[Federal Register Volume 81, Number 240 (Wednesday, December 14, 2016)]
[Rules and Regulations]
[Pages 90416-90522]
[FR Doc No: 2016-28804]

Vol. 81

Wednesday,

No. 240

December 14, 2016

Part II

 Department of Transportation

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National Highway Traffic Safety Administration

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49 CFR Parts 571 and 585

Federal Motor Vehicle Safety Standards; Minimum Sound Requirements for
Hybrid and Electric Vehicles; Final Rule

Federal Register / Vol. 81 , No. 240 / Wednesday, December 14, 2016 /
Rules and Regulations

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Parts 571 and 585

[Docket No. NHTSA-2016-0125]
RIN 2127-AK93

Federal Motor Vehicle Safety Standards; Minimum Sound
Requirements for Hybrid and Electric Vehicles

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

ACTION: Final rule.

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SUMMARY: To reduce the risk of pedestrian crashes, especially for the
blind and visually-impaired, and to satisfy the mandate in the
Pedestrian Safety Enhancement Act (PSEA) of 2010 this final rule
establishes a new Federal motor vehicle safety standard (FMVSS) setting
minimum sound requirements for hybrid and electric vehicles. This new
standard requires hybrid and electric passenger cars, light trucks and
vans (LTVs), and low speed vehicles (LSVs) to produce sounds meeting
the requirements of this standard. This final rule applies to electric
vehicles (EVs) and to those hybrid vehicles (HVs) that are capable of
propulsion in any forward or reverse gear without the vehicle's
internal combustion engine (ICE) operating. This standard will help to
ensure that blind, visually impaired, and other pedestrians are able to
detect and recognize nearby hybrid and electric vehicles, as required
by the PSEA.

DATES: Effective date: This rule is effective February 13, 2017.
    Compliance date: Initial compliance is required, in accordance with
the phase-in schedule, on September 1, 2018. Full compliance is
required on September 1, 2019.
    Petitions for reconsideration: Petitions for reconsideration of
this final rule must be received not later than January 30, 2017.
    Incorporation by Reference: The incorporation by reference of
certain publications listed in the standard is approved by the Director
of the Federal Register as of February 13, 2017.

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

FOR FURTHER INFORMATION CONTACT:
    For non-legal issues, Mr. Mike Pyne, Office of Crash Avoidance
Standards (telephone:<PHONE_NUMBER>) (fax:<PHONE_NUMBER>). Mr. Pyne's
mailing address is National Highway Traffic Safety Administration, NVS-
123, 1200 New Jersey Avenue SE., Washington, DC 20590.
    For legal issues, Mr. Thomas Healy, Office of the Chief Counsel
(telephone:<PHONE_NUMBER>) (fax:<PHONE_NUMBER>). Mr. Healy's mailing
address is National Highway Traffic Safety Administration, NCC-112,
1200 New Jersey Avenue SE., Washington, DC 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary
    A. Summary of Requirements of the Final Rule
    B. Costs and Benefits
II. Background and Summary of Notice of Proposed Rulemaking
    A. Pedestrian Safety Enhancement Act and National Traffic and
Motor Vehicle Safety Act
    B. Safety Problem
    C. Research on Vehicle Emitted Sounds and Detectability
    D. Notice of Proposed Rulemaking
    E. Summary of Comments to the NPRM
III. Final Rule and Response to Comments
    A. Summary of the Final Rule
    B. Applicability of the Standard
    C. Critical Operating Scenarios
    D. Crossover Speed
    E. Acoustic Parameters for Detection of Motor Vehicles
    F. Acoustic Parameters for Recognition of Motor Vehicles
    G. Frequency (Pitch) Shifting and Volume Change
    H. Sameness
    I. Customer Acceptance
    J. Test Conditions
    K. Test Procedure
    L. Phase-in of Requirements
IV. International Harmonization and Stakeholder Consultation
V. Analysis of Costs, Benefits, and Environmental Effects
    A. Benefits
    B. Costs
    C. Comparison of Costs and Benefits
    D. Retrospective Review
    E. Environmental Assessment
VI. Regulatory Notices and Analyses
    Executive Order (E.O.) 12866 (Regulatory Planning and Review),
E.O. 13563, and DOT Regulatory Policies and Procedures
    Executive Order 13609: Promoting International Regulatory
Cooperation
    National Environmental Policy Act
    Regulatory Flexibility Act
    Executive Order 13132 (Federalism)
    Executive Order 12988 (Civil Justice Reform)
    Unfunded Mandates Reform Act
    Paperwork Reduction Act
    Executive Order 13045
    National Technology Transfer and Advancement Act
    Executive Order 13211
    Regulation Identifier Number (RIN)

I. Executive Summary

    The PSEA requires NHTSA to establish performance requirements for
an alert sound that is recognizable as a motor vehicle in operation
that allows blind and other pedestrians to detect nearby electric
vehicles or hybrid vehicles operating at lower speeds. This final rule
establishes FMVSS No.141, Minimum Sound Requirements for Hybrid and
Electric Vehicles, which requires hybrid and electric passenger cars
and LTVs with a gross vehicle weight rating (GVWR) of 4,536 kg (10,000
lbs.) or less and LSVs, to produce sounds meeting the requirements of
this standard so both blind and sighted pedestrians can more easily
detect and recognize by hearing these vehicles. Both blind and sighted
pedestrians have greater difficulty detecting hybrid and electric
vehicles at low speeds than vehicles with ICE engines because hybrid
and electric vehicles produce measurably less sound at those speeds.\1\
At higher speeds, in contrast, tire and wind noise are the primary
contributors to a vehicle's noise output, so the sounds produced by
hybrid and electric vehicles and ICE vehicles are similar.
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    \1\ Garay-Vega, L; Hastings, A.; Pollard, J.K.; Zuschlag, M. &
Stearns, M. (2010, April). Quieter Cars and the Safety of Blind.
Pedestrians: Phase 1. DOT HS 811 304. Washington, DC: National
Highway Traffic Safety Administration.
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    Hybrid vehicles with gross vehicle weight rating (GVWR) of 4,536 kg
(10,000 lbs.) or less are 1.18 times more likely than an ICE vehicle to
be involved in a collision with a pedestrian and 1.51 times more likely
to be involved in a collision with a pedalcyclist. NHTSA assumes that
this difference in accident rates is mostly attributable to the
pedestrians' inability to detect the presence of these vehicles through
hearing.
    To further evaluate the assumption that the difference in crash
rates is mostly attributable to differences in vehicle emitted sound,
the agency conducted research to see if there was a difference in the
ability of pedestrians to detect approaching hybrid and electric
vehicles versus ICE vehicles. The agency also conducted research to
examine how the frequency composition of a sound influenced the ability
of pedestrians to detect that sound in the presence of ambient noise.
Section II.C provides much more information on this research and how
the agency used it in the context of this rulemaking.

A. Summary of Requirements of the Final Rule

    On January 14, 2013, NHTSA published a notice of proposed
rulemaking (NPRM) specifying minimum sound requirements for hybrid and
electric vehicles.\2\ The NPRM discussed three alternative means for
the agency to establish requirements for, and measure compliance with,
minimum levels of vehicle emitted sound. In the NPRM, the agency
proposed its preferred alternative which was to establish minimum
requirements for vehicle emitted sound using a psychoacoustic model.
Sounds meeting the proposed requirements would contain acoustic
elements designed to enhance detection and to aid pedestrians in
recognizing the sound as coming from a motor vehicle. We believed that
the preferred alternative placed the greatest emphasis on ensuring the
vehicle emitted sounds were detectable to pedestrians. In addition to
the preferred alternative, the NPRM also discussed minimum sound
requirements for HVs and EVs designed to resemble sounds produced by
ICE vehicles. This alternative would place a greater emphasis on
recognizability than the preferred alternative. Compliance with both of
these alternatives would be determined using a compliance test that
measured the sound produced by the vehicle.
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    \2\ 78 FR 2797.
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    In order to provide an alternative that would allow the most
flexibility in the types of sounds that manufacturers could choose to
add to vehicles to alert pedestrians, we also discussed using human
factors testing to determine whether a sound used to alert pedestrians
was recognizable as a motor vehicle.
    After careful consideration of all available information, including
the public comments submitted in response to the NPRM,\3\ the agency
has decided to adopt the preferred alternative in the NPRM and many of
the elements of the proposed rule. In the final rule, as proposed, the
agency requires hybrid and electric vehicles to emit sound while the
vehicle is stationary with the vehicle propulsion system activated.
(However, in the final rule this requirement does not apply to vehicles
that are parked with the propulsion system activated--see below.) Also
as proposed, the agency requires hybrid and electric vehicles to emit
minimum sound levels while in reverse and while the vehicle is in
forward motion up to 30 km/h. The final rule also adopts the agency's
proposal to conduct compliance testing outdoors.
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    \3\ ``Federal Motor Vehicle Safety Standards; Minimum Sound
Requirements for Hybrid and Electric Vehicles,'' 78 FR 2798 (January
14, 2013).
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    With regard to the scope of the final rule and what level of sound
to emit and when, however, the agency is adopting numerous changes to
the proposal in response to additional analysis conducted by the agency
and in response to comments, including the following:
     The final rule will only apply to four-wheeled hybrid and
electric vehicles with a gross vehicle weight rating (GVWR) of 4,536 kg
(10,000) pounds or less. The NPRM proposed that this rule would also
apply to hybrid and electric vehicles with a GVWR over 4,536 kg
(10,000) pounds and to electric motorcycles. We believe that we do not
have enough information at this time to apply the minimum acoustic
requirements of this final rule to these vehicles.
     In this final rule, the agency is reducing the number of
one-third octave bands for which there are minimum requirements. The
NPRM proposed that vehicles would have to emit sound meeting minimum
requirements in eight one-third octave bands. To comply with this final
rule, hybrid and electric vehicles will instead have to meet a
requirement specifying either two or four one-third octave bands.
Vehicles complying with the four-band requirement must meet minimum
sound pressure levels in any four non-adjacent one-third octave bands
between 315 Hz and 5000 Hz, including the one-third octave bands
between 630 Hz and 1600 Hz (these bands were excluded in the NPRM).
Vehicles complying with the two-band requirement must meet minimum
sound pressure levels in two non-adjacent one-third octave bands
between 315 Hz and 3150 Hz. For the two-band requirement, one band must
be below 1000 Hz and the second band must be at or above 1000 Hz, and
the two bands used to meet the two-band requirement also must meet a
minimum band sum requirement.
     The NPRM proposed that the fundamental frequency of the
sound emitted by a hybrid or electric vehicle must vary as the vehicle
changes speed by one percent per km/h for speeds between 0 and 30 km/h
to allow pedestrians to detect vehicle acceleration and deceleration.
This requirement was referred to as ``pitch shifting,'' and it is not
required in the final rule. Instead, the final rule assists pedestrians
in detecting increases in vehicle speed by requiring vehicle-emitted
sound to increase in sound pressure level by a specified amount as the
vehicle's speed increases. The agency acknowledges that the concept of
increasing sound pressure level with increased speed is not a direct
replacement for pitch shifting, but we believe it is a reasonable
alternative that will provide useful audible information to pedestrians
about the operating state of nearby vehicles.
     The NPRM proposed that sound emitted by hybrid and
electric vehicles must contain one tone no higher than 400 Hz and emit
broadband content including each one-third octave band from 160 Hz to
5000 Hz so that sounds emitted by these vehicles would be recognizable
as motor vehicles. The final rule does not adopt these proposed
requirements. We believe that pedestrians will use other cues to
recognize EVs and HVs such as the location of the sound source and the
frequency and level changes caused by the motion of the sound.
     In order to ensure that hybrid and electric vehicles of
the same make, model, and model year emit the same sound, as required
by the PSEA, the NPRM proposed that vehicles of the same make, model,
and model year must emit the same level of sound, within 3 dB(A), in
each one-third octave band from 160 Hz to 5000 Hz. We have instead
decided to ensure that EVs and HVs of the same make, model, and model
year emit the same sound by requiring that all vehicles of the same
make, model, and model year use the same alert system hardware and
software, including specific items such as the same digital sound file
where applicable, to produce sound used to meet the minimum sound
requirements in today's final rule.
     The NPRM proposed that each hybrid and electric vehicle
must meet minimum sound requirements anytime the vehicle's propulsion
system is activated, including when the vehicle is stationary. The
final rule requires each hybrid and electric vehicle to meet minimum
sound requirements any time the vehicle's propulsion system is
activated, including when the vehicle is stationary, unless the
vehicle's gear selector is in the ``park'' position or the parking
brake is applied (the latter for HVs and EVs with manual
transmissions).
     The NPRM proposed a phase-in schedule that required each
manufacturer of hybrid and electric vehicles to begin meeting the
requirements of the final rule with 30 percent of the hybrid and
electric vehicles they produce three years before the date for full
compliance established in the PSEA. In the final rule, we have modified
the phase-in schedule to provide additional time for compliance

for manufacturers of light vehicles; 50 percent of each manufacturer's
HV and EV production must comply with this final rule one year before
the date for full compliance established in the PSEA of September 1,
2019.

B. Costs and Benefits

    As discussed in detail in Section V of this notice, the benefits of
this final rule will accrue from injuries to pedestrians that will be
avoided, based on the anticipated ability of this rule to reduce the
pedestrian injury rate for HVs and EVs to that of ICE vehicles. As
discussed in Section II.B, a traditional analysis of pedestrian
fatalities is not appropriate for this rulemaking. If we assume that
HVs and EVs increase their presence in the U.S. fleet to four percent
of all vehicle registrations in model year 2020, a total of 2,464
injuries to pedestrians and pedalcyclists would be expected over the
lifetime of the 2020 model year fleet due to the pedestrians' and
pedalcyclists' inability to detect these vehicles by their sense of
hearing. Taking into account the agency's estimate of detectability of
vehicle alert sounds complying with this final rule, which is discussed
in the Final Regulatory Impact Assessment, we estimate that the benefit
of reducing the pedestrian and pedalcyclist injury rate per registered
vehicle for EVs HVs to ICE vehicles when four percent of the fleet is
HVs and EVs would be 2,390 fewer injured pedestrians and pedalcyclists.
We do not include any quantifiable benefits in pedestrian or
pedalcyclist injury reduction for EVs because we believe it is
reasonable to assume that EV manufacturers would have installed alert
sounds in their cars without passage of the PSEA and this proposed
rule.\4\ We also estimate that this rule will result in 11 fewer
injured pedestrians and pedalcyclists caused by LSVs.
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    \4\ As further discussed in the agency's Final Regulatory Impact
Analysis, due to foresight on the part of light electric vehicle
manufacturers, paired with consumer expectations and style choices,
light vehicle EVs are all assumed to be equipped with speaker
systems. NHTSA assumes the sound alert benefits for these vehicles
are attributable to the market and not the rule. This assumption
makes our benefit figures conservative. On the other hand, we did
not assume that electric LSVs would be voluntarily equipped with
speaker systems since none of these vehicles were known to have such
systems currently.
    \5\ Scaled benefits and costs for low-speed vehicles (LSVs) are
estimated to be directly proportional to costs for light vehicles
based on sales. Scaled costs include both installation costs for the
system and fuel costs.

                                         Table 1--Discounted Benefits for Passenger Cars and LTVs, MY2020, 2013$
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                                                  Pedestrians                           Pedalcyclists                         Total PED + CYC
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            3%  Discount                             Total                                  Total                                  Total
                                     3% Discount   monetized    Total ELS   3% Discount   monetized    Total ELS   3% Discount   monetized    Total ELS
                                        factor      benefits                   factor      benefits                   factor      benefits
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(PC)...............................       0.8024      $132.3M         9.70      0.80243      $168.8M        14.55       0.8024      $301.1M        24.25
(LTV)..............................       0.7867         7.9M         0.58      0.78673         9.4M         0.80       0.7867        17.4M         1.39
                                    --------------------------------------------------------------------------------------------------------------------
    Total..........................            0       140.3M        10.29            0       178.3M        15.35            0       318.5M        25.64
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7% Discount                                   7%        Total    Total ELS           7%        Total    Total ELS           7%        Total    Total ELS
                                        Discount    monetized                  Discount    monetized                  Discount    monetized
                                          factor     benefits                    factor     benefits                    factor     benefits
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(PC)...............................       0.6268      $102.5M         7.50      0.62684      $130.5M        11.24       0.6268      $233.0M        18.74
(LTV)..............................       0.6077         6.1M         0.45      0.60775         7.2M         0.61       0.6077        13.3M         1.06
                                    --------------------------------------------------------------------------------------------------------------------
    Total..........................            0       108.6M         7.94            0       137.7M        11.85            0       246.3M        19.80
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                                                  Table 2--Total Costs for PCs and LTVs, MY2020, 2013$
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                                                                                Avg.
                                                     Sales        Sales     Fuel costs/   Fuel costs    install      Install    Total cost/  Total costs
                                                                 impacted       veh        (total)     costs/veh   costs total      veh
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3% discount:
    (PC)........................................    8,000,000      483,462        $4.70   $2,272,270       $74.36  $35,951,512       $79.06  $38,223,782
    (LTV).......................................    8,000,000       46,428         5.30      246,067        71.97    3,341,333        77.27    3,587,400
                                                 -------------------------------------------------------------------------------------------------------
        Total...................................   16,000,000      529,889        $4.75   $2,518,337       $74.15  $39,292,845       $78.91  $41,811,182
7% discount:
    (PC)........................................    8,000,000      483,462        $3.80   $1,837,155       $74.36  $35,951,512       $78.16  $37,788,667
    (LTV).......................................    8,000,000       46,428         4.20      194,996        71.97    3,341,333        76.17    3,536,329
                                                 -------------------------------------------------------------------------------------------------------
        Total...................................   16,000,000      529,889         3.84    2,032,151        74.15   39,292,845        77.99   41,324,996
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                                                  Table 3--Costs and Scaled Benefits for LSVs, MY2020 5
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                                            Sales ratio                                       Scaled                                          Scaled
            Discount rate (%)              LSV to light        Sales       Scaled costs      injuries       Scaled ELS        Scaled      benefits minus
                                            vehicle (%)                                      (undisc.)                       benefits      scaled costs
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3.......................................            0.47           2,500        $197,264           11.28          0.1210      $1,502,807      $1,305,543
7.......................................            0.47           2,500         194,970           11.28          0.0934       1,161,989         967,019
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    NHTSA estimates that the fuel and installation cost of adding a
speaker system in order to comply with the requirements of this rule is
$129.84 per vehicle for unequipped hybrid light vehicles (i.e.,
vehicles that did not previously have any alert system components
installed), and $54.99 for electric light vehicles. We estimate that
for model year (MY) 2020, which is the first model year to which the
requirements of this final rule will apply to the entire light vehicle
fleet, this final rule will apply to 529,889 passenger cars and LTVs.
The estimated costs for manufacturers of complying with this rule is
$39.29M in MY 2020, and we would expect that due to the additional
weight that these components add to the vehicles in which they are
installed, if manufacturers make no other changes to reduce vehicle
weight, these vehicles would consume an additional 2.3 more gallons of
fuel over the lifetime of a passenger car and 2.5 more gallons of fuel
over the lifetime of a light truck which would result in an average
fuel cost of $4.75 per vehicle for over the lifetime of MY 2020
vehicles subject to the rule at the 3-percent discount rate and $3.84
per vehicle for over the lifetime of MY 2020 vehicles subject to the
rule at the 7-percent discount rate.).
    To more easily compare the costs and benefits of this rulemaking,
we have converted pedestrian and pedalcyclist injuries avoided into
equivalent lives saved. We estimate that the impact of this rule in
pedestrian and pedalcyclist injury reduction in light vehicles and LSVs
will be 25.76 equivalent lives saved at the 3-percent discount rate and
19.92 equivalent lives saved at the 7-percent discount rate (summing
values from Table 1 and Table 3). Converting that to dollars, the
benefits of this rule for the HV portion of the MY 2020 light vehicle
and LSV fleet are $320.0 million at the 3-percent discount rate and
$247.5 million at the 7-percent discount rate (Table 4).\6\ NHTSA
estimates that the cost per equivalent life saved for the light EV, HV,
and LSV fleet would range from a cost of $1.67 million to a cost
savings of $0.10 million across the 3-percent and 7-percent discount
levels, respectively. When compared to our comprehensive cost estimate
of the value of a statistical life of $9.2 million, this final rule is
cost effective.
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    \6\ NHTSA's benefits calculation does not include light EVs
because manufacturers of light EVs were already adding sound to
those vehicles prior to NHTSA issuing the NPRM. However, this
analysis includes LSVs because those vehicles currently do not have
added sound.

  Table 4--Total Benefits and Costs Summary for Light Vehicles and Low
                      Speed Vehicles, MY2020, 2013$
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                                            3% Discount     7% Discount
                                               rate            rate
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Total Monetized Benefits................         $320.0M         $247.5M
Total Costs (Install + Fuel)............            42.M           41.5M
    Total Net Impact (Benefit-Costs)....          278.0M           205.9
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II. Background and Summary of Notice of Proposed Rulemaking

A. Pedestrian Safety Enhancement Act and National Traffic and Motor
Vehicle Safety Act

    On January 4, 2011, the Pedestrian Safety Enhancement Act of 2010
(Pub. L. 111-373) was signed into law. The Pedestrian Safety
Enhancement Act (PSEA) requires NHTSA to conduct a rulemaking to
establish a Federal Motor Vehicle Safety Standard (FMVSS) \7\ requiring
an ``alert sound'' \8\ for pedestrians to be emitted by all types of
motor vehicles \9\ that are electric vehicles \10\ (EVs) or hybrid
vehicles \11\ (HVs). Trailers are specifically excluded from the
requirements of the PSEA.
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    \7\ NHTSA is delegated authority by the Secretary of
Transportation to carry out Chapter 301 of Title 49 of the United
States Code. See 49 CFR 501.2. This includes the authority to issue
Federal motor vehicle safety standards. See 49 U.S.C. 30111.
    \8\ The definition of the term ``alert sound'' is discussed
below.
    \9\ Section 2(4) of the PSEA defines the term ``motor vehicle''
as having the meaning given such term in section 30102(a)(6) of
title 49, United States Code, except that such term shall not
include a trailer (as such term is defined in section 571.3 of title
49, Code of Federal Regulations). Section 30102(a)(6) defines
``motor vehicle'' as meaning a vehicle driven or drawn by mechanical
power and manufactured primarily for use on public streets, roads,
and highways, but does not include a vehicle operated only on a rail
line.
    \10\ Section 2(10) of the PSEA defines ``electric vehicle'' as a
motor vehicle with an electric motor as its sole means of
propulsion.
    \11\ Section 2(9) of the PSEA defines ``hybrid vehicle'' as a
motor vehicle which has more than one means of propulsion. As a
practical matter, this term is currently essentially synonymous with
``hybrid electric vehicle.''
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    The PSEA requires NHTSA to establish performance requirements for
an alert sound that allows blind and other pedestrians to reasonably
detect a nearby EV or HV. The PSEA defines ``alert sound,'' as that
term is used in the statute, as a vehicle-emitted sound that enables
pedestrians to discern the presence, direction,\12\ location, and
operation of the vehicle.\13\ Thus, in order for a vehicle to satisfy
the requirement in the PSEA to provide an ``alert sound,'' the sound
emitted by the vehicle must satisfy that definition. The alert sound
must not require activation by the driver or the pedestrian, and must
allow pedestrians to reasonably detect an EV or HV in critical
operating scenarios such as constant speed, accelerating, or
decelerating.
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    \12\ The PSEA does not specify whether vehicle ``direction'' is
to be defined with reference to the vehicle itself (thus meaning
forward or backward) or the pedestrian.
    \13\ PSEA Section 2(2).
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    In addition to those operating scenarios, the definition of alert
sound in the PSEA requires the agency to establish requirements for a
sound while the vehicle is stationary but active and when the vehicle
is operating in reverse. PSEA states that the alert sound must allow
pedestrians to ``discern vehicle presence, direction, location, and
operation.'' \14\ We read the requirement that pedestrians be able to
``discern vehicle presence'' along with the requirements that the sound
allow pedestrians to discern direction, location, and operation. The
term ``presence'' means something that is in the immediate vicinity.
The term ``operation'' means a state of being functional or operative.
Read together, the definition of alert sound requires that pedestrians
be able to detect vehicle presence when the vehicle is in operation. A
vehicle with its gear selector not in ``park'' is in an operational
state even though it may not be moving. It is therefore the agency's
position that the provision of the PSEA that requires pedestrians to be
able to detect the presence of a vehicle in operation requires that the
vehicle emit a minimum sound level when its gear selector is in any
position other than ``park,'' whether that be when the vehicle is
moving forward, stationary, or operating in reverse.
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    \14\ Public Law 111-373, 2(2), 124 Stat. 4086 (2011).

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    The agency believes that it is reasonable to conclude that Congress
intended the term ``operation'' in the PSEA to be the condition in
which a driver is operating the vehicle, as opposed to just the
operation of the vehicle's propulsion system. It is the operation of
the vehicle by a driver, not the operation of the vehicle's propulsion
system, that creates the safety risk to pedestrians who fail to detect
hybrid and electric vehicles. Consequently, when the vehicle's gear
selector is in ``park,'' the propulsion system may or may not be
activated but, in such a condition when the propulsion system is
activated, the vehicle is not operable by the driver until the gear
selector is moved from ``park'' to some other gear selector position.
Therefore, we have determined that the PSEA does not require us to
establish minimum sound requirements for when a vehicle has its gear
selector control in the ``park'' position.
    Because the PSEA directs NHTSA to issue these requirements as an
FMVSS under the National Traffic and Motor Vehicle Safety Act (Vehicle
Safety Act),\15\ the requirements must comply with that Act as well as
the PSEA. The Vehicle Safety Act requires each safety standard to be
performance-oriented, practicable \16\ and objective \17\ and meet the
need for safety. In addition, in developing and issuing a standard,
NHTSA must consider whether the standard is reasonable, practicable,
and appropriate for each type of motor vehicle covered by the standard.
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    \15\ 49 U.S.C. Chapter 301.
    \16\ In a case involving passive occupant restraints, the U.S.
Circuit Court of Appeals for the District of Columbia said that the
agency must consider public reaction in assessing the practicability
of required safety equipment like an ignition interlock for seat
belts. Pacific Legal Foundation v. Department of Transportation, 593
F.2d 1338 (D.C. Cir. 1978). cert. denied, 444 U.S. 830 (1979).
    \17\ In a case involving passive occupant restraints, the U.S.
Circuit Court of Appeals for the 6th Circuit said, quoting the House
Report (H.R. 1776, 89th Cong. 2d Sess. 1966, p. 16) for the original
Vehicle Safety Act, that ``objective criteria are absolutely
necessary so that `the question of whether there is compliance with
the standard can be answered by objective measurement and without
recourse to any subjective determination.' '' Chrysler v. Department
of Transportation, 472 F.2d 659 (6th Cir. 1972).
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    As an FMVSS, the minimum sound standard in today's final rule will
be enforced in the same fashion as other safety standards issued under
the Vehicle Safety Act. Thus, violators of the standard will be subject
to civil penalties.\18\ Vehicle manufacturers will be required to
conduct a recall and provide remedy without charge if their vehicles
are determined to fail to comply with the standard or if the vehicle's
alert sound were determined to contain a safety related defect.\19\
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    \18\ 49 U.S.C. 30112 and 30165.
    \19\ 49 U.S.C. 30118-30120.
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    Under the PSEA, the standard must specify performance requirements
for an alert sound that enables blind and other pedestrians to
reasonably detect EVs and HVs operating below their crossover
speed.\20\ The PSEA specifies several requirements regarding the
performance of the alert sound to enable pedestrians to discern the
operation of vehicles subject to the Act. First, the alert sound must
be sufficient to allow a pedestrian to reasonably detect a nearby EV or
HV operating at constant speed, accelerating, decelerating or operating
in any other scenarios that the Secretary deems appropriate.\21\
Second, it must reflect the agency's determination of the minimum sound
level emitted by a motor vehicle that is necessary to allow blind and
other pedestrians to reasonably detect a nearby EV or HV operating at
or below the crossover speed.\22\ Today's final rule will ensure that
EVs and HVs are detectable to pedestrians by specifying performance
requirements for sound emitted by these vehicles so that they will be
audible to pedestrians across a range of ambient noise environments,
including those typical of urban areas.
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    \20\ Section 2(3) of the PSEA defines ``crossover speed'' as the
speed at which tire noise, wind resistance, or other factors make an
EV or HV detectable by pedestrians without the aid of an alert
sound. The definition requires NHTSA to determine the speed at which
an alert sound is no longer necessary.
    \21\ PSEA Section 3(a). Under the PSEA, as with most legislation
like it, the Secretary of Transportation delegates responsibility
for achieving the legislation's objectives to the appropriate
Department of Transportation Administration, in this case NHTSA.
    \22\ PSEA Section 3(b).
---------------------------------------------------------------------------

    Nothing in the PSEA specifically requires the alert sound to be
electrically generated. Therefore, if manufacturers wish to meet the
minimum sound level requirements specified by the agency through the
use of sound generated by the vehicle's power train or any other
vehicle component, there are no conflicts with the PSEA to limit their
flexibility to do so.
    The alert sound must also reflect the agency's determination of the
performance requirements necessary to ensure that each vehicle's alert
sound is recognizable to pedestrians as that of a motor vehicle in
operation.\23\ We note that the requirement that the alert sound be
recognizable as a motor vehicle in operation does not mean that the
alert sound be recognizable as a vehicle with an internal combustion
engine (ICE). The PSEA defines ``conventional motor vehicle'' as ``a
motor vehicle powered by a gasoline, diesel, or alternative fueled
internal combustion engine as its sole means of propulsion.'' \24\ We
believe that if Congress had intended the alert sound required by the
PSEA to be recognizable as an ICE vehicle, Congress would have
specified that the sound must be recognizable as a ``conventional motor
vehicle'' in operation rather than a motor vehicle because Congress
acts purposefully in its choice of particular language in a
statute.\25\
---------------------------------------------------------------------------

    \23\ PSEA Section 3(b)(2).
    \24\ PSEA Section 2(5).
    \25\ See Keene Corp. v. United States, 508 U.S. 200, 208 (1993)
(stating the cannon of statutory construction that ``where Congress
includes particular language in one section of a statute but omits
it in another . . ., it is generally presumed that Congress acts
intentionally and purposely in the disparate inclusion or
exclusion.'').
---------------------------------------------------------------------------

    While the mandate that NHTSA develop performance requirements for
an alert sound that is recognizable as a motor vehicle does not mean
that the sound must be based solely on sounds produced by ICE vehicles,
the mandate does impose substantive requirements that the agency must
follow during the rulemaking. The Vehicle Safety Act defines a motor
vehicle as a ``vehicle driven or drawn by mechanical power and
manufactured primarily for use'' on public roads.\26\ The requirement
that the agency develop performance requirements for recognizability
means that the pedestrian alert sound required by this standard must
include acoustic characteristics common to all sounds produced by
vehicles driven by mechanical power that make those sounds recognizable
as a motor vehicle based on the public's experience and expectations of
those sounds.
---------------------------------------------------------------------------

    \26\ 49 U.S.C. 30102(a)(6).
---------------------------------------------------------------------------

    The PSEA mandates that the standard shall not require the alert
sound to be dependent on either driver or pedestrian activation. It
also requires that the safety standard allow manufacturers to provide
each vehicle with one or more alert sounds that comply, at the time of
manufacture, with the safety standard. Thus, a manufacturer may, if it
so chooses, equip a vehicle with different sounds to denote different
operating scenarios, such as stationary, forward or reverse. Each
vehicle of the same make and model must emit the same alert sound or
set of sounds. The standard is required to prohibit manufacturers from
providing anyone, other than the manufacturer or dealers, with a device
designed to disable, alter, replace or modify the alert sound or set of
sounds emitted from the vehicle. This language prohibits NHTSA from
allowing

manufacturers from installing an off switch or volume control switch
that allows the driver to turn off or turn down the alert sound used to
meet the requirements of this standard.
    Additionally, vehicle manufacturers, distributors, dealers, and
motor vehicle repair businesses would be prohibited from rendering the
sound system inoperative under Section 30122 of the Vehicle Safety Act.
A manufacturer or a dealer, however, is allowed to alter, replace, or
modify the alert sound or set of sounds in order to remedy a defect or
non-compliance with the safety standard.
    It is the agency's intention that the requirements of this standard
be technology neutral. For this reason, we have chosen to establish
minimum sound requirements for a vehicle-level test, as opposed to a
component-based bench test or some other type of test, to ensure any
kind of technology used can be properly tested.
    The agency interprets the requirement in the PSEA that each vehicle
of the same make and model emit the same sound as applying only to
sound added to a vehicle for the purposes of complying with this
standard. We also interpret the PSEA requirement that NHTSA prohibit
manufacturers from providing anyone with a means of modifying or
disabling the alert sound and the prohibition on making required safety
systems inoperative contained in Section 30122 of the Vehicle Safety
Act as applying only to sound added to a vehicle for the purposes of
complying with this proposed standard.
    Many changes to a vehicle could affect the sound produced by that
vehicle. In issuing this proposal the agency does not wish to prevent
manufacturers, dealers, and repair businesses from making modifications
to a vehicle such as adding a spoiler or changing the vehicle's tires
that may have the effect of changing the sound produced by the vehicle.
    The PSEA requires that the final rule provide a phase-in period, as
determined by the agency. In response to that requirement, full
compliance with the standard must be achieved for all vehicles
manufactured on or after September 1st of the calendar year beginning
three years after the date of publication of the final rule. This final
rule is establishing the requirement for 100-percent compliance for all
light vehicles subject to the requirements of this rule produced for
sale in the U.S. by all manufacturers no later than September 1, 2019.
This requirement includes a one-year, 50-percent phase-in period
beginning September 1, 2018.

B. Safety Problem

Comparing the Vehicle-to-Pedestrian Crash Experience of ICE Vehicles to
HVs and EVs
Crash Risk
    Public safety advocacy groups have raised pedestrian safety
concerns regarding HVs because a vehicle using an electric motor may be
quieter than an ICE vehicle and may not emit the sounds that non-
motorists rely on for warning as vehicles approach them.
    In 2009, NHTSA released the report ``Incidence of Pedestrian and
Bicyclist Crashes by Hybrid Electric Passenger Vehicles'' which found
that, when comparing similar vehicles, 77 out of 8,387 total HVs
reported to be in any crash incident were involved in pedestrian
crashes, and 3,578 out of 559,703 total ICE vehicles were involved in
similar pedestrian crashes.\27\ The report used data collected from 12
individual states. The years for which data were available varied
across different states. Generally, the data used ranged from the years
2000 to 2006. The ratio of pedestrian crashes to overall crashes was
40-percent higher for HVs than for other vehicles. In situations
involving certain low-speed maneuvers, HVs were twice as likely to be
involved in a pedestrian crash as ICE vehicles in similar situations.
---------------------------------------------------------------------------

    \27\ R. Hanna (2009) Incidence of Pedestrian and Bicyclists
Crashes by Hybrid Electric Passenger Vehicles, Report No. DOT HS 811
204. U.S. Dept. of Transportation, Washington, DC.
    Available at http://www-nrd.nhtsa.dot.gov/Pubs/811204.PDf.
---------------------------------------------------------------------------

    In 2011 NHTSA released a second report ``Incidence Rates of
Pedestrian And Bicyclist Crashes by Hybrid Electric Passenger Vehicles:
An Update'' which verified these previous findings \28\ by adding
additional years of state crash files as well as by increasing the
number of states included in the analysis from 12 to 16, which
increased the number of crashes included in the analysis. Overall, a
statistical approach referred to as odds ratios indicated that the odds
of an HV being in either a pedestrian or bicycle crash is greater than
the odds of an ICE vehicle being in a similar crash, 19-percent higher
for pedestrian crash odds and 38-percent higher for bicycle crash
odds.\29\ The crash factors of speed limit, vehicle maneuver, and
location were examined to determine the relative incidence rates of HVs
versus ICE vehicles and whether the odds ratio was different under
different circumstances. The analysis also indicated that the largest
differences between the involvement of HVs and ICE vehicles in
pedestrian crashes occur with speed limits of 35 mph and lower and
during certain maneuvers typically executed at low speed such as making
a turn, starting up, and pulling into or backing out of a parking
space. HVs were about 1.38 times more likely to be involved in a
pedestrian crash than a vehicle with an ICE during a low speed
maneuver. The results of the updated analysis show trends similar to
those first reported in our 2009 analysis. The sample sizes of
pedestrian and bicycle crashes were re-examined to verify that there
was sufficient statistical power in this updated analysis.
---------------------------------------------------------------------------

    \28\ Wu, et al. (2011) Incidence Rates of Pedestrian And
Bicyclist Crashes by Hybrid Electric Passenger Vehicles: An Update,
Report No. DOT HS 811 526. Dept. of Transportation, Washington, DC.
Available at http://www-nrd.nhtsa.dot.gov/Pubs/811526.pdf.
    \29\ The incidence rates for pedestrian and pedalcyclist crashes
involving HVs and EVs were calculated from the State data by
comparing the pedestrian and pedalcyclist crash rates for all HVs
contained in the State data set with the crash rates for all ICE
vehicles from that data set. Because this proposal does not apply to
HVs that always have their ICE turned on while moving, the agency
removed the Honda Civic and the Honda Accord from the HV category
and included those vehicles in the calculations as ICE vehicles in
estimating the incidence rate used in the benefit calculations.
---------------------------------------------------------------------------

    The state data set that NHTSA used to determine the pedestrian and
pedalcyclist crash rates for HVs did not include any information about
the vision status of the pedestrians involved in the crashes, so we
were unable to determine whether any of the pedestrians involved in
these crashes were blind or visually-impaired.
    While this updated analysis provides insightful comparisons of the
incidence rates of HVs versus ICE vehicles involved in pedestrian
crashes, there are some limitations to consider: The use of data from
16 states cannot be used to directly estimate the national problem
size; and there is still not enough data to draw conclusions in all
scenarios of interest such as for individual low-speed maneuvers such
as making a turn, starting up, or in parking lots.
    It has been an ongoing concern that HVs have a very small share
among all vehicles (approximately 0.5 percent). The conditional
probability of HV pedestrian or pedalcyclist crashes is very small if
whole populations of both HV and ICE are included. Therefore, the
sample size of HV may have an impact on the comparison of crash rates
between HVs and ICE vehicles. For this reason, NHTSA has further
updated the comparison between HV and ICE crash data in order to
include additional HV crashes.

    In our recent calculations \30\ we used the latest State data
available up to 2011 from the same 16 states, in which the sample sizes
of HV vehicles of all crashes are increased to 68,950 (with 420
pedestrian crashes for all hybrid vehicle models). The earlier research
obtained the pedestrian crash odds ratios of HV versus ICE vehicle with
much smaller sample sizes. The new analysis showed that after the Honda
Civic and Accord models are moved from the hybrid category to the ICE
category the odds ratio of HV vs. ICE pedestrian crashes for all speeds
is 1.21 and the odds ratio for slower speed maneuvers is 1.52. This
analysis also shows that the odds ratio of HV vs. ICE pedalcyclist
crashes is 1.58 for all speeds including all speed maneuvers, and 1.50
for slower maneuvers.
---------------------------------------------------------------------------

    \30\ Wu, J., 2015, ``Updated Analysis of Pedestrian and
Pedalcyclist Crashes of Hybrid Vehicles with Larger Samples and
Multiple Risk Factors.''
---------------------------------------------------------------------------

    In the NPRM, the agency asked for comments on whether the
differences in pedestrian crash rates between HV and ICE vehicles are
solely due to pedestrians' inability to detect these vehicles based on
sound, or whether there may be other factors that we have not
identified that affect the difference in crash rates.
    Ideally, in order to determine whether this lack of sound is
causing accidents, NHTSA would have compared accident rates for HVs and
EVs with and without sound. However, there have not been enough HVs and
EVs with sound for a long enough period of data to be able reasonably
conduct this analysis. NHTSA has also been unable to directly measure
the pedestrian and pedalcyclist crash rates per mile travelled for HVs
and EVs to the rates for ICEs because the Agency does not have data on
VMT for HVs and EVs. Therefore, we have instead used the number of
other types of crashes vehicles are involved in and using that as a
proxy for VMT. While this is a standard technique in analyzing crash
risk, it does raise the possibility that there may be other
explanations than the lack of sound for hybrids having higher-than-
average rates of pedestrian and pedalcyclist crashes relative to other
crashes.
    Various comments noted that the agency should consider the
possibility that factors other than sound will have an impact on the
difference in crash rates between HVs and ICE vehicles. Commenters
stated that driver characteristics and higher rates of exposure to
pedestrians were factors that could contribute to the higher rate of
pedestrian crashes among HVs when compared to ICE vehicles.
    Nissan North America, Inc. (Nissan) stated that NHTSA should take
into account the fact that the ``making a turn'' and ``backing''
maneuvers, which constitute a majority of the low speed maneuvers
examined in the agency's crash analysis, are maneuvers during which it
is difficult for drivers to detect pedestrians. American Honda Motor
Co. (Honda) stated that NHTSA should examine whether there is a
significant difference between HEV/EV pedestrian crashes and ICE
pedestrian crashes for vehicles starting from stationary.
    Advocates stated that elevated crash rates between EVs/HEVs and
pedestrians and pedalcyclists, concerns of blind advocacy groups, and
the international attention focused on the issue support the conclusion
that minimum sound requirements for EVs and HEVs will reduce the rate
of pedestrian crashes involving these vehicles. The Insurance Institute
for Highway Safety stated that, according to research from the Highway
Data Loss Institute (HDLI), hybrid vehicles where 17.2 percent more
likely to cause injuries to pedestrians than their ICE vehicle
counterparts.
Agency Response to Comments
    After review of the comments received on the NPRM, we utilized a
multivariate logistic regression model to examine whether other
variables besides type of powertrain in the State Data System
contributed to increased risk of pedestrian collisions. In addition, we
utilized the calculated odds ratio to compare HVs and ICEs using a
case-control analysis. The variables that NHTSA examined in the
regression are: Whether the vehicle was an HV or ICE; whether the
vehicle was involved in a low-speed maneuver at the time of the crash;
city size; driver age; vehicle age; and calendar year. The results of
the regression analysis show that an HV may have 1.18 times higher
likelihood of hitting a pedestrian than an ICE after accounting for
these other confounding risk factors included in the State Data System.
NHTSA believes that our case-control analysis, the results of our
multivariate logistic regression, and the results of HDLI's research
show that there is a difference in crash rates between HVs and ICE
vehicles that is attributable to sound. We note that we were unable to
calculate a statistically significant difference in crash rates between
HVs and ICE vehicles for pedestrian crashes when the vehicle was
starting from a stopped position because of the small number of crashes
involving HVs in the State Data System.
    We have considered the fact that many of the crashes in the low-
speed maneuver data in our crash analysis include crashes in which the
driver was making a turn or backing and may have had an obstructed view
of the pedestrian. Because backing crashes are addressed by our recent
final rule to increase the field of view requirements of FMVSS No. 111,
Rear Visibility, we have adjusted our benefits calculation for this
rulemaking to remove those crashes addressed by FMVSS No. 111. Also,
the fact that the driver's view may have been obstructed supports the
need to establish minimum sound requirements for HVs and EVs so that
pedestrians can detect when those vehicles are pulling out or
approaching in situations in which the pedestrian is potentially
obscured from the driver's view.
Fatalities
    The Fatality Analysis Reporting System (FARS) contains a census of
all traffic fatalities. HVs and EVs that struck and killed a pedestrian
were identified using the Vehicle Identification Numbers (VINs)
contained in the 2001 through 2009 FARS files. During this period,
there were 53 pedestrian fatalities attributed to crashes involving 47
HVs and three EVs. Almost all of these fatalities (47 of the 53)
involved vehicles that were identified as passenger vehicles. In 2008,
there were 10 HVs or EVs that struck and killed 10 pedestrians, and in
2009, there were 11 HVs or EVs that struck and killed 11 pedestrians.
    However, these fatalities are not included in the target population
for analysis under this rulemaking for two reasons. The first is that
pedestrian fatalities are not as likely to occur at low speeds for
which the rate of HV pedestrian collisions is significantly higher than
collisions between ICE vehicles and pedestrians. Today's final rule
establishes minimum sound requirements for hybrid and electric vehicles
operating at speeds up to 30 km/h (18.6 mph). A majority of pedestrian
fatalities occur when the vehicle involved in the collision is not
travelling at a low speed. Overall, 67 percent of the pedestrian
fatalities involving HVs or EVs and with known speed limits occurred at
a speed limit above 35 mph.\31\ For all pedestrian fatalities with
known speed limits, 62 percent occurred at a speed limit above 35 mph
and 61 percent of those

involving passenger vehicles occurred at a speed limit above 35
mph.\32\ The goal of this rule is to prevent injuries to pedestrians
that result from pedestrians being unable to hear nearby hybrid and
electric vehicles operating at low speeds. At speeds of 35 mph and
above, at which a majority of fatal crashes involving pedestrians
occur, it is very unlikely that lack of sound is the cause as the sound
levels produced by hybrid and electric vehicles at those speeds are the
same as the sound levels produced by ICE vehicles. Establishing minimum
sound requirements for hybrid and electric vehicles operating at speeds
up to 30 km/h is expected to prevent injury crashes but not necessarily
have an impact on those crashes involving pedestrian fatalities, based
on existing data.
---------------------------------------------------------------------------

    \31\ For those pedestrian fatalities that occurred on roads with
a posted speed limit of 35 mph or less, we do not have any data on
actual travel speed of the vehicles involved. Therefore, we are not
able to tell if the vehicles involved were travelling at a speed at
which they would be required to meet the requirements of the final
rule.
    \32\ Data particularly tied to other speeds, such as 20 mph, is
not available because of the structure of the databases used, i.e.,
the relevant data variable is whether the speed limit was above or
below 35 mph at the crash location.
---------------------------------------------------------------------------

    The second reason is that the rate of pedestrian fatalities per
registered vehicle for HVs and EVs is not larger (and is in fact
smaller) than that for ICE vehicles. Using 2008 data, the fatality rate
for pedestrians in crashes with HVs and EVs is 0.85 fatalities per
100,000 registered vehicles, and the corresponding rate for ICE
vehicles is 1.57 per 100,000 vehicles.
    There also could be fatalities involving HVs and EVs that occur in
non-traffic crashes in places such as driveways and parking lots.
However, a comprehensive search for HVs and EVs involved in pedestrian
fatalities could not be undertaken because NHTSA's Not in Traffic
Surveillance (NiTS) system does not provide VINs, and a search for
model names that indicate hybrid or electric vehicles did not identify
any crashes involving pedestrian fatalities.
Low-Speed Vehicles
    NHTSA has no data on pedestrian or pedalcyclist crash rates for
low-speed vehicles due to the low rate of sales of these vehicles as a
percentage of the light vehicle fleet. NHTSA also has not found any
examples of crashes involving LSVs and pedestrians or pedalcyclists
that appear to be caused by the lack of sound in LSVs. However, we
assume that the safety problem with these vehicles will be similar to
that for HVs based on the acoustic profile of these vehicles.
Need for Independent Mobility of People Who Are Visually-Impaired
    In addition to addressing the safety need in the traditional sense
of injuries avoided as a result of preventing vehicle-pedestrian
crashes, NHTSA believes it is important to note another dimension of
safety that should be taken into account with respect to pedestrians
who are blind or visually-impaired. Pedestrians who are blind or
visually-impaired need to be able to travel independently and safely
throughout their communities without fear and risk of injury, both as a
result of collisions with motor vehicles and as a result of other
adverse events in the environments they must negotiate. To a far
greater extent than is the case for sighted people, vehicle sounds help
to define a blind or visually-impaired person's environment and
contribute to that person's ability to negotiate through his/her
environment in a variety of situations.\33\
---------------------------------------------------------------------------

    \33\ National Federation of the Blind (2011) How People Who are
Blind Use Sound for Independent Travel, memorandum to the docket,
NHTSA-2011-0148-0028, Washington, DC. That memorandum is the source
for this information.
---------------------------------------------------------------------------

    The modern white cane and the techniques for its use help the user
to navigate and allow sighted people to recognize that a person is
blind or visually-impaired. Today, the ``structured discovery'' method
of teaching independent travel for visually-impaired people emphasizes
learning to use information provided by the white cane, traffic sounds,
and other cues in the environment to travel anywhere safely and
independently, whether the individual has previously visited the place
or not.
    Whether a blind or visually-impaired person uses a white cane or
guide dog, the primary purpose of both travel tools is to help the
blind traveler identify and/or avoid obstacles in his or her path using
the sense of touch. The remaining information needed by a blind or
visually-impaired person to safely and independently travel is provided
primarily through the sense of hearing.
    When traveling with a white cane or guide dog, the primary sound
cue used by blind pedestrians is the sound of vehicle traffic, which
serves two purposes: navigation and collision avoidance. Navigation
involves not only ascertaining the proper time to enter a crosswalk and
maintain a straight course through an intersection while crossing, but
also the recognition of roadways and their traffic patterns and their
relationship to sidewalks and other travel ways a blind or visually-
impaired person might use.
    Sound emitted by individual vehicles, as opposed to the general
sound of moving traffic, is critical. The sound of individual vehicles
helps to alert blind travelers to the vehicle's location, speed, and
direction of travel. For example, a blind or visually-impaired person
moving through a parking lot can hear and avoid vehicles entering or
exiting the lot or looking for parking spaces; a blind person walking
through a neighborhood can hear when a neighbor is backing out of a
driveway. The vehicle sound also indicates to a blind or visually-
impaired pedestrian whether a vehicle is making a turn, and if so, in
which direction. The sound of individual vehicles also allows the blind
traveler to detect and react to unusual or unexpected vehicle movement.
The sound of a vehicle that has an activated starting system but is
stationary (usually referred to as ``idling'' for vehicles with
internal combustion engines) alerts the blind or visually-impaired
traveler to the fact that the vehicle is not simply parked and that it
may move at any moment. If a blind person is approaching a driveway and
notes a vehicle that is stationary but running he or she will wait for
the vehicle to pull out, or for an indication that it will not, for
example by noting that the vehicle remains stationary for some time,
indicating that the driver has no immediate plans to move.
    In the NPRM, the agency described how the acoustic cues provided by
vehicles help blind pedestrians discern changes in the road-way,
determine whether an intersection has a traffic control device, and
navigate intersections with unusual characteristics such as three-way
intersections or roundabouts. The sounds made by traffic including the
sounds of idling vehicles allow blind pedestrians to determine when it
is safe to cross the street and maintain a straight travel path while
walking through the intersection.
    Using the white cane or guide dog and the sound of traffic, people
who are blind or visually-impaired have been able to navigate safely
and independently for decades. Blind and visually-impaired people
travel to school, the workplace, and throughout their communities to
conduct the daily functions of life primarily by walking and using
public transportation. Safe and independent pedestrian travel is
essential for blind or visually-impaired individuals to obtain and
maintain employment, acquire an education, and fully participate in
community life. Short of constantly traveling with a human companion, a
blind or visually-impaired pedestrian simply cannot ensure his or her
own safety or navigate effectively without traffic sound. To the extent
that there are more and more HVs and EVs on the road that are hard to

detect, people who are blind or visually-impaired will lose a key
means--the sound of traffic--by which they determine when it is safe to
cross streets, but also by which they orient themselves and navigate
safely throughout their daily lives, avoiding dangers other than
automobiles.

C. Research on Vehicle Emitted Sounds and Detectability

Early Research on Quiet Vehicles and Public Meeting
    NHTSA began collaborating with a working group within the Society
of Automotive Engineers International (SAE) in August 2007 to identify
effective ways to address the safety issue of quiet hybrid and electric
vehicles. This working group included representatives from the Alliance
of Automobile Manufacturers, Global Automakers, the visually impaired
community and NHTSA.
    On June 23, 2008, NHTSA held a public meeting to bring together
government policymakers, stakeholders from the visually impaired
community, industry representatives, and public interest groups to
discuss the technical and safety policy issues associated with hybrid
vehicles, electric vehicles, and quiet internal combustion engine (ICE)
vehicles, and the risks they present to visually impaired pedestrians.
After this public meeting, NHTSA issued a research plan to investigate
hybrid and electric vehicles and pedestrian safety.\34\ The objectives
of the research plan were to identify critical safety scenarios for
visually impaired pedestrians, identify requirements for blind
pedestrians' safe mobility (emphasizing acoustic cues from vehicles and
ambient conditions), identify potential countermeasures, and describe
the countermeasures' advantages and disadvantages.
---------------------------------------------------------------------------

    \34\ A copy of the research plan is available at
www.regulations.gov (Docket No. NHTSA-2008-0108-0025).
---------------------------------------------------------------------------

    In 2009 NHTSA issued the report ``Incidence of Pedestrian and
Bicyclist Crashes by Hybrid Electric Passenger Vehicles,'' discussed in
Section II.B of this notice, and a report titled ``Research on Quieter
Cars and the Safety of Blind Pedestrians, A Report to Congress.'' \35\
The report to Congress briefly discussed the quieter vehicle safety
issue, how NHTSA's research plan would address the issue, and the
status of the agency's implementation of that plan.
---------------------------------------------------------------------------

    \35\ Research on Quieter Cars and the Safety of Blind
Pedestrians, A Report to Congress. U.S. Dept. of Transportation,
Washington, DC, October 2009, available at http://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2010/RptToCongress091709.pdf.
---------------------------------------------------------------------------

    In 2010 through 2014 the agency continued relevant quiet car
research as briefly discussed below.
Phase 1 Research
    In April 2010, NHTSA issued a report that began addressing the
tasks listed in the research plan. This report, titled ``Quieter Cars
and the Safety of Blind Pedestrians: Phase I,'' documents the overall
sound levels and general spectral content for a selection of ICE
vehicles and HVs in different operating conditions, evaluates vehicle
detectability for two background noise levels, and considers the
viability of countermeasure concepts categorized as vehicle-based,
infrastructure-based, and systems requiring vehicle-pedestrian
communications.\36\
---------------------------------------------------------------------------

    \36\ Garay-Vega, et al. (2010) Quieter Cars and the Safety of
Blind Pedestrians: Phase I, Report No. DOT HS 811 304, U.S. Dept. of
Transportation, Washington, DC. Available at http://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2010/811304rev.pdf.
---------------------------------------------------------------------------

    The results show that the overall sound levels for the HVs tested
are noticeably lower at low speeds than for the ICE vehicles tested.
Overall, study participants were able to detect any vehicle sooner in
the low ambient noise condition. ICE vehicles tested were detected
sooner than their HV counterpart vehicles except for the test scenario
in which the target vehicle was slowing down. In this scenario, HVs
were detected sooner because of the distinctive sound emitted by the
regenerative braking system on the HVs. Response time to detect a
target vehicle varies by vehicle operating condition, ambient sound
level, and vehicle type (i.e., ICE vehicle versus HV or EV mode).
    As part of Phase 1 research, NHTSA sought to identify operating
scenarios necessary for the safety of visually impaired pedestrians.
The researchers identified these scenarios based on crash data,
literature reviews, and unstructured conversations with blind
pedestrians and orientation and mobility specialists. Scenarios were
defined by combining pedestrian vehicle environments, vehicle type,
vehicle maneuver/speed/operation, and considerations of ambient sound
level. The operating scenarios identified in Phase 1 were: Vehicle
approaching at low speed; vehicle backing out (as if coming out of a
driveway); vehicle travelling in parallel and slowing (like a vehicle
that is about to make a turn); vehicle accelerating from a stop; and a
vehicle that is stationary.
    In Phase 1, NHTSA also compared the auditory detectability of HVs
and ICE vehicles by pedestrians who are legally blind. Forty-eight
independent travelers, with self-reported normal hearing, listened to
binaural \37\ audio recordings of two HVs and two ICE vehicles in three
operating conditions, and two different ambient sound levels. The
operating conditions included a vehicle: Approaching at a constant
speed (6 mph); backing out at 5 mph; and slowing from 20 to 10 mph (as
if to turn right). The ambient sound levels were a quiet rural (31.2
dB(A)) and a moderately noisy suburban ambient (49.8 dB(A)). Overall,
participants took longer to detect the two HVs tested (operated in
electric mode), except for the slowing maneuver. Vehicle type, ambient
level, and operating condition had a significant effect on response
time.
---------------------------------------------------------------------------

    \37\ Binaural recordings reproduce the acoustic characteristics
of the sound similar to how a human perceives it. Binaural
recordings reproduce a more realistic three dimensional sensation
than conventional stereo and are intended for playback through
headphones, rather than loudspeakers.
---------------------------------------------------------------------------

    Table 5 shows the time-to-vehicle arrival at the time of detection
by vehicle type, and ambient condition. Considering all three
independent variables, there was a main effect of vehicle, vehicle
maneuver, and ambient sound level. Similarly, there were interaction
effects between vehicle type and ambient, vehicle type and maneuver,
ambient and vehicle maneuver, and a three way interaction between
ambient, vehicle type and vehicle maneuver.

              Table 5--Average Time-to-Vehicle Arrival by Scenario, Vehicle Type, and Ambient Sound
----------------------------------------------------------------------------------------------------------------
                                                            Low ambient                    High ambient
                    Scenario                     ---------------------------------------------------------------
                                                        HVs        ICE vehicles         HVs        ICE vehicles
----------------------------------------------------------------------------------------------------------------
Approaching at 6 mph............................             4.8             6.2             3.3             5.5
Backing out at 5 mph............................             3.7             5.2             2.0             3.5

Slowing from 20 to 10 mph.......................             2.5             1.3             2.3             1.1
----------------------------------------------------------------------------------------------------------------

    The Phase 1 research showed that HVs were more difficult for
pedestrians to detect by hearing than ICE vehicles. The Phase 1
research report also discussed various countermeasures to mitigate
pedestrian safety risks associated with quiet vehicles. The Phase 1
report also concluded that a vehicle-based audible alert signal was the
countermeasure that both provided all the necessary information to
blind pedestrians to make safe travel decisions and produced benefits
for other pedestrians and for pedalcyclists.
Phase 2 Research
    In October 2011 NHTSA released a second report examining issues
involving hybrid and electric vehicles and blind pedestrian safety
titled ``Quieter Cars and the Safety of Blind Pedestrians, Phase 2:
Development of Potential Specifications for Vehicle Countermeasure
Sounds.'' \38\ The Phase 2 research developed various methods to
specify a sound to be used as a vehicle-based audible alert signal that
could be used to provide information at least equivalent to the cues
provided by ICE vehicles, including speed change, and evaluated sounds
using human factors testing to examine whether the sounds could be
detected and recognized as vehicle sounds. This research used acoustic
data acquired from a sample of ten ICE vehicles to examine the sound
levels at which synthetic vehicle sounds used could be set, and used
psychoacoustic models to examine issues of detectability and masking of
ICE-like sounds and alternative sounds, and also included a human
factors study to examine the detectability of synthetic sounds.
---------------------------------------------------------------------------

    \38\ Garay-Vega, et al. (2011) Quieter Cars and the Safety of
Blind Pedestrians, Phase 2: Development of Potential Specifications
for Vehicle Countermeasure Sounds, Report No. DOT HS 811 496. Dept.
of Transportation, Washington, DC. Available at http://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2011/811496.pdf.
---------------------------------------------------------------------------

    The methods for specifying sounds discussed in the Phase 2 final
report assumed that the vehicle acoustic countermeasure should:
     Provide information at least equivalent to that provided
by ICE vehicles, including speed change; and
     Provide for detection of a vehicle in residential,
commercial, and other suburban and urban environments in which blind
pedestrians would expect to be able to navigate using acoustic cues.
Note: Human factors tests for Phase 2 were conducted in an ambient of
approximately 58-61 dB(A).
    As part of the Phase 2 research, Volpe conducted a human factors
study to compare the auditory detectability of potential sounds for
hybrid and electric vehicles operating at a low speed and how those
sounds compared to an ICE control vehicle. The human factors testing in
Phase 2 suggested that synthetic sounds resembling an ICE produce
similar detection distances as actual ICE vehicles. In some instances,
the results indicated that synthetic sounds designed according to
psychoacoustic principles can produce double the detection distances
relative to the reference vehicle. The results also suggested that
synthetic sounds that contain only the fundamental combustion noise are
relatively ineffective. None of the analyses found a significant effect
of vision ability.\39\ Participants who were legally blind, on average,
were no better or worse than sighted participants in detecting the
approach sounds.
---------------------------------------------------------------------------

    \39\ All participants were required to wear a blindfold during
the study.
---------------------------------------------------------------------------

Phase 3 Research
    In order to develop possible test procedures and requirements for
an FMVSS proposing to establish minimum acoustic requirements for
hybrid and electric vehicles, NHTSA initiated a third phase of research
to develop an objective, repeatable test procedure and objective
specifications for minimum sound requirements. NHTSA's Vehicle Research
and Test Center (VRTC), as part of its effort to develop a test
procedure, conducted acoustic measurements and recordings of several
HVs and EVs and those vehicle's ICE pair vehicles.\40\ Volpe used these
recordings as well as data from the Phase 1 and Phase 2 research to
identify parameters and criteria for sounds to be detectable and
recognizable as a motor vehicle.
---------------------------------------------------------------------------

    \40\ Evans and Harris. (2012) Quieter Vehicle Performance Test
Development Research Report, U.S. Dept. of Transportation,
Washington, DC. Available at www.regulations.gov, Document ID:
NHTSA-2011-0148-0047.
---------------------------------------------------------------------------

VRTC Acoustic Measurements
    The primary focus of Phase 3 research conducted by VRTC was to
develop an objective and repeatable test procedure to measure vehicle-
emitted sound. This work consisted mainly of evaluation of the new SAE
J2889-1, Measurement of Minimum Noise Emitted by Road Vehicles, test
method, and several variations used to test operating conditions that
were not included in SAE J2889-1, and development of a practical test
procedure for collecting test track acoustic data from HVs, EVs and ICE
vehicles. The data collected was then evaluated to begin establishing
potential performance criteria. The draft version of SAE J2889-1 used
by VTRC included recommended procedures for measuring minimum sound
pressure levels of vehicle-emitted sound but did not include any
recommended performance requirements for minimum levels of vehicle-
emitted sound. SAE J2889-1 was still in draft form at the start of the
research, but the version published in September 2011 was not
significantly different from the draft.
    The research was conducted using three HVs, one EV, and four ICE
vehicles. The vehicles were used to gather sample data on the
difference in sound pressure levels between ICE sounds and EV or HV
sounds. VRTC also gathered data to determine how synthetic vehicle
sounds emitted from speakers projected around the vehicle, as referred
to as the directivity of the sound, and sound quality levels. Some of
the hybrid and electric vehicles were tested with multiple alert
sounds. Some of the hybrid and electric vehicles were also tested with
no alert sound at all, to examine the difference between the sound
pressure level produced by hybrid and electric vehicles and ICE
vehicles.
    One of the purposes of the Phase 3 acoustic measurements was to
gather additional data on the difference in sound levels between ICE
vehicles and EVs and HVs operating in electric mode. For the pass-by
tests at 10 km/h in Phase 3, the ICE vehicles were between 6.2 and 8.5
dB(A) louder than the EV/

HVs without added sound. At 20 km/h the difference between the HV/EVs
and ICE vehicles varied, but the average delta was 3.5 dB(A) louder for
the ICE vehicles. At 30 km/h the sound levels of the HV/EVs approached
the levels of the ICE vehicles and the individual measurements for the
two types of vehicles have considerable overlap. Table 6 shows the
results of HV/EV vehicles with no sound alert as compared to their ICE
counterparts.

       Table 6--Pass-By Sound Level for HV/EV Vehicles Without Alert Sound Versus Counterpart ICE Vehicles
----------------------------------------------------------------------------------------------------------------
                                                                    HV/EV Sound      ICE Sound    ICE minus HEV/
                  Manufacturer                      Speed, km/h      Level, dB       Level, dB        EV, dB
----------------------------------------------------------------------------------------------------------------
Nissan..........................................              10            50.5            56.6             6.1
                                                              20            60.0            62.3             2.3
                                                              30            66.5            68.1             1.6
Prototype Vehicle G.............................              10            51.4            59.9             8.5
                                                              20            60.5            63.1             2.6
                                                              30            67.0            67.5             0.5
Prototype Vehicle H.............................              10            51.2            59.7             8.5
                                                              20            59.3            64.5             5.2
                                                              30            65.3            69.2             3.9
Average.........................................              10            51.0            58.7             7.7
                                                              20            59.9            63.3             3.4
                                                              30            66.3            68.3             2.0
----------------------------------------------------------------------------------------------------------------

    The measurements from the startup and stationary but active
scenarios were used to measure the directivity of the vehicles' sound.
The purpose of measuring the directivity pattern of the vehicles was to
compare the directivity pattern of ICE vehicles to those hybrid and
electric vehicles equipped with a speaker system. For the ICE vehicles,
the sound pressure level behind the vehicle was 6 to 10 dB lower than
that directly in front of the vehicle. For the hybrid and electric
vehicles with a speaker system, the sound level behind the vehicle was
12 to 15 dB lower behind the vehicle. There was a systematic difference
from left to right for some vehicles, particularly with an artificial
sound.
Volpe Acoustic Analysis
    As another part of the Phase 3 research, Volpe conducted an
analysis of existing acoustic data and data collected during the
previously mentioned VTRC testing to develop recommendations for
performance requirements for minimum levels of vehicle emitted sound to
be proposed in the NPRM. This work consisted of examining the frequency
ranges, minimum sound levels for selected one-third octave bands, and
requirements for broadband noise and tones as possible criteria for
setting minimum requirements for vehicle-emitted sound. Evaluations
were conducted using a loudness model \41\ to determine when the sounds
might be detectable in a given ambient. Of the several different
loudness models examined by Volpe, Moore's Loudness provided the most
pertinent information about the perceived loudness and detectability of
a sound. Two approaches were used to identify potential detectability
specifications for alert sounds to be included in the NPRM: (1) Sound
parameters based on a loudness model and detection distances and (2)
sound parameters based on the sound of ICE vehicles.
---------------------------------------------------------------------------

    \41\ Loudness models are computer simulations used to estimate
the minimum sound levels needed for alert sounds to be detectable in
the presence of ambient noise.
---------------------------------------------------------------------------

    Volpe's work in developing the sound specifications based on a
loudness model and detection distances was guided by several aspects of
the agency's Phase 1 and Phase 2 research. Volpe analyzed the acoustic
data of the sounds used in the human factors research in Phase 2 from a
psychoacoustic perspective to determine the loudness of the sounds and
whether the sounds would be detectable in several different ambient
environments. Because the response of the study participants in the
human factors experimentation in Phase 2 varied significantly due to
variations in the ambient,\42\ Volpe determined that any analysis of
sounds using a loudness model should use a synthetic ambient that did
not vary with respect to the frequency profile or overall sound
pressure level. Volpe used a synthetic ambient sound with the loudness
model during Phase 3 in developing the specifications contained in the
NPRM.
---------------------------------------------------------------------------

    \42\ Garay-Vega, et al. (2011) Quieter Cars and the Safety of
Blind Pedestrians, Phase 2: Development of Potential Specifications
for Vehicle Countermeasure Sounds, Report No. DOT HS 811 496. Dept.
of Transportation, Washington, DC. Available at http://www.nhtsa.gov/DOT/NHTSA/NVS/Crash%20Avoidance/Technical%20Publications/2011/811496.pdf.
---------------------------------------------------------------------------

    This research showed that pedestrians' ability to detect synthetic
sounds would be maximized if the alert signal contains detectable
components over a wide frequency range. The research also explored how
tones and broadband content could enhance the detectability of
synthetic alert sounds. The report used acoustic data for directivity
to estimate minimum sound levels for `reverse' or `backing' maneuvers.
Volpe then used the results of this analysis of the detectability of
sounds as estimated by psychoacoustic models to make recommendations
for potential minimum sound levels for the NPRM.
    In addition to using psychoacoustic models to develop
recommendations for minimum sound specifications, Volpe created a set
of minimum sound specifications based on the sound produced by ICE
vehicles. Volpe considered multiple minimum sound specifications in an
attempt to derive at the most optimal approach for defining sound
specification requirements in order to provide recommendations for a
variety of sound specifications for NHTSA to seek comment on in the
NPRM. Volpe created the specification based on the sound produced by
ICE vehicles (using data captured during Volpe's Phase 2 research) and
recordings of vehicles provided by automobile manufacturers. Volpe
aggregated this data to create minimum acoustic specifications based on
the mean sound levels of ICE vehicles and the mean sound levels of ICE
vehicles minus one standard deviation.
Agency Research and Analysis Conducted Since the NPRM
    After the NPRM was issued, NHTSA conducted research to examine
additional aspects of minimum sound requirements for hybrid and
electric vehicles. The research involved human

factors testing and acoustic modeling to examine the detectability of
sounds with different acoustic characteristics. The research also
involved acoustic measurement of heavy-duty vehicles and motorcycles,
analysis of indoor testing conducted by Transport Canada, and
additional light vehicle testing to refine the test procedure proposed
in the NPRM. The research is documented in multiple separate research
reports and is summarized below. In some cases, as identified below,
more details of the research are provided in the appropriate sub-
sections of Section III of this preamble. In those cases, the agency
discusses the important aspects of the research that were utilized to
make decisions finalized in this rule.
Human Factors Research and Acoustic Modeling
    In the NPRM, NHTSA proposed minimum sound pressure levels for a
specific set of one-third octave bands that included low frequency
bands (315, 400, and 500 Hz) and high-frequency bands (2000, 2500,
3150, 4000, and 5000 Hz) for various operating conditions. These
proposed specifications for minimum sound pressure levels were
identified based on a psychoacoustic loudness modeling approach and
safe detection distances.\43\ After the NPRM was published, the agency
conducted a study to quantify the differences between predicted
detection levels of vehicle sounds in the presence of an ambient (as
indicated by the loudness model) and the actual responses by
participants listening to these vehicle sounds through headphones. This
was done in order to evaluate the accuracy of the psychoacoustic model
in predicting when sounds would be detected. The study also explored
the effect of different factors such as the number of bands at
threshold, adjacent and non-adjacent bands, and signal type (e.g., pure
tones, bands of noise).\44\ In addition to the human factors study,
Volpe also conducted an analysis of acoustic data in order to predict
the probability that a sound would be detected in different ambients as
the number of one-third octave bands making up the sound changes.
---------------------------------------------------------------------------

    \43\ Hastings, et al. (2012). Research on Minimum Sound
Specification for Hybrid and Electric Vehicles. Docket NHTSA-2011-
0148-0048.
    \44\ Hastings, et al. Detectability of Alert Signals for Hybrid
and Electric Vehicles: Acoustic Modeling and Human Subjects
Experiment. (2015) Washington, DC: DOT/NHTSA.
---------------------------------------------------------------------------

    The key performance metrics for the human factors study were the
response time and associated time-to-vehicle arrival. Response time is
the elapsed time, in seconds, from the start of the trial to the
instant the participant presses the push-button as an indication he/she
detected the target signal. The time-to-vehicle arrival is the elapsed
time, in seconds, from first detection of a target signal to the
instant the vehicle passes the pedestrian location. The detection
distance is the separation between the vehicle and the pedestrian
location at the moment of detection. The detection distance can be
computed from the time-to-vehicle arrival and vehicle speed. Signals
meeting the minimum sound levels, computed according to the approach
described in the NPRM, are expected to be detectable at least 2.0
seconds or 5 meters away (for a vehicle approaching at 10 km/h). Table
7 shows the time-to-vehicle arrival and detection distances for the
signals examined in this study. The signals used in the study included
sounds developed by Volpe to test different hypotheses involving the
detection model, recordings of prototype synthetic sounds provided by
vehicle manufacturers, and a recording of an ICE vehicle. The
``Source'' column in Table 7 describes the origin of each sound.

                                                              Table 7--Sound Stimuli Tested
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Time-to-         Vehicle
       Signal ID           Significant component         Levels, dB(A)              Source                Comment             vehicle       distance at
                              frequencies, Hz                                                                               arrival, s     detection, m
--------------------------------------------------------------------------------------------------------------------------------------------------------
3.....................  315, 400, 500, 630, 2000,    Threshold............  Simulation...........  Tone @315 Hz, TNR 9               4.9            13.6
                         2500, 3150, 4000, 5000.                                                    dB.
6.....................  315, 400, 500, 630, 2000,    Threshold............  Simulation...........  Tone @630 Hz, TNR 9               4.3            11.9
                         2500, 3150, 4000, 5000.                                                    dB.
9.....................  315, 400, 500, 630, 2000,    Threshold............  Simulation...........  Tone @2500 Hz, TNR 9              4.5            12.5
                         2500, 3150, 4000, 5000.                                                    dB.
10....................  315, 400, 500, 630, 2000,    Threshold............  Simulation...........  NNPRM + 630 Hz.......             4.4            12.2
                         2500, 3150, 4000, 5000.
11....................  315........................  Threshold............  Simulation...........  Single Noise Band....             2.3             6.4
12....................  630........................  Threshold............  Simulation...........  Single Noise Band....             2.9             8.1
13....................  2500.......................  Threshold............  Simulation...........  Single Noise Band....               2             5.6
14....................  315, 400, 500, 2000, 2500,   Threshold............  Simulation...........  NPRM.................             4.3            11.9
                         3150, 4000, 5000.
15....................  50 to 10,000...............  Threshold............  Simulation...........  Noise in all Bands...             4.6            12.8
17....................  315, 400, 500..............  46, 54, 48...........  Prototype Recording..  ASG as Recorded (No               5.8            16.1
                                                                                calibration).
18....................  315, 400, 500, 2000, 2500,   Threshold............  Prototype Recording..  ASN (Calibrated to                4.5            12.5
                         3150, 4000, 5000.                                                          match NPRM).
19....................  2500.......................  56...................  Prototype Recording..  ASN as Recorded (No               5.8            16.1
                                                                                calibration).
20....................  315, 400, 500, 2000, 2500,   Threshold............  Prototype Recording..  ASV Sound4                        6.7            18.6
                         3150, 4000, 5000.                                                          (Calibrated to match
                                                                                NPRM).
23....................  4000, 5000, 6300, 8000,      37, 36, 34, 32, 31...  ICE Recording........  ASF ICE (No                       3.1             8.6
                         10000.                                                                     Calibration).
25....................  315, 400, 500..............  Threshold............  Simulation...........  Low Frequency Noise..             4.2            11.7
26....................  315, 630, 2000, 5000.......  Threshold............  Simulation...........  Non-adjacent Noise...             4.5            12.5
27....................  630, 800, 1000, 1250, 1600.  Threshold............  Simulation...........  Mid-frequency Noise..             3.7            10.3
28....................  800, 2500..................  39, 45...............  Simulation...........  1 below threshold, 1              2.2             6.1
                                                                                at threshold.
29....................  800, 2500..................  45, 39...............  Simulation...........  both below threshold.             1.4             3.9

30....................  800, 2500..................  50, 50...............  Simulation...........  1 ~ threshold, 1                  3.6            10.0
                                                                                above threshold.
31....................  2000, 2500, 3150, 4000,      Threshold............  Simulation...........  High Frequency Noise.             3.2             8.9
                         5000.
32....................  315........................  Threshold............  Simulation...........  Pure Tone............             3.1             8.6
33....................  630........................  Threshold............  Simulation...........  Pure Tone............             2.9             8.1
34....................  2500.......................  Threshold............  Simulation...........  Pure Tone............             2.4             6.7
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The data showed that all signals tested in the study exceeded the
2.0-second detection criterion except for signal 29, which was detected
1.4 seconds before pass-by.\45\ Exceeding the 2.0-second detection
criterion was expected for signals with content in more than one one-
third octave band, since the modeled thresholds were based on a signal
with content in a single band. Content in multiple one-third octave
bands could increase the time-to-vehicle arrival if subjects aggregated
the energy across bands or if they utilized a `best' single band
strategy. That is, with more one-third octave bands, the signal can be
more easily detected either because it is stronger overall or because,
given the many possible random factors that could affect detectability,
more components creates a greater probability that at least one band
will be easier to detect.
---------------------------------------------------------------------------

    \45\ Signal 29 had two components, and the levels were set below
the minimum detection thresholds.
---------------------------------------------------------------------------

    An ICE vehicle (signal 23), without calibration to minimum one-
third octave band levels for detection used in the NPRM, was detected
3.1 seconds away on average. Two prototype alert signals (signals 17,
19), without calibration to minimum one-third octave band levels for
detection used in the NPRM, were detected 5.8 seconds away. In general,
signals with a pure tone (signals 32, 33, 34) were detected sooner than
signals with a single band of noise at the same frequency (signals 11,
12, 13). For example, the average time-to-vehicle arrival was 3.1
seconds for a pure tone at 315 Hz and 2.3 seconds for a single band of
noise at the same frequency. A statistical analysis also found that the
interaction of sound type (tones or noise) and frequency was
significant.
    The study results indicated that, except for frequency sensitivity
for high frequency components, the modeling approach for determining
detection thresholds was conservative, meaning that the study
participants were able to detect sounds sooner than predicted by the
model. In order to correct for frequency sensitivity differences and to
develop the best agreement between modeled detection thresholds and
those of the participants so that the minimum one-third octave band
levels for detection in the final rule more closely align with
pedestrians' ability to detect sounds in the real world, Volpe
performed a linear regression to reconcile the predicted detection
values in the model and the performance of the participants in the
experiment.
    In order to ensure that the model was as predictive of real-world
experience as possible, that is, in order to obtain the best agreement
between modeled detection thresholds and those of the participants, and
also to correct for frequency sensitivity differences, Volpe did a
series of linear regressions using different loudness metrics. The best
agreement between modeled and actual participant detection times
occurred when a detection threshold of 0.079 sones \46\ per ERB was
used \47\ (see Figure 1). The R-squared value achieved for this model
was 0.72, indicating that the model performs well on average although,
as anticipated, outcomes are not always exactly the same due to random
variation and other differences between the model predictions and
participant performance. Thus, the agency chose to use the detection
threshold of 0.079 sones per ERB in the Moore's model as the basis for
deriving the revised minimum levels for each of the one-third octave
bands in the final rule.
---------------------------------------------------------------------------

    \46\ Sone is a unit of subjective loudness on a linear scale.
The Moore's Loudness model used by the agency in the NPRM and this
final rule utilizes loudness (in sones) and partial loudness (in
sones per equivalent rectangular bandwidth or ``ERB'') parameters as
a basis for determining thresholds, i.e., minimum sound levels,
required for vehicle detection.
    \47\ Hastings A.; and McInnis, C. ``Detectability of Alert
Signals for Hybrid and Electric Vehicles: Acoustic Modeling and
Human Subjects Experiment'' Docket NHTSA-2011-0148. Washington, DC:
DOT/NHTSA.

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

[GRAPHIC] [TIFF OMITTED] TR14DE16.000

    The agency also conducted an analysis of acoustic recordings to
evaluate the detectability of signals with varying numbers of non-
adjacent components in the presence of additional ambient conditions
different from the standardized ambient used to develop the one-third
octave band minimum levels for detectability in the NPRM or this final
rule. The analysis provides an estimate of how often pedestrians would
be able to detect a sound signal in a 55 dB(A) ambient, with expected
spectral variation, as a function of the number of one-third octave
bands meeting the revised minimum thresholds.\48\ Ambient data were
collected at 17 locations along Centre Street in Newton, Massachusetts,
signalized and stop-controlled intersections (some with relatively high
traffic volume and some removed from the main road), one-way streets,
and side streets or driveways. The spectral shape of the ambient varies
from sample to sample, as would be expected given the different
locations in which they were collected. Some samples are dominated by
low frequency content while other samples are dominated by high
frequency content or have a mix of high and low frequency content. Each
ambient sample was normalized to an overall sound pressure level of 55
dB(A), so that the effect of the spectral content of each ambient on
the detectability of a signal could be examined in isolation from other
variables. This analysis differs from the modeling approach used to
develop the minimum one-third octave band levels for detection in the
NPRM and the final rule because that approach used a single ambient
that was chosen for consistency in development of minimum standards.
NHTSA refers to the resistance to masking of a signal evaluated using
this analysis as the ``robustness'' of the signal. Signals evaluated
for robustness contained from one to seven non-adjacent components
within the 315 to 5000 Hz frequency range. In most cases, these signals
were scaled so that the components just met the minimum one-third
octave band levels for detectability derived from the human factors
study.
---------------------------------------------------------------------------

    \48\ For practical reasons, this analysis is limited in that it
includes 17 measurement locations for the ambient that are in one
State, Massachusetts. Also, ambient samples were not categorized or
weighted according to `preferred crossable' opportunities for
pedestrians.
---------------------------------------------------------------------------

    This analysis predicted that, as ambient conditions vary, the
probability that at least one component is detectable increases with
increasing number of components when each component is set to the
minimum detection levels calculated based on the human factors study.
This is true for all operating conditions. For signals with content in
1, 2, 3, 4, 5, 6, and 7 one-third octave bands, the predicted
probabilities were about 55, 81, 93, 97, 98, 100, and 100 percent,
respectively. The analysis indicates that there is a rapid increase in
detectability as the number of components increases from 1 band to 4
bands when each band is set at the specified minimum detectable level.
Additional bands beyond 4 do not appear to increase the detectability
level significantly. An eight-band sound was not included in the
analysis because eight non-adjacent one-third octave bands do not fit
in the frequency range over which we are establishing minimum
requirements in the final rule. This analysis also showed that some
signals with content in only 2 one-third octave bands are expected to
be detected with the same frequency in multiple ambients as signals
with content in 4 one-third octave bands. Because signals with content
in 2 one-third octaves bands could be equally detectable as sounds with
content in 4 one-third octave bands the agency decided to include
minimum requirements for content in either 2 or 4 one-third octave
bands in the final rule.
Heavy Vehicle and Motorcycle Testing
    The research NHTSA conducted prior to the NPRM focused exclusively
on

light vehicles. However, since issuing the NPRM, the agency has
conducted some acoustic measurements on hybrid and electric heavy-duty
vehicles (GVWR over 10,000 lb.) and electric motorcycles.\49\ The test
protocol used for those measurements followed procedures in SAE-2889-1
(May 2012).
---------------------------------------------------------------------------

    \49\ Hastings, et al. Acoustic Data for Electric Heavy Vehicles
and Electric Motorcycles. (2014) DOT/NHTSA.
---------------------------------------------------------------------------

    Two electric motorcycles were tested at the Transportation Research
Center in Columbus, Ohio, on a test surface conforming to ISO 10844-
2011 specifications. NHTSA was able to apply the proposed test
procedure to the motorcycles without major issues.\50\ The overall
sound pressure levels for a 2012 model Brammo Enertia were 57.0, 63.2
and 66.5 dB(A) for the 10, 20, and 30 km/h pass-by, respectively. The
overall sound pressure levels for a 2012 model Zero S were between 6.2
to 7.9 dB lower with 49.1, 57.0 and 59.6 dB(A) for the 10, 20, and 30
km/h pass-by, respectively.
---------------------------------------------------------------------------

    \50\ One notable change is that the motorcycles were run just to
the right of the center of the lane with respect to the direction of
travel. This was done so the motorcycles' tires were not rolling on
the painted center line, since it was important to keep the tires on
the portion of the test track which had pavement meeting the ISO
specification (the painted center line is not intended to meet the
ISO specification.) Additionally, motorcycles were not tested in
reverse since they did not have reverse capabilities.
---------------------------------------------------------------------------

    The one-third octave band levels for the two motorcycles were
computed and compared to the minimum levels needed for detection (as
determined in NHTSA's research described in Section II.C \51\) in the
frequency range from 315 Hz to 5000 Hz. Results for the 2012 Brammo
Enertia show that the measured levels were equal or greater than the
minimum levels in two bands for the 10 km/h pass-by and in three bands
for the 20 km/h pass-by. Sound levels for the Enertia for the 30 km/h
pass-by did not meet the minimum levels for detection in any one-third
octave bands from 315 Hz to 5000 Hz. Sound levels for the 2012 Zero S
did not meet the minimum levels for detection in any of the bands for
all pass-by tests (i.e., 10, 20, and 30 km/h). While there is an
appreciable difference between the two models tested, these results
indicate that both models operate quietly over all or part of the range
of speeds up to 30 km/h. As discussed in Section III.B, the agency has
determined that, as with other types of hybrid and electric vehicles,
it is appropriate that the requirements of this final rule should apply
to hybrid and electric motorcycles.
---------------------------------------------------------------------------

    \51\ Hastings, et al. Detectability of Alert Signals for Hybrid
and Electric Vehicles: Acoustic Modeling and Human Subjects
Experiment. (2015) Washington, DC: DOT/NHTSA. As described in this
report, the minimum levels needed for detection were determined
using an acoustic loudness model that was adjusted for actual human
hearing responses to vehicle sounds and other sounds by using the
results of a series of human factors experiments conducted by Volpe
for NHTSA.
---------------------------------------------------------------------------

    NHTSA also collected acoustic data for a pure electric heavy
vehicle (Navistar eStar two-axle delivery van) on a surface compliant
with ISO 10844 and suitable for heavy vehicles. No issues were
encountered in applying the test protocol to the heavy vehicle tested.
It is important to note that only this one delivery truck was tested.
The agency was unable to obtain electric or hybrid heavy-duty vehicles
with different sizes and configurations for testing. The overall sound
pressure levels for the Navistar eStar were 55.4, 64.5, 73.4, and 75.2
dB(A) for the stationary, 10, 20, and 30 km/h pass-by scenarios,
respectively. The acoustic measurements for this vehicle were computed
and compared to the minimum levels needed for detection in the
frequency range from 315 Hz to 5000 Hz.\52\ The data showed that the
measured one-third octave band levels for the e-Star heavy vehicle are
equal to or greater than the minimum levels for detection in seven
bands for stationary, nine bands for the 10 km/h pass-by, eight bands
for the 20 km/h pass-by, and seven bands for the 30 km/h pass-by. Thus,
this vehicle generated appreciable sound at low speeds without the
addition of a pedestrian alert system, and we would expect this vehicle
to be detectable. However, because this testing was limited to only one
electric truck, the agency is not able to reach any general conclusions
that hybrid and electric heavy vehicles should be exempt from the final
rule.
---------------------------------------------------------------------------

    \52\ Hastings, et al. Detectability of Alert Signals for Hybrid
and Electric Vehicles: Acoustic Modeling and Human Subjects
Experiment. (2015) Washington, DC: DOT/NHTSA.
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    The agency also collected ``screening'' data for four hybrid and
electric heavy-duty vehicles. Screening tests were conducted in the
field (not on ISO 10844 sound pads) at convenient locations using
portable sound level meters. We note that the test protocol used for
the screening tests did not fulfill all the parameters stated in SAE-
J2889-1, and the measurements may not have been within the constraints
of the SAE standard for acoustic environment, operating conditions,
test surface, number of microphones, and microphone position. The
results obtained from screening data therefore may deviate appreciably
from results obtained using protocols and test conditions that strictly
adhere to the SAE standard. Data were collected at three locations,
Dayton, Ohio; Washington, DC; and Cambridge, Massachusetts. The four
vehicles in the screening tests were all transit buses and included a
New Flyer diesel-electric hybrid bus in Washington, DC; a trackless
electric trolley bus and a diesel-electric hybrid trolley bus in
Dayton, and a Neoplan trackless electric trolley bus in Cambridge. Each
vehicle was tested in as many of the applicable operating scenarios
(stationary, 10, 20, and 30 km/h pass-by) as possible. However, due to
vehicle or site limitations, not all vehicles were tested in all of
those operating scenarios.
    The screening data showed that the overall levels for these
vehicles range from 55.9 to 59.0 dB(A) for a stationary test; 61.7 to
69.3 dB(A) for a 10 km/h pass-by test; and 66 to 70.3 dB(A) for a 20
km/h pass-by test. The acoustic measurements for these vehicles were
computed and compared to the NPRM minimum levels for detection in the
frequency range from 315 Hz to 5000 Hz, for the eight bands included in
the NPRM.\53\ The data showed that the measured levels for the heavy
vehicles tested are equal to or greater than the minimum levels in five
to seven bands for stationary; five to eight bands for the 10 km/h
pass-by; two to five bands for the 20 km/h pass-by; and seven bands for
the 30 km/h pass-by. The screening data were informative about hybrid
and electric medium-duty and heavy-duty vehicle noise levels, but they
were not intended to be conclusive, and thus the agency did not
determine from this testing that it would be appropriate to exclude
medium and heavy vehicles from the final rule.
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    \53\ Hastings, et al. Detectability of Alert Signals for Hybrid
and Electric Vehicles: Acoustic Modeling and Human Subjects
Experiment. (2015) Washington, DC: DOT/NHTSA.
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Analysis of Indoor Test Data
    NHTSA also analyzed acoustic data measured in hemi-anechoic
chambers equipped with a chassis dynamometer.\54\ The data acquired at
indoor test facilities included measurements of electric, hybrid, and
internal combustion engine vehicles. NHTSA's analyses examined ambient
noise, repeatability, and reproducibility of the indoor acoustic
measurements. Acoustic data were collected at two indoor facilities:
The General Motors Milford Proving Grounds (MPG), in Milford, MI and
the International Automotive Components (IAC) facility,

in Plymouth, MI. Indoor test data was provided to NHTSA by Transport
Canada.\55\ Outdoor test data were collected by NHTSA's Vehicle
Research and Test Center (VRTC) at the Transportation Research Center
(TRC), East Liberty, OH, and NHTSA did a comparison of indoor and
outdoor measurements. The dataset available to support these analyses
included eight vehicles. Test vehicles were transported between the
Milford and Plymouth facilities so that the exact same vehicles were
used at both indoor test sites. Vehicle make and model were consistent
between indoor and outdoor testing,\56\ but the outdoor test results
have been aggregated over several testing efforts and do not in all
cases represent the exact same test vehicles.
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    \54\ Hastings, et al. Analysis of Acoustic Data for Hybrid and
Electric Vehicles measured on Hemi-Anechoic Chambers. Washington,
DC: DOT/NHTSA. A hemi-anechoic chamber is a specially-designed room
with walls that absorb sound waves for better acoustic analysis.
    \55\ Whittal, I.; Jonasch, R.; and Meyer, N. Quiet Vehicle
Sounds Test Data (2013) Transport Canada. Docket NHTSA-2011-0148-
0321.
    \56\ Indoor results from a 2012 Nissan Leaf were compared to
outdoor results from a 2010 Nissan Leaf.
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    Repeatability at each indoor test site was evaluated by computing
the standard error of the mean for each one-third octave band from the
sound pressure measurements, considering each measurement as an
estimate of the mean for each vehicle. The standard errors for these
two indoor test sites were typically around 0.5 to 0.75 dB for the 315
Hz one-third octave band and above. This indicates that about 95
percent of measured one-third octave band levels for a given vehicle
and operating speed will be within a range of 1 to 1.5 dB and, when estimating a mean value using four samples, the
mean value should be within about 0.5 to 0.75 dB of the true mean with
95-percent confidence.
    Measurement reproducibility between the two indoor test sites was
evaluated by comparing the average values of each vehicle at each one-
third octave band for each speed. The differences between sites were
about 2 dB on average at 10 km/h and only about 1 dB on average at 20
and 30 km/h. Although the average difference is generally less than 2
dB between the two sites, differences for specific vehicle/speed/
frequency pairs are still significant. When considering site-to-site
differences, the 95-percent confidence intervals for estimated means
range from 2.5 dB to 6.7 dB depending on the
one-third octave band. Bands at and below 400 Hz consistently have
standard deviations greater than 2 dB and bands 500 Hz and above
typically have standard deviations less than 2 dB (exceptions being 630
Hz and 800 Hz). The reproducibility between sites appears good. We
believe the measurement differences are due to inherent test
variability, as discussed in section III.K of this document, and also
to differences in each site's dynamometer/tire interaction.
    In addition to comparing the two indoor test sites to one another,
both facilities were also compared with outdoor measurements made at
TRC. Measurement reproducibility between each indoor test facility and
the outdoor test facility was evaluated by comparing the average sound
pressure levels of each vehicle at each one-third octave band for each
speed at the respective sites. Results showed that the indoor
facilities tend to have higher sound pressure levels, especially at 20
and 30 km/h. Because the differences are smaller at 10 km/h, it is not
likely that the differences in acoustic reflections from the indoor
floor and the outdoor pavement are causing the difference. Rather, it
is likely that the tire/dynamometer interaction is producing the higher
sound pressure levels. Considering confidence intervals of estimated
mean values for individual vehicle/speed/frequency pairs, the standard
deviation between TRC and MPG was as high as 5 dB and the standard
deviation between TRC and IAC was as high as 4.7 dB. Therefore,
tolerance values associated with 95-percent confidence intervals would
be as large as 9.8 and 9.2 dB respectively.
    These confidence intervals include site-to-site differences and
differences as a result of using different vehicles and in some cases
different model years. It is anticipated that this confidence interval
would be reduced if identical vehicles were tested. This indoor/outdoor
analysis involved only a very limited amount of data and the data in
some cases was not from the exact same vehicle. The agency would prefer
to conduct additional testing in a more highly controlled fashion to
allow for more conclusive results. In the absence of that, we have not
changed our position on using outdoor testing as proposed in the NPRM.
Acoustic Measurements of Hybrid and Electric Vehicles
    NHTSA's VRTC conducted additional acoustic measures for hybrid
vehicles, electric vehicles, low speed electric vehicles, and internal
combustion engine (ICE) vehicles to collect additional sound
measurements and to evaluate the repeatability of the test procedure
proposed in the NPRM.\57\ Sound levels were measured while vehicles
were stationary and while they were driving or coasting past
microphones at constant speeds of 10, 20, and 30 km/h.
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    \57\ Garrott, W. R., Hoover, R. L., Evans, L. R., Gerdus, E.,
and Harris, J. R., ``2012 Quieter Vehicle Testing Report: Measured
Sound Levels for Electric, Hybrid Electric, and Low Speed Vehicles''
Washington, DC, DOT/NHTSA, November 2016.
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    The repeatability of the measurement of the sound pressure level
was assessed by performing multiple tests with one vehicle (a 2010 Ford
Fusion) on one surface. The TRC ISO-compliant surface was used for this
work and tests were performed twice a month from April to October 2012.
Each test consisted of eight individual measurements for each scenario.
Results showed that the 95-percent confidence interval of the overall
sound pressure level ranged from 0.7 dB to 1.9
dB for the various scenarios. There was no significant systematic
change in overall sound pressure levels over the six month period.
    Data were also collected at different ISO 10844-compliant surfaces
to examine test reproducibility. The reproducibility of sound pressure
levels was estimated by testing the 2010 Ford Fusion twice on two other
ISO-compliant surfaces (at Ford Motor Company Proving Ground in Romeo,
Michigan, and at the Navistar Test Track in Fort Wayne, Indiana). The
average sound pressure levels for all scenarios on the other ISO
surfaces fell within the experimental errors of the average sound
pressure levels measured on the TRC ISO surface. The 95-percent
confidence interval of site-to-site variation for overall sound
pressure level ranged from 0.6 dB to 2.1 dB and
the 95-percent confidence estimates for reproducibility, including the
repeatability of the measurements, ranged from 1.3 dB to
2.4 dB.
    To determine if acoustic testing locations could include test areas
with surfaces that are not ISO-compliant, the agency investigated using
correction factors to adjust data from non-ISO-compliant surfaces, the
agency compared overall sound pressure levels measured on ISO 10844-
compliant surfaces to overall sound pressure levels measured on three
other asphalt surfaces of varying characteristics. The alternative
surfaces were located at TRC in East Liberty, OH, and included: A new
asphalt surface in the vehicle dynamics area; a sealed asphalt surface;
and a skid calibration lane. These pavements were appropriate examples
of potential test surfaces that are not ISO-compliant to examine the
impact that testing using different surfaces may have on measuring
vehicle sound.
    Overall sound pressure levels on the three asphalt surfaces were
compared to the results on the TRC ISO surface using the 2010 Ford
Fusion, and an EV with

an active external sound generator, as well as an EV without an active
external sound generator. Results showed that one surface tended to
produce overall sound pressure levels significantly lower than the ISO-
compliant surface at 0 and 10 km/h. Researchers concluded that this was
due to greater absorptivity of this asphalt composition. The other two
surfaces tended to generate results not significantly different than
the ISO-compliant surface when the vehicles were stationary or
traveling at 10 km/h. On these surfaces, sound levels increased more
rapidly than for the ISO surface as the vehicle speed increased. The
overall sound pressure levels at 20 and 30 km/h tended to be
significantly higher for these two surfaces compared to the ISO
surface. Researchers concluded that these surfaces tended to generate
more tire noise than the ISO-compliant surface. An attempt to use the
data from the Ford Fusion to normalize the sounds from the different
surfaces was unsuccessful. Consequently, we did not conclude that it is
feasible to test on surfaces other than an ISO-compliant one.
    To examine the sound levels emitted by low speed electric vehicles
(LSVs), VRTC tested five of examples of these vehicles. LSVs typically
are lighter than EVs and often use different tires, so it was prudent
to conduct separate measurements of LSVs rather than assume they are as
quiet as EVs. The sound levels produced by the LSVs were very similar
to those of the EVs, with the main difference being that four of the
LSVs were equipped with back-up beepers of varying sound pressure
levels. Other than during reverse acceleration, the LSVs showed overall
sound levels with standard deviations ranging from about 1 to 2.5 dB.
    To provide data for the agency's analysis of the crossover speed of
HVs and EVs, the agency tested additional HVs and one EV as well as a
number of ICE peer vehicles (in cases where a peer vehicle was
available for the HVs and the EV selected for testing) and compared the
ICE peer vehicle test results to the HV and EV results. At 10 km/h, the
three HVs tested (none with external sound generators) had an average
SPL 2.4 dB lower than their ICE peer vehicles. An EV without an active
external sound generator had an average SPL 7.3 dB lower than its ICE
peer vehicle. At 20 km/h, the three HVs (none with external sound
generators) had an average sound pressure level 1.1 dB lower than their
ICE peer vehicle and the EV without external sound had an average sound
pressure level of 3.5 dB below its ICE peer vehicle. At 30 km/h the HVs
and EV had sound pressure levels that were not significantly different
from their ICE peer vehicles. One-third octave band data and
comparisons were also reported.
    In addition, the agency compared the sound pressure levels of ICE
vehicles in motion with their engines running to the same ICE vehicles
coasting past the microphones with their engines turned off. These
comparisons were made at 10, 20, and 30 km/h. The sound pressure levels