Document ID: NHTSA-2016-0125-0001
Agency: nhtsa
Document Type: Rule
Title: Federal Motor Vehicle Safety Standards: Minimum Sound Requirements for Hybrid and Electric Vehicles
Posted Date: 2016-12-14T05:00Z

[Federal Register Volume 81, Number 240 (Wednesday, December 14, 2016)]
[Rules and Regulations]
[Pages 90416-90522]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2016-28804]

[[Page 90415]]

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  

[[Page 90416]]

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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: 202-366-4171) (fax: 202-493-2990). 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: 202-366-2992) (fax: 202-366-3820). 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.

[[Page 90417]]

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

[[Page 90418]]

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
                                    --------------------------------------------------------------------------------------------------------------------
            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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[[Page 90419]]

    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
------------------------------------------------------------------------
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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[[Page 90420]]

    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.
---------------------------------------------------------------------------

    \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\
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    \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

[[Page 90421]]

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.

[[Page 90422]]

    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

[[Page 90423]]

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

[[Page 90424]]

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.
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    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

[[Page 90425]]

 
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/

[[Page 90426]]

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

[[Page 90427]]

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

[[Page 90428]]

 
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.

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

[[Page 90429]]

[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

[[Page 90430]]

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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \53\ Hastings, et al. Detectability of Alert Signals for Hybrid 
and Electric Vehicles: Acoustic Modeling and Human Subjects 
Experiment. (2015) Washington, DC: DOT/NHTSA.
---------------------------------------------------------------------------

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,

[[Page 90431]]

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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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

[[Page 90432]]

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 
for the vehicles with their engines running were an average of 7.9 dB 
higher than in the coasting (engine-off) condition at 10 km/h (min. 4.3 
dB, max. 11.6 dB); 2.2 dB higher than in the coasting (engine off) 
condition at 20 km/h (min. 0.6 dB, max. 5.7 dB); and 0.9 dB higher than 
in the coasting (engine off) condition at 30 km/h (min. 0.5 dB; max. 
1.7 dB).

D. Notice of Proposed Rulemaking

    In the NPRM we proposed to apply the minimum sound requirements to 
all hybrid and electric passenger cars, light trucks and vans (LTVs), 
medium and heavy-duty trucks and buses, low speed vehicles (LSVs), and 
motorcycles, that are capable of propulsion in any forward or reverse 
gear without the vehicle's ICE operating.
    The proposed minimum sound requirements would apply to these HVs 
and EVs in three circumstances: (1) When operating up to 30 km/h (18 
mph), (2) when the vehicle's starting system is activated but the 
vehicle is stationary,\58\ and (3) when the vehicle is operating in 
reverse. The NPRM also contained requirements for the sound produced by 
hybrid and electric vehicles to increase and decrease in pitch as the 
vehicle increases and decreases speed so that pedestrians would be able 
to detect those changes. We proposed a crossover speed of 30 km/h 
because this was the speed at which tire noise, wind resistance noise, 
and other noises from the vehicle become the dominant noise and 
eliminate the need for added alert sounds.\59\
---------------------------------------------------------------------------

    \58\ The NPRM contained minimum sound requirements for the 
stationary but active condition because the definition of alert 
sound in the PSEA requires the agency to issue minimum sound 
requirements to allow pedestrians to detect the operation of nearby 
hybrid and electric vehicles, including those vehicles that are 
operating but stationary.
    \59\ For additional details about how and why the agency 
selected the crossover speed of 30 km/h refer to section III.D. in 
this document.
---------------------------------------------------------------------------

    The agency proposed to require HVs and EVs to make a minimum amount 
of sound in each of eight different one-third octave bands, under each 
of several test conditions. The agency developed the minimum sound 
levels for each one-third octave band using a detection model that 
estimated the distance at which a pedestrian would be able hear a given 
sound in the presence of a given ambient sound profile. In the NPRM, 
NHTSA proposed to require eight one-third octave bands with the 
perspective that required sounds should be detectable in a wide variety 
of ambients, including ambients that had different acoustic 
characteristics from the ambient that we used with our detection model. 
The NPRM also required that sound produced by EVs and HVs be 
recognizable to pedestrians as motor vehicle sounds by containing low 
frequency tones and broadband content because these are characteristics 
commonly associated with sounds produced by internal combustion 
engines.
    The compliance test procedure specified in the NPRM was to be 
performed outdoors and was based in part on SAE J2889-1 SEPT 2011. The 
compliance test procedure contained tests for stationary, reverse, and 
pass-by tests conducted at 10 km/h, 20 km/h, and 30 km/h. We explained 
in the NPRM that NHTSA believed that outdoor pass-by testing would be 
preferable to indoor testing in hemi-anechoic chambers using 
dynamometers because outdoor testing is more representative of the 
real-world interactions between pedestrians and vehicles. We also 
expressed concern that specifications for indoor testing were not as 
developed and did not have the same level of objectivity, 
repeatability, and reproducibility as test specifications for outdoor 
testing.
    The NPRM proposed a phase-in schedule consistent with the PSEA 
which would require ``full compliance with the required motor vehicle 
safety standard for motor vehicles manufactured on or after September 
1st of the calendar year that begins 3 years after the date on which 
the final rule is issued.'' In the NPRM we stated that if the final 
rule was issued January 4, 2014, compliance would commence on September 
1, 2015, which would mark the start of a three-year phase-in period. 
The NPRM proposed the following phase-in schedule:
     30 percent of the subject vehicles produced on or after 
September 1 of the first year of the phase-in;
     60 percent of the subject vehicles produced on or after 
September 1 of the second year of the phase-in;
     90 percent of the subject vehicles produced on or after 
September 1 of the third year of the phase-in; and
     100 percent of all vehicles produced on or after, by 
September 1 of

[[Page 90433]]

the year that begins three years after the date that the final rule is 
issued.
    In the NPRM, we tentatively concluded that this phase-in schedule 
was reasonable for manufacturers and allowed the fastest implementation 
of the standard for pedestrian safety.

E. Summary of Comments to the NPRM

    The agency received comments to the NPRM from a wide variety of 
commenters, including trade associations,\60\ vehicle 
manufacturers,\61\ advocacy groups,\62\ suppliers,\63\ academia,\64\ 
standards-development organizations,\65\ governments,\66\ and 
approximately 225 individuals.
---------------------------------------------------------------------------

    \60\ The trade associations representing manufacturers that 
submitted comments included the International Motorcycle 
Manufacturers Association (IMMA), the Truck and Engine Manufacturers 
Association (EMA), the Electric Drive Transportation Association 
(EDTA), the Motorcycle Industry Council (MIC) and the Organization 
Internationale DES Constructeurs d' Automobiles (OICA). The Alliance 
of Automobile Manufacturers and Global Automakers submitted a joint 
comment that is referenced here as the ``Alliance/Global'' comment.
    \61\ Such as Toyota Motor North America (Toyota), Volkswagen 
Group of America (Volkswagen), Porsche Cars North America (Porsche), 
Ford Motor Company (Ford), American Honda Motor Co. (Honda), 
Mercedes-Benz USA (Mercedes), General Motors Company (General 
Motors), Mitsubishi Motors R&D of America (Mitsubishi), Chrysler 
Group LLC (Chrysler), Navistar, Inc. (Navistar), Nissan North 
America, Inc. (Nissan) and BMW of North America, LLC (BMW).
    \62\ The public safety advocacy groups submitting comments to 
the proposal included National Federal of the Blind (NFB), National 
Council of State Agencies of the Blind, the Advocates for Highway 
Safety (the Advocates), Noise Pollution Clearinghouse, the Insurance 
Institute for Highway Safety (IIHS), Safe Kids Worldwide, the World 
Blind Union, and American Council of the Blind (ACB).
    \63\ Such as Denso International America, Inc. (Denso) and Hear 
for Yourself, LLC.
    \64\ Such as the Mercatus Center at George Mason University, 
Western Michigan University (Western Michigan), and Accessible 
Designs for the Blind (ADB).
    \65\ SAE International.
    \66\ The European Commission Enterprise and Industry 
Directorate-General (DG Enterprise), and the Disability and 
Communication Access Board of Hawaii.
---------------------------------------------------------------------------

    The primary issues raised by the advocacy groups and manufacturers 
concerned our proposal to require sound while hybrid and electric 
vehicles are stationary but active and our proposal to establish 
minimum sound requirements up to a speed of 30 km/h. Manufacturers and 
trade association groups argued that a sound at stationary is not 
required for safety. These commenters stated NHTSA should instead 
mandate a commencing motion sound that activated when the driver of an 
HV/EV removed her foot from the brake pedal. Manufacturers and trade 
associations also commented that the agency should only establish 
minimum sound requirements up to 20 km/h, arguing that above 20 km/h 
tire and wind noises are the dominant contributors to the sound 
produced by moving vehicles, and provide enough sound for pedestrians 
to safely detect hybrid and electric vehicles.
    NFB and ACB supported the agency's proposal to require that hybrid 
and electric vehicles produce sound in the stationary but active 
operating condition, because it would help blind and visually-impaired 
pedestrians be aware of nearby vehicles and avoid collisions. NFB, ACB, 
and Advocates also supported the agency's proposal to establish minimum 
sound requirements for speeds up to 30 km/h, stating that they believe 
that the agency's research supports establishing minimum sound 
requirements to those limits.
    Manufacturers and groups that represent manufacturers were 
supportive of the concept of adding sound to EVs and HVs to enhance 
pedestrian detection but expressed concern that the minimum sound 
requirements proposed in the NPRM were more restrictive than necessary 
to accomplish this goal. They argued that sounds meeting the 
requirements proposed in the NPRM would be annoying to consumers and 
might negatively affect sales of hybrid and electric vehicles. 
Regarding the agency's proposed compliance test procedure, 
manufacturers and groups that represent manufacturers requested the 
option to conduct compliance testing in indoor hemi-anechoic chambers 
using dynamometers, arguing that that is a more accurate and consistent 
method of testing because it is a more controlled environment that 
minimizes the kind of ambient variations that are expected in outdoor 
environments. They also raised issues regarding the agency's proposed 
method of measuring a vehicle's change in pitch as it increases or 
decreases speed, commenting that pitch shifting should be measured 
using a component-level test, i.e., a bench test procedure, rather than 
testing the entire vehicle.
    Manufacturers also disagreed with the agency's estimate of the cost 
of speaker systems needed to produce sounds capable of complying with 
the requirements in the NPRM, stating that speakers capable of 
producing the low frequency content specified in the proposed minimum 
sound requirements were more expensive than the agency estimated.
    Organizations that represent manufacturers of motorcycles and 
heavy-duty and medium-duty vehicles took issue with the agency's basis 
for applying the rule to the vehicles they manufacture, stating that 
the agency had not shown a safety need based on crash data. They stated 
that the final rule should not apply to those vehicles because hybrid 
and electric motorcycles and heavy- and medium-duty trucks and buses do 
not pose an increased risk to pedestrians over ICE vehicles.
    A number of individual commenters either expressed general support 
for the rule or general opposition to increasing the amount of sound 
produced by hybrid and electric vehicles. Several individuals also 
questioned why the agency was limiting the scope of the proposed rule 
to hybrid and electric vehicles. These commenters stated that the 
minimum sound requirements in the NPRM should apply to all vehicles 
including ICE vehicles that do not produce enough sound to be safely 
detected by pedestrians.

III. Final Rule and Response to Comments

A. Summary of the Final Rule

    Today's final rule generally adopts the proposed standard but 
modifies the requirements in several ways. As proposed, we will require 
hybrid and electric vehicles to emit sound at minimum levels while the 
vehicle is stationary (although not necessarily at all times when the 
vehicle propulsion system is active); while the vehicle is in reverse; 
and while the vehicle is in forward motion up to 30 km/h. Today's final 
rule also adopts the agency's proposal to conduct compliance testing 
outdoors.
    The agency is adopting numerous changes to the proposal in response 
to additional analysis conducted by the agency and in response to the 
comments on the proposal. The most significant change relates to the 
scope of the final rule. This final rule only applies to hybrid and 
electric passenger cars and LTVs with a GVWR of 4,536 kg (10,000) 
pounds or less and LSVs. This final rule does not apply to medium and 
heavy duty trucks and buses with a GVWR over 4,536 kg (10,000) pounds 
or to motorcycles. Based on a review of the available acoustic data 
regarding these vehicles and the comments, we have determined that we 
do not have enough information at this time to apply this final rule to 
medium and heavy duty vehicles and motorcycles.
    We have determined the final rule should apply to LSVs, because 
unlike electric motorcycles and medium and heavy duty trucks and buses 
with a GVWR over 4,536 kg (10,000) pounds, we have acoustic data 
showing that LSVs are quiet. Therefore, we do not have any 
justification to exclude them

[[Page 90434]]

from the coverage of the final rule given the requirements of PSEA.
    We have also made significant changes to the detectability 
specifications in the NPRM, i.e., what sounds HV/EVs are permitted to 
make that the agency would consider compliant with the standard. After 
further consideration of the NPRM specifications, we are establishing 
new specifications in this final rule that provide greater flexibility 
for manufacturers in this respect, but that will still allow 
pedestrians to safely detect EVs and HVs. Specifically, whereas in the 
NPRM we proposed that HV/EVs would have to meet minimum acoustic 
requirements in eight separate one-third octave bands, in this final 
rule, the agency is providing two alternative acoustic specifications, 
either of which the agency would consider to be compliant, and both of 
which reduce the number of one-third octave bands for which there are 
minimum levels. Under the first compliance option, hybrid and electric 
vehicles would have to meet minimum acoustic requirements in four one-
third octave bands instead of eight. Under the second compliance 
option, hybrid and electric vehicles would have to meet minimum 
acoustic requirements in two one-third octave bands, plus meet an 
overall sound pressure minimum.
    Under the four one-third octave band compliance option, the minimum 
sound requirements for each band would be slightly lower than the 
values proposed in the NPRM and the overall sound pressure of sounds 
meeting the four one-third octave band compliance option will be 
similar to those meeting the proposed requirements for eight bands in 
the NPRM. Under the two one-third octave band compliance option, the 
minimum sound requirements for each band are lower than those of the 
eight one-third octave band proposal in the NPRM for the low and mid 
frequency bands and higher than the minimum values in the NPRM for the 
high frequency one-third octave bands centered at 4000 Hz and 5000 Hz. 
Neither the four-band compliance option nor the two-band compliance 
option include requirements for tones or broadband content contained in 
the NPRM.
    For both the two-band and four-band compliance options, the final 
rule expands the range of acceptable one-third octave bands to include 
those between 630 Hz and 1600 Hz (these bands were excluded in the 
NPRM). Reducing the number of required one-third octave bands while 
expanding the number of possible bands that manufacturers can use to 
meet the minimum requirements provides additional flexibility to 
manufacturers for designing pedestrian alert systems. Sounds meeting 
these new requirements will have a similar overall sound pressure level 
to those meeting the requirements in the NPRM. These changes preserve 
the agency's goal of establishing requirements that will lead to 
pedestrian alert sounds that are detectable in ambient sound 
environments with different spectral shapes. The detectability 
specifications are discussed further in Section III.E of this final 
rule.
    The agency originally proposed to require ``pitch shifting,'' 
meaning that as HV/EVs increased or decreased in speed (from stationary 
up to the cutoff of 30 km/h), the frequency of the sound produced by 
the HV/EV had to vary up or down with speed by one percent per km/h. 
After further consideration, we have concluded that the proposed pitch 
shifting compliance test is likely to have repeatability issues and may 
involve subjective assessments in compliance evaluations. For those 
reasons, and also in response to information raised in manufacturers' 
comments, the agency has decided instead to require simply that the 
vehicle-emitted sound increase and decrease in volume by a specified 
amount as the vehicle's speed increases and decreases. The agency 
believes this revised requirement, like the proposed pitch shifting 
requirement, will appropriately convey to pedestrians when a vehicle is 
accelerating or decelerating. This approach also has a testing 
advantage in that changes in vehicle speed and corresponding changes in 
vehicle-produced sound can be determined using the same data collected 
during the stationary and constant-speed pass-by tests. This issue is 
discussed further in Section III.G of this final rule.
    The agency also proposed to require the pedestrian alert sound to 
contain a low frequency tone under 400 Hz to aid recognizability by 
pedestrians, stating that this would make the required alert sounds 
more similar to ICE vehicle sounds which typically include low 
frequencies. Based on additional analysis indicating that low-frequency 
tones are not essential for vehicle-emitted sounds to be recognized as 
motor vehicles in operation, and manufacturer comments arguing that 
low-frequency tones would be intrusive to vehicle occupants and 
expensive to reproduce, we have decided against including the proposed 
requirement in the final rule. Section III.F discusses this issue in 
more detail.
    Also to aid recognizability, we originally proposed to require that 
the vehicle-emitted sounds contain broadband sound between 160 Hz and 
5000 Hz. This means sound across a wide range of frequencies, and 
reflects the fact that ICE vehicles produce broadband sound when 
operating at low speed. We agree with commenters that this requirement 
is not critical for sound recognition because we believe that 
pedestrians will use other sound cues that provide more information in 
order to recognize sounds meeting the requirements of the final rule as 
vehicle-emitted sounds. In addition to the revised requirement that the 
alert sound level must increase as a vehicle increases speed, we 
believe that pedestrians would 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, so tones and broadband 
content are not essential for these vehicles to be recognizable. This 
issue is discussed more in Section III.F of this final rule.
    With regard to test procedures, the final rule also makes a number 
of changes from the proposal. We have modified the procedure for 
determining whether the sound produced by two hybrid or electric 
vehicles of the same make, model, and model year is the same. After 
further analysis, we have determined that requiring the sound produced 
by two hybrid or electric vehicles of the same make, model, and model 
year to be within three dB(A) for every one-third octave band between 
315 Hz and 5000 Hz would not guarantee that the sound produced by the 
two vehicles would be the same. We have instead decided to ensure that 
EVs and HVs of the same make, model, and model year produce 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. We have also made numerous other changes to the proposed 
test procedures in response to comments.
    While we have retained the requirement that EVs and HVs must 
generate an alert when stationary, the final rule requires an alert 
only when a vehicle's transmission gear selector is not in the ``Park'' 
position. We have changed the test procedure accordingly, and we will 
test this condition with the vehicle's gear selector in ``Drive'' or 
any forward gear. We believe that this modification to the stationary 
requirement will provide pedestrians with a way to detect those 
vehicles that

[[Page 90435]]

pose the greatest risk to them (i.e., those vehicles that could begin 
moving at any moment) while ensuring that EVs and HVs do not produce 
unwanted sound in situations in which they do not pose a threat to 
pedestrians, such as when they are parked. The final rule requirements 
and procedures also address vehicles with manual transmission. Test 
procedures are discussed in more detail in Sections III.J and III.K of 
this preamble.
    With regard to the phase-in schedule for the standard, we have 
simplified the proposed phase-in schedule by shortening it to include a 
single year of phase-in, rather than the three-year phase-in that the 
agency proposed in the NPRM. This simplification provides somewhat 
greater lead-time and responds to vehicle manufacturers' comments that 
the proposed phase-in was unnecessarily complex. Half of each 
manufacturer's HV and EV production must comply with this final rule by 
September 1, 2018, and 100 percent of each manufacturer's HV and EV 
production must comply with this final rule by September 1, 2019. The 
phase-in does not apply to multi-stage and small volume manufacturers: 
100 percent of their HV and EV production must comply with this final 
rule by September 1, 2019.

B. Applicability of the Standard

Definition of a Hybrid Vehicle
    The PSEA defines ``hybrid vehicle'' as ``a motor vehicle which has 
more than one means of propulsion.'' As discussed in the NPRM, we 
concluded that the definition in the PSEA requires the agency to apply 
the standard only to hybrid vehicles that are capable of propulsion 
without the vehicle's ICE operating, because if the ICE is always 
running when these vehicles are operating, then the fact that these 
vehicles may not provide sufficient sound for pedestrians to detect 
them cannot be attributed to the type of propulsion. Under the agency's 
interpretation of the definition of ``hybrid vehicle'' in the PSEA, 
more than one means of propulsion therefore means more than one 
independent means of propulsion. This definition of ``hybrid vehicle'' 
would exclude from the applicability of the proposed standard those 
vehicles that are equipped with an electric motor that runs only in 
tandem with the vehicle's ICE to provide additional motive power, for 
example a vehicle that cannot operate in a purely electric drive mode.
    The NPRM also stated that the PSEA did not limit the definition of 
``hybrid vehicle'' to hybrid-electric vehicles, so the proposed rule 
would apply to any vehicle with multiple independent means of 
propulsion. However, the definitions section of the NPRM regulatory 
text did not include a specific definition of ``hybrid vehicle.''
    Alliance/Global and OICA disagreed with the agency's proposal that 
the standard should apply to any vehicle with multiple independent 
means of propulsion, and argued that it should apply only to those 
vehicles that have an electric motor as the additional means of 
independent propulsion. Alliance/Global and OICA stated they do not 
believe that vehicles with non-electric hybrid powertrains should be 
subject to the requirements of the final rule, because the agency has 
not demonstrated that those vehicles are quiet. Alliance/Global and 
OICA also stated that the final rule should include a definition of 
``hybrid vehicle'' in paragraph S4 of the regulatory text.
Agency Response to Comments
    We agree that a definition of ``hybrid vehicle'' should be included 
in the rule and have added one. The definition appears in Section S4 of 
the regulatory text, and is based on the definition for a hybrid 
vehicle that was presented in the ``Application'' section of the NPRM 
preamble, where we stated that a hybrid vehicle is ``a motor vehicle 
that has more than one means of propulsion for which the vehicle's 
propulsion system can propel the vehicle in the normal travel mode in 
at least one forward drive gear or reverse without the internal 
combustion engine operating.''
    In response to the industry request to limit the scope of the rule 
to only HVs with an electric motor as the additional means of 
propulsion, we are aware that some alternative hybrid vehicles may use 
something other than an electric drive system in conjunction with an 
ICE, for example, a hybrid that uses hydraulic or flywheel energy 
storage in place of electric motor and batteries, although we currently 
are not aware of hybrid vehicles other than hybrid-electrics that are 
for sale in the U.S.
    Regardless of whether such vehicles are currently available for 
sale, however, we continue to believe that any hybrid operating under 
an independent, non-ICE means of propulsion should be required to meet 
the minimum sound requirements of this standard because we have no 
evidence that they may not be capable of operating as quietly as 
electric hybrids. From a safety perspective, the agency is concerned 
with all hybrids that might operate quietly, regardless of the power 
source for their non-ICE propulsion, and commenters provided no 
information about whether hybrid vehicles other than hybrid-electrics 
would be any less quiet than hybrid-electric vehicles when not equipped 
with pedestrian alert systems. As for hybrids other than electric ones, 
if the vehicle produces sound levels in excess of those required by 
this final rule then no additional alert would be required; if not, an 
additional alert would be required.
Vehicles With a GVWR Over 10,000 lbs.
    In the NPRM, we stated that the PSEA requires the agency to apply 
the requirements of the standard to all hybrid and electric motor 
vehicles which includes cars, multipurpose passenger vehicles, trucks, 
buses, low-speed vehicles and motorcycles.\67\ However, we acknowledged 
that ICE vehicles with a gross vehicle weight rating (GVWR) over 10,000 
pounds (lbs.) have a lower rate of collisions involving pedestrians 
than light ICE vehicles,\68\ and we stated that we were not able to 
calculate a separate incidence rate for collisions between pedestrians 
and hybrid and electric vehicles with a GWVR over 10,000 lbs. because 
the number of those vehicles in the on-road vehicle fleet was extremely 
limited. Because we were not able to calculate a separate incidence 
rate for collisions involving pedestrians and hybrid and electric heavy 
vehicles, we did not calculate the benefits of applying the rule to 
them in the NPRM. We stated in the NPRM that we believe that as the 
number of these vehicles in the fleet increases, the difference in 
pedestrian collision rate between heavy HV/EVs and heavy ICE vehicles 
would be similar to the difference in pedestrian collision rate between 
light HV/EVs and light ICE vehicles.
---------------------------------------------------------------------------

    \67\ The PSEA specifically excludes trailers from the scope of 
the required rulemaking.
    \68\ For the purposes of this document we refer to all motor 
vehicles with a GVWR over 10,000 lbs. as ``heavy-duty vehicles.''
---------------------------------------------------------------------------

    The agency also recognized at the time of the NPRM that we had very 
limited data about the sound levels produced by hybrid and electric 
heavy vehicles. We also acknowledged that there are a limited number of 
test pads having pavements that meet ISO 10844, Acoustics--
Specification of test tracks for measuring noise emitted by road 
vehicles and their tires, that can accommodate the extra weight of 
heavy vehicles.
    Manufacturers and organizations that represent manufacturers of 
heavy-duty vehicles stated that NHTSA should not apply the final rule 
to heavy-duty vehicles because the agency had not established that 
these vehicles are quiet, could not demonstrate a safety need to

[[Page 90436]]

merit applying the requirements of the proposal to these vehicles, and 
had not developed appropriate requirements and compliance tests for 
these vehicles. Safety advocacy organizations and organizations that 
represent individuals who are blind and visually-impaired, in contrast, 
stated that NHTSA should apply the requirements of the final rule to 
heavy-duty vehicles because these vehicles would pose an increased risk 
of collision with pedestrians if they were quiet.
    EDTA stated in its comments that NHTSA should defer application of 
minimum sound requirements in the final rule to heavy-duty vehicles, 
motorcycles and low-speed vehicles until the agency establishes a more 
complete record showing the need for these vehicles to meet those 
requirements. EDTA further stated that if the agency found that the 
requirements in the final rule should apply to heavy-duty vehicles, 
motorcycles and low-speed vehicles, the agency should develop 
audibility specifications that reflect the technologies, duty cycles 
and uses, and sound profiles specific to these types of vehicles.
    EMA and Navistar stated that NHTSA should exclude hybrid and 
electric vehicles with a GVWR over 10,000 lb. from the scope of this 
rulemaking until the agency identifies a potential unreasonable risk to 
safety caused by the quiet nature of these vehicles, develops acoustic 
requirements specifically for these vehicles, and develops appropriate 
compliance test procedures.
    EMA stated that, in addition to the incidence rate of collisions 
between pedestrians and heavy vehicles, NHTSA also should consider the 
exposure level of pedestrians to being struck by heavy-duty vehicles. 
EMA stated that certain heavy vehicles such as truck tractors do not 
typically operate in environments where pedestrians are present, so 
their risk of collision with pedestrians is much lower than the risk 
for passenger cars. In addition to having lower rates of exposure to 
pedestrians, heavy-duty vehicles make up a small fraction of the on-
road vehicle fleet when compared to light vehicles. EMA suggested that 
the risk of a pedestrian being struck by a heavy-duty vehicle is much 
lower than the risk of a pedestrian being struck by a light vehicle 
when the percentage of heavy vehicles in the on-road fleet and their 
exposure to pedestrians are considered. EMA further suggested that 
lower rate of collisions with pedestrians and the low exposure show 
that NHTSA should not apply a single countermeasure with the same test 
procedures to all hybrid and electric vehicles.
    EMA stated that NHTSA does not have any acoustic data that shows 
that heavy-duty hybrid and electric vehicles are quieter than heavy ICE 
vehicles and pose a safety risk to blind and other pedestrians. EMA 
stated that the NPRM did not contain any data comparing the sound 
produced by heavy-duty ICE vehicles to heavy-duty hybrid and electric 
vehicles. EMA stated that without acoustic data on heavy vehicles, 
NHTSA is unable to know what the crossover speeds are for heavy-duty 
vehicles or whether heavy-duty vehicles produce sufficient sound that 
they do not need to be equipped with a sound generation device. In 
addition, EMA stated that the crossover speed developed for light 
vehicles might be inappropriate for heavy-duty vehicles. Because these 
vehicles have larger tires than light vehicles and often have more 
tires and have a less aerodynamic body design they produce more sound 
than light vehicles under the same operating conditions.
    EMA stated in its comments that applying the requirements in the 
NPRM to heavy-duty vehicles would violate the PSEA because NHTSA has 
not determined a separate crossover speed for heavy vehicles. EMA 
stated that to comply with the PSEA NHTSA must determine the crossover 
speed for each type of heavy-vehicle to which the final rule would 
apply. EMA stated further that applying the NPRM to heavy-duty vehicles 
violates the Vehicle Safety Act because the NPRM did not assess whether 
a different standard was needed for heavy vehicles.
    Advocates commented that NHTSA should apply the final rule to 
hybrid and electric heavy vehicles. Advocates suggested that as 
advances in alternative energy increase, there will be a greater number 
of these types of vehicles. Advocates stated ``the agency should 
consider its findings that pedestrians and pedalcyclists, especially 
the visually-impaired, utilize the different sound of heavy vehicles 
when compared with light vehicles to modify their estimation of when it 
is safe to undertake a movement, like crossing a road, which may vary 
with vehicular traffic.'' \69\ For that reason, Advocates suggested 
NHTSA should consider establishing different acoustic requirements to 
ensure that pedestrians and others can accurately identify and 
distinguish between heavy and light EVs and HVs. Advocates further 
stated that NHTSA should standardize the backing sound across all heavy 
vehicles so that pedestrians and bicyclists can differentiate backing 
heavy vehicles from other vehicles.
---------------------------------------------------------------------------

    \69\ Document No. NHTSA-2011-0148-0270.
---------------------------------------------------------------------------

    ACB and NFB stated that the final rule should apply to heavy-duty 
hybrid and electric vehicles because these vehicles pose the same 
safety risks to pedestrians as light vehicles, and the number of these 
vehicles in the fleet will likely increase in the future.
    Western Michigan University stated that if the intent of the rule 
is to address potential hazards to the travel of blind pedestrians, 
then potentially quiet hybrid and electric heavy-duty vehicles should 
be required to meet the minimum sound requirements in the final rule. 
WMU stated that it was not aware of research on the audibility of 
hybrid and electric buses or light rail vehicles but that it seemed 
better to err on the side of caution and include heavy-duty hybrid and 
electric vehicles in the coverage of the final rule.
Agency Response to Comments
    Despite what was proposed in the NPRM, we have decided not to apply 
the requirements of this final rule to heavy-duty hybrid and electric 
vehicles. We reached this decision because we do not believe that we 
currently have enough information to determine whether the acoustic 
requirements or the crossover speed in this final rule are appropriate 
for heavy-duty hybrid and electric vehicles. Therefore, we plan to 
conduct further research on sound emitted by heavy-duty hybrid and 
electric vehicles before issuing a new NPRM proposing acoustic 
requirements for these vehicles.
    As described in Section II.C, after NHTSA issued the NPRM, we 
conducted testing to examine the sound levels produced by heavy-duty 
electric and hybrid vehicles. The agency tested the Navistar eStar 
Electric Heavy Vehicle following the procedures in SAE J2889-1, MAY 
2012, using an ISO asphalt pad meeting the specifications of 
International Standards Organization (ISO) 10844 ``Acoustics--
Specification of test tracks for measuring noise emitted by road 
vehicles and their tyres.'' \70\ The agency compared the acoustic 
recordings of the Navistar eStar to the four-band acoustic 
specifications in today's final rule. The eStar met or exceeded a 
number of minimum one-third octave levels at the 10, 20, and 30 km/h 
pass-by test conditions. According to the agency's detection model, 
given a background noise level at the standard ambient, a vehicle is 
detectable if it

[[Page 90437]]

meets or exceeds the minimum levels for detection in at least one of 
thirteen one-third octave bands. So the eStar without any noise 
enhancements would be expected to be detectable at least in the 
standard ambient at the tested pass-by speeds. For the stationary test, 
the eStar had acoustic content that met or exceeded the minimum values 
in three non-adjacent one-third octave bands. So in many ambient 
environments, in addition to the standard ambient, the eStar without 
any enhancements would be expected to be detectable at stationary.
---------------------------------------------------------------------------

    \70\ Hastings, et al., (2014) Acoustic Data for Hybrid and 
Electric Heavy-duty Vehicles and Electric Motorcycles.
---------------------------------------------------------------------------

    The agency also conducted screening tests in the field of the sound 
levels of a selection of other heavy-duty EVs and HVs using a 
simplified procedure. For these screening tests, NHTSA measured four 
different electric or hybrid-electric transit buses, as described in 
the agency's report ``Acoustic Data for Hybrid and Electric Heavy-duty 
Vehicles and Electric Motorcycles'' \71\ which provides details of 
those measurements.\72\ These screening tests were basic evaluations of 
the sound characteristics of these vehicles, and they were conducted at 
facilities belonging to transit agencies or at other suitable 
locations. Therefore they did not utilize an asphalt pad meeting the 
specifications in ISO 10844. Additionally, for these screening tests 
the agency used hand-held (or tripod-mounted) sound level meters rather 
than the requisite microphone array specified in SAE J2889-1.
---------------------------------------------------------------------------

    \71\ Hastings, et al., (2014) Acoustic Data for Hybrid and 
Electric Heavy-duty Vehicles and Electric Motorcycles.
    \72\ Using the informal measurement procedures to capture these 
recordings allowed the agency to gather data on heavy-duty hybrid 
and electric vehicles without the difficulty and expense of 
transporting these vehicles to a location where they could tested on 
a sound pad meeting the specifications of International Standards 
Organization (ISO) 10844 ``Acoustics--Specification of test tracks 
for measuring noise emitted by road vehicles and their tyres'' as 
required by SAE J2889-1.
---------------------------------------------------------------------------

    In conducting these screening measurements, the agency only 
recorded results for the eight one-third octave bands for which we 
proposed requirements in the NPRM. The agency compared the measurements 
to the revised minimum detectability thresholds based on our human 
factors research.
    Of the three vehicles the agency evaluated in the stationary 
condition, all had sound content in several bands, and all would have 
been detectable in some ambient conditions according to the agency's 
detection model. At the 10 km/h pass-by, all of the vehicles tested 
would be expected to be detectable according to the detection model. At 
the 20 km/h pass-by, three of the vehicles would be expected to be 
detectable according to the detection model, and two would have met the 
requirements of the final rule.\73\
---------------------------------------------------------------------------

    \73\ The agency only tested one of the four vehicles at 30 km/h.
---------------------------------------------------------------------------

    This heavy vehicle screening data showed that some hybrid and 
electric heavy-duty vehicles may already make sufficient sound in some 
operating conditions to be detected by pedestrians according to the 
agency's model. Because the data the agency collected during screening 
testing is limited in scope and was not obtained on an ISO 10844 
compliant surface, the agency needs to conduct further evaluation in 
this area before we can draw conclusions regarding the sound levels 
produced by these vehicles.
    Furthermore, the agency does not have any data on the crossover 
speed of heavy vehicles. Given that heavy vehicles have very different 
tires and wind noise characteristics than light vehicles, and these 
factors heavily influence crossover speed, it is possible that the 
light vehicle crossover speed is inappropriate for heavy vehicles. The 
agency anticipates conducting further research and evaluation to make 
these determinations and, if it proves necessary, to develop separate 
acoustic requirements for these vehicles.
    Regarding EMA and Advocates comments that the agency should develop 
a separate acoustic specification for heavy-duty vehicles, for the 
reasons discussed above NHTSA agrees and plans to conduct further 
evaluations on this issue.
    Given that NHTSA has not yet established that heavy hybrid and 
electric vehicles are too quiet to be detected without a pedestrian 
alert system, and the agency has not determined that the same acoustic 
requirements and crossover speed for light vehicles in today's final 
rule are appropriate for heavy vehicles, we are excluding both those 
categories from the applicability section of today's final rule, and we 
anticipate conducting a separate rulemaking effort to address the 
potential need for pedestrian alert systems on those vehicles.
Electric Motorcycles
    In the NPRM, we stated that we had tentatively concluded that the 
proposed rule should apply to electric motorcycles, because Congress 
defined ``electric vehicle'' broadly in the PSEA and did not exclude 
motorcycles from the definition. We acknowledged that the agency was 
not able to determine whether the incidence rate of collisions between 
pedestrians and electric motorcycles is different than the incidence 
rate of collisions between pedestrians and motorcycles with ICEs, but 
stated that we expected that the difference in pedestrian collision 
rates between electric motorcycles and their traditional ICE 
counterparts would be similar to the difference in pedestrian collision 
rates between light HVs and light ICE vehicles should the number of 
electric motorcycles in the fleet match the current market penetration 
of light HVs and EVs. Additionally, while we did not have data on the 
extent to which electric motorcycles are quieter than ICE motorcycles 
of the same type, we also noted that neither did we have information 
indicating whether electric motorcycles produced sound levels 
sufficient to allow pedestrians to detect these vehicles in time to 
avoid collisions. The NPRM did, however, cite crash statistics 
contained in BMW's comments on the NOI regarding incidents of 
motorcycle collisions with pedestrians. BMW cited data from NHTSA's 
General Estimates System (GES) for the period between 2005 and 2009 
shows that 1.07 percent of the pedestrians injured in motor vehicle 
crashes were injured in crashes involving motorcycles to illustrate the 
low rates of crashes between motorcycles and pedestrians.\74\
---------------------------------------------------------------------------

    \74\ BMW's comments on the NOI. Available at http://www.regulations.gov, Docket No. NHTSA-2011-0100-0020. Referring to 
the data cited, BMW argued in its NOI comments that based on the 
number of crashes between motorcycles and pedestrians and the 
percentage of all pedestrian crashes involving motorcycles, there is 
no safety need for minimum sound requirements for electric 
motorcycles.
---------------------------------------------------------------------------

    We also stated in the NPRM that the proposal was technology-neutral 
and that it would be possible for electric motorcycles to meet the 
requirements in the NPRM without the use of a speaker system if they 
already produced sufficient sound to meet the performance requirements. 
We sought comment on whether the minimum sound requirements should be 
applied to electric motorcycles.
    The comments that the agency received in response to the NPRM from 
organizations that represent motorcycle manufacturers for the most part 
reiterated the concerns expressed by MIC and BMW in response to the 
NOI. BMW and MIC stated in their comments to the NOI that, because of 
the unique attributes of motorcycles, there is no safety need for NHTSA 
to establish minimum sound levels for electric motorcycles. MIC 
reiterated this point in their NPRM comments. According to

[[Page 90438]]

MIC and BMW, motorcycle riders are able to better see and avoid 
pedestrians than automobile drivers because their view is unobstructed 
by pillars and sun visors and they are more alert because they 
themselves are vulnerable road users. BMW and MIC maintained that 
because motorcycles are unstable at low speeds, riders are required to 
maintain a high level of alertness, which minimizes the likelihood of 
collisions with pedestrians during low speed maneuvers.
    Also in their NOI comments, both BMW and MIC stated that adding a 
speaker system to a motorcycle could involve technical challenges not 
present for other vehicles because there is less space on the 
motorcycle to install the speaker and the weight of the speaker would 
have a greater impact on the vehicle's range. MIC and BMW also 
suggested that electric motorcycles should not be subject to the 
minimum sound level requirements in this proposal because electric 
motorcycles are not quiet.\75\
---------------------------------------------------------------------------

    \75\ MIC submitted measurements of overall sound pressure level 
of two electric vehicle models recorded at 8 km/h (5 mph) and 16 km/
h (10 mph) in its comments to the NOI. MIC did not provide any 
measurements of overall sound pressure level for ICE motorcycles as 
a comparison. Available at, www.regulations.gov, Docket No. NHTSA-
2011-0100-0028.
---------------------------------------------------------------------------

    MIC commented in response to the NPRM that motorcycles should be 
exempt from meeting the minimum sound requirements in the final rule 
because motorcycles, both electric and ICE, pose less of a risk to 
pedestrians than other vehicles, citing statistics that the collision 
rate between motorcycles and pedestrians is 0.27 percent compared with 
0.76 percent for other vehicles under conditions most likely to pose a 
threat to pedestrians (backing up, turning, entering or leaving parking 
spaces, starting, or slowing).\76\
---------------------------------------------------------------------------

    \76\ Docket No. NHTSA-2011-0148-0268.
---------------------------------------------------------------------------

    MIC argued that NHTSA's assumption that electric motorcycles will 
show a similar increase in rate of pedestrian collisions as four-
wheeled ``HEVs'' (MIC's term for hybrid and electric vehicles, 
collectively) is invalid because four-wheeled HEVs in fact do not pose 
a greater threat to pedestrians than ICE vehicles. MIC stated that the 
higher incidence of collisions between pedestrians and HEVs does not 
mean that HEVs collide with pedestrians at a higher frequency, arguing 
that NHTSA's comparison of incidence rates of pedestrian collisions 
between ICEs and HEVs to determine the overall frequency of pedestrian 
crashes between each group of vehicles is only valid if both classes of 
vehicles have similar overall crash rates. However, according to MIC, 
that is not the case, and the difference in overall crash rates is 
supported by FARS data which indicate that the overall crash rate for 
HEVs is only half of the overall crash rate for ICEs. MIC stated that 
the higher incidence rate of HEV-pedestrian collisions is likely to be 
artificial and driven by demographic factors other than sound, mainly 
that HEV drivers actually tend to be safer drivers on average, which 
makes their overall crash rate lower and which inflates their rate of 
pedestrian crashes as a percentage of all crashes. MIC pointed out that 
motorcycle pedestrian crash frequency is actually no higher than for 
ICEs. MIC stated that crash rate differences due to demographic factors 
are not uncommon and are, for example, what explain large differences 
in fatality rates between different types of motorcycles (e.g., touring 
bikes compared to sport bikes). Overall, MIC concluded that, because 
motorcycles have a lower overall crash rate than four-wheeled vehicles, 
the risk they pose to pedestrians is actually lower than the incidence 
rate of motorcycle-pedestrian crashes might indicate.
    MIC also argued that it is logical that motorcycles should have a 
lower rate of collisions with pedestrians because motorcycles require 
two hands to operate so there is a lower chance of the operator being 
distracted, which should decrease the risk to pedestrians.
    MIC stated that, in addition to having a low rate of crashes 
involving pedestrians, electric motorcycles are not quiet. MIC 
referenced a report submitted in response to the NPRM by Brammo, Inc., 
a manufacturer of electric motorcycles, that MIC believes shows that by 
design, electric motorcycles are not silent vehicles when moving.\77\ 
MIC stated that unlike EV automobiles, the engine and drivetrain are 
open and exposed to the surrounding environment, and will produce sound 
levels that exceed the sound level minimums proposed by NHTSA. MIC 
stated that two motorcycles tested by Brammo, the Empulse and the 
Enertia Plus, produced sound levels that were 8 to 18 dB(A) higher than 
the minimum requirements in the NPRM.
---------------------------------------------------------------------------

    \77\ The report submitted by Brammo, Inc. is available through 
www.regulations.gov, Docket No. NHTSA-2011-0148-0268.
---------------------------------------------------------------------------

    MIC also stated that the NPRM did not take into account that 
motorcycles do not have a reverse gear and therefore do not collide 
with pedestrians while backing.
    MIC stated that NHTSA should not establish minimum sound 
requirements for electric motorcycles until there is evidence that 
these vehicles pose a safety risk to pedestrians. MIC stated that if 
NHTSA does decide to establish minimum sound requirements for 
motorcycles, it should extend the exemption for small-volume 
manufacturers indefinitely.
    IMMA suggested that electric motorcycles do not introduce a new 
threat to blind and visually impaired pedestrians because blind and 
visually impaired pedestrians already are exposed to pedalcyclists on 
both the road and on sidewalks (and bicycles would not be any louder 
than electric motorcycles). Operators of electric motorcycles, like 
pedalcyclists, have the advantage of greater awareness of nearby 
pedestrians and greater ability to avoid them.
    IMMA stated that limited data exists on crashes between motorcycles 
and pedestrians and pedalcyclists but that there are a significant 
number of incidences of crashes involving motorcycles and four-wheeled 
vehicles, which it argued showed the high vulnerability of motorcycle 
riders and their inherent alertness to other road users including 
pedestrians. They also commented that motorcycles by design provide the 
operator with better vision of the surrounding environment which 
increases awareness of nearby pedestrians and pedalcyclists.
    IMMA commented that studies have shown that pedestrians are at 
greater risk of being struck by HVs while the vehicle is operating in 
reverse, but this is not a concern for motorcycles because the vast 
majority of motorcycles do not have a reverse gear and those that do 
cannot move quickly in reverse.
    IMMA stated that preliminary data shows that electric motorcycles 
are not quiet and suggested that this data, coupled with the fact the 
electric motorcycles do not pose an increased risk to pedestrians, 
shows that electric motorcycles should not be subject to the minimum 
sound requirements in the final rule.
    DG Enterprise stated that the detectability parameters determined 
for EVs and HEVs in the NPRM may require the installation of an alert 
sound system on other quiet vehicles such as electric motorcycles and 
mopeds as well as electrically assisted bicycles. DG Enterprise 
inquired whether NHTSA plans to mandate the installation of and 
``AVAS'' (Acoustic Vehicle Alerting Systems) in all these vehicle 
categories.
    Western Michigan stated that all quiet vehicles traveling at the 
slow speeds covered by the NPRM, whether they are light-duty EVs and 
HVs or electric motorcycles, have the potential of

[[Page 90439]]

causing harm to pedestrian who are blind.
Agency Response to Comments
    Although the agency proposed in the NPRM to include motorcycles in 
the final rule, we have decided not to apply the requirements of this 
final rule to electric motorcycles. As is the case with heavy hybrid 
and electric vehicles, we currently do not have enough information to 
determine whether the light vehicle acoustic requirements or the 
crossover speed in this final rule are appropriate for electric 
motorcycles. Instead, the agency is planning to conduct further 
research on sound emitted by electric motorcycles before issuing a new 
NPRM, if needed, to propose acoustic requirements for these vehicles.
    As described in Section II.C of this notice, after issuing the NPRM 
the agency conducted acoustic testing on two electric motorcycles 
following the procedures in SAE J2889-1, MAY 2012.\78\ The agency 
compared the one-third octave band measurements of these electric 
motorcycles to the minimum levels needed for detection based on the 
agency's detection model. The first motorcycle, the 2012 Brammo 
Enertia, had two one-third octave band measurements at the 10 km/h 
pass-by that met or exceeded the minimum levels for detection out of 
the thirteen one-third octave bands in the range of interest (315Hz to 
5kHz); for the 20 km/h pass-by, the Enertia met or exceeded the minimum 
in three of the thirteen bands. The second motorcycle that the agency 
evaluated, the 2012 Zero S, did not have any one-third octave bands 
that were equal to or greater than the minimum levels for detection at 
the speeds tested. The overall sound pressure levels for the Brammo 
Enertia in the 10 km/h, 20 km/h, and 30 km/h pass-bys were 57 dB(A), 
63.2 dB(A), and 66.5 dB(A). The overall sound pressure levels for the 
Zero S in the 10 km/h, 20 km/h, and 30 km/h pass-bys were 49.1 dB(A), 
57 dB(A), and 59.6 dB(A).
---------------------------------------------------------------------------

    \78\ Hastings, et al., (2014) Acoustic Data for Hybrid and 
Electric Heavy-duty Vehicles and Electric Motorcycles.
---------------------------------------------------------------------------

    According to the agency's detection model, a vehicle is detectable 
in the 55 dB(A) standard ambient utilized in the agency's acoustic 
evaluations if it meets or exceeds the minimum levels for detection in 
at least one of the thirteen one-third octave bands.\79\ When compared 
to the agency's detection model, the Brammo Enertia would be expected 
to be detectable in the 55 dB(A) standard ambient at 10 and 20 km/h. 
According to the agency's model, the Zero S would not be expected to be 
detectable in the 55 dB(A) ambient at any of the three speeds tested.
---------------------------------------------------------------------------

    \79\ While a sound with one one-third octave band at the 
detectable threshold would be expected to be detectable in the 55 
dB(A) ambient utilized in the agency's research, such a sound may 
not be detectable in other ambient conditions with the same overall 
sound pressure level depending on the spectral shape of the ambient.
---------------------------------------------------------------------------

    When compared to the average overall sound pressure level of four-
wheeled ICE vehicles, the sound level produced by the Brammo Enertia 
was similar, based on a broad selection of ICE measurement data which 
the agency acquired from its own testing and from other sources (shown 
in Table 13 of the NPRM). The Zero S produced a lower overall sound 
level than the ICE mean and also was lower than the mean-minus-one-
standard-deviation of the same ICE data (shown in Table 14 of the 
NPRM.)
    Based on comparing the one-third octave band data to the agency's 
detection model and comparing the overall sound pressure levels to the 
sound produced by four-wheeled ICE vehicles, the agency believes the 
acoustic data from these two electric motorcycles are inconclusive as 
to whether electric motorcycles might be too quiet for pedestrians to 
detect by hearing. Furthermore the agency has not collected any data or 
conducted any analysis regarding the crossover speed for electric 
motorcycles, which might be different from that of four-wheeled 
vehicles. Because our acoustic data show that one of the two electric 
motorcycles would be detectable by pedestrians within a safe detection 
distance, but the other one would not be, we believe that further 
evaluation of electric motorcycles is needed before we can determine if 
it is appropriate that they be subject to the same acoustic 
requirements and crossover speed as four-wheeled vehicles.
    Commenters stated that adding an alert system to a motorcycle would 
be a technical challenge because motorcycles are very different from 
cars in terms of layout and architecture, and a pedestrian alert system 
which includes a speaker is a significant amount of hardware to 
integrate into a motorcycle. NHTSA has not determined if this design 
burden would make it impracticable for electric motorcycles to be 
required to meet today's final rule.
    The agency also needs to further evaluate whether electric 
motorcycles require distinct specifications separate from four-wheeled 
vehicles. For example, there is nothing in the minimum sound 
requirements that would allow pedestrians to specifically recognize a 
vehicle as a motorcycle. Furthermore, motorcycles do not need a backing 
sound since they generally are not driven in reverse.\80\ For these 
reasons, this final rule does not apply to motorcycles, and we 
anticipate conducting a separate rulemaking effort to address the 
potential need for pedestrian alert systems on electric motorcycles.
---------------------------------------------------------------------------

    \80\ One or more models of touring motorcycle are fitted with a 
reverse feature that uses the engine starter motor to assist in 
backing, for example when the rider is unable to walk the motorcycle 
out of an inclined parking space. This feature is intended for 
limited use. Currently this feature is not present on any electric 
motorcycles. As a result, reverse operation is not considered to be 
a safety issue for motorcycles as it is with passenger cars.
---------------------------------------------------------------------------

Low Speed Vehicles
    In the NPRM, we stated that we had tentatively concluded that Low 
Speed Vehicles (LSV) should be required to meet the minimum sound 
requirements in the proposed standard. We stated that while we had not 
conducted any acoustic testing of these vehicles and had limited real-
world data on crashes involving LSVs and pedestrians, we expected LSVs 
equipped with electric motors would be extremely quiet.
    EDTA stated that NHTSA should defer application of minimum sound 
standards to LSVs until a more complete record establishing the need 
for standards for these vehicles exists. EDTA suggested that if the 
agency documents a need for LSVs to meet the minimum sound requirements 
in the final rule, the agency should then develop audibility 
specifications that reflect the technologies, duty cycles and uses, and 
sound profiles specific to these types of vehicles.
    Western Michigan stated that LSVs should be required to meet the 
requirements in the final rule because they could pose a potential 
hazard to blind pedestrians. NFB stated that the rule should apply to 
LSVs.
Agency Response to Comments
    We have decided to apply the minimum sound requirements in today's 
final rule to LSVs. The PSEA requires NHTSA to establish minimum sound 
requirements for all motor vehicles that are hybrid or electric motor 
vehicles. Because trailers are the only vehicles excluded from the 
scope of the required rulemaking, NHTSA's interpretation is that 
Congress intended for the agency to apply minimum sound requirements to 
all other vehicles that are HVs or EVs including LSVs.
    The agency tested five LSVs to determine the sound levels produced 
by these vehicles. The sound levels

[[Page 90440]]

produced by the LSVs for the 10 km/h, 20 km/h, and 30 km/h pass-bys 
were similar to the sound levels produced by the electric passenger 
cars that the agency evaluated during VTRC's testing in 2012.\81\ The 
sound levels produced by the LSVs when operating in reverse varied 
significantly because four of the five LSVs were equipped with back-up 
beepers.
---------------------------------------------------------------------------

    \81\ 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.
---------------------------------------------------------------------------

    Results of the acoustic testing of these LSVs confirmed the 
agency's understanding that these vehicles produce similar sound levels 
as EVs and HVs. Also, they operate in locations where pedestrian 
exposure is similar to that of EVs and HVs. Therefore, the agency 
believes that electric LSVs pose an increased risk to pedestrians when 
they are operating at low speed when compared to conventional vehicles. 
Vehicles in the LSV category have a maximum speed limitation of 25mph, 
so by definition LSVs operate at low speeds. These speeds are 
reflective of those for which HVs and EVs have the highest risk of 
involvement in pedestrian crashes when compared to ICE vehicles, as 
noted in Section II.B of today's final rule. The agency is not aware of 
any factors related to the use of LSVs that would mitigate the risk to 
pedestrians created by the low sound levels produced by these vehicles. 
Because of the low sound level produced by LSVs and the fact they 
operate primarily at low speeds, the agency believes that it is 
necessary for hybrid and electric LSVs to meet the minimum sound 
requirements in today's final rule. This is in contrast to electric 
motorcycles and EVs/HVs with a GVWR over 10,000 for which our test data 
were inconclusive regarding the sound levels those vehicles achieve 
before having any sound added.
    In response to the comment submitted by EDTA, NHTSA believes that 
acoustic requirements for light duty EVs and HVs are appropriate for 
LSVs. LSVs are not sufficiently different from vehicles that are not 
speed limited when those vehicles are traveling at low speeds, so LSVs 
do not require a separate acoustic specifications in order for 
pedestrians to detect them.
Quiet ICE Vehicles
    In the NPRM, we chose not to apply the proposed requirements to 
conventional ICE vehicles for the time being. We acknowledged that it 
is possible that some ICE vehicles may pose a risk to pedestrians 
because of the low level of sound that they produce when operating at 
low speeds. We stated in the NPRM that the agency would decide whether 
to apply the minimum sound requirements established for HVs and EVs to 
ICE vehicles after completing the Report to Congress on ICE vehicles, 
as required by the PSEA.
    We also stated in the NPRM that while some of the ICE vehicles the 
agency tested during our research did not meet the proposed 
requirements, these vehicles emit sound in areas of the audible 
spectrum not covered in the proposed requirements. We stated that this 
characteristic of ICE vehicles made it difficult to compare the 
detectability of ICE vehicles to hybrid and electric vehicles solely 
based on acoustic measurements.
    In response to the NPRM, we received several comments from members 
of the general public stating that if the agency chose to establish 
minimum sound requirements for hybrid and electric vehicles it should 
also establish requirements for quiet ICE vehicles. These commenters 
stated that NHTSA should make the determination regarding which 
vehicles will be subject to the final rule based on whether the vehicle 
poses an increased risk to pedestrians when operating at low speed not 
based on the vehicle's propulsion type. These commenters suggested that 
requiring only hybrid and electric vehicles to meet the requirements of 
the final rule discriminates against those types of vehicles.
    DG Enterprise inquired whether NHTSA had plans to require quiet ICE 
vehicles to meet the requirements of the final rule. DG Enterprise 
further inquired whether the agency considered that the minimum sound 
requirements in the final rule might influence the installation of 
alert sound systems on quiet ICE vehicles.
    WMU stated that, although increases in the number of hybrid and 
electric vehicles in the on-road fleet have brought about an increased 
awareness of the safety risks to pedestrians posed by quiet vehicles, 
there are many modern ICE vehicles that are too quiet to be safely 
detected by pedestrians who are blind. ADB stated that pedestrians who 
are blind are at just as much risk from a quiet ICE as they are from an 
EV or HV. ADB believes that quiet ICE vehicles should be subject to the 
final rule because the agency has not conducted enough research about 
the detectability of these vehicles.
Agency Response to Comments
    We have chosen to limit the application of the final rule to hybrid 
and electric vehicles. The PSEA required NHTSA to establish minimum 
sound requirements for hybrid and electric vehicles. After completing 
the rulemaking to establish minimum sound requirements for hybrid and 
electric vehicles, NHTSA is required to complete a study and submit a 
report to congress on whether there is a safety need to apply the final 
rule to ICE vehicles. If NHTSA subsequently determines that there is a 
safety need to apply the rule to ICE vehicles, the agency is required 
to initiate a rulemaking to do so. Because we have not yet completed 
the required report to Congress, we have not yet determined whether a 
safety need exists to apply the requirements of today's final rule to 
ICE vehicles. Because they agency has not yet determined whether a 
safety need exists for quiet ICE vehicles to produce additional sound, 
we have no basis at this time to subject these vehicles to the 
requirements of today's final rule.
    We are aware that some ICE vehicles do not meet the requirements of 
the final rule, and that this could lead to the inference that some ICE 
vehicles do not produce sufficient sound to allow pedestrians to detect 
these vehicles. We do not think that it is appropriate, however, to 
make the assumption--based solely on the data mentioned above--that 
some ICE vehicles must produce additional sound to be safely detected 
by pedestrians. As we stated in the NPRM, ICE vehicles produce sounds 
in areas of the audible spectrum that make it difficult to draw 
conclusions about how detectable they are by comparing them to the 
requirements in today's final rule. In addition, the sound produced by 
an ICE includes acoustic characteristics such as modulation that 
enhance detectability that are not included in the final rule. 
Therefore, it is likely that ICE vehicles that are readily detectable 
by pedestrians might not meet the requirements of the final rule.
    The agency will examine whether there is any crash data that shows 
that ICE vehicles that produce a lower sound level have an increased 
risk of crashes with pedestrians as part of the agency's investigation 
of whether there is a safety need to apply the requirements of today's 
final rule to ICE vehicles as part of the agency's report to Congress.

C. Critical Operating Scenarios

Stationary but Active
    The agency proposed to require hybrid and electric vehicles to meet

[[Page 90441]]

minimum sound requirements in the ``stationary but active'' condition. 
The agency used the term ``stationary but active'' to describe the 
state of a stationary hybrid or electric vehicle that has its 
propulsion system active. This is an important scenario to include 
because these vehicles typically do not idle in the way that an ICE 
vehicle does. The NPRM explained that the ``stationary but active'' 
condition included any time following activation of the vehicle's 
starting system without regard to the transmission gear position or any 
other factor affecting the vehicle's ability to begin moving (i.e., 
parking brake application). The NPRM proposed requiring EVs and HVs to 
meet the minimum sound requirements for the stationary but active 
condition beginning 500 milliseconds after the vehicle's starting 
system is activated.\82\
---------------------------------------------------------------------------

    \82\ The NPRM proposed that vehicles with manual transmissions 
meet the stationary but active requirement when the vehicle's gear 
selection control is in ``neutral.''
---------------------------------------------------------------------------

    In the NPRM, we explained that the PSEA required the agency to 
establish minimum sound requirements for this operating condition. The 
PSEA states that the required safety standard must allow pedestrians 
``to reasonably detect a nearby electric or hybrid vehicle in critical 
operating scenarios including, but not limited to constant speed, 
accelerating, or decelerating.'' \83\ This encompasses the possibility 
that ``stationary but active'' could be a ``critical operating 
scenario.'' Also, the PSEA defines ``alert sound'' as ``a vehicle-
emitted sound to enable pedestrians to discern vehicle presence, 
direction, location and operation.'' \84\ 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.\85\ We 
explained in the NPRM that in order to satisfy the definition of alert 
sound in the PSEA the agency was required to establish minimum sound 
requirements for EVs and HVs in the stationary but active operating 
condition.
---------------------------------------------------------------------------

    \83\ Public Law 111-373, 124 Stat. 4086 (January 4, 2011).
    \84\ Id.
    \85\ Given that the language of the PSEA definition of `alert 
sound' uses the conjunction `and' when listing the circumstances of 
vehicle operation that a pedestrian must be able to discern, i.e., 
``presence, direction, location, and operation,'' it is apparent 
that a pedestrian must be able to discern any vehicle operation, 
which would include the condition in which the vehicle could 
imminently be in motion and present a risk to a pedestrian.
---------------------------------------------------------------------------

    We also stated that, in addition to being a required operating 
condition under the PSEA, the agency believed that there was a safety 
need for hybrid and electric vehicles to emit a sound in the stationary 
but active condition. A sound emitted by an HV or EV when stationary 
but active is analogous to the sound produced by an ICE vehicle idling 
while at a standstill. We stated that this requirement ensures that the 
responsibility to avoid a collision between a vehicle and a pedestrian 
is shared between the driver of the vehicle and the pedestrian by 
providing pedestrians with an acoustic cue that a vehicle may begin 
moving at any moment. While there are some scenarios in which a driver 
starting from a stopped position should be able to see a pedestrian in 
front of the vehicle and thus avoid a crash, the driver may not always 
be relied upon, especially in situations where the driver may have an 
obstructed view. A driver pulling out of a parking space in a crowded 
parking lot is an example of a situation in which a driver might not be 
able to see a pedestrian and the pedestrian may step into the path of a 
vehicle just as the vehicle is beginning to move. If the pedestrian is 
able to hear the vehicle before it begins to move, the pedestrian would 
be able to exercise caution and avoid a collision by not stepping in 
the path of the vehicle.
    The agency also discussed incidents of HVs colliding with 
pedestrians when starting from a stopped position that appear in the 
data that the agency used for the statistical analysis of crashes 
between hybrid vehicles and pedestrians. The NPRM noted that instances 
of HVs starting from a stopped position and colliding with pedestrians 
are present in our data although the sample size is not large enough to 
prove a statistically significant incidence rate. We stated that this 
limited data showed there could be a safety risk which, if correct, 
would grow commensurate with the population of HV/EVs, such that it 
would be appropriate to require that vehicles provide adequate sound 
cues while stationary.
    In the NPRM, we also noted that sound cues produced by idling ICE 
vehicles are critical for safe navigation by blind pedestrians. The 
sound produced by vehicles idling while waiting to pass through an 
intersection provides a reference to visually-impaired pedestrians so 
they are able to cross a street in a straight line and arrive safely at 
the other side. The sound of vehicles idling on the far side of the 
street while waiting to pass through an intersection also provides 
visually-impaired pedestrians with a reference for how wide a street is 
so they can accurately gauge the amount of time needed to safely 
cross.\86\
---------------------------------------------------------------------------

    \86\ The NPRM also discussed how NHTSA staff traveled to the 
headquarters of the National Federation of the Blind in Baltimore, 
Maryland to receive training on white cane travel techniques used by 
individuals who are blind. This allowed NHTSA staff to experience 
firsthand the necessity of sound at stationary to the mobility of 
individuals who are blind. When approaching intersections, NHTSA 
staff found the sound of idling vehicles necessary for determining 
whether there was a vehicle present at the intersection and whether 
it was safe to cross.
---------------------------------------------------------------------------

    The NPRM further stated that the agency did not believe that there 
would be any incremental increase in cost that would result from 
requiring a sound at the stationary but active operating condition for 
vehicles already equipped with an alert sound system and that the draft 
EA showed that requiring sound at stationary would not have any 
appreciable impact on ambient noise levels.
    In their comments to the NOI and in meetings with agency staff 
prior to the NPRM, representatives from several auto manufacturers said 
that the agency should not establish minimum sound requirements for the 
stationary but active condition. These manufacturers did not believe 
there was a safety need for an alert sound when vehicles are 
stationary. They were concerned that the sound of EVs and HVs standing 
in highway traffic and other scenarios in which pedestrians would not 
be expected to be present would unnecessarily contribute to increases 
in environmental noise. Advocacy organizations for individuals who are 
blind or visually impaired, in contrast, argued prior to the NPRM that 
NHTSA should establish minimum sound requirements for the stationary 
but active condition. These organizations stated that sound made by 
stationary vehicles is necessary for the safety of blind or visually 
impaired pedestrians to avoid collisions with EVs and HVs operating at 
low speeds because it allows individuals who are blind to proceed with 
caution when they hear a nearby ``idling'' vehicle.
    The NPRM also discussed and sought comment on a suggestion from 
Mercedes for alerting nearby pedestrians that a hybrid or electric 
vehicle was about to begin moving without requiring a sound in the 
stationary but active condition. Mercedes had suggested that instead of 
emitting sound when the vehicle was stationary with the propulsion 
system active, hybrid and electric vehicles should be required to emit 
a ``commencing motion sound'' that would activate when the vehicle was 
in ``drive'' and the driver released his or her foot from the brake 
pedal.

[[Page 90442]]

When the driver released the brake pedal, the vehicle would emit a 
sound for a brief period that would be noticeably higher than the sound 
required at low speed. According to Mercedes, this brief, elevated 
sound would uniquely signal the onset of vehicle motion. Once the 
vehicle began to move, the alert sound would revert to a low-speed 
sound which would have to comply with the acoustic requirements 
proposed for speeds up to 10 km/h. The agency sought comment on using a 
``commencing motion sound'' approach.
    The NPRM also solicited comment on whether the final rule should 
allow the sound at stationary to be reduced or deactivated if the 
vehicle had been stationary for a prolonged period of time.
    Many industry commenters responding to the NPRM raised many of the 
same points raised in their comments to the NOI and in meetings with 
agency staff prior to the agency issuing the NPRM. Auto manufacturers 
and groups that represent them commented that sound at stationary is 
not necessary for safety, and that Europe and Japan do not require 
sound at stationary. Industry commenters expressed concern that 
requiring sound in the stationary but active condition could annoy 
drivers, which would harm EV and HV sales, and that it also would lead 
to increases in environmental noise pollution. These commenters also 
argued that a sound at stationary would mask the sound of other 
approaching vehicles.
    Industry commenters including Alliance/Global, Denso, EDTA, 
Mercedes, Mitsubishi, OICA, and Volkswagen requested that NHTSA require 
a ``commencing motion sound'' rather than establishing minimum sound 
requirements for either when a vehicle is in ``park'' or when the 
vehicle is in ``drive'' but is stationary. Some of these commenters 
pointed out that the NPRM did not define ``active'' and argued that 
NHTSA should define ``stationary but active'' specifically as the 
condition in which the vehicle's gear selector is in the ``drive'' 
position and the driver has released the service brake. Alliance/Global 
commented that requiring a commencing motion sound that activates when 
a vehicle begins moving would satisfy the requirement in the PSEA that 
the alert sound allow pedestrians to discern the presence, direction, 
location, and operation of the vehicle. Honda and Nissan, in addition 
to opposing a requirement for stationary sound without further research 
on the need for it, commented that NHTSA should not require a 
commencing motion sound and should instead leave that as an option for 
manufacturers. Some manufacturers, including Mercedes and Nissan, said 
that sound at stationary can mask the sound of other vehicles that are 
in motion. Mercedes stated that it had enlisted researchers to conduct 
some experimentation on this topic. They found in preliminary trials 
that it was easier for pedestrians to detect when a vehicle begins to 
move if the vehicle did not produce sound when stationary, and that 
this might be because the sound activates just as the vehicle initiates 
movement. Nissan also conducted trials that they said indicated that 
blind pedestrians were less aware of traffic moving adjacent to an 
alert-emitting stationary vehicle, i.e., when the stopped vehicle 
emitted no sound, the pedestrians were more aware of the nearby moving 
traffic.
    Volkswagen stated that vehicles that are not moving do not pose a 
threat to pedestrians or pedalcyclists. Volkswagen argued that it is 
unlikely that drivers will fail to make sure that the vehicle's path is 
clear of pedestrians when starting up from a full stop, and that in the 
rare case in which an inattentive driver begins to accelerate from a 
stop toward a pedestrian who is in or about to enter the vehicle's path 
in that case, a ``commencing motion'' sound would provide the 
pedestrian with a warning that the EV or HV is beginning to move, so 
that the pedestrian could take appropriate action.
    EMA commented that it is unreasonable to require heavy vehicles to 
emit sound continuously while idling because many types of heavy-duty 
vehicles must idle for extended periods in order to power a variety of 
utility functions such as operating on-board equipment like hydraulic 
lifts or pumps.
    Industry commenters also commented that the level of sound for the 
stationary condition proposed in the NPRM is too high, and sound level 
is higher than that of ICE vehicles at idle. They stated that, if NHTSA 
did decide to establish minimum sound levels for when a vehicle is 
stationary with an active propulsion system, those levels should be 
lower than the levels in the NPRM. In addition, the sound should be 
required only when the vehicle's gear selector is in the ``drive'' or 
``reverse'' position and not when the gear selector is in the ``park'' 
position.
    Volkswagen noted, ``for the foreseeable future, it is exceedingly 
unlikely that a blind pedestrian will encounter a line of vehicles 
stopped at a traffic light that is comprised entirely of EVs and HVs.'' 
\87\ Volkswagen stated that because ICE vehicles will be present a 
majority of the times that blind pedestrians are attempting to cross at 
signal-controlled intersections, the sound produced by the idling ICE 
vehicles will provide the acoustic cues needed to ``shoreline.'' \88\ 
Volkswagen stated that, by the time the market penetration of EVs and 
HVs increases to the level at which they would make up the majority of 
vehicles idling at an intersection, technology will eliminate the need 
for pedestrians who are blind to rely on vehicle-emitted sound to 
safely navigate intersections.
---------------------------------------------------------------------------

    \87\ See document no. NHTSA-2011-0148-0250, available at 
www.regulations.gov.
    \88\ ``Shoreline'' refers to the practice by which pedestrians 
who are blind use walls, handrails, curbs or other features parallel 
to their direction of travel to help guide them. They may also use 
traffic sound for shorelining.
---------------------------------------------------------------------------

    Alliance/Global stated that NHTSA should follow the European and 
Japanese guidelines for pedestrian alert sound systems which concluded 
that there is no safety need for hybrid and electric vehicles to emit 
sound while stationary. Alliance/Global also suggested that requiring a 
commencing motion sound as an alternative to requiring sound in the 
stationary but active condition ``would lower the ambient noise level 
at intersections, thus making it easier for pedestrians to detect the 
presence and operating patterns of other moving vehicles.'' \89\
---------------------------------------------------------------------------

    \89\ See document no. NHTSA-2011-0148-0251, available at 
www.regulations.gov.
---------------------------------------------------------------------------

    In general, commenters pointed out a number of reasons why sound in 
the stationary operating condition should not be required. They stated 
that EVs and HVs should only be required to emit sound when they are 
capable of moving, because vehicles with their gear selector in the 
``park'' position and vehicles with the parking brake engaged are not 
capable of motion so NHTSA should not establish minimum sound 
requirements for these conditions. For instance, Toyota stated that, 
according to NHTSA's interpretation of the PSEA, a vehicle is capable 
of being ``operated'' even without an operator being present in the 
vehicle, and that a vehicle that is stationary is inherently incapable 
of striking a pedestrian, and therefore should not be required to emit 
sound.\90\
---------------------------------------------------------------------------

    \90\ See document no. NHTSA-2011-0148-0272, available at 
www.regulations.gov.
---------------------------------------------------------------------------

    A number of commenters expressed concern about the environmental 
noise that would be created by alert sounds emitted by stationary 
vehicles. Alliance/Global stated that if EVs and HVs are required to 
produce an alert sound as soon as the starting system is activated,

[[Page 90443]]

they will be required to make noise under conditions for which there is 
no threat to pedestrians, which in turn will needlessly increase 
environmental noise levels. Volkswagen stated that requiring EVs and 
HVs to emit a sound at stationary would cause many hours of unnecessary 
sound emissions, which will annoy vehicle owners and add to overall 
noise pollution. Volkswagen also claimed that requiring sound at 
stationary would lead to unnecessary wear and tear on the sound 
generation system components.
    Representatives from Nissan, Toyota, Honda, GM, and Mitsubishi 
conducted a demonstration attended by NHTSA staff \91\ to show that a 
vehicle that emits sound when stationary could mask the presence of 
other vehicles. They conducted the demonstration to highlight 
situations in which they believed pedestrians would be able to better 
detect other approaching vehicles if nearby hybrid and electric 
vehicles did not emit sound while they are stationary. Their contention 
was that requiring a stationary hybrid or electric vehicle to emit 
sound could mask the sound of a moving vehicle that was approaching in 
an adjacent lane.
---------------------------------------------------------------------------

    \91\ See document no. NHTSA-2011-0148-0240, available at 
www.regulations.gov.
---------------------------------------------------------------------------

    Representatives from Nissan met with NHTSA staff and presented 
their analysis of when a sound at stationary would be beneficial to 
pedestrians and when it would mask the sound of an approaching vehicle 
that actually posed a threat to pedestrians.\92\ In this analysis, 
Nissan examined thirty different traffic scenarios. Nissan stated that 
it had found that requiring EVs and HVs to emit a sound at stationary 
would make it more difficult to detect an approaching vehicle that 
posed a threat to pedestrians in twenty of the thirty scenarios, would 
have no impact in eight of the scenarios, and would aid the pedestrian 
in detecting the threat vehicle in only two of the scenarios. Nissan 
indicated that it would be more difficult for pedestrians to detect an 
approaching vehicle that posed a threat in these twenty scenarios 
because a stationary EV or HV producing an ``idle'' sound would mask 
the approaching vehicle that posed the threat.
---------------------------------------------------------------------------

    \92\ See document no. NHTSA-2011-0148-0051, available at 
www.regulations.gov.
---------------------------------------------------------------------------

    Organizations that represent individuals who are blind or visually 
impaired and safety advocates including NFB, ACB, ADB, NCSAB, WBU, WMU, 
and Advocates stated that the agency should require hybrid and electric 
vehicles to produce sound when those vehicles are stationary with their 
propulsion systems active. Among the comments from these organizations 
was the contention that the sound of ``idling'' vehicles is useful for 
navigation by pedestrians who are blind in a number of scenarios and 
makes them aware of the presence of a nearby vehicle that is likely to 
start moving at any moment so the pedestrian has the opportunity to 
react safely once that vehicle begins to move. These organizations 
stated they do not believe that a ``commencing motion sound'' is 
sufficient to replace the acoustic cues provided by ``idling'' 
vehicles. However, some of these commenters suggested that they would 
not be opposed to a commencing motion sound if it is provided in 
addition to, not in place of, a stationary sound. Advocates commented 
that the sound required for a stationary vehicle in `park' could be at 
a lower acoustic level until such time as the brake pedal is applied.
    WMU stated ``pedestrians who are blind gain important information 
regarding vehicle presence from the sounds of idling vehicles'' \93\ 
and ``blind pedestrians often rely heavily on the sound of vehicles 
starting up from a stop at an intersection (signalized or not) to 
decide when to cross and to understand the geometry and operation of 
the intersection.'' \94\ These assertions were reflected to a great 
extent in comments from other organizations among this group.
---------------------------------------------------------------------------

    \93\ See document no. NHTSA-2011-0148-0180, available at 
www.regulations.gov.
    \94\ See id.
---------------------------------------------------------------------------

    WMU also stated that its research has shown that blind pedestrians 
have great difficulty detecting hybrid and electric vehicles (without 
an alert system) starting from a stopped position and, consequently, 
sound in the stationary but active condition should be required when 
the hybrid or electric vehicle's gear selection control is in ``park'' 
to alert blind pedestrians of potential conflict. WMU expressed concern 
that a hybrid or electric vehicle could be put into ``drive'' and begin 
moving quickly enough that a pedestrian walking near the vehicle would 
not have time to react.
    WMU also stated that, while a commencing motion sound does not 
replace sound at stationary, it does allow pedestrians to more easily 
identify vehicles starting from a stopped position. WMU suggested that, 
if a vehicle has been stationary for a long time, that vehicle is less 
likely to begin moving and should not be required to produce a sound 
for a prolonged period.
Agency Response to Comments
    As described in Section II.A of this final rule, NHTSA has 
concluded that the PSEA requires NHTSA's safety standard to specify 
that vehicles must have sound when stationary. However, based on 
careful review of the comments received, we have decided to modify the 
proposed sound at stationary requirement to apply only when a vehicle's 
gear selection control is not in the ``Park'' position.
    The definition of ``alert sound'' in the PSEA requires the agency 
to establish minimum sound requirements to allow pedestrians to detect 
the presence of nearby vehicles that are in operation. Of the comments 
that suggested that the agency define ``stationary but active'' as the 
condition in which the vehicle's gear selection control is in ``drive'' 
and the driver is not applying the brake pedal, none of those comments 
explained how that approach would fulfill the mandate in the PSEA that 
the minimum sound requirements allow pedestrians to detect the 
``presence'' and ``operation'' of a nearby vehicle, including one that 
is stationary.
    The agency believes that adopting the sound at stationary 
requirements will mitigate the potential risk to pedestrians from HVs 
and EVs starting from a stopped position. As we stated in the NPRM, 
there is evidence in the crash data that these types of crashes do 
occur. A sound at stationary would help both blind and sighted 
pedestrians because it would alert them to the presence of a vehicle 
that might start moving so they could avoid walking into the vehicle's 
travel path. We are concerned that a ``commencing motion'' sound would 
not always give a pedestrian who was entering the path of a vehicle 
sufficient time to react to avoid a collision, as argued by ACB and 
NFB. While we agree that the onset of an alert sound coincident with 
the commencement of motion on a vehicle that was not emitting sound 
when it was stationary might be of some benefit, because the contrast 
provided by the activation of the sound might better help pedestrians 
who are blind detect when the vehicle begins to move, we do not believe 
that this outweighs the fact that requiring sound at stationary will 
help all pedestrians avoid collisions with vehicles starting from a 
stopped position by providing an audible indication of a nearby vehicle 
that could begin moving at any time.
    While it may be some time in the future before it becomes likely 
that a pedestrian who is blind will encounter traffic that is comprised 
exclusively of EVs and HVs (as VW's comment

[[Page 90444]]

suggested), a sound at stationary can assist pedestrians who are blind 
with navigation and orientation tasks before that scenario becomes a 
reality. A sound at stationary can assist pedestrians who are blind in 
performing orientation and mobility tasks in commonplace situations 
such as when a pedestrian encounters a single EV or HV at an 
intersection where the traffic flow is light. As stated above, a sound 
at stationary also would provide immediate benefits to pedestrians who 
are blind by allowing them to avoid collisions with EVs and HVs 
starting from a stopped position.
    NHTSA does not believe that the possibility that a sound at 
stationary might mask the sound of other vehicles operating in the 
vicinity outweighs the benefits of requiring a sound in the stationary 
but active condition. After reviewing Nissan's analysis of scenarios, 
NHTSA is unable to determine whether a pedestrian who is blind would 
attempt to cross in the situations in which Nissan claimed that a sound 
at stationary would mask the sound of an approaching vehicle. For 
example, some of those scenarios involve a pedestrian who encounters a 
stationary vehicle that is being passed by another vehicle travelling 
in the same direction in an adjacent lane. The agency is unsure whether 
upon encountering a stationary vehicle, a pedestrian who is blind would 
proceed to cross in front of the vehicle without waiting for the 
vehicle to move away so the pedestrian can be sure no other traffic is 
present and that it is safe to cross.
    Nissan presented data showing that some of the company's customers 
would find the sound at stationary to be unacceptable. In one Nissan 
study, over 60 percent of the subjects found an alert sound at 
stationary to be acceptable when the overall sound pressure level was 
similar to that of sounds meeting the requirements of today's final 
rule.\95\ In a second Nissan study, which was conducted indoors, the 
number of participants who found an alert sound at stationary 
unacceptable was 50 percent with the windows of the vehicle rolled up 
when the overall sound pressure level was similar to that of sounds 
meeting the requirements of today's final rule.\96\ No other commenter 
provided data or survey results showing that a sound at stationary 
would affect customer acceptance. Nissan did not submit any data that 
would indicate that customers would decline to purchase a vehicle 
equipped with sound at stationary.
---------------------------------------------------------------------------

    \95\ See document no. NHTSA-2011-0148-0051, available at 
www.regulations.gov.
    \96\ See document no. NHTSA-2011-0148-0320, available at 
www.regulations.gov.
---------------------------------------------------------------------------

    NHTSA believes manufacturers will install alert sounds on vehicles 
that are acceptable to drivers because they do not want to annoy 
current or potential customers. We do not know whether the second study 
conducted by Nissan could have been influenced by the fact that the 
testing in question occurred indoors, and we would expect the 
circumstances under which a vehicle would be making a sound at 
stationary indoors to be limited. We do not believe that this second 
study is representative of the real-world situations in which a driver 
would be exposed to a sound at stationary. Given our questions about 
the findings of Nissan's second study, the fact that we do not have any 
other data on this issue from other manufacturers, and the fact that 
Nissan's original study showed that over 60 percent of customers would 
accept a sound at stationary, we do not have enough information to 
indicate that concerns regarding public acceptance of a sound at 
stationary are sufficient to outweigh the safety justifications for a 
sound at stationary or the requirements of the PSEA. Furthermore, a 
vast majority of ICE vehicles make a sound at stationary, and that 
sound does not deter customers from buying those vehicles.
    In reference to comments about stationary alert sounds having 
environmental impact, the agency conducted an environmental assessment 
and concluded that the requirements overall will have a minor impact on 
environmental noise.\97\
---------------------------------------------------------------------------

    \97\ ``Environmental Assessment--Minimum Sound Requirements for 
Hybrid and Electric Vehicles,'' docket no. NHTSA-2011-0100.
---------------------------------------------------------------------------

    After reviewing the comments and all information provided in 
response to the NPRM on this issue, the agency has decided to limit the 
requirements for the stationary but active condition to when an HV or 
EV's gear selector is not in ``Park.'' As stated in Section II.A, the 
term ``operation'' means a state of being functional or operative. 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 the operation of 
the vehicle's propulsion system. It is the operation of the vehicle by 
the driver, not the operation of the vehicle's propulsion system, that 
creates the safety risk to pedestrians who are unable to detect hybrid 
and electric vehicles.
    We note that, as a result of this decision, the terminology 
``Stationary but Active'' as used in the NPRM is no longer accurate 
because this final rule allows EVs and HVs to be ``active'' without 
emitting an alert sound. That is, the ignition of an HV or EV can be in 
the `on' position while the vehicle is not emitting an alert, assuming 
the vehicle's gear selector is in Park. This scenario would not have 
been allowed under the proposed requirement. Therefore, we have chosen 
to simply use the term ``stationary'' rather than ``stationary but 
active'' for this operating condition. Furthermore, the regulatory text 
adequately specifies the conditions for stationary tests, and the words 
``but active'' do not clarify any aspects of testing. For these 
reasons, the phrase ``stationary but active'' is not used in the final 
rule.
    We believe that requiring sound at stationary only if a vehicle's 
gear selector is not in the ``Park'' position will still allow 
pedestrians to avoid crashes with HVs and EVs starting from the stopped 
position, while also minimizing sound in situations in which vehicles 
may pose no immediate risk to pedestrians, such as when they are parked 
with their ignition turned on. HVs and EVs that are stationary pose a 
risk to pedestrians only if they could begin moving at any moment. When 
a vehicle is in Park, the driver must step on the brake and move the 
gear selector to Drive or Reverse and then release the brake in order 
to begin moving, which takes some time. Although there are situations 
in which a driver could quickly shift a vehicle into Drive and begin 
moving, there also are situations in which a vehicle in Park with its 
ignition turned on will remain stationary for a prolonged period of 
time. Without data to indicate which of these scenarios is predominant, 
we believe that requiring an alert sound while HVs and EVs are 
stationary but are not in ``Park'' appropriately balances pedestrian 
safety, as provided for in the PSEA, with concerns about producing 
sound when it is not necessary to alert pedestrians. Such concerns were 
expressed by a number of commenters including vehicle manufacturers but 
also by a large number of individuals who commented on the NPRM and who 
stated that adding alert sounds to vehicles will create noise in 
environments and circumstances that otherwise would be quiet.
    As with automatic-transmission HVs and EVs, our intent is that the 
stationary requirement will ensure that manual-transmission HVs and EVs 
also emit an alert sound in all routine in-traffic situations but not 
when they are parked. However, for manual-transmission vehicles, there 
is no gear selector

[[Page 90445]]

position exactly analogous to the Park position; the Neutral position 
is similar, but not the same. Automatic-transmission vehicles typically 
remain in Drive, i.e., not in Park, as long as they are in traffic, but 
they typically are in Park when stationary for more than a short time. 
In contrast, manual-transmission vehicles may routinely be in Neutral 
both in traffic (e.g., vehicles waiting at traffic lights) as well as 
when parked. If we were to specify that an alert sound is required on 
manual-transmission HVs and EVs only when the gear selector is in a 
position other than Neutral, that would fail to achieve the desired 
safety outcome because some routine in-traffic situations would not be 
covered (e.g., vehicles waiting at traffic lights). Consequently, we 
have decided to focus on parking brake usage as an alternative factor 
to determine when an alert is needed on a stationary HV or EV with a 
manual transmission. We are specifying in the stationary requirement 
that the alert sound on manual transmission-equipped HVs and EVs must 
activate any time the ignition is turned on and the parking brake is 
not in the applied position. Thus, a vehicle with a manual transmission 
that is parked and idling will not be required to emit an alert sound 
as long as the parking brake is applied. We believe that this approach 
responds to comments, that it is within the scope of the proposal, and 
that it meets the goal of improving safety for blind and other 
pedestrians while minimizing non-essential vehicle noise.
    As discussed elsewhere in today's final rule, the minimum sound 
level requirements for the stationary condition are based on the 
agency's detection model. These minimum requirements represent the 
sound levels that a pedestrian would need in order to hear a vehicle at 
a distance of two meters. For more discussion of the minimum sound 
requirements, see Section II.C in this notice.
Operation in Reverse
    In the NPRM, we stated that reverse is a critical operating 
scenario for which the agency should issue minimum sound requirements 
for HVs and EVs to provide acoustic cues to pedestrians when the 
vehicles are backing out of parking spaces or driveways, to prevent 
collisions between EVs and HVs and pedestrians, and to satisfy the 
requirements of the PSEA.\98\
---------------------------------------------------------------------------

    \98\ Because the PSEA requires NHTSA to issue minimum sound 
levels to allow pedestrians to discern vehicle presence and 
operation, and a vehicle moving in reverse is unquestionably 
operating, a minimum sound level is required for this condition.
---------------------------------------------------------------------------

    We also stated that HVs and EVs should be required to produce a 
sound while operating in reverse despite the agency's rear visibility 
requirements in FMVSS No. 111.
    The NPRM stated that NHTSA's report on the incidence rates of 
crashes between HVs and pedestrians found 13 collisions with 
pedestrians when an HV is backing up.\99\ We explained in the NPRM that 
while we could not establish a statistically significant incidence rate 
for backing crashes for HVs to compare to backing crashes involving 
ICEs due to the limited sample size, these accident reports do show 
that these crashes occur. We also stated that backing incidents occur 
in parking lots, garages, and driveways, as well as other ``off 
roadway'' locations that would not be captured in the State Data 
System, and thus they might be underreported.
---------------------------------------------------------------------------

    \99\ 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.
---------------------------------------------------------------------------

    Because of difficulties in conducting tests with the test vehicle 
is in motion in reverse, the NPRM stated that the agency would test the 
minimum sound requirements for reverse while the vehicle is stationary 
but with the reverse gear engaged.
    Alliance/Global stated that HVs and EVs should not be required to 
make sound while stationary in reverse. Alliance/Global also stated 
that HVs and EVs should emit the same overall sound pressure level as 
in the stationary but active condition when in reverse and only when 
the vehicle is in motion.
    Honda stated that the agency should not require pitch shifting when 
HVs and EVs are operating in reverse. Honda also stated that NHTSA 
should consider the role of pending changes to the requirements of 
FMVSS No. 111 that should serve to increase the driver's level of 
awareness of pedestrians who may be present while operating a vehicle 
in reverse.

Agency Response to Comments

    We have decided to establish minimum sound requirements applicable 
to HVs and EVs with their gear selection control in reverse, both when 
stationary and when moving. We are requiring HVs and EVs to produce a 
sound in reverse for the reasons stated in the NPRM and in our 
discussion regarding sound at stationary. An HV or EV with its gear 
selection control in reverse could start moving at any time and 
pedestrians should be aware of the presence of such a vehicle so they 
can avoid walking into the vehicle's path.
    As discussed in Section III.C, we are requiring the sound levels 
when the vehicle is in reverse to be slightly higher than when the 
vehicle is stationary and lower than the levels required for vehicles 
moving forward at more than 10 km/h because the vast majority of 
vehicle operation in reverse is likely to be limited to speeds around 
10 km/h. In addition, drivers may be less aware of pedestrians passing 
behind their vehicle because of obstructed visibility to the rear.
    For the reasons discussed in Section III.G, the final rule no 
longer contains requirements for pitch shifting, so there will be no 
such requirements when the vehicle is operating in reverse. We note 
that the requirement in the final rule that the volume of the sound 
produced by the vehicle increase as the vehicle increases speed does 
not apply when the vehicle is operating in reverse.
    The agency has considered the potential impact on today's final 
rule of the NHTSA rulemaking on FMVSS No. 111 to expand the required 
rear field of view.\100\ The expanded field-of-view requirements will 
reduce pedestrian crashes involving backing vehicles of all propulsion 
types. On the other hand, it will not eliminate those crashes. As we 
stated in the NPRM, establishing minimum sound level requirements for 
reverse operation will ensure that both the pedestrian and the driver 
continue to have the ability to avoid pedestrian-vehicle collisions. 
Nevertheless, we have adjusted the target population in our assessment 
of benefits to reflect the recent amendments to FMVSS No. 111 under 
which many vehicles will be equipped with rear vision cameras.
---------------------------------------------------------------------------

    \100\ See 79 FR 19178, April 7, 2014.
---------------------------------------------------------------------------

    The proposed requirements in the NPRM for operation in reverse 
allowed the use of back-up beepers that most heavy vehicles are 
equipped with as a means of compliance with the pedestrian alert safety 
standard. As noted elsewhere in this preamble, this final rule does not 
apply to medium and heavy vehicles, so the proposed requirement to 
allow the use of back-up beepers is not included in this final rule.
Acceleration and Deceleration
    In the NPRM, we did not include separate test procedures to measure 
vehicles when they are accelerating or decelerating. We stated that we 
chose not to propose separate requirements when EVs and HVs are 
accelerating and decelerating because of concerns that it was not 
feasible to test accelerating or decelerating vehicles accurately and 
repeatably. We stated that the proposed

[[Page 90446]]

pitch shifting requirements would allow pedestrians to detect the 
acceleration and deceleration of HVs and EVs, so separate acoustic 
requirements are not necessary. In the responses to the NPRM, the topic 
of acceleration and deceleration was not commented on separately from 
the topic of pitch shifting which is covered in Section III.G of this 
final rule.
    For the reasons stated in Section III.G, we have not included a 
requirement for pitch shifting in today's final rule. Today's final 
rule instead contains a requirement that the sound produced by a 
vehicle must increase and decrease in loudness as the vehicle changes 
speed. The agency believes that a change in sound level produced by EVs 
and HVs as their speed changes will provide an acoustic cue for 
pedestrians to detect acceleration and deceleration.
    In the NPRM, the required minimum level in each one-third octave 
band was greater at higher speeds to allow pedestrians to detect faster 
moving vehicles from farther away and to account for increased stopping 
distance at higher speeds. The NPRM, however, did not contain any 
maximum sound requirements, only minimums, at each operating condition 
so it would have been possible for an EV or HV to meet the acoustic 
requirements in the NPRM by producing the same, unvarying sound level 
from stationary up to 30 km/h. If a manufacturer chose this type of 
design, pedestrians would not have any acoustic cues to determine if 
the vehicle was changing speed if the sound produced by the vehicle 
also did not change in pitch. We believe this would make it more 
difficult for a blind pedestrian to distinguish a stopped or very slow-
moving vehicle from one that is moving faster, and to determine if an 
approaching vehicle is slowing to a stop. To avoid this situation, the 
agency is requiring that the sound level produced by EV and HV 
pedestrian alert systems must increase as vehicle speed increases and 
must decrease as speed decreases. This requirement is implemented in 
Section S5.2 of the regulatory text of this final rule.
Vehicles in Forward Motion at Constant Speed
    In the NPRM, the agency proposed that EVs and HVs produce sound 
sufficient to allow pedestrians to detect these vehicles at all speeds 
between 0 and 30 km/h (18.6 mph). The agency proposed to ensure that 
EVs and HVs produce a minimum sound level necessary for safe pedestrian 
detection at constant speeds by measuring vehicle sound output at 10 
km/h (6.2 mph), 20 km/h (12.4 mph), and 30 km/h (18.6 mph). The 
proposal contained minimum acoustic requirements up to the speed of 30 
km/h because, for the reasons discussed in the NPRM, the agency 
believed that 30 km/h was the appropriate crossover speed. The agency 
believed that it was necessary to include pass-by tests at speeds up to 
and including the crossover speed to ensure that EVs and HVs meet the 
minimum sound level requirements for all speeds within the range of 
speeds covered by the requirements.
    The agency received no comments related specifically to the 
proposed constant speed pass-by performance requirements or associated 
tests. However, many commenters including manufacturers, manufacturer 
organizations, and advocacy groups argued either for or against the 
proposed crossover speed of 30 km/h. The details of the comments on 
crossover speed are discussed in the next section (Section III.D).
Agency Response to Comments
    If a lower crossover speed had been selected for the final rule, 
the agency would have modified the pass-by test sequence to replace the 
30 km/h test speed with the lower crossover speed. However, the agency 
has decided to maintain the 30 km/h crossover speed. Because of this 
decision, the constant speed pass-by scenarios in the final rule will 
remain as proposed in the NPRM.

D. Crossover Speed

    In the NPRM, we stated that the agency had tentatively concluded 
that EVs and HVs should be subject to minimum sound requirements until 
they reach a speed of 30 km/h. The NPRM explained that the PSEA defined 
crossover speed as ``the speed at which tire noise, wind resistance, or 
other factors eliminate the need for a separate alert sound.'' We 
decided to propose a crossover speed of 30 km/h (18.6 mph) by examining 
the speed at which EVs and HVs produce a similar overall sound pressure 
level as their peer ICE vehicles, to determine the speed at which the 
powertrain noise of the ICE vehicle was no longer the dominant source 
of the vehicle sound. This peer vehicle method was one that NHTSA had 
used in research prior to the enactment of the PSEA. As far as the 
agency was aware, this method was a reasonable way to identify an 
appropriate crossover speed. We also examined the crash statistics from 
the State Data System to determine if there was a speed above which the 
rate of pedestrian crashes for HVs and ICE vehicles were the same.
    In the NPRM, we explained that the peer vehicle method measures the 
speed at which the sound level produced by an HV or EV and the sound 
level produced by the vehicle's ICE ``peer'' become indistinguishable 
from one another in terms of overall sound pressure. We stated that 
this should establish the crossover speed, although that speed may 
differ depending on the make and model of the test vehicles. This 
method estimates the speed at which an HV or EV generates a sound level 
equivalent to the sound level that would be generated if the HV or EV 
was powered by an ICE rather than by electric power. We stated that our 
measurements of vehicles showed that a gap in sound level between HVs 
or EVs and their ICE peer vehicles still existed at 20 km/h (12.4 mph) 
and became much smaller or negligible in most tests at 30 km/h. For 
that reason, NHTSA tentatively concluded in the NPRM that ensuring EVs 
and HVs produce a minimum sound level until they reach a speed of 30 
km/h will ensure that those vehicles produce sufficient sound to allow 
pedestrians to detect them. We requested comment specifically on 
whether the crossover speed should be 20 km/h instead of 30 km/h.
    We also stated in the NPRM that the difference in rates of 
involvement in pedestrian crashes between HVs and ICEs is highest, 
according to our crash analysis, when the vehicle involved was 
executing a low speed maneuver prior to the crash.\101\ Low-speed 
maneuvers do not have a defined speed range, but they include making a 
turn, slowing or stopping, backing, entering or leaving a parking space 
or driveway, and starting in traffic. Because vehicle noise increases 
as a vehicle goes faster, the agency tentatively concluded in the NPRM 
that a crossover speed of 30 km/h would ensure that EVs and HVs will 
produce sufficient sound up to the speed at which pedestrians can 
safely detect EVs and HVs without the aid of an alert system.
---------------------------------------------------------------------------

    \101\ 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.
---------------------------------------------------------------------------

    We noted in the NPRM that the agency was conducting an 
Environmental Assessment (EA) in connection with the rulemaking and the 
draft EA showed that the difference in ambient sound levels if the 
agency were to establish a crossover speed of 30 km/h compared to a 
crossover speed of 20 km/h was expected to be negligible.
    Several commenters to the NOI and participants in United Nations 
Economic Commission for Europe

[[Page 90447]]

(UNECE) informal working group meetings \102\ stated that the agency 
should adopt a crossover speed of 20 km/h.
---------------------------------------------------------------------------

    \102\ For more information about the agency's participation in 
the UNECE Quiet Road Transport Vehicles informal working group see 
NPRM, 78 FR 2848.
---------------------------------------------------------------------------

    In the NPRM we discussed research presented by JASIC. JASIC 
determined the crossover speed for several vehicles by measuring when 
the tire noise was dominant over engine noise. In this research JASIC 
compared the sound produced by a vehicle when tested a constant speed 
with the vehicle's ICE on to the sound produced by the same vehicle 
when tested with its ICE off. The purpose of this test was to determine 
the point at which the vehicle produce a similar sound level with its 
ICE off as it did with its ICE on. JASIC concluded from its research 
that tire noise was dominant for every ICE and hybrid vehicle tested at 
speeds that exceeded 20 km/h. Honda and Nissan mentioned the JASIC data 
as adequate justification for a 20 km/h crossover speed. The data 
indicated that JASIC evaluated six different vehicles, each found to 
have a crossover speed very close to 20 km/h. At the time the NPRM was 
issued, the agency did not believe the JASIC data was sufficient for a 
20 km/h crossover speed determination.
    In the NPRM, the agency solicited comments on whether 20 km/h 
should be the crossover speed instead of the proposed speed of 30 km/h. 
The agency also requested additional research data that could be used 
to support a 20 km/h crossover speed decision.
    All of the vehicle manufacturers and the organizations that 
represent manufacturers stated in their comments that NHTSA should 
adopt a crossover speed of 20 km/h in the final rule. These commenters 
stated that a crossover speed of 30 km/h is overly burdensome and would 
lead to increases in traffic noise. They also stated that the 
difference in sound of HVs and EVs compared to ICE vehicles is marginal 
at 20 km/h, and that a crossover speed of 30 km/h is not necessary to 
achieve safety goals. Manufacturers stated that at speeds higher than 
20 km/h, tire and wind noise interfere with measurement of the alert 
sound. These commenters also stated that the agency should adopt 20 km/
h as a crossover speed to align with UNECE and Japanese government 
recommended practices for pedestrian alert systems.
    Alliance/Global stated that by the time an EV or HV reaches a 
cruising speed of 20 km/h, the sound it makes is practically 
indistinguishable from an equivalent ICE vehicle. Alliance/Global 
claims that at 20 km/h the EV or HV in electric power mode is only 
slightly quieter than an ICE vehicle. Alliance/Global also stated tire 
noise above 20 km/h interferes with the alert sound, making the 
detection and measurement of specific sound content in one-third octave 
frequencies much more difficult. Alliance/Global stated that a 
crossover speed above 20 km/h is not needed to fulfil the safety goals 
of the final rule.
    The European Union commented that the limits on crossover or 
``threshold'' speed indicated in the NPRM--30 km/h for forward motion 
and 18 km/h for reverse motion [the agency notes, however, that the 
latter figure does not reflect any proposed requirement, and may have 
been an oversight in the EU comment letter]--are considered excessive 
as many if not most EVs and HEVs produce sufficient noise emissions in 
the 20-25 km/h and 10-12 km/h speed ranges for forward and reverse 
motions, respectively. This can be attributed to the fact that EVs and 
HEVs use low-rolling resistance tires which produce more noise 
emissions than conventional ones as well as to the increased 
drivetrain/powertrain noise emissions when the vehicle is in reverse.
    Honda said that acoustic data shows a convergence of the vehicle's 
sound profiles between the engine-on and engine-off condition at 20 km/
h, and that acoustic sound requirements at 20 km/h or more might not be 
necessary.
    Toyota explained that data presented by the Quiet Road Transport 
Vehicles (QRTV) group have indicated that the appropriate crossover 
speed is 20 km/h, because tire and wind noise exceed the noise of 
traditional ICE vehicle engines above this speed. Toyota mentioned that 
existing Japanese and European guidelines have adopted 20 km/h as the 
appropriate crossover speed and recommended that NHTSA do the same.
    Volkswagen stated that the crossover speed in the final rule should 
be 20 km/h. Volkswagen stated that for customer satisfaction reasons it 
will design the alert sound to fade out gradually above the crossover 
speed, rather than abruptly shutting off immediately upon reaching the 
crossover speed. (Otherwise a driver travelling at the specified 
crossover speed would be highly aware of, and almost certainly annoyed 
by, a sound that toggled on and off abruptly as the vehicle crossed and 
re-crossed this speed.) Volkswagen suggested that other vehicle 
manufacturers will also implement alert sounds that fade out gradually, 
further weakening the rationale for setting a higher, 30 km/h, 
crossover speed in the final rule.
    DG Enterprise stated that a 30 km/h crossover speed would be 
excessive because most EVs and HVs already produce sufficient sound in 
the 20-25 km/h speed range to be detected by pedestrians. DG Enterprise 
believes these vehicles make enough sound to be detectable because they 
use low-rolling resistance tires that produce more noise than 
conventional tires.
    Advocacy groups for individuals who are blind stated in their 
comments that the crossover speed should be 30 km/h and that NHTSA had 
provided sufficient data to justify that decision.
    NFB stated that the agency should establish a crossover speed of 30 
km/h which would ensure that EVs and HVs are detectable when operating 
on quieter paved surfaces and/or when using quieter tires.
Agency Response to Comments
    In this final rule, the agency has decided to maintain the 
crossover speed of 30 km/h as proposed in the NPRM.
    In development of the NPRM and final rule the agency carefully 
considered the term ``crossover speed,'' what it means, and how it 
should be determined. The PSEA requires an alert be added to electric 
and hybrid vehicles up to the ``crossover speed.'' The PSEA defines 
crossover speed as ``the speed at which tire noise, wind resistance, or 
other factors eliminate the need for a separate alert sound as 
determined by the Secretary.'' ``Alert sound'' was itself defined as 
``a vehicle-emitted sound to enable pedestrians to discern vehicle 
presence, direction, location, and operation.''
    To date, it has been a common understanding that when ICE vehicles 
are operated at low speeds, they are detectable primarily due to the 
sounds generated by their internal combustion engine and drivetrain, 
and secondarily due to tire noise and wind resistance noise, which are 
speed dependent, and to other factors. At higher speeds, the sound 
generated by an ICE vehicle's tires, wind resistance, and other factors 
become the primary sound source, and the engine sound becomes secondary 
(there are exceptions, such as vehicles designed to have prominent 
noise from a tuned exhaust system.) Therefore, ICE vehicles generally 
are detectable at lower speeds because of the sound produced by the ICE 
and are detectable at higher speeds because of sound produced by the 
vehicle's tires, wind resistance, and other factors. A vehicle reaches 
its crossover speed when it can be detected based on these other, non-
ICE sound sources. The effort to

[[Page 90448]]

determine the speed at which this occurs is complicated by the fact 
that conventional vehicles emit a complex composition of sounds and 
tones at various overall sound pressure levels, such that crossover 
speed might not be that same from one vehicle model to another. 
Furthermore, it would be impractical for the agency to set different 
crossover speeds for different vehicles. Thus, in order to ensure that 
all vehicles to which this rule applies can be safely detected by 
pedestrians, the agency believes it must set crossover speed at a value 
that captures the higher end of the range of crossover speeds that 
exists among light vehicles.
    The agency explained in the NPRM that, in the absence of a detailed 
analysis supporting another crossover speed, the agency tentatively 
concluded that a crossover speed of 30km/h would ensure that 
pedestrians will be able to safely detect EVs and HVs in situations in 
which these vehicles pose an increased risk to pedestrians because of 
their quiet nature.
    After considering the comments received and evaluating vehicle 
measurements utilizing the method proposed by JASIC, as well as an 
analysis utilizing the agency's vehicle detection criteria, we have 
decided to require a crossover speed of 30 km/h in this final rule as 
proposed in the NPRM. No new compelling data was submitted to the 
agency that can be used to conclude that reducing the crossover speed 
from the proposed 30 km/h to 20 km/h is justified.
    Because other methods (i.e., the peer vehicle method and JASIC 
method) used to determine the crossover speed were inconclusive, as 
discussed later in this section, and did not directly answer the 
question of when the vehicles in the analysis produced enough sound to 
be detected by pedestrians, NHTSA did some additional evaluation of 
sounds produced by ICE vehicles with their IC engines turned off using 
the one-third octave band detectability thresholds from our acoustic 
model. The model used was the same one that was the source of the 
agency's minimum detection requirements in this final rule. We 
conducted this analysis after the NPRM comment period had closed to 
assist in considering the comments we had received. A technical paper 
on this crossover speed analysis has been included in the docket.\103\
---------------------------------------------------------------------------

    \103\ Quiet Car Coast Down Analysis (Final Rule) (June 2015).
---------------------------------------------------------------------------

    By applying the detectability model to the measurements of sounds 
produced by the eleven ICE vehicles listed below with their IC engines 
turned off, we were able to assess if any of the A-weighted one-third 
octave band levels from any of the test vehicles met or exceeded the 20 
km/h band threshold levels needed for a vehicle to be detectable in a 
standardized 55 dBA ambient, and to compare that outcome to the number 
of bands that met or exceeded the thresholds at 30 km/h. (We note that 
this was a re-analysis of vehicle data already collected, i.e., this 
evaluation did not involve additional vehicle testing.) Whereas the 
peer vehicle and JASIC methods are relative measures because they 
compare one vehicle's overall sound to another vehicle's overall sound, 
this most recent NHTSA evaluation compared vehicle sounds directly to 
detection criteria.
    The results of this analysis are summarized below according to test 
speed and vehicle model. The one-third octave bands listed are those 
for which the given test vehicle met or exceeded the threshold in 
NHTSA's final rule:
10 km/h with the IC engine off--
     2012 Mini Cooper at 2000, 2500, 4000,and 5000 Hz
     2012 Ford Focus at 5000 Hz
20 km/h with the IC engine off--
     2012 Ford Focus at 800, 1000, and 1600 Hz
30 km/h with the IC engine off--
     2010 Buick LaCrosse at 1000, and 1600 Hz
     2012 Mini Cooper at 630, 800, 1000, 1600, 2000 Hz
     2012 Ford Focus at 800, 1000, 1600 and 2000 Hz
     2012 Lexus RX 350, 2011 Cadillac CTS, 2011 Honda Odyssey, 
2012 Honda Fit, 2012 Toyota Camry, 2012 Toyota Corolla, and 2012 VW 
Golf ICE at 1600 Hz
    These results show that at 20 km/h only one of the eleven tested 
vehicles had any one-third octave bands that met or exceeded the 
corresponding threshold for detection.\104\ Therefore, ten of the 
eleven vehicles would not be detectable to pedestrians at 20 km/h only 
based on the tire and wind noise produced by the vehicle. This 
indicates that at 20 km/h it is unlikely that pedestrians would be able 
to detect a majority of EVs and HVs without an alert sound. Therefore, 
according to this data, a crossover speed of 20 km/h does not meet the 
requirements of the PSEA. At 30 km/h, four models had multiple bands 
that met or exceeded thresholds, and another seven models met or 
exceeded the threshold in the 1600 Hz band.
---------------------------------------------------------------------------

    \104\ There are several important caveats in the use of this 
crossover speed analysis. The most important one is that the vehicle 
data is for coasting ICE vehicles (because the goal is to measure 
tire and wind noise), and thus it does not include the engine noise 
that the test vehicles would have in normal operation. Consequently, 
this evaluation should not be used to judge the sound level in 
actual operation of any of the test vehicles. Other caveats are 
enumerated in the docketed analysis paper.
---------------------------------------------------------------------------

    Our conclusion from this analysis is that at 20 km/h few HVs and 
EVs make sufficient sound to be detectable to pedestrians without the 
aid of a pedestrian alert system.
    In light of this, and given other uncertainties discussed below, 
the agency has decided in this final rule to maintain the 30 km/h 
crossover speed proposed in the NPRM.
    Regarding the different analysis relied upon by JASIC and other 
commenters to support a 20 km/h crossover speed, we sought additional 
data because the JASIC data was limited to a small number of test 
vehicles. So, in addition to the agency's detection-based analysis 
discussed above, in order to address crossover speed comments, NHTSA 
conducted tests using the same method that JASIC had used to derive its 
recommended 20 km/h crossover speed. As described previously in this 
section, the method involves comparing sound pressure levels from the 
same vehicle measured on the track during coast-down (engine off), 
which approximates an EV or HV in electric mode, and pass-by (engine 
on) performance tests. Under this analysis, the speed at which coast-
down sound level is similar to the pass-by sound level is considered 
the crossover speed for that particular vehicle. This method identifies 
the speed at which the sound level due to all factors including tire 
and wind resistance noise, which are factors cited in the PSEA, is very 
close to the sound level of the same vehicle with its ICE operating. 
This method is similar to the peer vehicle method that the agency used 
in the NPRM, but it uses a single test vehicle in two operating 
conditions (engine-on and engine-off).
    In other words, at any speed higher than the crossover determined 
according to this method there is no perceived difference between the 
sound produced by an HV or EV without an alert and the same vehicle 
with an ICE because the predominant sound in both test conditions comes 
from the tires and aerodynamic noise, and these factors are consistent 
for both test conditions.
    NHTSA measured coast-down and pass-by sound pressure levels for 
eleven different ICE vehicles at 10, 20 and 30 km/h test speeds. The 
results are shown in Table 8.

[[Page 90449]]

                              Table 8--Pass-By vs. Coast-down Measurements for Eleven Vehicles at 10, 20, and 30 km/h \105\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                 Overall SPL (dBA)
                                                         -----------------------------------------------------------------------------------------------
                                                                      10 km/h                         20 km/h                         30 km/h
                                                         -----------------------------------------------------------------------------------------------
                                                              Pass-by       Coast-down        Pass-by       Coast-down        Pass-by       Coast-down
                                                            (engine on)    (engine off)     (engine on)    (engine off)     (engine on)    (engine off)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.................................  2012 Toyota Camry...            57.8            48.4            62.1            60.3            67.2            66.6
2.................................  2012 Toyota Corolla.            56.5            48.5            61.4            59.8            67.2            66.6
3.................................  2012 VW Golf........            57.0            49.4            62.3            60.9            68.3            67.4
4.................................  2012 Mini Cooper....            58.7            50.8            65.6            59.9            68.3            67.2
5.................................  2011 Cadillac CTS...            56.7            50.4            62.0            60.2            68.1            66.7
6.................................  2012 Toyota Yaris...            56.1            46.2            59.9            57.8            65.1            64.4
7.................................  2012 Honda Fit......            56.6            48.3            62.2            59.3            66.6            66.1
8.................................  2010 Buick Lacrosse.            55.8            49.9            63.8            60.4            68.4            66.7
9.................................  2011 Honda Odyssey..            56.5            52.2              63            62.4            69.4            68.8
10................................  2012 Lexus RX 350...            59.7            48.1            61.7            60.1            67.3            66.5
11................................  2012 Ford Focus.....            57.5            49.3            62.6            60.8            68.0            67.1
    Average.......................  ....................            57.2            49.2            62.4            60.2            67.7            66.7
--------------------------------------------------------------------------------------------------------------------------------------------------------

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

    \105\ 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.
---------------------------------------------------------------------------

    From these data, coast-down measurements were subtracted from pass-
by measurements to determine if, and at what speed, crossover occurred 
for each vehicle. The data are shown in Table 9. As explained in the 
NPRM,\106\ differences in sound pressure level of less than 3dB 
generally are not distinguishable to humans (differences of 3dB might 
be noticeable only if two sounds were heard one after the other such 
that they could be directly compared). Based on this understanding, 
differences identified in Table 9 of less than 3 dB would indicate that 
the vehicle crossover speed has been achieved.
---------------------------------------------------------------------------

    \106\ see NPRM, 78 FR 2838.
    [GRAPHIC] [TIFF OMITTED] TR14DE16.001
    
    These results indicate that at the vehicle speed of 10 km/h all 
eleven vehicles had coast-down sound pressure levels significantly less 
than their associated pass-by levels, meaning that none of the vehicles 
had attained its respective crossover speed. At 30 km/h, all eleven 
vehicles had coast-down sound pressure levels close to or within 3 dB 
of their associated pass-by levels, meaning that every vehicle had 
reached its respective crossover speed. Thus, the additional testing 
clarified that 10 km/h would not be sufficient and that all vehicles 
would reach their crossover speed by 30 km/h (when using the criterion 
that the results from the two test conditions are within 3 dB.)
    The results at 20 km/h were less conclusive. Of the eleven vehicles 
tested, all had coast-down sound pressure levels below their respective 
pass-by test levels. However, all but two of the vehicles got to within 
a 3-dB differential, and the average differential of all vehicles was 
2.2 dB. The two vehicles that did not were the Mini and Buick Lacrosse, 
which had sound differentials greater than 3 dB (5.7 dB and 3.4 dB, 
respectively) and thus did not reach the crossover speed as defined by 
the agency. These two vehicle models had the highest pass-by sound 
pressure levels of the eleven vehicles, and their coast-down sound 
pressure was close to the average level for all eleven vehicles. While 
we note that it is possible to interpret this narrow data sample as 
demonstrating that a lower crossover speed may be sufficient for a 
portion of the HV/EV fleet, we also conducted additional analysis and 
considered additional factors in arriving at our decision to maintain 
the approach to require the pedestrian alert sound up

[[Page 90450]]

to 30 km/h, provided that vehicles are not able to satisfy the 
performance requirements without an alert sound.
    This comparison of the engine-on and engine-off measurements for 
these vehicles does not directly answer the question of when a vehicle 
makes enough sound to be detected by pedestrians. We believe that it 
also demonstrates that at 20 km/h there is a question of whether some 
vehicles produce enough sound based on tire and wind noise alone to be 
detected by pedestrians.
    Other factors we considered include the difference in pavements 
encountered in traffic compared to the ISO sound pad that is needed for 
testing, and the use of tires with low rolling resistance. The test 
data used to evaluate crossover speed were obtained on an ISO sound pad 
with a specified asphalt pavement. On public roadways, varying pavement 
conditions will be encountered that can increase or decrease a 
vehicle's acoustic sound profile. Also, low rolling resistance tires 
may tend to increase vehicle sound profiles, but not all vehicles will 
be operated with low rolling resistance tires. While these factors 
could increase vehicle noise, they also might decrease it. Selecting 
the higher crossover speed would ensure safety is not compromised when 
real-world roadway conditions result in the latter case.
    Another consideration is that limitations in available crash data 
do not permit the agency to make determinations regarding safety 
benefits at specific speeds. Because the vehicle speed at the time of a 
crash into a pedestrian is not available in the data set, the agency is 
not able to quantify what portion of the safety benefits associated 
with today's final rule would be lost if we were to adopt a value for 
crossover speed below the real-world values for some specific vehicle 
models.
    However, we continue to believe that this rule will prevent some 
unqualifiable number of additional injuries by adopting a 30 km/h 
crossover speed as opposed to a 20 km/h crossover speed. As discussed 
previously, our crash analysis indicated that the odds ratio of an HV 
being involved in a crash with a pedestrian was 1.52 when the vehicle 
in question was executing a low speed maneuver immediately prior to the 
crash. This means that HVs and EVs are 52 percent more likely to be 
involved in an incident with a pedestrian than an ICE vehicle under 
these circumstances. Low-speed maneuvers include making a turn, slowing 
or stopping, backing, entering or leaving a parking space or driveway, 
and starting in traffic. The agency also concludes that a crossover 
speed of 30 km/h (18 mph) will ensure that EVs and HVs will produce 
sufficient sound to allow pedestrians to safely detect them during low-
speed maneuvers in which these vehicles would otherwise pose a risk to 
pedestrians because of the low sound level they produce. Because we 
believe that drivers may execute these low speed maneuvers at speeds up 
to at least 30 km/h, and these maneuvers represent the highest risk of 
crash between an EV or HV and a pedestrian, more injuries will be 
avoided due to this rule with a crossover speed of 30 km/h than with a 
crossover speed of 20 km/h.
    As a further consideration, we note that a vehicle is not required 
to have added alert sound at any speed at which it meets the minimum 
detection requirements in this final rule. It would be acceptable for 
an alert system to be designed to turn off at some speed below the 30 
km/h crossover speed if it could be demonstrated that, between that 
lower cut-off speed and 30 km/h, it meets the detectability 
specifications without the assistance of an alert system.

E. Acoustic Parameters for Detection of Motor Vehicles

    In the NPRM, the agency proposed minimum sound levels for a 
specific set of one-third-octave bands \107\ that included low-to-mid-
frequency bands (315, 400, and 500 Hz) as well as high-frequency bands 
(2000, 2500, 3150, 4000, and 5000 Hz) for various vehicle operating 
conditions including stationary, reverse and forward motion up to 30 
km/h. These one-third octave bands were selected in an effort to 
maximize the detectability of the proposed alert sounds while taking 
into consideration the masking effects of common ambient noise and the 
degraded hearing of some pedestrians. Specifying minimum sound pressure 
levels for a wide range of one-third octave bands means that sounds 
meeting the specifications will be detected in a wider range of ambient 
conditions with various acoustic profiles.
---------------------------------------------------------------------------

    \107\ Octave band and one-third octave band scales facilitate 
identifying the specific frequencies of sounds. Octave bands 
separate the range of frequencies audible to humans into ten bands, 
and the one-third octave bands split each of the ten octave bands 
into three smaller frequency bands. Each scale in the breakdown 
provides more information about the sound being analyzed.
---------------------------------------------------------------------------

    Low frequency bands (below 315 Hz) were not included in the 
proposed specifications due to the expected strong masking effects of 
the ambient noise at low frequencies and the premise that they do not 
contribute as much to detection. In addition, alert system devices, 
particularly speakers, that are able to produce high level, low-
frequency sounds would most likely have to be larger, heavier, and more 
costly. Specifications for the low-to-mid-range frequency bands between 
315 and 500 Hz were included to assist pedestrians in detecting HVs and 
EVs in ambient noise environments such as areas near construction 
activity with significant high frequency noise. In the NPRM, the agency 
omitted mid-frequency bands from 630 to 1600 Hz because many common 
ambient conditions include frequencies within this range. One-third 
octave band standards in this range would have to be set at a 
relatively high level to effectively compensate for the masking effects 
caused by ambient noise conditions. But these bands contribute more 
than other bands to a vehicle's overall alert sound level for the same 
increase in detectability. By omitting minimum requirements for the 
one-third octave bands in the 630 to 1600 Hz frequency range in the 
proposal, the agency was attempting to ensure that alert sounds allow 
pedestrians to safely detect nearby EVs and HVs without unnecessarily 
increasing overall ambient noise levels.\108\ The high-frequency bands 
up to 5000 Hz provide good detectability for pedestrians with normal 
hearing.
---------------------------------------------------------------------------

    \108\ NPRM, ``Federal Motor Vehicle Safety Standards; Minimum 
Sound Requirements for Hybrid and Electric Vehicles, 78 FR 2829, 
(Jan. 14, 2013).
---------------------------------------------------------------------------

    The proposed sound specifications were based on a psychoacoustic 
modeling approach in combination with safe detection distances. The 
inherent assumptions for this analytical approach were that: \109\
---------------------------------------------------------------------------

    \109\ Hastings, et al. (2012). Research on Minimum Sound 
Specification for Hybrid and Electric Vehicles. Docket NHTSA-2011-
0148-0048.
---------------------------------------------------------------------------

     A vehicle should be detectable in the presence of a 
moderate suburban ambient, i.e., ambient at 55 dB(A); \110\
---------------------------------------------------------------------------

    \110\ In the NPRM we stated that we chose an ambient with a 55 
dB(A) overall sound pressure level because this represented a 
reasonable level below the 60 dB(A) ambient in which pedestrians 
would no longer be able to reasonably rely on hearing to detect 
approaching vehicles.
---------------------------------------------------------------------------

     a psychoacoustic model can be used to determine minimum 
levels for detection of one-third octave bands in the presence of an 
ambient;
     sounds should be detectable in multiple one-third octave 
bands to increase the likelihood that a pedestrian will be able to 
detect the sound in multiple ambients with differing acoustic profiles; 
and

[[Page 90451]]

     minimum detection distances can be based on vehicle 
stopping distances and driver reaction times.
    The agency used Moore's Partial Loudness model \111\ to estimate 
the minimum sound levels needed for a sound to be detectable in the 
presence of an ambient. The first step in our approach was to determine 
the minimum levels for detection, using Moore's model and a simplified 
ambient, for a pedestrian at the vehicle location. We stated that the 
distance at which a pedestrian would need to hear a vehicle is at least 
as long as the distance travelled during the driver's reaction time, 
plus the vehicle's stopping distance. We calculated these distances 
from the guide on highway design \112\ of the American Association of 
State Highway Transportation Officials (AASHTO) according to the 
following formula:
---------------------------------------------------------------------------

    \111\ Moore, B.C.J., Glasberg, B.R., and Baer, T. (1997). A 
Model for the Prediction of Thresholds, Loudness and Partial 
Loudness, J. Audio Eng. Soc. 45, 224-240.
    \112\ American Association of State Highway and Transportation 
Officials, A Policy on Geometric Design of Highways and Streets, 
Chapter 3 Elements of Design (2004).
[GRAPHIC] [TIFF OMITTED] TR14DE16.002

---------------------------------------------------------------------------
Where:

t = brake reaction time, sec.
V = design speed, km/h
a = deceleration rate, m/s\2\

    We explained that we chose a reaction time of 1.5 seconds because 
that is the mean reaction time for surprise events \113\ such as an 
object suddenly moving into a driver's path. We chose the 5.4 m/s\2\ 
deceleration rate corresponding to dry pavement braking because most of 
the pedestrian crashes that the agency identified occurred in clear 
conditions. If we had decided to use instead a slower deceleration rate 
for wet pavement conditions, we believe the necessary sound profile for 
detection would have to be louder and for a longer period because it 
would take a greater distance to stop, and thus would be unnecessarily 
loud for most conditions.
---------------------------------------------------------------------------

    \113\ Green (2000) How Long Does It Take to Stop? Methodological 
Analysis of Driver Perception-Brake Times.'' Transportation Human 
Factors 2(3) 195-216.
---------------------------------------------------------------------------

    Based on calculations using these values, the agency determined 
that the desired detection distances were 5 meters in front of the 
vehicle for the 10 km/h (6.2 mph) pass-by, 11 meters for the 20 km/h 
(12.4 mph) pass-by, and 19 meters for 30 km/h (18.6 mph) pass-by. The 
results of these computations were rounded to the nearest meter. 
Moore's Partial Loudness Model was then used to derive the minimum 
sound levels required for detection for each driving condition and one-
third octave band. Levels were increased by 0.5 dB to provide a small 
safety factor, and were then rounded up to the nearest integer for 
simplicity. The resulting NPRM levels are shown in Table 10.

                                Table 10--NPRM Minimum Sound Levels for Detection
----------------------------------------------------------------------------------------------------------------
  One-third octave band center    Stationary but
          frequency, Hz              activated        Backing         10 km/h         20 km/h         30 km/h
----------------------------------------------------------------------------------------------------------------
315.............................              42              45              48              54              59
400.............................              43              46              49              55              59
500.............................              43              46              49              56              60
2000............................              42              45              48              54              58
2500............................              39              42              45              51              56
3150............................              37              40              43              49              53
4000............................              34              36              39              46              50
5000............................              31              34              37              43              48
Overall A-weighted SPL Measured               49              52              55              62              66
 at SAE J2889-1 PP' line........
----------------------------------------------------------------------------------------------------------------

    We explained in the NPRM that while we were setting the sound 
pressure levels for each one-third octave band based on the distance 
from the vehicle at which we wanted pedestrians to be able to hear 
approaching vehicles, because of practical reasons we would measure 
sound emission for compliance purposes at a distance of 2 meters and 
scale the required levels accordingly. We used the following method to 
calculate what the sound level would need to be 2 meters from the 
vehicle's path to be detected within the prescribed stopping distance. 
Table 11 shows how the sound produced by a vehicle attenuates when 
measured using the procedure in SAE J2889-1.

                      Table 11--SPL Adjustment (dBA) From Source to SAE Microphone Location
----------------------------------------------------------------------------------------------------------------
 
----------------------------------------------------------------------------------------------------------------
Speed, km/h.....................................................              10              20              30
X source, meters................................................               5              11              19
Y source,* meters...............................................               2               2               2
r0,** meters....................................................             2.3             2.3             2.3
r1,** meters....................................................             5.5            11.2            19.1
r doubling......................................................             1.2             2.3             3.0
Attenuation, dB.................................................            -5.8           -12.3           -16.8
----------------------------------------------------------------------------------------------------------------
* Assume effective source is at center of vehicle since propagation is forward.
** Assume Z = 1.2.

`X' represents the horizontal distance from the source to the P-P' line 
while `Y' is the 45perpendicular distance from the source to the 
microphones in SAE J2889-1. `Z' represents the height of the microphone 
in meters as specified in SAE J2889-1. The values in Table 11 were 
calculated using the following

[[Page 90452]]

formula and assuming a value of 1.2 meters for Z:
---------------------------------------------------------------------------

    \114\ Attenuation rate = 4.5 dB for the first distance doubling 
and 6 dB per distance doubling thereafter.
[GRAPHIC] [TIFF OMITTED] TR14DE16.003

    In the NPRM, the agency also indicated its intent to conduct 
additional research before issuing a final rule to confirm that sounds 
meeting the proposed requirements would be detected as predicted by the 
model, and we sought comments on the following topics (NPRM pp. 2832-
2833):
     What improvements would make the acoustic specifications 
more effective and make alert sounds more detectable?
     Should NHTSA require vehicles to emit sound that meets the 
four one-third octave band requirements only at 2000 Hz and above as an 
alternative to requirements for eight one-third octave bands?
     What is the optimum number of bands that should contain 
minimum sound level requirements, and what should the corresponding 
levels be?
    In addition to requirements with minimum content in the eight one-
third octave bands between 315 Hz and 500 Hz and 2000 Hz and 5000 Hz, 
the NPRM also considered acoustic requirements with minimum content in 
two one-third octave bands with a minimum requirement for the overall 
sound pressure level of the sound. NHTSA stated, when discussing this 
possible two-band approach in the NPRM, that it was seeking comment on 
the acoustic profile of the minimum sound requirements, as well as on 
the number of one-third octave bands for which the agency should 
establish requirements. We stated in the NPRM that the reason we were 
not proposing to adopt requirements for content in two one-third octave 
bands was that a sound with content in only two one-third octave bands 
would not be detectable in as many ambient noise environments as sounds 
with minimum content in eight one-third octave bands. On the topic of 
acoustic parameters for detection, the agency received a joint comment 
from Alliance/Global, as well as comments from OICA, Chrysler, Ford, 
GM, Honda, Mercedes, Nissan, Porsche, Toyota, the National Federation 
of the Blind, the American Council of the Blind, the World Blind Union, 
the National Council of State Agencies for the Blind, the Disability 
and Communication Access Board, the Insurance Institute for Highway 
Safety, Advocates for Highway and Auto Safety, Accessible Design for 
the Blind, and Western Michigan University. Subsequent to the NPRM 
comment period, NHTSA also received a late comment submitted jointly by 
the Alliance, Global, the NFB, and the ACB, and the agency had 
additional correspondence with those commenters, which is recorded in 
the docket.
    Four main issues were discussed by the commenters relating to the 
acoustic parameters proposed for detection: (1) The number and level of 
one-third octave bands required; (2) the methods used to determine 
detection distances and associated sound specifications; (3) the range 
of frequencies used; and (4) vehicle marketability.
    Fifteen of the above commenters discussed the first issue about the 
number and levels of one-third octave bands required. Alliance/Global 
\115\ stated that NHTSA's proposed specification in the NPRM is too 
conservative. They suggested deleting the requirement for frequency 
content in eight one-third octave bands and replacing it with a 
simplified two-band approach. Specifically, they recommended using a 
minimum overall SPL and minimum sound levels in at least two octave 
bands. In their suggested approach, one band would be required in a low 
frequency range (less than 1000 Hz) and one band would be required in a 
high frequency range (1000 Hz up to 3150 Hz), separated by at least one 
one-third octave band. Alliance/Global suggested the following levels 
(Table 12) but noted that further discussion within the QRTV group that 
is developing a GTR is needed before these values can be fully 
recommended:
---------------------------------------------------------------------------

    \115\ NHTSA-2011-0148-0251.

          Table 12--Alliance/Global Recommended Two-Band Levels
------------------------------------------------------------------------
                                                        Individual band
      Test condition \116\           Overall SPL       SPL  (two bands)
------------------------------------------------------------------------
Stationary/Backing.............  48 dB..............  44 dB
10 km/h........................  53 dB..............  46 dB
20 km/h........................  58 dB..............  51 dB
------------------------------------------------------------------------

    Alliance/Global stated that NHTSA's target for detectability 
performance can be  achieved with two one-third octave bands set at the 
levels proposed in the NPRM, and the minimum levels for additional 
bands can be reduced while maintaining the same detectability 
performance. Alliance/Global stated that if NHTSA chooses to require in 
the final rule that sounds emitted by EVs and HVs must have content in 
more than two one-third octave bands, the agency should reduce the 
minimum levels for each one-third octave band according to the total 
number of required bands. Chrysler, GM, Honda, and Mercedes stated that 
they support the two-band approach suggested by Alliance/Global.
---------------------------------------------------------------------------

    \116\ The Alliance/Global recommendations did not include 
suggested minimums for 30 km/h in accordance with their comments 
that crossover speed should be limited to 20 km/h.
---------------------------------------------------------------------------

    Ford argued that based on its study of this subject, not all eight 
one-third octave bands are needed for a sound to be detectable 5 meters 
away. Ford's study consisted of a human factors test where audio 
recordings of vehicle

[[Page 90453]]

sounds were presented to participants using headphones. Sounds tested 
by Ford were an ICE vehicle sound, an electric vehicle without an alert 
sound, and three alert sounds, but those sounds did not meet all of the 
agency's proposed minimum one-third octave bands levels. Sounds were 
mixed with a 55 dB(A) masking noise. Twenty-four Ford employees and 
four visually impaired individuals participated in the study. Ford 
stated that all vehicles were detected before the 5-meter critical 
distance, except for the vehicle without an alert. They also reported 
that participants recognized the vehicles with alert sounds at least at 
the same rate as the ICE vehicle sound.
    Nissan stated that a sound with a sound pressure level equivalent 
to the ICE fleet minimum with a two-peak sound profile is appropriate 
for detectability. Nissan stated that having one peak frequency 
component between 600 and 800 Hz helps detectability for aging 
pedestrians with high frequency hearing loss. A second peak frequency 
component between 2000 and 5000 Hz would provide detectability for 
pedestrians with normal hearing. Nissan also suggested that the 
required frequency content of alert sounds at around 1000 Hz (the 
typical frequency for road traffic noise) should be reduced to avoid 
additional contribution to traffic noise.
    Porsche stated that the specified levels in the NHTSA proposal will 
lead to very loud and unpleasant alert sounds. They suggested 
specifying at least two bands, but allowing up to eight bands. Porsche 
explained that the levels to be met should be a function of the number 
of bands selected. They explained that if more bands are used, the 
levels per band can be lower to achieve the same detectability. They 
suggested that, for example, if eight bands are used, then the levels 
in each band should be reduced by 6 dB (e.g., the agency's proposed 
minimum level of 43 dB(A) for the 500 Hz one-third octave band for the 
stationary condition would be reduced to 37 dB(A)), and if four bands 
are used, the levels in each band should be reduced by 4 dB.
    Toyota supported the use of an overall level and at least two one-
third octave bands, consistent with the Alliance/Global recommendation. 
Toyota provided results from a study that it conducted to confirm the 
detectability performance of the suggested approach. In that study, 33 
individuals (from 20 to 49 years old) participated. The ambient noise 
level varied from 51 to 59 dB(A).\117\ The test vehicle was a Toyota 
Prius V approaching at 20 km/h. The study indicated that the overall 
level of the test vehicle was 58 dB(A) with sound energy in multiple 
bands. The sound level in the 800 Hz and 2000 Hz bands were each 51 
dB(A), which accounted for nearly half of the sound's acoustic energy. 
Toyota reported that the measured detection distance exceeded the NHTSA 
target detection distance in the NPRM for this operating condition.
---------------------------------------------------------------------------

    \117\ The Toyota comment did not include details about the 
spectral shape of the ambient, which would be important to better 
understand the possible masking conditions and their impact on the 
test vehicle alert sound acoustic profile.
---------------------------------------------------------------------------

    OICA stated that the proposed specification for eight bands will 
force very loud devices with unpleasant sounds. They suggested that the 
sound specifications within the UNECE-GTR development group. They 
stated that NHTSA should consider requiring a specific number of tones 
which could be in the same one-third octave band, rather than requiring 
a specific number of one-third octave bands.\118\
---------------------------------------------------------------------------

    \118\ We note here that this suggestion could result in an alert 
signal with only one distinct component, for example, a single 
amplitude-modulated tone.
---------------------------------------------------------------------------

    The American Council of the Blind (ACB) stated that the most 
appropriate approach to the sound specifications would be to set the 
minimum sound level based on the levels produced by light ICE vehicles 
because this is the sound pedestrians currently use for safe 
navigation. ADB stated ``octave bands are not as great at predicting 
detection as overall sound levels'' based on research conducted by WMU. 
WMU stated that their research has shown that individual octave bands 
are not as useful in determining detection as is the overall sound 
level and that, while some regulatory direction in octave band make-up 
of alert sounds might be useful, there is limited justification for a 
requirement as restrictive as the NHTSA proposal. WMU stated that their 
previous research had shown a limited advantage for content in the 500 
Hz band in some situations, and their statistical analysis showed 
significant predictive value for overall sound pressure levels rather 
compared to content in any particular band. WMU also commented that 
detecting a single approaching vehicle may not be the same as detecting 
quiet vehicles when other vehicles are present. In response to the 
request for comments on requiring vehicles to emit sound that meets 
only the one-third octave band requirements for 2000 Hz and above as an 
alternative to meeting all eight one-third octave bands, WMU stated 
that for a pedestrian with hearing loss content at lower frequencies is 
needed and that potential sounds should have a fairly broadband 
frequency spectrum. WMU suggested that identifying two frequency bands 
that are most useful for detection, similar to Nissan's approach, may 
be appropriate.
    As mentioned above, NHTSA also received a joint letter, submitted 
to the docket and treated as a late comment, from the Alliance, Global, 
the NFB, and the ACB.\119\ These commenters agreed on several technical 
and policy issues. They stated that the number of bands should be 
reduced from a minimum of eight to at least two, between 160 Hz and 
either 3150 or 5000 Hz, and that at least one band should be below 
either 1000 or 1600 Hz. Within each individual frequency band, they 
stated that sound levels should be revised with input from available 
research. They also suggested establishing limits on overall sound 
pressure level, but did not provide specific values.
---------------------------------------------------------------------------

    \119\ NHTSA-2011-0148-0322
---------------------------------------------------------------------------

    The second main topic discussed by the commenters concerned the 
methods used by the agency to determine detection distances and 
associated sound specifications. Eleven of the commenters listed above 
provided comments on this topic.
    In their joint comment, the Alliance, Global, NFB and ACB agreed 
with the detection distance methodology in the NPRM and with the values 
used for the deceleration rate and the brake reaction time. The World 
Blind Union (WBU), the National Council of State Agencies for the Blind 
(NCSAB), the Disability and Communication Access Board, and the 
Insurance Institute for Highway Safety, all agreed that the methodology 
used by NHTSA to set the minimum sound levels seemed reasonable and 
appropriate. OICA stated that the NPRM approach to establish detection 
distance as a function of vehicle speed is reasonable but only when 
applied to the overall sound pressure level.
    Advocates for Highway and Auto Safety also generally agreed with 
specifications based on detection distance. They commented on the 
driver reaction time used in the detection distance computation and 
suggested that the 1.5 sec. used by NHTSA may be too short. They 
indicated that NHTSA should examine reaction times for drivers in 
relation to pedestrians and pedalcyclists in establishing this value.
    Accessible Design for the Blind (ADB) expressed support for the 
NPRM approach to minimum sound levels but questioned the detection 
distance used in NHTSA's analysis. ADB questioned

[[Page 90454]]

whether the detection distance used in NHTSA's formulation represents 
distances that are sufficient for pedestrians to detect, recognize, 
judge distance and trajectory, decide to initiate a crossing, and 
initiate a crossing, particularly at busy intersections. They also 
indicated that the specifications proposed in the NPRM are based on the 
detection of a single vehicle in the absence of other vehicles, which 
they believe is not realistic.
    WMU indicated that the detection distance used in the development 
of the sound specification may be too short because it may not 
correspond to the time needed to detect a vehicle, process the 
information, and decide to take action. WMU explained that the 
detection distance formula used does not account for variability among 
pedestrians including those with hearing loss.
    On the third issue about the range of frequencies used, the 
Alliance/Global, OICA and NFB provided comments. Alliance/Global said 
that one-third octave bands from 630 to 1600 Hz should not be excluded 
from the useable range as NHTSA did in the NPRM because ``these 
frequencies will clearly contribute to the detectability.'' OICA 
recommended that no sound be required above 2 kHz as they believe that 
is not representative of vehicle sounds. OICA stated that manufacturers 
should be allowed to use the range from 125 Hz to 3000 Hz and suggested 
that low frequencies could aid with detectability but may have cost 
implications. OICA recommended that low frequencies should be an option 
for manufacturers and if used, believe the regulatory scheme should 
give credit to manufacturers for using low frequencies.\120\ NFB stated 
that manufacturers should have flexibility to create sounds that are 
pleasant and not annoying to vehicle occupants and requested that the 
agency consider not requiring sound in the lowest one-third octave 
bands. NFB stated that manufacturers can limit the sound inside the 
vehicle and meet the safety need of pedestrians without including 
content in each of the eight proposed one-third octave bands.
---------------------------------------------------------------------------

    \120\ No explanation was provided by OICA about how or why 
vehicle manufacturers should be given credit for using low 
frequencies.
---------------------------------------------------------------------------

    The fourth main issue raised in comments relates to vehicle 
marketability. These comments are addressed in section III.I of this 
notice.
Agency Response to Comments
Detectability Model Conclusions
    After considering all comments received in response to the NPRM, 
and the results of agency research conducted since the NPRM was issued, 
we have decided to modify the proposed minimum specifications for 
detection of vehicles subject to this rule. While the number of one-
third octave bands for which the agency is establishing requirements 
for minimum content and the requirements related to detection of 
changes in vehicle speed differ from the NPRM, the underlying 
analytical framework on which the minimum acoustic requirements in the 
final are based has not changed. The minimum acoustic requirements for 
each one-third octave band in the final rule remain based on the same 
formula used to develop the requirements proposed in the NPRM albeit 
with slightly different inputs to that formula. Furthermore, the 
overall sound pressure level and one-third octave band levels of sounds 
meeting the requirements of the final rule will be similar to the 
corresponding levels of sounds meeting the eight one-third octave band 
requirements in the NPRM.
    After considering the comments and the agency's further evaluations 
conducted in response to comments, we decided to reduce the number of 
one-third octave bands for which we are requiring content from the 
eight one-third octave band requirement proposed in the NPRM to either 
a four one-third octave band compliance option or a two one-third 
octave band compliance option, the latter including an overall SPL 
specification.
    Under the four one-third octave band compliance option, the minimum 
sound requirements for each band would be slightly lower than the 
values proposed in the NPRM, and the overall sound pressure of sounds 
meeting the four one-third octave band compliance option will be 
similar to those meeting the proposed requirements for eight bands in 
the NPRM. Under the two one-third octave band compliance option, the 
minimum sound requirements for each band are lower than those in the 
eight one-third octave band proposal in the NPRM for the low and mid 
frequency bands and higher than the minimum values in the NPRM for the 
high frequency one-third octave bands centered at 4000 Hz and 5000 Hz.
    In the NPRM, NHTSA stated that it planned to conduct additional 
research once the NPRM was issued to validate the model used to develop 
the minimum sound requirements in the NPRM. The purpose of this 
research was to determine whether the model accurately predicted when 
sounds would be detected by human listeners at the distances predicted 
by the model.
    Volpe conducted a human factors study to quantify differences 
between predicted detection levels (as indicated by Moore's Partial 
Loudness model) of vehicle sounds in the presence of a standardized 
ambient used to calculate the minimum requirements proposed in the NPRM 
and actual responses of participants listening to these vehicle sounds 
through headphones.\121\ The study also evaluated the effect of several 
factors on detectability, including the number of one-third octave band 
components contained in a sound, adjacency of bands, and signal type 
(e.g., pure tones, bands of noise). Fifty-two demographically diverse 
subjects were exposed to a simulation of a vehicle passing by them (as 
a pedestrian) at 10 km/h, in ambient noise conditions of 55 dB(A). In 
the study, a selection of 24 different sound signals were played back 
over the participants' headphones. The signals were based on 
synthesized and recorded sources and included pure tones, single noise 
bands, multiple adjacent noise bands, multiple non-adjacent noise 
bands, tones mixed with noise, a signal based on a recorded ICE, and 
signals from prototype alert systems. Signals with various numbers of 
bands were included in the study, ranging from one to four non-adjacent 
bands and from one to twenty-four continuous or semi-continuous bands. 
With the exception of the ICE vehicle sound, the two recorded prototype 
alert signals, and the three two-band samples, all signals were 
calibrated to just meet the NPRM specifications for safe detection in 
each band with signal content.\122\
---------------------------------------------------------------------------

    \121\ Hastings A.; and McInnis, C. ``Detectability of Alert 
Signals for Hybrid and Electric Vehicles: Acoustic Modeling and 
Human Subjects Experiment,'' (2015) Washington, DC: DOT/NHTSA.
    \122\ The NPRM did not include specifications for the one-third 
octave bands from 630Hz-1600Hz. Some alert signals considered by 
Volpe during the human factors study did include one-third octave 
bands in this range. Volpe derived the appropriate level for those 
bands the same way the minimum levels for the bands included in the 
NPRM were developed. For details, refer to the Volpe research 
report, Hastings A.; and McInnis, C. (2015). ``Detectability of 
Alert Signals for Hybrid and Electric Vehicles: Acoustic Modeling 
and Human Subjects Experiment''. Washington, DC: DOT/NHTSA.
---------------------------------------------------------------------------

    The study results indicated that, except for frequency sensitivity 
of high frequency components, the modeling approach for determining the 
minimum level needed in each one-third octave band was conservative, 
meaning that the participants responded to signals

[[Page 90455]]

somewhat sooner on average than the model predicted. With an 
understanding that the model was conservative overall but less accurate 
at the higher frequencies, model adjustments were made as discussed in 
section II.C of this preamble to provide more accurate results 
necessary for development of the final minimum one-third octave band 
levels specified in this rule.
    Although not directly tested in the study, we found a general trend 
that the minimum one-third octave band levels as proposed in the NPRM 
could be reduced when increasing the number of one-third octave bands. 
We also found that using non-adjacent one-third octave bands instead of 
adjacent bands maintained the detectability of sounds more effectively 
while limiting the overall level. Consequently, we have incorporated 
non-adjacency as one of the specifications in the final rule alert 
requirements. We have decided not to adjust the minimum one-third 
octave band levels to account for the number of required bands because 
in this final rule we have reduced the number of required bands from 
eight bands to either two or four bands.
    The study results also indicate that sounds with minimum content in 
eight, four, and two one-third octave bands were all detected by study 
participants prior to the two-second time-to-vehicle arrival point 
necessary for safety.
    As discussed above, NHTSA received several comments from 
manufacturers and groups that represent manufacturers stating that 
agency should adopt the acoustic requirements with content in two one-
third octave bands plus a requirement for a minimum overall sound 
pressure level discussed in the NPRM. These commenters believed that 
NHTSA's goal in the NPRM of ensuring that sounds produced by hybrid and 
electric vehicles are detectable to pedestrians in a variety of 
ambients could be accomplished by requiring minimum acoustic content in 
two one-third octave bands. In response to these comments and the joint 
comment submitted by the Alliance, Global, NFB and ACB recommending 
that the agency require minimum content in only two bands, NHTSA 
decided to conduct additional analysis to determine the likelihood that 
sounds with content in fewer than eight bands would be masked in 
different ambient environments.
    The resulting analysis provided an estimate of how often a sound 
signal would be detected as a function of the number of one-third 
octave bands. Real-world ambient conditions are not consistent, and we 
wish to draw conclusions about detectability beyond the standardized 55 
dB(A) ambient used to create the proposed requirements in the NPRM. The 
ambient data used in this analysis was recorded at 17 locations along 
Centre Street in Newton, Massachusetts.\123\ Ambient samples were taken 
at intersections (signalized and stop-sign-controlled), one-way 
streets, side streets, and driveways. Samples had a mix of low, mid, 
and high frequencies. Some samples were dominated by low frequency 
content, i.e., the environment had other vehicles in close proximity 
operating at and/or accelerating from low speeds, while other samples 
were dominated by high frequency content, i.e., the environment had 
other vehicles in close proximity operating at higher constant speeds. 
Each ambient sample was normalized \124\ to an overall sound pressure 
level of 55 dB(A) without affecting the spectral variation. Volpe then 
used the adjusted acoustic model to test how signals with different 
numbers of components perform across this wide variety of ambient 
conditions. This approach of testing signals in varying ambient 
conditions but at a consistent overall level allowed us to determine 
the performance of signals as a function of the number of components in 
the signal. Specifically, this method provides a measure of 
``robustness'' of the signal which is the metric we use to gauge how 
likely it is that one or more of the signal components will be heard by 
pedestrians in a range of ambient conditions.
---------------------------------------------------------------------------

    \123\ Ambient data were collected in 2010 (Hastings, et al. 
2011). Walkthroughs were conducted with different orientation and 
mobility instructors; data were collected on different days of the 
week and time of day.
    \124\ Each ambient sample had to be normalized to an overall SPL 
of 55dB(A) to ensure a comparable analysis was conducted for 
detectability utilizing different numbers of one-third octave bands. 
As discussed in the NPRM and this final rule, a standardized 55dB(A) 
ambient was used to derive the minimum one-third octave band 
specifications. The ambient used also had a standardized one-third 
octave band frequency composition. To analyze the robustness of 
various alerts, the multiple ambients collected had various overall 
SPLs, either less than or greater than 55dB, and various frequency 
compositions. For a proper evaluation of the various ambients, each 
ambient's overall SPL had to be normalized, that is adjusted to 55 
dB, while maintaining each individual sample's unique frequency 
profile. To normalize each ambient sample, the sample was broken 
down into its one-third octave band levels and then each level was 
decreased or increased the same percentage until the overall level 
for that particular ambient sample equaled 55dB(A). For consistent 
comparisons of vehicle alert sounds in these different ambients, the 
key data was the frequency composition, or acoustic profile, across 
the one-third octave bands for each ambient collected.
---------------------------------------------------------------------------

    NHTSA's approach in evaluating various signals was to set the band 
levels for each component at the appropriate psychoacoustic thresholds 
according to the modified Moore's model after the model had been 
adjusted using the results of Volpe's human factors experiment. The 
adjusted acoustic model was used to measure the performance of signals 
having various numbers of frequency components from one up to seven 
one-third octave bands by evaluating how readily each signal was 
detected in the presence of a broad range of measured ambients 
normalized to the 55 dB(A) level.

[[Page 90456]]

[GRAPHIC] [TIFF OMITTED] TR14DE16.004

    Figure 2 shows the ``robustness'' \125\ of single and multiple one-
third octave band alert specifications, and includes up to seven bands 
because that is the maximum number that can be non-adjacent over the 
315 to 5000 Hz range. This analysis shows that, on average, signals 
with minimum content in four one-third octave bands can be detected in 
97 percent of ambient environments examined. This analysis also shows 
that sounds with content in only two one-third octave bands show strong 
resistance to masking if the minimum content is in certain bands. 
Additionally, this analysis shows that sounds with content in more than 
four one-third octave bands are only marginally more resistant to 
masking than sounds with four bands. Based on this analysis, NHTSA 
agrees with the commenters that the agency can accomplish the goals 
articulated in the NPRM of ensuring that sounds produced by EVs and HVs 
are detectable to pedestrians in a variety of ambients by requiring 
minimum content in fewer than eight one-third octave bands.
---------------------------------------------------------------------------

    \125\ We use the term ``robustness'' to indicate how resistant a 
signal is to masking by background noise from a wide selection of 
different normalized ambient conditions covering a range of spectral 
content.
---------------------------------------------------------------------------

    Given that the rationale for specifying minimum content in eight 
one-third octave bands in the NPRM was to ensure that sounds meeting 
the requirements of the NPRM were resistant to masking, NHTSA is 
reducing the number of bands in response to comments suggesting that 
requiring minimum content in eight one-third octave bands it not 
necessary for safety. As the latest NHTSA research demonstrated, 
reducing the number of bands with minimum requirements from eight to 
either four or two one-third octave bands would not impact the 
effectiveness of sounds meeting the minimum requirements of the final 
rule in providing alerts to pedestrians.
    We believe that the four-band requirements and the two-band 
requirements have equivalent performance in terms of detectability by 
pedestrians and will be equally detectable in a variety of different 
ambients.
    Under the four-band compliance option, the agency is requiring that 
the four bands used to meet the detectability requirements must be non-
adjacent one-third octave bands in the frequency range from 315 Hz to 
5000 Hz. This range includes the eight one-third octave bands for which 
we proposed requirements in the NPRM. In response to comments, NHTSA 
has decided that the final rule will also allow manufacturers to comply 
with the minimum acoustic requirements by placing acoustic content in 
the mid-range frequency bands excluded from the NPRM.
    In order to comply, the alert signal must meet or exceed the given 
levels in at least four non-adjacent bands for each given vehicle 
operating condition. Also, the four bands must span a range of at least 
nine one-third octave bands. NHTSA believes that the four one-third 
octave band compliance option achieves the goals articulated in the 
NPRM of ensuring that sounds meeting this standard are detectable in a 
variety of ambients and responds to comments submitted to the NPRM 
claiming that the requirements in the NPRM were too restrictive and 
would require unpleasant sounds.
    Because of the number of comments received on this issue, NHTSA 
also decided to explore allowing the two one-third octave band 
compliance option discussed in the NPRM. Under the two-band compliance 
option, minimum sound pressure levels are required in two non-adjacent 
one-third octave bands from 315 to 3150 Hz. One of the two bands must 
be below 1000 Hz and the second band must be at or above 1000 Hz. The 
two bands used must each meet the minimum requirements and together 
must also meet a specified overall SPL.
    By including both a four-band specification and a two-band 
specification in this final rule, NHTSA is providing vehicle 
manufacturers with the flexibility to choose either compliance option 
in the new safety

[[Page 90457]]

standard. We believe this approach adequately addresses a great 
majority of comments concerning the eight-band detectability 
specification proposed in the NPRM.
    In addition, based on the foregoing, we have implemented slight 
changes to the minimum one-third octave band levels as a result of our 
human factors testing and acoustic model adjustments discussed above. 
As explained, these slight changes provide better agreement between the 
modeled levels and the levels indicated by the responses of the 
experiment participants when listening to various signals (see Figure 
1) Table 13 provides the final rule minimum one-third octave band 
levels for each operating condition.\126\
---------------------------------------------------------------------------

    \126\ These levels are based on a single one-third octave band 
of noise producing a detectable signal assuming a threshold of 0.079 
sones per ERB for the maximum of the partial specific loudness which 
is the threshold value that provides the best fit between modeled 
detection times and those of the experiment participants. The 
adjustments account for model biasing for specific operating 
conditions, repeatability/reproducibility as discussed in section 
III.K of this final rule, and calculation rounding. For details see: 
Hastings A.; and McInnis, C. ``Detectability of Alert Signals for 
Hybrid and Electric Vehicles: Acoustic Modeling and Human Subjects 
Experiment,'' (2015) Washington, DC: DOT/NHTSA.

                             Table 13--Final Rule Minimum Sound Levels for Detection
----------------------------------------------------------------------------------------------------------------
  One-third octave band center
          frequency, Hz             Stationary        Reverse         10km/h          20 km/h         30 km/h
----------------------------------------------------------------------------------------------------------------
315.............................              39              42              45              52              56
400.............................              39              41              44              51              55
500.............................              40              43              46              52              57
630.............................              40              43              46              53              57
800.............................              41              44              47              53              58
1000............................              41              44              47              54              58
1250............................              42              45              48              54              59
1600............................              39              41              44              51              55
2000............................              39              42              45              51              55
2500............................              37              40              43              50              54
3150............................              34              37              40              47              51
4000............................              32              35              38              45              49
5000............................              31              33              36              43              47
Overall A-weighted SPL Range....           43-47           46-50           49-53           55-59           60-64
----------------------------------------------------------------------------------------------------------------

    The minimum one-third octave band requirements in the final rule 
for the eight one-third octave bands for which the agency proposed 
requirements in the NPRM are slightly lower than the values proposed in 
the NPRM for all test conditions. Alert signals just meeting these 
requirements are expected to have overall levels similar to sounds 
meeting the proposed requirements of the NPRM, ranging from 43 to 47 
dB(A) for stationary; 46 to 50 dB(A) for reverse; 49 to 53 dB(A) for 10 
km/h; 55 to 59 dB(A) for 20 km/h; and 60 to 64 dB(A) for 30 km/h.
    As proposed, our detectability requirements were set so that EVs 
and HVs are detectable in an ambient with a 55 dB(A) overall sound 
pressure level. It has been our understanding that pedestrians who are 
blind use sound for navigation in environments for which the ambient is 
at or below 55dB(A), and they rely on more than just sound when the 
ambient increases above that level.\127\ The NPRM explained that, in 
NHTSA's development of requirements for minimum vehicle sound levels, 
the agency chose to use a standardized ambient \128\ at a level of 55 
dB(A) as an alternative to recordings of actual traffic.\129\ Based 
partly on research conducted by Pedersen et al. 2011,\130\ NHTSA 
selected an ambient with a 55 dB(A) noise level and a specific spectral 
shape (see Figure 2, p. 2818 in the NPRM) that the Pedersen research 
had found to be representative of many common urban ambients. Because 
alert sounds that are detectable in the standardized 55 dB(A) ambient 
also would be detectable in ambients with similar spectral shapes and 
lower overall sound pressure levels, the 55 dB(A) standardized ambient 
was appropriate for detectability computations and was utilized 
throughout NHTSA's development of the minimum sound levels included in 
this final rule.
---------------------------------------------------------------------------

    \127\ In the NPRM we stated that we chose an ambient with a 55 
dB(A) overall sound pressure level because this represented a 
reasonable level below the 60 dB(A) ambient in which pedestrians 
would no longer be able to reasonably rely on hearing to detect 
approaching vehicles.
    \128\ The standardized ambient is a ``synthetic'' background 
noise consisting of white noise filtered to have the same spectrum 
as what a pedestrian would hear in real traffic but without the 
variations in amplitude over time. This synthetic noise is similar 
to actual traffic noise but is more consistent and repeatable and 
thus is better suited to the acoustic research that NHTSA conducted.
    \129\ The NPRM included a lengthy discussion of how masking of 
vehicle sounds by ambient noise (also called background noise) is a 
fundamental factor in developing minimum vehicle sound levels. For 
research purposes, background noise can come from recordings of 
actual traffic, but such recordings are likely to include random 
fluctuations or peaks from transient sources like the passage of 
nearby traffic, construction noise, or aircraft that introduce 
variability when conducting human factors testing or when applying 
detectability models.
    \130\ Pedersen, et al. (2011). White paper on external sounds 
for electric cars--Recommendations and guidelines.
---------------------------------------------------------------------------

    Our approach of using human subject responses to set detection 
thresholds indicates how quiet alert sounds can be before they can no 
longer be heard and ensures that the alert sound requirements in the 
final rule will have the least possible impact on overall environmental 
noise while still providing pedestrians with the vehicle sounds they 
need to navigate traffic situations.
    In this final rule, for the reasons discussed above, the agency has 
decided to reduce the eight one-third octave band requirement as 
proposed in the NPRM to a four one-third octave band requirement. The 
agency is requiring that the four bands used to meet the detectability 
requirements must be non-adjacent one-third octave bands in the 
frequency range from 315 Hz to 5000 Hz because the results of the human 
factors study suggests that signals with non-adjacent bands are more 
detectable than signals with adjacent bands. Also, these bands must 
span a range of at least nine one-third octave bands. This is 
consistent with comments made by Alliance/Global. Signal components in 
adjacent one-third octave bands can mask each other more effectively 
than signal components in non-adjacent one-third octave bands. Masking 
reduces the effectiveness of the alert signal. Further,

[[Page 90458]]

four components that span nine bands will be more widely spaced than 
four components in adjacent bands. This will increase the probability 
that pedestrians will be able to detect at least one signal component. 
This is especially true for pedestrians with age-related hearing loss. 
Signals in the mid-range one-third octave bands from 630 Hz to 1600 Hz, 
which are most strongly masked by the typical ambient conditions 
encountered by pedestrians, were excluded in the NPRM in an effort to 
reduce the overall level since components in this frequency range would 
need to be set at higher sound pressure levels. However, our decision 
to require only four bands in the final rule and to include those mid-
range frequencies provides manufacturers with more flexibility and 
addresses comments about the exclusion of those frequencies in the 
NPRM. In order to comply with the four one-third octave band compliance 
option, the alert signal must meet or exceed the given levels in at 
least four non-adjacent bands for a given operating condition. Figure 3 
provides an example of a four-band signal.
[GRAPHIC] [TIFF OMITTED] TR14DE16.005

    In response to commenters who believe that sounds meeting the NPRM 
requirements will be too loud and will contribute to increases in 
environmental noise, we believe that our human factors testing has 
confirmed our analysis in the NPRM that sounds produced by EVs and HVs 
need to have content meeting the minimum thresholds we have specified 
to ensure detectability. At the same time, the agency has determined in 
its Environmental Assessment that the impact of alerts meeting the 
requirements of this final rule are expected to be negligible.
    Several auto manufacturers also commented that sounds meeting the 
proposed requirements in the NPRM would intrude into vehicle interiors 
and be annoying to drivers. We believe that reducing the number of 
required bands and including frequencies from 630 Hz to 1600 Hz in the 
eligible range for compliance so that alert systems can utilize the 
entire range from 315 to 5000 Hz will provide manufacturers with the 
flexibility to design alert sounds that are non-intrusive and are 
acceptable to their customers.
Two One-Third Octave Band Compliance Option
    Because of the number of commenters stating that the agency should 
adopt final rule with minimum content requirements in two one-third 
octave bands, NHTSA decided to explore a two one-third octave band 
compliance option in addition to the four-band compliance option 
discussed above. As shown in Figure 2 above, the average detectability 
of a vehicle sound in the presence of a range of ambients starts to 
decrease if there are fewer than four one-third octave bands with 
content at threshold levels. However, Figure 2 also shows that some of 
the signals with fewer than four bands at threshold levels perform well 
above the average and do achieve a high degree of detectability in the 
range of ambients. For this reason we have determined that alert sounds 
with content in fewer than four one-third octave bands can be 
acceptable choices but need additional specifications to ensure that 
they are as detectable as signals with content in four or more bands.
    The two-band alternative that the agency is including in this rule 
closely matches the two-band approach suggested by commenters to the 
NPRM, but with a few important differences which are discussed below. 
By including both a four-band specification and a two-band 
specification in this final rule, NHTSA is providing vehicle 
manufacturers with the flexibility to choose either alternative for 
compliance with the new safety standard. In this section of today's 
preamble, we discuss how the agency concluded that a two-

[[Page 90459]]

band alternative is warranted and how we developed the two-band 
alternative using specifications suggested in NPRM comments.
    In their NPRM comments, Alliance/Global suggested an acoustic 
specification for HVs and EVs that consisted of a minimum overall sound 
level along with a minimum level in two one-third octave bands.\131\ 
The following were the particular levels they recommended:
---------------------------------------------------------------------------

    \131\ See docket NHTSA-2011-0148-0251, Alliance/Global comment, 
p. 5.

              Table 14--Levels Suggested by Alliance/Global
------------------------------------------------------------------------
                                                 A-weighted dB
                                     -----------------------------------
                                      Minimum level in     Overall SPL
                                       each of 2 Bands        level
------------------------------------------------------------------------
0 km/h, Reverse.....................                44                48
10 km/h.............................                46                53
20 km/h.............................                51                58
------------------------------------------------------------------------

    Two other criteria were part of Alliance/Global's suggested 
approach:

--That one of the two one-third octave bands should be in a frequency 
region below 1000 Hz and the other should be at or above 1000 Hz;
--That the two components of the signal should not be in adjacent one-
third octave bands.
    A number of other NPRM commenters, particularly vehicle 
manufacturers, endorsed the two-band approach as suggested by Alliance/
Global.
    In a follow-up letter submitted to the docket in February 2014 
(treated as a late NPRM comment) a group of commenters (Alliance, 
Global, the National Federation of the Blind, and the American Council 
of the Blind) expressed their agreement on recommending a general 
approach of specifying two bands with an overall SPL level. In that 
comment letter, the suggested parameters were somewhat less specific 
compared to the original Alliance/Global suggestion or the compliance 
option discussed in the NPRM. The letter provided no minimum band 
levels for the two bands and left undecided the upper limit frequency 
(either 3150 Hz or 5000 Hz) as well as the breakpoint between the low 
and the high frequency (either 1000 Hz or 1600 Hz). The joint 
commenters indicated that further refinement of the two-band approach 
to finalize the levels and the frequency ranges may be needed and 
should be based on discussion among interested parties. They stated 
that those discussions should take place in the QRTV working group 
responsible for developing the GTR.
    In developing the four-band approach that is included in today's 
final rule, NHTSA evaluated signals with different numbers of bands 
including signals with two bands. The details of that evaluation are 
discussed above and shown in Figure 2. As discussed, NHTSA's approach 
in evaluating various signals was to set the band levels for each 
component at the appropriate psychoacoustic thresholds according to 
Moore's model which was adjusted using the results of Volpe's human 
factors experiment. The adjusted acoustic model was used to analyze the 
performance of signals having various numbers of frequency components 
from one up to eight by predicting how readily each signal would be 
detected in the presence of the standardized 55 dB(A) ambient.
    As discussed previously, Figure 2 demonstrates the robustness of 
single-band and multiple-band alerts when each band is set at the 
minimum threshold levels for detection based on the acoustic model the 
agency used. We used this same robustness methodology to evaluate the 
Alliance/Global two-band approach. Because their suggested approach did 
not specify different levels for different frequency bands, there are 
limitless possibilities for two-band signals that would meet the 
Alliance/Global method. However, the range of possible signals just 
meeting the requirement can be categorized according to the following 
four signal type scenarios:
    (1) Scenario A: The level of the lower frequency band of the two 
bands is set at the suggested minimum, and the level of the higher 
frequency band is set such that the combination of the two bands meets 
the overall level (see Figure 4);
    (2) Scenario B: The level of the higher frequency band of the two 
bands is set at the suggested minimum level and the level of the lower 
frequency band is set such that the combination meets the overall level 
(similar to Figure 4);
    (3) Scenario C: The two bands both are set at the suggested minimum 
level, and there is low level content over many frequencies that on its 
own may not be audible but that, when combined with the two prominent 
bands, brings the signal up to the specified overall level (see Figure 
5);
    (4) Scenario D: The two bands are equal and their level is set such 
that the combination of the two bands meets the overall level (see 
Figure 6).

[[Page 90460]]

[GRAPHIC] [TIFF OMITTED] TR14DE16.006

[GRAPHIC] [TIFF OMITTED] TR14DE16.039

[[Page 90461]]

[GRAPHIC] [TIFF OMITTED] TR14DE16.007

    The range of all possible signals meeting the criteria will fall 
somewhere within these four signal types. For simplicity, we have 
considered these four types in our analysis. It is expected that the 
robustness of other signals will be within the range observed for these 
four types.
    The results of our robustness analysis of two-band signals meeting 
the Alliance/Global suggested method are shown in Figure 7. Two-band 
signals are plotted according to which of the four signal categories 
(Scenarios A, B, C, or D, above) they fall in, with averages indicated 
for each category. Again, this shows the percentage of times that each 
signal category would be detected in the normalized sampled ambient 
conditions. Note that three vehicle speeds plus stationary are 
indicated in Figure 7. In the suggested specifications provided in the 
Alliance/Global comment, the minimum band values increased with 
increasing speed but only enough to partially account for the increase 
in sound level needed to maintain adequate detection time over the 
whole speed range. Consequently, unlike in NHTSA's acoustic 
specifications, the performance of the Alliance/Global approach changes 
at higher speeds.
    From Figure 7 it can be seen that, at idle, two-band signals 
meeting the Alliance/Global approach are robust regardless of which 
type of signal is considered. However, as vehicle speed increases, 
robustness decreases. Figure 7 indicates that the robustness 
performance of certain two-band signals, particularly those in the 
Scenario C category, declines significantly to the point that, on 
average, they would be detected only about 35 percent of the time at 20 
km/h in the sampled ambient conditions.\132\
---------------------------------------------------------------------------

    \132\ Figure 7 includes values plotted at 30km/h. The data 
depicted at 30km/h is hypothetical data derived by VOLPE because 
Alliance/Global's suggested alert requirements went up to only 20km/
h.

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

[[Page 90462]]

[GRAPHIC] [TIFF OMITTED] TR14DE16.008

    This analysis led us to conclude that adopting the two-band 
Alliance/Global approach as it was suggested in their comments would 
allow some poor-performing alert signals to comply with the final rule. 
However, this analysis also led us to conclude that some two-band 
signals perform as well by our measures as the signals meeting the 
four-band requirements in this final rule, and that a two-band approach 
would be acceptable as long as it is specified in such a way as to 
exclude poor-performing two-band signals. Our analysis of two-band 
signals highlights two minor changes that we can make to modify the 
Alliance suggestion in order to increase robustness of two-band signals 
to that of the NHTSA four-band approach:
    (1) Instead of expressing the required sound level in terms of 
overall SPL, we can use a band sum that accounts only for the sound 
energy in the two required bands; this criterion would negate the 
possibility ability to augment the two bands with acoustic energy that 
may not be audible, i.e., that may not contribute to detectability and 
robustness.
    (2) We can adjust the required minimum band sum to achieve 
robustness equal to that of the four-band specification. This provides 
a high degree of flexibility in signal design. For example, a system 
designer can make the two components equal, or can set one component at 
the minimum level and compensate by setting the second component high 
enough to reach the required minimum band sum level.
    In order to optimize the Alliance/Global's suggested two-band 
approach using these modifications, the minimum band sum levels at each 
speed were iteratively determined. The results are shown in Table 15. 
We refer to this specification as an ``optimized'' two-band approach 
because it excludes two-band signals that have lower robustness (those 
signals that would be detectable in a lower number of ambients 
according to our analysis) while preserving the levels suggested by the 
Alliance/Global to the greatest extent possible.

             Table 15--Optimized Levels for Two-Band Signals
------------------------------------------------------------------------
                                                 A-weighted dB
                                     -----------------------------------
                                      Minimum level in   Band sum of the
                                       each of 2 bands       2 bands
------------------------------------------------------------------------
0 km/h..............................                44                48
10 km/h.............................                46                55
20 km/h.............................                51                61
30 km/h.............................                56                66
------------------------------------------------------------------------

    Figure 8 shows the robustness performance of two-band signals that 
meet this optimized approach. Note that there now are three sound 
scenarios (A, B, and D) instead of the four discussed in Figure 7. 
Scenario C that used broadband content to enhance the two bands is no 
longer viable under the optimized approach. It can be seen that all 
two-band combinations meeting the optimized criteria will now be 
detectable in upwards of 97 percent of the normalized sampled ambient 
conditions and, on average, they reach

[[Page 90463]]

at least the level of robustness achieved by the four-band approach.
[GRAPHIC] [TIFF OMITTED] TR14DE16.009

    Also note that the optimized specification includes levels for 30 
km/h because, as discussed in the crossover speed section of today's 
final rule (Section III.D), the agency has decided to include acoustic 
requirements for vehicle speeds up to 30 km/h.
    The overall levels for both the optimized two-band specification 
and the four-band specification (``S4 Bands'') are summarized in Table 
16. For comparison, Table 16 also shows the levels suggested in the 
Alliance/Global comment. It can be seen that for each overall SPL value 
given for the optimized two-band approach, the level is within the 
ranges for the four-band specification.

                                  Table 16--Overall Levels of Three Approaches
----------------------------------------------------------------------------------------------------------------
                                                              Minimum level, dB(A) *
                                 -------------------------------------------------------------------------------
                                    Stationary        Reverse         10 km/h         20 km/h         30 km/h
----------------------------------------------------------------------------------------------------------------
S4 Bands **.....................           47-50           49-53           52-56           59-62           63-67
Alliance/Global.................              48              48              53              58              NA
Optimized 2-band................              48          *** 52              55              61              66
----------------------------------------------------------------------------------------------------------------
* Based on Partial Specific Loudness Threshold = 0.079 sones/ERB.
** Overall SPL depends on which four bands are selected.
*** SPL for 10 km/h with 3 dB subtracted.

    For the Reverse specifications, the Alliance/Global comment set the 
band minimum levels and the overall level equal to the corresponding 
levels for the stationary operating condition. In the optimized two-
band specification, to be consistent with the four-band approach and 
the method used in the NPRM, we are setting the band minimum and 
overall SPL by subtracting 3 dB from the level required at 10 km/h. 
That method is the same one NHTSA employed in the NPRM to set the 
levels for Reverse. For the band minimum, subtracting 3 dB from the 10 
km/h level yields a value that is about the same as the band minimum 
the Alliance/Global suggested for Reverse, so the value we are adopting 
is the same as the one they suggested. For the overall level, 
subtracting 3 dB from the 10 km/h level yields a value for band sum 
that is somewhat higher than the overall SPL for Reverse suggested in 
Alliance/Global's comment, as shown in Table 16. To be consistent with 
the 4-band requirements and the method used in the NPRM to set Reverse 
requirements, we are using the higher value. This will account for the 
fact that sound level for Reverse operation needs to be higher than 
sound level in the Stationary condition, as explained in Section III.C 
of this preamble.
    The modifications we have discussed to make two-band signals as 
robust as four-band signals will not make the two-band and four-band 
options the same in all respects. For example, the four-band option is 
somewhat less restrictive because the minimum levels for the one-third 
octave bands are lower than the

[[Page 90464]]

levels required with the two-band option. Also, the two-band approach 
is more likely to result in a signal that has an individual component 
that exceeds minimum detection thresholds in a particular band due to 
the need to meet the overall SPL requirement, which would make that 
component relatively prominent. We note that this does not mean that 
environmental noise will be increased because, as shown in Table 16, 
the band sum levels for the two-band approach are lower at all speeds 
than the overall sound pressure levels that can be reached by alerts 
meeting the four-band approach. As discussed in Section V.D of today's 
final rule, our environmental assessment indicates that neither the 
two-band nor four-band approach would have significant environmental 
noise impact.
    In summary, we have decided that including both compliance options 
in this final rule allows manufacturers the flexibility to choose the 
approach that best suits their design goals, while accomplishing the 
agency's goals in the NPRM by providing a robustly detectable signal 
for pedestrians without significant environmental impact. The detection 
requirements for compliance of alert systems designed to meet the four-
band and two-band specifications are given in the regulatory text of 
today's final rule.
Overall Sound Pressure Level
    In the NPRM, the agency specified alert requirements at the one-
third octave band level and not at the overall sound pressure level. 
NHTSA's position was that the overall sound level may be sufficient for 
ICEs, which intrinsically produce sound over a broad range of 
frequencies at all speeds and have acoustic characteristics such as 
modulation that enhance detectability, but not sufficient for 
inherently quiet vehicles operating solely on electric motors at low 
speeds. The agency continues to believe that one-third octave band 
requirements assure that a vehicle's total sound is detectable by a 
broad range of pedestrians over many ambient conditions.
    ADB commented that, ``octave bands are not as great at predicting 
detection as overall sound levels'' based on research conducted by WMU. 
WMU stated that its research has shown that individual octave bands are 
not as useful in determining detection as is the overall sound level. 
WMU stated that while some regulatory specification in octave band 
make-up of alert sounds might be useful, there is limited justification 
for such a restrictive requirement. WMU also stated that a pedestrian 
with hearing loss would need to have available content at lower 
frequencies and that any potential sound should have a fairly broad 
frequency spectrum. WMU suggested that identifying two frequency bands 
that are most useful for detection, similar to Nissan's approach, may 
be appropriate.
    The agency has reviewed the research cited by ADB and conducted by 
WMU on the correlation between overall sound pressure level and 
detectability. While this research does show that overall sound level 
had a good correlation with detectability, it does not appear that it 
addressed whether specifying levels in multiple octave bands influences 
the detectability outcome. The agency does not believe that the cited 
studies adequately support the proposition that overall sound pressure 
level is a better metric than one-third octave band sound pressure 
level. Furthermore, the WMU comments about specifying low frequencies 
to assist with hearing loss, and about requiring a broad frequency 
spectrum, and also that specifying two frequency bands may be 
appropriate, implies that they did not conclude that an overall 
specification by itself necessarily would be sufficient.
    During the course of developing FMVSS No. 141, the agency has 
carefully considered overall sound pressure levels and corresponding 
individual one-third octave band sound pressure levels. The agency 
agrees that there can be a strong correlation between overall sound 
pressure level and detectability. However, we also believe that 
regulating only the overall sound pressure level leaves open the 
possibility of alert signals that may be undetectable in many common 
situations. Agency research indicates that alert sounds with the same 
overall sound pressure level often do not provide the same degree of 
detectability or robustness. This topic is discussed in sections that 
follow in this preamble where we identify how the agency derived the 
two compliance options specified in this final rule. Through our 
research, the agency has determined that for an alert signal to be as 
``robust'' as possible, i.e. for a signal to be heard by the most 
diverse range of pedestrians across the widest range of ambient 
conditions, specific combinations of one-third octave bands in 
different frequencies must be included in the requirements of the final 
rule. The requirements for one-third octave bands at various 
frequencies contribute to the overall sound pressure level of the sound 
emitted by the vehicle. Conversely, the agency maintains that minimum 
one-third octave band sound levels are essential to establish minimum 
requirements for detection, and that specifying overall sound pressure 
level alone would not be an acceptable approach for this final rule.
Stopping Distance
    Many of the commenters agreed with the agency's approach for using 
stopping distance for determining detectability requirements. Two of 
the commenters, however, ADB and WMU, questioned the distance 
calculated and used. ADB and WMU questioned whether the detection 
distances used are sufficient for pedestrians to detect, recognize, 
judge distance and trajectory, decide to initiate a crossing, and 
initiate a crossing, particularly at busy intersections. WMU explained 
that the detection distance formula used does not account for 
variability among pedestrians including those with hearing loss.
    After considering the ADB and WMU comments, we have decided to 
continue to follow the approach used in the NPRM where we derived 
stopping distance using a driver reaction time of 1.5 seconds and a 
deceleration rate of 5.4 m/s\2\. The agency's main premise for the 
calculation of the time that should be allowed for detection of 
approaching vehicles was the total vehicle stopping distance needed to 
avoid pedestrian collisions. While the pedestrian's reaction time is 
important, as is providing as much time as possible for pedestrians to 
make crossing decisions, the critical factor is that the pedestrian 
should hear the alert of an approaching vehicle no later than the time 
and distance the driver would need in order to react and stop the 
vehicle before colliding with the pedestrian.
    Furthermore, the alert requirements specified in the final rule 
include a small safety margin that will extend the timing and distance 
for both the driver and the pedestrian. As discussed previously, the 
minimum one-third octave band levels derived for detectability were 
increased by 0.5 dB and rounded up to the closest whole decibel. Also, 
because our minimum requirements are based on the levels needed to 
detect a signal having content in a single one-third octave band, our 
requirement that signals must include multiple one-third octave bands 
provides an additional margin of safety. We believe that requiring EVs 
and HVs to produce sounds with content in multiple one-third octave 
bands will provide an additional safety margin of time and distance due 
to the increased overall sound pressure level resulting from the 
combination of one-third octave bands. In addition, the

[[Page 90465]]

specifications in this final rule are minimum levels for compliance. 
Vehicle manufacturers are likely to exceed the minimums by some amount 
in order to provide themselves with a margin of compliance. We believe 
these factors address concerns that the reaction time the agency used 
was insufficient.

F. Acoustic Parameters for Recognition of Motor Vehicles

    In the NPRM, we stated that recognition includes two aspects: 
Recognition that the sound is emanating from a motor vehicle that may 
pose a safety risk to the pedestrian, and recognition of the vehicle's 
operating mode (acceleration, deceleration, constant speed, reverse or 
stationary but activated) so that the pedestrian can take appropriate 
measures to avoid a collision with the vehicle. The acoustic 
specification in the NPRM contained acoustic characteristics similar to 
the sounds that pedestrians associate with current ICE vehicles.
    Based on our initial assessment of simulated sounds and engineering 
judgment, the agency determined in the NPRM that the sound emitted by 
the vehicle to meet the detection requirements must contain at least 
one tone. A component is defined as a tone if the total sound level in 
a critical band centered about the tone is 6 dB greater than the noise 
level in the band.\133\ In the NPRM, we proposed requiring the sound 
emitted by the vehicle to have at least one tone at a frequency no 
higher than 400 Hz. The agency also proposed that the sound emitted by 
the vehicle must have content in each one-third octave band from 160 Hz 
to 5000 Hz.
---------------------------------------------------------------------------

    \133\ The agency explained that a component is considered to be 
a tone if the Tone-to-Noise ratio according to ANSI S1.13-1995\73\ 
is greater than or equal to 6 dB.
---------------------------------------------------------------------------

    Simulated sounds in the initial assessment were developed for the 
stationary but activated, constant speed pass-by, and accelerating 
pass-by conditions. Pass-by sounds included Doppler shifts (changes in 
frequency by a source moving relative to an observer) and simulated 
acceleration (a pitch or frequency shifting tied to a change in vehicle 
speed.) The sound pressure level changed as a function of speed and as 
a function of position relative to the microphone receiver during the 
pass-by simulations. During the original development of criteria for 
recognition, we stated that an alert signal should sound like an ICE in 
order to be recognizable. In order to identify qualities of the ICE 
vehicle, ICE sounds were evaluated in the quiet ambient conditions 
present during the recordings,134 135 which allowed low-
frequency combustion related tones and wide range broadband content 
\136\ to be audible.
---------------------------------------------------------------------------

    \134\ 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.
    \135\ Hastings, A., Pollard, J. K., Garay-Vega, L., Stearns, M. 
D., & Guthy, C. (October, 2011). Quieter Cars and the Safety of 
Blind Pedestrians, Phase 2: Development of Potential Specifications 
for Vehicle Countermeasure Sounds. DOT HS 811 496. Washington, DC: 
National Highway Traffic Safety Administration.
    \136\ Broadband content is content over a wide frequency range 
that could be spectrally continuous or periodic. Periodic content 
can be generated by engine combustion related harmonics or by 
periodic tire/pavement interactions, such as caused by transversely 
tined pavement. Continuous content can be generated by turbulence at 
the engine intake and exhaust ports, by non-periodically tined fan 
blades as well as by aerodynamic noise and random tire/pavement 
interactions.
---------------------------------------------------------------------------

    The agency sought comments on the following topics related to the 
proposed recognition requirements:
     Suggestions for the minimum sound level of low frequency 
content that should be included in the agency's recognition 
requirements;
     Information as to whether speakers that manufacturers may 
wish to use to meet the requirements of the proposal are capable of 
producing any measurable content in the 160 Hz one-third octave band; 
and
     Information about the cost of a speaker system that is 
able to reproduce some measurable content at the 160 Hz one-third 
octave band versus the cost of a speaker system that is only capable of 
producing sound above 315 Hz.
    The Agency received comments from Alliance/Global; SAE; OICA; 
Honda; Nissan; Porsche; Mercedes; Denso; National Federation for the 
Blind; Western Michigan University; Accessible Design for the Blind; 
The Seeing Eye, Inc.
    According to Alliance/Global, bands below 500 Hz should not be 
required. They stated that these bands are not necessary for 
recognition and will add significant cost to the alert sound system. 
Alliance/Global also stated that isolating and measuring low frequency 
content under outdoor test conditions would be impracticable. Alliance/
Global stated that prescribing an objective definition to 
recognizability using one-third octave bands is not possible because 
there are many ways to provide sounds that have similar acoustic 
characteristics. Finally, they do not recommend one-third octave band 
requirements in the 160 Hz band because existing speakers that are 
practical for alert systems cannot emit sound which contains 
frequencies as low as 160 Hz.
    OICA stated that a tone that is pitched would simulate the sound of 
a machine and this in combination with the tire/road noise would be 
enough to recognize the sound as coming from a vehicle. They also 
stated that broadband band should not be required.
    SAE indicated that the metric used to define `tone' (ANSI S1.13--
1995), in the proposed regulatory text, is not robust to all possible 
sound designs and would explicitly exclude sound characteristics 
identified as contributing to detection and recognition in the 
preamble.
    Ford stated that it conducted a study to examine recognition of a 
given sound as the sound of a motor vehicle. The study consisted of a 
human factors test in which audio recordings of vehicle sounds were 
presented to participants using headphones. Participants were asked to 
assess how recognizable the sounds were in the presence of background 
noise. The study included 24 Ford employees and 4 blind individuals. 
Sounds tested included an ICE vehicle, a vehicle without an alert 
sound, and three alert sounds. Two tests were completed; recognition of 
a stationary sound and recognition of a 10 km/h pass-by. Additional 
tests were conducted to examine recognition of the sound as an object 
to avoid. Ford concluded that adding motion to the sound (pass-by vs. 
stationary) increased recognition as either a motor vehicle or an 
object to avoid. They also explained that it is not necessary to meet 
all proposed minimum levels in the 315 Hz, 400 Hz, and 500 Hz one-third 
octave bands for vehicles or alert sounds to be recognized as motor 
vehicles.
    Honda indicated that the generation of low frequency sound is 
technically challenging, creates extra cost, and adds weight to the 
vehicle. Honda explained that the sound entering into the passenger 
compartment could be significant, which could cause annoyance. Honda 
suggested that this would require testing and an iterative design 
process to minimize negative effects.
    Nissan stated that low frequency content alone will not ensure that 
a sound is recognized as a motor vehicle. Nissan suggested that 
requiring frequency content in this region means that either broadband 
or narrowband content (e.g. tones) could be used, which would sound 
quite different than an ICE.
    Mercedes indicated that the proposed specification is restricting 
manufacturers flexibility to produce alert sounds for EVs and HVs that 
are effective yet pleasant to consumers and

[[Page 90466]]

expressed concerns about potential impacts to market penetration. 
Mercedes explained that low one-third octave frequency bands down to 
315 Hz and broadband content down to 160 Hz are difficult to isolate 
inside the vehicle cabin and this may result in adding vehicle weight 
due to added insulation. Mercedes also mentioned that a speaker would 
need to increase in size in order to accommodate the proposed lower 
frequency requirements.
    Porsche mentioned that pitch shifting is the most important factor 
to characterize motor vehicles. Porsche suggested that the number of 
frequencies and the frequency range be kept flexible. Porsche also 
indicated that broadband sound should not be required. Porsche stated 
that all sounds emitted by a vehicle are based on tones while broadband 
sound comes from tire noise. Porsche also explained that broadband 
sounds would require different devices and cannot be generated by the 
prototype control modules currently used by Porsche.
    Denso requested clarification of the definition of the terms 
``tone'' and ``critical band.'' Denso also mentioned that the agency 
did not identify sound pressure levels for the broadband requirement in 
the NPRM. Denso stated that the broadband requirement may not be as 
effective for recognition and localizability because the sound emitted 
by the vehicle speaker system may be masked by ambient sound if no 
sound level for the broadband content is specified.
    NFB stated that recognition requirements were included in the PSEA 
to prevent excessive customization. They stated that the inclusion of 
pitch shifting will potentially be sufficient to insure recognition.
    WMU indicated that the inclusion of tones is unlikely to enhance 
recognition because tones are readily masked by sounds in the 
environment, especially by sound from other vehicles. WMU also 
indicated that many blind pedestrians would not detect sound energy 
above 2000 Hz, especially those with hearing loss; therefore, this is 
not a reliable way to enhance recognition. WMU indicated that rhythmic, 
cyclic aspect of a sound would enhance recognition. In terms of speaker 
capabilities, they suggested that the cost of using speakers capable of 
producing sound energy in the 160 Hz range is not balanced by 
additional benefits. They explained that their studies have not found 
this low range to be useful for detection and noted that tones can be 
annoying.
    Comments from the Accessible Design for the Blind (ADB) are 
consistent with WMU. ADB indicated that tones are masked by the ambient 
and that most people find tones to be annoying. ADB stated that added 
sound should be the same for all EVs and HVs. ADB explained that this 
would help with recognition and prompt interpretation of the sound as 
the sound of a vehicle. In response to the request for comments about 
the minimum levels of low frequency content that should be included for 
recognition, ADB stated that they are not aware of any research that 
supports the notion that adding low frequency content makes sounds more 
recognizable.
    The Seeing Eye, Inc., stated that, for recognition purposes, it is 
important that all vehicles regardless of manufacturer, emit the same 
standardized sound.
Agency Response to Comments
    After reviewing the comments and conducting additional research, we 
have decided to remove the requirements in paragraph S5.2 of the NPRM 
requiring EVs and HVs to produce sound that includes broadband content 
and low frequency tones. We believe these acoustic characteristics are 
not necessary for pedestrians to recognize artificial sounds produced 
by EVs and HVs as coming from a motor vehicle in operation.
    During the agency's initial work to develop criteria for 
recognition, the agency assumed that an alert signal should sound like 
an ICE in order to be recognizable. In order to identify qualities of 
the ICE vehicle, ICE sounds were evaluated in the quiet ambient 
conditions present during the recordings \137\ which allowed low-
frequency combustion related tones to be audible. These low frequency 
tones make up part of the sound of a typical ICE vehicle at low speeds 
in quiet ambients. However, these low frequency tones are masked in 
many ambient conditions, and in particular the 55 dB(A) ambient used 
for determining the minimum sound requirements described in the 
NPRM.\138\ In such cases pedestrians would need to use other cues to 
recognize a vehicle (ICE or otherwise), such as the location of the 
sound source (e.g. on the street at a stop light), the frequency and 
level changes caused by sound source motion (e.g. on the street 
approaching or passing the pedestrian), etc.
---------------------------------------------------------------------------

    \137\ 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.; see also Hastings, A. et al. 
(2011). Quieter Cars and the Safety of Blind Pedestrians, Phase 2: 
Development of Potential Specifications for Vehicle Countermeasure 
Sounds. DOT HS 811 496. Washington, DC: National Highway Traffic 
Safety Administration.
    \138\ OICA measured stationary but activated levels are 
presented in Table 29 of the Phase III report. Comparing these data 
with the associated minimum threshold levels described in the NPRM, 
it can be seen that for most vehicles in Table 29 many of the 
measured vehicle one-third octave band levels are below the computed 
thresholds for the 55 dB(A) ambient used in the NPRM. Thus these 
components would not be reliably detectable in such an ambient.
---------------------------------------------------------------------------

    A recent study by NHTSA examined several alert signals in the 
presence of a 55 dB(A) ambient for a vehicle traveling at 10 km/h.\139\ 
The signals included simulations based on recorded vehicles, tones, and 
noise components over a frequency range from 315 to 5000 Hz. Some 
signals had only a single component, e.g. a tone or a noise at 315, 630 
or 2500 Hz, or multiple components, e.g. low frequencies (315 to 500 
Hz), high frequencies (2000 to 5000 Hz), or components matching the 
NPRM frequencies. Participants were asked to indicate when they heard a 
sound that would influence their decision to cross a street. The study 
provides a practical indication of a pedestrians ability to recognize 
sounds emitted by HVs and EVs as motor vehicle sounds since recognition 
is required in order to respond to the detected signal in the form of 
making a decision regarding whether it is safe to cross a street.
---------------------------------------------------------------------------

    \139\ Hastings A.; and McInnis, Catherine. ``Detectability of 
Alert Signals for Hybrid and Electric Vehicles: Acoustic Modeling 
and Human Subjects Experiment'' (2015) Washington, DC: DOT/NHTSA.
---------------------------------------------------------------------------

    All alert signals tested (with the exception of one signal that had 
levels below NPRM values) were detected and recognized on average by 
the minimum safe detection time of 2.0 seconds or greater. These 
results are consistent with comments by the Alliance/Global and with 
the study submitted by Ford. Based on these results, it appears that 
vehicle recognition cued by an alert signal in the presence of a 
ambient at 55 dB(A), which is the target ambient for detection, does 
not require that the alert signal contain low frequency tones. Because 
low frequency tones are not necessary for pedestrians to recognize 
sounds as vehicles sounds, could also add cost to the system, and may 
be annoying when not masked by the ambient, the agency is not including 
a requirement for low frequency tones in the final rule.
    Similarly, the agency study showed that participants detected and 
recognized alert signals with a wide

[[Page 90467]]

range of sound characteristics including signals that do not include 
broadband content over the entire range from 160 Hz to 5000 Hz. For 
example, several signals in the study consisted of only a single pure 
tone or a single one-third octave band of noise and were detected and 
recognized at a safe distance provided the component met minimum levels 
as determined by the detection model. Based on these results, it 
appears that vehicle recognition cued by an alert signal in the 
presence of a 55 dB(A) ambient does not require broadband content in 
all one-third octave bands from 160 Hz to 5000 Hz. Given the potential 
costs associated with meeting the low frequency requirements of such 
broadband content and the fact that signals meeting the detection 
criteria are safely detectable, the agency is not including a broadband 
content requirement in the final rule specification.
    Overall, the agency believes that pedestrians would use other cues 
to recognize a vehicle (ICE or otherwise), such as the location of the 
sound source (e.g. on the street at a stop light), and the frequency 
and level changes caused by sound source motion (e.g. on the street 
approaching or passing the pedestrian), etc. (See Section III.G on 
`Frequency (Pitch) Shifting and Volume Change').

G. Frequency (Pitch) Shifting and Volume Change

    The NPRM contained a requirement for frequency shifting which gives 
the pedestrian information about the acceleration or deceleration of an 
approaching vehicle. The PSEA required NHTSA to include sounds to alert 
pedestrians to acceleration and deceleration. As discussed in the NPRM, 
this information is important to the pedestrian in making a decision 
about whether or not to cross in front of a vehicle. The driver of an 
accelerating vehicle probably does not intend to stop and, according to 
the NPRM, ``the sound of accelerating vehicles in the parallel street 
indicates, for example, that the perpendicular traffic does not have 
the right of way and thus a crossing opportunity is available''. A 
decelerating vehicle on a path parallel to the pedestrian may be 
slowing to make a turn into the pedestrian's path if she or he were to 
cross the street.
    The proposal required that the fundamental frequency of the sound 
emitted by the vehicle increase with speed by at least one percent per 
km/h between 0 and 30 km/h (18.6 mph). The NPRM did not include a test 
procedure associated with this requirement but stated that frequency 
shifting could be verified by comparing the fundamental frequency from 
the compliance tests at stationary, 10 km/h (6.2 mph), 20 km/h (12.4 
mph), and 30 km/h (18.6 mph). The NPRM provided a definition for the 
fundamental frequency but did not specify how the fundamental 
frequencies at each vehicle speed should be compared.
    As mentioned, the agency did not include a separate acoustic 
measurement procedure for frequency shifting in the NPRM, instead 
relying on other requirements specified and the increase in overall 
sound level as the vehicle increases speed (or the decrease in sound 
level as the vehicle decelerates) to provide enough information so that 
pedestrians will be able to determine when EVs and HVs are accelerating 
and decelerating. One reason why a separate acoustic measurement 
procedure was not included was due to the concerns about the 
feasibility of testing. The agency stated that it would be difficult 
for even an experienced test driver to repeatedly achieve and maintain 
a specific rate of acceleration or deceleration on a test track if such 
a test was required. Given the difficulty of ensuring a repeatable 
acoustic test for acceleration and the fact that information about 
changes in vehicle speed could be provided by varying sound pressure 
levels, NHTSA determined that the test procedure did not need to 
include a dynamic test for acceleration or deceleration.
    The NPRM explained that manufacturers and their representatives, in 
meetings with NHTSA staff, expressed concerns that it is difficult to 
measure the change in frequency of a sound produced by a vehicle by 
measuring a complete vehicle during a pass-by test. Manufacturers 
requested that the agency measure frequency shifting using a component-
level test, meaning that the alert system hardware is removed from the 
vehicle and tested as a separate unit.
    In the NPRM, we said that we were hesitant to include a component-
level test because we wanted the standard to be technology neutral and 
because we do not wish to limit technological innovation. As further 
explained, the agency was aware that manufacturers might use different 
technologies to comply with the standard, so defining the hardware 
components subject to the component-level test could prove difficult. 
The agency sought comment on including a component-level test to 
measure frequency shifting in the test procedure.
    In the NPRM, the agency said that the proposed method for measuring 
frequency shifting depends on the presence of a strong tone in the 
sound. A tone is an acoustic component with well-defined features that 
make it relatively easy to recognize compared to noise. The pitch, or 
frequency, of an alert sound could be verified by tracking this tone as 
it increases in frequency for each pass-by test as the vehicle 
increases speed. In the proposal, we said it would be difficult to 
verify a sound's increase in frequency if the sound does not have any 
strong tones. We mentioned our concerns about identifying the tone of a 
sound and tracking this tone as the vehicle increases speed. The NPRM 
mentioned that we planned to conduct further research on this issue. We 
explained that if it was not possible to identify a tone to track in 
order to verify the increase in a sound's frequency, we may have to use 
a different method to verify the increase. The agency sought comments 
on this issue.
    The agency received comments on frequency shifting from SAE, 
Alliance/Global, OICA, and Porsche. The agency also separately received 
a joint comment submitted by the Alliance, Global, the American Council 
of the Blind (ACB), and the National Federation of the Blind (NFB).
    Several commenters stated that the NPRM did not include a test 
procedure to measure compliance with the proposed frequency shifting 
requirements. These commenters recommended that the agency use the 
frequency shift procedures specified in SAE J2889-1 to measure 
compliance with the frequency shifting requirements and that the agency 
allow indoor testing or component level testing to measure frequency 
shifting.
    SAE commented that use of indoor facilities for the measurement of 
the frequency shift is necessary to obtain accurate results. SAE said 
that provisions for indoor measurement either at a component level or a 
simulated full-vehicle level are included in SAEJ2889-1 (May 2012). SAE 
also mentioned that in a December 2012 meeting with NHTSA, an 
alternative method of analysis was under investigation to eliminate the 
need for prior knowledge of the signal.
    Alliance/Global mentioned that tonal tracking for frequency 
shifting becomes quite difficult at higher speeds (30 km/h) due the 
tire noise masking, particularly when testing outdoors. Alliance/Global 
stated they prefer an indoor component level test because they think 
that is the best way to ensure that the correct tones are being tracked 
and that noise from tires (at higher speeds), accessory equipment, or 
other sounds not intended for pedestrian safety, are not incorrectly 
counted

[[Page 90468]]

toward the sound measurement. Alliance/Global indicated that they are 
not aware of a procedure that can identify these tones during whole-
vehicle testing.
    OICA suggested that NHTSA change the definition of ``fundamental 
frequency'' in S4 to read, ``[Frequency] shift frequency means, for 
purposes of this regulation, any frequency or frequencies used to 
comply with S5.1.6.''
    OICA suggested requiring that the frequency of the sound shift 
frequency within each individual gear ratio rather than over the entire 
range of speeds between 0 and 30 km/h. OICA stated that this will allow 
for the simulation of an ICE vehicle using different gear ratios within 
the tested speed range. Furthermore, OICA indicated that there might be 
various ways to determine the frequency tone and rate and suggested 
that NHTSA leave the way to measure it to the individual manufacturer. 
OICA indicated that there is no known method to identify the proper 
tone in all situations without specifying the tone in advance. OICA 
stated that information about the signal under evaluation will be 
necessary.
    Porsche made reference to the signal processing requirements in SAE 
J2889-1 (7.2.3) and stated ``The fundamental frequency is dependent on 
the setup of the analysis system and is typically less than two 
Hertz.'' Porsche also suggested that NHTSA change the definition of 
fundamental frequency in S4 to read . . . ``S4 Fundamental frequency 
means, for purposes of this regulation, any prominent frequency of a 
valid measurement taken in S7.''
    In the joint comment submitted by Alliance/Global/NFB/ACB, those 
commenters agreed that at least one frequency emitted by the vehicle 
must vary with speed by at least an average of one percent per mph over 
the range from 5 mph to the crossover speed. They indicated that this 
frequency may also contribute to meeting the spectral and overall sound 
pressure level requirements.
Agency Response to Comments
    After reviewing the comments and conducting additional research on 
the topic of frequency shifting, we have decided not to include a 
requirement that a vehicle's emitted sound must change in frequency as 
the vehicle changes speed. Although this characteristic is still 
considered useful and we encourage its use on hybrid and electric 
vehicles for enhanced detectability and recognizability, a test 
procedure to determine compliance with requirements for frequency shift 
at this time has been deemed unfeasible.
    As proposed in the NPRM and finalized here, the sound pressure 
level in each one-third octave band changes as speed increases, leading 
to an increasing overall sound pressure level that corresponds to the 
behavior of an ICE vehicle. Thus pedestrians will be able to tell if an 
EV or HV is accelerating or decelerating based on the increase or 
decrease in sound level emitted from the vehicle, just as they would be 
able to in the case of an ICE vehicle. In this final rule, the agency 
has chosen to use the increase and decrease in sound produced by the 
vehicle at different speeds as an alternative to frequency shifting.
    We have decided to identify this alternative method by the term 
``relative volume change.'' Basically, the method of ``relative volume 
change'' involves summing and comparing the normalized measured one-
third octave band levels for each of the operating speeds for each test 
vehicle. For each operating speed, the normalized sum of the measured 
one-third octave bands should increase by a specified minimum amount at 
each successive speed interval. Further details about the ``relative 
volume change'' method and why the agency believes the original 
frequency shifting requirement is not feasible are discussed below.
    The agency acknowledges comments regarding the lack of a test 
procedure to measure frequency shifting in the NPRM. Many of the 
commenters requested that, in lieu of a test procedure being included 
in the rule, the agency adopt the frequency shifting procedure set 
forth in SAE J2889-1 Section S7.2. In essence, this procedure calls for 
identification of a frequency that has changed as a function of vehicle 
speed, which can be measured and can be tracked during the operating 
conditions specified. However, the SAE procedure, as stated in appendix 
B-5 of the SAE standard, requires prior knowledge of the frequencies to 
be tracked (``The persons conducting the test know what frequencies 
should be produced by the device or vehicle under measurement''). NHTSA 
believes that the need for prior knowledge of the frequencies precludes 
a readily verifiable and practicable test procedure. Also, the 
procedure set forth in J2889-1, Section 7.2, requires an acoustics 
expert to determine both the starting frequency (and/or tone) as well 
as the shifted frequencies as speed increases, to verify compliance. 
The agency believes that this contributes to a lack of objectivity in 
the SAE test procedure for measuring frequency shifting. The agency 
believes that it would be difficult to reliably and repeatably verify 
compliance because the frequencies identified for frequency shifting by 
different technicians are unlikely to always be exactly the same.
    Since issuing the NPRM, the agency has conducted additional 
research in an attempt to develop a cohesive methodology for analyzing 
and verifying frequency shifting. NHTSA considers frequency shifting 
measurement to consist of three main steps: (1) Measurement of the 
signal to be used in the analysis and its conversion to the 
corresponding frequency domain; (2) identification of the alert sound 
tonal components that meet the definition of tone and that are expected 
to shift at each of the measured operating conditions (stationary, 10 
km/h, 20 km/h, and 30 km/h); and (3) calculation of the actual 
magnitude of frequency shifting that has occurred from the identified 
tonal components. Of these steps, step one, recording the measurements 
and converting them to the frequency domain, is relatively routine as 
this is a standard signal processing technique. Also, in step three, 
once the proper tones and base frequencies of the vehicle alert have 
been identified and have been determined to be a continuous result of 
frequency shifting, it is relatively easy to mathematically determine 
the amount of frequency shifting that has occurred. From both a process 
basis and a calculation basis, steps one and three appear consistent 
with the methodology specified in SAE J2889-1.
    Unfortunately, in step two above, identification and validation of 
tonal components is exceptionally difficult. The procedure detailed in 
Section S7.2 of SAE J2889-1 specifically requires that the person 
conducting the test know in advance what frequencies are shifting to 
avoid having to subjectively identify and verify the critical tones 
produced by the vehicle alert system. To identify and validate tonal 
components, the test operator first must know precisely how a tone is 
defined. The NPRM defined a component as a tone if the total sound 
level in a critical band centered about the main tonal frequency is 6 
dB greater than the noise level in the band; however, the terms ``noise 
level'' and ``critical band'' were left undefined, and this omission 
was cited by the commenters. As such, the language in the NPRM was 
insufficient to resolve a tone in a way that would allow frequency 
shifting determinations.
    During further research into defining a tone, NHTSA found that 
there are four main ways of identifying and verifying tones: By using 
predetermined

[[Page 90469]]

information from manufacturers; visually, by plotting various sound 
data and determining an overall pattern; by utilizing a small amount of 
predetermined information (such as the base frequencies measured while 
the vehicle is in a stationary mode) and assuming a rate of frequency 
shifting to determine values for 10 km/h, 20 km/h, and 30 km/h; or 
lastly by utilizing a computer program to analyze sound data and search 
for tonal characteristics. Identification and verification of tones, 
regardless of method, is further complicated by the fact that vehicles 
do not generate a simple sound pattern and in general have a mixture of 
many tones, coupled with broadband noise as well, which is consistent 
with what commenters said. There are also pre-existing sound sources 
that have tonal and inherent frequency shifting qualities (for example, 
tires can produce a sound that has specific tonal qualities that will 
shift to a higher frequency that is proportional to the increasing 
speed of the wheel). These sound sources can work together to make 
searching for vehicle alert system tones very difficult and subjective.
    NHTSA investigated using visual methods to identify tones: plotting 
the frequency levels versus sound levels as a function of both 
frequency and time as the vehicle is accelerated at a constant rate (a 
so-called ``run-up'' graph, presented as a spectrogram plot) where 
prominent frequency components can be tracked as they change due to 
frequency shifting; or by graphing sound levels as a function of 
frequency (referred to as the discrete method) for each speed condition 
(stationary, 10 km/h, 20 km/h, and 30 km/h) and identifying prominent 
frequency components which seem to be a function of frequency shifting. 
An example of these types of visual plots can be found in Figure B-1 of 
SAE J2889. Because the discrete method looks at individual test cases, 
there is no guarantee that the frequencies identified will be a result 
of continuous frequency shifting, and that the frequencies are not 
instead merely tonal artifacts present in the individual test case. It 
would be left up to the judgment of an acoustics expert to make this 
determination. Also, utilizing the run-up method would require the 
judgment of an acoustics engineer to determine the characteristics of a 
potential tone, identifying center frequencies, and determining if 
irregularities are present. Although it may be more objective than 
discrete visualization, this method can yield multiple interpretations 
of the same data, which makes it inherently subjective and unsuitable 
for the purposes of safety standard compliance.
    The other methods for determining tones both require technical data 
from the manufacturer. Either the manufacturer would have to supply all 
of the data on frequency shifting, specifying all tones which will be 
used to calculate compliance, or the manufacturer would have to provide 
a smaller amount of information, such as the tonal components at 
stationary, and the agency then would have to assume a rate of 
frequency shifting as a function of speed and would estimate where the 
new tonal components should lie. Unfortunately, this process also is 
not objective, as the agency would be relying on information from the 
manufacturers and on acoustics experts to validate that information.
    NHTSA also investigated the use of automated procedures utilizing 
ANSI S1.13: 2005, ISO 3745, and SAE J2889-1. However, NHTSA has been 
unable to produce a fully workable automated method. More research 
would be needed, but it is uncertain if the agency could ultimately 
develop repeatable, reliable, and objective procedures that do not 
require verification by an expert.
    In light of the above discussion highlighting the impracticality of 
identifying and verifying tones without prior knowledge of the expected 
frequency shift, NHTSA agrees with the note 2 of Section S7.2.5.1.1 of 
SAE J2889 Rev DEC2014, ``. . . there is no known identification 
specification that can clearly identify frequencies which shift with 
vehicle operating conditions, primarily vehicle speed, when the 
frequency content of the desired signal and any background noise is 
unknown.'' Since no practicable test methodology consistent with the 
requirements of an FMVSS has been developed to date to objectively 
determine frequency shifting, the agency is not including a requirement 
for frequency shifting in the final rule.
    Nevertheless, the agency encourages manufacturers to include 
frequency shifting in their development of alert sounds as this 
shifting does provide aural information to pedestrians about whether 
they are at risk or not and about the distance, speed, and acceleration 
of approaching vehicles. These are useful cues for pedestrian 
navigation.
    In the future, should a practicable, objective method to quantify 
frequency shifting of vehicle alert sounds be developed, NHTSA may 
reconsider its decision to exclude a frequency shifting requirement 
from the safety standard.
Relative Volume Change
    Because it is not feasible to include requirements for frequency 
shifting in the final rule for the reasons discussed above, the agency 
has decided to include in the final rule a requirement for vehicle-
emitted sound level or ``volume'' rather than in frequency to increase 
as the vehicle increases speed. The agency has decided to include this 
volume change requirement as a means for pedestrians to utilize the 
sounds emitted by a vehicle to determine if a vehicle is accelerating 
or decelerating. The agency understands that the concept of ``relative 
volume change'' is not a direct replacement for frequency shifting, but 
we believe it is a reasonable alternative. While frequency shifting 
would be a more certain method for determining vehicle acceleration and 
deceleration, volume change will provide useful audible information to 
pedestrians about the operating state of nearby vehicles. We believe 
that the volume change specifications will partially compensate for the 
absence of pitch shifting requirements.
    To better understand the concept, as a vehicle approaches a 
pedestrian at a constant speed, the pedestrian would hear the vehicle 
alert sound increase in volume, identifying that the vehicle is 
approaching but maybe not accelerating or decelerating. However, if the 
vehicle is approaching a pedestrian and accelerating (or decelerating), 
the alert sound will increase (or decrease) in volume more rapidly as 
the vehicle approaches while transitioning between 0 km/h and 10 km/h, 
between 10 km/h and 20 km/h, and between 20 km/h and 30 km/h. A rapid 
ramp up in volume as the vehicle approaches will be indicative of a 
vehicle accelerating, and a rapid reduction in volume as the vehicle 
approaches will be indicative of a vehicle decelerating.
    The minimum detection thresholds which are contained in this final 
rule increase with speed. Consequently, vehicles that meet the minimum 
requirements, without exceeding them, will have an innate volume 
increase commensurate with the increase in speed. The minimum 
specifications incorporate a volume change of approximately 6 dB 
between stationary and 10 km/h, approximately 6 dB between 10 km/h and 
20 km/h, and approximately 5 dB between 20 km/h and 30 km/h. However, 
manufacturers could design alert signals that have only a single sound 
level, such as one that meets the highest sound level requirements 
(those required at 30 km/h) across all speeds (thus exceeding the 
minimum levels at stationary, 10 km/h

[[Page 90470]]

and 20 km/h). In this case, the alert would have no built-in volume 
change with increasing or decreasing speed, and the potential 
pedestrian cue to increasing or decreasing vehicle speed would not 
exist. The ``relative volume change'' requirement specified in this 
final rule will ensure a minimum sound level increase and decrease as a 
vehicle reaches each successive higher or lower speed operating 
condition.
    In discussing the minimum acoustic requirements for the eight one-
third octave bands in the NPRM, NHTSA said the minimum requirements in 
each one-third octave band increased as the vehicle increased in speed 
to give pedestrians more time to detect faster moving vehicles and to 
allow the pedestrian to determine whether the vehicle was accelerating 
or decelerating. While the minimum acoustic requirements in the NPRM 
increased for each test speed, the NPRM did not include maximum sound 
requirements for each test speed. This meant that a vehicle could 
comply with the requirements of the NPRM by meeting the minimum 
acoustic requirements for the highest test speed for all test speeds 
without any variation in the sound produced by the vehicle. In other 
words, a vehicle alert system could be designed such that it would emit 
the loudest required sound level in all test conditions from stationary 
up to 30 km/h. Under this scenario, a pedestrian would have limited 
ability to detect changes in vehicle speed without pitch shifting 
because the sound produced by the vehicle would not change as the 
vehicle changed speed. To eliminate this possibility, NHTSA has 
included the volume change requirements in the final rule to ensure 
that the alert sound varies produced as vehicle changes speed.
    Since an alert signal's acoustic components can change from one 
operating condition to the next, changes in the overall SPL level will 
not necessarily correspond to changes in the level of individual one-
third octave bands. Also, the overall sound pressure level is 
influenced by bands that are outside of the range of one-third octaves 
covered by NHTSA's specifications (i.e., those greater than 5000 Hz and 
less than 315 Hz). Therefore, in order to evaluate changes in perceived 
volume level, we will consider only the one-third octave bands that 
account for sound energy contained in the range from 315 Hz to 5000 Hz. 
Normalized one-third octave band values are derived by subtracting the 
minimum one-third octave values specified for the stationary operating 
condition from each of the one-third octave band alert measurements. 
This normalization process allows measurements of different one-third 
octave bands to be compared by accounting for the differences in the 
minimum levels specified for each band. The logarithmic sum of the 
thirteen normalized one-third octave band levels is then determined 
(i.e., the ``band sum'').
[GRAPHIC] [TIFF OMITTED] TR14DE16.010

    Finally, the relative volume change is calculated as the difference 
in these band sum values between consecutive operating speed 
conditions.
    Evaluating the increase in band sum values from one speed to the 
next then provides a metric for ``relative volume change.'' This 
approach allows for the tracking of volume as a function of speed, as 
the volume is characterized by the sound pressure levels above the 
minimum levels required at the baseline stationary operating condition. 
It also allows for the rejection of one-third octave bands outside of 
the range of interest (315 Hz to 5000 Hz). Another key characteristic 
of this approach is that frequency is not tracked, which provides 
design flexibility because different one-third octave bands can be 
prominent at different speeds.
    The relative volume change procedure will utilize the same vehicle 
measurement data collected for the determination of compliance with the 
minimum detection standards. That is, the volume change determination 
uses the average values for the thirteen one-third octave bands of the 
first four valid, ambient-corrected runs, from the louder side of the 
vehicle (left or right), for each operating condition (Stationary, 10 
km/h, 20 km/h, and 30 km/h). By comparing the calculated band sum at a 
given operating speed with the band sum value for the next lower speed 
condition, a relative volume change can be computed.
    An example calculation is provided in Figure 9.

[[Page 90471]]

[GRAPHIC] [TIFF OMITTED] TR14DE16.011

    Figure 9 illustrates the four-step procedure used to calculate the 
relative volume change for sample data for the 10 km/h to 20 km/h 
conditions as follows:
    Step 1: Calculate the average measured one-third octave band level 
for each of the 13 one-third octave bands (315 Hz to 5000 Hz) using the 
four valid test runs identified for each of the test operating 
scenarios (stationary, 10 km/h (11+/- 1km/h), 20 km/h (21+/- 1km/h), 
and 30 km/h (31+/- 1km/h)).
    Step 2: Calculate the normalized values for each of the 13 one-
third octave bands for each of the operating scenarios, relative to the 
minimum SPL requirements specified for the stationary operating 
scenario. The normalized values are calculated by subtracting the 
minimum SPL values specified for the stationary operating condition 
from each of the one-third octave band averages calculated for each 
operating scenario (stationary, 10 km/h (11+/- 1km/h), 20 km/h (21+/- 
1km/h), and 30 km/h (31+/- 1km/h)).
    Step 3: Calculate the BAND SUM for each critical operating scenario 
(stationary, 10 km/h (11+/- 1km/h), 20 km/h (21+/- 1km/h), and 30 km/h 
(31+/- 1km/h)) as follows:
[GRAPHIC] [TIFF OMITTED] TR14DE16.012

Where:

i represents each of the 13 one-third octave bands.
Normalized Band Leveli is the calculated normalized value for each 
of the 13 one-third octave bands.

    Step 4: Calculate the relative volume change between each operating 
scenario (stationary to 10 km/h; 10 km/h to 20 km/h; 20 km/h to 30 km/
h) by subtracting the BAND SUM of the lower speed test case from the 
BAND SUM of the next higher speed test case.
    The performance specifications for the relative volume change 
requirement were derived based upon the minimum detection standards for 
each operating condition. The minimum detection standards increase with 
speed such that, if a vehicle just meets the minimum standards at each 
operating condition, its relative volume change would be approximately 
6 dB between stationary and 10 km/h, approximately 6 dB between 10 km/h 
and 20 km/h, and approximately 5 dB between 20 km/h and 30 km/h. It is 
the agency's desire to ensure that vehicles equipped with compliant 
alert sounds are only as loud as they need to be for detection by

[[Page 90472]]

pedestrians, and not excessively louder. To meet the relative volume 
change requirements, a manufacturer could simply increase the sound 
levels well beyond the minimum standards to achieve the required 
separation at each speed interval. However, we believe that 
manufacturers will also want to reduce alert sounds to the greatest 
extent possible while meeting the minimum standards in order to 
maximize customer satisfaction and minimize environmental noise. To 
accomplish the goal of minimizing excessive noise, the relative volume 
change values should not exceed the already established differences of 
6 dB, 6 dB, and 5 dB built into the minimum operating condition 
specifications. The relative volume change specifications that NHTSA 
has decided to require are provided in Table 17.

          Table 17--Minimum Relative Volume Change Requirements
------------------------------------------------------------------------
                                                              Minimum
                                                             relative
              Critical operating scenarios                volume change,
                                                                dB
------------------------------------------------------------------------
Between:
  Stationary and 10 km/h................................               3
  10 km/h and 20 km/h...................................               3
  20 km/h and 30 km/h...................................               3
------------------------------------------------------------------------

    These performance levels were established using the following 
criteria. First, as explained above, to minimize alert sound levels, 
the maximum volume change between operating scenarios would be 6 dB, 6 
dB, and 5 dB, respectively. So, as a starting point, the relative 
volume change requirements should not exceed these values. Second, a 
manufacturer might choose to design an alert signal that exceeds the 
minimum values at a given speed and just meets the minimum values at 
the next higher speed. Such a design would have a decreased relative 
volume change, i.e., less than 5 dB or 6 dB, between operating 
conditions. Third, as discussed in the NPRM, the sound level change 
that can be discerned by an untrained observer is approximately 3 dB, 
so the relative volume change between each successive operating 
scenario should be at least 3 dB in order to be useful. Considering all 
these criteria, we want to target relative volume changes within the 
range of 3 dB to 6 dB. Within this range, we have decided to specify 3 
dB as the minimum volume change requirement for the transitions between 
successive operating conditions. This means that the manufacturer can 
incorporate a 3 dB volume change or any level above 3 dB to meet the 
specified requirements. The minimum requirement of 3 dB between each 
operating condition ensures the volume change will be discernable while 
providing manufacturers with the greatest flexibility in the design of 
their alert systems.
    It is NHTSA's expectation that the volume change requirement will 
provide pedestrians with the audible cues needed to discern vehicle 
acceleration and deceleration. However, we reiterate that frequency 
shifting still is a useful characteristic of a vehicle alert system, 
and we encourage system designers to incorporate frequency shifting 
even though this final rule does not include specific requirements for 
it.
    Lastly, in regards to the commenters who requested that the 
proposed test procedure for frequency shifting be modified to allow for 
indoor testing and/or testing at the component level, those comments 
are no longer applicable since the agency has decided to exclude a 
frequency shifting test. In regard to comments about indoor and 
component testing in general, we have addressed that issue in Section 
III.K of today's final rule, where we have stated that NHTSA will 
conduct compliance testing on complete vehicles on outdoor test tracks.

H. Sameness

    The NPRM criterion for sameness was that the alert sound of two 
example vehicles must have a sound pressure level within 3 dB(A) in 
every one-third octave band between 315 Hz and 5000 Hz. That 
requirement would limit the amount of variation in one-third octave 
bands over a range of frequencies when measured on a stationary 
vehicle. We proposed that requirement as an objective way to determine 
if the alert sounds produced by two different vehicles of the same make 
and model are the same.
    In the NPRM, the agency interpreted the PSEA language on sameness 
as applying ``only to sound added to a vehicle for the purposes of 
complying with the NHTSA regulation'' [NPRM, p. 2804]. The proposed 
sameness criteria were not intended to apply to sounds generated by a 
vehicle's tires or body parts or by the mechanical operations of the 
vehicle.
    In the NPRM, NHTSA stated that we interpret a vehicle ``model'' as 
a specific grouping of similar vehicles within a vehicle line. The 
Federal Motor Vehicle Theft Prevention Standard,\140\ defines vehicle 
line as ``a name which a manufacturer applies to a group of vehicles of 
the same make that have the same body or chassis, or otherwise are 
similar in construction or design.'' If a manufacturer calls a group of 
vehicles by the same general name as it applies to another group, but 
adds a further description to that name (e.g., Ford Fusion Hybrid, or 
Toyota Prius Three), the further description indicates a unique model 
within that line.
---------------------------------------------------------------------------

    \140\ 49 CFR part 541.
---------------------------------------------------------------------------

    Also, the NPRM conveyed that the requirement for vehicles of the 
same make and model to have the same sound or set of sounds does not 
apply across model years. For example, a model year 2020 Prius Two 
could have a different sound than a 2019 Prius Two (same model but 
different model years). A 2019 Prius Two could have a different sound 
than a 2019 Prius Four (same model year but different models). All 
Prius Two's from the 2019 model year would be required to emit the same 
sound or set of sounds (same model and model year).
    The PSEA includes language that requires ``the same sound or set of 
sounds for all vehicles of the same make and model.'' We interpreted 
this to mean that a manufacturer may choose to equip a vehicle to have 
different sounds for different operating modes such as forward, 
reverse, and stationary [NPRM, p. 2804]. Each sound would have to meet 
the corresponding performance requirements in each operating mode. We 
did not interpret this language in the PSEA to mean that a vehicle can 
have more than one alert sound for a given operating mode, such as a 
suite of sounds that a driver can select from according to personal 
preference.
    In general, commenters from industry stated that speaker tolerances 
make it impossible to make all vehicles of the same year/make/model 
produce the same sound in accordance with the NPRM criterion, i.e., to 
have the same sound level, within 3.0 dB, in each of the 
thirteen specified one-third octave bands. Also, industry commenters 
favor an indoor, component-level test for sameness, rather than an 
outdoor test conducted on an ISO pad.
    Advocacy groups that provided comments on the proposed sameness 
requirement generally supported it, or supported some performance-based 
assessment of sameness, but did not suggest specific technical criteria 
for such a performance test.
    Alliance/Global stated on behalf of their member companies that the 
classification of sounds by an objective metric that would determine 
sameness first needs to have ``sameness'' defined. The NPRM proposal 
for a three decibel limit in each one-third octave band is not 
sufficient for the measurement uncertainty, let alone production 
variation, according to Alliance/Global.

[[Page 90473]]

Alliance/Global recommended that sameness be measured at a component 
level under indoor laboratory conditions. They stated that their only 
practical course of action to assure sameness between two vehicles is 
to compare the input signals to the speakers (the output from the 
signal generator or the programmed digital sound file). Alliance/Global 
stated that measuring sameness through microphone recordings of 
operating vehicles is not possible as a practical matter. Furthermore, 
due to the variation in production speakers, it also is not reasonable 
to require them to emit the same sound within the proposed three 
decibel specification. They acknowledged that the requirement cannot be 
deleted altogether because it is included in the PSEA. Alliance/Global 
also agreed with OICA that NHTSA should allow manufacturers the option 
of demonstrating compliance with the sameness requirement through 
comparisons of elements such as the software sound file, input to the 
speakers, etc.
    OICA stated that the proposed sameness criterion needs revision, 
pointing out that industry has already shown that even 6 dB may not be 
a sufficient tolerance between vehicles of the same make and model. 
OICA stated that the measurement uncertainty is the most significant 
factor, and that the proposed allowance of 3 dB is not commensurate 
with the measurement uncertainty. OICA suggested that NHTSA should 
carefully consider how sameness is defined as that will drive the 
necessary measurement procedures. OICA noted that sound-generating 
devices that use the same software will inherently have the same sound, 
even when the sound is altered slightly through various factors such as 
installation into a vehicle. Using the same software also means that 
vehicles will produce the same sound even when the hardware is changed 
somewhat, according to OICA. OICA also noted that NHTSA could resolve 
issues with measurement of Sameness by specifying a requirement that 
applies to the software sound file. Citing the PSEA language, ``The 
Secretary shall allow manufacturers to provide each vehicle with one or 
more sounds that comply with the motor vehicle safety standard at the 
time of manufacture,'' OICA stated that vehicle manufacturers should be 
allowed to offer vehicles to customers with more than one alert sound 
and to equip vehicles with multiple alert sounds for the driver to 
select from during vehicle operation, as long as each of the sounds 
fulfils the minimum requirements defined in the safety standard. OICA 
suggested that the language of Section S5.3 should state that two 
vehicles of the same make, model, and model year must ``emit the same 
sound within a set of sounds,'' and that their overall sound level 
should be required to be within 6 dB(A).
    Denso stated that this requirement is not feasible for a number of 
reasons. For one, there is inherent variability in vehicle sound 
characteristics and in speaker and amplifier characteristics and 
performance. When combining this variability, it is very difficult to 
limit the sound difference to within 3 dB(A) between two vehicles, even 
for vehicles having nominally identical sound systems, according to 
Denso. Denso stated that sound pressure levels will decrease by 
approximately one decibel when the ambient temperature increases from 0 
to 40 degrees Celsius. Therefore, Denso suggested it is very difficult 
to measure the sound level within a tolerance of 1.5 dB 
with good repeatability in outdoor conditions. In addition, since the 
perception of sound depends on ambient conditions (wind direction, wind 
speed, temperature, atmospheric pressure, etc.) and surrounding noise, 
Denso stated that ICE vehicles of the same model have up to a 3 dB and 
greater sound level difference. For these reasons, Denso requested that 
NHTSA not adopt a requirement for sameness.
    The SAE stated that, although 3 dB may be an acceptable tolerance 
on overall SPL, it is not sufficient for one-third octave bands. SAE 
also stated that restricting one-third octave band variation does not 
guarantee sameness in any reasonable sense related to this regulation. 
Sounds can be filtered to meet the same one-third octave requirements, 
yet still could be perceived as substantially different by pedestrians. 
SAE provided an example of two sound files having the same overall SPL 
and very similar average spectral distribution, but different time 
signals. Despite their similarities, the two sound files were from 
recordings of completely different sounds. SAE stated that this 
demonstrates how sounds can appear to be similar based on a selected 
measurement criterion when in fact they might be very different in how 
they sound to listeners.
    Honda stated the criterion for sameness in the NPRM is too 
stringent and cannot be complied with due to the variability of sound-
producing devices. An attachment to Honda's comment graphically 
represented the variability in repeated testing of the same vehicles. 
[We note there was very little explanation of the data in Honda's 
comment; the graphic showed that one-third octave band measurements in 
repeated tests of the same vehicle appeared to vary by up to about 7 
dB; but the results were quite different for the various one-third 
octaves and for the different test vehicles Honda tested, with 
variability in some instances being close to zero.] Honda suggested 
that NHTSA should specify an overall sound level and require that there 
be two peak frequencies that fall within specified frequency ranges.
    Advocates for Highway and Auto Safety stated that, to ensure that 
different vehicles of the same make/model have the same sound, the 
agency must establish a test procedure for comparing different vehicles 
of the same make and model to ensure compliance and production 
uniformity along with meeting the FMVSS sound requirements.
    Accessible Designs for the Blind stated that sameness should be 
tested at all speeds from idle up to the crossover point speed. ADB 
stated it does not believe that testing at idle only is appropriate for 
establishing the standard. ADB stated that changing a vehicle's tires 
or body design is likely to affect the vehicle's sound profile and 
therefore it is essential that the single sound specified be well 
documented as detectable and localizable under common traffic and 
ambient sound conditions by visually-impaired pedestrians who are at 
least 60 years of age. There will be differences in the perceived sound 
even if it is generated using the same wav file. The nature of the 
loudspeaker and where and how it is mounted will also result in 
differences. Perceived sound will, of course, also vary by road 
surface. ADB rejected the notion that a variety of sounds will be 
consistently and accurately recognized by pedestrians as coming from 
vehicles. Any added sound should be the same for all EVs and HVs in 
order to be maximally recognized and quickly interpreted as being a 
vehicular sound, according to ADB. ADB stated that having more than one 
sound is likely to decrease any safety benefit added sound might 
provide for visually-impaired pedestrians.
    In a February 2014 letter to NHTSA co-signed by the Alliance, 
Global, the NFB, and the ACB, the co-signers jointly submitted their 
mutually agreed-upon position about aspects of the PSEA's sameness 
requirement. They stated that vehicles with the same overall sound 
pressure level, within a reasonable engineering and manufacturing 
tolerance, should be considered as having the same sound.

[[Page 90474]]

    The joint letter said that vehicles of different model years should 
not be considered to be the same make and model. In other words, only 
vehicles of the same make, model, and model year should be required to 
emit the same sound.
    The joint commenters also expressed their agreement about two other 
aspects of the PSEA Sameness requirement: First, OEMs should have 
flexibility to provide EV/HVs with some number of driver-selectable 
sounds instead of just a single sound; and second, OEMs should be 
allowed to install updated sounds once per model year to address any 
dissatisfaction that might arise on the part of vehicle owners with the 
alert sounds their HV/EVs are originally manufactured with. The latter 
would be separate from updates that OEMs might need to make to remedy a 
noncompliance or for conducting a recall, as provided for in the PSEA. 
The joint commenters believe the language of the PSEA, which uses the 
terms ``one or more sounds'' and also ``sound or set of sounds'' allows 
for driver-selectable sounds and voluntary updating of sounds.
    We note that NHTSA did not receive comments specifically in 
response to our request for comment on the extent to which changing a 
vehicle's tires or body design would affect the vehicle's sound profile 
for the purposes of determining whether two example vehicles have the 
same sound.
Agency Response to Comments
    In light of the comments the agency received on the NPRM sameness 
requirement, we have reconsidered the proposed requirement and have 
decided that it is not appropriate for the final rule. We agree with at 
least one shortcoming that was pointed out by several commenters: Even 
if two vehicles' alert sounds are within three dB(A) in each specified 
one-third octave band, the alerts would not necessarily sound the same 
because sounds that have identical one-third octave sound pressure 
levels can vary considerably in terms of how they are perceived by a 
listener. In fact, it is possible for completely different types of 
sounds to have similar one-third octave band levels, even across a wide 
range of frequency bands.
    We now believe that the NPRM metric based on A-weighted one-third 
octave band sound pressure levels would be suitable only to identify 
``defective'' sounds, i.e., to identify when two sounds that are 
intended by design to sound the same are not the same, for example if a 
particular test vehicle had a damaged speaker. The main reason for this 
is that the NPRM method has relatively low resolution and would not 
distinguish between tonal signals and noise signals, which are 
different by definition but can have the same one-third octave band 
spectra. Consequently, even if two vehicles of the same make and model 
were to comply with the NPRM criterion, there would be little assurance 
that they in fact produce identical alert sounds.
    We also acknowledge the concern expressed in comments that speakers 
used in alert systems have some inherent manufacturing variation. 
However, NHTSA has not conducted tests to verify the level of speaker 
variation claimed by commenters.
    Regarding the Alliance/Global suggestion that overall sound 
pressure levels produced by two vehicles should be used to determine 
whether they are the same, we do not believe that method would provide 
a meaningful comparison. That approach would merely characterize how 
loudly two vehicles' alert sounds are perceived. That approach would 
not evaluate other acoustic characteristics that make sounds alike such 
as phase or spectral shape, and it normally would not distinguish 
between sounds that are obviously different to listeners. For example, 
music, construction noise, and thunder all can have the same overall A-
weighted sound pressure level.
Other Sameness Metrics Considered by NHTSA
    Subsequent to concluding that a requirement based on one-third 
octave levels is not appropriate for the final rule, the agency 
considered various alternatives for objectively determining that alert 
sounds among vehicles of the same make and model are the same.
    To address issues with the NPRM approach, we considered two 
additional types of acoustic metrics to evaluate the similarity of the 
alert sounds on vehicles of the same make and model: Power Spectrum 
Analysis and Frequency Response Functions (FRF). These are both 
acoustic metrics that could be used to analyze the actual output of the 
alert system speaker to quantify the difference between two sound 
signals. Both of these metrics characterize amplitude and frequency. 
The FRF is sensitive to phase as well. Both metrics have higher 
resolution than one-third octave bands.
    Power spectrum analysis generally has resolution sufficient for 
signals that do not change over time. However, temporal differences 
such as time reversal (e.g., playing of a signal in reverse) and 
amplitude modulations which change the perceived character of a sound 
may not show up as significant differences in the power spectrum of two 
signals. For this metric to be useful for evaluating sameness, it 
probably would be necessary to evaluate the statistical correlation 
(R\2\ value) of the power spectra of two sound signals and to specify a 
degree of correlation that must be achieved in order for the two sounds 
to be considered the same. For a variety of reasons including a lack of 
any established procedure using this method and also repeatability 
concerns, we do not know if it is feasible to develop a compliance 
requirement based on this method.
    Frequency Response Functions would provide a better comparison. For 
some alert sounds, the FRF could be used to show that certain periodic 
variations are highly correlated between two signals. However, other 
signal variations may not be correlated. Additionally, an evaluation of 
the FRF would require a standardized method to synchronize the phase 
between the two signals, and the agency currently does not have any 
such method.
    Overall, we have concluded that comparisons using Power Spectrum 
Analysis or Frequency Response Functions might provide a higher degree 
of confidence than the NPRM method that two unknown signals are the 
same, but developing a requirement and test procedure based on these 
metrics for a compliance test application may involve considerable 
additional agency research and testing.
    Furthermore, in order for either of these metrics to be useful in a 
compliance test, the measurement variability of the data collected for 
a sameness evaluation would have to be extremely low, such that even 
small differences in measurements of two example vehicles could be 
attributed to actual differences in their alert sounds. As discussed in 
the Repeatability/Reproducibility section (Section III.K) of this 
preamble, we have determined that the variability of pedestrian alert 
sound measurements is on the order of several decibels when measured on 
a vehicle in operation (although stationary tests like those used for 
Sameness tend to be somewhat less variable.) Although the level of 
variability of the NHTSA measurement procedure promulgated in today's 
final rule is sufficiently low for stationary, reverse, and pass-by 
tests, we believe it is inadequate for a sameness evaluation using 
power spectra and FRFs. For these metrics to be useful for sameness, we 
would need to obtain a clean signal prior to its exposure to external 
influences like speaker tolerances and ambient noise fluctuations.

[[Page 90475]]

    Another option would be to evaluate the alert signal at the point 
where it is transmitted to the alert system speaker, i.e., at the 
speaker input. While speaker input would have very high repeatability, 
this approach would require that the speaker inputs must be physically 
accessible, which the agency has found is not always the case. For 
example, speakers might be integrated into a sealed module that 
incorporates the control electronics, making access difficult without 
destructive measures.
    Another option is to evaluate the signal at the point where it is 
generated internally in the alert system. On typical alert systems, 
this would amount to evaluating the actual digital source of the alert 
sound, such as a wav file, or an equivalent digital element of the 
alert system from which the signal originates. NHTSA may not have the 
means to extract a digital file for a compliance evaluation of a test 
vehicle and would need the assistance of the vehicle manufacturer. At 
that point, a more practical option might be for NHTSA to simply 
request that information from the vehicle manufacturer. However, even 
if an OEM were to provide NHTSA with a digital source file from two 
vehicles of the same make and model, it is uncertain whether the agency 
could verify that they are identical.
    Because alternative acoustic metrics have these issues, we believe 
they are not viable for a regulatory application, and we have decided 
not to adopt acoustic metrics for the sameness requirement in the final 
rule. Instead, as detailed later in this section, we have concluded 
that the final rule requirement for sameness should be based on 
certification by vehicle manufacturers that vehicles of the same make 
and model are designed to have identical alert sounds. That is, they 
must certify that vehicles of the same make, model, and model year are 
the same with respect to their alert system hardware and software 
components, the source of the alert sound (such as a digital file) and 
vehicle inputs used to vary the sound, as well as all other elements of 
the alert system.
Other Sameness Issues--Selectable Sounds and Mid-Year Updates
    In the proposed regulatory text in the NPRM, paragraph S8 was 
included to prevent alert sound modifications, except in case of a 
vehicle recall. That section of the regulatory text also prohibited 
systems from being designed to allow access by anyone other than the 
OEM or a service provider, so that individuals would not be able to 
tamper with or replace the alert sound in their vehicles.
    The joint comment of the Alliance, Global, the NFB, and the ACB 
addressed both the issue of ``selectable'' sounds and the issue of 
alert sounds being updated or improved after vehicles are delivered to 
customers. Regarding the first issue, the joint commenters stated that 
they believe the PSEA allows vehicles to be equipped with more than one 
sound for a given operating condition. This comment would mean, for 
example, that a particular vehicle make/model might have an alert sound 
X, an alert sound Y, and an alert sound Z for when the vehicle is in 
forward motion at a given speed, and the driver could select X, Y, or Z 
based on personal preference and could switch among those choices at 
any time. Regarding the second issue, the joint commenters stated the 
PSEA allows a manufacturer or dealer to provide vehicle owners with 
opportunities at any time during a model year to update the alert sound 
or sounds with which their vehicle came equipped from the factory. They 
contended that this allowance exists under the PSEA even in cases where 
the original sound is not defective or out of compliance with the 
safety standard, and that updates may be provided for aesthetic 
purposes rather than for remedy of a recalled alert system (the latter 
being expressly provided for in the PSEA.)
    Given our understanding of the PSEA, we are not including 
provisions requested by these commenters that would allow for driver-
selectable pedestrian alert sounds and mid-year updates of pedestrian 
alert sounds. As such, the provision in paragraph S8 of the NPRM 
regulatory text, which specifically prohibits alert sound modifications 
except for recall purposes and also prohibits systems designed so as to 
allow manipulation or modification of the alert sound by anyone other 
than the OEM or a service provider, is adopted in this final rule 
without modification. We believe that this approach is necessary to 
satisfy the requirements contained in the PSEA language and that 
allowing a means for owners to select or modify alert sounds, or to 
allow vehicle manufacturers, dealers, or other vehicle service entities 
to replace or update alert sounds outside the auspices of a recall 
action, would be in conflict with the language of the PSEA. 
Furthermore, by not allowing driver-selectable sounds, the final rule 
adheres more closely to the PSEA requirement that vehicles of a given 
make and model must have the same alert sound.
Compliance Evaluation of Sameness
    After fully considering the NPRM comments on sameness and other 
acoustic metrics, we have concluded that the compliance requirement for 
sameness in this final rule should not be based on acoustic performance 
measurements, including the one proposed in the NPRM. The difficulties 
and unknowns with comparing direct measurements of acoustic metrics, as 
well as the potential need for more agency research in this area if we 
decided to use any of the metrics discussed above, leads us to conclude 
that, currently, the most effective and expedient way for NHTSA to 
evaluate sameness is to explicitly require that specific design aspects 
of vehicle alert systems must be the same, particularly the software 
and hardware that comprise the systems.
    Although this approach would not be based on acoustic measurement, 
it would provide assurance that the design of alert systems on vehicles 
of a given make and model are consistent from one vehicle to the next 
because the vehicle manufacturer would be certifying not just that the 
sounds are the same but that the hardware and software components that 
are used to generate the alert sound are the same from vehicle to 
vehicle.
    This approach is consistent with the comments NHTSA received in 
response to the NPRM. In response to NHTSA's request for comment in the 
NPRM regarding its proposed method of measuring whether the sound 
produced by two vehicles was the same, the Alliance/Global joint 
comment stated that the only way to verify sameness was to measure the 
digital signal output of the sound generator or to examine the digital 
sound file itself. Alliance/Global further referenced statements by 
OICA supporting a method of determining sameness based on the 
examination of the software and hardware making up the sound generation 
system. Alliance/Global stated in their comments that ``OICA notes that 
current sound generating devices that use the same software will 
inherently have the same sound, even when the sound is altered slightly 
through various factors, such as installation into a vehicle. The 
Alliance and Global agree with OICA that NHTSA should allow 
manufacturers the option of demonstrating compliance with the sameness 
requirement through comparisons such as: The software sound file, input 
to the speakers, etc.'' After reviewing the comments and its own data, 
NHTSA agrees that the best method for satisfying the requirement in the 
PSEA to require vehicles of the same

[[Page 90476]]

make and model to make the same sound is to examine the hardware and 
software of the subject vehicles and to require that hardware and 
software to be the same.
    As stated previously, we believe that the Vehicle Safety Act and 
PSEA requirement can be satisfied by this methodology. Aside from being 
a requirement in the PSEA, requiring vehicles of the same make and 
model to emit the same sound limits the universe of sounds produced by 
EVs and HVs that pedestrians, both blind and sighted, must be able to 
identify as vehicle sounds. This is important because pedestrians must 
be able to recognize the sound produced by an EV or an HV as a vehicle-
emitted sound for this rule to reduce crashes between pedestrians and 
EVs and HVs.
    If we can establish that vehicles of the same make and model are 
alike with respect to the hardware and software they utilize for their 
alert systems, that information will be sufficient to establish their 
sameness because the sounds they generate would be effectively the 
same. That is, if two vehicles are designed the same in regard to 
having the same software and hardware to generate alert sounds, then 
any overall differences in the sound produced would not be perceptible 
in a meaningful way to pedestrians. Thus, this approach achieves the 
intent of the PSEA sameness requirement.
    Consistent with the NPRM, we are applying the sameness criterion 
only to sounds added to vehicles for the purpose of complying with this 
final rule. In that way, tire noise, wind noise, and any other noise 
associated with vehicle motion and that is not generated by the 
pedestrian alert system is not subject to the sameness requirement.
    We note that NHTSA has taken a similar approach in other FMVSS 
where we have relied on manufacturer's assurance and documentation that 
a system is designed to comply with the safety standard. For example, 
when NHTSA created the safety standard for Electronic Stability 
Control, FMVSS No. 126, S5.6 ``ESC System Technical Documentation,'' 
was included for compliance of ESC systems with an understeer 
requirement. In NHTSA's development of FMVSS No. 126, the agency was 
unable to devise an understeer test that was both accurate and 
repeatable. The agency instead took the approach of identifying certain 
system design characteristics and verifying them by requesting 
information from the OEM. Standard No. 126 lists items such as a system 
diagram, a written explanation of the system operational 
characteristics, a logic diagram, and a discussion of processor inputs 
and calculations relating to vehicle understeer as examples of evidence 
that may be used to validate the manufacturer's certification.
    In the case of pedestrian alert systems, we are taking that 
approach. In our development of today's final rule on FMVSS No. 141, we 
have not successfully devised a meaningful, accurate and repeatable 
test for sameness. The reasons for this are discussed previously in 
this section. Instead, we are including a requirement that critical 
aspects of the alert system design must be the same from vehicle to 
vehicle.
    We also believe that this approach is consistent with the Vehicle 
Safety Act. While Congress intended that NHTSA issue performance 
standards when it passed the Vehicle Safety Act, courts interpreting 
the Vehicle Safety Act have recognized that in some instances it is 
necessary for NHTSA to issue a design restrictive standard in order to 
achieve a desired performance or to ensure safety.\141\ In Chrysler v. 
Department of Transportation, the Sixth Circuit upheld a FMVSS issued 
pursuant to the Vehicle Safety Act restricting the design of headlamps. 
The court held that the design restriction on headlamps in the standard 
was consistent with the Vehicle Safety Act because it fulfilled the 
important safety purpose of ensuring that replacement headlamps were 
readily available to consumers. We believe that the provisions in this 
final rule requiring that certain aspects of the vehicle alert sound 
system be the same in all vehicles of the same make and model, in 
addition to fulfilling a requirement in the PSEA, fulfils the safety 
purpose of helping pedestrians to recognize sounds produced by EVs and 
HVs as vehicle emitted sounds.
---------------------------------------------------------------------------

    \141\ See Washington v. Dep't of Transp., 84 F.3d 1222, (10th 
Cir. 1996); Chrysler Corp. v. Dep't of Transp., 515 F.2d 1052, 1058 
(6th Cir. 1975).
---------------------------------------------------------------------------

    To implement this approach for the sameness requirement, we are 
modifying the proposed regulatory text in paragraph S5.5 (was NPRM 
paragraph S5.3) to state that any two vehicles of the same make, model, 
and model year shall generate their pedestrian alert sound using the 
same external sound generation system including the software and 
hardware that are part of the system. Furthermore, we are adding a 
definition of Pedestrian Alert System within the regulatory text of 
S5.5 which lists the common components of pedestrian alert systems. In 
this way, by certifying that a pedestrian alert system meets S5.5, the 
manufacturer is explicitly certifying that the following specific 
hardware and software components of the system are the same from 
vehicle to vehicle: The alert system hardware components including 
speakers, speaker modules, and control modules, as evidenced by 
specific details such as part numbers and technical illustrations; the 
location, orientation, and mounting of the hardware components within 
the vehicle; the digital sound file or other digitally encoded source; 
the software and/or firmware and algorithms which generate the 
pedestrian alert sound and/or which process the digital source file to 
generate a pedestrian alert sound; vehicle inputs including vehicle 
speed and gear selector position utilized by the alert system; any 
other design features necessary for vehicles of the same make, model, 
and model year to have the same pedestrian alert sound at each given 
operating condition specified in this safety standard.
    To verify the OEM's certification of an alert system in the 
agency's annual compliance evaluations, NHTSA's Office of Vehicle 
Safety Compliance may request that the manufacturer make available to 
the agency specific design documentation relating to the alert system 
used on same make, model, and model year vehicles. The documentation 
that a manufacturer could provide to demonstrate that the sound 
produced by two vehicles of the same make and model is the same may 
include documents such as: A description of the source of the alert 
sound, such as the digital sound file; a copy of the digital file (if 
applicable); any algorithms for processing/manipulating the digital 
file to generate an alert sound; vehicle inputs such as speed signal 
that are needed to process and generate the alert sound; and details 
such as part numbers showing that vehicles of the same make, model, and 
model year are consistently equipped with identical alert system 
components.

I. Customer Acceptance

    In the NPRM we discussed presentations provided by vehicle 
manufacturers regarding consumer acceptance of adding sound to vehicles 
to provide pedestrian detection. Nissan submitted a presentation 
stating that over 60 percent of Nissan Leaf owners surveyed found that 
added noise was acceptable if the overall sound pressure level of the 
sound was 55 dB-A or quieter for the forward moving condition.
    The NPRM also discussed the ways in which NHTSA crafted the 
proposal to account for concerns about the community noise impacts of 
the

[[Page 90477]]

proposal so that sounds complying with the requirements of the final 
rule would not unnecessarily contribute to noise pollution. In 
consideration of community noise impacts the NPRM omitted the mid-range 
frequencies from the proposed acoustic requirements as these are the 
frequencies that contribute the most to increasing the overall sound 
pressure level of sound.
    NHTSA also conducted a draft Environmental Assessment (EA) to 
analyze the environmental effects of the proposed rule. The analysis in 
the EA most relevant to analyzing the impact of the rule on consumer 
acceptance is the single car pass-by analysis. This analysis is 
designed to show what a person standing near the road way would hear 
when a EV or HV emitting sound complying with the NPRM passed by. In an 
urban ambient with an overall sound pressure level of 55 dB(A) a 
listener standing near the roadway would not be able to perceive the 
difference between a EV/HV that did not produce added sound and an EV/
HV that complied with the requirements of the NPRM.\142\ In a non-urban 
ambient with an overall sound pressure level of 35 dB(A) the difference 
between the single-vehicle pass-by for EVs/HVs meeting the minimum 
sound requirements in the NPRM and those without the added sound would 
be 3.1 to 6.3 dB, depending on speed, and 10.1 dB at stationary. In the 
non-urban ambient a single vehicle pass by of an EV/HV meeting the 
minimum sound requirements of the NPRM would produce less sound than an 
average ICE vehicle although this difference would only be noticeable 
at stationary.
---------------------------------------------------------------------------

    \142\ NHTSA, Minimum Sound Requirements for Hybrid and Electric 
Vehicles; Draft Environmental Assessment (2013), at 39-40.
---------------------------------------------------------------------------

    We received several comments in response to the NPRM that certain 
aspects of the proposal would be annoying to passengers or drivers or 
would not be accepted by consumers. We also received several comments 
from members of the general public stating that the whole concept of 
adding any sound to hybrid and electric vehicles would be annoying and 
would lead to decreased sales of EVs and HVs.
    Alliance/Global stated in their joint comment that the loudness and 
frequency composition of sounds meeting the proposed requirements would 
be unpleasant to vehicle occupants. Specifically sounds with minimum 
content in eight one-third octave bands would be too loud to be 
accepted by consumers.
    Alliance/Global further stated that because the proposed 
requirements did not contain requirements for mid-range one-third 
octave bands from 500 Hz to 2000 Hz, resulting sound would have a 
shrill unpleasant character. Alliance/Global stated that, based on past 
experience with shrill sounds, their members fear that costumers may be 
unwilling to purchase EVs and HVs if they are equipped with sounds 
meeting the proposed requirements.
    GM stated that the proposed sound levels and operating conditions 
are in excess of the safety needs of pedestrians and further explained 
that this would likely result in customer annoyance leading to 
customers disabling the alert sound and also affecting vehicle 
purchases. Chrysler and Honda also expressed concerns about 
marketability and customer acceptance.
    Toyota also stated that sounds meeting the requirements of the NPRM 
would be too loud and would discourage consumers from purchasing EVs 
and HVs. Toyota commented that it had examined customer acceptance of 
sounds meeting the NPRM specifications. Toyota used a prototype speaker 
and included 56 Prius owners (ages 20 to 55 years old). Participants 
were asked to drive an alert-equipped vehicle on a specific route and 
then rate the sound. The operating conditions experienced during the 
study included slow acceleration; 40 km/h pass-by; slow deceleration; 
and 16 km/h pass-by. Toyota reported that 68 percent of the drivers 
were somewhat dissatisfied or very dissatisfied with their overall 
experience with the sound emitted by the test vehicle. Toyota asked the 
participants how the sound might affect their future vehicle purchases, 
and 54 percent of the drivers indicated a somewhat negative or very 
negative impact, while 46 percent indicated no impact or a somewhat 
positive impact. Toyota also mentioned that a sound meeting the 
proposed requirements in the NPRM resulted in an increase in the 
interior noise relative to the same vehicle with the alert system 
turned off.
    WBU commented that allowing the sound to be emitted over fewer one-
third octave bands may alleviate manufacturers concerns about consumer 
acceptance of alert systems.
    Several commenters also stated that requiring a sound while the 
vehicle is stationary would lead to lower consumer acceptance of EVs 
and HVs. Nissan submitted with its comment the result of a customer 
survey that indicated that over 60 percent of costumers would accept an 
idle sound with an overall sound pressure level of 49 dB-A or less.
    NHTSA also received comments from OICA stating that the 
requirements in the NPRM requiring that the sound produced by EVs and 
HVs contain tones would make sounds complying with the NPRM annoying to 
vehicle occupants. Mercedes expressed concern that including 
requirements for low one-third octave frequency bands down to 315 Hz 
and broadband content down to 160 Hz may affect consumer acceptance of 
sounds meeting the requirements of the NPRM because sounds with content 
in this area of the spectrum are difficult to isolate from the vehicle 
cabin.
Agency Response to Comments
    As discussed in Section III.E of this notice, the agency made 
several changes to the acoustic requirements of the NPRM in this final 
rule. In response to comments from manufacturers, the final rule allows 
compliance with its acoustic requirements by placing minimum content in 
the mid-range one-third octave bands from 500 Hz to 2000 Hz. We believe 
that this change will increase manufacturer's flexibility to create 
sounds that are pleasing to motorists and pedestrians. NHTSA does not 
believe that the overall sound pressure level of sounds meeting the 
requirements of this final rule will discourage consumers from 
purchasing EVs or HVs or effect consumers acceptance of the 
requirements in the final rule. The overall sound pressure level of 
sounds meeting the requirements of the final rule for the 10 km/h pass 
by are between 53-56 dB(A). According to Nissan's presentation, 60 
percent of consumers would accept added sound to their vehicle if the 
overall sound pressure level of the sound was 55 dB(A) or quieter for 
the forward moving condition. NHTSA believes that the Nissan study 
indicates that consumers will accept sounds meeting the requirements of 
the final rule.
    While the minimum sound requirements in the final rule increase 
above 55 dB(a) for the 20 km/h and 30 km/h pass-by tests, sound emitted 
from other sources on the vehicle, such as the tires, increases as the 
vehicle increases speed as well. NHTSA believes that the increased 
sound from these other sources will limit the extent to which drivers 
notice, and are negatively affected by, the sound produced in 
compliance with this final rule at 20 km/h and 30 km/h.
    NHTSA finds that it is difficult to draw conclusions about consumer 
acceptance of sounds meeting requirements of the final rule from the 
survey submitted by Toyota. The Toyota survey does not breakout the 
views of the participants in the survey by operating speed like the 
survey

[[Page 90478]]

conducted by Nissan. One of the conditions included by Toyota was a 40 
km/h pass-by for which the agency did not propose requirements in NPRM. 
Furthermore, the Toyota study did not state the overall sound pressure 
level of the sound to which the participants were exposed during the 
test. We believe that reducing the number of required one-third octave 
bands to either four or two and allowing manufacturers to comply with 
the requirements of the final rule by placing minimum content in the 
mid-range one-third octave bands from 500 Hz to 2000 Hz will allow 
manufacturers more flexibility to create pleasing sounds.
    The final EA replicates the findings of the draft EA indicating 
that sounds emitted by EVs/HVs in compliance with this final rule will 
be noticeably louder than EVs/HVs without added noise but will produce 
less sound than the average ICE vehicle. For this reason we do not 
believe that the requirements in the final rule will lead to sounds 
that will be so loud as to be annoying to drivers and pedestrians or to 
effect consumers' desire to buy these vehicles. Furthermore, according 
to the analysis of national annual noise caused by this final rule in 
the Final EA, EVs and HVs subject to the final rule would only be 
required to emit sound in compliance with this rule during 2.3 percent 
of all travel hours in urban areas.\143\ Therefore, the amount of time 
during which drivers and pedestrians would be exposed to sounds 
produced in compliance with the final rule is limited which also limits 
the possibility for annoyance to drivers and pedestrians.
---------------------------------------------------------------------------

    \143\ NHTSA, Minimum Sound Requirements for Hybrid and Electric 
Vehicles; Final Environmental Assessment (2016), at p. 56. (docket 
NHTSA-2011-0100).
---------------------------------------------------------------------------

    This is not the case for LSVs, however. These vehicles have top 
speeds of greater than 20 mph and less than 25 mph and, because final 
rule would require sound at speeds of up to 18.6 mph, sound is likely 
to be nearly constant for these vehicles. In addition, these vehicles 
are often open, lacking windows and, sometimes doors. For this reason, 
occupants of these vehicles are likely to hear the required sounds more 
so than occupants of other vehicles. However, we did not receive any 
comments indicating that consumer acceptance of sounds required by this 
final rule would be a greater issue for owners of LSVs than other 
vehicles to which this rule applies.\144\
---------------------------------------------------------------------------

    \144\ Note that the category of Low Speed Vehicles is defined in 
NHTSA regulations as vehicles whose top speed is more than 20 mph 
and not more than 25 mph. Electric vehicles with top speed of 20 mph 
or less, like many electric golf carts for example, are not 
considered LSVs and, in fact, are not regulated as motor vehicles, 
and thus are not subject to this final rule.
---------------------------------------------------------------------------

    The agency addressed comments regarding consumer acceptance of a 
sound at stationary in Section III.I of this notice. We note briefly 
here that we do not believe that the requirements in the final rule for 
EVs and HVs to emit a sound at stationary will substantially affect 
consumer acceptance of the requirements in the final rule. As indicated 
by the survey conducted by Nissan, 60 percent of consumers accepted a 
sound at stationary with an overall sound pressure level similar to the 
levels required by the final rule.
    We note that the final rule does not contain the requirements for 
broadband sound, low frequency content, and tones proposed in the NPRM. 
In satisfying the mandate in the PSEA to establish minimum sound 
requirements for EVs and HVs, NHTSA has taken several steps to minimize 
the impacts of the requirements on drivers and pedestrians while also 
ensuring that these vehicles are detectable to pedestrians when 
operating at low speed. This includes reducing the number of required 
bands and removing requirements for tones and low frequency content. 
Given these changes from the NPRM to the final rule, NHTSA believes 
manufacturers will be able to design pedestrian alert sounds that will 
be accepted by drivers and pedestrians.

J. Test Conditions

Ambient Temperature Range for Testing
    In the NPRM, we proposed that, for sound measurement testing, the 
ambient temperature be in the range 5 to 40 [deg]C. This proposal is 
consistent with SAE J2889-1. However, SAE J 2889-1 contains a note 
stating that testing of some vehicles may not be possible in warmer 
weather conditions (above 20 [deg]C) since such things as battery 
cooling fans (if there is one) will always be running. Since the NPRM 
proposed that measurements that contain sounds emitted by any component 
of a vehicle's battery thermal management system be considered not 
valid, the NPRM stated that SAE J2889-1 note will also apply to FMVSS 
No. 141 sound measurement testing. Therefore, in the NPRM preamble, 
NHTSA requested comments on narrowing the permitted temperature range 
to 5 to 20 [deg]C to improve test repeatability and to remove issues 
with battery cooling fans running.
    We received comments from Alliance/Global and Honda regarding the 
ambient temperature during testing. Both commenters were opposed to 
narrowing the permitted temperature range to 5 to 20 [deg]C to improve 
test repeatability and to remove issues with battery cooling fans 
running. Honda also recommended that the ambient weather conditions be 
measured at the specified microphone height in FMVSS No. 141 S6.4 with 
a tolerance of 0.02 meters instead of the specified 
microphone height with a tolerance of 0.0254 meters that 
was proposed in the NPRM.
Agency Response to Comments
    After the NPRM was issued, NHTSA analyzed the sound measurement 
repeatability data that it collected in 2012 for a Ford Fusion to 
determine if there were systematic effects of the atmospheric 
conditions, particularly temperature, on measured sound pressure level 
for the vehicle's 10 km/h pass-by. This data consisted of 96 individual 
measurements taken over a six-month period from April to September of 
2012. For each individual measurement the following data was recorded:
     Overall Sound Pressure Level (dBA)
     Temperature ([deg]C)
     Wind Speed (m/s)
     Wind Direction (degrees from North)
     Atmospheric Pressure (Pa)
     Relative Humidity (%)
    Analysis of variance for each variable's effect on overall sound 
pressure level showed no statistically significant variation (at the 
[alpha] = 0.05 level) for any variable over the range of the data. 
Linear modeling of all terms also showed no statistically significant 
effect on overall sound pressure level for any variable.\145\
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    \145\ For a complete analysis see, 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.
---------------------------------------------------------------------------

    Since ambient temperature has no statistically significant effect 
on measured sound data, NHTSA agrees with the commenters that we should 
not restrict ambient temperatures to between 5 [deg]C and 20 [deg]C 
(however, we note that the tendency of thermal management system 
cooling fans to activate at higher temperatures may effectively limit 
testing to this temperature range). Doing so could limit compliance 
testing opportunities while not providing any test accuracy or 
repeatability benefit. We would expect a vehicle's thermal management 
system to operate more frequently in tests during warmer ambient 
conditions. As discussed in Section III.K, the agency has clarified 
when a test can be deemed invalid, including instances when cooling 
fans engage intermittently

[[Page 90479]]

during testing. Therefore, the final rule will permit sound 
measurements to be made when the ambient temperature is in the range 
from 5 [deg]C and 40 [deg]C.
    Honda's other recommendation was that the ambient weather 
conditions be measured at the specified microphone height in FMVSS No. 
141, paragraph S6.1, with a tolerance of 0.02 meters. NHTSA 
agrees that the 0.02 meters tolerance instead of the 
proposed height tolerance of 0.0254 meters that was 
proposed in the NPRM is more consistent with SAE J2889-1.
    The NPRM used the microphone positions of S7.1 of SAE J2889-1 and 
also used the microphone height tolerance of 0.02 meters. 
It seems logically consistent to use the same height tolerance of 
0.02 meters for the meteorological instrumentation. Making 
this change is not expected to have any impact on the stringency of the 
compliance test. It will merely make testing slightly easier to 
perform. Therefore, the final rule will have a meteorological 
measurement height tolerance of 0.02 meters (2.0 centimeters).
Tire Inflation Pressure
    In the NPRM, NHTSA proposed that, prior to sound measurement 
testing, the vehicle's tires be inflated to the recommended tire 
inflation pressure listed on the vehicle's tire placard.
    EMA recommended that NHTSA adopt the tire inflation pressure 
requirements for medium and heavy trucks in FMVSS No. 121, Air Brake 
Systems. NHTSA's proposal deviates from the test procedure in FMVSS No. 
121 which states that tires will be inflated as specified by the 
vehicle manufacturer for its GVWR.
    EMA cited two factors in support of its suggestion to harmonize the 
test procedures in this final rule with those contained in FMVSS No. 
121 for tire fitment and inflation pressure. First, EMA pointed out 
that a conflict between FMVSS No. 121 and FMVSS No. 141 would add a 
burden to manufacturers without any safety benefit by imposing a unique 
tire inflation pressure specification for the new FMVSS. Second, EMA 
stated that ``the tire inflation pressures on a heavy-duty vehicle's 
certification label or tire information label may lead to inaccurate 
tire inflations.'' EMA stated that a heavy-duty vehicle's certification 
label or tire inflation pressure label contain the recommended cold 
inflation pressures for the tires identified on those labels; however, 
it is possible that the vehicle may be equipped with a tire not listed 
on those two labels.
Agency Response to Comments
    The agency has considered EMA's comments and agrees that the 
correct inflation pressure should be used for all applicable vehicles. 
For passenger cars, multipurpose passenger vehicles, light trucks, and 
buses (with GVWR of 4,536 kg or less) the requirement as proposed in 
the NPRM is appropriate. For low-speed vehicles, the required 
certification label generally includes tire size and inflation pressure 
information. All low-speed vehicles tested to date by the agency's 
Compliance division have shown the requisite tire inflation pressure 
information on the certification label.
    To address EMA's comments and ensure that all vehicles subject to 
the new safety standard are addressed in the language relating to 
recommended inflation pressure, paragraph S6.6(e) of the regulatory 
text has been revised.
Tire Conditioning
    In the NPRM, NHTSA proposed that, prior to sound measurement 
testing, the vehicle's tires be conditioned by driving it around a 
circle 30 meters (100 feet) in diameter at a speed that produces a 
lateral acceleration of approximately 0.5 to 0.6 g for three clockwise 
laps, followed by three counterclockwise laps. This tire conditioning 
procedure was derived from ISO 362, ``Road Noise for Passenger Vehicle 
Tires.''
    Honda and OICA recommended that NHTSA not require tire conditioning 
prior to testing unless NHTSA can show differences in measured acoustic 
data attributable to conditioning. OICA recommended changing the tire 
conditioning language to state that before sound measurements are 
started, the tires shall be brought to their normal operating 
conditions.
Agency Response to Comments
    NHTSA does not have measured acoustic data showing differences that 
are attributable to tire conditioning. However, NHTSA's goal for tire 
conditioning matches the OICA recommendation that, before sound 
measurements are started, the tires be brought to their normal 
operating conditions. NHTSA also thinks that sound measurement testing 
with brand new tires may produce non-representative sounds due to mold 
vents and mold lubricant. The goal of tire conditioning is to remove 
sound anomalies caused by these effects. We believe that achieving this 
goal will require minimal effort during testing. Therefore, NHTSA will 
retain tire conditioning in the final rule for passenger cars, 
multipurpose passenger vehicles, light trucks, and buses with a GVWR of 
4,536 kilograms or less, and low-speed vehicles. The final rule only 
specifies how NHTSA (not manufacturers) will perform compliance testing 
and, as with other NHTSA safety standards, manufacturers may elect not 
to adopt specific portions of a test procedure if they are convinced 
that doing so will not affect how their test results compare to the 
results from NHTSA compliance testing.
Self-Locking Doors
    In the NPRM, NHTSA proposed that the test vehicle's doors are shut 
and locked for all measurements of vehicle pedestrian alert sounds.
    NHTSA received comments on this topic from OICA and Alliance/
Global. Commenters requested that NHTSA clarify the vehicle condition 
section of the final rule test procedure for self-locking doors by 
adding a sentence saying that in the case of self-lockable vehicles, 
the doors shall be locked before starting measurement.
Agency Response to Comments
    NHTSA does not think that it is necessary to add clarification 
about vehicles with self-locking doors to the regulatory text. The 
applicable proposed regulatory text, as contained in the NPRM, is 
S6.6(b): ``The vehicle's doors are shut and locked and windows are 
shut.'' This seems quite clear. This text requires that all doors, 
whether self-locking or not, be locked prior to testing. This text is 
used in this final rule in re-numbered paragraph S6.6(a).
Accessory Equipment
    In the NPRM, NHTSA proposed that, for sound measurement testing, 
all accessory equipment (air conditioner, wipers, heat, HVAC fan, 
audio/video systems, etc.) be turned off. We also stated that 
propulsion battery cooling fans and pumps and other components of the 
vehicle's propulsion battery thermal management system are not 
considered accessory equipment.
    NHTSA received comments on this topic from OICA and Alliance/
Global. Commenters requested that NHTSA state that accessory equipment 
that cannot be shut off need not be shut off. The commenters suggested 
that the compliance test procedure prohibit the use of any results 
which include sound from any vehicle systems other than those which 
would be constantly engaged under the specified performance conditions.
Agency Response to Comments
    NHTSA's goal during compliance testing is to measure the sound

[[Page 90480]]

produced by the vehicle when it is in its quietest state after sale to 
the general public. It is not to test the vehicle in some artificially 
quiet state that will never be attained by the driving public. These 
comments are in accord with NHTSA's goal for compliance testing. The 
point made by commenters, that accessory equipment that cannot be shut 
off need not be shut off, is sensible, is in the spirit of what NHTSA 
is trying to accomplish, and clarifies a point not addressed 
previously. Therefore, in the final rule we are adding the phrase 
``that can be shut down'' to the proposed regulatory text of section 
S6.6(c) in the NPRM that dealt with accessory equipment. The re-worded 
requirement is in Section S6.6(b) of the final rule regulatory text.
Vehicle Test Weight
    In the NPRM, we proposed that, for sound measurement testing, the 
vehicle test weight will be the curb weight (as defined in 571.3) plus 
125 kilograms. Equipment, driver, and ballast should be evenly 
distributed between the left and right side of the vehicle. The vehicle 
test weight should not exceed the GVWR or Gross Axle Weight Ratings 
(GAWRs) of the vehicle.
    Commenters addressed three issues related to vehicle test weight: 
the need for the final rule to specify vehicle test weight, the need 
for a vehicle test weight tolerance, and what the specified vehicle 
test weight should be.
    Both Alliance/Global and OICA commented that vehicle test weight 
has no effect on measured vehicle sounds. Honda commented that, since 
FMVSS No. 141 testing is being conducted at relatively low vehicle 
speeds (a maximum of 30 km/h), small changes in vehicle test weight 
would have a minimal effect on measured vehicle sounds. Alliance/Global 
and OICA both commented that, if the final rule does specify vehicle 
test weight, then, for practical reasons, a vehicle test weight 
tolerance should be specified. Alliance/Global and Honda both 
recommended using the vehicle test weight specified in SAE J2889-1 
(manufacturer-defined unloaded weight + one person + measurement 
instruments).
Agency Response to Comments
    NHTSA believes that a vehicle test weight specification is 
necessary. While we have not conducted research in this area, we 
believe it is reasonable to anticipate that if a large load (relative 
to the curb weight of the vehicle) is placed in a vehicle (say 1,000 
pounds in a passenger car's trunk or 30,000 pounds on a heavy truck), 
there would likely be some change in the sound produced by the vehicle 
during testing. Therefore, we believe it is necessary to specify 
vehicle test weight in the final rule.
    In specifying vehicle test weight in other rules, NHTSA has not 
provided a weight tolerance. Organizations performing a test should 
make reasonable efforts to comply with the test specifications exactly 
as written. Therefore, we are choosing not to do so here and FMVSS No. 
141 will not contain a vehicle test weight tolerance.
    Since NHTSA agrees with the commenters that the sound produced by a 
vehicle at the relatively low test speeds being used for FMVSS No. 141 
testing is not sensitive to minor changes in vehicle loading, minor 
deviations in vehicle test weight from the exact values specified in 
the rule should not have any effect.
    As to what the vehicle test weight specified in final rule should 
be, NHTSA wants to measure sounds produced by lightly loaded vehicles. 
We believe that, all else being equal, the tires of a heavily loaded 
vehicle will produce a louder sound than will the tires of that same 
vehicle when it is lightly loaded.
    NHTSA has identified three possible alternatives for vehicle test 
weight in FMVSS No. 141. These are:
    1. Retain the NPRM vehicle test weight specification. This does not 
seem to have any particular advantages and has multiple disadvantages. 
Some of the disadvantages are that this test vehicle weight 
specification does not match that contained in SAE J2889-1; this 
vehicle test weight specification is not used by other FMVSS; and this 
vehicle test weight specification imposes weight limits on NHTSA test 
drivers. To elaborate on the last point, since the proposed NPRM 
regulatory text would require the weight above vehicle curb weight to 
be evenly balanced from side-to-side, the test driver for NPRM-based 
compliance tests cannot weigh more than 62.5 kg (138 pounds). Since a 
50th-percentile adult male weighs 76 kg (168 pounds), the use of this 
vehicle test weight specification could create difficulties in finding 
drivers to perform compliance testing.
    2. Specify the SAE J2889-1 vehicle test weight specification for 
NHTSA tests. This was the method recommended by commenters. It would 
harmonize with SAE J2889-1, and it has the advantage that NHTSA could 
use any test drivers. It has two disadvantages. First, it would mean 
that the weight of the test vehicle will vary with the weight of the 
test driver (i.e., the test weight is not a precisely specified number 
of pounds above the manufacturer-defined unloaded weight). This may not 
matter since we believe that the external sounds generated by a vehicle 
are relatively insensitive to vehicle weight. Second, this vehicle test 
weight specification is inconsistent with any other FMVSS. A given 
NHTSA test vehicle often is tested by NHTSA and by manufacturers to 
determine compliance with multiple 100-series FMVSS at one time, with 
compliance testing for one standard being performed right after that 
for another. Adopting the SAE J2889-1 vehicle test weight specification 
would require a test vehicle undergoing such a sequence of compliance 
tests to be reloaded before and after FMVSS No. 141 testing slightly 
increasing the costs of performing such testing.
    3. Specify a vehicle test weight that is specified by other NHTSA 
FMVSS. These test weights are different depending on vehicle class and 
brake system type. For pedestrian alert sound testing, a fairly lightly 
loaded weight would be used, not the heavier loading specified in some 
FMVSS. The vehicle test weight specifications used by other FMVSS are 
as follows:
     FMVSS No. 105 is applicable to vehicles with hydraulic or 
electric service brake systems and a GVWR greater than 3,500 kg (7,716 
pounds). FMVSS No. 105 defines Lightly Loaded Vehicle Weight (LLVW), 
for vehicles with a GVWR of 10,000 pounds or less, as equal to unloaded 
vehicle weight plus 400 pounds including driver and instrumentation. 
FMVSS No. 121 is applicable to vehicles with air brake systems. FMVSS 
No. 121 tests at a weight equal to unloaded vehicle weight plus 500 
pounds including driver and instrumentation plus not more than an 
additional 1,000 pounds for a roll bar structure on the vehicle (if 
needed).
     FMVSS No. 135 is applicable to vehicles with a GVWR of 
3,500 kg (7,716 pounds) or less. FMVSS No. 135 defines Lightly Loaded 
Vehicle Weight (LLVW) as equal to unloaded vehicle weight plus 180 kg 
(396 pounds) including driver and instrumentation.
     FMVSS No. 500 is applicable to low speed vehicles. FMVSS 
No. 500 defines the test weight as equal to unloaded vehicle weight 
plus 78 kg (170 pounds) including driver and instrumentation.
    NHTSA does not believe that any one of these alternatives is better 
for safety than any other. As was previously stated, NHTSA thinks that 
the sound produced by a vehicle at the relatively low test speeds being 
used for FMVSS No. 141 testing is not sensitive to minor changes in 
vehicle loading. Therefore, NHTSA's goal in selecting a test vehicle 
weight specification is to choose one that will minimize the economic 
burden of performing compliance testing. We

[[Page 90481]]

think that this alternative is best achieved through the selection of 
the third alternative listed above changing to the vehicle test weights 
specified by other NHTSA FMVSS. Vehicle test weights will therefore be 
specified by vehicle type and GVWR in the final rule.
Battery Charge During Testing
    In the NPRM, NHTSA proposed that, for sound measurement testing, 
the vehicle's electric propulsion batteries, if any, be fully charged.
    NHTSA received comments on this topic from Advocates, Alliance/
Global, Honda, Navistar, and OICA. Advocates requested that NHTSA 
either establish a battery charging procedure or require that the 
vehicle be charged in accordance with the manufacturer's stated 
charging procedure as outlined in vehicle documentation to ensure that 
the ICE or other vehicle non-essential systems do not start during 
sound testing procedures. Alliance/Global and OICA recommended using 
the language from the charging procedure in SAE J2889-1. OICA stated 
that many hybrids cannot be charged by external charge devices and that 
by driving the vehicle a 100-percent charge level will nearly never be 
reached. Honda pointed out that controlling the battery condition of a 
hybrid vehicle to attain a specific level of charge can be difficult. 
Honda recommended testing with the propulsion battery at a normal (as 
is) condition and deleting this requirement as being unnecessary. 
Navistar recommended that batteries be charged to the manufacturer's 
recommended full state of charge.
Agency Response to Comments
    NHTSA agrees with Advocates that the battery needs to be 
sufficiently charged during sound measurement testing so that the ICE 
or other vehicle non-essential systems do not automatically activate. 
Provided that this condition is met, the battery's state of charge 
during sound measurement testing should have no impact on the safety of 
the vehicle. NHTSA also agrees with commenters that precisely 
controlling the battery condition of a hybrid vehicle to attain a 
specific level of charge can be difficult. However, getting the 
battery's state of charge during testing high enough that the ICE or 
other vehicle non-essential systems do not automatically activate 
should be feasible.
    Following review of the comments, NHTSA has decided to accept the 
OICA and Alliance/Global recommendations and use the SAE J2889-1 
language for the battery charge specifications in paragraph 7.1.2.2. 
This will accomplish our two objectives of (1) having a battery's state 
of charge during testing be high enough that the ICE or other vehicle 
non-essential systems do not automatically activate, and (2) specifying 
a practicable, achievable, battery state of charge for testing.
Battery Thermal Management Systems
    In the NPRM, NHTSA proposed that measurements that included sounds 
emitted by any component of a vehicle's propulsion battery thermal 
management system are not considered valid. In addition, when testing a 
hybrid vehicle with an ICE that runs intermittently, measurements that 
contain sounds emitted by the ICE would not be considered valid 
measurements.
    NHTSA received comments on this topic from OICA and Alliance/
Global. Commenters pointed out that the battery's thermal management 
system might always be running when the vehicle is performing the test 
scenarios. Therefore, they requested that NHTSA state that a battery 
thermal management system that would normally be operating during the 
specified test conditions need not be shut down. The commenters 
suggested that the compliance test procedure prohibit the use of any 
results which include sound from any vehicle systems other than those 
which would be constantly engaged under the specified performance 
conditions.
Agency Response to Comments
    NHTSA's goal during compliance testing is to measure the sound 
produced by the vehicle when it is in its quietest state after sale to 
the general public. It is not to test the vehicle in some artificially 
quiet state that will never be attained by members of the driving 
public. These comments are in accord with NHTSA's goal for compliance 
testing. The commenters' statement, that a battery thermal management 
system that would normally be operating during the specified test 
conditions need not be shut down, is sensible and is consistent with 
what NHTSA is trying to accomplish. Clarifying this will address an 
important test factor that was not covered in the proposed version of 
the regulatory text. This factor is addressed in S7.1.2 and S7.3.2 of 
the regulatory text in this final rule. We have modified both of these 
subsections by adding appropriate wording to include systems which 
would be constantly engaged under the specified test performance 
conditions (backing, stationary, forward motion at specified speeds).

K. Test Procedure

Indoor Testing

    In the NPRM, the agency tentatively concluded that outdoor 
acoustics testing was preferable to indoor testing in hemi-anechoic 
chambers. The agency explained that outdoor testing was more 
representative of real-world vehicle-to-pedestrian interactions, and 
that outdoor tests, especially pass-by tests, transmit to the 
pedestrian not just vehicle-generated sounds (e.g., engine-powertrain 
and pedestrian alert system), but also sounds from the vehicle body's 
interaction with the atmosphere (wind noise) and road test surface 
(tire noise). These complete sound profiles are transmitted to the 
pedestrian over the ``outdoor ambient'' noise. Outdoor sounds also 
contain a Doppler shift when the vehicle is moving relative to the 
pedestrian.
    Conversely, the NPRM also explained, when a vehicle is tested on an 
indoor dynamometer in a hemi-anechoic chamber, the body of the vehicle 
is static and does not produce aerodynamic noise. The agency said that 
it was unclear how representative the tire noise generated during 
rotation on the curved dynamometer test rollers is of actual tire-road 
noise. As explained, the vehicle approach and passing of the 
microphones could be simulated by phasing a row of microphones next to 
the vehicle, and interior tire noise could be digitally replaced with 
exterior tire noise recordings, however, the agency has not determined 
the fidelity of such methods.\146\ The agency voiced its concern about 
both the availability of repeatable specifications for all aspects of 
indoor testing and the availability of hemi-anechoic chambers in which 
to conduct compliance testing.
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    \146\ see https://www.bksv.com/en/products/PULSE-analysis-software/acoustic-application-software/pass-by-noise-testing/indoor-testing-7793 (weblink last accessed 2November2016).
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    The NPRM mentioned the agency's belief that specifications for 
outdoor testing have a more detailed history of objective and 
repeatable performance than specifications for indoor testing. The 
agency noted that a substantial amount of development and refinement 
has gone into the test procedures and facilities used for outdoor 
vehicle noise testing.
    The NPRM explained that SAE J2889-1 contains specifications on the 
cut-off frequency of the indoor hemi-anechoic test facility and 
requirements. However, the agency stated that it was not aware of 
specifications for dynamometer drum surface textures, materials, 
diameters, road loads coefficients (i.e., to produce

[[Page 90482]]

appropriate engine RPMs), etc. to allow comparable results between 
different indoor dynamometers.
    Lastly, the NPRM explained that there are some advantages to 
testing indoors. Testing in an indoor hemi-anechoic chamber would not 
be influenced by weather conditions or high ambient noise levels that 
can affect outdoor testing. Indoor testing could be more predictable 
and time efficient than outdoor pass-by testing because testing time 
would not be limited by weather and noise conditions at the test site. 
The agency sought comment on the availability of hemi-anechoic 
facilities that could accommodate indoor pass-by testing and the 
desirability of including a test procedure for indoor pass-by testing 
in this standard.
    Auto manufacturers and groups that represent them, along with SAE, 
stated in their comments that the agency should allow indoor testing in 
the compliance test procedure. According to Alliance/Global, OEMs would 
prefer and support the use of indoor measurement facilities meeting 
specifications contained in SAE J2889-1and ISO 16254. Alliance/Global 
\147\ explained that in consideration of the practicability and 
repeatability of the required tests, they believe that the test 
conditions specified in the final rule should allow both the outdoor 
testing and indoor hemi-anechoic testing which are specified in SAE 
J2889-1. The Alliance/Global mentioned that some of its members have 
indoor hemi-anechoic chambers for pass-by testing and some do not, but 
all can gain access to them.
---------------------------------------------------------------------------

    \147\ NHTSA-2011-0148-0251.
---------------------------------------------------------------------------

    Honda stated it is necessary to include indoor test procedures in 
the final rule and requested the agency allow use of an anechoic 
chamber as an option for system testing. Honda stated that this option 
will be more practical for automakers and can yield more consistent and 
repeatable results without compromising the quality of the sound 
measurements. Honda explained that indoor chamber tests are necessary 
not only for pass-by tests, but for stationary vehicle tests using an 
artificial speed signal and component-based pitch shifting tests.
    OICA stated that indoor test facilities meeting the specifications 
in SAE J-2889-1 are an acceptable alternative to outdoor testing. 
According to OICA, hemi-anechoic test facilities are widely available 
for testing and should be allowed but not required. OICA mentioned that 
some specifications for the facilities will be needed but did not 
elaborate further.
    SAE explained that to achieve the goals of practical, repeatable, 
and reproducible test results, the use of indoor and component level 
test facilities are necessary. Furthermore, SAE stated that for 
measuring the acoustic one-third octaves at any speed greater than 
zero, the use of indoor facilities will be necessary to reduce 
measurement uncertainty.
Agency Response to Comments
    In this final rule, the agency is specifying performance 
requirements for vehicle-emitted sounds that are detectable and 
recognizable to a pedestrian as a motor vehicle in operation. All 
components of the vehicles' sound profile that convey the signature of 
a motor vehicle in operation (including aerodynamic and tire noise) up 
to the crossover speed are important facets of the vehicle's sound 
performance. Upon consideration of the above comments, and as explained 
further below, the agency has decided to only specify requirements for 
outdoor testing as proposed in the NPRM. Vehicle manufacturers may 
choose to test their vehicles indoors but the final rule has not added 
that option to the regulatory text.
    As previously mentioned, the agency believes that outdoor testing 
is more representative of real-world vehicle-to-pedestrian 
interactions, and that outdoor tests, especially pass-by tests, 
reproduce not just vehicle sounds that are internally generated (e.g., 
engine-powertrain and pedestrian alert system), but also sounds from 
the vehicle body's interaction with the atmosphere (wind noise) and 
road test surface (tire noise). When a vehicle is tested on an indoor 
dynamometer in a hemi-anechoic chamber, the body of the vehicle is 
static and does not produce aerodynamic noise. Additionally, the agency 
does not know how representative the tire noise generated during 
rotation on the curved dynamometer test rollers is of actual tire-road 
noise.
    To date, the agency has had limited experience and access to 
testing for and measuring acoustic sound levels on dynamometers in 
hemi-anechoic test chambers. As we stated in the NPRM, the test setup 
and test execution procedures for outdoor testing have long been 
established.\148\ As mentioned previously, a substantial amount of 
development and refinement has gone into the test procedures and 
facilities used for outdoor vehicle noise testing. Establishment of 
corresponding indoor procedures to be used in hemi-anechoic chambers on 
dynamometers requires further development and validation. SAE J2889-1 
contains specifications for indoor testing but does not appear to 
provide the specifications for dynamometer drum surface textures, 
materials, diameters, road loads coefficients (i.e., to produce 
appropriate engine RPMs), etc. to allow comparable results between 
different indoor dynamometers and outdoor ISO 10844 noise pads.
---------------------------------------------------------------------------

    \148\ 78 FR 2836 (Jan. 14, 2013).
---------------------------------------------------------------------------

    The agency continues to be concerned that hemi-anechoic chambers 
that have four-wheel dynamometer drive capabilities are not widely 
available for commercial testing. The agency was able to locate a large 
number of outdoor 10844 noise pads in the United States, most of which 
were available for paid use by outside parties. As mentioned in the 
NPRM, one vehicle manufacturer stated that it has nine noise pads 
throughout its global operations and we believe the standardized 
outdoor noise pads have widespread commercial availability.
    While indoor testing is appealing because it eliminates inclement 
weather and seasonal downtimes, which may provide more flexibility for 
manufacturers, we believe this is outweighed by the fact that outdoor 
testing will provide a more representative real-world condition 
including realistic interaction of the vehicle and vehicle alert system 
with the outdoor environment. The NHTSA acoustic measurement procedures 
incorporate strategies such as the rejection of test runs having 
extraneous background noise to ensure that interaction with the outdoor 
environment does not affect test results.
    Several of the commenters explained that we should allow indoor 
testing as specified in SAE J2889-1. In addition to conducting indoor 
testing in a hemi-anechoic chamber using a dynamometer to simulate 
vehicle motion, it is possible to conduct pass-by testing in an indoor 
hemi-anechoic chamber, provided sufficient space is available to allow 
testing of all test conditions. SAE J2889-1 seems to allow for both 
methods of indoor testing. Full vehicle indoor pass-by testing in a 
hemi-anechoic chamber without a dynamometer (i.e., an indoor track) 
would capture elements of the vehicle sound profile (including 
aerodynamic and tire noise) that contribute to the detectability of the 
vehicle's sound signature until the vehicle reaches the crossover 
speed. Therefore, indoor pass-by testing in a hemi-anechoic chamber is 
able to record all aspects of the vehicle's sound profile while still 
achieving the convenience and efficiency advantages of indoor

[[Page 90483]]

testing. In this case, an indoor pass-by procedure, without a 
dynamometer, would be the same as the outdoor pass-by procedure 
contained in Section 7.1.5.4 of SAE J2889-1 DEC 2014 except that the 
50-meter radius free of reflecting objects around the test track would 
not apply. The provision in SAE J2889-1 DEC 2014 that the hemi-anechoic 
chamber used for indoor pass-by testing comply with ISO 3745 or ISO 
26101 would ensure that reflection from the test enclosure would not 
interfere with the vehicle's sound measurement.
    The Alliance/Global \149\ mentioned that some OEMs have indoor 
facilities large enough to execute full vehicle pass-by tests at 
required test speeds but did not provide corresponding details. The 
agency is not aware of the availability of hemi-anechoic chambers that 
are large enough to accommodate indoor pass-by tests and continues to 
believe that the existence of such facilities is limited, which would 
be an issue if NHTSA favored this approach as an option and wanted to 
conduct its own compliance testing in such an environment.
---------------------------------------------------------------------------

    \149\ NHTSA-2011-0148-0251.
---------------------------------------------------------------------------

    SAE stated that when measuring the acoustic one-third octaves at 
any speed in excess of zero, the use of indoor facilities is necessary 
to reduce measurement uncertainty. SAE also explained that to achieve 
the goals of practical, repeatable, and reproducible test results, the 
use of indoor and component level test facilities are necessary. NHTSA 
has issued a technical report presenting an analysis of its indoor test 
data for hybrid and electric vehicles.\150\ This report includes the 
analysis of acoustic measurements in hemi-anechoic chambers equipped 
with chassis dynamometers. The analysis includes data for electric, 
hybrid, and internal combustion engine vehicles and examines ambient 
noise, repeatability and reproducibility of vehicle acoustic signals 
(measurements). The analysis includes a limited comparison of indoor 
and outdoor test data provided by Transport Canada and NHTSA in 
conjunction with Transportation Research Center (TRC).
---------------------------------------------------------------------------

    \150\ See Hastings et al. ``Analysis of Indoor Test Data for 
Hybrid and Electric Vehicles.'' (2015) U.S. Dept. of Transportation, 
Washington, DC.
---------------------------------------------------------------------------

    Test results between two indoor test sites (General Motors Milford 
Proving Grounds (MPG) and International Automotive Components (IAC)) 
and one outdoor test site (TRC) were compared. Repeatability, as 
measured by standard errors for each indoor site was good. The 
estimated mean value was found to be within 0.5 to 0.75 dB of the true 
mean with 95% confidence depending on the one-third octave band being 
analyzed. Reproducibility of estimated means between the two indoor 
tests sites was about 2 dB on average; however, individual measurements 
had significant variation resulting in a 95% confidence interval range 
of +/-2.5 dB to +/-6.7 dB depending on the one-third octave band.
    In addition to comparing the two indoor test facilities to one 
another, both facilities were also compared with outdoor measurements 
made at TRC. Measurement reproducibility between each indoor test 
facility and TRC was evaluated by comparing the average values of each 
vehicle at each one-third octave band for each speed at the respective 
sites. Results indicate that the indoor facilities tend to have higher 
acoustic sound 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. We believe that these results show that it may be necessary to 
conduct further studies about the tire/dynamometer interaction before 
any level of confidence can be established with the procedures 
utilizing a dynamometer. Because our research shows that the tire/
dynamometer interaction could influence the repeatability of the test 
and because there are no specifications for dynamometer drums or other 
aspects of indoor testing that would increase repeatability, we believe 
that the procedures for indoor testing are not currently sufficient to 
be used by the agency for compliance testing.
    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. Thus 95% confidence 
intervals would be as large as +/-9.8 and +/-9.2 dB respectively. It is 
important to keep in mind that these confidence intervals included not 
only site-to-site differences, tire/dynamometer differences, and 
differences as a result of using different vehicles and in some cases 
different model years, therefore, these confidence intervals can be 
considered a worst case. It is expected that confidence intervals for 
the same vehicles would be smaller.
    In response to the SAE comment, we note the limited data available 
seem to demonstrate that there is measurement variability inherent in 
the procedures utilized indoors and outdoors. For the one-third octave 
bands, higher levels of variability were noted between several indoor 
facilities and between indoor and outdoor facilities. The variability 
noted may be associated with different dynamometers used and the fact 
that the comparison vehicles were not in all cases the exact same 
vehicles. The agency believes that further research and specification 
refinements are required to establish and properly validate indoor 
testing utilizing dynamometers. Further discussion on test 
repeatability and reproducibility is provided in Section III.K of this 
document.
    In conclusion, after considering recent agency research and the 
comments received on the NPRM, the agency continues to believe outdoor 
testing on an ISO test pad is preferable to indoor testing in hemi-
anechoic chambers with dynamometers. Section S7 of the final rule 
specifies the test procedures for outdoor testing.
    We again note that vehicle manufacturers' testing can deviate from 
the procedures in an FMVSS, which communicate the method the agency 
will use to determine whether a vehicle complies with the requirements 
of that standard. Vehicle manufacturers may choose to test their 
vehicles indoors for the purpose of demonstrating compliance with the 
standard, but the final rule has not added that option to the 
regulatory text. The agency believes that further developments, 
refinements and validation are required before the indoor hemi-anechoic 
chambers equipped with chassis dynamometers can be specified by the 
agency. If further developments, data and information become available 
in the future the agency may decide at that time to revisit the 
possibility of adding the indoor testing option.
Test Surface for Compliance Testing
    In the NPRM, NHTSA proposed that the test surface used during 
compliance testing meet the requirements of ISO 10844:2011.
    NHTSA received comments on this topic from OICA, Alliance/Global, 
and EMA. OICA and Alliance/Global recommended that NHTSA allow 
compliance testing on a test surface meeting the requirements of either 
ISO 10844:2011 or ISO 10844:1994. They supported this recommendation by 
stating that they believe that surfaces meeting the requirements of ISO 
10844:1994 and ISO 10844:2011 are technically equivalent.

[[Page 90484]]

Agency Response to Comments
    NHTSA agrees with OICA and Alliance/Global that surfaces meeting 
the requirements of ISO 10844:1994 and ISO 10844:2011 seem to be 
technically equivalent. Our understanding is that the major impetus for 
the 2011 update of the ISO 10844 standard was to incorporate laser 
profilometry technology that has recently become available which allows 
more precise measurements of the porosity of the surface. NHTSA's 
understanding is that the majority of surfaces that are within the 1994 
standard should pass the 2011 standard without change. We know that 
this was the case for the Transportation Research Center, Inc.'s 
(TRC's) ISO sound pad that has been used for much of NHTSA's testing. 
Prior to NHTSA's testing, TRC's ISO sound pad was certified under ISO 
10844:1994. At NHTSA's request, TRC recertified their sound pad under 
ISO 10844:2011; this required certification testing but no structural 
changes to the sound pad.
    Thus a 1994 certified sound pad is likely to generate a sound 
profile equivalent to that generated on a 2011 certified surface. 
During the NHTSA's 2011 testing, a Ford Fusion vehicle was tested on 
both ISO 10844-1994 and ISO 10844-2011 surfaces and no significant 
difference in sound profile levels were found.
    For light vehicle sound measurement, NHTSA has had no difficulties 
in finding sound pads certified to ISO 10844-2011 for its testing.
    NHTSA prefers to harmonize FMVSS No. 141 with SAE J2889-1 absent 
rationale for departing from that standard. The updated version of SAE 
J2889-1 that was released in December 2014 specifies performing outdoor 
sound testing on a surface that meets the requirements of ISO 
10844:1994, ISO 10844:2011, or ISO 10844:2014. Since NHTSA believes 
these three surfaces to be technically equivalent, we are expanding the 
list of test surfaces specified for FMVSS No. 141 compliance testing to 
include those certified to any of the above three versions of ISO 
10844.
    Based on the preceding discussion, all types of vehicles to which 
this rule applies will be tested on surfaces that meet either ISO 
10844:1994, ISO 10844:2011, or ISO 10844:2014 specifications.
Vehicle Start-Up/Activation
    The NPRM proposed in Section S5.1.1 that a vehicle must emit sound 
meeting the specifications for the stationary-but-active operating 
condition ``within 500 milliseconds of activation of the vehicle's 
starting system.'' The NPRM test procedure to measure compliance with 
the proposed stationary-but-active condition included a separate 
microphone two meters in front of the vehicle on the vehicle 
centerline.\151\ We stated in the NPRM that this other microphone is 
needed in addition to the two specified in SAE J2889-1 to measure the 
sound that a pedestrian standing directly in front of a vehicle would 
hear. We wanted to ensure that there was no drop off in sound level 
from the side of the vehicle where the measurement is taken to the 
front of the vehicle, where the sound would be beneficial in warning 
pedestrians standing in front of the vehicle of its presence.
---------------------------------------------------------------------------

    \151\ The vehicle centerline is referred to as the CC' line in 
the test setup diagram in J2889-1.
---------------------------------------------------------------------------

    There were a number of comments on the proposed stationary-but-
active requirement, focusing on two aspects of the regulatory language: 
(1) The start-up delay of 500 milliseconds for the alert to begin, and 
(2) the meaning of ``activation of the vehicle's starting system'' for 
HVs and EVs.
    We note here that these two issues are directly related to the 
sound-at-stationary requirement which is discussed in Section III.C, 
``Critical Operating Scenarios,'' in today's final rule. Many of the 
NPRM comments addressed start-up delay and definition of `activation' 
to the extent that they opposed any requirement for an alert sound in 
the ``Stationary-but-Active'' operating condition. Because comments on 
the ``Stationary-but-Active'' operating condition were summarized in 
that previous section of this final rule, and we wish to avoid 
duplication, we are not repeating all of those comments here. Rather, 
we focus here on aspects of the Stationary-but-Active comments that 
directly relate to Start-up, the definition of Activation, and the 
associated measurement procedure.
    Commenters, mainly OEMs, said that 500 milliseconds is too rapid to 
emit sound in a controlled fashion, and that it is technically 
unfeasible to achieve the one-third octave band levels in that short an 
interval.
    Advocates stated that NHTSA should provide data to support the 
requirement that the alert sound must initiate and meet the acoustic 
specifications within 500 milliseconds of activation to justify that 
this is an appropriate amount of time to warn pedestrians. Advocates 
also suggested the agency should investigate the delay times of typical 
vehicles, i.e., the delay between when a vehicle is started and when it 
is able to begin moving. NHTSA's analysis to support the 500 
milliseconds requirement also should consider whether a lower sound 
level is appropriate for the parked condition.
    Honda stated that NHTSA should clarify the definition and the 
measurement procedure of ``after the vehicle's starting system is 
engaged'' in the NPRM. If the definition of ``activation is the instant 
when the driver operates the vehicle's starting system, then it may be 
possible to engage the alert sound within 500 milliseconds. However, it 
may be difficult to consistently achieve the specified one-third octave 
levels in each of the eight bands as specified by NHTSA in the proposed 
rule.
    Mitsubishi stated that the alert sound should start when a vehicle 
is shifted out of Park, and the 500 milliseconds interval should start 
at that point. Mitsubishi stated that it would be technically 
impracticable to meet the 500 milliseconds requirement from the moment 
a driver first activates the propulsion system. Mitsubishi also pointed 
out the need for NHTSA to define ``activation of the vehicle's starting 
system.''
    Denso commented that 500 milliseconds is not enough time to 
initiate the alert sound, and that only individual vehicle 
manufacturers can determine how much of a delay is necessary for a 
given vehicle. Denso also said that the safety risk to pedestrians can 
be avoided if the alert sound is emitted beginning at the moment that a 
vehicle commences motion. In that regard, Denso suggested introducing 
minimum SPL requirements for a vehicle commencing-motion sound in place 
of the minimum SPL requirements for a vehicle at ``start-up and 
stationary but activated.''
    WMU stated that 500 milliseconds should provide enough time from a 
safety standpoint because, in most cases, a driver does not initiate 
movement for several seconds after first starting up a vehicle. This 
would give any nearby pedestrian several seconds of acoustic warning.
    We also received comments from Alliance/Global stating that, for 
testing in the stationary condition, we should amend the test procedure 
to eliminate the additional measurement at a point two meters in front 
of the vehicle on the vehicle centerline since that would have applied 
only to the stationary test which they were in favor of excluding from 
the final rule.
    A number of commenters challenged the proposed requirement on the 
basis that 500 milliseconds is too short an interval for an alert 
system to become active upon vehicle start-up because

[[Page 90485]]

vehicle manufacturers cannot ensure that an alert system is fully 
engaged and operating at the required sound level in such a short 
amount of time. Commenters stated that one reason for this is speaker 
transients, i.e., once sound production begins it takes a while for it 
to stabilize. Therefore, while a vehicle's alert system may be capable 
of emitting some level of sound within 500 milliseconds, it may not 
achieve the specified sound pressure levels in each one-third octave 
band until a considerably longer time has elapsed after start-up.
    Commenters also questioned how NHTSA intends to measure the lag 
time between starting system activation and the initiation of the alert 
sound. OEMs and industry groups commented that the NPRM did not define 
what ``activation of a vehicle's starting system'' means exactly. 
Without an exact definition, any attempt to measure the lag time would 
be subject to arbitrary selection of a starting point which could 
result in inconsistent measurements.
Agency Response to Comments
    As a consequence of our decision discussed in Section III.C of this 
final rule to require sound at stationary only when a vehicle's gear 
selector is not in ``Park,'' and also due to the fact that vehicles are 
designed so that they must be in ``Park'' in order to be started, the 
proposed requirement for an alert to initiate within 500 milliseconds 
of vehicle activation is no longer applicable. Therefore, that proposed 
requirement is not included in this final rule.
    In addition, our decision on sound-at-stationary obviates the need 
for NHTSA to define the term ``activation of the vehicle's starting 
system'' as it appeared in the proposed S5.1.1 regulatory text. Because 
alert system engagement will not depend on when a vehicle is started, 
no definition of ``activation'' is necessary.
    We note that this decision does not mean that vehicles would have 
to be in motion before they are required to emit an alert sound. 
Vehicles that are not moving must emit an alert sound unless they are 
in a condition typical of a vehicle that may remain parked for some 
time. Vehicles that are stationary still would have to emit sound if 
they are, for example, waiting at a red traffic light (assuming the 
drivers do not shift to Park, in the case of automatic transmission 
vehicle, or apply the parking brake in the case of manual transmission 
vehicles). This means that vehicles that are in Park with an activated 
ignition and which are not in traffic, and which therefore are unable 
to drive off until they are put into gear, would not have to emit 
sound. For example, vehicles that are parked but idling so that 
occupants can use the heat or air-conditioning would not have to emit 
sound. We recognize that this will distinguish EVs/HVs from ICE 
vehicles since the latter emit sound whenever their engines are 
running, even in Park (although this may not be the case for ICE 
vehicles with stop-start capability.) On the other hand, an ICE vehicle 
could be parked with its ignition in the `ON' position but with its 
engine not running.
    We have decided to maintain the use of the additional front-center 
microphone for determining compliance with the stationary-but-active 
requirement. We believe this is important to ensure that pedestrians 
standing or passing in front of EVs and HVs are able to detect them. If 
the agency did not ensure that sounds produced by EVs and HVs met the 
minimum sound requirements in today's final rule two meters in front of 
the vehicle it would be possible that a pedestrian standing in front of 
an EV or HV would not be able to hear it within the vehicle's safe 
detection distance.
Vehicle Speed During Compliance Testing
    In the NPRM, NHTSA proposed that the instrumentation used to 
measure vehicle speed during compliance testing be capable of 
continuous speed measurement over the entire zone from the `AA' Line to 
the `BB' Line with an accuracy of 1.0 km/h.
    NHTSA's proposal also set a speed tolerance for valid test runs. 
For a test run to be valid, the vehicle speed must be within 1.0 km/h of the target speed for that run as the vehicle travels 
through the measurement zone from the AA' Line to the PP' Line.
    NHTSA received comments on the instrumentation used to measure 
vehicle speed during compliance testing from Honda and Alliance/Global. 
Commenters requested that NHTSA allow independent,\152\ as well as 
continuous, speed measurement during compliance testing. Honda 
requested that the accuracy specification for speed measurement 
equipment match that contained in SAE J2889-1 ( 0.5 km/h 
for continuous speed measurement devices or  0.2 km/h for 
independent speed measurement instrumentation). Alliance/Global also 
requested that the accuracy specification for independent speed 
measurement equipment match that contained in SAE J2889-1.
---------------------------------------------------------------------------

    \152\ SAE J2889-1 defines independent speed measurement as being 
when two or more separate devices are used to measure the vehicle's 
speed as it crosses the AA', BB', and PP' Lines. In comparison, 
continuous speed measurement uses one device to measure the 
vehicle's speed as it travels through the entire zone from the AA'' 
Line to the BB' Line.
---------------------------------------------------------------------------

    NHTSA received comments on the speed tolerance for valid test runs 
while the vehicle is traveling forward from Alliance/Global. They 
recommended changing the speed tolerance to -0.0/+2.0 km/h. Their 
justification for recommending this is to correct the inconsistency 
between the standard's performance requirement and compliance test 
procedure while still maintaining an overall tolerance of 2.0 km/h.
Agency Response to Comments
    NHTSA wants to harmonize FMVSS No. 141 with SAE J2889-1 when 
feasible and consistent with the agency's focus on safety. For the 
instrumentation used to measure vehicle speed during compliance 
testing, we see no reason not to harmonize with SAE J2889-1.
    Allowing independent speed measurement will not affect compliance 
test severity (or the safety benefits provided by this standard) 
because the 10 meters between the AA' Line and the PP' Line is not 
enough distance to permit the vehicle to vary more than minimally from 
the target speed.
    In the most recent versions of SAE J2889-1, the accuracy 
specification for the continuous speed measurement instrumentation 
(0.5 km/h) is tighter than the earlier SAE J2889 (Sept 
2011) version and the NHTSA's proposal of 1.0 km/h. The SAE 
J2889-1 continuous speed measurement accuracy specification is known to 
be both feasible and practical since NHTSA's commercially-purchased 
sound measurement equipment package includes speed measurement 
instrumentation with an accuracy specification of 0.1 km/h. 
The SAE J2889-1 independent speed measurement accuracy specification 
(0.2 km/h) is tighter than the SAE J2889-1 continuous speed 
measurement accuracy specification. While NHTSA does not have first-
hand knowledge of independent speed measurement, we believe that the 
SAE J2889-1 accuracy specification should be both feasible and 
practical. Therefore, NHTSA accepts Honda's recommendation and will 
make the FMVSS No. 141 speed measurement instrumentation accuracy 
specification identical to that contained in the most recent version of 
SAE J2889-1.
    Alliance/Global made a good point regarding the speed tolerance for 
valid test runs while the vehicle is traveling

[[Page 90486]]

forward. NHTSA's proposal required the vehicle to emit sounds having a 
specified level that varied with the speed of the vehicle. The required 
level varied in a stepwise manner with the steps occurring at multiples 
of 10 km/h, i.e., at 10, 20, and 30 km/h. In other words, NHTSA 
proposed that the vehicle emit sound with one sound pressure level at, 
for example, 9.9 km/h and with a different sound pressure level at 10.0 
km/h. NHTSA also proposed that compliance testing be performed at 
multiples of 10 km/h, i.e., at 10, 20, and 30 km/h. The problem is 
that, when testing at, for example, 10 km/h, due to the 1.0 
km/h speed tolerance, valid tests could be performed at any speed from 
9.0 through 11.0 km/h, inclusive. Therefore, a test performed at 9.9 
km/h would be a valid test as would a test performed at 10 km/h. 
However, as previously discussed, these two tests would have different 
required sound pressure levels.
    The Alliance/Global suggestion would avoid this problem by changing 
the speed tolerance to -0/+2 km/h. This would mean that a valid 10 km/h 
test would have to have a speed in the range from 10.0 to 12.0 km/h, 
inclusive. Alternatively, the proposed 10 km/h pass-by compliance test 
would become an 11 km/h pass-by test with a 1.0 km/h speed 
tolerance.
    The Alliance/Global suggestion is a departure from SAE J2889-1 
(which has a 10 km/h pass-by test with a 1.0 km/h speed 
tolerance). However, this idea allows NHTSA to vary the required level 
of the sounds emitted by the vehicle in a stepwise manner with the 
steps occurring at multiples of 10 km/h, i.e., at 10, 20, and 30 km/h. 
Adopting this suggestion will have only a very minor effect on the 
severity of FMVSS No. 141 compliance tests making them a little easier 
to pass since each test will now, on the average, be performed at a 1.0 
km/h faster speed. Therefore, tires, aerodynamics, etc., will 
contribute slightly more sound thereby reducing the sound that needs to 
be generated by the vehicle's external sound generation system. 
However, the differences in sounds due to this 1.0 km/h speed up are 
expected to be minor.
    Considering all of the preceding discussion, NHTSA has decided to 
adopt the Alliance/Global suggestion and change the compliance test 
speed tolerance to -0/+2 km/h. NHTSA will make this revised tolerance 
applicable to all three moving vehicle compliance tests, including the 
10, 20, and 30km/h pass-by tests.
Repeatability/Reproducibility
    NHTSA is addressing measurement variability in the final rule as a 
result of comments that were received on the NPRM, coupled with 
additional testing and analysis conducted by the agency which indicate 
that measurement repeatability and reproducibility (the latter across 
test facilities), may impact compliance testing results if not properly 
accounted for. The NPRM discussed how the agency would attempt to 
minimize test variability. However, adequate treatment was not given to 
the potential effect measurement tolerance may have on compliance 
testing.
    A critical component of every Federal motor vehicle safety standard 
is a compliance test procedure that is objective, repeatable and 
reproducible. The test procedure must be objective such that differing 
parties, including OEMs and test laboratories will interpret and 
execute the procedures the same way. The test procedure must be 
repeatable and reproducible such that the results obtained are the same 
results from test-to-test at the same test facility and across 
different test facilities.
    In the NPRM, the agency discussed its approach for minimizing test 
variability. The test procedure specified in the NPRM requires that all 
tests be conducted on a track with a surface that meets the 
requirements of ISO 10844:2011 which specifies, among other things, a 
very particular type of pavement to be used so as to minimize the 
contribution of tire noise to the sound measured. As mentioned in the 
NPRM, using a specified test track surface would minimize test 
variability.
    The NPRM also contained provisions for specific environmental 
conditions (temperature and wind specifications), vehicle conditions 
(tire set-up and conditioning, door and window opening adjustments, 
vehicle accessory settings and vehicle loading), and track/
instrumentation layout restrictions. These provisions are also 
important for minimizing test variability. The NPRM explained that the 
instruments used to make the acoustical measurements required under our 
proposal must meet the requirements of paragraph 5.1 of SAE J2889-1. 
This SAE paragraph describes procedures for calibration of the 
acoustical equipment. Use of such instruments and calibration 
procedures will ensure that test measurements can be duplicated 
repeatedly on the same vehicle at one facility, or at different test 
facilities.
    In the NPRM, the agency addressed the issue of intermittent vehicle 
sound caused by the vehicle's battery cooling fan by requiring that any 
vehicle sound measurements taken while the cooling fan is operating be 
discarded. At the time, the agency believed that this helped address 
repeatability issues caused by battery cooling fans. The NPRM required 
that for all operating conditions, four consecutive valid measurements 
be within 2 dB(A). As explained, this repetition and decibel level 
restriction would ensure repeatability of vehicle sounds without the 
presence of unwanted ambient spikes, other non-vehicle sounds, or 
intermittent sounds the vehicle may happen to make that are not 
associated with its normal operating sound.
    The agency received individual comments from Honda, Alliance/
Global, Toyota, SAE, Nissan, and Denso. These comments generally fell 
into two categories: The expected variance in recorded measurements in 
terms of size and sources of variability; and the consequences of 
manufacturers taking steps to address repeatability in compliance 
testing.
    Honda offered two comments regarding measurement variability. The 
first dealt with outdoor testing stating ``The Notice of Proposed 
Rulemaking (NPRM) requires testing of the one-third octave requirement 
at an outdoor site, but we are concerned that this poses practical 
concerns due to the low repeatability of test results which will be 
influenced by the presence of background noise.'' Honda also explained 
that it believes the ``like vehicle requirements'' are too stringent, 
and practically cannot be met due to the variability of sound producing 
devices. Honda provided an attachment with plots that indicate the 
differences in four tests by the same vehicle is more than 3dB.
    Alliance/Global stated, ``The loudness in NHTSA's proposal is 
created by summing required broadband content in eight one-third octave 
bands when the sound in each band is already loud enough for detection 
purposes. The resultant sum is a sound that is, at a minimum, 6 dB 
louder than necessary. When a compliance margin (for repeatability and 
reproducibility) and production variation is added on, this proposed 
alert sound becomes 9-12 dB louder than necessary. The decibel sound 
scale is logarithmic, so this represents a doubling in the perceived 
sound levels.''
    Alliance/Global further said that they were concerned that the run-
to-run variability is greater than the levels proposed in the NPRM. 
They stated, ``Given the uncertainties noted by SAE for the measurement 
of one-third octaves proposed in the NPRM, we

[[Page 90487]]

suggest that the tolerance should be increased to 9 dB. This applies to 
all measures of performance for compliance purposes.''
    SAE discussed measurement uncertainties in its comments. SAE said 
that for the measurements of overall Sound Pressure Levels (SPL) the 
identified site-to-site variation at 80% confidence interval is 1.4 dB. SAE said that the uncertainty for the measurements of 
one-third octave results ``has not yet been determined,'' but will be 
larger than the uncertainty for the overall SPL. According to SAE, for 
indoor measurements, the site-to-site variation of one-third octave 
levels at 95% confidence interval is expected to be in excess of 2 dB. For outdoor measurements, the site-to-site variation at 95% 
confidence interval is expected to be in excess of 6.0 dB. 
According to SAE, these estimated uncertainties should be considered 
when specifying tolerances for regulatory compliance. SAE also 
mentioned that any variation in sound output due to vehicle component 
production variability will be in addition to the measurements 
variation noted.
    Denso commented on the variability of the speaker unit itself, 
stating ``There is inherent variability in vehicle sound 
characteristics and in speaker and amplifier characteristics and 
performance. When combining this variability, it is very difficult to 
limit the sound difference within 3 dB(A) between the two vehicles, 
even for vehicles having nominally identical sound systems.'' Denso 
also went on to comment that for a 40 degree rise in temperature (0 
[deg]C to 40 [deg]C) the overall sound level would decrease by 1 dB. 
Nissan, similar to Denso, suggested in its comments that sound levels 
must be increased by the variation of speakers.
    In general, comments received stated that the variability present 
in the vehicles sound measurement is higher than the agency accounted 
for in the NPRM, and that variability could be substantial even when 
using the measurement procedures set forth in SAE J2889-1. There was 
also concern expressed by the commenters that if manufacturers increase 
vehicle alert sound pressure levels above the minimum standards to 
ensure a reasonable compliance margin, the vehicle alert sound may 
become excessively loud.
Agency Response to Comments
    Upon review and further consideration of the comments received it 
appears that the provisions for addressing variability included in the 
NPRM and discussed above are not sufficient to properly address all the 
test variability inherent in measuring vehicle acoustic alert sounds. 
To further address the issue of variability, the agency has decided to 
reduce the minimum standards required in this final rule by 4 dB in 
each one-third octave band as further discussed below. We expect sounds 
produced by EVs and HVs will exceed the minimum one-third octave band 
values in the final rule because manufacturers will design alert 
systems in order to ensure a margin of compliance. For this reason, we 
believe that vehicles complying with the final rule, the requirements 
of which have been reduced by 4 dB in each one-third octave band from 
the values provided by our revised detection model, will still emit 
alert sounds that are loud enough for pedestrians to safely detect EVs 
and HVs.
    During its research, NHTSA conducted a series of tests to determine 
the actual level of variability in the one-third octave band 
measurements.\153\ To do this, NHTSA analyzed data from a 2010 Ford 
Focus, combining over 100 individual test runs recorded at the 10 km/h 
test condition, including right and left side microphone recordings, 
that were measured at three facilities (71 test runs at Transportation 
Research Center in Marysville Ohio, 17 test runs at the Ford Motor 
Company Proving Ground in Romeo, Michigan, and 16 test runs at the 
Navistar test track in Fort Wayne, Indiana) over a period of 6 months. 
Test data were considered valid if there were no anomalies apparent in 
the sound recordings. The recorded files were analyzed using NHTSA's 
sound analysis code.
---------------------------------------------------------------------------

    \153\ NHTSA Technical Report '' Repeatability, Reproducibility, 
and Sameness of Quiet Vehicle Test Data'' (2016) Gerdus, E., Hoover, 
R.L., and Garrott, W.R.
---------------------------------------------------------------------------

    The data from the test runs were further processed using a 
bootstrap method \154\ into three datasets, consisting of 10,000 \155\ 
samples of eight randomly selected individual test runs, for each 
facility. These samples were then processed into the one-third octave 
bands utilizing the compliance procedure (the average of the first four 
valid test runs within 2 dB), generating 10,000 sets of the 13 one-
third octave bands between 315 Hz and 5000 Hz. Analyzing the datasets 
for the individual test sites, the maximum 95% confidence interval for 
the individual one-third octave bands recorded on the TRC ISO sound pad 
was 1.6 dB at 800 Hz and 1000 Hz. For the Ford MPG ISO test 
pad, the maximum value for the 95% CI of the individual one-third 
octave bands was 2.0 dB at 315 Hz, and at the Navistar ISO 
pad it was 1.2 dB at 400 Hz. Looking at all three sites, 
the overall effective maximum variation occurs in the 315 Hz one-third 
octave band with a 95% CI of 2.5 dB. A summary of the 
results is in Table 18.
---------------------------------------------------------------------------

    \154\ ``Bootstrap method'' is a statistical procedure wherein a 
data set consisting of a relatively small set of measurements is 
resampled many times over to obtain a much larger data set. This can 
improve statistical estimates and confidence intervals. For example, 
for the Ford Fusion tests on the TRC ISO sound pad at 10 km/h, NHTSA 
ran twelve test series, each consisting of eight runs, for a total 
of 96 runs. To improve our estimate of the variability in these 96 
tests, we used a bootstrap method in which all of the 96 runs were 
consolidated into one set. Single runs then were drawn randomly from 
this set and the measurement values including one-third octave band 
levels were recorded. The run drawn was then returned to the set. 
This process was repeated thousands of times using the computational 
capability of a computer. For the Fusion data, 80,000 runs 
comprising 10,000 test series were drawn in this manner which made 
it easy to directly determine the 95% confidence interval for these 
vehicle tests. We used a similar procedure to evaluate vehicle 
measurements from the Navistar and Ford MPG test facilities, to make 
up three data sets (one from each of the three test facilities).
    \155\ The dataset size of 10,000 was selected to maximize the 
overall accuracy of the analysis while maintaining a reasonable 
total computation time.

                   Table 18--Comparison of Mean and 95% Confidence Limit for the One-Third Octave Frequencies for the Three Test Sites
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                        TRC                          Ford MPG                        Navistar
                                         ------------------------------------------------------------------------------------------------     Overall
                Frequency                                       95%                             95%                             95%        effective 95%
                                            Mean level      Confidence      Mean level      Confidence      Mean level      Confidence      confidence
                                          recorded dB(A)       limit      recorded dB(A)       limit      recorded dB(A)       limit           limit
--------------------------------------------------------------------------------------------------------------------------------------------------------
315.....................................            41.6             1.3            40.4             2.0            41.8             0.6             2.5
400.....................................            42.5             1.1            41.1             1.1            42.7             1.2             2.0
500.....................................            44.1             1.0            44.3             0.9            44.4             1.0             1.7

[[Page 90488]]

 
630.....................................            46.1             1.2            45.6             1.6            46.5             0.8             2.2
800.....................................            48.4             1.6            50.4             1.3            48.3             1.1             2.3
1000....................................            49.0             1.6            50.7             1.0            49.1             0.7             2.0
1250....................................            48.8             1.4            50.1             1.1            48.9             0.6             1.9
1600....................................            49.7             1.5            51.0             1.1            49.3             0.9             2.1
2000....................................            48.6             1.5            48.7             1.0            48.0             0.5             1.9
2500....................................            46.6             1.2            46.7             1.1            46.2             0.7             1.8
3150....................................            45.2             1.2            45.1             1.0            44.9             0.9             1.8
4000....................................            44.0             0.9            43.9             0.8            43.4             0.9             1.5
5000....................................            41.9             0.8            42.0             1.2            41.5             0.8             1.6
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Furthermore, NHTSA conducted research into the effects of speaker 
variability on one-third octave band repeatability using a limited 
sample of vehicles. Testing was performed on a group of four model-year 
2014 Toyota Prius V vehicles under stationary conditions, in a hemi-
anechoic chamber, with only the alert sound generator active to 
minimize potential variability from other sources. This testing found 
that when a single vehicle was tested in the chamber, run-to-run 
variability had a 95 CI of 0.2 dB, operating with only the 
speaker active. Overall speaker variability consists of more than just 
the repeatability of any one individual speaker, as manufacturing 
tolerances will add variability when multiple speakers are tested. To 
estimate overall speaker variability, the agency analyzed the data 
across all four Prius vehicles tested. When all four vehicles were 
tested in the chamber, run-to-run variability increased to 0.8 dB.\156\
---------------------------------------------------------------------------

    \156\ See NHTSA Technical Report '' Repeatability, 
Reproducibility, and Sameness of Quiet Vehicle Test Data'' (2016) 
Gerdus, E., Hoover, R.L., and Garrott, W.R.
---------------------------------------------------------------------------

    Based upon the limited test data from this analysis, NHTSA 
estimates an overall test variability of 3.3 dB, including 
both the effective test procedure variability (2.5 dB) and 
the measured speaker variability (0.8 dB). The commenters 
indicated that the true variability is unknown and recommended that a 3 
to 9 dB increase is appropriate. To account for other, unknown sources 
of variability, the agency has decided to add an additional small 
tolerance to the variability identified during its research. 
Considering both the measured and the unknown variability, we have 
concluded that a tolerance of 4 dB adequately accounts for actual test 
variability.
    NHTSA agrees with Alliance/Global, as well as the other commenters 
that manufacturers will take into account measurement variability when 
designing alert systems to ensure compliance with the specified 
performance requirements. It is possible that with this margin added, 
the alert sound would significantly exceed the minimum sound 
requirements. As such, NHTSA has decided in this final rule to reduce 
the minimum levels that were indicated by our detectability modeling 
effort. We are implementing a reduction of 4 dB in each one-third 
octave band for all test conditions to offset the margin of compliance 
that we acknowledge is needed to address test variability and that we 
believe OEMs will build into their alert systems. As discussed above, 
our repeatability analysis has shown that a 4 dB adjustment will be 
adequate for this purpose.
    It must be made clear that the reduced minimum levels specified in 
this final rule, which include the 4-dB adjustment described above, are 
the absolute minimums allowed for safety purposes. Testing variability 
is not a justification for failing to meet these minimums which have 
been adjusted specifically to address concerns about test 
repeatability. The agency intends to pursue potential enforcement 
actions on measured levels below these minimum standards. The agency 
believes that by virtue of this 4-dB reduction in the level specified 
in each one-third octave band, manufacturers can build a reasonable 
margin of compliance into their alert systems while maintaining 
acceptable overall sound levels. We also believe this reduction, along 
with other changes in the final rule compared to the NPRM such as the 
reduction in the number of required one-third octave bands, further 
addresses concerns about customer acceptance, noise intrusion, and 
other concerns about the safety standard requiring alert sounds that 
are excessively loud.
Ambient Noise Correction
    In the NPRM, NHTSA proposed that the ambient noise be measured for 
at least 30 seconds before and after a series of vehicle tests. A 10-
second sample was then to be taken from these measurements and used to 
determine both the overall ambient noise SPL and the ambient noise 
level for each one-third octave band. The 10-second sample selected was 
to include ambient levels that were representative of the ambient 
levels that occurred during the actual vehicle measurement. As 
explained in the NPRM, it is important to know the background noise 
level during the test to get an accurate measurement of the sound made 
by the vehicle alone. Because NHTSA's proposed requirements were 
established using a one-third octave band basis, we stated that ambient 
corrections should also be calculated on a one-third octave band basis.
    The NPRM explained that SAE J2889-1 contains a procedure for 
correcting vehicle measurements at the overall sound pressure level to 
account for ambient influence. In the NPRM, we also acknowledged that 
the variance of a signal is greater on a one-third octave band basis 
than at the overall level, and thus it may be difficult to apply the 
ambient correction procedure in SAE J2889-1 to one-third octave bands. 
The NPRM further stated that SAE J2889-1 requires a peak-to-peak 
variation of less than 2 dB in order to do a valid correction. We also 
pointed out that, even if the fluctuation of the overall sound pressure 
level of the ambient is less than 2 dB, the fluctuation in some 
individual one-third octave bands would likely be higher. To address 
this concern, we proposed a procedure that

[[Page 90489]]

allowed one-third octave band correction within certain limits on both 
the peak-to-peak ambient fluctuation and the level difference between 
the vehicle measurement and the ambient. These criteria were provided 
in Table 6 in the regulatory text contained in the NPRM. They were 
chosen in order to provide a high degree of confidence that 
contamination due to an unobserved, random fluctuation would not impact 
the final reported level by more than about one half of one decibel. In 
the NPRM, we explained that increasing the acceptable peak-to-peak 
variability in the ambient correction procedure will allow for testing 
to be conducted in ambient sound environments in which the agency would 
expect to be able to make accurate measurements. NHTSA conveyed its 
position that this approach would increase flexibility in the locations 
and times when outdoor testing can be conducted without significantly 
compromising the accuracy of measurements. We sought comment on this 
topic.
    NHTSA received comments on ambient noise correction from Alliance/
Global, Honda, OICA and SAE. The comments from these organizations on 
this topic have been divided into three issues: Validity of applying 
ambient correction to one-third octave bands; a conflict in the 
correction procedure; and ambient measurement time interval.
    All commenters stated that measured one-third octave band sound 
levels generated by the vehicle could not be corrected for ambient 
noise while maintaining adequate repeatability. As stated by Honda 
``[t]he time-to-time variance of the one-third octave level of ambient 
noise is large and the ambient noise measurement and vehicle noise 
measurement are not simultaneous so that compensating by one-third 
octave level is not realistic for achieving repeatability.'' All four 
organizations therefore recommended only performing ambient noise 
correction for the measured overall SPL generated by the vehicle using 
the procedures contained in SAE J2889-1.
    OICA questioned the proposed procedure to correct the measured one-
third octave band sound levels generated by the vehicle for ambient 
noise. They pointed out that the proposed procedure contains a 
contradiction. It requires measurement of both the sounds generated by 
the test vehicle during a test and of the ambient noise at the same 
time and using the same equipment. The problem is that sound 
measurement during testing records both sounds generated by the vehicle 
(signal) and ambient noise. There is no objective method to disentangle 
the signal from the ambient noise in the recorded signal.
    Finally, OICA questioned which 10 seconds should be analyzed out of 
each 30-second-long ambient noise measurement since NHTSA did not 
specify which 10 seconds.
Agency Response to Comments
    NHTSA believes, based upon data collected and testing experience 
gained over the past several years, that measured one-third octave band 
sound levels generated by a vehicle can be corrected for ambient noise 
while maintaining adequate repeatability.
    NHTSA conducted a substantial amount of vehicle sound measurement 
repeatability testing using a 2010 Ford Fusion (with an internal 
combustion engine) to develop this rule.\157\ That testing included a 
large number of ambient noise measurements. Testing was performed on 
the ISO sound pad of the Transportation Research Center, Inc. in East 
Liberty, Ohio, and was analyzed to examine ambient noise variability. 
All of this testing was performed at night to minimize the ambient 
noise.
---------------------------------------------------------------------------

    \157\ 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.
---------------------------------------------------------------------------

    Analyses of NHTSA's measured ambient sound data found substantial 
variability. The overall ambient SPL varied over a 15.9 dB range from a 
low of 29.5 dB to a high of 45.4 dB. The ambient one-third octave band 
levels varied over a 24.4 dB range with a low of 13.6 dB and a high of 
38.0 dB.\158\ This ambient sound data was measured over a six month 
period from April to September of 2012.
---------------------------------------------------------------------------

    \158\ Ibid.
---------------------------------------------------------------------------

    NHTSA's calculations indicate that these large variations in 
ambient noise levels had only a minimal effect on the measured one-
third octave band sound levels generated by the vehicle following 
ambient noise correction.
    As per the procedure proposed in the NPRM, any sound generated by 
the vehicle at the one-third octave band level (and per SAE J2889-1 for 
the overall SPL) will not be corrected at all if it is more than 10 dB 
above the ambient noise level. NHTSA examined its vehicle sound 
measurement repeatability testing to see how frequently this situation 
occurred.
    NHTSA analyzed MY2010 Ford Fusion sound data measurement 
repeatability for five scenarios: Stationary, reverse, 10 km/h pass-by 
test, 20 km/h pass-by test, and 30 km/h pass-by test. The vehicle was 
quietest during the stationary and reverse scenarios.
    None of the Ford Fusion sound data collected during the 10 km/h 
pass-by test, 20 km/h pass-by test, or 30 km/h pass-by test were within 
10 dB of ambient levels. Therefore, no ambient noise correction was 
performed for any of these tests at the overall SPL and one-third 
octave band level.
    For the stationary scenario, 82.3 percent of tests were more than 
10 dB above ambient noise levels and did not require correction. The 
remaining 17.7 percent of tests needed to have either the overall SPL 
or one or more measured one-third octave band levels corrected. 
However, none of these tests had measured signal levels that were less 
than 3 dB above ambient noise levels (the differential below which 
tests are considered invalid).
    Electric or hybrid vehicles with an alert meeting the requirements 
of this rule may be quieter than is the 2010 Ford Fusion. This may 
result in more electric and hybrid vehicle sound tests not giving 
results that are 10 dB or more above ambient. Nevertheless, NHTSA 
believes that the effects of ambient level variability on vehicle sound 
measurement repeatability will be limited.
    The purpose of ambient noise correction is to reduce variability in 
vehicle sound measurements due to variations in the ambient noise 
level. NHTSA uses the minimum ambient noise levels, collected before 
and after a test series, for ambient correction. By doing so, the 
ambient noise levels are expected to vary little with time during a 
test session. Distinct, transient loud sounds such as chirping birds, 
overhead planes, car doors being slammed, etc., will affect the maximum 
ambient noise levels but not the minimum ambient noise levels. The 
minimum ambient noise levels are expected to be primarily the result of 
more slowly varying environmental factors such as steady state wind 
speed, the test site geometry, and the foliage on nearby vegetation. 
Therefore, NHTSA believes that the minimum ambient noise levels used 
for correction will typically be similar before, during, and after a 
test series. The ambient noise correction is expected to eliminate the 
effects of this slowly varying ambient noise from the measured sound 
levels for a vehicle.
    NHTSA also recognizes that distinct, louder events such as passing 
vehicles or wind gusts could, if they were to occur at certain times 
during a vehicle's operational sound measurement, increase both the 
measured vehicle sound and sound measurement variability. Therefore, 
NHTSA has

[[Page 90490]]

added regulatory text in the final rule stating that measurements 
containing any distinct, transient, loud sounds (e.g., chirping birds, 
overhead planes, passing trains, car doors being slammed, etc.) are 
considered invalid. Further discussion about determining the validity 
of vehicle measurements can be found in Section III.K.
    In September 2014, the agency received a copy of the latest draft 
of ISO 16254, Acoustics--Measurement of sound emitted by road 
vehicles,\159\ and in December 2014 SAE issued a revised version of SAE 
J2889-1.\160\ Both standards are of interest to the agency because, 
unlike the May 2012 version of SAE J2889-1, they both attempt to 
address measurements at the one-third octave band level as well as 
overall SPL level. These standards appear to agree with the various 
comments, including the comments received from SAE, advising against 
ambient corrections at the one-third octave band level. Both standards 
specifically state, ``Background compensation is not permitted for one-
third octave band measurements.'' Both standards also specify that when 
analyzing the one-third octave band measurements the level of 
background noise in each one-third octave band of interest shall be at 
least 6dB below the measurement of the vehicle under test in each 
respective one-third octave band. In effect, both standards state that 
the one-third octave bands cannot be corrected for ambient noise and 
that the only one-third octave bands useful for evaluation are those 
bands found to have at least a 6 dB difference between the vehicle 
measured value and the ambient measured value.
---------------------------------------------------------------------------

    \159\ NHTSA-2011-0148-0334.
    \160\ In December 2014, SAE issued a revised SAE J2889-1. That 
version of J2889-1 contains the same proscription on background 
correction at the one-third octave band level as does ISO 16254.
---------------------------------------------------------------------------

    The NPRM proposed that no corrections are needed at the one-third 
octave band level when there is at least a 10 dB difference between the 
vehicle measured value and the ambient measured value. The ISO and SAE 
standards reduce this cut-off point for one-third octave band levels to 
a 6 dB difference. Based upon the earlier discussion of test data, our 
experience has been that very few ambient corrections are required at 
the 10 dB difference level. Even fewer would be required at the 6dB 
difference level, which has the potential to reduce the number of test 
runs needed for a vehicle compliance evaluation. We agree with the 
commenters that one-third octave bands are not viable if they are 
within 3 dB of the ambient, and thus it is not necessary to consider 
whether bands at that difference level should be corrected or not.
    Accordingly, we have decided to revise the required difference 
between the vehicle and ambient at the one-third octave band level from 
10dB as proposed in the NPRM to 6 dB, the same as in the draft ISO and 
revised SAE standards, as the threshold difference between when one-
third octave bands should or should not be corrected for ambient 
conditions. Additionally, for the one-third octave bands having 3 dB to 
6 dB separation between the vehicle and ambient measurements, the 
agency has decided to continue to correct as proposed in the NPRM. The 
draft ISO and SAE standards reject all the one-third octave bands with 
separation less than 6dB whereas now the agency's procedure considers 
them usable in an attempt to reduce possible test burden by rejecting 
fewer sound measurements. Finally, as proposed in the NPRM, any bands 
found to have a separation of less than 3 dB would be considered 
unusable. These revisions have been incorporated into the respective 
tables in the final rule.
    Finally, based upon further consideration of the comments received, 
evaluation of the ambient data collected, and review of the latest ISO 
and SAE documents received, we have decided to make a few additional 
revisions to the ambient correction paragraph S6.7 in the final rule. 
These additional revisions to S6.7 are as follows:
     Ambient corrections may be required at the overall sound 
pressure level when considering which four valid test runs can be used 
for performance evaulation during each operating scenario. Ambient 
corrections at the one-third octave band level may also be required 
during the one-third octave band evaluations for each operating 
scenario. For clarification purposes Table 6 as proposed in the NPRM 
will be replaced with two new tables, Tables 6 and 7, one for overall 
SPL corrections and one for one-third octave band corrections when 
required. As in the NPRM, both of these tables are derived from Table 2 
in SAE J2889-1.
     The first column in Table 2 of SAE J2889-1 and Table 6 in 
the NPRM differentiate between ambient noise levels greater than or 
less than 25 dB. We do not believe this differentiation is required. 
Table 2 in SAE J2889-1 applies to overall SPL correction. NHTSA 
understands that SAE J2889-1 included the 25 dB breakpoint to separate 
overall SPL correction because an ambient noise of less than 25 dB in 
an outdoor setting is extremely quiet and unlikely to occur. If such a 
low ambient did occur, then the overall vehicle SPL would require 
correction only if it was within 10 dB of the ambient noise, i.e., if 
the overall SPL of the vehicle test was quieter than 35 dB. However, 
any vehicle that produces an overall SPL of less than 35 dB is very 
quiet and most likely would not comply with the requirements of this 
final rule or be heard by pedestrians. SAE J2889-1 states that in this 
situation, no overall SPL correction should be made. Instead, the 
technician conducting the test should report that the corrected overall 
SPL will be less than the measured signal overall SPL. NHTSA desires to 
correct both overall SPL and one-third octave band levels when 
necessary. Since overall SPL is the antilog of the logarithmic sum of 
all one-third octave band levels, the one-third octave band levels 
will, for any wide-band sound, be substantially lower than overall SPL. 
During NHTSA's outdoor testing, we have never seen an ambient overall 
SPL that is below 25 dB. However, we routinely have seen ambient one-
third octave band levels below 25 dB, with some being as low as 14 dB. 
Furthermore, for some scenarios and one-third octave bands, NHTSA's 
minimum safety standard criteria are set at a level below 35 dB. NHTSA 
needs a robust correction procedure that is applicable when one-third 
octave band ambient levels are below 35 dB. If ambient is less than 25 
dB in one or more one-third octave bands and the difference between 
ambient and vehicle measurements in those bands is less than 6 dB, we 
still need a way to make corrections. Therefore, NHTSA has decided to 
use the ambient noise correction procedure regardless of the level of 
ambient noise present. To accomplish this, we have removed the 25 dB 
limitation by deleting the first column and the last two rows from both 
tables.
     The second column in Table 6 of the NPRM and Table 2 of 
SAE J2889-1 sets peak-to-peak limits on the variability of measured 
ambient conditions relative to the corresponding differences measured 
between the vehicle alert sound profile and the measured ambient sound 
levels. According to the tables, the larger that difference, the larger 
the acceptable ambient peak-to-peak variation. OICA mentioned that the 
proposed procedure for ambient noise correction was confusing and 
contained a contradiction. According to OICA, the notes to NPRM Table 6 
indicated that in some test scenarios the ambient noise levels must be 
measured at the same

[[Page 90491]]

time as the actual vehicle, i.e., during the vehicle pass-by run, and 
using the same microphones. The NPRM did not state how this should be 
done. We have considered OICA's comment and agree that the notes in 
conjunction with the proposed Table 6 are confusing and contradictory. 
Ambient measurements during actual vehicle tests are not possible 
without subjective determination as to what sounds are ambient noise 
versus what are generated by the test vehicle. NHTSA does not intend to 
measure ambient and vehicle sounds at the same time through the same 
microphones. The purpose of column 2 is to ensure the validity and 
minimum variability of ambient sound files collected just prior to and 
after vehicle tests. The objective is to avoid ambient sound 
measurements that contain any distinct, transient, sounds (e.g., 
chirping birds, overhead planes, car doors being slammed, etc.) for 
correcting vehicle sound files. We understand that column 2 is intended 
to provide a quantitative method for determining when distinct, 
transient, sounds are too loud and risk causing excessive variability 
in ambient sound measurements. Clearly, a high variability in ambient 
sound can have a compounding effect on vehicle sound pressure 
variability. Such variability could have a major impact on measurement 
repeatability. Due to ambient differences, test results from one day to 
another for the same vehicle might not be the same. To minimize the 
likelihood of ambient variability, the agency has decided, as 
originally proposed in the NPRM, to use the minimum ambient level 
instead of the maximum ambient level. Use of the minimum ambient was 
discussed in more detail previously in this section. Furthermore, 
variability of the ambient sounds measured during any vehicle test may 
also cause difficulties in capturing the true vehicle alert profile. To 
address OICA's issue we have deleted the entire second column and the 
associated notes from NPRM Table 6. We have also added regulatory text 
stating that measurements containing any distinct, transient, loud 
sounds (e.g., chirping birds, overhead planes, car doors being slammed, 
etc.) are considered invalid.
     The entries in some cells in Column 4 of NPRM Table 6 and 
Table 2 of SAE J2889-1 are confusing. It is not clear what an entry of 
``Do not correct, but report OBLtestcorr,j < 
OBLtest,j'' means in the context of a NHTSA compliance test. 
Since, as previously discussed, the last two rows of NPRM Table 6 have 
been deleted, the entry of ``Do not correct, but report 
OBLtestcorr,j < OBLtest,j'' appears in 
only one cell of the table. The row containing this cell will only be 
used when the separation between the measured vehicle sound (signal) 
and the ambient (either overall SPL or one-third octave band level as 
appropriate) is less than or equal to 3 dB. NHTSA believes that a 
signal- to-ambient difference of 3 dB or less is too small to ensure 
the ambient is not influencing the measurement. Therefore, test runs 
performed for which the overall measured SPL does not exceed the 
ambient measured SPL by more than 3.0 dB should be considered not valid 
and should not be used. For test runs for which the overall measured 
SPL exceeds the ambient measured SPL by more than 3.0 dB, it is 
possible that the measured sound level may not exceed the ambient sound 
level in one or more one-third octaves. When this happens, it is 
acceptable to use the data from the one-third octave bands for which 
the measured sound levels exceeded the ambient sound levels by more 
than 3.0 dB. However, the data for those particular one-third octave 
bands for which the measured sound level was too close to the ambient 
sound are considered not valid and cannot be used.
    Appropriate modifications also have been made to paragraph S6.7 of 
the regulatory text, describing how to perform ambient noise 
corrections.
    These decisions are clarifications and refinements that are needed 
for consistent compliance testing. Because they address practical 
issues that arise from application of the ambient correction procedures 
of the NPRM, which in turn are based as closely as possible on SAE 
J2889-1, we believe these changes are within the scope of the NPRM. In 
one case, we deleted a specification that doesn't apply to NHTSA 
testing and thus is not relevant for this final rule. Another change 
clears up confusion arising from a contradiction in the ambient 
correction table as it appeared in the NPRM. Another arises from the 
agency's decision to do ambient corrections at the one-third octave 
band level which the agency explicitly proposed in the NPRM (some 
commenters disagreed with that approach, and we have addressed those 
comments in this preamble.)
    Overall, these technical changes are consistent with the SEA/ISO 
standard which the agency has referenced in the NPRM and which 
commenters urged NHTSA to adhere to. Furthermore, as we've noted, these 
refinements in the ambient correction procedure will have a very 
minimal impact on the outcomes of a small minority of tests, and they 
do not constitute any greater test stringency or an increase in the 
required sound levels over those proposed in the NPRM.
    In response to OICA's question as to which 10 seconds should be 
analyzed out of each 30 seconds (or more), NHTSA has decided that the 
entire ambient noise measurement (including an interval of 30 seconds 
or more taken before a test series and another interval of 30 seconds 
or more taken after a test series) should be analyzed. Since ambient 
noise correction is based upon the minimum ambient noise collected 
before and after a test series, analyzing the entire period collected 
instead of two 10-second periods may result in a lower minimum ambient 
noise. Having a lower minimum ambient noise makes it less likely that 
ambient noise correction of the measured vehicle sound will be 
necessary. In the event that ambient noise correction is necessary, 
having a lower minimum ambient noise reduces the magnitude of the 
resulting correction resulting in a slightly easier compliance pass/
fail criterion.
    It is NHTSA's belief that making this change to the ambient noise 
correction procedures will have no effect on safety because NHTSA 
intends to perform compliance testing on ISO sound pads during times 
with as low an ambient noise as is reasonably achievable. This will 
minimize the need for ambient noise corrections during NHTSA compliance 
testing.
Conditions for Discarding Results
    The NPRM discussed the agency's approach for measuring the sound 
produced by hybrid vehicles (HVs) without their associated internal 
combustion engines (ICEs) operating because of the need to measure the 
sound of those vehicles' in their quietest state. As explained, the 
proposal was designed to ensure that HVs and EVs emit a minimum level 
of sound in situations in which the vehicle is operating in electric 
mode because in that mode these vehicles do not provide sufficient 
sound cues for pedestrians. Therefore, we proposed to control the 
situation in which an ICE engine does start operating during a test by 
invalidating test measurements that are taken when a vehicle's ICE is 
operating. The proposed test procedure stated that when testing an HV 
with an ICE that runs intermittently, measurements that contain sounds 
emitted by the ICE are not considered valid.
    The NPRM also discussed that tests occurring within the temperature 
range specified in SAE J2889-1 can produce

[[Page 90492]]

divergent results when a vehicle is tested at different temperatures. 
In high ambient temperatures, the battery cooling fan, part of the 
thermal management system on electric vehicles, can activate 
intermittently while the vehicle is operating. As discussed, the agency 
decided to address the issue of intermittent vehicle sound caused by 
the vehicle's battery cooling fan by requiring that any vehicle sound 
measurements taken while the cooling fan is operating be discarded. 
While the agency believed that this would address repeatability issues 
caused by battery cooling fans, we noted that there may be other 
vehicle functions that produce inconsistent sound levels as a result of 
the ambient temperature. The agency tentatively concluded that we had 
sufficiently controlled this situation in the test procedure by 
invalidating measurements in which any component of the vehicle's 
thermal management system (i.e. a cooling pump or fan) is engaged. We 
solicited comments on other vehicle functions that produce varying 
noise levels at different ambient temperatures.
    Furthermore, to ensure the goal of testing the vehicle in its 
quietest state, the NPRM specified the vehicle test condition that all 
accessory equipment on the vehicle should be turned off. This step was 
included because the vehicle's air conditioning system, heating system, 
and windshield wipers, for example, can all produce sound when 
activated which can introduce inconsistency into the acoustic 
measurements.
    The NPRM went on to explain that for all operating conditions, the 
proposed test procedure (and that of SAE J2889-1) specified that four 
consecutive valid measurements be within 2 dB(A). This repetition and 
decibel level restriction are to ensure repeatability of vehicle sounds 
without the presence of unwanted ambient spikes, other non-vehicle 
sounds, or intermittent sounds the vehicle may happen to make that are 
not associated with its quiet operating state.
    As explained in the NPRM, the agency has no preference in how 
manufacturers choose to comply with the minimum sound level 
requirements in this standard. If the agency could rely on battery 
cooling fans on electric vehicles or the ICEs on hybrid vehicles to be 
activated whenever the vehicle is turned on or is moving, this may be a 
satisfactory manner for a manufacturer to comply with the minimum sound 
level requirements. However, if the battery cooling fans and the ICEs 
on hybrid-electrics are only running intermittently, then sounds 
produced by these vehicle systems cannot be relied upon to provide 
sound to pedestrians for safety purposes under all conditions. While 
the proposed specifications requiring four valid measurements within 2 
dB(A) would to some extent address repeatability issues caused by 
intermittent vehicle noise, the agency explained that it wanted to 
guard against a situation in which measurements are accepted with the 
battery cooling fans active on an EV or the ICE engaged on a hybrid-
electric if those noise sources are intermittently engaged.
    The agency also acknowledged, as discussed in the NPRM, that it may 
be possible that not all the HVs to which this proposal would apply are 
designed to be operated in EV-only mode for every operating condition 
for which the safety standard would specify requirements. Because the 
agency would be testing HVs in their quietest state, the test procedure 
and requirements as proposed were not designed to test a vehicle that 
produces added sound while its ICE is operating. Therefore, the agency 
stated it would not require that HVs meet the requirements of the 
proposal for a given operating condition if they are not capable of 
operating in electric-only mode in that operating condition. For 
example, if a vehicle is not designed to operate in electric-only mode 
above 25 km/h, it would not be required to meet the requirements in the 
proposal at any speed above that (e.g. at 30 km/h). The NPRM also 
included a provision to exclude an HV from meeting the minimum sound 
requirement for a given operating condition after ten consecutive tests 
during which the vehicle's ICE is operating during the entire test.
    In response to the NPRM and the issue of invalid test results, 
OICA, Alliance/Global, Nissan, SAE and Advocates provided comments.
    OICA recommended discarding any measurements that are influenced by 
the presence of vehicle functions that produce intermittent sounds. 
According to OICA, intermittent sound sources include cooling fans and 
pumps, and air conditioning components. OICA said that turning off the 
A/C and minimizing powertrain operation before executing a test will 
reduce the incursion of these sounds. OICA explained that ``experienced 
engineers must know what is truly an intermittent sound for a specific 
vehicle, and what is part of the normal vehicle emitted sound.'' OICA 
also asked the question about how the regulation will handle a vehicle 
whose thermal management system is always operational.
    The comments received from Alliance/Global were similar to those 
provided by OICA. These commenters recommended that the agency clarify 
for testing purposes that all auxiliary equipment capable of being shut 
off actually is shut off as part of the test procedure. Alliance/Global 
along with OICA provided several suggested regulatory text edits to 
address their related concerns.
    Nissan stated that given the complexity of EV and HEV technology 
and the expectation for future system innovation, it believes that OEMs 
would need to identify potential vehicle systems and components which 
could contribute to the overall noise measurement on a model-by-model 
basis.
    SAE explained that the 2dB criteria was included in the SAE and ISO 
standards as a data quality check and was designed to provide some 
objective criteria to assist the user of the standard to know when 
unrelated transient sounds are likely to have occurred. SAE said that 
engineering judgment by an experienced test engineer is still required 
to determine when other unrelated sounds have occurred, and a decision 
to invalidate a measurement must be made. SAE noted that there may be 
certain accessories that cannot be turned off. When tested, those 
accessories should be in the lowest noise emission mode. SAE referred 
to paragraphs 7.1.2.3 and 7.1.2.4 in SAE J2889-1 May 2012 which further 
defines accessory loads and multi-mode operation.
    Advocates for Highway Safety commented that the requirements should 
prohibit use of any test results which include sounds from any vehicle 
systems other than those which would be constantly engaged under the 
specified test conditions (backing, active but stationary, forward 
motion).
Agency Response to Comments
    The agency has considered the comments received and the suggested 
changes to the regulatory text. Based on review of the comments, NHTSA 
finds general agreement with the agency's overall approach for 
identification of valid and invalid test runs. The goal is to identify 
and utilize those test runs that exhibit a vehicle's quietest operating 
mode. In consideration of Nissan's comments about the complexity of EV/
HV technology, the agency anticipates that there will be a need to 
inquire about specific noise-generating technologies and systems 
utilized on test vehicles prior to

[[Page 90493]]

conducting FMVSS No. 141compliance testing. We note that NHTSA uses 
this approach to enforce other safety standards. For example, in FMVSS 
No. 126; Electronic Stability Control Systems, there is a requirement 
for the vehicle manufacturer to make available technical documentation 
about the ESC understeer countermeasures. Similarly, in FMVSS No. 226, 
Ejection Mitigation, there is a requirement for the vehicle 
manufacturer to make technical information about rollover sensing 
systems available to NHTSA. With this information, the agency can 
identify which systems produce noise continuously rather than 
intermittently. Once this is established, test runs that include sounds 
from intermittent ICE operations and/or intermittent thermal management 
system activations can and will be deemed invalid.
    Advocates recommended modifying the language to ``prohibit use of 
any test results which include sounds from any vehicle systems other 
than those which would be constantly engaged under the specified 
performance conditions (backing, active but stationary, forward motion 
up to 18 mph).'' During testing, all accessory equipment that can be 
physically turned off will be turned off. OICA asked about a thermal 
management system that is operational at all times. To address that, 
systems and accessories that cannot be turned off will be operated in 
their quietest mode. As mentioned by SAE, the agency agrees that 
engineering judgment by an experienced test engineer will be required 
to determine when other unrelated sounds have occurred, and a decision 
to invalidate a measurement must be made.
    In consideration of the comments received and associated changes to 
the regulatory text that were suggested, the agency has decided to 
revise the regulatory text in the final rule accordingly.
    The NPRM regulatory text addressed situations where the ICE 
``remains active for the entire duration of the test,'' but we also 
need to be concerned with an ICE or thermal management system that 
operates intermittently. If any of these three conditions occur during 
ten consecutive tests the vehicle is not required to meet the 
applicable requirements. The agency has considered the total number of 
tests that may have to be executed to acquire the necessary four valid 
tests and has decided to include an absolute number of tests that must 
be attempted before the test sequence can be terminated.
    The NPRM regulatory text did not specifically state that all 
accessories that can be physically shut off should be shut off during 
testing. That text has been added to the final rule.
Calculation of Results
    The NPRM explained that the proposed compliance test procedure was 
consistent with the Society of Automotive Engineers Surface Vehicle 
Standard J2889-1, ``Measurement of Minimum Noise Emitted by Road 
Vehicles,'' September 2011,\161\ and that several sections of the SAE 
standard were incorporated by reference into the proposed FMVSS 
regulatory text. The agency further discussed that for all pass-by 
operating conditions, the proposed test procedure (and that of SAE 
J2889-1) specified that at least four valid test trials must be 
completed while recording corresponding acoustic sound measurements for 
each operating condition, and upon completion of testing the first four 
valid trials with an overall SPL within 2 dB(A) of each other would be 
chosen for analysis. We explained that this repetition and decibel 
level restriction were to ensure repeatability of vehicle sound 
measurements without unwanted ambient disturbances, other non-vehicle 
sounds, or intermittent sounds the vehicle may happen to make that are 
not associated with its operating mode.
---------------------------------------------------------------------------

    \161\ The agency recognized that SAE had published an updated 
version of J2889-1 in May 2012. At that time we had not yet 
evaluated the new version, but said we intended to do so before 
publishing a final rule.
---------------------------------------------------------------------------

    The proposed rule required that for each pass-by test, the sound 
emitted by the vehicle at the specified speed be recorded throughout 
the measurement zone specified in S6.4. The regulatory text 
specifically stated in S7.3(a), ``The test result shall be the lowest 
value (average of the two microphones) of the four valid pass-bys. The 
test result shall be reported to the first significant digit after the 
decimal place.'' The proposed regulatory text also stated in S7.3(b), 
``The test result shall be corrected for the ambient sound level in 
each one-third octave band according to the procedure in S6.7 and the 
correction criteria given in Table 6 and reported to the first 
significant digit after the decimal place.''
    The NPRM also explained that to ensure measurements can be 
duplicated repeatably on the same vehicle at one facility or at 
different facilities, the instruments used to make the acoustical 
measurements should meet the requirements of paragraph 5.1 of SAE 
J2889-1. Since the filter roll-off rates used affect the results of the 
acoustic measurements at the one-third octave band level, the NPRM 
explained that SAE J2889-1 requires conformance with ANSI S1.11. ANSI 
S1.11 specifies a wide range for filter roll-off rates, and these 
rates, if selected at the upper and lower extremes of the range, could 
produce different results. The agency sought comment on whether the 
test procedure should specify a maximum roll-off rate that is finite.
    The agency also considered in the NPRM whether the procedures for 
analyzing the frequency spectrum in SAE J2889-1 were sufficient to 
ensure that the results of the acoustic measurements were recorded in a 
consistent manner. The agency asked additional questions about which 
filter roll-off rates have been used, if the one-third octave band 
analysis should be done in the frequency domain or in the time domain, 
and if an exponential window should be used when conducting the 
frequency analysis.
    Several organizations including Alliance/Global (combined comment), 
SAE, OICA, NFB, Honda, and Toyota submitted comments regarding the need 
to clarify the procedures for processing the acoustic measurements used 
to determine vehicle compliance.
    Alliance/Global stated that the NPRM was ambiguous as to what SPLs 
should be reported when four sets of measurements are made with two 
microphones. They suggested that the agency proposal was not clear if 
side-to-side measurements are to be averaged with the lower of the four 
measurements reported or if each side's four measurements are to be 
averaged and the lower measurement reported. Alliance/Global also 
stated that they do not agree with the use of the SAE J2889-1 ambient 
background correction procedures when applied to one-third octave band 
measurements as proposed because it differs from the ISO/SAE procedures 
which recommends correcting for ambient background only at the overall 
SPL level, not at the one-third octave band level. According to the 
Alliance/Global, its members said that they support the test procedures 
as specified in SAE J2889-1.
    SAE commented that, ``Section S7.3(a) proposed text is unclear.'' 
SAE explained that the four measurement runs are to be averaged 
independently per side, and then the lower of the two sides is chosen 
to be the intermediate or final result, as applicable, in accordance 
with SAE J2889-1. The NFB supported the SAE comments on the proper 
measurement procedure. OICA said that the overall SPL values should be 
averaged per side and that the reported final result is from the 
vehicle side with the lower average overall SPL level.
    Toyota stated, as mentioned in the Alliance/Global joint comment, 
that the

[[Page 90494]]

measurement procedure in the NPRM introduces significant variability 
within the results and that a more appropriate measurement procedure 
would be that which is specified by SAE J2889-1. Honda stated that it 
supports the principle of taking four measurements, averaging the lower 
values from each side, and reporting the calculated value, per SAE 
J2889-1.
    In regards to roll-off filter selection for post processing 
acoustic files, Alliance/Global supported the use of ANSI S1.11-2004 
Class 1 one-third octave filters as specified in SAE J2889-1. While 
they acknowledged the agency's concern regarding filter roll-off rates, 
they stated that the roll-off rate has a very small impact on the one-
third octave results (approximately 0.15 dB). Honda also voiced 
concerns regarding filter roll-off rates, in that specifying a maximum 
and sub-infinite roll-off rate in this test procedure would represent a 
change to the general standard of one-third octave analysis already 
commonly used by automakers. Honda stated that this change would create 
an extra testing burden and would require additional time for 
development of the appropriate test instruments and test procedures.
Agency Response to Comments
    It has been the agency's intention to follow the SAE J2889-1 \162\ 
test procedures, when feasible and consistent with the agency's focus 
on safety. As discussed in the NPRM and in this final rule, the agency 
has decided to evaluate HVs and EVs for detectability and recognition 
at the one-third octave band level rather than at the overall sound 
pressure level. To do this, the agency will follow the procedures 
specified in SAE J2889-1 for: (1) Obtaining the ambient sound files 
both before and after execution of a series of test trials; (2) 
measuring the sound profiles for each of the first four valid test 
trials as appropriate for each test condition; and (3) determining 
which recorded sound files to use for the one-third octave band 
evaluation. It should be noted that the agency's final rule test 
procedure augments SAE J2889-1 by specifying how exactly the selected 
acoustic measurements will be corrected for ambient conditions and 
evaluated at the one-third octave band level, which is a critical step 
in the compliance test procedure and one that is not fully detailed in 
SAE J2889-1.
---------------------------------------------------------------------------

    \162\ In the NPRM the agency officially referenced SAE Standard 
J2889-1, dated September 2011, and noted that SAE had published an 
updated version of J2889-1 in May 2012 but that we had not evaluated 
that later version and intended to do so before publishing the final 
rule. In the May 2012 version, SAE added testing protocols for 
vehicle commencing motion sound and for frequency shift 
measurements, neither of which the agency has decided to utilize as 
discussed in this final rule. The May 2012 version also included 
paragraph updates and re-numbering. In December 2014, SAE issued 
another revision to J2889-1. In the final rule we have decided to 
update the official reference for the SAE J2889-1 standard from the 
September 2011 version to the December 2014 version and have updated 
references throughout the FMVSS No. 141 standard accordingly. A 
number of OEMs, including some of those that commented on the FMVSS 
No. 141 NPRM, are parties to the SAE committee that created J2889-1, 
and they presumably had a hand in subsequent updates. The agency has 
decided to use the Dec. 2014 version since that is the most up-to-
date and since the older versions seemed to leave open some 
important technical details that are addressed to some extent in the 
latest version. Safety groups and other non-industry commenters did 
not address SAE recommended practices, so we assume they are 
indifferent about which version of the SAE standard is referenced in 
this final rule.
---------------------------------------------------------------------------

    All of the commenters indicated that the agency's proposed ambient 
correction and test procedure, S6.7 and S7, do not exactly follow the 
procedures in SAE J2889-1. SAE specifically said that our proposed 
regulatory text was unclear, and the Alliance/Global stated our 
proposed text was ambiguous. More specifically, the commenters noted 
that the proposed regulatory text specified that, for each of the four 
consecutive valid test runs collected during the pass-by tests, the 
left and right microphone files are averaged together and then the one 
run with the lowest overall SPL value was used to evaluate the one-
third octaves to determine compliance. On the other hand, the 
commenters noted that SAE J2889-1 clearly requires that the four data 
files recorded on the left side of the test vehicle are averaged, and 
the four data files recorded on the right side of the vehicle are 
averaged, and then the side of the vehicle with the lowest average 
overall SPL value should be selected to evaluate the one-third octave 
bands for compliance.
    The agency has evaluated these comments and has further scrutinized 
the proposed text and the procedure specified in SAE J2889-1. We have 
decided that the regulatory text as proposed did not match that in SAE 
J2889-1 and agree that the text should be unambiguous. We note that the 
agency's intent has been to follow SAE J2889-1 as closely as possible 
but to expand and add the necessary details not currently specified in 
SAE J2889-1 for the final evaluation of the one-third octave bands.
    We further considered how the recorded acoustic data files should 
be evaluated, and we have concluded that averaging the data files on 
each side of the test vehicle separately as required in J2889-1 
provides the most realistic results. During a pass-by scenario, a 
pedestrian listening to a vehicle driving by will be positioned on 
either the left or right side of the vehicle. Since the pedestrian will 
be on one side of the vehicle or the other as it passes, the SAE J2889-
1 procedures appropriately select the side of the vehicle that is found 
to be the quietest during the test runs. Taking an average that 
includes sound from both the left and right microphones as specified in 
the NPRM would not provide an accurate representation of what any 
pedestrian would hear. Therefore, the regulatory text has been revised 
to agree with the SAE standard.
    As mentioned previously, Alliance/Global suggested that the 
proposed regulatory text was ambiguous in regards to the steps involved 
in analyzing vehicle acoustic measurements. Upon closer examination of 
our proposed text, we believe the text should be revised to add some 
clarification and additional detail. To that end, we are providing here 
a detailed, step-by-step explanation in conjunction with several 
figures to further illustrate the process. The corresponding regulatory 
text in this final rule has been revised accordingly to make the 
procedures as unambiguous as possible.
    The process of executing vehicle measurements in each test 
condition (stationary, reverse, pass-bys), collecting necessary sound 
files, determining test run validity, and processing sound files to 
verify vehicle compliance can be broken down into five main steps, 
which are discussed in detail later in this section, and which can be 
briefly summarized as follows:
    1. For a given test condition, execute test runs and collect 
acoustic sound files;
    2. Eliminate invalid test runs and discard the corresponding sound 
files;
    3. Identify the first four valid vehicle test runs that have 
overall SPLs within 2dBA of each other;
    4. Take an average of the four overall SPLs from the left side of 
the test vehicle; separately, take an average of the four overall SPLs 
from the right side of the test vehicle; the lesser of these two 
averages will determine whether the left side or right side sound data 
are to be used for one-third octave band analysis.
    5. Evaluate either the left side or right side sound data 
(whichever had the lower average in Step 4) at the one-third octave 
band level to determine compliance.
    Each of these five steps is discussed in more detail below.
    For a given test condition, execute test runs and collect acoustic 
sound files: To begin the process, multiple test runs (at

[[Page 90495]]

least four, but generally five to seven based on NHTSA's experience) 
must be completed for each test condition (stationary, reverse, pass-
by) as specified in the regulatory test procedures. Immediately before 
and after each test condition, at least 30 seconds of ambient noise 
must be recorded. During each test run, a left (driver's side) and 
right (passenger side) acoustic sound data file must be recorded. For 
the stationary tests, data from a third microphone located directly 
ahead of the test vehicle is also recorded.
    Eliminate invalid test run acoustic sound files: The sound files 
collected from each microphone during each test run are evaluated for 
validity. The specifics for determining validity of each test run sound 
file are discussed in Section III.K, Conditions for discarding 
measurements. Each test run deemed valid must be numbered sequentially 
based upon the chronological order in which it was executed on the test 
track, and each must include a left (driver's side), right (passenger 
side), and for the stationary test condition a front center acoustic 
sound file. Sound files shall be identified with, and shall retain, 
their test run sequence number and their association with left side and 
right side microphone locations.
    Identify first four valid test run sound files within 2dBA: After a 
group of test run sound files have been determined as valid, further 
evaluation is required to identify the ``first four valid test run 
sound files with overall SPLs within 2dBA.'' Figure 10 identifies a 
flow diagram that depicts this process which is derived directly from 
SAE J2889-1.
[GRAPHIC] [TIFF OMITTED] TR14DE16.013

    For each test run, a valid left (driver's side) and a valid right 
(passenger side) sound file must exist. For each sound file the maximum 
overall SPL must be determined. Ultimately, the four test runs to be 
used for the compliance evaluation must be sequentially the first four 
valid test runs that have four left side files within 2.0dB(A) overall 
SPL and four right side files within 2.0 dB(A) overall SPL. The left 
and right side files must come from the same set of four test runs. 
This test run selection process as depicted in Figure 10 is as follows:
    Step 1: Number each valid sound measurement test run sequentially 
in the chronological order it was completed on the test track- e.g., 
Run 1, Run 2, Run 3, . . . Run N. Each test run must have a 
corresponding left (driver's side) and right (passenger side) acoustic 
sound file.
    Step 2: Determine the maximum overall SPL value for the left and 
right side sound files from each of the first 4 test runs.
    Step 3: Compare the four left side (driver's side) maximum overall 
SPL values. Calculate the difference between the largest and smallest 
of the four values. Use the same process to determine the difference 
between the largest and smallest of the four right side (passenger 
side) maximum overall

[[Page 90496]]

SPL values. If the difference is less than or equal to 2.0 dB(A) on 
both the left and right sides, then these four test runs will be used 
for the compliance evaluation, and the test run selection process for 
the given operating condition is complete. The selected runs will be 
considered the ``first four valid test runs within 2dBA.'' Otherwise, 
continue to Step 4.
    Step 4: Add data from a fifth test run to the analysis.
    Step 5: For the driver`s side microphone, list all possible 
combinations of four runs for which the largest overall SPL from any of 
the four runs minus the smallest overall SPL from any of the four runs 
is less than or equal to 2.0 dB(A).
    Step 6: For the passenger side microphone, list all possible 
combinations of four runs for which the largest overall SPL from any of 
the four runs minus the smallest overall SPL from any of the four runs 
is less than or equal to 2.0 dB(A).
    Step 7: Examine the list of run combinations developed in both Step 
5 and Step 6. If a set of four runs (e.g., Run 1, Run 2, Run 4, and Run 
5) appears in both the Step 5 and Step 6 lists, enter it into a new 
list (the Step 7 list).
    Step 8: The Step 7 list can possibly contain zero, one, or more 
entries. If the Step 7 list has zero entries, skip to Step 10. If the 
Step 7 list contains exactly one entry, then that entry is the set of 
runs for which final data will be analyzed. For this case, terminate 
the run selection procedure. This set of runs will be considered the 
``first four valid test run sound files within 2.0dBA.'' If the Step 7 
list contains more than one entry, go to Step 9.
    Step 9: Case for which the Step 7 list contains more than one 
entry. Sum the run numbers for each set of runs in the Step 7 list. For 
example, if an entry contains Run 1, Run 2, Run 4, and Run 5, then the 
sum of its run numbers would be 12 (1+2+4+5). Select the entry which 
has the lowest sum of run numbers. This set of runs is the set for 
which final data will be analyzed for compliance. At this point, 
terminate the run selection procedure. This set of runs will be 
considered the ``first four valid test run sound files within 2.0dBA.'' 
[Note: When there are five runs being considered, it is mathematically 
impossible for the sums of the run numbers for the two entries in the 
Step 7 list to be exactly the same. One entry will always have a lower 
value. However, in NHTSA's experience there have been cases in which 
six or seven test runs are needed to find a set of four shared by the 
driver's and passenger's sides that have Overall SPLs within 2.0 dB(A). 
It might be possible (although the agency has not yet had it happen) in 
these situations for the sums of the run numbers for the two entries in 
the Step 7 list to be exactly the same. If this occurs, our procedure 
will be to eliminate the combination of four runs containing the 
highest run number. If the highest run number is the same in both four-
run combinations, we then will eliminate the combination of four runs 
containing the second highest run number, and so on.]
    Step 10: Case for which the Step 7 list contains zero entries. In 
this situation, add data from another test run to the analysis and 
return to Step 5. [Note: In NHTSA's experience, there have been 
instances in which it was necessary to examine data from as many as 
seven runs to find a set of four that are shared by the driver's and 
passenger's sides that have Overall SPLs within 2.0 dB(A).]
    Note that, although data recorded by the front microphone are not 
considered when determining the ``first four valid test runs within 
2dB(A),'' those data are used when evaluating compliance with the 
directivity requirement. The front microphone data to be used for 
directivity are the data recorded during the ``first four valid test 
runs within 2dB(A)'' determined according to the procedure above.
    Average sound files on test vehicle left and right sides to 
determine final files for one-third octave band processing: After the 
``first four valid test runs within 2.0dBA'' have been identified, the 
four acoustic sound files from each side of the vehicle recorded during 
those four runs are analyzed to determine which side of the vehicle was 
the quietest during test execution. Figure 11 is a flow diagram that 
depicts the process used to further identify the acoustic data files on 
a particular side of the test vehicle that will be used to evaluate 
vehicle compliance at the one-third octave band level. For each of the 
eight acoustic sound data files (four left side files and four right 
side files) the maximum overall SPL value must be identified. Each of 
the eight acoustic data file maximum overall SPL values are then 
corrected for the recorded ambient conditions as specified in the final 
rule. Finally, the four ambient-corrected maximum overall SPL values on 
each side of the vehicle are averaged together for one comprehensive 
ambient-corrected value for each side of the vehicle. The side of the 
vehicle with the lowest average ambient-corrected maximum overall SPL 
value is the side of the vehicle that is further evaluated for 
compliance at the one-third octave band level. Each of the four 
acoustic data files on the side of the vehicle with the lowest average 
ambient-corrected maximum overall SPL value are then used for the one-
third octave band evaluation as depicted in the flow diagram in Figure 
12.

[[Page 90497]]

[GRAPHIC] [TIFF OMITTED] TR14DE16.014

    In the event that the average corrected maximum overall SPL values 
for the driver's and passenger's sides are exactly equal, then the 
sound from the passenger's side will be analyzed.
    Evaluate final sound files at one-third octave band level for 
compliance verification: Figure 12 indicates the flow process for 
analyzing the selected four acoustic data files for the one-third 
octave band analysis. As shown in Figure 11, the side of the vehicle 
found to have the lowest overall average and corrected SPL value is the 
side of the vehicle that is further evaluated for compliance 
verification. The side selected has four individual acoustic data 
files. Each file is broken down into its one-third octave band levels. 
The identified one-third octave band levels in each of the four files 
are then corrected for the measured ambient levels as specified in the 
final rule. The four corrected values in each one-third octave band are 
then averaged together to get the average corrected sound pressure 
level in each one-third octave band. The averaged corrected values in 
each one-third octave band are then compared directly to the minimum 
standards specified in this final rule to determine compliance.
    The stationary test condition, ``first four valid test runs within 
2dB(A)'' also has front microphone acoustic data. Each sound file for 
the front microphone is broken down into its one-third octave band 
levels. The identified one-third octave band levels in each of the four 
files are then corrected for the measured ambient levels as specified 
in the final rule. The four values calculated in each one-third octave 
band are then averaged together to get the average ambient-corrected 
sound pressure level in each one-third octave band. The averaged, 
corrected values in each one-third octave band are then compared 
directly to the minimum standards specified in this final rule to 
determine compliance.
    As explained previously, the process established in this final rule 
augments the process specified in the SAE standard by clarifying the 
steps depicted in Figure 12 for processing the selected sound files for 
the one-third octave band analysis. The current version of SAE J2889-1 
does not correct one-third octave band data, as required in this final 
rule.

[[Page 90498]]

[GRAPHIC] [TIFF OMITTED] TR14DE16.015

    To address commenter issues discussed above and to add 
clarification, the final rule test procedure (paragraph S7) replaces in 
its entirety the proposed regulatory text of the corresponding section 
of the NPRM.
Data Post-Processing
    In the NPRM, the agency sought comment on data post-processing 
topics including filter roll-off rates, measurement domains and type 
windows used for frequency analyses. Few comments were received, but 
the one topic that was commented on was filter roll-off rates. The 
commenters strongly supported using the ANSI S1.11-2004 Class 1 one-
third octave filters as specified in SAE J2889-1.
    We agree that the ANSI S1.11 filters should be used for processing 
the acoustic sound files. However, as mentioned in the NPRM, the 
selected filter roll-off rates could affect the results of the acoustic 
measurements at the one-third octave band level. Furthermore, there are 
other attributes (i.e., sound analysis code window size, time used for 
exponential averaging, and the precise details of the implementation of 
the sound analysis code) that should also be considered for use in the 
data post-processing routines that can impact the final results. All of 
these critical attributes must be evaluated and defined to ensure an 
objective test procedure is specified that provides reproducible and 
repeatable test results.
    Over the past few years, the agency has used two different sound 
analysis codes for processing acoustic sound files. The first code, 
which NHTSA licensed from Bruel and Kjaer, is the B&K Pulse Reflex\TM\ 
Code (the B&K Code), and is an integral part of a commercial off-the-
shelf acoustic sound measurement system. NHTSA has utilized this system 
and software code for much of its early research testing. The B&K Code 
is a data analysis software that uses preprogrammed building blocks, 
known as elements, to form processing chains. For the purpose of 
processing sound recordings two processing chains were used, one for 
determining the overall sound pressure levels and one for determining 
the 13 one-third octave sound levels.
    The second analysis code that has been used by the agency is one 
developed by the Volpe National Transportation Systems Center (the 
Volpe Code). This sound analysis code was written using 
MatlabTM. While Matlab is a proprietary engineering based 
technical programming language, the source code developed for acoustic 
data processing is the property of the United States Department of 
Transportation and can be made publically available. This code uses a 
more traditional, language based, programing structure.
    The agency is aware of other acoustic measurement instrumentation 
and associated codes that can also be used to collect and process 
acoustic sound files but none of these other systems/codes have been 
evaluated. It is our understanding that among these codes, the two used 
by NHTSA and some of the other available codes function similarly. 
Figure 13 depicts the general process used by these various codes to 
derive the overall and one-third octave band sound values.
    The general process involves loading the sound data file, applying 
the defined acoustic sound weighting, and then performing the necessary 
respective processing to arrive at both the overall sound pressure 
level and one-third octave band values. The respective processing 
routines will be further outlined in the following sections.

[[Page 90499]]

[GRAPHIC] [TIFF OMITTED] TR14DE16.016

    For evaluation purposes, the sound data recorded during some test 
runs were analyzed using both the B&K Pulse code and the Volpe code. 
Some test runs were also analyzed using two different sets of user-
specified parameters. Analysts looking at the results from these runs 
noted that there were slightly different overall sound pressure levels 
and one-third octave band levels for the exact same sound data 
depending upon the sound analysis code and the user-selectable 
parameters used. While the differences that were seen were not large 
(less than 2.0 dBA), NHTSA believed that it needed to understand the 
source of the differences before either code could be used in a 
compliance test. Therefore, NHTSA undertook further research work after 
publication of the NPRM to evaluate and resolve this issue.
    The objective of this research was to select one sound analysis 
code and one set of user-selectable parameters for use in compliance 
testing of measured vehicle sound data. Our criteria for choosing an 
appropriate sound analysis code were:
     The code must generate correct results for mathematically-
generated test cases for which the correct result is known.
     The code must meet all of the filter requirements for one-
third octave band filters that are contained in the ANSI S1.11-2004 
Class 1 standard.
     The code can be made publically available so all 
individuals and organizations know the exact methods, specified 
parameters, and filtering being used by NHTSA.
    Table 19 shows the standard settings for the user definable 
parameters that can be set in each of the code packages that were 
evaluated.

                               Table 19--Analysis Code User-Selectable Parameters
----------------------------------------------------------------------------------------------------------------
                                      Acoustic test data analysis settings
-----------------------------------------------------------------------------------------------------------------
            Parameter                             B&K Pulse                             Volpe Matlab
----------------------------------------------------------------------------------------------------------------
General Settings:
    Sampling Frequency...........  65536 Hz..............................  65536 Hz.
    Processing Window............  Test Scenario Dependent...............  Test Scenario Dependent.
    Acoustic Weighting...........  A or Linear Weighting.................  A or Z Weighting.
Overall Sound Pressure Level
 Settings:

[[Page 90500]]

 
    Frequency span...............  25600 Hz..............................  24000 Hz.
    Overall Averaging............  Linear................................  None.
    Averaging time...............  0.05..................................  None.
One-Third Octave Band Analysis
 Settings:
    Bandwidth (Fractional Octave)  \1/3\--Base 10 Exact..................  \1/3\--Base 10 Exact.
    Upper Nominal Center           5000 Hz...............................  5000 Hz.
     Frequency.
    Lower Nominal Center           315 Hz................................  315 Hz.
     Frequency.
    Type of Octave Band Averaging  Exponential...........................  Exponential.
    Type of Time Weighting.......  Fast..................................  Fast.
    Averaging Time...............  \1/4\ seconds.........................  \1/4\ seconds.
    Tau (Time Constant)..........  \1/8\ seconds (Fast)..................  \1/8\ seconds (Fast).
----------------------------------------------------------------------------------------------------------------

    NHTSA began evaluating both codes by running the same vehicle sound 
data file through both code packages, looking to see how consistent the 
codes were relative to each other. The outcome was that each code gave 
slightly different results, even while using consistent parameter 
settings.
    To systematically determine the differences between the two 
packages, both the B&K and the Volpe sound analysis codes were checked 
to ensure that they provided known output results for known input 
values. This was done through the development of test cases that were 
processed using each of the sound analysis codes. The test cases 
consist of simple pure tones which are computer-generated rather than 
taken from actual sound recordings, and thus they have none of the 
complexity of actual acoustic measurements. The test cases provide 
elemental inputs for which the correct outputs are known in advance. 
The test cases were used to evaluate the accuracy of a given code's 
analysis routine and to compare the outputs of the two different 
analysis methods.
    Test Case 1 was a series of pure tones. The sound pressure of each 
tone as a function of time is given by a constant-amplitude, constant-
frequency, single sine wave. Multiple pure tones were generated, each 
at a different constant-frequency. For this research, two constant-
amplitudes corresponding to 40 and 60 dB sounds were used. To be 
certain of capturing all important effects for each of the 13 one-third 
octave bands of interest to NHTSA (which have nominal center 
frequencies ranging from 315 Hz to 5,000 Hz), the pure tones for Test 
Case 1, developed using Matlab\TM\, were generated at 201 individual 
frequencies each corresponding to \1/8\th of a one-third octave band 
(\1/24\th of a full octave). The frequency range over which they span 
is, nominally, 70Hz-22,300Hz. This range encompasses six full one-third 
octave bands both above, and six full one-third octave bands below, the 
13 one-third octave bands of interest to NHTSA. This range was chosen 
to ensure a full profile of how each code responds to known inputs was 
generated and understood.
    The following aspects of sound analysis code were checked using 
Test Case 1 data files:
     The correctness of the calculated amplitude, when no 
frequency weighting (Z-weighting) was applied, for a pure tone at a 
frequency corresponding to the center of each of the one-third octave 
bands of interest.
     The correctness of the calculated amplitude, when A-
weighting was applied, for a pure tone at a frequency corresponding to 
the center of each of the one-third octave bands of interest.
     The correctness of the band-pass filters that split 
frequency-weighted sound pressure level data into 13 one-third octave 
bands. NHTSA and commenters want these band-pass filters to meet all of 
the Type 1 filter requirements for one-third octave band filters that 
are contained in the standard ``ANSI S1.11-2004''. The Test Case 1 
frequencies include all of the frequencies listed in Table B1,'' of 
ANSI S1.11-2004 for the 13 one-third octave bands of interest to NHTSA.
    For the second test case, Test Case 2, thirteen pure tones were 
superimposed to form one sound-pressure signal. These thirteen pure 
tones were at the frequencies corresponding to the center of each of 
the one-third octave bands of interest. No frequency weighting (i.e., 
Z-weighting) was applied.
    Two test runs were made using Test Case 2. The first had a 40 dB 
pure tone centered at each of the one-third octave bands of interest 
(giving an Overall SPL for this test run of 51.1394 dB). The second 
used thirteen pure tones at 60 dB (giving an Overall SPL for this test 
run of 71.1394 dB). This test case was used to check the correctness of 
the calculated amplitudes when no frequency weighting (Z-weighting) was 
applied to a complex sound data waveform.
    In general, in comparing the two analysis codes using Test Case 2, 
NHTSA found very little or no difference between the calculated 
amplitudes regardless of weighting type (A- or Z-weighting) for the 
individual pure tones located at the center frequencies of each of the 
13 one-third octave bands. Each code set gave either 40 or 60 dB at 
each center frequency, as expected. The results from the two analysis 
codes were also consistent when the overall SPL for the 13 center 
frequencies were combined, and both the Volpe Matlab code and the B&K 
Pulse code produced the correct results of 51.1 dB and 71.1 dB for the 
40 dB and 60 dB inputs, respectively.
    However, in looking at the test results from Test Case 1, the two 
analysis codes were not consistent regarding their band-pass filter 
function that splits frequency-weighted sound pressure data into the 13 
one-third octave bands. When comparing the output of each of the 201 
frequencies described in Test Case 1 to the requirements specified in 
ANSI S1.11-2004, NHTSA found that the B&K software tended to 
insufficiently attenuate the frequency bands away from the nominal one-
third octave band. An example of this is shown below in Figure 14 which 
plots the minimum and maximum ANSI filter requirements, the output of 
the B&K Pulse code, and the output of the Volpe Matlab code, for the 
one-third octave band centered at 1000 Hz.

[[Page 90501]]

[GRAPHIC] [TIFF OMITTED] TR14DE16.017

    While some bands displayed better adherence to the ANSI S1.11 
specifications, all of the 13 one-third octave bands displayed similar 
results as the 1000 Hz band shown above for the B&K software. On the 
other hand, the Volpe Matlab code processed data fell well within the 
filter attenuation limits specified in ANSI S1.11-2004 Class 1 across 
all bands. Complete results for all the individual one-third octave 
bands can be found in the corresponding NHTSA research report.\163\
---------------------------------------------------------------------------

    \163\ Dr. W. Riley Garrott, Richard, L. Hoover, Eric Gerdus, and 
Sughosh J. Rao, ``Selecting a Sound Analysis Code for Use With NHTSA 
Test Procedure to Characterize Vehicle Sound'' NHTSA Technical 
Report.DOT HS 812 284.
---------------------------------------------------------------------------

    The results of our research indicate that the two codes analyzed 
have different filter algorithms. This results in the two codes 
calculating slightly different one-third octave band levels. The exact 
filtering algorithm used in the B&K code is unknown because the code is 
proprietary. The filtering algorithm used in the Volpe code is known 
and can be made public. Given the results of our examination of the two 
post-processing methods, NHTSA has decided to use the Volpe Matlab code 
for the agency's future compliance testing programs. As explained 
above, one reason for this is that the Matlab code appears to be in 
full agreement with ANSI S1.11-2004 specifications and requirements. 
Also, the source code is not proprietary, and it can be made publically 
available. To resolve any potential problems with post-processing code 
conflicts, the agency will make the Matlab code to be used publically 
available, either as part of the agency's compliance test procedure, or 
posted on the agency's Web site. This approach will help the agency 
with its recent efforts to increase public communications and 
transparency. In reference to the other parameters that the agency 
inquired about in the NPRM, measurement domains and type windows used 
for frequency analyses, no direct comments were received so the agency 
has made decisions according to what it believes are technically 
correct. All the parameters that will be used for post processing the 
acoustic files will be specified in the publically available Matlab 
code.

L. Phase-In of Requirements

    The PSEA directed NHTSA to establish a phase-in period to set forth 
the dates by which production vehicles must comply with the new FMVSS 
No. 141. The PSEA also stated that NHTSA must require full compliance 
``on or after September 1st of the calendar year that begins three 
years after the date on which the final rule is issued.''
    To address these requirements in the PSEA, the NPRM proposed a 
phase-in over three model years for new hybrid and electric vehicles 
produced for sale in the U.S., and full compliance of all new hybrid 
and electric vehicles by September 1, 2018. The three-year phase-in was 
based on a `30/60/90' phase-in schedule. Given that the NPRM assumed 
publication of a final rule in calendar year 2014, the phase-in 
requirements proposed in the NPRM were: 30 percent of each OEM's HV and 
EV production in compliance by September 1, 2015; 60 percent by 
September 1, 2016; 90 percent by September 1, 2017; and 100 percent by 
September 1, 2018. The proposed phase-in schedule was intended to be 
applicable to all manufacturers of HVs and EVs, except small volume and 
final stage manufacturers. The latter were allowed to postpone 
compliance until the date on which other manufacturers were required to 
have all their vehicles brought into compliance, i.e., September 1, 
2018.
    The NPRM also included amendments to Part 585 Reporting 
Requirements to allow for OVSC verification of each manufacturer's 
phase-in of pedestrian alert systems.
    With the exception of two advocacy groups, all commenters opposed 
the phase-in requirements as proposed in

[[Page 90502]]

the NPRM. The NFB and NCSAB supported the phase-in schedule as 
proposed. The NCSAB stated that the rule should be completed by January 
2014, according to the PSEA. Neither commenter suggested an alternative 
phase-in schedule.
    All other commenters requested that NHTSA provide more lead time 
for compliance with the new safety standard. Some favored eliminating 
the phase-in altogether and establishing a single date for full 
compliance for all production hybrid and electric vehicles. 
Alternatively, commenters requested that NHTSA begin the phase-in at a 
later date, unless changes were made in the final rule to adopt 
performance requirements much less stringent than those in the NPRM. 
Honda and Alliance/Global requested that NHTSA allow for carry-forward 
credits which would give a manufacturer credit for meeting one of the 
phase-in stages prior to the deadline for that stage, and the 
manufacturer could use that credit if it did not fully meet a deadline 
of a later stage.
    A heavy vehicle OEM commented that the proposed Part 585 phase-in 
reporting should not apply to a manufacturer that achieves 100 percent 
early compliance, and also stated that paragraph S9.5 of the NPRM, 
regarding phase-in for multi-stage vehicles, is unnecessary because 
only a final stage manufacturer would be responsible for meeting the 
phase-in requirements.
    Porsche, a light vehicle manufacturer that produces only one hybrid 
model, provided proprietary production estimates through September 2018 
indicating that they would not meet the 90 percent level by the third 
year of the proposed phase-in.
    The EDTA commented that, due to the complexity of the proposal, as 
well as the technology needed to implement it, substantial lead time 
will be needed to design, develop, test and certify new alert systems. 
EDTA stated that it joined with Alliance/Global in recommending that, 
if the final rule is substantially the same as the proposal, the phase-
in specified in the final rule should be limited to a single 100-
percent compliance date that is set in accordance with the PSEA (i.e., 
September 1st of the calendar year that begins three years after the 
date on which the final rule is issued).
    Honda commented that, if the final rule must be complied with 
starting in September 2015, it would need more time to meet all the 
requirements proposed in the NPRM (modification of speakers, control 
unit, vehicle structural modifications, etc.). Therefore, Honda 
requested at least two or more years from the date that the final rule 
is issued before the phase-in requirements begin. As mentioned above, 
Honda also requested that a credit system be established as part of the 
phase-in.
    Toyota stated that it is committed to pedestrian safety, and as 
such, has already equipped every hybrid and electric vehicle it 
produced since model year 2012 under the Toyota and Lexus brands 
(currently, there is no Scion HV or EV) with a pedestrian alert sound 
meeting the existing Japanese guidelines. However, Toyota noted that 
the proposed requirements of the NPRM would require significant 
redesign of Toyota's current production alert system, which will in 
turn require substantial development and test time. Therefore, Toyota 
recommended elimination of the phase-in requirements and suggested that 
NHTSA consolidate the schedule by simply requiring full compliance for 
all HVs and EVs by September 1, 2018 (assuming the final rule is 
published in calendar year 2014 or earlier).
    Alliance/Global commented that it would not be possible for 
manufacturers to meet a phase-in beginning September 1, 2014. If the 
requirements of the final rule were to be substantially similar to the 
NPRM, they recommend foregoing the phase-in and going directly to full 
implementation on September 1, 2018. However, if the final rule instead 
were to approximate the Alliance/Global recommendations, then a phase-
in period is feasible beginning with vehicles built on or after 
September 1, 2015, and ending with vehicles built on or after September 
1, 2018 (those dates would need to be adjusted should the final rule be 
significantly delayed beyond the original January 2014 deadline).
    Alliance/Global also commented that currently there are no EVs or 
HVs produced by their member companies that are capable of meeting the 
requirements proposed by NHTSA. They stated that several strategies had 
been considered, including reprogramming an existing alert sound 
control module. They also stated they had interviewed suppliers who 
currently manufacture alert systems in an effort to explore all 
possible solutions for meeting the NPRM. They concluded that 
considerably more time would be needed than a September 1, 2014 start 
of phase-in would allow to package/repackage components, develop new 
systems, source the components, and certify the new systems.
    However, Alliance/Global commented that such a phase-in schedule as 
the one they suggested still would need assistance from carry-forward 
credits (including early carry-forward credits). They recommended full 
credits for EVs and HVs that comply with their suggested sound 
specifications (assuming those were implemented in the NHTSA final 
rule) and half-credit (i.e., two vehicles equal one credit) for EVs and 
HVs that are equipped with pedestrian alert systems that do not meet 
the Alliance/Global suggested requirements, but that nevertheless 
comply with the spirit and purpose of the PSEA. If NHTSA specifies a 
phase-in, Alliance/Global stated that carry-forward credits are 
necessary for their member companies to avoid needless compliance 
expenditure on vehicle models imminently due to be phased out of 
production.
    Alliance/Global commented that small manufacturers should not be 
required to comply until the end of the phase-in period. Because no 
current EV or HV pedestrian alert sound voluntarily implemented by 
vehicle manufacturers meets NHTSA's proposed requirements, if the 
agency proceeds to a final rule that is substantially similar to the 
NPRM, Alliance/Global would prefer that NHTSA does not specify a phase-
in, and instead allows all manufacturers the maximum amount of time to 
comply with the requirements of the new safety standard.
    Finally, Alliance/Global stated that phase-in language needs to 
clarify that requirements pertain only to vehicles described in the 
Applicability section of the regulation and not to every type of 
vehicle that a full-line manufacturer produces.
    The MIC commented that, if NHTSA does decide to establish minimum 
sound requirements for motorcycles, it should extend the phase-in 
exemption for small manufacturers, including motorcycle manufacturers, 
indefinitely.
    Nissan requested that the phase-in begin at least two years 
following the issuance of a final rule. Nissan also requested that 
NHTSA provide for the use of advanced credits for vehicles that comply 
before the final date for compliance.
    Denso commented that vehicle manufacturers, as well as equipment 
suppliers, need three years of lead time before beginning phase-in of 
complying vehicles.
    Navistar questioned how the proposed phase-in meshes with Parts 567 
and 568 regarding certification of multistage vehicles.
    OICA commented that the Phase-in should include only those vehicles 
to which the performance requirements are meant to apply, i.e., certain 
hybrid and electric vehicles.

[[Page 90503]]

Agency Response to Comments
    Given that this final rule is being published in calendar year 2016 
and, furthermore, given that the PSEA stipulates full compliance on and 
after September 1st of the calendar year that begins three years after 
the date on which the final rule is issued, NHTSA is requiring 
compliance for 100 percent of HVs and EVs produced for sale in the U.S. 
by all manufacturers by no later than September 1, 2019. This 
compliance date is set forth in the Applicability section of the 
regulatory text of this final rule.
    In addition, after review of the comments submitted, NHTSA is 
adopting a one-year, 50 percent phase-in. Under this phase-in, 50 
percent of the total production volume of each manufacturer's hybrid 
and electric vehicles to which the safety standard applies, and which 
are produced by the manufacturer for sale in the United States., must 
comply by no later than September 1, 2018.
    This phase-in does not apply to multi-stage and small volume 
manufacturers. Those manufacturers would have until September 1, 2019, 
to comply. This should not have any significant effect on traffic 
safety because of the relatively small number of vehicles they produce.
    Because the phase-in period will have a duration of only one year, 
carry-forward credits would not be of any benefit. Therefore, NHTSA is 
not making any provisions in this rule for carry-forward credits.
    The agency's decision on the phase-in issues is a compromise that 
responds to comments about reducing the phase-in or eliminating it 
altogether. The one year phase-in addresses the mandatory PSEA 
requirements and ensures that any delay in getting complying vehicles 
to market will be minimized. At the same time, it responds to 
commenters' requests for additional lead time to comply and to their 
suggestions that the NPRM phase-in should be consolidated and 
simplified. A one-year phase-in provides additional flexibility for 
manufacturers as to when they bring their model lines into compliance.
    Furthermore, NHTSA has reviewed current model lines of vehicle 
manufacturers using OVSC annual compliance information and has 
determined that several of the OEMs that produce HVs and/or EVs have 
only one or two such models among their vehicle lines. This is one 
factor that we have considered in choosing an appropriate phase-in 
period. These manufacturers will benefit from a shortened phase-in 
schedule that provides additional lead time prior to the initial date 
on which the phase-in begins.

IV. International Harmonization and Stakeholder Consultation

    NHTSA is required by the PSEA to consult with the following 
organizations as part of this rulemaking: The Environmental Protection 
Agency (EPA) to assure that any alert sound required by the rulemaking 
is consistent with noise regulations issued by that agency; consumer 
groups representing visually-impaired individuals; automobile 
manufacturers and trade associations representing them; technical 
standardization organizations responsible for measurement methods such 
as the Society of Automotive Engineers, the International Organization 
for Standardization (ISO), and the UNECE World Forum for Harmonization 
of Vehicle Regulations (WP.29).
    The agency has established three dockets to enhance and facilitate 
cooperation with outside entities including international 
organizations. The first docket (No. NHTSA-2008-0108) was created after 
the 2008 public meeting was held; it contains a copy of the notice of 
public meeting in the Federal Register, a transcript of the meeting, 
presentations prepared for the meeting and comment submissions. It also 
includes NHTSA's research plan, our ``Notice of Intent to Prepare an 
Environmental Assessment for the Pedestrian Safety Enhancement Act of 
2010'' published on July 12th 2011 in the Federal Register, and the 
agency's Phase 1 and 2 research reports. (The Notice of Intent [NOI] 
and the agency's research are discussed more fully in other parts of 
this document.) The second docket (No. NHTSA-2011-0100) was created to 
collect comments on the NOI; it also includes a copy of that notice. 
The third docket (No. NHTSA-2011-0148) was created in September 2011 to 
include materials related to the rulemaking process (``The Pedestrian 
Safety Enhancement Act of 2010,'' Phase 1 and 2 research reports, 
statistical reports, meeting presentations, etc.), and outside 
comments.
    On June 25, 1998, the United States signed the 1998 Global 
Agreement, which entered into force on August 25, 2000. This agreement 
was negotiated under the auspices of the United Nations Economic 
Commission for Europe (UNECE) under the leadership of the U.S., the 
European Community (EC) and Japan. The 1998 Agreement provides for the 
establishment of Global Technical Regulations (GTRs) regarding the 
safety, emissions, energy conservation and theft prevention of wheeled 
vehicles, equipment and parts. By establishing GTRs under the 1998 
Agreement, the Contracting Parties seek to pursue harmonization in 
motor vehicle regulations not only at the national and regional levels, 
but worldwide as well.
    As a general matter, governments, vehicle manufacturers, and 
ultimately, consumers, both here and abroad, can expect to achieve cost 
savings through the formal harmonization of differing sets of standards 
when the contracting parties to the 1998 Global Agreement implement new 
GTRs. Formal harmonization also improves safety by assisting us in 
identifying and adopting best safety practices from around the world 
and reducing diverging and unwarranted regulatory requirements. The 
harmonization process also allows manufacturers to focus their 
compliance and safety resources on regulatory requirements whose 
differences government experts have worked to converge as narrowly as 
possible. Compliance with a single standard will enhance design 
flexibility and allow manufacturers to design vehicles that better meet 
safety standards, resulting in safer vehicles. Further, we support the 
harmonization process because it allows the agency to leverage scarce 
resources by consulting with other governing bodies and international 
experts to share data and knowledge in developing modernized testing 
and performance standards that enhance safety.
    Under the 1998 Agreement, countries voting in favor of establishing 
a GTR, agree in principle to begin their internal implementation 
processes for adopting the provisions of the GTR, e.g., in the U.S., to 
issue an NPRM or Advanced NPRM, within one year. The ultimate decision 
whether or not to adopt the GTR is at each contracting party's 
discretion, however, based on its determination that the GTR meets or 
does not meet its safety needs. The UNECE World Forum for Harmonization 
of Vehicle Regulations (WP.29) administers the 1998 Agreement.
    In 2009, the Ministry of Land, Infrastructure, Transport and 
Tourism (MLIT) of Japan assembled a committee to study the issue of the 
quietness of HVs. The committee concluded that an Approaching Vehicle 
Audible System (AVAS) was a realistic alternative to allow pedestrians 
who are blind or visually-impaired to detect quiet vehicles. In 2010, 
MLIT announced guidelines for AVAS based on the recommendations of the 
study committee. Although several vehicles were considered in the 
initial scope, MLIT concluded that AVAS should be

[[Page 90504]]

installed only on HVs that can run on electric motors, EVs and fuel-
cell vehicles. In terms of the activation condition, the MLIT 
recommended that AVAS automatically generate sound at least in a speed 
range from the start of a vehicle until reaching 20 km/h (12 mph) and 
when moving in reverse. The AVAS would not be required when a vehicle 
is stopped. The system may include a switch to temporarily halt the 
operation of the AVAS. The reason for including this switch is because 
the committee believes that the system is not needed on expressways 
where there are no pedestrians and to reduce other issues such as 
drivers deliberately increasing vehicle speed in order to stop the 
AVAS.
    In its March 2011 session, WP.29 determined that vehicles propelled 
in whole or in part by electric means, present a danger to pedestrians 
and consequently adopted Guidelines covering alert sounds for electric 
and hybrid vehicles that are closely based on the Japanese Government's 
guidelines. The Guidelines were published as an annex to the UNECE 
Consolidated Resolution on the Construction of Vehicles (R.E.3). 
Considering the international interest and work in this new area of 
safety, the U.S. decided to lead the efforts on the new GTR, with Japan 
as co-sponsor, and develop harmonized pedestrian alert sound 
requirements for electric and hybrid-electric vehicles under the 1998 
Global Agreement. Development of the GTR for pedestrian alert sound has 
been assigned to the Group of Experts on Noise (GRB), the group most 
experienced with vehicle sound emissions. GRB is in the process of 
assessing the safety, environmental and technological concerns to 
develop a GTR that leverages expertise and research from around the 
world and feedback from consumer groups. The U.S. is the co-chair (with 
Japan) of the informal working group on Quiet Road Transport Vehicles 
(QRTV) assigned to develop the GTR and, therefore, will guide the 
informal working group's development of the GTR. GRB will meet 
regularly and report to WP.29 until the establishment of the new GTR. 
NHTSA has been participating in the QRTV's meetings since its 
foundation and has kept the group informed about ongoing agency 
research activities as well as the results from completed research 
studies. At the time the NPRM was issued, the QRTV informal group had 
held five sessions to discuss development of a GTR on quiet vehicles.
    NHTSA has also hosted roundtable meetings with industry, technical 
organizations and groups representing people who are visually-impaired 
for the purpose of consulting with these groups on topics related to 
this rulemaking. Participating in these meetings were representatives 
from the Alliance of Automotive Manufacturers, the Global Automakers 
(formerly Association of International Automobile Manufacturers 
(AIAM)), American Council of the Blind, The American Foundation of the 
Blind (AFB), the National Federation of the Blind (NFB), The 
International Organization for Standardizations (ISO), The Society of 
Automotive Engineers (SAE), the International Organization of Motor 
Vehicles Manufacturers (OICA), The Environmental Protection Agency 
(EPA) and Japan Automobile Manufacturers Association (JAMA).
    Representatives of the EPA have also been included in our 
activities with outside organizations. They have been kept updated on 
our research activities and have actively participated in our outreach 
efforts. NHTSA has also kept up to date on EPA activities on the 
international front through the activities of the UNECE Working Party 
of Noise (GRB).
    The American Foundation of the Blind, the American Council of the 
Blind and the National Federation of the Blind have provided NHTSA with 
invaluable information about visually-impaired pedestrian safety needs 
since the 2008 Public Meeting was held.
    The Alliance of Automobile Manufacturers and Global Automakers have 
met separately with the agency to discuss our research findings and 
their ideas regarding this rulemaking. Members of both organizations 
have also met separately with the agency to discuss their own research 
findings and ideas for a potential regulatory approach to address the 
safety issues of interest to the agency.
    Automotive manufacturers that produce EVs for the U.S. market have 
developed various pedestrian alert sounds, recognizing that these 
vehicles, when operating at low speeds, may pose an elevated safety 
risk to pedestrians. They have made vehicles with sound alert systems 
available for lease by NHTSA for research purposes. This information 
has been helpful in the agency decision making process.
    The Society of Automotive Engineers (SAE) established the Vehicle 
Sound for Pedestrians (VSP) subcommittee in November 2007 with the 
purpose of developing a recommended practice to measure sounds emitted 
by ICE vehicles and alert sounds for use on EVs and HVs. Their efforts 
resulted in recommended practice SAE J2889-1, Measurement of Minimum 
Noise Emitted by Road Vehicles. The agency had been sending a liaison 
to VSP meetings starting in 2008. SAE is the U.S. technical advisory 
group to the International Organization for Standardization (ISO), and 
they both have cooperated in the development of the industry safety 
standard. The ISO document (ISO/NP 16254, Measurement of Minimum Noise 
Emitted by Road Vehicles) and the SAE document are technically 
identical. The agency used SAE J2889-1 and ISO 16254 as references in 
the NHTSA test procedure development. Other international 
organizations, such as the International Organization of Motor Vehicle 
Manufacturers (OICA) and Japan Automobile Manufacturers Association 
(JAMA) have provided NHTSA with research findings and also have 
attended various quiet vehicle meetings.
    In the NPRM, the agency concluded that the voluntary guidelines 
adopted by the Japanese government, and subsequently by the UNECE WP.29 
Committee, did not have the level of detail necessary for NHTSA to 
establish objective minimum performance requirements for creation of an 
FMVSS. We did not believe that the agency would be able to tell if a 
sound fell within one of the exclusions by means of an objective 
measurement, nor would we be able to adequately ensure that sound 
levels would be detectable by pedestrians or provide manufacturers with 
a set of requirements that they would be able to meet. The NPRM noted 
that the WP.29 QRTV work was scheduled to be completed in 2014, and a 
draft GTR adopted in November 2014.
    OICA, EU, Chrysler, EDTA, VW, and Alliance/Global all suggested 
delaying the development of a U.S. regulation on minimum noise levels 
until WP.29 has had sufficient time to develop a globally harmonized 
set of regulations via the GTR process. They stated that establishment 
of separate requirements that may or may not be harmonized with the 
recommendations under negotiation through WP.29 would harm development 
of electric drive vehicles globally and constrain the growth of the 
market as a whole.
    OICA, EU, VW, and Alliance/Global commented that the PSEA statute 
does not provide enough time for WP.29 to address all remaining 
technical issues in development of a globally harmonized standard that 
the U.S. could then adopt. EU commented that if the agency is unable to 
delay publication of a final rule that would harmonize with the 
international community, it should at a minimum ensure that any U.S. 
regulations are consistent with the recommendations of the WP.29 
Informal

[[Page 90505]]

Working Group on Quiet Road Transport Vehicles.
    The EU questioned to what extent NHTSA had taken into consideration 
the conclusions and results of the QRTV-IWG. They believed a delay in 
the NPRM process and the finalization of the new FMVSS until the new 
GTR has been drafted would contribute towards a common approach and an 
overall consensus at the international level with respect to EVs and 
HEVs.
    VW and Alliance/Global commented that if NHTSA is unable to delay 
the enactment based on statutes within the PSEA, NHTSA should inform 
the United States Congress that additional time to complete this 
rulemaking is required in order to allow for completion of the GTR so 
that a harmonized regulation can be achieved.
    Alliance/Global commented that in accordance with the QRTV Terms of 
Reference, the development of the GTR should be concluded in the fall 
of 2014, with status reports provided along the way so that the public 
can monitor the status of the activity. Alliance/Global explained that 
the benefits of having consensus on a global technical regulation are 
enormous and any potential downside related to allowing an accelerated 
GTR process to conclude prior to finalizing the NHTSA regulation will 
be negligible given that a majority of current production EVs and HVs 
are already voluntarily equipped with audible pedestrian alert systems.
    EU, VW, Chrysler, and Alliance/Global all supported using the GTR 
process to finalize any remaining technical issues towards a globally 
harmonized standard.
    WBU and MB supported using the NPRM as a basis for development of 
the WP.29 GTR.
Agency Response to Comments
    The NPRM stated that the recommendations of the QRTV informal 
working group do not include objective criteria with which the agency 
could ensure vehicles comply with an FMVSS. The agency maintains that 
this is still the case. Further, as discussed above, the agency has 
determined that a crossover speed of 30 km/h is necessary because our 
conclusion from the data we have acquired to date from all sources 
(i.e., from commenters and from our own vehicle evaluations) is that 
some hybrid and electric vehicles continue to need sound enhancement at 
speeds above 20 km/h in order to ensure that they are adequately 
detectable.
    Most of the commenters recommended that the agency wait until the 
WP.29 World Forum can complete development of a GTR for minimum sound 
levels, or, at a minimum, work closely with the QRTV in development of 
requirements that could be recognized globally. The agency, through its 
leadership role in the QRTV informal group, continues to work with the 
international community in development of criteria that are technically 
sound and objective. We note that the WP.29 QRTV work has been extended 
until late 2015, at the earliest, with expected eventual adoption of a 
GTR on minimum noise requirements for electrically driven vehicles. 
Adoption of the GTR is only the beginning of the process of regulating 
minimum noise levels by signatories of the 1998 UN agreement. After a 
GTR on minimum noise requirements is adopted, NHTSA would still need to 
issue an NPRM or an SNPRM (Supplemental Notice of Proposed Rulemaking) 
to begin the process of adopting the GTR as an FMVSS. This could result 
in several additional years of delay before an FMVSS mandating sound 
for EVs and HVs could be issued. We do not believe that a delay of this 
length is justified from a safety perspective. We believe the agency's 
approach in development of this final rule to be consistent with both 
the mission and safety goals of the agency and with the PSEA and Safety 
Act.
    We agree with WBU and MB that development of U.S. regulations for 
minimum noise levels might aid WP.29 in addressing some of the 
technical issues that hinder development of a global regulation that is 
both measurable and enforceable. We note that the leadership role of 
the U.S. delegation in development of a global regulation for minimum 
noise levels is consistent with the comments regarding using the GTR 
process to refine a harmonized regulation. In that light, we believe 
that development of a U.S. regulation would aid WP.29 in drafting a 
global regulatory framework that is both measureable and enforceable.
    The agency has also continued to actively monitor the work that has 
been done internationally by SAE and ISO. The SAE recently issued an 
updated version of J2889-1 dated December 2014. The ISO recently 
submitted the latest draft of ISO 16254 to the agency's docket.\164\ 
The agency has taken into consideration these documents to the extent 
possible for the development of this final rule.
---------------------------------------------------------------------------

    \164\ NHTSA-2011-0148-0334.
---------------------------------------------------------------------------

V. Analysis of Costs, Benefits, and Environmental Effects

A. Benefits

    As stated above in the discussion of the statistical analysis of 
safety need done for this rulemaking (see Section II.B), the data from 
16 states cannot be used to directly estimate the national problem 
size. Also, an analysis of pedestrian fatalities rather than injuries 
is not appropriate for this rulemaking. The target population analysis 
will therefore focus on injuries only.
    The PSEA directs NHTSA to establish minimum sound requirements for 
EVs and HVs as a means of addressing the increased rate of pedestrian 
crashes for these vehicles. In calculating the benefits of this 
rulemaking we have assumed that adding sound to EVs and HVs will bring 
the pedestrian crash rates for these vehicles in line with the 
pedestrian crash rates for ICE vehicles because the minimum sound 
requirements in the proposed rule would ensure that EVs and HVs are at 
least as detectable to pedestrians as ICE vehicles. This approach 
assumes that EVs and HVs have higher pedestrian crash rates than ICE 
vehicles because of the differences in sound levels produced by these 
vehicles. Therefore, the target population for this rulemaking is the 
number of crashes that would be avoided if the crash rates for hybrid 
and electric vehicles were the same as the crash rate for ICE vehicles.
    No quantifiable benefits are estimated for EVs because we assume 
that EV manufacturers would have added alert sounds to their cars in 
the absence of this proposed rule and the PSEA.
    NHTSA was not able to directly measure the safety differences 
between hybrids with and without sound. Although there are now some 
hybrids in the market that produce sounds to alert pedestrians and 
pedalcyclists, the agency is unable to directly measure the 
effectiveness rate of sound by using data from these new hybrid 
vehicles because there is not sufficient crash data on new model hybrid 
vehicles with sound to be able to make a statistically significant 
comparison to hybrids without sound. The agency's data base for low 
speed injuries is a sample, and data on crashes involving hybrid 
vehicles that emit sound is limited. Furthermore, the data set used to 
analyze differences in crash rates for this rulemaking consists of 
crash data from 16 states. At this time, only half of the states have 
submitted data for the 2012 or later calendar years. Since we believe 
that most hybrid vehicles have been equipped with some type of alert 
sound only since 2012, any effect that voluntary adoption would

[[Page 90506]]

have on pedestrian crash rates would not be captured by this data set. 
In addition, none of the recently introduced hybrids with sounds were 
designed to meet all of the requirements in this rule. Therefore, any 
change in crash rate between original quiet HVs and these voluntarily-
equipped HVs would not necessarily be indicative of the full safety 
benefits of compliant sounds.
    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. To calculate the difference in crash rates between HVs and ICEs 
NHTSA computes the ratio of the number of pedestrian and pedalcyclist 
crashes involving HVs to the number of other types of accidents 
involving HVs and compares it to a similar ratio for ICEs. While this 
is a standard technique in analyzing crash risk, it does raise a 
problem in this case because NHTSA was not able to control for VMT. 
NHTSA assumes that any difference in these ratios is attributable to 
the lack of sound in HVs. However, it is possible that there are other 
explanations for differences. For example, there may be reasons other 
than sound for why HVs have higher numbers of pedestrian and 
pedalcyclist accidents. Or there may be reasons why ICEs have higher 
numbers of other types of accidents.\165\ This could result in a lower 
ratio for ICEs even if the two types of vehicles had similar pedestrian 
and pedalcyclist crash rates.
---------------------------------------------------------------------------

    \165\ For example, HLDI compared overall rates of injury for 
hybrid vehicles and their ICE non-hybrid twins and found that crash 
rates are lower for hybrids. HLDI concluded that the heavier weight 
of hybrids was an important factor in this lower overall crash rate 
for hybrids. Highway Loss Data Institute. ``Injury Odds and Vehicle 
Weight Comparison of Hybrids and Conventional Counterparts.'' HLDI 
Bulletin 28(10). Arlington, VA, 2011.
---------------------------------------------------------------------------

    The first step in NHTSA's analysis was to use injury estimates from 
the 2006-2012 National Automotive Sampling System--General Estimates 
System (NASS-GES) and both 2007 and 2008-2011 Not in Traffic 
Surveillance (NiTS) database to provide an average estimate for 
combined in-traffic and relevant not-in-traffic crashes. In order to 
combine the GES and NiTS data in a meaningful way, it was assumed that 
the ratio of GES to NiTS will be constant for all years 2006 to 2012.
    Because both the GES and NiTS databases rely on police-reported 
crashes, these databases do not accurately reflect all vehicle crashes 
involving pedestrians because many of these crashes are not reported to 
the police. The agency estimates that the number of unreported crashes 
for pedestrians is equal to 100.8 percent of the reported crashes. That 
is to say, for every 100 police-reported pedestrian crashes, there 
exist 100.8 additional unreported pedestrian crashes.
    Table 20 shows the reported and unreported crashes by injury 
severity. Only injury counts will be examined for the purpose of 
benefits calculations and, as such, fatalities and uninjured (MAIS 0) 
counts are not included.

     Table 20--Estimated Annual Quiet Cars Target Population Injuries Reported (GES 2006-2012, NiTS 2007, 2008-2011) and Unreported Pedestrians and
                                                                Pedalcyclists, by Vehicle
--------------------------------------------------------------------------------------------------------------------------------------------------------
                       MAIS level                                1               2               3               4               5           TOTAL 1-5
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                 Reported (GES+NiTS) and Unreported Injured Pedestrians
--------------------------------------------------------------------------------------------------------------------------------------------------------
Passenger Car (PC)......................................          69,453          11,093           2,249             529             214          83,538
Light Trucks & Vans (LTV)...............................          47,604           7,852           1,629             387             156          57,626
                                                         -----------------------------------------------------------------------------------------------
    Total Light Vehicles (PC+LTV).......................         117,056          18,945           3,877             916             370         141,164
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                Reported (GES+NiTS) and Unreported Injured Pedalcyclists
--------------------------------------------------------------------------------------------------------------------------------------------------------
MAIS level..............................................               1               2               3               4               5       TOTAL 1-5
Passenger Car (PC)......................................          42,943           6,148           1,082             239              84          50,495
Light Trucks & Vans (LTV)...............................          26,932           3,957             715             160              56          31,820
                                                         -----------------------------------------------------------------------------------------------
    Total Light Vehicles (PC+LTV).......................          69,875          10,105           1,796             400             140          82,315
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The estimates in Table 20 are based on the current make-up of the 
fleet for all propulsion types. Next, we make the assumption that 
because the hybrid and electric vehicles pose a higher risk of 
pedestrian collisions, each hybrid and electric vehicle is producing 
more injuries per year than their ICE counterparts. Thus, while the 
2006-2012 time period resulted in 141,164 pedestrian injuries annually, 
this injury count is the result of the mixed hybrid/electric/ICE fleet 
during that period. Based on the odds ratios from our crash analysis, 
we can calculate what size of theoretical ICE-only fleet would have 
been needed to generate as many injuries during that same time period.
    The estimated injuries in Table 21 and Table 22 are created by 
combining the estimated percentage of annual sales of hybrid and 
electric vehicles for MY2020 from Table 23 with the odds ratio of 1.18, 
representing the increased risk of an HV being involved in a pedestrian 
crash, and the odds ratio of 1.51, representing the increased risk of 
an HV being involved in a pedalcyclist crash.\166\ Thus, when 
considering pedestrians injured by MY2020 vehicles and assuming these 
pedestrian crashes occurred because the pedestrians failed to detect 
these vehicles by hearing, the rulemaking applies to the 877 injury 
difference between that theoretical ICE-only fleet (140,663 injuries) 
and the estimated lifetime injuries from the MY2020 fleet (141,567). 
Given the effectiveness assumption of 97 percent, the rulemaking 
addresses 850 of those 877 injuries. When considering pedalcyclists 
injured by MY2020 vehicles, the rulemaking is applied to the 1,514 
injury difference between that theoretical fleet (81,455 injuries) and 
the estimated lifetime injuries from the MY2020 fleet (83,015). Given 
our assumption that the pedestrian and pedalcyclists crash rates for 
LSVs without sound is similar to that for other types of light vehicles 
without sound, the rule would also reduce pedestrian injuries by 4 over 
the lifetime of the MY2020 fleet of LSVs and

[[Page 90507]]

pedalcyclist injuries by 7 over the lifetime of the MY2020 fleet of 
LSVs.
---------------------------------------------------------------------------

    \166\ Wu, J. (2015). Updated Analysis of Pedestrian and 
Pedalcyclist Crashes by Hybrid Vehicles with Larger Samples and 
Multiple Risk Factors. Washington, DC: National Highway Traffic 
Safety Administration.
    \167\ Table values may not add up to the correct total due to 
rounding.
    \168\ Table values may not add up to the correct value due to 
rounding.

                                     Table 21--Enhanced Injury Rate (EIR) for Pedestrians for 2020 Model Year \167\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                              Injuries   Injuries
                                                         Mild      Strong     EVs +                 Total     assuming   assuming    Injury
                                                       hybrids    hybrids   fuel cell  ICEs  (%)     (%)      100% ICE  predicted  difference   Benefits
                                                         (%)        (%)         (%)                            fleet      fleet
--------------------------------------------------------------------------------------------------------------------------------------------------------
Passenger Car.......................................       6.94       6.86       0.21      87.02     101.03     83,101     83,953         853        827
Light Trucks & Vans.................................       7.97       0.59       0.08      91.45     100.09     57,563     57,614          51         50
                                                     ---------------------------------------------------------------------------------------------------
Total...............................................  .........  .........  .........  .........  .........    140,663    141,567         904        877
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                    Table 22--Enhanced Injury Rate (EIR) for Pedalcyclists for 2020 Model Year \168\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                              Injuries   Injuries
                                                         Mild      Strong     EVs +                 Total     assuming   assuming    Injury
                                                       hybrids    hybrids   fuel cell  ICEs  (%)     (%)      100% ICE  predicted  difference   Benefits
                                                         (%)        (%)         (%)                            fleet      fleet
--------------------------------------------------------------------------------------------------------------------------------------------------------
Passenger Car.......................................       6.94       8.80       0.21      87.02     102.97     49,737     51,215       1,479      1,434
Light Trucks & Vans.................................       7.97       0.76       0.08      91.45     100.26     31,719     31,800          81         79
                                                     ---------------------------------------------------------------------------------------------------
Total...............................................  .........  .........  .........  .........  .........     81,455     83,015       1,560      1,514
--------------------------------------------------------------------------------------------------------------------------------------------------------

    As discussed in the Final Regulatory Impact Analysis (FRIA), MAIS 
injury levels are converted to dollar amounts. The benefits across 
passenger cars, LTVs, and LSVs of reducing 2,401 pedestrian and 
pedalcyclist injuries, or 32 undiscounted equivalent lives saved (19.80 
equivalent lives at the 7-percent discount rate and 25.64 at the 3-
percent discount rate), is estimated to be $320 million at the 3-
percent discount rate and $247.5 million at the 7-percent discount 
rate.
    The agency calculated the benefits of this rule by calculating the 
``injury differences'' between ICE vehicles and HVs. The ``injury 
differences'' assume that the difference between crash rates for ICEs 
and non-ICEs is explained wholly by the difference in sounds produced 
by these two vehicle types of vehicles and the failure of pedestrians 
and pedalcyclists to detect these vehicles by hearing. It is possible 
that there are other factors responsible for some of the difference in 
crash rates, which would mean that adding sound to hybrid and electric 
vehicles would not reduce pedestrian and pedalcyclist crash rates for 
hybrids to that of ICE vehicles. Based on research conducted by NHTSA's 
VOPLE Center,\169\ NHTSA also assumes the sound added to hybrid and 
electric vehicles will be 97-percent effective in providing warning to 
pedestrians as the sound produced by a vehicle's ICE.
---------------------------------------------------------------------------

    \169\ See ``Robustness'' discussion in Section III.E.
---------------------------------------------------------------------------

    In addition to the benefits in injury reduction due to this rule, 
there is also the benefit to blind and visually impaired individuals of 
continued independent mobility. The increase in navigational ability 
resulting from this rule is hard to quantify and thus this benefit is 
mentioned but not assigned a specific productivity or quality of life 
monetization. By requiring alert sounds on hybrid and electric 
vehicles, blind pedestrians will be able to navigate roads as safely 
and effectively as if the fleet were entirely ICE vehicles. The benefit 
of independent navigation leads to the ability to travel independently 
and will, therefore, also lead to increased employment and the ability 
to live independently.

B. Costs

    Based on Ward's Automotive Yearbook 2014,\170\ there were 597,035 
hybrid engine installations in light vehicles (96 percent were in 
passenger cars and 4 percent were in light trucks) sold in MY2013, 
which accounts for 3.5 percent of the total 17.2 million MY2013 light 
vehicles. There were a smaller number of MY2013 electric vehicles: 
17,480 passenger cars and 1,046 LTVs, representing 0.1 percent of the 
overall sales. The Annual Energy Outlook (AEO) for 2014 provides future 
estimates of the fleet broken down into hybrid and electric 
vehicles.\171\ The number of vehicles that the agency projects will be 
required to meet the standard is shown in Table 23.
---------------------------------------------------------------------------

    \170\ Ward's Automotive Yearbook CD. Path: \2014 YB CDROM\5. 
North America\c. U.S. Auto Industry\3. Engines\Engines by Type.xls
    \171\ In calculating the costs of this rule the agency only 
included those vehicles that can operate solely via the vehicle's 
electric motor. The agency did not included ``micro hybrids'' whose 
ICE is always running when the vehicle is motion when calculating 
the costs of this rule.

Table 23--Estimated/Predicted Hybrid and Electric Vehicle Sales Proposed
                To Be Required To Provide an Alert Sound
------------------------------------------------------------------------
                                          Estimated 2013  Predicted 2020
                                           sales source:   sales source:
                                              Ward's        AEO & NHTSA
------------------------------------------------------------------------
Low-Speed Vehicles......................           1,500           2,500

[[Page 90508]]

 
Light Vehicles Electric.................          18,526          15,020
Light Vehicles Fuel Cells...............               0           5,606
Light Vehicles Hybrid...................       597,035 *         506,701
                                         -------------------------------
    Light Vehicles subtotal.............         594,061         527,327
                                         -------------------------------
        Total Sales.....................         602,061         561,327
------------------------------------------------------------------------
* Note--This estimate of vehicle sales includes micro-hybrids which the
  rule does not apply to. This overestimation of hybrid vehicle sales is
  addressed in the MY2020 column, where propulsion source is provided by
  AEO.

    The Nissan Leaf and other fully electric vehicles come equipped 
with an alert sound system. Based on what manufacturers have 
voluntarily provided in their fully electric vehicles, the agency 
assumes that fully electric vehicles and hydrogen fuel-cell vehicles 
will provide an alert sound system voluntarily and, therefore, for 
costing purposes we assumed a small upgrade cost in order to bring 
these existing systems up to compliance. In addition, we assume that 
some hybrid light vehicles, particularly those manufactured by Toyota, 
come equipped with some form of speaker system, similar to the ones 
expected to be found on electric vehicles. Furthermore, www.energy.gov 
data indicates that these partially-equipped light vehicles make up 
about 67% of the hybrids that fall under the rule. Thus, the number of 
light vehicles that have to add (or upgrade) an alert sound system for 
costing purposes for MY2020 is 561,327 vehicles.
    Based on informal discussions with suppliers and industry experts, 
in addition to confidential documents provided to the agency, we 
estimate that the total consumer cost for a system that produces sounds 
meeting the requirement of this rule is $125.34 per hybrid light 
vehicle. In cases where a sound system already exists on a light 
vehicle (hybrid vehicles voluntarily equipped, electric vehicles, and 
fuel cell vehicles), we assume a cost of $50.49. This estimate includes 
the cost of a dynamic speaker system that is packaged for protection 
from the elements and that is attached with mounting hardware and 
wiring in order to power the speaker(s) and receive signal inputs, and 
a digital signal processor that receives information from the vehicle 
regarding vehicle operating status (to produce sounds dependent upon 
vehicle speed, for example.) We assume there will be no other 
structural changes or installation costs associated with complying with 
the rule's requirements. We believe the same system can be used for 
both LSVs and light vehicles. We estimate that the added weight of the 
system would increase fuel costs for light vehicles by about $4 to $5 
over the lifetime of the vehicle. Average vehicle costs reflect the 
different installation costs determined by propulsion source and 
vehicle make as described above.

             Table 24--Cost Summary (in $M, 2013 Economics)
------------------------------------------------------------------------
                                            3% Discount     7% Discount
                                             rate ($)        rate ($)
------------------------------------------------------------------------
Per vehicle costs:
Passenger Cars, Per Vehicle *...........          $79.06          $78.16
Light Trucks, Per Vehicle *.............           77.27           76.17
Low Speed Vehicles (LSVs), Per Vehicle *           78.91           77.99
Total Cost by Vehicle Type:.............
Passenger Cars..........................           38.2M           37.8M
Light Trucks............................            3.6M            3.5M
Light Vehicles, PCs + LTVs Subtotal.....           41.8M           41.3M
Low Speed Vehicles (LSVs)...............            0.3M            0.3M
    Total (PC + LTV + LSV)..............           42.1M           41.6M
------------------------------------------------------------------------

    In addition to the quantifiable costs discussed above, there may be 
a cost of adding sound to quiet vehicles to owners who value quietness 
of vehicle operation and to society at large. NHTSA is not aware of a 
method to quantify the value of quietness for a driver's own vehicle. 
Some sound from these systems may intrude into the passenger 
compartment. The use of multiple speakers with directional 
characteristics might mitigate these costs. Sound insulation also can 
counteract interior noise, and a sensitivity analysis for sound 
insulation cost is provided in the accompanying FRIA.
    As explained further in the Environmental Assessment (EA), we 
expect that the increase in noise from the alert sound will be no 
louder than that from an average ICE vehicle and that aggregate sound 
from these vehicles will not create an appreciable increase over 
current noise levels. Given the low increase in overall noise caused by 
this rule, we expect that any costs that may exist due to added sound 
will be minimal. NHTSA has not found any way to value the increase in 
noise to society at large, and, thus it is a non-quantified cost.

C. Comparison of Costs and Benefits

    Comparison of costs and benefits expected due to this rule provides 
a

[[Page 90509]]

savings of $0.4 million per equivalent life saved to a cost of $0.04 
million per equivalent life saved across the 3-percent and 7-percent 
discount levels. This falls under NHTSA's value of a statistical life 
of $10.8 million, (for MY2020) and therefore this rulemaking is assumed 
to be cost beneficial. Since the lifetime monetized benefits 
(VSL+Economic) of MY2020 light vehicles (and LSVs) is expected to be 
between $197.6M and $244.9M, the net impact of the rule on light 
vehicles and LSVs is a positive one, even with the estimated $46 
million required to install speakers \172\ and $3 million in lifetime 
fuel costs.
---------------------------------------------------------------------------

    \172\ Based on the assumption in this analysis that 
manufacturers will install speakers to meet the rule.

          Table 25--Discounted Benefits (PC+LTV) MY2020, 2013$
------------------------------------------------------------------------
                                                  Total PED + CYC
                                         -------------------------------
                                               Total
                                             Monetized       Total ELS
                                             Benefits
------------------------------------------------------------------------
3% discount                               ..............  ..............
    (PC)................................    $301,146,801           24.25
    (LTV)...............................      17,381,812            1.39
                                         -------------------------------
        Total...........................     318,528,614           25.64
------------------------------------------------------------------------
7% discount                               ..............  ..............
    (PC)................................     233,031,924           18.74
    (LTV)...............................      13,258,335            1.06
                                         -------------------------------
        Total...........................     246,290,259           19.80
------------------------------------------------------------------------

                  Table 26--Total Costs (PC+LTV) 2013$
------------------------------------------------------------------------
                                          Total cost/veh    Total costs
------------------------------------------------------------------------
3% discount                               ..............  ..............
    (PC)................................          $79.06     $38,223,782
    (LTV)...............................           77.27       3,587,400
                                         -------------------------------
        Total...........................           78.91      41,811,182
------------------------------------------------------------------------
7% discount:
    (PC)................................           78.16      37,788,667
    (LTV)...............................           76.17       3,536,329
                                         -------------------------------
        Total...........................           77.99      41,324,996
------------------------------------------------------------------------

                                      Table 27--Net Impacts (PC+LTV) 2013$
----------------------------------------------------------------------------------------------------------------
                                                                                                   Net costs/ELS
                                                                  Net impact/veh    Net impact        (in $M)
----------------------------------------------------------------------------------------------------------------
3% Discount                                                       ..............  ..............  ..............
    (PC)........................................................         $543.83    $262,923,019            -0.1
    (LTV).......................................................          297.12      13,794,413            0.93
                                                                 -----------------------------------------------
        Total...................................................          522.22     276,717,432           -0.04
----------------------------------------------------------------------------------------------------------------
7% Discount                                                       ..............  ..............  ..............
    (PC)........................................................          403.84     195,243,258            0.33
    (LTV).......................................................          209.40       9,722,005            1.67
                                                                 -----------------------------------------------
        Total...................................................          386.81     204,965,263             0.4
----------------------------------------------------------------------------------------------------------------

    The net impact of this rule on LSVs is also expected to be 
positive. The net benefits of the minimum sound requirements for these 
vehicles is $1,023,934 at the 3-percent discount rate and $788,953 at 
the 7-percent discount rate. Thus, the total net impact of the rule 
considering both the MY2016 light vehicle and LSV fleet is positive.

[[Page 90510]]

                                               Table 28--Costs and Scaled Benefits for LSVs, MY2020 \173\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                            Sales ratio                                       Scaled                                          Scaled
              Discount rate                LSV to light        Sales       Scaled costs      injuries       Scaled ELS        Scaled      benefits minus
                                              vehicle                                        (undisc.)                       benefits      scaled costs
--------------------------------------------------------------------------------------------------------------------------------------------------------
3%......................................           0.47%           2,500        $197,264           11.28          0.1210      $1,189,469      $1,305,543
7%......................................           0.47%           2,500         194,970           11.28          0.0934         848,651         967,019
--------------------------------------------------------------------------------------------------------------------------------------------------------

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

    \173\ Scaled benefits and costs for low speed vehicles are 
estimated to be directly proportional to light vehicles based on 
sales. Scaled costs include both installation costs for the system 
and fuel costs.
---------------------------------------------------------------------------

D. Retrospective Review

    NHTSA has been unable to directly compare pedestrian and 
pedalcyclist crash rates for hybrids with and without sound because 
sufficient data is not yet available. As a result, we have not been 
able to directly determine whether lack of sound is the cause of the 
difference in pedestrian and pedalcyclist crash rates between hybrids 
and ICEs. For this reason, we intend conduct an expedited retrospective 
review of this rule once data are available. Although some hybrid 
manufacturers began putting alert sound in their vehicles around 2012, 
the state data from this period needed for our analysis is just 
starting to become available. While these voluntarily equipped vehicles 
will not be fully compliant with this rule, within the next four years 
we will conduct a preliminary study to determine whether adding sound 
eliminates some pedestrian and pedalcyclist crashes should we have 
sufficient data for such analysis. It will take several more years 
until data from fully compliant vehicles are available for analysis. 
Therefore, we expect to complete our retrospective review of this rule 
within eight years of when this rule is finalized. For LSVs, sufficient 
data may not be available and it may be necessary to use a Special 
Crash Investigation to determine whether adding sound makes these types 
of vehicles safer than those without sound should we be able to 
identify any such crashes.

E. Environmental Assessment

    The agency has prepared an Environmental Assessment (EA) to analyze 
and disclose the potential environmental impacts of a reasonable range 
of minimum sound requirements for HVs and EVs, including a preferred 
alternative. The alternatives the agency analyzed include a No Action 
Alterative, under which the agency would not establish any minimum 
sound requirements for EVs/HVs, and two action alternatives. Under 
Alternative 2 (the final rule), the agency would require a sound 
addition at speeds at or below 30 km/h and would require that covered 
vehicles produce sound at the stationary but active operating 
condition. Under Alternative 3, the agency would require a minimum 
sound pressure level of 48 A-weighted dB for speeds at or below 20 km/
h; there would be no sound requirement when the vehicle is stationary.
    In order to determine the potential environmental impacts of the 
alternatives, NHTSA estimated the amount of travel covered by vehicles 
and changes in sound level projected to occur under each of the 
alternatives. NHTSA separately analyzed the projected environmental 
impacts of each of the three alternatives in both urban and non-urban 
environments because differences in population, vehicle speeds, and 
deployment of EVs/HVs in these areas could affect the potential 
environmental impacts. The EA calculates the potential noise impacts of 
the alternatives in two different ways.
    In one analysis, NHTSA analyzed the potential for change in sound 
levels experienced by an individual listener near a roadway as a result 
of the final alternatives by single vehicle passes by. In the second 
analysis, NHTSA compared the sound levels experienced by a single 
listener among sets of vehicles with varying percentages of EVs/HVs 
when these vehicles were assumed to have no minimum sound requirement 
versus when producing the sound level specified under each of the 
action alternatives. For this analysis, NHTSA calculated the difference 
in sound perceived by a person standing either 7.5 or 15 meters (25 or 
50 feet, respectively) away from the source to replicate the difference 
in sound between the alternatives experienced by a person standing near 
a busy roadway.
    Our first analysis for both action alternatives suggest that in 
urban environments, a single listener would not perceive a noticeable 
difference in sound when standing 7.5 meters from the roadway compared 
to the no action alternative. In a non-urban environment, a single 
listener would not perceive a noticeable difference under Alternative 
3, but under the Preferred Alternative a single listener would perceive 
a noticeable difference in sound level when standing 7.5 meters from 
the roadway compared to the no action alternative.
    The results from second analysis show that changes in overall sound 
levels near a busy roadway for either action alternative compared to 
the No Action Alternative would not exceed 3 dB, the commonly used 
threshold for noticeability by human listeners, even assuming that up 
to 20% of vehicles on the road are EVs/HVs, which is nearly three times 
the deployment level currently projected for 2035. When non-urban or 
urban ambient sound levels are taken into account, the perceived sound 
level change is further reduced to well under the 3 dB threshold.
    In addition to analyzing the projected impact of the action 
alternatives on an individual listener, NHTSA computed the magnitude of 
the change in sound levels nationally as a result of the alternatives. 
This analysis takes into account the National Household Travel Survey 
(NHTS) distribution of trip miles, the Annual Energy Outlook (AEO) 
forecast of the deployment of EVs/HVs, and Environmental Protection 
Agency (EPA) drive cycle speed distributions. Because the action 
alternatives would only affect specific vehicles in certain operating 
conditions, this analysis calculates the total U.S. vehicle operations 
affected by the action alternatives as a proportion of total U.S. 
vehicle operations, and analyzes the overall change in sound levels 
projected to occur as a result of the action alternatives.
    Based on this analysis of national impacts, NHTSA projects that 
under the Preferred Alternative, 2.3 percent of all urban U.S. light 
duty vehicle hours travelled and 0.3 percent of all non-urban U.S. 
light duty vehicle hours travelled potentially would be impacted by the 
minimum sound requirement. Under Alternative 3, NHTSA projects that 0.9 
percent of all urban U.S. light duty vehicle hours and 0.1 percent of 
all nonurban U.S. light duty vehicle hours potentially would be 
impacted by the minimum sound requirement.

[[Page 90511]]

    Given the extremely small percentage of vehicle hours travelled 
impacted by this rule and the fact the sounds under the final rule 
would only be noticeable to a single listener standing 7.5 meters from 
the roadway under the single vehicle pass by condition, the 
environmental impacts of the final rule are expected to be negligible. 
In addition, the EA anticipates no or negligible additional impacts on 
wildlife; topography, geology, and soils; hazardous materials, 
hazardous waste, and solid waste; water resources; historical and 
archeological resources; farmland resources; air quality and climate; 
and environmental justice populations.

VI. Regulatory Notices and Analyses

Executive Order (E.O.) 12866 (Regulatory Planning and Review), E.O. 
13563, and DOT Regulatory Policies and Procedures

    The agency has considered the impact of this rulemaking action 
under E.O. 12866, E.O. 13563, and the Department of Transportation's 
regulatory policies and procedures. This action was reviewed by the 
Office of Management and Budget under E.O. 12866. This action is 
``significant'' under the Department of Transportation's regulatory 
policies and procedures (44 FR 11034; February 26, 1979).
    This action is significant because it is the subject of 
congressional interest and because it is a mandate under the PSEA. The 
agency has prepared and placed in the docket a Final Regulatory Impact 
Analysis.
    We estimate the total fuel and installation costs of this rule to 
the light EV, HV and LSV fleet to be $41.8M at the 3-percent discount 
rate and $41.3M at the 7-percent discount rate. We estimate that the 
impact of this rule in pedestrian and pedalcyclist injury reduction in 
light vehicles and LSVs will be 30.69 equivalent lives saved at the 3-
percent discount rate and 24.75 equivalent lives saved at the 7-percent 
discount rate. The benefits of applying this rule to light EVs and HVs 
are estimated to be $260.1 million at the 3-percent discount rate and 
$209.5 million at the 7-percent discount rate. Thus, this action is 
also significant because it has an annual economic impact greater than 
$100 million.

Executive Order 13609: Promoting International Regulatory Cooperation

    The policy statement in Section 1 of Executive Order 13609 
provides, in part:

    The regulatory approaches taken by foreign governments may 
differ from those taken by U.S. regulatory agencies to address 
similar issues. In some cases, the differences between the 
regulatory approaches of U.S. agencies and those of their foreign 
counterparts might not be necessary and might impair the ability of 
American businesses to export and compete internationally. In 
meeting shared challenges involving health, safety, labor, security, 
environmental, and other issues, international regulatory 
cooperation can identify approaches that are at least as protective 
as those that are or would be adopted in the absence of such 
cooperation. International regulatory cooperation can also reduce, 
eliminate, or prevent unnecessary differences in regulatory 
requirements.

    We received several comments regarding the impact of the rulemaking 
schedule on the development of GTR of this topic. As discussed in 
Section IV of this notice, given the deadlines for issuing a final rule 
provided in the PSEA, the agency did not think that it would be 
feasible to delay issuing a final rule until after the GTR is 
completed.
    NHTSA also received comments regarding the approach taken in 
guidelines developed by the UNECE and Japan regarding the crossover 
speed and whether HVs and EVs should be required to produce sound when 
they are not in motion. For the reasons discussed in Section III.D of 
this notice, we believe that a crossover speed of 30 km/h is necessary 
to ensure that blind, visually-impaired, and sighted pedestrians can 
safely detect EVs and HVs operating at low speeds. For the reasons 
discussed in Section III.C of this notice, we believe that EVs and HVs 
must produce sound when stationary with their gear selector is in any 
position other than park to prevent collisions and because of the 
language of the PSEA.

National Environmental Policy Act

    Concurrently with this final rule, NHTSA is releasing a Final EA, 
pursuant to the National Environmental Policy Act, 42 U.S.C. 4321-4347, 
and implementing regulations issued by the Council on Environmental 
Quality (CEQ), 40 CFR part 1500, and NHTSA, 49 CFR part 520. NHTSA 
prepared the EA to analyze and disclose the potential environmental 
impacts of the requirements of the proposed action and a range of 
alternatives. The EA analyzes direct, indirect, and cumulative impacts 
and analyzes impacts in proportion to their significance.
    Because this rule will increase the amount of sound produced by a 
certain segment of the vehicle fleet, the EA considers the possible 
impacts of increased ambient noise levels on both urban and rural 
environments. The EA also describes potential environmental impacts to 
a variety of resources including biological resources, waste, and 
environmental justice populations. The findings of the EA are 
summarized in Section V.D.
    The Final EA is available in Docket No. NHTSA-2011-0100 at http://www.regulations.gov/ as well as on NHTSA's Web site at http://www.nhtsa.gov/. Additionally, hard copies may be obtained by contacting 
Mike Pyne, Safety Standards Engineer, National Highway Traffic Safety 
Administration, 1200 New Jersey Ave. SE., Washington, DC 20590-0001.
    I have reviewed the Final EA, which is hereby incorporated by 
reference. As described in that Final EA and summarized above, this 
rulemaking is anticipated to have no or negligible impacts on the human 
environment. Based on the Final EA, I conclude that implementation of 
any of the action alternatives (including the final rule) will not have 
a significant effect on the human environment and that a ``finding of 
no significant impact'' (see 40 CFR 1501.4(e)(1) and 1508.13) is 
appropriate. This statement constitutes the agency's ``finding of no 
significant impact,'' and an environmental impact statement will not be 
prepared.

Regulatory Flexibility Act

    Pursuant to the Regulatory Flexibility Act (5 U.S.C. 601 et seq., 
as amended by the Small Business Regulatory Enforcement Fairness Act 
(SBREFA) of 1996), whenever an agency is required to publish a notice 
of rulemaking for any proposed or final rule, it must prepare and make 
available for public comment a regulatory flexibility analysis that 
describes the effect of the rule on small entities (i.e., small 
businesses, small organizations, and small governmental jurisdictions). 
The Small Business Administration's regulations at 13 CFR part 121 
define a small business, in part, as a business entity ``which operates 
primarily within the United States.'' \174\ No regulatory flexibility 
analysis is required if the head of an agency certifies the rule will 
not have a significant economic impact on a substantial number of small 
entities. SBREFA amended the Regulatory Flexibility Act to require 
Federal agencies to provide a statement of the factual basis for 
certifying that a rule will not have a significant economic impact on a 
substantial number of small entities.
---------------------------------------------------------------------------

    \174\ 13 CFR 121.105(a).
---------------------------------------------------------------------------

    In issuing this rule, I the undersigned hereby certify that this 
rule will not have a significant economic impact on a substantial 
number of small entities.

[[Page 90512]]

We believe that the rulemaking will not have a significant economic 
impact on the small vehicle manufacturers because the systems are not 
technically difficult to develop or install and the cost of the systems 
between $50.49 and $125.34 is small in proportion to the overall 
vehicle cost for most small vehicle manufacturers.
    This rule will directly affect motor vehicle manufacturers and 
final-stage manufacturers that produce EVs and HVs. The majority of 
motor vehicle manufacturers will not qualify as a small business. There 
are less than five manufacturers of light hybrid and electric vehicles 
that would be subject to the requirements of this proposal that are 
small businesses. Similarly, there are several manufacturers of low-
speed vehicles that are small businesses.
    Because the PSEA applies to all motor vehicles (except trailers) in 
its mandate to reduce quiet vehicle collisions with pedestrians, all of 
these small manufacturers that produce hybrid or electric vehicles are 
affected by the requirements in today's final rule. However, the 
economic impact upon these entities will not be significant for the 
following reasons.
    (1) The cost of the systems is a small proportion of the overall 
vehicle cost for even the least expensive electric vehicles.
    (2) This final rule provides a three year lead-time and allows 
small volume manufacturers the option of waiting until the end of the 
phase-in (September 1, 2018) to meet the minimum sound requirements.

Executive Order 13132 (Federalism)

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

Executive Order 12988 (Civil Justice Reform)

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

Unfunded Mandates Reform Act

    Section 202 of the Unfunded Mandates Reform Act of 1995 (UMRA) 
requires federal agencies to prepare a written assessment of the costs, 
benefits, and other effects of proposed or final rules that include a 
Federal mandate likely to result in the expenditure by State, local, or 
tribal governments, in the aggregate, or by the private sector, of more 
than $100 million annually (adjusted for inflation with base year of 
1995). Adjusting this amount by the implicit gross domestic product 
price deflator for 2010 results in $136 million (110.659/81.536 = 
1.36).
    As noted previously, the agency has prepared a detailed economic 
assessment in the FRIA. We estimate the annual total fuel and 
installation costs of this final rule to the light EV, HV and LSV fleet 
to be $41.8 million at the 3-

[[Page 90513]]

percent discount rate and $41.3 million at the 7-percent discount rate. 
Therefore, this rule is not expected to result in the expenditure by 
State, local, or tribal governments, in the aggregate, or by the 
private sector, of more than $136 million annually.

Paperwork Reduction Act

    Under the Paperwork Reduction Act of 1995, a person is not required 
to respond to a collection of information by a Federal agency unless 
the collection displays a valid OMB control number. The final rule 
contains reporting requirements so that the agency can determine if 
manufacturers comply with the phase in schedule.
    In compliance with the PRA, this notice announces that the 
Information Collection Request (ICR) abstracted below has been 
forwarded to OMB for review and comment. The ICR describes the nature 
of the information collections and their expected burden. This is a 
request for new collection.
    Agency: National Highway Traffic Safety Administration (NHTSA).
    Title: 49 CFR part 575.141, Minimum Sound Requirements for Hybrid 
and Electric Vehicles.
    Type of Request: New collection.
    OMB Clearance Number: Not assigned.
    Form Number: The collection of this information will not use any 
standard forms.
    Requested Expiration Date of Approval: Three years from the date of 
approval.
    Summary of the Collection of Information: This collection would 
require manufacturers of passenger cars, multipurpose passenger 
vehicles, trucks, buses, and low speed vehicles subject to the phase-in 
schedule to provide motor vehicle production data for one year: 
September 1, 2018 to August 31, 2019.
    Description of the Need for the Information and Use of the 
Information: The purpose of the reporting requirements will be to aid 
NHTSA in determining whether a manufacturer has complied with the 
requirements of Federal Motor Vehicle Safety Standard No. 141, Minimum 
Sound for Hybrid and Electric Vehicles, during the phase-in of those 
requirements.
    Description of the Likely Respondents (Including Estimated Number, 
and Proposed Frequency of Response to the Collection of Information): 
The respondents are manufacturers of hybrid and electric passenger 
cars, multipurpose passenger vehicles, trucks, buses, and low-speed 
vehicles with a GVWR of 4,536 kg (10,000 lbs.) or less. The agency 
estimates that there are approximately 21 such manufacturers. The 
proposed collection would occur one per year.
    Estimate of the Total Annual Reporting and Recordkeeping Burden 
Resulting from the Collection of Information: NHTSA estimates that the 
total annual burden is 42 hours (2 hours per manufacturer per year).
    Comments are invited on:
     Whether the collection of information is necessary for the 
proper performance of the functions of the Department, including 
whether the information will have practical utility.
     Whether the Department's estimate for the burden of the 
information collection is accurate.
     Ways to minimize the burden of the collection of 
information on respondents, including the use of automated collection 
techniques or other forms of information technology.
    A comment to OMB is most effective if OMB receives it within 30 
days of publication. Send comments to the Office of Information and 
Regulatory Affairs, Office of Management and Budget, 725 17th Street 
NW., Washington, DC 20503, Attn: NHTSA Desk Officer. PRA comments are 
due within 30 days following publication of this document in the 
Federal Register.
    The agency recognizes that the collection of information contained 
in today's final rule may be subject to revision in response to public 
comments and the OMB review.

Executive Order 13045

    Executive Order 13045 \175\ applies to any rule that: (1) Is 
determined to be economically significant as defined under E.O. 12866, 
and (2) concerns an environmental, health or safety risk that NHTSA has 
reason to believe may have a disproportionate effect on children. If 
the regulatory action meets both criteria, we must evaluate the 
environmental health or safety effects of the proposed rule on 
children, and explain why the proposed regulation is preferable to 
other potentially effective and reasonably feasible alternatives 
considered by us.
---------------------------------------------------------------------------

    \175\ 62 FR 19885 (Apr. 23, 1997).
---------------------------------------------------------------------------

    This rule will not pose such a risk for children. The primary 
effects of this rule are to ensure that hybrid and electric vehicles 
produce enough sound so that pedestrians can detect them. We expect 
this rule to reduce the risk of injuries to children and other 
pedestrians.

National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act (NTTAA) requires NHTSA to evaluate and use existing voluntary 
consensus standards in its regulatory activities unless doing so would 
be inconsistent with applicable law (e.g., the statutory provisions 
regarding NHTSA's vehicle safety authority) or otherwise impractical.
    Voluntary consensus standards are technical standards developed or 
adopted by voluntary consensus standards bodies. Technical standards 
are defined by the NTTAA as ``performance-based or design-specific 
technical specification and related management systems practices.'' 
They pertain to ``products and processes, such as size, strength, or 
technical performance of a product, process or material.''
    Examples of organizations generally regarded as voluntary consensus 
standards bodies include the American Society for Testing and Materials 
(ASTM), the Society of Automotive Engineers (SAE), and the American 
National Standards Institute (ANSI). If NHTSA does not use available 
and potentially applicable voluntary consensus standards, we are 
required by the Act to provide Congress, through OMB, an explanation of 
the reasons for not using such standards.
    The agency uses certain parts of voluntary consensus standard SAE 
J2889-1, Measurement of Minimum Noise Emitted by Road Vehicles, in the 
test procedure contained in this final rule. SAE J2889-1 only contains 
measurement procedures and does not contain any minimum performance 
requirements. The agency did not use any voluntary consensus standards 
for the minimum acoustic requirements contained in today's final rule 
because no such voluntary consensus standards exist. The agency added 
additional test scenarios other than those contained in SAE J2889-1 
because those additional test scenarios address aspects of performance 
not covered in that standard.
    The agency also used voluntary consensus standard ISO 10844 
``Acoustics--Test Surface for Road Vehicle Noise Measurements,'' to 
specify the road surface to be used for compliance testing under this 
standard. We also used ANSI S1.11 ``Specification for Octave-Band and 
Fractional-Octave-Band Analog and Digital Filters,'' to specify the 
filter roll-offs to be used during the analyses of data collected 
during compliance testing.

Incorporation by Reference

    As discussed earlier in the relevant portions of this document, we 
are incorporating by reference various

[[Page 90514]]

materials into the Code of Federal Regulations in this rulemaking. The 
standards we are incorporating are ANSI S1.11-2004, ``Specification for 
Octave-Band and Fractional-Octave-Band Analog and Digital Filters,'' 
the 1994, 2011, and 2014 versions of ISO 10844 \176\ and SAE Standard 
J2889-1 Dec. 2014, ``Measurement of Minimum Noise Emitted by Road 
Vehicles,''
---------------------------------------------------------------------------

    \176\ The 1994 version of ISO 10844 is titled ``Acoustics--Test 
Surface for Road Vehicle Noise Measurements'' the 2011 and 2014 
versions of ISO 10844 are titled ``Acoustics--Specification of test 
tracks for measuring noise emitted by road vehicles and their 
tyres.''
---------------------------------------------------------------------------

    Under 5 U.S.C. 552(a)(1)(E), Congress allows agencies to 
incorporate by reference materials that are reasonably available to the 
class of persons affected if the agency has approval from the Director 
of the Federal Register. As a part of that approval process, the 
Director of the Federal Register (in 1 CFR 51.5) directs agencies to 
discuss (in the preamble) the ways that the materials we are 
incorporating by reference are reasonably available to interested 
parties.
    NHTSA has worked to ensure that standards being considered for 
incorporation by reference are reasonably available to the class of 
persons affected. In this case, those directly affected by incorporated 
provisions are NHTSA and parties contracting with NHTSA to conduct 
testing of new vehicles. New vehicle manufacturers may also be affected 
to the extent they wish to conduct NHTSA's compliance test procedures 
on their own vehicles. These entities have access to copies of 
aforementioned standards through ANSI, ISO and SAE International for a 
reasonable fee. These entities have the financial capability to obtain 
a copy of the material incorporated by reference. Other interested 
parties in the rulemaking process beyond the class affected by the 
regulation include members of the public, safety advocacy groups, etc. 
Such interested parties can access the standard by obtaining a copy 
from the aforementioned standards development organizations.
    Interested parties may also access the standards through NHTSA. All 
approved material is available for inspection at NHTSA, 1200 New Jersey 
Avenue SE., Washington, DC 20590, and at the National Archives and 
Records Administration (NARA). For information on the availability of 
this material at NHTSA, contact NHTSA's Office of Technical Information 
Services, phone number (202) 366-2588.

Executive Order 13211

    Executive Order 13211 \177\ applies to any rule that: (1) Is 
determined to be economically significant as defined under E.O. 12866, 
and is likely to have a significant adverse effect on the supply, 
distribution, or use of energy; or (2) that is designated by the 
Administrator of the Office of Information and Regulatory Affairs as a 
significant energy action. If the regulatory action meets either 
criterion, we must evaluate the adverse energy effects of the proposed 
rule and explain why the proposed regulation is preferable to other 
potentially effective and reasonably feasible alternatives considered 
by NHTSA.
---------------------------------------------------------------------------

    \177\ 66 FR 28355 (May 18, 2001).
---------------------------------------------------------------------------

    This rule seeks to ensure that hybrid and electric vehicles are 
detectable by pedestrians. The average weight gain for a light vehicle 
is estimated to be 1.5 pounds (based upon a similar waterproof speaker 
used for marine purposes), resulting in 2.3 more gallons of fuel being 
used over the lifetime of a passenger car and 2.5 more gallons of fuel 
being used over the lifetime of a light truck. When divided by the life 
time of the vehicle (26 years for passenger cars and 36 years for light 
trucks) the yearly increase in fuel consumption attributed to this 
proposed rule would be negligible. Therefore, this proposed rule would 
not have a significant adverse effect on the use of energy. 
Accordingly, this rulemaking action is not designated as a significant 
energy action.

Regulation Identifier Number (RIN)

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

List of Subjects in 49 CFR Part 571

    Imports, Incorporation by reference, Motor vehicle safety, 
Reporting and recordkeeping requirements, Tires.

Regulatory Text

    In accordance with the forgoing, NHTSA is amending 49 CFR part 571 
as follows:

PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS

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

    Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.95.

0
2. In Sec.  571.5:
0
a. Redesignate paragraphs (c)(1) through (4) as paragraphs (c)(2) 
through (5);
0
b. Add new paragraph (c)(1);
0
c. Add paragraphs (i)(2) through (4); and
0
d. Redesignate paragraph (l)(49) as paragrapgh (l)(50) and, and add new 
paragraah (l)(49).
    The additions read as follows:

Sec.  571.5  Matter incorporated by reference.

* * * * *
    (c) * * *
    (1) ANSI S1.11-2004, ``Specification for Octave-Band and 
Fractional-Octave-Band Analog and Digital Filters,'' approved February 
19, 2004, into Sec.  571.141.
* * * * *
    (i) * * *
    (2) ISO 10844:1994(E) ``Acoustics--Test Surface for Road Vehicle 
Noise Measurements,'' First edition, 1994-09-01, into Sec.  571.141.
    (3) ISO 10844: 2011(E) ``Acoustics--Specification of test tracks 
for measuring noise emitted by road vehicles and their tyres,'' Second 
edition, 2011-02-01 into Sec.  571.141.
    (4) ISO 10844: 2014(E) ``Acoustics--Specification of test tracks 
for measuring noise emitted by road vehicles and their tyres,'' Third 
edition, 2014-05-15 into Sec.  571.141.
* * * * *
    (l) * * *
    (49) SAE Standard J2889-1, ``Measurement of Minimum Noise Emitted 
by Road Vehicles,'' December 2014 into Sec.  571.141.
* * * * *

0
3. Section 571.141 is added to read as follows:

Sec.  571.141   Standard No. 141; Minimum Sound Requirements for Hybrid 
and Electric Vehicles.

    S1. Scope. This standard establishes performance requirements for 
pedestrian alert sounds for motor vehicles.
    S2. Purpose. The purpose of this standard is to reduce the number 
of injuries that result from electric and hybrid vehicle crashes with 
pedestrians by providing a sound level and sound characteristics 
necessary for these vehicles to be detected and recognized by 
pedestrians.

[[Page 90515]]

    S3. Application. This standard applies to--
    (a) Electric vehicles with a gross vehicle weight rating (GVWR) of 
4,536 Kg or less that are passenger cars, multipurpose passenger 
vehicles, trucks, or buses;
    (b) Hybrid vehicles with a gross vehicle weight rating (GVWR) of 
4,536 Kg or less that are passenger cars, multi-purpose passenger 
vehicles, trucks, or buses; and
    (c) Electric vehicles and hybrid vehicles that are low speed 
vehicles.
    S4. Definitions. Band or one-third octave band means one of 
thirteen one-third octave bands having nominal center frequencies 
ranging from 315 to 5000Hz. These are Bands 25 through 37 as defined in 
Table A1, Mid-band Frequencies for One-Third-Octave-Band and Octave-
Band Filters in the Audio Range, of ANSI S1.11-2004: ``Specification 
for Octave-Band and Fractional-Octave-Band Analog and Digital Filters'' 
(incorporated by reference, see Sec.  571.5).
    Band sum means the combination of Sound Pressure Levels (SPLs) from 
selected bands that produce an SPL representing the sound in all of 
these bands. Band sum is calculated with the following equation:
[GRAPHIC] [TIFF OMITTED] TR14DE16.018

where SPLi is the sound pressure level in each selected 
band.
    Electric vehicle means a motor vehicle with an electric motor as 
its sole means of propulsion.
    Front plane of the vehicle means a vertical plane tangent to the 
leading edge of the vehicle during forward operation.
    Hybrid vehicle means a motor vehicle which has more than one means 
of propulsion for which the vehicle's propulsion system can propel the 
vehicle in the normal travel mode in at least one forward drive gear or 
reverse without the internal combustion engine operating.
    Rear plane means a vertical plane tangent to the leading edge of 
the rear of the vehicle during operation in reverse.
    S5. Requirements. Subject to the phase-in set forth in S9 of this 
standard, each hybrid and electric vehicle must meet the requirements 
specified in either S5.1 or S5.2. subject to the requirements in S5.3. 
Each vehicle must also meet the requirements in S5.4 and S5.5.
    S5.1 Performance requirements for four-band alert sounds.
    S5.1.1 Stationary. When stationary the vehicle must satisfy 
S5.1.1.1 and S5.1.1.2 whenever the vehicle's propulsion system is 
activated and:
    (i) In the case of a vehicle with an automatic transmission, the 
vehicle's gear selector is in Neutral or any gear position other than 
Park that provides forward vehicle propulsion;
    (iii) in the case of a vehicle with a manual transmission, the 
vehicle's parking brake is released and the gear selector is not in 
Reverse.
    S5.1.1.1 For detection, the vehicle must emit a sound having at 
least the A-weighted sound pressure level according to Table 1 in each 
of four non-adjacent bands spanning no fewer than 9 of the 13 bands 
from 315 to 5000 Hz.
    S5.1.1.2 For directivity, the vehicle must emit a sound measured at 
the microphone on the line CC' having at least the A-weighted sound 
pressure level according to Table 1 in each of four non-adjacent bands 
spanning no fewer than 9 of the 13 bands from 315 to 5000Hz.

   Table 1--One-Third Octave Band Min. SPL Requirements for Sound When
             Stationary and Constant Speeds Less Than 10km/h
------------------------------------------------------------------------
                                                           Min SPL,  A-
       One-third octave band center frequency, Hz           weighted dB
------------------------------------------------------------------------
315.....................................................              39
400.....................................................              39
500.....................................................              40
630.....................................................              40
800.....................................................              41
1000....................................................              41
1250....................................................              42
1600....................................................              39
2000....................................................              39
2500....................................................              37
3150....................................................              34
4000....................................................              32
5000....................................................              31
------------------------------------------------------------------------

    S5.1.2 Reverse. For vehicles capable of rearward self-propulsion, 
whenever the vehicle's gear selector is in the Reverse position, the 
vehicle must emit a sound having at least the A-weighted sound pressure 
level according to Table 2 in each of four non-adjacent bands spanning 
no fewer than 9 of the 13 bands from 315 to 5000Hz.

 Table 2--One-Third Octave Band Min. SPL Requirements for Sound while in
                                 Reverse
------------------------------------------------------------------------
                                                           Min SPL,  A-
       One-third octave band center frequency, Hz           weighted dB
------------------------------------------------------------------------
315.....................................................              42
400.....................................................              41
500.....................................................              43
630.....................................................              43
800.....................................................              44
1000....................................................              44
1250....................................................              45
1600....................................................              41
2000....................................................              42
2500....................................................              40
3150....................................................              37
4000....................................................              35
5000....................................................              33
------------------------------------------------------------------------

    S5.1.3 Constant pass-by speeds greater than 0 km/h but less than 20 
km/h. When at a constant speed greater than 0 km/h but less than 20 km/
h the vehicle must emit a sound having at least the A-weighted sound 
pressure level according to Table 1 or Table 3 as applicable based upon 
vehicle test speed in each of four non-adjacent bands spanning no fewer 
than 9 of the 13 bands from 315 to 5000 Hz.

 Table 3--One-Third Octave Band Min. SPL Requirements for Constant Pass-
    by Speeds Greater Than or Equal to 10 km/h but Less Than 20 km/h
------------------------------------------------------------------------
                                                           Min SPL,  A-
       One-third octave band center frequency, Hz           weighted dB
------------------------------------------------------------------------
315.....................................................              45
400.....................................................              44
500.....................................................              46
630.....................................................              46
800.....................................................              47
1000....................................................              47
1250....................................................              48
1600....................................................              44
2000....................................................              45
2500....................................................              43
3150....................................................              40

[[Page 90516]]

 
4000....................................................              38
5000....................................................              36
------------------------------------------------------------------------

    S5.1.4 Constant pass-by speeds greater than or equal to 20km/h but 
less than 30 km/h. When at a constant speed equal to or greater than 20 
km/h but less than 30 km/h the vehicle must emit a sound having at 
least the A-weighted sound pressure level according to Table 4 in each 
of four non-adjacent bands spanning no fewer than 9 of the 13 bands 
from 315 to 5000 Hz.

 Table 4--One-Third Octave Band Min. SPL Requirements for Constant Pass-
    by Speeds Greater Than or Equal to 20 km/h but Less Than 30 km/h
------------------------------------------------------------------------
                                                           Min SPL,  A-
       One-third octave band center frequency, Hz           weighted dB
------------------------------------------------------------------------
315.....................................................              52
400.....................................................              51
500.....................................................              52
630.....................................................              53
800.....................................................              53
1000....................................................              54
1250....................................................              54
1600....................................................              51
2000....................................................              51
2500....................................................              50
3150....................................................              47
4000....................................................              45
5000....................................................              43
------------------------------------------------------------------------

    S5.1.5 Constant 30km/h pass-by. When at a constant speed of 30-32 
km/h the vehicle must emit a sound having at least the A-weighted sound 
pressure level according to Table 5 in each of four non-adjacent bands 
spanning no fewer than 9 of the 13 bands from 315 to 5000 Hz.

Table 5--One-Third Octave Band Min. SPL Requirements for 30-32 km/h Pass-
                                   By
------------------------------------------------------------------------
                                                           Min SPL,  A-
       One-third octave band center frequency, Hz           weighted dB
------------------------------------------------------------------------
315.....................................................              56
400.....................................................              55
500.....................................................              57
630.....................................................              57
800.....................................................              58
1000....................................................              58
1250....................................................              59
1600....................................................              55
2000....................................................              55
2500....................................................              54
3150....................................................              51
4000....................................................              49
5000....................................................              47
------------------------------------------------------------------------

    S5.2 Performance requirements for two-band alert sounds. When 
operating under the vehicle speed conditions specified in Table 6, the 
vehicle must emit sound having two non-adjacent one-third octave bands 
from 315 to 3150 Hz each having at least the A-weighted sound pressure 
level according to the minimum SPL requirements in Table 6 and spanning 
no fewer than three one-third octave bands from 315 to 3150 Hz. One of 
the two bands meeting the minimum requirements in Table 6 shall be the 
band that has the highest SPL of the 315 to 800 Hz bands and the second 
band shall be the band meeting the minimum requirements in Table 6 that 
has the highest SPL of the 1000 to 3150 Hz bands. The two bands used to 
meet the two-band minimum requirements must also meet the band sum 
requirements as specified in Table 6.

 Table 6--One-Third Octave Band Minimum Requirements for Two-Band Alert
------------------------------------------------------------------------
                                               A-weighted SPL, dB(A)
                                         -------------------------------
              Vehicle speed                 Minimum in
                                             each band       Band sum
------------------------------------------------------------------------
Reverse.................................              40              48
Stationary and up to but not including                40              44
 10 km/h................................
10 km/h up to but not including 20 km/h.              42              51
20 km/h up to but not including 30 km/h.              47              57
30 km/h.................................              52              62
------------------------------------------------------------------------

    S5.2.1 When tested according to the test procedure in S7.1 the 
vehicle must emit a sound measured at the microphone on the line CC' 
having at least two non-adjacent octave bands from 315 to 3150 Hz each 
having at least the A-weighted sound pressure level, indicated in the 
``Minimum in Each Band'' column in Table 6 for the ``Stationary up to 
but not including 10 km/h'' condition. The two bands used to meet the 
two-band minimum requirements must also meet the Band Sum as specified 
in Table 6.
    S5.3 If a hybrid vehicle to which this standard applies is 
evaluated for compliance with requirements in S5.1.1 through S5.1.5 or 
S5.2 (Stationary, Reverse, Pass-by at 10 km/h, 20 km/h, and 30 km/h, 
respectively), and during testing to any one of those requirements the 
vehicle is measured for ten consecutive times without recording a valid 
measurement, or for a total of 20 times without recording four valid 
measurements because the vehicle's ICE remains active for the entire 
duration of a measurement or the vehicle's ICE activates intermittently 
during every measurement, the vehicle is exempted from meeting the 
specific requirement that was under evaluation at the time the ICE 
interfered in the prescribed manner.
    S5.4 Relative volume change to signify acceleration and 
deceleration. The sound produced by the vehicle in accordance with 
paragraph S5 shall change in volume, as calculated in S7.6, from one 
critical operating condition to the next in accordance with the 
requirements in Table 7.

[[Page 90517]]

          Table 7--Minimum Relative Volume Change Requirements
------------------------------------------------------------------------
                                                                Minimum
                                                               relative
             Critical operating speed intervals                 volume
                                                                change,
                                                                  dB
------------------------------------------------------------------------
Between:
    Stationary and 10 km/h..................................           3
    10 km/h and 20 km/h.....................................           3
    20 km/h and 30 km/h.....................................           3
------------------------------------------------------------------------

    S5.5 Sameness requirement
    S5.5.1 Any two vehicles of the same make, model, and model year (as 
those terms are defined at 49 CFR 565.12) to which this safety standard 
applies shall use the same pedestrian alert system and shall be 
designed to have the same pedestrian alert sound when operating in any 
given condition for which an alert sound is required in Section S5 of 
this safety standard.
    S5.5.2 For the purposes of this requirement, a pedestrian alert 
system includes all hardware and software components that are utilized 
to generate an alert sound. Aspects of an alert system which shall be 
the same include, if applicable: Alert system hardware components 
including speakers, speaker modules, and control modules, as evidenced 
by specific details such as part numbers and technical illustrations; 
the location, orientation, and mountings of the hardware components 
within the vehicle; the digital sound file or other digitally encoded 
source; the software and/or firmware and algorithms which generate the 
pedestrian alert sound and/or which process the digital source to 
generate a pedestrian alert sound; vehicle inputs including vehicle 
speed and gear selector position utilized by the alert system; any 
other design features necessary for vehicles of the same make, model, 
and model year to have the same pedestrian alert sound at each given 
operating condition specified in this safety standard.
    S6. Test Conditions.
    S6.1 Weather conditions. The ambient conditions specified by this 
section will be met at all times during the tests described in S7. 
Conditions will be measured with the accuracy required in S6.3.3 at the 
microphone height specified in S6.4 +/-0.02 m.
    S6.1.1 The ambient temperature will be between 5 [deg]C (41 [deg]F) 
and 40 [deg]C (104 [deg]F).
    S6.1.2 The maximum wind speed at the microphone height is no 
greater than 5 m/s (11 mph), including gusts.
    S6.1.3 No precipitation and the test surface is dry.
    S6.1.4 Background noise level. The background noise level will be 
measured and reported as specified in S6.7, Ambient correction.
    S6.2 Test surface. Test surface will meet the requirements of ISO 
10844:1994, ISO 10844:2011, or ISO 10844:2014 (incorporated by 
reference, see Sec.  571.5).
    S6.3 Instrumentation.
    S6.3.1 Acoustical measurement. Instruments for acoustical 
measurement will meet the requirements of S5.1 of SAE J2889-1 
(incorporated by reference, see Sec.  571.5).
    S6.3.2 Vehicle speed measurement. Instruments used to measure 
vehicle speed during the constant speed pass-by tests in S7 of this 
standard will be capable of either continuous measurement of speed 
within 0.5 km/h over the entire measurement zone specified 
in S6.4 or independent measurements of speed within 0.2 km/
h at the beginning and end of the measurement zone specified in S6.4.
    S6.3.3 Meteorological instrumentation. Instruments used to measure 
ambient conditions at the test site will meet the requirements of S5.3 
of SAE J2889-1 (incorporated by reference, see Sec.  571.5).
    S6.4 Test site. The test site will be established per the 
requirements of 6.1 of SAE J2889-1 (incorporated by reference, see 
Sec.  571.5), including Figure 1, ``Test Site Dimensions'' with the 
definitions of the abbreviations in Figure 1 as given in Table 1of SAE 
J2889-1 (incorporated by reference, see Sec.  571.5). Microphone 
positions will meet the requirements of 7.1.1 of SAE J2889-1 
(incorporated by reference, see Sec.  571.5).
    S6.5 Test set up for directivity measurement will be as per S6.4 
with the addition of one microphone meeting the requirements of S6.3.1 
placed on the line CC', 2m forward of the line PP' at a height of 1.2m 
above ground level.
    S6.6 Vehicle condition
    (a) The vehicle's doors are shut and locked and windows are shut.
    (b) All accessory equipment (air conditioner, wipers, heat, HVAC 
fan, audio/video systems, etc.) that can be shut down, will be off. 
Propulsion battery cooling fans and pumps and other components of the 
vehicle's propulsion battery thermal management system are not 
considered accessory equipment. During night time testing test vehicle 
headlights may be activated.
    (c) Vehicle's electric propulsion batteries, if any, are charged 
according to the requirements of S7.1.2.2 of SAE J2889-1 (incorporated 
by reference, see Sec.  571.5). If propulsion batteries must be 
recharged during testing to ensure internal combustion engine does not 
activate, manufacturer instructions will be followed.
    (d) Vehicle test weight, including the driver and instrumentation, 
will be evenly distributed between the left and right side of the 
vehicle and will not exceed the vehicle's GVWR or GAWR:
    (1) For passenger cars, and MPVs, trucks, and buses with a GVWR of 
4,536 kg (10,000 pounds) or less, the vehicle test weight is the 
unloaded vehicle weight plus 180 kg (396 pounds);
    (2) For LSVs, the test weight is the unloaded vehicle weight plus 
78 kg (170 pounds).
    (e) Tires will be free of all debris and each tire's cold tire 
inflation pressure set to:
    (1) For passenger cars, and MPVs, trucks, and buses with a GVWR of 
4,536 kg (10,000 pounds) or less, the inflation pressure specified on 
the vehicle placard in FMVSS No. 110;
    (2) For LSVs, the inflation pressure recommended by the 
manufacturer for GVWR; if none is specified, the maximum inflation 
pressure listed on the sidewall of the tires.
    (f) Tires are conditioned by driving the test vehicle around a 
circle 30 meters (100 feet) in diameter at a speed that produces a 
lateral acceleration of 0.5 to 0.6 g for three clockwise laps followed 
by three counterclockwise laps;
    S6.7 Ambient correction.
    S6.7.1 Measure the ambient noise for at least 30 seconds 
immediately before and after each series of vehicle tests. A series is 
a test condition, i.e. stationary, reverse, 10 km/h pass-by test, 20 
km/h pass-by test, or 30 km/h pass-by test. Ambient noise data files 
will be collected from each microphone required by the test procedures 
in S7.
    S6.7.2 For each microphone, determine the minimum A-weighted 
overall ambient SPL during the 60 seconds (or more) of recorded ambient 
noise consisting of at least 30 seconds recorded immediately before and 
at least 30 seconds immediately after each test series.
    S6.7.3 For each of the 13 one-third octave bands, the minimum A-
weighted ambient noise level during the 60 seconds (or more) from the 
two 30 second periods of ambient noise recorded immediately before and 
after each test series will be determined for each microphone.
    S6.7.4 To correct overall SPL values for ambient noise, calculate 
the difference, for each microphone, between the measured overall SPL 
values for a test vehicle obtained in sections S7.1.4(b) and S7.3.4(b) 
and the minimum overall ambient SPL values

[[Page 90518]]

determined in S6.7.2, above. Using Table 8, determine a correction 
factor for each microphone. Subtract the correction factor from the 
overall SPL value measured under sections S7.1.4(b) and S7.3.4(b) to 
calculate the corrected overall SPL value. Any test for which the 
minimum overall SPL of the ambient is within 3 dB of the uncorrected 
overall SPL of the vehicle is invalid and not analyzed further.
    S6.7.5 To correct one-third octave band sound levels for ambient 
noise, calculate the difference, for each microphone, between the 
uncorrected level for a one-third octave band (obtained in sections 
S7.1.5(b), S7.1.6(b) and S7.3.5(b)) and the minimum ambient level in 
the same one-third octave band as determined in S6.7.3. Use Table 9 to 
determine if a correction is required for each microphone and one-third 
octave band. If a correction is required, subtract the appropriate 
correction factor in Table 9 from the uncorrected one-third octave band 
sound level to calculate the corrected level for each one-third octave 
band. If the level of any ambient one-third octave band is within 3 dB 
of the corresponding uncorrected one-third octave band level, then that 
one-third octave band is invalid and not analyzed further.

           Table 8--Overall SPL Corrections for Ambient Noise
------------------------------------------------------------------------
 Difference between vehicle measurement and
            ambient noise level                       Correction
------------------------------------------------------------------------
Greater than 10 dB.........................  0 dB.
Greater than 8 dB but less than or equal to  0.5 dB.
 10 dB.
Greater than 6 dB but less than or equal to  1.0 dB.
 8 dB.
Greater than 4.5 dB but less than or equal   1.5 dB.
 to 6 dB.
Greater than 3 dB but less than or equal to  2.5 dB.
 4.5 dB.
Less than or equal to 3 dB.................  Invalid test run.
------------------------------------------------------------------------

         Table 9--1/3 Octave Band Corrections for Ambient Noise
------------------------------------------------------------------------
 Difference between vehicle 1/3 octave band
   sound pressure level and ambient noise             Correction
                   level
------------------------------------------------------------------------
Greater than 6 dB..........................  0 dB.
Greater than 4.5 dB but less than or equal   1.5 dB.
 to 6 dB.
Greater than 3 dB but less than or equal to  2.5 dB.
 4.5 dB.
Less than or equal to 3 dB.................  Specific 1/3 octave band is
                                              not useable.
------------------------------------------------------------------------

    S7. Test Procedure.
    S7.1 Vehicle stationary
    S7.1.1 Execute stationary tests and collect acoustic sound files.
    (a) Position the vehicle with the front plane at the line PP', the 
vehicle centerline on the line CC' and the starting system deactivated. 
For vehicle equipped with a Park position, place the vehicle's gear 
selector in ``Park'' and engage the parking brake. For vehicles not 
equipped with a Park position, place the vehicle's gear selector in 
``Neutral'' and engage the parking brake. Activate the starting system 
to energize the vehicle's propulsion system.
    (b) For vehicles equipped with a Park position for the gear 
selector, after activating the starting system to energize the 
vehicle's propulsion system, apply and maintain a full application of 
the service brake, disengage the vehicle parking brake and then place 
the vehicle's gear selector in ``Drive,'' or any forward gear. For 
vehicles not equipped with a Park position for the gear selector, after 
activating the starting system to energize the vehicle's propulsion 
system, apply and maintain a full application of the service brake, 
disengage the vehicle parking brake, disengage the manual clutch (fully 
depress and hold the clutch pedal), and place the vehicle's gear 
selector in any forward gear.
    (c) Execute multiple tests to acquire at least four valid tests 
within 2 dBA overall SPL in accordance with S7.1.2 and S7.1.3. For each 
test, measure the sound emitted by the stationary test vehicle for a 
duration of 10 seconds.
    (d) During each test a left (driver's side), a right (passenger 
side), and a front-center acoustic file will be recorded.
    S7.1.2. Eliminate invalid tests.
    (a) Determine validity of sound files collected during S7.1.1 
tests. Measurements that contain any distinct, transient, loud sounds 
(e.g., chirping birds, overhead planes, trains, car doors being 
slammed, etc.) are considered invalid. Measurements that contain sounds 
emitted by any vehicle system that is automatically activated and 
constantly engaged during the entire 10 second performance test are 
considered valid. Measurements that contain sound emitted by any 
vehicle system that is automatically activated and intermittently 
engaged at any time during the stationary performance test, are 
considered invalid. Additionally, when testing a hybrid vehicle with an 
internal combustion engine, measurements that include sound emitted by 
the ICE either intermittently or continuously are considered invalid. A 
valid test requires a valid left side, a valid right side, and a valid 
front-center acoustic sound file.
    (b) Sequentially number all tests which are deemed valid based upon 
the chronological order in which they were conducted. Acoustic files 
will be identified with a test sequence number and their association 
with the left side, right side, or front center microphone.
    S7.1.3 Identify first four valid tests within 2dBA.
    (a) For each valid test sound file identified in S7.1.2, determine 
a maximum overall SPL value, in decibels. Each SPL value will be 
reported to the nearest tenth of a decibel.
    (b) Compare the first four left-side SPL values from S7.1.3(a) of 
this paragraph, and determine the range by taking the difference 
between the largest and smallest of the four values. In the same 
manner, determine the range of SPL values for the first four right-side 
and the first four front-center sound files. If the range for the left 
side, right side, and front-center are all less than or equal to 2.0 
dB, then the twelve sound files associated with the first four valid 
tests will be used for the one-third octave band evaluations in S7.1.5. 
and S7.1.6. If the range of the SPL values for

[[Page 90519]]

the left side are not within 2 dBA, or for the right side are not 
within 2 dBA, or for the front-center of the vehicle are not within 2 
dBA, an iterative process will be used to consider sound files from 
additional sequential tests until the range for all three microphone 
locations are within 2 dBA for the same sequence number recordings for 
all three locations.
    S7.1.4 Compare the average overall SPL for the left and right side 
of the test vehicle to determine which is lower.
    (a) Document the maximum overall SPL values in each of the eight 
acoustic data files (four left side files and four right side files) 
identified in S7.1.3.
    (b) Correct each of the eight SPL values from S7.1.4(a) according 
to S6.7 using the ambient sound level recorded during the test. The 
results will be reported to the nearest tenth of a decibel.
    (c) Calculate a left-side average and a right-side average from the 
ambient-corrected overall SPL values from S71.4(b), and determine the 
lower of the two sides. The result will be reported to the nearest 
tenth of a decibel.
    (d) If the left-side value from S7.1.4(c) is the lower one, then 
the left side acoustic data will be further evaluated for compliance at 
the one-third octave band levels in accordance with S7.1.5. If the 
left-side value from S7.1.4(c) is not the lower one, the right-side 
acoustic data will be further evaluated for compliance at the one-third 
octave band level in accordance with S7.1.5.
    S7.1.5 Select one-third octave bands to be used for evaluating 
compliance with detection requirements.
    (a) For each of the four left-side or right-side acoustic files, 
which ever was selected in S7.1.4, determine the sound pressure level 
in each one-third octave band from 315 Hz up to and including 5000 Hz.
    (b) Correct the one-third octave band levels in all four sound 
files to adjust for the ambient sound level recorded during the test 
according to paragraph S6.7.
    (c) For each one-third octave band, average the corrected levels 
from the four sound files. The results will be reported to the nearest 
tenth of a decibel.
    (d) For alerts designed to meet the four one-third octave band 
alert sound requirements:
    (i) Select any four one-third octave bands that are non-adjacent to 
each other and that span a range of at least nine one-third octave 
bands in the range of 315 Hz up to and including 5000 Hz to evaluate 
according to paragraph S7.1.5(d)(ii). This step will be repeated until 
compliance is established or it is determined that no combination 
meeting this selection criterion can satisfy paragraph S7.1.5(d)(ii).
    (ii) Compare the average corrected sound pressure level from 
S7.1.5(c) of this paragraph in each of the four one-third octave bands 
selected in paragraph S7.1.5(d)(i) to the required minimum level of the 
corresponding one-third octave band specified in paragraph S5.1.1, 
Table 1, to determine compliance.
    (e) For alerts designed to meet the two-one-third octave band 
requirements:
    (i) Select the two highest one-third octave bands that are non-
adjacent to each other and within the range of 315 Hz up to and 
including 3150 Hz to evaluate according to paragraph (ii), below. This 
step will be repeated until compliance is established or it is 
determined that no combination meeting this selection criterion can 
satisfy paragraph S7.1.5(e)(ii).
    (ii) Compare the average corrected sound pressure level from (c) in 
each of the two one-third octave bands selected in paragraph 
S7.1.5(e)(i) to the required minimum level of the corresponding one-
third octave band specified in paragraph S5.2 Table 6. Also, compare 
the band sum of the two bands to the required minimum level in Table 6.
    S7.1.6 Procedure for selected one-third octave bands to be used for 
evaluating compliance with directivity requirements.
    (a) Determine the one-third octave band levels associated with the 
four front center sound files selected in S7.1.3.
    (b) The identified one-third octave band levels in each of the four 
sound files will be corrected for the measured ambient levels as 
specified in paragraph S6.7.
    (c) The four corrected sound pressure level values calculated from 
each of the four sound files in each one-third octave band will be 
averaged together to get the average corrected sound pressure level in 
each one-third octave band.
    (d) For alerts designed to meet the four one-third octave band 
requirements.
    (i) Select any four one-third octave bands that are non-adjacent to 
each other and that span a range of at least nine one-third octave 
bands in the range of 315 Hz up to and including 5000 Hz to evaluate 
according to paragraph S7.1.6(d)(ii). This step will be repeated until 
compliance is established or it is determined that no combination 
meeting this selection criterion can satisfy paragraph S7.1.6(d)(ii).
    (ii) Compare the average corrected sound pressure level from (c) of 
this paragraph in each of the four one-third octave bands selected in 
paragraph S7.1.6(d)(i) to the required minimum level of the 
corresponding one-third octave band specified in paragraph S5.1.1, 
Table 1, to determine compliance.
    (e) For alerts designed to meet the two one-third octave band 
requirements.
    (i) Select the two highest one-third octave bands that are non-
adjacent to each other and within the range of 315 Hz up to and 
including 3150 Hz to evaluate according to paragraph (ii), below. One 
band shall be below 1000 Hz and one band shall be at or greater than 
1000 Hz. This step will be repeated until compliance is established or 
it is determined that no combination meeting this selection criterion 
can satisfy paragraph S7.1.6(e)(ii).
    (ii) Compare the average corrected sound pressure level from 
S7.1.6(c) of this paragraph in each of the two one-third octave bands 
selected in paragraph S7.1.6(e)(i) to the required minimum level of the 
corresponding one-third octave band specified in paragraph S5.2 Table 
6. Also, compare the band sum of the two bands to the required minimum 
level in Table 6.
    S7.2 Reverse. Test the vehicle per S7.1 (S7.1.1-S7.1.5), except 
that the rear plane of the vehicle is placed on line PP', no third 
microphone (front center) is used, and the vehicle's gear selector is 
placed in ``Reverse.''
    S7.3 Constant speed pass-by tests at speeds greater than 0 km/h but 
less than 20 km/h.
    S7.3.1 Execute pass-by tests at 11km/h (+/-1 km/h) and collect 
acoustic sound files.
    (a) For each test, measure the sound emitted by the test vehicle 
while at a constant speed of 11km/h (+/- 1km/h) throughout the 
measurement zone specified in S6.4 between lines AA' and PP'. Execute 
multiple test runs at 11km/h (+/-1km/h) to acquire at least four valid 
tests within 2dBA in accordance with S7.3.2 and S7.3.3.
    (b) During each test, record a left (driver's side) and a right 
(passenger side) acoustic sound file.
    S7.3.2 Eliminate invalid tests and acoustic sound files
    (a) Determine validity of sound files collected during S7.3.1 
tests. Measurements that contain any distinct, transient, background 
sounds (e.g., chirping birds, overhead planes, car doors being slammed, 
etc.) are considered invalid. Measurements that contain sounds emitted 
by any vehicle system that is automatically activated and constantly 
engaged during the entire performance test are considered valid. 
Measurements that contain sound

[[Page 90520]]

emitted by any vehicle system that is automatically activated, and 
intermittently engaged at any time during the performance test, are 
considered invalid. Additionally, when testing a hybrid vehicle with an 
internal combustion engine that runs intermittently during a specific 
test, measurements that contain sound emitted by the ICE are considered 
invalid. A valid test requires both a valid left side and a valid right 
side acoustic sound file.
    (b) Tests which are deemed valid will be numbered sequentially 
based upon the chronological order in which they were collected. Sound 
files will retain their test sequence number and their association with 
the left side or right side microphone.
    S7.3.3 Identify ``first four valid tests within 2 dBA''.
    (a) For each valid test sound file identified in S7.3.2, determine 
a maximum overall SPL value, in decibels. The SPL value will be 
reported to the nearest tenth of a decibel.
    (b) Compare the first four left side maximum overall SPL values. Of 
the four SPL values calculate the difference between the largest and 
smallest maximum SPL values. The same process will be used to determine 
the difference between the largest and smallest maximum SPL values for 
the first four right side maximum SPL values. If the difference values 
on the left and right sides of the test vehicle are both less than or 
equal to 2.0 dB, then the eight sound files associated with the first 
four valid tests will be used for the final one-third octave band 
evaluation in accordance with S7.3.4. and S7.3.5. If the first four 
test sound files on each side of the vehicle are not within 2 dBA, an 
iterative process will be used to consider sound files from additional 
sequential tests until the range for both microphone locations are 
within 2 dBA for the same sequence number recordings for both 
locations.
    S7.3.4 Determine average overall SPL value on each side (left and 
right) of test vehicle.
    (a) Document the maximum overall SPL value in decibels for each of 
the eight acoustic sound data files (four left-side files and four 
right-side files) identified in S7.3.3.
    (b) Each of the eight acoustic sound data file maximum overall SPL 
values will be corrected for the recorded ambient conditions as 
specified in paragraph S6.7. The test results will be reported to the 
nearest tenth of a decibel.
    (c) Calculate the average of the four overall ambient-corrected SPL 
values on each side of the vehicle to derive one corrected maximum 
overall SPL value for each side of the vehicle. The result will be 
reported to the nearest tenth of a decibel.
    (d) The side of the vehicle with the lowest average corrected 
maximum overall SPL value will be the side of the vehicle that is 
further evaluated for compliance at the one-third octave band levels in 
accordance with S7.3.5.
    S7.3.5 Complete one-third octave band evaluation for compliance 
verification.
    (a) The side of the vehicle selected in S7.3.4 will have four 
associated individual acoustic sound data files. Each sound file shall 
be broken down into its one-third octave band levels.
    (b) The identified octave band levels in each of the four sound 
files will be corrected for the measured ambient levels as specified in 
paragraph S6.7.
    (c) The four corrected sound pressure level values calculated from 
each of the four sound files in each one-third octave band will be 
averaged together to get the average corrected sound pressure level in 
each one-third octave band.
    (d) For alerts designed to meet the four one-third octave band 
requirements.
    (i) Select any four one-third octave bands that are non-adjacent to 
each other and that span a range of at least nine one-third octave 
bands in the range of 315 Hz up to and including 5000 Hz to evaluate 
according to paragraph S7.3.5(d)(ii). This step will be repeated until 
compliance is established or it is determined that no combination 
meeting this selection criterion can satisfy paragraph S7.3.5(d)(ii).
    (ii) Compare the average corrected sound pressure level from 
S7.3.5(c) in each of the four one-third octave bands selected in 
paragraph S7.3.5(d)(i) to the required minimum level of the 
corresponding one-third octave band specified in paragraph S5.1.3, 
Table 3, to determine compliance.
    (e) For alerts designed to meet the two one-third octave band 
requirements.
    (i) Select the two highest one-third octave bands that are non-
adjacent to each other and within the range of 315 Hz up to and 
including 3150 Hz to evaluate according to paragraph S7.3.5(e)(ii). 
This step will be repeated until compliance is established or it is 
determined that no combination meeting this selection criterion can 
satisfy paragraph S7.3.5(e)(ii).
    (ii) Compare the average corrected sound pressure level from 
S7.3.5(c) in each of the two one-third octave bands selected in 
paragraph S7.3.5(e)(i) to the required minimum level of the 
corresponding one-third octave band specified in paragraph S5.2 and 
Table 6. Also, compare the band sum of the two bands to the required 
minimum level in Table 6.
    S7.3.6 Repeat S7.3.1-S7.3.5 using any other constant vehicle speed 
equal to or greater than 10 km/h but less than 20 km/h.
    S7.4 Constant speed pass-by tests at speeds greater than or equal 
to 20 km/h but less than 30 km/h. Repeat the test of S7.3 at 21 km/h 
(+/-1km/h). In S7.3.6, the 21km/h (+/-1km/h) test speed can be replaced 
using any constant speed greater than or equal to 20 km/h but less than 
30 km/h.
    S7.5 Constant speed pass-by tests at 30 km/h. Repeat the test of 
S7.3 at 31 km/h (+/-1km/h)
    S7.6 Relative volume change. The valid test run data selected for 
each critical operating scenario in S7.1 (S7.1.5(c)), S7.3 (S7.3.5(c)), 
S7.4 and S7.5 will be used to derive relative volume change as required 
in S5.4 as follows:
    S7.6.1 Calculate the average sound pressure level for each of the 
13 one-third octave bands (315 Hz to 5000 Hz) using the four valid test 
runs identified for each critical operating scenario from S7.1.3 and 
S7.3.3 (stationary, 10 km/h (11+/-1km/h), 20 km/h (21+/-1km/h), and 30 
km/h (31+/-1km/h)).
    S7.6.2 For each critical operating scenario, normalize the levels 
of the 13 one-third octave bands by subtracting the corresponding 
minimum SPL values specified in Table 1 for the stationary operating 
condition from each of the one-third octave band averages calculated in 
S7.6.1.
    S7.6.3 Calculate the NORMALIZED BAND SUM for each critical 
operating scenario (stationary, 10 km/h (11+/-1km/h), 20 km/h (21+/-
1km/h), and 30 km/h (31+/-1km/h)) as follows:
[GRAPHIC] [TIFF OMITTED] TR14DE16.019

[[Page 90521]]

Where:

i represents the 13 one-third octave bands and Normalized Band 
Leveli is the normalized one-third octave band value derived in 
S7.6.2.

    S7.6.4 Calculate the relative volume change between critical 
operating scenarios (stationary to 10km/h; 10km/h to 20 km/h; 20km/h to 
30 km/h) by subtracting the NORMALIZED BAND SUM of the lower speed 
operating scenario from the NORMALIZED BAND SUM of the next higher 
speed operating scenario. For example, the relative volume change 
between 10 km/h (11+/-1km/h) and 20 km/h (21+/-1km/h) would be the 
NORMALIZED BAND SUM level at 21+/-1km/h minus the NORMALIZED BAND SUM 
level at 11+/-1km/h.
    S8 Prohibition on altering the sound of a vehicle subject to this 
standard. No entity subject to the authority of the National Highway 
Traffic Safety Administration may:
    (a) Disable, alter, replace or modify any element of a vehicle 
installed as original equipment for purposes of complying with this 
Standard, except in connection with a repair of a vehicle malfunction 
related to its sound emission or to remedy a defect or non-compliance 
with this standard; or
    (b) Provide any person with any mechanism, equipment, process or 
device intended to disable, alter, replace or modify the sound emitting 
capability of a vehicle subject to this standard, except in connection 
with a repair of vehicle malfunction related to its sound emission or 
to remedy a defect or non-compliance with this standard.
    S9 Phase-in schedule.
    S9.1 Hybrid and Electric Vehicles manufactured on or after 
September 1, 2018, and before September 1, 2019. For hybrid and 
electric vehicles to which this standard applies manufactured on or 
after September 1, 2018, and before September 1, 2019, except vehicles 
produced by small volume manufacturers, the quantity of hybrid and 
electric vehicles complying with this safety standard shall be not less 
than 50 percent of one or both of the following:
    (a) A manufacturer's average annual production of hybrid and 
electric vehicles on and after September 1, 2015, and before September 
1, 2018;
    (b) A manufacturer's total production of hybrid and electric 
vehicles on and after September 1, 2018, and before September 1, 2019.
    S9.2 Hybrid and Electric Vehicles manufactured on or after 
September 1, 2019. All hybrid and electric vehicles to which this 
standard applies manufactured on or after September 1, 2019, shall 
comply with this safety standard.

0
4. Section 571.500 is amended by adding paragraph S5.(b)(12) to read as 
follows:

Sec.  571.500  Standard No. 500; Low-speed vehicles.

* * * * *
    S5.(b) * * *
    (12) An alert sound as required by Sec.  571.141.
* * * * *

PART 585--PHASE-IN REPORTING REQUIREMENTS

0
4. The authority citation for part 585 is revised to read as follows:

    Authority:  49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.95

0
5. Add Subpart N to read as follows:
Subpart N--Minimum Sound Requirements for Hybrid and Electric Vehicles 
Reporting Requirements
Sec.
585.128 Scope.
585.129 Purpose.
585.130 Applicability.
585.131 Definitions.
585.132 Response to inquiries.
585.133 Reporting requirements.
585.134 Records.

Subpart N--Minimum Sound Requirements for Hybrid and Electric 
Vehicles Reporting Requirements

Sec.  585.128   Scope.

    This subpart establishes requirements for manufacturers of hybrid 
and electric passenger cars, trucks, buses, multipurpose passenger 
vehicles, and low-speed vehicles to submit a report, and maintain 
records related to the report, concerning the number of such vehicles 
that meet minimum sound requirements of Standard No. 141, Minimum Sound 
Requirements for Hybrid and Electric Vehicles (49 CFR 571.141).

Sec.  585.129  Purpose.

    The purpose of these reporting requirements is to assist the 
National Highway Traffic Safety Administration in determining whether a 
manufacturer has complied with the minimum sound requirements of 
Standard No. 141, Minimum Sound for Hybrid and Electric Vehicles (49 
CFR 571.141).

Sec.  585.130  Applicability.

    This subpart applies to manufacturers of hybrid and electric 
passenger cars, trucks, buses, multipurpose passenger vehicles, and 
low-speed vehicles subject to the phase-in requirements of Sec.  
571.141, S9.1 Hybrid and Electric Vehicles manufactured on or after 
September 1, 2018, and before September 1, 2019.

Sec.  585.131  Definitions.

    (a) All terms defined in 49 U.S.C. 30102 are used in their 
statutory meaning.
    (b) Bus, gross vehicle weight rating or GVWR, low-speed vehicle, 
multipurpose passenger vehicle, passenger car, truck, and motorcycle 
are used as defined in Sec.  571.3 of this chapter.
    (c) Production year means the 12-month period between September 1 
of one year and August 31 of the following year, inclusive.
    (d) Electric Vehicle, and hybrid vehicle are used as defined in 
Sec.  571.141 of this chapter.

Sec.  585.132   Response to inquiries.

    At any time during the production year ending August 31, 2018, each 
manufacturer shall, upon request from the Office of Vehicle Safety 
Compliance, provide information identifying the vehicles (by make, 
model and vehicle identification number) that have been certified as 
complying with the requirements of Standard No. 141, Minimum Sound 
Requirements for Hybrid and Electric Vehicles (49 CFR 571.141). The 
manufacturer's designation of a vehicle as a certified vehicle is 
irrevocable.

Sec.  585.133  Reporting requirements.

    (a) Phase-in reporting requirements. Within 60 days after the end 
of the production year ending August 31, 2018, each manufacturer shall 
submit a report to the National Highway Traffic Safety Administration 
concerning its compliance with the requirements of Standard No. 141 
Minimum Sound Requirements for Hybrid and Electric Vehicles (49 CFR 
571.141) for its vehicles produced in that year. Each report shall 
provide the information specified in paragraph (b) of this section and 
in Sec.  585.2 of this part.
    (b) Phase-in report content--
    (1) Basis for phase-in production goals. Each manufacturer shall 
provide the number of hybrid vehicles and electric vehicles 
manufactured in the current production year or, at the manufacturer's 
option, in each of the three previous production years. A manufacturer 
that is, for the first time, manufacturing vehicles for sale in the 
United States must report the number of vehicles manufactured during 
the current production year.
    (2) Production of complying vehicles--
    Each manufacturer shall report for the production year being 
reported on, and

[[Page 90522]]

each preceding production year, to the extent that vehicles produced 
during the preceding years are treated under Standard No. 141 as having 
been produced during the production year being reported on, information 
on the number of vehicles that meet the requirements of Standard No. 
141, Minimum Sound Requirements for Hybrid and Electric Vehicles (49 
CFR 571.141).

Sec.  585.134  Records.

    Each manufacturer shall maintain records of the Vehicle 
Identification Number for each vehicle for which information is 
reported under Sec.  585.133 until December 31, 2023.

    Issued on November 10, 2016 in Washington, DC, under authority 
delegated in 49 CFR 1.95 and 501.5.
Mark R. Rosekind,
Administrator.
[FR Doc. 2016-28804 Filed 12-13-16; 8:45 am]
 BILLING CODE 4910-59-P