3,500 kilograms (7,716 pounds) or less,
manufactured on or after September 1, 2002.
Proposal
As stated, the intention of the standard is to ensure safe braking
performance in a variety of conditions. Paragraph S5.3.1 currently
requires independent manual controls for activation of the service
brakes and the parking brake. In an ADS-equipped vehicle without
manually operated driving controls, the ADS would perform the driving
task and any vehicle occupants would be passengers. The ADS would
operate the service brakes and the parking brake without the need for a
foot-operated service brake pedal, or a hand- or foot-operated parking
brake control. Therefore, some manufacturers may want the ability to
remove these manual controls. It is NHTSA's expectation that if these
controls are removed, passengers will still be provided with a means to
direct an ADS-operated vehicle to come to a stop, though how a
passenger would indicate they wanted the ADS-operated vehicle to stop
\9\ would likely vary by manufacturer.
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\9\ NHTSA is taking no position at this time as to how a
passenger should be able to direct an ADS-operated vehicle to stop,
or how the ADS should respond to such direction. NHTSA will continue
to consider this issue as it addresses ADS performance. In the
meantime, the agency will oversee the ability of passengers to
request stops, and responses by the ADS to such requests, using its
defect authority. Until NHTSA establishes FMVSS on this topic,
manufacturers have the responsibility to ensure that the design and
performance of such systems do not pose an unreasonable risk to
safety.
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In some vehicles, the inclusion of a brake pedal that directly
overrides ADS operation could pose a safety risk through intentional or
unintentional misuse by a vehicle passenger. In addition, operation of
the parking brake is the responsibility of the vehicle operator; a
passenger that is not
[[Page 38596]]
responsible for operating the vehicle is not responsible for control of
the parking brake. For these reasons, NHTSA proposes to amend S5.3.1 to
clarify that the requirements for a foot-operated service brake control
and a separate hand or foot-controlled parking brake only apply to
vehicles equipped with manually operated driving controls. The
requirement for independent operation of the service brakes and the
parking brake would be unchanged. NHTSA seeks comment on potential
consequences of removing the requirements for hand- and foot-operated
brakes in ADS-operated vehicles. For vehicles without manually operated
driving controls, NHTSA also proposes to require that the service brake
control and the parking brake control are activated by on-board
systems. This clause precludes the use of an external command system in
which the braking signal can only be sent from outside the vehicle,
rather than being directed by an on-board ADS. Further, in an ADS-
operated vehicle, a control that is designed for operation by a vehicle
occupant to direct the vehicle to a stop and is not the primary braking
control would not be considered part of the service or parking brake
controls. NHTSA seeks comment on other considerations and concerns
related to ADS vehicle operation.
To clarify the terminology in FMVSS No. 135 for vehicles with and
without manually operated driving controls, NHTSA is proposing to add a
definition for service brake control. Though the term is not defined
explicitly in FMVSS No. 135, service brake control is used throughout
the standard to refer to the brake pedal. For all vehicles subject to
FMVSS No. 135, the service brake control would mean the vehicle
component used to activate a service brake system. As NHTSA has always
used foot-operated service brake control to mean a pedal, the service
brake control for a vehicle with manually operated driving controls
would specifically refer to a foot-operated pedal. For vehicles without
manually operated driving controls, the service brake control would be
the vehicle component that translates the electronic braking command
into mechanical input to the service brake system. For example, in lieu
of muscular force applied to a service brake pedal, an ADS-operated
vehicle might use a linear actuator to initiate braking. As the linear
actuator would receive an electronic signal to engage the brakes and
translate that signal into physical displacement, it would function as
the service brake control. The agency has tentatively concluded that
the proposed definition is non-restrictive, as physical actuation of
one or more components occurs even in brake systems with electronics,
hydraulics, and pneumatics. The proposed definition does not preclude
the use of non-mechanical braking by means of a regenerative braking
system (RBS) because a vehicle equipped with an RBS must also have
mechanical brakes. However, NHTSA has considered that it may be
appropriate to define the service brake control as a ``vehicle
component or subsystem'' to clarify the meaning for vehicles with
certain technologies such as an RBS or a distributed brake-by-wire
system. For example, in a vehicle with a distributed brake-by-wire
system, it would be appropriate to consider the component sending
command signals to the brake unit on each wheel as part of the service
brake control. NHTSA requests comment on the proposed definition and
potential alternatives.
NHTSA also proposes to modify the definition for stopping distance
to clarify the measurement for vehicles with and without manually
operated driving controls. The proposed definition does not modify how
the stopping distance is determined for vehicles that have a service
brake pedal. Stopping distance is still the distance traveled by a
vehicle from the point of initial application of force to the service
brake control to the point at which the vehicle reaches a full stop.
For vehicles without a service brake pedal, as physical force would not
be applied to the service brake control, the stopping distance would be
the distance traveled by the vehicle from the point of initial
transmission of an electronic command signal to the service brake
control to the point at which the vehicle reaches a full stop. ADS-
operated vehicles will need to translate the necessary level of braking
determined by the ADS from a command signal into physical deceleration.
In a vehicle without manually operated driving controls, the test input
would be provided to the service brake control as if commanded by the
ADS. NHTSA proposes that both definitions for stopping distance would
be functionally equivalent in evaluating the physical capability of the
brakes, even though braking is initiated through different means.
NHTSA is proposing minor edits to two other definitions to account
for ADS-operated vehicles that do not have a driver, by changing
``driver action'' to ``any driver action'' in the definition of brake
power unit, and changing ``driver'' to ``any occupant'' in the
definition of lightly loaded vehicle weight. NHTSA is also condensing
the term ``lightly loaded vehicle weight'' to the acronym ``LLVW'' in
the definition of maximum speed. NHTSA also proposes to add a clause in
S5.1.3 to clarify that the RBS in an electric vehicle without manually
operated driving controls would be considered part of the service brake
system.
For test procedures and performance requirements, NHTSA proposes
changes to S7 to clarify application of the service brake control, as
pedal force specifications do not apply to vehicles without hand- or
foot-operated controls. The maximum pedal forces specified in S7 are
intended to ensure that the brakes are easily operable by drivers of
varying physical strength and will be retained for all brake systems
with hand- or foot-operated brake controls. When muscular force is not
used to apply the brake control, applied force specifications are
unnecessary. For these reasons, and to account for design variations
between different vehicles and ADSs, the proposed service brake test
procedures state that manufacturer specifications are used for the
brake control input when testing vehicles without manually operated
driving controls. Regardless of the activation mechanism for the
service brakes and the parking brake, all vehicles subject to FMVSS No.
135 would still need to meet the braking performance requirements of
the standard; NHTSA is not proposing any ADS-specific changes to the
stopping distance requirements.
The proposed modifications to the standard are intended to maintain
the current level of safety performance while ensuring that the
standard is not design restrictive. To ensure vehicle compliance with
FMVSS No. 135, NHTSA would request data and demonstration of vehicle
braking performance from vehicle manufacturers if unable to test the
vehicles independently. Laboratory and regulatory compliance testing
procedures may be developed and implemented over time as vehicles
without manually operated driving controls become more common,
including a potential standardized method for NHTSA to input braking
commands during compliance testing. At this time, NHTSA intends to work
with certifying entities as needed to ensure that all vehicles on
public roadways meet the applicable safety requirements.
In addition to ADS-specific changes, NHTSA is proposing to
streamline and make technical corrections to the standard. NHTSA
proposes to remove the subsections of S7 that only apply to vehicles
without ABS. This is because
[[Page 38597]]
all vehicles subject to FMVSS No. 135 currently are required to have
ABS in accordance with FMVSS No. 126, ``Electronic stability control
systems for light vehicles.'' \10\ FMVSS No. 135 contains testing
requirements and definitions that were adopted prior to the
establishment of FMVSS No. 126, when vehicles may not have been
equipped with ABS and needed additional safeguards for safe braking
performance. The wheel lockup sequence and adhesion utilization
requirements in S7.2 and S7.4 are specific to vehicles without ABS. The
standard also contains definitions and instrumentation specifications
for those test procedures that are no longer used and may be removed
without consequence. Keeping these vestigial sections in the standard
is not beneficial. For these reasons, NHTSA proposes to remove
definitions for ``Adhesion utilization curves,'' ``Brake factor,''
``Brake hold-off pressure,'' ``Braking ratio,'' and ``Objective brake
factor;'' paragraphs S6.4.2 and S6.4.3 for torque wheel test
instrumentation; and sections S7.2 and S7.4 for wheel lockup sequence
and adhesion utilization test procedures and performance requirements.
In addition, NHTSA previously reserved section S7.3 for use as ABS
performance testing. Given the requirements of FMVSS No. 126 render
this reservation unnecessary, the subsection title will be removed.
Sections S7.2, S7.3, and S7.4 will be left as [RESERVED]. With the
proposed changes, the test order in Table 1 would also be revised to
remove S7.2 through S7.4.
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\10\ 49 CFR 571.126.
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As all vehicles subject to FMVSS No. 135 are equipped with ABS,
NHTSA proposes to modify S5.3.2, by removing the language stating,
``for vehicles equipped with ABS.'' NHTSA also proposes to remove the
word ``manual,'' to clarify that any control to disable the ABS is
prohibited. As revised, S5.3.2 would read, ``A control to disable the
ABS, either fully or partially, is prohibited.'' Likewise, the `if
equipped' clause for ABS in S6.3.6 would be removed, resulting in,
``The ABS is fully operational for all tests, except where specified in
the following sections.'' NHTSA will also simplify the language in the
Application section for clarity, removing references to dates that have
passed.
Other revisions throughout S7 would correct the erroneous notation
for initial brake temperature (IBT) and pedal force specifications.
Specifically, the lower bounds for IBT and pedal force are stated as
maximum values rather than minimum values. Because the specifications
are written correctly in the publicly available laboratory test
procedure document \11\ and existing vehicle service brake systems meet
the requirements as intended when tested for compliance, NHTSA believes
these corrections will not result in changes to vehicle brake systems.
Another proposed revision for clarity is to move test condition
paragraph S7.7.3 (h) to S7.7.2, designating it as new paragraph S7.7.2
(e), because it is more appropriately categorized as a vehicle
condition; the contents of the paragraph would remain unchanged. NHTSA
further proposes to revise S7.10.3 (g) of the brake warning telltale
test procedure because the pressure level or fluid level determination
is only applicable for a hydraulic circuit failure and indirectly
refers to the activation conditions in S5.5.1 (a). The revised text
explicitly states to verify the brake warning telltale has been
activated, and if the activation is due to a hydraulic circuit failure,
to record the brake fluid level drop, differential pressure, or supply
pressure drop necessary to activate the telltale, in alignment with
S5.5.1 (a)(1) through (3). All other test specifications would remain
unchanged.
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\11\ See https://www.nhtsa.gov/sites/nhtsa.gov/files/documents/tp-135-01_tag.pdf.
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b. Telltales and Indicators
Background
Section S5.5 of FMVSS No. 135 requires a brake system warning
indicator that shall be in front of and in clear view of the driver and
which shall be activated when the ignition switch is in the ``on''
position and whenever a variety of conditions occur, including gross
loss of fluid or fluid pressure, electrical functional failure,
application of the parking brake, brake lining wear-out, and other
brake system or subsystem failures. The purpose of the brake system
warning indicator is to inform the driver when there is a malfunction
in the braking system and to provide feedback when the parking brake is
engaged.
Proposal
NHTSA proposes to rename ``brake system warning indicator'' to
``brake system warning telltale'' to align with the definitions of
telltales and indicators found in FMVSS No. 101, ``Controls and
displays.'' A telltale is defined in FMVSS No. 101 as ``an optical
signal that, when illuminated, shows the actuation of a device, a
correct or improper functioning or condition, or a vehicle system's
failure to function.'' Each of the conditions in which the brake system
warning indicator must be activated are conveying information related
to improper functioning or failure to function (S5.5.1(a), (b), (d),
(e), (f), and (g)), or the actuation of a device (S5.5.1(c)). Further,
FMVSS No. 101 classifies display items related to brake system warnings
as telltales. This change in language to be consistent with other
telltale requirements clarifies meaning and reduces confusion.
Section S5.5 of FMVSS No. 135 requires the brake system warning
telltale to be mounted in front of and in clear view of the driver. A
driver is defined in 49 CFR part 571.3 as the occupant of a motor
vehicle seated immediately behind the steering control system. By this
definition, an ADS-equipped vehicle without manually operated driving
controls does not have a driver because the vehicle is not equipped
with manually operated driving controls, including a steering control
system. As such, the occupants of a vehicle without manually operated
driving controls would be designated as passengers.
Some stakeholders have indicated that telltales are relevant only
to the driver, and the information merely needs to be conveyed to the
ADS for vehicles designed not to be operated by a human driver. NHTSA
tentatively disagrees with this approach. The agency believes that
certain telltales provide safety critical information that is necessary
to provide human occupants with contextual information about the risk
they may incur should they use the vehicle. The brake system warning is
one such telltale, as it provides information about the operational
safety of the vehicle. This telltale is also among those NHTSA has
consistently treated as requiring special prominence given the safety
critical nature of the information this telltale conveys.\12\ A
passenger would utilize the information from this telltale to make
safety-related decisions about whether and how to use the vehicle.
Information about a system or subsystem malfunction, for example, may
elicit passenger responses such as electing not to initiate a trip,
stopping an ongoing trip, or reporting the malfunction. NHTSA proposes
that for vehicles without manually operated driving controls, the brake
system warning telltale must be clearly visible to occupants in all
designated seating positions, but seeks comment on this approach. The
agency believes this is superior to requiring the telltale to be
visible only to the passenger in the front left designated seating
position (i.e., the
[[Page 38598]]
traditional ``driver's seat'') because, for these vehicles, there will
be no need for passengers to occupy any particular seating position for
the vehicle to operate. NHTSA has previously addressed other telltale
requirements for vehicles without manually operated driving controls by
stating that the visual warnings must be provided to all front row
occupants.\13\ However, NHTSA acknowledges that the ``front row'' may
be unclear in vehicles with novel seating configurations. NHTSA
requests comment on the proposed requirement and seeks information on
other options that would fulfill the safety purpose while being design
neutral. For instance, if a vehicle showed a brake system warning
telltale on a screen visible to some, but not all occupants, and would
not allow a trip to commence unless an occupant acknowledged the
existence of the underlying condition and elected to proceed, would
this provide a superior means of communication than a passive display
in view of all occupants? Would such an approach be appropriate if
displayed on a required application on an occupant's mobile phone for a
vehicle that does not include any screens? The agency is interested in
how best to ensure that important telltales are communicated to vehicle
occupants while allowing for design flexibility.
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\12\ See, e.g., 49 CFR 571.101 S.5.5.5.
\13\ 49 CFR 571.305a
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For vehicles with manually operated driving controls, the brake
system warning telltale will still be required to be mounted in front
of and in clear view of the driver. In addition, for all ADS-operated
vehicles, NHTSA further encourages the use of supplemental
notifications communicating safety-relevant information to passengers
via app notifications, in-vehicle alerts, or other methods, in addition
to the required telltales.
FMVSS No. 135 requires the brake warning system telltale to appear
when the parking brake is activated to alert the driver and reduce the
likelihood of driving with the parking brake activated. For ADS-
equipped vehicles that do not have manually operated driving controls,
NHTSA tentatively concludes that such an activation does not serve a
safety purpose because the ADS would control and monitor the status of
the parking brake as part of normal vehicle operation. NHTSA proposes
to add a clause to S5.5.1(c) of FMVSS No. 135 excepting vehicles
without manually operated driving controls from the requirement to
activate the brake system warning telltale when application of the
parking brake occurs.
Regardless of telltales for vehicle occupants, NHTSA expects an ADS
to be aware of the operational status of each safety critical vehicle
system and subsystem and respond appropriately to identified
degradations, failures, and malfunctions that create risks to safe
performance. In other words, NHTSA expects ADS-equipped vehicles to
adjust their operation if a safety critical vehicle system is in a
degraded state. As with any ADS-equipped vehicle, NHTSA will not
hesitate to use its strong and broad defect enforcement authority to
address unsafe ADS performance. NHTSA requests comment on whether a
performance standard would be appropriate for ADS response in the event
of a brake system degradation, failure, or malfunction. If so, how
should such performance requirements be constructed? Comments
containing supporting data are the most informative.
c. Parking Brake Requirements
Background
A parking brake is defined in 49 CFR part 571.3 as ``a mechanism
designed to prevent the movement of a stationary motor vehicle.''
Section S5.2 of FMVSS No. 135 requires that each vehicle be equipped
with a parking brake system of a friction type with solely mechanical
means to retain engagement. Section S7.12 contains the test procedure
and performance requirements for the parking brake system; it requires
that the parking brake system can hold the vehicle stationary for 5
minutes in both a forward and reverse direction on a 20 percent grade.
As previously discussed, the final rule establishing FMVSS No. 135,
``Passenger car brake systems,'' was published in 1995 to harmonize
passenger vehicle braking requirements with European standards, and
replaced the application of FMVSS No. 105, ``Hydraulic brake systems,''
to passenger cars. The requirement for a friction-type parking brake
was carried over to FMVSS No. 135 from FMVSS No. 105. The requirement
appears to have been based on industry best practice that emerged when
brake failure was more common, before the widespread use of split
service brake systems, to address the potential need for the parking
brake to serve as an emergency brake if the primary braking system
failed. FMVSS No. 135 did not include a dynamic vehicle deceleration
requirement for the parking brake, though it was proposed in the
original NPRM in 1985.
In the NPRM for FMVSS No. 135, published May 10, 1985,\14\ and
again in a supplemental NPRM published January 14, 1987,\15\ NHTSA
proposed a dynamic parking brake test intended to be consistent with
international regulations and to ensure that a driver could use the
parking brake to stop a moving vehicle in emergency situations. Several
vehicle manufacturers submitted comments opposing inclusion of a
dynamic parking brake test. After reviewing the comments, NHTSA agreed
that a dynamic parking brake test would provide no significant safety
benefits. The decision was based on the state of brake system
technology and the fact that FMVSS No. 105 did not include a dynamic
parking brake test. As noted by commenters, the international
requirement pre-dated the widespread use of split service brake systems
and the justification for using the parking brake in an emergency was
no longer relevant. NHTSA had no evidence that complete brake failure
(simultaneous failure of both circuits of a split brake system)
occurred with any significant frequency. NHTSA was also concerned that
applying the parking brake in emergency situations could cause wheel
lockup and instability. The agency further noted that the initial
impetus to harmonize with the European requirements for a dynamic
parking brake requirement would likely become moot, given that the
United Nations (UN) Economic Commission for Europe was discussing
deletion of the requirement.
---------------------------------------------------------------------------
\14\ 50 FR 19744.
\15\ 52 FR 1474.
---------------------------------------------------------------------------
Currently, UN Regulation No. 13, ``Uniform provisions concerning
the approval of vehicles of categories M, N and O with regard to
braking,'' and No. 13-H, ``Uniform provisions concerning the approval
of passenger cars with regard to braking,'' require that the parking
braking system in subject vehicles hold ``by a purely mechanical
device.'' The UN regulations further require that the ``parking braking
systems shall act on braking surfaces connected to the wheels through
components of adequate strength;'' in practice, this language
effectively requires a friction type system. There are no dynamic
parking brake requirements. There is a proposed amendment to the
regulations submitted by industry to allow use of ``a park lock device
as an alternative to or in combination with the means acting on the
braking surfaces.'' The amendment is under consideration but has not
yet been adopted. Likewise, the Alliance for Automotive Innovation
submitted
[[Page 38599]]
comment to the Department of Transportation requesting that NHTSA
remove the friction-type parking brake requirement from FMVSS No.
135.\16\ Vehicle and equipment manufacturers have developed other
parking brake designs (e.g., mechanical drivetrain locks) that may be
better suited to different vehicle use cases. Manufacturers are only
permitted to supplement, not replace, the friction type system under
the existing requirements.\17\
---------------------------------------------------------------------------
\16\ Docket DOT-OST-2025-0026.
\17\ NHTSA Interpretation ID: 18165.135.
---------------------------------------------------------------------------
Proposal
The purpose of the parking brake is to prevent inadvertent vehicle
movement when parked. NHTSA maintains that the parking brake system
must use solely mechanical means to retain engagement to meet the
safety need. The parking brake is intended to keep the vehicle from
unintended roll-away and must stay engaged regardless of the
operational state of the vehicle, including potential loss of electric
power. This precludes the adoption of fully electrically actuated
parking brakes, which may lose the ability to hold the vehicle if power
is lost. However, NHTSA agrees that the requirement for a friction-type
system is unnecessarily restrictive, as there is no demonstrated need
for the parking brake to be designed as a dynamic emergency brake, and
other mechanisms have been designed that can perform the same function.
The existing performance requirement for the parking brake system to
hold the vehicle stationary for five minutes in both a forward and
reverse direction on the grade would remain unchanged, as would the
requirement that the system retain engagement through solely mechanical
means. For these reasons, NHTSA proposes to remove the friction type
specification for the parking brake system.
Effective Date
As provided by 49 U.S.C. 30111(d), an FMVSS may not become
effective before the 180th day after the standard is prescribed or
later than one year after it is prescribed. However, NHTSA may provide
a different effective date after finding, for good cause shown, that a
different effective date is in the public interest. NHTSA must publish
the reasons supporting such a finding. Similarly, 5 U.S.C. 553(d)
provides that a final rule cannot become effective until at least 30
days after the date of publication except, among other reasons, the
rule grants or recognizes an exemption, relieves a restriction, or for
good cause found and published with the rule. It is in the public
interest for this proposed rule, if adopted, to be effective
immediately. This proposed rule clarifies existing requirements and
removes unnecessary regulatory requirements for ADS-equipped vehicles
without manually operated controls. There is no need for lead time for
regulated entities to comply with this proposed rule. NHTSA seeks
comment on whether the rule could be made effective within a time
period shorter than 180 days or upon publication of any final rule.
IV. Request for Comment
NHTSA seeks public comment on the proposed changes, including the
proposed exceptions to the requirements for hand- and foot-operated
brake controls, the proposed definitions, the proposed revisions to the
test procedures, the proposed telltale requirements for vehicles
without manually operated driving controls, and the proposed removal of
the friction type parking brake requirement. NHTSA will submit a
redline-change version of the standard in its entirety to the docket to
facilitate review of the proposed changes.
V. Rulemaking Analyses and Notices
Executive Order (E.O.) 12866 and E.O. 14192
NHTSA has considered the impact of this rulemaking action under
Executive Orders 12866 and 14192. This action was reviewed by the
Office of Management and Budget (OMB) as a significant regulatory
action under section 3(f) of E.O. 12866. This proposed rule, if
finalized as proposed, is expected to be an E.O. 14192 deregulatory
action because it removes an unnecessary regulatory burden for the
reasons discussed above. At this stage, the agency has not quantified
any potential benefits or costs. For this rule, NHTSA does not
anticipate any new regulatory costs, as it would remove unnecessary
requirements and provide clarity and flexibility without adding any new
requirements. NHTSA does not anticipate any safety disbenefits for the
proposed changes. The benefits to this rule would be reduced compliance
costs and potential safety benefits from removing the ability of an
occupant to interfere with the safe operation of the vehicle by the
ADS. However, given the still-developing nature of this market, NHTSA
cannot quantify the number of vehicles that may be potentially affected
by this proposed rule. Further, NHTSA believes that it is more likely
that these vehicles would seek exemptions from this standard rather
than include the unnecessary equipment. Though NHTSA could seek to
quantify compliance costs on a per-vehicle basis, any estimate that was
based on traditional vehicle configurations may not be accurate, given
the different design and nature of ADS-equipped vehicles without
manually operated driving controls. NHTSA requests comment on these
assumptions and any other information that could help quantify their
impacts in the final rule.
Regulatory Flexibility Act
Under the Regulatory Flexibility Act (RFA) (5 U.S.C. 601-612) (as
amended by the Small Business Regulatory Enforcement Fairness Act
(SBREFA) of 1996; 5 U.S.C. 601 et seq.), agencies must prepare and make
available for public comment a regulatory flexibility analysis that
describes the effect of the rulemaking on small entities (i.e., small
businesses, small organizations, and small government jurisdictions).
No regulatory flexibility analysis is required, however, if the head of
an agency or an appropriate designee certifies that the rulemaking will
not have a significant economic impact on a substantial number of small
entities. NHTSA has concluded and hereby certifies that this proposed
rule will not have a significant economic impact on a substantial
number of small entities; therefore, an analysis is not included. This
proposed rule will only except certain vehicles from standards that are
not applicable to them.
National Environmental Policy Act
The Department has analyzed the environmental impacts of this
notice of proposed rulemaking pursuant to the National Environmental
Policy Act of 1969 (NEPA) (42 U.S.C. 4321 et seq.). Pursuant to 49 CFR
1.81, the Secretary has delegated the ``functions'' under NEPA to the
Administrators ``as they relate to the matters within the primary
responsibility of each Operating Administration.'' NHTSA has determined
that this rule is categorically excluded pursuant to 23 CFR
771.118(c)(4). Categorical exclusions are actions identified in an
agency's NEPA procedures that do not normally have a significant impact
on the environment and therefore do not require either an environmental
assessment (EA) or environmental impact statement (EIS). See DOT Order
5610.1D Sec. 9. In analyzing the applicability of a categorical
exclusion, the agency must also consider whether extraordinary
circumstances are present that would warrant the preparation of an EA
or EIS.
[[Page 38600]]
Id. Sec. 9(b). The Department's Operating Administrations (OAs) may
apply CEs established in another OA's procedures. Id. Sec. 9(f). To do
so, the Operating Administration ``must evaluate the action for
extraordinary circumstances identified in the OA procedures in which
the CE is established to determine if a normally excluded action may
have a significant impact and coordinate with the originating OA to
ensure that the CE is being applied correctly.'' Id. This rulemaking,
which proposes to amend FMVSS No. 135, ``Light vehicle brake systems,''
to update the regulatory language and exempt ADS-equipped vehicles
without manually operated driving controls from certain requirements
that presume a person in the vehicle is driving, is categorically
excluded pursuant to 23 CFR 771.118(c)(4): Planning and administrative
activities not involving or leading directly to construction, such as:
Training, technical assistance and research; promulgation of rules,
regulations, directives, or program guidance; approval of project
concepts; engineering; and operating assistance to transit authorities
to continue existing service or increase service to meet routine
demand. NHTSA has coordinated with the Federal Transit Administration
to ensure that this CE is being applied correctly. NHTSA does not
anticipate any environmental impacts, and there are no extraordinary
circumstances present in connection with this rulemaking.
Executive Order 13132 (Federalism)
NHTSA has examined this rule pursuant to Executive Order 13132 (64
FR 43255, August 10, 1999) and has concluded tentatively that no
additional consultation with States, local governments, or their
representatives is mandated beyond the rulemaking process. The agency
has concluded tentatively that this rule, does not have sufficient
federalism implications to warrant consultation with State and local
officials or the preparation of a federalism summary impact statement.
NHTSA expects that this rule, if adopted, would 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 have a preemptive effect 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. NHTSA is
not aware of any State motor vehicle equipment or inspection laws or
regulations that require ADS-equipped vehicles that do not have manual
driving controls to be equipped with a brake pedal. However, NHTSA
seeks comment on whether any such State requirements exist that would
be preempted by this rule, if adopted.
The express preemption provision described above is subject to a
savings clause under which compliance 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 generally are preserved.
NHTSA rules can also preempt State law if complying with the FMVSS
would render the motor vehicle manufacturers liable under State tort
law. 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 generally will not be
preempted. 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. 861 (2000).
Pursuant to Executive Orders 13132 and 12988, NHTSA has considered
whether this proposed rule would 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. This
rule addresses the application to vehicles without manually operated
driving controls of requirements that a hand- or foot-operated service
brake pedal be installed on the vehicle for operation by a human
driver. As the requirement to meet stopping distance is not changed by
this rule, NHTSA believes this change will have no effect on safety.
Thus, NHTSA tentatively concludes that no conflict with State common
law causes of action would occur. Without any conflict, there could not
be any implied preemption of a State common law tort cause of action.
NHTSA also seeks comment on this tentative conclusion.
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.
Privacy Act
Please note that 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), or online at
www.transportation.gov/privacy.
National Technology Transfer and Advancement Act
Section 12(d) of the National Technology Transfer and Advancement
Act of 1995 (NTTAA), Public Law 104-113, as amended by Public Law 107-
107 (15 U.S.C. 272), directs the agency to evaluate and use voluntary
consensus standards in its regulatory activities unless doing so would
be inconsistent with applicable law or is otherwise impractical.
Voluntary consensus standards are technical standards (e.g.,
[[Page 38601]]
materials specifications, test methods, sampling procedures, and
business practices) that are developed or adopted by voluntary
consensus standards bodies, such as the Society of Automotive Engineers
(SAE). The NTTAA directs us to provide Congress (through OMB) with
explanations when the agency decides not to use available and
potentially applicable voluntary consensus standards.
Unfunded Mandates Reform Act
Section 202 of the Unfunded Mandates Reform Act of 1995 (UMRA),
Public Law 104-4, 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). This NPRM would not result in a
cost of $100 million or more when adjusted for inflation to either
State, local, or tribal governments, in the aggregate, or the private
sector. Thus, this NPRM is not subject to the requirements of sections
202 of the UMRA.
Executive Order 13609 (Promoting Regulatory Cooperation)
The policy statement in section 1 of Executive Order 13609
provides, in part: The regulatory approaches taken by foreign
governments may differ from those taken by U.S. regulatory agencies to
address similar issues. In some cases, the differences between the
regulatory approaches of U.S. agencies and those of their foreign
counterparts might not be necessary and might impair the ability of
American businesses to export and compete internationally. In meeting
shared challenges involving health, safety, labor, security,
environmental, and other issues, international regulatory cooperation
can identify approaches that are at least as protective as those that
are or would be adopted in the absence of such cooperation.
International regulatory cooperation can also reduce, eliminate, or
prevent unnecessary differences in regulatory requirements.
Severability
The issue of severability of FMVSSs is addressed in 49 CFR 571.9.
It provides that if any FMVSS or its application to any person or
circumstance is held invalid, the remainder of the part and the
application of that standard to other persons or circumstances is
unaffected. Comments are requested on the severability of this proposed
FMVSS.
Regulation Identifier Number
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.
Rulemaking Summary, 5 U.S.C. 553(b)(4)
As required by 5 U.S.C. 553(b)(4), a summary of this rule can be
found in the Abstract section of the Department's Unified Agenda entry
for this rulemaking at www.reginfo.gov. A summary of this proposal can
be found at regulations.gov/document/NHTSA-2026-0728 under the Document
Details tab.
VI. Public Participation
How long do I have to submit comments?
Please see DATES section at the beginning of this document.
How do I prepare and submit comments?
Your comments must be written in English.
To ensure that your comments are correctly filed in the
Docket, please include the Docket Number shown at the beginning of this
document in your comments.
Your comments must not be more than 15 pages long. (49 CFR
553.21). We established this limit to encourage you to write your
primary comments in a concise fashion. However, you may attach
necessary additional documents to your comments. There is no limit on
the length of the attachments.
If you are submitting comments electronically as a PDF
(Adobe) File, NHTSA asks that the documents be submitted using the
Optical Character Recognition (OCR) process, thus allowing NHTSA to
search and copy certain portions of your submissions. Comments may be
submitted to the docket electronically by logging onto the Docket
Management System website at www.regulations.gov. Follow the online
instructions for submitting comments.
You may also submit two copies of your comments, including
the attachments, to Docket Management at the address given above under
ADDRESSES.
Please note that pursuant to the Data Quality Act, in order for
substantive data to be relied upon and used by the agency, it must meet
the information quality standards set forth in the OMB and DOT Data
Quality Act guidelines. Accordingly, we encourage you to consult the
guidelines in preparing your comments. OMB's guidelines may be accessed
at http://www.whitehouse.gov/omb/fedreg/reproducible.html. DOT's
guidelines may be accessed at http://www.bts.gov/programs/statistical_policy_and_research/data_quality_guidelines.
How can I be sure that my comments were received?
If you wish Docket Management to notify you upon its receipt of
your comments, enclose a self-addressed, stamped postcard in the
envelope containing your comments. Upon receiving your comments, Docket
Management will return the postcard by mail.
How do I submit confidential business information?
You should submit a redacted ``public version'' of your comment
(including redacted versions of any additional documents or
attachments) to the docket using any of the methods identified under
ADDRESSES. This ``public version'' of your comment should contain only
the portions for which no claim of confidential treatment is made and
from which those portions for which confidential treatment is claimed
has been redacted. See below for further instructions on how to do
this.
You also need to submit a request for confidential treatment
directly to the Office of the Chief Counsel. Requests for confidential
treatment are governed by 49 CFR part 512. Your request must set forth
the information specified in part 512. This includes the materials for
which confidentiality is being requested (as explained in more detail
below); supporting information, pursuant to part 512.8; and a
certificate, pursuant to part 512.4(b) and part 512, Appendix A.
You are required to submit to the Office of the Chief Counsel one
unredacted ``confidential version'' of the information for which you
are seeking confidential treatment. Pursuant to part 512.6, the words
``ENTIRE PAGE CONFIDENTIAL BUSINESS INFORMATION'' or ``CONFIDENTIAL
BUSINESS INFORMATION CONTAINED WITHIN BRACKETS'' (as applicable) must
appear at the top of each page containing information claimed to be
confidential. In the latter situation, where not all information on the
page is claimed to be confidential, identify each item of information
for which confidentiality is requested within brackets: ``[ ].''
[[Page 38602]]
You are also required to submit to the Office of the Chief Counsel
one redacted ``public version'' of the information for which you are
seeking confidential treatment. Pursuant to part 512.5(a)(2), the
redacted ``public version'' should include redactions of any
information for which you are seeking confidential treatment (i.e., the
only information that should be unredacted is information for which you
are not seeking confidential treatment).
NHTSA is currently treating electronic submission as an acceptable
method for submitting confidential business information to the agency
under part 512. Please do not send a hardcopy of a request for
confidential treatment to NHTSA's headquarters. The request should be
sent to Dan Rabinovitz in NHTSA's Office of the Chief Counsel (NCC) at
[email protected]. You may either submit your request via email
or request a secure file transfer link. Manufacturers or any companies
that already have a Confidential Business Information (CBI) Portal
account or an Enterprise Account with NHTSA should use the CBI Portal
for their submission. If you submit a CBI request, please also email a
courtesy copy of the request to Mr. David Jasinski at
[email protected].
Will the agency consider late comments?
We will consider all comments that Docket Management receives
before the close of business on the comment closing date indicated
above under DATES. To the extent possible, we will also consider
comments that Docket Management receives after that date. If Docket
Management receives a comment too late for us to consider in developing
the final rule, we will consider that comment as an informal suggestion
for future rulemaking action.
How can I read the comments submitted by other people?
You may read the comments received by Docket Management at the
address given above under ADDRESSES. The hours of the Docket are
indicated above in the same location. You may also see the comments on
the internet. To read the comments on the internet, go to
www.regulations.gov. Follow the online instructions for accessing the
dockets.
Please note that, even after the comment closing date, we will
continue to file relevant information in the Docket as it becomes
available. Further, some people may submit late comments. Accordingly,
we recommend that you periodically check the Docket for new material.
List of Subjects in 49 CFR Part 571
Motor vehicle safety, Motor vehicles.
Proposed Regulatory Text
In consideration of the foregoing, NHTSA proposes to amend 49 CFR
part 571 as set forth below.
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, 30117, and 30166;
delegation of authority at 49 CFR 1.95 and 501.8.
0
2. Section 571.135 is revised to read as follows:
Sec. 571.135 Standard No. 135; Light vehicle brake systems.
S1. Scope. This standard specifies requirements for service brake
and associated parking brake systems.
S2. Purpose. The purpose of this standard is to ensure safe braking
performance under normal and emergency driving conditions.
S3. Application. This standard applies to passenger cars. This
standard also applies to multi-purpose passenger vehicles, trucks and
buses with a gross vehicle weight rating (GVWR) of 3,500 kilograms
(7,716 pounds) or less.
S4. Definitions.
Antilock brake system or ABS means a portion of a service brake
system that automatically controls the degree of rotational wheel slip
during braking by:
(1) Sensing the rate of angular rotation of the wheels;
(2) Transmitting signals regarding the rate of wheel angular
rotation to one or more controlling devices which interpret those
signals and generate responsive controlling output signals; and
(3) Transmitting those controlling signals to one or more modulator
devices which adjust brake actuating forces in response to those
signals.
Backup system means a portion of a service brake system, such as a
pump, that automatically supplies energy in the event of a primary
brake power source failure.
Brake power assist unit means a device installed in a hydraulic
brake system that reduces the amount of muscular force that a driver
must apply to actuate the system, and that, if inoperative, does not
prevent the driver from braking the vehicle by a continued application
of muscular force on the service brake control.
Brake power unit means a device installed in a brake system that
provides the energy required to actuate the brakes, either directly or
indirectly through an auxiliary device, with any driver action
consisting only of modulating the energy application level.
Electric vehicle or EV means a motor vehicle that is powered by an
electric motor drawing current from rechargeable storage batteries,
fuel cells, or other portable sources of electrical current, and which
may include a non-electrical source of power designed to charge
batteries and components thereof.
Electrically-actuated service brakes means service brakes that
utilize electrical energy to actuate the foundation brakes.
Functional failure means a failure of a component (either
electrical or mechanical in nature) which renders the system totally or
partially inoperative yet the structural integrity of the system is
maintained.
Hydraulic brake system means a system that uses hydraulic fluid as
a medium for transmitting force from a service brake control to the
service brake and that may incorporate a brake power assist unit, or a
brake power unit.
Initial brake temperature or IBT means the average temperature of
the service brakes on the hottest axle of the vehicle 0.32 km (0.2
miles) before any brake application.
Lightly loaded vehicle weight or LLVW means unloaded vehicle weight
plus the weight of a mass of 180 kg (396 pounds), including any
occupant and instrumentation.
Maximum speed of a vehicle or VMax means the highest speed
attainable by accelerating at a maximum rate from a standing start for
a distance of 3.2 km (2 miles) on a level surface, with the vehicle at
its LLVW, and, if an EV, with the propulsion batteries at a state of
charge of not less than 95 percent at the beginning of the run.
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 braking torque
is progressively increased.
Pressure component means a brake system component that contains the
brake system fluid and controls or senses the fluid pressure.
Regenerative braking system or RBS means an electrical energy
system that is installed in an EV for recovering or dissipating kinetic
energy, and which uses the propulsion motor(s) as a retarder for
partial braking of the EV while returning electrical energy to the
propulsion battery(s) or dissipating electrical energy.
[[Page 38603]]
Service brake control means the vehicle component used to activate
a service brake system. For a vehicle with manually operated driving
controls, this is a foot-operated pedal. For a vehicle without manually
operated driving controls, this is the vehicle component that
translates the electronic braking command into mechanical input to the
service brake system.
Snub means the braking deceleration of a vehicle from a higher
reference speed to a lower reference speed that is greater than zero.
Split service brake system means a brake system consisting of two
or more subsystems actuated by a single control, designed so that a
single failure in any subsystem (such as a leakage-type failure of a
pressure component of a hydraulic subsystem except structural failure
of a housing that is common to two or more subsystems, or an electrical
failure in an electric subsystem) does not impair the operation of any
other subsystem.
Stopping distance means the distance traveled by a vehicle from the
point of initial application of force to the service brake control to
the point at which the vehicle reaches a full stop, if the vehicle has
manually operated driving controls. For a vehicle without manually
operated driving controls, stopping distance means the distance
traveled by the vehicle from the point of initial transmission of an
electronic command signal to the service brake control to the point at
which the vehicle reaches a full stop.
Variable brake proportioning system means a system that has one or
more proportioning devices which automatically change the brake
pressure ratio between any two or more wheels to compensate for changes
in wheel loading due to static load changes and/or dynamic weight
transfer, or due to deceleration.
Wheel lockup means 100 percent wheel slip.
S5. Equipment requirements.
S5.1. Service brake system. Each vehicle must be equipped with a
service brake system acting on all wheels.
S5.1.1. Wear adjustment. Wear of the service brakes must be
compensated for by means of a system of automatic adjustment.
S5.1.2. Wear status. The wear condition of all service brakes must
be indicated by either:
(a) Acoustic or optical devices warning the driver at his or her
driving position when lining replacement is necessary, or
(b) A means of visually checking the degree of brake lining wear,
from the outside or underside of the vehicle, utilizing only the tools
or equipment normally supplied with the vehicle. The removal of wheels
is permitted for this purpose.
S5.1.3. Regenerative braking system.
(a) For an EV equipped with RBS and a service brake pedal, the RBS
is considered to be part of the service brake system if it is
automatically activated by an application of the service brake pedal,
if there is no means provided for the driver to disconnect or otherwise
deactivate it, and if it is activated in all transmission positions,
including neutral.
(b) For an EV equipped with RBS and without manually operated
driving controls, the RBS is considered to be part of the service brake
system.
(c) For an EV that is equipped with both ABS and RBS that is part
of the service brake system, the ABS must control the RBS.
S5.2. Parking brake system. Each vehicle must be equipped with a
parking brake system with solely mechanical means to retain engagement.
S5.3. Controls.
S5.3.1.
(a) The parking brake must be controlled independently of the
service brakes.
(b) For vehicles with manually operated driving controls, the
service brakes must be activated by means of a foot pedal, and the
parking brake must be operable by either a hand or foot control.
(c) For vehicles without manually operated driving controls, the
service brake control and parking brake control must be activated by
on-board systems.
S5.3.2. A control to disable the ABS, either fully or partially, is
prohibited.
S5.4. Reservoirs.
S5.4.1. Master cylinder reservoirs. A master cylinder must have a
reservoir compartment for each service brake subsystem serviced by the
master cylinder. Loss of fluid from one compartment must not result in
a complete loss of brake fluid from another compartment.
S5.4.2. Reservoir capacity. Reservoirs, whether for master
cylinders or other type systems, must have a total minimum capacity
equivalent to the fluid displacement resulting when all the wheel
cylinders or caliper pistons serviced by the reservoirs move from a new
lining, fully retracted position (as adjusted initially to the
manufacturer's recommended setting) to a fully worn, fully applied
position, as determined in accordance with S7.17(c) of this standard.
Reservoirs must have completely separate compartments for each
subsystem except that in reservoir systems utilizing a portion of the
reservoir for a common supply to two or more subsystems, individual
partial compartments must each have a minimum volume of fluid equal to
at least the volume displaced by the master cylinder piston servicing
the subsystem, during a full stroke of the piston. Each brake power
unit reservoir servicing only the brake system must have a minimum
capacity equivalent to the fluid displacement required to charge the
system piston(s) or accumulator(s) to normal operating pressure plus
the displacement resulting when all the wheel cylinders or caliper
pistons serviced by the reservoir or accumulator(s) move from a new
lining, fully retracted position (as adjusted initially to the
manufacturer's recommended setting) to a fully worn, fully applied
position.
S5.4.3. Reservoir labeling. Each vehicle equipped with hydraulic
brakes must have a brake fluid warning statement that reads as follows,
in letters at least 3.2 mm (\1/8\ inch) high: ``WARNING: Clean filler
cap before removing. Use only __ fluid from a sealed container.''
(Inserting the recommended type of brake fluid as specified in 49 CFR
571.116, e.g., ``DOT 3.'') The lettering must be:
(a) Permanently affixed, engraved or embossed;
(b) Located so as to be visible by direct view, either on or within
100 mm (3.94 inches) of the brake fluid reservoir filler plug or cap;
and
(c) Of a color that contrasts with its background, if it is not
engraved or embossed.
S5.4.4. Fluid level indication. Brake fluid reservoirs must be so
constructed that the level of fluid can be checked without need for the
reservoir to be opened. This requirement is deemed to have been met if
the vehicle is equipped with a transparent brake fluid reservoir or a
brake fluid level indicator meeting the requirements of S5.5.1(a)(1).
S5.5. Brake system warning telltales. Each vehicle must have one or
more visual brake system warning telltales which meet the requirements
of S5.5.1 through S5.5.5. For vehicles with manually operated driving
controls, all brake system warning telltales must be mounted in front
of and in clear view of the driver. For vehicles without manually
operated driving controls, all brake system warning telltales must be
in clear view of all designated seating positions. In addition, a
vehicle manufactured without a split service brake system must be
equipped with an auditory warning signal that activates under the
conditions specified in S5.5.1(a).
[[Page 38604]]
S5.5.1. Activation. A telltale must be activated when the vehicle
power (ignition or start) switch is in the ``on'' (``run'') state and
whenever any of conditions (a) through (g) occur:
(a) A gross loss of fluid or fluid pressure (such as caused by
rupture of a brake line but not by a structural failure of a housing
that is common to two or more subsystems) as indicated by one of the
following conditions (chosen at the option of the manufacturer):
(1) A drop in the level of the brake fluid in any master cylinder
reservoir compartment to less than the recommended safe level specified
by the manufacturer or to one-fourth of the fluid capacity of that
reservoir compartment, whichever is greater.
(2) For vehicles equipped with a split service brake system, a
differential pressure of 1.5 MPa (218 psi) between the intact and
failed brake subsystems measured at a master cylinder outlet or a slave
cylinder outlet.
(3) A drop in the supply pressure in a brake power unit to one-half
of the normal system pressure.
(b) Any electrical functional failure in an antilock or variable
brake proportioning system.
(c) Application of the parking brake, except in vehicles without
manually operated driving controls.
(d) Brake lining wear-out, if the manufacturer has elected to use
an electrical device to provide an optical warning to meet the
requirements of S5.1.2(a).
(e) For a vehicle with electrically-actuated service brakes,
failure of the source of electric power to those brakes, or diminution
of state of charge of the batteries to less than a level specified by
the manufacturer for the purpose of warning a driver of degraded brake
performance.
(f) For a vehicle with electric transmission of the service brake
control signal, failure of a brake control circuit.
(g) For an EV with a regenerative braking system that is part of
the service brake system, failure of the RBS.
S5.5.2. Function check.
(a) All telltales must be activated as a check function by either:
(1) Automatic activation when the vehicle power (ignition or start)
switch is transitioned to the ``on'' (``run'') state when the engine is
not running, or when the vehicle power (ignition or start) switch is in
a state between ``on'' (``run'') and ``start'' that is designated by
the manufacturer as a check state, or
(2) A single manual action by the driver, such as momentary
activation of a test button or switch mounted on the instrument panel
in front of and in clear view of the driver, or, in the case of a
telltale for application of the parking brake, by applying the parking
brake when the vehicle power (ignition or start) switch is in the
``on'' (``run'') state.
(b) In the case of a vehicle that has an interlock device that
prevents the engine from being started under one or more conditions,
check functions meeting the requirements of S5.5.2(a) need not be
operational under any condition in which the engine cannot be started.
(c) The manufacturer must explain the brake check function test
procedure in the owner's manual.
S5.5.3. Duration. Each telltale activated due to a condition
specified in S5.5.1 must remain activated as long as the condition
exists, whenever the vehicle power (ignition or start) switch is in the
``on'' (``run'') state, whether or not the engine is running.
S5.5.4. Function. When a telltale is activated, it may be
continuous or flashing, except that the telltale on a vehicle not
equipped with a split service brake system must be flashing. The
auditory warning required for a vehicle manufactured without a split
service brake system may be continuous or intermittent.
S5.5.5. Labeling.
(a) Each telltale must display a word or words in accordance with
the requirements of Standard No. 101 (49 CFR 571.101) and this section,
which must be legible to the driver under all daytime and nighttime
conditions when activated. Unless otherwise specified, the words must
have letters not less than 3.2 mm (\1/8\ inch) high and the letters and
background must be of contrasting colors, one of which is red. Words or
symbols in addition to those required by Standard No. 101 and this
section may be provided for purposes of clarity.
(b) Vehicles manufactured with a split service brake system may use
a common brake warning telltale to indicate two or more of the
functions described in S5.5.1(a) through S5.5.1(g). If a common
telltale is used, it must display the word ``Brake.''
(c) A vehicle manufactured without a split service brake system
must use a separate telltale to indicate the failure condition in
S5.5.1(a). This telltale must display the words ``STOP--BRAKE FAILURE''
in block capital letters not less than 6.4 mm (14 inch) in height.
(d) If separate telltales are used for one or more of the
conditions described in S5.5.1(a) through S5.5.1(g), the telltales must
display the following wording:
(1) If a separate telltale is provided for the low brake fluid
condition in S5.5.1(a)(1), the words ``Brake Fluid'' must be used
except for vehicles using hydraulic system mineral oil.
(2) If a separate telltale is provided for the gross loss of
pressure condition in S5.5.1(a)(2), the words ``Brake Pressure'' must
be used.
(3) If a separate telltale is provided for the condition specified
in S5.5.1(b), the letters and background must be of contrasting colors,
one of which is yellow. The telltale must be labeled with the words
``Antilock'' or ``Anti-lock'' or ``ABS''; or ``Brake Proportioning,''
in accordance with Table 1 of Standard No. 101.
(4) If a separate telltale is provided for application of the
parking brake as specified for S5.5.1(c), the single word ``Park'' or
the words ``Parking Brake'' may be used.
(5) If a separate telltale is provided to indicate brake lining
wear-out as specified in S5.5.1(d), the words ``Brake Wear'' must be
used.
(6) If a separate telltale is provided for the condition specified
in S5.5.1(g), the letters and background must be of contrasting colors,
one of which is yellow. The telltale must be labeled with the symbol
``RBS.'' RBS failure in a system that is part of the service brake
system may also be indicated by a yellow lamp that also indicates
``ABS'' failure and displays the symbol ``ABS/RBS.''
(7) If a separate telltale is provided for any other function, the
display must include the word ``Brake'' and the appropriate additional
labeling.
S5.6. Brake system integrity. Each vehicle must meet the complete
performance requirements of this standard without:
(a) Detachment or fracture of any component of the braking system,
such as brake springs and brake shoes or disc pad facings other than
minor cracks that do not impair attachment of the friction facings. All
mechanical components of the braking system must be intact and
functional. Friction facing tearout (complete detachment of lining)
must not exceed 10 percent of the lining on any single frictional
element.
(b) Any visible brake fluid or lubricant on the friction surface of
the brake, or leakage at the master cylinder or brake power unit
reservoir cover, seal, and filler openings.
S6. General test conditions. Each vehicle must meet the performance
requirements specified in S7 under the following test conditions and in
accordance with the test procedures and test sequence specified. Where
a range of conditions is specified, the vehicle must meet the
requirements at all points within the range.
S6.1. Ambient conditions.
[[Page 38605]]
S6.1.1. Ambient temperature. The ambient temperature is any
temperature between 0 [deg]C (32 [deg]F) and 40 [deg]C (104 [deg]F).
S6.1.2. Wind speed. The wind speed is not greater than 5 m/s (11.2
mph).
S6.2. Road test surface.
S6.2.1. Pavement friction. Unless otherwise specified, the road
test surface produces a peak friction coefficient (PFC) of 1.02 when
measured using an ASTM F2493 standard reference test tire, in
accordance with ASTM E1337-19 (incorporated by reference, see Sec.
571.5), at a speed of 64.4 km/h (40 mph), without water delivery.
S6.2.2. Gradient. Except for the parking brake gradient holding
test, the test surface has no more than a 1 percent gradient in the
direction of testing and no more than a 2 percent gradient
perpendicular to the direction of testing.
S6.2.3. Lane width. Road tests are conducted on a test lane 3.5 m
(11.5 ft) wide.
S6.3. Vehicle conditions.
S6.3.1. Vehicle weight.
S6.3.1.1. For the tests at GVWR, the vehicle is loaded to its GVWR
such that the weight on each axle as measured at the tire-ground
interface is in proportion to its gross axle weight rating, with the
fuel tank filled to 100 percent of capacity. However, if the weight on
any axle of a vehicle at LLVW exceeds the axle's proportional share of
the GVWR, the load required to reach GVWR is placed so that the weight
on that axle remains the same as at LLVW.
S6.3.1.2. For the test at LLVW, the vehicle is loaded to its LLVW
such that the added weight is distributed in the front passenger seat
area.
S6.3.2. Fuel tank loading. The fuel tank is filled to 100 percent
of capacity at the beginning of testing and may not be less than 75
percent of capacity during any part of the testing.
S6.3.3. Lining preparation. At the beginning of preparation for the
road tests, the brakes of the vehicle are in the same condition as when
the vehicle was manufactured. No burnishing or other special
preparation is allowed, unless all vehicles sold to the public are
similarly prepared as a part of the manufacturing process.
S6.3.4. Adjustments and repairs. These requirements must be met
without replacing any brake system parts or making any adjustments to
the brake system except as specified in this standard. Where brake
adjustments are specified (S7.1.3), adjust the brakes, including the
parking brakes, in accordance with the manufacturer's recommendation.
No brake adjustments are allowed during or between subsequent tests in
the test sequence.
S6.3.5. Automatic brake adjusters. Automatic adjusters are
operational throughout the entire test sequence. They may be adjusted
either manually or by other means, as recommended by the manufacturer,
only prior to the beginning of the road test sequence. S6.3.6. Antilock
brake system (ABS). The ABS is fully operational for all tests, except
where specified in the following sections.
S6.3.7. Variable brake proportioning valve. If a vehicle is
equipped with a variable brake proportioning system, the proportioning
valve is fully operational for all tests except the test for failed
variable brake proportioning system.
S6.3.8. Tire inflation pressure. Tires are inflated to the pressure
recommended by the vehicle manufacturer for the GVWR of the vehicle.
S6.3.9. Engine. Engine idle speed and ignition timing are set
according to the manufacturer's recommendations. If the vehicle is
equipped with an adjustable engine speed governor, it is adjusted
according to the manufacturer's recommendations.
S6.3.10. Vehicle openings. All vehicle openings (doors, windows,
hood, trunk, convertible top, cargo doors, etc.) are closed except as
required for instrumentation purposes.
S6.3.11. State of charge of batteries for EVs.
S6.3.11.1. The state of charge of the propulsion batteries is
determined in accordance with SAE Recommended Practice J227a (1976)
(incorporated by reference, see Sec. 571.5). The applicable sections
of J227a (1976) are 3.2.1 through 3.2.4, 3.3.1 through 3.3.2.2, 3.4.1
and 3.4.2, 4.2.1, 5.2, 5.2.1 and 5.3.
S6.3.11.2. At the beginning of the burnish procedure (S7.1 of this
standard) in the test sequence, each propulsion battery is at the
maximum state of charge recommended by the manufacturer, as stated in
the vehicle operator's manual or on a label that is permanently
attached to the vehicle, of, if the manufacturer has made no
recommendation, not less than 95 percent. During the 200-stop burnish
procedure, the propulsion batteries are restored to the maximum state
of charge determined as above, after each increment of 40 burnish stops
until the burnish procedure is complete. The batteries may be charged
at a more frequent interval during a particular 40-stop increment only
if the EV is incapable of achieving the initial burnish test speed
during that increment. During the burnish procedure, the propulsion
batteries may be charged by external means or replaced by batteries
that are at a state of charge of not less than 95 percent. For an EV
having a manual control for setting the level of regenerative braking,
the manual control, at the beginning of the burnish procedure, is set
to provide maximum regenerative braking throughout the burnish.
S6.3.11.3. At the beginning of each performance test in the test
sequence (S7.2 through S7.17 of this standard), unless otherwise
specified, an EV's propulsion batteries are at the state of charge
recommended by the manufacturer, as stated in the vehicle operator's
manual or on a label that is permanently attached to the vehicle, or,
if the manufacturer has made no recommendation, at a state of charge of
not less than 95 percent. No further charging of any propulsion battery
occurs during any of the performance tests in the test sequence of this
standard. If the propulsion batteries are depleted during a test
sequence such that the vehicle reaches automatic shut-down, will not
accelerate, or the low state of charge brake warning lamp is
illuminated, the vehicle is to be accelerated to brake test speed by
auxiliary means. If a battery is replaced rather than recharged, the
replacement battery is charged and measured for state of charge in
accordance with these procedures.
S6.3.12. State of charge of batteries for electrically-actuated
service brakes. A vehicle equipped with electrically-actuated service
brakes also performs the following test series. Conduct 10 stopping
distance tests from a speed of 100 kph or the maximum vehicle speed,
whichever is less. At least two of the 10 stopping distances must be
less than or equal to 70 meters. The vehicle is loaded to GVWR and the
transmission is in the neutral position when the service brake control
is actuated and throughout the remainder of the test. Each battery
providing power to the electrically-actuated service brakes, is in a
depleted state of charge for conditions (a), (b), or (c) of this
paragraph as appropriate. An auxiliary means may be used to accelerate
an EV to test speed.
(a) For an EV equipped with electrically-actuated service brakes
deriving power from the propulsion batteries and with automatic shut-
down capability of the propulsion motor(s), the propulsion batteries
are at not more than five percent above the EV actual automatic shut-
down critical value. The critical value is determined by measuring the
state-of-charge of each propulsion battery at the instant that
automatic shut-down occurs.
(b) For an EV equipped with electrically-actuated service brakes
deriving power from the propulsion
[[Page 38606]]
batteries and with no automatic shut-down capability of the propulsion
motor(s), the propulsion batteries are at an average of not more than
five percent above the actual state of charge at which the brake
failure warning signal, required by S5.5.1(e) of this standard, is
illuminated.
(c) For a vehicle which has one or more auxiliary batteries that
provides electrical energy to operate the electrically-actuated service
brakes, each auxiliary battery is at not more than five percent above
the actual state of charge at which the brake failure warning signal,
required by S5.5.1(e) of this standard, is illuminated.
S6.3.13. Electric vehicles.
S6.3.13.1.
(a) For an EV equipped with an RBS that is part of the service
brake system, the RBS is operational during the burnish and all tests,
except for the test of a failed RBS.
(b) For an EV equipped with an RBS that is not part of the service
brake system, the RBS is operational and set to produce the maximum
regenerative braking effect during the burnish, and is disabled during
the test procedures. If the vehicle is equipped with a neutral gear
that automatically disables the RBS, the test procedures which are
designated to be conducted in gear may be conducted in neutral.
S6.3.13.2. For tests conducted ``in neutral,'' the test operator of
an EV with no ``neutral'' position (or other means such as a clutch for
disconnecting the drive train from the propulsion motor(s)) does not
apply any electromotive force to the propulsion motor(s). Any
electromotive force that is applied to the propulsion motor(s)
automatically remains in effect unless otherwise specified by the test
procedure.
S6.4. Brake temperature measurement. 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, as shown in Figure 1. 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
metal rubbing surface of a drum or rotor. For center-grooved shoes or
pads, thermocouples are installed within 3 mm (.12 in) to 6 mm (.24 in)
of the groove and as close to the center as possible.
BILLING CODE 4910-59-P
[GRAPHIC] [TIFF OMITTED] TP26JN26.056
BILLING CODE 4910-59-C
Figure 1--Typical Plug-Type Thermocouple Installations
S6.5. Procedural conditions.
S6.5.1. Brake controls. For a vehicle with a service brake pedal,
all service brake system performance requirements, including the
partial system requirements of S7.7, S7.10 and S7.11, must be met
solely by use of the service brake pedal.
S6.5.2. Test speeds. If a vehicle is incapable of attaining the
specified normal test speed, it is tested at a speed that is a multiple
of 5 km/h (3.1 mph) that is 4 to 8 km/h (2.5 to 5.0 mph) less than its
maximum speed and its performance must be within a stopping distance
given by the formula provided for the specific requirement.
S6.5.3. Stopping distance.
S6.5.3.1. The braking performance of a vehicle is determined by
measuring
[[Page 38607]]
the stopping distance from a given initial speed.
S6.5.3.2. Unless otherwise specified, the vehicle is stopped in the
shortest distance achievable (best effort) on all stops. Where more
than one stop is specified for a given set of test conditions, a
vehicle is deemed to comply with the corresponding stopping distance
requirements if at least one of the stops is made within the prescribed
distance.
S6.5.3.3. In the stopping distance formulas given for each
applicable test (such as S<=0.10V + 0.0060V\2\), S is the maximum
stopping distance in meters, and V is the test speed in km/h.
S6.5.4. Vehicle position and attitude.
S6.5.4.1. The vehicle is aligned in the center of the lane at the
start of each brake application. Steering corrections are permitted
during each stop.
S6.5.4.2. Stops are made without any part of the vehicle leaving
the lane and without rotation of the vehicle about its vertical axis of
more than 15[deg] from the center line of the test lane at
any time during any stop.
S6.5.5. Transmission selector control.
S6.5.5.1. For tests in neutral, a stop or snub is made in
accordance with the following procedures:
(a) Exceed the test speed by 6 to 12 km/h (3.7 to 7.5 mph);
(b) Close the throttle and coast in gear to approximately 3 km/h
(1.9 mph) above the test speed;
(c) Shift to, or select, neutral; and
(d) When the test speed is reached, apply the brakes.
S6.5.5.2. For tests in gear, a stop or snub is made in accordance
with the following procedures:
(a) With the transmission selector in the control position
recommended by the manufacturer for driving on a level surface at the
applicable test speed, exceed the test speed by 6 to 12 km/h (3.7 to
7.5 mph);
(b) Close the throttle and coast in gear; and
(c) When the test speed is reached apply the brakes.
(d) To avoid engine stall, a manual transmission may be shifted to
neutral (or the clutch disengaged) when the vehicle speed is below 30
km/h (18.6 mph).
S6.5.6. Initial brake temperature (IBT). If the lower limit of the
specified IBT for the first stop in a test sequence (other than a
parking brake grade holding test) has not been reached, the brakes are
heated to the IBT by making one or more brake applications from a speed
of 50 km/h (31.1 mph), at a deceleration rate not greater than 3 m/s\2\
(9.8 fps\2\).
S7. Road test procedures and performance requirements. Each vehicle
must meet all the applicable requirements of this section, when tested
according to the conditions and procedures set forth below and in S6,
in the sequence specified in Table 1:
Table 1--Road Test Sequence
------------------------------------------------------------------------
Section
Testing order No.
------------------------------------------------------------------------
Vehicle loaded to GVWR:
1 Burnish.................................................. S7.1
2 Cold effectiveness....................................... S7.5
3 High speed effectiveness................................. S7.6
4 Stops with engine off.................................... S7.7
Vehicle loaded to LLVW:
5 Cold effectiveness....................................... S7.5
6 High speed effectiveness................................. S7.6
7 Failed antilock.......................................... S7.8
8 Failed proportioning valve............................... S7.9
9 Hydraulic circuit failure................................ S7.10
Vehicle loaded to GVWR:
10 Hydraulic circuit failure............................... S7.10
11 Failed antilock......................................... S7.8
12 Failed proportioning valve.............................. S7.9
13 Power brake unit failure................................ S7.11
14 Parking brake........................................... S7.12
15 Heating snubs........................................... S7.13
16 Hot performance......................................... S7.14
17 Brake cooling........................................... S7.15
18 Recovery performance.................................... S7.16
19 Final inspection........................................ S7.17
------------------------------------------------------------------------
S7.1. Burnish.
S7.1.1. General information. Any pretest instrumentation checks are
conducted as part of the burnish procedure, including any necessary
rechecks after instrumentation repair, replacement or adjustment.
Instrumentation check test conditions are in accordance with the
burnish test procedure specified in S7.1.2 and S7.1.3.
S7.1.2. Vehicle conditions.
(a) Vehicle load: GVWR only.
(b) Transmission position: In gear.
S7.1.3. Test conditions and procedures. The road test surface
conditions specified in S6.2 do not apply to the burnish procedure.
(a) IBT: <=100 [deg]C (212 [deg]F).
(b) Test speed: 80 km/h (49.7 mph).
(c) Service brake control: Adjust service brake control as
necessary to maintain specified constant deceleration rate.
(d) Deceleration rate: Maintain a constant deceleration rate of 3.0
m/s\2\ (9.8 fps\2\).
(e) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(f) Number of runs: 200 stops.
(g) Interval between runs: The interval from the start of one
service brake application to the start of the next is either the time
necessary to reduce the IBT to 100 [deg]C (212 [deg]F) or less, or the
distance of 2 km (1.24 miles), whichever occurs first.
(h) Accelerate to 80 km/h (49.7 mph) after each stop and maintain
that speed until making the next stop.
(i) After burnishing, adjust the brakes as specified in S6.3.4.
S7.2. [Reserved]
S7.3. [Reserved]
S7.4. [Reserved]
S7.5. Cold effectiveness.
S7.5.1. Vehicle conditions.
(a) Vehicle load: GVWR and LLVW.
(b) Transmission position: In neutral.
S7.5.2. Test conditions and procedures.
(a) IBT: Between 65 [deg]C (149 [deg]F) and 100 [deg]C (212
[deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Service brake control: For vehicles with a service brake pedal,
the applied pedal force is between 65 N (14.6 lbs) and 500 N (112.4
lbs). For vehicles without manually operated driving controls, the
service brake control is activated in accordance with manufacturer
specifications.
(d) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
(g) For each stop, bring the vehicle to test speed and then stop
the vehicle under the specified conditions.
S7.5.3. Performance requirements.
(a) Stopping distance for 100 km/h test speed: <=70m (230 ft).
(b) Stopping distance for reduced test speed: S<=0.10V +
0.0060V\2\.
S7.6. High speed effectiveness. This test is not run if vehicle
maximum speed is less than or equal to 125 km/h (77.7 mph).
S7.6.1. Vehicle conditions.
(a) Vehicle load: GVWR and LLVW.
(b) Transmission position: In gear.
S7.6.2. Test conditions and procedures.
(a) IBT: Between 65 [deg]C (149 [deg]F) and 100 [deg]C (212
[deg]F).
(b) Test speed: The test speed is 160 km/h (99.4 mph) or 80 percent
of Vmax, whichever is slower.
(c) Service brake control: For vehicles with a service brake pedal,
the applied pedal force is between 65 N (14.6 lbs) and 500 N (112.4
lbs). For vehicles without manually operated driving controls, the
service brake control is activated in accordance with manufacturer
specifications.
(d) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
[[Page 38608]]
S7.6.3. Performance requirements.
Stopping distance: S<=0.10V + 0.0067V\2\.
S7.7. Stops with Engine Off.
S7.7.1. General information. This test is for vehicles equipped
with one or more brake power units or brake power assist units. This
test is also for EVs.
S7.7.2. Vehicle conditions.
(a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
(c) Vehicle engine: Off (not running).
(d) Vehicle power switch: May be returned to the ``on'' state after
turning the engine off, or a device may be used to ``kill'' the engine
while leaving the power switch in the ``on'' state.
(e) For an EV, this test is conducted with no electrical power
supplied to the vehicle's propulsion motor(s), but with the RBS and
brake power or power assist still operating, unless cutting off the
supply of electrical power to the propulsion motor(s) also disables
those systems.
S7.7.3. Test conditions and procedures.
(a) IBT: Between 65 [deg]C (149 [deg]F) and 100 [deg]C (212
[deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Service brake control: For vehicles with a service brake pedal,
the applied pedal force is between 65 N (14.6 lbs) and 500 N (112.4
lbs). For vehicles without manually operated driving controls, the
service brake control is activated in accordance with manufacturer
specifications.
(d) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
(g) All system reservoirs (brake power and/or assist units) are
fully charged and the vehicle's engine is off (not running) at the
beginning of each stop.
S7.7.4. Performance requirements.
(a) Stopping distance for 100 km/h test speed: <=70m (230 ft.)
(b) Stopping distance for reduced test speed: S <=0.10V +
0.0060V\2\.
S7.8. Antilock functional failure.
S7.8.1. Vehicle conditions.
(a) Vehicle loading: LLVW and GVWR.
(b) Transmission position: In neutral.
S7.8.2. Test conditions and procedures.
(a) IBT: Between 65 [deg]C (149 [deg]F) and 100 [deg]C (212
[deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Service brake control: For vehicles with a service brake pedal,
the applied pedal force is between 65 N (14.6 lbs) and 500 N (112.4
lbs). For vehicles without manually operated driving controls, the
service brake control is activated in accordance with manufacturer
specifications.
(d) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
(g) Functional failure simulation:
(1) Disconnect the functional power source, or any other electrical
connector that creates a functional failure when disconnected.
(2) Determine whether the brake system telltale is activated when
any electrical functional failure of the antilock system is created.
(3) Restore the system to normal at the completion of this test.
(h) If more than one antilock brake subsystem is provided, repeat
test for each subsystem.
S7.8.3. Performance requirements. For service brakes on a vehicle
equipped with one or more antilock systems, in the event of any single
functional failure in any such system, the service brake system must
continue to operate and must stop the vehicle as specified in S7.
8.3(a) or S7. 8.3(b).
(a) Stopping distance for 100 km/h test speed: <=85 m (279 ft).
(b) Stopping distance for reduced test speed: S <=0.10V +
0.0075V\2\.
S7.9. Variable brake proportioning system functional failure.
S7.9.1. Vehicle conditions.
(a) Vehicle load: LLVW and GVWR.
(b) Transmission position: In neutral.
S7.9.2. Test conditions and procedures.
(a) IBT: Between 65 [deg]C (149 [deg]F) and 100 [deg]C (212
[deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Service brake control: For vehicles with a service brake pedal,
the applied pedal force is between 65 N (14.6 lbs) and 500 N (112.4
lbs). For vehicles without manually operated driving controls, the
service brake control is activated in accordance with manufacturer
specifications.
(d) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
(g) Functional failure simulation:
(1) Disconnect the functional power source or mechanical linkage to
render the variable brake proportioning system inoperative.
(2) If the system utilizes electrical components, determine whether
the brake system telltale is activated when any electrical functional
failure of the variable proportioning system is created.
(3) Restore the system to normal at the completion of this test.
(h) If more than one variable brake proportioning subsystem is
provided, repeat the test for each subsystem.
S7.9.3. Performance requirements. The service brakes on a vehicle
equipped with one or more variable brake proportioning systems, in the
event of any single functional failure in any such system, must
continue to operate and must stop the vehicle as specified in S7.9.3(a)
or S7.9.3(b).
(a) Stopping distance for 100 km/h test speed: <=110 m (361 ft).
(b) Stopping distance for reduced test speed: S <=0.10V +
0.0100V\2\.
S7.10. Hydraulic circuit failure.
S7.10.1. General information. This test is for vehicles
manufactured with or without a split service brake system.
S7.10.2. Vehicle conditions.
(a) Vehicle load: LLVW and GVWR.
(b) Transmission position: In neutral.
S7.10.3. Test conditions and procedures.
(a) IBT: Between 65 [deg]C (149 [deg]F) and 100 [deg]C (212
[deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Service brake control: For vehicles with a service brake pedal,
the applied pedal force is between 65 N (14.6 lbs) and 500 N (112.4
lbs). For vehicles without manually operated driving controls, the
service brake control is activated in accordance with manufacturer
specifications.
(d) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(e) Test surface: PFC of 1.02.
(f) Alter the service brake system to produce any single failure.
For a hydraulic circuit, this may be any single rupture or leakage type
failure, other than a structural failure of a housing that is common to
two or more subsystems. For a vehicle in which the brake signal is
transmitted electrically between the brake pedal and some or all of the
foundation brakes, regardless of the means of actuation of the
foundation brakes, this may be any single failure in any circuit that
electrically transmits the brake signal. For an EV with RBS that is
part of the service brake system, this may be any single failure in the
RBS.
(g) Verify the brake warning telltale has been activated. For a
hydraulic circuit failure, record the brake fluid level, differential
pressure, or supply pressure drop necessary to activate the brake
warning telltale.
(h) Number of runs: After the brake warning telltale has been
activated, make the following stops depending on the type of brake
system:
(1) 4 stops for a split service brake system.
[[Page 38609]]
(2) 10 consecutive stops for a non-split service brake system.
(i) For vehicles with a service brake pedal, each stop is made by a
continuous application of the service brake control.
(j) Restore the service brake system to normal at the completion of
this test.
(k) Repeat the entire sequence for each of the other subsystems.
S7.10.4. Performance requirements. For vehicles manufactured with a
split service brake system, in the event of any failure in a single
subsystem, as specified in S7.10.3(f) of this standard, and after
activation of the brake system telltale as specified in S5.5.1, the
remaining portions of the service brake system must continue to operate
and must stop the vehicle as specified in S7.10.4(a) or S7.10.4(b). For
vehicles not manufactured with a split service brake system, in the
event of any failure in any component of the service brake system, as
specified in S7.10.3(f), and after activation of the brake system
telltale as specified in S5.5.1 of this standard, the vehicle must stop
10 times consecutively as specified in S7.10.4(a) or S7.10.4(b).
(a) Stopping distance from 100 km/h test speed: <=168 m (551 ft).
(b) Stopping distance for reduced test speed: S <=0.10V +
0.0158V\2\.
S7.11. Brake power unit or brake power assist unit inoperative
(System depleted).
S7.11.1. General information. This test is for vehicles equipped
with one or more brake power units or brake power assist units.
S7.11.2. Vehicle conditions.
(a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
S7.11.3. Test conditions and procedures.
(a) IBT: Between 65 [deg]C (149 [deg]F) and 100 [deg]C (212
[deg]F).
(b) Test speed: 100 km/h (62.1 mph).
(c) Service brake control: For vehicles with a service brake pedal,
the applied pedal force is between 65 N (14.6 lbs) and 500 N (112.4
lbs). For vehicles without manually operated driving controls, the
service brake control is activated in accordance with manufacturer
specifications.
(d) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 6 stops.
(f) Test surface: PFC of 1.02.
(g) Disconnect the primary source of power for one brake power
assist unit or brake power unit, or one of the brake power unit or
brake power assist unit subsystems if two or more subsystems are
provided.
(h) If the brake power unit or power assist unit operates in
conjunction with a backup system and the backup system is automatically
activated in the event of a primary power service failure, the backup
system is operative during this test.
(i) Exhaust any residual brake power reserve capability of the
disconnected system.
(j) Make each of the 6 stops. For vehicles equipped with a service
brake pedal, stop the vehicle with a continuous application of the
service brake control.
(k) Restore the system to normal at completion of this test.
(l) For vehicles equipped with more than one brake power unit or
brake power assist unit, conduct tests for each in turn.
(m) For vehicles with electrically-actuated service brakes (brake
power unit), this test is conducted with any single electrical failure
in the electrically-actuated service brakes instead of a failure of any
other brake power or brake power assist unit, and all other systems
intact.
S7.11.4. Performance requirements. The service brakes on a vehicle
equipped with one or more brake power assist units or brake power
units, with one such unit inoperative and depleted of all reserve
capability, must stop the vehicle as specified in S7.11.4(a) or
S7.11.4(b).
(a) Stopping distance from 100 km/h test speed: <=168 m (551 ft).
(b) Stopping distance for reduced test speed: S <=0.10V +
0.0158V\2\.
S7.12. Parking brake.
S7.12.1. Vehicle conditions.
(a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
(c) Parking brake burnish:
(1) For vehicles with parking brake systems not utilizing the
service friction elements, the friction elements of such a system are
burnished prior to the parking brake test according to the published
recommendations furnished to the purchaser by the manufacturer.
(2) If no recommendations are furnished, the vehicle's parking
brake system is tested in an unburnished condition.
(d) Parking brake applications: 1 application and up to 2
reapplications, if necessary.
S7.12.2. Test conditions and procedures.
(a) IBT:
(1) Parking brake systems utilizing service brake friction
materials are tested with the IBT <=100 [deg]C (212 [deg]F) and have no
additional burnishing or artificial heating prior to the start of the
parking brake test.
(2) Parking brake systems utilizing non-service brake friction
materials are tested with the friction materials at ambient temperature
at the start of the test. The friction materials have no additional
burnishing or artificial heating prior to or during the parking brake
test.
(b) Parking brake control force for vehicles equipped with a hand-
or foot-operated parking brake control: Hand control <=400 N (89.9
lbs); foot control <=500 N (112.4 lbs).
(c) Hand force measurement locations: The force required for
actuation of a hand-operated brake system is measured at the center of
the hand grip area or at a distance of 40 mm (1.57 in) from the end of
the actuation lever as illustrated in Figure 3.
(d) Parking brake applications: 1 application and up to 2
reapplications, if necessary.
BILLING CODE 4910-59-P
[[Page 38610]]
[GRAPHIC] [TIFF OMITTED] TP26JN26.057
BILLING CODE 4910-59-C
Figure 3--Location for Measuring Brake Application Force (Hand Brake)
(e) Test surface gradient: 20 percent grade.
(f) Drive the vehicle onto the grade with the longitudinal axis of
the vehicle in the direction of the slope of the grade.
(g) Stop the vehicle and hold it stationary by applying the service
brake and place the transmission in neutral.
(h) With the service brake applied sufficiently to just keep the
vehicle from rolling, apply the parking brake as specified in
S7.12.2(i) or S7.12.2(j).
(i) For a vehicle equipped with mechanically-applied parking
brakes, make a single application of the parking brake control with a
force not exceeding the limits specified in S7.12.2(b). For a vehicle
using an electrically-activated parking brake, apply the parking brake
by activating the parking brake control.
(j) In the case of a parking brake system that does not allow
application of the specified force in a single application, a series of
applications may be made to achieve the specified force.
(k) Following the application of the parking brakes, release all
force on the service brake control and, if the vehicle remains
stationary, start the measurement of time.
(l) If the vehicle does not remain stationary, reapplication of a
force to the parking brake control at the level specified in S7.12.2(b)
as appropriate for the vehicle being tested (without release of the
ratcheting or other holding mechanism of the parking brake) is used up
to two times to attain a stationary position.
(m) Verify the operation of the parking brake application telltale.
(n) Following observation of the vehicle in a stationary condition
for the specified time in one direction, repeat the same test procedure
with the vehicle orientation in the opposite direction on the same
grade.
S7.12.3. Performance requirement. The parking brake system must
hold the vehicle stationary for 5 minutes in both a forward and reverse
direction on the grade.
S7.13. Heating snubs.
S7.13.1. General information. The purpose of the snubs is to heat
up the brakes in preparation for the hot performance test which follows
immediately.
S7.13.2. Vehicle conditions.
(a) Vehicle load: GVWR only.
(b) Transmission position: In gear.
S7.13.3. Test conditions and procedures.
(a) IBT:
(1) Establish an IBT before the first brake application (snub)
between 55 [deg]C (131 [deg]F) and 65 [deg]C (149 [deg]F).
(2) IBT before subsequent snubs are those occurring at the distance
intervals.
(b) Number of snubs: 15.
(c) Test speeds: The initial speed for each snub is 120 km/h (74.6
mph) or 80 percent of Vmax, whichever is slower. Each snub is
terminated at one-half the initial speed.
(d) Deceleration rate:
(1) Maintain a constant deceleration rate of 3.0 m/s\2\ (9.8
fps\2\).
(2) Attain the specified deceleration within one second and
maintain it for the remainder of the snub.
(e) Service brake control: Adjust as necessary to maintain
specified constant deceleration rate.
(f) Time interval: Maintain an interval of 45 seconds between the
start of brake applications (snubs).
(g) Accelerate as rapidly as possible to the initial test speed
immediately after each snub.
(h) Immediately after the 15th snub, accelerate to 100 km/h (62.1
mph) and commence the hot performance test.
S7.14. Hot performance.
S7.14.1. General information. The hot performance test is conducted
immediately after completion of the 15th heating snub.
[[Page 38611]]
S7.14.2. Vehicle conditions.
(a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
S7.14.3. Test conditions and procedures.
(a) IBT: Temperature achieved at completion of heating snubs.
(b) Test speed: 100 km/h (62.1 mph).
(c) Service brake control:
(1) For vehicles with a service brake pedal, the first stop is done
with an average pedal force not greater than the average pedal force
recorded during the shortest GVWR cold effectiveness stop. For vehicles
without a service brake pedal, the first stop is done with an average
control input not greater than the average control input recorded
during the shortest GVWR cold effectiveness stop.
(2) For vehicles with a service brake pedal, the second stop is
done with a pedal force not greater than 500 N (112.4 lbs). For
vehicles without a service brake pedal, the manufacturer's recommended
input is used for the second stop.
(d) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 2 stops.
(f) Immediately after the 15th heating snub, accelerate to 100 km/h
(62.1 mph) and commence the first stop of the hot performance test.
(g) If the vehicle is incapable of attaining 100 km/h, it is tested
at the same speed used for the GVWR cold effectiveness test.
(h) Immediately after completion of the first hot performance stop,
accelerate as rapidly as possible to the specified test speed and
conduct the second hot performance stop.
(i) Immediately after completion of the second hot performance
stop, commence S7.15.
S7.14.4. Performance requirements.
(a) For the first hot stop, the stopping distance must be less than
or equal to a calculated distance which is based on 60 percent of the
deceleration actually achieved on the shortest GVWR cold effectiveness
stop. The following equations are used in calculating the performance
requirement:
[GRAPHIC] [TIFF OMITTED] TP26JN26.058
Where:
dc = the average deceleration actually achieved during
the shortest cold effectiveness stop at GVWR (m/s\2\),
Sc = actual stopping distance measured on the shortest
cold effectiveness stop at GVWR (m), and
V = cold effectiveness test speed (km/h).
(b) In addition to the requirement in S7.14.4(a), the stopping
distance for at least one of the two hot stops must be S <=89 m (292
ft) from a test speed of 100 km/h (62.1 mph) or, for reduced test
speed, S <=0.10V + 0.0079V\2\. The results of the second stop may not
be used to meet the requirements of S7.14.4(a).
S7.15. Brake cooling stops.
S7.15.1. General information. The cooling stops are conducted
immediately after completion of the hot performance test.
S7.15.2. Vehicle conditions.
(a) Vehicle load: GVWR only.
(b) Transmission position: In gear.
S7.15.3. Test conditions and procedures.
(a) IBT: Temperature achieved at completion of hot performance.
(b) Test speed: 50 km/h (31.1 mph).
(c) Service brake control: Adjust as necessary to maintain
specified constant deceleration rate.
(d) Deceleration rate: Maintain a constant deceleration rate of 3.0
m/s\2\ (9.8 fps\2\).
(e) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(f) Number of runs: 4 stops.
(g) Immediately after the hot performance stops drive 1.5 km (0.93
mi) at 50 km/h (31.1 mph) before the first cooling stop.
(h) For the first through the third cooling stops:
(1) After each stop, immediately accelerate at the maximum rate to
50 km/h (31.1 mph).
(2) Maintain that speed until beginning the next stop at a distance
of 1.5 km (0.93 mi) from the beginning of the previous stop.
(i) For the fourth cooling stop:
(1) Immediately after the fourth stop, accelerate at the maximum
rate to 100 km/h (62.1 mph).
(2) Maintain that speed until beginning the recovery performance
stops at a distance of 1.5 km (0.93 mi) after the beginning of the
fourth cooling stop.
S7.16. Recovery performance.
S7.16.1. General information. The recovery performance test is
conducted immediately after completion of the brake cooling stops.
S7.16.2. Vehicle conditions.
(a) Vehicle load: GVWR only.
(b) Transmission position: In neutral.
S7.16.3. Test conditions and procedures.
(a) IBT: Temperature achieved at completion of cooling stops.
(b) Test speed: 100 km/h (62.1 mph).
(c) Service brake control: For vehicles equipped with a service
brake pedal, the average pedal force is no greater than the average
pedal force recorded during the shortest GVWR cold effectiveness stop.
For vehicles without a service brake pedal, the average control input
is no greater than the average control input recorded during the
shortest GVWR cold effectiveness stop.
(d) Wheel lockup: No lockup of any wheel is allowed for longer than
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
(e) Number of runs: 2 stops.
(f) Immediately after the fourth cooling stop, accelerate at the
maximum rate to 100 km/h (62.1 mph).
(g) Maintain that speed until beginning the first recovery
performance stop at a distance of 1.5 km (0.93 mi) after the beginning
of the fourth cooling stop.
[[Page 38612]]
(h) If the vehicle is incapable of attaining 100 km/h, it is tested
at the same speed used for the GVWR cold effectiveness test.
(i) Immediately after completion of the first recovery performance
stop accelerate as rapidly as possible to the specified test speed and
conduct the second recovery performance stop.
S7.16.4. Performance requirements.
The stopping distance, S, for at least one of the two stops must be
within the following limits:
[GRAPHIC] [TIFF OMITTED] TP26JN26.059
where dc and V are defined in S7.14.4(a).
S7.17. Final inspection. Inspect:
(a) The service brake system for detachment or fracture of any
components, such as brake springs and brake shoes or disc pad facings.
(b) The friction surface of the brake, the master cylinder or brake
power unit reservoir cover, and seal and filler openings, for leakage
of brake fluid or lubricant.
(c) The master cylinder or brake power unit reservoir for
compliance with the volume and labeling requirements of S5.4.2 and
S5.4.3. In determining the fully applied worn condition, assume that
the lining is worn to
(1) rivet or bolt heads on riveted or bolted linings or
(2) within 0.8 mm (1/32 inch) of shoe or pad mounting surface on
bonded linings or
(3) the limit recommended by the manufacturer, whichever is larger
relative to the total possible shoe or pad movement. Drums or rotors
are assumed to be at nominal design drum diameter or rotor thickness.
Linings are assumed adjusted for normal operating clearance in the
released position.
(d) The brake system telltales, for compliance with operation in
various key positions, lens color, labeling, and location, in
accordance with S5.5.
Issued in Washington, DC, under authority delegated in 49 CFR
1.95 and 501.7.
Jonathan Morrison,
Administrator.
[FR Doc. 2026-12981 Filed 6-25-26; 8:45 am]
BILLING CODE 4910-59-P