\128\ ISO 7000--Graphical symbols for use on equipment--
Registered symbols.
    \129\ SAE J2400 (info. report, not RP or standard), 2003-08.
Human Factors in Forward Collision Warning Systems: Operating
Characteristics and User Interface Requirements.

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

[GRAPHIC] [TIFF OMITTED] TP06JY23.004

    Because the symbol in SAE J2400 relates the idea of a frontal crash
without depicting a particular forward object, this symbol could
visually represent and apply to scenarios when approaching a lead
vehicle but also scenarios approaching pedestrians or other objects
which may be relevant to AEB systems. To prevent different vehicle
types from having different FCW alerts, NHTSA proposes the same FCW
characteristics and reasoning in both the light vehicle NPRM and this
NPRM. Therefore, NHTSA has taken account of considerations for
pedestrian scenarios, because the light vehicle proposed rule contains
a requirement that FCW and AEB systems function in the case of an
imminent collision with a pedestrian. NHTSA finds the SAE J2400 symbol
to be most applicable to the FCW requirements in this proposal. NHTSA
proposes that FCW visual signals using a symbol must use the SAE J2400
(2003-08) symbol.
    Some other vehicle models employ a word-based visual warning, such
as ``STOP!'' or ``BRAKE!'' SAE J2400 also includes a word-based visual
warning recommendation consisting of the word, ``WARNING.'' A well-
designed warning should instruct people about what to do or what not to
do to avoid a hazard. The potential benefit of a word-based warning for
FCW is that it can communicate to the driver an instruction about what
to do to avoid or mitigate the crash, thereby expediting the driver's
initiation of an appropriate crash avoidance response. However,
Consumer Reports noted in its online ``Guide to forward collision
warning'' that for some models, visual warning word use was found to be
confusing to some drivers surveyed.\130\ Respondents reported a common
complaint that ``their vehicle would issue a visual ``BRAKE'' alert on
the dash, but it wouldn't bring the car to a stop . . .'' This
confusion as to whether the word is meant to communicate what the
driver should do or what the vehicle is doing may stem from drivers
assuming that any information presented within the instrument panel
area is communicating something relating to the vehicle's condition or
state, as symbols presented in that location generally do. Presenting a
word-based warning in a higher location away from the instrument panel,
as recommended by SAE J2400, may be interpreted more accurately by
drivers as well as increase the likelihood of FCW visual warning
perception by drivers.\131\ NHTSA requests comments on this issue and
any available objective research data that relates to the effectiveness
of word-based FCW visual signals in instrument panel versus head-up
display locations. NHTSA also requests comments regarding whether
permitting word-based warnings that are customizable in terms of
language settings is necessary to ensure warning comprehension by all
drivers.
---------------------------------------------------------------------------

    \130\ ``Guide to forward collision warning: How FCW helps
drivers avoid accidents.'' Consumer Reports. https://www.consumerreports.org/car-safety/forward-collision-warning-guide/
(last accessed April 2022).
    \131\ SAE J2400 2003-08 (Information report). Human Factors in
Forward Collision Warning Systems: Operating Characteristics and
User Interface Requirements.
---------------------------------------------------------------------------

    One plausible benefit of a word-based visual warning is that some
word choices that instruct the driver to initiate a particular action,
such as ``STOP!,'' would be fully applicable to lead vehicles and other
obstacles or pedestrians, whereas a symbol containing an image of a
lead vehicle would not be directly applicable to other crash-imminent
scenarios. Although this NPRM does not propose requiring pedestrian
AEB, NHTSA believes the warning should not be directed specifically at
lead vehicle AEB. As the response desired from the driver, to apply the
brakes, the content of the visual warning need not be specific to the
type of forward obstacle, but needs simply to communicate the idea of
an impending forward crash. NHTSA requests comments and any available
research data regarding the use and effectiveness of obstacle-specific
symbols and word-based visual warnings and the relative effectiveness
of word-based visual warnings compared to symbols.
    While many current vehicle models present a visual FCW signal
within the instrument panel, drawing a driver's eyes downward away from
the roadway to the instrument panel during a forward crash-imminent
situation is likely to have a negative impact on the effectiveness of
the driver's response to the FCW. Research indicates that a visual FCW
signal presented in the instrument panel can slow driver response.\132\
The research findings support the SAE J2400 recommendation advising
against the use of instrument panel based visual FCWs.\133\ SAE J2400
(2003-08) states:
---------------------------------------------------------------------------

    \132\ ``Evaluation of Forward Collision Warning System Visual
Alert Candidates and SAE J2400,'' SAE Paper No. 2009-01-0547,
https://trid.trb.org/view/1430473.
    \133\ SAE J2400 2003-08 (Information report). Human Factors in
Forward Collision Warning Systems: Operating Characteristics and
User Interface Requirements.

    Visual warnings shall be located within a 10-degree cone of the
driver's line of sight. Qualitatively, this generally implies a top-
of-dashboard or head-up display location. A conventional dashboard
location shall not be used for the visual warning. The rationale for
this is based on the possibility that an instrument panel-based
---------------------------------------------------------------------------
visual warning may distract the driver from the hazard ahead.

    This FCW visual signal location guidance is also consistent with
ISO 15623, which states that the FCW visual signal shall be presented
in the ``main glance direction.'' Current vehicles equipped with head-
up displays have the ability to present a FCW visual signal within the
driver's forward field of view. Furthermore, some GM vehicles not
equipped with head-up displays currently have the ability to present a
FCW visual signal reflected onto the

windshield in the driver's forward line-of-sight. Despite the FCW
visual signal being considered secondary to the auditory signal, NHTSA
agrees that the effectiveness of a FCW visual signal would be maximized
for both hearing and hearing-impaired drivers if the signal is
presented at a location within the driver's forward field of view above
the instrument panel. To ensure maximum conspicuity of the FCW visual
signal (be it word-based or a symbol), NHTSA proposes that it be
presented within a 10-degree cone of the driver's line of sight. The
line of sight would be based on the forward-looking eye midpoint
(Mf) as described in FMVSS No. 111, ``Rear visibility,''
S14.1.5.
    The FCW visual signal would be required to be red as is generally
used to communicate a dangerous condition and as recommended by ISO
15623 and SAE J2400 (2003-08). Because the FCW visual signal is
intended to be confirmatory for the majority of drivers, the symbol
would be required to be steady burning.
iv. FCW Haptic Signal Discussion
    NHTSA considered also specifying a complementary haptic FCW signal
as part of the proposed FCW specifications. Currently, only a portion
of U.S. vehicles equipped with forward collision warning include a
haptic warning component. For example, General Motors vehicles equipped
with the haptic warning feature can present either a haptic seat pulse
(vibration) or auditory warning based on a driver-selectable setting.
Some other vehicle manufacturers, such as Stellantis and Audi, use a
brake pulse, or brief deceleration of the vehicle, as part of the FCW.
Some Hyundai/Kia models incorporate a haptic steering wheel vibration
into the FCW. As haptic steering wheel signals are used by many lane
keeping features of current vehicles to encourage drivers to steer the
vehicle back toward the center of the lane, providing a haptic FCW
signal via the steering wheel may result in driver confusion and be
less effective in eliciting a timely and beneficial driver response.
    ISO 15623 allows a haptic signal as an alternative to an auditory
signal.\134\ It permits a haptic brake pulse warning with a duration of
less than 1 second when the driver is not already applying the brakes.
ISO 15623 also allows actuation of a seat belt pretensioner as a haptic
FCW signal.
---------------------------------------------------------------------------

    \134\ ISO 15623--Forward vehicle collision warning systems--
Performance requirements and test procedures.
---------------------------------------------------------------------------

    Some research has shown that haptic FCW signals can improve crash
avoidance response. NHTSA research on ``Driver-Vehicle Interfaces for
Advanced Crash Warning Systems'' found that a haptic signal delivered
via the seat belt pretensioner would be beneficial in eliciting an
effective crash avoidance response from the vehicle operator. The
research showed for FCWs issued at 2.1-s time to collision (TTC) that
seat belt pretensioner-based FCW signals elicited the most effective
crash avoidance performance.\135\ Haptic FCW signals led to faster
driver response times than did auditory tonal signals. FCW modality had
a significant effect on participant reaction times and on the speed
reductions resulting from participants' avoidance maneuvers (regardless
of whether a collision ultimately occurred). Brake pulsing or seat belt
tensioning were found to be effective for returning distracted drivers'
attention to the forward roadway and eliciting desirable vehicle
control responses; seat vibration similar to a virtual rumble strip
(vibrating the front of the seat) was not found to rapidly and reliably
return driver attention to the forward roadway within the research.
Similarly, research by Aust (2014) found that ``combining sound with
seat belt jerks or a brake pulse leads to significantly faster response
times than combining the sound with a visual warning'' and stated,
``these results suggest that future FCWs should include a haptic
modality to improve driver performance.'' \136\ Aust (2014) also found
use of a haptic seat belt FCW signal to be slightly more effective (100
ms faster driver response) than a haptic brake pulse in one of two
scenarios (response times were equal in a second scenario). Despite
these promising research results associated with use of a seat belt
based FCW haptic component, NHTSA was unable to identify any current
U.S. vehicle models equipped with a haptic seat belt FCW component.
---------------------------------------------------------------------------

    \135\ Lerner, N., Singer, J., Huey, R., Brown, T., Marshall, D.,
Chrysler, S., . . . & Chiang, D.P. (2015, November). Driver-vehicle
interfaces for advanced crash warning systems: Research on
evaluation methods and warning signals. (Report No. DOT HS 812 208).
Washington, DC: National Highway Traffic Safety Administration.
    \136\ Aust, M. (2014) Effects of Haptic Versus Visual Modalities
When Combined With Sound in Forward Collision Warnings. Driving
Simulation Conference 2014, Paper number 36. Paris, France,
September 4-5, 2014.
---------------------------------------------------------------------------

    Other studies found FCW haptic brake pulses effective at getting a
driver's attention and that drivers are more likely to detect a brake
pulse if it produces a sensation of ``jerk'' or ``self-motion.''
137 138 Kolke reported reaction times shortened by one-third
(approximately 0.3 s, non-significant) when a brake pulse was added to
an audio-visual warning.\139\ One usability drawback is that drivers
tend to report that vehicle brake pulses are too disruptive, which can
lead to unfavorable annoyance.\140\
---------------------------------------------------------------------------

    \137\ Lee, J.D., McGehee, D.V., Brown, T.L., & Nakamoto, J.
(2012). Driver sensitivity to brake pulse duration and magnitude.
Ergonomics, 50(6), 828-836.
    \138\ Brown, S.B., Lee, S.E., Perez, M.A., Doerzaph, Z.R.,
Neale, V.L., & Dingus, T.A. (2005). Effects of haptic brake pulse
warnings on driver behavior during an intersection approach.
Proceedings of the Human Factors and Ergonomics Society 49th Annual
Meeting, 1892-1896.
    \139\ Kolke, Gauss, and Silvestro (2012). Accident reduction
through emergency braking systems in passenger cars. Presentation at
the 8th ADAC/BASt-Symposium ``Driving Safely in Europe.'' October 5,
2012, Workshop B.
    \140\ Campbell, J.L., Brown. J.L., Graving, J.S., Richard, C.M.,
Lichty, M.G., Sanquist, T., . . . & Morgan, J.L. (2016, December).
Human factors design guidance for driver-vehicle interfaces (Report
No. DOT HS 812 360). Washington, DC: National Highway Traffic Safety
Administration.
---------------------------------------------------------------------------

    Presentation of a FCW haptic signal via the driver's seat pan has
also been investigated. NHTSA's ``Human factors design guidance for
driver-vehicle interfaces'' contains best practice information for
implementation of haptic displays, including ``Generating a Detectable
Signal in a Vibrotactile Seat.'' \141\ In a large-scale field test of
FCW and LDW systems on model year 2013 Chevrolet and Cadillac vehicles,
the University of Michigan Transportation Research Institute and GM
found that GM's Safety Alert Seat, which provides haptic seat vibration
pulses, increases driver acceptance of both FCW and LDW systems
compared to auditory signals.\142\
---------------------------------------------------------------------------

    \141\ Campbell, J.L., Brown. J.L., Graving, J.S., Richard, C.M.,
Lichty, M.G., Sanquist, T., . . . & Morgan, J.L. (2016, December).
Human factors design guidance for driver-vehicle interfaces (Report
No. DOT HS 812 360). Washington, DC: National Highway Traffic Safety
Administration.
    \142\ Flannagan, C., LeBlanc, D., Bogard, S., Nobukawa, K.,
Narayanaswamy, P., Leslie, A., Kiefer, R., Marchione, M., Beck, C.,
and Lobes, K. (2016, February), Large-scale field test of forward
collision alert and lane departure warning systems (Report No. DOT
HS 812 247), Washington, DC: National Highway Traffic Safety
Administration.
---------------------------------------------------------------------------

    NHTSA's March 2022 request for comments notice on the NCAP sought
comment on which FCW modalities or modality combinations should receive
credit and asked specific questions regarding haptic signals and
whether certain types should be excluded from consideration (e.g.,
because they may be such a nuisance to drivers that they are more
likely to disable the FCW or AEB system). A preliminary review of
comments on that notice found multiple comments highlighting a need for
more

research relating to FCW signals. The National Transportation Safety
Board highlighted a need for additional information regarding haptic
signals presented in different locations stating ``[w]ithout examining
the efficacy of different means of providing haptic alerts and defining
appropriate, research-supported implementations, a prudent approach
would give credit only for audible unimodal alerts or for bi-modal
alerts that include audible alerts.'' Rivian stated ``[t]he agency
should award credit to systems that provide both audible and haptic
alerts and provide the option to turn either of them OFF based on
driver preference. These audible or haptic alerts should be in sync
with providing a visual alert of an impending collision. The agency
should recommend the decibel level and the haptic feedback location and
type as a baseline and based on research on reducing nuisance to the
driver.''
    Given the lack of consensus within available research as to the
best location for a FCW haptic signal (seat belt, seat pan, steering
wheel, or brake pulse), and NHTSA's ongoing review of comments
submitted in response to the March 2022 request for comments, NHTSA is
not at this time proposing to require a haptic FCW component, but
invites comment on whether requiring FCW to contain a haptic component
presented via any location may increase FCW effectiveness or whether a
FCW haptic signal presented in only one specific, standardized location
should be allowed.
    While the FCW auditory signal is envisioned as being the primary
means of warning the driver, providing a haptic FCW signal that would
complement or supplant the auditory warning signal would likely improve
FCW perception for hearing-impaired drivers. Some drivers also may
prefer an alternative modality to auditory warnings (e.g., due to
annoyance caused by the auditory warning). However, the degree of
additional benefit that may be accrued by requiring a haptic FCW signal
in addition to a well-designed auditory and visual FCW that meets the
specifications proposed is not known.
    A haptic FCW signal, to be effective, would necessarily require the
driver to be in physical contact with the vehicle component through
which the haptic signal is presented in order to perceive the warning.
For example, if the driver is not wearing a seat belt, a haptic FCW
signal presented via the seat belt would not be effectively received. A
seat pan based haptic FCW signal would be unlikely to have such a non-
contact issue. NHTSA is interested in research data documenting the
comparison of a compliant auditory-visual FCW to that same FCW with an
added haptic component. NHTSA also welcomes any objective data
documenting the relative effectiveness of different haptic signal
presentation locations for FCW use.
3. Performance Test Requirements
    This NPRM would require that, when approaching a lead vehicle
during testing, the subject vehicle must provide a forward collision
warning and subsequently apply the brakes to avoid a collision. This
performance requirement is conducted under a defined set of conditions,
parameters (e.g., relative vehicle speeds and distances), and test
procedures.
    For all vehicle tests where the subject vehicle approaches a lead
vehicle, NHTSA is proposing that the minimum performance requirement is
complete avoidance of the lead vehicle. NHTSA chose the performance
criterion of collision avoidance because it maximizes the safety
benefits of the rule as compared to a metric that might permit a
reduced speed collision. NHTSA has tentatively concluded that a no-
contact criterion for the performance test requirements is practicable
to achieve, consistent with the need for safety, and may be necessary
to ensure test repeatability.
    NHTSA also seeks comment on the potential consequences if vehicle
contact were allowed during testing. First, NHTSA seeks comment on how
allowing contact during testing would affect the safety benefits of AEB
systems. Second, NHTSA seeks comment on whether allowing contact during
testing would create additional testing burdens. Specifically, NHTSA is
concerned that any performance test requirement that allows for vehicle
contact not resulting in immediate test failure could result in the
non-repeatability of testing without expensive or time-consuming
interruptions to testing, and seeks comment on this concern. For
instance, if a test vehicle were to strike the lead vehicle test
device, even at a low speed, sensors on the vehicle could become
misaligned or the vehicle test device may be damaged, including in ways
that are not immediately observable. For example, damage to the test
device might affect the radar cross section that requires a long
verification procedure to discover.
4. Performance Test Scenarios
    NHTSA is proposing three track test scenarios to evaluate AEB
performance. The test scenarios have the subject vehicle travelling
toward a lead vehicle which is ahead in the same lane. However, the
lead vehicle may be either stopped, moving at a constant but slower
speed, or decelerating to a stop.
    These three tests were chosen because they represent the three most
common pre-crash scenarios involving a lead vehicle. A NHTSA research
study of heavy vehicles comprising the striking vehicle in rear-end
crashes in the United States determined that four pre-crash scenarios
exist in data of both fatal and non-fatal crashes.\143\ These four
scenarios include the three listed above, and also a ``cut-in'' case in
which a lead vehicle changed lanes or merged into the path of the heavy
vehicle just prior to the crash. The cut-in scenario was excluded from
the test scenarios for this proposal because the research study shows
that it was much less likely to occur than the other three
scenarios.\144\
---------------------------------------------------------------------------

    \143\ Woodrooffe, J., et al. ``Performance Characterization and
Safety Effectiveness Estimates of Forward Collision Avoidance and
Mitigation Systems for Medium/Heavy Commercial Vehicles,'' Pg. 12.
Report No. UMTRI-2011-36, UMTRI (August 2012). Available at https://www.regulations.gov/document/NHTSA-2013-0067-0001 (last accessed
June 9, 2022).
    \144\ The cut-in scenario represents less than 5% of the pre-
crash scenarios.
---------------------------------------------------------------------------

i. Stopped Lead Vehicle
    This test recreates a roadway scenario where the subject vehicle
encounters a lead vehicle which is stopped ahead in the same lane.
Figure 5 shows the basic setup for the stopped lead vehicle scenario.
The subject vehicle is driven toward the stationary lead vehicle at a
constant speed, and the accelerator is only released if a forward
collision warning is issued. The test ends when the subject vehicle
either automatically stops without impact, or proceeds to strike the
lead vehicle.
    NHTSA proposes testing under two conditions for the subject
vehicle: testing without any manual brake application (to test the CIB
component) and testing with manual brake application (to ensure that
the driver's application of the brake pedal does not inhibit the
functionality of the AEB system). Testing with no brake application
simulates a driver who does not intervene in response to an FCW alert
prior to a crash. Testing with brake application simulates a driver who
applies the brakes, but the manual brake application is insufficient to
prevent a collision.
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[GRAPHIC] [TIFF OMITTED] TP06JY23.005

ii. Slower-Moving Lead Vehicle
    This test recreates a roadway scenario where the subject vehicle
encounters a lead vehicle that is moving at a constant but slower speed
ahead in the same lane. Figure 6 shows the basic setup for the slower-
moving lead vehicle scenario. The subject vehicle is driven toward the
lead vehicle at a constant speed, and its accelerator is then released
after the AEB system in the subject vehicle issues a forward collision
warning. The test ends when the subject vehicle either slows down to a
speed less than or equal to the lead vehicle's speed without impact or
strikes the lead vehicle. As with the stopped lead vehicle test, NHTSA
proposes testing under two conditions for the subject vehicle: without
any manual brake application and with manual brake application.
[GRAPHIC] [TIFF OMITTED] TP06JY23.006

iii. Decelerating Lead Vehicle
    This test recreates a roadway scenario where the subject vehicles
encounter a lead vehicle that is slowing down ahead in the same lane.
At the start of the test, both the subject vehicle and lead vehicle
travel at the same constant speed, while maintaining a predetermined
relative distance, or headway. The lead vehicle then begins to
decelerate, reducing the headway. Once the AEB system in the subject
vehicle issues a forward collision warning, the subject vehicle's
accelerator is released. The test ends when the subject vehicle either
automatically stops without impact or strikes the lead vehicle. As with
the prior two tests, NHTSA proposes testing under two conditions for
the subject vehicle: without any manual brake application and with
manual brake application. Figure 7 shows the basic setup for the
decelerating lead vehicle scenario.
[GRAPHIC] [TIFF OMITTED] TP06JY23.007

BILLING CODE 4910-59-C

5. Parameters for Vehicle Tests
    The test procedures for each scenario reference a set of
parameters. These parameters are presented in Table 16, where each row
represents a potential combination of parameters to be used for a test
run. The parameters define the speeds, decelerations, headways, and
manual brake applications used for the choreography of the vehicle test
scenarios. Specifically, these include:

 Subject Vehicle Speed (VSV)--speed at which the
subject vehicle travels toward the lead vehicle
 Lead Vehicle Travel Speed (VLV)--speed at which the
lead vehicle travels in the same direction as the subject vehicle
 Headway--the distance between the subject vehicle and the lead
vehicle
 Lead Vehicle Deceleration--the rate at which the lead vehicle
reduces its speed
 Manual Brake Application--specifies whether or not the service
brakes of the subject vehicle will be applied ``manually,'' or via a
brake controller

                                                Table 16--Test Parameters When Approaching a Lead Vehicle
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                  Speed (km/h)
          Test scenarios           ------------------------------------------        Headway (m)        Lead vehicle decel. (g)        Manual brake
                                               VSV                  VLV                                                                application
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stopped Lead Vehicle..............  Any 10-80...............               0  ........................  .......................  no.
                                    Any 70-100..............               0  ........................  .......................  yes.
Slower-Moving Lead Vehicle........  Any 40-80...............              20  ........................  .......................  no.
                                    Any 70-100..............              20  ........................  .......................  yes.
Decelerating Lead Vehicle.........  50......................              50  Any 21-40...............  Any 0.3-0.4............  no.
                                    50......................              50  Any 21-40...............  Any 0.3-0.4............  yes.
                                    80......................              80  Any 28-40...............  Any 0.3-0.4............  no.
                                    80......................              80  Any 28-40...............  Any 0.3-0.4............  yes.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Some of these parameters are proposed as ranges.\145\ The use of
ranges allows NHTSA to ensure AEB system performance remains consistent
under a variety of conditions and that no substantial degradation in
performance occurs at any point within the range. NHTSA tentatively
concludes that requiring a minimum performance only at discreet,
predetermined values within these proposed ranges may not ensure that
AEB system performance is sufficiently robust to meet the need for
safety.
---------------------------------------------------------------------------

    \145\ In instances where an FMVSS includes a range of values for
testing and/or performance requirements, the use of the word ``any''
is consistent with 49 CFR 571.4.
---------------------------------------------------------------------------

i. Vehicle Speed Parameters
    The proposed test speed ranges were selected considering two
primary factors. The first factor is the practical ability of AEB
technology to consistently operate and avoid contact with a lead
vehicle at the widest reasonable range of speeds. A larger range of
speeds could yield more safety benefits. Also, a larger range of speeds
will more thoroughly test the capabilities of the AEB system. NHTSA,
through its understanding of vehicle braking systems described in
established standards such as FMVSS Nos. 105 and 121, knows that
testing stopping distance at 60 mph is indicative of the service brake
performance over a range of speeds, and in those cases testing at a
single speed is acceptable. However, as observed in vehicle testing for
NHTSA research, AEB performance during testing at interstate speeds
does not necessarily indicate what the same system's performance will
be at lower speeds. Thus, NHTSA tentatively concludes that testing over
a range of speeds is necessary to fully assess AEB performance.
    The second factor is the practical limit of safely conducting
vehicle tests of AEB systems. NHTSA's testing must be safe and
repeatable as permitted by track conditions and testing equipment. For
example, if the AEB system does not intervene as required or if test
parameters inadvertently fall outside of the specified limits, it
should be possible to safely abort the test. In the event the subject
vehicle does collide with the lead vehicle, the test should be designed
so that it does so in a manner that will not injure the testing
personnel nor cause excessive property damage. Additionally, test
tracks may be constrained by available space and there may be
insufficient space to accelerate a heavy vehicle up to a high speed and
still have sufficient space to perform a test. Many types of heavy
vehicles are not capable of accelerating as quickly as lighter vehicles
and reaching high test speeds may require long distances that exceed
what is available at many vehicle testing facilities. At approximately
100 km/h, the agency found that constraints with available test track
length, in conjunction with the time required to accelerate the vehicle
to the desired test speed, made performing these high speed tests with
heavy vehicles logistically challenging.\146\ The agency has
tentatively concluded that at this time the maximum practicable test
speed is 100 km/h.
---------------------------------------------------------------------------

    \146\ During testing of a 2021 Freightliner Cascadia at speeds
approaching 100 km/h, NHTSA experienced difficulty establishing
valid test conditions due to insufficient track length.
---------------------------------------------------------------------------

    The maximum speed of 100 km/h is included in the test speed range
when manual braking is present; the manual braking will guarantee a
speed reduction even if the AEB system does not activate before
reaching the lead vehicle, which would limit potential damage to the
test equipment and reduce other potential risks. When no manual braking
is allowed, the maximum test speed would be 80 km/h so that, in the
event the AEB system does not provide any braking at all, risk to
personnel and damage to test equipment are reduced. Over 82 percent of
rear-end crashes where the heavy vehicle is the striking vehicle occur
at speeds below 80 km/h.\147\ However, the majority of fatal crashes
occur at speeds above 80 km/h, and approximately 40 percent of these
occur at travel speeds between 80 and 100 km/h. The stopped lead
vehicle test scenario uses a no-manual-braking test speed range of 10
to 80 km/h and a manual-braking test speed range of 70 to 100 km/h.
Together, these test speed ranges overlap with the travel speeds at
which heavy vehicle rear-end crashes occur in the real world, while
reducing the potential risk and damage to test equipment and vehicles
and not

exceeding the practical physical size limits of test tracks.
---------------------------------------------------------------------------

    \147\ This is based on analysis of 2017-2019 crash data.
---------------------------------------------------------------------------

    Similarly, the slower-moving lead vehicle test scenario uses speed
ranges of 40 to 80 km/h and 70 to 100 km/h for the subject vehicle,
while the lead vehicle travels ahead at a constant speed of 20 km/h.
The lower end of the subject vehicle test speed range is 40 km/h so
that the subject vehicle is traveling faster than the lead vehicle. The
decelerating lead vehicle tests are run at either 50 or 80 km/h. This
test is performed at two discreet speeds rather than at ranges of
speeds because the main factors that test AEB performance are the
variation of headway, or the distance between the subject vehicle and
lead vehicle, and how hard the lead vehicle brakes. Additionally,
because these tests contain a larger number of variables requiring more
complex test choreography, limiting the test to two discreet test
speeds reduces the number of potential test conditions and reduces
potential test burden.
    During each test run in any of the test scenarios, the vehicle test
speed will be held constant until the test procedure specifies a
change. NHTSA is proposing that vehicle speed would be maintained
within a tolerance range of 1.6 km/h of the chosen test value. This is
important for test consistency. Vehicle speed determines the time to
collision, which is a critical variable in AEB tests. In NHTSA's
experience, both the subject vehicle and lead vehicle speeds can be
reliably controlled within the 1.6 km/h tolerance range, and speed
variation within that range yields consistent test results. A tighter
speed tolerance is burdensome and unnecessary for repeatability as it
may result in a higher test-rejection rate, without any greater
assurance of accuracy of the test track performance.
    NHTSA's vehicle testing suggested that the selected speed ranges
for the various scenarios are within the capabilities of at least some
recent model year AEB-equipped production vehicles. For example, the
2021 Freightliner Cascadia avoided collision in the stopped lead
vehicle test at all speeds between 40 and 85 km/h, most speeds between
30 and 90 km/h (except 30 and 60 km/h) in the slower-moving lead
vehicle test, and in all decelerating lead vehicle tests that were run
at the proposed parameters. This vehicle's AEB system did not prevent a
collision at lower speeds between 20 and 35 km/h for the stopped lead
vehicle test. However, the 2021 Dodge Ram 550 avoided collision in all
stopped lead vehicle tests from 10 to 40 km/h. In many test cases where
current AEB systems did not prevent a collision, the AEB significantly
reduced the speed before the collision. While these current AEB systems
perform a bit differently depending on the vehicle, given that this
notice proposes a lead time for manufacturers to come into compliance
with the proposed performance requirement, the agency expects that
compliance with these requirements would be achievable.
ii. Headway
    The decelerating lead vehicle test scenario includes a parameter
defining how far ahead the lead vehicle is from the subject vehicle at
the beginning of the test, which is referred to as headway. Headway and
lead vehicle deceleration are the main factors for the dynamics of the
decelerating lead vehicle test since both the lead and subject vehicles
start the test at the same constant speed. At the start of the test,
when the vehicles are both travelling at 50 km/h, the proposed headway
specification is any distance between 21 m and 40 m.\148\ When the
vehicles are both travelling at 80 km/h, the proposed headway
specification is any distance between 28 m and 40 m. Headways are
proposed as a range in order to assure AEB functionality over a wider
range of driving scenarios. A basic kinematic simulation of heavy
vehicle AEB braking under the proposed test parameters, assuming
factors such as AEB response time and foundation brake reaction time/
deceleration similar to what was observed in testing, indicated that
headways shorter than 21 and 28 m would not be realistic to achieve and
would inevitably result in a collision.
---------------------------------------------------------------------------

    \148\ The bounds of the headway range are consistent with the
headways in the April 2021 European New Car Assessment Programme
(Euro NCAP), Test Protocol--AEB Car-to-Car systems, Version 3.0.3
for the same scenario.
---------------------------------------------------------------------------

    The upper limit of 40 m was chosen because testing at longer
headways does not provide additional insight into AEB performance with
regard to decelerating lead vehicles. At headways greater than 40 m,
the lead vehicle decelerating may come to a full stop prior to the
subject vehicle actuating the brakes. This essentially becomes a
stopped lead vehicle test. Allowing for a range of headways during
testing also makes the choreography of the test possible by providing a
tolerance for the headway. At the start of the test, the speed of both
the subject vehicle and lead vehicle are the same and are maintained
within the tolerance specified (plus or minus 1.6 km/h). As each
vehicle's speed fluctuates a bit differently within these bounds, in
turn the headway between the vehicles accordingly fluctuates as well.
As long as the headway fluctuation is within the proposed range, the
test can still be considered valid, and no headway tolerance needs to
be established.
iii. Lead Vehicle Deceleration Parameter
    The decelerating lead vehicle test scenario includes a deceleration
parameter that dictates how quickly the lead vehicle will slow down in
front of the subject vehicle. The agency has tentatively concluded that
this parameter range of 0.3g to 0.4g represents real-world, manual
application of the service brake. Previous NHTSA research had
identified 3.0 m/s\2\ (.306g) as ``reasonably comfortable for passenger
car occupants'' and that on average, drivers brake in such a manner
that the vehicle decelerates at an average of 0.48g when presented with
a unexpected obstacle.\149\ The upper limit of the lead vehicle braking
is proposed at 0.4g to avoid a test condition in which the lead vehicle
would provide greater brake inputs than those necessary to meet the
minimum stopping distance requirements. NHTSA took into consideration
the stopping distance requirements for heavy vehicles under FMVSS Nos.
105 and 121 and the resulting average decelerations that those vehicles
would be required to achieve. For example, an air-braked tractor
trailer under FMVSS No. 121 would need to brake at 0.41g to meet the
stopping distance of 310 ft from 60 mph.\150\ Given the headway
parameters and vehicle speeds in this proposal, the agency believes a
lead vehicle deceleration above 0.4g would create a requirement that
could effectively reduce the minimum stopping distance requirements for
vehicles generally.
---------------------------------------------------------------------------

    \149\ Gregory M. Fitch, Myra Blanco, Justin F. Morgan, Jeanne C.
Rice, Amy Wharton, Walter W. Wierwille, and Richard J. Hanowski
(April 2010). Human Performance Evaluation of Light Vehicle Brake
Assist Systems: Final Report (Report No. DOT HS 811 251) Washington,
DC: National Highway Traffic Safety Administration, pgs. 13 and 101.
    \150\ This assumes an average deceleration that is achieved
after an initial brake actuation time of 0.45 seconds, as this is
the maximum actuation time allowed by FMVSS No. 121.
---------------------------------------------------------------------------

6. Manual Brake Application in the Subject Vehicle
    Each of the three lead vehicle test scenarios includes tests that
are conducted with manual brake application in the subject vehicle. The
process for testing with manual brake application is identical to what
is considered a test for dynamic brake support or DBS in NHTSA's NCAP
for light vehicles. While the term DBS is

not usually associated with heavy vehicles, NHTSA is including this
requirement in this proposal to ensure that the driver's application of
the brake pedal does not inhibit the functionality of the AEB system if
the driver's brake application is insufficient to avoid a crash. The
manual brake application procedure specifies that the subject vehicle's
service brakes are applied by using a robotic brake controller to
ensure accurate and consistent test conduct.
    A NHTSA study that examined light vehicle drivers' behavior in
response to potential frontal crash situations found that they
typically exhibit multi-stage braking behavior.\151\ This means that
the drivers initially applied and held the brake moderately, and then
continued to a full application if perceived to be necessary. A
subsequent NHTSA study concluded that a significant portion of heavy
vehicle operators display the same multi-stage braking behavior.\152\
The agency believes that in real world cases where the operator may
apply insufficient brake force to avoid a rear-end collision, an AEB
system should apply the necessary supplemental braking necessary to
avoid a collision. Furthermore, by using manual brake application in
the test scenarios, NHTSA is able to test AEB performance at higher
test speeds.
---------------------------------------------------------------------------

    \151\ Mazzae, E., Barickman, F., Scott Baldwin, G., and
Forkenbrock G., ``Driver Crash Avoidance Behavior with ABS in an
Intersection Incursion Scenario on Dry Versus Wet Pavement,'' SAE
Technical Paper 1999-01-1288, 1999, doi:10.4271/1999-01-1288.
    \152\ Every, J., Salaani, M., Barickman, F., Elsasser, D., et
al., ``Braking Behavior of Truck Drivers in Crash Imminent
Scenarios,'' SAE International Journal of Commercial Vehicles,
7(2):2014, doi:10.4271/2014-01-2380.
---------------------------------------------------------------------------

    In real world cases, the brake pedal can be applied by a heavy
vehicle operator in an infinite number of ways (varying force, reaction
time, duration, etc.). Since the manual brake application represents an
operator's response to an unexpected obstacle and the forward collision
warning, the agency is proposing a brake pedal application that results
in a mean deceleration of 0.3g. A heavy vehicle field study by NHTSA
indicated that when presented with an FCW triggered by a valid object
and requiring a crash avoidance maneuver, the operators braked on
average at a maximum of 0.3g.\153\ Manually applying the brake at 0.3g
also is a low enough value to improve the capability of observing an
AEB automatic braking intervention that is occurring simultaneously on
top of that. The minimum stopping distance requirements for heavy
vehicles in existing FMVSSs require braking at around 0.4g. Thus
hypothetically, if a heavy vehicle's service brakes were manually
applied at a higher deceleration of 0.4g for example, and the brakes
were only capable of a maximum of 0.4g of deceleration, AEB
intervention would be incapable of producing additional deceleration
and would not be observable.
---------------------------------------------------------------------------

    \153\ Grove, K., Atwood, J., Hill, P., Fitch, G., Blanco, M.,
Guo, F., . . . & Richards, T. (2016, June). Field study of heavy-
vehicle crash avoidance systems. (Final report. Report No. DOT HS
812 280). Washington, DC: National Highway Traffic Safety
Administration.
---------------------------------------------------------------------------

    There are two methods to perform the manual brake application--
using either displacement feedback or hybrid feedback. Both methods are
intended to be carried out by a robotic brake pedal controller in
closed loop operation, and the method that is most suitable to the
subject vehicle is chosen. Regardless of the method, it is necessary
initially to determine a pedal position which, in the absence of any
automatic braking from the AEB system, results in an average vehicle
deceleration of 0.3g. The displacement feedback method then simply
requires moving the brake pedal to the 0.3g position quickly, at a rate
of 254 mm/s,\154\ and then maintaining that position. However,
automatic braking in certain vehicles requires the pedal position to
move further toward the floor, and can cause conflict with the
displacement feedback method's control of pedal position, in turn
adversely affecting test results.\155\ The hybrid feedback pedal
control method provides a solution to this conflict. The hybrid method
initially requires the same pedal position control, but then almost
immediately begins to control the force on the pedal (and not the
position) to maintain the 0.3g deceleration. If the AEB system
thereafter requires further movement of the pedal, the brake controller
is able to ``follow'' the pedal while still applying the appropriate
force.\156\ NHTSA is proposing that the brake will be applied 1.0
second after the vehicle has provided a FCW; this is based on the
average time it takes a driver to react when presented with an
obstacle.\157\ Although these average decelerations and reaction times
are based on behavior of light vehicle drivers, we feel that it is
sufficient basis to simulate a scenario in which a heavy vehicle
operator brakes partially and insufficiently to fully avoid a rear-end
collision.
---------------------------------------------------------------------------

    \154\ Previous NHTSA research related to AEB examined pedal
application rates by drivers in emergency and non-emergency
situations, and determined that pedal application rate is important
in AEB testing with manual braking, and that the appropriate
application rate is 254 mm/s. NHTSA, August 2014. Automatic
Emergency Braking System (AEB) Research Report, An Update of the
June 2012 Research Report Titled, ``Forward-Looking Advanced Braking
Technologies Research Report.'' Docket NHTSA-2012-0057-0037.
    \155\ NHTSA, August 2014. Automatic Emergency Braking System
(AEB) Research Report, An Update of the June 2012 Research Report
Titled, ``Forward-Looking Advanced Braking Technologies Research
Report.'' Docket No. NHTSA-2012-0057-0037.
    \156\ Id.
    \157\ Previous NHTSA research has shown that on average, it
takes drivers 1.04 s to begin pressing the brake when presented with
an unexpected obstacle and 0.8 s when presented with an anticipated
obstacle. Gregory M. Fitch, Myra Blanco, Justin F. Morgan, Jeanne C.
Rice, Amy Wharton, Walter W. Wierwille, and Richard J. Hanowski
(2010, April) ``Human Performance Evaluation of Light Vehicle Brake
Assist Systems: Final Report'' (Report No. DOT HS 811 251),
Washington, DC: National Highway Traffic Safety Administration, p.
101.
---------------------------------------------------------------------------

B. Conditions for Vehicle Tests

    The test conditions are used to control the environmental, road
surface, subject vehicle, and equipment conditions to ensure
consistency both to define potential variabilities in conditions under
which an AEB system would be expected to operate while also providing
consistent conditions to reduce test variability due to extraneous
factors. NHTSA recognizes that there are an unlimited number of non-
ideal environmental conditions present in the real world, and it would
be unreasonable to attempt to reproduce most of them within practical
constraints in the testing environment. Thus, in many cases, the
proposed test conditions were chosen to represent near-ideal conditions
with the goal of reducing variability in the test results. For example,
if testing were conducted at below-freezing temperatures with snowfall,
it would be difficult to interpret whether poor test results were due
to the AEB system or reduced road surface friction.
    Many of the proposed conditions were selected based on research
data and engineering practices, and reasonable deduction. In some
cases, as appropriate, the agency considered that conditions should be
the same or similar to what is specified in other heavy vehicle brake-
related FMVSS. This usage of pre-established conditions may help reduce
testing burden, since fewer testing conditions would need to be
adjusted between different FMVSS brake-related compliance tests. It
also ensures that the minimum stopping distance requirements in the
braking standards would be achievable during an AEB test.
    Each test procedure for the three scenarios specifies a point at
which thereafter the test conditions described in this section apply
and will be maintained. For the stopped lead vehicle and slower-moving
lead vehicle

test scenarios, this point is at a 5 second time to collision. For the
decelerating lead vehicle test scenario, this point is 1 second prior
to the onset of lead vehicle deceleration.
1. Environmental Conditions
    The ambient temperature range specified in this proposal is 2 to 40
degrees Celsius; this is the same range as specified in FMVSS No. 136,
which avoided testing at 0 degrees Celsius because it could impact tire
performance and in turn the variability of test results.
    The maximum wind speed is 5 m/s, which is the same as what is
specified in FMVSS No. 136. This value was chosen to reduce the
potential lateral displacement of certain heavy vehicles.
    NHTSA considered that certain environmental conditions should be
near-ideal to prevent sensor performance degradation and maintain
repeatability of vehicle testing. First, ambient illumination would be
at or above 2,000 lux. This represents daytime illumination that is at
a minimum equivalent to an overcast day.\158\ A NHTSA study has shown
that darkness can cause degradation of sensor performance.\159\ NHTSA
analysis shows that 87 percent of heavy vehicle rear-end crashes occur
during daylight conditions.\160\ Therefore, NHTSA tentatively concludes
that daylight testing is necessary to ensure that AEB systems address
the rear-end crash safety problem.
---------------------------------------------------------------------------

    \158\ During an overcast day (no sun), when the solar altitude
is around 6 degrees, the light intensity on a horizontal surface is
around 2,000 lux. Illuminating Engineering Society of North America.
1979. ``Recommended Practice of Daylighting.''
    \159\ NHTSA, August 2014. ``Automatic Emergency Braking System
(AEB) Research Report--An Update of the June 2012 Research Report
Titled, `Forward-Looking Advanced Braking Technologies Research
Report.' '' Docket NHTSA-2012-0057-0037.
    \160\ Data are from 2017-2019 FARS and CRSS crash databases, as
discussed in the PRIA section on initial AEB target population.
---------------------------------------------------------------------------

    Second, during testing, the sun would not be below 15 degrees of
elevation and within 25 degrees laterally from the center plane of the
subject vehicle. This specification reduces the likelihood of glare or
washout for camera-based sensors that could lead to degradation of
sensor and AEB system performance.\161\
---------------------------------------------------------------------------

    \161\ NHTSA, August 2014. ``Automatic Emergency Braking System
(AEB) Research Report--An Update of the June 2012 Research Report
Titled, `Forward-Looking Advanced Braking Technologies Research
Report.' '' Docket NHTSA-2012-0057-0037.
---------------------------------------------------------------------------

    Visibility also would not be affected by fog, smoke, ash or other
particulate, as recommended in previous agency research findings.\162\
This improves test repeatability and also aligns with many real-world,
rear-end crash conditions. A review of NHTSA's crash data indicates
that 81 percent of those occur when the weather conditions are clear or
cloudy and with no precipitation.\163\
---------------------------------------------------------------------------

    \162\ NHTSA, August 2014. ``Automatic Emergency Braking System
(AEB) Research Report--An Update of the June 2012 Research Report
Titled, `Forward-Looking Advanced Braking Technologies Research
Report.' '' Docket NHTSA-2012-0057-0037.
    \163\ This is also supported by another study (Grove, Atwood,
Fitch and Blanco, M, 2016, ``Field Study of Heavy-Vehicle Crash
Avoidance Systems'') which concluded that over 88 percent of heavy
vehicle crashes occurred when the conditions were, clear, partly
cloudy, or overcast.
---------------------------------------------------------------------------

2. Road Surface Conditions
    The road surface upon which vehicle tests will be conducted must
also be in a defined condition to help achieve repeatable testing. The
proposed conditions specify that the road surface is free of debris,
irregularities, or undulations, such as loose pavement, large cracks,
or dips. These could affect the vehicle's ability to brake properly or
maintain its heading, and ultimately reduce the repeatability of a
test. The test surface is also required to be level, with a slope
between 0 and 1 degrees, because the slope of a road surface can affect
the performance of an AEB-equipped vehicle.\164\ A surface that slopes
up and down could obstruct a sensor's view of an object ahead. It could
also influence the dynamics and layout involved in the proposed AEB
test scenarios, as travelling up or down a slope makes braking to a
stop more or less difficult. In order to have predictable tire
adherence under braking, the surface must also be dry and have a
controlled coefficient of friction. NHTSA is proposing that the test
track surface have a peak friction coefficient of 1.02 when measured in
accordance with ASTM International (ASTM) E1337 \165\ using an ASTM
F2493 standard reference test tire and without water delivery.\166\
Surface friction is a critical factor in brake system performance
testing, including AEB, since it correlates with tire grip and the
achievable stopping distance. The presence of moisture will
significantly change the measured performance of a braking system. A
dry surface is more consistent and provides for greater test
repeatability. Also, the proposed peak friction coefficient is the same
value that NHTSA uses for brake performance testing.
---------------------------------------------------------------------------

    \164\ Kim, H. et al., ``Autonomous Emergency Braking Considering
Road Slope and Friction Coefficient,'' International Journal of
Automotive Technology, 19, 1013-1022 (2018).
    \165\ ASTM International, ASTM E1337, ``Standard Test Method for
Determining Longitudinal Peak Braking Coefficient (PBC) of Paved
Surfaces Using Standard Reference Test Tire.''
    \166\ See 87 FR 34800 (June 8, 2022), Final Rule, Federal Motor
Vehicle Safety Standards, Consumer Information; Standard Reference
Test Tire.
---------------------------------------------------------------------------

    This proposal specifies up to two straight lines be marked on the
test surface to simulate lane markings. In order to provide flexibility
for different road configurations at a variety of test track
facilities, lane markings may or may not be present during testing. If
present, the lines would be of any color or configuration (e.g., solid,
dashed, double-line, etc.). If two lines are used, they would be
parallel to each other and between 2.7 to 4.5 m apart, which is
representative of typical lane widths.
    Lastly, the environment would not contain obstructions that could
interfere with detection of a lead vehicle or other test equipment
ahead and have an unintentional effect on the field of view of the AEB
system, in turn compromising test repeatability. Thus, the subject
vehicle during testing would not travel beneath overhead structures
such as signs, bridges, or gantries, and each compliance test would be
conducted without any vehicles, obstructions, or stationary objects
within one lane width of either side of the subject vehicle path unless
called for in the test procedure.
3. Subject Vehicle Conditions
    Many of the subject vehicle conditions exist to ensure that a
vehicle chosen for testing is in a working condition that represents
the vehicle as it is sold into the market, and capable of performing as
intended by the manufacturer. Thus, the vehicle conditions specify that
no AEB malfunction telltale is active, vehicle components ahead of AEB
sensors are clean and do not obstruct the sensors, the original tires
are installed and properly inflated, and non-consumable fluids (e.g.,
brake fluid, engine coolant, etc.) are full.
    Other conditions exist to ensure that vehicle performance is
comparable to that found in the real world. Prior to testing, the
vehicle's service brakes are burnished according to the burnishing
procedures already used in FMVSS No. 121 or 105 testing, as appropriate
for the vehicle prior to the beginning of testing. Burnishing helps to
gradually seat and condition new brake components, particularly the
brake pads and rotors/drums, which come into contact and provide
friction under braking. Burnishing helps achieve optimal and repeatable
brake performance. If burnishing was done previously, for example due
to the running of compliance tests for other FMVSS, it would not be
repeated.
    The agency also proposes that the brake temperatures be between 66
and

204 degrees Celsius prior to the beginning of a test, which is the same
as specified in FMVSS No. 136. In the agency's experience, this initial
temperature range allows the brakes to perform well without being under
or over heated during testing, and the upper end of 204 degree Celsius
does not require unreasonably long cool-down time between test runs.
    The agency has also considered that vehicles may have adjustable
characteristics or configurable systems that a vehicle operator may
choose to adjust, and some of these are factors that could affect the
outcome of an AEB test. Since each vehicle operator could potentially
choose different settings for these systems, the testing would ensure
that AEB systems are capable of meeting the test requirements
regardless of which choices were made. Accordingly, this proposal
specifies that these adjustable factors will be nearly in any
configurable level during testing. Consumable fluids (e.g., fuel,
diesel exhaust fluid, etc.) and propulsion battery charge will be
between 5-100 percent of their capacity. Cruise control systems would
be tested in any available setting, including adaptive cruise control
modes. In the event that adaptive cruise control is engaged and remains
engaged during the event, the FCW would not be required. This is
because an adaptive cruise control system is intended to slow the
vehicle to avoid a collision prior to a collision being imminent and
without notification to the driver.\167\
---------------------------------------------------------------------------

    \167\ Adaptive cruise control is a driver assistance technology
that automatically adjusts vehicle speed to maintain a certain
distance from a vehicle ahead.
---------------------------------------------------------------------------

    Forward collision warnings would be tested in any configurable
setting. If the vehicle is equipped with an engine-braking system,
tests would be conducted with the system either engaged or disengaged.
The controls for the headlamps and regenerative braking would be tested
in any available position.
    Regarding the weight of the subject vehicle during testing, this
proposal specifies that the vehicle is loaded to its gross vehicle
weight rating. Truck tractors will be loaded to its GVWR by connecting
a control trailer. The specifications for this control trailer, which
is an unbraked, single-axle flatbed, are equivalent to those found in
FMVSS No. 136. The agency believes it is important to test the
performance of AEB systems when the vehicle is at its heaviest
allowable condition, because heavy vehicles often travel in a fully
loaded condition and it generally presents the most challenging
scenario for braking (i.e., stopping a heavier vehicle is more
difficult). This loading condition is identical to the loaded condition
specified for FMVSS stopping distance assessment. This may improve
testing efficiency for NHTSA by having fewer loading conditions
specified among FMVSS.
    Finally, because a vehicle will be tested at its GVWR, this
proposal specifies that, if a vehicle is equipped with a liftable axle,
it will be placed in the down position during testing.

C. Proposed Requirements for False Activation

1. No Automatic Braking Requirement
    NHTSA proposes a requirement that the subject vehicle, when
presented with two false activation test scenarios, must not
automatically apply braking that results in a peak deceleration of more
than 0.25g when manual braking is not applied, nor a peak deceleration
of more than 0.45g when manual braking is applied. False activation
refers to cases where the AEB systems automatically activates the
service brakes although there is no object present in the path of the
vehicle with which it would collide. The associated vehicle tests are
run both with and without manual braking. During test runs without
manual braking, the AEB system must not initiate braking that results
in a peak deceleration of more than 0.25g. A 0.25g deceleration is
below the 0.3g threshold described earlier as a comfortable
deceleration which has a low probability of creating safety concerns
such as rear-end crashes (if the subject vehicle would brake too
hard).\168\ Also, 0.25g is an easily measurable deceleration when
testing.
---------------------------------------------------------------------------

    \168\ Gregory M. Fitch, Myra Blanco, Justin F. Morgan, Jeanne C.
Rice, Amy Wharton, Walter W. Wierwille, and Richard J. Hanowski
(2010, April) Human Performance Evaluation of Light Vehicle Brake
Assist Systems: Final Report (Report No. DOT HS 811 251) Washington,
DC: National Highway Traffic Safety Administration, p. 13.
---------------------------------------------------------------------------

    During test runs when manual braking is being applied, the AEB
system must not initiate braking that results in a peak deceleration of
more than 0.45g. When testing using manual braking, the goal is to have
a manual braking deceleration of 0.3g, and so the AEB system must not
cause more than approximately 0.15g of additional deceleration. This
0.15g amount is less than the 0.25g of peak deceleration permitted in
tests without manual braking--however, allowing the same 0.25g above
manual braking would mean that up to a total peak deceleration of 0.55g
would be permitted. Because 0.55g could exceed the maximum deceleration
capacity of certain heavy vehicles, it would, in turn, render the test
impossible to fail for those vehicles. Therefore, the lower threshold
of additional deceleration is proposed for false activation tests with
manual braking.
2. Vehicle Test Scenarios
    Under this proposal, the false activation requirement would be
evaluated by executing two vehicle test scenarios--a steel trench plate
test and a pass-through test. The steel trench plate test was chosen
because in previous agency testing that included eight different false
activation test scenarios, the steel trench plate scenario was the only
one that produced false activation of the AEB system.\169\ The pass-
through test is similar to the United Nations Economic Commission for
Europe (UNECE) Regulation 131 pass-through test.\170\
---------------------------------------------------------------------------

    \169\ Snyder, A., Martin, J., & Forkenbrock, G. (2013, July).
``Evaluation of CIB system susceptibility to non-threatening driving
scenarios on the test track.'' (Report No. DOT HS 811 795).
Washington, DC: National Highway Traffic Safety Administration.
    \170\ UNECE Regulation 131, ``Uniform provisions concerning the
approval of motor vehicles with regard to the Advanced Emergency
Braking Systems (AEBS),'' see 6.8 False reaction test, U.N.
Regulation No. 131 (Feb. 27, 2020), available at https://unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2015/R131r1e.pdf.
---------------------------------------------------------------------------

    The proposed false activation tests establish only a baseline for
system functionality. For practical reasons they are not comprehensive,
nor sufficient to eliminate susceptibility to false activations in the
myriad of circumstances in the real world. However, the proposed tests
are a practicable means to establish a minimum threshold of
performance. The agency expects that vehicle manufacturers will design
AEB systems to thoroughly address the potential for false
activations.\171\ Manufacturers have a strong market incentive to
mitigate false positives and have been successful even in the absence
of specific requirements.
---------------------------------------------------------------------------

    \171\ From NHTSA's NCAP Request for Comments notice regarding
AEB: ``Specifically, the Alliance stated that vehicle manufacturers
will optimize their systems to minimize false positive activations
for consumer acceptance purposes, and thus such tests will not be
necessary. Similarly, Honda stated that vehicle manufacturers must
already account for false positives when considering marketability
and HMI.'' 87 FR 13452 at 13460.
---------------------------------------------------------------------------

i. Steel Trench Plate
    This test recreates a roadway scenario where the subject vehicles
encounter a steel trench plate which is placed on the road surface
ahead in the same lane. The subject vehicle is driven at 80 km/h toward
the steel trench plate at a constant speed.

    The tests would be conducted either with or without manual brake
application. Manual braking is included in these scenarios to ensure
that even when a vehicle's service brake is actuated, false activation
would not occur. For tests without manual braking, the accelerator is
only released if a forward collision warning is issued. For test with
manual braking, the accelerator is released at either the forward
collision warning or 1 second prior to the manual braking, whichever
occurs first. Manual braking begins when the subject vehicle is 1.1
seconds away from the steel trench plate. The test ends when the
subject vehicle either comes to a stop prior to crossing over the
leading edge of the steel trench plate, or it proceeds to drive over
the steel trench plate. Figure 8 shows the basic setup for the steel
trench plate scenario.
[GRAPHIC] [TIFF OMITTED] TP06JY23.008

    Unlike the test scenarios in which the subject vehicle approaches a
lead vehicle, the agency proposes that the false activation tests be
run at a single speed rather than over a range of speeds. False
activations occurring at interstate speeds would create the most severe
unintended consequences of AEB braking. Therefore, the proposal
includes only a test at a single speed of 80 km/h.
ii. Pass-Through
    This test recreates a roadway scenario where the subject vehicle
must travel between two parked cars that are adjacent to the left and
right sides of the subject vehicle's travel lane. The parked cars are
represented by two vehicle test devices. The lateral distance between
the parked cars is 4.5 m, which is sufficient to give the subject
vehicle enough space to pass between them and yet be close enough to be
in the field of view of AEB sensors. The subject vehicle is driven
along the center of the travel lane and toward the gap between the
parked cars at a speed of 80 km/h. For tests without manual braking,
the accelerator is only released if a forward collision warning is
issued. For tests with manual braking, the accelerator is released at
either the forward collision warning or 1 second prior to the manual
braking, whichever occurs first; manual braking begins when the front
plane of the subject vehicle is 1.1 seconds away from the rear plane of
the two parked cars).
[GRAPHIC] [TIFF OMITTED] TP06JY23.009

D. Conditions for False Activation Tests

    The false activation requirement is conducted under a set test
conditions identical to those used for AEB tests. However, there are
equipment conditions which apply specifically to these false activation
tests.
    The equipment conditions that apply to the two false positive
scenarios in this proposal relate to the steel trench plate and the
vehicles used for the pass-through test. The steel trench plate is a
piece of equipment that represents a steel plate typically used to
cover excavation holes or irregularities in the road surface during
construction work, and which is meant to be driven over by

vehicles. The steel trench plate specified in this proposal is made of
ASTM A36 steel, a common structural steel alloy, and has the dimensions
2.4 m x 3.7 m x 25 mm. Any metallic fasteners used to secure the steel
trench plate are flush with the top surface of the plate, to avoid
effectively increasing the profile height and radar cross-section of
the plate. The two vehicles used for the pass-through test are vehicle
test devices identical to those that would be used in the lead vehicle
testing.

E. Potential Alternatives to False Activation Tests

    As alternatives to these two false activation tests, NHTSA is
considering requiring a robust documentation process, or specifying a
data storage requirement. NHTSA is considering requiring this
documentation and data in addition to or in place of the proposed false
activation tests. First, NHTSA seeks comment on the anticipated impacts
on safety and the certification burden if the agency were to finalize a
rule that did not contain one or both of the proposed false positive
tests.
    The agency is considering requiring that manufacturers maintain
documentation demonstrating that process standards were followed
specific to the consideration of false application of automatic
braking. Other industries where safety-critical software-controlled
equipment failures may be life threatening (e.g., aviation,\172\
medical devices \173\) are regulated in some respects via process
controls ensuring that software development engineering best practices
are followed. This approach recognizes that system tests are limited in
their ability to evaluate complex, and constantly changing software
driven control systems.
---------------------------------------------------------------------------

    \172\ 14 CFR 33.201(a) The engine must be designed using a
design quality process acceptable to the Federal Aviation
Administration, that ensures the design features of the engine
minimize the occurrence of failures, malfunctions, defects, and
maintenance errors that could result in an in-flight shutdown, loss
of thrust control, or other power loss.
    \173\ 21 CFR 920.30(a)(1) Each manufacturer of any class III or
class II device, and the class I devices listed in paragraph (a)(2)
of this section, shall establish and maintain procedures to control
the design of the device in order to ensure that specified design
requirements are met.
---------------------------------------------------------------------------

    Software development lifecycle practices that include risk
management, configuration management, and quality systems are used in
various safety-critical industries. ISO 26262 Road vehicles--Functional
safety and related standards are examples of methods for overseeing
software development practices. The agency is considering that a
process standards approach could be a viable and practical way of
regulating the risk of false positives, as false activation of braking
is a complex engineering problem with multiple factors and conditions
that must be considered in the real world. The agency seeks public
comment on all aspects of requiring that manufacturers document that
they have followed process standards in the consideration of the real-
world false activation performance of the AEB system.
    Finally, the agency considered requiring targeted data recording
and storage of significant AEB activations. These data could then be
used by manufacturers to improve system performance, or by the agency
to review if a particular alleged false activation is part of a safety
defect investigation. The agency is considering requiring that an AEB
event that results in a speed reduction of greater than 20 km/h should
activate the recording and storage of the following key information:
date, time, engine hours (the time as measured in hours and minutes
during which an engine is operated), AEB activation speed, AEB exit
speed (vehicle speed at which the automatic braking is completely
released), AEB exit reason (e.g. driver override with throttle, or
brake, or system decision), location, and camera image data. This
information could be used by investigators to analyze the source of the
activation and determine if an activation was falsely applied. Such
data would need to be accessible by the agency and potentially the
vehicle operator for a full and transparent analysis. The agency seeks
comment on all aspects of this data collection approach as an
alternative to false positive testing, including whether this list of
potential elements is incomplete, overinclusive, or impractical.

F. Proposed Requirements for Malfunction Indication

    NHTSA is proposing that AEB systems must continuously detect system
malfunctions. If an AEB system detects a malfunction that prevents it
from performing its required safety function, the vehicle would be
required to provide the vehicle operator with a warning. The warning
would be required to remain active as long as the malfunction exists
while the vehicle's starting system is on. NHTSA would consider a
malfunction to include any condition in which the AEB system fails to
meet the proposed performance requirements. NHTSA is proposing that the
driver must be warned in all instances of component or system failures,
sensor obstructions, environmental limitations (like heavy
precipitation), or other situations that would prevent a vehicle from
meeting the proposed AEB performance requirements. While NHTSA is not
proposing the specifics of the telltale, NHTSA anticipates that the
characteristics of the alert will be documented in the vehicle owner's
manual and provide sufficient information to the vehicle operator to
identify it as an AEB malfunction.
    NHTSA considered proposing requirements pertaining to specific
failures and including an accompanying test procedure. For instance,
the agency could develop or use available tests that specify
disconnecting sensor wires, removing fuses, or covering sensors to
simulate field malfunctions. Such requirements are not included in the
proposed regulatory text, but NHTSA is interested in comments on this
issue.
    NHTSA also considered proposing minimum requirements for the
malfunction telltale, to standardize ways of communicating to the
vehicle operator. NHTSA understands that some malfunctions of the AEB
system require repair (loose wires, broken sensors, etc.) while other
malfunctions are temporary and will correct themselves over time (ice
buildup on a camera). The agency considered requiring that the
malfunction telltale convey the actions that a driver should take when
a malfunction is detected. Such requirements are not included in the
proposed regulatory text, but NHTSA is interested in comments on this
issue. NHTSA seeks comment, including cost and benefit data, on the
potential advantages of specifying test procedures that would describe
how the agency would test a malfunction telltale and on the level of
detail that this regulation should require of a malfunction telltale.
Additionally, the agency considered requiring more details for the
telltale itself, such as a standardized appearance (color, size, shape,
illuminance). The agency seeks comment on the need and potential safety
benefits of requiring a standardized appearance of the malfunction
telltale and what standardized characteristics would achieve the best
safety outcomes.

G. Deactivation Switch

    The proposed regulatory text does not permit vehicle manufacturers
to install a manual deactivation switch that would enable the vehicle
operator to switch off the AEB. The text is silent regarding the
permissibility of a switch but, under the framework of the FMVSS

and NHTSA's interpretations of the standards, a deactivation switch
would be prohibited if it would allow an AEB system to be deactivated
in any circumstance in which the standard requires an AEB system to
function. This is consistent with other FMVSS, such as FMVSS No. 108,
``Lamps, reflective devices, and associated equipment,'' which is
silent about a switch deactivating the stop lamps but where NHTSA has
interpreted the standard as prohibiting such a switch.\174\ Standards
in which a deactivation switch is permitted expressly permit the switch
in the regulatory text, for example, FMVSS No. 126, ``Electronic
stability control systems for light vehicles,'' where the standard
specifically permits and regulates the performance of a deactivation
switch,\175\ and FMVSS No. 208, ``Occupant crash protection,'' where
the standard permitted an on-off switch for the air bag for the front
passenger seat on particular vehicles.\176\
---------------------------------------------------------------------------

    \174\ https://isearch.nhtsa.gov/files/23833.ztv.html (last
accessed August 31, 2022).
    \175\ FMVSS No. 126, ``ESC systems for light vehicles,'' S5.4:
The manufacturer may include an ``ESC Off'' control whose only
purpose is to place the ESC system in a mode or modes in which it
will no longer satisfy the performance requirements of S5.2.1,
S5.2.2, and S5.2.3.
    \176\ FMVSS No. 208, ``Occupant crash protection.'' FMVSS No.
208 was written such that it permited such switches only on vehicles
configured with no back seat or a back seat too small to accommodate
a rear-facing child restraint system. This was an interim step to
allow advanced air bag technology to mature and be fully
implemented.
---------------------------------------------------------------------------

    NHTSA and FMCSA realize a switch or other method that could
deactivate a vehicle's AEB system could be useful in some
circumstances. There might be some heavy vehicle design or aftermarket
equipment installations where the configuration of the vehicle could
potentially interfere with the AEB sensing system. For example, a
snowplow might be attached in a manner that obstructs an AEB sensor.
Some vehicles may have uses where an AEB system may be incompatible
with its operating environment, for example, logging operations or
other on/off road environments.
    Special conditions could be addressed by drafting the standard to
allow manual deactivation under limited circumstances when the system
is compromised. However, an FMVSS in which deactivation of the system
is easily accomplished would likely reduce the safety benefit of the
proposed rule. NHTSA seeks comments on the merits of and need for
manual deactivations of AEB systems. If the standard were to permit a
deactivation mechanism of some sort, how could NHTSA allow for
deactivations while ensuring the mechanism would not be abused or
misused by users? Alternatively, NHTSA is interested in comments on the
approach of the standard's restricting the automatic deactivation of
the AEB system generally but providing for special conditions in which
the vehicle is permitted to automatically deactivate or otherwise
restrict braking authority given to the AEB system.
    NHTSA seeks comment on the merits of various performance
requirements related to manual deactivation switches for AEB systems.
The agency seeks comment on the appropriate performance requirements if
the agency were to permit the installation of a manually operated
deactivation switch. Such requirements might include limitations such
that the default position of the switch be ``AEB ON'' with each cycle
of the starting system or that the deactivation functionality be
limited to specific speeds.

H. System Documentation

    NHTSA seeks comment on alternate regulatory approaches that might
be appropriate for regulating complex systems that depend heavily on
software performance. FMVSS have historically included requirements
that can be inspected or tested by the agency to verify compliance. In
some cases, such as in FMVSS No. 126, the agency has required
manufacturers to maintain technical documentation available for agency
review upon request to ensure that electronic stability control systems
were designed to mitigate vehicle understeer (49 CFR 571.126 S5.6). The
agency established this requirement in the absence of suitable test
procedures for evaluating understeer.
    In the case of AEB, there are similar limits to testing systems in
controlled environments. AEB systems operating on roadways will be
subject to many scenes and stimuli that are not present on a test
track--e.g., precipitation, lighting, roadway curvature and elevation
changes, signage, other road users, animals, debris, etc.--and these
scenes and stimuli could potentially influence real world effectiveness
of AEB systems. The agency seeks comment on documentation requirements
that may be effective in encouraging real world effectiveness (e.g.,
maximizing true positive rate and minimizing false positive rate) and
in ensuring that AEB systems are developed and maintained in a manner
that minimizes performance risks.
    The agency is considering requirements for manufacturers to
document a risk-based design approach identifying and mitigating
reasonably foreseeable risks alongside configuration management records
of all software/hardware updates performed by the manufacturer.
Manufacturers would also need to disclose certain servicing and system
limitation requirements and make AEB-related data stored in vehicles
available. Examples of requirements under consideration include:
     Manufacturers must establish and maintain procedures that
provide a risk-based approach in designing, implementing, and (if
applicable) updating each system required under this standard.
Manufacturers must maintain documentation over the system lifetime
detailing the outcome of the risk-based approach taken to ensure the
safety of such systems.
     Where servicing is required to maintain system
performance, each manufacturer must establish and maintain instructions
and procedures for performing and verifying that the servicing meets
the specified requirements.
     Certain information must be disclosed to consumers at the
time of first sale in a single document such as an owner's manual:
    [cir] If servicing requirements include periodic maintenance, the
maintenance schedule must be identified.
    [cir] Manufacturers must include a statement describing the
limitations of AEB and explaining that AEB is an emergency system that
does not replace the need for normal actuation of the service brakes.
     Each manufacturer must maintain documentation that
captures the full system configuration, including all hardware,
software, and firmware, for each vehicle at the time of first sale and
at the time of any update to the system configuration by the
manufacturer.
     Each AEB system or a system that communicates with the AEB
system must store information logging at least the last three AEB
activation events or all AEB activation events occurring within the
past three drive cycles.
     The vehicle must store the status of the AEB system
(active, inactive, disabled, warning, engaged, disengaged,
malfunctioning, etc.).
    NHTSA believes that manufacturers that have installed AEB systems
in their fleet may already be meeting many of the documentation
requirements above. The agency seeks comment on the suitability of
these requirements and on any changes that manufacturers would have to
introduce in their internal processes and consumer-facing documentation
(e.g., owner's manuals). NHTSA is interested in learning

whether manufacturers find discrepancies between real-world performance
and data collected on test tracks with surrogate vehicles.

I. ESC Performance Test

    This proposal would require nearly all heavy vehicles to have an
ESC system that meets the equipment requirements, general system
operational capability requirements, and malfunction detection
requirements of FMVSS No. 136. However, this proposal would not require
vehicles not currently required to have ESC systems to meet any test
track performance requirements for ESC systems because NHTSA is
conscious of the potential testing burden on small businesses and the
multi-stage vehicle manufacturers involved in class 3 through 6 vehicle
production. NHTSA requests comments on whether the agency should
establish performance requirements for ESC for all vehicles covered by
this proposal. If ESC performance requirements would be appropriate,
NHTSA seeks comment on which regulatory tests and requirements would be
appropriate for the class 3-8 vehicles which this notice proposes to
make applicable to FMVSS No. 136. NHTSA also seeks comment on whether
manufacturers of these vehicles should have the option to certify to
FMVSS No. 126 or FMVSS No. 136, whether a new ESC test procedure should
be developed for some or all of these vehicles, or whether NHTSA should
give the manufacturer the option to choose the ESC standard to which to
certify.
    NHTSA conducted some limited ESC testing for class 3-6 vehicles, as
part of research efforts during the development of FMVSS No. 136, which
was established in 2015, and as part of its recent AEB testing.\177\
The ESC testing performed has however been sufficient to indicate that
the test procedures currently established in FMVSS Nos. 126 and 136
would require modification in order to better suit class 3 through 6
vehicles. For example, the vehicle test speeds specified in FMVSS No.
136, which are designed to induce ESC activation in class 7 and 8
trucks and buses at speeds under 48 km/h (30 mph), did not induce ESC
activation in the vehicles that were tested. This testing indicates
that the maximum test speeds and speed reduction requirements would
likely need to be modified.
---------------------------------------------------------------------------

    \177\ This information is available in ``ESC Track Test Data for
Class 3-6 Vehicles,'' which has been placed in the docket identified
in the heading of this NPRM.
---------------------------------------------------------------------------

J. 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. NHTSA seeks comment on the issue of severability.

VIII. Vehicle Test Device

    NHTSA has proposed the same vehicle test device described below for
use in the proposed requirements for AEB for light vehicles. An
identical discussion of the vehicle test device appears in the NPRM
proposing the FMVSS for light vehicles.

A. Description and Development

    To ensure repeatable and reproducible testing that reflects how a
subject vehicle would be expected to respond to an actual vehicle in
the real world, this proposal includes broad specifications for a
vehicle test device to be used as a lead vehicle or pass through
vehicle during testing. NHTSA is proposing that the vehicle test device
be based on certain specifications defined in ISO 19206-3:2021, ``Road
vehicles--Test devices for target vehicles, vulnerable road users and
other objects, for assessment of active safety functions--Part 3:
Requirements for passenger vehicle 3D targets.'' \178\ The vehicle test
device is a tool that NHTSA proposes to use to facilitate the agency's
compliance tests to measure the performance of AEB systems required by
the proposed FMVSS. This NPRM describes the vehicle test device that
NHTSA would use.
---------------------------------------------------------------------------

    \178\ https://www.iso.org/standard/70133.html. May 2021.
---------------------------------------------------------------------------

    The surrogate vehicle NHTSA currently uses in its research testing
is the Global Vehicle Target (GVT). The GVT is a full-sized, harmonized
surrogate vehicle developed to test crash avoidance systems while
addressing the limitations of earlier generation surrogate vehicles. To
obtain input from the public and from industry stakeholders, NHTSA
participated in a series of five public workshops and three radar
tuning meetings between August 2015 and December 2016. These workshops
and meetings provided representatives from the automotive industry with
an opportunity to inspect, measure, and assess the realism of prototype
surrogates during the various stages of development. Workshop and
meeting participants were permitted to take measurements and collect
data with their own test equipment, which they could then use to
provide specific recommendations about how the surrogate vehicle's
appearance, to any sensor, could be improved to increase realism.
    After feedback from automotive vehicle manufacturers and suppliers
was incorporated into an earlier design of the GVT, a series of high-
resolution radar scans were performed by the Michigan Tech Research
Institute (MTRI) under NHTSA contract. These measurements provided an
independent assessment of how the radar characteristics of the GVT
compared to those from four real passenger cars.\179\ This study found
that the GVT has generally less radar scatter than the real vehicles to
which it was compared. However, MTRI found that ``even though the [GVT]
may more often reflect a greater amount of energy than the [real]
vehicles, it is not exceeding the maximum energy of the returns from
the vehicles. Thus, a sensor intended for the purpose of detecting
vehicles should perform well with the [GVT].'' \180\
---------------------------------------------------------------------------

    \179\ The comparison passenger cars used were a 2008 Hyundai
Accent, a 2004 Toyota Camry, a 2016 Ford Fiesta hatchback, and a
2013 Subaru Impreza.
    \180\ Buller, W., Hart, B., Aden, S., and Wilson, B. (2017, May)
``Comparison of RADAR Returns from Vehicles and Guided Soft Target
(GST),'' Michigan Technological University, Michigan Tech Research
Institute. Docket NHTSA-2015-0002-0007.
---------------------------------------------------------------------------

    NHTSA also performed tests to determine the practicality of using
the GVT for test-track performance evaluations by examining how
difficult it was to reassemble the GVT after it was struck in a test.
Using a randomized matrix designed to minimize the effect of learning,
these tests were performed with teams of three or five members familiar
with the GVT reassembly process. NHTSA found that reassembly of the GVT
on the robotic platform takes approximately 10 minutes to complete;
however, additional time is often required to re-initialize the robotic
platform GPS afterwards.\181\
---------------------------------------------------------------------------

    \181\ Snyder, Andrew C. et al., ``A Test Track Comparison of the
Global Vehicle Target (GVT) and NHTSA's Strikeable Surrogate Vehicle
(SSV),'' July 2019. https://rosap.ntl.bts.gov/view/dot/41936.
---------------------------------------------------------------------------

    Finally, NHTSA conducted its own crash imminent braking tests to
compare the speed reduction achieved by three passenger cars as they
approached the GVT, compared to the Strikable Surrogate Vehicle (SSV),
the surrogate vehicle NHTSA currently uses for its NCAP AEB tests.
These tests found that any differences that might exist between the GVT
and the SSV were small enough to not appreciably influence the outcome
of vehicle testing.\182\
---------------------------------------------------------------------------

    \182\ Id.
---------------------------------------------------------------------------

    When used during AEB testing, the GVT is secured to the top of a
low-

profile robotic platform. The robotic platform is essentially flat and
is movable and programmable. The vehicle test device's movement can be
accurately and repeatably defined and choreographed with the subject
vehicle and testing lane through the use of data from the robotic
platform's on-board inertial measurement unit, GPS, and closed-loop
control facilitated by communication with the subject vehicle's
instrumentation. The shallow design of the robotic platform allows the
test vehicle to drive over it. The GVT is secured to the top of the
robotic platform using hook-and-loop fastener attachment points, which
allow the pieces of the GVT to easily and safely break away without
significant harm to the vehicle being tested if struck.
    The internal frame of the GVT is constructed primarily of vinyl-
covered foam segments held together with hook-and-loop fasteners. The
GVT's exterior is comprised of multiple vinyl ``skin'' sections
designed to provide the dimensional, optical, and radar characteristics
of a real vehicle that can be recognized as such by camera and radar
sensors.\183\ If the subject vehicle impacts the GVT at low speed, the
GVT is typically pushed off and away from the robotic platform without
breaking apart. At higher impact speeds, the GVT breaks apart as the
subject vehicle essentially drives through it.
---------------------------------------------------------------------------

    \183\ ``A Test Track Comparison of the Global Vehicle Target
(GVT) and NHTSA's Strikeable Surrogate Vehicle,'' DOT HS 812-698.
---------------------------------------------------------------------------

B. Specifications

    The most recent, widely-accepted iteration of vehicle test device
specifications is contained in ISO 19206-3:2021.\184\ Using data
collected by measuring the fixed-angle/variable-range radar cross
section for several real vehicles, ISO developed generic
``acceptability corridors,'' which are essentially boundaries that the
vehicle test device's radar cross section must fit within to be deemed
representative of a real vehicle.\185\ All vehicles that ISO tested
have radar cross section measurements that fit within the boundaries
set forth in the ISO standard.
---------------------------------------------------------------------------

    \184\ Road vehicles--Test devices for target vehicles,
vulnerable road users and other objects, for assessment of active
safety functions--Part 3: Requirements for passenger vehicle 3D
targets.
    \185\ The vehicles tested to develop the ISO standard are: 2016
BMW M235i, 2006 Acura RL, 2019 Tesla Model 3, 2017 Nissan Versa,
2018 Toyota Corolla, 2019 Ford Fiesta.
---------------------------------------------------------------------------

    This proposal would incorporate by reference ISO 19206-3:2021 into
NHTSA's regulations and specify that the vehicle test device meets
several specifications in ISO 19206-3:2021, in addition to other
specifications identified by NHTSA. Because the GVT was considered
during the development of ISO 19206-3:2021, the GVT would meet the
standard's specifications. However, should the design of the GVT change
or a new vehicle test device be developed, reference to the more
general specifications of ISO 19206-3:2021 should ensure that NHTSA is
able to test with such other vehicle test devices and should also
ensure that such vehicle test devices have properties needed by an AEB
system to identify it as a motor vehicle.
    The vehicle test device's physical dimensions are proposed to be
consistent with those of the subcompact and compact car vehicle class.
The specific range of dimensions in this proposal for individual
surfaces of the vehicle test device are incorporated from ISO 19206-
3:2021, Annex A, Table A.4. These include specifications for the test
device's width and the placement of the license plate, lights, and
reflectors relative to the rear end of the vehicle test device.
    The vehicle test device is proposed to have features printed on its
surface to represent features that are identifiable on the rear of a
typical passenger vehicle, such as tail lamps, reflex reflectors,
windows, and the rear license plate. The proposed color ranges for the
various surface features, including tires, windows, and reflex
reflectors are incorporated from ISO 19206-3:2021, Annex B, Tables B.2
and B.3. Table B.2 specifies the colors of the tires, windows, and
reflectors, which reflect the colors observed the in the real world.
The color of the exterior of the vehicle is specified to be a range
representing the color white, which provides a high color contrast to
the other identifiable features. White is also a common color for motor
vehicles.\186\ The proposed reflectivity ranges for the various
features on the vehicle test device are incorporated from ISO 19206-
3:2021, Annex B, Table B.1. Table B.3 specifies the recommended
minimum, mean, and maximum color range for the white body, specifically
the outer cover.
---------------------------------------------------------------------------

    \186\ Globally, white was the most popular color for light
vehicles in 2021. https://gmauthority.com/blog/2022/02/white-was-
the-most-popular-car-color-again-in-2021/
#:~:text=According%20to%20PPG%2C%2035%20percent,by%20silver%20at%2011
%20percent.
---------------------------------------------------------------------------

    Because many AEB systems rely on radar sensors in some capacity to
identify the presence of other vehicles, the vehicle test device must
have a radar cross section that would be recognized as a real vehicle
by an AEB system. In particular, the vehicle test device must have a
radar cross section consistent with a real vehicle when approached from
the rear over a range of distances.
    NHTSA is proposing that the radar cross section of the vehicle test
device fall within an ``acceptability corridor'' when measured using an
automotive-grade radar sensor. This acceptability corridor would be
defined by the upper and lower boundaries specified by ISO 19206-
3:2021, Annex C, Equations C.1 and C.2, using the radar cross section
boundary parameters defined in ISO 19206-3:2021, Annex C, Table C.3 for
a fixed viewing angle of 180 degrees. NHTSA is aware that, unlike some
predecessor specification documents such as Euro NCAP Technical
Bulletin 025 from May 2018, ISO 19206-3:2021 does not specify that the
radar cross section measurements be verified using a specific model of
radar. Rather, the ISO standard specifies that the radar sensor used
have certain specifications and operational characteristics. NHTSA's
proposal similarly does not specify that the vehicle test device's
initial radar cross section be measured with a specific model or brand
of radar. NHTSA only proposes that the radar sensor used to validate
the radar cross section operate within the 76-81 GHz bandwidth, have a
horizontal field of view of at least 10 degrees, a vertical field of
view of at least 5 degrees, and a range greater than 100 m.
Additionally, NHTSA's proposal does not specify that the VTD's radar
cross section during in-the-field verifications be performed to
objectively assess whether the radar cross section still falls within
the acceptability corridor. NHTSA seeks comment about whether use of
the optional field verification procedure provided in ISO 19206-3:2021,
Annex E, section E.3 should be used.
    Because the test procedures proposed in this rule only involve
rear-end approaches by the subject vehicle, NHTSA is at this time only
proposing to establish specifications applicable for the rear end of
the vehicle test device. NHTSA seeks comment on whether the
specifications for the vehicle test device should include all sides of
the vehicle. If NHTSA were to include, in a final rule, specifications
for all sides of a vehicle test device, NHTSA anticipates that those
specifications would also be incorporated from ISO 19206-3:2021.

C. Alternatives Considered

    One alternative test device that NHTSA considered for use in this
proposal was the agency's self-developed Strikable Surrogate Vehicle
(SSV) device, which NHTSA currently uses in its NCAP testing of AEB
performance. NHTSA adopted the use of

the SSV as part of its 2015 NCAP upgrade, under which the agency began
testing AEB performance.\187\ The SSV resembles the rear section of a
2011 Ford Fiesta hatchback. The SSV is constructed primarily from a
rigid carbon fiber mesh, which allows it to maintain a consistent shape
over time (unless damaged during testing). To maximize visual realism,
the SSV shell is wrapped with a vinyl material that simulates paint on
the body panels and rear bumper, and a tinted glass rear window. The
SSV is also equipped with a simulated United States specification rear
license plate. The taillights, rear bumper reflectors, and third brake
light installed on the SSV are actual original equipment from a
production vehicle. NHTSA testing shows that AEB systems will recognize
the SSV and will respond in a way that is comparable to how they would
respond to an actual vehicle.\188\
---------------------------------------------------------------------------

    \187\ 80 FR 68604.
    \188\ 80 FR 68607.
---------------------------------------------------------------------------

    While the SSV and GVT are both recognized as real vehicles by AEB
systems from the rear approach aspect, the SSV has several
disadvantages. The foremost disadvantage of the SSV is how easily it
can be irreparably damaged when struck by a subject vehicle during
testing, particularly at high relative velocities. While NHTSA has
tried to address this issue by attaching a foam bumper to the rear of
the SSV to reduce the peak forces resulting from an impact by the
subject vehicle, the SSV can still easily be damaged to a point where
it can no longer be used if the relative impact speed is sufficiently
high (greater than 40 km/h (25 mph)); this speed is much lower than the
maximum relative impact speed of 80 km/h (50 mph) potentially
encountered during the AEB tests performed at the maximum relative
speeds proposed in this notice). Also, unlike the GVT, which has its
movement controlled by precise programming and closed loop control, the
SSV moves along a monorail secured to the test surface, which may be
visible to a camera-based AEB system.
    In addition to the vehicle test device specifications, NHTSA seeks
comment on specifying a set of real vehicles to be used as vehicle test
devices in AEB testing. UN ECE Regulation No. 152 specifies that the
lead vehicle be either a regular high-volume passenger sedan or a
``soft target'' meeting the specifications of ISO 19206-1:2018.\189\ UN
ECE regulation does not require the use of real vehicles as targets,
but rather offers them as an alternative to manufacturers to homologate
their systems, at their choice. Although NHTSA has tentatively
concluded that the specification in UN ECE Regulation No. 152 of any
high-volume passenger sedan is not sufficiently specific for an FMVSS,
NHTSA seeks comment on whether it should create a list of vehicles from
which NHTSA could choose a lead vehicle for testing. Unlike the UN ECE
regulation, which provides flexibility to manufacturers, inclusion of a
list of vehicles would provide flexibility to the agency in the
assessment of the performance of AEB systems. Such a list would be in
addition to the vehicle test device proposed in this document, to
provide assurance of vehicle performance with a wider array of lead
vehicles. For example, the list could include the highest selling
vehicle models in 2020.
---------------------------------------------------------------------------

    \189\ U.N. Regulation No. 152, E/ECE/TRANS/505/Rev.3/Add.151/
Amend.1 (Nov. 4, 2020), available at https://unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2020/R152am1e.pdf.
---------------------------------------------------------------------------

    Using actual vehicles has various challenges, including the
potential for risk to individuals conducting the tests and damage to
the vehicles involved, and assuring a safe testing environment that
could encounter high energy collisions between real vehicles in cases
of poor AEB system performance or AEB or test equipment malfunctions.
NHTSA seeks comment on the utility and feasibility of test laboratories
safely conducting AEB tests with real vehicles, such as through
removing humans from test vehicles and automating scenario execution,
and how laboratories would adjust testing costs to factor in the risk
of damaged vehicles.
    Beyond the practical safety limits and cost of testing described
above, managing a list of relevant lead vehicles would require the
standard to be updated periodically to keep pace with the vehicle fleet
and to ensure that lead vehicles are available years after a final
rule. NHTSA seeks comments on the merits and potential need for testing
using real vehicles, in addition to using a vehicle test device, as
well as challenges, limitations, and incremental costs of such.

IX. Proposed Compliance Date Schedule

    NHTSA proposes a two-tiered phase-in schedule for meeting the new
standard. For heavy vehicles currently subject to FMVSS No. 136, any
vehicle manufactured on or after the first September 1 that is three
years after the date of publication of the final rule must meet the
proposed heavy vehicle AEB standard. To illustrate, if the final rule
were published on October 1, 2023, the compliance date would be
September 1, 2027. For heavy vehicles not currently subject to FMVSS
No. 136, with some exclusions, those manufactured on or after the first
September 1 that is four years after the date of publication of the
final rule must meet the amendments to FMVSS No. 136 that would require
ESC systems and the proposed AEB requirements. In the provided example
of a final rule published on October 1, 2023, that date would be
September 1, 2028. Small-volume manufacturers, final-stage
manufacturers, and alterers would be provided an additional year, added
to the dates above, to meet the requirements of this proposal.
    Consistent with 49 U.S.C. 30111(d), NHTSA has tentatively concluded
that good cause exists for this proposal to take effect more than one
year after publication of a final rule because it would not be feasible
for all heavy vehicles to be equipped with AEB systems that meet the
proposed performance requirements within one year. Furthermore, NHTSA
seeks comments on whether this proposed phase-in schedule appropriately
addresses challenges to the implementation of AEB for specific
categories of heavy vehicles. The agency is particularly interested in
information about single-unit trucks with permanently installed work-
performing equipment installed on the front of or extending past the
front of the vehicle (e.g., auger trucks, bucket trucks, cable reel
trucks, certain car carriers, etc.), where AEB sensors may be located.
NHTSA seeks comments to discern the best way to implement the
applicability of AEB on class 3-6 single-unit trucks, considering all
scenarios such as vehicle configuration, vehicle service applicability,
and cargo type, which, among other factors, can affect vehicle dynamics
and drivability. The manufacture of single-unit trucks is more complex
than that of truck tractors due to wider variations in vehicle weight,
wheelbase, number of axles, center of gravity height, and cargo type.
These factors, and others, bear on the calibration and performance of
ESC. For example, ESC system design depends on vehicle dynamics
characteristics, such as the total vehicle weight and location of that
weight (center of gravity), which will differ depending on the final
vehicle configuration. Because ESC has been a prerequisite for
voluntary adoption of AEB, single-unit trucks not having had ESC
requirements suggests that AEB implementation has been slower and that
there is a need for effective date flexibility.
    NHTSA is also aware that many, if not most, manufacturers of
single-unit trucks are final-stage manufacturers, which are typically
small businesses. To

provide more flexibility to small businesses to meet the proposed rule,
this NPRM proposes to permit small-volume manufacturers, final-stage
manufacturers, and alterers an additional year to meet the requirements
of the final rule. The additional time would provide flexibility to the
manufacturers to install ESC and collaborate with AEB suppliers to meet
the proposed requirements.
    FMCSA proposes that vehicles currently subject to FMVSS No. 136
(i.e., those manufactured on or after August 1, 2019, the initial
compliance date for FMVSS No. 136) would be required to comply with
FMCSA's proposed ESC regulation on the final rule's effective date.
Vehicles with a GVWR greater than 4,536 kilograms (10,000 pounds) not
currently subject to FMVSS No. 136 would be required to meet the
proposed ESC regulation on or after the first September 1 that is five
years after the date of publication of the final rule.
    FMCSA proposes that, for vehicles currently subject to FMVSS No.
136, any vehicle manufactured on or after the first September 1 that is
three years after the date of publication of the final rule would be
required to meet the proposed heavy vehicle AEB standard. FMCSA
proposes that vehicles with a gross vehicle weight rating greater than
4,536 kilograms (10,000 pounds) not currently subject to FMVSS No. 136
and vehicles supplied to motor carriers by small-volume manufacturers,
final-stage manufacturers, and alterers would be required to meet the
proposed heavy vehicle AEB standard on or after the first September 1
that is five years after the date of publication of the final rule.
    This proposed implementation timeframe simplifies FMCSR training
and enforcement because the Agency expects a large number of final
stage manufacturers supplying vehicles to motor carriers in the
category of vehicles with a gross vehicle weight rating greater than
4,536 kilograms (10,000 pounds).
    FMCSA will require the ESC and AEB systems to be inspected and
maintained in accordance with Sec.  396.3.

X. Retrofitting

    The Secretary has the statutory authority to promulgate safety
standards for commercial motor vehicles and equipment subsequent to
initial manufacture. The Secretary has delegated authority to NHTSA, in
coordination with FMCSA, to promulgate safety standards for commercial
motor vehicles and equipment subsequent to initial manufacture when the
standards are based upon and similar to an FMVSS.\190\
---------------------------------------------------------------------------

    \190\ Sec. 101(f) of Motor Carrier Safety Improvement Act of
1999 (Pub. L. 106-159; Dec. 9, 1999). 49 CFR 1.95(c).
---------------------------------------------------------------------------

    NHTSA considered, but decided against, proposing to require
retrofitting of in-service vehicles with GVWR greater than 4,536 kg
(10,000 lbs.) with AEB systems. NHTSA believes that retrofitting in-
service vehicles with AEB systems could be very complex and costly
because of the integration between an AEB system and the vehicles'
chassis, engine, and braking systems. There may be changes that would
have to be made to an originally manufactured vehicle's systems that
interface with an AEB system, such as plumbing for new air brake valves
and lines and a new electronic control unit for a revised antilock
braking system and a new electronic stability control system. NHTSA
might also have to develop and establish additional requirements to
ensure that AEB control components on in-service (used) vehicles are at
an acceptable level of performance for a compliance test of AEB. This
would be likely given the uniqueness of each vehicle's maintenance
condition, particularly for items such as tires and brake components,
which are foundational for AEB performance (and which are subject to
high demands of wear-and-tear).
    Nonetheless, although this NPRM does not propose requiring heavy
vehicles to be equipped with AEB subsequent to initial manufacture,
NHTSA requests comment on the following issues related to retrofitting
to learn more about the technical and economic feasibility of a
retrofit requirement going forward.
     The complexity, cost, and burdens of a requirement to
retrofit in-service vehicles with AEB.
     The changes that would be needed to an originally
manufactured vehicle's systems that interface with an AEB system, such
as plumbing for new air brake valves and lines and a new electronic
control unit for a revised ABS and a new ESC system.
     Approaches NHTSA could take to identify portions of the
on-road fleet to which a retrofit requirement could apply. For a
retrofitting requirement, should the requirement distinguish among in-
service vehicles based on the vehicles' date of manufacture? Is it
reasonable to assume that older in-service vehicles would have greater
challenges to meet a retrofit requirement? What should, for example,
the original manufacture date be of vehicles that should be subject to
a retrofit requirement?
     Should there be provisions to ensure that the various
components related to AEB performance (e.g., brakes and tires) are at
an acceptable level of performance for a compliance test, given the
uniqueness of the maintenance condition for vehicles in service,
especially for items particularly subject to wear-and-tear (e.g., brake
components and tires)?
     Relatedly, would it be warranted to vary the performance
requirements for retrofitted vehicles, so that the requirements would
be less stringent for used vehicles? If yes, what would be appropriate
level of stringency? If not, how can the requirements be adjusted for
in-service vehicles?
     NHTSA requests comment on other options the agency could
take to identify portions of the on-road fleet to which a retrofit
requirement should apply. Are there other voluntary improvements that
heavy vehicle operators would consider in attaining the benefits
provided by AEB for their in-service vehicles?

XI. Summary of Estimated Effectiveness, Cost, Benefits, and Comparison
of Regulatory Alternatives

A. Crash Problem

    NHTSA's assessment of available safety data indicates that between
2017 and 2019, an average of approximately 60,000 crashes occurred
annually in which a heavy vehicle rear-ended another vehicle. These
crashes resulted in an annual average of 388 fatalities, approximately
30,000 non-fatal injuries, and 84,000 property-damage-only vehicles.
Additionally, class 3-6 heavy vehicles were involved in approximately
17,000 rollover and loss of control crashes annually. These crashes
resulted in 178 fatalities, approximately 4,000 non-fatal injuries, and
13,000 property-damage-only vehicles annually. In total, these rear-
end, rollover, and loss of control crashes add up to 77,000 annually,
which represent 1.2 percent of all police-reported crashes and over 14
percent of all crashes involving heavy vehicles. In total, these
crashes resulted in 566 fatalities and 34,000 non-fatal injuries. These
crashes also damaged 97,000 vehicles in property-damage-only crashes.

B. AEB System Effectiveness

    NHTSA evaluated the effectiveness of AEB indicates based on the
efficacy of the system in avoiding a rear-end crash. This relates to
the proposed requirement that a vehicle avoid an imminent rear-

end collision under a set of test scenarios. One method of estimating
effectiveness would be to perform a statistical analysis of real-world
crash data and observe the differences in statistics between heavy
vehicles equipped with AEB and those not equipped with AEB. However,
this approach is not feasible currently due to the low penetration rate
of AEB in the on-road vehicle fleet. Consequently, NHTSA estimated the
effectiveness of AEB systems using performance data from the agency's
vehicle testing. Effectiveness was assessed against all crash severity
levels collectively, rather than for specific crash severity levels
(i.e., minor injury versus fatal).
    The AEB effectiveness estimates were derived from performance data
from four vehicles tested by NHTSA, and the agency is continuing its
effort to test a larger variety of vehicles to further evaluate AEB
system performance. These vehicles were subject to the same test
scenarios (stopped lead vehicle, slower-moving lead vehicle, and
decelerating lead vehicle) that are proposed in this notice, and
effectiveness estimates are based on each vehicle's capacity to avoid a
collision during a test scenario. For example, if a vehicle avoided
colliding with a stopped lead vehicle in four out of five test runs,
its effectiveness in that scenario would be 80 percent. The test
results for each vehicle were combined into an aggregate effectiveness
value by vehicle class range and crash scenario, as displayed in Table
17.

                    Table 17--AEB Effectiveness (%) by Vehicle Class Range and Crash Scenario
----------------------------------------------------------------------------------------------------------------
                                                            Stopped lead      Slower-moving    Decelerating lead
                  Vehicle class range                         vehicle          lead vehicle         vehicle
----------------------------------------------------------------------------------------------------------------
7-8....................................................               38.5               49.2               49.2
3-6....................................................               43.0               47.8               47.8
----------------------------------------------------------------------------------------------------------------

    As shown in Table 17, after aggregating class 7 and class 8
together, AEB would avoid 38.5 percent of rear-end crashes for the
stopped lead vehicle scenario, and 49.2 percent of slower-moving and
decelerating lead vehicle target crashes. For class 3-6, AEB is 43.0
percent effective against stopped lead vehicle crashes and 47.8 percent
against slower-moving and decelerating lead vehicle target crashes.
These effectiveness values are the values used for assessing the
benefits of this proposed rule. Further detail on the derivation of AEB
effectiveness can be found in the PRIA accompanying this proposal.

C. ESC System Effectiveness

    ESC effectiveness rates were adopted from those estimated in the
final regulatory impact analysis for the final rule implementing heavy
vehicle ESC requirements in FMVSS No. 136.\191\ In that final rule, a
range of ESC crash avoidance effectiveness was established for the
first-event rollover crashes but only a single-point estimate was
established for loss of control crashes. ESC was estimated to be 40 to
56 percent effective at preventing rollover crashes and 14 percent
effective at preventing loss-of-control crashes. For simplicity, and to
correspond with the single-point estimate for loss of control crashes,
the PRIA used the mid-point between the lower and upper bounds of the
estimated range as the effectiveness for rollovers.
---------------------------------------------------------------------------

    \191\ Final Regulatory Impact Analysis, FMVSS No. 136 Electronic
Stability Control on Heavy Vehicles, June 2014, Docket No. NHTSA-
2015-0056.
---------------------------------------------------------------------------

    The propensity for vehicles to experience rollover and loss-of-
control crashes is influenced by their body type and center of gravity,
and the implementation of ESC varies. ESC was estimated to be less
effective on class 7 and 8 vehicles than it was on light vehicles,
especially for rollover crashes.\192\ Vehicle characteristics for class
3 through 6 vehicles range between that of light trucks and vans and
class 7 and 8 vehicles, it would be plausible to assume that ESC
effectiveness would be between the effectiveness estimated in the FMVSS
No. 126 and FMVSS No. 136 final rules. Nevertheless, this NPRM uses the
effectiveness estimates from the FMVSS No. 136 final rule.
---------------------------------------------------------------------------

    \192\ Dang, J. (July 2007) Statistical Analyzing of the
Effectiveness of Electronic Stability Control (ESC) Systems--Final
Report, DOT HS 810 794, Washington, DC, https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/810794.

            Table 18--ESC Effectiveness (%) by Crash Scenario
------------------------------------------------------------------------
                                                                Loss of
               Vehicle class range                 Rollover     control
------------------------------------------------------------------------
3-6.............................................       48.0        14.0
------------------------------------------------------------------------

D. Avoided Crashes and Related Benefits

    Considering the annual heavy vehicle rear-end, rollover, and loss
of control crashes, as well as the effectiveness of AEB and ESC at
avoiding these crashes, the proposed rule would prevent an estimated
19,118 crashes, 155 fatalities, and 8,814 non-fatal injuries annually.
In addition, the proposed rule would eliminate an estimated 24,828
PDOVs annually. The benefit estimates include assumptions that likely
result in the underestimation of the benefits of this proposal because
it only reflects the benefits from crash avoidance. That is, the
benefits only reflect those resulting from crashes that are avoided as
a result of the AEB and ESC performance proposed. It is likely that AEB
will also reduce the severity of crashes that are not prevented. Some
of these crashes may include fatalities and significant injuries that
will be prevented or mitigated by AEB.
    Table 19 tabulates these benefits in two ways, one by vehicle class
and one by technology. These benefits are measured for the portion of
the vehicle fleet that has not voluntarily adopted AEB prior to the
NPRM. These benefits also assume reduced performance under dark or
hazardous weather conditions. The estimated annual benefits would be
the undiscounted lifetime benefits once the proposal is fully
implemented (four years after publication of a final rule). The
undiscounted lifetime benefits for each new model year of vehicles
would equal the annual benefits of the on-road fleet when that fleet
has been fully equipped with this technology. The actual annual
benefits will increase each year as the on-road vehicle fleet is
replaced with vehicles that would be subject to the proposed
requirements.

                      Table 19--Undiscounted Estimated Annual Benefits of the Proposed Rule
----------------------------------------------------------------------------------------------------------------
                                                                                Non-fatal
                                                      Crashes       Fatalities       injuries          PDOVs
----------------------------------------------------------------------------------------------------------------
By Vehicle Class:
    Class 7-8...................................           5,691              40           2,822           7,958
    Class 3-6...................................          13,427             115           5,992          16,870
                                                 ---------------------------------------------------------------
        Total...................................          19,118             155           8,814          24,828
By Technology:
    AEB.........................................          16,224             106           8,058          22,713
    ESC.........................................           2,894              49             756           2,115
                                                 ---------------------------------------------------------------
        Total...................................          19,118             155           8,814          24,828
----------------------------------------------------------------------------------------------------------------

E. Technology Costs

    The AEB system is estimated to cost $396 per vehicle. The unit cost
includes all the components, labor cost for training customers, tuning
the system to ensure the performance of AEB, and the AEB malfunction
telltale. The component unit costs were based on the agency's 2018
weight and teardown study, which accounted for scale efficiencies in
production and labor.\193\ The cost for an ESC system would range from
$320 to $687, which was calculated by adjusting the assumed unit cost
for ESC in the FMVSS No. 136 final rule for inflation.\194\ Therefore,
for vehicles that need both AEB and ESC, the total unit cost would
range from $716 to $1,083 per affected vehicle.\195\ The total number
of affected vehicles including trucks and buses are estimated to be
569,792 units annually: 164,405 units for class 7-8 and 405,387 units
for class 3-6 vehicles. The total cost corresponding to the estimated
annual benefits is estimated to be $353 million ($288 million for class
7-8 and $65 million for class 3-6). The affected vehicle units were
based on the 10 year average of units sold between 2011 and 2020.\196\
---------------------------------------------------------------------------

    \193\ ``Cost and Weight Analysis of Heavy Vehicle Forward
Collision Warning (FCW) and Automatic Emergency Braking (AEB)
Systems for Heavy Trucks,'' September 27, 2018, Contract number:
DTNH2216D00037, Task Order: DTNH2217F00147.