2798 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

DEPARTMENT OF TRANSPORTATION 

National Highway Traffic Safety 

Administration 

49 CFR Parts 571 and 585 

[Docket No. NHTSA–2011–0148] 

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: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: As required by the Pedestrian 

Safety Enhancement Act (PSEA) of 2010 

this rule proposes to establish a Federal 

motor vehicle safety standard (FMVSS) 

setting minimum sound requirements 

for hybrid and electric vehicles. This 

new standard would require hybrid and 

electric passenger cars, light trucks and 

vans (LTVs), medium and heavy duty, 

trucks, and buses, low speed vehicles 

(LSVs), and motorcycles to produce 

sounds meeting the requirements of this 

standard. This proposed standard 

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 would ensure 

that blind, visually-impaired, and other 

pedestrians are able to detect and 

recognize nearby hybrid and electric 

vehicles, as required by the PSEA, by 

requiring that hybrid and electric 

vehicles emit sound that pedestrians 

would be able to hear in a range of 

ambient environments and contain 

acoustic signal content that pedestrians 

will recognize as being emitted from a 

vehicle. 

The benefit of reducing the pedestrian 

injury rate per registered vehicle of HVs 

to ICE vehicles when 4.1% of the fleet 

is HV and EV would be 2790 fewer 

pedestrian and pedalcyclist injuries. We 

also estimate that this proposal will 

result in 10 fewer pedestrian and 

pedalcyclist injuries caused by LSVs. 

Thus, 2800 total injured pedestrians are 

expected to be avoided due to this 

proposal representing 35 equivalent 

lives saved. We do not estimate any 

quantifiable benefits for EVs because it 

is our view that EV manufacturers 

would have installed alert sounds in 

their cars without passage of the PSEA 

and this proposed rule. Comparison of 

costs and benefits expected due to this 

rule provides a cost of $0.83 to $0.99 

million per equivalent life saved across 

the 3 and 7 percent discount levels for 

the light EV and HV and LSV fleet. 

According to our present model, a 

countermeasure that allows a vehicle to 

meet the proposed minimum sound 

requirements would be cost effective 

compared to our comprehensive cost 

estimate of the value of a statistical life 

of $6.3 million. 

DATES: Comments must be received on 

or before March 15, 2013. 

ADDRESSES: You may submit comments 

to the docket number identified in the 

heading of this document by any of the 

following methods: 

• Federal eRulemaking Portal: go to 

http://www.regulations.gov. Follow the 

online instructions for submitting 

comments. 

• Mail: Docket Management Facility, 

M–30, U.S. Department of 

Transportation, West Building, Ground 

Floor, Rm. W12–140, 1200 New Jersey 

Avenue SE., Washington, DC 20590. 

• Hand Delivery or Courier: West 

Building Ground Floor, Room W12–140, 

1200 New Jersey Avenue SE., between 

9 a.m. and 5 p.m. Eastern Time, Monday 

through Friday, except Federal holidays. 

• Fax: (202) 493–2251. 

Regardless of how you submit your 

comments, you should mention the 

docket number of this document. 

You may call the Docket at 202–366– 

9324. 

Instructions: For detailed instructions 

on submitting comments and additional 

information on the rulemaking process, 

see the Public Participation heading of 

the Supplementary Information section 

of this document. Note that all 

comments received will be posted 

without change to http:// 

www.regulations.gov, including any 

personal information provided. 

Privacy Act: Please see the Privacy 

Act heading under Rulemaking 

Analyses and Notices. 

FOR FURTHER INFORMATION CONTACT: 

For non-legal issues, Ms. Gayle 

Dalrymple, Office of Crash Avoidance 

Standards (telephone: 202–366- 5559) 

(fax: 202–493–2990). Ms. Dalrymple’s 

mailing address is National Highway 

Traffic Safety Administration, NVS– 

112, 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 

II. Background 

III. Pedestrian Safety Enhancement Act of 

2010 

IV. Consultation With External Organizations 

V. Safety Problem 

A. Comparing the Vehicle to Pedestrian 

Crash Experience of Internal Combustion 

Engine Vehicles to Hybrid and Electric 

Vehicles 

B. Need for Independent Mobility of 

People Who Are Visually Impaired and 

Blind 

VI. NHTSA Research and Industry Practices 

A. NHTSA Phase 1 Research 

B. NHTSA Phase 2 Research 

C. NHTSA Phase 3 Research 

D. International Approach to Pedestrian 

Alert Sounds 

E. SAE Sound Measurement Procedure 

F. Alert Sounds Currently Provided by 

Manufacturers 

G. The Notice of Intent To Prepare an 

Environmental Assessment 

VII. NHTSA’s Proposal 

A. Acoustic Specifications Developed To 

Enhance Detection and Recognition 

B. Critical Operating Scenarios 

1. Stationary But Activated 

2. Reverse 

3. Acceleration and Deceleration 

4. Constant Speed 

C. Application 

1. The Definition of Hybrid Vehicle 

2. Vehicles With a GVWR Over 10,000 lbs 

3. Electric Motorcycles 

4. Low Speed Vehicles 

5. Quiet Internal Combustion Engine 

Vehicles 

D. Requirements 

1. Acoustic Parameters Designed 

According to a Detectability Model 

2. Recognizability Requirements 

3. Prohibition Against Modifying a Vehicle 

Sound 

4. Phase-in Schedule 

E. Compliance Test Procedure 

1. Test Condition 

2. Vehicle Condition 

3. Test Procedure 

a. Start-up 

b. Stationary But Activated and Directivity 

c. Reverse 

d. Constant Speed 

e. Pitch Shifting 

f. Recognizability 

g. Vehicles of the Same Make and Model 

Emitting the Same Sound 

VIII. Alternatives Considered But Not 

Proposed 

A. Requiring Vehicle Sound To Be 

Playback of an Internal Combustion 

Engine Recording 

B. Requiring That the Alert Sound Adapt 

to the Ambient 

C. Acoustic Profile Designed Around 

Sounds Produces by Internal 

Combustion Engine Vehicles 

D. Acoustic Profiles Suggested by 

Manufacturers 

E. International Guidelines for Vehicle 

Alert Sounds 

F. Suggestions in Comments to the Notice 

of Intent That Did Not Satisfy the 


tkelley on DSK3SPTVN1PROD with 
Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2799 

1Public Law 111–373, 124 Stat. 4086 (January 4, 

2011). 

2 Id. at Section 2(2). 

Statement of Purpose and Need for the 

Rulemaking 

G. Possible Jury Testing for Recognition of 

a Synthetic Sound 

IX. NHTSA’s Role in the Development of a 

Global Technical Regulation 

X. Analysis of Costs, Benefits and 

Environmental Effects 

A. Benefits 

B. Costs 

C. Comparison of Costs and Benefit 

D. Environmental Effects 

XI. Regulatory Notices and Analyses 

I. Executive Summary 

As required by the PSEA,1 this rule 

proposes to establish FMVSS No.141, 

Minimum Sound Requirements for 

Hybrid and Electric Vehicles, which 

would require hybrid and electric 

passenger cars, LTVs, medium and 

heavy duty trucks and buses, LSVs, and 

motorcycles to produce sounds meeting 

the requirements of this standard. This 

proposed standard applies to EVs and to 

those HVs that are capable of propulsion 

in any forward or reverse gear without 

the vehicle’s ICE operating. The PSEA 

requires NHTSA to establish 

performance requirements for an alert 

sound that is recognizable as motor 

vehicle in operation that allows blind 

and other pedestrians to reasonably 

detect a nearby EV or HV operating 

below the crossover speed. The 

crossover speed is the speed at which 

tire noise, wind noise, and other factors 

eliminate the need for a separate alert 

sound. The PSEA defines ‘‘alert sound’’ 

as ‘‘a vehicle-emitted sound to enable 

pedestrians to discern vehicle presence, 

direction, location and operation.’’ 2 The 

legal authority for this rulemaking 

comes from the PSEA and 49 U.S.C. 

30111. 

This standard will ensure that blind, 

visually-impaired, and other pedestrians 

are able to detect and recognize nearby 

hybrid and electric vehicles by requiring 

that hybrid and electric vehicles emit 

sound that pedestrians will be able to 

hear in a range of ambient environments 

and contain acoustic signal content that 

pedestrians will recognize as being 

emitted from a vehicle. The proposed 

standard establishes minimum sound 

requirements for hybrid and electric 

vehicles when operating under 30 

kilometers per hour (km/h) (18 mph), 

when the vehicle’s starting system is 

activated but the vehicle is stationary, 

and when the vehicle is operating in 

reverse. 

The requirements of this proposal 

apply only to those HVs that are capable 

of propulsion in any forward or reverse 

gear without the vehicle’s ICE operating 

because these were the vehicles that the 

agency believes fall under the definition 

of ‘‘hybrid vehicle’’ contained in the 

PSEA. The agency chose a crossover 

speed of 30 km/h because this was the 

speed at which the sound levels of the 

hybrid and electric vehicles measured 

by the agency approximated the sound 

levels produced by similar ICE vehicles. 

This proposal contains minimum sound 

requirements for the activated but 

stationary operating condition because 

the definition of alert sound in the 

PSEA, as explained in Section III of this 

NPRM, requires the agency to issue 

minimum sound requirements to allow 

pedestrians to detect hybrid and electric 

vehicles. We have tentatively 

determined that this requirement can be 

best met by requiring vehicles to emit 

sound in this operating condition. 

At lower speeds, hybrid and electric 

vehicles produce less sound than 

vehicles propelled by an ICE. At higher 

speeds, tire and wind noise are the main 

contributors to vehicles noise output so 

at higher speeds the sounds produced 

by hybrid and electric vehicles and ICE 

vehicles are similar. Because hybrid and 

electric vehicles do not produce as 

much sound as ICE vehicles when 

operating at lower speeds, pedestrians 

and other road users may not be aware 

of the presence of a nearby hybrid or 

electric vehicle. If a hybrid vehicle is 

involved in a low speed maneuver 

(defined as making a turn, slowing or 

stopping, backing up, entering or 

leaving a parking space, or starting in 

traffic), it is 1.38 times more likely than 

an ICE vehicle to be involved in a 

collision with a pedestrian and 1.33 

times more likely to be involved in a 

collision with a pedalcyclist. We believe 

that this difference in accident rates is 

mostly attributable to the pedestrians’ 

inability to detect these vehicles by 

hearing them during these maneuvers. 

We seek comment on this assumption. 

Statistics for pedestrian collision rates 

of hybrid and electric vehicles with a 

GVWR over 4,536 kg (10,000 lb), and 

motorcycles were not available because 

of the limited penetration of these 

vehicles into the fleet. NHTSA expects 

that should the penetration of hybrid 

and electric heavy vehicles, and 

motorcycles reach the current rate of 

penetration of light hybrid and electric 

vehicles into the fleet, then the 

difference in pedestrian collision rates 

between hybrid and electric heavy 

vehicles, and motorcycles and their 

traditional ICE counterparts will be 

similar to the difference in pedestrian 

collision rates between light HVs and 

light ICE vehicles. 

In addition to analyzing crash data, 

the agency measured the sound 

produced by HVs, EVs and ICE vehicles 

to determine the difference in sound 

output between the propulsion types at 

different speeds and 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 used acoustic models to 

determine the frequency composition of 

sounds that would give pedestrians the 

best chance to detect approaching 

hybrid and electric vehicles without 

contributing undesirably to surrounding 

ambient noise levels. 

The proposed standard ensures that 

pedestrians will be able to determine 

whether a hybrid or electric vehicle is 

accelerating or decelerating by requiring 

the frequency content of the sound 

emitted by the vehicle to increase in a 

manner that is similar to the sound 

produced by ICE vehicles when 

accelerating and decelerating. The 

agency developed the minimum sound 

specifications contained in this proposal 

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. The standard also requires, as 

mandated by the PSEA, that all vehicles 

of the same make, model and model 

year emit the same sound. 

The PSEA requires that the final rule 

establishing this standard be issued by 

January 4, 2014 and include a phase-in 

schedule that concludes with ‘‘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.’’ For example 

the means that if the final rule is issued 

January 4, 2014, compliance would 

commence on September 1, 2015, which 

would mark the start of a three-year 

phase-in period. We tentatively 

conclude that the following phase in 

schedule is reasonable for 

manufacturers and allows the fastest 

implementation of the standard for 

pedestrian safety: 

30 percent of the subject vehicles 

produced on or after September 1of the 

first year of the phase in; 

60 percent of the subject vehicles 

produced on or after September 1of the 

second year of the phase in; 

90 of the subject vehicles produced on 

or after September 1of the third year of 

the phase in; and 

100 percent of all vehicles produced 

on or after, by September 1 of the year 

that begins three years after the date that 

the final rule is issued. 


tkelley on DSK3SPTVN1PROD with 
2800 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

3Scaled benefits and costs for low speed vehicles 

are estimated directly proportional to light vehicles 

based on sales. Scaled costs include both 

installation costs for the system and fuel costs. 

As discussed in detail in Section X of 

this notice, the benefits of this proposed 

rule, if made final, will accrue from 

injuries to pedestrians that will be 

avoided, assuming that the rule will 

cause the pedestrian injury rate for HVs 

and EVs to decrease to that of ICE 

vehicles. As discussed in Section V, a 

traditional analysis of pedestrian 

fatalities is not appropriate for this 

rulemaking. If HVs and EVs continue to 

rise in popularity and increase their role 

in the U.S. fleet to four percent of all 

vehicle registrations, unchanged by 

rulemaking or industry action, a total of 

2,790 injured pedestrians and 

pedalcyclists would be expected over 

the life time of the 2016 model year fleet 

due to the pedestrians’ and 

pedalcyclists’ inability to detect these 

vehicles by hearing. We estimate that 

the benefit then of reducing the 

pedestrian injury rate per registered 

vehicle of HVs to ICE vehicles when 

four percent of the fleet is HV and EV 

would be 2,790 fewer injured 

pedestrians and pedalcyclists. We do 

not estimate any quantifiable benefits in 

pedestrian or pedalcyclist injury 

reduction for EVs because it is our view 

that EV manufacturers would have 

installed alert sounds in their cars 

without passage of the PSEA and this 

proposed rule. We also estimate that 

this proposal will result in 10 fewer 

injured pedestrians and pedalcyclists 

caused by LSVs. 

DISCOUNTED BENEFITS FOR PASSENGER CARS (PCS) AND LTVS, MY2016, 2010$ 

3% 

discount 

Pedestrians Pedalcyclists Total PED + CYC 

3% discount 

factor 

Total monetized 

benefits Total ELS 3% discount factor 

Total monetized 

benefits Total ELS 3% discount factor 

Total monetized 

benefits 

Total 

ELS 

(PC) ....... 0.8034 $58,640,938 9.27 0.8034 $64,106,653 10.14 0.8034 $122,747,591 19.41 

(LTV) ...... 0.8022 26,945,946 4.26 0.8022 28,319,549 4.48 0.8022 55,265,495 8.74 

Total .................... 85,586,884 13.54 .................... 92,426,203 14.62 .................... 178,013,086 28.15 

7% 

discount 

Pedestrians Pedalcyclists Total PED + CYC 

7% discount 

factor 

Total monetized 

benefits Total ELS 7% discount factor 

Total monetized 

benefits Total ELS 7% discount factor 

Total monetized 

benefits 

Total 

ELS 

(PC) ....... 0.6700 $48,903,944 7.73 0.6700 $53,462,108 8.46 0.6700 $102,366,052 16.19 

(LTV) ...... 0.6303 21,171,815 3.35 0.6303 22,251,074 3.52 0.6303 $43,422,889 6.87 

Total .................... 70,075,758 11.08 .................... 75,713,183 11.97 .................... 145,788,941 23.06 

TOTAL COSTS FOR PCS AND LTVS, MY2016, 2010$ 

3% 

discount Sales Sales impacted 

Fuel costs/ 

veh 

Fuel costs 

(total) 

Install costs/ 

veh 

Install costs 

total 

Total cost/ 

veh Total costs 

(PC) .......... 9,032,303 439,586 $4.73 $2,079,240 $30.00 $13,187,566 $34.73 $15,266,805 

(LTV) ........ 7,164,729 231,685 5.33 1,234,880 30.00 6,950,542 35.33 8,185,421 

Total .. 16,197,032 671,270 4.94 3,314,119 30.00 20,138,107 34.94 23,452,226 

7% 

discount Sales Sales impacted 

Fuel costs/ 

veh 

Fuel costs 

(total) 

Install costs/ 

veh 

Install costs 

total 

Total cost/ 

veh Total costs 

(PC) .......... 9,032,303 439,586 $3.83 $1,683,613 $30.00 $13,187,566 $33.83 $14,871,178 

(LTV) ........ 7,164,729 231,685 4.23 980,026 30.00 6,950,542 34.23 7,930,568 

Total .. 16,197,032 671,270 3.97 2,663,639 30.00 20,138,107 33.97 22,801,746 

COSTS AND SCALED BENEFITS FOR LSVS, MY2016 3

Discount rate 

Sales ratio 

LSV to light 

vehicle 

Sales Scaled costs Scaled injuries 

(undisc.) Scaled ELS Scaled benefits 

Scaled 

benefits 

minus scaled 

costs 

3% ................................ 0.37% 2,500 $87,268 10.39 0.1049 $662,971 $575,703 

7% ................................ 0.37% 2,500 84,845 10.39 0.0859 542,959 458,114 


tkelley on DSK3SPTVN1PROD with 
Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2801 

4Society of Automotive Engineers (2011) 

Measurement of Minimum Noise Emitted by Road 

Vehicles, SAE–J2889–1. Warrendale, PA. Available 

at http://standards.sae.org/wip/j2889/1/. 

5 73 FR 31187; May 30, 2008. 

6The presentations are in document # 0012 and 

the transcript is in document # 0023 (Docket No. 

NHTSA–2008–0108–0012 and Docket No. NHTSA– 

2008–0108–0023, respectively). 

7Quieter Cars and the Safety of Blind Pedestrians: 

The NHTSA Research Plan, April 2009, available at 

http://www.regulations.gov/ 

#!documentDetail;D=NHTSA-2008-0108-0025. 

8R. 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. 

NHTSA estimates the fuel and 

installation cost of adding a speaker 

system in order to comply with the 

requirements of this proposal to be 

around $35 per vehicle for light 

vehicles. We estimate the total fuel and 

installation costs of this proposal to the 

light EV, HV and LSV fleet to be $23.6M 

at the 3 percent discount rate and 

$22.9M at the 7 percent discount rate. 

The estimated total installation cost for 

hybrid and electric heavy and medium 

duty trucks and buses and electric 

motorcycles is $1.48M for MY 2016. We 

have only calculated the benefits of this 

proposal for light EVs, HVs and LSVs 

because we do not have crash rates for 

hybrid and electric heavy and medium 

duty trucks and buses and electric 

motorcycles. To estimate the benefits of 

this proposal we have converted injured 

pedestrians and pedalcyclists avoided 

into equivalent lives saved. We estimate 

that the impact of this proposal in 

pedestrian and pedalcyclist injury 

reduction in light vehicles and LSVs 

will be 28.15 equivalent lives saved at 

the 3 percent discount rate and 23.06 

equivalent lives saved at the 7 percent 

discount rate. The benefits of this 

proposal for the light EV and HV and 

LSV fleet are $178.7M at the 3 percent 

discount rate and $146.3M at the 7 

percent discount rate. Comparison of 

costs and benefits expected due to this 

proposal for the light EV, HV and LSV 

fleet provides a cost of $0.83 to $0.99 

million per equivalent life saved across 

the 3 and 7 percent discount levels. 

According to our present model, a 

countermeasure that allows a vehicle to 

meet the proposed minimum sound 

requirements would be cost effective 

compared to our comprehensive cost 

estimate of the value of a statistical life 

of $6.3 million. 

TOTAL BENEFITS AND COSTS SUMMARY FOR LIGHT VEHICLES AND LOW SPEED VEHICLES, MY2016, 2010$ 

3% discount rate 7% discount rate 

Total Monetized Benefits ................................................................................................................. $178.7M $146.3M 

Total Costs (Install+Fuel) ................................................................................................................ 23.5M 22.9M 

Total Net Impact (Benefit—Costs) ................................................................................................... 155.2M 123.4M 

II. Background 

Whether or not a vehicle can be easily 

detected by the sound it makes is a 

product of vehicle type, vehicle speed, 

and ambient sound level. Quieter 

vehicles, such as EVs and HVs, can 

reduce pedestrians’ ability to assess the 

state of nearby traffic and, as a result, 

can have an impact on pedestrian safety. 

EVs and HVs may pose a safety problem 

for pedestrians, in particular pedestrians 

who are blind or visually impaired and 

who therefore rely on auditory cues 

from vehicles to navigate. For these 

pedestrians, the primary safety issue 

arises when an HV or EV operates 

quietly using its electric motor for 

propulsion at low speeds. This is also 

the case when other auditory cues, such 

as the noise from the vehicle’s tires and 

wind resistance, are less noticeable. 

Since August 2007, NHTSA has been 

monitoring the work of the Society of 

Automotive Engineers’ (SAE) Vehicle 

Sound for Pedestrians (VSP) Committee. 

Participants in the VSP committee 

include vehicle manufacturers, 

suppliers, consulting firms, government, 

and other interested parties. The VSP 

committee’s primary goal is to develop 

a test procedure to measure the 

minimum sound output of a motor 

vehicle. In September 2011, the SAE 

published the test procedure, 

Measurement of Minimum Noise 

Emitted by Road Vehicles, (SAE–J2889– 

1).4 The purpose of J2889–1 is to 

provide an objective, technology-neutral 

test to measure the minimum sound 

emitted by a vehicle in a specified 

ambient noise condition. This is a test 

procedure only and does not describe 

the VSP committee’s rationale, provide 

recommendations about how sounds for 

HVs and EVs should be developed or 

produced, nor does it specify the 

ambient condition at which a vehicle 

sound should be detectable for the 

safety of pedestrians. 

On May 30, 2008, NHTSA published 

a notice 5 in the Federal Register 

announcing that the agency would hold 

a public meeting on June 23, 2008 for 

government policymakers, stakeholders 

from organizations representing people 

who are blind or visually impaired, 

industry representatives, and public 

interest groups to discuss the technical, 

environmental and safety issues 

associated with EVs, HVs, and quiet ICE 

vehicles, and the safety of pedestrians. 

The presentations submitted at the 

public meeting and a transcript of the 

meeting can be found in Docket No. 

NHTSA–2008–0108 on the Web site 

http://www.regulations.gov.6 Topics 

discussed at the meeting included a 

statement of the problem, general 

pedestrian safety, sound measurement 

and mobility, automotive industry 

perspective, SAE work and status, 

potential solutions, and noise 

abatement. At the conclusion of the 

public meeting, NHTSA indicated the 

agency’s intention to put together a 

research plan and encouraged 

participants to add comments and ideas 

to the docket. NHTSA issued a research 

plan to investigate the topic of quieter 

vehicles and the safety of pedestrians on 

May 6, 2009.7

In September 2009, NHTSA published 

a technical report documenting the 

incidence of crashes involving hybridelectric passenger vehicles and 

pedestrians and pedalcyclists.8 The 

analysis included a sample of 8,387 

hybrid and 559,703 ICE vehicles. The 

analysis used data from 12 states and a 

subset of model-year 2000 and later 

vehicles. The results of the crash data 

analysis show that HVs are two times 

more likely than ICE vehicles to be in 

a pedestrian crash where the vehicle is 

backing out, slowing/stopping, starting 

in traffic, and entering or leaving a 

parking space/driveway. The vehicles 

involved in such crashes are likely to be 

moving at low speeds at which the 

difference between the sounds emitted 

by ICE vehicles and HVs is substantial. 

The crash incidence rate for the 

combined set of maneuvers is 0.6 

percent and 1.2 percent for ICE vehicles 

and HVs respectively and the difference 

is statistically significant. Some of the 

factors considered in this analysis are: 

(1) vehicle maneuver prior to the crash; 

(2) speed limit as a proxy for vehicle 

travel speed; and (3) weather and 


tkelley on DSK3SPTVN1PROD with 
2802 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

9Research 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. 

10 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. 

11 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. 

12 Goodes et al. (2009) Investigation into the 

Detection of a Quiet Vehicle by the Blind 

Community and the Application of an External 

Noise Emitting System, SAE 2009–01–2189. Society 

of Automotive Engineers, Warrendale, PA; Maurer 

(2008) The Danger Posed by Silent Vehicles. 

National Federation of the Blind. Remarks made for 

the United Nations Economic Commission for 

Europe, Working Party on Noise. 47th GRB session 

February 19, 2008 Geneva. Informal Document No. 

GRB–47–10. http://www.unece.org/trans/doc/2008/ 

wp29grb/ECE-TRANS-WP29-GRB-47-inf10e.pdf. 

13The level and frequency of sounds masked by 

the ambient will depend on the sound pressure 

level and shape of that ambient. For a full 

description of the typical urban ambient used in 

this study, see the full report cited in footnote 11. 

lighting condition at the time of the 

crash. 

In October 2009, NHTSA issued a 

report entitled ‘‘Research on Quieter 

Cars and the Safety of Blind Pedestrians, 

A Report to Congress.’’ 9 The report 

briefly discusses the quieter vehicle 

safety issue, how NHTSA’s research 

plan would address the issue, and the 

status of the agency’s research in 

implementing that plan. 

In April 2010, NHTSA issued a report 

presenting results of Phase 1 of the 

agency’s research.10 This report 

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 countermeasure 

concepts that are categorized as vehiclebased, infrastructure-based, and systems 

requiring vehicle-pedestrian 

communications. 

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 twins 

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 in EV mode). 

NHTSA initiated additional research 

(Phase 2) in March 2010 to explore 

potential audible countermeasures to be 

used in vehicles while operating in 

electric mode in specific low speed 

conditions.11 The potential 

countermeasures explored included 

quantitative specifications for sound 

levels and spectral profiles for 

detectability. The feasibility of 

objectively specifying other aspects of 

sound quality for the purpose of 

predicting recognizability was also 

explored. 

In our Phase 2 study, researchers 

assumed that acoustic countermeasures 

should provide alerting information at 

least equivalent to the cues provided by 

ICE vehicles. Groups representing 

people who are blind or visually 

impaired have expressed a preference 

for sound(s) that will be recognized as 

that of an approaching vehicle so that it 

will be intuitive for all pedestrians.12 In 

the Phase 2 research, acoustic data 

acquired from a sample of ICE vehicles 

was used to determine the sound levels 

at which synthetic vehicle sounds, 

developed as countermeasures, could be 

set. ICE equivalent sounds were 

specified using overall A-weighted 

sound levels and, one-third octave band 

spectral content. (See Appendix A, 

‘‘Glossary of Sound Engineering Terms’’ 

and Appendix B, ‘‘Acoustic Primer’’ for 

definitions and explanations of all 

acoustic terms used in this notice.) 

Psychoacoustic models and human 

subject testing were used to explore 

issues of detectability, masking, and 

recognition of ICE-like and alternative 

sound countermeasures. Psychoacoustic 

models showed that frequency 

components between 1600 and 5000 Hz 

were more detectable due to strong 

signal strength and relatively low 

ambient levels in this range. Also, 

frequency components below 315 Hz 

were often masked by urban ambient 

noise.13 Human subject studies were 

conducted to evaluate countermeasure 

sounds in a controlled outdoor 

environment for six miles per hour 

forward pass-by with the counter 

measure sound output set at 59.5 Aweighted dB and then at 63.5 Aweighted dB measured 2 meters from 

the vehicle centerline. The sounds 

included ICE-like sounds, alternative 

(non-ICE-like) sounds designed 

according to psychoacoustic principles 

to improve detectability, and sounds 

that combine alternative sounds with 

some ICE-like components. In addition 

to the countermeasure sounds, an ICE 

vehicle sound was included in the study 

as a baseline for comparison purposes. 

The results of this research show that 

synthetic sounds that resemble those of 

an ICE produce detection distances 

similar to actual ICE vehicles. Some of 

the synthetic sounds examined in the 

study that were designed according to 

psychoacoustic principles produced 

detection distances twice as long as 

those of ICE sounds. The study 

participants had difficulty detecting 

synthetic sounds that contained only 

the fundamental of the combustion 

noise of the engine (the lowest 

frequency associated with the 

combustion). 

This research examined four potential 

ways in which countermeasure sounds 

could be specified. The study examined 

countermeasure sounds based on 

recordings of ICE vehicles, synthetically 

generated countermeasure sounds that 

emulate the sounds of an ICE, non-ICE 

like countermeasure sounds designed 

for maximum detectability at a given 

sound-pressure level, and synthetically 

generated sounds that have special 

characteristics to enhance detection and 

characteristics that ensure that the 

sounds contain ICE-like components to 

enhance recognizability. The report 

noted that an objective specification for 

non-ICE-like sounds is more difficult to 

develop than one for synthetic sound 

generators that emulate the sound of 

typical ICEs. The report also noted that 

the former approach could result in a 

wider variety of sounds, some of which 

might be not recognized as a vehicle or 

might be perceived as annoying. 

In early 2011, NHTSA initiated 

additional research and data collection 

activities to further support this 

rulemaking (Phase 3). Acoustic 

measurements and analyses were 

completed to support the development 

of specifications for alerting sounds and 

test procedures for compliance with 

agency requirements. Acoustic data was 

gathered from eight vehicles: four ICE 

vehicles and four EVs/HVs with alerting 

sounds (one production and three 

prototype vehicles). The SAE J2889–1 

test procedure was used to measure the 

sound levels for the stopped and passby conditions. Acoustic measurements 

were completed on an ISO 10844:1994 

noise pad. All HVs and EVs were 

measured in electric propulsion mode. 

Variations on SAE J2889–1 were used 

to explore other aspects such as 

directivity, sound level as a function of 

vehicle speed, and to capture binaural 

recordings. Directivity refers to the 

relative proportions of acoustical energy 


tkelley on DSK3SPTVN1PROD with 
Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2803 

14NHTSA 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. 49 U.S.C. 30111. 

15The definition of that term is discussed below. 

16Section 2(4) 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. 

17Section2(10) of the PSEA defines ‘‘electric 

vehicle’’ as a motor vehicle with an electric motor 

as its sole means of propulsion. 

18Section 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.’’ 

19The 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. 

20Section 2(2). 

21Public Law 111–373, § 2(2), 124 Stat. 4086 

(2011). 

22 49 U.S.C. Chapter 301. 

23 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). 

24 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). 

25 49 U.S.C. 30112 and 30165. 

26 49 U.S.C. 30118–30120. 

that is emitted from a source, in this 

case a vehicle, as a function of direction 

to the front, back, left, and right. 

Binaural recordings were captured for 

potential use in future research 

activities. Acoustic measurements, 

modeling, and sound simulation tools 

were used to identify sound attributes 

that aid in detection of alert sounds and 

recognition of these sounds as a motor 

vehicle. 

Two approaches were considered in 

the development of parameters for alert 

sounds. In one approach, sound levels 

for the alert sound were developed 

using loudness models and a calculation 

of safe detection distances. In the other 

approach, sound levels for alert sounds 

were based on the sound of current ICE 

vehicles. This research focused on 

developing specifications that can be 

applied to all sounds and that are 

objective and practical. 

All of the research activities 

summarized above are described in 

more detail in Section VI. NHTSA 

Research and Industry Practices. 

III. Pedestrian Safety Enhancement Act 

of 2010 

On January 4, 2011, the Pedestrian 

Safety Enhancement Act of 2010 (Public 

Law 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) 14

requiring an ‘‘alert sound’’ 15 for 

pedestrians to be emitted by all types of 

motor vehicles 16 that are electric 

vehicles 17 (EVs) or hybrid vehicles 18

(HVs). The covered types of vehicles 

include light vehicles (passenger cars, 

vans, sport utility vehicles and pickup 

trucks), as well as LSVs, motorcycles, 

medium and heavy trucks and buses. 

Trailers are specifically excluded from 

the requirements of the PSEA. 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 a vehicle-emitted 

sound that enables pedestrians to 

discern the presence, direction,19

location, and operation of the vehicle.20

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. In addition 

to the operating scenarios previously 

mentioned the definition of alert sound 

in the PSEA requires the agency to 

establish requirements for a sound 

while the vehicle is activated but 

stationary and when the vehicle is 

operating in reverse. 

The agency has concluded that the 

requirement in the PSEA that the alert 

sound must allow pedestrians to 

‘‘discern vehicle presence, direction, 

location, and operation,’’ 21 requires the 

agency to establish minimum sound 

requirements for the stationary but 

activated operating condition. The 

requirement that pedestrians be able to 

discern vehicle presence must be read 

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 an engaged 

ignition is in a state of being functional 

even though it may not be moving. It is 

the agency’s position that the provision 

that pedestrians be able to detect the 

presence of a vehicle that is turned on 

requires that the vehicle emit a 

minimum sound level when the vehicle 

is stationary, but the starting system is 

activated. 

The agency believes that the PSEA 

requires the agency to establish 

requirements for a sound while the 

vehicle is moving reverse for the same 

reason that a sound while the vehicle is 

stationary is required. The PSEA 

requires minimum sound level 

requirements promulgated by NHTSA to 

allow pedestrians to discern vehicle 

presence and operation. A vehicle 

moving in reverse is unquestionably 

operating, thus a minimum sound level 

is required for this condition. 

The PSEA also requires that the 

minimum sound level requirements 

promulgated by NHTSA allow 

pedestrians to discern the direction of 

the vehicle. This language also indicates 

that the PSEA requires any standard to 

establish minimum sound requirements 

for when the vehicle is operating in 

reverse. 

Because the PSEA directs NHTSA to 

issue these requirements as a FMVSS 

under the National Traffic and Motor 

Vehicle Safety Act (Vehicle Safety 

Act),22 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,23 and objective 24 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. 

As a FMVSS, the pedestrian alert 

sound system standard we are 

proposing today would be enforced in 

the same fashion as other safety 

standards issued under the Vehicle 

Safety Act. Thus, violators of the 

standard would be subject to civil 

penalties.25 A vehicle manufacturer 

would be required to conduct a recall 

and provide remedy without charge if 

its vehicles were determined to fail to 

comply with the standard or if the 

vehicle’s alert sound were determined 

to contain a safety related defect.26

Under the PSEA, the standard must 

specify performance requirements for an 

alert sound that enables blind and other 

pedestrians to reasonably detect EVs 


tkelley on DSK3SPTVN1PROD with 
2804 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

27Section 2(3) of the PSEA defines ‘‘cross-over 

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. 

28Section 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. 

29Section 3(b). 

30Section 3(b)(2). 

31Section 2(5). 

32Keene Corp. v. United States, 508 U.S. 200, 208 

(1993). 

33 49 U.S.C. § 30102(a)(6). 

and HVs operating below their crossover speed.27 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 and 

operating in any other scenarios that the 

Secretary deems appropriate.28 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 below the 

cross-over speed.29 NHTSA plans to 

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 in the 

ambient noise environment typical of 

urban areas. 

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 is nothing in 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.30 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.’’ 31 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.32 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.33 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. For 

example, pitch shifting and increases in 

sound pressure level denote changes in 

speed and are common to all vehicles 

driven by mechanical power. Further, 

sounds that the public currently 

recognizes as generated by a vehicle 

driven by mechanical power have tonal 

components. 

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 reverse or start up. 

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. 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. 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. 

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. The agency recognizes that, in the 

near term, most manufacturers would 

install speaker systems that emit 

synthetically developed sounds in order 

to meet the requirements of the 

proposed standard. 

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 proposed 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 agency will test to ensure sounds 

produced by two vehicles of the same 

model are the same (within 3 Aweighted dB) at the stationary condition 

so that a determination of the sameness 

of the sounds is not dependent on tire 

or wind noise or other factors that could 

influence a vehicle’s sound output. The 

agency will not consider any 

modifications made to a vehicle that 

affect the mechanical, tire or wind noise 

produced by that vehicle to make an 

alert sound added to the vehicle 

inoperative. 

The PSEA requires NHTSA to 

consider the overall community noise 

impact of any alert sound required by 

the new safety standard. In addition, 

NHTSA will consider the environmental 

analysis required by the National 

Environmental Policy Act (NEPA) when 

setting the standard. 

As part of the rulemaking process, 

NHTSA is required to consult with 

various other organizations. This is 

further described in Section IV below. 


tkelley on DSK3SPTVN1PROD with 
Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2805 

34http://www.regulations.gov/ 

#!searchResults;rpp=10;po=0;s=NHTSA–2008– 

0108. 

35http://www.regulations.gov/ 

#!searchResults;rpp=10;po=0;s=%252BNHTSA– 

2011–0100. 

36http://www.regulations.gov/ 

#!searchResults;rpp=10;po=0;s=NHTSA–2011– 

0148. 

37http://standards.sae.org/j2889/1_201109. 

38http://www.iso.org/iso/iso_catalogue/ 

catalogue_tc/ 

catalogue_detail.htm?csnumber=56019. 

In addition to requiring NHTSA to 

publish a final rule establishing the 

standard requiring an alert sound for 

EVs and HVs by January 4, 2014, the 

PSEA requires that the agency provide 

a phase-in period, as determined by 

NHTSA. However, 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. Thus, if the 

final rule were promulgated sometime 

in 2014, the three-year period after the 

date of publication of the final rule 

would end sometime in 2017. The first 

calendar year that would begin after that 

date in 2017 would be calendar year 

2018. Thus, under that time scenario, 

full compliance would be required not 

later than September 1, 2018. 

Finally, the PSEA requires NHTSA to 

conduct a study and report to Congress 

whether the agency believes that there 

is a safety need to require the alert 

sounds required by the FMVSS 

promulgated to meet the mandate of the 

Act for some motor vehicles with 

internal combustion engines. The report 

must be submitted to Congress by 

January 4, 2015. If NHTSA determines 

that there is a safety need to require 

alert sounds for those motor vehicles the 

agency must initiate a rulemaking to 

require alert sounds for them. 

IV. Consultation With External 

Organizations 

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 visuallyimpaired 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, and 

the United Nations Economic 

Commission for Europe (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) 34 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 later 

in this document.) The second docket 

(No. NHTSA–2011–0100) 35 was created 

to collect comments on the NOI; it also 

includes a copy of that notice. The third 

docket (No. NHTSA–2011–0148) 36 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.), outside 

comments and items to be released in 

the future up to and including this 

Notice of Proposed Rulemaking. 

NHTSA has since 2009 also been 

hosting a series of roundtable meetings 

with industry, technical organizations 

and groups representing people who are 

visually-impaired. Below are the dates 

and topics of discussion: 

• April 14th, 2009: Status of Phase 1 

research and industry updates. 

• August 4th, 2009: Phase 1 research 

plan. 

• January 25th, 2010: Final results of 

Phase 1 research and industry updates. 

• June 24th, 2010: Phase 2 research 

plan and status of Phase 2 work. 

• February 22nd, 2011: Final results 

of Phase 2 research. Attendees were 

asked to submit comments. 

The following organizations have 

been participating in these meetings: 

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 visuallyimpaired pedestrian safety needs since 

the 2008 Public Meeting was held. 

The Alliance of Automotive 

Manufacturers and Global Automakers 

(formerly the Association of 

International Automobile Manufacturers 

(AIAM)) 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 standard 

SAE J2889–1, Measurement of Minimum 

Noise Emitted by Road Vehicles.37 The 

agency has been sending liaisons to the 

VSP meetings since 2008. SAE is the 

U.S. technical advisory group to the 

International Organization for 

Standardizations (ISO) and they both 

have cooperated in the development of 

the standard. The ISO document (ISO/ 

NP 16254 Measurement of minimum 

noise emitted by road vehicles) 38 and 

SAE document are reported to be 

technically identical but this has not 

been confirmed by NHTSA at this time. 

The agency is currently using standard 


tkelley on DSK3SPTVN1PROD with 
2806 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

39http://www.iso.org/iso/iso_catalogue/ 

catalogue_tc/ 

catalogue_detail.htm?csnumber=45358. 

40Papers relating to the informal group periodic 

meetings may be found at http://live.unece.org/ 

trans/main/wp29/wp29wgs/wp29grb/qrtv_1.html, 

http://live.unece.org/trans/main/wp29/wp29wgs/ 

wp29grb/qrtv_2.html, http://live.unece.org/trans/ 

main/wp29/wp29wgs/wp29grb/qrtv_3.html, http:// 

live.unece.org/trans/main/wp29/wp29wgs/wp29grb/ 

qrtv_4.html, http://live.unece.org/trans/main/wp29/ 

wp29wgs/wp29grb/qrtv_5.html, and http:// 

live.unece.org/trans/main/wp29/wp29wgs/wp29grb/ 

qrtv_6.html. 

41See footnote 6. 

42Wu 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. 

43The 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 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. 

SAE J2889–1 and ISO10844 39 as 

references in the test procedure 

development. 

The UNECE World Forum WP.29 

determined that road transportation 

vehicles propelled in whole or in part 

by electric means present a danger to 

pedestrians and directed the Working 

Party on Noise (GRB) to assess what 

necessary steps WP.29 should take to 

help mitigate the problem. In response, 

GRB established an informal group on 

Quiet Road Transport Vehicles 

(QRTV) 40 to carry out the necessary 

activities to address the quieter vehicles 

issue and the potential need for global 

harmonization. NHTSA has been 

participating in the QRTV’s meetings 

since its foundation in 2010 and has 

kept the group informed about ongoing 

agency research activities as well as the 

results from completed research studies. 

At its March 2011 meeting, WP.29 

adopted guidelines covering alert 

sounds for electric and hybrid vehicles 

that are closely based on the Japanese 

guidelines discussed more fully later in 

this document. 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. has proposed working on a new 

GTR, with Japan as co-sponsor, to 

develop harmonized pedestrian alert 

sound requirements for electric and 

hybrid-electric vehicles under the 1998 

Global Agreement. WP.29 is now 

working to develop a GTR that will 

consider international safety concerns 

and leverage expertise and research 

from around the world. Meetings of the 

working group are planned to take place 

regularly with periodic reports to WP.29 

until the expected establishment date 

for the new GTR in November 2014. 

NHTSA is currently leading the GTR 

development process. 

Other international organizations, 

such as the International Organization 

of Motor Vehicles Manufacturers (OICA) 

and Japan Automobile Manufacturers 

Association (JAMA) have been 

providing NHTSA with their own 

research findings and have also been 

attending our quiet vehicle meetings. 

V. Safety Problem 

A. Comparing the Vehicle to Pedestrian 

Crash Experience of ICE Vehicles and 

HVs and EVs 

Crash Risk 

Passenger hybrid electric vehicles first 

became available to consumers in 2000, 

and their numbers as well as their 

proportion of the passenger vehicle fleet 

have risen every year since their 

introduction. According to the R.L. Polk 

and Company National Vehicle 

Population Profile, there were 18,628 

registered passenger HVs in 2001. By 

2004, there were 145,194 registered HVs 

comprising 0.1 percent of the passenger 

vehicle fleet. By 2009, the number had 

grown to 1,382,605 registered HVs 

comprising 0.6 percent of the fleet. 

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.41 The report used 

data collected from 12 individual states. 

The years for which data was available 

varied across different states. Generally, 

the data used ranged from the years 

2000 to 2006. HV crashes had an overall 

40 percent higher chance to involve 

pedestrians. 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. 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. 

Therefore, we were unable to determine 

whether any of the pedestrians involved 

in these crashes were blind or visually 

impaired. 

A recent analysis updated and 

verified these previous findings 42 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, with a total of 24,297 HVs 

(approximately three times the HVs of 

the 2009 study) and 1,001,000 ICE 

vehicles by Honda and Toyota, with five 

different models, in 16 States during 

2000–2008. This updated analysis 

indicates that a total of 186 HVs and 

5,699 ICE vehicles were involved in 

pedestrian crashes. A total of 116 HVs 

and 3,052 ICE vehicles were involved in 

crashes with bicycles. Overall, a 

statistical analysis referred to as odds 

ratios indicates 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.43 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. 

This finding also indicates 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, typically low-speed, maneuvers 

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 after 

completing a low speed maneuver. The 

results in this updated analysis show 

trends similar to those first reported in 

our 2009 report. The sample sizes of 

pedestrian or bicycle crashes were 

verified to validate the sufficient 

statistical powers in this updated 

analysis. 

The rate of crashes between HVs and 

pedalcyclists was different than the rate 

of crashes between HVs and 

pedestrians. While a larger percentage of 

pedalcyclist crashes for both HVs and 

ICE vehicles occurred at posted speed 

limits of 35 mph and below, the 

difference in rates of pedalcyclist 

crashes between HVs and ICE vehicles 

was higher at speed limits above 35 

mph that at speed limits of 35 mph and 

below. For posted speed limits of 35 

mph and below HVs showed an 


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44National Federation of the Blind (2011) How 

People Who are Blind Use Sound for Independent 

Travel, memorandum to the docket NHTSA–2011– 

0148, Washington, DC. This memorandum is the 

source for this information. 

increased rate of pedalcyclist crashes 

when compared to ICE vehicles, 

however, the results were not statically 

significant. The difference in 

pedealcyclist crash rates between HVs 

and ICE vehicles was also greater when 

driving straight as compared to lowspeed maneuvers. 

This updated analysis further 

included all vehicle models from all 

manufacturers during the period 

covered by the study, beyond the five 

models from Toyota and Honda, and a 

similar pedestrian crash trend was also 

found from the expanded data. 

Comparisons restricted to HV and 

similar ICE pairs (Prius and Corolla; 

Civic HV and ICE model) only were also 

made. These comparisons also resulted 

in similar conclusions about HV 

pedestrian crashes relative to ICE 

vehicle pedestrian crashes, including 

that the odds of an HV being in a 

pedestrian crash is greater than the odds 

of an ICE vehicle being in a similar 

crash. 

Despite the similarities in the overall 

sound level produced by the two 

vehicles, the differential crash rate for 

the Civic HV and the ICE version of the 

Civic was even larger than for other 

pairs of HVs and ICEs. We note that the 

HV Civic is much different than the 

other hybrid vehicles in the analysis 

because when the agency tested this 

vehicle, we could not get the ICE engine 

to shutoff even at idle. Thus, unlike the 

other HVs tested, the ICE was always on 

in this vehicle, but we acknowledge that 

in the real-world, the ICE may shut-off 

at some point. We do know that, 

although sound levels are similar, there 

are differences between the frequency 

profile of the HV and ICE Civics, but we 

do not know how pedestrians would 

perceive this difference either in general 

or in the low-speed maneuvers used in 

our crash analysis. The agency seeks 

comments on whether the differences in 

pedestrian crash rates between HVs and 

ICEs are solely due to a pedestrians’ 

inability to detect the vehicle based on 

the vehicle’s sound while operating 

below the crossover speed or whether 

there may be other factors that we have 

not identified that affect the difference 

in crash rates between the two types of 

vehicles. 

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; there is still not enough data to 

draw conclusions in all scenarios of 

interest such as for individual lowspeed maneuvers like making a turn, 

starting up, or in parking lots. 

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 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. This proposal 

would establish minimum sound 

requirements for hybrid and electric 

vehicles operating at speeds of 30 km/ 

hr (18 miles per hour (mph)) and below. 

A majority of pedestrian fatalities occur 

when the vehicle involved in the 

collision is travelling at a speed greater 

than 18 mph. Overall, 67 percent of the 

pedestrian fatalities involving HVs or 

EVs and with known speed limits 

occurred at a speed limit above 35 mph. 

For all pedestrian fatalities with known 

speed limits, 62 percent occurred at a 

speed limit above 35 mph and 61 

percent of those involving passenger 

vehicles occurred at a speed limit above 

35 mph. The goal of this proposal is to 

prevent injuries to pedestrians that 

result from pedestrians being unable to 

hear nearby hybrid and electric 

vehicles. At speeds of 35 mph and 

above, at which a majority fatal crashes 

involving pedestrians occur, the sound 

levels produced by hybrid and electric 

vehicles are the same as the sound 

levels produced by ICE vehicles. 

Therefore, establishing minimum sound 

requirements for hybrid and electric 

vehicles operating at low speeds is not 

expected to have an impact on 

pedestrian fatalities. 

The second reason is that the rate of 

pedestrian fatalities per registered 

vehicle for HVs and EVs is not larger 

(and is in fact lower) 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. 

B. 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 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 contributes to that person’s ability 

to negotiate through his/her 

environment in a variety of situations.44

Two long-established navigation aids 

that visually-impaired people use are 

the white cane and a guide dog. 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. 

Of the thirteen guide dog schools 

currently operating in the United States, 

most require applicants for guide dogs 

to have at least some skill in traveling 

with a long white cane, since the basic 

techniques for using a white cane and 

a guide dog are similar in many 


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respects. A guide dog does not lead a 

person but simply guides him or her 

around obstacles; the handler is still 

responsible for navigation. 

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 travel safely 

and independently 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 alerts 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. 

The sound of a vehicle starting is 

important for the same reason. If a blind 

person is approaching a driveway and 

notes a vehicle that is stationary but 

running, or hears a vehicle start, 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. 

Because traffic sound is a navigation 

aid for blind and visually-impaired 

pedestrians, as well as an indispensable 

part of traveling safely, blind people 

listen to the sound of traffic actively and 

constantly when they are walking, even 

when they are not at an intersection. 

The sound of traffic helps blind 

individuals follow the roadway; this is 

critical, even when there is a sidewalk, 

to keep the blind individual on course. 

Traffic sounds also allow the detection 

of roadway changes like curves, forks, or 

merges. The sound of traffic is 

particularly important in negotiating 

intersections. By listening to the traffic, 

a blind or visually-impaired traveler can 

determine how the intersection is 

controlled (traffic signal, stop sign, etc.); 

how many lanes of traffic are involved; 

and any unusual characteristics of the 

intersection (e.g., three-way 

intersections or roundabouts). These 

determinations can be made by listening 

to the sounds of vehicle engines—often 

through one or two entire signal 

cycles—to determine driver behavior, 

which is usually a reliable indicator of 

the characteristics of the intersection. 

This includes the sound of stationary 

vehicles—particularly in multi-lane or 

oddly shaped intersections—because it 

is important to identify which lanes of 

traffic are active, when, and for how 

long; and to then follow the line of 

traffic that most nearly parallels the 

direction in which the traveler wishes to 

proceed. At the same time that the blind 

traveler is listening to the overall traffic 

pattern, he or she also listens for cues 

from individual vehicles, particularly 

when determining the precise moment 

to enter the crosswalk. At signaled 

intersections, an idling vehicle in the 

street parallel to the path of the traveler 

that accelerates and moves through the 

intersection is an indication that a 

traffic signal has just changed and that 

it is safe to proceed into the cross street, 

with maximum time to complete the 

crossing. In general, by crossing when 

the traffic flow is parallel to him or her, 

a blind individual can safely cross most 

intersections without difficulty. The 

individual will use the sound of the 

parallel traffic while crossing to 

maintain a roughly straight line through 

the intersection. Figure 1 shows several 

examples of how a blind pedestrian 

would use the sound of traffic to cross 

a complex intersection. 

Example 1: A blind pedestrian standing at 

corner A (facing corner B) ready to cross, will 

wait for the stationary vehicles behind him/ 

her to start moving as an indication that the 

traffic light has changed. Then, the 

pedestrian will proceed to cross the street 

and follow the parallel line of traffic on his 

left (from A to B) confident there is enough 

time to safely cross the street. 

Example 2: A blind pedestrian standing at 

corner A (facing corner C) ready to cross, will 

use the sound of the stationary vehicles on 

his/her left and the parallel traffic on his/her 

right as guides to follow a straight path while 

crossing. 

Example 3: A blind pedestrian at corner 

C (facing corner D) ready to cross, will wait 

for the traffic from C to A to stop and the 

parallel traffic across the intersection to start, 

to safely walk from corner C to Corner D. The 

sounds from the stationary vehicles on his/ 

her left and the parallel traffic across the 

intersection serve as guides to keep a straight 

path while crossing. 


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45 see footnote 8. 

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 visuallyimpaired pedestrian simply cannot 

ensure his or her own safety or navigate 

effectively without traffic sound. To the 

extent that there are more and more HVs 

and EVs on the road that are hard to 

detect, people who are blind or visually 

impaired will lose a key means—the 

sound of traffic—by which they 

determine when it is safe to cross 

streets, but also by which they orient 

themselves and navigate safely 

throughout their daily lives, avoiding 

dangers other than automobiles. 

VI. NHTSA Research and Industry 

Practices 

On May 6, 2009 NHTSA issued a 

research plan describing the research 

relating to quieter vehicles it planned to 

conduct. This section reports on the 

research completed to date. 

A. NHTSA Phase 1 Research 45

In April 2010 NHTSA released a 

report titled ‘‘Quieter Cars and the 

Safety of Blind Pedestrians: Phase 1’’ 

referred to as Phase 1. This report 

documented a study conducted by the 

John A. Volpe National Transportation 

Systems Center (Volpe) under an 

interagency agreement. This study 

documents the overall sound levels and 

general spectral content for a selection 

of HVs and ICE vehicles in different 

operating conditions, evaluates vehicle 

detectability for two ambient sound 

levels, and considers countermeasure 

concepts. The study investigated 

operating scenarios of concern for 

pedestrians who are blind or visually 

impaired, documented acoustic 

measurements of hybrid, electric and 

ICE vehicles and ambient environments 

in which blind or visually impaired 

pedestrians might reasonably be 

expected to make travel decisions based 

on sound alone, examined the auditory 

detectability of vehicles in safety 

scenarios of concern to individuals who 

are blind or visually impaired and 

examined potential countermeasures. 

Safety Scenarios for Pedestrians Who 

Are Blind or Visually-Impaired 

As part of Phase 1 research NHTSA 

sought to identify operating scenarios 

necessary for the safety of visuallyimpaired 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 are: 

• Vehicle approaching at low speed: 

One of the strategies used by 

pedestrians who are blind is to cross 

when the road is quiet. This technique 

assumes that it is safe to proceed when 

a vehicle is loud enough to be heard far 

enough away, there are no other 

masking sounds present, and no other 

vehicles are detected. 

• Vehicle backing out (as if coming 

out of a driveway): There is a concern 


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46See footnote 7, 47See footnote 39. 48The SAE J2889–1 draft test method covers only 

two operating conditions: stationary vehicle and 10 

km/h (6 mph) constant speed pass by. This study 

follows recommendations of the SAE draft method 

with regard to instrument settings, calibration, 

meteorological monitoring, etcetera; however, it 

deviates from the SAE method with respect to 

operating condition, data measured, as well as 

height, distance, and orientation of the 

microphones. For each measurement, one-half 

second contiguous average SPLs were measured. 

The maximum of these for each event were 

analyzed for the development of Table 1. These 

levels are representative of the sound level when 

the vehicle is at or near the microphone line (line 

PP’ in SAE J2889–1, Figure 1). 

49See Docket for this notice, Item # NHTSA– 

2011–0148–0004. 

50See footnote 8; Garay-Vega et al., Auditory 

Detectability of Hybrid Electric Vehicles by 

Pedestrians Who Are Blind. 90th Annual Meeting 

Transportation Research Board January 23–27, 

(2011), Washington, DC Available at http:// 

amonline.trb.org/12ktc8/1. 

51Binaural 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. 

quieter vehicles may not be detectable 

when backing out. This scenario is 

complex for pedestrians since it is 

difficult to anticipate where there may 

be a driveway and the driver’s visibility 

may be limited. The pedestrian may 

have limited time to react and respond 

to avoid a conflict. 

• Vehicle travelling in parallel and 

slowing: Pedestrians who are blind often 

need to distinguish between a vehicle 

moving through an intersection and a 

vehicle turning into their path. The 

pedestrian needs to perceive this 

information when the vehicle is in the 

parallel street, before it turns into his or 

her path. The sound of slowing vehicles 

in the parallel street helps pedestrians 

identify turning vehicles. 

• Vehicle accelerating from stop: 

Pedestrians who are blind use the sound 

of traffic in the parallel street to 

establish alignment and to identify a 

time to cross. 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. Pedestrians may initiate their 

crossing as soon as they detect the surge 

of parallel traffic or may delay the 

decision to make sure traffic is moving 

straight through the intersection and not 

turning into their path. A delay in 

detecting the surge of parallel traffic 

may impact the opportunity to complete 

a crossing within the designated 

walking interval. 

• Vehicle stationary: The sound of 

vehicles idling provides important cues. 

For example, the sound of a vehicle in 

the far lane gives cues about the width 

of the road (number of lanes), and 

conveys information about the distance 

to walk and the time needed to navigate 

across the street. A quieter vehicle may 

not be detected when it is stationary at 

intersections or parking lots and it may 

start moving suddenly at the same time 

a pedestrian enters the conflicting path. 

NHTSA was able to gather crash data 

for collisions involving pedestrians and 

HVs when the HV was operating in one 

of the scenario described above (the 

crash report did not separately analyze 

vehicle starting from a stop and the 

vehicle stationary conditions) 

immediately prior to the crash in both 

the crash report released by NHTSA in 

September of 2009 46 and the updated 

crash report released in October 2011.47

The 2011 report analyzed the crash rates 

for vehicles making a turn, slowing/ 

stopping, backing, entering and leaving 

a parking space/driveway and starting 

in traffic separately and then analyzed 

all those operating conditions together. 

Because of the sample size an 

independent odds ratio was not 

available for any of the scenarios. When 

taken together, however, these low 

speed operating conditions show a 

statistically significant 1.38 odds ratio 

showing an increased risk of pedestrian 

collisions. 

For this study, the sounds emitted by 

HVs and ICE vehicles were measured 

and recorded under operating 

conditions representative of the 

previously identified safety scenarios.48

The operating conditions were as 

follows: (1) a vehicle backing up at 5 

mph (mimicking a vehicle backing out 

of a driveway); (2) a vehicle slowing 

from 20 to 10 mph (mimicking a vehicle 

preparing to turn right from the parallel 

street); (3) a vehicle approaching at a 

low constant speed (6 mph and 10 

mph); (4) a vehicle accelerating from a 

stop; and (5) a vehicle idling. Average 

A-weighted sound levels for each of the 

six vehicles tested are reported in Table 

1. 

TABLE 1—OVERALL A-WEIGHTED SOUND LEVEL AT THE MICROPHONE LOCATION (12 FT) 

[Average A-weighted level, LAeq0.5s, dB] 

Scenario/vehicle operation 2010 Toyota 

Prius 

2009 Toyota 

Matrix 

Honda Civic 

Hybrid 

Honda Civic 

ICE 

2009 Toyota 

Highlande 

Hybrid 

2008 Toyota 

Highlander 

Approaching at 6 mph ............................. 44.7 53.5 49.3 52.0 53.2 55.5 

Backing out (5 mph) ................................ 44.2 51.3 48.5 58.2 45.9 52.7 

Slowing from 20 to 10 mph ..................... 53.0 54.2 56.6 55.0 53.0 55.4 

Acceleration ............................................. 62.9 63.1 65.4 63.5 64.8 64.9 

Idling or Stationary but activated ............. 1 47.8 44.8 46.0 1 48.1 

1Background. 

Additionally, measurements were 

collected for vehicles approaching at 

moderate constant speeds (20 mph, 30 

mph, and 40 mph) in order to document 

the convergence, if any, of HVs and ICE 

vehicles at higher speeds. In general, 

HVs were quieter below approximately 

20 mph, above which either the 

vehicle’s ICE engine turned on, tire and 

road noise became dominant, or both. 

HVs also tended to have less high 

frequency content than ICEs at low 

speeds. Further details and results from 

this study can be found in NHTSA’s 

final report DOT HS 811 304.49

Auditory Detectability of Vehicles in 

Critical Safety Scenarios 50

In Phase 1, NHTSA 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 51 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 


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(operated in electric mode), except for 

the slowing maneuver. Vehicle type, 

ambient level, and operating condition 

had a significant effect on response 

time. 

Data collection included missed 

detection frequency and response time 

(and corresponding time-to-vehicle 

arrival and detection distance). Missed 

detection frequency is defined as 

instances when the target vehicle is 

present and the participant fails to 

respond. Response time is computed as 

the time from the start of a trial to the 

instant the participant presses a space 

bar as an indication he/she detects the 

target vehicle. Time-to-vehicle-arrival is 

the time from first detection of a target 

vehicle to the instant the vehicle passes 

the microphone line/pedestrian 

location. Detection distance is the 

longitudinal space between the vehicle 

and the pedestrian (microphone) 

location at the instant the participant 

indicated detection of a target vehicle. 

A repeated measure of analysis of 

variance (ANOVA) was used to analyze 

the main and interaction effects of the 

independent variables: vehicle type, 

vehicle maneuver and ambient sound 

level. A separate analysis was 

completed for each scenario, and a pairwise t-test compared each vehicle with 

the other (ICE vehicle and HV twins) for 

each ambient sound level. The time-tovehicle arrival for each vehicle-ambient 

condition is shown in Table 2, Table 3 

and Table 4 for each of three scenarios. 

Vehicle Approaching at 6 mph (9.6 

km/h) Pass by: The first traveling 

situation examined was a pedestrian 

standing on the curb waiting to cross a 

one-way street when there may be 

vehicles approaching from the left. 

Some trials included a target vehicle 

and some trials only included 

background noise. The target vehicle in 

this scenario was traveling from the left 

at a constant speed of 6 mph. There 

were vehicles in the background in all 

trials. The pedestrian had to be able to 

detect a vehicle that would affect the 

decision about when to start to cross the 

street. This scenario tested the distance 

and time at which a pedestrian can 

detect a vehicle approaching at low 

speed. On average, participants took 1.1 

seconds longer to detect vehicles in the 

high ambient sound condition than in 

the low ambient sound condition. The 

main effect of ambient was statistically 

significant. The mean time-to-vehiclearrival was 5.5 and 4.3 seconds for the 

low and high ambient condition 

respectively. Participants detected both 

ICE vehicles sooner than the HV twins. 

The main effect of vehicle type was 

statistically significant. The interaction 

effect of vehicle type and ambient was 

also statistically significant, meaning 

that the difference between when a 

passenger was able to detect an ICE 

vehicle versus its HV twin was greater 

when ambient was high than when it 

was low. Table 2 presents the individual 

differences between ICE vehicles and 

their HV peers (i.e., Prius vs. Matrix and 

Highlander hybrid vs. Highlander ICE); 

pair-wise comparisons are statistically 

significant within a given ambient 

condition. Participants were more likely 

to miss the Toyota HVs than the Toyota 

ICE vehicles approaching at a constant 

low speed. The missed detection rates 

in the low ambient condition were: 0.02 

for the Prius; 0.01 for the Matrix; 0.03 

for the Highlander Hybrid; and 0.0 for 

the Highlander ICE vehicle. The 

corresponding values in the high 

ambient condition were: 0.21 for the 

Prius; 0.02 for the Matrix; 0.04 for the 

Highlander; and 0.01 for the Highlander 

ICE vehicle. 

TABLE 2—TIME-TO-VEHICLE ARRIVAL AND DETECTION DISTANCE FOR 6 MPH VEHICLE PASS-BY BY VEHICLE TYPE AND

AMBIENT CONDITION

Vehicle Ambient sound 

level 

Time-to-vehicle 

arrival (s) 

Detection distance 

(ft) 

2010 Toyota Prius ........................................................................................................ Low ................... 4.3 37.9 

High .................. 2.4 20.9 

2009 Toyota Matrix ....................................................................................................... Low ................... 5.5 48.4 

High .................. 4.6 40.5 

2009 Highlander Hybrid ................................................................................................ Low ................... 5.3 46.6 

High .................. 4.1 36.6 

2008 Highlander ICE .................................................................................................... Low ................... 6.8 59.4 

High .................. 6.3 55.1 

Vehicle Backing Out (5 mph (8 km/h) 

Reverse): The second traveling situation 

was a pedestrian walking along a 

sidewalk with driveways on the left 

side; the pedestrian heard distant 

vehicles in the background in all trials. 

This is similar to walking in an area that 

is a few blocks away from a main road. 

The target vehicle was a nearby vehicle 

backing towards the pedestrian at a 

constant speed of 5 mph. This task is 

complex for pedestrians since it is 

difficult to anticipate where there may 

be a driveway and when a vehicle will 

move out of a driveway. In addition, a 

driver’s visibility may be limited and 

the pedestrian may have very limited 

time to respond to avoid a conflict. The 

main effect of ambient was statistically 

significant. The average time-to-vehiclearrival was 4.4 and 2.7 seconds for the 

low and high ambient condition, 

respectively. Participants took longer to 

detect both HVs than their ICE twins. 

The main effect of vehicle type was 

statistically significant. Table 3 shows 

the individual differences between ICE 

vehicles and their HV twins; pair-wise 

comparisons were statistically 

significant within a given ambient 

condition. Participants were more likely 

to miss the Toyota HVs than the Toyota 

ICE vehicles in the backing out session. 

The missed detection rates in the low 

ambient condition were: 0.05 for the 

Prius; 0.02 for the Matrix; 0.10 for the 

Highlander Hybrid; and 0.02 for the 

Highlander ICE. The corresponding 

values in the high ambient condition 

were: 0.11 for the Prius; 0.0 for the 

Matrix; 0.26 for the Highlander; and 

0.02 for the Highlander ICE. On average, 

participants took longer to detect 

vehicles in the high ambient sound 

condition than in the low ambient 

sound condition. 


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2812 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

TABLE 3—TIME-TO-VEHICLE ARRIVAL AND DETECTION DISTANCE FOR VEHICLE BACKING OUT BY VEHICLE AND AMBIENT

CONDITION

Vehicle Ambient sound level Time-to-vehicle 

arrival(s) 

2010 Toyota Prius .................................................................................................... Low ......................................................... 4.0 

High ........................................................ 2.5 

2009 Toyota Matrix ................................................................................................... Low ......................................................... 5.2 

High ........................................................ 3.6 

2009 Highlander Hybrid ............................................................................................ Low ......................................................... 3.3 

High ........................................................ 1.4 

2008 Highlander ICE ................................................................................................ Low ......................................................... 5.2 

High ........................................................ 3.3 

Vehicle Traveling in Parallel Lane 

and Slowing (Slowing from 20 to 10 

mph (32 to 16 km/h): The third and last 

traveling situation examined in the 

study was a pedestrian trying to decide 

when to start crossing a street with the 

signal in his/her favor and a surge of 

parallel traffic on the immediate left. 

The sound of slowing vehicles in the 

parallel street helps blind pedestrians 

identify turning vehicles. In some trials 

(no-signal condition), a vehicle 

continued straight through the 

intersection at 20 mph, so pedestrians 

can cross whenever they choose. 

However, in other trials there was a 

vehicle slowing from 20 mph to 10 mph 

as if to turn right into the pedestrian 

path (target vehicle). The pedestrian had 

to be able to detect when the vehicle 

was slowing. This scenario tests 

whether the pedestrian perceived this 

information when the vehicle was in the 

parallel street. Participants were more 

likely to miss the ICE vehicles 

approaching in the parallel lane and 

slowing than the HVs in the same 

situation. Table 4 shows the time-tovehicle arrival and detection distance 

for the ‘vehicle slowing’ scenario. Pairwise comparisons (HV vs. ICE twin) 

were statistically significant within a 

given ambient condition. On average, 

participants detected HVs sooner than 

their ICE vehicle twins. The main effect 

of vehicle type was statistically 

significant. The trend observed in the 

vehicle-slowing scenario (i.e., HVs are 

detected sooner than their ICE vehicle 

twins) may be explained by a noticeable 

peak in the 5000 Hz one-third octave 

band for the HVs tested during this 

operation. The tone emitted was 

associated with the electronic 

components of the vehicles when 

braking (e.g., regenerative braking). The 

missed detection rates in the low 

ambient condition were: 0.05 for the 

Prius; 0.31 for the Matrix; 0.03 for the 

Highlander Hybrid; and 0.17 for the 

Highlander ICE vehicle. The missed 

detection rates in the high ambient 

condition were: 0.05 for the Prius; 0.35 

for the Matrix; 0.03 for the Highlander 

Hybrid; and 0.17 for the Highlander ICE 

vehicle. 

TABLE 4—TIME-TO-VEHICLE ARRIVAL AND DETECTION DISTANCE FOR VEHICLE DECELERATING FROM 20 TO 10 MPH BY

VEHICLE TYPE AND AMBIENT CONDITION

Vehicle Ambient sound 

level 

Time-to-vehicle 

arrival(s) 

Detection distance 

(ft) 

2010 Toyota Prius ........................................................................................................ Low ................... 2.0 35.9 

High .................. 1.9 33.8 

2009 Toyota Matrix ....................................................................................................... Low ................... 1.1 18.0 

High .................. 0.8 12.8 

2009 Highlander Hybrid ................................................................................................ Low ................... 3.0 58.8 

High .................. 2.7 51.6 

2008 Highlander ICE .................................................................................................... Low ................... 1.5 25.7 

High .................. 1.3 21.8 

Table 5 shows the time-to-vehicle 

arrival 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

Scenario 

Low ambient High ambient 

HVs ICE Vehicles HVs ICE Vehicles 

Approaching at 6 mph ............................................................. 4.8 6.2 3.3 5.5 

Backing out (5 mph) ................................................................ 3.7 5.2 2.0 3.5 

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


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Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2813 

52See footnote 11. 

B. NHTSA 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.’’ The research 

conducted by Volpe first sought to 

define acoustic specifications to be used 

as alert sounds for quiet vehicles based 

on the sounds produced by ICE 

vehicles. Volpe then analyzed the 

loudness of the ICE sounds in a 

suburban ambient using psychoacoustic 

modeling. Volpe used human subject 

testing to evaluate the performance of 

several different varieties of 

countermeasure sounds including ICE 

sounds. Based on the results from the 

Phase I research, the psychoacoustic 

modeling and the human subjects 

testing Volpe developed potential 

specifications for vehicle 

countermeasure sounds. 

The Phase 2 research developed 

various options and approaches to 

specify vehicle sounds that could be 

used to provide information at least 

equivalent to the cues provided by ICE 

vehicles, including speed change. In 

this research, acoustic data acquired 

from a sample of 10 ICE vehicles was 

used to determine the sound levels at 

which synthetic vehicle sounds, 

developed as countermeasures, could be 

set. ICE-equivalent sounds were 

specified as overall A-weighted sound 

levels and spectral content at the onethird octave band level. Psychoacoustic 

models and human-subject testing were 

used to explore issues of detectability, 

masking, and recognition of ICE-like 

and alternative sound countermeasures. 

The researchers determined that the 

elements of a specification for vehicle 

sounds should consider sound output 

levels; pitch changes that convey 

changes in vehicle speed; and acoustic 

qualities that determine whether the 

sound is perceived as a vehicle. The 

options discussed in the Phase 2 final 

report 52 assume 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. 

Note: Human-subject tests for Phase 2 

were conducted in an ambient level of 

approximately 58–61 dB (A). 

Phase 2 work focused initially on the 

following two ideas: (1) the lack of 

detectability of quieter vehicles can be 

remediated if they are fitted with 

synthetic sound generators that emulate 

the sound of typical ICEs; and (2) the 

specifications for the vehicle sounds can 

be defined in terms of objective 

parameters—namely, overall sound 

output as measured by the SAE J2889– 

1 procedure and spectral distribution 

specifications for the minimum amount 

of sound level in one-third-octave 

bands. 

Recognizability is more complex than 

detectability. Most sounds, and sounds 

as complex as those emitted by an ICE, 

have numerous properties in addition to 

loudness and spectral distribution that 

affect human perception. Among these 

properties are rise time, decay time, 

repetition rates, variations in pitch and 

loudness, and phase relations among 

various components of the sound. These 

challenges can be demonstrated, for 

example, by playing a recording of a 

sound backwards, for example, that 

changes in these properties can render 

a sound unrecognizable even though 

loudness and spectral distribution are 

unchanged. There are no established 

quantitative metrics for many qualities 

of a sound that a person might use for 

recognition. 

In the Phase 2 report Volpe first 

considered whether HVs and EVs 

should be equipped with sounds that 

are based on the acoustic profile of ICE 

vehicles. This concept is based on the 

assumption that the ICE vehicles 

measured in this study are typical of the 

current fleet, emit an acceptable amount 

of noise during low-speed operations, 

and that some (e.g., ICE-like) 

countermeasure sounds can be based on 

the statistical average of real-vehicle 

spectral characteristics. Researchers 

developed the potential specifications 

for alert sounds shown in Table 6 and 

Table 7 based on acoustic analysis of 

sounds produced by ICE vehicles to 

demonstrate what acoustic 

specifications for a vehicle alert sound 

might look like. The derivations of these 

data are given in Section 5 of the Phase 

2 final report. 

TABLE 6—MINIMUM OVERALL AWEIGHTED LEVEL (LAEQ, 1/2; SEC) 

BY VEHICLE OPERATION

Vehicle operation LAeq, 1/2 sec,

dB(A) 

6 mph .................................... 61.1 

10 mph .................................. 63.6 

15 mph .................................. 68.1 

20 mph .................................. 70.2 

Acceleration .......................... 66.7 

Start-up ................................. 70.7 

Stationary but activated ........ 55.2 

Table 7 shows the corresponding 

minimum A-weighted one-third-octaveband spectra for each operating mode. 

ICE vehicles have energy components in 

all frequencies (e.g., 100 to 20k Hz), 

however, the psychoacoustic models 

implemented in this study show that 

energy components in the one-third 

octave bands ranging from 1600 Hz to 

5000 Hz contributed the most to 

detection, and those ranging from 315 

Hz to 1600 Hz contributed additional 

detection and pitch information. These 

spectral distribution limits are derived 

from the procedures described in 

Section 6 of the Phase 2 final report. 

TABLE 7—A-WEIGHTED ONE-THIRD-OCTAVE-BAND SPECTRA AT MICROPHONE LINE LAEQ, 1/2 SEC

1/3 Octave band center 

frequency, Hz 6 mph 10 mph 15 mph 20 mph Acceleration Startup Stationary but activated 

100 to 20000 ................ 61.1 63.6 68.1 70.2 66.7 70.7 55.2 

315 ............................... 43.9 46.9 50.2 52.5 49.8 44.2 37.3 

400 ............................... 46.5 48.7 53.0 54.1 51.4 46.6 39.0 

500 ............................... 47.9 51.2 55.6 57.1 53.4 51.8 42.1 

630 ............................... 49.0 52.5 56.9 59.1 54.6 52.4 42.3 

800 ............................... 51.1 54.6 59.5 62.3 55.1 55.2 43.2 

1000 ............................. 51.4 55.2 60.2 63.2 55.6 57.8 44.9 

1250 ............................. 52.2 54.6 59.6 62.2 57.2 60.5 46.3 

1600 ............................. 52.0 54.3 58.8 61.3 57.0 61.1 45.4 


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2814 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

53 In this section of the notice the word ‘‘option’’ 

refers to countermeasure concepts developed in 

Phase 2 research and not rulemaking options 

considered by the agency when developing this 

proposal (see Sections VII and VIII for NHTSA’s 

proposal and alternatives considered, respectively). 

54Stanton & Edworthy (Eds.) (1999) Human 

Factors in Auditory Warnings 

TABLE 7—A-WEIGHTED ONE-THIRD-OCTAVE-BAND SPECTRA AT MICROPHONE LINE LAEQ, 1/2 SEC—Continued 

1/3 Octave band center 

frequency, Hz 6 mph 10 mph 15 mph 20 mph Acceleration Startup Stationary but activated 

2000 ............................. 50.3 52.0 56.1 57.9 55.7 60.5 44.6 

2500 ............................. 49.1 50.3 53.9 54.9 55.1 61.1 43.8 

3150 ............................. 48.6 49.2 52.4 52.1 54.9 61.6 44.1 

4000 ............................. 46.9 47.5 50.5 49.5 53.2 60.9 42.4 

5000 ............................. 44.1 45.0 47.8 46.4 50.8 59.2 40.3 

The Volpe Center examined two 

options 53 under this first concept (ICElike sounds): 

Recordings of Actual ICE Sounds 

The first option under the ICE-like 

sound concept explored using 

recordings of actual ICE vehicles as alert 

sounds. Recordings would be made 

when the vehicle is operating at 

constant speeds, forward from 0 to 20 

mph and in reverse at 6 mph. Other 

components of the vehicles noise output 

(e.g., tire noise, aerodynamic noise, AC 

fan noise) would be emitted regardless 

of whether an ICE is in use and would 

not be included in these recordings. 

Sound generation systems with signal 

processing capabilities would be used to 

continuously and monotonically vary 

the sounds from one operating 

condition to the next according to 

vehicle input (e.g. vehicle speed 

sensors, throttle sensors, etc.). In this 

option, emitted sounds would be based 

on standardized recordings with 

processing limited to pitch shifting in 

proportion to vehicle speed and 

interpolation between sounds. 

Synthesized ICE-Equivalent Sounds 

The second option under the ICE-like 

sound concept explored using simulated 

ICE sounds directly synthesized by a 

digital-signal processor (DSP) 

programmed to create ICE-like sounds 

(based on actual target sounds) that 

would vary pitch and loudness 

depending on vehicle inputs. This is in 

contrast to the first option, described 

above, in which the sounds come 

directly from recordings of actual 

vehicles, and the processor must store 

and interpolate among files representing 

every mode of operation and for every 

speed within the 0 to 20-mph range. 

Here, the resulting synthesized sounds 

would resemble those of the first option, 

but have fewer spectral components. A 

synthesizer could be simpler and 

cheaper than a sound generator based 

on real ICE sounds. For this option, 

target sounds, recorded from actual 

vehicles for the operations specified 

above would be used. The synthesized 

sounds would then be developed to 

match the spectral shape of these target 

sounds. (Note: by definition, powerspectra spectral lines have a resolution 

of 1 Hz). 

Sound generation systems with signal 

processing capabilities would be used to 

continuously and monotonically vary 

the sounds from one operating 

condition to the next according to 

vehicle input (e.g. vehicle speed 

sensors, throttle sensors, etc.) and the 

synthesis algorithms developed for their 

sounds. The two options listed above 

assume that band-limited (315 Hz to 

5000 Hz) ICE-like sounds will be 

recognizable as motor vehicles. 

Alternative, Non-ICE-Like Sounds 

Designed for Detectability 

The second concept, described in the 

Phase 2 final report, consists of 

alternative countermeasure sounds with 

acoustic characteristics different from 

ICE vehicles. Some of the 

countermeasures evaluated in the 

human-subject studies have sound 

characteristics that could improve 

detectability when compared to ICEequivalent sounds. The following sound 

characteristics can improve detectability 

of a sound source 54: 

• Pulsating quality with pulse widths 

of 100 to 200 msec. 

• Inter-pulse intervals of about 150 

msec. 

• Fundamental tonal component in 

150 to 1000 Hz range. 

• At least three prominent harmonics 

in the 1 to 4 kHz range. 

• Pitch shifting denoting vehicle 

speed change. 

The design of a non-ICE sound 

involves a complex tradeoff among 

several factors including annoyance, 

cost, detectability, and overall sound 

pressure level values. While the 

required sound pressure level values for 

non-ICE-like sounds will generally be 

lower than for ICE-like sounds for the 

same detection distance, there is no 

objective basis upon which to calculate 

the difference in sound pressure level 

values for the class of non-ICE sounds 

as a whole. Rather, the equivalent 

detectability sound pressure level value 

for a particular non-ICE sound must 

initially be determined experimentally 

by a jury process that rates detectability. 

As psychoacoustic models improve, it 

may be possible to use them in place of 

jury testing to determine minimum 

sound pressure level specifications for 

these sounds, but that approach is not 

yet sufficiently accurate. 

In this concept sound generation 

systems with signal processing 

capabilities would be used to 

continuously and monotonically vary 

the pitch and amplitude of sounds as 

appropriate to operating conditions 

according to vehicle inputs (e.g. vehicle 

speed sensors, throttle sensors, etc.). 

The appropriate relationship between 

sound amplitude and throttle position 

would need to be determined. The 

detectability of a specific non-ICE sound 

can be best determined only through 

human subjects testing, at the present 

state of the art. 

Hybrid of Options Discussed Above 

A third concept to designing 

countermeasure sounds, explored in the 

Phase II report, would be a combination 

of the concepts (i.e. using ICE-like or 

non-ICE-like sounds) discussed above, 

with the goal of gaining the benefits of 

each, while minimizing the 

disadvantages. Simulated ICE sound 

could be generated which would vary 

pitch and loudness depending on 

vehicle inputs. This system could 

simultaneously generate both ICE-like 

sounds at a lower sound pressure level 

than the concepts based on ICE sounds 

discussed above, and synthetic sounds 

designed for optimal alerting potential 

with minimal annoyance. The ICE-like 

sound components may not be heard in 

higher urban ambient-noise conditions, 

but their association with the alerting 

sound would be learned over time from 

when the pedestrian is exposed to the 

sound in lower ambients. This method 

would most likely depend on jury 

testing of human subjects to set the 

sound level for detection. 


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Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2815 

55As measured by the SAE J–2889 draft test 

procedure (SAE J–2889, draft, 2009). 

Human Subject Evaluation of 

Detectability 

A human subject study was 

conducted to compare the auditory 

detectability of potential sounds for 

hybrid and electric vehicles operating at 

a low speed. The sounds evaluated 

included: (1) Sounds produced by 

vehicles with integrated sound systems 

rented from manufacturers, and (2) 

sounds produced by prototype systems 

rented from manufacturers, and played 

back by loudspeakers temporarily 

mounted on HVs rented separately. Five 

vendors, motor vehicle manufacturers or 

suppliers of automotive electronics, 

provided prototypes of synthetic sound 

generators for EVs or HVs. The five 

systems were labeled ‘‘A’’ to ‘‘E’’. A 

total of nine sounds were evaluated: A1, 

A2, A5, B, C, D, E1, E3, and E4. Sounds 

were evaluated at two sound pressure 

levels typical of ICE vehicles at low 

speeds (i.e., A-weighted SPL of 59.5 dB 

and 63.5 dB).55 An ICE vehicle that 

produced A-weighted SPL of 60 dB in 

the 6 mph pass-by test was used as a 

reference in this evaluation. The ICE 

vehicle was labeled ‘R’. 

Sound A1 was an engine like sound 

with a turbine-like whine that had a 

prominent peek that varied from 150 Hz 

to 300 Hz based on vehicle speed. 

Sound A2 was an engine sound with 

enhanced valve noise with prominent 

signal content between 100 Hz and 200 

Hz. Sound A5 was a whirring sound 

with a diesel engine sound. The 

fundamental signal content of the 

whirring part of the sound for sound A5 

was between 400 Hz and 600 Hz based 

on vehicle speed. Sound B emulated the 

exhaust note (the fundamental of the 

combustion noise) of an engine. The 

sound did not contain appreciable 

components above 250 Hz. Sound C was 

a Wavy, turbo-like sound with most of 

its energy as broadband noise in the 200 

Hz to 5000 Hz range. Sound D was a 

broadband sound designed to suggest an 

electric motor coupled to other rotating 

machinery. Sound E1 was a pure engine 

noise with most of its energy below 300 

Hz. Sound E3 was an engine-like sound 

with a ‘whirring’ character and a flatter 

spectral distribution than Sound E1 and 

had none of the prominent harmonics of 

the combustion note. Sound E4 

contained short bursts of predominantly 

high-frequency sound with the peak 

amplitude of the fundamental varying in 

frequency from about 450 Hz to 700 Hz 

based on speed. 

Data was collected outdoors during 

three independent sessions conducted 

on three days in July and August 2010. 

The first session included four operating 

modes: idle (stationary), acceleration 

from stop, start-up and 6 mph forward 

pass-by. The following two sessions 

included the 6 mph forward pass-by. 

The HVs used in the study were 

operated in electric mode during the 

pass-by trials. The sample included 79 

participants 34 of which were sighted 

and 45 of which were legally blind. The 

legally blind participants were 

independent travelers and all 

participates had self-reported normal 

hearing. 

The study took place in a parking lot 

located on the USDOT/Volpe Center 

campus in Cambridge, Massachusetts. 

The test site has the acoustic 

characteristic of an urban area with a 

typical ambient noise of approximately 

A-weighted sound pressure level of 58– 

61 dB. The dependent variables 

examined in the study included raw 

detection distance, proportion of 

detection, time-to-vehicle arrival, and 

detection distance. Raw detection 

distance is the number of feet the 

vehicle was from the participant when 

the participant indicated she or he 

heard the sound. A failure to detect the 

sound before the vehicle passed was 

treated as missing data. Proportion of 

detection is the proportion of trials of a 

given condition in which the participant 

detected the sound anytime before the 

vehicle passed the participant. Time-tovehicle-arrival is the time, in seconds, 

from detection of a target vehicle sound 

to the instant the vehicle passes the 

pedestrian location. Detection distance 

is the calculated distance, feet, to the 

target vehicle at the moment each 

subject responded. 

Each subject had a push button device 

which they used to indicate when they 

detected a nearby vehicle. Participants 

were asked to press a response button 

when they detected and recognized a 

vehicle that would affect their decision 

about when to start crossing the street. 

Table 8 shows the mean detection 

distances for the sounds evaluated in 

the human-subject studies for the 6 mph 

pass-by; sounds at the top of the list can 

be described as sounds designed 

according to psychoacoustic principles 

and sounds at the end of the list can be 

described as ICE-like sounds with only 

the fundamental combustion noise or 

otherwise lacking in the qualities that 

support detectability. The results show 

that high amplitude sounds (A-weighted 

SPL of 63.5 dB) were detected more 

often and at greater distances than low 

amplitude sounds (A-weighted SPL of 

59.5 dB). 

TABLE 8—MEAN DETECTION DISTANCE (FT) FOR ALL SOUNDS AT TWO AMPLITUDES AND FOR THE REFERENCE ICE 

VEHICLE

Sound number 

Average 

detection 

distance (feet) 

for amplitude 

equal 59.5 

dB(A) 

Average 

detection 

distance (feet) 

for amplitude 

equal 63.5 

dB(A) 

E4 ............................................................................................................................................................................. 72 85 

A2 ............................................................................................................................................................................. 57 77 

E3 ............................................................................................................................................................................. 52 70 

A5 ............................................................................................................................................................................. 50 47 

ICE vehicle, 60 dB(A) .............................................................................................................................................. 41 NA 

A1 ............................................................................................................................................................................. 35 44 

C .............................................................................................................................................................................. 32 41 

E1 ............................................................................................................................................................................. 30 32 

B ............................................................................................................................................................................... 20 25 

D .............................................................................................................................................................................. 19 NA 


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2816 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

56The reference sound ‘R’ and sound ‘D’ were 

excluded from this analysis since they did not differ 

in amplitude. 

57The acoustic characteristics of these sounds are 

discussed in Section 5.2 of NHTSA Report No. DOT 

HS 811 496. 

58All participants were required to wear a 

blindfold during the study. 

59 Diagrams showing the microphone setup for all 

the scenarios are contained in the Phase 3 report 

from VRTC. 

Results show that A2, A5, E3, and E4 

have significantly better detectability 

than the ICE reference sound at 6 mph. 

These sounds never have significantly 

worse detectability in any condition. 

Thus, these sounds overall have better 

detectability than the ICE reference 

sound. In contrast, sounds A1, B, C, D, 

and E1 all have significantly worse 

detectability than the reference sound 

for the 6 mph forward pass-by. These 

sounds never have significantly better 

detectability in any of the conditions 

presented to subjects. Thus, these 

sounds overall have worse detectability 

than the reference sound. 

The analysis also indicated significant 

main effects of sound and a significant 

three-way interaction of session, sound, 

and direction. This implies that the 

relative performance of each sound, 

including the reference sound, is jointly 

contingent on the direction it comes 

from and the session it was presented 

in. The directional effect results 

primarily from the fact that the roof-top 

fans on buildings to the west were the 

predominant source of ambient noise, 

which can mask vehicles approaching 

from the west compared with vehicles 

approaching from the east. The 

detectability of each sound relative to 

the reference was evaluated by 

comparing each sound to the reference 

vehicle for the corresponding session 

and direction condition of each. 

To compare the detectability of the 

sounds to each other, a mixed design 

ANOVA was performed on detectability 

with session and vision as betweensubjects independent variables, and 

sound, direction, and amplitude as 

within-subject independent variables.56

Sounds were ranked by comparing each 

to the other (t-tests) for each session bydirection-by-amplitude condition. To 

assist in the control for family-wise 

error rate, the analyses only included 

the four sounds shown to be superior to 

the reference sound. Results show that 

E4 has overall significantly better 

detectability than the other sounds, and 

within each condition it is never worse 

than any other sound, except for one 

condition when compared to A2. 

Sounds A2 and E3 are overall not 

significantly different than each other, 

showing only a difference in a single 

condition. Sound A5 has overall 

significantly worse detectability than 

the other sounds, and within each 

condition is it never better, except for 

one condition when compared to E3. 

The overall ranking of the sounds from 

most to least detectable is therefore: E4, 

A2 and E3, and A5.57

In summary, the human subject 

testing in Phase 2 suggest that synthetic 

sounds that resemble those of an ICE 

produce similar detection distances as 

actual ICE vehicles. In some instances, 

synthetic sounds designed according to 

psychoacoustic principles can produce 

double the detection distances relative 

to the reference vehicle. The results also 

suggest that synthetic sounds that 

contain only the fundamental 

combustion noise are relatively 

ineffective. None of the analyses found 

a significant effect of vision ability.58

Participants who are legally blind, on 

average, were no better or worse than 

sighted participants in detecting the 

approach sounds. 

C. NHTSA Phase 3 Research 

The third phase of NHTSA’s research 

involving quiet vehicles consisted of 

developing an objective, repeatable test 

procedure and objective specifications 

for minimum sound requirements for 

hybrid and electric vehicles. NHTSA’s 

Vehicle Research and Test Center 

(VRTC) conducted acoustic 

measurements and recordings of several 

HVs and EVs and those vehicle’s ICE 

pair vehicles. 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. 

VRTC Acoustic Measurements 

The primary focus of Phase 3 research 

conducted by VRTC was to evaluate the 

new SAE J2889–1 test method and 

several variations used to test operating 

conditions that were not included in 

SAE J2889–1 and provide data to 

establish performance criteria. The 

research was conducted using 3 HVs, 1 

EV, and 4 ICE vehicles. 

SAE J2889–1 was still in draft form at 

the start of the project, but the final 

version published in September of 2011 

was not significantly different from the 

draft. The vehicles were used to gather 

sample data on the difference in sound 

pressure levels between ICE sounds and 

EV or HV sounds as well as directivity 

and sound quality levels using eleven 

test scenarios developed for this 

program (4 static and 7 pass-by). Some 

of the hybrid and electric vehicles were 

tested with multiple alert sounds. Some 

the hybrid and electric vehicles were 

also tested with no alert sound at all to 

determine crossover levels. 

A significant modification to the SAE 

procedure was the addition of a laser at 

the microphone line-labeled as PP’ in 

SAE J2889–1. This addition enabled 

recording the time at which the leading 

edge of the vehicle reached the 

microphone location. 

Test Scenarios 59

VRTC measured the vehicle sound 

output for the operating scenarios listed 

below for ICE vehicles, hybrid and 

electric vehicles with an alert sound 

active, and hybrid and electric vehicles 

with no alert sound active. The overall 

goal of the research was to capture as 

much acoustic data as possible for both 

ICE sounds and artificial sounds added 

to hybrid and electric vehicles as alert 

sounds so that the sounds could be 

analyzed when the agency was the 

establishing acoustic specifications 

contained in this proposal. 

• Scenario 1: SAE J2889–1 modified 

Startup (8 microphones). This set up 

was used to generate a 360 degree sound 

or directivity profile for the vehicle. 

• Scenario 2: SAE J2889–1 modified 

Stationary but active (8 microphones). 

This scenario was the same as Scenario 

1 except that the sound of the vehicle 

while stationary was recorded. 

• Scenario 3: SAE J2889–1 modified 

Startup (5 microphones). Data from this 

recording can be used can be used to 

generate a 180 degree sound or 

directivity profile for the vehicle. 

• Scenario 4: SAE J2889–1 modified 

Stationary but active (5 microphones). 

This scenario was the same as Scenario 

3 except that the sound of the vehicle 

while stationary was recorded. 

• Scenario 5: SAE J2889–1 10 km/h 

Forward Constant Speed (2 

microphones). This test produced result 

from 2 microphones on either side of 

the vehicle centerline. 

• Scenario 6: SAE J2889–1 20 km/h 

Forward Constant Speed (2 

microphones). This test produced result 

from 2 microphones on either side of 

the vehicle centerline. 

• Scenario 7: SAE J2889–1 30 km/h 

Forward Constant Speed (2 

microphones). This test produced result 

from 2 microphones on either side of 

the vehicle centerline. 

• Scenario 8: SAE J2889–1 10 km/h 

Reverse Constant Speed (2 

microphones). This test was pass-by 

noise test with data being recorded as 

the vehicle is driven backwards though 

the noise test pad with two 


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microphones on either side of the 

vehicle centerline. 

• Scenario 9: 0 to 10 km/h Forward 

Acceleration to Constant Speed (2 

microphones) The vehicle was 

positioned 2 meters before the PP’ line 

and accelerated at 0.1 g from 0 to 10 km/ 

h pass-by noise test with data being 

recorded by two microphones on either 

side of the vehicle centerline as the 

vehicle is accelerated though the 

remainder of the noise test pad. 

• Scenario 10: 30 to 10 km/h Forward 

Deceleration to Constant Speed (2 

microphones). The vehicle was driven 

at 30 km/h into the test zone and began 

deceleration at 0.1 g to 10 km/h at the 

PP’ line. 

• Scenario 11: 0 to 10 km/h Reverse 

Acceleration to Constant Speed (2 

microphones). The vehicle was 

positioned 2 meters before the PP’ line 

and accelerated from 0 to 10 km/h with 

data being recorded by microphones on 

both sides of the vehicle centerline as 

the vehicle was accelerated though the 

remainder of the noise test pad. 

When testing the vehicle in the 

scenarios described above VRTC 

identified some challenges. The test 

drivers found that it was difficult to 

reliably maintain a low travel speed for 

some vehicles during the 10 km/hr 

forward pass-by test as these vehicles 

tried to shift gears or the electric 

controls energized or de-energized. 

During the pass-by tests conducted in 

reverse at 10 km/hr the test drivers 

experienced some of the same 

difficulties experienced during the 

forward pass-by testing. Also, it was 

very difficult to maintain the vehicle in 

the center of the lane. Testing in reverse 

could only be done during daylight 

hours due to difficulty in driving 

backwards, drifting in the lane and 

possible equipment damage. During the 

testing of the vehicle accelerating from 

0 to 10 km/hr the test drivers 

encountered difficulty in maintaining a 

consistent acceleration rate. Positioning 

the vehicle for this test and starting the 

data acquisition was very labor 

intensive 

When testing the vehicle decelerating 

from 30 to 10 km/hr the test drivers 

encountered difficulty in maintaining a 

consistent deceleration rate. 

Determining the starting point of 

deceleration was difficult. Some vehicle 

braking rates were difficult to maintain 

the 0.1 g rate. During braking the 

vehicles’ regenerative braking systems 

transitioned back and forth from 

mechanical to regenerative braking. 

When testing the vehicles while 

accelerating in reverse the test drivers 

encountered difficulty in maintaining a 

consistent acceleration rate and 

maintaining the center of the lane for 

the remainder of the test pad. 

Positioning the vehicle and starting the 

data acquisition was very labor 

intensive for this test. 

Interpretation of Results 

One of the purposes of the Phase 3 

acoustic measurements was to gather 

additional data on the difference in 

sound levels between EVs and HVs 

operating in electric mode and ICE 

vehicles. For the pass-by tests in Phase 

3 the ICE vehicles were 6.2 to 8.5 Aweighted dB louder than the EV/HVs 

without added sound at 10 km/h. At 20 

km/h the difference between the HV/ 

HVs and ICE vehicles varied, but the 

average level was 3.5 A-weighted dB 

louder for the ICE vehicles. At 30 km/ 

h the sound levels of the HV/HVs 

approached the levels of the ICE 

vehicles and the individual 

measurements for the two types of 

vehicles have considerable overlap. 

Table 9 shows the results of HEV/EV 

vehicles with no sound alert system as 

compared to their ICE counterpart. 

TABLE 9—PASS-BY SOUND LEVEL FOR HEV/EV VEHICLES WITHOUT ALERT SOUND ACTIVE VERSUS COUNTERPART ICE 

VEHICLES

Manufacturer Speed, km/h 

HEV/EV 

Sound level, 

dB 

ICE Sound 

level, dB 

ICE minus 

HEV/EV, dB 

Nissan .............................................................................................................. 10 50.5 56.6 6.2 

20 60.0 62.3 2.2 

30 66.5 68.1 1.5 

Prototype Vehicle G ......................................................................................... 10 51.4 59.9 8.5 

20 60.5 63.1 0.6 

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 3.5 

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 from 6 to 10 dB less than that 

directly in front of the vehicle. For the 

vehicles with an speaker system the 

sound level behind the vehicle was 12 

to 15 dB lower behind the vehicle, and 

in some cases the sound level at the 

microphone behind the vehicle was not 

distinguishable from a quiet background 

sound level of 40 dB. There was a 

systematic difference from left to right 

for some vehicles, particularly with an 

artificial sound. 

Acoustic Analysis Performed by Volpe 

As part of the Phase 3 research Volpe 

examined the frequency range, 

minimum sound level for selected onethird octave bands, and requirements for 

broadband noise and tones as possible 

criteria for vehicle sound using a 

loudness model to determine when the 

sounds might be detectable in a given 

ambient. Also considered were the 

relative proportions of acoustical energy 

emitted from a vehicle as a function of 

direction (directivity) and ways to 

denote changes in vehicle speed. Two 

approaches were used to identify 

potential detectability specifications for 

alert sounds to be included in the 

NPRM: (a) sound parameters based on a 

loudness model and detection distances 

and (b) sound parameters based on the 

sound of ICE vehicles. 


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60Pedersen et al. (2011). White paper on external 

sounds for electric cars—Recommendations and 

guidelines. Delta-Senselab. Copenhagen. 

61For a discussion of loudness models see page 

67. 

62See footnote 59. 

Volpe’s work in developing the 

acoustic 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. 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. 

Because the response of the study 

participants in the human subject 

experimentation in Phase 2 varied 

significantly due to variations in the 

ambient, 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 this 

proposal. Volpe also observed during 

the human factors research that sounds 

with strong tonal components were 

more detectable. 

Volpe developed the specifications 

based on the sound of ICE vehicles 

using measurements of ICE vehicles 

captured in Phase 2 and acoustic data 

provided by representatives of auto 

manufacturers. 

Before presenting these two 

approaches, it is important to explain 

how background noise, critical 

frequency range, and loudness models 

relate to the detectability of a sound. 

Background Noise 

When talking about the detectability 

of a sound, it is important to understand 

masking and background noise (ambient 

noise). Masking occurs when the 

perception of one sound is affected by 

the presence of an unrelated sound. 

Background noise can affect the extent 

to which masking occurs. Two 

characteristics of background sounds are 

of primary importance: overall sound 

pressure level and the frequency content 

or shape of the frequency spectrum. 

Masking depends on the signal-to-noise 

ratio in the different frequency bands 

and therefore cannot be estimated from 

the overall A-weighted sound level 

alone. Acoustic data for background 

noise can be obtained from recordings of 

background noise made at various 

locations. Recordings of actual traffic 

may include peaks (e.g., passage of 

nearby loud vehicles) that can introduce 

variability when using human subjects 

for testing or when applying 

detectability models. An alternative to 

recordings of the actual traffic is to use 

standardized synthetic background 

noise. Synthetic background noise 

consists of, for example, 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 (e.g., those caused 

by the passage of a particular loud 

vehicle or aircraft). This broadband 

noise creates masking while reducing 

the issues associated with fluctuations 

or peaks. The standardized noise is an 

advantage for repeatability. For more 

information about this, see Pedersen et 

al. 2011.60

A standardized background noise was 

used in Phase 3 in the implementation 

of Moore’s Loudness model to compute 

minimum sound levels for detection in 

a given one-third octave band and to 

identify frequency ranges relevant for 

alert sounds.61 The ambient selected for 

these analyses is representative of many 

common urban ambients.62 Being 

detectable in this ambient would mean 

that the alert sound would be detectable 

in other ambients with lower overall 

levels and similar spectral shapes. The 

spectral shape is given in Figure 2. The 

overall A-weighted level for detection 

computations was 55 dB). Results for 60 

A-weighted dB can be accurately 

estimated by adding 5 dB to the results 

from the 55 A-weighted dB analysis. 

Similarly, results for 50 A-weighted dB 

can be accurately estimated by 

subtracting 5 dB from the results from 

the 55 A-weighted dB analysis. 

Critical Frequency Range 

Critical frequency regions, defined by 

a set of one-third octave bands, are 

determined by applying psychoacoustic 

principles for a given ambient 

condition. The purpose of identifying a 

critical frequency region(s) is to ensure 

that a sound signal is emitted from the 

vehicle such that it would be expected 

to be detectable at a reasonable distance 

away from a pedestrian. Due to masking 

effects of the ambient and potential 

hearing loss of the pedestrian, 

opportunities for detection will be 

maximized if the alert signal contains 

detectable components over a wide 

frequency range. 

Frequencies in the audible range for 

children and most young adults are 

from about 20 to 20,000 Hz. Human 


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Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2819 

63Fletcher, H. and Munson, W. A. (1933). 

Loudness, its definition, measurement, and 

calculation. Journal of the Acoustic Society of 

America. 5 (1), 82–108. 

64See footnote 11 Chapter 6. 

65Feddersen et al. (1957). Localization of high 

frequency tones. Journal of the Acoustical Society 

of America. 5, 82–108. 

66 Yost, W.A. (1994) Fundamentals of Hearing: An 

Introduction. San Diego: Academic Press. 

67American National Standard (1995). Procedure 

for the computation of loudness of steady sound 

(ANSI S1.13). New York, New York: Secretariat, 

Acoustical Society of America. 

68Moore et al. (1997). A model for the prediction 

of thresholds, loudness, and partial loudness, J. 

Audio Eng. Soc. 45(5). 

69Moore and Glasberg (1997). A model of 

loudness perception applied to cochlear hearing 

loss. Auditory Neuroscience, 3, 289–311. 

70A value of 0 sones is approximately the 

threshold of perception. Moore models threshold to 

be at 0.003 sones to match ISO 389–7:2005 to 

within 0.2 dB over the frequency range from 50 to 

12,500 Hz (ANSI S3.4–2007). 

71Loudness contours is a graphical representation 

of frequency (x-axis) versus levels (y-axis) such that 

tones of different frequency and different level are 

judged to be equally loud. 72See footnote 67, 289–311. 

hearing is more sensitive in the 500– 

5,000 Hz range than it is at low 

frequencies or very high frequencies.63

Exposure to loud noise and age-related 

factors often diminish a person’s 

sensitivity to sound at higher 

frequencies. Mid-range frequencies 

(approximately 320—5120 Hz) are 

perceived with greater loudness than 

lower (20 to 320 Hz) or higher 

frequencies (5000 to 20,000 Hz). 

Frequencies below 300 Hz are 

commonly masked by urban background 

noise.64

Localization of sounds is 

accomplished through multiple 

neurophysiological processes, each of 

which is most effective in a different 

range of frequencies. Above 1600 Hz, 

inter-aural level differences (caused by 

the shadowing effect of the head) 

become the primary directional cues. 

For some combinations of frequency 

and angular orientation between sound 

source and listener, cancellation of the 

direction cues can occur. Hence, an 

accurate localization of a sound source 

is most likely to occur when it contains 

multiple high-frequency components 

that are audible above the background 

noise.65 66

A person’s relative sensitivity to 

different frequencies varies with 

loudness. Loudness is a numerical 

designation of the strength, expressed in 

units called ‘‘sones,’’ of a sound that is 

proportional to the subjective 

magnitude as estimated by listeners 

having normal hearing (ANSI S3.4 

2007).67 Loudness models predict this 

strength by accounting for how the 

human auditory system processes both 

the amplitude and frequency 

characteristics of a sound. 

Loudness Models 

Sound-pressure-level-based metrics, 

such as, the A-weighted level, provide 

a first estimate of the perceived 

loudness of a sound. These metrics fail 

to account for several factors that affect 

the perceived loudness including: the 

level dependence of the frequency 

sensitivity, level dependence on 

frequency selectivity, and frequency 

based masking effects. The level 

dependence of the frequency sensitivity 

refers to the fact that for the same 

change in sound pressure level for a low 

frequency sound and a high frequency 

sound, the low frequency sound will be 

perceived as increasing in loudness 

more than the high frequency sound. 

The level dependence of the frequency 

selectivity refers to how the human 

auditory system separates frequency 

components of a complex sound’s 

signal. Frequency-based masking is used 

to describe how a high-energy 

component can prevent or reduce the 

perception of a lower-energy component 

at a different frequency. That is, for 

example, an ambient with a high level 

of low-frequency sound can mask a 

signal with components in a higher 

frequency range. 

Several psychoacoustic models exist 

that relate sound pressure level data to 

the perceived loudness of the signal or 

its detectability/audibility. Moore’s 

Loudness model 68 69 was used in Phase 

3 to estimate the minimum sound level 

needed for a sound to be detectable in 

the presence of an ambient. This model 

is useful for the prediction of thresholds 

in quiet ambients and for thresholds in 

the presence of a masker,70 as well as for 

computing equal loudness contours.71

This model was developed for use with 

ISO 226, Normal Equal-Loudness 

Contours, (1987) and the absolute 

thresholds found in ISO 389–7, 

Acoustics—Reference zero for the 

calibration of audiometric equipment— 

Part 7: Reference threshold of hearing 

under free-field and diffuse-field 

listening conditions, (1996). Since the 

model’s original development, both of 

these standards have been updated to 

ISO 226 (2003) and ISO 389–7 (2005). 

There are newer implementations of 

Moore’s model that reflect these new 

data. However, we are not aware of any 

implementations that include these 

updates as well as provide for 

computing thresholds in the presence of 

a masker. Since computing thresholds 

in the presence of a masker is of 

fundamental importance for the work in 

Phase 3, and since the updates represent 

‘‘fine tuning’’ of the model, the 1997 

model was identified as the most 

suitable choice. 

Moore’s Loudness model, as 

described in Moore and Glasberg 

(1997),72 accounts for the following 

factors: how the sound is presented to 

the subject (free field, diffuse field, via 

headphones); transmission through the 

pinna (outer ear) and the middle ear; 

frequency sensitivity and selectivity; 

excitation compression/amplification; 

the transformation of pressure entering 

the cochlea to an excitation pattern 

(determined from the magnitude of 

auditory filter output); transformation 

from an excitation pattern to specific 

loudness for sounds in quiet ambient 

environments and in the presence of a 

masker (specific loudness is analog to 

power spectral density); and integration 

of specific loudness (integrating the area 

under the curve of a power spectral 

density function gives the total power of 

that function). 

The general procedure for running the 

model is to provide un-weighted onethird octave band levels for both the 

signal and the masker and to provide 

information on how the signal is 

presented. For the purposes of the Phase 

3 work, free-field, frontal presentation 

was used, which is both accurately and 

conservatively compared to diffuse field 

or headphones. The model provides 

several levels of detail in the results, 

including the specific loudness as a 

function of the number of equivalent 

rectangular bandwidths. It is the integral 

of this function, or simply Loudness in 

sones that was utilized in Phase 3. 

This model was adequate for the 

needs of Phase 3. However, since this is 

a time-invariant model, it does not take 

into account differences in duration 

(sounds with very short durations are 

perceived differently than long duration 

sounds due to the temporal windows 

associated with the auditory system). 

Nor does it account for periodic 

modulations including the effect of comodulation masking release. 

As part of the Phase 3 research, in 

addition to exploring the detectability of 

sounds, the agency examined acoustic 

characteristics that make sounds 

recognizable. Recognition includes two 

aspects: 1) recognition that the sound is 

emanating from a motor vehicle, and, 2) 

recognition of the type of operation that 

the vehicle is conducting so that the 

pedestrian can take appropriate 

measures. Our research has shown that 

sounds that contain both broadband 

components and tones are more likely to 

be recognized as vehicles. Sounds that 

contain only high frequencies have a 

synthetic (and unpleasant) character. 


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2820 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

73Secretariat, Acoustical Society of America 

(1995). Procedure for the computation of loudness 

of steady sound, American National Standard ANSI 

S1.13. New York, NY. 

74MLIT and JASIC (2010). Guidelines for Measure 

Against Quietness Problem of HV. GRB Informal 

group on Quiet Road Transport Vehicles (QRTV) 

Working papers of the 3rd informal meeting. Tokyo, 

13–15 July 2010. Available at: http:// 

www.unece.org/trans/main/wp29/wp29wgs/ 

wp29grb/QRTV_3.html. 

Sounds with lower frequency tones and 

broadband components have a more 

closely resemble the sound produced by 

an ICE vehicle. In the Phase 2 human 

factors research Volpe observed that 

sounds with strong tonal components 

were more detectable. 

While developing the acoustic 

parameters contained in this proposal 

during Phase 3, parameters that were 

critical to recognition were determined 

by simulating sounds. Sound 

simulations were developed for the 

following vehicle operating scenarios: 

stationary but activated, constant speed 

pass-bys, and accelerating pass-bys. 

Pass-bys included Doppler shifts and 

accelerations also included a pitch 

shifting tied to vehicle speed. The 

sound pressure levels changed as a 

function of speed and as a function of 

position relative to the receiver during 

the vehicle pass-by sound simulations. 

Roughly two hundred sounds were 

generated and evaluated. Based on 

initial assessment of these sounds and 

engineering judgment, at least one tone 

(and preferably more) should be 

included in the acoustic specifications 

for HVs and EVs for the purpose of 

recognition. The lowest tone should 

have a frequency no greater than 400 

Hz. 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. (Note: the methodology 

in ANSI S1.13–1995 appears to be 

overly conservative for the Phase 3 

work. It may be better to: a) either 

reduce the bandwidth, or b) include all 

tones within the band for this 

calculation for the current application. 

Comments are specifically sought on 

this issue). 

Broadband components, which may 

be modulated, should be in each onethird octave band from 160 Hz to 5000 

Hz. Tones at frequencies above 2000 Hz 

do not contribute to recognition. To aid 

in recognition of vehicle acceleration 

and deceleration, the pitch (as measured 

by the fundamental frequency) should 

increase and decrease by at least one 

percent per km/hr of speed over the 

range from 0 km/hr to 30 km/hr. 

Additional cues for recognition will be 

obtained by the movement of the 

vehicle relative to the pedestrian, and 

were not considered for potential 

acoustic specifications. 

The following are recommendations 

to increase recognition based on the 

Phase 3 research: 

• No greater than 50 percent 

amplitude modulation at stationary but 

activated, at a frequency equal to the 

modeled combustion frequency. 

• Ratios of the total tonal power to 

the total broadband power should not 

exceed 15 dB. (Note: this is not the same 

as the Tone-to-Noise Ratio). 

• Multiple harmonics with a 

fundamental equal to a hypothetical 

combustion frequency. 

• The lowest harmonic included 

should be as low in frequency as the 

countermeasure system can reliably 

produce. 

• The first or second harmonic 

present should have the highest 

amplitude with higher harmonics 

generally decreasing in amplitude. 

• Amplitude should increase as a 

function of speed beyond the required 

change for minimum detection (but not 

beyond the maximum level). 

The agency solicits comments 

regarding the specific values, e.g. 50 

percent, 15 dB, etc., as well as why 

characteristics should be included/ 

excluded from this list. 

In addition to the recommendations 

for the recognition of HV and EV sounds 

contained above, the Phase 3 research 

found the acoustic requirements for HVs 

and EVs should include pitch shifting as 

an element to enhance recognition. A 

pitch shifting requirement would keep 

out melodies or sounds that change over 

time. The low-frequency requirement 

would convey the sound of rotating 

machinery. Limiting amplitude 

modulation would reduce annoyance 

and help with recognition, as will 

excluding frequency modulation and 

the noise component of the sound filter 

shapes with high roll-off rates. 

D. International Approach to Pedestrian 

Alert Sounds 

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 

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. 

The MLIT included the following 

guidelines for the type and volume for 

the sound generator system: 

• ‘‘The sound shall be continuous 

sound associating motor vehicles 

running condition.’’ 

• ‘‘Siren, chime, bells, melody, horns 

sounds, animals, insects, and sound of 

natural phenomenon such as wave, 

wind, river current, etc., are not 

allowed.’’ 

• ‘‘The sounds generated shall be 

automatically altered in volume or tone 

depending on the vehicle speed for 

easier recognition of the movement of 

the vehicle.’’ 

• ‘‘Sound volume shall not exceed a 

level of the sound generated when 

vehicles driven by internal combustion 

only run at speed of 20 km/h.’’ 

The use of ‘add-on’ devices, 

generating sound continuously for five 

seconds or longer, have been approved 

in order to increase AVAS penetration. 

MLIT will look into social acceptability 

and verification of technology 

implementation issues before moving 

from a voluntary process to a mandate.74

In addition to the actions taken in 

Japan the United Nations Economic 

Commission for Europe (UNECE) World 

Forum for Harmonization of Vehicle 

Regulation has an informal group on 

Quiet Road Transport Vehicles (QRTV). 

The objective of the QRTV is to 

‘‘[d]etermine the viability of ‘quiet 

vehicle’ audible acoustic signaling 

techniques and the potential need for 

their global harmonization.’’ The 

QRTV’s program plan includes: review 

the available research; determine human 

factors needed for pedestrians; develop 

technical performance parameters for 

vehicles based on human factors needs; 

determine audible sound characteristics 

and ways to convey desired vehicle 

performance information to pedestrians; 

and determine technical and 


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75QRTV (2010). Terms of Reference and Rules of 

Procedure for the GRB Informal Group on Quiet 

Road Transport Vehicles (QRTV). Available at: 

http://www.unece.org/trans/main/wp29/wp29wgs/ 

wp29grb/QRTV_1.html. 

76http://www.unece.org/fileadmin/DAM/trans/ 

main/wp29/wp29wgs/wp29gen/wp29fdoc/ECETRANS-WP29-78-r2e.pdf. 

77See footnote 2. 

78 ISO/NP 16254 Measurement of Minimum 

Noise Emitted by Road Vehicles. http:// 

www.iso.org/iso/iso_catalogue/catalogue_tc/ 

catalogue_detail.htm?csnumber=56019. 79 Konet et al. (2011) Development of 

Approaching Vehicle Sound for Pedestrians (VSP) 

for Quiet Electric Vehicles. SAE International. 

Paper No. 2011–01–0928. Abstract available at: 

http://saeeng.saejournals.org/content/4/1/ 

1217.abstract. 

80 76 FR 40860 (July 12, 2011). The agency 

intends this proposal to be technology neutral. The 

statement of purpose and need in the NOI 

acknowledges, for the purposes of the agency’s 

NEPA analysis of the environmental impacts of this 

rulemaking action, that many manufacturers will 

choose to install speaker systems on their vehicles 

in order to meet the minimum sound requirements 

in this proposal. This proposal establishes 

minimum sound requirements that HVs and EVs 

must meet. It does not specify that vehicles must 

be equipped with a speaker system. 

economical feasibility of potential 

audible warning techniques.75

UNECE has adopted guidelines 

substantially similar to the MLIT 

guidelines discussed above with the 

same requirements and 

recommendations.76 The guidelines are 

intended to provide manufacturers with 

recommendations to follow in 

developing alert sound systems for 

adding sound to quiet vehicles. 

E. SAE Sound Measurement Procedure 

SAE J2889–1 SEP2011, Measurement 

of Minimum Noise Emitted by Road 

Vehicles,77 is a performance-based and 

technology neutral test standard. The 

standard specifies an objective method 

for measuring the minimum noise 

emitted by road vehicles. The standard 

reflects the development of engine and 

propulsion technologies that cannot be 

correctly tested under other SAE 

standards. SAE J2889–1 SEP2011 

specifies test site and meteorological 

conditions, as well as the ambient noise 

level under which the sound should be 

recorded. The standard includes 

provisions for outdoor and indoor 

(hemi-anechoic) testing. The test 

procedure includes specifications for 

microphone position, condition of 

vehicles (e.g., battery state, tires, 

warning signals), operating condition 

(i.e., 10 km/hr (6 mph) and stopped), 

measurement readings, and reporting 

requirements. SAE J2889–1 is derived 

from SAE 2805, Measurement of Noise 

Emitted by Accelerating Road Vehicles, 

and therefore some of the requirements 

related to ambient, equipment, and 

facilities are the same. 

The standard also includes 

procedures to evaluate external vehicle 

sound generator systems for alerting 

pedestrians about a vehicle’s operating 

conditions. The outcome includes 

various acoustic metrics for the external 

vehicle sound generators such as sound 

pressure level, frequency content, and 

changes in sound pressure level and 

frequency as a function of vehicle 

speed. SAE J2889–1 SEP2011 does not 

account for psychoacoustic factors such 

as annoyance, recognizability, or 

detectability. 

SAE published a second version of 

SAE J2899–1 in May of 2012. This 

version, SAE J2889–1 MAY2012, in 

addition to the provisions described 

above, contains a bench test to allow the 

alert sound’s shift in pitch to be 

measured on a component level and a 

procedure to measure the alert sound’s 

shift in pitch on a vehicle level indoors. 

SAE J2889–1 MAY2012 also contains a 

procedure for measuring a 

‘‘commencing motion’’ sound. 

The International Organization for 

Standardization (ISO) is cooperating 

with SAE in its efforts to develop a 

vehicle minimum noise measurement 

standard. The ISO document ISO/NP 

16254 Measurement of Minimum Noise 

Emitted by Road Vehicles 78 and SAE 

J2889–1 are reportedly technically 

identical but this has not yet been 

confirmed by NHTSA because the ISO 

document is still in draft form. 

F. Alert Sounds Currently Provided by 

Manufacturers 

Automotive manufacturers that 

produce EVs for the U.S. market have 

recently developed various pedestrian 

alert sounds. At the time that PSEA was 

enacted, most manufacturers of HVs had 

not typically been equipping those 

vehicles with alert sounds for the U.S. 

market. As of the date of this writing, 

we have detailed knowledge of only one 

system developed by Nissan. We know 

that others are under development and 

that several manufacturers plan to equip 

their vehicles with these systems in the 

near future. Nissan has developed a 

system called Approaching Vehicle 

Sound for Pedestrians (VSP) for the 

2011 Nissan Leaf.79 The system consists 

of a digital sound synthesizer connected 

to a speaker mounted under the hood of 

the vehicle and a sound control system. 

The sound controller gets three inputs: 

Vehicle speed, gear position, and brake 

signal. The VSP has an on/off switch 

located in the instrument panel for 

temporary deactivation by the driver. A 

forward sound activates at low speeds, 

fades off as the vehicle reaches 30 km/ 

hr (18 mph) and fades back on as the 

vehicle speed reduces to 25 km/hr. The 

pitch increases proportionally with 

vehicle speed. A unique sound is 

activated when the gear is in ‘‘reverse’’ 

and when the vehicle starts from a 

stopped position. No sound is emitted 

when the vehicle is in ‘‘drive’’ gear but 

stationary, but the vehicle does emit a 

sound when stationary in ‘‘reverse’’ 

gear. The sounds emitted from the 

vehicle are digitally generated as 

opposed to being a recording of an ICE 

vehicle, and plays through speakers. 

Nissan indicates that the sound was 

designed to achieve the same 

detectability as ICE sound while 

maintaining a quiet cabin for the driver 

and without being intrusive to 

communities. The VSP was developed 

based on three design guidelines. First, 

increase peak frequency content 

between 600 and 800 Hz to improve 

detectability for aging pedestrians with 

high frequency hearing loss. Second, 

increase peak frequency content 

between 2000 and 5000 Hz to improve 

detectability of pedestrians with normal 

hearing. Lastly, reduce frequency 

content at around 1000 Hz to avoid 

noise intrusion. The VSP was set to 

have a similar sound pressure level as 

a Nissan Versa 1.8L at 10 km/hr (6 mph) 

while having two peaks at 630 Hz and 

2500 Hz, and a valley at 1000 Hz. 

G. The Notice of Intent To Prepare an 

Environmental Assessment 

On July 12, 2011, the agency 

published a Notice of Intent to Prepare 

an Environmental Assessment (NOI) 

seeking comment on the alternatives 

that the agency should consider when 

analyzing the environmental 

consequences of a proposed quiet 

vehicle rule. The NOI stated that the 

purpose and need of the rulemaking was 

to ‘‘require EVs and HVs, which tend to 

be quieter than the ICE vehicles, to be 

equipped with a pedestrian alert sound 

system that would activate in certain 

vehicle operating conditions to aid 

blind and other pedestrians in detecting 

the presence, direction, location, and 

operation of those vehicles.’’ 80

The NOI discussed the following five 

alternatives that the agency planned on 

considering in its analysis of the 

environmental consequences of the rule 

and requested that the commenters 

propose other alternatives for the agency 

to consider: (1) Taking no action; (2) 

requiring alert sounds based on 

recordings of ICE vehicles; (3) 

specifying acoustic requirements for 

synthetic sounds that would closely 

resemble sounds produced by ICE 

vehicles; (4) setting requirements for 

alert sounds that possess aspects of both 


tkelley on DSK3SPTVN1PROD with 
2822 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

81See Section VIII. E. for a discussion of why we 

are not proposing to adopt the Japanese or ECE 

guidelines. 

sounds produced by ICE vehicles and 

acoustic elements that contribute to 

detectability; and (5) using 

psychoacoustic principals to develop 

requirements for alert sounds that 

would have enhanced detectability but 

would not necessarily have a reference 

to sounds produced by ICE vehicles. 

The NOI stated that it was likely that a 

rule that allowed alternatives 4 and 5 

would need to include a jury testing 

procedure to ensure that the sounds 

were recognizable to pedestrians as a 

motor vehicle in operation. 

Comments Received in Response to NOI 

In response to the NOI, NHTSA 

received 33 comments from state 

governments and Indian tribes, 

advocacy organizations for individuals 

who are blind, national and 

international standards organizations, 

auto manufacturers, heavy vehicle 

manufacturers, trade organizations that 

represent motor vehicle manufacturers, 

component manufacturers, 

environmental groups and private 

individuals. The agency received 

comments on both the technical and 

environmental aspects of the NOI. 

Most of the commenters expressed 

support for all of the alternatives, except 

the no action alternative. All the 

commenters that commented on 

possible methods for determining 

compliance with the various 

alternatives stated that the performance 

criteria for alert sounds should be based 

on objective factors and that jury testing 

was not an appropriate method for 

determining compliance with an 

FMVSS. 

Several of the commenters requested 

that the agency set the minimum sound 

level requirements for EVs and HVs to 

the sound levels produced by quiet ICE 

vehicles rather than the average sound 

pressure level produced by ICEs. These 

commenters expressed concerns that if 

NHTSA set the minimum sound 

pressure level requirements for EVs and 

HVs to the average sound level 

produced by ICE vehicles, this would 

stop noise reduction trends in vehicle 

design. Commenters that stated that the 

minimum sound level requirements for 

EVs and HVs should be tied to quiet ICE 

vehicles were also concerned about 

minimizing the environmental effects of 

adding sound to EVs and HVs and 

driver acceptance of the added sounds. 

One commenter stated that the acoustic 

specifications developed by the agency 

should include a dB level dip in the 

mid-range frequencies around 1000 Hz 

to limit the community noise impact of 

adding sound to hybrid and electric 

vehicles. 

Several commenters also questioned 

whether there was a safety need for the 

agency to set minimum sound level 

requirements for the stationary but 

activated operating condition. Most 

motor vehicle manufacturers stated that 

the agency should only require that EVs 

and HVs produce sound until the 

vehicle reaches a speed of 20 km/hr (12 

mph) while advocacy groups for 

individuals who are blind stated that 

EVs and HVs should produce sound 

until 32 km/hr (20 mph). 

Light vehicle manufacturers stated 

that the agency should not be overly 

concerned with writing the acoustic 

specifications for the alert sound to 

prevent the use of annoying noises. 

These manufacturers stated that they 

did not believe it was necessary to try 

to prevent annoying sounds because 

manufacturers would not use annoying 

sounds as alert sounds because they do 

not want to annoy their customers. 

Several commenters stated that the 

agency should adopt the ECE guidelines 

for alert sound systems (the ECE 

guidelines are based on the Japanese 

guidelines discussed in Section VIII.E), 

as the agency’s requirements for alert 

sounds for HVs and EVs. These 

commenters believed that the ECE 

guidelines provide manufacturers with 

flexibility in developing sounds while 

appropriately balancing the needs of 

pedestrians and concerns about 

environmental noise impact. In 

discussions with the agency 

manufacturers have stated that they 

believe that the ECE guidelines would 

address the agency’s concerns about 

annoying alert sounds.81

Several commenters pointed out 

potential drawbacks in requiring an 

alert sound that was a recording of an 

ICE vehicle. 

The commenters requested that the 

agency maintain a significant degree of 

flexibility in developing acoustic 

specifications for alert sounds. Several 

commenters stated they did not believe 

that all of the characteristics that the 

agency used to describe sounds 

comprising alternative 5 were necessary 

to provide effective pedestrian alert 

sounds. Advocacy groups for 

individuals who are blind also stated 

that the agency should not allow alert 

sounds with none of the acoustic 

characteristics of current ICE vehicles 

and that the agency should not consider 

alternative 5 in specifying acoustic 

requirements for an alert sound. 

Some of the manufacturers of heavy 

vehicles stated that heavy-duty hybrid 

vehicles that are not capable of electric 

propulsion should be exempt from the 

requirements of the standard because 

these vehicles produce sufficient sound 

for pedestrians to detect them in all 

operating conditions, including 

stationary but activated. Several 

commenters also stated that motorcycles 

should be exempt from the requirements 

of the proposal. 

A few of the commenters questioned 

whether adding sound to HVs and EVs 

was an appropriate means of addressing 

the increased rate of collisions between 

HVs and EVs and pedestrians. Three of 

these commenters believed that 

avoiding pedestrian collisions was the 

responsibility of the driver. One 

commenter believed that NHTSA 

should address crashes between HVs 

and EVs and pedestrians by adding 

advanced pedestrian crash avoidance 

technology to these vehicles. 

VII. NHTSA’s Proposal 

NHTSA has considered three different 

viable alternatives for ensuring that HVs 

and EVs provide detectable, 

recognizable sound cues for pedestrians 

on which the agency seeks comments. 

These alternatives include setting the 

minimum sound levels for EVs and HVs 

based on the sound level required for a 

safe detection distance which is the 

agency’s preferred alternative, setting 

the minimum sound levels for EVs and 

HVs based on the sound levels 

produced by light ICE vehicles and 

using a jury testing procedure instead of 

acoustic specifications to ensure that 

sounds produced by HVs and EVs are 

recognizable. The alternatives differ in 

the manner in which they balance 

recognizability, regulatory feasibility, 

and manufacturer flexibility. In this 

section, we propose the alternative that 

we believe is the best approach. The 

other two alternatives that are not being 

proposed, jury testing for recognizability 

and acoustic profiles designed around 

sounds produced by ICE vehicles, are 

discussed in detail in Section VIII of 

this notice. 

Under our proposal EVs and HVs 

would be required to produce sounds 

that conform to the specifications listed 

in S5 of the Proposed Regulatory Text 

(see Section XIII of this notice). Our 

proposal is similar to Alternative 4 

described in the previously referenced 

NOI as it contains acoustic elements 

designed to enhance detection and to 

aid with recognition of motor vehicle 

operation. Through a compliance test, 

the agency would be able to easily 

measure the sound produced by an EV 

or HV and determine whether that 

sound conforms to the requirements in 

S5 of the proposed regulatory text. The 


tkelley on DSK3SPTVN1PROD with 
Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2823 

82 40 CFR parts 201–211. 

83Public Law 111–373, 124 Stat. 4086 (January 4, 

2011). 

84 Id. 

85This condition is commonly referred to as an 

‘‘idling’’ vehicle for vehicles with internal 

combustion engines. However, the term ‘‘idle’’ 

technically refers to an engine state, not a vehicle 

state, and has no relevance to electric motors. The 

description used here ‘‘stationary but activated’’ 

means the vehicle is not moving, but its starting 

system is activated. 

86Public Law 111–373, § 2(2), 124 Stat. 4086 

(2011). 

agency developed the acoustic 

specifications contained in this proposal 

using a loudness model and a 

representative urban ambient sound 

level to ensure that sounds fitting the 

specifications would be detectable in a 

wide range of ambient noise conditions. 

The agency has included 

specifications for low frequency because 

the agency believes that the low 

frequency one-third octave band 

requirements contained in S5 will assist 

pedestrians in recognizing sounds that 

conform to the requirements as being 

produced by a motor vehicle. The low 

frequency content of the sounds 

produced by current ICE engines is the 

spectral component that pedestrians 

hear and associate with these sounds. 

While the agency believes that the 

specifications in S5 provide 

manufacturers a significant degree of 

flexibility to develop vehicle sounds, 

the specifications do place some 

constraints on the sounds that 

manufacturers are able to use as 

countermeasure sounds. These 

constraints will ensure that 

countermeasure sounds will be 

recognizable and provide the needed 

auditory cues to be useful to 

pedestrians, while avoiding unnecessary 

environmental impact. 

The agency also developed and is 

seeking comment on a set of minimum 

sound requirements for HVs and EVs 

using an analysis of sounds produced by 

ICE vehicles. The proposed 

requirements include minimum sound 

pressure level specifications in different 

one-third octave bands so the frequency 

content of sounds produced by HVs and 

EVs would resemble the spectral 

content of ICE vehicles. Sounds that 

meet these proposed requirements 

would resemble sounds described in 

Alternative 3 of the NOI. Relative to the 

other two viable alternatives, this 

approach would place primary 

emphasis on feasibility and 

recognizability. 

A. Acoustic Specifications Developed 

To Enhance Detection and Recognition 

This NPRM proposes performance 

requirements for sounds produced by 

HVs and EVs so that pedestrians can 

detect, recognize, and locate these 

vehicles. While NHTSA acknowledges 

that many manufacturers will choose to 

install a speaker system to comply with 

the requirements of this proposal, this is 

a technology neutral proposal, so 

manufacturers would be able to choose 

any means of compliance they wish so 

long as the vehicle produces a sound 

that complies with the acoustic 

specifications in Section XIII of this 

notice. 

The agency has sought to balance 

community noise impact with the safety 

of pedestrians in developing the 

acoustic specifications contained in this 

proposal. For people living in 

communities near highways and along 

busy streets, elevated noise levels can be 

annoying and diminish quality of life. 

The agency recognizes the contributions 

motor vehicles make to ambient sound 

levels in urban areas and near highways. 

The DOT’s Federal Highway 

Administration has previously 

conducted studies (not part of this 

rulemaking) that examine noisereducing pavements in an attempt to 

reduce tire noise produced by vehicles. 

We note the research on noise reduction 

that is being conducted by other 

operating administrations within DOT 

in order to emphasize that this proposal 

is not contrary to, and will not interfere 

with, noise reduction efforts. In setting 

a minimum requirement for sound 

produced by HVs and EVs, the agency 

has sought to ensure these sound level 

requirements would not contribute to 

transportation noise pollution. A 

majority of transportation noise is 

caused by vehicles traveling at high 

speed. In this proposal, the agency 

would set minimum sound 

requirements for vehicles traveling at 

lower speeds. The proposal would not 

affect vehicle noise output during the 

high speed scenarios that contribute to 

noise pollution. Furthermore, as 

required by the PSEA, the agency 

considered the maximum noise 

emission requirements for heavy 

vehicles and motorcycles issued by the 

Environmental Protection Agency (EPA) 

in setting the minimum sound 

requirements contained in this 

proposal.82

In developing this proposal, NHTSA 

sought to maintain the current situation 

involving ICE vehicles in which the 

pedestrian and the driver share 

responsibility for avoiding pedestrian 

vehicle collisions. Thus, a pedestrian 

must be able to hear a vehicle from the 

point at which the vehicle would no 

longer be able to safely stop if the 

pedestrian decided to walk into an 

intersection. A pedestrian must be able 

to initiate a street crossing with the 

knowledge that there are no vehicles 

present that would be unable to stop 

before colliding with the pedestrian. At 

distances farther than the vehicle’s 

stopping distance, the driver would be 

able to respond to the presence of a 

pedestrian and avoid a collision. At 

distances within which the driver 

would not be able to respond to the 

presence of a pedestrian and stop the 

vehicle, the pedestrian must be able to 

hear the vehicle so the pedestrian can 

share responsibility for avoiding a crash 

by not stepping into the street. 

B. Critical Operating Scenarios 

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 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. In addition to the 

critical operating conditions mentioned 

above, the agency believes that the 

definition of ‘‘alert sound’’ in the PSEA 

requires the agency to establish 

minimum sound requirements for when 

a vehicle is in a stationary but activated 

condition and while operating in 

reverse. 

1. Stationary But Activated 

It is NHTSA’s position that the 

scenario in which the vehicle is 

stationary, but its starting system is 

activated 85 is a critical operating 

scenario because the definition of ‘‘alert 

sound’’ contained in the PSEA requires 

that a pedestrian be able to locate a 

nearby vehicle that is running; it is the 

agency’s position that including this 

scenario satisfies that provision of the 

PSEA. Furthermore, sound provided by 

idling ICE vehicles is essential to 

assisting visually-impaired pedestrians 

in making safe travel decisions. Sounds 

made by vehicles that are stationary but 

activated address collisions between 

pedestrians and HVs and EVs starting 

from a stopped position. 

The agency has concluded that the 

requirement in the PSEA that the alert 

sound required by the agency should 

allow pedestrians to ‘‘discern vehicle 

presence, direction, location, and 

operation,’’ 86 requires the agency to 

establish minimum sound requirements 

for the stationary but activated operating 


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87See footnote 36. 

condition. As discussed in Section III of 

this notice, when read together the 

terms ‘‘presence’’ and ‘‘operation’’ in 

the definition of alert sound in PSEA 

require the agency to establish 

minimum sound requirements when the 

vehicle is stationary, but the starting 

system is activated. 

As discussed in Section V of this 

notice, sound cues produced by idling 

ICE vehicles are critical for the safety of 

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 reference provided 

by idling vehicles is especially 

important to provide auditory cues for 

visually-impaired pedestrians crossing 

streets at complex intersections where 

the streets intersect at nonperpendicular angles. The sound of 

vehicles idling on the far side of the 

street while waiting to pass through an 

intersection also provides visuallyimpaired pedestrians with a reference of 

how wide a street is so they can 

accurately gauge the amount of time 

needed to safely cross. 

A sound emitted by an HV or EV 

when stationary but activated is 

analogous to the ICE vehicle idling and 

ensures that the responsibility to avoid 

a crash 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 

stop should be able to see a pedestrian 

in front of the vehicle and thus avoid a 

crash, the driver may not always be able 

to be relied upon, especially in 

situations where the driver may have an 

obstructed view. A driver pulling out of 

a parking space in a 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 

with the vehicle by not stepping in front 

of the vehicle. 

In deciding to include a sound 

requirement for HVs and EVs at the 

stationary but activated condition, we 

also relied on the experiences of agency 

staff when attempting to navigate street 

crossings while blindfolded. NHTSA 

staff traveled to the national 

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. The meeting included a class 

room session and a session in which the 

participants from NHTSA were 

blindfolded and trained on navigation 

using a white cane outside on city 

streets with blind and visually impaired 

individuals as guides. The participants 

from NHTSA attempted to navigate city 

streets and cross at non-signaled 

intersections while blindfolded. 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. 

Our October 2011 statistical report on 

the incidence rates of crashes between 

HVs and pedestrians 87 also supports 

stationary but activated as a critical 

operating scenario for pedestrians. The 

report shows six incidents of collisions 

when the vehicle was starting from a 

stopped position. While the difference 

in HV and ICE vehicle crashes with 

pedestrians for vehicles starting from a 

stopped position is not statistically 

significant, this can be partially 

attributed to the limited penetration of 

HVs in the fleet. There were no EV 

collisions with pedestrians documented 

in NHTSA’s report because electric 

vehicles were not widely available in 

2008, the last year for which data is 

available. Overall, EVs and HVs 

represent a small percentage of the total 

vehicle fleet and fully electric vehicles 

have yet to be introduced to the U.S. 

fleet in significant numbers. Therefore, 

the sample size of HVs represented in 

the State Data System, and the number 

of HV pedestrian collisions, remains 

extremely small. The limited available 

crash data does show that HVs have 

collided with pedestrians when starting 

from a stopped position even though the 

sample size is not large enough to prove 

a statistically significant incidence rate. 

The growing penetration of HVs and 

EVs into the vehicle fleet means that 

vehicle collisions with pedestrians 

when an HV or EV is starting from a 

stopped position represents a safety 

concern that is rising to a level of 

significance, for which the agency 

believes it is appropriate to require that 

vehicles provide adequate sound cues 

while stationary but activated. In 

passing the PSEA, Congress directed 

NHTSA to be proactive in addressing 

the risk to pedestrians posed by HVs 

and EVs. Congress did not intend for 

NHTSA to wait until crashes between 

pedestrians and HVs and EVs starting 

from a stop rise to the level where 

NHTSA has a data set that shows that 

a sound for the stationary but activated 

condition is needed. 

The agency does not believe that 

establishing minimum sound 

requirements for EVs and HVs operating 

in the stationary but active condition 

will have any noticeable impact on 

ambient noise levels. As discussed in 

Section X.D, NHTSA has conducted an 

Environmental Assessment (EA) to 

analysis the environmental effects of 

this rulemaking. The EA shows that the 

difference in ambient sound levels if the 

agency issues minimum sound 

requirements for the stationary but 

active condition compared to if the 

agency did not require sound at that 

condition would be negligible. 

The agency does not believe that there 

would be any incremental cost to 

requiring a sound at the stationary but 

active operating condition to a vehicle 

that is already equipped with an alert 

sound system. Rather, as with all other 

required operating scenarios, a vehicle 

with an alert sound system could be 

reconfigured to play a sound at the 

stationary but active condition through 

a simple software modification, which 

would not require any additional 

equipment to be installed on the 

vehicle. 

In comments on the NOI and in 

meetings between representatives from 

various auto manufacturers and NHTSA 

staff, several manufacturers stated that 

the agency should not establish 

minimum sound requirements for the 

stationary but activated condition. 

These manufacturers do not believe 

there is a safety need for an alert sound 

when vehicles are stationary but 

activated. 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 impact. 

Advocacy organizations for 

individuals who are blind or visually 

impaired believe that the agency should 

establish minimum sound requirements 

for the stationary but active condition. 

In meetings with agency rulemaking 

staff, representatives from NFB have 

stated that a sound at the stationary but 

active operating scenario is necessary 

for the safety of blind or visually 

impaired pedestrians in avoiding 

collisions with EVs and HVs operating 

at low speeds. Representatives from 

NFB stated that blind individuals 

exercise greater caution when they hear 

a nearby idling ICE vehicle because they 

know that the vehicle could begin 

moving at any moment. Representatives 

from NFB stated that a nearby vehicle 

that made no sound that could start 


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88 Docket No. NHTSA–2011–0148–0029. 

moving at any moment presents a safety 

hazard to blind or visually impaired 

pedestrians because the vehicle could 

collide with a blind or visually impaired 

pedestrians without the pedestrian even 

knowing that the vehicle posed a danger 

to them. The agency believes that 

minimum sound levels for EVs and HVs 

operating when stationary but activated 

are necessary from a safety perspective 

for the reasons previously discussed. 

The agency believes that it is important 

to establish minimum sound 

requirements for the stationary but 

activated condition so that the sound 

will alert nearby pedestrians of the 

presence of a vehicle without unduly 

contributing to overall ambient noise 

levels. The agency believes that the 

safety interest in assisting pedestrians 

with detecting nearby vehicles and 

providing the visually-impaired with 

acoustic cues necessary to make safe 

travel decisions justifies establishing 

minimum sound level requirements for 

EVs and HVs operating when stationary 

but activated. 

The agency acknowledges that with 

the technology under consideration 

today for adding sound to HVs and EVs, 

most vehicles that would be subject to 

this proposed rule (should it become 

final) will establish compliance by 

means of adding a sound generating 

system that includes at least one 

speaker. Requiring a sound at this 

condition may result in manufacturers 

adding speakers to some vehicles (for 

example motorcycles or some heavy 

vehicles) that may not otherwise need a 

speaker to meet the requirements of the 

other operating conditions in today’s 

proposal (because the vehicle operation 

in those conditions makes enough 

sound without adding an artificial 

sound). However, we believe that the 

definition of alert sound in the PSEA 

requires the agency to establish 

minimum sound requirements for this 

condition. We seek comment on the 

number of vehicles to which this 

proposal would apply that would only 

require speakers to meet the acoustic 

requirements in this proposal at the 

stationary but active condition. 

Also, the agency solicits comment on 

possible configurations of the alert 

sound that would lower or deactivate 

the alert sound in situations in which 

pedestrians would not be present. One 

of the methods proposed for mitigating 

the noise caused by stationary EVs and 

HVs would be to allow the vehicle to 

reduce or turn off its sound after the 

vehicle had been stationary for a period 

of five to ten minutes. The agency does 

not believe that a switch that would 

allow the driver to turn off the vehicle’s 

sound is a viable option for controlling 

the noise impact of EVs and HVs when 

stationary but activated because the 

PSEA specifically forbids the agency 

from allowing the driver to deactivate 

the sound; in addition, the agency 

believes that allowing drivers to 

deactivate the sound would compromise 

pedestrian safety. 

As an alternative to requiring a sound 

when the vehicle is activated but not 

moving, Mercedes-Benz USA, LLC 

(Mercedes) stated that the agency 

should instead include acoustic 

specifications for a ‘‘commencing 

motion sound’’ that would be activated 

as soon as the vehicle starts moving.88

Mercedes stated that the specifications 

for such a sound should be the same as 

the specifications for the sound at 10 

km/hr (6 mph). Mercedes stated that the 

sound pressure level of the 

‘‘commencing motion sound’’ should be 

noticeably higher than the sound 

pressure level required for low speeds. 

Volkswagen Group of America, Inc. also 

stated that the agency should require a 

‘‘commencing motion sound’’ instead of 

a sound when the vehicle is activated 

but stationary. We seek comment on 

whether requiring a ‘‘commencing 

motion sound’’ is as an effective 

approach to implementing the 

requirements in the PSEA that an alert 

sound allow pedestrians to discern the 

‘‘presence, direction, location and 

operation’’ of the vehicle as establishing 

minimum sound requirements for when 

the vehicle is activated but stationary. 

2. Reverse 

The agency believes that reverse is a 

critical operating scenario for which the 

agency should issue minimum sound 

level requirements for HVs and EVs to 

provide acoustic cues to pedestrians to 

prevent pedestrian collisions and to 

satisfy the requirements of the PSEA. 

Requirements for the reverse operation 

of EVs and HVs will ensure that these 

vehicles provide sound cues to 

pedestrians so pedestrians will be able 

to avoid these vehicles when the 

vehicles are backing out of parking 

spaces or driveways. 

Several manufacturers in meetings 

with NHTSA staff stated that minimum 

sound requirements for EVs and HVs 

operating in reverse were not necessary 

because the agency’s proposed 

amendments to FMVSS No. 111, Rear 

Visibility, as required by the Cameron 

Gulbransen Kids Transportation Safety 

Act, would allow drivers to see 

pedestrians while backing and thus 

avoid collisions. NHTSA’s proposed 

amendments to FMVSS No. 111, while 

intended to address vehicle collisions 

with pedestrians while backing, do not 

fully ensure that EVs and HVs will not 

experience higher rates of pedestrian 

collisions than ICE vehicles while 

backing. 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. If 

EVs and HVs do not produce audible 

sound levels during reverse operations, 

pedestrians, especially those who are 

blind and visually impaired, would not 

have the opportunity to avoid collisions 

with backing vehicles because they 

would not be able to tell that they are 

being threatened by a backing vehicle. 

NHTSA’s report on the incidence 

rates of crashes between HVs and 

pedestrians found 13 collisions with 

pedestrians when a HV is backing. The 

difference between the incidence rates 

of HVs involved in pedestrian crashes 

while backing and the incidence rate of 

ICE vehicles involved in pedestrian 

crashes while backing was not 

statistically significant. We do not 

believe that the lack of a statistically 

significant difference in incidence rates 

between ICE vehicles and HVs involved 

in pedestrian crashes while backing can 

be attributed to the absence of a safety 

problem related to a vehicle’s noise 

level during this operating condition. As 

discussed above, the absence of a 

difference in the incidence rates in 

backup pedestrian crashes between ICE 

vehicles and HVs is, the agency 

believes, due to the low penetration of 

these vehicles into the fleet and the 

sample size of HVs and EVs in the State 

Data System. Also, backing incidents 

with pedestrians may tend to be 

underreported because they occur in 

parking lots, garages, and drive ways, as 

well as other ‘‘off roadways’’ that 

traditionally have not been captured by 

existing data collection systems. 

NHTSA believes that the PSEA 

requires the agency to set minimum 

sound requirements for the backing 

scenario for the same reason that the 

agency believes that minimum sound 

requirements are necessary for the 

stationary but activated condition. The 

PSEA requires minimum sound level 

requirements promulgated by NHTSA to 

allow pedestrians to discern vehicle 

presence and operation. A vehicle 

moving in reverse is unquestionably 

operating, thus a minimum sound level 

is required for this condition. 

The PSEA also requires that the 

minimum sound level requirements 

promulgated by NHTSA allow 

pedestrians to discern the direction of 

the vehicle. This language also indicates 

that the PSEA requires any standard to 

establish minimum sound requirements 


tkelley on DSK3SPTVN1PROD with 
2826 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

89The agency is aware that a vast majority of 

vehicles that are equipped with an electric motor 

to provide additional motive power when the 

vehicle is accelerating are equipped with idle-stop. 

For a discussion of why the agency has chosen not 

to require vehicles equipped with idle-stop that are 

not capable of propulsion by a means other than the 

vehicle’s ICE to meet the minimum sound level 

requirements in this proposed standard see Section 

VII.C.5. 

90The PSEA specifically excludes trailers from 

the scope of the required rulemaking. 

for when the vehicle is operating in 

reverse. 

3. Acceleration and Deceleration 

Section 5 of the proposed regulatory 

text would ensure that sounds produced 

by EVs and HVs that meet the 

requirements of this proposal will allow 

pedestrians to determine when a vehicle 

is accelerating or decelerating. Pitch 

shifting is the sound characteristic that 

pedestrians currently associate with an 

accelerating vehicle based on the 

sounds produced by an ICE vehicle. The 

agency included requirements for pitch 

shifting in S5 to ensure that components 

of the sounds produced by EVs and HVs 

moved along the frequency spectrum in 

a manner similar to those of ICE 

vehicles as vehicle speed increases. 

Pitch shifting will also denote that the 

vehicle is decelerating. The sound 

pressure level in each one-third octave 

band required in S5 changes as speed 

increases, leading to an increasing 

overall sound pressure level that 

corresponds to the behavior of an ICE 

vehicle. Thus, in addition to the 

acoustic cues provided by pitch shifting, 

pedestrians will be able to tell if an EV 

or HV is accelerating or decelerating 

based on the increase or decrease in 

sound emitted from the vehicle, just as 

they would be able to in the case of an 

ICE vehicle. 

The agency did not include a separate 

acoustic measurement procedure for 

acceleration and deceleration because 

we believe that the requirements for 

pitch shifting and the increase in overall 

sound level as the vehicle increases 

speed (or the decrease in sound level as 

the vehicle decelerates) will provide 

enough information so that pedestrians 

will be able to determine when EVs and 

HVs are accelerating and decelerating. 

The agency also decided not to include 

acoustic measurement procedures for 

acceleration and deceleration because of 

concerns about the feasibility of testing 

in these conditions. It is difficult for 

even an experienced test driver to 

repeatedly achieve and maintain a 

specific rate of acceleration or 

deceleration over the distance used in 

the proposed test procedure. Given the 

difficulty of ensuring repeatable results 

of an acoustic test measuring 

acceleration and the fact that 

information about changes in vehicle 

speed is provided by pitch shifting and 

increases and decreases in sound 

pressure level corresponding to changes 

in vehicle speed, NHTSA decided that 

the test procedure did not need to 

include a dynamic test for acceleration 

or deceleration. 

4. Constant Speed 

The agency is proposing 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/hr (6 mph), 20 km/hr (12 mph) 

and 30 km/hr (18 mph). The agency’s 

proposal would ensure EVs and HVs 

produce sound that is sufficient to allow 

pedestrians to detect these vehicles at 

all speeds between 0 and 10 km/hr (6 

mph), 10 km/hr (6 mph), 20 km/hr (12 

mph), and 30 km/hr (18 mph) by 

requiring that the minimum sound 

levels be attained for all speeds between 

these test speeds. The proposal contains 

minimum acoustic requirements up to 

the speed of 30 km/hr (18 mph) because, 

for the reasons discussed in Section 

VII.E.3 of this notice, the agency 

believes that this is the appropriate 

cross over speed. Manufacturers have 

suggested in meetings with the agency 

that the test procedure for sound 

measurement should only specify a pass 

by test at 10 km/hr (6 mph) because, 

according to manufacturers, this is the 

speed at which the sound levels 

produced by ICE vehicles and EVs and 

HVs differ the most. The agency 

believes that it is 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 

for which requirements are specified. 

C. Application 

1. The Definition of Hybrid Vehicle 

The PSEA defines hybrid vehicle as a 

vehicle with more than one means of 

propulsion. The agency has concluded 

that the definition in the PSEA requires 

the agency to apply the standard only to 

hybrid vehicles that are capable of 

propulsion in any forward or reverse 

gear without the vehicle’s ICE operating. 

Under the agency’s interpretation of the 

definition of hybrid vehicle in the 

PSEA, more than one means of 

propulsion means more than one 

independent means of propulsion. This 

proposed definition of hybrid vehicle 

would exclude from the application of 

the proposed standard those vehicles 

that are equipped with an electric motor 

that runs in tandem with the vehicle’s 

ICE to provide additional motive power 

when the vehicle is accelerating.89

Because the ICE is always running 

when these vehicles are in motion on 

hybrids that employ the electric engine 

to provide additional power when 

accelerating, the fact that these vehicles 

may not provide sufficient sound for 

pedestrians to detect them cannot be 

attributed to the vehicle’s propulsion 

source. If a pedestrian cannot hear this 

type of vehicle it is because of the 

quietness of the vehicle’s ICE. 

Therefore, we believe that it is most 

appropriate to address vehicles that are 

equipped with an electric motor that 

provides assistance to the ICE when the 

vehicle is accelerating in the report to 

Congress regarding the safety need to 

establish minimum sound requirements 

for quiet ICE vehicles required by the 

PSEA. 

The agency would also like to note 

that the definition of ‘‘hybrid vehicle’’ 

in the PSEA is not limited to hybridelectric vehicles. Thus, the standard 

would apply to hybrid vehicles that 

operate using hydraulic propulsion 

independently of the vehicle’s ICE. 

2. Vehicles With a GVWR Over 10,000 

Pounds 

NHTSA is proposing that the acoustic 

specifications in Section XIII apply to 

all hybrid and electric motor vehicles 

covered by the PSEA, including all 

hybrid and electric passenger cars, 

multipurpose vehicles, trucks, buses, 

low-speed vehicles and motorcycles.90

Across the entire fleet (ICE, hybrid, 

and electric vehicles included), heavy 

vehicles have a lower pedestrian crash 

rate than light vehicles (10,000 pounds 

and less). Only 0.3 percent of all heavy 

vehicle crashes involved pedestrians 

while 0.59 percent of all light vehicle 

crashes involve pedestrians. The 

pedestrian crash rate of heavy vehicles 

involved in low-speed maneuvers is 

also lower than that of light vehicles. 

Only 0.42 percent of all heavy vehicle 

crashes at low speeds involved 

pedestrians while 0.80 percent of all 

low speed light vehicle crashes involve 

pedestrians. 

NHTSA was not able to determine a 

separate pedestrian crash rate for hybrid 

and electric heavy duty vehicles based 

on the data available in the State Data 

System. The sample of all crashes of 

hybrid and electric heavy vehicles in 

the State Data System is extremely 

limited and the State Data System did 

not, when it was examined, contain any 

incidents of hybrid or electric heavy 

vehicle pedestrian crashes. The agency 


tkelley on DSK3SPTVN1PROD with 
Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2827 

91 In its comments to the Notice of Intent to 

Prepare an Environmental Assessment (NOI) that 

the agency issued to solicit comments on the 

environmental consequence of this rulemaking, 

Hino Motors, Ltd. stated that it is planning on 

introducing a heavy-duty hybrid truck that is 

capable of propulsion using only the electric motor. 

Hino, however, stated that even when the truck is 

being propelled by the electric motor the ICE will 

remain on in order to power auxiliary systems. 

Comment of Hino Motors Ltd. available at 

www.regulations.gov, Docket No. NHTSA–2011– 

0100–0015. 

believes that the lack of crash data on 

hybrid and electric heavy vehicles is 

due to the very low market penetration 

of these vehicles at the present time. 

Therefore, the agency attributes the lack 

of any hybrid or electric heavy vehicle 

pedestrian crashes not to the fact that 

these vehicles provide sufficient sounds 

levels to allow safe pedestrian detection 

but instead to the fact that these 

vehicles are not present in the fleet in 

any significant numbers. The agency 

believes that it is reasonable to assume 

that as hybrid and electric heavy 

vehicles achieve a higher penetration 

into the vehicle fleet that the difference 

between the crash rates for hybrid and 

electric heavy vehicles and ICE heavy 

vehicles will be similar to the difference 

in crash rates between light hybrid and 

electric vehicles and light ICE vehicles. 

We note that the PSEA did not 

exclude vehicles with a GVWR over 

10,000 pounds from the scope of the 

required rulemaking. We believe 

Congress intended the agency to be 

proactive in addressing the safety 

problem posed by quiet hybrid and 

electric heavy vehicles before hybrid 

and electric heavy vehicle pedestrian 

crashes begin to show up in crash data 

bases in significant numbers. In other 

words, through the passage of the PSEA, 

Congress has determined that there is a 

safety need for HVs and EVs of various 

sizes to produce a minimum sound 

level. 

The agency recognizes that there are 

some challenges in including vehicles 

with GVWR over 10,000 lbs in the 

current rulemaking. The agency has not 

determined the extent to which hybrid 

heavy vehicles produce less sound than 

their traditional ICE peer vehicles. The 

agency also is not aware of the extent to 

which hybrid electric vehicles with a 

GVWR of over 10,000 lbs are capable of 

propulsion using only electric power 

without the ICE running.91 Heavy 

vehicle manufacturers, in their 

comments on our NOI, stated that to the 

extent that heavy vehicles are not 

capable of propulsion solely by some 

means other than the vehicle’s ICE, they 

should be exempt from the requirements 

of this proposal. 

While the agency is today proposing 

to include heavy vehicles as part of this 

rulemaking, we note that the agency 

intends to conduct further research 

before issuing a final rule to determine 

the sound levels produced by heavyduty hybrid and electric vehicles and to 

establish whether the sound 

requirements for light vehicles are also 

appropriate for heavy vehicles. 

The agency is also aware of practical 

concerns about acoustic testing of heavy 

vehicles. The agency is aware that there 

are a limited number of noise pads 

necessary for vehicle acoustics testing 

that can accommodate heavy vehicles. 

We seek comment on whether it is 

necessary to test heavy vehicles on a 

noise pad meeting the requirements of 

ISO 10844, Acoustics—Specification of 

test tracks for measuring noise emitted 

by road vehicles and their tires. In the 

alternative the agency is considering 

specifying an acoustic testing surface for 

heavy vehicle testing that is based on a 

typical vehicle test track pavement. 

The agency also has not validated 

whether the sound specifications that it 

has developed based on research 

conducted on light vehicles would 

provide appropriate countermeasure 

sounds for heavy-duty vehicles. We seek 

comment on this issue. 

The agency is aware that many heavy 

and medium duty trucks are equipped 

with backup alarms to provide warning 

when the vehicle is backing. Because we 

do not want to require that these 

vehicles produce additional sound if 

they are already producing sound when 

backing, we would not require vehicles 

with a GVWR over 10,000 pounds to 

meet the acoustic specifications in 

S5.1.2 when backing. Instead, these 

vehicles would only be required to 

produce a sound with an overall sound 

pressure level of 52 A-weighted dB 

when backing. We seek comment on 

this issue. In addition, the agency also 

has yet to determine whether it is 

necessary from a safety perspective for 

pedestrians to differentiate light 

vehicles from heavy vehicles. The 

agency is aware, based on conversations 

with advocacy groups representing 

people that are visually-impaired, that a 

visually-impaired person may wait a 

longer amount of time than normal to 

cross a street after hearing a heavy truck 

pass in order to avoid colliding with a 

trailer that might be attached to the 

truck. 

The agency also seeks comment 

regarding the appropriateness of 

limiting the application of this proposal 

to vehicles with a gross vehicle weight 

rating of 10,000 pounds and less. 

Another regulatory option that the 

agency considered for heavy-duty HVs 

and EVs would require that these 

vehicles produce only a minimum 

sound pressure level rather than the full 

set of acoustic specifications in S5. 

Pending planned research on the sounds 

emitted by heavy vehicles, ICE, HV, and 

EV, the agency has tentatively 

concluded that applying the full 

acoustic specifications that the agency 

intends to apply to light vehicles to 

heavy vehicles would better fulfill the 

requirements of the PSEA. 

3. Electric Motorcycles 

The agency has tentatively concluded 

that the minimum sound level 

requirements in S5 proposed in this 

notice should apply to electric 

motorcycles (we are not aware of the 

existence of any hybrid motorcycles). 

Motorcycles are not specifically 

excluded by the PSEA. Also, the agency 

has yet to determine that these vehicles 

provide sound levels that are sufficient 

to allow pedestrians to detect these 

vehicles in time to avoid collisions. 

Table 10 shows the number of 

collisions between motorcycles and 

pedestrians from 2000 until 2008. This 

data was obtained from the State Data 

System. Because the State Data System 

does not include any data regarding the 

power source used by motorcycles, the 

agency was not able to determine if the 

incidence rate of collisions between 

pedestrians and electric motorcycles is 

different between the incidence rate of 

collisions between pedestrians and 

motorcycles with ICEs. 


tkelley on DSK3SPTVN1PROD with 
2828 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

92BMW’s comments on the NOI. Available at, 

www.regulations.gov, Docket No. NHTSA–2011– 

0100–0020. 

93MIC submitted measurements of overall sound 

pressure level of two electric vehicle models 

recorded at 8 km/hr (5 mph) and 16 km/hr (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. 

TABLE 10—PRELIMINARY RESULTS OF MOTORCYCLE CRASHES

[16 States during 2000–08] 

Backing 

entering/exit 

parking spots, 

turning, 

starting, and 

slowing 

Straight 

moving and 

other normal 

speeds 

Total 

Pedestrian crashes ...................................................................................................................... 55 438 493 

Other crashes and missing data ................................................................................................. 20,669 90,371 111,040 

Total ...................................................................................................................................... 20,724 90,809 111,533 

As with heavy-duty vehicles, there are 

challenges in establishing minimum 

sound levels for electric motorcycles in 

this rulemaking. The agency has not 

determined the extent to which electric 

motorcycles have a greater risk of 

collisions with pedestrians than 

motorcycles with ICEs or the extent to 

which electric motorcycles are quieter 

than ICE motorcycles of the same type. 

The agency has not measured any 

motorcycles according to the procedures 

contained in this proposal so the agency 

has yet to determine whether the 

measurement procedure used to 

measure sound emitted by 4-wheeled 

vehicles would be appropriate for 

motorcycles. 

BMW of North America, LLC (BMW), 

in its comments on the NOI (discussed 

in Section VI.G. above), submitted crash 

data on incidents of motorcycle 

collisions with pedestrians. BMW stated 

that based on the number of crashes 

between motorcycles and pedestrians 

and the percentage of pedestrian crashes 

involving motorcycles, there is no safety 

need for minimum sound requirements 

for electric motorcycles. BMW cited 

several different sources of data to 

illustrate the low rates of crashes 

between motorcycles and pedestrians. 

2009 statistics from the New York 

Department of Motor Vehicles show that 

approximately 0.4 percent of 

pedestrian/motor vehicle collisions 

involved motorcycles.92 Data from the 

FARS for the period between 2005 and 

2009 shows that only 0.7 percent of the 

pedestrian fatalities during that period 

involved motorcycles colliding with 

pedestrians. Data from the NHTSA’s 

General Estimates System (GES) for the 

same time period shows that 1.07 

percent of the pedestrians injured in 

motor vehicle crashes were injured in 

crashes involving motorcycles. 

Both BMW and the Motorcycle 

Industry Council (MIC) stated that 

because of unique attributes of 

motorcycles, there is no safety need for 

NHTSA to establish minimum sound 

levels for electric motorcycles. 

According to 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. 

Both BMW and MIC stated that 

adding a speaker system to a motorcycle 

could involve technical challenges not 

present for other vehicles. MIC and 

BMW claimed that it would be more 

difficult to add a speaker to a 

motorcycle than a passenger car because 

there is less space available on a 

motorcycle for a speaker system, the 

weight of the system would be a larger 

percentage of the vehicle’s weight, 

which could affect low-speed stability, 

energy consumption by the speaker 

system would have a greater impact on 

a vehicle’s range, and the price of 

installing the system would be higher 

than that for other vehicles. MIC and 

BMW also claimed that electric 

motorcycles should not be subject to the 

minimum sound level requirements in 

this proposal because electric 

motorcycles are not quiet.93

The agency acknowledges that 

establishing minimum sound 

requirements for electric motorcycles 

raises unique issues that are not present 

for other light vehicles. The agency, 

however, notes that because this 

proposal is technology neutral, it would 

be possible for electric motorcycles to 

meet the requirements of this proposal 

without the use of a speaker system. The 

agency seeks comment on whether the 

minimum sound level requirements in 

this proposal should apply to electric 

motorcycles. The agency seeks comment 

on the crash risk to pedestrians and 

pedalcyclists posed by electric 

motorcycles and the cost of the proposal 

as applied to these vehicles. 

4. Low-Speed Vehicles 

The agency has tentatively concluded 

that low-speed vehicles (LSVs) must 

meet the requirements in this proposal. 

While the agency expects that LSVs that 

run via an electric motor are extremely 

quiet, the agency has not conducted any 

acoustic measurements of these vehicles 

to determine the amount of sound they 

produce. The agency has very limited 

real-world data on crashes involving 

LSVs so the rate at which these vehicles 

are involved in pedestrian collisions is 

unknown. The agency has not yet 

determined the extent to which 

minimum sound levels developed for 

light vehicles would be appropriate for 

LSVs. The agency seeks comment on 

whether the requirements in this 

proposal should apply to LSVs. 

5. Quiet ICE Vehicles 

The agency does not intend to require 

a minimum sound level for quiet ICE 

vehicles in this rulemaking. The agency 

is aware that, similar to HVs and EVs, 

some ICE vehicles may pose a risk to 

pedestrians because of the low level of 

sound that they produce when operating 

at low speeds. The PSEA requires the 

agency to study and report to Congress 

whether there is a need for the agency 

to apply the minimum sound 

requirement established for HVs and 

EVs to ICE vehicles so that these 

vehicles can be readily detected by 

pedestrians. If, after the study, the 

agency determines that there is a safety 

need to apply these minimum sound 

requirements to quiet ICE vehicles, 

NHTSA is required to initiate a 

rulemaking to do so. The agency is also 

aware that many manufacturers intend 


tkelley on DSK3SPTVN1PROD with 
Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2829 

94 Vehicles equipped with an idle stop function 

shut down or slow the vehicle’s engine when the 

vehicle comes to a stop. Because the vehicle’s 

engine shuts off, the vehicle is no longer providing 

any acoustic cues to pedestrians to indicate its 

presence. 

95The agency’s research to develop the minimum 

specifications for alert sounds for hybrid and 

electric vehicles is discussed in greater detail in the 

agency’s report ‘‘Research on Minimum Sound 

Specifications for Hybrid and Electric Vehicles.’’. 

Available at Docket No. NHTSA–2011–0148–0048. 

96American Association of State Highway and 

Transportation Officials, A Policy on Geometric 

Design of Highways and Streets, Chapter 3 Elements 

of Design (2004). 

97See footnote 5. 

98 Green (2000) How Long Does It Take to Stop? 

Methodological Analysis of Driver Perception-Brake 

Times.’’ Transportation Human Factors 2(3) 195– 

216. 

to make idle stop technology available 

on ICE vehicles in the near future.94 The 

agency realizes that the introduction of 

ICE vehicles equipped with idle stop 

means that there will be ICE vehicles 

that will be effectively silent when the 

vehicle is not moving. While the agency 

does not propose, in this rulemaking, to 

require that ICE vehicles equipped with 

idle stop produce a minimum sound 

level while at idle, the agency plans to 

consider whether vehicles equipped 

with idle stop have a greater risk of 

collision with pedestrians than vehicles 

that produce a sound at idle with an eye 

toward a rulemaking in the future to 

address this issue. 

D. Requirements 

The agency’s preferred method for 

establishing minimum sound 

requirements for EVs and HVs uses a 

detectability model to determine the 

sound that the vehicle needs to produce 

to allow pedestrians to detect the 

vehicle at a given distance. The sounds 

that meet the minimum requirements 

using the detection model would be 

similar to those described in Alternative 

4 in the NOI. 

1. Acoustic Parameters Designed 

According to a Detectability Model 

The two critical aspects of the 

minimum sound level requirements in 

this proposed approach are that the 

sound be detectable and recognizable. 

This approach addresses the 

detectability aspect of the minimum 

sound level requirements by 

determining the sound specifications 

needed for a pedestrian to detect a 

vehicle at a safe distance and by 

examining the typical ambient sound 

profile to determine which one-third 

octave bands contribute the most to a 

pedestrian’s ability to detect vehicles.95

This proposal addresses the pedestrian 

recognition aspect of the minimum 

sound requirements by insuring that the 

sound has aspects that allow 

pedestrians to recognize the sound as 

being produced by a motor vehicle and 

by allowing the pedestrian to recognize 

the mode of operation of the vehicle. 

The agency developed the minimum 

detectability requirements for HVs and 

EVs by first determining the distance at 

which a pedestrian would need to hear 

a vehicle in order to make a decision 

about whether it was safe to cross the 

street. Thus, the distance at which a 

pedestrian would need to hear a vehicle 

is at least as long as the vehicle’s 

stopping distance. At distances shorter 

than a vehicle’s stopping distance the 

pedestrian must be able to hear the 

vehicle, otherwise a situation might 

develop in which the pedestrian steps 

off the curb (because s/he cannot hear 

the vehicle) and the driver of the vehicle 

would be unable to stop the vehicle in 

time to avoid a collision with the 

pedestrian. 

The agency set the distance at which 

it believes that the pedestrian should be 

able to hear an approaching HV or EV, 

also referred to as the detection 

distance, using stopping sight distances 

computed from the guide on highway 

design 96 of the American Association of 

State Highway Transportation Officials 

(AASHTO). Stopping sight distance is 

the distance that enables a vehicle 

traveling at or near the design speed to 

stop before reaching an object in its 

path. The stopping sight distance is the 

sum of the driver reaction distance and 

the braking distance. The driver 

reaction distance is the distance 

traveled by a vehicle from the instant 

the object becomes visible to the driver 

to the instant the driver applies the 

brakes. The braking distance is the 

distance needed to stop the vehicle once 

the driver applies the brakes. The sight 

distance for a vehicle traveling at the 

design speed and on a level road can be 

computed with the following formula: 

Where: 

t = brake reaction time, s 

V = design speed, km/hr 

a = deceleration rate, m/s2

Drivers typically brake at an average 

emergency deceleration of about 5.4 

m/s2 on dry roads. A comfortable 

deceleration for most drivers braking on 

wet surfaces is 3.4 m/s2. Drivers’ 

expectation plays a role in driver 

reaction time. Mean reaction time to 

unexpected, but common, events is 

about 1.25 seconds. Mean reaction time 

for surprise events, such as an object 

suddenly moving into the drivers’ path 

is about 1.5 seconds. A longer reaction 

time, of 2.5 seconds would consider the 

capabilities of almost all drivers, 

including older drivers and distracted 

drivers. 

The values used as the basis for this 

proposal are 5.4 m/s2 for deceleration 

and 1.5 seconds for brake reaction time. 

We chose the 5.4 m/s2 deceleration rate 

corresponding to dry pavement braking 

because most of the pedestrian crashes 

that the agency identified occurred in 

clear conditions 97 and the slower 

deceleration rate for wet pavement, we 

believe, would result in a sound profile 

that is unnecessarily loud for most 

conditions. The agency believes that 1.5 

seconds is an appropriate value to use 

for driver reaction time (to stopped 

objects) because this represents the 

reaction time of most drivers for 

surprise events.98

Based on calculations using these 

values, the agency determined that the 

desired detection distances were 2 

meters in front of the vehicle for 

stationary but activated, 5 m in front of 

the vehicle for the 10 km/hr (6 mph) 

pass by, 11 m for the 20 km/h (12 mph) 

pass-by operation, and 19 m for 30 

km/h (18 mph) pass-by operation. The 

results of this computation were 

rounded up to the nearest meter. Levels 

were increased by 0.5 dB to provide a 

small safety factor and rounded to the 

nearest integer for simplicity. This small 

increase was deemed sufficient due to 

other conservative aspects of the 

estimation, e.g. multiple detection 

opportunities due to the multiple 

components. The agency solicits 

comment on the appropriateness of a 1.5 

second reaction time and 5.4 m/s2

declaration rate in determining the 

desired detection distances. 

Due to a variety of factors that affect 

the manner in which sound moves 

through an environment, it is not 

practical to measure sound with the 

specificity that the agency desires from 

the distances at which pedestrians need 

to be able to detect the sound. 

Atmospheric absorption, ground 

conditions and divergence of sound all 

affect sound measurements conducted 

at distances greater than the two meters 

specified in SAE J2889–1. Acoustic 

measurements conducted at distances 

greater than two meters are not able to 

accurately record a sound’s frequency 

profile at the one-third octave band 

level. Furthermore, because of 

attenuation, a sound’s decibel level 

decreases the further a measurement is 

taken from the sound source. At the 

detection distances that the agency 


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2830 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

99Pedersen et al. White Paper on External Sounds 

of Electric Cars-Guidelines and Recommendations. 

Available at http://media.wix.com/ugd/64a49a_

43313ad70e7c40f43150cf747b2e5c44

.pdf?dn=A520040+-+DSTN+-+White+paper+

electric+cars+-+av122410+-+ECT+LR.pdf. 

100The Presentation that Honda gave at the 

meeting is available on regulations.gov. Docket No. 

NHTSA–2011–0100–0038. 

believes are necessary for pedestrians to 

be able to hear vehicles, the sound 

pressure level sounds produced by 

vehicles begin to approach the ambient. 

As the sound pressure level begins to 

approach that of the ambient sound 

level, it is more difficult to measure the 

frequency composition of the sound. 

Based on the factors discussed above, 

the agency determined that the best 

approach for determining the minimum 

sound level HVs and EVs need to 

produce to ensure safe detectability 

would be to determine what the sound 

level would need to be at two meters 

from the vehicle in order to allow the 

pedestrian to hear the sound at the 

desired detection distance. 

Using the method below, it is possible 

to determine what the sound levels of 

the vehicle will need to be at a distance 

of two meters from the vehicle so that 

pedestrians will be able to detect the 

sound at the desired detection distance. 

The table below depicts how the sound 

produced by the vehicle attenuates 

when measured using the procedure in 

SAE J2889–1. 

TABLE 11—COMPUTATION OF ADJUSTMENT OF SPL (A-WEIGHTED DB) FROM SOURCE TO SAE MICROPHONE LOCATION

Speed, km/hr ......................................................................................................................... 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 ...................................................................................................................... ¥6 .0 ¥12 .2 ¥16 .8 

* Assume effective source is at center of vehicle since propagation is forward. 

** Assume Z = 1.2. 

X represents the distance from the 

source while Y is the distance from the 

source to the microphones in SAE 

J2889–1. Z represents the height of the 

microphone in meters specified in SAE 

J2889–1. The values in the Table 11, 

above, were calculated using the 

formula below assuming a 1.2 meters 

value for Z. 

A critical factor for establishing a 

minimum sound for pedestrians based 

on a desired detection distance is the 

ambient noise environment in which 

the pedestrian is attempting to detect 

the vehicle. The agency selected an 

ambient of 55 A-weighted dB to develop 

the minimum sound level 

specifications. The agency choose an 

ambient sound pressure level of 55 Aweighted dB because that is a level 

representative of a moderate suburban 

ambient where pedestrians would be 

expected to be able to detect vehicles 

based on hearing alone. In conversations 

with the agency during Phase 1 

research, visually-impaired individuals 

indicated that in noisier suburban 

ambient conditions, they would not try 

to cross streets unassisted. The ambient 

levels that the agency measured during 

Phase 1 research for which visuallyimpaired pedestrians would be expected 

to cross using hearing alone were 49.5 

A-weighted dB and 49.8 A-weighted dB. 

In selecting an ambient at which the 

agency expects that pedestrians should 

be able to detect an approaching vehicle 

using their hearing, the agency relied on 

recommendations for quiet vehicle alert 

sound specifications developed by 

Danish acoustics experts.99 In 

developing the recommendations the 

Danish researchers measured different 

ambient levels around Copenhagen. The 

ambient levels in residential areas 

where pedestrians would be expected to 

detect an approaching vehicle using 

their hearing was 55 A-weighted dB. 

In a presentation to NHTSA staff, 

Honda Motor Company (Honda) stated 

that the ambient at which pedestrians 

would reasonably be able to detect 

vehicles using hearing alone is around 

52.5 A-weighted dB.100 Honda based 

this conclusion on a human factors 

approach in which recordings of three 

different ambient sound levels (quiet 

residential, moderate suburban, and 

urban) were played and participants 

were asked whether they would rely on 

hearing alone to detect an approaching 

vehicle. While the study did not include 

any visually-impaired participants, the 

agency agrees that pedestrians—those 

that are visually impaired and others 

that are not—could not be reasonably 

expected to detect approaching vehicles 

in ambient conditions near 60 Aweighted dB. 

The agency believes that a 55 Aweighted dB ambient represents a 

reasonable level below the 60 Aweighted dB ambient (in which 

pedestrians would no longer be able to 

reasonably rely on hearing to detect 

approaching vehicles). 

The spectral distribution of the 

ambient is another factor that affects the 

detectability of an alerting sound. Tonal 

components of an alerting sound in 

portions of the ambient spectrum that 

are not strong contribute to 

detectability. Using a loudness model 

and synthetic ambient that represent a 

typical urban ambient profile in which 

a pedestrian would be attempting to 

detect a vehicle, the agency developed 

minimum sound level requirements for 

selected one-third octave bands. 

In order to aid pedestrian detection 

and recognition of sounds produced by 

EVs and HVs, the agency has tentatively 

concluded that the sound level 

produced by a vehicle will increase 

with an increase in vehicle speed. The 

agency has two goals in increasing the 

vehicle’s sound level as the vehicle 

increases speed. First, increasing the 

vehicle’s sound level as the vehicle 

increases speed will allow pedestrians 

to detect the vehicle from a greater 

distance to correspond to the vehicle’s 

increased sight stopping distance at 

higher speeds and the greater distance 

necessary to stop the vehicle. Second, 

ICE vehicles produce increasing sound 

levels as they accelerate so the sound 

produced by HVs and EVs will mimic 

the behavior of ICE sounds to enhance 

recognition. 

In developing the acoustic 

specifications in this proposal, the 

agency considered one-third octave 

bands from 160 Hz to 5000 Hz. When 

all one-third octave bands from 160 Hz 

to 5000 Hz are set to a minimum audible 

level, it can be demonstrated that, 

relative to the overall sound level, some 


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bands are less efficient at providing a 

detectable signal. That is, bands below 

315 Hz and bands from 630 to 1600 Hz 

increase the overall levels more for the 

same contribution to detection. The 

levels of these bands are indicated by 

arrows in Figure 3. The arrows in the 

figure point to the regions of the 

spectrum that are most effective for 

warning sounds, i.e., those where the 

threshold is not too high and the 

ambient is not too high to mask sounds 

at the threshold. 

Due to masking effects of the ambient 

and potential hearing loss of the 

pedestrian, opportunities for detection 

will be maximized if the 

countermeasure signal contains 

detectable components over a wide 

frequency range; therefore, a minimum 

level is proposed for a set of one-third 

octave bands that includes midfrequency one-third octave bands (315, 

400, and 500 Hz) as well as high 

frequency one-third octave bands (2000, 

2500, 3150, 4000, and 5000 Hz). Low 

frequency bands (below 315 Hz) were 

not considered due to the expected 

strong masking effects of the ambient at 

low frequencies. The agency chose these 

one-third octave bands because these 

bands contributed the most to detection 

without increasing the overall levels of 

the sound. Specifying minimum sound 

pressure level requirements 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 different 

acoustic profiles. Specifications for the 

mid-range frequency bands between 315 

and 500 Hz will assist pedestrians in 

detecting HVs and EVs in ambient noise 

environments such as areas near 

construction activity with a significant 

degree of high frequency signal content. 

Low-frequency bands (below 315 Hz) 

are omitted because they do not 

contribute to detection and the 

likelihood that many practical 

countermeasure devices may not be able 

to produce high level, low-frequency 

sounds. 

In consideration of community noise 

impact, the agency omitted midfrequency bands from 630 to 1600 Hz 

from the acoustic specifications 

because, for the ambient considered, 

these bands contributed more to the 

overall sound level than other bands for 

the same increase in detectability. By 

omitting minimum sound level 

requirements for the one-third octave 

bands in the 630 to 1600 Hz frequency 

range, the agency is able to ensure that 

the alert sounds allow pedestrians to 

safely detect nearby EVs and HVs 

without contributing unnecessarily to 

an increase in overall ambient noise 

levels. 

Table 12 shows the one-third octave 

band frequency requirements for vehicle 

emitted sounds for all of the test 

conditions in S7 of the proposed 

regulatory text. 

TABLE 12—MINIMUM SOUND LEVELS FOR DETECTION

One-third octave band center frequency, Hz Stationary but 

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 


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101The agency notes that the acoustic 

specifications in Table 12 would not necessarily be 

an appropriate method for determining whether ICE 

vehicles are detectable. While the agency intends 

this proposal to be technology neutral, the agency 

recognizes that at least for vehicles that are capable 

of electric only propulsion, manufacturers will have 

to add some sound to the vehicle in order to comply 

with this standard. 

102NHTSA–2011–0148–0025, available at 

www.regulations.gov. 

TABLE 12—MINIMUM SOUND LEVELS FOR DETECTION—Continued 

One-third octave band center frequency, Hz Stationary but 

activated Backing 10 km/h 20 km/h 30 km/h 

3150 ..................................................................................... 37 40 43 49 53 

4000 ..................................................................................... 34 36 39 46 50 

5000 ..................................................................................... 31 34 37 43 48 

Overall A-weighted SPL Measured at SAE J2889–1 PP’ 

line .................................................................................... 49 52 55 62 66 

The agency is not including 

requirements for overall sound pressure 

level in the proposed standard. Because 

each one-third octave band contributes 

to the overall sound pressure level of a 

sound it is possible to determine what 

the sound pressure level of sounds 

meeting the requirements of Table 12 

would be. The overall sound pressure 

level of sounds meeting the 

requirements for each one-third octave 

band listed in Table 12 would be 49 Aweighted dB when is in the stationary 

condition, 52 A-weighted dB when 

backing, 55 A-weighted dB at 10 km/hr 

(6 mph), 62 A-weighted dB at 20 km/hr 

(12 mph), and 66 A-weighted dB at 30 

km/hr (18 mph). 

The agency has tentatively concluded 

that the sound emitted by EVs and HVs 

must meet the minimum sound pressure 

level requirements for every one-third 

octave band listed in Table 12. The 

agency chose to require sounds emitted 

by EVs and HVs to meet minimum 

sound pressure level requirements for 

all of the one-third octave bands listed 

in Table 12 because these one-third 

octave bands all contribute to 

pedestrians’ ability to detect these 

sounds. The agency realizes that 

requiring HVs and EVs to emit sounds 

meeting the minimum sound level 

requirements for every one-third octave 

band listed in Table 12 would make 

these vehicles more detectable than 

current ICE vehicles for some ambient 

noise environments. A majority of the 

ICE vehicles tested during the agency’s 

Phase 2 and Phase 3 research would not 

meet the requirements in Table 12 for 

the one-third octave bands below 2000 

Hz.101 While these vehicles did not 

meet all of the one-third octave band 

specifications in Table 12, these 

vehicles were still considered to be 

detectable under the agency’s detection 

model. The agency’s detection model 

considers a vehicle to be detectable if it 

exceeds the minimum sound pressure 

levels listed in Table 12 for any single 

one-third octave band. A majority of the 

ICE vehicles tested by the agency were 

detectable in at least two one-third 

octave bands for the 10 km/hr (6 mph) 

pass by test. Even though the agency’s 

detection model would consider a 

vehicle to be detectable if it meets one 

of the one-third octave bands levels in 

Table 12, requiring a sound to meet the 

minimum levels in more than one onethird octave band increases the 

likelihood that sound will be detectable 

in a wider range of ambient noise 

conditions. The agency’s detection 

model was created using a specific 

ambient. While the ambient noise 

profile used with the agency’s detection 

model is typical of ambient 

environments in which pedestrians 

would generally be attempting to detect 

HVs and EVs, requiring sounds emitted 

by these vehicles to meet all the onethird octave bands in Table 12 would 

increase the chance that these vehicles 

will be detectable in ambient noise 

environments different from the one 

used in the loudness model. 

The fact that ICE vehicles also 

produce sound in one-third octave 

bands outside those listed in Table 12— 

which may contribute to the 

detectability of these vehicles—makes it 

difficult to compare sounds produced 

by ICE vehicles with specifications for 

synthetic sounds to be emitted by HVs 

and EVs. Because the sounds produced 

by ICE vehicles include signal content 

in a far broader range of frequencies 

than listed in Table 12, we believe the 

proposed minimum one third-octave 

band requirements represent a 

reasonable approach to ensure that HVs 

and EVs are at least as detectable as 

ICEs. The specifications in Table 12 

were developed so that the synthetically 

generated sounds that manufacturers 

add to vehicles to meet the requirements 

of this standard would be detectable, 

recognizable, and would not contribute 

to noise pollution. 

The agency believes that requiring 

EVs and HVs to produce sounds 

meeting the acoustic requirements in 

Table 12 will reduce the risk of crashes 

between EVs and HVs and pedestrians 

to same risk level of crashes between 

ICE vehicles and pedestrians. Numerous 

studies by motor vehicle manufacturers 

and academics have found that sound, 

or lack thereof, influences pedestrians’ 

decisions about when to cross a street. 

The agency’s Phase 2 research showed 

that sounds with certain acoustic 

characteristics were at least as 

detectable to the study participants as 

the sound produced by ICE vehicles. 

Some studies have shown that sounds 

designed using psychoacoustic 

principals are more detectable than the 

sounds produced by ICE vehicles.102 To 

date no studies have linked the increase 

in the detectability of a sound to a 

reduction in the risk of crashes between 

EVs and HVs and pedestrians. 

The agency believes that sounds 

meeting the requirements in Table 12 

will be as detectable as an ICE vehicle. 

If the sound produced by EVs and HVs 

is detectable to pedestrians, they will be 

able to respond to the presence of a 

vehicle thereby avoiding a collision. 

The agency plans to conduct additional 

research before issuing a final rule to 

confirm that sounds meeting the 

requirements in Table 12 will be 

detectable at the distances predicted in 

the detection model. We seek comment 

to improve the specifications in Table 

12 to make the sounds more detectable 

and to increase the effectiveness of the 

specifications in reducing collisions 

between EVs and HVs and pedestrians. 

Requiring EVs and HVs to emit sound 

meeting the minimum levels in every 

one-third octave band in Table 12 will 

also enhance pedestrians’ ability to 

recognize the sounds emitted by EVs 

and HVs because pedestrians associate 

low-frequency signal content with ICE 

vehicles. 

For the reasons discussed above, as an 

alternative to requiring EVs and HVs to 

meet the minimums for every one-third 

octave band listed in Table 12 the 

agency seeks comment on requiring 

these vehicles to emit sounds that meet 

only the one-third octave band 

requirements for 2000 Hz and above. 

The one-third octave band levels in 


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Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2833 

103Public Law 111–373, § 3(b)(3), 124 Stat. 4086 

(2011). 

104See Hastings et al. (2012) ‘‘Research on 

Minimum Sound Specifications for Hybrid and 

Electric Vehicles.’’ U.S. Dept. of Transportation, 

Washington, DC. Available at Docket No. NHTSA– 

2011–0148–0048. 

Table 12 represent a conservative 

approach, from a safety perspective, to 

determining the sound level that an HV 

or EV would need to make in order to 

allow a pedestrian to detect the vehicle 

from a desired safe detection distance. 

Thus, it is possible that pedestrians may 

be able to hear these vehicles at 

distances farther than predicted by the 

agency’s model. The agency plans to 

conduct additional research before 

issuing a final rule to validate the 

assumptions relied upon in determining 

the sound levels contained in Table 12. 

We are seeking comment on the number 

of bands that should contain minimum 

sound level requirements and what 

those minimum sound level 

requirements should be, if the agency 

chooses to restrict the number of onethird bands for which we would require 

a minimum sound pressure level. Along 

with comments on the specifications in 

Table 12, the agency is seeking 

recordings of sounds that manufacturers 

may wish to add to EV and HV vehicles. 

The agency plans to analyze any 

recordings submitted in response to this 

proposal along with other recordings 

made during further research in 

finalizing the acoustic performance 

requirements for the alert sound. For 

more information about submitting 

recordings to the agency along with 

comments please see the instructions for 

public participation in Section XII of 

this proposal. 

The agency seeks comment of the 

possibility of allowing light hybrid and 

electric vehicles to meet the minimum 

sound requirements for the backing 

scenario with a beeping sound similar to 

the sound made by a backing truck. The 

agency has yet to determine that a 

backup beeping sound would be 

appropriate for light vehicles because 

this sound is normally associated with 

backing heavy vehicles and thus many 

not be recognizable as light motor 

vehicle. The agency also seeks comment 

on whether such a sound would be 

annoying to the public. 

The agency is also seeking comment 

on whether we should establish a 

maximum sound level requirement in 

addition to the minimum sound level 

requirements contained in this proposal. 

The PSEA directs NHTSA to ‘‘consider 

the overall community noise impact’’ of 

the specifications contained in this 

proposal.103 One way that the agency 

could address the overall community 

noise impact of this proposal would be 

to establish maximum sound levels for 

hybrid and electric vehicles. We seek 

comment on what the maximum levels 

should be were they to be included in 

the final rule. 

The agency notes that motor vehicle 

manufacturers attempt to limit the noise 

emissions of their vehicles in response 

to customer preferences. The agency 

believes that manufacturers will limit 

the sound output of hybrid and electric 

vehicles so as not to increase the sound 

output of these vehicles beyond the 

minimum levels contained in this 

proposal. The agency is hesitant to 

establish maximum sound levels 

because we do not wish to increase the 

complexity of compliance with the 

standard by establish tolerances that 

manufacturers must meet. 

In October, 2012, representatives from 

Nissan Motor Co., Ltd. (Nissan) 

presented results of the company’s 

research to agency rulemaking staff. 

Nissan conducted a survey to gauge 

costumer acceptance of the sounds 

currently emitted by the Nissan Leaf. 

Nissan also conducted a study to 

evaluate the detectability of different 

sounds. Nissan interviewed blind 

pedestrians to ask them when they 

believed a sound at idle would and 

would not be useful. 

In November, 2012, Ford Motor 

Company (Ford) met with agency 

rulemaking staff to present the results of 

human factors research conducted by 

the company. The experiment included 

both blind and sighted participants. 

During the experiment the participants 

were presented recordings of various 

sounds approaching either from the 

right or from the left. The participants 

were asked to identify when they heard 

the sound and then asked to identify the 

direction from which the sound was 

approaching. Ford compared the 

participants’ ability to detect the sounds 

to the detection distances discussed in 

the agency’s report on sound 

specifications for hybrid and electric 

vehicles.104

2. Recognizability Requirements 

The recognizability approach analyzes 

the sounds produced by ICE vehicles 

and sets the acoustic requirements for 

HVs and EVs so that they would contain 

acoustic characteristics similar to the 

sounds that pedestrians associate with 

current ICE vehicles. 

While the agency believes that the 

mid-range frequency specifications in 

Table 12 will contribute to pedestrians’ 

ability to recognize the sounds as being 

produced by a motor vehicle, we believe 

that the requirements for low-frequency 

broadband and low-frequency tones in 

the agency’s recognizability 

requirements adequately ensure that 

pedestrians will be able to recognize 

these sounds. Further, the lowfrequency components in many ICE 

sounds may be masked by the ambient 

level chosen for our model. However, 

this low-frequency content contributes 

to recognition because it is associated 

with the sound perceived by the 

pedestrian in lower ambients and that 

association is remembered. Therefore, 

this low-frequency content does not 

need to be detectable in every ambient 

to contribute to the recognizability of a 

sound. Consistent with the assumption 

that ICE vehicles are recognizable, low 

frequency content of alert sounds for 

HVs and EVs does not need to be 

detectable in the 55 dB ambient to 

ensure that these vehicles can be 

recognized by pedestrians. 

Recognition includes two aspects: (1) 

recognition that the sound is emanating 

from a motor vehicle that may pose a 

safety risk to the pedestrian, and (2) 

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. Sounds that 

contain both broadband noise and tones 

can produce sounds that are recognized 

as vehicles. Sounds that contain only 

high frequencies have a synthetic (and 

unpleasant) character. Sounds with 

lower frequency tones and noise sound 

more like the sounds typically 

associated with a conventional (ICE) 

motor vehicle. 

While the one-third octave band 

requirements listed in Table 12 include 

some requirements for lower frequency 

signal content for vehicle emitted 

sounds, low frequency tones are 

necessary to provide additional cues to 

allow pedestrians to recognize these 

sounds. Tones are not necessary to 

achieve a certain sound pressure level 

in a one-third octave band. A vehicleemitted sound would be able to meet a 

minimum sound pressure level 

requirement for a one-third octave band 

if it contained broadband noise at a high 

enough level. In addition to the 

detectability requirements in Table 12, 

our proposal requires that the lowest 

tone of the vehicle emitted sound must 

have a frequency not greater than 400 

Hz. Low-frequency tones are the tones 

that contribute the most to 

recognizability so tones less than 2000 

Hz contribute to recognition while tones 

above 2000 Hz contribute to detection. 

ICE vehicles produce low, mid, and 

high-frequency tones. The lowest 

frequencies are related to the 


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combustion frequency of the engine. 

The low frequency components 

contribute to the perceived power of the 

vehicle. Low-frequency tones in 

simulated sounds will contribute the 

most to recognition because these are 

closer in frequency to the low order 

harmonics of the engine fundamental. 

The agency is also proposing a general 

requirement for broadband noise in the 

requirements designed to ensure that EV 

and HV emitted sounds are 

recognizable. Sounds produced by 

current ICE vehicles are broadband in 

nature, meaning that the sounds have 

some minimal signal content across a 

wide part of the frequency spectrum. 

Also, it is easier for a pedestrian to tell 

which direction a sound is coming from 

if the sound contains broadband 

characteristics. (Broadband sounds are 

also easier for pedestrians to localize 

than narrow band sounds.) In order for 

sounds emitted by EVs and HVs to 

provide sufficient broadband content to 

allow pedestrians to recognize these 

sounds as being produced by a motor 

vehicle, the agency is proposing to 

require these sounds to have some 

measurable content in each one-third 

octave band from 160 Hz to 5000 Hz. 

This means that sounds emitted by EVs 

and HVs are required to possess some 

acoustic signal content above 0 Aweighted dB at all frequencies in the 

one-third octave bands between 160 Hz 

to 5000 Hz. 

In the event that the agency decides 

to only require minimum sound 

pressure levels in Table 12 for the onethird octave bands of 2000 Hz and 

above, the agency would retain 

requirements for broadband signal 

content in the one-third octave bands 

between 315 Hz and 500 Hz to ensure 

that the sound retained aspects that 

contribute to recognizability. In order to 

ensure that the sounds produced by EVs 

and HVs are recognizable to pedestrians, 

the agency is proposing some minimum 

low frequency signal content. In the 

event that the agency decides to limit 

the requirements in Table 12 to onethird octave bands above 2000 Hz, 

sounds produced by HVs and EVs 

would be required to emit a sound with 

a sound pressure level of 30 A-weighted 

dB in the one-third octave bands 

between 315 Hz and 500 Hz. The 30 Aweighted dB level corresponds to the 

one-third band levels measured for a 

quiet urban ambient during the agency’s 

Phase 2 research. The agency would not 

expect this signal content to be 

detectable in the 55 dB ambient; it 

would only be present to assist 

pedestrians in recognizing the sound. 

The agency seeks comment on the 

minimum sound pressure levels of low 

frequency content that should be 

included in the agency’s recognizability 

requirements. 

The agency recognizes that the 

speakers that manufacturers may wish 

to use on EVs and HVs to meet the 

minimum sound requirements 

contained in this proposal may not be 

able to produce tones as low as 160 Hz. 

The agency believes that most of the 

speakers that manufacturers wish to use 

will be capable of producing at least 

some signal content in the 160 Hz onethird octave band. The agency solicits 

comment on the issue of whether 

speakers that manufacturers may wish 

to use to meet the requirements of this 

proposal are capable of producing any 

measurable signal content in the 160 Hz 

one-third octave band. The agency also 

solicits comment on the cost of a 

speaker system that is able to reproduce 

some measurable content at the 160 Hz 

one-third octave band versus a speaker 

system that is only capable of producing 

sound above 315 Hz. 

Pitch shifting is also a critical element 

to aid in pedestrian recognition of 

vehicle sounds. Pitch shifting is the 

movement of the tones of a sound along 

the frequency scale. Pitch shifting 

mimics the behavior of an ICE vehicle 

as it increases speed. Based on analysis 

of sounds produced by ICE vehicles the 

agency believes that the pitch of a 

vehicle sound should increase with 

increasing vehicle speed, or decrease 

with decreasing vehicle speed by at 

least one percent per km/hr of vehicle 

speed. 

3. Prohibition Against Modifying a 

Vehicle’s Sound 

The PSEA also requires that the 

FMVSS developed in this rulemaking 

‘‘prohibit manufacturers from providing 

any mechanism for anyone other than 

the manufacturer or the dealer to 

disable, alter, replace, or modify the 

sound or set of sounds, except * * * in 

order to remedy a defect or noncompliance.’’ Our proposal extends this 

prohibition to any entity subject to 

NHTSA’s authority (manufacturers, 

distributors, dealers, and repair 

businesses), allows for repair of a 

vehicle malfunction (in addition to the 

PSEA’s defect and non-compliance), 

and also prohibits any entity subject to 

our authority from providing the means 

to defeat or change the sound emission 

to any other person, except for repair of 

a malfunction associated with the 

vehicle’s sound emission. The goal of 

this section is to avoid the situation 

where vehicle sounds are changed, at 

the request of the consumer, to 

something individualized and no longer 

associated with the specific make/model 

of motor vehicle, or indeed even 

recognizable as a motor vehicle at all. 

4. Phase-in Schedule 

Lastly, the PSEA directs NHTSA to 

include a phase-in schedule for 

compliance with the new FMVSS. ‘‘The 

Secretary shall promulgate the required 

motor vehicle safety standard pursuant 

to this subsection no later than 36 

months after the date of the enactment 

of this Act.’’ The Act further requires, at 

section 3(c), a phase-in period for 

compliance, with full compliance of all 

motor vehicles subject to the standard 

manufactured on or after the September 

1 of the calendar year that begins three 

years after the date of the final rule. For 

example, if the final rule were issued on 

January 4, 2014, full compliance would 

be required for all subject motor 

vehicles manufactured on or after 

September 1, 2018. The maximum 

duration of the phase-in period would 

therefore be January 4, 2014 through 

September 1, 2018. Vehicle model years 

typically begin September 1, for 

example, the 2014 model year will run 

from September 1, 2013 to August 31, 

2014. In light of this traditional 

production schedule, we tentatively 

conclude it would be unreasonable to 

require manufacturers to build any 

vehicles to the new FMVSS by 

September 1, 2014, for the 2015 model 

year, in this example. However, most 

manufacturers are now involved in 

planning some form of sound emission 

for vehicles they know will be affected 

by the new standard. Changes to any 

sounds provided before the final rule 

date will likely be made by software, not 

hardware, changes and manufacturers 

will be familiar with the test procedure 

through the use of the SAE J2889–1. 

We therefore tentatively conclude that 

the following phase-in schedule is 

reasonable for manufacturers and allows 

the fastest implementation of the 

standard for pedestrian safety: 

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 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 the year 

that begins three years after the date that 

the final rule is issued. 

Small volume manufacturers will not 

need to comply with the requirements 

of this proposal until the end of the 

phase-in period. We seek comment on 

the appropriateness of this proposed 

schedule. 


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Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2835 

105The agency recognizes that SAE published an 

updated version of J2889–1 in May 2012. We have 

not yet evaluated this new version, but intend to 

do so before publishing a final rule. 

We have not included provisions for 

carry-forward credits in the proposed 

regulatory text; however, we seek 

comment on allowing carry-forward 

credits in the phase-in schedule to give 

manufacturers flexibility in meeting the 

phase-in requirements. 

E. Compliance Test Procedure 

The compliance test procedure 

proposed in this notice is consistent 

with the Society of Automotive 

Engineers Surface Vehicle Standard 

J2889–1, ‘‘Measurement of Minimum 

Noise Emitted by Road Vehicles,’’ 

September 2011.105 Several sections of 

the SAE Standard are incorporated by 

reference into our proposed FMVSS. 

This industry standard was developed 

for use by manufacturers to test their 

own vehicles. The compliance test 

procedure proposed by the agency must 

deviate, however, in some respects so 

that it can be used by a third-party 

testing entity with little or no detailed 

knowledge of all of the vehicle’s 

systems and their development. 

Some particular differences between 

the SAE J2889–1 and our proposed test 

procedure are: 

• This proposal is limited to outdoor 

testing, while the SAE standard has an 

alternative for indoor testing. 

• The SAE procedure contains 

different methods for different vehicle 

operating modes, and for vehicles fitted 

with external sound generating systems 

versus vehicles without. Our proposal is 

uniform for all vehicles and stated in 

technology neutral terms so that it can 

be applied to any new motor vehicle to 

which the requirements in this proposal 

would apply. 

1. Test Condition 

SAE J2889–1 paragraph 6.2 specifies 

the ambient weather conditions under 

which the acoustics testing should be 

conducted. The ambient weather 

conditions should be measured at the 

microphone height. SAE J2889–1 

specifies an ambient temperature 

between 5 degrees Celsius (°C) (41 

degrees Fahrenheit (°F)) and 40 °C (104 

°F). The ambient weather conditions are 

restricted to ensure accurate repeatable 

measurement. SAE J2889–1 states that 

the ambient temperature may need to be 

restricted to a narrower temperature 

range so that all key vehicle functions 

can be run in their quietest state per the 

manufacturer’s specifications. 

The agency has found during the 

course of research conducted in support 

of this rulemaking that tests that occur 

within the temperature range specified 

in SAE J28889–1 can produce divergent 

results when a vehicle is tested at 

different temperatures. In high ambient 

temperatures, the battery cooling fan on 

pure electric vehicles activates 

intermittently while the vehicle is 

operating. The agency has 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 believes that it has 

addressed repeatability issues caused by 

battery cooling fans, as stated in SAE 

J2889–1, it is possible that there are 

other vehicle functions that produce 

varying sound levels based on the 

ambient temperature level. Therefore, 

we are soliciting comment on the other 

vehicle functions that produce varying 

noise levels at different ambient noise 

levels. The agency is also soliciting 

comment on specifying a low ambient 

temperature for acoustics testing of 

between 5 °C (41 °F) and 20 °C (68 °F) 

to ensure that the vehicle will be in its 

quietest state during testing. The 

disadvantage of doing so is that it 

further limits the number of outdoor 

testing days available. The agency 

tentatively concludes that we have 

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. 

SAE J2889–1 test conditions specify a 

maximum wind speed of 5 m/s (11 

mph) because wind speeds higher than 

this level can interfere with acoustic 

measurement. We have adopted this 

condition in our test conditions. 

SAE J2889–1 specifies that the 

ambient noise at the test site should be 

measured for at least 10 seconds before 

and 10 seconds after a series of vehicle 

tests. The measurements of the 

minimum A-weighted sound pressure 

level and one-third octave band 

frequency content of the ambient noise 

level are made using the same 

microphones in the same locations used 

to measure the vehicle sound as 

specified in Figure 1 of SAE J2889–1. 

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 we are proposing requirements 

on the one-third octave band basis we 

believe that ambient corrections should 

also be calculated on the one-third 

octave band basis. In order to ensure 

accurate measurements SAE J2889–1 

contains a procedure for correcting the 

overall sound pressure level 

measurement to remove any ambient 

influences. 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 we are proposing requirements 

on a one-third octave band basis we 

believe that ambient corrections should 

also be calculated on a one-third octave 

band basis. In order to ensure accurate 

measurements, SAE J2889–1 contains a 

procedure for correcting the overall 

sound pressure level measurement to 

account for ambient influences. Because 

the variance of a signal is greater on a 

one-third octave band basis than on the 

overall, it may be difficult to apply the 

ambient correction procedure in SAE 

J2889–1 to ambient corrections on a 

one-third octave band basis. SAE J2889– 

1 requires a peak-to-peak variation of 

less than two dB in order to do a valid 

correction. Even if the peak fluctuation 

of the overall sound pressure level of 

the ambient is less than two dB, the 

fluctuation in individual one-third 

octave bands would likely be higher. In 

meetings with agency rulemaking staff, 

manufacturers have stated that it would 

be difficult to apply the method for 

correcting for the ambient in SAE 

J2889–1 to one-third octave bands. 

In response to these concerns we are 

proposing to include a procedure that 

allows for ambient correction if the 

peek-to-peek fluctuation of the ambient 

is less than eight dB when the signal 

that is being measured is more than six 

dB higher than the ambient in that onethird octave band or less than six dB 

when the signal that is being measured 

is more than three dB higher than the 

ambient in that one-third octave band. 

These criteria were chosen in order to 

provide a high degree of confidence that 

contamination due to an unobserved, 

random fluctuation will not impact the 

final reported level by more than one 

half of one decibel. 

We believe 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. We 

believe that this approach will increase 

flexibility in the locations and times 

when outdoor testing can be conducted 

without significantly compromising the 

accuracy of measurements. 

In October of 2012, members of the 

SAE VSP committee presented research 

to the agency regarding the use of the 

test procedures in SAE 2889–1 and 

issues related to correcting for the 

influence of the ambient in 

measurements on the one-third octave 

band basis. The VSP committee also 


tkelley on DSK3SPTVN1PROD with 
2836 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

106http://www.bksv.com/Products/ 

PULSEAnalyzerPlatform/PULSESolutionsOverview/ 

AcousticApplications/PassbyNoiseTesting/ 

IndoorPassbyNoiseTesting.aspx. 

107http://www.iso.org/iso/iso_catalogue/ 

catalogue_ics/ 

catalogue_detail_ics.htm?csnumber=25971. 

108http://www.iso.org/iso/iso_catalogue/ 

catalogue_tc/ 

catalogue_detail.htm?csnumber=45358. 

raised issues regarding measuring pitch 

shifting and the influence of ambient 

noise and tire noise on pitch shifting 

measurements. Members of the VSP 

committee stated that analyzing pitch 

shifting measurements will require a 

narrowband analysis. The VSP 

committee stated that the procedure for 

correcting measurements of the overall 

sound pressure level of a signal for the 

influence of ambient should not be 

applied to measurements of individual 

one-third octave bands. The VSP 

committee stated that outdoor testing 

raised issues regarding interference with 

measurements by the ambient. Members 

of the VSP committee also expressed 

concern that manufacturers would not 

be able to sufficiently attenuate the low 

frequency tones discussed in the 

agency’s research to prevent those tones 

from intruding into the occupant 

compartment. Members of the VSP 

committee stated that pass-by 

measurements at 20 km/h (12 mph) and 

30 km/h (18 mph) are influenced by tire 

noise. Members of the VSP committee 

believe that issues related to the 

influence of ambient noise on 

measurements of the vehicle and issues 

related to measuring pitch shifting can 

be solved by the use of indoor testing to 

measure regulatory compliance. We 

seek comment on the points raised by 

the VSP Committee. 

The agency is considering whether 

the procedures for analyzing the 

frequency spectrum in SAE J2889–1 are 

sufficient to ensure that the results of 

the acoustic measurements are recorded 

in a consistent manner. The agency has 

the following questions about the 

measurement correction procedure and 

the recording of results of acoustic 

measurements: 

• What roll-off rates have been used? 

• Have entities conducting research 

on minimum sound emitted by quiet 

vehicles completed the 1⁄3 octave band 

analysis of their measurements in the 

frequency domain or the time domain? 

• Volpe staff have been using an 

exponential window (to be consistent 

with SAE procedures for the 

measurement of overall levels) when 

conducting frequency analysis. In the 

presentation by VSP committee a 

committee member discussed using a 

Hanning window for the analysis. Does 

the agency need to provide additional 

procedures for conducting the one-third 

octave band analysis? 

The agency has tentatively concluded 

that outdoor acoustics testing is 

preferable to indoor testing in hemianechoic chambers. Outdoor testing is 

more representative of real world 

vehicle-to-pedestrian interactions. Also, 

the agency is concerned 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. 

Outdoor tests, especially pass-by tests 

at speed, 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 some level of ‘‘outdoor 

ambient’’ background noise and with 

Doppler shift when the vehicle is 

moving relative to the pedestrian. Passby tests allow a recording of vehicle 

sound parameters (levels, content, 

phase, etc.) against a trace of time and 

distance from the pedestrian’s location. 

Conversely, when a vehicle is tested 

on an indoor dynamometer in a hemianechoic chamber, the body of the 

vehicle is static and does not produce 

aerodynamic noise. It is unclear how 

representative the tire noise generated 

during rotation on the curved 

dynamometer test wheels is of actual 

tire-road noise. The vehicle approach 

and passing of the microphones can be 

simulated by phasing a row of 

microphones next to the vehicle, and 

interior tire noise can be digitally 

replaced with exterior tire noise 

recordings. However, the agency has not 

determined the fidelity of such 

methods.106

The agency also believes that 

specifications for outdoor testing have a 

more detailed history of objective and 

repeatable performance than 

specifications for indoor testing. A 

substantial amount of development and 

refinement has gone into the test 

procedures and facilities used for 

outdoor vehicle noise testing. For 

instance, outdoor tests such as the ISO 

362 ‘‘Acoustics Measurement of noise 

emitted by accelerating road vehicles— 

Engineering method’’ 107 have been in 

use since its issuance in 1994 for 

measurement of maximum vehicle 

noise. One key to achieving repeatable 

test results with ISO 362 at multiple 

testing locations was the 

standardization of a common road test 

surface. The 1994 and subsequent 

versions of ISO 10844 ‘‘Acoustics— 

Specification of test tracks for 

measuring noise emitted by road 

vehicles and their tyres’’ 108 specify test 

surface materials, absorption, texture, 

and compaction to allow comparable 

test results from different outdoor noise 

test pads. 

SAE J2889–1 contains specifications 

on the cut-off frequency of the indoor 

hemi-anechoic test facility and 

requirements to meet ISO 3745 

‘‘Acoustics—Determination of sound 

power levels of noise sources using 

sound pressure—Precision methods for 

anechoic and hemi-anechoic rooms,’’ or 

ISO 26101 ‘‘Acoustics—Test methods 

for the qualification of free-field 

environments.’’ However, the agency is 

not aware of 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. 

The agency intends to specify 

performance requirements for vehicleemitted sounds that are detectable and 

recognizable to a pedestrian as a motor 

vehicle in operation. Therefore, 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 

cross-over speed are important facets of 

the vehicle’s sound performance. 

The agency is concerned that hemianechoic 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 U.S., most of which were available 

for paid use by outside parties. 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. 

The agency found limited availability 

of indoor hemi-anechoic chambers that 

had four-wheel dynamometer drive 

capabilities. Additionally, the 

availability of indoor hemi-anechoic 

dynamometer chambers that can 

accommodate all motor vehicles 

covered by the PSEA, such as 

motorcycles, trucks, buses, etc., was 

found to be far more limited. While 

indoor testing does not have the 

seasonal downtimes of some outdoor 

test facilities, and may be more 

predictable and time efficient, we 

believe the cost of test time at indoor 

test facilities will be higher than at 

outdoor proving ground noise pads. 

There may also be difficulties locating 


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Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2837 

and scheduling indoor facilities large 

enough to accommodate the heavy 

vehicles subject to this rule. 

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 hemianechoic chamber. Indoor pass-by 

testing in a hemi-anechoic chamber 

would capture elements of the vehicle 

sound profile (including aerodynamic 

and tire noise) that contribute to the 

recognizability of the vehicle’s sound 

signature until the vehicle reaches the 

cross over 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 testing. 

An indoor pass-by procedure would be 

the same as the pass-by procedure 

contained in Section 7.3.2.2 of SAE 

J2889–1 SEP2011 except that 50 meter 

radius free of reflecting objects around 

the test track would not apply. The 

provision in SAE J2889–1 SEP2011 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 would not 

interfere with the vehicle’s sound 

measurement. 

The agency is not aware of the 

availability of hemi-anechoic chambers 

that are large enough to accommodate 

indoor pass-by tests. The agency 

believes that the existence of such 

facilities is limited. The agency seeks 

comment on the availability of hemianechoic facilities that could 

accommodate indoor pass-by testing 

and the desirability of including a test 

procedure for indoor pass-by testing in 

this standard. 

The agency realizes 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 passby testing. It is possible that 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 

seeks comment on including a test 

procedure for indoor hemi-anechoic 

chamber acoustics measurement in this 

standard. 

The agency’s test procedure specifies 

that the acoustic measurements for all 

test conditions shall be conducted on a 

test 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 coming from 

the vehicle. Doing so helps to minimize 

test variability between repeat tests of 

the same vehicle at the same facility and 

variations in measurements taken at 

different facilities. 

Instruments used to make the 

acoustical measurements required under 

our proposal must meet the 

requirements of paragraph 5.1 of SAE 

J2889–1. This paragraph also 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. Manufacturers, in meetings 

with agency rulemaking staff, have 

stated that the filter roll-off rate can 

affect the results of acoustic 

measurement at the one-third octave 

band level. Paragraph 7.1.6.2 of SAE 

J2889–1 requires conformance with 

ANSI S1.11, which specifies a wide 

range for filter roll-off rates. (See ANSI 

S1.11 Table1, Figure 1, and Annex B.) 

Filters with roll-off rates at the two 

extremes of the range could produce 

different results. The agency seeks 

comment on whether the test procedure 

in this proposal should specify a 

maximum roll-off rate that is not 

infinite. 

The test site envisioned by our 

proposal must be established per the 

requirements of S6.1.1 of SAE J2889–1, 

including Figure 1, ‘‘Test Site 

Dimensions’’ with the definitions of the 

abbreviations in Figure 1 as given in 

Table 1, S4 of SAE J2889–1. All 

references to microphone line PP′ and 

vehicle centerline CC′ are per Figure 1 

of SAE J2889–1. Microphones are to be 

set on the PP′ line on both sides of the 

vehicle, two meters from the vehicle 

centerline (CC′). Use of the test set up 

described in the SAE’s Figure 1 will 

ensure repeatable test measurements 

from run to run, vehicle to vehicle, and 

among various test facilities. 

2. Vehicle Condition 

The agency’s goal in measuring the 

vehicle’s sound level in the test 

procedure is to measure the vehicle at 

its quiet state. The test procedure in the 

agency’s proposal contains a 

specification for vehicle condition to 

ensure that there is no variability in the 

results of the acoustics testing and that 

the vehicle will be tested at its quietest 

state. The vehicle condition 

specifications state that the tires should 

be pressurized per the tire placard and 

conditioned by driving, clockwise and 

counterclockwise, 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. This removes 

mold sheen from new tires. The SAE 

J2889–1 test procedure used in our 

research has a further requirement that 

tires have at least 80 percent of their 

tread depth. NHTSA has not included 

such a requirement because we are 

proposing that only new vehicles with 

less than 100 miles on their odometers 

at the start of testing be used. This is the 

normal agency protocol for compliance 

testing in general. The vehicle condition 

specifications also state that the tire 

treads should be free of debris, because 

pebbles and other objects in the 

vehicle’s tire tread can produce a 

clicking sound that can increase the 

vehicle’s sound level and interfere with 

acoustics measurements during pass by 

testing. 

The vehicle test condition states that 

all doors should be shut and locked 

before commencement of testing. This 

step is included in the proposed vehicle 

condition specifications because some 

vehicles are equipped with automatic 

locks that lock the vehicle once the 

vehicle reaches a certain speed. The 

sound produced by the locking doors 

can introduce variability into the test 

results. 

The proposed vehicle test condition 

specifies that all the accessory 

equipment on the vehicle should be 

turned off. This step is included because 

the vehicle’s air conditioning system, 

heating system, and windshield wipers 

can all produce sound when activated 

that can introduce variability into the 

acoustic measurements in S7 of the 

proposed regulatory text. 

The agency wishes to measure the 

sound produced by the vehicle with the 

ICE off because we are attempting to 

measure the sound of HVs and EVs in 

those vehicles’ quietest states. This 

proposal is designed to ensure that these 

vehicles emit a minimum level of sound 

in situations in which the vehicle is 

operating in electric mode because in 

that mode the vehicle did not provide 

sufficient sound cues for pedestrians. 

Therefore, we propose 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 states 

when testing a hybrid vehicle with an 

ICE that runs intermittently, 

measurements that contain sounds 

emitted by the ICE are not considered 

valid. 

As discussed below, the agency is not 

requiring that HVs meet the 

requirements of this proposal for a given 

operating condition if they are not 

capable of operating in EV only mode in 


tkelley on DSK3SPTVN1PROD with 
2838 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

109Public Law 111–373, § 2(3), 124 Stat. 4086 

(2011). 

110Springer Handbook of Acoustics, Thomas D. 

Rossing (Ed.), Springer Science and Media LLC, 

New York, 2007, page 472. 

111One of the HVs tested during the Phase 3 

research was excluded from the crossover speed 

analysis because the agency was not able to 

deactivate the vehicle’s sound alert system. Because 

the sound alert system on that vehicle remained 

active the agency was not able to compare the 

sound level of the vehicle while operating in 

electric mode to sound level emitted by the 

vehicle’s ICE peer. 

that condition. The agency’s method for 

determining whether a vehicle is 

incapable of operating in EV mode 

above a certain speed requires that the 

batteries on the vehicle be fully charged 

at the beginning of the test sequence; 

otherwise the vehicle may be 

improperly exempted from meeting the 

requirements for a given condition. The 

agency believes that the hybrid vehicles 

to which this proposal would apply are 

equipped with an indicator that 

provides information on the state of 

charge of the propulsion batteries. The 

agency is also considering adding a 

vehicle charging procedure to charge the 

vehicle’s propulsion batteries prior to 

each test sequence. This procedure 

would involve a set of vehicle 

maneuvers designed to charge the 

vehicle propulsion batteries. The agency 

seeks comment on whether there are 

HVs to which this proposal would apply 

that do not visually indicate their 

propulsion batteries state of charge to 

the driver. The agency also seeks 

comment on whether a battery charging 

procedure should added to the test 

procedure. 

3. Test Procedure 

The agency proposal contains steps 

for measuring the sound of the vehicle 

at startup, stationary but activated, 

reverse, 10 km/h (6 mph) pass by, 20 

km/h (12 mph) pass by and 30 km/h (18 

mph) pass by. The agency has 

tentatively concluded that EVs and HVs 

should produce a minimum sound at 

least until they reach a speed of 30 km/ 

h (18 mph). 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.’’ 109 Because we intend for the 

proposed standard to be technology 

neutral, we are not including a 

requirement for when an alert sound 

added to a vehicle must be active in the 

regulatory text. Instead, the proposed 

standard includes required minimum 

sound pressure levels that vehicles 

subject to the standard are required to 

meet at different test speeds so that 

these vehicles will make sufficient 

sound to allow pedestrians to detect 

them. 

The agency established the proposed 

top crossover of 30 km/hr (18 mph) by 

examining the speed at which EVs and 

HVs produce a similar amount of sound 

to their peer ICE vehicles. In comparing 

the sound produced by HVs and EVs to 

the sound produced by ICE vehicles, the 

agency sought to determine the speed at 

which the ICE was no longer the 

dominant sound source of the vehicle 

and tire and wind noise were the main 

source of vehicle sound output. We also 

examined the crash statistics from the 

State Data System to determine if there 

was a speed at which the rate of 

pedestrian crashes for HVs and ICE 

vehicles were the same. 

NHTSA’s research indicates that the 

speed at which the sound levels 

produced by HVs and EVs and the 

sound levels produced by those 

vehicles’ ICE peers become 

indistinguishable differs depending on 

make and model. The difference in 

sound pressure level between sounds is 

not distinguishable to humans over time 

if the sounds are within 3 A-weighted 

dB of each other.110 The sound level of 

three of the HVs tested during the 

agency’s Phase 1 research were within 

3 A-weighted dB of their ICE peer 

vehicles at 16 km/h (10 mph) with the 

sound levels for all HVs meeting those 

of their peer ICE vehicles at 32 km/h (20 

mph). 

During the agency’s Phase 3 research, 

an EV (Nissan Leaf) and three HVs with 

prototype sound systems and their ICE 

peer vehicles were tested to compare the 

sound levels of HVs and EVs and their 

ICE peers when stationary but activated, 

10 km/h (6 mph), 20 km/h (12 mph), 

and 30 km/h (18 mph).111 Only one of 

the HVs tested during the Phase 3 

research was within 3 A-weighted dB of 

its ICE peer at 20 km/h (12 mph), the 

same hybrid produced a sound level 3.5 

A-weighted dB above its ICE peer at 30 

km/h (18 mph). The sound level 

produced by the Nissan Leaf was 5 Aweighted dB lower than its ICE peer, the 

Nissan Versa, at 20 km/h (12 mph) and 

4 A-weighted dB lower than the Versa 

at 30 km/h (18 mph) with its sound 

generation system turned off. The other 

HV tested was 5 A-weighted dB lower 

than its ICE peer at 20 km/h (12 mph) 

and 4 A-weighted dB lower than its ICE 

peer vehicle at 30 km/h (18 mph). The 

sound levels produced by the Nissan 

Leaf and the HVs were not as high as the 

overall levels of sounds that would meet 

the proposed requirements for every 

one-third octave band listed in Table 12 

at 20 km/h (12 mph) (see Table 12). 

Both HVs produced sound levels as high 

as sounds meeting the requirements for 

every one-third octave band in Table 12 

at 30 km/h (18 mph) and the Nissan 

Leaf produced a sound only 2 Aweighted dB lower. 

The acoustic measurements for the 

agency’s Phase 3 research were 

conducted on a test surface conforming 

to ISO 10844 (1998) and acoustic 

measurements conducted during Phase 

1 research were taken on the VRTC test 

track which does not conform to ISO 

10844 (1998). Even though the Phase 1 

and Phase 3 measurements were taken 

on different surfaces the direct 

comparison between the EV or HV and 

its ICE peer remains valid, as EVs and 

HVs were measured on the same test 

surface as their respective ICE peer 

vehicles. 

Our research data from Phase 1 and 

Phase 3 shows that the sound level gap 

between HVs or EVs and their ICE peer 

vehicles still exists at 20 km/hr (12 

mph) and becomes much smaller or 

negligible in some tests at 30 km/hr (18 

mph). Also, the EVs and HVs tested in 

Phase 3 research did not meet our 

minimum sound pressure level 

detectability requirements at 20 km/hr 

(12 mph). For these reasons, NHTSA 

tentatively concludes that ensuring EVs 

and HVs produce a minimum sound 

level until they reach a speed of 30 km/ 

hr (18 mph) will ensure that these 

vehicles produce sufficient sound to 

allow pedestrians to detect them. The 

agency believes that the minimum 

sound level requirements will ensure 

that these vehicles produce sufficient 

sound to allow for safe pedestrian 

detection at this speed. Thus, the 

requirements in this proposal, if made 

final, would require that EVs or HVs 

that do not currently produce enough 

sound for pedestrians to detect them 

while traveling at 30 km/hr (18 mph) 

would have to increase their sound 

output. The agency solicits comments 

on the determination of 30 km/hr (18 

mph) as the appropriate upper limit for 

light EVs/HVs and additional data on 

similar tests performed on the same type 

of vehicles. 

At speeds greater than 30 km/hr (18 

mph), the agency has tentatively 

concluded that EVs and HVs produce 

sufficient sound for safe pedestrian 

detection. The agency believes that 

vehicles that will require a 

countermeasure sound to meet the 

minimum sound requirements at 30 km/ 

hr (18 mph) will continue to produce 

those countermeasure sounds at higher 

speeds so that the added sound will 

phase out at speeds greater than the 

crossover speed. The agency believes 

that manufacturers are likely to 

gradually phase the countermeasure 

sound off at speeds above the crossover 


tkelley on DSK3SPTVN1PROD with 
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112See footnote 36. 

113http://www.regulations.gov/ 

#!documentDetail;D=NHTSA-2011-0148-0022. 

114http://www.unece.org/trans/main/wp29/ 

wp29wgs/wp29grb/qrtv_8.html. 

speed to avoid annoyance caused by a 

sharp drop in sound level if the 

countermeasure was terminated exactly 

at 30 km/hr (18 mph). 

The crashes used in our statistical 

analysis discussed earlier came from 

areas where the posted speed limit was 

less than or equal to 35 mph. As 

discussed previously, this analysis 

indicated that the odds ratio of an HV 

being involved in a crash with a 

pedestrian was 1.38 when the vehicle in 

question completed a low speed 

maneuver immediately prior to the 

crash.112 This means that HVs and EVs 

were 38 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 

tentatively concludes that a crossover 

speed of 30 km/hr (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. The odds ratio of a 

HV being involved in a pedestrian crash 

while going straight is 0.96. This means 

that HVs are no more likely to be 

involved in pedestrian crashes when 

going straight than ICE vehicles. 

The agency does not believe that 

establishing a crossover speed of 30 km/ 

h will have any noticeable impact on 

ambient noise levels. As discussed in 

Section X.D, NHTSA has conducted an 

EA to analysis the environmental effects 

of this rulemaking. The EA shows 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 would be 

negligible. A single EV or HV travelling 

at 30 km/h that produced sound 

meeting the requirements of this 

proposal would not be noticeable to a 

person standing 7.5 meters from the 

roadway in a 55 A-weighted dB ambient 

environment representative of urban 

areas. 

The guidance document developed by 

UNECE recommends that EVs and HVs 

emit pedestrian alert sounds beginning 

when the vehicle starts moving and 

continuing until the speed of the vehicle 

reaches 20 km/hr (12 mph). The 

Alliance of Automobile Manufacturers 

also suggested 20 km/hr (12 mph) as the 

crossover speed.113

During QRTV’s eighth meeting, the 

Japan Automobile Standards 

Internationalization Center (JASIC) 

presented its research on crossover 

speed.114 It determined the crossover 

speed by measuring when the tire noise 

was dominant over engine noise for 

several vehicles. JASIC concluded that 

the tire noise was dominant for every 

ICE vehicle and HV they tested at 

speeds that exceeded 20 km/h (12 mph). 

It also concluded that the difference 

between sound levels of HVs and ICEs 

occurred at speeds below 20 km/h (12 

mph). The agency solicits comments on 

whether 20 km/h (12 mph) should be 

considered the crossover speed, as an 

alternative to the 30 km/h (18 mph) 

crossover speed as well as additional 

research data that support this speed. 

In the absence of more detailed 

analysis supporting another crossover 

speed, the agency tentatively concludes 

that a crossover speed of 30 km/hr (18 

mph) will 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 while also 

minimizing community noise impact by 

ensuring that the sound is not active 

when it is no longer necessary. 

In order to ensure that HVs and EVs 

produce a minimum level of sound to be 

detectable by pedestrians until the 

crossover speed, the agency is proposing 

to measure the minimum sound of the 

vehicle at 30 km/hr (18 mph). Because 

the agency’s proposal is technology 

neutral, a manufacturer can choose how 

to comply with the minimum level 

sound requirements at the 30 km/hr (18 

mph) pass by. Thus, no countermeasure 

sound would be required if a vehicle 

subject to the requirements of this 

standard produces sound sufficient to 

meet the requirements in section S5 of 

our proposed regulatory text at 30 km/ 

hr (18 mph). 

For all operating conditions, our 

proposed test procedure (and that of 

SAE J2889–1) specifies that four 

consecutive valid measurements be 

within 2 A-weighted dB. 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 normal operating 

sound. 

The test procedure also specifies that 

test runs in which the vehicle’s ICE, (for 

HVs), or battery cooling system activate 

must be discarded. As stated earlier, it 

is the agency’s goal to measure the 

minimum sound levels of vehicles 

subject to this standard in their quietest 

state. It is because these vehicles are 

capable of very quiet operation that the 

agency is requiring a minimum sound 

level to ensure pedestrians can detect 

them. 

The agency also found that a hybrid 

vehicle’s ICE engine turning on during 

the test can introduce variability into 

the test results. 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 pure electric vehicles or the ICE 

engines on hybrid vehicles to be 

activated whenever the vehicle is turned 

on or moving this would be a 

satisfactory manner for a manufacturer 

to comply with the minimum sound 

level requirements. The fact that both 

the battery cooling fans and the ICEs on 

hybrid-electrics are only running 

intermittently means that sounds 

produced by these vehicle functions 

cannot be relied on to provide sound to 

pedestrians under all conditions. While 

the specifications requiring four valid 

measurements with 2 A-weighted dB 

would to some extent address 

repeatability issues caused by 

intermittent vehicle noise, the agency 

wants 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. 

The agency realizes 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 this 

proposal would specify requirements. 

Because the agency would be testing 

HVs in their quietest state, the test 

procedure and requirements in this 

proposal are not designed to test a 

vehicle that is producing added sound 

while its ICE is operating. Therefore, the 

agency would not require that HVs meet 

the requirements of this proposal for a 

given operating condition if they are not 

capable of operating in EV only mode in 

that condition. For example, if a vehicle 

is not designed to operate in EV only 

mode above 25 km/h it would not be 

required to meet the requirements in 

this proposal at any speed above that 

(e.g. at the typical 30 km/h crossover 

speed). 

The test procedure in S7 calls for 4 

valid consecutive measurements and 

tests in which the vehicle’s ICE is 

running are not considered valid. Thus, 

according to these test procedure, it 

would not be possible to test vehicles 

that do not operate in EV only mode in 

one of the conditions for which we are 


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115NHTSA–2011–0148–0031. 

proposing minimum sound 

requirements. Therefore, we have 

included a provision in the proposal 

that excludes an HV from meeting the 

minimum sound requirement for a given 

operating condition after 10 consecutive 

tests during which the vehicle’s ICE is 

on for the entire test. 

a. Start-Up 

The proposed regulatory text in 

Section XIII of this notice would require 

that the vehicle’s stationary but 

activated sound commence within 500 

milliseconds of when the vehicle’s 

starting system engages. The proposal 

does not currently contain 

specifications for a separate ‘‘start-up’’ 

sound. The requirement that the 

stationary but activated sound 

commence within 500 milliseconds of 

when the vehicle’s starting system 

engages establishes how soon the 

vehicle must meet the requirements of 

the proposal after it is turned on. The 

agency believes it is important for the 

pedestrian to be aware of a vehicle as 

soon as its starting system is activated. 

We believe 500 milliseconds is adequate 

time for the vehicle’s starting system to 

engage after the driver has initialized 

the process by whatever method is used 

on that vehicle (i.e., turning a key or 

pressing a button) and for the staring 

system to communicate with other 

vehicle systems. We seek comment on 

whether 500 milliseconds is a sufficient 

amount of time for the alert sound to 

activate after the vehicle’s starting 

system is engaged. We also seek 

comment on whether 500 milliseconds 

is an appropriate amount of for the alert 

sound to activate after the vehicle’s 

staring system is engaged from a safety 

prospective. 

While the agency has not included 

separate acoustic requirements in 

Section XIII to signal that the driver has 

turned on the vehicle, the agency is 

considering whether we should include 

such requirements in the final rule. If 

the agency decides to include a different 

acoustic cue to signal that the driver 

started the vehicle, we would require 

that the sound start within 500 

milliseconds of the driver initializing 

the starting process and continue for 

two seconds. The sound pressure levels 

that the agency measured for vehicle 

starting sounds during the Phase 2 

research were between 65 A-weighted 

dB and 75 A-weighted dB. The startup 

sounds that the agency measured during 

the Phase 2 research were 11 Aweighted dB to 15 A-weighted dB 

louder than the sound produced by 

those vehicles when stationary but 

activated. The agency recognizes that a 

start-up sound of 75 A-weighted dB is 

probably higher than necessary to alert 

pedestrians to the presence of a starting 

vehicle. Were the agency to require a 

different start-up sound, the agency 

would want the difference between the 

start-up sound and the sound produced 

by the vehicle when stationary but 

activated to mirror the difference in 

sound pressure levels between 

stationary but activated and start-up in 

ICE vehicles so that a pedestrian would 

be able to differentiate between the two 

operating conditions. Thus, a start-up 

sound for HVs and EVs would be 11 to 

15 A-weighted dB higher than the 

requirements proposed for stationary 

but activated in Section XIII (see Table 

1, S5.1.1 of the proposed regulatory 

text). The agency solicits comments on 

whether a start-up sound should be 

included as an operating condition for 

which the agency should establish 

minimum sound requirements as well 

as the acoustic requirements that are 

different from the requirements for the 

stationary but activated sound. 

The microphone position for the startup sound test is the same as the 

microphone position for the stationary 

but activated condition test described 

below. 

b. Stationary But Activated and 

Directivity 

The test procedure used to measure 

the compliance of the vehicle to the 

startup, stationary but activated, and 

directivity requirements of Section 5 of 

the proposed regulatory text is based on 

the ‘‘stopped condition’’ test of 

paragraph 7.3.2.1 of SAE J2889–1. The 

front plane of the vehicle is positioned 

at the microphone line (PP’), the vehicle 

is stationary and four consecutive 10 

second measurements are taken. 

Measurements are considered invalid if 

they contain sounds emitted by any 

component of the vehicle’s battery 

thermal management system (cooling 

fans or pumps), or they come from an 

ICE on an HV equipped with an ICE that 

runs intermittently. These provisions 

help to ensure that the vehicle is 

measured in its quietest state. The pass/ 

fail requirements for this test, as for all 

the tests, are a set of sound pressure 

level measurements in each of eight 

one-third octave bands, which were 

chosen for their ability to contribute to 

detectability without unnecessarily 

adding to the overall sound pressure 

level of the vehicle in that condition. 

The agency is proposing that the 

vehicle be tested for minimum sound 

level at the stationary but activated 

operating condition with the vehicle’s 

gear selection in park (for vehicles fitted 

with a park position). The agency has 

decided to test at the stationary but 

activated condition while the vehicle is 

first turned on and while the vehicle is 

in park instead of testing while the 

vehicle’s gear selection is in drive 

because the agency believes that the 

vehicle must produce a sound level 

while at park that is sufficient to allow 

pedestrians to avoid collisions with 

vehicles pulling out of parking spaces 

and driveways. The agency believes that 

the alert sound activating when the 

vehicle is shifted into drive will provide 

insufficient warning of the presence of 

a vehicle that is about to pull out of a 

parking space or a driveway. It is likely 

that drivers will shift into drive and 

commence vehicle motion with minimal 

delay. In this situation, an alert sound 

that activated when the vehicle was 

shifted into drive would provide little to 

no warning that there was a nearby 

vehicle. The agency believes that testing 

the vehicle’s minimum sound level 

while in drive would reduce the 

effectiveness of the requirement of a 

sound when stationary but activated 

and testing the vehicle’s sound level 

while the vehicle is in park will 

decrease the number of collisions 

between EVs and HVs and pedestrians 

caused by the vehicle’s quietness. 

In an email to the Director of the 

Office Crash Avoidance Standards the 

NFB expressed concern that establish 

minimum sound requirements for when 

the vehicle’s gear selection was in drive 

but not in park would mean that blind 

and visually impaired pedestrians 

would not be able to detect the presence 

of nearby vehicles that had just been 

turned on in ‘‘a parking space, 

driveway, or other location.’’ 115

Representatives from motor vehicle 

manufacturers have urged the agency to 

establish minimum sound requirements 

for the stationary but active scenario 

when the vehicle’s gear selection is in 

drive. 

The agency realizes that a sound in 

park may not be necessary for safety in 

situations in which a vehicle is 

stationary for long periods of time. This 

includes situations in which the vehicle 

is in park but still ‘‘on’’ while the driver 

is preparing to exit the vehicle or while 

the driver is waiting for someone. In 

these situations, the vehicle is unlikely 

to commence movement at a moment’s 

notice, which lessens the need for the 

vehicle to emit some minimum sound 

level. The agency solicits comment on 

approaches that could be adopted to 

ensure that the vehicle is not producing 

sounds in situations in which the sound 

is not needed for pedestrian safety. One 

of the approaches that the agency is 

considering for mitigating noise caused 


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Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2841 

by idling vehicles would be to allow the 

countermeasure sound to deactivate 

when the vehicles is shifted from drive 

into park. Another option would be for 

the sound to deactivate after the vehicle 

has been in park for some amount time 

such as two or five minutes. We seek 

comment on how to mitigate 

unnecessary noise from vehicles idling 

for long periods of time, while 

preserving the stationary but activated 

sound when needed for pedestrians’ 

safe navigation. 

Our proposal contains a requirement 

and a test procedure for measuring the 

directivity of the sound emitted by the 

vehicle because the stationary but 

activated and pass by tests measure the 

sound at two microphones two meters 

on either side of the vehicle’s centerline. 

The pedestrian, however, will be 

passing in front of the vehicle. We want 

to ensure that there is 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 

pedestrian hears the sound. The 

directivity measurement involves 

placing a third microphone at the 

vehicle’s centerline, two meters in front 

of the vehicle. This measurement is 

done when stationary but activated and 

the sound that is measured by the center 

microphone must meet the same sound 

pressure level requirements in the same 

one-third octave bands as the sound 

measured by the side microphones. 

c. Reverse 

Our proposal contains a requirement 

and a test procedure for sound while the 

vehicle is backing because this is one of 

the critical operating scenarios we have 

identified in our research and statistical 

studies. The requirement is limited to 

vehicles capable of rearward selfpropulsion. This means that 

motorcycles (and other motor vehicles, 

possibly low speed vehicles) 

constructed without a reverse gear, such 

that they cannot move rearward under 

their own power will not be required to 

make a sound when moving backward 

(presumably by being pushed). For all 

other vehicles, whenever the gear 

selection control is in reverse, the 

vehicle must emit a sound meeting the 

specified sound pressure level in each 

of eight one-third octave bands. These 

sound pressure level requirements are 

greater than those when stationary but 

activated, but less than those for the 10 

km/hr (6 mph) pass by test, because, 

while we know the vehicle will be 

moving while backing, we know it will 

almost always move at less than 10 km/ 

hr. The test for backing is done when 

stationary but activated with the rear 

plane of the vehicle on the microphone 

line because it is very difficult for a test 

driver to reliably and repeatedly back a 

vehicle through the test area at any 

constant speed. 

d. Constant Speed Tests 

Constant speed pass by tests are 

required at 10 km/hr (6 mph), 20 km/ 

hr (12 mph), and 30 km/hr (18 mph). 

The vehicle passes through the 

measurement area specified in SAE 

J2889–1 at a constant speed and the 

sound profile is captured at the 

microphone line. Four consecutive valid 

measurements are required and must be 

within 2 A-weighted dB of each other. 

As in the stationary but activated test, 

invalid measurements are those that 

contain sounds emitted by any 

component of a vehicle’s battery 

thermal management system, or that 

come from the ICE on a hybrid vehicle 

with an ICE that runs intermittently. 

The requirement is stated as a set of 

sound pressure levels in each of eight 

one-third octave bands, at any speed 

greater than or equal to10 km/hr (6 

mph), but less than 20 km/hr (12 mph). 

The constant speed pass by tests at 

20km/hr (12 mph) and 30 km/hr (18 

mph) are conducted in the same manner 

as the 10km/hr (6 mph) test but each 

have their own set of required sound 

pressure levels. Requirements are in the 

same eight one-third octave bands, but 

sound pressure levels are higher than 

the 10km/hr (6 mph) test, because the 

pedestrian needs a longer detection 

distance to avoid a faster moving 

vehicle. As discussed above, an HV 

would not be required to meet the 

requirements for a given test speed if it 

was not capable of operating in EV only 

mode at that speed. 

e. Pitch Shifting 

Our proposal contains a requirement 

for pitch shifting to signify acceleration 

and deceleration. Sounds to alert 

pedestrians to acceleration and 

deceleration are required by the 

language of the PSEA. Pitch shifting 

gives the pedestrian information about 

the acceleration or deceleration of an 

approaching vehicle. This information 

is important to the pedestrian in making 

a decision about whether or not to cross 

in front of a vehicle. An accelerating 

vehicle does not intend to stop. A 

decelerating vehicle on a path parallel 

to the pedestrian may be slowing to 

make a right turn into the pedestrian’s 

path if she or he were to cross the street. 

The proposed requirement is that the 

fundamental frequency of the sound 

emitted by the vehicle increase with 

speed by at least one percent per km/hr 

between 0 and 30 km/hr (18 mph). 

There is no test procedure associated 

with this requirement. Pitch shifting is 

verified by comparing the fundamental 

frequency from the stationary but 

activated, 10 km/hr (6 mph), 20 km/hr 

(12 mph), and 30 km/hr (18 mph) tests. 

The agency is aware that the pitch of 

the sound produced by a traditional ICE 

vehicle does not increase linearly 

because as a vehicle transitions to a 

higher gear, the revolutions per minute 

of the engine drop, and therefore so 

does the frequency of the sound 

produced by the engine. The agency 

notes that it is possible that the sound 

produced by an HV or EV may not 

increase linearly in pitch because the 

sound output may change as the vehicle 

transitions from a lower gear to a higher 

gear. The agency does not believe that 

this phenomenon will have a significant 

impact on the agency’s method for 

measuring pitch shifting because a 

majority of the electric motors on 

vehicles subject to this proposed 

standard have single gear transmissions. 

While the pitch shifting requirement 

contained in this proposal does not 

exactly mimic the sound produced by a 

traditional ICE vehicle, increasing pitch 

is a characteristic that pedestrians 

associate with an accelerating vehicle 

based on experience. Because the pitch 

shifting requirement only applies while 

the vehicle is traveling at speeds 

between 0 km/hr and 30 km/hr (18 

mph), the sound produced by a vehicle 

meeting the requirements of this 

proposal will be similar to the sounds 

produced by a traditional ICE vehicle. 

The agency believes that the pitch 

shifting requirement contained in this 

proposal will approximate the acoustic 

behavior of traditional ICE vehicles 

closely enough to provide pedestrians 

with valuable information about a 

vehicle’s change in speed. 

Manufacturers and their 

representatives, in meetings with 

NHTSA staff, have expressed concerns 

that it is difficult to measure the change 

in pitch of a sound produced by a 

vehicle on a vehicle level during a pass 

by test. Manufacturers have requested 

that the agency measure pitch shifting 

using a component level test. 

The agency is hesitant to include a 

component level test because we want 

the standard to be technology neutral 

and because we do not wish to limit 

technological innovation. Further, the 

agency is aware that manufacturers plan 

to use different technologies to comply 

with this standard so defining the 

component subject to the component 

level test could prove difficult. The 

agency is aware that some sounds 

produced by a vehicle do not 

necessarily shift in pitch as the vehicle 

increases speed. However, the agency 


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believes that it is possible using the test 

procedures in S7 to accurately measure 

the change in pitch of a sound added to 

a vehicle for purposes of complying 

with this proposed standard. 

The agency seeks comment on 

including a component level test to 

measure pitch shifting in the test 

procedure. If the agency included a 

component level test in the final rule, it 

would apply to devices added to a 

vehicle to generate sound for purposes 

of complying with this proposed 

standard. A sound generation device 

would be defined as a device that is not 

connected to the vehicle’s propulsion 

source or drive train that is installed on 

a vehicle for the purposes of generating 

sound. Under such a test the agency 

would place a microphone one meter in 

front of the sound generating device 

mounted 0.5 m above the floor. The 

agency would then input into the device 

a signal corresponding to the vehicle 

speeds 0 km/hr, 10 km/hr (6 mph), 20 

km/hr (12 mph), and 30 km/hr (18 mph) 

and make 5 second recording of the 

output of the sound generating device at 

each speed. The measurement would 

have to be conducted under the 

conditions in S6.1 with the instruments 

specified in S6.3.1. The performance 

requirements for a component level 

pitch shifting measurement would be 

the same as the proposed requirements 

in S5.1.6. 

The agency’s proposed method for 

measuring pitch shifting depends on the 

presence of a strong tone in the sound. 

The pitch of a sound is verified by 

tracking this tone as it increases in 

frequency for each pass by test as the 

vehicle increases speed. It is difficult to 

verify a sound’s increase in pitch if the 

sound does not have any strong tones. 

The agency has some concerns about 

identifying the tone of a sound and 

tracking this tone as the vehicle 

increases speed. The agency plans to 

conduct further research to verify that it 

is possible to track a tone’s increase in 

frequency as the vehicle increases 

speed. If it is not possible to identify a 

tone to track in order to verify the 

increase in a sound’s pitch, the agency 

may use a different method to verify the 

increase in a sound’s pitch. Possible 

methods to quantify pitch shifting 

include in-situ and bench tests of 

constant speed or accelerating pass-by 

events. A method to track tonal 

components is needed. Additional 

measurements, not currently being 

collected in the compliance test 

procedure, such as engine RPM may be 

required in order to apply the 

verification procedure for pitch shifting 

to spectrally complex sounds. We 

request comments on this issue. 

f. Recognizability 

The PSEA also requires that our new 

standard have performance 

requirements that ensure the sound 

emitted by an HV or EV is one that is 

recognizable as a motor vehicle. Our 

proposal includes requirements to 

address recognizability. The sound 

emitted by the vehicle to meet 

requirements for each of the critical 

operating scenarios must contain at least 

one tone, and at least one tone no higher 

than 400 Hz. 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. The criteria set for determining 

the appropriate tone-to-noise ratio could 

be refined. Possible refinements to the 

tone-to-noise ratio criteria to better suit 

the current application include a) 

reduction in the bandwidth, or b) 

inclusion of all tones within the band 

for the tone-to-noise calculation, and c) 

possibility of changing the 6 dB 

criterion. 

The sound must also have broadband 

content in each one-third octave band 

from 160 Hz to 5000 Hz. Broadband 

components are those that have energy 

at all frequencies within a one-third 

octave band. This broadband 

component requirement could be met, 

for example, by Gaussian distributed 

random noise, a set of damped sine 

waves whose damping and spacing 

covers a one-third octave band, or a 

combination of tones and noise. 

g. Vehicles of the Same Make and Model 

Emitting the Same Sound 

Pursuant to the PSEA, NHTSA is 

required to ensure that vehicles of the 

same make and model emit the same 

sound or set of sounds. We interpret a 

vehicle model as a specific grouping of 

similar vehicles within a vehicle line. 

49 CFR part 541, Federal Motor Vehicle 

Theft Prevention Standard, defines 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. 

The proposed standard would require 

vehicles of the same make and model to 

emit the same sound or set of sounds for 

a particular model year. Thus a 2012 

Prius Two could have a different sound 

than a 2012 Prius Four. A 2012 Prius 

Two could also have a different sound 

than a 2013 Prius Two. All Prius Twos 

from the 2012 model year would be 

required to emit the same sound or set 

of sounds. 

We are only proposing to require that 

only sounds added to vehicles for the 

purpose of complying with this 

proposed standard be the same. The 

requirement that sounds emitted by 

vehicles of the same make and model be 

the same does not apply to sounds 

generated by a vehicle’s tires or body 

design or sounds generated by the 

mechanical functions of the vehicle. 

Because NHTSA intends only to test 

whether sounds added to a vehicle for 

purposes of complying with this 

standard are the same, we propose to 

test for this requirement at the 

stationary condition. Testing at the 

stationary condition will ensure that the 

agency is able to test sound added to the 

vehicle without interference from other 

sources of vehicle noise. We seek 

comment on testing to ensure that 

sound produced by two different 

vehicles of the same make and model is 

same at additional test scenarios other 

than idle. We also seek comment on the 

extent to which changing a vehicle’s 

tires or body design would affect the 

vehicle’s sound profile. 

The agency proposes to consider the 

sounds produced by two vehicles to be 

the same if, when tested according to 

S7.2, the sound emitted by the two 

vehicles has a sound pressure level 

within 3 A-weighted dB for every onethird octave band between 315 Hz and 

5000 Hz. The agency seeks comment on 

this method for determining if two 

sounds are the ‘‘same.’’ 

VIII. Alternatives Considered But Not 

Proposed 

As discussed below, the reason that 

the agency did not propose many of the 

alternatives described in this section 

was because of difficulties in 

compliance testing. These alternative 

methods for developing sounds could be 

used so long as the resulting sounds 

meet the requirements of the proposal. 

The agency believes that allowing 

multiple compliance alternatives would 

make compliance testing unduly 

complicated. The agency seeks 

comment on modifications to the 

acoustic specifications contained in 

Section XII of this proposal. To the 

extent that the suggested modifications 

allow for increased flexibility without a 

decrease in safety, the agency will 

consider adopting the comments in the 

final rule. 


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Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2843 

116See footnote 8. 

A. Requiring Vehicle Sound To Be 

Playback of an ICE Recording 

The agency considered specifying that 

the alert sound used on EVs and HVs be 

a recording of an ICE peer vehicle. After 

further consideration and based on 

comments on the NOI, the agency 

concludes that a recording based on an 

ICE vehicle is not a viable regulatory 

option for ensuring that EVs and HVs 

produce sound levels sufficient to allow 

pedestrians to safely detect them. The 

agency believes that it is not practical to 

require that the alert sound be a 

recording of an ICE vehicle because of 

concerns about enforcing such a 

standard, because the recording of an 

ICE engine might not be as detectable as 

the sounds that the agency is proposing, 

and because of the expense of creating 

and replaying the recording. In addition 

manufacturers have expressed a desire 

for flexibility in developing pedestrian 

alert sounds and this approach is 

unnecessarily limiting in that aspect. 

The agency believes that requiring an 

alert sound based on a recording of an 

ICE vehicle would unnecessarily 

complicate the agency’s compliance 

testing. Under the compliance test that 

the agency was considering for an alert 

sound based on a recording of an ICE 

vehicle, manufacturers would be 

required to report to the agency which 

vehicle the alert sound was recorded 

from. The agency would then test both 

the vehicle the alert sound was recorded 

from and the EV or HV on which the 

alert sound was installed and compare 

the acoustic profiles of the two sounds. 

Testing two vehicles would double the 

time and expense of conducting 

compliance testing. While the agency 

does not require manufacturers to 

conduct any testing to certify their 

vehicles, the agency recognizes that 

many manufacturers choose to follow 

the test procedure in the agency’s 

standards to be assured of compliance. 

Thus, increasing the amount of vehicles 

tested would also increase 

manufacturers’ testing costs. 

The agency does not believe that the 

recording of an ICE would be as 

detectable as the sounds meeting the 

specifications in S5 of this proposal. 

Most of the frequency content produced 

by an ICE is in the lower frequency part 

of the spectrum where the ambient is 

highest. Because ICE sounds have a 

significant amount of low frequency 

signal content, they are more likely to be 

masked by the ambient than sounds 

with higher frequency tones or high 

frequency broad band. The agency’s 

Phase 2 research indicated that sounds 

that contain only elements produced by 

the fundamental combustion of the ICE 

are relatively ineffective in providing 

adequate detection. An alert sound that 

was based on a recording of an ICE 

vehicle would not allow manufacturers 

to use sounds that had tones in 

frequencies for which the ambient is not 

very strong and that might be more 

detectable than a recording of an ICE. 

In their comments on the NOI, 

manufacturers have stated that it can be 

more expensive to create and replay an 

alert sound based on a recording of an 

ICE vehicle than to create and replay a 

synthetic sound. Manufacturers have 

stated that they would have to conduct 

recordings at several vehicle speeds and 

then process the sound so that when 

played through a speaker system 

mounted on the vehicle it would 

produce a smooth sound that mimics 

the sound produced by the ICE vehicle 

on which the recording was based. 

Creating the recording at several 

different speeds adds an additional 

expense in creating the sound that is not 

present in synthetic sounds. The 

recordings would have to be captured 

by multiple vehicle pass bys or through 

recordings conducted indoors in hemianechoic dynamometer chambers, both 

of which would entail significant cost. 

Playing back the sound so that it 

sounded like an ICE vehicle would 

likely require costly high performance 

signal processing. High performance 

signal processing is necessary for 

systems to be able to accurately 

reproduce sounds for acceleration and 

deceleration. One commenter also stated 

that the vehicle on which the alert 

sound was installed would have to have 

a larger data storage capacity to replay 

an alert sound recorded from an ICE 

vehicle. The commenter stated that the 

vehicle would require this additional 

storage capacity because the system 

would have to retain a recording of the 

ICE at each speed below the crossover 

speed in order to reproduce the 

recording. This additional storage 

would lead to additional expense for the 

alert sound system. 

Commenters also stated that a 

recording of an ICE played back over a 

speaker mounted on an EV or HV would 

not sound exactly like the recorded 

vehicle because speaker systems that 

manufacturers would be using cannot 

reproduce sound with that level of 

accuracy. The inability of speakers 

mounted on vehicles to reproduce the 

sound of the recorded vehicle at a high 

level would diminish the advantages in 

the level of pedestrian recognition of the 

alert sound that the agency had hoped 

to gain in requiring that the alert sound 

be a recording of an ICE vehicle. 

In comments on the NOI and in 

meetings with NHTSA staff, 

manufacturers have stated that they 

wish to have a certain degree of 

flexibility to develop sounds that 

pedestrians will find recognizable and 

detectable but will also be pleasing to 

the driver. Given the other difficulties 

present in requiring an alert sound 

based on a recording of an ICE vehicle, 

the agency does not believe that the 

benefit gained from requiring an alert 

sound based on a recording of an ICE 

vehicle justifies restricting manufacturer 

choice regarding the sounds that can be 

used as alert sounds especially since 

some of the sounds that manufacturers 

may wish to use could be more 

detectable than recordings of ICE 

vehicles. 

Given that alert sounds based on 

recordings of ICE sounds would be more 

expensive to test, create, and replay 

than the sounds fitting the parameters in 

Section XIII and the marginal benefit to 

pedestrians in recognizing ICE sounds 

that might be gained from using a 

recording of an ICE as an alert sound, 

the agency believes that the 

specifications in Section XIII present a 

more feasible approach to establishing 

minimum sound levels for EVs and 

HVs. 

B. Requiring That the Alert Sound 

Adapt to the Ambient 

The agency considered requiring that 

the sound level of the alert sound vary 

based on the ambient noise level in the 

environment surrounding the vehicle. 

The agency is aware that technology is 

available for back-up alarms for heavy 

vehicles and construction equipment 

that vary the sound pressure level of the 

alert sound based on the sound pressure 

level of the ambient. 

The agency decided not to pursue this 

approach because it was not justified 

based on safety need, because of 

concerns about the impact of 

environmental noise, and because of 

concerns about the sophistication of this 

technology. Based on conversations 

with the groups representing the 

visually-impaired community and a 

review of literature describing 

navigation by visually-impaired 

individuals, we have tentatively 

concluded that pedestrians who are 

visually impaired are taught not to 

attempt to cross intersections using 

hearing alone in urban environments 

with a high ambient noise levels.116 The 

agency believes that sounds meeting the 

specifications in Section XIII will 

provide adequate detectability for 

pedestrians in ambient environments in 

which sound cues are necessary to assist 

pedestrians in avoiding collisions with 


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2844 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

vehicles. The agency is concerned that 

an alert sound that reacts to the ambient 

noise level could contribute to an 

increase in the overall ambient noise 

level and contribute to noise pollution. 

An alert sound that would be detectable 

over a high urban ambient sound level 

would raise the overall ambient level 

simply by its presence. Multiple 

vehicles with variable noise alert 

devices would contribute to noise 

pollution by driving the ambient sound 

pressure level higher and higher by 

reacting to the sound being produced by 

other vehicles. The agency is concerned 

that this technology is not at a stage 

where it can avoid the feedback effect of 

two equipped vehicles reacting to each 

other and thereby increasing the overall 

noise level. 

Because an alert sound that adapted 

to the ambient environment would 

provide little additional safety benefit 

and could lead to increases in noise 

pollution, the agency decided that such 

a device should not be required in this 

rulemaking. 

C. Acoustic Profile Designed Around 

Sounds Produced by ICE Vehicles 

The agency is hesitant to set the 

minimum sound level requirements for 

quiet vehicles to mean levels produced 

by ICE vehicles. Setting the minimum 

sound requirements for HVs and EVs at 

the mean levels produced by ICE 

vehicles could have the effect of cutting 

off efforts by manufacturers to reduce 

vehicle noise emissions. This would 

also serve to increase the overall levels 

of vehicle noise emissions because 

vehicles that had been quieter would 

now be required to produce sound at the 

mean sound level of ICE vehicles. 

Acoustic requirements based on the 

sound level of ICE vehicles also include 

a pitch shifting requirement, as we have 

proposed in this notice. 

The agency is also hesitant to set the 

minimum sound levels for HVs and EVs 

at 3 (or 2) standard deviations below the 

mean sound level produced by ICE 

vehicles because then sound levels may 

not be high enough to allow pedestrians 

to detect these vehicles. The agency has 

yet to determine whether all ICE 

vehicles produce sound levels that are 

sufficient enough to allow pedestrians 

to readily detect them. Because the 

PSEA requires the agency to study 

whether quiet ICE vehicles pose an 

increased risk of collisions with 

pedestrians, the agency does not believe 

that it is in a position to assume that 

very quiet ICE vehicles are easily 

detectable by pedestrians. 

As discussed in Section VI.C of this 

notice, in our Phase 3 research we 

developed a set of minimum sound 

level criteria for HVs and EVs based on 

the sounds produced by current ICE 

vehicles. While we are not proposing 

acoustic specifications based on the 

sound profile of ICE vehicles at this 

time we seek comment on the acoustic 

specifications below. 

As discussed in section VII.D.1, the 

following one-third octave bands were 

identified as critical for vehicle 

detectability: 315, 400, 500, 2000, 2500, 

3150, 4000, and 5000 Hz. A total of 152 

measurements of stationary but 

activated and 10 km/hr (6 mph) forward 

pass-by events were analyzed to 

determine levels for these two 

operations. Data came from three 

different sources (the International 

Organization of Motor Vehicles 

Manufacturers (OICA), Phase 2 as 

described above, and Phase 3 research). 

Sound levels for backing were derived 

from the 10 km/hr (6 mph) forward 

levels but adjusted downward by 3 dB 

to account for directivity. In particular, 

the sound pressure level in the rear of 

an ICE vehicle is about 3 dB lower than 

what is measured at the SAE 2889–1 

microphones. Two versions of potential 

requirements based on measured ICE 

levels are provided below. Table 13 

shows minimum A-weighted sound 

levels based on the mean levels of ICE 

vehicles in the dataset. Table 14 shows 

minimum A-weighted sound levels 

based on the mean levels minus one 

standard deviation. Mean levels minus 

two standard deviations were also 

considered, however, these levels are 

not expected to be sufficiently 

detectable in many cases. 

TABLE 13—MINIMUM A-WEIGHTED SOUND LEVELS BASED ON ICE MEAN LEVELS

One-third octave band center frequency, Hz Stationary but 

activated Backing 10 km/hr 20 km/hr 30 km/hr 

315 ....................................................................................... 40 42 45 52 55 

400 ....................................................................................... 41 44 47 53 57 

500 ....................................................................................... 43 45 48 54 59 

2000 ..................................................................................... 44 46 49 55 59 

2500 ..................................................................................... 44 46 49 53 56 

3150 ..................................................................................... 43 44 47 52 54 

4000 ..................................................................................... 41 42 45 49 51 

5000 ..................................................................................... 37 40 43 45 48 

Overall A-weighted SPL Measured at SAE J2889–1 

PP’line .............................................................................. 52 54 57 62 66 

TABLE 14—MINIMUM A-WEIGHTED SOUND LEVELS BASED ON ICE MEAN LEVELS MINUS ONE STANDARD DEVIATION

One-third octave band center frequency, Hz Stationary but 

activated Backing 10 km/hr 20 km/hr 30 km/hr 

315 ....................................................................................... 34 37 40 48 52 

400 ....................................................................................... 35 40 43 49 53 

500 ....................................................................................... 37 42 45 51 56 

2000 ..................................................................................... 39 42 45 50 54 

2500 ..................................................................................... 39 41 44 49 51 

3150 ..................................................................................... 39 40 43 47 49 

4000 ..................................................................................... 36 37 40 42 44 

5000 ..................................................................................... 29 34 37 38 40 

Overall A-weighted SPL Measured at SAE J2889–1 

PP’line .............................................................................. 46 49 52 58 61 


tkelley on DSK3SPTVN1PROD with 
Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2845 

117A presentation given at a meeting with 

NHTSA staff with the details of the proposal is 

available in the rulemaking docket accessible 

through regulations.gov. NHTSA–2011–0148–0022. 

Note, neither the mean nor the mean 

minus one standard deviation have 

levels that are as high as those for our 

proposed requirement specification 

(Table 12) at the low frequencies. This 

does not indicate a disagreement 

between the two approaches, but rather 

indicates that low frequencies of typical 

ICEs are not as detectable in the ambient 

used in the modeling as typical ICE 

high-frequency components. Finally, 

Table 14 has levels that are as high as 

Table 12 for stationary but activated 

only at 3150 and 4000 Hz. Again, this 

does not mean that vehicles with levels 

below the mean will never be 

detectable, but rather that they will not 

likely be detectable for the ambient that 

was used in the modeling. 

D. Acoustic Profiles Suggested by 

Manufacturers 

The Alliance of Automotive 

Manufacturers (the ‘‘Alliance’’) 

submitted acoustic specifications that 

could serve as minimum sound 

requirements for HVs and EVs.117 The 

Alliance proposed that the agency 

specify that HVs and EVs emit a sound 

with frequency content between 150 Hz 

and 3000 Hz. The Alliance proposal 

would require that sound emitted by 

HVs and EVs have at least two one-third 

octave bands with a sound pressure 

level of 44 A-weighted dB within this 

frequency range with one of the onethird octave bands being above 500 Hz 

and an overall sound pressure level of 

48 A-weighted dB. 

The agency believes that 

specifications for sound levels in only 

two one-third octave bands would not 

guarantee that sounds produced by HVs 

and EVs would be detectable in the 

range of ambient conditions in which 

the agency believes that pedestrians 

would need to detect them. If a sound 

has a greater number of one-third octave 

bands, it is more likely to be detectable 

at a given ambient. Sounds containing 

only one or two one-third octave bands 

with elevated sound pressure levels 

would be masked by ambient sound 

with strong spectral content in the same 

one-third octave bands which would 

hinder the ability of pedestrians to 

detect the sound. If a sound has elevated 

sound pressure levels at a wide range of 

one-third octave bands, it is less likely 

that an ambient will mask all of the 

bands that would increase the 

likelihood that the sound would be 

detectable. 

We do not believe that the suggestion 

submitted by the Alliance specifies the 

one-third octave bands for which a 

minimum sound level is required in 

enough detail. The placement of onethird octave bands in the frequency 

spectrum influences the detectability of 

a sound. While the Alliance’s suggestion 

would require one of the one-third 

octave bands to be at a frequency band 

above 500 Hz, the agency does not 

believe that this specification would 

ensure that the sounds would be loud 

enough for pedestrians to detect them at 

speeds above 0 km/hr. Based on the 

agency’s detection model, a one-third 

octave band with a sound pressure level 

of 44 A-weighted dB would not be 

detectable at 10 km/hr (6 mph) if the 

frequency of the one-third octave band 

was below 3150 Hz. A sound with two 

one-third octave bands with a sound 

pressure level of 44 A-weighted dB 

would be masked by the ambient if 

those one-third octave bands were both 

positioned in mid-range frequencies for 

which the ambient level is highest. 

We believe that the agency’s proposal 

would better ensure that sounds 

produced by HVs and EVs would be 

recognizable to pedestrians as a motor 

vehicle in operation. The Alliance’s 

suggestion does not include 

requirements for broadband, low 

frequency sound that contributes to 

recognizability. 

These suggestions have been 

considered, but they do not meet either 

the requirements of the PSEA or the 

safety need because the suggestions are 

not specific enough about the placement 

of required one-third octave bands in 

the frequency spectrum to adequately 

ensure the detectability of the sound 

and they do not contain specifications 

for recognition. However, we will 

consider any further comments from the 

Alliance and all other commenters to 

this proposal with regard to the sound 

that should be made and, to the extent 

those comments are persuasive, they 

will be useful in creating the final rule. 

The agency seeks 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. 

In its comments on the NOI, Nissan 

described the acoustic profile of the 

sound that is emitted by the Nissan 

Leaf. Nissan described the Leaf sound as 

having two peaks in sound pressure 

level with one peak near 2500 Hz and 

one peak near 600 Hz. Nissan stated that 

it included the 2500 Hz peak in sound 

pressure level to provide enhanced 

detection for pedestrians with normal 

hearing and the 600 Hz in sound 

pressure level to provide detection for 

pedestrians with age related hearing 

loss. The Leaf sound does not include 

mid-range one-third octave bands so 

that sound does not contribute to overall 

increases in ambient noise. 

As discussed above, the agency 

believes that sound should be present in 

multiple high frequency one-bands to 

increase the likelihood that a pedestrian 

will be able to detect the sound in 

multiple ambients with differing 

acoustic profiles. Like the Leaf sound, 

the acoustic specifications in this 

proposal do not contain requirements 

for the one-third octave bands that 

would contribute to the greatest increase 

in overall levels. The one-third octave 

band levels in Table 12 would ensure 

that pedestrians with age related hearing 

loss would be able to detect the sounds 

meeting these requirements. They 

would have a significant amount of 

detectable content below 2000 Hz 

which, according to Nissan, is the 

threshold for age related hearing loss. 

The agency believes that the acoustic 

specifications for minimum sound level 

requirements for HVs and EVs in the 

agency’s proposal will provide 

manufacturers flexibility to develop 

alerts that are detectable and 

recognizable to pedestrians and pleasing 

to drivers. While the specifications 

described in the agency’s proposal are 

more detailed than those contained in 

proposals that the agency received from 

manufacturers and their representatives, 

the agency believes that the 

specifications in its proposal place a 

greater emphasis on recognizability than 

specifications submitted by 

manufacturers. The agency’s 

specifications will also ensure that 

sounds produced by HVs and EVs will 

be detectable in a wider range of 

ambient sounds than would be the case 

in suggestions submitted by 

manufacturers because specifications for 

a wider range of one-third octave bands 

increases the likelihood that the sound 

pressure level in any one one-third 

octave band will exceed the ambient for 

that frequency. 

E. International Guidelines for Vehicle 

Alert Sounds 

As discussed in Section VI.D above, 

the Japanese government issued 

voluntary guidelines for manufacturers 

to use when installing alert sounds on 

HVs and EVs. The ECE has also adopted 

these guidelines for use on a voluntary 

basis. In their comments on the NOI, 

several manufacturers stated that the 

agency should use these guidelines as a 

basis for ensuring that HVs and EVs 

produce sound levels sufficient to allow 

pedestrians to detect these vehicles. 


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2846 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

The agency does not believe that these 

guidelines have the level of detail 

necessary to serve as the basis for an 

FMVSS. The guidelines do not contain 

objective minimum requirements that 

manufacturers would be required to 

meet. The guidelines state that levels of 

sounds produced by HVs and EVs 

should not exceed the levels produced 

by ICE vehicles of the same class. The 

agency does not believe that this 

description of the sound levels would 

adequately ensure that these vehicles 

will be detectable by pedestrians or 

provide manufacturers with a set of 

requirements that they would be 

expected to meet. 

The guidelines also do not contain an 

objective description of the acoustic 

characteristics that the sound should 

possess. Rather, the guidelines list what 

the sounds should not sound like. The 

guidelines state that vehicle emitted 

sounds should not sound like ‘‘siren[s], 

chime[s], bells, melody, horn[] sounds, 

animals, insects, [or] sound[s] of natural 

phenomenon such as wave[s], wind, [or] 

river current[s].’’ We do not believe that 

we would be able to tell whether a 

sound fell within one of the exclusions 

by means of an objective acoustic 

measurement because these descriptions 

do not contain any measurable values. 

F. Suggestions in Comments to the NOI 

That Did Not Satisfy the Statement of 

Purpose and Need for the Rulemaking 

Several of the commenters to the NOI 

suggested that the agency either take no 

action or address HV and EV collisions 

with pedestrians by other means. The 

PSEA requires the agency to establish an 

FMVSS that sets minimum sound 

requirements for HVs and EVs so taking 

no action was not a viable alternative. 

One commenter suggested that the 

agency use advanced pedestrian crash 

avoidance technologies as a means of 

addressing collisions between HVs and 

EVs and pedestrians. While these 

technologies offer a promising means of 

preventing collisions between 

pedestrians and all vehicles, they are 

not yet mature or widespread enough 

for the agency to be able to consider 

making these devices a mandatory piece 

of safety equipment on a vehicle at this 

time. Furthermore, requiring advanced 

pedestrian crash avoidance devices on 

HVs and EVs would not meet the 

requirements of the PSEA. 

G. Possible Jury Testing for 

Recognizability of a Synthetic Sound 

The PSEA requires the agency to 

develop performance requirements to 

determine whether pedestrian alert 

sounds required by the standard are 

recognizable as being emitted by a 

motor vehicle in operation. The agency 

has tentatively decided that a 

compliance test for recognizability 

based solely on acoustic measurements 

over spectral distribution detailed above 

is the best way to ensure recognizability 

while, at the same time, allowing 

manufacturers the flexibility to design 

sounds representative of each make/ 

model of vehicle. While the agency 

believes that sounds that fall within the 

agency’s acoustic parameters will be 

recognizable to the public as a motor 

vehicle in operation, it is possible that 

manufacturers may wish to use sounds 

that would be equally as recognizable as 

those sounds meeting the agency’s 

proposed specifications but would fail 

to satisfy the requirements proposed. 

Notwithstanding the agency’s 

tentative decision to use a set of sound 

parameters to achieve recognizability, 

we solicit comment on the possibility of 

allowing another compliance procedure 

designed to ensure that pedestrian alert 

sounds are recognizable and detectable. 

We are considering, but not proposing, 

allowing compliance through jury 

testing of sounds that would not meet 

the agency’s acoustic specifications for 

recognizability. Allowing jury testing of 

sounds may give manufacturers greater 

flexibility in meeting the requirements 

of the standard. We specifically are 

soliciting comment on the desirability 

and the feasibility of a jury testing 

procedure for ensuring that sounds 

would be recognizable as a motor 

vehicle. 

While the agency believes that human 

subject testing could provide an 

accurate evaluation of the 

recognizability of the pedestrian alert 

sound, the agency recognizes jury 

testing poses its own challenges. While 

the agency has tentatively concluded 

that jury testing is objective and 

repeatable as required by the Motor 

Vehicle Safety Act, manufacturers have 

expressed technical concerns about 

compliance testing by the agency using 

human subjects. 

Under the jury testing framework 

envisioned by the agency, 

manufacturers would be required to 

submit information to NHTSA 

demonstrating that the sounds emitted 

by their vehicles are recognizable as a 

motor vehicle in operation. Under this 

framework, manufacturers would 

conduct a jury test according to 

procedures established by NHTSA and 

then submit to NHTSA documentation 

of the results of the jury and a 

certification that the jury test was 

conducted according to the procedures 

established by the agency. 

After NHTSA received documentation 

of the manufacturer’s jury test, the 

agency would examine the documents 

to ensure that the test was conducted 

properly. The agency would also 

include the same performance test for 

detectability in the standard as is 

proposed today. 

While the agency believes that a 

compliance test using jury testing is 

objective and repeatable, manufacturers 

have expressed concerns in discussions 

with the agency about being subjected to 

a jury based performance standard. We 

recognize that automobile 

manufacturers face significant penalties 

in the event that they are determined to 

be noncompliant with a FMVSS. In an 

effort to provide manufacturers with 

regulatory certainty and in 

acknowledging that the agency does not 

currently specify any jury-based 

compliance testing, we have concluded 

that the most feasible approach to jury 

testing at this time would be for the 

agency to require manufacturers to 

conduct the jury tests themselves and 

submit their results to NHTSA as part of 

their vehicle certification. Thus, the 

manufacturers’ records that the jury test 

was conducted properly with the jury 

determining that the sound was 

recognizable would constitute the 

manufacturers’ certification. 

The agency believes that a 

certification procedure outlined above 

would be objective and repeatable, as 

required by the Motor Vehicle Safety 

Act. While recognizability may be 

described as a subjective concept, the 

procedure envisioned by the agency for 

determining whether a sound is 

recognizable as a motor vehicle would 

be stated in objective terms. The 

standard would specify the composition 

of the jury, the jury size, how to conduct 

the jury test, and pass fail criteria. The 

jury procedure would be repeatable 

because the underlying statistics dictate 

that if the required percentage of jurors 

finds the ICE control sound and non-ICE 

sound recognizable as a motor vehicle, 

a different jury would make the same 

determination of whether the non-ICE 

sound is recognizable or not. In 

conducting a compliance test to 

determine if the sound complied with 

the standard, NHTSA would not 

conduct its own jury testing; instead the 

agency would review the manufacturer’s 

documentation of its jury process to 

ensure the testing performed by the 

manufacturer was conducted according 

to the standard. Thus, a manufacturer 

would not be subject to the possibility 

that a jury test done by NHTSA would 

come to a different conclusion about the 

sound than the jury test conducted by 

the manufacturer. 

The jury testing procedure envisioned 

by the agency would provide an 


tkelley on DSK3SPTVN1PROD with 
Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2847 

118 472 F.2d 659 (D.C. Cir. 1972). 

119The jury composition requirements would 

allow for a slight deviation from the requirement 

that the jury be composing of equal numbers males 

in females in the event that the jury consisted of 

an odd number of subjects. 

120Available at http://media.wix.com/ugd/ 

64a49a_43313ad70e7c40f43150cf747b2e5

c44.pdf?dn=A520040+-+DSTN+-+White+paper+

electric+cars+-+av122410+-+ECT+LR.pdf. 

objective, repeatable method for 

determining compliance as required 

under the United States Court of 

Appeals for the District of Columbia 

Circuit’s interpretation of the Motor 

Vehicle Safety Act in Chrysler v. 

Department of Transportation.118 As 

discussed above, this jury test procedure 

would not subject the manufacturer to 

any subjective determination regarding 

compliance. Manufacturers would be 

assured of compliance if they conducted 

their jury test according to the agency’s 

procedure and properly documented the 

process and results. 

The jury of human subjects would be 

comprised of a sample size to make the 

jury results as repeatable as possible 

across multiple juries. Under the jury 

testing framework that the agency 

would mandate, the jury members 

would be exposed to two different 

sounds, a control sound and the sound 

that the manufacturer wished to use to 

meet the requirements of this standard. 

The jury members would be asked to 

identify whether each sound was a 

regular and detectable vehicle sound or 

not. The jury size that the agency would 

require under this alternative 

certification procedure would depend 

on the statistical power the agency 

wished to achieve, the recognition rate 

of the ICE-like control sound, and 

recognition rate that the agency would 

specify for non-ICE sounds. 

Assuming a 90 percent statistical 

power, a 90 percent ICE recognition rate 

and a minimum candidate sound 

recognition rate of 65 percent, (that is, 

65 percent of the jury would have to 

find the candidate sound recognizable 

and detectable for the manufacturer to 

certify the vehicle with the candidate 

sound) the jury sample size would need 

to be at least 28 people to provide 

results that would be repeatable. If the 

statistical power and ICE recognition 

rate were 90 percent and the minimum 

candidate sound recognition rate was 

changed to 75 percent, the size of the 

jury would increase to 54 people. If the 

ICE recognition rate was lowered to 85 

percent and the statistical power was 

maintained at 90 percent, a minimum 

recognition rate of 65 percent for the 

candidate sound would require a jury of 

45 people. A minimum recognition rate 

of 75 percent for the candidate sound 

under the same circumstances would 

require a jury of 140 people. Thus, the 

size of the jury increases as the gap 

between ICE recognition rate and the 

candidate sound recognition rate closes. 

In the event that the agency were to 

adopt a jury based approach in the 

pedestrian alert sound standard for 

determining recognizability, the jury 

size would be determined based on the 

agency’s decision of the statistical 

power, ICE-recognition rate, and 

minimum candidate sound recognition 

that the agency believes will ensure that 

pedestrians will be able to safely 

recognize the vehicle equipped with the 

candidate alert sound. We have 

tentatively concluded that jury testing to 

determine the recognizability of sounds 

should be conducted at a 90 percent 

statistical power. The agency seeks 

comment on the general approach to 

jury testing that the agency is 

considering as discussed above. 

Specifically, the agency would like 

comment on the appropriate size of the 

jury for testing to determine whether 

sounds are recognizable as a motor 

vehicle, the statistical power that should 

be used for the test, the reference ICE 

recognition rate that should be required, 

and the minimum candidate sound 

recognition rate that should be required. 

If the agency were to specify a jury 

test for recognizability, the agency 

would specify the specific demographic 

composition of the jury to ensure that 

the jury testing results would be 

repeatable across all segments of the 

public. The standard would require the 

jury to be composed of adults between 

the ages of 18 and 69 years old, with 

equal numbers of male and female 

participants.119 Subjects from the 18–29 

year-old, 30–49 year-old age, and 50–69 

year-old age groups would each make 

up one-third of the jury. Subjects would 

be required to be willing to be screened 

for hearing threshold shift in the 500 Hz 

to 8,000 Hz frequency range. Subjects 

with an estimated hearing loss of 20 dB 

or more above the normal range for the 

500 Hz to 8,000 Hz range would be 

excluded from the study. Jury subjects 

would also be prohibited from being 

employees of the manufacturer 

conducting the testing or otherwise 

interested in the outcome of the test. 

A jury test for recognizability of 

pedestrian alert sounds specified by the 

agency would be conducted using 

headphones in an audiometric test 

room. The jury test procedure would 

specify a maximum acceptable ambient 

for the audiometric test room in which 

the jury test would be conducted similar 

to the acceptable ambient for audio 

testing described in ANSI S3.1–1991, 

Maximum Permissible Ambient Noise 

Levels for Audiometric Test Rooms, 

American National Standard. NHTSA 

would also require that jury testing be 

conducted with high quality head 

phones. NHTSA has concluded that 

headphones are preferable to a test 

utilizing loudspeakers. Headphones 

allow for greater flexibility in the setup 

of the jury room. Further, jury members 

listening to the sounds via headphones 

would not be influenced by their seating 

position or the room’s acoustics. 

The manufacturer conducting the jury 

test would be required to use a vehicle 

of the same make to create the ICE 

control sound used in the jury testing 

and would be required to submit that 

sound to NHTSA as part of its 

certification documentation. The audio 

file played for the subjects would be 

required to include synthetic urban 

noise, filtered according to a 

specification developed by Torben 

Pedersen in ‘‘White Paper on External 

Sounds of Electric Cars,’’ 120 as 

background to simulate ambient that 

pedestrians would encounter when 

attempting to detect an EV or HV in the 

everyday environment. The audio file 

used for jury testing should be created 

using a binaural recording technique 

that accurately reproduces the qualities 

of a moving sound source. This is 

ordinarily accomplished by making 

recordings of actual vehicle pass-bys. 

The agency believes that the operating 

scenario under which the vehicle was 

recorded will influence whether the jury 

members will think the sound is 

recognizable. The agency believes that 

the sound used for the jury evaluation 

should be recorded while the vehicle is 

accelerating. The sound of a vehicle 

accelerating provides many of the sound 

cues that the agency is addressing 

through the acoustic specifications for 

recognizability The agency included 

specifications for pitch shifting in 

today’s proposal so that when the 

vehicle is accelerating the vehicle is 

providing acoustic cues about its 

changing speed The agency also 

believes that pitch shifting contributes 

to recognizability. Because the sounds 

that manufacturers may want to 

evaluate using this alternative 

framework should continue to provide 

pedestrians with cues that the vehicle is 

changing speed and because 

information provided by the sound that 

a vehicle makes while it is accelerating 

contributes to recognizability, the 

agency believes that the jury should 

evaluate the sound produced by the 

vehicle while it is accelerating, in 

addition to constant speed pass-by. 


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2848 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

The sample of the pedestrian alert 

sound played to the jury should be 10 

seconds in length for both the ICE 

control sound and the candidate sound 

the manufacturer is attempting to 

certify. The control sound and the 

candidate sound the manufacturer is 

seeking to evaluate would be played in 

a random sequence for each jury 

member. Thus, some members of the 

jury would hear the control sound first 

while others would hear the candidate 

sound first. The agency would specify 

the loudness at which the sound would 

be played for the jurors as well as the 

level of the synthetic ambient noise. 

Responses would be recorded using 

bubble-in survey forms with the bubbles 

representing yes or no for each sound 

for both the ICE control sound and the 

sound the manufacturer is seeking to 

certify. These forms would require 

minimal training for jury members as 

most jury members would likely be 

familiar with these forms. The jury 

instructions would consist of the 

following statement: 

In this evaluation you will be presented a 

pair of sounds. You are asked to indicate 

whether you believe that each of the sounds 

is recognizable as a motor vehicle sound or 

not. Select the response listed on the form 

that corresponds with your view of that 

sound. If you think that sound A is 

recognizable as a motor vehicle sound select 

yes, if you do not think that sound A is 

recognizable as a motor vehicle select no. 

After you have made your selection for sound 

A, evaluate sound B and check the box that 

corresponds with your view on whether 

Sound B is recognizable as a motor vehicle 

sound. If you think that sound B is 

recognizable as a motor vehicle sound select 

yes, if you do not think that sound B is 

recognizable as a motor vehicle select no. 

Since the objective of the experiment is to 

understand the individual’s reaction to the 

sounds, there are no right or wrong answers. 

The agency seeks comment on the 

jury instructions outlined above. The 

agency is specifically interested in 

instructions that result in a yes or no 

answer and that would not lead 

members of the jury to prejudge the 

sound. The agency recognizes that 

asking whether the sound is a regular 

and detectable vehicle sound may 

influence the jury to a certain degree. 

However, in order for the results of the 

jury test to be repeatable, jury responses 

would need to come in the form of yes 

or no answers. 

The validity of the jury test would be 

dependent on the jury members 

identifying the ICE control sound at the 

percentage required by the standard. If 

the jury members do not recognize the 

ICE control sound with the specificity 

required in the standard, the jury results 

must be discarded and the test 

invalidated. If the required percentage 

of jurors found both the candidate 

sound and ICE control sound to be 

recognizable as a motor vehicle in 

operation at the required recognition 

rates, the manufacturer would be able to 

certify the vehicle to the pedestrian alert 

standard. 

IX. NHTSA’s Role in the Development 

of a Global Technical Regulation 

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 (UN/ECE) 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 

US, 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 UN/ 

ECE World Forum for Harmonization of 

Vehicle Regulations (WP.29) 

administers the 1998 Agreement. Four 

committees coordinate the activities of 

WP.29: AC.2 manages the coordination 

of work of WP.29, while AC.3 is the 

‘‘Executive Committee’’ for the 1998 

Agreement. There are also six 

permanent subsidiary bodies of WP.29, 

known as GRs (Groups of Rapporteurs) 

that assist WP.29 in researching, 

analyzing and developing technical 

regulations. 

At 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 US has decided 

to lead the efforts on the new GTR, with 

Japan as co-sponsor, and develop 

harmonized pedestrian alert sound 

requirements for electric and hybridelectric 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 

US, along with Japan, is the co-chair of 

the informal working group 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 

expected establishment of the new GTR 

in November 2014. 

Prime Minister Stephen Harper and 

President Barack Obama created the 

U.S.-Canada Regulatory Cooperation 

Council (RCC) on February 4, 2011 to 

increase regulatory cooperation between 

the United States and Canada. One of 

the action items of the RCC is to work 

to develop joint plans to address hybrid 

and electric vehicles and pedestrian 

safety. Pursuant to the RCC, the agency 

has been collaborating with Transport 

Canada on areas of research of mutual 


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121See footnote 42. 

interest regarding sound produced by 

hybrid and electric vehicles. 

X. 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 

V), the use of data from 16 states cannot 

be used to directly estimate the national 

problem size and, an analysis of 

pedestrian fatalities 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 rate for hybrid and 

electric vehicles was 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. 

First, injury estimates from the 2006– 

2010 National Automotive Sampling 

System—General Estimates System 

(NASS–GES) and 2007 Not in Traffic 

Surveillance (NiTS) were used to 

provide an average estimate for 

combined in-traffic and relevant not-intraffic 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 2010. 

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, for a 

total of 200.8 crashes. 

Table 15 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 15—QUIET CARS TARGET POPULATION INJURIES REPORTED (GES, NITS) 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) ................................................................................ 75,401 12,490 2,561 613 248 91,313 

Light Trucks & Vans (LTV) ...................................................................... 51,761 8,627 1,771 423 171 62,753 

Total Light Vehicles (PC+LTV) ......................................................... 127,163 21,116 4,332 1,037 419 154,067 

Reported (GES+NiTS) and Unreported Injured Pedalcyclists 

Passenger Car (PC) ................................................................................ 43,795 6,329 1,105 247 88 51,564 

Light Trucks & Vans (LTV) ...................................................................... 28,840 4,184 730 162 58 33,974 

Total Light Vehicles (PC+LTV) ......................................................... 72,635 10,513 1,835 409 146 85,538 

The estimates in Table 15 are based 

on the current make-up of the fleet for 

all propulsion types. This means that 

the total target population described 

above across 2006 to 2010 is not only 

the result of 100% of the combined sales 

of all vehicle propulsion types, but also 

it is assumed to be equal to 100.67% of 

the injuries resulting from a fleet 

comprised of only ICE vehicles (due to 

the increased rate of these incidents for 

EVs and HVs). The estimated injuries in 

Table 16 are created by combining the 

percentage of annual sales of hybrid and 

electric vehicles with the odds ratio of 

1.19, representing the increased risk of 

an HV being involved in a pedestrian 

crash, and the odds ratio of 1.44, 

representing the increased risk of an HV 

being involved in a pedalcyclist 

crash.121 Thus, when considering 

pedestrians injured by MY2016 vehicles 

and assuming these pedestrian and 

pedalcyclist crashes occurred because 

the pedestrians and pedalcyclists failed 

to detect these vehicles by hearing, the 

rulemaking is responsible for the 1,223 

injury difference between that 

theoretical ICE-only fleet (153,271 

injuries) and the estimated lifetime 

injuries from the MY2016 fleet 

(154,494). When considering 

pedalcyclists injured by MY2016 

vehicles, the rulemaking is responsible 

for the 1,567 injury difference between 

that theoretical fleet (84,516 injuries) 

and the estimated lifetime injuries from 

the MY2016 fleet (86,084). The rule 

would also reduce 5 pedestrian injuries 

over the lifetime of the MY 2016 fleet of 

LSVs and 5 pedalcyclist injuries over 

the lifetime of the MY 2016 fleet of 

LSVs. 


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2850 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

122Table values may be off by one due to 

rounding. 

123Table values may be off by one due to 

rounding. 

124 In calculating the costs of this proposal 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 proposal. 

TABLE 16—ENHANCED INJURY RATE (EIR) FOR PEDESTRIANS FOR 2016 MODEL YEAR 122

Mild 

hybrids 

(percent) 

Strong 

hybrids 

(percent) 

EVs + 

fuel cell 

(percent) 

ICEs 

(percent) 

Total 

(percent) 

Injuries 

assuming 

100% 

ICE 

fleet 

Injuries 

assuming 

predicted 

fleet 

Benefits 

Passenger Car ................................................. 4.46 5.79 0.50 90.18 100.92 90,706 91,545 839 

Light Trucks & Vans ........................................ 5.62 3.85 0.04 91.11 100.61 62,565 62,949 384 

Total .......................................................... ................ ................ ................ ................ ................ 153,271 154,494 1,223 

ENHANCED INJURY RATE (EIR) FOR PEDESTRIANS FOR 2016 MODEL YEAR 123

Mild 

hybrids 

(percent) 

Strong 

hybrids 

(percent) 

EVs + 

fuel cell 

(percent) 

ICEs 

(percent) 

Total 

(percent) 

Injuries 

assuming 

100% 

ICE fleet 

Injuries 

assuming 

predicted 

fleet 

Benefits 

Passenger Car ................................................. 4.46 7.01 0.50 90.18 102.14 50,777 51,865 1,087 

Light Trucks & Vans ........................................ 5.62 4.66 0.04 91.11 101.42 33,739 34,219 480 

Total .......................................................... ................ ................ ................ ................ ................ 84,516 86,084 1,567 

The agency has not estimated the 

benefits associated with applying the 

requirements of this proposal to hybrid 

and electric vehicles with a GVWR over 

4,536 kg (10,000 pounds), and electric 

motorcycles because the agency was 

unable to determine separate pedestrian 

collision rates for these vehicle types. 

The agency is unsure whether using the 

difference in rates between light ICE 

vehicle pedestrian crashes and light HV 

and EV pedestrian crashes would be an 

appropriate means of calculating the 

benefits of applying the requirements of 

this proposal to these other classes of 

vehicles. As discussed in the 

Preliminary Regulatory Impact Analysis 

(PRIA), MAIS injury levels are 

converted to dollar amounts. The 

benefit of reducing 2,800 pedestrian and 

pedalcyclist injuries, or 35 equivalent 

lives saved, is estimated to be $ 178.7M 

at the 3 percent discount rate and 

$146.3M at the 7 percent discount rate 

for the light vehicle and LSV fleet. 

The agency calculated the benefits of 

this proposal 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. NHTSA also assumes the 

sound added to hybrid and electric 

vehicles will be as effective in providing 

warning to pedestrians as the sound 

produced by a vehicle’s ICE. NHTSA 

seeks comment on the underlying 

assumptions used in calculating the 

benefits of this proposal. 

In addition to the benefits in injury 

reduction due to this proposal there is 

also the benefit to blind individuals of 

continued independent mobility. The 

increase in navigational ability resulting 

from this proposal 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, 2011 there were 306,882 

hybrid engine installations in light 

vehicles (74% were in passenger cars 

and 26% were in light trucks) in MY 

2010 (these were 2.8% of sales in 2010 

of 10,796,533). There were a small 

number of electric vehicles (an 

estimated 852 from NHTSA’s data not 

Ward’s) sold in 2010, the larger sellers 

(GM Volt and Nissan Leaf) were 

introduced later. The Annual Energy 

Outlook (AEO) for 2011 provides 

estimates of the fleet by year for hybrid 

and electric vehicles.124 The number of 

vehicles that the agency projects will be 

required to meet the standard is shown 

in TABLE 17. 

TABLE 17—ESTIMATED/PREDICTED HYBRID AND ELECTRIC VEHICLE SALES PROPOSED TO BE REQUIRED TO PROVIDE AN

ALERT SOUND

Estimated 2010 

sales 

Predicted 2016 

sales 

2016 sales for 

costing purposes 

Low-Speed Vehicles .................................................................................................. 1,500 2,500 2,500 

Light Vehicles Electric ............................................................................................... 852 46,200 ..............................

Fuel Cells ................................................................................................................... 0 2,900 ..............................

Light Vehicles Hybrid ................................................................................................. 289,282 671,300 671,300 


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TABLE 17—ESTIMATED/PREDICTED HYBRID AND ELECTRIC VEHICLE SALES PROPOSED TO BE REQUIRED TO PROVIDE AN

ALERT SOUND—Continued 

Estimated 2010 

sales 

Predicted 2016 

sales 

2016 sales for 

costing purposes 

Light Vehicles Total ................................................................................................... 290,143 720,400 ..............................

Medium and Heavy Truck ......................................................................................... 2,000 21,500 21,500 

Buses ......................................................................................................................... 3,000 5,000 5,000 

Motorcycles ................................................................................................................ 1,500 5,000 5,000 

Total Sales .......................................................................................................... 298,143 754,400 705,300 

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 

would have provided an alert sound 

system on their own and, therefore, for 

costing purposes we assumed that this 

is not a cost of the proposal. However, 

those vehicles’ alert sounds may not 

meet the proposed standard and, the 

rulemaking may force a change in a 

manufacturer’s sound alert. We assume 

that manufacturers would incur no 

incremental cost for that change, as it is 

anticipated to be a simple software 

modification. Thus, the incremental 

number of light vehicles that have to 

add an alert sound system for costing 

purposes for MY 2016 is 720,400- 

46,200–2,900 = 671,300. 

Based on informal discussions with 

suppliers and industry experts, the 

agency estimates that the total consumer 

cost for a system that produces sounds 

meeting the requirement of this 

proposal is around $30 per vehicle. This 

estimate includes the cost of a dynamic 

range speaker system that is protected 

from the elements and attached with 

mounting hardware and wiring to both 

power the speaker 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 status). We seek comment of the 

cost of a speaker system used to produce 

sounds meeting the requirements 

contained in this proposal. We assume 

there will be no other structural changes 

or installation costs associated with 

complying with the rule’s requirements 

and seek comment on this assumption. 

We believe the same system can be used 

for both low-speed vehicles and light 

vehicles. We estimate that the added 

weight of the system would increase 

fuel costs for light vehicles around $5 

over the life time of the vehicle. 

TABLE 18—TOTAL COSTS

3% Discount rate 7% Discount rate 

Passenger Cars Per Vehicle ........................................................................................................... $34.73 $33.83. 

Light Trucks Per Vehicle ................................................................................................................. $35.33 $34.23. 

All Passenger Cars .......................................................................................................................... $15.27 Million $14.87 Million. 

All Light Trucks ................................................................................................................................ $8.19 Million $7.93 Million. 

Total for Light Vehicles .................................................................................................................... $23.45 Million $22.80 Million. 

Low-speed Vehicles Per Vehicle ..................................................................................................... $30.24 $30.24. 

Low-speed Vehicles Total Cost ....................................................................................................... $0.08 $0.08. 

Partial Costs for All Medium/Heavy Trucks, Buses, and Motorcycles ............................................ $1.48 Million $1.48 Million. 

Total .......................................................................................................................................... $25.00 Million $24.36 Million. 

In addition to the quantifiable costs 

discussed above, there may be a cost of 

adding sound to quiet vehicles to 

owners who value quiet. NHTSA does 

not know how to put a value on quiet 

for a driver’s own vehicle. We are also 

unsure of the extent to which the added 

sound will reach the passenger 

compartment of the vehicle and request 

comment on this issue. Nor does the 

agency know how to put a value or a 

cost on the increase in noise that the 

alert sound from other vehicles would 

produce. 

As explained further in the Draft 

Environmental Assessment (Draft EA) 

that the agency has analyzed the 

potential environmental effects of this 

rulemaking, we expect that the increase 

in noise from the alert sound will be no 

louder than that from an average ICE 

vehicle and that there will not be an 

appreciable aggregate sound from these 

vehicles. 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. 

Nevertheless, we ask commenters 

whether the increase in noise brought 

about by this proposal has any cost and 

how to value it. NHTSA also seeks 

comment on whether manufacturers are 

taking any actions beyond adding 

speakers and typical noise reduction 

efforts in response to adding sound to 

quiet vehicles and the cost of such 

actions. NHTSA has not found any way 

to value the increase in noise, and, thus 

it is a non-quantified cost. 

C. Comparison of Costs and Benefits 

Because we have calculated the costs 

of this rule to all applicable hybrid and 

electric vehicles, but not calculated the 

benefits of applying this proposal to the 

medium and heavy duty trucks and 

buses and electric motorcycles the 

comparison of costs and benefits only 

takes into account light vehicles and 

low-speed vehicles. Comparison of costs 

and benefits expected due to this rule 

provides a cost of $0.83 to $0.99 million 

per equivalent life saved across the 3 

and 7 percent discount levels. This falls 

under NHTSA’s value of a statistical life 

of $6.3M, and therefore this rulemaking 

is assumed to be cost beneficial. Since 

the lifetime benefits of MY2016 light 

vehicles is expected to be between 

$145.8M and $178M, the net impact of 

the rule is a positive one, even with the 


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2852 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

125Based on the assumption in this analysis that 

manufacturers will install speakers to meet the 

proposal. 

126Scaled benefits and costs for low speed 

vehicles are estimated directly proportional to light 

vehicles based on sales. Scaled costs include both 

installation costs for the system and fuel costs. 

estimated $20.1M required to install 

speakers 125 and $3M in lifetime fuel 

costs. 

TABLE 19—DISCOUNTED BENEFITS MY 

2016, 2010$ 

3% Discount 

Total 

monetized 

benefits 

Total ELS 

TOTAL PED + CYC 

(PC) .................. $122,747,591 19.41 

(LTV) ................. 55,265,495 8.74 

Total .............. 178,013,086 28.15 

7% Discount 

Total 

monetized 

benefits 

Total ELS 

TOTAL PED + CYC 

(PC) .................. $102,366,052 16.19 

(LTV) ................. 43,422,889 6.87 

Total .............. 145,788,941 23.06 

TABLE 20—TOTAL COSTS 2010$ 

3% Discount Total 

cost/veh Total costs 

(PC) .................. $34.70 $15,253,618 

TABLE 20—TOTAL COSTS 2010$— 

Continued 

3% Discount Total 

cost/veh Total costs 

(LTV) ................. 35.30 8,178,471 

Total .............. 34.91 23,432,088 

7% Discount Total 

cost/veh Total costs 

(PC) .................. $33.80 $14,857,991 

(LTV) ................. 34.20 7,923,618 

Total .............. 33.94 22,781,608 

TABLE 21—NET IMPACTS 2010$ 

3% Discount Net impact/veh Net impact Net costs/ELS 

(in $M) 

(PC) ............................................................................................................................ $244.53 $107,493,974 0.79 

(LTV) .......................................................................................................................... 203.24 47,087,024 0.94 

Total .................................................................................................................... 230.28 154,580,998 0.83 

7% Discount Net impact/veh Net impact Net costs/ELS 

(in $M) 

(PC) ............................................................................................................................ $199.07 $87,508,062 0.92 

(LTV) .......................................................................................................................... 153.22 35,499,271 1.15 

Total .................................................................................................................... 183.25 123,007,333 0.99 

The net impact of this proposal to 

LSVs is also expected to be positive. 

The net benefits of the minimum sound 

requirements for these vehicles is 

$662,971 at the 3 percent discount rate 

and $542,959 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. 

TABLE 22—COSTS AND SCALED BENEFITS FOR LSVS, MY2016 126

Discount rate 

Sales ratio 

LSV to light 

vehicle 

Sales Scaled costs Scaled injuries 

(undisc.) Scaled ELS Scaled benefits 

Scaled 

benefits 

minus 

scaled costs 

3% ................................ 0.37% 2,500 $87,268 10.39 0.1049 $662,971 $575,703 

7% ................................ 0.37% 2,500 84,845 10.39 0.0859 542,959 458,114 

D. Environmental Effects 

The agency has prepared a Draft 

Environmental Assessment (Draft EA) to 

analyze and disclose the potential 

environmental impacts of a reasonable 

range of potential 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, which is the Preferred 

Alternative and is equivalent to the 

agency’s proposal, 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 the Draft EA, 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. National Household Travel 

Survey data for 2009 shows that nonurban households account for 31 

percent of all vehicle miles traveled 

(VMT) but just 14 percent of VMT 

associated with trips at an average speed 

of less than 20 km/h, indicating that 

these households spend a much smaller 

percent of travel time at slow speeds 

associated with congested traffic than 

do households in urban areas. The Draft 

EA estimates the direct and indirect 

impacts of the alternatives in both urban 

and non-urban areas by taking into 


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account the higher percentage of total 

VMT that takes place in non-urban 

areas, the lower percentage of VMT 

traveled at slow speeds in non-urban 

areas, and the lower percentage of EV/ 

HV sales expected in non-urban areas. 

In the Draft EA, NHTSA estimated the 

amount of total annual U.S. passenger 

vehicle driving time spent in the 

stationary but active operating 

condition, at speeds up to 20 km/h, and 

at speeds between 20 and 30 km/h. 

Using forecasts of EV/HV deployment 

levels in 2035, NHTSA projected the 

percentage of total U.S. light duty 

driving hours that would be impacted 

by the standards (e.g., vehicles driven at 

speeds that would enable the alert 

sound). Based on these assumptions, 

NHTSA projects that under Alternative 

2 (the Preferred Alternative), 2.3 percent 

of all urban and 0.3 percent of all nonurban light vehicle travel hours would 

be affected by the minimum sound 

requirements in 2035. Under Alternative 

3, 0.9 percent of all urban and 0.1 

percent of all non-urban light vehicle 

travel hours would be affected by the 

minimum sound requirements in 2035. 

The agency’s analysis also shows that 

in either urban or non-urban 

environments, assuming EV/HV 

deployment levels of either 10 percent 

and 20 percent, the agency’s Preferred 

Alternative would have negligible to 

minimal effects on overall community 

noise levels. Under the Preferred 

Alternative, in a simulated high-traffic 

condition, the agency found a difference 

in sound level of no greater than 0.3 

dB(A), as measured by a receiver 7.5 

meters from a roadway, at all speeds 

and under all conditions compared to 

the No Action Alternative. Even if EVs/ 

HVs were to reach 50 percent 

deployment, Alternative 2 is projected 

to amount to a maximum difference of 

0.9 dB above the sound level under the 

No Action Alternative in non-urban 

environments and 0.7 dB in urban 

environments. Because differences in 

sound pressure of less than 3 dB are 

generally not noticeable by humans, the 

environmental impacts of this proposal 

are expected to be negligible. Although 

sound level differences are greater for 

single vehicle pass-by events the 

difference would be similar to the 

existing variation that results from 

differences between ICE vehicle models. 

Thus, although the individual event 

may be noticeable, overall the 

noticeable noise levels in the case of 

single-car pass-by are considered to 

cause only a minor impact. 

XI. 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 PRIA. 

We estimate the total fuel and 

installation costs of this proposal to the 

light EV, HV and LSV fleet to be $23.5M 

at the 3 percent discount rate and 

$22.9M at the 7 percent discount rate. 

The estimated total installation cost for 

hybrid and electric heavy and medium 

duty trucks and buses and electric 

motorcycles is $1.48M meaning that the 

total costs for this rule are between $25 

and $24.36 million, depending on the 

discount rate. We have only calculated 

the benefits of this proposal for light 

EVs, HVs and LSVs because we do not 

have crash rates for hybrid and electric 

heavy and medium duty trucks and 

buses and electric motorcycles. We 

estimate that the impact of this proposal 

in pedestrian and pedacyclist injury 

reduction will be 28.15 equivalent lives 

saved at the 3 percent discount rate and 

23.06 equivalent lives saved at the 7 

percent discount rate. The benefits of 

this proposal for the light EV and HV 

and LSV fleet are $178.7M at the 3 

percent discount rate and $146.3M 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. 

NHTSA requests public comment on 

whether (a) ‘‘regulatory approaches 

taken by foreign governments’’ 

concerning the subject matter of this 

rulemaking and (b) the above policy 

statement have any implications for this 

rulemaking. 

National Environmental Policy Act 

Concurrently with this NPRM, NHTSA 

is releasing a Draft 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 Draft EA to 

analyze and disclose the potential 

environmental impacts of the proposed 

minimum sound requirements for HVs 

and EVs and a range of alternatives. The 

Draft EA analyzes direct, indirect, and 

cumulative impacts and analyzes 

impacts in proportion to their 

significance. 

Because this proposal would increase 

the amount of sound produced by a 

certain segment of the vehicle fleet, the 

Draft EA considers the possible impacts 

of increased ambient noise levels on 

both urban and rural environments. The 

Draft EA also describes potential 

environmental impacts to a variety of 

resources. The resources that may be 

affected by the proposed action and 

alternatives include biological 

resources, noise, and environmental 

justice. 

The agency’s analysis in the Draft EA 

shows that in either urban or non-urban 

environments, assuming EV/HV 

deployment levels of either 10 percent 

and 20 percent, the agency’s Preferred 

Alternative would have negligible to 

minimal effects on overall community 

noise levels. Even if EVs/HVs were to 

reach 50 percent deployment, the 

agency’s Preferred Alternative is 

projected to amount to a maximum 

difference of 0.9 dB above the sound 

level under the No Action Alternative in 

non-urban environments and 0.7 dB in 

urban environments. Because 

differences in sound pressure of less 

than 3 dB are generally not noticeable 

by humans, the environmental impacts 

of this proposal are expected to be 

negligible. 

For additional information on 

NHTSA’s NEPA analysis, please see the 

Draft EA. 


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127 13 CFR 121.105(a). 

128CODA, Fisker Automotive Inc., Via, Phoenix, 

and Tesla. However, it is our view that the 

manufacturers of electric vehicles would face little 

costs due to this rule because they would have 

installed alert sounds in their vehicles without this 

proposed rule. 

129 In the low-speed vehicle group there are 

Columbia ParCar Corp., Club Car, LLC, Miles 

Electric Vehicles LLC, STAR Electric Car Sales, 

Tomberlin, Wheego Electric Cars, Inc., Wildfire, 

GTT Electric and others. 

130Boulder Electric Vehicle and Smith Electric 

Vehicles are producing or have plans to produce 

electric vehicles with a GVWR over 10,000 lb. 

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.’’ 127 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 

proposal will not have a significant 

economic impact on a substantial 

number of small entities. 

I hereby certify that this proposed rule 

would not have a significant economic 

impact on a substantial number of small 

entities. We believe that the rulemaking 

would 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 ($30) 

is small in proportion to the overall 

vehicle cost for most small vehicle 

manufacturers. 

This proposal would directly affect 

motor vehicle manufacturers and finalstage manufacturers. The majority of 

motor vehicle manufacturers will not 

qualify as a small business. There are 

five manufacturers of light hybrid and 

electric vehicles that would be subject 

to the requirements of this proposal that 

are small businesses.128 Similarly, there 

are several manufacturers of low-speed 

vehicles129 and electric motorcycles that 

are small businesses. 

We believe there are very few 

manufacturers of heavy trucks in the 

United States which can be considered 

small businesses. The agency is aware 

that many manufacturers of medium 

duty trucks are small businesses. The 

agency is aware of at least two small 

manufacturers who are producing 

electric trucks with a GVWR over 10,000 

lb.130 In addition to the two 

manufacturers of medium duty electric 

vehicles identified by the agency, we 

believe that there may be other small 

manufacturers who are currently 

producing these vehicles. 

NHTSA believes there are 

approximately 37 bus manufacturers in 

the United States. Of these, 27 bus 

manufacturers are large business and 10 

are small businesses. Three of these 

small manufacturers produce electric 

buses—E-bus Inc., Enova Systems, and 

Gillig Corporation. 

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 ($30) is a 

small proportion of the overall vehicle 

cost for even the least expensive electric 

vehicles. 

(2) This proposal would provide a 

three year lead-time and would allow 

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 

proposed 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 proposed 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 


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structure of the regulatory text) and 

objectives of today’s proposed rule and 

finds that this proposed rule, like many 

NHTSA rules, would prescribe only a 

minimum safety standard. As such, 

NHTSA does not intend that this 

proposed rule would preempt state tort 

law that would effectively impose a 

higher standard on motor vehicle 

manufacturers than that established by 

today’s proposed rule. Establishment of 

a higher standard by means of State tort 

law would not conflict with the 

minimum standard proposed 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 PRE. We estimate the 

annual total fuel and installation costs 

of this proposal to the light EV, HV and 

LSV fleet to be $23.5M at the 3 percent 

discount rate and $22.9M at the 7 

percent discount rate. The estimated 

total installation cost for hybrid and 

electric heavy and medium duty trucks 

and buses and electric motorcycles is 

$1.48M. Therefore, this proposal 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 $136M 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 NPRM 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, motorcycles and low 

speed vehicles subject to the phase-in 

schedule to provide motor vehicle 

production data for the following three 

years: September 1, 2015 to August 31, 

2016; September 1, 2016 to August 31, 

2017; and September 1, 2017 to August 

31, 2018. 

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 phasein 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, motorcycles and lowspeed vehicles. The agency estimates 

that there are about 73 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 146 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. 

The procedure for the evaluation of 

vehicle sounds by human subjects 

contained in Section VIII.G of this 

proposal would also constitute a 

collection of information for the 

purposes of the PRA. If the agency 

decides to adopt the procedure 

described in Section VIII.G in the final 

rule then agency would submit an ICR 

to OMB before the final rule is issued in 

compliance with the PRA. 


tkelley on DSK3SPTVN1PROD with 
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131 62 FR 19885 (Apr. 23, 1997). 132 66 FR 28355 (May 18, 2001). 133See 49 CFR § 553.21. 

Executive Order 13045 

Executive Order 13045 131 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. 

This proposed rule would not pose 

such a risk for children. The primary 

effects of this proposal 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 

proposal. 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 this proposal 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. As discussed in Section 

VII.E.1, the proposal does not include a 

procedure for indoor testing because of 

the limited availability of indoor test 

facilities and because test surfaces for 

indoor testing are not sufficiently 

specified. 

Executive Order 13211 

Executive Order 13211 132 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. 

The proposed 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 proposed 

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. 

Plain Language 

Executive Order 12866 requires each 

agency to write all rules in plain 

language. Application of the principles 

of plain language includes consideration 

of the following questions: 

• Have we organized the material to 

suit the public’s needs? 

• Are the requirements in the rule 

clearly stated? 

• Does the rule contain technical 

language or jargon that isn’t clear? 

• Would a different format (grouping 

and order of sections, use of headings, 

paragraphing) make the rule easier to 

understand? 

• Would more (but shorter) sections 

be better? 

• Could we improve clarity by adding 

tables, lists, or diagrams? 

• What else could we do to make the 

rule easier to understand? 

If you have any responses to these 

questions, please include them in your 

comments on this proposal. 

Privacy Act 

Anyone is able to search the 

electronic form of all comments 

received into any of our dockets by the 

name of the individual submitting the 

comment (or signing the comment, if 

submitted on behalf of an organization, 

business, labor union, etc.). You may 

review DOT’s complete Privacy Act 

statement in the Federal Register 

published on April 11, 2000 (Volume 

65, Number 70; Pages 19477–78) or you 

may visit http://www.dot.gov/ 

privacy.html. 

Public Participation 

How do I prepare and submit 

comments? 

Your comments must be written and 

in English. To ensure that your 

comments are correctly filed in the 

Docket, please include the docket 

number of this document in your 

comments. Your comments must not be 

more than 15 pages long.133 We 

established this limit to encourage you 

to write your primary comments in a 

concise fashion. However, you may 

attach necessary additional documents 

to your comments. There is no limit on 

the length of the attachments. 

Please submit your comments by any 

of the following methods: 


tkelley on DSK3SPTVN1PROD with 
Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2857 

134Optical character recognition (OCR) is the 

process of converting an image of text, such as a 

scanned paper document or electronic fax file, into 

computer-editable text. 135See 49 CFR § 512. 

• Federal eRulemaking Portal: go to 

http://www.regulations.gov. Follow the 

instructions for submitting comments 

on the electronic docket site by clicking 

on ‘‘Help’’ or ‘‘FAQ.’’ 

• Mail: Docket Management Facility, 

M–30, U.S. Department of 

Transportation, West Building, Ground 

Floor, Rm. W12–140, 1200 New Jersey 

Avenue SE., Washington, DC 20590. 

• Hand Delivery or Courier: West 

Building Ground Floor, Room W12–140, 

1200 New Jersey Avenue SE., between 

9 a.m. and 5 p.m. Eastern Time, Monday 

through Friday, except Federal holidays. 

• Fax: (202) 493–2251. 

If you are submitting comments 

electronically as a PDF (Adobe) file, we 

ask that the documents submitted be 

scanned using Optical Character 

Recognition (OCR) process, thus 

allowing the agency to search and copy 

certain portions of your submissions.134

Please note that pursuant to the Data 

Quality Act, in order for substantive 

data to be relied upon and used by the 

agency, it must meet the information 

quality standards set forth in the OMB 

and DOT Data Quality Act guidelines. 

Accordingly, we encourage you to 

consult the guidelines in preparing your 

comments. OMB’s guidelines may be 

accessed at http://www.whitehouse.gov/ 

omb/fedreg/reproducible.html. DOT’s 

guidelines may be accessed at http:// 

dmses.dot.gov/submit/ 

DataQualityGuidelines.pdf. 

How can I be sure that my comments 

were received? 

If you submit your comments by mail 

and wish Docket Management to notify 

you upon its receipt of your comments, 

enclose a self-addressed, stamped 

postcard in the envelope containing 

your comments. Upon receiving your 

comments, Docket Management will 

return the postcard by mail. 

How do I submit acoustic recordings? 

If you wish to submit acoustic 

recordings along with your comments 

please sent the recordings to NHTSA at 

the address given above under FOR

FURTHER INFORMATION CONTACT. If you 

wish to request confidential treatment of 

the records please follow the 

instructions listed below. 

In order to be of use to the agency, 

NHTSA is requesting that any 

recordings submitted to the agency be 

16-bit with a sampling frequency of 44.1 

kHz or better and made with a 

stationary binaural head facing 

perpendicular to the vehicle’s trajectory. 

As well as any recording made using a 

binaural head, it would be useful to the 

agency, if possible, for recordings 

submitted to include a recording from a 

monaural microphone made according 

to SAE J2889–1. The agency requests 

that a Calibration Tone be included in 

each set of recordings. The agency also 

requests that the level and frequency of 

the Calibration Tone be indicated, e.g. 

94 dB at 1000 Hz. 

In order to be of use in the agency’s 

analysis, we request that idle recordings 

be at least 30 seconds long and 

preferably 60 seconds long. Constant 

speed pass-by recordings should 

include at least 15 seconds of approach 

towards the microphone and at least 5 

seconds departing from the microphone. 

Ideally the recording will start before 

the vehicle is audible. We are requesting 

the recording of time after departure so 

that we have additional data for analysis 

of tone-to-noise ratio, Doppler shifts, 

and Head-Related Transfer Function 

(HRTF) effects, but do not need 

recordings up until the point at which 

the vehicle is no longer audible. The 

agency requests that commenters 

identify the distance of vehicle from 

microphone at start of recording as well 

as the distance between the microphone 

and the vehicle center line. The agency 

requests that commenters identify the 

operating scenario of the vehicle when 

the recording was made. 

In order to help us with our analysis, 

we request that commenters submit 

information about the make, model and 

year of the vehicle being recorded along 

with the recording. We also request that 

commenters identify whether the 

recording is of an ICE vehicle or an EV/ 

HV equipped with an alert sound. The 

agency requests that commenters submit 

the minimum A-weighted level and 

maximum A-weighted level while using 

a fast (125 ms exponential) time 

weighting of the sound produced by the 

vehicle along with the recording. 

In order to assist the agency in 

analyzing recordings submitted in 

response to the NPRM we request that 

commenters inform the agency whether 

the recording was conducted on an ISO 

noise pad, in a semi-anechoic chamber 

or on a test bench. For outdoor testing 

it would be useful for commenters to 

provide measurements of the air and 

pavement temperature, and wind speed 

at the time of the recording as well as 

photographs of the test site if available. 

For more information about how the 

agency collected data for its research 

please see Chapter 4.1.5, Data Collection 

Protocol, in the agency’s Phase I 

research report. 

How do I submit confidential business 

information? 

If you wish to submit any information 

under a claim of confidentiality, you 

should submit three copies of your 

complete submission, including the 

information you claim to be confidential 

business information, to the Chief 

Counsel, NHTSA, at the address given 

above under FOR FURTHER INFORMATION

CONTACT. When you send a comment 

containing information claimed to be 

confidential business information, you 

should include a cover letter setting 

forth the information specified in our 

confidential business information 

regulation.135

In addition, you should submit a 

copy, from which you have deleted the 

claimed confidential business 

information, to the Docket by one of the 

methods set forth above. 

Will the agency consider late 

comments? 

We will consider all comments 

received before the close of business on 

the comment closing date indicated 

above under DATES. To the extent 

possible, we will also consider 

comments received after that date. 

Therefore, if interested persons believe 

that any new information the agency 

places in the docket affects their 

comments, they may submit comments 

after the closing date concerning how 

the agency should consider that 

information for the final rule. 

If a comment is received too late for 

us to consider in developing a final rule 

(assuming that one is issued), we will 

consider that comment as an informal 

suggestion for future rulemaking action. 

How can I read the comments submitted 

by other people? 

You may read the materials placed in 

the docket for this document (e.g., the 

comments submitted in response to this 

document by other interested persons) 

at any time by going to http:// 

www.regulations.gov. Follow the online 

instructions for accessing the dockets. 

You may also read the materials at the 

Docket Management Facility by going to 

the street address given above under 

ADDRESSES. The Docket Management 

Facility is open between 9 a.m. and 5 

p.m. Eastern Time, Monday through 

Friday, except Federal holidays. 

List of Subjects 

49 CFR Part 571 

Motor vehicle safety, Reporting and 

recordkeeping requirements, Tires. 


tkelley on DSK3SPTVN1PROD with 
2858 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

49 CFR Part 585 

Motor vehicle safety, Reporting and 

recordkeeping requirements. 

Proposed Regulatory Text 

For reasons discussed in the 

preamble, NHTSA proposes to amend 

49 CFR part 571 as follows: 

PART 571—FEDERAL MOTOR 

VEHICLE SAFETY STANDARDS 

■ 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. 

■ 2. In § 571.5, paragraphs (i)(2) and 

(l)(50) are added to read as follows: 

§ 571.5 Matter incorporated by reference. 

* * * * * 

(i) * * * 

(2) ISO 10844:2011 ‘‘Acoustics—Test 

Surface for Road Vehicle Noise 

Measurements,’’ into § 571.141. 

* * * * * 

(l) * * * 

(50) SAE Standard J2889–1 SEP2011, 

‘‘Measurement of Minimum Noise 

Emitted by Road Vehicles,’’ the 

following sections only into § 571.141: 

S4, Table 1, S5.1, S5.3, S6.1.1, S6.4, 

S6.5, S7.1. 

* * * * * 

■ 3. Section 571.141 is added to read as 

follows: 

§ 571.141 Standard No. 141; Minimum 

Sound Requirements for Hybrid and 

Electric Vehicles. 

S1. Scope. This standard establishes 

performance for pedestrian alert sounds 

from motor vehicles. 

S2. Purpose. The purpose of this 

standard is to reduce the number of 

deaths and injuries that result from 

electric and hybrid vehicles crashes 

with pedestrians by providing a sound 

level and sound characteristics 

necessary for these vehicles to be 

detected and recognized by pedestrians. 

S3. Application. This standard 

applies to— 

(a) Electric vehicle passenger cars, 

multipurpose passenger vehicles, 

trucks, buses, motorcycles, and lowspeed vehicles; 

(b) Passenger cars, multi-purpose 

passenger vehicles, trucks, buses, and 

low-speed vehicles with more than one 

means of propulsion for which the 

vehicle’s propulsion system can propel 

the vehicle in the normal travel mode in 

reverse and at least one forward drive 

gear without the internal combustion 

engine operating and; 

(c) Motorcycles with 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 without 

the internal combustion engine 

operating. 

S4. Definitions. 

Broadband content means a 

measureable acoustic signal (greater 

than 0 A-weighted dB) at all frequencies 

within a one-third octave 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. 

Fundamental frequency means, for 

purposes of this regulation, the lowest 

frequency of a valid measurement taken 

in S7. 

Rear plane means a vertical plane 

tangent to the leading edge of the 

vehicle when the vehicle is in a 

condition in which it is capable of 

reverse self-mobility. 

S5. Requirements. Subject to the 

phase-in set forth in S9 of this standard, 

each vehicle must meet the 

requirements specified in S5 under the 

test conditions specified in S6 and the 

test procedures specified in S7 of this 

standard. 

S5.1 Performance Requirements for 

critical operating scenarios. The vehicle 

must satisfy the requirements of this 

section when tested under the test 

conditions of S6 and the test procedures 

of S7. 

S5.1.1 Start up and stationary but 

activated. When measured according to 

the test conditions of S6 and the test 

procedure of S7.2, the vehicle must, 

within 500msec of activation of its 

starting system, emit a sound having at 

least the A-weighted sound pressure 

level in each of the one-third octave 

bands according to Table 1. The vehicle 

must also emit a sound meeting these 

requirements whenever moving at less 

than 10 km/h. 

(a) Directivity. When measured 

according to the test conditions of S6 

and test procedure of S7.2, the sound 

measured at the microphone on the line 

CC’ must have at least the A-weighted 

sound pressure level in each of the onethird octave bands according to Table 1. 

TABLE 1—ONE-THIRD OCTAVE BAND

MIN. SPL REQUIREMENTS FOR

SOUND WHEN STATIONARY BUT ACTIVATED

One-third octave band center 

frequency, Hz 

Min SPL, Aweighted dB 

315 ........................................ 42 

400 ........................................ 43 

TABLE 1—ONE-THIRD OCTAVE BAND

MIN. SPL REQUIREMENTS FOR

SOUND WHEN STATIONARY BUT ACTIVATED—Continued 

One-third octave band center 

frequency, Hz 

Min SPL, Aweighted dB 

500 ........................................ 43 

2000 ...................................... 42 

2500 ...................................... 39 

3150 ...................................... 37 

4000 ...................................... 34 

5000 ...................................... 31 

S5.1.2 Backing. For vehicles capable 

of rearward self-propulsion, whenever 

the vehicle’s gear selection control is in 

the reverse position, the vehicle must 

emit a sound having at least the Aweighted sound pressure level in each 

of the one-third octave bands according 

to Table 2 as measured according to the 

test conditions of S6 and the test 

procedure of S7.3. 

TABLE 2—ONE-THIRD OCTAVE BAND

MIN. SPL REQUIREMENTS FOR

SOUND WHILE BACKING

One-third octave band center 

frequency, Hz 

Min SPL, Aweighted dB 

315 ........................................ 45 

400 ........................................ 46 

500 ........................................ 46 

2000 ...................................... 45 

2500 ...................................... 42 

3150 ...................................... 40 

4000 ...................................... 36 

5000 ...................................... 34 

S5.1.3 Constant 10 km/h pass by. 

When tested under the conditions of S6 

and the procedures of S7.4, the vehicle 

must emit a sound having at least the Aweighted sound pressure level in each 

of the one-third octave bands according 

to Table 3 at any speed greater than or 

equal to 10 km/h, but less than 20 km/ 

h. 

S5.1.3.1 If after a vehicle to which 

this standard applies according to 

paragraph S3(b) or S3(c) is tested in 

accordance with paragraphs S7.4, for 

ten consecutive times without recording 

a valid measurement because the 

vehicle’s ICE remains active for the 

entire duration of the test, the vehicle is 

not required to meet the requirements in 

S5.1.3. 

TABLE 3—ONE-THIRD OCTAVE BAND

MIN. SPL REQUIREMENTS FOR 10 

KM/H PASS-BY

One-third octave band center 

frequency, Hz 

Min SPL, Aweighted dB 

315 ........................................ 48 

400 ........................................ 49 


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Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2859 

TABLE 3—ONE-THIRD OCTAVE BAND

MIN. SPL REQUIREMENTS FOR 10 

KM/H PASS-BY—Continued 

One-third octave band center 

frequency, Hz 

Min SPL, Aweighted dB 

500 ........................................ 49 

2000 ...................................... 48 

2500 ...................................... 45 

3150 ...................................... 43 

4000 ...................................... 39 

5000 ...................................... 37 

S5.1.4 Constant 20km/h pass by. 

When tested under the conditions of S6 

and the procedures of S7.5, the vehicle 

must emit a sound having at least the Aweighted sound pressure level in each 

of the one-third octave bands according 

to Table 4 at any speed greater than or 

equal to 20 km/h but less than 30 km/ 

h. 

S5.1.4.1 If after a vehicle to which 

this standard applies according to 

paragraph S3(b) or S3(c) is tested in 

accordance with paragraphs S7.5, for 

ten consecutive times without recording 

a valid measurement because the 

vehicle’s ICE remains active for the 

entire duration of the test, the vehicle is 

not required to meet the requirements in 

S5.1.4. 

TABLE 4—ONE-THIRD OCTAVE BAND

MIN. SPL REQUIREMENTS FOR 20 

KM/H PASS-BY

One-third octave band center 

frequency, Hz 

Min SPL, Aweighted dB 

315 ........................................ 54 

400 ........................................ 55 

500 ........................................ 56 

2000 ...................................... 54 

2500 ...................................... 51 

3150 ...................................... 49 

4000 ...................................... 46 

5000 ...................................... 43 

S5.1.5 Constant 30km/h pass by. 

When tested under the conditions of S6 

and the procedures of S7.6, the vehicle 

must emit a sound having at least the Aweighted sound pressure level in each 

of the one-third octave bands according 

to Table 5 at 30 km/h. 

S5.1.5.1 If after a vehicle to which 

this standard applies according to 

paragraph S3(b) or S3(c) is tested in 

accordance with paragraphs S7.6, for 

ten consecutive times without recording 

a valid measurement because the 

vehicle’s ICE remains active for the 

entire duration of the test, the vehicle is 

not required to meet the requirements in 

S5.1.5. 

TABLE 5—ONE-THIRD OCTAVE BAND

MIN. SPL REQUIREMENTS FOR 30 

KM/H PASS-BY

One-third octave band center 

frequency, Hz 

Min SPL, Aweighted dB 

315 ........................................ 59 

400 ........................................ 59 

500 ........................................ 60 

2000 ...................................... 58 

2500 ...................................... 56 

3150 ...................................... 53 

4000 ...................................... 50 

5000 ...................................... 48 

S5.1.6 Pitch shifting to signify 

acceleration and deceleration. The 

fundamental frequency of the sound 

emitted by the vehicle must vary with 

speed by at least one percent per km/h 

between 0 and 30 km/h. 

S5.2 Performance requirements for 

recognition as a motor vehicle. 

S5.2.1 The sound emitted by the 

vehicle to meet the requirements in 

S5.1.1 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. 

S5.2.2. The sound emitted by the 

vehicle to meet the requirements in 

S5.1.1 must have at least one tone no 

higher than 400 Hz. 

S5.2.3 The sound emitted by the 

vehicle to meet the requirements in 

S5.1.1 must have broadband content in 

each one-third octave band from 160 Hz 

to 5000 Hz. 

S5.3 Any two vehicles of the same 

make, model, and model year (as those 

terms are defined at 49 CFR 565.12) 

must emit the same sound as measured 

by the test required in S5.1.1 within 3 

A-weighted dB in each one-third octave 

band from 160 Hz to 5000 Hz 

S6. Test Conditions. 

S6.1 Weather conditions. The 

ambient conditions required by this 

section must be met at all times during 

the tests described in S7. Conditions 

must be measured with the accuracy 

required in S6.3.3 at the microphone 

height required in S6.4 +/¥ 2.54 cm. 

S6.1.1 The ambient temperature will 

be between 5 °C (41 °F) and 40 °C (104 

°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 must be 

measured and reported as in S6.4 of 

SAEJ2889–1 (incorporated by reference, 

see § 571.5). 

S6.2 Test surface. Test surface shall 

meet the requirements of ISO 

10844:2011 (incorporated by reference, 

see § 571.5). 

S6.3 Instrumentation. 

S6.3.1 Acoustical measurement. 

Instruments for acoustical measurement 

must meet the requirements of S5.1 of 

SAE J2889–1 (incorporated by reference, 

see § 571.5). 

S6.3.2 Vehicle speed measurement. 

Instruments used to measure vehicle 

speed during S7.4 and S7.5 of this 

standard must be capable of continuous 

measurement within ± 1.0 km/h over 

the entire test distance in S7.4 and S7.5. 

S6.3.3 Meteorological 

instrumentation. Instruments used to 

measure ambient conditions at the test 

site must meet the requirements of S5.3 

of SAE J2889–1 (incorporated by 

reference, see § 571.5). 

S6.4 Test site. The test site must be 

established per the requirements of 

S6.1.1 of SAE J2889–1 (incorporated by 

reference, see § 571.5), including Figure 

1, ‘‘Test Site Dimensions’’ with the 

definitions of the abbreviations in 

Figure 1 as given in Table 1, S4 of SAE 

J2889–1 (incorporated by reference, see 

§ 571.5). Microphone positions must 

meet the requirements of S7.1 of SAE 

J2889–1 (incorporated by reference, see 

§ 571.5). 

S6.5 Test set up for directivity 

measurement must 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) Tires will be fitted and pressurized 

per the vehicle’s tire placard. Tire tread 

will be free of all debris. Tires will be 

conditioned according to the following 

procedure: 

(1) Drive the test vehicle 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. 

(b) The vehicle’s doors are shut and 

locked and windows are shut. 

(c) All accessory equipment (air 

conditioner, wipers, heat, HVAC fan, 

audio/video systems, etc.) 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. 

(d) Test weight of the vehicle 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. Do not exceed the GVWR or 

GAWRs of the vehicle. 

(e) Vehicle’s electric propulsion 

batteries, if any, are fully charged. 


tkelley on DSK3SPTVN1PROD with 
2860 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

S6.7 Ambient correction 

S6.7.1 Measure the background 

noise for at least 30 seconds before and 

after a series of vehicle tests. 

S6.7.2 A 10-second sample taken 

from these measurements will be used 

to calculate the reported background 

noise. 

S6.7.3 The 10-second sample 

selected will include background levels 

that are representative of the 

background levels that will occur during 

the vehicle measurement. 

S6.7.4 The minimum A-weighted 

SPL in the selected 10-second sample as 

the overall background noise level, Lbgn

will be reported. The average Aweighted SPL in the same 10-second 

sample will also be noted. 

S6.7.5 The minimum A-weighted 1⁄3

octave band levels (OBLs) (per ANSI 

S1.11, Class 1) in the selected 10-second 

sample will be reported as the 1⁄3 octave 

band background noise level, OBLbgn, fc. 

The average A-weighted 1⁄3 octave band 

level in the same 10-second sample for 

each 1⁄3 octave band will also be noted. 

S6.7.6 each 1⁄3 octave band of the 

measured jth test result within a test 

condition OBLtest,j,fc, will be corrected 

according to Table 6 to obtain the noisecorrected level OBLtestcorr, j, fc which is 

the OBLtest, j, fc minus the correction 

factor, Lcorr. 

TABLE 6—CORRECTIONS FOR BACKGROUND NOISE

1⁄3 Octave band noise level 

OBLbgn,fc

* Peak-to-Peak 1⁄3 octave band 

background noise level 

OBLbgn,fc,p-p

1⁄3 Octave band level of jth test 

result, ith frequency, minus 1⁄3

octave band noise level DL = 

OBLtest,j,fc¥OBL bgn,fc

Correction Lcorr

≥ 25 dB(A) .................................... ** .................................................. > 10 dB ............................................ 0 dB. 

< 8 dB .......................................... > 8–10 dB ........................................ 0.5 dB. 

> 6–8 dB .......................................... 1.0 dB. 

< 6 dB .......................................... > 4.5–6 dB ....................................... 1.5 dB. 

> 3–4.5 dB ....................................... 2.5 dB. 

≤ 3 dB .............................................. Do not correct, but report 

OBLtestcorr,j < OBLtestj. 

< 25 dB(A) .................................... ≤10 dB ............................................. Do not correct, but report: 

OBLtestcorr,j < OBLtestj. 

** .................................................. > 10 dB ............................................ 0 dB. 

* Ensure that maximum allowable peak-to-peak variation occurs in not more than one measurement for each operation during the portion of the 

measurement that will be reported, e.g. within the second prior to pass-by or during an entire active but stationary measurement. 

** Ensure that the background level is at least 10 dB below the measurement during any portion of the measurement that will be reported, e.g. 

within the second prior to pass-by or during an entire active but stationary measurement. 

S7. Test Procedure. 

S7.1 Vehicle stationary but activated 

S7.1.1 Position the vehicle 

stationary with the front plane at the 

line PP’, the centerline on the line CC’ 

and the starting system deactivated. 

For vehicles equipped with a Park 

position, place the vehicle’s gear 

selection control in ‘‘Park’’. For vehicles 

not equipped with a Park position, place 

the vehicle’s gear selection control in 

‘‘Neutral’’ and engage the parking brake. 

Activate the starting system to energize 

the vehicle’s starting system. 

S7.1.2. The vehicle minimum sound 

pressure level shall be measured per 

S7.3.2.1 and S7.4.1 of SAE J2889–1 

(incorporated by reference, see § 571.5) 

and corrected for the ambient sound 

level in each 1⁄3 octave band according 

to the procedure in S6.7 and the 

correction criteria given in Table 6. 

S7.1.3.1 Four consecutive valid 

measurements must be within 2 Aweighted dB Measurements that contain 

sounds emitted by any component of a 

vehicle’s battery thermal management 

system are not considered valid. When 

testing a hybrid vehicle with an internal 

combustion engine that runs 

intermittently, measurements that 

contain sounds emitted by the ICE are 

not considered valid. 

S7.2 Backing. Test the vehicle per 

S7.1, except that the rear plane of the 

vehicle is placed on line PP’. 

S7.3 Pass-By test at 10km/h 

(a) Measure the sound emitted by the 

vehicle at a constant 10 km/h (+/¥ 1 

km/h) throughout the measurement 

zone specified in S6.4 between lines 

AA’ and PP’. 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. 

(b) Four consecutive valid 

measurements must be within 2 Aweighted dB. Measurements that 

contain sounds emitted by any 

component of a vehicle’s battery 

thermal management system are not 

considered valid. When testing a hybrid 

vehicle with an ICE that runs 

intermittently, measurements that 

contain sounds emitted by the ICE are 

not considered valid. The test result 

shall be corrected for the ambient sound 

level in each 1⁄3 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. 

S7.4 Pass by test at 20 km/h. Repeat 

the test of S7.3 at 20 km/h. 

S7.5 Pass by test at 30 km/h. Repeat 

the test of S7.3 at 30 km/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 noncompliance 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 noncompliance with this standard. 

S9 Phase-in schedule 

S9.1 Vehicles manufactured on or 

after September 1, 2015, and before 

September 1, 2016. For vehicles 

manufactured on or after September 1, 

2015, and before September 1, 2016 the 

number of vehicles complying with this 

standard must not be less than 30 

percent of: 

(a) The manufacturer’s average annual 

production of vehicles manufactured on 

or after September 1, 2012, and before 

September 1, 2015; or 


tkelley on DSK3SPTVN1PROD with 
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(b) The manufacturer’s production on 

or after September 1, 2015, and before 

September 1, 2016. 

S9.2 Vehicles manufactured on or 

after September 1, 2016, and before 

September 1, 2017. For vehicles 

manufactured on or after September 1, 

2016, and before September 1, 2017, the 

number of vehicles complying with this 

standard must not be less than 60 

percent of: 

(a) The manufacturer’s average annual 

production of vehicles manufactured on 

or after September 1, 2013, and before 

September 1, 2016; or 

(b) The manufacturer’s production on 

or after September 1, 2016, and before 

September 1, 2017. 

S9.3 Vehicles manufactured on or 

after September 1, 2017, and before 

September 1, 2018. For vehicles 

manufactured on or after September 1, 

2017, and before September 1, 2018, the 

number of vehicles complying with this 

standard must not be less than 90 

percent of: 

(a) The manufacturer’s average annual 

production of vehicles manufactured on 

or after September 1, 2014, and before 

September 1, 2017; or 

(b) The manufacturer’s production on 

or after September 1, 2017, and before 

September 1, 2018. 

S9.4 Vehicles manufactured on or 

after September 1, 2018. All vehicles 

manufactured on or after September 1, 

2018 must comply with this standard. 

S9.5 Vehicles produced by more 

than one manufacturer. 

S9.5.1 For the purpose of calculating 

average annual production of vehicles 

for each manufacturer and the number 

of vehicles manufactured by each 

manufacturer under S9.1 through S9.3, 

a vehicle produced by more than one 

manufacturer must be attributed to a 

single manufacturer as follows, subject 

to S9.6.2: 

(a) A vehicle that is imported must be 

attributed to the importer. 

(b) A vehicle manufactured in the 

United States by more than one 

manufacturer, one of which also 

markets the vehicle, must be attributed 

to the manufacturer that markets the 

vehicle. 

S9.5.2 A vehicle produced by more 

than one manufacturer must be 

attributed to any one of the vehicle’s 

manufacturers specified by an express 

written contract, reported to the 

National Highway Traffic Safety 

Administration under 49 CFR Part 585, 

between the manufacturer so specified 

and the manufacturer to which the 

vehicle would otherwise be attributed 

under S9.6.1. 

S9.6 Small volume manufacturers. 

Vehicles manufactured during any of 

the three years of the September 1, 2015 

through August 31, 2018 phase-in by a 

manufacturer that produces fewer than 

5,000 vehicles for sale in the United 

States during that year are not subject to 

the requirements of S9.1, S9.2,S9.3 and 

S9.5. 

S9.7 Final-stage manufacturers and 

alterers. Vehicles that are manufactured 

in two or more stages or that are altered 

(within the meaning of 49 CFR 567.7) 

after having previously been certified in 

accordance with Part 567 of this chapter 

are not subject to the requirements of 

S9.1 through S9.5. Instead, all vehicles 

produced by these manufacturers on or 

after September 1, 2018 must comply 

with this standard. 

PART 585—PHASE–IN REPORTING 

REQUIREMENTS 

■ 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. 

■ 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 

§ 585.128 Scope. 

This subpart establishes requirements 

for manufacturers of hybrid and electric 

passenger cars, trucks, buses, 

multipurpose passenger vehicles, lowspeed vehicles, and motorcycles 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). 

§ 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). 

§ 585.130 Applicability. 

This subpart applies to manufacturers 

of hybrid and electric passenger cars, 

trucks, buses, multipurpose passenger 

vehicles, low-speed vehicles, and 

motorcycles. 

§ 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 

§ 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 is used as defined 

in § 571.141 of this chapter. 

§ 585.132 Response to inquiries. 

At any time during the production 

years ending August 31, 2016, August 

31, 2017, and 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. 

§ 585.133 Reporting requirements. 

(a) Phase-in reporting requirements. 

Within 60 days after the end of each of 

the production years ending August 31, 

2016, August 31, 2017, and 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 (d) of this section 

and in § 585.2 of this part. 

(b) Phase-in report content—(1) Basis 

for phase-in production goals. Each 

manufacturer shall provide the number 

of 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 


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production year being reported on, and 

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). 

§ 585.134 Records. 

Each manufacturer shall maintain 

records of the Vehicle Identification 

Number for each vehicle for which 

information is reported under § 585.133 

until December 31, 2023. 

Note: The following appendices will not 

appear in the Code of Federal Regulations. 

Appendix A—Glossary of Sound 

Engineering Terms 

Acoustic Pressure: A pressure variation 

about a medium’s mean pressure caused by 

a sound wave. 

Acoustic Wave: A wave that propagates 

acoustic pressure through a medium, such as 

air. 

Ambient (also called ambient noise or 

background noise): Relating to the immediate 

environment or surroundings. Generally 

refers to unwanted sounds. In an acoustic 

measurement, after the main sound being 

studied is suppressed or removed, this is the 

remaining sum of sounds taken from the 

environment of the measurement. 

Amplitude: The value of the sound 

pressure at any instant. 

Amplitude Modulation: When the 

amplitude of a sound changes as a function 

of time. 

Attenuation: A decrease in the intensity of 

a sound. 

Auditory Filter: A measure of the auditory 

systems frequency selectivity. An auditory 

filter is a band pass filter that closely 

approximates the shape of a rounded 

exponential filter or, to a lesser degree, a onethird octave band filter. 

Auditory Flutter/Flicker: Auditory 

sensation produced when a continuous 

sound is disturbed at a slow, intermittent 

rate. 

Auditory Fusion: Series of short successive 

sounds that are perceived as one continuous 

sound. 

A-weighting: A filter that attenuates low 

and high frequencies and amplifies some 

mid-range frequencies. The A-weighting 

curve approximates the equal loudness 

contour at 40 dB. 

Bandwidth: Range of frequencies. For 

example, a speaker may have an effective 

bandwidth from 150 to 5000 Hz. 

Alternatively, it is the minimum frequency 

subtracted from the maximum frequency. For 

the above example, this would be 5000—150 

or 4850 Hz. 

Band-Pass Filter: A type of filter that only 

allows a specific range of frequencies to pass 

through while attenuating all other 

frequencies. For example, a one-third octave 

band filter centered at 1000 Hz would pass 

sounds with frequencies from about 890 to 

1120 Hz while attenuating frequencies 

outside this range. 

Band Pressure Level: The pressure level of 

a sound wholly contained within a particular 

frequency band. 

Band-Stop Filter: A type of filter that 

attenuates a particular range of frequencies 

while allowing frequencies outside the band 

to pass through. 

Basilar Membrane: A membrane inside the 

cochlea that supports the organ of corti and 

vibrates as a response to sound. 

Broadband: Signal with a spectrum that 

covers a broad range of frequencies. 

Broadband levels: Levels regarding signal 

quantities that cover a wide range of 

frequencies. 

Cochlea: A small snail shell-shaped tube 

within the inner ear that houses the receptor 

organs responsible for converting mechanical 

vibration into electro-chemical signals for the 

brain to process. 

Condenser: Type of microphone that uses 

acoustic pressure to change the distance 

between two plates of a capacitor. The 

changing distance between the two plates 

causes the voltage across the capacitor to 

change. 

Consonant: Auditory experience where 

sounds are harmonic. 

Dichotic: Event in which sounds heard by 

both ears are different. 

Diffraction: The bending of waves as they 

travel around an object or across an 

impedance change. 

Digital Recorder: A device that converts 

acoustic waves into electric signals and 

stores them in its memory to be replayed 

back. 

Dipole: Usually constructed with two 

monopoles with equal but opposing 

strengths. 

Directivity: The relative proportions of 

acoustical energy that are emitted from a 

source as a function of direction, typically 

expressed in polar coordinates. 

Dissonant: An auditory experience where 

sounds are in-harmonic, usually referred to 

as noise. 

Divergence: The physical spreading of the 

sound waves over an area. Divergence 

attenuates a sound as a function of distance. 

See also ‘‘Line Source’’ and ‘‘Point Source’’. 

Decibel (dB): Ten times the logarithmic 

ratio of a physical quantity to a reference 

value. For example, 

Sound Pressure Level = 10 log10(P2/Pref2) 

where P is the acoustic pressure and Pref is 

equal to 20 bPa for air. 

Doppler Effect: Change in the frequency of 

a sound wave due to the relative velocity 

between the source and the observer. As the 

sound source approaches the observer, the 

frequency is perceived to be higher and as it 

moves away it is perceived to be lower. 

Dull: A semitone less than the natural 

pitch of a given tone. Sound composed of a 

greater proportion of low frequencies. 

Dynamic Microphone: Type of microphone 

that uses a small metal coil positioned to be 

within a particular magnetic field attached to 

a diaphragm. Acoustic pressure causes the 

diaphragm to move the coil through the 

magnetic field and a current is generated. 

Equivalent Rectangular Bandwidth (ERB): 

An idealized rectangular filter with a 

bandwidth defined such that it passes the 

same energy as an associated auditory filter. 

A set of contiguous ERB filters can be used 

to represent the frequency scale in a 

psychoacoustic sense. For example, an 

auditory filter centered at 1000 Hz has an 

equivalent rectangular bandwidth of 132 Hz 

and it takes 15.6 contiguous equivalent 

rectangular bandwidths to cover the auditory 

range below 1000 Hz. An auditory filter 

centered at 4000 Hz has an equivalent 

rectangular bandwidth of 456 Hz and it takes 

27.1 contiguous equivalent rectangular 

bandwidths to cover the auditory range 

below 4000 Hz. 

Equal Loudness Contour: A contour of 

levels (y-axis) versus frequency (x-axis) such 

that tones of different frequency and different 

level are judged to be equally loud. 

Equal Loudness Principle: Mid-range 

frequencies (approx. 320—5120 Hz) are 

perceived with greater intensity than lower 

(20 to 320 Hz) or higher frequencies (5000 to 

20,000 Hz). 

Filter: A system that selectively passes 

some elements and attenuates others as a 

function of frequency. 

Flat Response: A flat frequency-response 

curve, i.e. a response that does not change 

with frequency, sometimes referred to as Z or 

un-weighted. 

Free Field: A sound field without 

boundaries such that sound is not reflected 

or scattered. 

Frequency: Number of times a particle in 

a medium contracts and expands (cycles) per 

unit of time. Typically expressed in Hertz 

(Hz); one cycle per second is equal to 1 Hz. 

Humans can detect sound waves with a wide 

range of frequencies, nominally ranging 

between 20 to 20,000 Hz. 

Frequency Response: The response of a 

system to an input as a function of frequency. 

The response can be characterized by 

including both the magnitude as a function 

of frequency and the phase as a function of 

frequency. The magnitude describes the 

amplitude of the output relative to the input 

while the phase describes the time delay 

between the input and output of the system. 

Frequency Modulation: Changing 

frequency as a function of time. 

Fundamental Frequency: The lowest 

frequency of a waveform. 

Hair Cells: Sensory receptors found in the 

organ or corti on the basilar membrane in the 

cochlea that have hair-like structures 

(stereocilia). Hair cells transform sound 

waves into nerve impulses. 

Half-power Point: Frequency at which the 

power output of an amplifier reduces to half 

of its mid-band level. 

Harmonics: Components of a sound that 

are integer multiples of a fundamental 

frequency in the sound. 

Harmonic Distortion: The ratio (normally 

expressed as a percentage) of the sum of the 

acoustic power of all of the harmonics 

generated by the device under test to the 

power of the fundamental, pure tone being 

produced. Harmonic distortion increases 

rapidly as a device is driven close to its 

maximum output capability or when a 

speaker is driven at frequencies outside its 

intended range. 


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Head-Related-Transfer-Function (HRTF): 

Essentially a frequency response that is also 

a function of angle. It accounts for how a 

sound changes to an observer due to the 

relative position of the source and the head, 

pinna, and torso of the observer. 

Hertz (Hz): The unit associated with 

frequency. One cycle per second equals one 

Hertz. 

In-harmonic: A frequency component that 

is not an integer multiple of another 

frequency. 

Inner Ear: The innermost portion of the ear 

located behind the middle ear. It contains the 

cochlea and the vestibular system. 

Line Source: A sound source that 

geometrically forms a line. Line sources 

attenuate at 3 dB per distance doubling 

perpendicular to the source. One example is 

roadway noise; another is a stack of speakers 

at a concert. 

Longitudinal waves: Waves moving in the 

same direction as it is being propagated. 

Loud: Producing much noise, being easily 

audible. 

Loudness: Attribute of an auditory 

sensation that humans can use to judge 

sound intensity. Loudness is used to rank 

sounds on a scale from quiet to loud. 

Malleus: One of the three ossicles (bones) 

in the middle ear, it is attached to the 

tympanic membrane (ear drum) and the body 

of the incus (anvil). 

Masking: Phenomenon when the 

perception of a sound is diminished by the 

presence of another sound. 

Microphone: A device that converts 

acoustic waves into electrical signals. 

Middle Ear: Air cavity behind the 

tympanic membrane (ear drum) and before 

the inner ear. 

Minimum Audible Field: the threshold for 

detecting sound in a sound field. 

Minimum Audible Threshold: Also known 

as the absolute threshold of hearing, it refers 

to the minimum sound level of a pure tone 

that the average ear with normal hearing can 

hear without any other sound in its 

environment. 

Modulation: A change in the dimension of 

a stimulus. For example see ‘‘Amplitude 

Modulation’’ or ‘‘Frequency Modulation’’. 

Monopole: A single point in space that is 

an acoustic source. 

Narrow band: A limited range of frequency, 

as opposed to a wide band, which tends to 

include frequencies from the low to high end, 

a narrow band focuses in on a particular 

range. 

Natural Frequency: Frequency at which a 

system has maximum, or near maximum, 

response. 

Noise: Sound wave(s) that is made up of 

random sounds. Sound wave(s) that is 

viewed as an undesirable sound. 

Octave (also called octave band): Interval 

between two frequencies that have a ratio of 

2:1. The range of human hearing covers 

approximately 10 octaves. For example, if the 

first octave is 20 to 40 Hz the next octave is 

40 to 80 Hz, the next is 80 to 160 Hz, etc. 

One-third Octave Band: Frequency band 

that is one-third of an octave band or whose 

lower and upper limits are 21⁄3 times the 

center frequency apart, as defined by their 

half-power points. For example a one-third 

octave band centered at 1000 Hz has upper 

and lower cutoff frequencies at about 890 and 

1120 Hz and a bandwidth of 230 Hz. A onethird octave band centered at 4000 Hz has 

upper and lower cutoff frequencies at about 

3560 and 4490 Hz and a bandwidth of 930 

Hz. 

Organ of Corti: Also known as the spiral 

organ, it is located in the inner ear and 

contains hair cells, which act as receptors to 

sound waves. 

Outer Ear: The visible outer part of the ear 

that directs sound waves through the canal 

within the temporal bone and delivers them 

to the tympanic membrane (ear drum). 

Pascal: Unit used to measure pressure; it is 

equal to 9.8692×10¥6 atm. 

Period: The time interval in which 

successive occurrences of a recurring or 

cyclic phenomenon occur. The reciprocal of 

frequency. 

Phase: The time relationship between two 

or more sounds reaching a receiver. The 

sounds are in phase when their amplitudes 

add. The sounds are out-of-phase when their 

amplitudes subtract. 

Phon: A unit used to measure the loudness 

level of a sound in dB. 

Pink Noise: A random noise whose 

amplitude is inversely proportional to 

frequency. Pink Noise sounds more natural 

than white noise. 

Pinna: External part of the human ear, also 

known as the auricle. 

Pitch: The sensation of a frequency. 

Attribute of an auditory sensation that 

humans can use to order sounds on a musical 

scale. A high pitch sound corresponds to a 

high frequency sound wave. A low pitch 

sound corresponds to a low frequency sound 

wave. 

Pitch Strength: Perception of how strong a 

pitch seems to be according to a listener. Two 

sounds with equal frequencies can be 

perceived to have different strengths. 

Point Source: A sound source whose 

dimensions are sufficiently small that it can 

be treated as a point. Point sources attenuate 

at 6 dB per distance doubling. One example 

is of a point source is a stationary ICE vehicle 

at idle. 

Power: A measure of energy supplied or 

consumed per unit of time, usually expressed 

in Watts (W). A sound with a power of only 

one-trillionth of one W can be audible in an 

otherwise quiet environment; a jackhammer 

has an acoustic power output of about 1 W. 

Propagation: The advancement of a sound 

wave in a particular direction traveling 

through a medium. 

Psychoacoustics: A branch of 

psychophysics that studies the psychological 

correlations between acoustic and 

psychological parameters. 

Pure Tone: A sound characterized by the 

fact that it is comprised of only one 

frequency. 

Quiet: Causing little to no noise. 

Reflection: A change in the direction of 

propagation of a wave due to boundary, for 

example pavement. 

Refraction: Bending of waves due to a 

change in the speed of sound in the medium, 

for example, due to a temperature change in 

the air. 

Resonance: The response of a system to 

input at a natural frequency. 

Reverberation: Repetition of sound 

resulting from reflected sound waves. 

Reverberant Field: A sound field resulting 

from a large number of reflections from 

boundaries within an enclosed area. 

Ribbon: A type of microphone that 

converts sound into an electrical signal by 

placing a ribbon between the two poles of a 

magnet to generate electromagnetic 

induction. 

Roll-off Rate: The steady attenuation that 

occurs on either end of a frequency range 

which is typically expressed in dB/octave or 

in dB/decade. 

Roughness: Level of dissonance. 

Sharp: A semitone above the natural pitch 

of a given tone. Sound composed of a greater 

proportion of high frequencies. 

Sinusoid (Sine): Used to graphically 

represent a sound wave. A trigonometric 

function of an angle describing the ratio 

between the length of the opposite side of the 

triangle from which the angle is drawn, and 

the length of the adjacent side of the triangle. 

Sone: Unit of subjective loudness on a 

linear scale. A sound that is 14 sones is twice 

as loud as a 7 sone sound. 

Sound Intensity: The sound power passing 

through an area in a sound field, expressed 

as Watts per square meter. 

Sound Intensity Level: The logarithmic 

measurement of sound intensity with respect 

to a reference level. 

SIL = 10 log10(I2/Iref2) 

where I is the acoustic intensity and Iref is 

equal to 10¥12 W/m2 for air. 

Sound Pressure Level (SPL): Level of a 

sound relative to a reference pressure and 

measured in decibels. 

SPL = 10 log10(P2/Pref2) 

where P is the root mean square of the 

acoustic pressure and Pref is equal to 20 

microPascals (mPa) for air. Examples of aweighted sound pressure levels include: 

threshold of human hearing (0 dB(A)), 

quiet office (40 dB(A)), noisy restaurant 

(70 dB(A)), rock concert (110 dB(A)), 

pain (140 dB(A)) 

Sound Level Meter: Instrument used to 

measure sound pressure levels, often used for 

noise pollution studies. 

Spectral Balance: The relative pressure 

levels of components of a sound at various 

frequencies. This is often described by a 

spectral plot with frequency in the horizontal 

axis and sound pressure level/Hz on the 

vertical axis. 

Stationary Sound: A sound whose root 

mean squared amplitude does not change 

with time. Examples include a fan running at 

a constant speed, a waterfall, and a constant 

tone or hum. 

Tonalness (tonality): Harmonic effect of 

being in a certain key. 

Transverse Waves: Waves moving in right 

angles to their propagation. 

Tympanic Membrane: Also known as the 

ear drum, a membrane in the inner ear that 

vibrates as a response to sound, or changes 

in air pressure. 

Un-weighted Spectrum: A spectrum 

recorded with uniform amplification at all 

frequencies. In contrast, many spectra are 

recorded after the signal is processed through 

filters that approximate the variation in 


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136While it is convenient to represent sound 

waves as transverse waves, where the motion is 

perpendicular to the wave propagation, they are in 

actuality longitudinal waves, where the motion is 

parallel to the wave propagation. 

137Acoustic energy is equal to the acoustic 

intensity integrated over the area. In an 

environment with no reflecting boundaries, the 

acoustic intensity is proportional to the acoustic 

pressure squared. 

138Since timbre includes all other perceptual 

characteristics other than the loudness and pitch of 

a sound, it includes the perception of modulations, 

attack, decay, sharpness, roughness, etc. 

sensitivity with frequency that occurs in 

human hearing (e.g., the A-weighted filter). 

See also ‘‘Flat Response’’. 

.wav: Waveform Audio File Format, a type 

of file format used to storing audio. 

White Noise: Noise with spectrum level 

that does not vary as a function of frequency. 

Appendix B. Acoustic Primer 

This primer introduces and describes what 

sound is, its components, how it is perceived 

by humans and how the different 

components of a sound can be measured. 

Sound can be described using physical 

principles but is also a perceptual 

phenomenon. Humans can perceive various 

qualities of sound, not all of which have 

established quantitative measures. Humans 

can also perceive the direction, distance and 

movement of sound sources. The information 

included here provides background and 

context to concepts put forth in the NPRM. 

What is sound? 

A sound is said to exist when the static 

pressure of a medium (typically air) is 

disturbed by periodic pressure variations 

(sound waves) that propagate through the 

medium and are perceived by a listener. The 

pressure variations in the medium are due to 

the compression and rarefaction of molecules 

in the medium. In regions of compression, 

the density of molecules is high and the 

number of molecule collisions increases 

relative to the static pressure condition. In 

regions of rarefaction, the density of 

molecules is low and the number of molecule 

collisions decreases relative to the static 

pressure condition. Over time, the pressure 

in a given region will increase and decrease 

as the sound wave propagates through the 

medium. The change in pressure relative to 

the static pressure is called the acoustic or 

sound pressure. 

In the simplest case, sound pressure can be 

represented as a function of time by a 

sinusoidal wave for a specific location in 

space, as shown in Figure 1.136 Here, the 

baseline represents the static pressure. The 

difference in pressure from the baseline to 

the peak of the wave is the peak amplitude 

of the acoustic pressure; the higher the 

amplitude, the louder the sound. As time 

progresses, the pressure increases and 

decreases cyclically for this location. The 

period of the wave can be defined by the time 

that it takes to go from one peak to the next; 

a longer period indicates a lower pitch. 

Another way to quantify the rate of change 

of a wave is by its frequency. The frequency 

of a wave is the inverse of the period and the 

unit is Hertz (Hz); the lower the frequency, 

the lower the pitch. The wavelength of a 

sound wave is similar to the period of the 

wave, except that rather than considering the 

time to go from one peak to the next for a 

given location in space, one considers the 

distance to go from one peak to the next for 

a given instant in time. The wavelength is 

mathematically related to the period by l = 

cT, where l is the wavelength, c is the speed 

of sound in the medium and T is the period. 

The relative location of sound source and 

listener in an environment can have a strong 

effect on the final sound that is received by 

the listener. As a sound propagates away 

from the source, the acoustic energy 137 is 

spread over a greater area in a manner similar 

to ripples in a pond. In a pond, the ripple’s 

diameter becomes larger but the amplitude 

becomes smaller the further they travel from 

the source. Similarly, the further a sound 

propagates from a source, the quieter the 

sound will tend to be. For a point source 

radiating sound into free space, the intensity 

of that sound will diminish by a factor of four 

for each doubling of distance from the source 

to listener (inverse square law). However, in 

typical environments, reflections and 

atmospheric absorption also affect the sound 

level. The latter effect is greatest for high 

frequencies, so when a sound propagates 

long distances, the high frequency 

components of a sound will tend to decrease 

more than the low frequency components. 

This affect is most noticeable for distances 

greater than a hundred meters. Finally, sound 

propagation can be affected by intervening 

surfaces, which can reflect and block sound 

propagation. Highway barriers are a classic 

example of surfaces intended to block sound 

propagation. By placing these barriers 

between traffic and the listener, the sound 

due to the traffic can be reduced at the 

listener’s position. A ‘‘live’’ gymnasium is an 

example of an environment with many 

reflective surfaces. Due to the reflective 

surfaces, sound waves can arrive 

simultaneously at the listener from the same 

source even though the sounds were emitted 

at slightly different times. The combination 

of these direct and reflected sound waves 

create interference patterns that can cause the 

level to be higher or lower. Constructive 

interference occurs when the sounds are ‘‘in 

phase’’, that is, when the peaks line up. 

Destructive interference occurs when the 

sounds are ‘‘out of phase’’, that is, when 

peaks line up with valleys. 

How is sound perceived? 

Amplitude and frequency of sound 

pressure are physical attributes of sound that 

can be related to perceptual dimensions such 

as loudness, pitch, and timbre.138 Humans 

interpret these psychological dimensions 

subjectively, but some of them can be 

quantified through psychoacoustic modeling. 

Psychoacoustics is the study of how humans 


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perceive sound and forms the basis for 

extracting objective data from the physical 

characteristics of acoustic pressure to 

quantify how humans perceive the loudness, 

pitch, and timbre of a sound. However, some 

of the properties of sounds that are important 

to recognition or the characterization of a 

sound as pleasant or annoying have no 

established metrics. 

The loudness of a sound (by definition, a 

subjective measure) is primarily related to 

the sound pressure level of a sound, but is 

also influenced by its frequency. Loudness 

(or loudness level) is measured in sones (or 

phons). The loudness level of a sound in 

phons is equal to the sound pressure level in 

dB of a 1000-Hz tone that is perceived to be 

equal in loudness to the sound of interest. 

For example, all sounds that are judged to be 

equal in loudness to a 40dB–SPL, 1000 Hz 

tone have a loudness level equal to 40 phons. 

Loudness level (phons) increases 

logarithmically, while loudness (sones) 

increases linearly. For a human to judge a 

sound to be twice as loud, the sound needs 

to be increased by roughly 10 phons or by 

twice the number of sones, for example the 

perceived loudness approximately doubles 

for 40, 50, 60, 70, 80 phons or 1, 2, 4, 6, 8, 

16 sones. The relationship between perceived 

loudness and the physical acoustic pressure 

of a sound is non-linear in both amplitude 

and frequency, as illustrated in Figure 2. This 

means that the relative loudness (and 

detectability) of two sounds with the same 

SPL value can change substantially 

depending on their amplitude and frequency. 

Pitch is directly related to frequency. 

Roughly speaking, humans interpret the 

fundamental frequency of a sound to be its 

pitch; the higher the frequency, the higher 

the pitch; the lower the frequency, the lower 

the pitch. A sound wave with a high 

frequency produces the sensation of a high, 

sharp pitch and a low frequency produces a 

low, dull pitch. Pitch strength refers to the 

strength of the pitch’s sensation. The pitch 

strength is dependent on the tone-to-noise 

ratio. The tonal components of a sound have 

periodic, sinusoidal waveforms, while the 

noise components are random (e.g., wind 

noise). However, if noise is constrained by 

some physical or electronic process to 

contain a relatively narrow band of 

frequencies, it can produce the sensation of 

pitch, e.g., some turbine sounds. The greater 

the noise levels relative to the tone level, the 

weaker the pitch strength. 

There is a strong correlation between the 

pitch of a sound and the spectral location of 

its frequency components. When there are 

multiple frequency components present that 

are integer multiples of a single lowest 

frequency, the sound is said to be harmonic. 

The lowest frequency is commonly referred 

to as the fundamental. If there are harmonics 

present, the ability to detect pitch is 

improved. Even when the fundamental is not 

present (case of the missing fundamental), 

the human auditory system compensates for 

the loss of the lower harmonic. For example, 

a tone complex of 600, 800 and 1200 Hz is 

judged to have a pitch of 400 Hz because this 

corresponds to the shortest common wave 

period. 

Timbre describes the characteristics of a 

sound that allow the listener to differentiate 

two sounds with the same pitch and 

loudness. The timbre of a sound is based 

predominantly on characteristics of the 

sound’s spectrum but is also dependent on 

temporal characteristics. Characteristics of 

the spectrum that effect timbre include: the 

relative strength of the tonal and noise 

character of the sound (pitch strength and 


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2866 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

tonality); the number of harmonics (harmonic 

richness); and the relative level of high 

frequencies and low frequencies components 

(sharpness and dullness). Temporal 

characteristics include the musical concepts 

of ‘‘attack, sustain, and decay’’ as well as 

‘‘vibrato’’ or modulations. A violin, a muted 

bell, and a voice can all create a sound at the 

same pitch and loudness, but the violin will 

have a short attack, long sustain, and 

moderate decay. The muted bell will have a 

short attack, a short sustain, and a short 

decay. The voice will have a long attack, a 

moderate sustain, and a moderate decay. The 

violin and voice can be expressed either with 

or without vibrato (modulations). 

Temporal effects on timbre can also be 

considered outside of the musical context. 

Humans can perceive sounds as being 

constant, changing or impulsive. A sound is 

perceived to be constant when the physical 

aspects, such as the tonal frequencies and 

levels, are unvarying and steady. An example 

would be standing next to an idling vehicle. 

Since the car is stationary and the engine 

speed is constant, the sound emitted from the 

engine does not vary significantly (assuming 

a well-functioning engine). Slow changes in 

pitch or loudness at a rate of about c second 

or longer lead to the perception of a changing 

sound. A good example of a changing sound 

is that of a siren on an emergency vehicle. 

If the rate of change is very quick, for 

example over a time less than c second, the 

sound will be perceived as impulsive. Sound 

with a very high rate of change such as gun 

fire and individual combustions produce 

impulsive sounds. 

It is rare that humans hear only one sound 

at a time. This is because one sound may 

overshadow, very closely resemble, or 

interfere with the perception of another 

sound that does not share the same physical 

characteristics. When one sound interferes 

with the perception of another sound, it is 

called masking. The masking threshold is the 

point at which one sound’s audibility or 

detectability is lost because of the masking 

sound. It can be measured in the laboratory 

by presenting subjects with different target 

sounds (stimuli) of different amplitudes and 

frequencies in combination with various 

masking sounds, and testing the subjects to 

determine under which conditions they can 

detect the targets. The level of the masking 

sound is used as an indicator of the amount 

masking the sound provided for the stimulus. 

How is sound quantified? 

Sound is most commonly quantified in 

decibels (dB). A decibel is a logarithmic unit 

of magnitude based on the ratio of two 

powers. In terms of acoustics, the ratio, 

commonly referred to as the sound pressure 

level, is between the mean-squared acoustic 

pressure relative to a reference mean-squared 

acoustic pressure. The reference for sound 

pressure level measurements in air is 

typically 20 micro-Pascals. However, when 

sounds are processed electronically, standard 

practice is to represent their intensity on a dB 

scale where 0 is the maximum amplitude that 

can be handled without distortion. In this 

frame of reference, levels are usually negative 

numbers. 

Usually, acoustic equipment used for 

measurements is A-weighted to approximate 

the frequency response of human hearing 

(see Figure 2) to sounds of moderate 

loudness. 

The distribution of acoustic energy in a 

sound can be represented graphically with a 

full spectrum plot, like that shown in Figure 

3, or more compactly by breaking the 

spectrum into a relatively small number of 

bands, usually 30 for a one-third octave 

analysis, shown in Figure 4. 


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Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 2867 

Due to the breadth of this spectrum, octave 

bands and one-third octave band scales were 

created to facilitate identifying the specific 

frequency of sounds. Octave bands separate 

the range of human audible frequencies into 

ten bands and the one-third octave bands 

split each of the ten octave bands into three 

bands. Each scale in the breakdown provides 

more information about the sound being 

analyzed. An octave band is split by the 

interval between two frequencies and 

identified by the center frequency within the 

bands: 31.5 Hz, 63 Hz, 125 Hz, 250 Hz, 500 

Hz, 1 kHz, 2 kHz, 4 kHz, 8, kHz and 16 kHz. 

Since there are ten octaves, there are 30 onethird octave bands. A one-third octave band 

extends from one-sixth of an octave below 

the center frequency to one-sixth above an 

octave frequency. The measurement of how 

humans perceive the loudness of a sound is 

dependent on the sound pressure level and 


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80 

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O~ ______ ~ __ ~ __ ~~~~~~L-______ ~ __ ~ __ -L~waL-~~ 

102 103 

Frequency, Hz 

Figure 3. Full Spectrum of an Alerting Sound 

(vertical scale is in dB / Hz referenced to 20 micro-Pascals: the logarithmic horizontal axis is in Hertz) 

60 

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1IIIIIII II II IIIIIII 

IIIIIIII II II IIIIIIII 0. I.D 0. 0. 0. If) 0..0..0. 0. ..:.:: ..::,::.::,c...¥...¥..::,:: .::,c • ...¥.~ . .::,c.::,c ..::,::..::,:: ..::,:: 0. ("".1.(.00 If) ..- 0 O~ 0"- If)(.O ("".Ilf) l,() .q-. IJ:) ~. co 0 IJ:)(.O 0 

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Qne:-ThirdOctal(eBanctCenterfreql.JerrcV, HZ 

Figure 4. Example of an A-Weighted, One-Third Octave Plot of Noise Emission 

from a Vehicle Passing at 10 mph 
2868 Federal Register / Vol. 78, No. 9 / Monday, January 14, 2013 / Proposed Rules 

can be used as a way to determine the 

annoyance qualities of a sound. The values 

from a one-third-octave analysis can also be 

easily presented in tabular form (Table 1), 

while those from a full-spectrum cannot. 

TABLE 8—EXAMPLE OF ONE-THIRD-OCTAVE DATA IN TABULAR FORM: SUMMARY OF AMBIENT LEVELS DURING ICE 

MEASUREMENTS, A-WEIGHTED LEVEL, DB(A) 

1⁄3 octave band center frequency, Hz 

Linear average 

(1⁄3 octave 

band) 

Min (overall 

A-weighted) 

Max (overall 

A-weighted) 

Min (1⁄3 octave 

band) 

Max (1⁄3

octave band) 

100 to 20k ............................................................................ 49.6 46.1 53.4 45.3 54.7 

100 ....................................................................................... 34.6 30.7 34.1 30.7 38.4 

125 ....................................................................................... 35.5 32.4 36.8 32.4 42.1 

160 ....................................................................................... 36.1 32.1 37.9 32.0 41.5 

200 ....................................................................................... 36.9 32.7 37.9 32.7 41.2 

250 ....................................................................................... 36.5 33.9 38.1 33.1 40.7 

315 ....................................................................................... 36.5 32.5 37.6 32.1 41.5 

400 ....................................................................................... 36.0 31.9 38.1 31.8 39.7 

500 ....................................................................................... 36.7 33.6 39.8 33.1 41.1 

630 ....................................................................................... 38.2 34.4 41.7 34.0 42.2 

800 ....................................................................................... 40.2 36.0 46.1 35.8 46.1 

1k ......................................................................................... 41.1 36.4 46.4 36.4 46.4 

12.5k .................................................................................... 40.0 35.3 45.1 35.3 45.1 

16k ....................................................................................... 37.6 32.9 43.1 32.9 43.1 

2k ......................................................................................... 34.7 30.3 37.8 30.3 37.8 

2.5k ...................................................................................... 34.5 32.8 35.4 30.8 42.1 

3.15k .................................................................................... 35.5 36.9 37.1 30.0 39.6 

4k ......................................................................................... 34.0 33.0 34.3 28.3 40.2 

5k ......................................................................................... 29.0 25.0 29.8 24.3 32.8 

6.3k ...................................................................................... 25.7 22.3 26.9 19.7 31.7 

8k ......................................................................................... 20.2 16.6 22.4 14.1 24.2 

10k ....................................................................................... 14.4 10.3 17.3 7.6 18.3 

12.5k .................................................................................... 8.9 5.0 11.7 3.2 13.0 

16k ....................................................................................... 3.1 0.7 5.6 ¥0.8 8.7 

20k ....................................................................................... ¥1.9 ¥3.1 ¥0.4 ¥3.5 2.0 

Summary 

The acoustic science described above was 

intended to provide novices enough 

knowledge to understand the data and 

discussions put forth in the NPRM. Sound is 

a form of energy that is created when a 

medium vibrates, creating pressure variations 

(compressions and rarefactions of molecules) 

within a medium (such as air) which creates 

a pattern called a wave. Sound pressure over 

time creates peaks and valleys which make 

up the wavelength. The difference in acoustic 

pressure from the ambient pressure (no 

contraction of the medium) to the peak or 

valley of a wavelength is called the 

amplitude; the higher the amplitude, the 

louder the sound. The period of a wave is the 

time it takes for a cycle (a peak and a valley) 

to complete; a longer period indicates a lower 

pitch. The frequency of a sound is the 

number of complete wave cycles that pass by 

a given point in space every second; the 

higher the frequency, the higher the pitch. 

The wavelength, amplitude, period and 

frequency are physical attributes of a sound 

wave that affect the human perception of 

loudness, pitch and timbre. These 

perceptions can be quantified using 

psychoacoustics. Psychoacoustics is the 

study of how humans perceive sound and 

forms the basis for extracting objective data 

from the physical characteristics of acoustic 

pressure (sound). Using the physical 

characteristics and psychoacoustic analysis, a 

sound is usually measured in decibels (dBs) 

within an octave. Octaves can be further 

broken down into one-third octave bands 

which provide more information about the 

spectral content of sound being analyzed. 

After reading this primer, the reader should 

understand what ‘‘sound’’ is, identify its 

different components, and understand how 

humans perceive sound and how each of 

these contributes to measuring sound. 

References 

[1] Christopher L. Morfey, Dictionary of 

Acoustics, Academic Press, 2001. 

[2] ANSI S1.1–1994, Acoustical Terminology, 

American National Standards Institute, 

1994. 

[3] CEI IEC 50(801), International 

Electrotechnical Vocabulary—Chapter 

801: Acoustics and Electroacoustics, 

International Electrotechnical 

Commission, 2nd Edition, 1994. 

[4] ANSI S3.20–1973, Psychoacoustical 

Terminology, American National 

Standards Institute, 1973. 

[5] Brian C. J. Moore, An Introduction to the 

Psychology of Hearing, Academic Press, 

4th Edition, 1997. 

[6] Lawrence E. Kinsler, Austin R. Frey, Alan 

B. Coppens, and James V. Sanders, 

Fundamentals of Acoustics, John Wiley 

and Sons, 3rd Edition, 1982. 

[7] E. Zwicker and H. Fastl, Psychoacoustics: 

Facts and Models, Springer, 2nd Edition, 

1999. 

[8] Leo L. Beranek, Acoustical Measurements, 

American Institute of Physics, 1988. 

[9] Garay-Vega, Lisandra; Hastings, Aaron; 

Pollard, John K.; Zuschlag, Michael; and 

Stearns, Mary D., Quieter Cars and the 

Safety of Blind Pedestrians: Phase 2, 

John A. Volpe National Transportation 

Systems Center, DOT HS 811 496 

October 2011, available at http:// 

www.nhtsa.gov/DOT/NHTSA/NVS/ 

Crash%20Avoidance/ 

Technical%20Publications/2011/ 

811496.pdf. 

Issued in Washington, DC on January 7, 

2013, under authority delegated in 49 CFR 

1.95. 

Christopher J. Bonanti, 

Associate Administrator for Rulemaking. 

[FR Doc. 2013–00359 Filed 1–9–13; 4:15 pm] 

BILLING CODE 4910–59–P 

DEPARTMENT OF TRANSPORTATION 

National Highway Traffic Safety 

Administration 

49 CFR Parts 571 and 585 

[Docket No. NHTSA–2011–0100] 

Draft Environmental Assessment for 

Rulemaking To Establish Minimum 

Sound Requirements for Hybrid and 

Electric Vehicles 

AGENCY: National Highway Traffic 

Safety Administration (NHTSA), 

Department of Transportation (DOT). 

ACTION: Notice of availability. 


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