17236 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

DEPARTMENT OF TRANSPORTATION 

National Highway Traffic Safety 

Administration 

49 CFR Parts 571 and 585 

[Docket No. NHTSA–2007–27662] 

RIN 2127–AJ77 

Federal Motor Vehicle Safety 

Standards; Electronic Stability Control 

Systems; Controls and Displays 

AGENCY: National Highway Traffic 

Safety Administration (NHTSA), DOT. 

ACTION: Final rule. 

SUMMARY: As part of a comprehensive 

plan for reducing the serious risk of 

rollover crashes and the risk of death 

and serious injury in those crashes, this 

document establishes a new Federal 

motor vehicle safety standard (FMVSS) 

No. 126 to require electronic stability 

control (ESC) systems on passenger cars, 

multipurpose passenger vehicles, 

trucks, and buses with a gross vehicle 

weight rating of 4,536 Kg (10,000 

pounds) or less. ESC systems use 

automatic computer-controlled braking 

of individual wheels to assist the driver 

in maintaining control in critical driving 

situations in which the vehicle is 

beginning to lose directional stability at 

the rear wheels (spin out) or directional 

control at the front wheels (plow out). 

Preventing single-vehicle loss-ofcontrol crashes is the most effective way 

to reduce deaths resulting from rollover 

crashes. This is because most loss-ofcontrol crashes culminate in the vehicle 

leaving the roadway, which 

dramatically increases the probability of 

a rollover. Based on the best available 

data, drawn from crash data studies, 

NHTSA estimates that the installation of 

ESC will reduce single-vehicle crashes 

of passenger cars by 34 percent and 

single vehicle crashes of sport utility 

vehicles (SUVs) by 59 percent, with a 

much greater reduction of rollover 

crashes. NHTSA estimates that ESC has 

the potential to prevent 71 percent of 

the passenger car rollovers and 84 

percent of the SUV rollovers that would 

otherwise occur in single-vehicle 

crashes. 

NHTSA estimates that ESC would 

save 5,300 to 9,600 lives and prevent 

156,000 to 238,000 injuries in all types 

of crashes annually once all light 

vehicles on the road are equipped with 

ESC systems. The agency further 

anticipates that ESC systems would 

substantially reduce (by 4,200 to 5,500) 

the more than 10,000 deaths each year 

on American roads resulting from 

rollover crashes. 

Manufacturers equipped about 29 

percent of model year (MY) 2006 light 

vehicles sold in the U.S. with ESC, and 

intend to increase the percentage to 71 

percent by MY 2011. This rule requires 

installation of ESC in 100 percent of 

light vehicles by MY 2012 (with 

exceptions for some vehicles 

manufactured in stages or by small 

volume manufacturers). Once all light 

vehicles in the fleet have ESC, of the 

overall projected annual 5,300 to 9,600 

highway deaths and 156,000 to 238,000 

injuries prevented by stability control 

systems installed either voluntarily or 

under this rulemaking, we would 

attribute 1,547 to 2,534 prevented 

fatalities (including 1,171 to 1,465 

involving rollover) to this rulemaking, 

in addition to the prevention of 46,896 

to 65,801 injuries by increasing the 

percentage of light vehicles with ESC 

from 71 percent to 100 percent. 

DATES: Effective Date: This final rule is 

effective June 5, 2007. The 

incorporation by reference of certain 

publications listed in the rule is 

approved by the Director of the Federal 

Register as of June 5, 2007. 

Compliance Date: Consistent with the 

phase-in commencing September 1, 

2008, all new light vehicles must be 

equipped with an ESC system that 

meets the requirements of the standard 

by September 1, 2011, with the 

following exceptions. Vehicle 

manufacturers need not meet the 

standard’s requirements for control and 

display requirements for the ESC 

malfunction indicator telltale and ‘‘ESC 

Off’’ switch and telltale (if provided) 

until September 1, 2011 (i.e., at the end 

of the phase-in), and vehicles produced 

by final-stage manufacturers and alterers 

must be equipped with a compliant ESC 

system (including the control and 

display requirements) by September 1, 

2012. However, manufacturers may 

voluntarily certify vehicles to FMVSS 

No. 126 and earn carry-forward credits 

for compliant vehicles, produced in 

excess of the phase-in requirements, 

that are manufactured between June 5, 

2007, and the conclusion of the phasein. 

Petitions for Reconsideration: If you 

wish to submit a petition for 

reconsideration of this rule, your 

petition must be received by May 21, 

2007. 

ADDRESSES: Petitions for reconsideration 

should refer to the docket number above 

and be submitted to: Administrator, 

Room 5220, National Highway Traffic 

Safety Administration, 400 Seventh 

Street, SW., Washington, DC 20590. 

See the SUPPLEMENTARY INFORMATION

portion of this document (Section VI; 

Rulemaking Analyses and Notice) for 

DOT’s Privacy Act Statement regarding 

documents submitted to the agency’s 

dockets. 

FOR FURTHER INFORMATION CONTACT: For 

non-legal issues, you may call Mr. 

Patrick Boyd, Office of Crash Avoidance 

Standards (Telephone: 202–366–6346) 

(Fax: 202–366–7002). 

For legal issues, you may call Mr. Eric 

Stas, Office of the Chief Counsel 

(Telephone: 202–366–2992) (Fax: 202– 

366–3820). 

You may send mail to both of these 

officials at National Highway Traffic 

Safety Administration, 400 Seventh 

Street, SW., Washington, DC 20590. 

SUPPLEMENTARY INFORMATION: 

Table of Contents 

I. Executive Summary 

A. Requirements of the Final Rule 

B. Lead Time and Phase-in 

C. Differences Between the Final Rule and 

the Notice of Proposed Rulemaking 

D. Impacts of ESC and of the Final Rule 

II. Background 

A. Overview of the Safety Problem 

B. The Agency’s Comprehensive Response 

to Rollover 

C. Congressional Mandate Under Section 

10301 of the Safe, Accountable, Flexible, 

Efficient Transportation Equity Act: A 

Legacy for Users of 2005 

D. Electronic Stability Control as a 

Countermeasure to Address SingleVehicle Crashes and Rollovers 

III. September 2006 Notice of Proposed 

Rulemaking (NPRM) and Public 

Comments 

A. The NPRM 

B. Summary of the Public Comments on 

the NPRM 

IV. The Final Rule and Response to Public 

Comments 

A. Summary of the Requirements 

B. Lead Time and Phase-in 

C. Response to Public Comments by Issue 

Major Issues 

1. Approach of the ESC NPRM 

(a) ESC Mandate vs. ESC Standardization 

(b) ESC as Part of a Comprehensive 

Rollover Safety Program 

(c) Need for Common Terminology 

2. The Definition of ‘‘ESC System’’ as the 

Basis of the Standard 

3. Stringency of the Standard 

4. Understeer Requirements 

5. Lateral Responsiveness Criteria 

6. Definition of ‘‘ESC System’’ and 

Required Equipment 

(a) Clarification of Performance 

Expectations 

(b) Clarification of Threshold Speed 

(c) Estimation of Sideslip—Request to Add 

Derivative 

(d) Request for Alternate Transducers 

(e) Interaction with Other Vehicle Systems 

(f) ESC Operation in Reverse 

7. ESC Performance Requirements 

(a) Definition for ‘‘Lateral Acceleration’’ 

(b) Lateral Displacement Calculation 

(c) Yaw Rate Calculation 


ycherry on PROD1PC64 with RULES2
Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17237 

1 70 FR 49223, at 49229 (August 23, 2005). 

(d) Temperature and Pavement 

Specifications 

(e) Data Processing Issues 

(i) Determination of Beginning of Steering 

(ii) Determination of End of Steering 

(iii) Removing Offsets 

(iv) Use of Interpolation 

(v) Method for Determining Peak Steering 

Wheel Angle 

(vi) Need for a Common Data Processing 

Kernel 

(f) ESC Initialization Period 

(g) ESC Calibration 

Other Issues 

8. ESC Malfunction Detection 

Requirements 

(a) Types of Malfunctions to be Detected 

(b) Practicability Problems with 

Malfunction Detection 

(c) Monitoring When System is Off 

(d) Minimum Performance Level 

9. ESC Telltale Requirements 

(a) ESC Telltale 

(i) Telltale Symbol Text Enhancements 

(ii) Telltale Symbol Alternative: Substitute 

Text 

(iii) Waiver of Yellow Color Requirement 

for ESC Telltale When Message/ 

Information Center is Used 

(iv) Telltale Illumination Strategy 

(v) Telltale Extinguishment 

(vi) Telltale Location 

(vii) Use of ESC Malfunction Telltale to 

Indicate Malfunctions of Related 

Systems/Functions 

(b) ‘‘ESC Off’’ Indication 

(i) ‘‘ESC Off’’ Symbol Alternative: Use of 

Text 

(ii) Waiver of Yellow Color Requirement 

When ‘‘ESC Off’’ is Indicated Via 

Message/Information Center Text 

(iii) ‘‘ESC Off’’ Telltale Clarification 

(iv) ‘‘ESC Off’’ Telltale Strategy 

(v) Use of Two-Part Telltales 

(vi) Conditions for Illumination of ‘‘ESC 

Off’’ Telltale: Speed 

(vii) Conditions for Illumination of ‘‘ESC 

Off’’ Telltale: Direction 

(c) Alerting the Driver of ESC Activation 

(i) Visual and Auditory Indications of ESC 

Activation 

(ii) Flashing Telltales as Activation 

Indication of Intervention by Related 

Systems/Functions 

(d) Bulb Check 

(i) Waiver of Bulb Check for Message/ 

Information Centers 

(ii) Clarification Regarding Bulb Check 

10. System Disablement and the ‘‘ESC Off’’

Control 

(a) Provision of an ‘‘ESC Off’’ Control 

(b) Switch for Complete ESC Deactivation 

(c) ESC Operation After Malfunction and 

‘‘ESC Off’’ Control Override 

(d) Default to ‘‘ESC On’’ Status 

(e) Operation of Vehicle in 4WD Low 

Modes 

(f) ‘‘ESC Off’’ Control Requirements 

(i) Labeling of the ‘‘ESC Off’’ Control 

(ii) Location of the ‘‘ESC Off’’ Control 

11. Test Procedures 

(a) Accuracy Requirements 

(b) Tolerances 

(c) Location of Lateral Accelerometer 

(d) Calculation of Lateral Displacement 

(e) Maximum Steering Angle 

(f) Vehicle Test Weight 

(g) Data Filtering 

(h) Outriggers 

(i) Ambient Temperature Range 

(j) Brake Temperatures 

(k) Wind Speed 

(l) Rounding of Steering Wheel Angle at 0.3 

g 

(m) Vehicle Speed Specification for the 

Slowly Increasing Steer Test 

(n) Alternative Test Procedures 

(o) Representativeness of Real World 

Conditions 

12. Lead Time and Phase-in 

(a) Lead Time for ESC Telltale(s) 

(b) Phase-in Schedule 

13. Impacts on the Aftermarket 

(a) System Adaptability and Sharing ESC 

Information 

(b) ‘‘Make Inoperative’’ Prohibition 

(c) Pass-through Certification 

14. Compliance with Relevant Legal 

Requirements 

(a) Regulatory Flexibility Act 

(b) Executive Orders 12866 and 13258 

(c) Vehicle Safety Act 

15. ESC Outreach Efforts 

(a) ESC Test Procedures Workshop 

(b) Public Information Campaign 

16. Miscellaneous Issues 

(a) Linking Brake Light Illumination to ESC 

Activation 

(b) Vehicles with Dual Wheels on the Rear 

Axle 

(c) ESC Operation with Towed Trailers 

(d) Wheelchair-Accessible Vehicles 

V. Benefits and Costs 

A. Summary 

B. ESC Benefits 

C. ESC Costs 

VI. Regulatory Analyses and Notices 

Appendix: Technical Explanation in 

Response to Comments on Understeer 

I. Executive Summary 

As part of a comprehensive plan 1 that 

seeks to reduce the serious risk of 

rollover crashes and the risk of death 

and serious injury in those crashes, and 

that includes a number of 

complementary rulemaking actions, this 

rule establishes Federal Motor Vehicle 

Safety Standard (FMVSS) No. 126, 

Electronic Stability Control Systems, 

which requires passenger cars, 

multipurpose passenger vehicles 

(MPVs), trucks, and buses that have a 

gross vehicle weight rating (GVWR) of 

4,536 kg (10,000 pounds) or less to be 

equipped with an ESC system that 

meets the requirements of the standard. 

ESC systems use automatic, computercontrolled braking of individual wheels 

to assist the driver in maintaining 

control (and the vehicle’s intended 

heading) in situations where the vehicle 

is beginning to lose directional stability 

(e.g., where the driver misjudges the 

severity of a curve or over-corrects in an 

emergency situation). In such situations 

(which occur with considerable 

frequency), intervention by the ESC 

system can assist the driver in 

preventing the vehicle from leaving the 

roadway, thereby preventing fatalities 

and injuries associated with crashes 

involving vehicle rollover or collision 

with various objects (e.g., trees, highway 

infrastructure, other vehicles). 

Based upon current estimates 

regarding the effectiveness of ESC 

systems, we believe that an ESC 

standard could save thousands of lives 

each year, providing potentially the 

greatest safety benefits produced by any 

safety device since the introduction of 

seat belts. The following discussion 

highlights the research and regulatory 

efforts that have culminated in this 

safety standard. 

Since the early 1990’s, NHTSA has 

been actively engaged in finding ways to 

address the problem of vehicle rollover, 

because crashes involving rollover are 

responsible for a disproportionate 

number of fatalities and serious injuries 

(over 10,000 of the 33,000 fatalities of 

vehicle occupants in 2004). Although 

various options were explored, the 

agency ultimately chose to add a 

rollover resistance component to its 

New Car Assessment Program (NCAP) 

consumer information program in 2001. 

In response to NCAP’s market-based 

incentives, vehicle manufacturers made 

modifications to their product lines to 

increase their vehicles’ geometric 

stability and rollover resistance by 

utilizing wider track widths (typically 

associated with passenger cars) on many 

of their newer sport utility vehicles 

(SUVs) and by making other 

improvements to truck-based SUVs 

during major redesigns (e.g., 

introduction of roll stability control). 

This approach was successful in terms 

of reducing the much higher rollover 

rate of SUVs and other high-center-ofgravity vehicles, as compared to 

passenger cars. However, manipulating 

vehicle configuration alone cannot 

entirely resolve the rollover problem 

(particularly when consumers continue 

to demand vehicles with greater 

carrying capacity and higher ground 

clearance). 

Accordingly, the agency began 

exploring technologies that could 

confront the issue of vehicle rollover 

from a different perspective or line of 

inquiry, which led to today’s final rule. 

We believe that the ESC requirement 

offers a complementary approach that 

may provide substantial benefits to 

drivers of both passenger cars and LTVs 

(light trucks/vans). Undoubtedly, 

keeping vehicles from leaving the 

roadway is the best way to prevent 

deaths and injuries associated with 

rollover, as well as other types of 


ycherry on PROD1PC64 with RULES2
17238 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

2Pub. L. 109–59, 119 Stat. 1144 (2005). 

3An equipment requirement is necessary because 

it would be almost impossible to devise a single 

performance test that could not be met through 

some action by the manufacturer other than 

providing an ESC system. Establishing a battery of 

performance tests to achieve our intended results is 

not possible at this time because we have not been 

able to develop a practical, repeatable limitundersteer test, and there are no applicable tests in 

vehicle dynamics literature. Although the agency 

has undertaken its own preliminary research efforts 

related to understeer, the complexity of such 

research would require several years of additional 

work before any conclusions could be reached 

regarding an ESC understeer performance test. 

Given this, the agency determined that it had 

three available options: (1) Delay the ESC final rule 

and conduct research and development; (2) drop 

the understeer requirement and amend the standard 

once an ESC performance test is developed; or (3) 

include a requirement for understeer as part of the 

definition of ‘‘ESC System,’’ along with requiring 

specific components that will permit the system to 

intervene in excessive understeer situations. 

The agency eliminated the first and second 

options on the grounds of safety. 

The agency believes that the third option, 

adopting an understeer requirement as part of the 

definition of ‘‘ESC System,’’ along with a 

requirement for specific equipment suitable for that 

purpose, will accomplish the purposes of the 

statutory mandate. Such requirement is objective in 

terms of explaining to manufacturers what type of 

performance is required and the minimal 

equipment necessary for that purpose. The agency 

can verify that the system has the necessary 

hardware and logic for understeer mitigation. Since 

the necessary components for effective understeer 

intervention are already present on all ESC systems, 

we believe that manufacturers are highly unlikely 

to decrease their ESC systems’ understeer 

capabilities simply because the standard does not 

have a specific test for understeer. The agency 

believes that its chosen approach will ensure that 

vehicle manufacturers maintain understeer 

intervention as a feature of the ESC system, without 

delaying the life-saving benefits of the ESC rule. In 

the meantime, the agency will conduct additional 

research in the area of ESC understeer intervention 

and consider taking additional action, as 

appropriate. 

Even with an understeer test, the ultimate 

practicability of a standard without an equipment 

requirement remains in doubt because of the 

possible large number of test conditions that would 

be required. 

4 60 FR 13216 (March 10, 1995). 

5The Society of Automotive Engineers is an 

association of engineers, business executives, 

educators, and students who share information and 

exchange ideas for advancing the engineering of 

mobility systems. SAE currently has over 90,000 

members in approximately 97 countries. The 

organization’s activities include development of 

standards, events, and technical information and 

expertise used in designing, building, maintaining, 

and operating self-propelled vehicles for use on 

land or sea, in air or space. See http://www.sae.org. 

crashes. Based on its crash data studies, 

NHTSA estimates that the installation of 

ESC systems will reduce single vehicle 

crashes of passenger cars by 34 percent 

and single vehicle crashes of sport 

utility vehicles (SUVs) by 59 percent. Its 

effectiveness is especially great for 

single-vehicle crashes resulting in 

rollover, where ESC systems were 

estimated to prevent 71 percent of 

passenger car rollovers and 84 percent 

of SUV rollovers in single vehicle 

crashes (see Section V). 

In short, we believe that preventing 

single-vehicle loss-of-control crashes is 

the most effective way to reduce 

rollover deaths, and we believe that ESC 

offers considerable promise in terms of 

meeting this important safety objective 

while maintaining a broad range of 

vehicle choice for consumers. In fact, 

among the agency’s ongoing and 

planned rulemakings, it is the single 

most effective way of reducing the total 

number of traffic deaths. It is also the 

most cost-effective of those rulemakings. 

We note that this final rule also 

satisfies the recent mandate in section 

10301 of the Safe, Accountable, 

Flexible, Efficient Transportation Equity 

Act: A Legacy for Users of 2005 

(SAFETEA–LU).2 That provision 

requires the Secretary of Transportation 

to ‘‘establish performance criteria to 

reduce the occurrence of rollovers 

consistent with stability enhancing 

technologies’’ and to ‘‘issue a proposed 

rule * * * by October 1, 2006, and a 

final rule by April 1, 2009.’’ In light of 

the tremendous life-saving potential 

anticipated to be associated with a 

requirement for ESC to be standard 

equipment on all light vehicles, the 

agency determined that, consistent with 

its mission to save lives, prevent 

injuries and reduce economic costs due 

to road traffic crashes, it was important 

to issue a final rule as soon as possible 

and accelerate the rate of installation. 

Accordingly, today’s final rule is being 

published well in advance of the 

statutory deadline under SAFETEA–LU. 

The balance of this notice discusses 

(1) The background regarding the size of 

the safety problem, the agency’s 

comprehensive response to rolloverrelated safety problems, the agency’s 

mandate under SAFETEA–LU, and ESC 

systems as a countermeasure to address 

single-vehicle crashes and rollovers (see 

Section II); (2) the agency’s September 

2006 NPRM for ESC and public 

comments on that proposal (see Section 

III); (3) the requirements and 

implementation of the final rule, 

including a detailed discussion 

regarding resolution of the issues raised 

in public comments (see Section IV); 

and (4) costs and benefits associated 

with the final rule (see Section V). 

However, before turning to this more 

detailed analysis, we summarize the key 

points of the final rule, including the 

requirements for ESC systems under 

FMVSS No. 126, lead time and phasein, differences between the final rule 

and the NPRM, and the anticipated 

impacts of the final rule. 

A. Requirements of the Final Rule 

After careful consideration of all 

available information, including the 

public comments, the agency has 

decided to adopt in the ESC final rule 

most of the elements of the proposed 

rule. Consistent with SAFETEA–LU, 

NHTSA is requiring all light vehicles to 

be equipped with an ESC system with, 

at the minimum, the capabilities of 

current production systems. We believe 

that a requirement for such ESC systems 

is desirable in terms of both ensuring 

technological feasibility and providing 

the desired safety benefits in a costeffective manner. Although vehicle 

manufacturers have been increasing the 

portion of the light vehicle fleet 

equipped with ESC, we believe that 

given the relatively high cost of this 

technology, a mandatory standard is 

necessary to maximize the safety 

benefits associated with electronic 

stability control, and is required by 

SAFETEA–LU. 

In order to realize these benefits, we 

have decided to require vehicles to be 

equipped with an ESC system meeting 

definitional requirements and to pass a 

dynamic test. The definitional 

requirements specify the necessary 

elements of a stability control system 

that is capable of both effective 

oversteer and understeer intervention. 

These requirements are necessary due to 

the extreme difficulty in establishing 

tests adequate, by themselves, to ensure 

the desired level of ESC functionality in 

a variety of circumstances.3 The test that 

we are adopting is necessary to ensure 

that the ESC system is robust and meets 

a level of performance at least 

comparable to that of current ESC 

systems. This approach is similar to the 

one we took, for similar reasons, in 1995 

in mandating antilock brakes for 

medium and heavy vehicles pursuant to 

the Intermodal Surface Transportation 

Efficiency Act (ISTEA) of 1991.4

These requirements are summarized 

below: 

• Consistent with the definition of 

ESC contained in a voluntary consensus 

standard, the Society of Automotive 

Engineers 5 (SAE) Surface Vehicle 

Information Report J2564 (rev. June 

2004), we are requiring vehicles covered 

under the standard to be equipped with 

an ESC system that: 

(1) Augments vehicle directional 

stability by applying and adjusting the 

vehicle brake torques individually to 

induce a correcting yaw moment to a 

vehicle; 

(2) Is computer-controlled, with the 

computer using a closed-loop 


ycherry on PROD1PC64 with RULES2
Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17239 

6A ‘‘closed-loop algorithm’’ is a cycle of 

operations followed by a computer that includes 

automatic adjustments based on the result of 

previous operations or other changing conditions. 

7 ‘‘Yaw rate’’ means the rate of change of the 

vehicle’s heading angle measured in degrees/second 

of rotation about a vertical axis through the 

vehicle’s center of gravity. 

8 ‘‘Sideslip’’ means the arctangent of the lateral 

velocity of the center of gravity of the vehicle 

divided by the longitudinal velocity of the center 

of gravity. 

9The standard was developed based on new 

vehicles produced in 2005 and 2006. The definition 

of ESC is limited to four-wheel ESC systems 

because existing two-wheel ESC systems are not 

capable of understeer invention or four-wheel 

automatic braking during an intervention, even 

though these systems also produced substantial (but 

lesser) benefits. 

algorithm 6 to limit vehicle oversteer 

and to limit vehicle understeer; 

(3) Has a means to determine vehicle 

yaw rate 7 and to estimate its sideslip 8

or the time derivative of sideslip; 

(4) Has a means to monitor driver 

steering input; 

(5) Has an algorithm to determine the 

need, and a means to modify engine 

torque, as necessary, to assist the driver 

in maintaining control of the vehicle, 

and 

(6) Is operational over the full speed 

range of the vehicle (except at vehicle 

speeds less than 15 km/h (9.3 mph) or 

when being driven in reverse). 

• The ESC system, as defined above, 

is also required to be capable of 

applying brake torques individually at 

all four wheels and to have an algorithm 

that utilizes this capability.9 Except for 

the situations specifically set forth in 

part (6) of the definition of ‘‘ESC 

System’’ above, the system is also 

required to be operational during all 

phases of driving, including 

acceleration, coasting, and deceleration 

(including braking). It is also required to 

be capable of activation even if the antilock brake system or traction control 

system is also activated. 

• In order to ensure that a vehicle is 

equipped with an ESC system that 

meets the definition of ‘‘ESC System’’

under S4, the final rule requires vehicle 

manufacturers to submit, upon the 

request of NHTSA’s Office of Vehicle 

Safety Compliance, ESC system 

technical documentation as to when 

understeer intervention is appropriate 

for a given vehicle (see S5.6). 

Specifically, NHTSA may seek 

information such as a system diagram 

that identifies all ESC components, a 

written explanation describing the ESC 

system’s basic operational 

characteristics, a logic diagram 

supporting the explanation of system 

operations, and a discussion of the 

pertinent inputs to the vehicle computer 

or calculations within the computer and 

how its algorithm uses that information 

and controls ESC system hardware to 

limit vehicle understeer. 

• We are also requiring vehicles 

covered under the standard to meet a 

performance test. It must satisfy the 

standard’s stability criteria and 

responsiveness criterion when subjected 

to the sine with dwell steering 

maneuver test. This test involves a 

vehicle’s coasting at an initial speed of 

50 mph while a steering machine steers 

the vehicle with a steering wheel 

pattern as shown in Figure 2 of the 

regulatory text. The test maneuver is 

then repeated over a series of increasing 

maximum steering angles. This test 

maneuver was selected over a number of 

other alternatives because we decided 

that it has the best set of characteristics, 

including severity of the test, 

repeatability and reproducibility of 

results, and the ability to address lateral 

stability and responsiveness. 

The maneuver is severe enough to 

produce spinout for most vehicles 

without ESC. The stability criteria for 

the test measure how quickly the 

vehicle stops rotating after the steering 

wheel is returned to the straight-ahead 

position. A vehicle that continues to 

rotate for an extended period after the 

driver steers straight is out of control, 

which is what ESC is designed to 

prevent. The quantitative stability 

criteria are expressed in terms of the 

percent of the peak yaw rate after 

maximum steering that persists at a 

period of time after the steering wheel 

has been returned to straight ahead. 

They require that the vehicle yaw rate 

decrease to no more than 35 percent of 

the peak value after one second and that 

it continue to drop to no more than 20 

percent after 1.75 seconds. Since a 

vehicle that simply responds very little 

to steering commands could meet the 

stability criteria, a minimum 

responsiveness criterion is applied to 

the same test. 

• Because the benefits of the ESC 

system can only be realized if the 

system is functioning properly, we are 

requiring that a telltale be mounted 

inside the occupant compartment in 

front of and in clear view of the driver. 

The ESC malfunction telltale is required 

to illuminate after the occurrence of one 

or more malfunctions that affect the 

generation or transmission of control or 

response signals in the vehicle’s ESC 

system. Such telltale must remain 

continuously illuminated for as long as 

the malfunction(s) exists, whenever the 

ignition locking system is in the ‘‘On’’

(‘‘Run’’) position. 

• In certain circumstances, drivers 

may have legitimate reasons to 

disengage the ESC system or limit its 

ability to intervene, such as when the 

vehicle is stuck in sand/gravel, is being 

used while equipped with snow chains, 

or is being run on a track for maximum 

performance. Accordingly, under this 

final rule, vehicle manufacturers may 

include a driver-selectable switch that 

places the ESC system in a mode in 

which it does not satisfy the 

performance requirements of the 

standard (e.g., ‘‘sport’’ mode or full-off 

mode). However, if the vehicle 

manufacturer chooses this option, it 

must ensure that the ESC system always 

returns to the fully-functional default 

mode at the initiation of each new 

ignition cycle, regardless of the mode 

the driver had previously selected (with 

certain exceptions for low speed offroad axle/transfer case selections that 

turn off ESC, but cannot be reset 

electronically). If the vehicle 

manufacturer chooses this option, it 

must also provide an ‘‘ESC Off’’ control 

and a telltale that is mounted inside the 

occupant compartment in front of and 

in clear view of the driver. Such telltale 

must remain continuously illuminated 

for as long as the ESC is in a mode that 

renders it unable to meet the 

performance requirements of the 

standard, whenever the ignition locking 

system is in the ‘‘On’’ (‘‘Run’’) position. 

• We are not requiring the ESC 

system to be equipped with a roll 

stability control system. Roll stability 

control systems involve relatively new 

technology. There is currently an 

insufficient body of data to judge the 

efficacy of such systems. However, the 

agency will continue to monitor the 

development of these systems. 

B. Lead Time and Phase-In 

In order to provide the public with 

what are expected to be the significant 

safety benefits of ESC systems as rapidly 

as possible, compliance with this final 

rule is set to commence on September 

1, 2008. That date marks the start of a 

three-year phase-in period. Subject to 

the special provisions discussed below, 

NHTSA has decided to require 

compliance in accordance with the 

following schedule: 55 percent of a 

vehicle manufacturer’s light vehicles 

manufactured during the period from 

September 1, 2008 to August 31, 2009; 

75 percent of those manufactured 

during the period from September 1, 

2009 to August 31, 2010; 95 percent of 

those manufactured during the period 

from September 1, 2010 to August 31, 

2011, and all light vehicles thereafter. 

For the reasons discussed in detail in 

Section IV.B of this notice, we believe 

that it is practicable for vehicle 

manufacturers to meet the requirements 

of the phase-in discussed above, subject 


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10We note that carry-forward credits may not be 

used to defer the mandatory compliance date of 

September 1, 2011 for all covered vehicles. 

11We note here that we anticipate that much of 

this information is proprietary and would be 

submitted under a request for confidential 

treatment pursuant to 49 CFR Part 512. 

to the exceptions below. Because ESC is 

so cost-effective and has such high 

benefits in terms of potential fatalities 

and injuries that may be prevented, the 

agency has decided that it is important 

to require ESC installation in light 

vehicles as quickly as possible. Given 

the product plans we have from six 

vehicle manufacturers, and the desire to 

provide manufacturers with flexibility 

by having a carry-forward provision, we 

have chosen the most aggressive phasein alternative that we believe is 

reasonable (i.e., 55/75/95%). In doing 

so, we have carefully considered the 

financial and technological 

practicability of the final rule (in 

keeping with our statutory mandate), 

while at the same time facilitating ESC 

installation in the light vehicle fleet as 

expeditiously as possible. 

With the above said, the agency has 

decided that it is appropriate to provide 

the following exceptions to the phasein. First, we have decided to defer the 

standard’s requirements related to the 

ESC telltales and controls until the end 

of the phase-in (i.e., September 1, 2011 

for most manufacturers; September 1, 

2012 for final-stage manufacturers and 

alterers). Although vehicle 

manufacturers generally commented 

that they could bring their ESC systems 

into full compliance (including the 

control and telltale requirements), they 

stated that additional lead time would 

be necessary to accomplish those 

changes, suggesting that they could do 

so by the end of the phase-in. As a 

complicating matter, vehicle 

manufacturers and their trade 

associations explained that even though 

most current ESC systems would largely 

meet the performance requirements of 

the proposed standard, manufacturers’

inability to meet the proposed control 

and display requirements would 

prevent them from earning the carryforward credits needed to comply with 

the ESC phase-in schedule. Our analysis 

demonstrates that the safety benefits 

associated with early introduction of 

ESC systems, even without standardized 

controls and displays, far outweigh the 

benefits of delaying the standard until 

all systems can fully meet the control 

and display requirements (see FRIA’s 

lead time/phase-in discussion). 

Accordingly, we believe that it is 

preferable to move rapidly to implement 

the standard, but to delay the 

compliance date only for the ESC 

control and telltale requirements. 

As proposed, vehicle manufacturers 

may earn carry-forward credits for 

compliant vehicles, produced in excess 

of the phase-in requirements, which are 

manufactured between the effective date 

of the final rule and the conclusion of 

the phase-in period.10

This final rule excludes small volume 

manufacturers (i.e., manufacturers 

producing less than 5,000 vehicles for 

sale in the U.S. market in one year) from 

the phase-in, instead requiring those 

manufacturers to fully comply with the 

standard beginning on September 1, 

2011. 

In addition, consistent with the policy 

set forth in NHTSA’s February 14, 2005 

final rule on certification requirements 

for vehicles built in two or more stages 

and altered vehicles (70 FR 7414), finalstage manufacturers and alterers are 

excluded from the requirements of the 

phase-in and are permitted an 

additional one year for compliance (i.e., 

until September 1, 2012). However, 

final-stage manufacturers and alterers 

may voluntarily certify compliance with 

the standard prior to this date. 

C. Differences Between the Final Rule 

and the Notice of Proposed Rulemaking 

As noted above, NHTSA has decided 

to adopt most of the provisions in the 

NPRM as part of this final rule. We 

made a number of changes in response 

to the public comments on the NPRM. 

The main differences between the 

NPRM and the final rule involve an 

increase in the percentages of FMVSS 

No. 126-compliant vehicles that must be 

produced during the phase-in period, a 

delay in the requirements for 

standardized symbols and acronyms for 

ESC controls and displays until the end 

of the phase-in, and the inclusion of 

engine control as part of the standard’s 

definition of ‘‘ESC system.’’

The following points briefly describe 

the main differences between the NPRM 

and this final rule. 

• In order to increase fleet installation 

of life-saving ESC systems, the phase-in 

schedule for ESC is being accelerated to 

require 55 percent phase-in in the first 

year, 75 percent in the second year, and 

95 percent in the third year, rather than 

the 30 percent, 60 percent, and 90 

percent schedule that was proposed (see 

S8.1, S8.2, and S8.3 in the regulatory 

text of this final rule). 

• The effective date for the 

requirement to use standardized 

symbols and acronyms as well as certain 

malfunction detection and ‘‘ESC Off’’

control functions has been moved to the 

end of the phase-in period. This was 

done in recognition of the fact that 

manufacturers will be relying on the 

carry-forward and compliance credits 

for vehicles in current production that 

pass all the ESC performance 

requirements, but currently lack the 

standardized controls and displays 

features proposed in the NPRM (see 

S5.3.1, S5.3.2; S5.3.4; S5.3.9; S5.4.2; 

S5.5.2; S5.5.3; S5.5.6). 

• The definition of ‘‘ESC System’’ has 

been changed to require ESC systems 

with engine control, a feature that 

allows the ESC system to reduce vehicle 

speed during an intervention by cutting 

engine power as well as by brake 

application (see S4 ESC (5)). It was a 

feature on most vehicles in the crash 

data analysis and on all the vehicles in 

the ESC cost study. 

• The definition of ‘‘ESC System’’ has 

been changed to delete the word ‘‘as 

appropriate’’ from the description of 

when the system must intervene to 

mitigate vehicle understeer (see S4 ESC 

(2)). Instead, in order to ensure that a 

vehicle is equipped with an ESC system 

that meets the definition of ‘‘ESC 

System’’ under S4, we have decided to 

require vehicle manufacturers to submit, 

upon the request of NHTSA’s Office of 

Vehicle Safety Compliance, ESC system 

technical documentation as to when 

understeer intervention is appropriate 

for a given vehicle (see S5.6). 

Specifically, NHTSA may seek 

information such as a system diagram 

that identifies all ESC components, a 

written explanation describing the ESC 

system’s basic operational 

characteristics, a logic diagram 

supporting the explanation of system 

operations, and a discussion of the 

pertinent inputs to the vehicle computer 

or calculations within the computer and 

how its algorithm uses that information 

and controls ESC system hardware to 

limit vehicle understeer.11

• The ‘‘ESC System’’ definition and 

performance requirements have been 

changed to refer to generating brake 

torques at all four wheels individually, 

rather than applying individual brakes, 

so that the action of regenerative braking 

by electric motors is included (see S4 

ESC (1); S5.1.1). 

• The definition of ‘‘ESC System’’ has 

been further changed to recognize that 

some systems operate by estimating the 

time derivative of side slip, rather than 

by measuring side slip directly. The 

final rule also defines the low speed 

threshold for ESC operation as 15 km/ 

h (see S4 ESC (3), (6)). 

• The responsiveness criterion has 

been changed to a two-stage criterion 

with a lower lateral displacement 

requirement for large vehicles (i.e., ones 


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12We note that the costs for passenger cars are 

higher because a greater portion of those vehicles 

require installation of ABS in addition to ESC. 

13For brevity, we use the term ‘‘light trucks’’ in 

this document to refer to multipurpose passenger 

vehicles (e.g., vans, minivans, and SUVs), trucks, 

and buses with a GVWR of 4,536 kilograms (10,000 

pounds) or less. 

over 7,716 pounds GVWR). It is applied 

during tests with a peak commanded 

steering angle of five times or greater 

than the steering wheel angle necessary 

to produce 0.3g steady-state lateral 

acceleration. This is a change from 

applying it simply for tests with steering 

wheel angles greater than 180 degrees. 

It compensates for the slower steering 

gear ratios of large vehicles. (see S5.2; 

S5.2.3; S6.3.5). 

• Low-speed four-wheel-drive (4WD) 

modes that have the side effect of 

turning off ESC and that are selected by 

mechanical controls that cannot be 

automatically reset electrically are 

excluded from the requirement for 

automatic ESC restoration at the next 

ignition cycle (see S5.4.1). 

• Under the final rule, outriggers will 

be used for testing of trucks, MPVs, and 

buses, and the maximum weight and 

roll moment of inertia are also specified 

for outriggers (see S6.3.4). 

• The ESC malfunction detection test 

procedure has been modified to include 

a short driving and turning procedure so 

that ESC systems with self-diagnostics 

requiring vehicle motion can 

accomplish their function (see S7.10.2). 

D. Impacts of ESC and of the Final Rule 

Based on its analysis of the best 

available data, NHTSA estimates that 

ESC—both installed voluntarily and 

under this regulatory mandate—will 

save 5,300 to 9,600 lives and prevent 

156,000 to 238,000 injuries in all types 

of crashes annually once all light 

vehicles on the road are equipped with 

ESC systems. A large portion of these 

savings will come from preventing large 

numbers of rollover crashes. ESC 

systems will substantially reduce (by 

4,200 to 5,500) the more than 10,000 

deaths that occur on American roads 

each year as a result of rollover crashes. 

Manufacturers installed ESC in about 

29 percent of model year (MY) 2006 

light vehicles sold in the U.S., and 

intend to increase the percentage of ESC 

installation in light vehicles to 71 

percent by MY 2011. This rule 

accelerates that rate of installation by 

requiring a 100 percent installation rate 

by MY 2012 (with exceptions for some 

vehicles manufactured in stages or by 

small volume manufacturers). We took 

that step because, in response to public 

comments and our review of vehicle 

manufacturers’ production plans, we 

determined that it is practicable to 

increase the percentage of new light 

vehicles that must comply with 

Standard No. 126 under the phase-in, 

thereby accelerating the benefits 

expected to be provided by ESC 

systems. 

As the discussion below 

demonstrates, ESC not only has a very 

significant life-saving and injurypreventing potential in absolute terms, 

but it also achieves these benefits in a 

very cost-effective manner vis-a`-vis 

other agency rulemakings. ESC offers 

consistently strong benefits and costeffectiveness across all types of light 

vehicles, including passenger cars, 

SUVs, vans, and pick-up trucks. Of the 

5,300 to 9,600 highway deaths and 

156,000 to 238,000 MAIS 1–5 injuries 

that we project will be prevented 

annually for all types of crashes once all 

light vehicles on the road are equipped 

with ESC, we attribute 1,547 to 2,534 

prevented fatalities (including 1,171 to 

1,465 involving rollover) to this 

rulemaking, in addition to the 

prevention of 46,896 to 65,801 injuries. 

The agency estimates that the 

production-weighted, average cost per 

vehicle to meet the proposed standard’s 

requirements will be $58 ($90.3 per 

passenger car and $29.2 per light 

truck).12 These are incremental costs 

over the manufacturers’ MY 2011 plans 

for installation of ABS, which is 

expected to be installed in almost 93 

percent of the light vehicle fleet, and 

ESC, which is expected to be installed 

in 71 percent of the light vehicle fleet. 

Vehicle costs are estimated to be $368 

(in 2005$) for anti-lock brakes (ABS) 

and an additional $111 for ESC, for a 

total system cost of $479 per vehicle. 

The total annual vehicle cost of this 

regulation, based on ESC installation 

beyond manufacturers’ planned 

percentages, is expected to be 

approximately $985 million. 

In terms of cost-effectiveness, this 

final rule is expected to save 1,547 to 

2,534 lives and prevent 46,896 to 65,801 

injuries at a cost of $0.18 to $0.33 

million per equivalent life saved at a 3 

percent discount rate and $0.26 to $0.45 

million at a 7 percent discount rate. 

The final rule is highly cost-effective 

even when passenger cars are 

considered alone. The passenger car 

portion of the final rule will save 945 

lives and prevent 32,196 injuries at a 

cost of $0.38 million per equivalent life 

saved at a 3 percent discount rate and 

$0.50 at a 7 percent discount rate. 

II. Background 

A. Overview of the Safety Problem 

The following discussion explains the 

nature and scope of the safety problem 

which the agency seeks to address 

through this rulemaking for ESC, based 

upon our analysis of recent singlevehicle crash and rollover statistics. 

About one in seven light vehicles 

involved in police-reported crashes 

collides with something other than 

another vehicle. However, the 

proportion of these single-vehicle 

crashes increases steadily with 

increasing crash severity, and almost 

half of serious and fatal injuries occur 

in single-vehicle crashes. We can 

describe the relationship between crash 

severity and the number of vehicles 

involved in the crash using information 

from the agency’s crash data programs. 

We limit our discussion here to ‘‘light 

vehicles,’’ which consist of passenger 

cars, multipurpose passenger vehicles 

(MPVs), trucks, and buses with a gross 

vehicle weight rating (GVWR) of 4,536 

kilograms (10,000 pounds) or less.13

The 2000–2005 data from the National 

Automotive Sampling System (NASS) 

Crashworthiness Data System (CDS) and 

2005 data from the Fatality Analysis 

Reporting System (FARS) were 

combined to estimate the current target 

population for this rulemaking. It 

includes 27,680 people who were killed 

as occupants of light vehicles (both 

single-vehicle and multi-vehicle 

crashes). Over half of these (15,191) 

occurred in single-vehicle crashes. Of 

these, 8,596 occurred in rollovers. 

About 1.0 million injuries (AIS 1–5) 

occurred in crashes that could be 

affected by ESC, almost 458,000 in 

single vehicle crashes (of which almost 

half were in rollovers). Multi-vehicle 

crashes that could be affected by ESC 

accounted for 12,485 fatalities and 

almost 547,000 injuries. 

Rollover crashes are complex events 

that reflect the interaction of driver, 

road, vehicle, and environmental 

factors. We can describe the relationship 

between these factors and the risk of 

rollover using information from the 

agency’s crash data programs. 

According to 2005 data from FARS, 

10,836 people were killed as occupants 

in light vehicle rollover crashes, which 

represents 34 percent of all occupants 

killed that year in crashes. Of those, 

8,769 were killed in single-vehicle 

rollover crashes. Seventy-four percent of 

the people who died in single-vehicle 

rollover crashes were not using a seat 

belt, and 61 percent were partially or 

completely ejected from the vehicle 

(including 50 percent who were 

completely ejected). FARS shows that 

55 percent of light vehicle occupant 

fatalities in single-vehicle crashes 

involved a rollover event. 


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14See Docket Number NHTSA 2003–14622–1. 15Pub. L. 109–59, 119 Stat. 1144 (2005). 

16See 49 U.S.C. 30123 note (2003). 

17Pub. L. 106–414, 114 Stat. 1800 (2000). 

Using data from the 2000–2004 NASS 

CDS files, we estimate that 266,000 light 

vehicles were towed from a policereported rollover crash each year (on 

average), and that 29,000 occupants of 

these vehicles were seriously injured. Of 

these 266,000 light vehicle rollover 

crashes, 219,000 were single-vehicle 

crashes. Sixty-one percent of those 

people who suffered a serious injury in 

a single-vehicle tow-away rollover crash 

were not using a seat belt, and 52 

percent were partially or completely 

ejected (including 41 percent who were 

completely ejected). Estimates from 

NASS CDS indicate that 82 percent of 

tow-away rollovers were single-vehicle 

crashes, and that 88 percent (197,000) of 

the single-vehicle rollover crashes 

occurred after the vehicle left the 

roadway. An audit of 1992–96 NASS 

CDS data showed that about 95 percent 

of rollovers in single-vehicle crashes 

were tripped by mechanisms such as 

curbs, soft soil, pot holes, guard rails, 

and wheel rims digging into the 

pavement, rather than by tire/road 

interface friction as in the case of 

untripped rollover events. 

B. The Agency’s Comprehensive 

Response to Rollover 

As mentioned above, this final rule 

for ESC is but one part of the agency’s 

comprehensive plan to address the issue 

of vehicle rollover. The following 

discussion provides background on 

NHTSA’s comprehensive plan to reduce 

rollover crashes. In 2002, the agency 

formed an Integrated Project Team (IPT) 

to examine the rollover problem and to 

make recommendations on how to 

reduce rollovers and to improve safety 

when rollovers nevertheless occur. In 

June 2003, based on the work of that 

team, the agency published a report 

titled, ‘‘Initiatives to Address the 

Mitigation of Vehicle Rollover.’’ 14 The 

report recommended improving vehicle 

stability, ejection mitigation, roof crush 

resistance, as well as road 

improvements and behavioral strategies 

aimed at consumer education. 

Since then, the agency has been 

working to implement these 

recommendations as part of its 

comprehensive agency plan for reducing 

the serious risk of rollover crashes and 

the risk of death and serious injury 

when rollover crashes do occur. It is 

evident that the most effective way to 

reduce deaths and injuries in rollover 

crashes is to prevent the rollover crash 

from occurring. This final rule adopting 

a new Federal motor vehicle safety 

standard for electronic stability control 

systems is one key part of that 

comprehensive agency plan. 

Moreover, we note that the agency 

also published a notice of proposed 

rulemaking in the Federal Register in 

August 2005, seeking to upgrade our 

safety standard on roof crush resistance 

(FMVSS No. 216); that notice, like the 

present one, contains an in-depth 

discussion of the rollover problem and 

the countermeasures which the agency 

intends to pursue as part of its 

comprehensive response to the rollover 

problem (see 70 FR 49223 (August 23, 

2005)). 

C. Congressional Mandate Under 

Section 10301 of the Safe, Accountable, 

Flexible, Efficient Transportation Equity 

Act: A Legacy for Users of 2005 

During the course of the ongoing 

agency’s research into ESC systems, 

Congress passed the Safe, Accountable, 

Flexible, Efficient Transportation Equity 

Act: A Legacy for Users of 2005 

(SAFETEA–LU).15 Section 10301 of that 

Act contains legislative mandates for the 

agency to initiate a number of 

rulemakings, including ones for rollover 

prevention and occupant ejection 

prevention. In relevant part, that 

provision states: 

(a) In General.—The Secretary [of 

Transportation] shall initiate rulemaking 

proceedings, for the purpose of establishing 

rules or standards that will reduce vehicle 

rollover crashes and mitigate deaths and 

injuries associated with such crashes for 

motor vehicles with a gross vehicle weight 

rating of not more than 10,000 pounds. 

(b) Rollover Prevention.—One of the 

rulemaking proceedings initiated under 

subsection (a) shall be to establish 

performance criteria to reduce the occurrence 

of rollovers consistent with stability 

enhancing technologies. The Secretary shall 

issue a proposed rule in this proceeding by 

rule by October 1, 2006, and a final rule by 

April 1, 2009. 

This SAFETEA–LU mandate is 

consistent with the agency’s efforts 

under its Comprehensive Rollover 

Safety Program (discussed above). The 

agency’s research efforts had already 

identified electronic stability control 

systems as a mature and effective 

technology which has had adequate 

time to be analyzed in both the 

scientific literature, as well as by 

NHTSA researchers. These research 

results strongly suggest that fleet-wide 

installation of ESC systems should yield 

tremendous benefits in terms of the 

prevention of fatalities and injuries. 

Although the agency considered other 

potential ‘‘stability enhancing 

technologies,’’ there was no evidence to 

demonstrate that they would meet the 

need for motor vehicle safety (see 

Section IV.C.3 below). Accordingly, the 

agency has determined that adopting a 

requirement for installation of ESC 

systems in light vehicles would be 

consistent with the statutory mandate 

under section 10301 of SAFETEA–LU. 

Under our interpretation of that 

statutory provision, Congress provided 

the agency discretion to evaluate 

various stability enhancing technologies 

and to adopt a requirement for a system 

that the agency determines would best 

reduce the occurrence of rollovers. The 

agency agrees with Congress regarding 

the tremendous life-saving potential 

associated with ESC as a proven 

stability enhancing technology, and 

because of the agency’s prior efforts, it 

was possible to publish today’s final 

rule well in advance of the statutory 

deadline under SAFETEA–LU. 

As this final rule makes clear, the 

agency has decided to implement the 

statutory mandate contained in section 

10301 of SAFETEA–LU through 

promulgation of a Federal motor vehicle 

safety standard for ESC pursuant to 49 

U.S.C. Chapter 301, Motor Vehicle 

Safety. Adoption of an FMVSS for ESC 

meets the statutory directive to 

‘‘establish performance criteria’’

consistent with stability enhancing 

technologies. Furthermore, this 

approach is consistent with the agency’s 

implementation of the statutory 

mandate for tire pressure monitoring 

systems contained in section 1316 of the 

Transportation Recall Enhancement, 

Accountability, and Documentation 

(TREAD) Act.17

D. Electronic Stability Control as a 

Countermeasure to Address SingleVehicle Crashes and Rollovers 

General Principles of ESC System 

Operation 

Although Electronic Stability Control 

(ESC) systems have been known by a 

number of different trade names such as 

Vehicle Stability Control (VSC), 

Electronic Stability Program (ESP), 

StabiliTrak and Vehicle Stability 

Enhancement (VSE), their function and 

performance are similar. They are 

systems that use computer control of 

individual wheel brakes to help the 

driver maintain control of the vehicle 

during extreme maneuvers by keeping 

the vehicle headed in the direction the 

driver is steering even when the vehicle 

nears or reaches the limits of road 

traction. 

When a driver attempts an ‘‘extreme 

maneuver’’ (e.g., one initiated to avoid 


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Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17243 

a crash or due to misjudgment of the 

severity of a curve), the driver may lose 

control if the vehicle responds 

differently as it nears the limits of road 

traction than it does during ordinary 

driving. The driver’s loss of control can 

result in either the rear of the vehicle 

‘‘spinning out’’ or the front of the 

vehicle ‘‘plowing out.’’ As long as there 

is sufficient road traction, a highly 

skilled driver may be able to maintain 

control in many extreme maneuvers 

using countersteering (i.e., momentarily 

turning away from the intended 

direction) and other techniques. 

However, average drivers in a panic 

situation in which the vehicle is 

beginning to spin out would be unlikely 

to countersteer to regain control. 

ESC uses automatic braking of 

individual wheels to adjust the vehicle’s 

heading if it departs from the direction 

the driver is steering. Thus, it prevents 

the heading from changing too quickly 

(spinning out) or not quickly enough 

(plowing out). Although it cannot 

increase the available traction, ESC 

affords the driver the maximum 

possibility of keeping the vehicle under 

control and on the road in an emergency 

maneuver using just the natural reaction 

of steering in the intended direction. 

Keeping the vehicle on the road 

prevents single-vehicle crashes, which 

are the circumstances that lead to most 

rollovers. However, if the speed is 

simply too great for the available road 

traction, even a vehicle with ESC will 

unavoidably drift off the road (but not 

spin out). Furthermore, ESC cannot 

prevent road departures due to driver 

inattention or drowsiness rather than 

loss of control. 

How ESC Prevents Loss of Vehicle 

Control 

The following explanation of ESC 

operation illustrates the basic principle 

of yaw stability control, but it does not 

attempt to explain advanced 

refinements of the yaw control strategy 

described below that use vehicle 

sideslip (lateral sliding that may not 

alter yaw rate) to optimize performance 

on slippery pavements. 

An ESC system maintains what is 

known as ‘‘yaw’’ (or heading) control by 

determining the driver’s intended 

heading, measuring the vehicle’s actual 

response, and automatically turning the 

vehicle if its response does not match 

the driver’s intention. However, with 

ESC, turning is accomplished by 

applying a brake force at a single wheel 

rather than by steering input. (The 

uneven brake force from braking only 

one wheel creates a yaw torque or 

moment that rotates the vehicle around 

a vertical axis.) 

Speed and steering angle 

measurements are used to determine the 

driver’s intended heading. The vehicle 

response is measured in terms of lateral 

acceleration and yaw rate by onboard 

sensors. If the vehicle is responding in 

a manner corresponding to driver input, 

the yaw rate will be in balance with the 

speed and lateral acceleration. 

The concept of ‘‘yaw rate’’ can be 

illustrated by imaging the view from 

above of a car following a large circle 

painted on a parking lot. One is looking 

at the top of the roof of the vehicle and 

seeing the circle. If the car starts in a 

heading pointed north and drives half 

way around circle, its new heading is 

south. Its yaw angle has changed 180 

degrees. If it takes 10 seconds to go half 

way around the circle, the ‘‘yaw rate’’ is 

180 degrees per 10 seconds or 18 deg/ 

sec. If the speed stays the same, the car 

is constantly rotating at a rate of 18 deg/ 

sec around a vertical axis that can be 

imagined as piercing its roof. If the 

speed is doubled, the yaw rate increases 

to 36 deg/sec. 

While driving in a circle, the driver 

notices that he must hold the steering 

wheel tightly to avoid sliding toward 

the passenger seat. The bracing force is 

necessary to overcome the lateral 

acceleration that is caused by the car 

following the curve. The lateral 

acceleration is also measured by the 

ESC system. When the speed is doubled 

the lateral acceleration increases by a 

factor of four if the vehicle follows the 

same circle. There is a fixed physical 

relationship between the car’s speed, 

the radius of its circular path, and its 

lateral acceleration. 

The ESC system uses this information 

as follows: Since the ESC system 

measures the car’s speed and its lateral 

acceleration, it can compute the radius 

of the circle. Since it then has the radius 

of the circle and the car’s speed, the ESC 

system can compute the correct yaw rate 

for a car following the path. Of course, 

the system includes a yaw rate sensor, 

and it compares the actual measured 

yaw rate of the car to that computed for 

the path the car is following. If the 

computed and measured yaw rates 

begin to diverge as the car that is trying 

to follow the circle speeds up, it means 

the driver is beginning to lose control, 

even if the driver cannot yet sense it. 

Soon, an unassisted vehicle would have 

a heading significantly different from 

the desired path and would be out of 

control either by oversteering (spinning 

out) or understeering. 

When the ESC system detects an 

imbalance between the measured yaw 

rate of a vehicle and the path defined by 

the vehicle’s steering wheel angle, 

speed, and lateral acceleration, the ESC 

system automatically intervenes to turn 

the vehicle. The automatic turning of 

the vehicle is accomplished by uneven 

brake application rather than by steering 

wheel movement. If only one wheel is 

braked, the uneven brake force will 

cause the vehicle’s heading to change. 

Figure 1 shows the action of ESC using 

single wheel braking to correct the onset 

of oversteering or understeering. (Please 

note that all Figures discussed in this 

preamble may be found at the end of the 

preamble, immediately preceding the 

proposed regulatory text.) 

• Oversteering. In Figure 1 (bottom 

panel), the vehicle has entered a left 

curve that is extreme for the speed it is 

traveling. The rear of the vehicle begins 

to slide which would lead to a vehicle 

without ESC turning sideways (or 

‘‘spinning out’’) unless the driver 

expertly countersteers. In a vehicle 

equipped with ESC, the system 

immediately detects that the vehicle’s 

heading is changing more quickly than 

appropriate for the driver’s intended 

path (i.e., the yaw rate is too high). It 

momentarily applies the right front 

brake to turn the heading of the vehicle 

back to the correct path. It will also cut 

engine power to gently slow the vehicle 

and, if necessary, apply additional 

brakes (while maintaining the uneven 

brake force to create the necessary yaw 

moment). The action happens quickly 

so that the driver does not perceive the 

need for steering corrections. Even if the 

driver brakes because the curve is 

sharper than anticipated, the system is 

still capable of generating uneven 

braking if necessary to correct the 

heading. 

• Understeering. Figure 1 (top panel) 

shows a similar situation faced by a 

vehicle whose response as it nears the 

limits of road traction is to slide at the 

front (‘‘plowing out’’ or understeering) 

rather than oversteering. In this 

situation, the ESC system rapidly 

detects that the vehicle’s heading is 

changing less quickly than appropriate 

for the driver’s intended path (i.e., the 

yaw rate is too low). It momentarily 

applies the left rear brake to turn the 

heading of the vehicle back to the 

correct path. Again, it will also cut 

engine power to gently slow the vehicle 

and, if necessary, apply additional 

brakes (while maintaining the uneven 

brake force to create the necessary yaw 

moment). 

While Figure 1 may suggest that 

particular vehicles go out of control as 

either vehicles prone to oversteer or 

vehicles prone to understeer, it is just as 

likely that a given vehicle could require 

both understeer and oversteer 

interventions during progressive phases 


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17244 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

18Liebemann et al., (2005) Safety and 

Performance Enhancement: The Bosch Electronic 

Stability Control (ESP), 19th International 

Technical Conference on the Enhanced Safety of 

Vehicles (ESV), Washington, DC. 

19Aga M, Okada A. (2003) Analysis of Vehicle 

Stability Control (VSC)’s Effectiveness from 

Accident Data, 18th International Technical 

Conference on the Enhanced Safety of Vehicles 

(ESV), Nagoya. 

Dang, J. (2004) Preliminary Results Analyzing 

Effectiveness of Electronic Stability Control (ESC) 

Systems, Report No. DOT HS 809 790. U.S. Dept. 

of Transportation, Washington, DC. 

Farmer, C. (2004) Effect of Electronic Stability 

Control on Automobile Crash Risk, Traffic Injury 

Prevention Vol. 5:317–325. 

Kreiss J-P, et al. (2005) The Effectiveness of 

Primary Safety Features in Passenger Cars in 

Germany. 19th International Technical Conference 

on the Enhanced Safety of Vehicles (ESV), 

Washington, DC. 

Lie A., et al. (2005) The Effectiveness of ESC 

(Electronic Stability Control) in Reducing Real Life 

Crashes and Injuries. 19th International Technical 

Conference on the Enhanced Safety of Vehicles 

(ESV), Washington, DC. 

of a complex avoidance maneuver such 

as a double lane change. 

Although ESC cannot change the tire/ 

road friction conditions the driver is 

confronted with in a critical situation, 

there are clear reasons to expect it to 

reduce loss-of-control crashes, as 

discussed below. 

In vehicles without ESC, the response 

of the vehicle to steering inputs changes 

as the vehicle nears the limits of road 

traction. All of the experience of the 

average driver is in operating the 

vehicle in its ‘‘linear range’’, i.e., the 

range of lateral acceleration in which a 

given steering wheel movement 

produces a proportional change in the 

vehicle’s heading. The driver merely 

turns the wheel the expected amount to 

produce the desired heading. 

Adjustments in heading are easy to 

achieve because the vehicle’s response 

is proportional to the driver’s steering 

input, and there is very little lag time 

between input and response. The car is 

traveling in the direction it is pointed, 

and the driver feels in control. However, 

at lateral accelerations above about onehalf ‘‘g’’ on dry pavement for ordinary 

vehicles, the relationship between the 

driver’s steering input and the vehicle’s 

response changes (toward oversteer or 

understeer), and the lag time of the 

vehicle response can lengthen. When a 

driver encounters these changes during 

a panic situation, it adds to the 

likelihood that the driver will lose 

control and crash because the familiar 

actions learned by driving in the linear 

range would not be the correct steering 

actions. 

However, ordinary linear range 

driving skills are much more likely to be 

adequate for a driver of a vehicle with 

ESC to avoid loss of control in a panic 

situation. By monitoring yaw rate and 

sideslip, ESC can intervene early in the 

impending loss-of-control situation with 

the appropriate brake forces necessary 

to restore yaw stability before the driver 

would attempt an over correction or 

other error. The net effect of ESC is that 

the driver’s ordinary driving actions 

learned in linear range driving are the 

correct actions to control the vehicle in 

an emergency. Also, the vehicle will not 

change its heading from the desired 

path in a way that would induce further 

panic in a driver facing a critical 

situation. 

Besides allowing drivers to cope with 

emergency maneuvers and slippery 

pavement using only ‘‘linear range’’

skills, ESC provides more powerful 

control interventions than those 

available to even expert drivers of nonESC vehicles. For all practical purposes, 

the yaw control actions with non-ESC 

vehicles are limited to steering. 

However, as the tires approach the 

maximum lateral force sustainable 

under the available pavement friction, 

the yaw moment generated by a given 

increment of steering angle is much less 

than at the low lateral forces occurring 

in regular driving 18. This means that as 

the vehicle approaches its maximum 

cornering capability, the ability of the 

steering system to turn the vehicle is 

greatly diminished, even in the hands of 

an expert driver. ESC creates the yaw 

moment to turn the vehicle using 

braking at an individual wheel rather 

than the steering system. This 

intervention remains powerful even at 

limits of tire traction because both the 

braking force of the individual tire and 

the reduction of lateral force that 

accompanies the braking force act to 

create the desired yaw moment. 

Therefore, ESC can be especially 

beneficial on slippery surfaces. While a 

vehicle’s possibility of staying on the 

road in a critical maneuver ultimately is 

limited by the tire/pavement friction, 

ESC maximizes an ordinary driver’s 

ability to use the available friction. 

Overview of ESC Effectiveness in 

Preventing Single-Vehicle and Rollover 

Crashes 

Crash data studies conducted in the 

U.S., Europe, and Japan indicate that 

ESC is very effective in reducing singlevehicle crashes. Studies of the behavior 

of ordinary drivers in critical situations 

using the National Advanced Driving 

Simulator also show a very large 

reduction in instances of loss of control 

when the vehicle is equipped with ESC. 

Based on its crash data studies, NHTSA 

estimates that ESC will reduce single 

vehicle crashes of passenger cars by 34 

percent and single vehicle crashes of 

SUVs by 59 percent. NHTSA’s latest 

crash data study also shows that ESC is 

most effective in reducing single-vehicle 

crashes that result in rollover. ESC is 

estimated to prevent 71 percent of 

passenger car rollovers and 84 percent 

of SUV rollovers in single vehicle 

crashes. It is also estimated to reduce 

some multi-vehicle crashes but at a 

much lower rate than its effect on single 

vehicle crashes. The following 

discussion explains in detail the 

research finding upon which the agency 

has relied in determining the 

anticipated effectiveness of ESC 

systems. 

Electronic stability control can 

directly reduce a vehicle’s susceptibility 

to on-road untripped rollovers as 

measured by the ‘‘fishhook’’ test that is 

part of NHTSA’s NCAP rollover rating 

program. The direct effect is mostly 

limited to untripped rollovers on paved 

surfaces. However, untripped on-road 

rollovers are a relatively infrequent type 

of rollover crash. In contrast, the vast 

majority of rollover crashes occur when 

a vehicle runs off the road and strikes 

a tripping mechanism such as soft soil, 

a ditch, a curb or a guardrail. 

We expect that requiring ESC to be 

installed on light trucks and passenger 

cars would result in a large reduction in 

the number of rollover crashes by 

greatly reducing the number of singlevehicle crashes. As noted previously, 

over 80 percent of rollovers are the 

result of a single-vehicle crash. The 

purpose of ESC is to assist the driver in 

keeping the vehicle on the road during 

impending loss-of-control situations. In 

this way, it can prevent the exposure of 

vehicles to off-road tripping 

mechanisms. We note, however, that 

this yaw stability function of ESC is not 

direct ‘‘rollover resistance’’ and cannot 

be measured by the NCAP rollover 

resistance rating. 

Although ESC is an indirect 

countermeasure to prevent rollover 

crashes, we believe it is the most 

powerful countermeasure available to 

address this serious risk. Effectiveness 

studies by NHTSA and others 

worldwide 19 estimate that ESC reduces 

single vehicle crashes by at least a third 

in passenger cars and perhaps reduces 

loss-of-control crashes (e.g., road 

departures leading to rollovers) by an 

even greater amount. In fact, NHTSA’s 

latest data study that is discussed in this 

section found a reduction in singlevehicle crashes leading to rollover of 71 

percent for passenger cars and 84 

percent for SUVs. Thus, ESC can reduce 

the numbers of rollovers of all vehicles, 

including lower center of gravity 

vehicles (e.g., passenger cars, minivans 

and two-wheel drive pickup trucks), as 


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Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17245 

20Papelis et al. (2004) Study of ESC Assisted 

Driver Performance Using a Driving Simulator, 

Report No. N04–003–PR, University of Iowa. 

21See Footnote 10. 

22 Dang, J. (2004) Preliminary Results Analyzing 

Effectiveness of Electronic Stability Control (ESC) 

Systems, Report No. DOT HS 809 790. U.S. Dept. 

of Transportation, Washington, DC. 

23 Dang, J. (2006) Statistical Analysis of The 

Effectiveness of Electronic Stability Control (ESC) 

Systems, U.S. Dept. of Transportation, Washington, 

DC (publication pending peer review). A draft 

version of this report, as supplied to peer reviewers, 

has been placed in the docket for this rulemaking. 

well as of the higher center of gravity 

vehicle types (e.g., SUVs and four-wheel 

drive pickup trucks). ESC can affect 

both crashes that would have resulted in 

rollover as well as other types of crashes 

(e.g., road departures resulting in 

impacts) that result in deaths and 

injuries. 

Human Factors Study on the 

Effectiveness of ESC 

A study by the University of Iowa 

using the National Advanced Driving 

Simulator demonstrated the effect of 

ESC on the ability of ordinary drivers to 

maintain control in critical situations.20

A sample of 120 drivers equally divided 

between men and women and between 

three age groups (18–25, 30–40, and 55–

65) was subjected to the following three 

critical driving scenarios. The 

‘‘Incursion Scenario’’ forced drivers to 

attempt a double lane change at high 

speed (65 mph speed limit signs) by 

presenting them first with a vehicle that 

suddenly backs into their lane from a 

driveway and then with another vehicle 

driving toward them in the left lane. 

The ‘‘Curve Departure Scenario’’

presented drivers with a constant radius 

curve that was uneventful at the posted 

speed limit of 65 mph followed by 

another curve that appeared to be 

similar but that had a decreasing radius 

that was not evident upon entry. The 

‘‘Wind Gust Scenario’’ presented drivers 

with a sudden lateral wind gust of short 

duration that pushed the drivers toward 

a lane of oncoming traffic. The 120 

drivers were further divided evenly 

between two vehicles, an SUV and a 

midsize sedan. Half the drivers of each 

vehicle drove with ESC enabled, and 

half drove with ESC disabled. 

In 50 of the 179 test runs performed 

in a vehicle without ESC, the driver lost 

control. In contrast, in only six of the 

179 test runs performed in a vehicle 

with ESC, did the driver lose control. 

One test run in each ESC status had to 

be aborted. These results demonstrate 

an 88 percent reduction in loss-ofcontrol crashes when ESC was engaged. 

The study also concluded that the 

presence of an ESC system helped 

reduce loss of control regardless of age 

or gender, and that the benefit was 

substantially the same for the different 

driver subgroups in the study. Because 

of the obvious danger to participants, an 

experiment like this cannot be 

performed safely with real vehicles on 

real roads. However, the National 

Advanced Driver Simulator provides 

extraordinary verisimilitude with the 

driver sitting in a real vehicle, seeing a 

360-degree scene and experiencing the 

linear and angular accelerations and 

sounds that would occur in actual 

driving of the specific vehicle. 

Crash Data Studies of ESC Effectiveness 

There have been a number of studies 

of ESC effectiveness in Europe and 

Japan beginning in 2003.21 All of them 

have shown large potential reductions 

in single-vehicle crashes as a result of 

ESC. However, the sample sizes of 

crashes of vehicles new enough to have 

ESC tended to be small in these studies. 

A preliminary NHTSA study published 

in September 2004 22 of crash data from 

1997–2003 found ESC to be effective in 

reducing single-vehicle crashes, 

including rollover. Among vehicles in 

the study, the results suggested that ESC 

reduced single vehicle crashes in 

passenger cars by 35 percent and in 

SUVs by 67 percent. In October 2004, 

the Insurance Institute for Highway 

Safety (IIHS) released the results of a 

study of the effectiveness of ESC in 

preventing crashes of cars and SUVs. 

The IIHS found that ESC is most 

effective in reducing fatal single-vehicle 

crashes, reducing such crashes by 56 

percent. NHTSA’s later peer-reviewed 

study 23 of ESC effectiveness found that 

ESC reduced single vehicle crashes in 

passenger cars by 34 percent and in 

SUVs by 59 percent, and that its 

effectiveness was greatest in reducing 

single vehicle crashes resulting in 

rollover (71 percent reduction for 

passenger cars and an 84 percent 

reduction for SUVs). It also found 

reductions in fatal single-vehicle 

crashes and fatal single-vehicle rollover 

crashes that were commensurate with 

the overall crash reductions cited. ESC 

reduced fatal single-vehicle crashes in 

passenger cars by 35 percent and in 

SUVs by 67 percent and reduced fatal 

single-vehicle crashes involving rollover 

by 69 percent in passenger cars and 88 

percent in SUVs. 

(a) NHTSA’s preliminary study 

In September, 2004, NHTSA issued an 

evaluation note on the Preliminary 

Results Analyzing the Effectiveness of 

Electronic Stability Control (ESC) 

Systems. The study evaluated the 

effectiveness of ESC in reducing single 

vehicle crashes in various domestic and 

imported cars and SUVs. It was based 

on Fatality Analysis Reporting System 

(FARS) data from calendar years 1997–

2003 and crash data from five States that 

reported partial Vehicle Identification 

Number (VIN) information in their data 

files (Florida, Illinois, Maryland, 

Missouri, and Utah) from calendar years 

1997–2002. The data were limited to 

mostly luxury vehicles because ESC first 

became available in 1997 in luxury 

vehicles such as Mercedes-Benz and 

BMW. The analysis compared specific 

make/models of passenger cars and 

SUVs with ESC versus earlier versions 

of the same make/models, using multivehicle crash involvements as a control 

group. 

The passenger car sample consisted of 

mainly Mercedes-Benz and BMW 

models (61 percent). Mercedes-Benz 

installed ESC in certain luxury models 

in 1997 and had made it standard 

equipment in all their models (except 

one) by 2000. BMW also installed ESC 

in certain 5, 7, and 8 series models as 

early as 1997 and had made it standard 

equipment in all their models by 2001. 

The passenger car sample also included 

some luxury GM cars, which constituted 

23 percent of the sample, and a few cars 

from other manufacturers. GM cars 

where ESC was offered as standard 

equipment are the Buick Park Avenue 

Ultra, the Cadillac DeVille, Seville STS 

and SLS, the Oldsmobile Aurora, the 

Pontiac Bonneville SSE and SSEi, and 

the Chevrolet Corvette. The SUV make/ 

models in the study with ESC include 

Mercedes-Benz (ML320, ML350, ML430, 

ML500, G500, G55 AMG), Toyota 

(4Runner, Landcruiser), and Lexus 

(RX300, LX470). 

The first set of analyses used multivehicle crash involvements as a control 

group, essentially assuming that ESC 

has no effect on multi-vehicle crashes. 

Specific make/models with ESC were 

compared with earlier versions of 

similar make/models using multivehicle crash involvements as a control 

group, creating 2x2 contingency tables 

as shown in Tables 1 and 2. The study 

found that single vehicle crashes were 

reduced by 

1 ¥ {(699/1483)/(14090/19444)} = 35 

percent 

for passenger cars and by 67 percent for 

SUVs (Table 1). Similarly, fatal single 

vehicle crashes were reduced by 30 

percent in cars and by 63 percent in 

SUVs (Table 2). Reductions of single 

vehicle crashes in passenger cars and 

SUVs were statistically significant at the 

.01 level, as evidenced by chi-square 

statistics exceeding 6.64 in each 2x2 

contingency table (Table 1). Reductions 

of fatal single vehicle crashes are 


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17246 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

statistically significant at the .01 level in 

SUVs and at the .05 level in passenger 

cars with chi-square statistic greater 

than 3.84 (Table 2). 

TABLE 1.—EFFECTIVENESS OF ESC IN REDUCING SINGLE VEHICLE CRASHES IN PASSENGER CARS AND SUVS

[Preliminary study with 1997–2002 crash data from five States] 

Single vehicle 

crashes 

Multi-vehicle 

crashes 

(control group) 

Passenger Cars 

No ESC ........................................................................................................................................................... 1483 ................. 19444 

ESC ................................................................................................................................................................. 699 ................... 14090 

Percent reduction in single vehicle crashes in passenger cars with ESC ..................................................... 35% .................. ..............................

Approximate 95 percent confidence bounds .................................................................................................. 29% to 41% ...... ..............................

Chi-square value ............................................................................................................................................. 84.1 .................. ..............................

SUVs 

No ESC ........................................................................................................................................................... 512 ................... 6510 

ESC ................................................................................................................................................................. 95 ..................... 3661 

Percent reduction in single vehicle crashes in SUVs with ESC .................................................................... 67% .................. ..............................

Approximate 95 percent confidence bounds .................................................................................................. 60% to 74% ...... ..............................

Chi-square value ............................................................................................................................................. 104.4 ................ ..............................

TABLE 2.—EFFECTIVENESS OF ESC IN REDUCING FATAL SINGLE VEHICLE CRASHES IN PASSENGER CARS AND SUVS

[Preliminary study with 1997–2003 FARS data] 

Fatal single vehicle crashes 

Fatal multi-vehicle 

crashes 

(control group) 

Passenger Cars 

No ESC ........................................................................................................................................................... 186 ................... 330 

ESC ................................................................................................................................................................. 110 ................... 278 

Percent reduction in fatal single vehicle crashes in passenger cars with ESC ............................................. 30% .................. ..............................

Approximate 95 percent confidence bounds .................................................................................................. 10% to 50% ...... ..............................

Chi-square value ............................................................................................................................................. 6.0 .................... ..............................

SUVs 

No ESC ........................................................................................................................................................... 129 ................... 199 

ESC ................................................................................................................................................................. 25 ..................... 103 

Percent reduction in fatal single vehicle crashes in SUVs with ESC ............................................................ 63% .................. ..............................

Approximate 95 percent confidence bounds .................................................................................................. 44% to 81% ...... ..............................

Chi-square value ............................................................................................................................................. 16.1 .................. ..............................

NHTSA has now updated and 

modified last year’s report, extending it 

to model year 1997–2004 vehicles—and 

to calendar year 2004 for the FARS 

analysis and calendar year 2003 for the 

State data analysis. Nevertheless, even 

as of 2004, a large proportion of the 

vehicles equipped with ESC were still 

luxury vehicles. Moreover, only 

passenger cars and SUVs had been 

equipped with ESC—no pickup trucks 

or minivans. 

The State databases included crash 

cases from California (2001–2003), 

Florida (1997–2003), Illinois (1997–

2002), Kentucky (1997–2002), Missouri 

(1997–2003), Pennsylvania (1997–2001, 

2003), and Wisconsin (1997–2003). The 

FARS database included fatal crash 

involvements from calendar years 1997 

to 2004. The extra year of exposure and 

the availability of data from more states 

significantly increased the sample size 

of crashes of vehicles with ESC. In the 

preliminary study, the state crash 

database contained 699 single-vehicle 

crashes of cars with ESC and 95 singlevehicle crashes of SUVs with ESC. The 

FARS database contained 110 singlevehicle crashes of cars with ESC and 25 

single-vehicle crashes of SUVs with 

ESC. For the updated study, the state 

crash database contains 2,251 singlevehicle crashes of cars with ESC and 

553 single-vehicle crashes of SUVs with 

ESC, and the FARS database of fatal 

single-vehicle crashes contains 157 and 

47 crashes respectively, for passenger 

cars and SUVs with ESC. 

The larger sample of crashes in the 

updated study facilitated a new analysis 

of the effectiveness of ESC on specific 

subsets of single-vehicle crashes (SV 

run-off-road crashes and SV crashes 

resulting in rollover). It also facilitated 

the use of a more focused control group 

of crashes that were unlikely to be 

affected by ESC so that a new analysis 

of the effect of ESC on multi-vehicle 

crashes could be undertaken. 

The basic analytical approach was to 

estimate the reduction of crash 

involvements of the types that are most 

likely to have benefited from ESC—

relative to a control group of other types 

of crashes where ESC is unlikely to have 

made a difference in the vehicle’s 

involvement. Crash types taken as the 

new control group (non-relevant 

involvements because ESC would in 

almost all cases not have prevented the 

crash) were crash involvements in 

which a vehicle: 

(1) Was stopped, parked, backing up, 

or entering/leaving a parking space prior 

to the crash, 


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Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17247 

(2) Traveled at a speed less than 10 

mph, (3) Was struck in the rear by another 

vehicle, or 

(4) Was a non-culpable party in a 

multi-vehicle crash on a dry road. 

The types of crash involvements where 

ESC would likely or at least possibly 

have an effect are: 

(1) All single vehicle crashes, except 

those with pedestrians, bicycles, or 

animals (SV crashes). 

(2) Single vehicles crashes in which a 

vehicle ran off the road (SV ROR) and 

hit a fixed object and/or rolled over. 

(3) Single vehicles crashes in which a 

vehicle rolled over (SV Rollover), 

mostly a subset of SV ROR. 

(4) Involvements as a culpable party 

in a multi-vehicle crash on a dry or wet 

road (MV Culpable). 

(5) Collisions with pedestrians, 

bicycles, or animals (Ped, Bike, Animal). 

In the updated study we performed 

the state data analysis separately for 

each state. Then we used the median of 

the estimates from the seven states as 

the best indicator of the central 

tendency of the data, and the variation 

of the seven states as a basis for judging 

statistical significance and estimating 

confidence bounds. The results of this 

analysis are presented in Table 3. 

TABLE 3.—UPDATED STUDY—MEAN EFFECTIVENESS OF ESC IN REDUCING CRASHES IN PASSENGER CARS AND SUVS

BASED ON SEPARATE ANALYSES OF 1997–2003 CRASH DATA FROM SEVEN STATES

SV Crashes SV ROR SV Rollover MV Culpable Ped, bike, 

animal 

Passenger Cars 

Mean percent reduction of listed crash type in 

passenger cars with ESC.

34% .................. 46% .................. 71% .................. 11% .................. 34%. 

Approximate 90 percent confidence bounds ........ 20% to 46% ...... 35% to 55% ...... 60% to 78% ...... 4% to 18% ........ 5% to 55%. 

SUVs 

Mean percent reduction of listed crash type in 

SUVs with ESC.

59% .................. 75% .................. 84% .................. 16% .................. ¥4% not statistically significant. 

Approximate 90 percent confidence bounds ........ 47% to 68% ...... 68% to 80% ...... 75% to 90% ...... 7% to 24% ........ ¥28% to 15%. 

Fatal crashes were analyzed 

separately using the FARS database as 

was done in the preliminary study, but 

larger sample sizes were possible 

because of an additional year of data. 

The results are given in Table 4. 

TABLE 4.—UPDATED STUDY—EFFECTIVENESS OF ESC IN REDUCING FATAL CRASHES OF PASSENGER CARS AND SUVS

BASED ON 1997–2004 FARS DATA

SV Crashes SV ROR SV Rollover MV Culpable Ped, bike, 

animal Control group 

Passenger Cars 

No ESC .................................. 223 ................... 217 ................... 36 ..................... 176 ................... 46 ..................... 166 

ESC ........................................ 157 ................... 154 ................... 12 ..................... 156 ................... 69 ..................... 181 

Percent reduction of listed 

crash type in passenger 

cars with ESC.

35% .................. 36% .................. 69% .................. 19% not statistically significant.38% not statistically significant.

Approximate 90 percent confidence bounds.20% to 51% ...... 19% to 51% ...... 52% to 87% ...... ¥2% to 39% .... ¥87% to 12%.

Chi-square value .................... 8.58 .................. 8.17 .................. 12.45 ................ 1.82 .................. 2.14.

SUVs 

No ESC .................................. 197 ................... 191 ................... 106 ................... 108 ................... 56 ..................... 153 

ESC ........................................ 47 ..................... 38 ..................... 9 ....................... 48 ..................... 40 ..................... 109 

Percent reduction of listed 

crash type in SUVs with 

ESC.

67% .................. 72% .................. 88% .................. 38% .................. 0% not statistically significant.

Approximate 90 percent confidence bounds.55% to 78% ...... 62% to 82% ...... 81% to 95% ...... 16% to 60% ...... ¥40% to 40%.

Chi-square value .................... 29.57 ................ 36.44 ................ 42.4 .................. 4.89 .................. 0.00.

The effectiveness of ESC in reducing 

fatal single-vehicle crashes is similar to 

the effectiveness in reducing singlevehicle crashes from state data that 

included mostly non-fatal crashes. In 

the case of fatal crashes as well, the 

effectiveness of ESC in reducing singlevehicle rollover crashes was particularly 

high. The effectiveness of ESC in 

reducing fatal culpable multi-vehicle 

crashes of SUVs was also higher than in 

the analysis of state data, while the 

parallel analysis of multi-vehicle 

crashes of passenger cars did not 

achieve statistical significance. 

The updated study of ESC 

effectiveness yielded robust results. The 

analysis of state data and a separate 

analysis of fatal crashes both reached 

similar conclusions on ESC 

effectiveness. ESC reduced single 

vehicle crashes of passenger cars by 34 

percent and single vehicle crashes of 


ycherry on PROD1PC64 with RULES2
17248 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

24Without an equipment requirement, it would 

be almost impossible to devise a single performance 

test that could not be met through some action by 

the manufacturer other than providing an ESC 

system. Even a battery of performance tests still 

might not achieve our intended results, because 

although it might necessitate installation of an ESC 

system, we expect that it would be unduly 

cumbersome for both the agency and the regulated 

community. 

25A ‘‘closed-loop algorithm’’ is a cycle of 

operations followed by a computer that includes 

automatic adjustments based on the result of 

previous operations or other changing conditions. 

26 ‘‘Yaw rate’’ means the rate of change of the 

vehicle’s heading angle measured in degrees/second 

of rotation about a vertical axis through the 

vehicle’s center of gravity. 

27 ‘‘Sideslip’’ means the arctangent of the lateral 

velocity of the center of gravity of the vehicle 

divided by the longitudinal velocity of the center 

of gravity. 

SUVs by 59 percent. The separate 

analysis of only fatal crashes supported 

the analysis of state data that included 

mostly non-fatal crashes. Therefore, the 

overall crash reductions demonstrated a 

significant life-saving potential for this 

technology. The effectiveness of ESC in 

reducing SV crashes shown in the latest 

data (Tables 3–4) is similar to the results 

of the preliminary analysis. 

The effectiveness of ESC tended to be 

at least as great and possibly even 

greater for more severe crashes. 

Furthermore, the effectiveness of ESC in 

reducing the most severe type of crash 

in the study, the single-vehicle rollover 

crash, was remarkable. ESC reduced 

single-vehicle rollover crashes of 

passenger cars by 71 percent and of 

SUVs by 84 percent. This high level of 

effectiveness also carried over to fatal 

single-vehicle rollover crashes. 

The benefits presented in Section V 

were calculated on the basis of the 

single-vehicle crash and single-vehicle 

rollover crash effectiveness results of 

Table 3 for reductions in non-fatal 

crashes and of Table 4 for reductions in 

fatal crashes. The single-vehicle rollover 

crash effectiveness results were applied 

only to first harmful event rollovers 

with the lower single-vehicle crash 

effectiveness results applied to all other 

rollover crashes for a more conservative 

benefit estimate. 

III. September 2006 Notice of Proposed 

Rulemaking (NPRM) and Public 

Comments 

A. The NPRM 

As noted above, NHTSA published an 

NPRM on September 18, 2006 that 

proposed to establish FMVSS No. 126, 

Electronic Stability Control Systems (71 

FR 54712). Specifically, it proposed to 

require passenger cars, multipurpose 

passenger vehicles, trucks, and buses 

with a GVWR of 4,536 kg (10,000 

pounds) or less to be equipped with an 

ESC system that meets the requirements 

of the standard. As proposed, the 

vehicle would be required to meet a 

definitional requirement (i.e., specifying 

the necessary elements of a stability 

control system that would be capable of 

both effective oversteer and understeer 

intervention) and to pass a dynamic 

performance test. These requirements 

are necessary due to the extreme 

difficulty in establishing a test adequate 

to ensure the desired level of ESC 

functionality.24 The test is necessary to 

ensure that the ESC system is robust and 

meets a level of performance at least 

comparable to that of current ESC 

systems. 

The NPRM included the following 

points, which highlighted the key 

provisions of the proposed 

requirements. However, for a more 

complete discussion—including 

detailed information on the proposal, as 

well as various potential performance 

tests (for both lateral stability and 

vehicle responsiveness) and regulatory 

alternatives considered by the agency—

interested persons are encouraged to 

consult the NPRM. 

• Consistent with the industry 

consensus definition of ESC contained 

in the Society of Automotive Engineers 

(SAE) Surface Vehicle Information 

Report J2564 (rev. June 2004), we 

proposed to require vehicles covered 

under the standard to be equipped with 

an ESC system that: 

(1) Augments vehicle directional 

stability by applying and adjusting the 

vehicle’s brakes individually to induce 

correcting yaw torques to a vehicle; 

(2) Is computer-controlled, with the 

computer using a closed-loop 

algorithm 25 to limit vehicle oversteer 

and to limit vehicle understeer when 

appropriate; 

(3) Has a means to determine vehicle 

yaw rate 26 and to estimate its 

sideslip 27; 

(4) Has a means to monitor driver 

steering input, and 

(5) Is operational over the full speed 

range of the vehicle (except below a 

low-speed threshold where loss of 

control of the vehicle is unlikely). 

• The proposed ESC system, as 

defined above, would also be required 

to be capable of applying all four brakes 

individually and to have an algorithm 

that utilizes this capability. The system 

would also be required to be operational 

during all phases of driving, including 

acceleration, coasting, and deceleration 

(including braking), and it would be 

required to remain operational when the 

antilock brake system or traction control 

system is activated. 

• We also proposed to require 

vehicles covered under the standard to 

satisfy the standard’s stability criteria 

and responsiveness criterion when 

subjected to the Sine with Dwell 

steering maneuver test. This test 

involves a vehicle coasting at an initial 

speed of 50 mph while a steering 

machine steers the vehicle with a 

steering wheel pattern as shown in 

Figure 2 of the NPRM. The test 

maneuver is then repeated over a series 

of increasing maximum steering angles. 

This test maneuver was selected over a 

number of other alternatives, because 

we tentatively decided that it has the 

most optimal set of characteristics, 

including severity of the test, 

repeatability and reproducibility of 

results, and the ability to address lateral 

stability and responsiveness. 

The maneuver is severe enough to 

produce spinout for most vehicles 

without ESC. The stability criteria for 

the test measure how quickly the 

vehicle stops turning after the steering 

wheel is returned to the straight-ahead 

position. A vehicle that continues to 

turn for an extended period after the 

driver steers straight is out of control, 

which is what ESC is designed to 

prevent. The stability criteria are 

expressed in terms of the percent of the 

peak yaw rate after maximum steering 

that persists at a period of time after the 

steering wheel has been returned to 

straight ahead. The criteria require that 

the vehicle yaw rate decrease to no more 

than 35 percent of the peak value after 

one second and that it continues to drop 

to no more than 20 percent after 1.75 

seconds. Since a vehicle that simply 

responds very little to steering 

commands could meet the stability 

criteria, a minimum responsiveness 

criterion is applied to the same test. It 

requires that the ESC-equipped vehicle 

must move laterally at least 1.83 meters 

(half a 12 foot lane width) during the 

first 1.07 seconds after the initiation of 

steering (a discontinuity in the steering 

pattern that is convenient for timing a 

measurement). 

• Because the benefits of the ESC 

system can only be realized if the 

system is functioning properly, we 

proposed to require a telltale be 

mounted inside the occupant 

compartment in front of and in clear 

view of the driver and be identified by 

the symbol shown for ‘‘ESC Malfunction 

Telltale’’ in Table 1 of FMVSS No. 101, 

Controls and Displays. The ESC 

malfunction telltale would be required 

to illuminate not more than two minutes 

after the occurrence of one or more 

malfunctions that affect the generation 

or transmission of control or response 

signals in the vehicle’s ESC system. 


ycherry on PROD1PC64 with RULES2
Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17249 

28Although commonly referred to as the 1998 

Global Agreement, this provision is more formally 

titled the ‘‘1998 Agreement Concerning the 

Establishing of Global Technical Regulations for 

Wheeled Vehicles, Equipment and Parts which can 

be Fitted and/or be Used on Wheeled Vehicles.’’

29See http://www.unece.org/trans/doc/2007/ 

wp29/ECE-TRANS-WP29-2007-17e.doc. 

30Comments were received from the following 

automobile manufacturers and related trade 

associations: (1 and 2) Alliance of Automobile 

Manufacturers and Association of International 

Automobile Manufacturers (joint comments); (3) 

Honda Motor Co. Ltd. and American Honda Motor 

Co., Inc.; (4) Nissan North America, Inc.; (5) Porsche 

Cars North America, Inc.; (6) Toyota Motor North 

America, Inc., and (7) Verband der 

Automobilindustrie. 

31Comments were received from the following 

automobile equipment suppliers and their trade 

associations: (1) BorgWarner Torq Transfer Systems, 

Inc.; (2) Continental Automotive Systems; (3) 

Delphi Corporation; (4) Motor & Equipment 

Manufacturers Association; (5) Oxford Technical 

Solutions, Ltd.; (6) RLP Engineering; (7) Robert 

Bosch Corporation; (8) Specialty Equipment Market 

Association, and (9) TRW Automotive. 

32Comments were received from the following 

safety advocacy organizations: (1) Advocates for 

Highway and Auto Safety; (2) Consumers Union; (3) 

Insurance Institute for Highway Safety, and (4) 

Public Citizen. 

33Comments were received from the following 

other interested organizations: (1) National Mobility 

Equipment Dealers Association, and (2) SUVOA. 

Such telltale would be required to 

remain continuously illuminated for as 

long as the malfunction(s) exists, 

whenever the ignition locking system is 

in the ‘‘On’’ (‘‘Run’’) position. (Vehicle 

manufacturers would be permitted to 

use the ESC malfunction telltale in a 

flashing mode to indicate ESC 

operation.) 

• In certain circumstances, drivers 

may have legitimate reasons to 

disengage the ESC system or limit its 

ability to intervene, such as when the 

vehicle is stuck in sand/gravel or when 

the vehicle is being run on a track for 

maximum performance. Accordingly, 

under this proposal, vehicle 

manufacturers would be permitted to 

include a driver-selectable switch that 

places the ESC system in a mode in 

which it would not satisfy the 

performance requirements of the 

standard (e.g., ‘‘sport’’ mode or full-off 

mode). However, if the vehicle 

manufacturer chooses this option, it 

would be required to ensure that the 

ESC system always returns to a mode 

that satisfies the requirements of the 

standard at the initiation of each new 

ignition cycle, regardless of the mode 

the driver had previously selected. 

Furthermore, the manufacturer would 

be required to provide an ‘‘ESC Off’’

switch and a telltale that are mounted 

inside the occupant compartment in 

front of and in clear view of the driver 

and which are identified by the symbol 

or text shown for ‘‘ESC Off’’ in Table 1 

of FMVSS No. 101. Such telltale would 

be required to remain continuously 

illuminated for as long as the ESC is in 

a mode that renders it unable to meet 

the performance requirements of the 

standard, whenever the ignition locking 

system is in the On (‘‘Run’’) position. 

• We did not propose to require the 

ESC system to be equipped with a roll 

stability control function (or a separate 

system to that effect). Roll stability 

control systems involve relatively new 

technology, and we decided that there is 

currently insufficient data to judge the 

efficacy of such systems. However, the 

agency stated that it will continue to 

monitor the development of roll 

stability control systems. The NPRM 

also stated that vehicle manufacturers 

may supplement the ESC system we are 

proposing to require with a roll stability 

control system/feature. 

In order to provide the public with 

the expected significant safety benefits 

of ESC systems as rapidly as possible, 

the NPRM proposed to require all light 

vehicles covered by this standard to be 

equipped with a FMVSS No. 126- 

compliant ESC system by September 1, 

2011 (subject to the exception below). 

The agency proposed that compliance 

would commence on September 1, 2008, 

subject to the following phase-in 

schedule: 30 percent of a vehicle 

manufacturer’s light vehicles 

manufactured during the period from 

September 1, 2008 to August 31, 2009 

would be required to comply with the 

standard; 60 percent of those 

manufactured during the period from 

September 1, 2009 to August 31, 2010; 

90 percent of those manufactured 

during the period from September 1, 

2010 to August 31, 2011, and all light 

vehicles thereafter. 

The NPRM stated that in order to 

encourage early compliance, the agency 

proposed that vehicle manufacturers 

would be permitted to earn carryforward credits for compliant vehicles, 

produced in excess of the phase-in 

requirements, which are manufactured 

between the effective date of the final 

rule and the conclusion of the phase-in 

period. However, under the proposal, 

beginning September 1, 2011, all 

covered vehicles would be required to 

comply with the standard, without 

regard to any earlier carry-forward 

credits. 

We proposed to exclude multi-stage 

manufacturers and alterers from the 

requirements of the phase-in and to 

extend by one year the time for 

compliance by those manufacturers (i.e., 

until September 1, 2012). This NPRM 

also proposed to exclude small volume 

manufacturers (i.e., manufacturers 

producing less than 5,000 vehicles for 

sale in the U.S. market in one year) from 

the phase-in, instead requiring such 

manufacturers to fully comply with the 

standard on September 1, 2011. 

International Discussions of a Potential 

Global Technical Regulation on ESC 

Based upon the agency’s analysis of 

available research, we believe that the 

benefits of ESC are more broadly 

applicable than to just the U.S. driving 

environment. Instead, we believe that 

ESC has the potential to greatly benefit 

road users in all parts of the world. 

Therefore, throughout the development 

of its ESC proposal, NHTSA made 

particular efforts to keep other 

governments informed on the progress 

of its rulemaking. The agency 

accomplished this through several 

bilateral exchanges, as well as through 

its role in the United National World 

Forum for the Harmonization of Vehicle 

Regulations (WP.29) in Geneva, 

Switzerland. 

Specifically, the United States 

negotiated the placement of electronic 

stability control systems on the Program 

of Work of WP.29 under the 1998 Global 

Agreement,28 in order to formalize and 

facilitate information exchange on this 

topic. Since early 2005, agency officials 

have provided formal presentations on 

the ESC rulemaking to WP.29 and its 

specialized subsidiary body for stability 

control systems four times during 

formal session meetings. More recently, 

in November 2006, the NHTSA 

Administrator delivered remarks at the 

140th session of WP.29, in which she 

outlined the benefits of this new 

technology and encouraged the Forum 

to pursue the development of a Global 

Technical Regulation (GTR) for ESC. 

The proposal 29 was met with great 

interest and was accepted by several of 

the government representatives in 

attendance. The representatives were 

especially impressed that the benefits of 

ESC technology are well-corroborated 

through several studies conducted 

independently around the world. 

Formal work to develop a GTR on 

electronic stability control is expected 

to begin in 2007. 

B. Summary of the Public Comments on 

the NPRM 

NHTSA received comments on the 

September 18, 2006 NPRM from a 

variety of interested parties, including 

seven automobile manufacturers and 

their trade associations,30 nine suppliers 

of automobile equipment and their trade 

association,31 four safety advocacy 

organizations,32 and two other 

interested organizations.33 Comments 


ycherry on PROD1PC64 with RULES2
17250 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

34A ‘‘closed-loop algorithm’’ is a cycle of 

operations followed by a computer that includes 

automatic adjustments based on the result of 

previous operations or other changing conditions. 

35 ‘‘Yaw rate’’ means the rate of change of the 

vehicle’s heading angle measured in degrees/second 

of rotation about a vertical axis through the 

vehicle’s center of gravity. 

36 ‘‘Sideslip’’ means the arctangent of the lateral 

velocity of the center of gravity of the vehicle 

divided by the longitudinal velocity of the center 

of gravity. 

were also received from eight 

individuals. All of these comments may 

be found in Docket No. NHTSA–2006–

25801. 

Although certain of the comments 

from individuals objected to the ESC 

proposal (on the grounds of cost, 

newness of the technology, and 

concerns that it inappropriately may 

wrest vehicle control from the driver 

during critical situations), the 

overwhelming majority of the 

commenters supported establishing a 

safety standard for ESC systems as 

required equipment on new light 

vehicles. Instead, the difference of 

opinion among the commenters 

involved the stringency of the standard 

(including a requirement for advanced 

features), the test procedures (including 

need for understeer performance 

requirements), and the proposed lead 

time and phase-in for implementing the 

new standard. Other topics included 

making the ‘‘ESC System’’ definition 

more performance-based, lateral 

responsiveness criteria, ESC 

performance requirements, ESC 

malfunction detection requirements, 

ESC telltale requirements, system 

disablement and the ‘‘ESC Off’’ switch, 

test procedures, impacts on the 

aftermarket, comments on the 

preliminary regulatory impact analysis 

(PRIA), ESC outreach efforts, and other 

topics. The following discussion 

summarizes the main issues raised by 

these public comments and the 

positions expressed on these topics. A 

more complete discussion of the public 

comments is provided under Section 

IV.C, which provides an explanation of 

the agency rationale for the 

requirements of the final rule and 

addresses related public comments by 

issue. 

IV. The Final Rule and Response to 

Public Comments 

A. Summary of the Requirements 

After careful consideration of the 

public comments on the NPRM, this 

final rule establishes FMVSS No. 126, 

Electronic Stability Control Systems. 

Specifically, it requires passenger cars, 

multipurpose passenger vehicles, 

trucks, and buses with a gross vehicle 

weight rating of 4,536 Kg (10,000 

pounds) or less to be equipped with an 

ESC system that meets the requirements 

of the standard, in order to assist the 

driver in maintaining control in critical 

driving situations in which the vehicle 

is beginning to lose directional stability 

at the rear wheels (spin out) or 

directional control at the front wheels 

(plow out). Subject to the phase-in 

schedule and the exceptions below, 

compliance with the requirements of the 

final rule commences for covered 

vehicles manufactured on or after 

September 1, 2008 (i.e., MY 2009). 

The following points highlight the key 

provisions of the final rule. 

• Consistent with the industry 

consensus definition of ESC contained 

in the Society of Automotive Engineers 

(SAE) Surface Vehicle Information 

Report J2564 (rev. June 2004), we are 

requiring vehicles covered under the 

standard to be equipped with an ESC 

system that: 

(1) Augments vehicle directional 

stability by applying and adjusting the 

vehicle brake torques individually to 

induce a correcting yaw moment to a 

vehicle; 

(2) Is computer-controlled, with the 

computer using a closed-loop 

algorithm 34 to limit vehicle oversteer 

and to limit vehicle understeer; 

(3) Has a means to determine vehicle 

yaw rate 35 and to estimate its sideslip 36

or the time derivative of sideslip; 

(4) Has a means to monitor driver 

steering input; 

(5) Has an algorithm to determine the 

need, and a means to modify engine 

torque, as necessary, to assist the driver 

in maintaining control of the vehicle, 

and 

(6) Is operational over the full speed 

range of the vehicle (except at vehicle 

speeds less than 15 km/h (9.3 mph) or 

when being driven in reverse). 

• The ESC system as defined above is 

also required to be capable of applying 

brake torques individually at all four 

wheels and to have an algorithm that 

utilizes this capability. Except for the 

situations specifically set forth in part 

(6) of the definition of ‘‘ESC System’’

above, the system is also required to be 

operational during all phases of driving, 

including acceleration, coasting, and 

deceleration (including braking), and it 

is required to be capable of activation 

even if the anti-lock brake system or 

traction control system is also activated. 

• In order to ensure that a vehicle is 

equipped with an ESC system that 

meets the definition of ‘‘ESC System’’

under S4, the final rule requires vehicle 

manufacturers to submit, upon the 

request of NHTSA s Office of Vehicle 

Safety Compliance, ESC system 

technical documentation as to when 

understeer intervention is appropriate 

for a given vehicle (see S5.6). 

Specifically, NHTSA may seek 

information such as a system diagram 

that identifies all ESC components, a 

written explanation describing the ESC 

system’s basic operational 

characteristics, a logic diagram 

supporting the explanation of system 

operations, and a discussion of the 

pertinent inputs to the vehicle computer 

or calculations within the computer and 

how its algorithm uses that information 

and controls ESC system hardware to 

limit vehicle understeer. 

• We are also requiring vehicles 

covered under the standard to meet 

performance tests. It must satisfy the 

standard s stability criteria and 

responsiveness criterion when subjected 

to the Sine with Dwell steering 

maneuver test. This test involves a 

vehicle coasting at an initial speed of 50 

mph while a steering machine steers the 

vehicle with a steering wheel pattern as 

shown in Figure 2 of the regulatory text. 

The test maneuver is then repeated over 

a series of increasing maximum steering 

angles. This test maneuver was selected 

over a number of other alternatives, 

because we decided that it has the most 

optimal set of characteristics, including 

severity of the test, repeatability and 

reproducibility of results, and the ability 

to address lateral stability and 

responsiveness. 

The maneuver is severe enough to 

produce spinout for most vehicles 

without ESC. The stability criteria for 

the test measure is how quickly the 

vehicle stops turning after the steering 

wheel is returned to the straight-ahead 

position. A vehicle that continues to 

turn for an extended period after the 

driver steers straight is out of control, 

which is what ESC is designed to 

prevent. The quantitative stability 

criteria are expressed in terms of the 

percent of the peak yaw rate after 

maximum steering that persists at a 

period of time after the steering wheel 

has been returned to straight ahead. The 

criteria require that the vehicle yaw rate 

decrease to no more than 35 percent of 

the peak value after one second and that 

it continues to drop to no more than 20 

percent after 1.75 seconds. Since a 

vehicle that simply responds very little 

to steering commands could meet the 

stability criteria, a minimum 

responsiveness criterion is applied to 

the same test. It requires that an ESCequipped vehicle with a GVWR of 7,716 

pounds or less must move laterally at 

least 6 feet during the first 1.07 seconds 

after the initiation of steering (a 

discontinuity in the steering pattern that 

is a convenient point for timing a 


ycherry on PROD1PC64 with RULES2
Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17251 

37 In April 2006, NHTSA sent letters to seven 

vehicle manufacturers requesting voluntary 

submission of information regarding their planned 

production of ESC-equipped vehicles for model 

years 2007 to 2012. Six manufacturers responded 

with product plans containing confidential 

information. These agency letters and manufacturer 

responses (with confidential information redacted) 

may be found in Docket No. NHTSA–2006–25801. 

38We note that manufacturers’ product plans 

have continued to evolve during the course of this 

rulemaking. For example, in a September 13, 2006 

press release, Ford Motor Company announced that 

100 percent of its light vehicle fleet would have 

ESC as standard equipment by MY 2010 (see 

http://www.consumeraffairs.com/news04/2006/09/ 

ford_stability.html). The agency has carefully 

considered such developments in setting the phasein schedule for this final rule. 

measurement). It also requires that a 

heavier vehicle with a GVWR up to 

10,000 pounds must move at least 5 feet 

laterally in the same maneuver for 

specified steering angles. 

• Because the benefits of the ESC 

system can only be realized if the 

system is functioning properly, we are 

requiring a telltale be mounted inside 

the occupant compartment in front of 

and in clear view of the driver and be 

identified by the symbol or text shown 

for ‘‘ESC Malfunction Telltale’’ in Table 

1 of FMVSS No. 101, Controls and 

Displays. The ESC malfunction telltale 

is required to illuminate after the 

occurrence of one or more malfunctions 

that affect the generation or 

transmission of control or response 

signals in the vehicle’s ESC system. 

Such telltale must remain continuously 

illuminated for as long as the 

malfunction(s) exists, whenever the 

ignition locking system is in the ‘‘On’’

(‘‘Run’’) position. (Vehicle 

manufacturers are permitted to use the 

ESC malfunction telltale in a flashing 

mode to indicate ESC operation.) 

• In certain circumstances, drivers 

may have legitimate reasons to 

disengage the ESC system or limit its 

ability to intervene, such as when the 

vehicle is stuck in sand/gravel, using 

snow chains, or when the vehicle is 

being run on a track for maximum 

performance. Accordingly, under this 

final rule, vehicle manufacturers may 

include a driver-selectable control that 

places the ESC system in a mode in 

which it would not satisfy the 

performance requirements of the 

standard (e.g., ‘‘sport’’ mode or full-off 

mode). However, if the vehicle 

manufacturer chooses this option, it 

must ensure that the ESC system always 

returns to the fully-functional default 

mode at the initiation of each new 

ignition cycle, regardless of the mode 

the driver had previously selected (with 

certain exceptions for low speed offroad axle/transfer case selections that 

turn off ESC but cannot be reset 

electronically). The manufacturer is 

required to provide an ‘‘ESC Off’’

control and a telltale that are mounted 

inside the occupant compartment in 

front of and in clear view of the driver 

and which are identified by the symbol 

or text shown for ‘‘ESC Off’’ in Table 1 

of FMVSS No. 101 or the text ‘‘ESC 

Off.’’ Such telltale must remain 

continuously illuminated for as long as 

the ESC is in a mode that renders it 

unable to meet the performance 

requirements of the standard, whenever 

the ignition locking system is in the 

‘‘On’’ (‘‘Run’’) position. 

B. Lead Time and Phase-in 

In order to provide the public as 

rapidly as possible with what are 

expected to be the significant safety 

benefits of ESC systems, NHTSA has 

decided to require all light vehicles 

covered by this standard to be equipped 

with a FMVSS No. 126-compliant ESC 

system by September 1, 2011 (with 

certain exceptions discussed below). 

This implementation date for full, 

mandatory compliance is the same as 

that proposed in the NPRM and is 

consistent with our stated intention to 

have 90 percent of the subject fleet 

equipped with ESC in the 2011 model 

year that starts September 1, 2010. The 

agency continues to believe that this 

schedule for full implementation of the 

safety standard for ESC is appropriate, 

in order to provide manufacturers 

adequate lead time to make necessary 

production changes. September 1, 2008 

marks the start of a three-year phase-in 

period for FMVSS No. 126. 

However, in response to public 

comments and upon further review of 

the production plans 37 voluntarily 

submitted by vehicle manufacturers, we 

have determined that it would be 

practicable to increase the percentage of 

new light vehicles that must comply 

with Standard No. 126 under the phasein, thereby accelerating the benefits 

expected to be provided by ESC 

systems. Because ESC is so costeffective and has such high benefits in 

terms of potential fatalities and injuries 

that may be prevented, the agency 

agrees that it is important to require ESC 

installation in light vehicles as quickly 

as possible. Accordingly, under this 

final rule, we are requiring the following 

phase-in schedule for FMVSS No. 126: 

55 percent of a vehicle manufacturer’s 

light vehicles manufactured during the 

period from September 1, 2008 to 

August 31, 2009 would be required to 

comply with the standard; 75 percent of 

those manufactured during the period 

from September 1, 2009 to August 31, 

2010; 95 percent of those manufactured 

during the period from September 1, 

2010 to August 31, 2011, and all light 

vehicles thereafter. (This compares to 

the NPRM’s proposal for a 30/60/90/all 

phase-in schedule over the same time 

periods.) 

In order to ensure the financial and 

technological practicability of the final 

rule (in keeping with our statutory 

mandate), while at the same time 

facilitating ESC installation in the light 

vehicle fleet as expeditiously as 

possible, the agency analyzed the 

product plans submitted by six vehicle 

manufacturers, whose combined 

production accounts for approximately 

87 percent of the new light vehicle 

fleet.38 As explained in Chapter VII of 

the FRIA, we examined three different 

potential phase-in schedules to find the 

right balance among these competing 

concerns. Based upon this product plan 

information and the desire to provide 

manufacturers with flexibility by having 

a carry forward provision, we have 

chosen the most aggressive phase-in 

alternative that we believe is reasonable 

(i.e., 55/75/95%). 

Two factors were controlling in 

making the decision as to which 

alternative to choose: (1) The ability of 

manufacturers to change vehicles from 

being equipped with optional ESC to 

standard ESC for MY 2010 and MY 

2011; and (2) Not forcing any 

manufacturer to install ESC in any 

make/model for which it was not 

planned to be at least an option. The 

agency did not believe there was enough 

lead time to redesign a make/model to 

include ESC by MY 2009. While there 

may be enough time to redesign such a 

make/model to include ESC by MY 

2010, given the carry forward provisions 

this was not necessary for any of the six 

manufacturers for MY 2010. The second 

consideration became a factor once 

again in MY 2011, in not going beyond 

95 percent (thereby obviating the costly 

need to redesign and develop tooling for 

a few vehicle lines which will not be 

produced in MY 2012). 

In general, we anticipate that vehicle 

manufacturers will be able to meet the 

requirements of the standard by 

installing ESC system designs currently 

in production (i.e., ones available in MY 

2006). Except for possibly some lowproduction-volume vehicles with 

infrequent design changes (addressed 

below), NHTSA believes that most other 

vehicles can reasonably be equipped 

with ESC within three to four model 

years. We have determined that the 

majority of vehicle manufacturers 

would be able to meet the first two years 

of the revised phase-in schedule, 

without revising their current 


ycherry on PROD1PC64 with RULES2
17252 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

39We note that the agency has considered the 

possibility that external forces (e.g., increases in 

gasoline prices, changing consumer preferences) 

might affect demand for specific types of vehicles, 

such as SUVs, which have higher ESC penetration. 

Such concerns provided further reason for the 

agency to adopt a phase-in schedule that included 

a provision for carry-forward credits. 

production plans for ESC-equipped 

vehicles, given available phase-in 

credits under the rule. For the other 

manufacturers, they will have to 

increase production of ESC-equipped 

vehicles to comply with this accelerated 

phase-in schedule, but the available 

lead time is sufficient to allow for 

orderly planning for this increase and to 

achieve full implementation. 

Furthermore, we do not believe that the 

final rule’s phase-in should pose ESC 

supply problems; public comments from 

vehicle manufacturers and ESC 

suppliers did not raise any such supply 

concerns, and our analysis of vehicle 

manufacturers’ production plans suggest 

that the selected phase-in schedule will 

result in an installation rate increase of 

only a few percentage points in any year 

of the phase-in. Overall, we have 

determined that the final rule’s phase-in 

schedule may be accomplished without 

disruptive changes in manufacturer and 

supplier production processes.39

After outlining the general parameters 

of the phase-in for FMVSS No. 126, we 

now turn to a number of exceptions or 

exclusions from the phase-in intended 

to address certain classes of vehicle 

manufacturers that may require 

additional time to achieve compliance 

and to address certain ESC components 

that may pose problems for a broader 

range of manufacturers in the short 

term. As an initial matter, we now 

understand from the public comments 

that vehicle manufacturers currently 

employ a variety of approaches for ESC 

controls and telltales, many of which 

would not meet the requirements of the 

agency’s proposal. As a complicating 

matter, vehicle manufacturers and their 

trade associations explained that even 

though most current ESC systems would 

largely meet the performance 

requirements of the proposed standard, 

manufacturers’ inability to meet the 

proposed control and display 

requirements would prevent them from 

earning the carry-forward credits 

needed to comply with the NPRM’s 

aggressive phase-in schedule. Vehicle 

manufacturers generally commented 

that they could bring their ESC systems 

into full compliance (including the 

control and telltale requirements) by the 

end of the phase-in, and they argued 

that it is the performance of the ESC 

systems themselves, not the messages 

provided by the controls and telltales, 

that impart safety benefits under the 

standard. 

After consideration of the numerous 

manufacturer comments on this issue, 

we have decided to defer the standard’s 

requirements related to the ESC telltales 

and controls until the end of the phasein (i.e., September 1, 2011 for most 

manufacturers; September 1, 2012 for 

final-stage manufacturers and alterers); 

however, at that point, all covered 

vehicles must meet all relevant 

requirements of the standard (i.e., no 

additional phase-in for the control and 

telltale requirements). Manufacturers 

are encouraged to voluntarily install 

compliant ESC controls and displays 

prior to the mandatory compliance date. 

Our rationale for this change from our 

proposal is as follows. 

We now understand that 

standardizing ESC controls and telltales 

will involve substantial design and 

production changes and that additional 

lead time will be required to effect those 

changes. In addition, our analysis 

demonstrates that the safety benefits 

associated with early introduction of 

ESC systems, even without standardized 

controls and displays, far outweigh the 

benefits of delaying the standard until 

all systems can fully meet the control 

and display requirements (see FRIA’s 

lead time/phase-in discussion). We do 

not believe that implementation of the 

entire standard should be delayed until 

technical changes related to the ESC 

controls and telltales can be fully 

resolved, because they would deny the 

public the safety benefits of ESC 

systems in the meantime. Accordingly, 

we believe that it is preferable to move 

rapidly to implement the standard, but 

to delay the compliance date only for 

the ESC control and telltale 

requirements. 

This final rule also excludes small 

volume manufacturers (i.e., 

manufacturers producing less than 

5,000 vehicles for sale in the U.S. 

market in one year) from the phase-in, 

instead requiring such manufacturers to 

fully comply with the standard on 

September 1, 2011. This exclusion 

should facilitate implementation for 

low-production-volume vehicles with 

infrequent design changes. 

Consistent with the policy set forth in 

NHTSA’s February 14, 2005 final rule 

on certification requirements for 

vehicles built in two or more stages and 

altered vehicles (70 FR 7414), final-stage 

manufacturers and alterers are excluded 

from the requirements of the phase-in 

and are permitted an additional one 

year for compliance (i.e., until 

September 1, 2012). However, finalstage manufacturers and alterers may 

voluntarily certify compliance with the 

standard prior to this date. 

Vehicle manufacturers may earn 

carry-forward credits for compliant 

vehicles, produced in excess of the 

phase-in requirements, which are 

manufactured between the effective date 

of the final rule and the conclusion of 

the phase-in period. (We note that carryforward credits may not be used to defer 

the mandatory compliance date of 

September 1, 2011 for all covered 

vehicles.) The final rule also includes 

phase-in reporting requirements for ESC 

systems (contained in Subpart I of 49 

CFR Part 585) which are consistent with 

the phase-in schedule discussed above. 

C. Response to Public Comments by 

Issue 

As noted previously, public 

comments on the September 2006 

NRPM for ESC raised a variety of issues 

with the NPRM’s proposed 

requirements. Each of these topics will 

be discussed in turn, in order to explain 

how these comments impacted the 

agency’s determinations in terms of 

setting requirements for this final rule. 

Major Issues 

1. Approach of the ESC NPRM 

Subject to the phase-in schedule set 

forth in S8, the NPRM for ESC proposed 

to require new vehicles covered by 

Standard No. 126 to be equipped with 

an ESC system that meets the 

requirements specified in S5 under the 

test conditions specified in S6 and the 

test procedures specified in S7 of this 

standard (see S5, Requirements). The 

proposed standard would apply to 

passenger cars, multipurpose passenger 

vehicles, trucks, and buses with a gross 

vehicle weight rating of 4,536 kilograms 

(10,000 pounds) or less (see S3.1, 

Application). 

NHTSA also noted that the ESC 

proposal would implement the 

provision in section 10301 of 

SAFETEA–LU, which requires the 

Secretary of Transportation to ‘‘establish 

performance criteria to reduce the 

occurrence of rollovers consistent with 

stability enhancing technologies’’ and to 

issue a final rule by April 1, 2009. 

A number of commenters on the 

NPRM raised issues regarding the 

general approach taken by the agency in 

terms of its proposal for ESC. These 

comments are discussed immediately 

below. 

(a) ESC Mandate vs. ESC 

Standardization 

Mr. Kiefer urged NHTSA to adopt 

specifications for standardization of ESC 

systems that manufacturers voluntarily 

choose to install, rather than mandating 


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Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17253 

40 70 FR 49223 (August 23, 2005). 

installation at this time. The commenter 

stated that this approach would provide 

a trial period during which the ESC 

requirements could be evaluated, prior 

to fleet-wide installation. 

We believe Mr. Kiefer’s suggested 

approach falls short in light of the 

advanced state of development of ESC 

systems. Moreover, our analysis of the 

real-world experience with ESC to date 

indicates that a rulemaking mandate for 

it will save thousands of lives each year 

on American roadways. Our analyses 

also indicate that a mandate for ESC 

will be among the most cost-effective of 

NHTSA’s rules ever. Moreover, the 

agency is not aware of any significant 

operational problems for ESC systems 

now in millions of vehicles on the 

American roads, nor have ESC suppliers 

or vehicle manufacturers indicated that 

there are such problems. Under these 

circumstances, there is no reason to 

delay proceeding to a mandate for this 

life-saving technology to be on all light 

vehicles. 

(b) ESC as Part of a Comprehensive 

Rollover Safety Program 

The comments of Advocates for 

Highway and Auto Safety (Advocates) 

included a lengthy discussion of what it 

perceives to be the agency’s failure to 

carry out a comprehensive rollover 

crash safety plan. Public Citizen 

similarly argued that the ESC 

rulemaking should be part of a 

comprehensive rollover plan, and in 

particular, it objected to the proposal’s 

failure to include a requirement for roll 

stability control (cited as currently in 

production on the Volvo XC–90). 

According to Public Citizen, a 

requirement for roll stability control 

would lead SUVs to be equipped with 

roll sensors, which it argued would in 

turn enhance safety features critical for 

ejection mitigation such as seatbelt 

pretensioners, advanced window 

glazing, and side impact airbags. 

As we have stated in the past and in 

the NPRM for this rule, the agency 

adopted such a comprehensive plan in 

June 2003, which envisions agency 

efforts (several of which are currently 

underway) to improve vehicle stability, 

ejection mitigation, roof crush 

resistance, as well as road 

improvements and behavioral strategies 

aimed at consumer education. The 

relevant legislative provisions contained 

in SAFETEA–LU are fully consistent 

with the agency’s ongoing efforts to 

prevent rollover crashes and to reduce 

their severity when they do occur. 

Our analysis demonstrates that ESC 

systems can have a major positive 

impact in terms of preventing loss of 

control and keeping the vehicle on the 

roadway, thereby preventing rollovers. 

Regarding our decision not to propose a 

requirement for roll stability control, the 

agency made this determination because 

there is little data available to assess 

whether that feature actually provides 

any additional safety benefits, given that 

it appears that some current systems 

add this feature to ESC. Note that we 

believe that current systems that include 

roll stability control will satisfy the 

requirements for ESC. Under 49 U.S.C. 

30111, a safety standard must be 

practicable, meet the need for motor 

vehicle safety, and be stated in objective 

terms; in setting the standard, relevant, 

available motor vehicle safety 

information must be considered. In this 

case, the dearth of information about 

roll stability control effectively 

precludes the agency from adopting a 

roll stability requirement, because it is 

not possible to determine whether this 

technology meets the need for safety. At 

the same time, this rule does not 

establish any barriers to automakers’

adding roll stability control to ESC 

systems, nor to customers’ demanding 

it. The issue of roll stability control and 

other ESC features is discussed in 

further detail in Section IV.C.3 of this 

document. 

Impact on Other NHTSA Rulemakings 

Advocates argued that the ESC NPRM 

and accompanying PRIA should take 

into account that rulemaking’s impact 

on the agency’s proposal 40 to upgrade 

FMVSS No. 216, Roof Crush Resistance. 

The commenter stated that the ESC 

benefits assessment is incomplete 

because it does not discuss how some 

unknown portion of fatalities due to 

roof crush will not occur as a result of 

ESC intervention to keep the vehicle on 

the road (i.e., by preventing the rollover 

crash entirely), and it makes essentially 

the same point regarding the roof crush 

NPRM. 

The agency agrees that the ESC rule 

would impact the agency’s rulemaking 

to amend FMVSS No. 216, Roof Crush 

Resistance. The benefits estimated in 

the PRIA for FMVSS No. 216, which 

accompanied the NPRM published on 

August 23, 2005 (70 FR 49223), reflect 

the impacts of ESC penetration into the 

fleet at that time. As a general matter, 

the impact of ESC on FMVSS No. 216 

should be addressed in the regulatory 

analyses for FMVSS No. 216 rather than 

in the ESC rule. Generally, the agency’s 

approach for estimating the actual 

benefits of any rulemaking is to adjust 

the benefits of a later rule to take into 

account the impacts of earlier rules. 

Therefore, for the ESC rulemaking, the 

PRIA and this FRIA estimated the 

overall benefits of the ESC rule and only 

address the impacts of prior 

rulemakings on this current rule. The 

impact of ESC on other future 

rulemakings would be addressed in 

those future rules respectively. The 

benefits of future rules, including the 

roof crush rulemaking, will reflect the 

installation of ESC in the vehicle fleet. 

(c) Need for Common Terminology 

According to Consumers Union, 

vehicle manufacturers currently utilize 

a variety of acronyms and proprietary 

trade names to identify their ESC 

systems, which in turn make it more 

difficult for consumers to know what to 

ask for when shopping for a vehicle. To 

limit consumer confusion, Consumers 

Union urged NHTSA to require uniform 

terminology for how ESC systems are 

identified, so as to facilitate vehicle-tovehicle comparisons. The organization 

recommended use of the nomenclature 

‘‘ESC’’ and the term ‘‘Electronic 

Stability Control,’’ which presumably 

already have broad consumer 

recognition. A similar comment was 

provided by Mr. Petkun. These 

commenters also argued that the agency 

should require the automobile industry 

and dealerships to provide training for 

sales staff so that they may better 

educate and more accurately advise 

potential buyers about the value of an 

ESC system. 

The agency appreciates the 

importance of providing consumers 

with clear information regarding vehicle 

safety features to use when deciding 

which vehicle to purchase, because we 

believe that such information serves a 

safety need (consistent with the 

agency’s motor vehicle information 

mandate under 49 U.S.C. Chapter 323, 

Consumer Information). However, we 

do not believe it is necessary to pursue 

the use of common terminology for ESC, 

for the following reasons. The primary 

concern engendering calls for common 

terminology involved a consumer’s 

ability to know whether a given vehicle 

is equipped with ESC or some other 

similar-sounding device (e.g., a 

manufacturer’s name for traction 

control), but that concern has essentially 

been eliminated by this final rule, 

which mandates installation of a 

compliant ESC system on all light 

vehicles by the end of the phase-in 

period. Absent that concern, there is no 

need for NHTSA to dictate how 

companies market their products. 

2. The Definition of ‘‘ESC System’’ as 

the Basis of the Standard 

As noted above, the NPRM proposed 

to require installation of an ESC system 


ycherry on PROD1PC64 with RULES2
17254 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

41 ‘‘Linear-handling’’ describes the conditions 

that average drivers usually face. Drivers are 

accustomed to a range of lateral acceleration in 

which a given steering wheel movement produces 

a proportional change in the vehicle’s heading, so 

that one knows with some degree of certainty where 

the vehicle will go when the wheel is turned a 

certain amount. 

‘‘Nonlinear-handling’’ is at the edge of, and 

beyond, the range of lateral acceleration to which 

drivers are normally accustomed (i.e., above about 

one-half ‘‘g’’ on dry pavement for ordinary 

vehicles). In such situations, the relationship 

between the driver’s steering input and the 

vehicle’s response changes, and the lag time of the 

vehicle’s response can lengthen. 

42Specifically, the commenter suggested 

modifying paragraphs S4 and S5.1.1 of the 

proposed standard to read as follows: 

S4 Definitions (1) ‘‘* * * augments vehicle 

directional stability by applying and adjusting the 

wheel forces to induce correcting yaw torques to a 

vehicle;’’

S5.1.1 ‘‘Is capable of dynamically adjusting all 

four wheel forces and has a control algorithm that 

utilizes this capability.’’

43 In order to accommodate such technology, the 

Alliance/AIAM recommended modifying S4 

(definition of ‘‘ESC system’’) and S5.1.1 of the 

proposal to read as follows: 

S4, Electronic Stability Control System or ESC 

System * * * 

(1) That augments vehicle directional stability by 

applying and adjusting vehicle brake torques 

individually to induce a correcting yaw moment to 

a vehicle. 

S5.1.1 Is capable of applying brake torques 

individually to all four wheels and has a control 

algorithm that utilizes this capability. 

that meets the definition contained in 

paragraph S4 of the standard, as well as 

the requirements of S5.1, Required 

Equipment. The proposed definition of 

‘‘ESC System’’ specified certain features 

that must be present on that equipment, 

including that it be capable of applying 

all four brakes individually and have a 

computer using a closed-loop algorithm 

to limit vehicle oversteer and to limit 

vehicle understeer when appropriate. In 

addition, the system must have a means 

to determine the vehicle’s yaw rate and 

to estimate its side slip, as well as a 

means to monitor driver steering inputs. 

Furthermore, the ESC system must be 

operational during all phases of driving 

including acceleration, coasting, and 

deceleration (including braking), except 

when the driver has disabled ESC or the 

vehicle is below a low speed threshold 

where loss of control is unlikely, and it 

must remain operational when the 

antilock brake system or traction control 

system is activated. The ESC system 

must also meet the proposed 

performance requirements for lateral 

stability and vehicle responsiveness (see 

S5.2). 

BorgWarner Torq Transfer Systems, 

Inc. (BorgWarner) stated that the 

proposed standard should not mandate 

a specific solution in terms of how an 

ESC system would operate (i.e., 

requiring a brake-base system), but 

instead it should adopt a performance 

standard that would encourage 

development of new and potentially 

improved technologies, ones which may 

provide more benefits and/or be more 

cost-effective than brake-based ESC 

systems. The commenter stated that it is 

ultimately the forces at the road/tire 

interface that are adjusted by the ESC, 

regardless of how that is accomplished. 

Accordingly, BorgWarner stated its 

opposition to the definition of ‘‘ESC 

System’’ as the basis of the standard 

because ‘‘* * * other systems such as 

effective design of suspension and 

steering geometry, active steering, active 

suspension, AWD active yaw control, 

torque vectoring yaw control, [and] 

electronically controlled axle 

differentials may increase the vehicle’s 

stability threshold such that loss of 

control is not imminent within the 

scope of the proposed testing 

procedure.’’

Delphi Corporation (Delphi) stated 

that there are currently various 

alternative technologies in various 

stages of development that may 

substitute for brake-based ESC systems. 

According to the commenter, these 

include active steering systems (Active 

Front Steer, Active Rear Steer, Steer by 

Wire, Electric Power Steering), active 

drivetrains (Active Differentials, 

Electronic Limited Slip Differentials, 

Electric Motor/Generator Devices for 

Propulsion/Braking), and active 

suspensions (Active Stabilizer Bars, 

Active Dampers, Active Springs). Delphi 

added that while brake-based ESC 

systems are usually restricted to limithandling conditions, other technologies 

(such as those mentioned above) can 

operate across a range of linear-handling 

to limit-handling (i.e., nonlinearhandling) conditions.41 The commenter 

stated that alternative technologies such 

as Active Front Steer and Active Rear 

Steer may actually prevent the vehicle’s 

tires from reaching total saturation in 

the first place, thereby avoiding 

unstable and unresponsive situations. 

Delphi also stated that systems using 

a combination of steering and braking 

actuation are more responsive and are 

not necessarily more objectionable to 

drivers because they are more predictive 

in their operation. Accordingly, Delphi 

recommended modifying the ESC 

definition in the regulatory text to 

permit any actuator device that can 

influence the tire/road forces to achieve 

improvements in vehicle stability and 

responsiveness.42

RLP Engineering expressed concern 

that the NPRM’s ‘‘equipment 

requirements’’ (i.e., definition of an 

‘‘ESC system’’) is based upon current 

component technology and 

methodology, which could become 

outdated. Instead of specifying 

components, the commenter 

recommended that the agency state 

certain objectives and required 

outcomes, namely requiring means and 

methods of detecting impending vehicle 

instability and subsequent means and 

methods for actively engaging 

appropriate countermeasures. RLP 

Engineering argued that such an 

approach would allow for advancement 

in the state of the art and elimination of 

obsolete vehicle componentry (with the 

potential for cost reduction). 

According to the Alliance of 

Automobile Manufacturers (Alliance) 

and the Association of International 

Automobile Manufacturers (AIAM), for 

some electric or hybrid vehicles, the 

industry expects that the appropriate 

ESC braking torques could be provided 

directly through the vehicle’s 

propulsion system (regenerative 

braking) without the need to apply the 

friction brake, as done by current ESC 

systems. The commenters stated that 

such systems would potentially provide 

enhanced safety benefits in terms of 

more rapid and precise applied braking 

intervention, as well as longer service 

life for the vehicle’s friction brakes.43

After careful consideration of the 

comments, we have decided to retain 

the approach set forth in the NPRM 

(with certain modifications), which 

would make the requirements 

associated with the definition of ‘‘ESC 

System’’ the primary basis of the 

standard. Our reasoning for this 

decision is as follows. 

The agency’s intention in the context 

of this ESC rulemaking has been to 

spread the proven safety benefits of 

current ESC systems across the light 

vehicle fleet. Available information 

shows that current brake-based ESC 

systems are effective and meet the need 

for motor vehicle safety. The agency is 

not aware of and commenters have not 

provided any information to 

demonstrate the efficacy of the ESCrelated technologies specified in their 

comments as an alternative to brakebased ESC systems. 

Furthermore, it is possible for a 

vehicle without ESC to be optimized to 

avoid spin-out in the narrowly defined 

conditions of the ESC oversteer 

intervention test (especially if the 

standard is silent on understeer) but to 

lack the advantages of ESC under other 

conditions. The agency has determined 

that it is not currently feasible to 

develop a comprehensive battery of tests 

that could substitute for the knowledge 

of what equipment constitutes ESC, and 

it remains to be seen if such approach 


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Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17255 

44The U.S. Environmental Protection Agency 

(EPA) experienced problems with heavy duty diesel 

manufacturers’ production of engines that met EPA 

standards during laboratory testing under EPA 

procedures but were turned off under highway 

driving conditions. On October 22, 1998, the 

Department of Justice and EPA announced a 

settlement with seven major diesel engine 

manufacturers. Accordingly, we do not believe that 

the industry’s ability to circumvent the 

requirements of the standard is a theoretical one, as 

would permit us to forgo a definition for ‘‘ESC 

System.’’

45 ‘‘Driving torque’’ is a force applied by the 

engine through the drive train in order to make a 

particular wheel turn faster than the others—similar 

to ‘‘braking torques’’ which brakes one wheel to 

make it turn slower than the others. Either force can 

be utilized by an ESC system to change the heading 

of the vehicle, although braking torque has the 

added benefit of helping slow the vehicle down. 

46Liebemann et al., Safety and Performance 

Enhancement: The Bosch Electronic Stability 

Control (ESP), 2005 ESC Conference. 

would ever be practical to set a purely 

performance-based standard that would 

ensure that manufacturers provide at 

least current ESC systems. Therefore, we 

have concluded that the standard’s 

definition of ‘‘ESC System’’ is necessary 

in order to ensure that light vehicles 

have the attributes of ESC systems that 

produced the large reduction of singlevehicle crashes and rollovers in our 

crash data study (as discussed in detail 

in Section II.D). We note that a similar 

approach of defining heavy truck ABS, 

rather than depending solely on 

performance requirements, has been 

successful under FMVSS No. 121, Air 

Brake Systems. The following 

discussion explains the identified 

obstacles to a strictly performance-based 

approach. 

Among the challenges associated with 

developing a performance test for ESC, 

the agency notes that manufacturers 

develop ESC algorithms using tests 

whose conditions are generally not 

repeatable (e.g., icy surfaces which 

change by the minute, wet/slippery 

surfaces which are not repeatable dayto-day) and through simulation. 

Manufacturers also use hundreds of 

conditions requiring weeks of testing for 

a given vehicle. However, it is not 

practicable to use these approaches as 

part of a safety standard. Furthermore, 

the agency cannot use subjective tests to 

determine compliance with a safety 

standard. 

It is possible to overcome these 

limitations by adopting the standard’s 

definition of ‘‘ESC System,’’ which is 

based on a Society of Automotive 

Engineers definition of what ESC is, and 

which includes those elements that 

account for the cost of those systems. 

There is no reason to believe that 

manufacturers will incur all the costs of 

the ESC equipment and capabilities 

required by the standard’s definition 

and then just program the system to 

achieve limited operation restricted to 

the test conditions of the standard. The 

standard’s definitional requirement for 

‘‘ESC System’’ requires, at a minimum, 

the equipment and capabilities of 

existing ESC system designs. This 

translates into the substantial fatality 

and injury benefits provided by existing 

ESC systems. 

Without the definition of ‘‘ESC 

System,’’ it would not be feasible to 

comprehensively assess the operating 

range of resulting devices, particularly 

for understeer intervention, that might 

be installed in compliance with the 

safety standards. If manufacturers were 

to only optimize the vehicle so as to 

pass only a few highly-defined tests, 

there public would not receive the full 

safety benefits provided by current ESC 

systems.44

Under this topic, we also note the 

comment from the Alliance/AIAM about 

test variability (in the responsiveness 

portion of the oversteer intervention 

test). Even under test conditions chosen 

for high repeatability, these commenters 

maintain that the performance 

requirements must be decreased to 

allow a larger margin of compliance. 

Such margins of compliance would 

make a very weak standard if based 

solely on tests that would be 

considerably less repeatable than those 

we are using. 

The Delphi comment also lists a 

number of systems and components that 

can influence wheel forces and suggests 

that it should be permissible for the 

definition of ESC to be satisfied by 

systems that can generate wheel force 

(i.e., a requirement more open than 

compelling a system that must operate 

through brake forces). However, the 

commenter did not provide any data to 

show the effectiveness of such systems, 

as would demonstrate that they meet the 

need for motor vehicle safety and that 

it would be appropriate to substitute 

them for proven brake-based ESC 

systems. We believe there are good 

reasons for the safety standard at least 

initially to be based on braking forces 

(noting that we have changed the 

definition to include all ‘‘braking’’

torques at the wheels (i.e., regenerative 

braking by an electric motor as well as 

the action of friction brakes)). While 

some of the devices mentioned by 

BorgWarner and Delphi could create 

yaw moments (for ESC interventions) by 

driving torques,45 yaw moments created 

by braking torques have an advantage in 

critical situations because they also 

cause the vehicle to slow down. 

These commenters also mention a 

number of steering-related concepts as 

an alternative means of meeting the 

standard’s requirements. Specifically, 

Delphi stated that active steering 

interventions (in a vehicle that 

combines steering and braking in its 

ESC) could operate at driving conditions 

well below critical levels of tire 

saturation (where steering interventions 

lose their power) and produce a more 

responsive vehicle. While active 

steering may be useful in certain 

situations, the steering interventions 

may not be very helpful at or near the 

limit of traction, which is arguably the 

critical situation at the heart of this 

rulemaking. Again, braking forces have 

an advantage over steering forces 

because they can create a more powerful 

yaw intervention when the vehicle is at 

the limit of traction.46

We understand that manufacturers of 

a small number of luxury cars are 

beginning to add active steering to ESC, 

as described by Delphi, which are very 

refined vehicle systems that are 

carefully designed so as to not annoy 

their drivers. We clarify that the 

standard in no way prohibits the 

addition of refinements to vehicles that 

retain the ability to create yaw moments 

with brake torques when necessary. The 

vehicles in question retain the brakebased ESC as the backstop for stability, 

because the brake interventions which 

are more noticeable to drivers retain 

their power in situations where the 

transparent steering interventions might 

not be powerful enough. Without data to 

assess the effectiveness of these 

potential alternative operating features 

for ESC (which commenters did not 

provide), we have decided that it would 

not be appropriate at this time to 

abandon the requirement for brake 

torque-based systems which have 

proven benefits, in favor of concepts 

that have not yet demonstrated any 

safety benefits, much less the enormous 

benefits associated with current brake 

torque-based ESC systems. 

We acknowledge that in requiring 

ESC as it now exists and has proven to 

be beneficial, we may be indirectly 

impacting hypothetical future 

technological innovations. We have to 

balance the benefits of saving thousands 

of lives a year by requiring ESC systems 

with the capabilities of current ESC 

systems, against the loss of savings in 

the future provided by some even more 

advanced ESC technologies. In this case, 

we believe that the opportunity to save 

this many lives must be selected. 

Should new advances lead to forms of 

ESC different than those currently 

required by this standard, interested 

parties can petition the agency to 

modify the regulation. We also note that 


ycherry on PROD1PC64 with RULES2
17256 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

47We note that many of the ESC-related features 

cited by the commenters may serve similar or 

complementary functions, which may vary to some 

extent from vehicle to vehicle. However, to the 

extent possible, we have tried to generally explain 

our understanding of these technologies either in 

footnotes or the textual discussion of this 

document. 

48 ‘‘Yaw stability’’ means an electronic stability 

control system of the type required by new FMVSS 

No. 126 and explained in section II.D of this 

preamble. 

49 ‘‘ABS’’ means anti-lock braking system, a 

system that controls rotational wheel slip in braking 

by sensing individual wheel speeds and adjusting 

brake actuating forces in response to those signals. 

ABS provides many of the components necessary 

for ESC. 

50 ‘‘Body roll control’’ is a utilization of electronic 

damping control to stiffen the body roll resistance 

in a curve to provide a more level ride. 

51 ‘‘Corner brake control’’ (CBC) is designed to 

improve vehicle stability during a braking event by 

adjusting the brake line pressure applied to the 

individual wheels. It is a refinement of ABS with 

some similarity to ESC, except that CBC 

intervention requires the driver to apply force to the 

brake pedal, whereas ESC interventions occur 

regardless of whether the driver has applied the 

brakes. 

52 ‘‘Electronic damping control’’ is an electronic 

system of shock absorbers having electricallycontrollable damping rates (stiffness) and a control 

module to operate them as a system. 

the vehicle manufacturers who are the 

directly regulated parties have not 

opposed using the definition for ‘‘ESC 

System’’ as the primary requirement of 

the standard, and some have actively 

supported it. We interpret this to mean 

that the vehicle manufacturers are not 

aware of any feasible alternative 

approach for providing efficacious 

electronic stability control in the near 

future, other than the approach 

described in the definition. 

3. Stringency of the Standard 

The NPRM proposed in S4 to require 

installation of an ESC system that: (1) Is 

capable of applying all four brakes 

individually and has a control algorithm 

that utilizes this capability; (2) is 

operational during all phases of driving 

including acceleration, coasting, and 

deceleration (including braking), except 

when the driver has disabled ESC or the 

vehicle is below a low speed threshold 

where loss of control is unlikely, and (3) 

remains operational when the antilock 

brake system or traction control system 

is activated (see S5.1). The ESC system 

also would have to meet the proposed 

performance requirements for lateral 

stability and vehicle responsiveness (see 

S5.2). 

Advocates expressed strong support 

for a mandate that ESC be provided on 

all light vehicles, but it urged the agency 

to adopt a more stringent standard in 

the final rule. Specifically, Advocates 

argued that the proposed requirements 

for ESC intervention to increase lateral 

stability and to restore proper 

directional heading are sub-optimal. 

The commenter also objected to what it 

characterized as the ‘‘minimal standard’’

that would be set by the proposal, one 

which effectively accommodates the 

lowest level of all existing ESC system 

designs and performance, rather than 

pushing for state-of-the-art technology. 

According to the commenter, the 

proposal would grandfather in all 

existing ESC designs, even though not 

all ESC systems have the same level of 

capabilities. 

Advocates also requested that the rule 

require certain operating functions 

present on many current ESC systems 

(e.g., automatic speed reduction 

achieved by automatic braking and 

engine de-powering/engine control, 

traction control, automatic steering, roll 

stability control), even though the 

agency based its benefits assessment in 

the PRIA by ‘‘piggybacking’’ onto these 

more robust ESC systems. The 

commenter stated that these additional 

features, which the agency suggests 

have some positive safety value, make 

some unknown (i.e., unquantified) 

contribution to the anticipated 

reduction in deaths, injuries, and crash 

severity associated with the ESC 

rulemaking. Advocates added that the 

PRIA’s estimated benefits may be 

inflated because, given the more 

truncated requirements of the proposed 

standard, there is no assurance that 

manufacturers will continue to install 

more complex ESC systems, a result that 

would detract from ESC as an advanced 

safety technology. 

In addition, Advocates urged that the 

agency continue its efforts to reconcile 

ESC intervention with effective roll 

stability control systems, characterizing 

the latter as the only means to directly 

intervene to prevent imminent rollover 

(as compared to ESC’s indirect 

contributions through oversteer and 

understeer intervention). Although the 

commenter seemed to acknowledge that 

incorporation of roll stability control 

requirements may not be possible 

immediately, it stated that the agency 

should eventually include performance 

specifications for this function as part of 

FMVSS No. 126. 

Consumers Union expressed general 

support for the ESC rulemaking, stating 

that stability control systems should be 

standard equipment on all vehicles, 

especially sport utility vehicles (SUVs). 

It further stated that, since 1998, it has 

conducted tests on 179 vehicles 

equipped with ESC systems, but it has 

found considerable variability in the 

level of performance across the systems 

provided. The commenter stated that 

better ESC systems act decisively but 

not prematurely, whereas other systems 

can be slow to react, help only in certain 

situations, and intervene too frequently 

during normal driving. Accordingly, 

Consumers Union recommended that 

NHTSA’s standard should be modeled 

after the ESC systems found to be ‘‘best 

performers,’’ which it characterized as 

ones that are intrusive and very evident 

in ‘‘at the limit’’ testing (i.e., at the point 

at which loss of vehicle control may be 

imminent), but less so during routine 

driving. 

In addition, Consumers Union stated 

that ESC calibration should be adjusted 

to match the type of vehicle for which 

the system has been developed so that 

it complements vehicle and driver 

characteristics (e.g., a more intrusive 

system for a minivan than for a sports 

sedan). 

Specifically, Consumers Union stated 

that the NPRM’s proposed steering 

response 1.07 seconds after the 

initiation of steering (minimum of 6 feet 

from the center line) is not aggressive 

enough, and accordingly, the 

commenter reasoned that it could allow 

manufacturers to fit low grip tires and 

slow steering to improve performance 

under the standard’s test procedures. 

Consumers Union expressed concern 

that manufacturers may seek to reduce 

costs by developing cheaper, less 

sophisticated ESC systems which may 

pass all the requirements of the 

standard, but which may be relatively 

less effective in terms of saving lives. 

Public Citizen commented that the 

agency’s ESC proposal is incomplete 

because it does not deal with the full set 

of technologies which make up many 

current ESC systems, instead proposing 

a more limited yaw stability standard. 

(Public Citizen also argued that the 

agency assessed benefits in the PRIA on 

these more advanced ESC systems). For 

example, Public Citizen noted that the 

Alliance of Automobile Manufacturers 

made a presentation to NHTSA in 

which it described a number of current 

features 47 on ESC systems, including 

yaw stability,48 traction control, ABS,49

brake assist, active steering, body roll 

control,50 vehicle roll stability control, 

corner brake control,51 and electronic 

damping control.52 Public Citizen 

specifically asked why the agency 

considered traction control to be only a 

‘‘convenience feature.’’

According to Public Citizen, the ESC 

equipment requirements are already 

out-of-date and will be obsolete by the 

time a final rule is published. The 

commenter argued that the proposal 

would mislead consumers into thinking 

that they are purchasing a true ESC 

system using the latest technology. 

Public Citizen stated that because the 

agency’s proposal would accept the 


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least extensive of current ESC 

technologies, it would merely ratify the 

status quo and not ‘‘reduce’’ rollover 

deaths as Congress required under 

SAFETEA–LU. The organization stated 

that the agency cannot rely upon an 

unenforceable expectation that vehicle 

manufacturers will continue to provide 

advanced ESC systems, and it expressed 

concern that some vehicle 

manufacturers might actually strip out 

certain ESC-related features on low-cost 

vehicles, thereby actually degrading 

vehicle safety. In contrast, Public 

Citizen argued that the agency should 

exert a ‘‘technology forcing’’ influence 

with respect to vehicle safety 

improvements. Thus, Public Citizen 

argued that the ESC proposal would not 

go far enough to improve vehicle safety. 

Public Citizen stated that the two 

studies of the effectiveness of ESC 

system prepared by NHTSA, which 

used Fatality Analysis Reporting System 

(FARS) data for 1997–2004 and State 

registration data for 1997–2003, 

surveyed a time period during which 

ESC technology was a relatively new 

technology. As a result, Public Citizen 

argued that those studies were 

confounded by small sample sizes and 

that the results, therefore, make it nearly 

impossible to support statistically 

significant claims regarding specific 

ESC configurations or to separate out 

the components which the agency 

decided not to include in its proposal. 

Again, Public Citizen commented that 

the PRIA for the ESC NPRM counts the 

benefits of more extensive ESC 

technologies, without counting the full 

costs for those systems. It argued that 

more properly, the agency should have 

measured the benefit of a yaw control 

system, which is more in line with the 

requirements of the agency’s proposal. 

In response to these comments 

requesting that the agency require 

additional features found on some ESC 

systems, we have decided to incorporate 

a requirement for ESC engine control 

but not to require other system 

components at this time. Although 

discussed in detail immediately below, 

the following summarizes our rationale 

for this decision. 

As a preliminary matter, we find no 

merit in Public Citizen’s arguments that 

the NPRM’s proposed ESC requirements 

fail to satisfy the requirements of the 

statutory mandate under SAFETEA–LU. 

As discussed previously, the statute 

provided the agency with discretion to 

adopt performance criteria for 

technologies consistent with stability 

enhancing technologies. Our research 

identified ESC systems as the most 

effective of these technologies, and our 

proposal was based upon the definition 

for ‘‘ESC System’’ promulgated by the 

Society of Automotive Engineers, a 

group which is broadly representative of 

industry experts. Furthermore, the 

Verband der Automobilindustrie (VDA), 

an association of German vehicle 

manufacturers, acknowledged that 

NHTSA’s definition corresponds to 

modern ‘‘state-of-the-art’’ ESC systems. 

The proposal also established 

performance criteria in the form of tests 

for lateral stability and vehicle 

responsiveness (see Section IV.C.4 and 

the Appendix for a discussion of the 

agency’s efforts to develop a 

performance test for understeer). 

Accordingly, this final rule meets the 

requirements of SAFETEA–LU. 

As discussed above, under 49 U.S.C. 

30111, a safety standard must be 

practicable, meet the need for motor 

vehicle safety, and be stated in objective 

terms; in setting the standard, relevant, 

available motor vehicle safety 

information must be considered. With 

the exception of engine control, all of 

the other ESC-related components lack 

supporting data to assess their 

effectiveness and to determine whether 

such technologies meet the need for 

safety. The commonality of design for 

ESC systems that were represented in 

the agency’s crash data study focused on 

individual brake application and engine 

control, and we note that in its 

comments, VDA stated that the agency’s 

proposed definition for ‘‘ESC system’’

captures the state-of-the-art. Again, even 

though certain later ESC designs 

incorporate some additional features, it 

was not possible to determine the safety 

benefits, if any, of these features because 

these features were not available on any 

of the ESC-equipped vehicles in the 

crash data study. Also, some of those 

features are directed at comfort and 

convenience rather than safety (as 

explained below). We do not believe 

that there is good reason to postpone the 

proven life-saving benefits of basic ESC 

systems until such time as the agency 

can conduct the necessary research to 

assess the panoply of related 

components. Accordingly, we believe 

that it is not necessary to specify 

additional components as part of the 

standard’s definition for ‘‘ESC system,’’

but instead, we leave it to the discretion 

of vehicle manufacturers to tailor the 

features of their individual ESC systems 

to the needs of a given vehicle. We note 

that the rule does not limit 

manufacturers’ ability to develop, 

install, and advertise stability control 

systems that go beyond its requirements. 

At the time of the agency’s analysis, 

the U.S. crash data available to NHTSA 

to evaluate the benefit of ESC did not 

include vehicles newer than 2003. 

However, the ESC systems of the 

vehicles that were part of the agency’s 

analysis proved extraordinarily 

effective, reducing single-vehicle 

crashes from 34 to 59 percent and 

reducing rollover in single-vehicle 

crashes (the crash type leading to over 

80 percent of rollovers) from 71 to 84 

percent. The results were statistically 

significant and in agreement with 

studies by other parties worldwide as 

cited in the NPRM. The rule requires 

ESC systems at least as capable as those 

that produced this extremely high level 

of demonstrated, real-world benefits at a 

reasonable cost to the public. It does not 

simply ‘‘grandfather’’ all existing ESC 

systems, and the performance criteria 

were developed using contemporary 

new vehicles produced in 2005 and 

2006. The basis of the standard is a 

definition of ESC that specifically 

excludes existing two-wheel ESC 

systems because they are not capable of 

understeer invention or four-wheel 

automatic braking during an 

intervention, even though these systems 

also produced substantial (but lesser) 

benefits. 

Engine Control 

‘‘Engine control’’ means the ability of 

an ESC system to determine the need, 

and a means to modify engine torque, as 

necessary, to assist the driver in 

maintaining control of the vehicle. 

The commenters argued that the 

benefit assessment included the 

contributions of ESC engine control. We 

have considered this comment and 

agree that ESC engine control was a 

feature on most vehicles in the crash 

data analysis and on all the vehicles in 

the ESC cost study. Because ESC engine 

control is likely to have influenced the 

estimated benefits reported in the PRIA, 

we are amending the ‘‘ESC System’’

definition in the standard to include a 

requirement for engine control based on 

the definition contained in SAE Surface 

Vehicle Information Report J2564: 

The system must have an algorithm to 

determine the need, and a means to modify 

engine torque, as necessary, to assist the 

driver in maintaining control of the vehicle. 

Other Features 

The commenters also claimed that the 

benefit assessment included the 

contributions of such features as 

automatic braking, traction control, 

active steering, brake assist, and roll 

stability control and that the standard 

would not achieve the expected benefits 

with the required ESC systems. 

However, we have determined that it is 

not necessary to make additional 

modifications related to the other 

features cited by commenters. We have 


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also decided that the commenters’

recommendations regarding the test 

criteria are likewise unnecessary. We 

address each of these topics in turn 

below. 

Automatic Braking 

‘‘Automatic braking’’ involves the 

application of other brakes in addition 

to the brake required to generate the 

necessary yaw torque (as described in 

the explanation of ESC operation in 

Section II.D), along with a heavier 

application at the initial brake location 

to maintain the yaw torque. 

A requirement for automatic braking 

would be redundant, because that 

feature is simply the application of 

other brakes in addition to the brake 

already required to generate the 

necessary yaw torque. All of the 

hardware required for this operation is 

already included in the definition of 

‘‘ESC System.’’ Automatic braking is 

just one of the strategies invoked by the 

basic operating software of ESC, but the 

circumstances when it is called for and 

the severity of the braking are 

determined when ESC is tuned for a 

specific vehicle. Making ESC a 

requirement will not reduce the use of 

automatic braking. If anything, use of 

ESC on a much greater number of 

vehicles will lead to more sophisticated 

basic software being delivered to vehicle 

manufacturers by suppliers. 

Traction Control 

‘‘Traction control’’ reduces engine 

power and applies braking to a spinning 

drive wheel in order to transfer torque 

to the other drive wheel on the axle. 

The commenters are mistaken in 

attributing ESC benefits to traction 

control. Traction control provides 

mobility in starting on slippery surfaces, 

but it offers no improvement in lateral 

stability beyond that already provided 

by ESC with engine control. ESC already 

reduces engine power when lateral 

instability is detected, and there is no 

further assistance that traction control 

could add. 

Active Steering 

‘‘Active steering’’ is a computercontrolled function that allows steering 

of the front axle (and possibly the rear) 

independent of driver input to maintain 

stability. As mentioned in Section IV.C2 

above, active steering interventions are 

not as powerful as ESC brake 

interventions in limit situations. (Our 

observations lead us to believe that 

active steering is being used to delay the 

onset of ESC interventions as a driver 

satisfaction feature.) 

Active steering did not affect our 

estimation of benefits because none of 

the vehicles in our data study were 

equipped with that feature. Also, only 

one of the new vehicles in our research 

to develop an oversteer test had this 

recently introduced feature. This 

vehicle was also the only new vehicle 

in our research that failed the oversteer 

test criteria. Ironically, this vehicle was 

equipped with more cutting edge 

technology than the rest of the new test 

vehicles. 

Brake Assist 

‘‘Brake assist’’ causes a maximum 

brake application if the driver presses 

the brake pedal very quickly in a 

manner indicative of panic braking, 

even if the driver is hesitant to brake 

hard. 

Similarly, the benefits we have 

attributed to ESC based upon our 

research have nothing to do with brake 

assist. It is a feature that predates ESC 

on the European vehicles in our test 

group that had it. Brake assist is not part 

of the ESC system; it does not affect yaw 

stability, and it was present on both the 

non-ESC control vehicles and the ESCequipped vehicles in our study. NHTSA 

is examining the merits of brake assist 

separately from its ESC research. 

Roll Stability Control 

‘‘Roll stability control’’ senses the 

vehicle’s body roll angle and applies 

high brake force to the outside front 

wheel to straighten the vehicle’s path 

and reduce lateral acceleration if the roll 

angle indicates probable tip-up. 

Roll stability control was not 

responsible for the huge reduction in 

rollovers in single-vehicle crashes of 71 

percent for cars and 84 percent for 

SUVs. None of the vehicles in the crash 

data study had roll stability control. The 

crash data study was a study of the 

benefits of yaw stability control. The 

first vehicle with roll stability control 

was the 2003 Volvo XC90 (cited by 

Public Citizen) which was not in our 

data study because it was a new vehicle 

without a non-ESC version that could 

serve as a control vehicle. It is also a 

low-production-volume vehicle that 

would have produced very few crash 

counts in the 1997–2003 crash data of 

our study. A similar roll stability control 

system was used on high-volume Ford 

Explorers starting in 2005, and 

eventually there will be enough 

Explorer data to evaluate the 

effectiveness of roll stability control. 

The agency will track the rollover rate 

of vehicles equipped with roll stability 

control through analysis of Stategenerated crash data and evaluate its 

effectiveness once a sufficient sample 

size becomes available (i.e., 

approximately three to four years). 

However, because our data study 

showed yaw stability control reducing 

rollovers of SUVs by 84% by reducing 

and mitigating road departures, and 

because on-road untripped rollovers are 

much less common events, the target 

population of crashes that roll stability 

control could possibly prevent may be 

very small. If and when roll stability 

control can be shown to be costeffective, then it could be a candidate 

for inclusion in the standard in 

subsequent rulemaking. 

In addition, the countermeasure of 

roll stability control systems is at least 

theoretically not benign. It reduces 

lateral acceleration by turning the 

vehicle away from the direction the 

driver is steering for at least a short 

distance. As noted previously, several 

individual commenters expressed strong 

dissatisfaction that we were proposing a 

mandatory safety device in which the 

driver yields at least some measure of 

vehicle control to a computer. This was 

an inaccurate criticism of the pure yaw 

stability control system we proposed, 

because such system would help the 

vehicle go in the direction the driver is 

steering. ESC engine control does 

require the system to override the 

driver’s throttle control which was a 

specific complaint of some commenters. 

However, requiring systems that 

actually countermand the driver’s 

steering control requires a high level of 

justification, a hurdle which roll 

stability control cannot yet surmount 

due to the newness of the technology 

and the corresponding lack of available 

data. 

Test Criteria 

In terms of future manufacturer 

actions, we note that Consumers Union 

criticized the test criteria as too weak to 

ensure that manufacturers will not 

create cheaper, less sophisticated 

systems that rely on poor tire traction or 

a reduced steering ratio to meet the 

performance test. To preclude such 

actions, we established criteria for 

vehicle responsiveness as well as lateral 

stability (see discussion under Section 

IV.C.5). 

Also, we do not agree with Consumers 

Union’s assertions that the standard’s 

test criteria are weak. The commenters 

offered no recommendations in terms of 

how test severity could be improved. As 

carefully explained in the NPRM, the 

agency knows of no test more suited for 

quantifying an ESC system’s ability to 

mitigate excessive oversteer while 

simultaneously facilitating the 

assessment of lateral displacement 

capability. Every vehicle we have 

evaluated using the lateral stability 

performance criteria has demonstrated 


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53Although Appendix 1 provides a technical 

definition of ‘‘understeer,’’ in lay terms it is 

probably best described as the normal condition of 

Continued 

profound differences between tests 

performed with fully enabled and fully 

disabled ESC. Thus, this test clearly 

distinguishes vehicles with properly 

tuned ESC systems from comparable 

vehicles not so equipped. 

4. Understeer Requirements 

Under the proposed requirement that 

vehicles be equipped with ESC systems 

meeting the proposed definition of ‘‘ESC 

System,’’ a system must be ‘‘computer 

controlled with a computer using a 

closed-loop algorithm to limit vehicle 

oversteer and to limit vehicle understeer 

when appropriate’’ (emphasis added). 

The NPRM did not propose a separate 

performance requirement for understeer. 

(All current ESC designs that NHTSA 

has studied appear to already include 

provisions for mitigating excessive 

understeer.) 

BorgWarner suggested that it is 

inconsistent for the ESC proposal to 

state that the system must meet an 

understeer requirement without 

defining a test or set of criteria to 

objectively measure compliance. 

Accordingly, BorgWarner stated that the 

agency should either include a 

performance requirement for understeer 

or eliminate the understeer requirement. 

The commenter suggested that the 

agency could amend the standard at a 

later date, once the parameters of the 

understeer performance requirement 

and associated test procedure have been 

developed. 

Delphi stated that while it supports 

the eventual incorporation of an 

understeer performance requirement 

into the ESC standard, the commenter 

believes that adoption of the agency’s 

proposal would yield significant safety 

benefits and that the agency should 

proceed quickly to a final rule. 

Accordingly, Delphi suggested leaving 

an understeer performance requirement 

for a separate future rulemaking. Delphi 

reasoned that, ultimately, an ESC 

system facing an extreme understeer 

situation must avoid overreaction that 

produces oversteer (excess yaw and side 

slip, which may lead to off-road tripped 

rollover) or produces excessive lateral 

acceleration that may induce on-road 

untripped rollover. 

Advocates faulted the NPRM, on both 

safety and legal grounds, for not 

proposing specific performance 

requirements for ESC understeer 

intervention. The commenter argued 

that because the agency has identified 

understeer intervention as one of the 

necessary elements for an ESC system, 

it is obligated to establish performance 

requirements (including appropriate test 

procedures), without which the 

understeer requirement is 

unenforceable. Otherwise, the 

commenter stated that some 

manufacturers might supply ESC 

systems that do not adequately 

compensate for understeer loss of 

control circumstances, arguing that 

there are already vast differences in 

tuning among various ESC systems. 

Advocates predicted that failure of the 

agency to specify understeer 

performance requirements would 

maintain or expand differences between 

ESC performance from one vehicle make 

or model to another and could cause the 

standard to forgo prevention of 

additional fatalities and injuries. 

Furthermore, Advocates argued that 

since SAFETEA–LU directs the agency 

to establish performance criteria for 

stability enhancing technologies (i.e., 

noting the plural nature of that statutory 

provision, which Advocates suggested 

requires something more than an 

oversteer criterion alone), including the 

understeer component that the agency 

has determined to be a necessary part of 

ESC systems from a safety perspective is 

also required from a legal perspective. 

Consumers Union expressed concern 

that the agency’s proposal does not 

assess an ESC-equipped vehicle’s ability 

to reduce understeer through the 

standard’s test procedures. The 

commenter inquired as to what 

percentage of the fatalities to be 

addressed by the standard are caused by 

understeer as opposed to oversteer, but 

the organization stated that it 

nevertheless believes that understeer is 

an issue that should be addressed by the 

agency. 

IIHS expressed its agreement with the 

agency’s approach to provide both a 

definition of an ESC system and a 

performance requirement for such 

systems. However, because the 

proposed ESC performance test does not 

fully address understeer, IIHS cautioned 

the agency to monitor the performance 

of ESC-equipped vehicles to ensure that 

they continue to be effective. 

Public Citizen also objected to the 

omission of a performance test for 

understeer intervention, stating that the 

agency has not addressed the understeer 

performance criteria used by industry or 

the potential loss of benefits that would 

be attributed to the failure to develop 

understeer performance criteria. 

According to Public Citizen, the agency 

should explain on the record the 

available test procedures for understeer 

that it examined and explain why those 

procedures are inadequate. The 

commenter stated that the agency itself 

has identified understeer intervention as 

an important component of the ESC 

system, but without any performance 

criteria, neither the agency nor the 

consumer will have any sense of the 

effectiveness of the system in that 

regard. Accordingly, the commenter 

argued that the NPRM is inadequate to 

meaningfully address rollover fatalities 

as required by the statute, so it 

demanded a supplemental notice of 

proposed rulemaking (SNPRM) to 

correct these perceived deficiencies. 

Although Mr. Sparhawk agreed that 

ESC systems are likely to provide 

substantial benefits, he raised two issues 

for resolution in the final rule. Mr. 

Sparhawk argued that NHTSA has not 

established an adequate record to justify 

adoption of an equipment requirement 

or to explain why development of a 

performance test for understeer was too 

difficult and too cumbersome for the 

agency and the regulated community. 

The commenter stated that the 

justification provided by the agency for 

not including an understeer test as part 

of the ESC proposal requires further 

factual and analytical development. 

Mr. Sparhawk questioned how, 

without an understeer test, the agency 

can determine whether that aspect of 

the ESC system has the desired level of 

functionality or whether the system will 

always function as expected. (The 

commenter cited NHTSA’s June 2003 

report titled ‘‘Initiatives to Address the 

Mitigation of Vehicle Rollover,’’ which 

noted system-to-system variability in 

terms of ESC performance.) 

The commenter also stated that 

numerous understeer tests have been 

developed in Asia, Europe, and North 

America, so the record should explain 

that these tests do exist, why they are 

inadequate, and the urgent need to 

move to a final rule even before the 

understeer issue can be fully resolved. 

Otherwise, one might ask why the 

agency simply did not wait for 

additional data on this key element 

before proceeding with its rulemaking. 

In addition, the commenter asked the 

agency to explain the factors, elements, 

or processes used by the agency to 

determine when any battery of tests is 

too difficult for incorporation in a 

regulation. Mr. Sparhawk also argued 

that there is no provision in the statute 

permitting the agency to consider 

burden on the agency or the regulated 

community as a factor when prescribing 

a safety standard. 

As background for the reader, all light 

vehicles (including passenger cars, 

pickups, vans, minivans, crossovers, 

and sport utility vehicles) are designed 

to understeer 53 in the linear range of 


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most cars for everyday driving. Light vehicles are 

designed to be slightly understeer in normal driving 

situations, because being understeer provides both 

stability (the vehicle is not hugely affected by, e.g., 

small gusts of wind) and lateral responsiveness 

(e.g., the vehicle is able to respond to the driver’s 

sudden decision to avoid an obstruction in the 

roadway by turning the wheel quickly). 

54The ‘‘linear range of lateral acceleration’’ is 

referred to in other parts of the preamble as ‘‘linearhandling’’ and ‘‘linear range,’’ and in very basic 

terms describes the normal situation of everyday 

driving, where a given turn by the driver of the 

steering wheel causes an expected amount of turn 

of the vehicle itself, because the vehicle is operating 

at the traction levels to which most drivers are 

accustomed. As the limits of the accustomed 

traction levels are approached (elsewhere called 

‘‘limit-handling’’), the vehicle begins to enter nonlinear range, in which the driver cannot predict the 

movement of the vehicle given a particular turn of 

the steering wheel, as on a slippery road or a sharp 

curve, where the driver can turn the wheel a great 

deal and get little response from the skidding 

vehicle. 

lateral acceleration,54 although 

operational factors such as loading, tire 

inflation pressure, and so forth can in 

rare situations make them oversteer in 

use. This is a fundamental design 

characteristic. Understeer provides a 

valuable, and benign, way for the 

vehicle to inform the driver of how the 

available roadway friction is being 

utilized, insofar as the driver can ‘‘feel’’

the response of the vehicle to the road 

as the driver turns the steering wheel. 

Multiple tests have been developed to 

quantify linear-range understeer 

objectively, including SAE J266, 

‘‘Steady-State Directional Control Test 

Procedures for Passenger Cars and Light 

Trucks,’’ and ISO 4138, ‘‘Road 

vehicles—Steady state circular test 

procedure.’’ These tests help vehicle 

manufacturers design their vehicles 

with an appropriate amount of 

understeer for normal linear-range 

driving conditions. Tests such SAE J266 

and ISO 4138 simply measure the small 

constant reduction in vehicle turning (in 

comparison to the geometric ideal for a 

given steering angle and wheelbase) that 

characterizes linear range understeer at 

relatively low levels of lateral 

acceleration. This is much different 

from limit understeer in loss-of-control 

situations where even large increases in 

steering to avoid an obstacle create little 

or no effect on vehicle turning. 

In the linear range of handling, ESC 

should never activate. ESC interventions 

occur when the driver’s intended path 

(calculated by the ESC control 

algorithms using a constant linear range 

understeer gradient) differs from the 

actual path of the vehicle as measured 

by ESC sensors. Since this does not 

occur while driving in the linear range, 

ESC intervention will not occur. 

Therefore, ESC has no effect upon the 

linear-range understeer of a vehicle. 

Our response to the comments is 

explained in more detail in Appendix 1, 

below. In overview, the agency 

recognizes that understeer intervention 

is one of the core functions of an ESC 

system, a feature common to all current 

production systems. The agency 

examined the available research for a 

potential ESC understeer test, but such 

research did not address understeer in 

the context of loss-of-control situations. 

Understeer tests in the literature (such 

as SAE J266 and ISO 4138) focus on 

linear range understeer properties and 

are not relevant to the operation of ESC, 

as explained above. 

Because there are no suitable tests of 

limit understeer performance in 

existence, NHTSA undertook its own 

preliminary research efforts related to 

understeer. However, the complexity of 

such research would require several 

years of additional work before any 

conclusions could be reached regarding 

an ESC understeer performance test. A 

principal complication is that 

manufacturers often program ESC 

systems for SUVs to avoid understeer 

intervention altogether on dry roads 

because of concern that the intervention 

could trigger tip-up or make the 

oversteer control of some vehicles less 

certain in high-speed situations. This 

common understanding of how current 

ESC systems operate related to 

understeer has also been observed in the 

course of NHTSA’s research; this 

principle was discussed in the NPRM, 

and no commenter disagreed with this 

operational understanding. 

We believe it would be unwise to 

disregard manufacturers’ exercise of 

caution in this circumstance, 

particularly in view of the remarkable 

reduction in rollover crashes of SUVs 

that manufacturers have achieved with 

current ESC strategies. Respect for the 

manufacturer’s discretion in understeer 

strategies is the reason why we added 

‘‘when appropriate’’ to the NPRM’s 

proposed requirement for understeer 

intervention in the ‘‘ESC System’’

definition, which was modeled on the 

SAE definition. As a result, tests of 

understeer intervention would have to 

be conducted on low-coefficient of 

friction (‘‘low-coefficient’’) surfaces. 

There are two kinds of low-coefficient 

test surfaces: (1) Those involving water 

delivery to the pavement and pavement 

sealing compounds such as Jennite to 

reduce the friction of wet asphalt, and 

(2) those involving water delivery to 

inherently slick surfaces such as basalt 

tile pads. Repeatable pavement watering 

is confounded by factors like time 

between runs, wind, slope, temperature, 

and sunlight. Jennite itself is not very 

durable, resulting in the coefficient 

changing with wear. Simply wetting the 

same surface used for the oversteer test 

would not produce a surface slippery 

enough to ensure that SUVs would 

intervene in understeer. Basalt tile is 

extremely expensive, as evidenced by 

the lack of large enough basalt test pads 

anywhere in the country for this kind of 

testing. Moreover, the coefficient of 

friction of basalt pads is extremely low, 

almost as low as glare ice. Causing 

manufacturers to optimize understeer 

intervention at extremely low 

coefficients like this may create overlyaggressive systems that compromise 

oversteer control on more moderate lowcoefficient surfaces. Given the 

practicability problems of repeatable 

low-coefficient testing, the need for 

compliance margins expressed by the 

Alliance (see Section IV.C.5) would 

likely result in very low criteria. 

Development of specific performance 

criteria is also problematic. In the 

oversteer performance test, the 

difference between the maximum yaw 

rate achieved and the zero when the 

vehicle is steered straight at the end of 

the maneuver is large and readily 

obvious. In contrast, the difference 

between understeer and the ultimate 

controlled drift, which is the most any 

ESC system can deliver when there is 

simply not enough traction for the 

steering maneuver, is difficult to 

differentiate. Also, the kind of optical 

instrumentation that a test would use to 

measure possible metrics in an 

understeer test such as body and wheel 

slip angles does not function reliably for 

tests on wet surfaces. There is a real 

question whether NHTSA can ever 

create criteria for understeer 

intervention that would be both 

stringent enough for testing and 

universal enough to be applied on cars 

and SUVs without upsetting legitimate 

design compromises. 

In light of the above, the agency 

determined that it had three available 

options: (1) Delay the ESC final rule 

until such time as the agency’s research 

was completed and an understeer 

performance test could be developed; 

(2) drop the understeer requirement 

from the proposed definition of ‘‘ESC 

System’’ and amend the standard at a 

future date once an ESC performance 

test is developed; or (3) include a 

requirement for understeer as part of the 

definition of ‘‘ESC System,’’ along with 

requiring specific components that will 

permit the system to intervene in 

excessive understeer situations (e.g., 

capability to brake at four wheels 

individually which is necessary for both 

oversteer and understeer intervention) 

and requiring that manufacturers make 

available to the agency, upon request, 


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sufficient engineering documentation to 

demonstrate the ESC system’s capability 

to limit understeer. 

The agency quickly decided to 

eliminate the option of delaying the ESC 

rulemaking, because of the extremely 

high life-saving potential of this 

rulemaking. To do so would run counter 

to the agency’s mission. 

Similarly, the agency decided that 

eliminating the understeer requirement 

from the rule and deferring its adoption 

until the completion of future research 

would also run counter to safety. As 

discussed in Section II.D, understeer 

intervention is one of the key beneficial 

features in current ESC systems, and we 

did not want to set a requirement that 

did not ensure the substantial benefits 

of current ESC systems. 

That left the agency with the third 

option (which we have retained in this 

final rule) of adopting an understeer 

requirement as part of the definition of 

‘‘ESC System,’’ along with a 

requirement for specific equipment 

suitable for that purpose. Such 

requirement is objective in terms of 

explaining to manufacturers what type 

of performance is required and the 

minimal equipment necessary for that 

purpose. The rule also requires that the 

manufacturer must submit to NHTSA, 

upon request, the engineering 

documentation necessary to 

demonstrate the system’s understeer 

capability (see S5.6). 

Specifically, in order to ensure that a 

vehicle is equipped with an ESC system 

that meets the definition of ‘‘ESC 

System’’ under S4, NHTSA’s Office of 

Vehicle Safety Compliance (OVSC) may 

ask the vehicle manufacturer to provide 

a system diagram that identifies all ESC 

components, a written explanation 

describing the ESC system’s basic 

operational characteristics, and a logic 

diagram supporting the explanation of 

system operations. In addition, 

regarding mitigation of understeer, 

OVSC may request a discussion of the 

pertinent inputs to the vehicle computer 

or calculations within the computer and 

how its algorithm uses that information 

and controls ESC system hardware to 

limit vehicle understeer. (In appropriate 

cases in the context of an enforcement 

proceeding, NHTSA might ask for 

additional data, including the results of 

a manufacturer’s understeer testing.) We 

note here that we anticipate that much 

of the above information is proprietary 

and would be submitted under a request 

for confidential treatment. 

In sum, the agency believes that the 

above information will permit the 

agency to understand the operation of 

the ESC system and to verify that the 

system has the necessary hardware and 

logic for mitigating excessive 

understeer. This ensures that vehicle 

manufacturers are required to provide 

understeer intervention as a feature of 

the ESC systems, without delaying the 

life-saving benefits of the ESC rule 

(including those attributable to 

understeer intervention). In the 

meantime, the agency will conduct 

additional research in the area of ESC 

understeer intervention and considering 

taking additional action, as appropriate. 

The Vehicle Safety Act requires that 

FMVSS be stated in objective terms. 

NHTSA believes that the understeer 

requirement is objective, even without a 

specific performance test. The definition 

of ‘‘ESC System’’ requires not only an 

understeer capability (part (2) of the 

definition), but also specific physical 

components that allow excessive 

understeer mitigation (part (1) of the 

definition). Based on agency evaluation 

of ESC-equipped vehicles so far, we 

have identified both the hardware and 

the algorithms necessary for an ESCequipped vehicle to be able to mitigate 

excessive understeer, as described in 

S5.1 of the standard and more fully in 

the Appendix. 

We note that in the proposed 

regulatory text, NHTSA defined ESC as 

including an algorithm that would 

‘‘limit vehicle understeer as 

appropriate,’’ which was intended to 

ensure the mitigation of excessive 

understeer already performed by 

existing ESC systems when the vehicle 

has entered the non-linear range and to 

prevent any backsliding of the 

technology. However, based upon the 

concern for objectivity, we have decided 

to delete the words ‘‘when appropriate’’

in paragraph (2) of the definition of 

‘‘ESC System’’ in S4. We believe that the 

provision for ESC system technical 

documentation contained in S5.6 

provides a clearer picture as to when 

understeer intervention is appropriate 

for a given vehicle. 

Thus, NHTSA plans to enforce the 

understeer requirement via a two part 

process: Ensuring that vehicles have all 

of the hardware needed to limit vehicle 

understeer (as required by FMVSS No. 

126), and checking engineering 

documentation (i.e., logic/system 

diagrams and other information 

discussed above) provided by the 

vehicle manufacturers upon request to 

show that the ESC system is capable of 

addressing vehicle understeer. 

Regarding Consumers Union’s 

question about what percentage of the 

fatalities to be addressed by the 

standard are caused by understeer as 

opposed to oversteer, we cannot 

quantify this from the available data. 

This is because it is exceedingly 

difficult to determine during or after an 

accident whether it was caused by 

oversteer or understeer, when both 

frequently occur at the same time during 

accidents. 

In conclusion, while NHTSA would 

like to include a performance standard 

for understeer intervention in FMVSS 

No. 126, we do not know of any suitable 

performance tests for excessive 

understeer mitigation. We are unwilling 

to forgo the large safety benefits that 

ESC will provide to the American 

public in the near future just because we 

might, some years from now, be able to 

produce a more refined standard. If, in 

the future, we see ways to amend 

FMVSS No. 126 in a manner that would 

increase motor vehicle safety, NHTSA 

would consider undertaking additional 

rulemaking at that time. 

5. Lateral Responsiveness Criteria 

The NPRM proposed that under each 

test performed under the test conditions 

of S6 and the test procedure of S7.9, the 

vehicle would be required to satisfy the 

responsiveness criterion of S5.2.3 

during each of those tests conducted 

with a steering amplitude of 180 degrees 

or greater. Specifically, proposed 

paragraph S5.2.3 provides that lateral 

displacement of the vehicle center of 

gravity with respect to its initial straight 

path must be at least 1.83 m (6 feet) 

when computed 1.07 seconds after 

initiation of steering. The NPRM further 

proposed that the computation of lateral 

displacement is performed using double 

integration with respect to time of the 

measurement of lateral acceleration at 

the vehicle center of gravity (see 

S5.2.3.1) and that time t=0 for the 

integration operation is the instant of 

steering initiation (see S5.2.3.2). 

The VDA expressed support for the 

agency’s proposed requirements for 

‘‘Metric Stability.’’ The commenter 

confirmed that in similar testing by its 

members, measured lateral accelerations 

and the subsequent double integration 

for the lateral displacements showed 

similar values to those tested during the 

agency’s development of the NPRM. It 

stated that its testing showed that all 

passenger cars reached the proposed 

limit of 1.83 m after 1.07 s, although 

SUVs were more borderline. The 

commenter also stated that the required 

lateral displacement for proposed 

steering wheel angles above 180 degrees 

was easily reachable for passenger cars, 

although more difficult to achieve for 

larger, heavier vehicles with more 

indirect steering ratios. According to the 

VDA, the accuracy of the lateral 

acceleration integration, up to 1.07 s 

after initiation of steering, is a sufficient 


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and reproducible measurement 

procedure. 

The VDA supported the agency’s 

requirement of stability criteria using 

yaw rate measured 1 sec and 1.75 sec 

after the end of steering. However, the 

VDA offered a recommendation 

regarding the proposed responsiveness 

test procedure. Specifically, the 

commenter urged the responsiveness 

metric to include the influence of 

steering ratios and possibly vehicle 

weight. 

Regarding parameters that may 

influence test results, the VDA stated 

that it did not conduct detailed tests to 

examine factors such as proving 

grounds, test track surface, slope, 

ambient climatic conditions, or brake 

temperatures. The commenter stated 

that this was not possible in its testing, 

because each vehicle manufacturer 

member carried out its own testing on 

its own test track. Accordingly, the VDA 

recommended that the agency should 

adopt the Alliance’s recommendations 

that take into account relevant 

tolerances and influencing parameters. 

The Alliance and AIAM stated their 

understanding that NHTSA’s intention 

in proposing a responsiveness metric as 

part of the ESC rulemaking was not to 

change the basic responsiveness 

characteristics of the current fleet of 

vehicles without ESC (which they argue 

are satisfactory from a safety 

standpoint), but to prevent vehicle 

manufacturers from inappropriately 

suppressing the vehicle’s natural level 

of responsiveness in order to enhance 

stability when the ESC system is 

activated. In support of this view, the 

commenters also pointed out that in the 

NPRM, the agency stated its expectation 

that approximately 98 percent of current 

ESC-equipped vehicles would comply 

with the proposal. However, the 

Alliance/AIAM argued that given the 

observed variability inherent in vehicle 

testing, the proposed responsiveness 

metric and criteria would not provide 

manufacturers with a sufficient margin 

to ensure compliance for a number of 

vehicles (primarily long wheelbase pickups and stretched limousines) being 

tested without ESC (i.e., in a base 

handling state). 

The Alliance/AIAM comments of 

November 17, 2006 presented 

considerable detail on three potential 

sources of variability: (1) Track 

variability; (2) temperature variability, 

and (3) run-to-run variability. While 

none of the 62 vehicles tested by 

NHTSA or the Alliance actually failed 

the proposed responsiveness criterion, 

the Alliance/AIAM attributed the 

success of some of the vehicles to test 

conditions (ambient temperature and 

test track) that were at the favorable end 

of the variability range. However, the 

commenters argued that for compliance 

testing purposes, manufacturers would 

have to certify that the vehicles would 

pass the performance test at the least 

favorable end of the variability range. 

Therefore, the Alliance/AIAM perceived 

the proposed responsiveness criterion as 

very demanding because of the large 

margin of compliance that would be 

necessary for certification, taking into 

account the sources of test variability. 

The Alliance/AIAM proposed several 

alternative responsiveness criteria in 

their November 17, 2006 comments in 

order to address the problem of 

insufficient compliance margins that the 

commenters attributed to the inherent 

level of test variability. These 

suggestions were based on lowering the 

lateral displacement criteria from 6 feet 

to 4.5 feet (in a range determined 

according to the test weight of the 

vehicle) or increasing the time for the 

vehicle to reach the 6-foot displacement. 

On December 21, 2006, the Alliance/ 

AIAM submitted a supplemental 

comment introducing the ideas of 

replacing the fixed steering angle of 180 

degrees used in the test with a 

normalized steering angle that takes into 

account differences in vehicle steering 

ratio and using the GVWR of the vehicle 

rather than the test weight to create a 

cut-off point to qualify larger vehicles 

for a reduced displacement criteria. The 

supplemental comment did not suggest 

reducing the stringency of the 

responsiveness test of the NPRM as 

much as the previous comment. Since 

NHTSA wants to preserve the 

stringency of the responsiveness test as 

much as possible, it considered the 

supplemental comment rather than the 

original comment in trying to address 

the concerns of the Alliance and AIAM. 

The Alliance/AIAM supplemental 

comment stressed the effect of GVWR 

and of steering ratio differences between 

vehicles on a reasonable criterion for 

lateral displacement in NHTSA’s Sine 

with Dwell test maneuver. It used 

NHTSA’s proposed criterion of 6 feet of 

lateral displacement for vehicles with a 

GVWR of 5,500 pounds or less, but the 

commenters suggested a small reduction 

to 5.5 feet for vehicles over 5,500 

pounds GVWR and up to 10,000 pounds 

GVWR. The supplemental comment also 

suggested using a normalized steering 

wheel angle (that would account for 

differences in steering ratios between 

vehicles) rather than simply 180 degrees 

of steering wheel rotation as the 

minimum amount of steering for 

responsiveness tests. The steering wheel 

angle would be normalized by dividing 

the first peak steering wheel angle by 

the steering wheel angle at 0.3g 

determined by the slowly increasingsteer test (thereby expressing the 

amount of steering as a unitless number 

or scalar rather than in degrees). The 

Alliance/AIAM suggested that the 

responsiveness criteria should be 

applied for tests using a normalized 

steering wheel angle of 5.0 or greater. 

NHTSA agrees with Alliance/AIAM 

comment regarding the use of the 

normalized steering wheel angle of 5.0 

as the minimum steering input for 

applying the responsiveness test 

criteria. The performance test in the 

NPRM already includes the procedure 

for normalizing the steering wheel angle 

and calls for performing the Sine with 

Dwell maneuver at normalized steering 

wheel angles including 5.0, 5.5, 6.0, and 

6.5, at which points responsiveness 

would be measured. For contemporary 

light vehicles, our data indicate that, on 

average, a normalized steering wheel 

angle of 5.0 is about 180 degrees. 

However, the heavier trucks and vans in 

the weight class with a GVWR up to 

10,000 pounds tend to have slower 

steering ratios, which means that 180 

degrees of rotation for those vehicles 

produces less steering motion of the 

front wheels than for cars (e.g., a 

normalized steering wheel angle of 5.0 

averages approximately 147 degrees for 

passenger cars, 195 degrees for SUVs, 

and 230 degrees for pickups). Since 

these are the vehicles whose inherent 

chassis properties limit responsiveness, 

the test becomes very difficult to pass if 

they are also tested at lower effective 

steering angles at the front wheels. 

Thus, the use of normalized steering 

wheel angles will remove a systematic 

disadvantage for trucks in the test 

procedure. 

In response to the Alliance/AIAM 

comment’s suggestion for applying the 

normalized steering angles to the first 

actual peak steering wheel angles 

measured during the test, we believe 

that there are problems with such an 

approach. Figure 2 of the regulatory text 

shows the ideal steering profile of the 

Sine with Dwell maneuver used to 

command the steering machine. A 

steering machine is utilized because it 

turns the steering wheel in the test 

vehicles with far greater precision and 

repeatability than is possible for a 

human driver. However, the power 

steering systems of some vehicles do not 

permit the steering machines to 

accomplish the desired steering profile. 

For the reasons discussed below, we 

believe the normalized steering angle 

should be based on the commanded 

angle of a steering machine (which 

replaces driver input during the test) 

with a high steering effort capacity 


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rather than on the measured maximum 

steering angle achieved by the machine. 

The Alliance/AIAM also suggested 

that NHTSA should specify a maximum 

steering torque capacity of 50 to 60 Nm 

for steering machines to reduce the 

variability caused by the choice of 

steering machine and to assure 

manufacturers that the tests would be 

carried out with powerful machines to 

maximize the steering input during the 

responsiveness test. NHTSA is 

specifying (in S6.3.5 of the final rule) 

that the steering machine used for the 

Sine with Dwell maneuver must be 

capable of applying steering torques 

between 40 and 60 Nm at steering wheel 

velocities up to 1200 degrees per 

second. This is a more rigorous 

specification than simply a maximum 

torque range that does not include speed 

capability, and it prevents NHTSA from 

conducting compliance tests with some 

of the less powerful machines in use by 

test facilities. 

However, even a robust steering 

machine cannot maintain the 

commanded steering profile with some 

vehicle power steering systems. Some of 

the electric power steering systems are 

especially marginal in that their power 

assistance diminishes at high steering 

wheel velocities. In the case of vehicle 

power steering limitations, the first 

steering angle peak in Figure 2 cannot 

be met, but the second peak as well as 

the frequency of the wave form are 

usually achieved. Thus, marginal 

vehicle power steering does not likely 

reduce the severity of the oversteer 

intervention part of the test, but it will 

reduce the steering input that helps the 

vehicle satisfy the responsiveness 

criteria. If NHTSA were to use the actual 

steering angle rather than the 

commanded steering angle as the 

normalized steering angle for the 

responsiveness test, it could create the 

unacceptable situation of vehicles that 

could not be tested for compliance, 

because the test would not allow for 

their evaluation. For example, if the 

steering machine could not achieve a 

normalized steering wheel angle of 5.0 

even when commanded to a normalized 

angle of 6.5 because of vehicle 

limitations, the vehicle could not be 

said to fail, no matter how poor its 

performance. 

Therefore, the agency has decided to 

use the commanded steering profile 

(using an assuredly robust steering 

machine), rather than the measured 

steering profile, to calculate the 

normalized steering wheel angle used to 

assess compliance with our lateral 

displacement requirement. We do not 

believe that this creates a practical 

problem. At this time, the larger 

vehicles have reasonably powerful 

steering systems that should enable 

them to achieve actual peak steering 

angles within at least 10 degrees of the 

commanded peak. Furthermore, under 

this approach to defining the steering 

input, the lateral displacement required 

for large vehicles would be reduced to 

5 feet rather than the 5.5 feet requested 

in the Alliance/AIAM supplemental 

comment (with its somewhat higher 

measured steering angle). The weaker 

electric power steering systems 

discussed above are typically found on 

cars, and cars tend to be responsive 

enough to pass the 6-foot lateral 

displacement criterion at normalized 

steering wheel angles of less than 5.0. 

Therefore, S5.2 of the proposed 

standard has been revised to read as 

follows: 

S5.2 Performance requirements. During 

each test performed under the test conditions 

of S6 and the test procedure of S7.9, the 

vehicle with the ESC system engaged must 

satisfy the stability criteria of S5.2.1 and 

S5.2.2, and it must satisfy the responsiveness 

criterion of S5.2.3 during each of those tests 

conducted with a commanded steering wheel 

angle of 5A or greater, where A is the steering 

wheel angle computed in S7.6.1. 

As noted above, the NPRM included 

a responsiveness criterion that specified 

a minimum lateral movement of 6 feet 

during the first 1.07 seconds of steering 

during the Sine with Dwell maneuver. 

The purpose of the criterion was to limit 

the loss of responsiveness that could 

occur with unnecessarily aggressive roll 

stability measures incorporated into the 

ESC systems of SUVs. This is a real 

concern, as our research has 

demonstrated that one such system 

reduced the lateral displacement 

capability of a mid-sized SUV below 

that attainable with a 15-passenger van, 

multiple unloaded long wheelbase 

diesel pickups, and even a stretched 

wheelbase limousine. 

A heavy-duty pickup truck 

understeers strongly in this test because 

of its long wheelbase and because it is 

so front-heavy under the test condition. 

The ESC standard is not intended to 

influence the inherent chassis 

properties of these vehicles (which were 

tested without ESC), because low 

responsiveness in the unloaded state is 

the consequence of a chassis with 

reasonable inherent stability in the 

loaded state. The standard must avoid 

causing vehicles to be designed with 

chasses that are unstable at GVWR and 

rely on ESC in normal operation. 

NHTSA is also aware that some very 

large vans with a high center of gravity, 

such as 15-passenger vans, rely on their 

ESC system to reduce responsiveness 

because of special concerns for loss of 

control and rollover. While it is 

necessary to respect the responsiveness 

limitations appropriate to large vehicles 

with commercial purposes, there is no 

need for lighter vehicles designed for 

personal transportation, including 

SUVs, to give up so much of the object 

avoidance capability of their chassis 

when tuning the ESC system. 

NHTSA agrees with the Alliance/ 

AIAM comment suggesting a lower 

responsiveness criterion for vehicles 

with higher GVWRs, but we disagree 

with the 5,500-pound GVWR break 

point suggested by the commenters. 

Some large passenger cars, such as the 

Mercedes-Benz S-class, have GVWRs 

near this level. With this break point, 

minivans like the Honda Odyssey and 

midsize SUVs like the Toyota 4Runner 

and Jeep Cherokee would be considered 

to have the same limitations as 15- 

passenger vans and trucks with a GVWR 

of 10,000 lbs. We believe a more 

representative break point was 

established by Standard No. 135, Light 

Vehicle Brake Systems, at a GVWR of 

3,500 kg (7,716 pounds). Accordingly, 

S5.2.3 of the proposed standard has 

been revised to read as follows: 

S5.2.3 The lateral displacement of the 

vehicle center of gravity with respect to its 

initial straight path must be at least 1.83 m 

(6 feet) for vehicles with a GVWR of 3,500kg 

(7,716 lb) or less, and 1.52 m (5 feet) for 

vehicles with a GVWR greater than 3,500 kg 

(7,716 lb) when computed 1.07 seconds after 

the Beginning of Steer (BOS). BOS is defined 

in S7.11.6. 

6. Definition of ‘‘ESC System’’ and 

Required Equipment 

As noted above, the NPRM proposed 

to require installation of an ESC system 

that: (1) Is capable of applying all four 

brakes individually and has a control 

algorithm that utilizes this capability; 

(2) is operational during all phases of 

driving including acceleration, coasting, 

and deceleration (including braking), 

except when the driver has disabled 

ESC or the vehicle is below a low speed 

threshold where loss of control is 

unlikely, and (3) remains operational 

when the antilock brake system or 

traction control system is activated (see 

S5.1). The ESC system must also meet 

the proposed performance requirements 

for lateral stability and vehicle 

responsiveness (see S5.2). 

Under S4 of the proposal, an ‘‘ESC 

System’’ is defined as a system that has 

all of the following attributes: (1) That 

augments vehicle directional stability by 

applying and adjusting the vehicle 

brakes individually to induce correcting 

yaw torques to a vehicle; (2) that is 

computer-controlled with the computer 

using a closed-loop algorithm to limit 


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55See Snyder et al., ‘‘NHTSA Light Vehicle ABS 

Performance Test Development’’ (NHTSA Technical 

Report), DOT HS 809 747 (June 2005), at 47. 

Available at http://www-nrd.nhtsa.dot.gov/vrtc/ca/ 

capubs/ABSperformancefinalreport.pdf. 

56United Nations Economic Commission for 

Europe, Regulation No. 13–H, ‘‘Approval of 

Passenger Cars with Regard to Braking, Rev. 2, 

World Forum for Harmonization of Vehicle 

Regulations (WP.29 ECE R13–H), May 11th 1998. 

Available at http://www.unece.org/trans/main/ 

wp29/wp29regs1–20.html. 

vehicle oversteer and to limit vehicle 

understeer when appropriate; (3) that 

has a means to determine the vehicle’s 

yaw rate and to estimate its side slip; (4) 

that has a means to monitor driver 

steering inputs, and (5) that is 

operational over the full speed range of 

the vehicle (except below a low-speed 

threshold where loss of control is 

unlikely). 

According to the VDA, it supports the 

definition for ‘‘ESC system’’ included in 

the agency’s proposal which 

‘‘corresponds to modern state-of-the-art 

ESC systems.’’

(a) Clarification of Performance 

Expectations 

Delphi expressed support for the 

approach in the agency’s ESC proposal 

to combine an ESC definitional 

requirement with a performance 

requirement (i.e., a lane change 

maneuver at 50 mph conducted on a dry 

surface), until such time as the agency 

can conduct relevant research into ESC 

operation on slippery surfaces and/or 

for extreme understeer condition, which 

may support future requirements under 

an amended standard. However, Delphi 

did recommend that the agency include 

an explicit statement in the final rule 

about the performance expectations 

across all operating conditions. 

Specifically, Delphi suggested that the 

final rule should state that a vehicle 

with ESC should be equally or more 

stable and equally or more responsive 

than a vehicle without ESC, across all 

speeds, road surface frictions, and 

maneuvers. The commenter also stated 

that improvements in handling stability 

should not significantly reduce 

handling responsiveness, and visaversa. 

We agree that, to the extent possible, 

improvements in handling stability 

should not significantly reduce 

handling responsiveness, and visaversa. To ensure that this goal is 

achieved, the standard includes a test 

with responsiveness criteria (discussed 

in Section IV.C.5) that requires ESCequipped vehicles to demonstrate an 

acceptable practical level of lateral 

displacement capability in response to a 

specified amount of steering. 

(b) Clarification of Threshold Speed 

In their comments, the Alliance/ 

AIAM agreed with that portion of the 

NPRM providing that ESC systems are 

not required to be operational at very 

low speeds, even though the system is 

technically ‘‘on.’’ However, the 

commenters argued that the proposed 

language in the definition of ‘‘ESC 

System’’ under S4 stating ‘‘except below 

a speed threshold where loss of control 

is unlikely’’ is not objective and could 

lead to uncertainty in compliance 

testing. Accordingly, the commenters 

recommended revising the relevant 

portion of that definition to read as 

follows: ‘‘That is operational over the 

full speed range of the vehicle (except 

at vehicle speeds less than 20 mph).’’

As reflected in the NPRM, we 

originally thought that it would be 

appropriate to provide flexibility by 

leaving determination of a ‘‘low-speed 

threshold where the loss of control is 

unlikely’’ to the discretion of vehicle 

manufacturers and ESC suppliers. 

However, we have decided to grant the 

industry’s request that we increase the 

specificity of S4 by providing a explicit 

threshold speed below which the ESC 

system need not operate. The Alliance/ 

AIAM suggested a low-speed threshold 

of 20 mph. 

To determine an appropriate lowspeed threshold, NHTSA must consider 

three factors: 

1. ESC should not be active when the 

vehicle’s Antilock Brake System (ABS) 

is not active. If the vehicle’s ESC was 

active but the ABS was inactive, then 

ESC brake applications could result in 

one or more of the vehicle’s wheels 

locking up. While one wheel locking up 

may not cause safety problems, if two or 

more wheels lock up, the vehicle may 

experience lateral instability. Even at 

low speeds, this situation may result in 

a safety problem. 

2. All ABSs must have a low-speed 

threshold below which the ABS 

becomes inactive. Otherwise, it would 

be impossible to use the vehicle’s brakes 

to bring a vehicle to a complete stop, 

because the ABS would keep activating 

and releasing the brakes when the driver 

tried to stop. FMVSS No. 135 does not 

currently contain performance 

requirements for ABSs; therefore, that 

standard does not set a low-speed 

threshold for them. However, S7 of 

FMVSS No. 135 does indicate that 

wheel lock-ups below a low-speed 

threshold are not a safety concern. See 

S7.1.3(e), S7.2.1(d), and S7.2.3(d) of 

FMVSS No. 135. Lock-ups at vehicle 

speeds above 15 km/h can cause safety 

problems.55 Similarly, ECE Regulation 

13–H,56 which does contain 

performance requirements for ABSs, 

sets a low-speed threshold of 15 km/h 

(9.3 mph). 

3. ESC systems obtain much of their 

information about the state of the 

vehicle from the ABS’s wheel-speed 

sensors. At low vehicle speeds, the ABS 

wheel-speed sensors rotate more slowly, 

which could create unacceptable 

amounts of noise in the data sent to 

ESC. The European standard (ECE 

Regulation No. 13–H) shows that sensor 

data of acceptable quality can be 

obtained at speeds down to 15 km/h (9.3 

mph), although certain changes may be 

required for some current ESC systems 

offered in the U.S. market. 

Based on the preceding analysis, and 

in order to promote consistency with 

other FMVSSs and relevant 

international regulations, we have 

decided upon 15 km/h (9.3 mph) as the 

appropriate low-speed threshold above 

which ESC must be active. Accordingly, 

paragraphs S4 and S5.1.2 of the 

regulatory text have been revised to read 

as follows: 

S4, ESC Definition, Part 6—(6) That is 

operational over the full speed range of the 

vehicle (except at vehicle speeds less than 15 

km/h (9.3 mph) or when being driven in 

reverse). * * * 

S5.1.2 Is operational during all phases of 

driving including acceleration, coasting, and 

deceleration (including braking), except 

when the driver has disabled ESC, the 

vehicle speed is below 15 km/h (9.3 mph), 

or the vehicle is being driven in reverse. 

Please note that these changes to the 

regulatory text provisions related to 

when the vehicle is driven in reverse 

arise from our response to another 

public comment discussed under 

Section IV.C.6(f) below. 

(c) Estimation of Sideslip—Request to 

Add Derivative 

Although the comments of Honda 

Motor Co. Ltd. and American Honda 

Motor Co., Inc. (Honda) agreed that, in 

order to ensure proper operation, it is 

necessary for the ESC system to 

determine the vehicle’s yaw rate (i.e., 

spin), it did not agree that 

manufacturers should be required to 

measure vehicle sideslip directly. The 

commenter stated that manufacturers 

should be permitted to utilize other 

available status variables for estimating 

the spin of a vehicle. Accordingly, 

Honda recommended modifying the 

definition of ‘‘Electronic Stability 

Control System’’ in S4, specifically by 

revising the third part of that definition 

as follows: ‘‘(3) That has a means to 

determine the vehicle’s yaw rate and to 

estimate its sideslip or side slip 

derivative.’’ As accompanying 

clarification, Honda recommended 

further clarification to state, ‘‘Sideslip or 


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side slip angle means the arctangent of 

the lateral velocity of the center of 

gravity of the vehicle divided by the 

longitudinal velocity of the center of 

gravity.’’

The Alliance/AIAM made a similar 

comment, arguing that many current 

ESC systems do not measure sideslip 

directly, but instead use a mathematical 

derivative with respect to time in order 

to determine the vehicle’s sideslip. 

Accordingly, the Alliance/AIAM 

recommended revising the ‘‘ESC 

System’’ definition in S4 by revising the 

third requirement of that definition as 

follows: ‘‘(3) That has a means to 

determine the vehicle’s yaw rate and to 

estimate its side slip or side slip 

derivative with respect to time.’’

The agency concurs with these 

comments. Because side slip and the 

derivative of side slip angle are 

intimately mathematically related, when 

one of these values is known, it is then 

possible to determine the other. This 

change will not have any impact on 

safety, because it merely permits a key 

value for ESC operation to be 

determined by alternate means. 

Accordingly, we have decided to modify 

the relevant portion of the ‘‘ESC 

System’’ definition in S4 to read as 

follows: 

(3) That has a means to determine the 

vehicle’s yaw rate and to estimate its side 

slip or side slip derivative with respect to 

time. 

(d) Request for Alternate Transducers 

RLP Engineering recommended 

changes to the proposed definition of 

‘‘ESC System,’’ particularly the 

requirement for the system to have a 

‘‘means to determine vehicle yaw rate 

and to estimate side slip.’’ According to 

the commenter, vehicle instability 

occurs only when there is tire sideslip, 

not necessarily when there is vehicle 

sideslip. RLP Engineering stated that 

detection of instability involves 

determination of the amount of tire 

sideslip and in which wheel(s) it is 

occurring (with front tire sideslip 

corresponding to understeer and rear 

tire sideslip corresponding to oversteer). 

The commenter stated that vehicle yaw 

rate sensors may or may not be relevant 

to determining tire sideslip, and in any 

event, there may be other and 

potentially better ways to determine 

vehicle stability. For example, RLP 

Engineering stated that a means of 

detecting tire sideslip directly within a 

wheel assembly may eliminate the need 

for a yaw rate sensor. It also stated that 

it could be possible for tire sideslip to 

occur in the absence of vehicle sideslip, 

such as in an extreme understeer 

condition. Accordingly, RLP 

Engineering recommend that the agency 

modify the definition of ‘‘Electronic 

Stability Control System’’ in S4, 

specifically by revising the third part of 

that definition to read as follows: ‘‘(3) 

That has a means to estimate tire contact 

patch sideslip.’’

RLP Engineering made a similar 

comment regarding the portion of the 

‘‘ESC System’’ definition pertaining to 

requirement (4) that the ESC system 

have ‘‘a means to monitor driver 

steering inputs * * *.’’ The commenter 

stated that current ESC systems use 

steering wheel angle data as one 

information component in estimating 

the intended path of a vehicle, as 

compared to its actual path. However, it 

again commented that if there is a 

means of detecting tire sideslip directly 

within a wheel assembly, there may be 

no need for the steering wheel angle 

sensor. Therefore, the commenter 

recommended deleting requirement (4) 

from the proposed definition of ‘‘ESC 

System.’’

When defining the ESC hardware and 

software requirements for the proposed 

FMVSS No. 126, we attempted to 

specify technology known to be 

effective in reducing real world crashes. 

Contemporary ESC systems meet all the 

requirements of S4, but they do not 

necessarily estimate the sideslip of the 

tire contact patch. As it happens, 

NHTSA has yet to see an effective 

technology for measuring the sideslip of 

the tire contact patch. While we are 

encouraged to learn of new technologies 

that may improve vehicle safety, 

quantifying their effectiveness is not 

possible until crash data become 

available, even if one would 

theoretically expect the alternative 

technology to affect vehicle performance 

in a similar manner as the proven 

technology. 

Therefore, we do not concur with RLP 

Engineering’s suggested revisions to S4. 

We have no effectiveness data for ESCtype systems that estimate the sideslip 

of the tire contact patch instead of 

determining the vehicle’s yaw rate, or 

estimating the vehicle’s sideslip, and 

monitoring the driver’s steering inputs. 

Until crash data exist for such systems, 

we are not willing to treat them as 

equivalent to compliant ESC systems 

under FMVSS No. 126, which have 

demonstrated that they can save 

thousands of lives each year. 

(e) Interaction With Other Vehicle 

Systems 

Although proposed paragraph S5.1.3 

states, ‘‘Remains operational when the 

antilock brake system or traction control 

system is activated,’’ the Alliance/AIAM 

stated that on current vehicles, these 

systems tend not to be functionally 

separate but instead are integrated into 

a single system. In order to allow 

subsystem arbitration to occur as 

needed to optimize ESC performance, 

the commenters recommended 

modifying paragraph S5.1.3 as follows: 

‘‘Remains capable of activation even if 

the antilock brake system or traction 

control system is also activated.’’

The agency agrees with the Alliance/ 

AIAM recommendations on this issue. 

Anti-lock brakes, traction control, and 

ESC systems all utilize the vehicle’s 

brake control system to accomplish their 

intended stability enhancement goals. It 

is imperative that the vehicle’s design 

logic for activation of these systems be 

integrated so that these systems can 

work in unison together addressing 

vehicle instabilities. Accordingly, we 

are amending S5.1.3 in the manner 

suggested by the commenters. 

(f) ESC Operation in Reverse 

The Alliance/AIAM, Robert Bosch 

Corporation (Bosch), Continental 

Automotive Systems (Continental), 

Delphi, and Nissan North America, Inc. 

(Nissan) all requested that the final rule 

not require ESC operability when the 

vehicle is driven in reverse, a 

functionality not presently part of 

current ESC systems and one which the 

commenters do not believe is a 

necessary part of the ESC rulemaking. 

Commenters further stated that 

requiring ESC operation in reverse 

would necessitate costly changes to 

current ESC systems. 

In response, we note that the agency 

never intended the ESC system to be 

operable when the vehicle is being 

driven in reverse. We agree that 

requiring operation in reverse would 

necessitate costly changes to current 

ESC systems with no anticipated safety 

benefit. Our belief is that the main 

safety problems while the vehicle is 

operating in reverse are backing into/ 

over pedestrians, backing over edges 

(drop-offs), and backing into inanimate 

objects (e.g., other vehicles, buildings). 

ESC is not expected to help prevent any 

of these types of crashes. 

Furthermore, vehicles are rarely 

driven rapidly in reverse. Therefore, the 

provision in S5.1.2 that ESC need not 

function when ‘‘the vehicle speed is 

below 15 km/h (9.3 mph)’’ means that 

ESC would typically not have to be 

active when the vehicle is in reverse. 

Requiring ESC to be active for those rare 

times when the vehicle is backing 

rapidly would be unreasonable, 

especially since having an active ESC in 

this situation would not improve safety. 


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Accordingly, the relevant provisions 

of the regulatory text have been revised 

to read as follows: 

S4, ESC Definition, Part 6—(6) That is 

operational over the full speed range of the 

vehicle (except at vehicle speeds less than 

15km/h (9.3 mph) or when being driven in 

reverse). * * * 

S5.1.2 Is operational during all phases of 

driving including acceleration, coasting, and 

deceleration (including braking), except 

when the driver has disabled ESC, the 

vehicle speed is below 15 km/h (9.3 mph), 

or the vehicle is being driven in reverse. 

Please note that the changes to the 

regulatory text about vehicle speeds less 

than 15km/h (9.3 mph) have been 

provided in response to another public 

comment discussed under Section 

IV.C.6(b) above. 

7. ESC Performance Requirements 

(a) Definition for ‘‘Lateral Acceleration’’

The Alliance/AIAM and Honda 

recommended that the agency include a 

definition in S4 of the final rule for the 

term ‘‘lateral acceleration,’’ suggesting 

use of the following definition from SAE 

J670e: ‘‘Lateral Acceleration—The 

component of the vector acceleration of 

a point in the vehicle perpendicular to 

the vehicle x axis (longitudinal) and 

parallel to the road plane.’’

The Alliance/AIAM stated that the 

NPRM does not define a method of 

determining lateral acceleration at the 

vehicle’s center of gravity (Aycg). In 

response, the commenters 

recommended that, in the final rule, the 

agency should specify that the 

accelerometers be placed on the 

centerline of the vehicle and on the 

floor between the front and rear seat 

whenever possible (or as close to that 

location as possible). With respect to 

Aycg, the commenters requested that 

the agency incorporate the following 

formula into the standard: 

The term ‘‘lateral acceleration’’ is 

used in the regulation text and so the 

agency has decided to add a definition 

to section S4. The agency will use the 

definition as recommended by the 

Alliance/AIAM and provided in SAE 

J670E, Vehicle Dynamics Terminology 

(rev. July 1976): 

Lateral Acceleration means the component 

of the vector acceleration of a point in the 

vehicle perpendicular to the vehicle x axis 

(longitudinal) and parallel to the road plane. 

The formula for computing lateral 

acceleration suggested by the 

commenters is an abbreviated version of 

what NHTSA has been using for many 

years. A qualitative description of 

NHTSA’s methods for determining the 

corrected lateral acceleration have been 

included in a new section S7.11 of the 

final rule that deals with data 

processing. A complete suite of the 

equations used by NHTSA (i.e., those 

applicable to not only lateral 

acceleration, but for longitudinal 

acceleration as well), are provided in 

the laboratory test procedure. 

Additionally, these equations have been 

incorporated into the Common Data 

Processing Kernel described in Section 

IV.C.7(e)(vi). 

(b) Lateral Displacement Calculation 

Regarding calculation of lateral 

displacement, paragraphs S5.2.3.1 and 

S5.2.3.2 of the proposal stated that such 

calculation would use double 

integration with respect to time of the 

measurement of lateral acceleration at 

the vehicle center of gravity (where 

time, t = 0, for the integration operation 

is the instant of steering initiation), as 

expressed by the following formula: 

Lateral dt Displacement = Ay ∫∫ C.G.

Delphi agreed that, given the short 

interval of time in the initial phase of 

the lane change maneuver, it is 

reasonable to use double integration of 

measured lateral acceleration to 

approximate the vehicle’s actual lateral 

displacement. Still, the commenter 

argued that the two are technically not 

exactly equivalent, because lateral 

acceleration is measured in the 

coordinate frame of the vehicle, whereas 

lateral displacement is in the fixed 

reference frame of the road (i.e., the 

surface of the earth). According to the 

commenter, the vehicle frame can rotate 

with respect to the earth frame, leading 


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to an error in the double integration 

method. Thus, Delphi stated that it 

should be expected that there will 

always be a small error in calculation of 

a vehicle’s lateral displacement due to 

coordinate system differences. 

Nevertheless, Delphi commented that 

this error is likely to be small enough to 

be insignificant when compared to the 

actual displacement encountered during 

a particular test maneuver, given that 

the vehicle’s rotation is small (less than 

20 degrees) in the early stage of the lane 

change maneuver. However, the 

commenter seemed to suggest that the 

agency should somehow acknowledge 

and account for such error as part of the 

ESC performance requirement. 

We agree with Delphi’s comment 

stating the double integration method 

used to calculate lateral displacement 

may produce a small error compared to 

actual displacement encountered during 

a particular test maneuver. However, 

like Delphi, we believe that because the 

integration interval is short (since lateral 

displacement is assessed 1.07 seconds 

after initiation of the maneuver’s 

steering inputs), the integration errors 

are expected to be so small as to be 

negligible. Therefore, we do not believe 

that any changes to the regulatory text 

are needed to account for this 

inaccuracy. 

(c) Yaw Rate Calculation 

The NPRM set forth the following 

stability criteria for ESC systems. The 

yaw rate measured one second after 

completion of the sine with dwell 

steering input (time T0 + 1 in Figure 1) 

must not exceed 35 percent of the first 

peak value of yaw velocity recorded 

after the beginning of the dwell period 

(y« Peak in Figure 1) during the same test 

run (see S5.2.1), and the yaw rate 

measured 1.75 seconds after completion 

of the Sine with Dwell steering input 

must not exceed 20 percent of the first 

peak value of yaw velocity recorded 

after the beginning of the dwell period 

during the same test run (see S5.2.2). 

The Alliance and AIAM requested a 

modification to the yaw rate ratio 

calculation methodology set forth in 

S5.2.1 and S5.2.2, which specify that

‘‘ * * * first peak value of yaw velocity 

recorded after the beginning of the 

dwell period. * * * ’’ The commenters 

stated that the first peak often occurs 

near the start of the dwell, and it can 

actually occur before the start of the 

dwell. In order to account for this 

possibility and to ensure that the 

calculation is correct and consistent in 

all cases, the Alliance/AIAM comments 

recommended revising the relevant 

language of S5.2.1 and S5.2.2 as follows: 

‘‘ * * * first peak value of yaw velocity 

recorded after the steering wheel angle 

changes sign (between first and second 

peaks) * * * ’’

According to Honda, the proposed 

rule would require that the tested 

vehicle suppress the yaw rate after 

completion of the Sine with Dwell 

steering input within the specified 

performance requirements, one of which 

is that the yaw rate may not exceed the 

specified threshold. Honda stated that 

the agency itself has acknowledged that 

in certain instances, negative yaw rates 

may be produced and measured. Thus, 

Honda recommended modifying S5.2.1 

and S5.2.2 to specify that the 

measurement is for the ‘‘absolute value 

of yaw rate’’ (rather than simply ‘‘yaw 

rate,’’ as proposed), in order ensure that 

any negative yaw rate is included in the 

standard’s yaw rate calculation. 

We agree with the Alliance/AIAM 

comment on this issue. Because their 

proposed regulatory language better 

expresses what NHTSA intended, we 

have decided to modify paragraphs 

S5.2.1 and S5.2.2 to read as follows: 

S5.2.1 The yaw rate measured one second 

after completion of the sine with dwell 

steering input (time T0 + 1 in Figure 1) must 

not exceed 35 percent of the first peak value 

of yaw rate recorded after the steering wheel 

angle changes sign (between first and second 

peaks) (y« Peak in Figure 1) during the same test 

run, and 

S5.2.2 The yaw rate measured 1.75 

seconds after completion of the sine with 

dwell steering input must not exceed 20 

percent of the first peak value of yaw rate 

recorded after the steering wheel angle 

changes sign (between first and second 

peaks) during the same test run. 

However, we do not agree with 

Honda’s comment. A negative yaw rate 

ratio can only be achieved when the 

yaw rate measured at a given instant in 

time is in an opposite direction of the 

second yaw rate peak, which can have 

a much different meaning than the 

absolute value of identical magnitude. 

Although it is very unlikely, taking the 

absolute value of the yaw rate at 1.0 or 

1.75 seconds after completion of steer 

could cause a compliant vehicle be 

deemed non-complaint if the respective 

yaw rate ratios are large enough. For 

example, if at 1.75 seconds after 

completion of steer a vehicle produces 

a yaw rate ratio of ¥21 percent, the 

vehicle would be in compliance with 

our proposed lateral stability criteria. 

However, if the absolute value of the 

yaw rate ratio were used (21 percent), 

the vehicle’s performance would be 

non-compliant. 

Requiring a provision that prevents a 

negative yaw rate ratio does not simplify 

the data analysis process, and can only 

confound interpretation of the test data. 

We see no reason to accept this 

recommendation from Honda. 

(d) Temperature and Pavement 

Specifications 

As part of the Alliance/AIAM 

comment regarding the effect on the 

margin of compliance for the 

responsiveness criterion (S5.2.3) of the 

observed variability inherent in vehicle 

testing, the parties made specific 

suggestions about the temperature and 

pavement specifications (S6) for the test. 

The NPRM proposed that the ambient 

temperature for testing would be 

between 0 °C (32 °F) and 40 °C (104 °F) 

(see S6.1.1). 

According to the Alliance/AIAM 

comments, their research demonstrates 

that responsiveness is reduced at higher 

temperatures, which is typical of 

vehicles with all-season tires. It 

recommended that testing should be 

conducted in a range of 50 °F to 104 °F, 

in order to reduce the temperature 

sensitivity effect demonstrated at low 

temperatures. The Alliance/AIAM 

comments stated that if this more 

restricted temperature range is 

multiplied by the temperature 

sensitivity of the relatively sensitive test 

vehicle examined, the maximum change 

in lateral displacement due to 

temperature variability should be 

limited to 0.3 to 0.4 feet. 

NHTSA understands the Alliance/ 

AIAM suggestion to be a comment on 

the general desirability of reducing 

sources of variability in vehicle testing, 

because its suggestion would have the 

effect of preventing NHTSA compliance 

testing at temperatures that favor a 

vehicle’s chance of passing the test. 

However, it also has the disadvantage of 

reducing the length of the testing season 

for NHTSA’s potential compliance test 

contractors located in colder States. We 

agree with the goal of better 

repeatability but prefer a minimum 

temperature of 7 °C (45 °F) for the sake 

of practicability. We believe that 

conducting testing down to 7 °C (45 °F) 

will still prevent the low temperature 

effects which the commenters seek to 

address and will not impact our ability 

to evaluate the performance of ESC 

systems. Accordingly, we are amending 

S6.1.1 to read as follows: 

S6.1.1 The ambient temperature is 

between 7 °C (45 °F) and 40 °C (104 °F). 

The NPRM proposed the following 

specifications for the road test surface 

(see S6.2). The test would be conducted 

on a dry, uniform, solid-paved surface 

(i.e., without irregularities and 

undulations such as dips and large 

cracks) (see S6.2.1). As proposed, the 

road test surface would be required to 

produce a peak friction coefficient (PFC) 


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of 0.9 ± 0.05 when measured using an 

American Society for Testing and 

Materials (ASTM) E1136 standard 

reference test tire, in accordance with 

ASTM Method E 1337–90, at a speed of 

64.4 km/h (40 mph), without water 

delivery (see S6.2.2). The proposal also 

specified that the test surface would 

have a consistent slope between level 

and 2% and that all tests are to be 

initiated in the direction of positive 

slope (uphill) (see S6.2.3). 

The Alliance/AIAM argued that the 

actual surfaces of many of the test 

facilities used to develop the supporting 

performance data (test facility 

characteristics provided in a table in the 

comments) would not meet the 

specifications in the standard. The 

commenters argued that the proposed 

requirement in S6.2.3 that ‘‘all tests are 

to be initiated in the direction of 

positive slope (uphill)’’ is unduly 

restrictive and would preclude the use 

of a number of test tracks where the 

slope runs either perpendicular or 

diagonal to the length of the track, 

because such tracks would not provide 

enough room to run the test. The 

commenter also stated that their review 

suggested that most test tracks have a 

slope of 1 percent or less. Accordingly, 

the Alliance/AIAM recommended that 

in the final rule, the agency should 

modify S6.2.3 as follows to tighten the 

proposed 2 percent maximum slope 

restriction to 1 percent and to eliminate 

the direction requirement. More 

importantly, the commenters argued 

that the lower end of the peak friction 

coefficient range was not representative 

of the test facilities used in the research. 

Therefore, the Alliance/AIAM 

recommended increasing the nominal 

specification from 0.9 ± 0.05 to 0.95 ± 

0.05. 

In response to these comments, we 

note that NHTSA based its surface 

coefficient specification on FMVSS No. 

135, Light Vehicle Brake Systems, which 

simply specifies a peak friction 

coefficient (PFC) of 0.9. While it is 

unlikely that any facility has exactly 

that PFC, NHTSA’s compliance testing 

for Standard No. 135 is performed on a 

surface with a PFC somewhat higher 

than the specification which creates a 

margin for clear enforcement, and 

manufacturers who are assuring 

themselves of compliance may wish to 

test on a surface slightly below the 

specification to create a compliance 

margin for themselves. In attempting to 

increase objectivity by putting a 

tolerance on the 0.9 PFC, the NPRM 

created the possibility of compliance 

tests for Standard No. 126 being 

performed on lower coefficient surfaces 

than those for Standard No. 135. That 

was not NHTSA’s intention, and we are 

changing the specification to match that 

in Standard No. 135, using the same 

compliance testing conventions. 

We are also reducing the maximum 

slope tolerance which eliminates the 

need for a directional specification. We 

agree that most test tracks have a slope 

of 1 percent or less, which is so slight 

that a directional specification is 

unnecessary—in effect, there is no 

uphill to worry about. Accordingly, we 

are amending S6.2.2 and S6.2.3 to read 

as follows: 

S6.2.2 The road test surface must produce 

a peak friction coefficient (PFC) of 0.9 when 

measured using an American Society for 

Testing and Materials (ASTM) E1136–93 

(1993) standard reference test tire, in 

accordance with ASTM Method E 1337–90 

(rev. 1996), at a speed of 64.4 km/h (40 mph), 

without water delivery. These standards are 

here incorporated by reference as explained 

in S3.2 above. 

S6.2.3 The test surface has a consistent 

slope between level and 1%. 

(e) Data Processing Issues 

In order to ensure consistent 

calculation of lateral displacement, the 

Alliance and AIAM recommended 

specification of the following details 

related to data processing in the 

regulatory text for FMVSS No. 126. 

(i) Determination of Beginning of 

Steering 

The Alliance/AIAM comments 

recommended that the start of steering 

be defined as the moment when the 

‘‘zeroed’’ steering wheel angle (SWA) 

passes through 5 degrees. The 

commenters stated that this 

modification is important to ensure that 

the start of steering is determined to 

accurately and consistently calculate 

performance metrics for the Sine with 

Dwell test. 

The process used by NHTSA to 

identify ‘‘beginning of steering’’ uses 

three steps. In the first step, the time 

when steering wheel velocity that 

exceeds 75 deg/sec is identified. From 

this point, steering wheel velocity must 

remain greater than 75 deg/sec for at 

least 200 ms. If the condition is not met, 

the next time steering wheel velocity 

that exceeds 75 deg/sec is identified and 

the 200 ms validity check is applied. 

This iterative process continues until 

the conditions are satisfied. In the 

second step, a zeroing range defined as 

the 1.0 second time period prior to the 

instant the steering wheel velocity 

exceeds 75 deg/sec (i.e., the instant the 

steering wheel velocity exceeds 75 deg/ 

sec defines the end of the ‘‘zeroing 

range’’) is used to zero steering wheel 

angle data. In the third step, the first 

instance the filtered and zeroed steering 

wheel angle data reaches ¥5 degrees 

(when the initial steering input is 

counterclockwise) or +5 degrees (when 

the initial steering input is clockwise) 

after the end of the zeroing range is 

identified. The time identified in Step 3 

is taken to be the beginning of steer. 

The agency agrees that an 

unambiguous reference point to define 

the start of steering is necessary in order 

to ensure consistency when computing 

the performance metrics measured 

during compliance testing. The practical 

problem is that typical ‘‘noise’’ in the 

steering measurement channel causes 

continual small fluctuations of the 

signal about the zero point, so departure 

from zero or very small steering angles 

does not indicate reliably that the 

steering machine has started the test 

maneuver. NHTSA’s extensive 

evaluation of zeroing range criteria (i.e., 

that based on the instant a steering 

wheel rate of 75 deg/sec occurs) has 

confirmed that the method successfully 

and robustly distinguishes the initiation 

of the Sine with Dwell steering inputs 

from the inherent noise present in the 

steering wheel angle data channel. As 

such, the agency has incorporated the 

75 deg/sec criterion described above 

plus the commenter’s suggestion of the 

5 degree steering measurement into 

S7.11, a new section on data processing 

added to the final rule in response to 

comments. The value for time at the 

start of steering, used for calculating the 

lateral responsiveness metrics described 

in Section IV.C.7(b), is interpolated. 

(ii) Determination of End of Steering 

The Alliance/AIAM recommended 

defining the end of steering event as the 

first occurrence of the ‘‘zeroed’’ steering 

wheel angle crossing zero degrees after 

the second peak of steering wheel angle. 

The commenters stated that this 

modification is important to ensure that 

the end of steering is determined to 

accurately and consistently calculate 

some of the performance metrics for the 

Sine with Dwell test. 

The agency agrees that an 

unambiguous point to define the end of 

steering is also necessary for 

consistency in computing the 

performance metrics measured during 

compliance testing. The agency has 

incorporated the commenter’s 

suggestion of the first occurrence of the 

‘‘zeroed’’ steering wheel angle crossing 

zero degrees after the second peak of 

steering wheel angle in S7.11, a new 

section on data processing added to the 

final rule. While signal noise results in 

continual zero crossings as long the data 

is being sampled, the first zero crossing 

after the steering wheel has begun to 


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return to the zero position is a logical 

end to the steering maneuver. 

(ii) Removing Offsets 

The Alliance/AIAM comments 

recommended that, given the potential 

for the accelerometers used in the 

measurement of lateral displacement to 

drift over time, the agency should use 

the data one second before the start of 

steering to ‘‘zero’’ the accelerometers 

and roll signal. 

Prior to the test maneuver, the driver 

must orient the vehicle to the desired 

heading, position the steering wheel 

angle to zero, and be coasting down (i.e., 

not using throttle inputs) to the target 

test speed of 50 mph. This process, 

known as achieving a ‘‘quasi-steady 

state,’’ typically occurs a few seconds 

prior to initiation of the maneuver, but 

can be influenced by external factors 

such as test track traffic, differences in 

vehicle deceleration rates, etc. Any 

zeroing performed on test data must be 

performed after a quasi-steady state 

condition has been satisfied, but before 

the maneuver is initiated. The proposed 

zeroing duration of one second provides 

a good combination of sufficient time 

(i.e., enough data is present so as to 

facilitate accurate zeroing of the test 

data) and performability (i.e., the 

duration is not so long that it imposes 

an unreasonable burden on the driver). 

For past research, NHTSA has used 

zeroing intervals between 0.5 and 1.0 

seconds. Our experience has shown the 

use of a 0.5 second interval is usually 

sufficient; however, the 1.0 second is 

more conservative and therefore 

preferred. We do not believe zeroing 

intervals longer than one second will 

improve the zeroing accuracy. 

(iv) Use of Interpolation 

According to the Alliance/AIAM, 

there are several events in the 

calculation of performance metrics that 

require determining the time and/or 

level of an event, including: (1) Start of 

steering; (2) 1.07 or 1.32 seconds after 

the start of steering; (3) end of steering; 

(4) 1 second after the end of steering, 

and (5) 1.75 seconds after the end of 

steering. The commenters recommended 

using interpolation for all of these 

circumstances, because such practice 

provides more consistent results and is 

less sensitive to differing sampling rates 

than other approaches (e.g., choosing 

the sample that is closest in time to the 

desired event). Interpolation is a way of 

computing the exact time that the 

continuous steering signal crossed zero, 

even though the digital samples did not 

coincide with the exact zero point, but 

rather consisted of one sample slightly 

before the time of zero-crossing and one 

slightly after. 

In determining specific timed and 

measured data points, the agency agrees 

with the Alliance and AIAM that the 

method of interpolation provides the 

most consistent results. Therefore, the 

agency will use this method during post 

data processing, as specified in S7.11. 

(v) Method for Determining Peak 

Steering Wheel Angle 

The Alliance/AIAM stated that 

because metrics for responsiveness are 

specified by steering wheel angle 

(SWA), a method for determining the 

actual SWA needs to be specified in the 

final rule for ESC. The commenters 

recommended using the first measured 

peak SWA, as it is the peak that directly 

influences the responsiveness 

measurement. 

For the reasons discussed in our 

response to public comments on our 

lateral responsiveness criteria, we have 

decided in the final rule to define the 

torque capacity of the steering machine 

used in the responsiveness test and to 

use the commanded peak steering angle, 

rather than the measured peak steering 

angle, as the indication of tests in which 

the vehicle must meet the 

responsiveness criteria (see Section 

IV.C.5). 

(vi) Need for a Common Data Processing 

Kernel 

According to the Alliance/AIAM, data 

processing methods have a significant 

impact on the results that are generated. 

The commenters stated that as a longerterm objective, the agency should work 

with interested parties to develop and 

incorporate into the standard (either 

directly or by reference) detailed 

algorithms for processing of data and 

stability/responsiveness metric 

calculations. The Alliance/AIAM 

commented that a similar procedure is 

already in place in other safety 

standards (e.g., FMVSS No. 208). 

The agency agrees that data 

processing methods can have a 

significant impact on the results 

generated. To address this issue we have 

added necessary data processing details 

to the regulation text of the standard 

and plan to include in the compliance 

test procedure the MATLAB code used 

for post-processing critical yaw rate and 

lateral displacement performance data. 

(f) ESC Initialization Period 

Delphi stated that most ESC systems 

typically require a short initialization 

period after the start of each new 

ignition cycle, during which time the 

ESC system is not operational. The 

commenter stated that during this 

period, the ESC performs diagnostic 

checks and sensor signal correlation 

updates. Delphi commented that the 

duration of this ESC initialization 

interval may depend upon several 

factors, including distance traveled, 

speed, and/or signal magnitudes. 

In response to other comments, we 

have modified S5.1.2 to clarify that ESC 

does not need to be active when the 

vehicle speed is below 15 km/h (9.3 

mph). Therefore, the ESC manufacturer 

has a short period of time, from the time 

the vehicle’s ignition is turned on to the 

time when the vehicle speed first 

exceeds 15 km/h (9.3 mph) to initialize 

ESC. The process of initializing ESC is, 

in many ways, similar to the process of 

initializing ABS. ABS systems typically 

have completed their initialization by 

the time the vehicle reaches speeds of 

5 km/h (3.1 mph) to 9 km/h (5.6 mph). 

Therefore, NHTSA believes that 

allowing up to a speed of 15 km/h (9.3 

mph) should be adequate to initialize 

ESC. 

Honda, Continental and the Alliance/ 

AIAM have pointed out that some types 

of diagnostic checks cannot be 

performed unless the vehicle is making 

turns or traveling at relatively high 

speeds. We have modified S7.10 to 

accommodate these types of diagnostic 

checks, as explained in the answer to 

Issue 8(b) below, ‘‘Practicability 

Problems with Malfunction Detection.’’

However, our expectation is that the 

ESC manufacturer can assume that the 

ESC has not malfunctioned and make 

the system operational once driving 

situations occur that permit these 

diagnostic checks to be performed. 

(g) ESC Calibration 

Mr. Petkun commented that the 

agency should require ESC systems to 

be calibrated to activate ‘‘at the precise 

moment that the vehicle may go out of 

control.’’ The commenter also suggested 

that the ESC system should be matched 

to the type of vehicle and complement 

driver characteristics; for example, Mr. 

Petkun stated that a minivan’s ESC 

might be tuned to respond to vehicle 

movements at a slightly earlier point 

than an ESC system on a sports coupe 

or sedan. 

With respect to Mr. Petkun’s first 

comment, it is important to recognize 

that determining when ESC intervention 

must occur is a complicated balance of 

effectiveness and intrusiveness. Loss of 

control is not usually a binary 

condition. As such, one of the 

challenges of designing ESC control 

algorithms is how to anticipate when a 

loss-of-control situation may occur. 

More conservative algorithms may be 

tuned to activate sooner than those 


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allowing the vehicle to achieve higher 

slip angles prior to activation. However, 

the longer an intervention is delayed, 

the more aggressive it must typically be 

later in the maneuver in order to still be 

effective. Therefore, determining when 

intervention should occur is a decision 

not only based on achieving good ESC 

performance, but also how sensitive 

individual drivers may be to the manner 

in which the intervention occurs. 

Although NHTSA has no way of 

resolving this subjective dilemma (an 

issue for each vehicle manufacturer and 

its ESC vendor to resolve), we can 

objectively assess how effective the final 

tuning is on a vehicle’s lateral stability 

and responsiveness using the Sine with 

Dwell test maneuver and our ESC 

performance criteria. 

In regards to Mr. Petkun’s second 

comment, our discussions with ESC 

suppliers and vehicle manufacturers 

indicate that while different vehicles 

may use much of the same modular ESC 

hardware, the software controlling how 

each system operates contains make/ 

model specific information. One way to 

ensure that the ESC software has been 

appropriately adapted to a particular 

make/model is to perform test track 

performance evaluations. We believe the 

Sine with Dwell maneuver, and the 

lateral stability and responsiveness 

performance criteria that evaluate the 

test output, provide an excellent way of 

assessing ESC system performance for 

all light vehicles. Regardless of whether 

the driver is operating a minivan or a 

sports car, we believe the vehicle’s ESC 

should perform in an effective manner, 

quantified by successfully satisfying our 

minimum performance standards. 

Other Issues 

8. ESC Malfunction Detection 

Requirements 

Under paragraph S5.3, ESC 

Malfunction, the NPRM proposed that 

the vehicle must be equipped with a 

telltale that provides a warning to the 

driver not more than two minutes after 

the occurrence of one or more 

malfunctions that affect the generation 

or transmission of control or response 

signals in the vehicle’s electronic 

stability control system. The proposal 

also set forth the following additional 

requirement related to ESC malfunction 

detection. 

Specifically, the ESC malfunction 

telltale would be required to be 

mounted inside the occupant 

compartment in front of and in clear 

view of the driver (see S5.3.1) and be 

identified by the symbol shown for 

‘‘ESC Malfunction Telltale’’ in Table 1 

of Standard No. 101 (49 CFR 571.101) 

(see S5.3.2). The ESC malfunction 

telltale would be required to remain 

continuously illuminated under the 

conditions specified in S5.3 for as long 

as the malfunction(s) exists, whenever 

the ignition locking system is in the 

‘‘On’’ (‘‘Run’’) position (see S5.3.3), and 

except as provided in paragraph S5.3.5, 

each ESC malfunction telltale must be 

activated as a check of lamp function 

either when the ignition locking system 

is turned to the ‘‘On’’ (‘‘Run’’) position 

when the engine is not running, or 

when the ignition locking system is in 

a position between ‘‘On’’ (‘‘Run’’) and 

‘‘Start’’ that is designated by the 

manufacturer as a check position (see 

S5.3.4). The ESC malfunction telltale 

need not be activated when a starter 

interlock is in operation (see S5.3.5). 

The ESC malfunction telltale must 

extinguish after the malfunction has 

been corrected (see S5.3.6). 

Under the proposal, manufacturers 

would be permitted to use the ESC 

malfunction telltale in a flashing mode 

to indicate ESC operation (see S5.3.7). 

As discussed below, several 

commenters raised a variety of concerns 

regarding operation of the ESC 

malfunction indicator (with malfunction 

telltale-related issues addressed later in 

this document under section IV.C.9, 

ESC Telltale Requirements). 

(a) Types of Malfunctions To Be 

Detected 

In its comments, Nissan objected to 

the use of the term ‘‘any ESC 

component’’ in the ESC malfunction 

detection portion of the standard’s 

proposed test procedures (see S7.10.1), 

because the company believes that the 

term is not objective and is overly 

broad. Nissan stated that there are 

certain vehicle components which may 

be considered part of the ESC system, 

but whose failure would not impact the 

ability of the vehicle to meet the 

performance requirements specified 

under S5.2. The company used the 

example of a malfunction of the ESC off 

switch, the disconnection of which, it 

argued, would not ‘‘affect the generation 

or transmission of control or response 

signals in the vehicle’s electronic 

stability control system.’’ Accordingly, 

Nissan argued that the agency should 

specify which components it deems to 

be part of the ESC system for 

malfunction testing purposes. 

Unless a suitable resolution can be 

found to the ‘‘any ESC component’’

issue identified by Nissan, the company 

argued that the agency should delay the 

effective date for the ESC malfunction 

detection requirements until the end of 

the phase-in. Otherwise, Nissan again 

stated that it may not be able to garner 

sufficient carry-forward credits to meet 

the certification requirements of the 

phase-in. 

Likewise, Toyota Motor North 

America, Inc. (Toyota) commented on a 

particular problem regarding ESC 

malfunction detection that could affect 

its phase-in compliance and carryforward credits. Specifically, the 

difficulty is encountered because 

Toyota’s ESC electronic control unit 

(ECU) is integrated into the vehicle’s 

ABS ECU. According to the commenter, 

the problem involves the proposed test 

procedures under S7.10.1, which 

provide for ‘‘simulate[ing] one or more 

ESC malfunction(s) by disconnecting 

the power source to any ESC 

component, or disconnecting any 

electrical connection between ESC 

components.’’ As its vehicles are 

currently designed with a single ABS/ 

ESC ECU, Toyota stated that if the 

power source is disconnected, only the 

vehicle’s ABS malfunction lamp will 

illuminate, not the ESC malfunction 

telltale (although the company 

anticipates meeting the requirements of 

S7.10.1 for all other types of ESC 

malfunctions). Although Toyota stated 

its belief that illumination of the ABS 

malfunction lamp would be sufficient to 

warn drivers of a loss of function to the 

entire ABS/ESC system, it agreed that it 

would be possible to redesign its system 

to meet the proposed requirements of 

S7.10.1. However, Toyota projects that it 

will not be possible to resolve this 

problem until the end of the phase-in 

period. 

In response to the concerns of Nissan 

and Toyota, we would start by noting 

that the agency has delayed the effective 

date of the controls and displays aspects 

of the ESC standard to the end of the 

phase-in in response to a number of 

similar comments. Stated another way, 

the ESC system must meet the 

malfunction detection requirements of 

the standard, according to the final 

rule’s general phase-in schedule, but it 

need not signal the driver in a 

standardized fashion until the end of 

the phase-in. This delay in the effective 

date for the controls and displays 

requirements of the rule includes the 

‘‘ESC Off’’ control and telltale, thereby 

resolving one specific concern raised by 

Nissan related to its ability to earn 

carry-forward credits. 

As to the broader issue of which 

vehicle components are subject to ESC 

malfunction testing, we believe that a 

rule of reason applies. Simply stated, if 

a vehicle malfunction were to ‘‘affect 

the generation or transmission of control 

or response signals in the vehicle’s 

electronic stability control system,’’ it 

must be detectable by the ESC system. 


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In other words, if the malfunction 

impacts the functionality of the ESC 

system, the ESC system must be capable 

of detecting it. For shared or connected 

components, a malfunction need only 

be detected to the extent it may impact 

the ESC system’s operation. This is 

precisely the same malfunction 

requirements currently established for 

tire pressure monitoring systems 

(TPMS) under FMVSS No. 138. We see 

no reason why such a requirement, 

which is appropriate in the TPMS 

context, would be considered overly 

broad here. Furthermore, manufacturers 

are in a better position than the agency 

in terms of knowing the vehicle 

components involved in ESC operation. 

As a specific example for the sake of 

clarity, we would consider the 

disconnection of the ‘‘ESC Off’’ switch 

to be a malfunction suitable for 

simulation under the standard, because 

it directly impacts ESC operability (even 

though a manufacturer voluntarily 

provides such a switch). However, we 

would not consider the disconnection of 

an ancillary function such as a hillholding aid that may be controlled by a 

shared ESC computer to be a fault in the 

ESC system itself. 

We are aware that because this final 

rule accelerates the phase-in schedule 

for ESC, it also creates greater pressure 

on manufacturers to earn carry-forward 

credits by installing compliant ESC 

systems as soon as possible. Again, 

because we think it is more important 

to have operating ESC systems sooner, 

we are moving the effective date of the 

standardization aspects of controls and 

displays to the end of the phase-in 

period. The specific difficulties recited 

by the commenters are analogous to the 

temporary lack of standardization that 

we find preferable to an overall phasein delay. Therefore, we have decided to 

address these manufacturers’ identified 

concerns in the following fashion. The 

test of the malfunction indicator calls 

for disconnecting various components 

to simulate a fault that should be 

detected. To reiterate the problems, 

when the power to the electronic 

control unit of some Toyota ESC 

systems is disconnected, the ABS 

malfunction telltale illuminates but the 

ESC malfunction telltale does not 

(because the control unit operates both 

systems), and disconnection of the 

optional ‘‘ESC Off’’ switch on some 

Nissan vehicles will not cause the 

malfunction telltale to illuminate. It has 

been the industry practice to provide a 

separate ESC malfunction telltale, in 

order to make consumers aware when 

this important safety device is 

potentially unavailable, but public 

comments have demonstrated that some 

additional time is necessary to 

standardize ESC malfunction telltale 

operation. We do not believe that 

vehicles with these minor deviations in 

the malfunction indicator should be 

disqualified for phase-in credit. 

One solution would be to move the 

provision for malfunction detection to 

the later effective date of the telltales 

and controls standardization. However, 

it is not necessary to relax the important 

requirement for a malfunction warning 

to avoid complicating the phase-in of 

ESC. Instead, we have decided to insert 

a very narrow temporary exception 

under paragraph S5.3.9 to address the 

specific malfunction testing issues 

brought forward by Nissan and Toyota: 

S.5.3.9 Prior to September 1, 2011, a 

disconnection of the power to the ESC 

electronic control unit may be indicated by 

the ABS malfunction telltale instead of the 

ESC malfunction telltale, and a 

disconnection of the ‘‘ESC Off’’ control need 

not illuminate the ESC malfunction telltale. 

(b) Practicability Problems With 

Malfunction Detection 

Under paragraph S7.10, ESC 

Malfunction Detection, the proposed 

test procedures for FMVSS No. 126 state 

that one or more ESC malfunction(s) 

would be simulated by disconnecting 

the power source to any ESC 

component, or disconnecting any 

electrical connection between ESC 

components (except for electrical 

connections for the telltale lamp(s)) (see 

S7.10.1). The proposed test procedures 

further provide, that with the vehicle 

stationary and the ignition locking 

system in the ‘‘Lock’’ or ‘‘Off’’ position, 

activate the ignition locking system to 

the ‘‘On’’ (‘‘Run’’) position and verify 

that within two minutes of activating 

the ignition locking system, the ESC 

malfunction indicator illuminates in 

accordance with S5.3 (see S7.10.2). 

TRW Automotive expressed concern 

that the ESC malfunction detection 

portion of the test procedures, as 

currently drafted, may pose a safety 

hazard to test technicians. Specifically, 

TRW Automotive stated that paragraph 

S7.10 does not indicate that the vehicle 

is to be turned off before ‘‘disconnecting 

the power source to any ESC 

component,’’ and paragraph S7.10.4 

merely states, ‘‘Restore the ESC system 

to normal operation and verify that the 

telltale has extinguished.’’ The 

commenter recommended that those 

two provisions be modified to explicitly 

state that the vehicle is to be in the ‘‘off’’

state prior to disconnecting or restoring 

the ESC system. 

Honda stated that its understanding of 

S7.10 is that this portion of the test 

procedure will be conducted with the 

vehicle stationary. However, Honda 

stated that vehicle motion is necessary 

for the system to be able to detect 

certain ESC malfunctions (e.g., damage 

to the pulser of the wheel speed sensor) 

and to later extinguish the telltale once 

the malfunction is corrected (similar 

comment provided by Bosch, 

Continental). Accordingly, Honda 

sought clarification that testing 

conducted pursuant to S7.10 will 

involve only those malfunctions 

amenable to detection based upon static 

activation and deactivation. 

Continental argued that some 

malfunctions are not time-based, but 

instead require comparisons of sensor 

outputs generated when the vehicle is 

driven. Accordingly, the commenter 

recommended elimination of the 

requirement that ESC malfunctions be 

detected within two minutes of 

occurrence, even if the vehicle is 

parked. Instead, Continental urged 

adoption of the following language: 

‘‘The vehicle must be equipped with a 

telltale that provides a warning to the 

driver when one or more malfunctions 

occur that affect the generation or 

transmission of control or response 

signals in the vehicles electronic 

stability control system.’’ (Similar 

comments were provided by Bosch and 

Delphi.) 

Similarly, the Alliance/AIAM 

commented that the proposed test 

procedure may be inadequate to detect 

a full range of electrical component 

failures, because some of these 

malfunctions cannot be detected when 

the vehicle is stationary. Instead, the 

commenters suggested that the agency 

adopt a more robust ESC malfunction 

test that would allow the engine to be 

running and the vehicle to be in motion 

as part of the diagnostic evaluation. To 

this end, the commenters suggested that 

the agency replace the existing 

provisions at S7.10.2 and S7.10.3 with 

the following language: 

S7.10.2 With the vehicle initially 

stationary and the ignition locking system in 

the ‘‘Lock’’ or ‘‘Off’’ position, activate the 

ignition system to the ‘‘Start’’ position and 

start the engine. Place the vehicle in a 

forward gear and obtain a steady speed of 30 

mph ± 5 mph. Drive the vehicle for at least 

two minutes, including at least one left and 

one right turning maneuver. Verify that 

within two minutes of obtaining this steady 

speed, the ESC malfunction indicator 

illuminates in accordance with 5.3. 

S7.10.3 Stop the vehicle, deactivate the 

ignition locking system to the ‘‘Off’’ of 

‘‘Lock’’ position. After a five-minute period, 

activate the vehicle’s ignition locking system 

to the ‘‘Start’’ position and start the engine. 

Verify that the ESC malfunction indicator 

again illuminates to signal a malfunction and 


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remains illuminated, as long as the engine is 

running or until the fault is corrected. 

NHTSA agrees with TRW Automotive 

that it is always prudent to make the 

disconnections and connections of ESC 

components with the power turned off, 

even though the components are 

generally powered by low-voltage DC 

current and the risk of harm to the 

vehicle would be greater than the risk to 

the technicians. Accordingly, we have 

amended paragraph S7.10.1 as follows, 

but we do not think the reminder need 

be repeated in S7.10.4 in view of other 

changes to its language being made. 

S7.10.1 Simulate one or more ESC 

malfunction(s) by disconnecting the power 

source to any ESC component, or 

disconnecting any electrical connection 

between ESC components (with vehicle 

power off). When simulating an ESC 

malfunction, the electrical connections for 

the telltale lamp(s) are not to be 

disconnected. 

NHTSA does not agree with Honda 

that S7.10 should be limited to only 

those malfunctions amenable to 

detection based upon static activation 

and deactivation. Our purpose in 

writing S7.10.2 was to ensure that ESC 

malfunctions would be detected within 

a reasonable time of starting to drive. 

The language proposed by the Alliance/ 

AIAM conforms to our original intent, 

while clarifying that the vehicle should 

be driven during the proposed twominute period so that the parts of its 

malfunction detection capability which 

depend on vehicle motion can operate. 

Accordingly, we are adopting the 

language suggested by the Alliance/ 

AIAM for S7.10.2 and S7.10.3. We 

believe that this change also addresses 

the comment by Continental that 

malfunction detection is not a timebased function but one that requires 

certain driving motions to make ESC 

self-testing possible. 

(c) Monitoring When System Is Off 

Honda sought clarification of the 

proposed standard to ensure that there 

is not an unintended requirement for 

the ESC system to maintain constant 

monitoring even when the ignition key 

is in the ‘‘off’’ position. Accordingly, 

Honda recommended modifying S5.3.6 

to read as follows: ‘‘The ESC 

malfunction telltale must extinguish at 

the initiation of the next ignition cycle 

after the malfunction has been 

corrected.’’ Honda also recommended 

modifying S7.10.4 to state: ‘‘Deactivate 

the ignition locking system to the ‘‘off’’

or ‘‘lock’’ position. Restore the ESC 

system to normal operation and verify 

that the telltale has extinguished.’’

Honda is correct that the agency does 

not expect the ESC system to maintain 

monitoring capability with vehicle 

turned off. However, we do not believe 

that it is necessary to restrict the 

extinguishing of the telltale to the exact 

instant of the initiation of the next 

ignition cycle. Therefore, we are 

amending paragraphs S5.3.6 (now 

S5.3.7) and S7.10.4 to read as follows: 

S5.3.7 The ESC malfunction telltale must 

extinguish at the next ignition cycle after the 

malfunction has been corrected. * * * 

S7.10.4 Deactivate the ignition locking 

system to the ‘‘off’’ or ‘‘lock’’ position. 

Restore the ESC system to normal operation, 

activate the ignition system to the ‘‘Start’’

position and start the engine. Verify that the 

telltale has extinguished. 

(d) Minimum Performance Level 

BorgWarner commented that the 

proposed ESC standard should set a 

defined minimum performance level for 

a vehicle when the ESC system is 

deactivated (i.e., ‘‘off’’) or when there is 

an ESC malfunction (which again may 

result in a failure mode of ESC ‘‘off’’). 

The commenter stated that unless this is 

done, negative safety consequences may 

arise under conditions where a driver is 

not aware of the vehicle’s baseline 

stability behavior. BorgWarner argued 

that establishing a minimum stability 

performance level for a deactivated ESC 

system would be analogous to the 

minimum performance standard which 

the agency adopted for ABS 

‘‘foundation’’ brake performance in the 

event ABS is deactivated due to a 

system malfunction. 

NHTSA considers ESC to be a safety 

feature added to vehicles whose basic 

chassis properties have been designed to 

match their intended purposes. Our 

discussion in Section IV.C.5 (Lateral 

Responsiveness Criteria) is based upon 

the expectation by both NHTSA and the 

industry that ESC will not cause 

changes in the basic chassis properties 

of vehicles. We expect that ESC 

activations will be rare events in panic 

situations and that drivers will not 

depend upon the ESC system in the 

ordinary operation of the vehicle. In the 

case of an ESC malfunction or failure, 

the ESC telltale warns the driver that the 

ESC system is non-operational and may 

require repair. However, pending the 

repair, the driver would be no more at 

risk than a person driving an older car 

without ESC. Unless future 

developments prove these assumptions 

to be false, there is no need for 

additional ‘‘minimum performance’’

requirements on base vehicles equipped 

with ESC. 

9. ESC Telltale Requirements 

(a) ESC Telltale 

As noted above, paragraph S5.3 of the 

ESC proposal would require each ESC 

system to include an ESC malfunction 

telltale mounted inside the occupant 

compartment in front of and in clear 

view of the driver (see S5.3.1) and 

identified by the symbol shown for 

‘‘ESC Malfunction Telltale’’ in Table 1 

of Standard No. 101 (49 CFR 571.101) 

(see S5.3.2). The ESC malfunction 

telltale would be required to remain 

continuously illuminated under the 

conditions specified in S5.3 for as long 

as the malfunction(s) exists, whenever 

the ignition locking system is in the 

‘‘On’’ (‘‘Run’’) position (see S5.3.3), and 

except as provided in paragraph S5.3.5, 

each ESC malfunction telltale must be 

activated as a check of lamp function 

either when the ignition locking system 

is turned to the ‘‘On’’ (‘‘Run’’) position 

when the engine is not running, or 

when the ignition locking system is in 

a position between ‘‘On’’ (‘‘Run’’) and 

‘‘Start’’ that is designated by the 

manufacturer as a check position (see 

S5.3.4). The ESC malfunction telltale 

need not be activated when a starter 

interlock is in operation (see S5.3.5). 

The ESC malfunction telltale must 

extinguish after the malfunction has 

been corrected (see S5.3.6). Under the 

proposal, manufacturers would be 

permitted to use the ESC malfunction 

telltale in a flashing mode to indicate 

ESC operation (see S5.3.7). 

Several commenters raised specific 

issues pertaining to the ESC 

malfunction telltale, which are set forth 

and addressed below. 

(i) Telltale Symbol Text Enhancement 

Although Advocates supported use of 

the ISO symbol, it argued that the 

telltale should also include the 

abbreviation ‘‘ESC,’’ because that would 

allow drivers to better understand that 

their vehicle is equipped with an ESC 

system. 

NHTSA shares the Advocates’

concern regarding the importance of 

promoting drivers’ understanding of 

ESC and whether or not their vehicle is 

equipped with ESC. However, we 

believe that augmenting the ESC 

malfunction telltale by adding the word, 

‘‘ESC,’’ is unlikely to address that 

concern. As explained in the NPRM, 

NHTSA’s research so far indicates that 

most drivers do not yet understand what 

‘‘ESC’’ means. Insofar as drivers will 

have to learn the precise meaning of any 

telltale offered by manufacturers to 

convey the idea of ESC, NHTSA does 

not believe it necessary at this time to 

specifically require a telltale that 


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57Paragraph S4 of FMVSS No. 101 (49 CFR 

571.101 S4) provides: 

S4. Definitions. 

Adjacent, with respect to a control, telltale or 

indicator, and its identifier means: 

(a) The identifier is in close proximity to the 

control, telltale or indicator; and 

(b) No other control, telltale, indicator, identifier 

or source of illumination appears between the 

identifier and the telltale, indicator, or control that 

the identifier identifies. 

includes both the symbol and the 

acronym. We have no evidence that 

both together will convey a greater 

benefit than either alone. Additionally, 

no other FMVSS has required both a 

symbol and a text term together for a 

telltale, so for the sake of consistency 

we are reluctant to do so now. We 

believe that the ESC malfunction telltale 

symbol and substitute ‘‘ESC’’ text can 

effectively be used interchangeably. We 

also believe that most drivers become 

increasingly familiar with the meaning 

of instrument panel telltales over time, 

and we expect that this will be the case 

with ESC telltales and substitute text, as 

well. 

Furthermore, NHTSA is sensitive to 

vehicle manufacturers’ stated concern 

that limited instrument panel area is 

available for locating telltales. Paragraph 

S5.2.3 of FMVSS No. 101, Controls and 

Displays, states that ‘‘[s]upplementary 

symbols, words, or abbreviations may be 

used at the manufacturer’s discretion in 

conjunction with any symbol, word, or 

abbreviation specified in Table 1 or 

Table 2.’’ Based on the above provision, 

augmenting the ISO symbol with the 

text ‘‘ESC’’ is permissible, provided that 

it does not violate the locational 

requirement contained in the definition 

of ‘‘adjacent’’ as specified in S4 of 

FMVSS No. 101.57

Therefore, for the reasons stated 

above, NHTSA believes that it is not 

necessary to require addition of the text 

‘‘ESC’’ to the ESC malfunction telltale. 

(ii) Telltale Symbol Alternative: 

Substitute Text 

The Alliance/AIAM asked the agency 

to permit the use of the symbol ‘‘ESC’’

without the ISO symbol, as an 

alternative to the proposed symbol 

when the warning is provided by the 

vehicle’s message/information center. 

These commenters argued that this 

approach is consistent with other 

FMVSS No. 101 Table 1 indicators. 

(Porsche Cars North America, Inc. 

(Porsche) made a similar comment.) 

NHTSA agrees with the commenters 

that the general approach of FMVSS No. 

101 is to provide flexibility to vehicle 

manufacturers via alternative text terms 

for telltales. Moreover, as the concept of 

ESC becomes more widely understood 

by drivers, we expect that offering the 

option of using the text term ‘‘ESC,’’ as 

opposed to manufacturer-specific ESC 

system acronyms, will facilitate driver 

recognition of the telltale. This 

promotes consistency in the telltale 

field, where there currently is little. 

Therefore, NHTSA has decided to 

permit use of the term ‘‘ESC’’ at the 

manufacturer’s discretion instead of the 

ISO symbol. As a result, we are 

modifying S5.3.2 to read as follows: 

S5.3.2 Effective September 1, 2011, must 

be identified by the symbol shown for ‘‘ESC 

Malfunction Telltale’’ or the specified words 

or abbreviations listed in Table 1 of Standard 

No. 101 (49 CFR 571.101); 

In the event that the text alternative 

for the ESC malfunction telltale is 

presented via the vehicle’s message/ 

information center (defined as a 

‘‘common space’’ under S4 of FMVSS 

No. 101), the conditions of S5.5.2 and 

S5.5.5 of FMVSS No. 101 (set forth 

below) must be met. While not specified 

in the proposed regulatory text, NHTSA 

believes it is necessary to modify S5.5.2 

and S5.5.5 of FMVSS No. 101 to place 

restrictions on the use of the ESC telltale 

in a common space. The amended 

language reads as follows: 

S5.5.2 The telltales for any brake system 

malfunction required by Table 1 to be red, air 

bag malfunction, low tire pressure, electronic 

stability control malfunction, passenger air 

bag off, high beam, turn signal, and seat belt 

must not be shown in the same common 

space.* * * 

S5.5.5 In the case of the telltale for a 

brake system malfunction, air bag 

malfunction, side air bag malfunction, low 

tire pressure, electronic stability control 

malfunction, passenger air bag off, high 

beam, turn signal, or seat belt that is designed 

to display in a common space, that telltale 

must displace any other symbol or message 

in that common space while the underlying 

condition for the telltale’s activation exists. 

Therefore, when presenting the ESC 

malfunction telltale in a vehicle’s 

common space display, the malfunction 

telltale must not appear in the same 

common space as any of the other listed 

telltales under paragraph S5.5.2 of 

FMVSS No. 101, and, when activated, it 

must displace any another message or 

symbol in its common space as long as 

the ESC malfunction condition exists, as 

required under paragraph S5.5.5 of 

FMVSS No. 101. For example, in the 

event that a failure of the ABS led to an 

ESC malfunction, both malfunctions 

would be required to be indicated to the 

driver and must be presented in 

separate common spaces. 

(iii) Waiver of Yellow Color 

Requirement for ESC Telltale When 

Message/Information Center Is Used 

The Alliance/AIAM asked the agency 

to waive the yellow color requirement 

when ESC malfunction indications are 

provided by the vehicle’s message/ 

information center, due to the difficulty 

associated with providing color in a 

message/information center (regardless 

of whether a text or symbol is used). 

The use of message/information 

centers for presentation of ESC 

malfunction information is permissible 

to the extent that the requirements of 

FMVSS No. 101 are met (see 49 CFR 

571.101 and discussion in Section 

IV.C.9(a)(ii) immediately above). The 

intent of the color requirements 

specified in Table 1 of FMVSS No. 101 

is that the color yellow be used to 

communicate to the driver a condition 

of compromised performance of a 

vehicle system that does not require 

immediate correction. The International 

Standards Organization (ISO) in its 

standard titled, ‘‘Road Vehicles—

Symbols for controls, indicators, and 

tell-tales’’ (ISO 2575:2004(E)), agrees 

with this practice through its statement 

of the meaning of the color yellow as 

‘‘yellow or amber: Caution, outside 

normal operating limits, vehicle system 

malfunction, damage to vehicle likely, 

or other condition which may produce 

hazard in the longer term.’’

In the context of ESC, the agency 

purposely chose to associate indication 

of an ESC system malfunction with a 

yellow, cautionary warning to the 

driver. NHTSA believes that this 

requirement must be maintained in 

order to properly communicate the level 

of urgency with which the driver must 

seek to remedy the malfunction of this 

important safety system. 

Furthermore, this policy is consistent 

with the agency’s decision in our 

September 7, 2005 final rule responding 

to petitions for reconsideration of the 

Tire Pressure Monitoring System 

(TPMS) final rule, in which petitioners 

raised the identical issue of waiving the 

yellow color requirement for TPMS 

malfunctions and low tire pressure 

warnings when presented via a 

message/information center (see 70 FR 

53079 (Sept. 7, 2005)). Therefore, 

NHTSA has decided to deny the request 

for waiver of the yellow color 

requirement for the ESC malfunction 

telltale or substitute text when a 

message/information center is used. 

(iv) Telltale Illumination Strategy 

Nissan stated that its current ESC 

systems utilize a telltale control logic 

that illuminates the ‘‘ESC Off’’ telltale 


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whenever the ESC malfunction telltale 

is illuminated. Nissan reasoned that this 

illumination strategy provides a clear 

message to the driver that the 

malfunctioning ESC system may not be 

able to perform normally and would 

therefore be ‘‘off’’ within the meaning of 

the standard’s performance 

requirements of S5.4, ESC Off Switch 

and Telltale (i.e., the system is in a 

mode that does not meet the 

requirements of S5.2, Performance 

Requirements). The commenter sought 

clarification that this telltale 

illumination strategy is permissible 

under the proposed ESC standard. (A 

similar comment was provided by the 

Alliance/AIAM.) 

Nissan has correctly interpreted the 

regulatory text to indicate that when an 

ESC malfunction situation exists, 

manufacturers may choose to illuminate 

the ‘‘ESC Off’’ telltale (per Table 1 of 

FMVSS No. 101) or display ‘‘ESC Off’’

text in a message/information center in 

addition to illuminating the separate 

ESC malfunction telltale to emphasize 

to the driver that ESC functionality has 

been reduced due to the failure of one 

or more ESC components. 

However, we believe that it is 

important to clarify here that the reverse 

situation (i.e., illuminating the ESC 

malfunction telltale in addition to the 

‘‘ESC Off’’ telltale when ESC has been 

manually switched off by the driver) is 

prohibited, unless an actual ESC 

malfunction condition exists. In such 

situations, an ESC system actively 

disengaged by the driver through an 

appropriate control is not 

malfunctioning, but is instead 

functioning properly. Furthermore, such 

an illumination strategy could cause 

driver confusion, which may in turn 

decrease confidence in the ESC system. 

(v) Telltale Extinguishment 

TRW Automotive urged NHTSA to 

clarify paragraph S5.3.6 of its proposal, 

which provides, ‘‘The ESC malfunction 

telltale must extinguish after the 

malfunction has been corrected.’’ The 

commenter argued that this provision 

may cause confusion, because it could 

be interpreted as implying that all ESC 

malfunctions will require corrective 

action by a third party (e.g., dealership, 

repair shop). Instead, TRW Automotive 

stated that there are numerous examples 

of situations in which outside 

intervention is not required to return the 

ESC system to normal operation, such as 

where a sensor may become temporarily 

inactive but subsequently returned to 

service. Accordingly, the company 

recommended revising S5.3.6 as 

follows: ‘‘The ESC malfunction telltale 

must extinguish after the ESC system 

has determined the malfunction no 

longer exists.’’

We clarify that in paragraph S5.3.6 of 

the NPRM, NHTSA did not intend to 

imply that all ESC malfunctions require 

corrective action by a third party. 

However, TRW Automotive’s suggested 

language is problematic, because, unlike 

the agency’s proposed language, it sets 

no requirement for the ESC system to 

actually determine and recognize that 

the malfunction no longer exists. 

Therefore, NHTSA has decided to retain 

the proposed requirement set forth in 

paragraph S5.3.6 without revision as 

part of this final rule. 

(vi) Telltale Location 

Consumers Union argued that, if the 

agency does decide to adopt a 

requirement for a visual warning of ESC 

activation, the standard should require 

an appropriate telltale in that vehicle’s 

‘‘instrument cluster’’ where its message 

would be more prominent, rather than 

in the vehicle’s center console (i.e., 

where the radio and climate control 

mechanisms are normally located). 

In paragraph S5.3.1 of the NPRM for 

FMVSS No. 126, NHTSA proposed to 

require that the ESC malfunction telltale 

‘‘[m]ust be mounted inside the occupant 

compartment in front of and in clear 

view of the driver.’’ In addition, 

paragraph S5.1.2 of FMVSS No. 101 

requires that ‘‘telltales and indicators 

* * * must be located so that, when 

activated, they are visible to the driver 

under the conditions of S5.6.1 and 

S5.6.2’’ (i.e., the driver has adapted to 

the ambient light roadway conditions 

and is properly restrained by the seat 

belts). NHTSA believes that these 

existing requirements are sufficiently 

stringent to ensure that vehicle 

manufacturers will locate the ESC 

malfunction telltale in a reasonable 

location, so the agency has decided that 

it is not necessary to specify that the 

ESC telltale must be located within the 

instrument panel area. 

(vi) Use of ESC Malfunction Telltale To 

Indicate Malfunctions of Related 

Systems/Functions 

The Alliance/AIAM commented that 

NHTSA should allow manufacturers to 

use the ESC malfunction indicator to 

indicate the malfunction of any ESCrelated system, including traction 

control, trailer stability assist, corner 

brake control, and other similar 

functions that use throttle and/or 

individual wheel torque control to 

operate and which share common 

components with the ESC system. The 

commenters stated that this approach 

would be directly analogous to the 

position the agency has taken with 

respect to the frontal air bag readiness 

indicator required by S4.5.2 of FMVSS 

No. 208, Occupant Crash Protection. 

The commenters quoted a letter from 

NHTSA to Porsche dated July 30, 1996, 

stating, ‘‘Since the dealer or repair 

business can inform the owner which 

system is malfunctioning, it does not 

matter that the indicator does not make 

that distinction.’’

NHTSA understands the commenters’

concerns regarding space limitations in 

the instrument panel for incorporation 

of additional telltales. While the 

International Standards Organization in 

its standard titled, ‘‘Road Vehicles—

Symbols for controls, indicators, and 

tell-tales’’ (ISO 2575:2004(E)), specifies 

telltales for ‘‘traction control’’ and 

‘‘traction control off or not available,’’

we agree that our established position 

noted by the commenter in relation to 

air bags may be similarly applied here. 

We believe that a single malfunction 

telltale that relates to a vehicle’s 

stability-related safety systems generally 

is sufficiently informative for the driver, 

and it should be effective in conveying 

to the driver that a malfunction has 

occurred which may require diagnosis 

and service by a repair facility. Thus, we 

are revising Table 1 of FMVSS No. 101 

to include a note referring to the ESC 

malfunction telltale that states: 

This symbol may also be used to indicate 

the malfunction of related systems/functions 

including traction control, trailer stability 

assist, corner brake control, and other similar 

functions that use throttle and/or individual 

torque control to operate and share common 

components with the ESC system. 

(b) ‘‘ESC Off’’ Indication 

If the vehicle manufacturer chooses to 

install a driver-selectable control (an 

‘‘ESC Off’’ control) that places the ESC 

system in a mode that does not satisfy 

the performance requirements of the 

standard, then the proposal would 

require the manufacturer to provide an 

‘‘ESC Off’’ telltale to alert the driver 

when the vehicle has been placed in 

such a mode (see S5.4.2). Specifically, 

the NPRM proposed that the ‘‘ESC Off’’

switch and telltale must be identified by 

the symbol shown for ‘‘ESC Off’’ in 

Table 1 of Standard No. 101 (49 CFR 

571.101) (see S5.4.3), and the telltale 

must be mounted inside the occupant 

compartment in front of and in clear 

view of the driver (see S5.4.4). The ESC 

telltale symbol indicating ‘‘ESC Off’’

proposed by NHTSA consists of the ISO 

symbol J.14 with the English word, 

‘‘Off,’’ beneath it. No text substitution 

for the ‘‘ESC Off’’ telltale was offered as 

part of the proposal. 

It further proposed that the ‘‘ESC Off’’

telltale remain continuously illuminated 


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for as long as the ESC is in a mode that 

renders it unable to satisfy the 

requirements of S5.2.1, S5.2.2 and 

S5.2.3 (see S5.4.5), and except as 

provided in paragraph S5.4.7, each 

‘‘ESC Off’’ telltale must be activated as 

a check of lamp function either when 

the ignition locking system is turned to 

the ‘‘On’’ (‘‘Run’’) position when the 

engine is not running, or when the 

ignition locking system is in a position 

between ‘‘On’’ (‘‘Run’’) and ‘‘Start’’ that 

is designated by the manufacturer as a 

check position (see S5.4.6). The ‘‘ESC 

Off’’ telltale would not need to be 

activated when a starter interlock is in 

operation (see S5.4.7). The ‘‘ESC Off’’

telltale would be required to extinguish 

after the ESC system has been returned 

to its fully functional default mode (see 

S5.4.8). 

Several commenters raised specific 

issues pertaining to the ESC Off control 

and telltale, which are set forth and 

addressed below. 

(i) ‘‘ESC Off’’ Symbol Alternative: Use of 

Text 

In their comments, the Alliance/ 

AIAM asked the agency to permit the 

use of the text ‘‘ESC Off’’ without the 

ISO symbol (J.14) to indicate that the 

ESC system has been switched off. The 

commenters argued that such approach 

is consistent with other FMVSS No. 101 

Table 1 indicators. 

Pursuant to the discussion in Section 

IV.C.9(a)(ii) above, NHTSA has decided 

to revise S5.4.3 (now S5.4.2 and S5.5.2) 

to permit use of the term ‘‘ESC Off’’ at 

the manufacturer’s discretion as follows: 

S5.4.2 Effective September 1, 2011, a 

control whose only purpose is to place the 

ESC system in a mode in which it will no 

longer satisfy the performance requirements 

of S5.2.1, S5.2.2 and S5.2.3 must be 

identified by the symbol shown for ‘‘ESC 

Off’’ in Table 1 of Standard No. 101 (49 CFR 

571.101) or the text, ‘‘ESC Off’’ as listed 

under ‘‘Word(s) or Abbreviations’’ in Table 1 

of Standard No. 101 (49 CFR 571.101); * * * 

S5.5.2 Effective September 1, 2011, the 

‘‘ESC Off’’ telltale must be identified by the 

symbol shown for ‘‘ESC Off’’ in Table 1 of 

Standard No. 101 (49 CFR 571.101) or the 

text, ‘‘ESC Off’’ as listed under ‘‘Word(s) or 

Abbreviations’’ in Table 1 of Standard No. 

101 (49 CFR 571.101). 

(ii) Waiver of Yellow Color Requirement 

When ‘‘ESC Off’’ Is Indicated Via 

Message/Information Center Text 

In their comments, the Alliance/ 

AIAM requested a waiver of the yellow 

color requirement when ‘‘ESC Off’’

indications are provided via the 

vehicle’s message/information center, 

due to the difficulty associated with 

providing color in a message/ 

information center. (Porsche made a 

similar comment.) 

As explained in Section IV.C.9(a)(iii) 

above, the use of message/information 

centers for presentation of required ESC 

information is permissible to the extent 

that the requirements of FMVSS No. 101 

are met (see 49 CFR 571.101 and 

discussion in Section IV.C.9(a)(ii) 

immediately above). The intent of the 

color requirements specified in Table 1 

of FMVSS No. 101 is that the color 

yellow be used to communicate to the 

driver a condition of compromised 

performance of a vehicle system that 

does not require immediate correction. 

The International Standards 

Organization in its standard titled, 

‘‘Road Vehicles—Symbols for controls, 

indicators, and tell-tales’’ (ISO 

2575:2004(E)), agrees with this practice 

through its statement of the meaning of 

the color yellow as ‘‘yellow or amber: 

Caution, outside normal operating 

limits, vehicle system malfunction, 

damage to vehicle likely, or other 

condition which may produce hazard in 

the longer term.’’

NHTSA believes that operating ESC in 

a mode other than ‘‘full on’’ qualifies as 

a condition of ‘‘compromised 

performance.’’ Therefore, NHTSA 

believes that the yellow color 

requirement must be maintained in 

order to properly communicate the 

condition of potentially decreased safety 

to the driver. Accordingly, NHTSA has 

decided to deny the request for waiver 

of the yellow color requirement for the 

‘‘ESC Off’’ telltale or substitute text 

when a message/information center is 

used. As noted in Section IV.C.9(a)(iii), 

this decision is consistent with the 

identical issues raised in petitions for 

reconsideration of the TPMS rule. 

(iii) ‘‘ESC Off’’ Telltale Clarification 

The Alliance/AIAM recommended 

that the final rule should clarify that the 

‘‘ESC Off’’ telltale can be illuminated 

whenever the ESC system is in a mode 

other than the fully active system, even 

if, at that level, the system would meet 

the requirements of FMVSS No. 126. 

As discussed above, paragraph S5.4 of 

the NPRM proposed to require that the 

‘‘ESC Off’’ telltale must remain 

continuously illuminated for as long as 

the ESC is in a driver-selected mode that 

renders it unable to satisfy the 

requirements of S5.2.1, S5.2.2 and 

S5.2.3 (see S5.4.5). In their comments, 

the Alliance/AIAM suggested that 

manufacturers should be permitted to 

use the ‘‘ESC Off’’ telltale to alert the 

driver that the system is in a mode less 

than fully active, regardless of whether 

it could meet the requirements of S5.2.1, 

S5.2.2 and S5.2.3 at that level. After 

careful consideration, NHTSA agrees 

that permitting vehicle manufacturers to 

employ an illumination strategy as 

suggested by the Alliance/AIAM may 

help to remind drivers when their 

vehicle’s ESC system has been placed in 

a mode of less than maximal 

effectiveness and to encourage them to 

rapidly return the system to fullyfunctional status. Certain modifications 

to the regulatory text are required to 

achieve this result, because S5.3.1(e) of 

FMVSS 101 reads, ‘‘A telltale must not 

emit light except when identifying the 

malfunction or vehicle condition it is 

designed to indicate, or during a bulb 

check.’’ Accordingly, it is necessary to 

add the following new paragraph S5.5.5 

(renumbering subsequent paragraphs): 

Notwithstanding S5.3.1(e) of 49 CFR 

571.101, the vehicle manufacturer may use 

the ‘‘ESC Off’’ telltale to indicate an ESC 

level of function other than the fully 

functional default mode even if the vehicle 

would meet S5.2.1, S5.2.2 and S5.2.3 at that 

level of ESC function. 

(iv) ‘‘ESC Off’’ Telltale Strategy 

Porsche sought clarification that the 

following ESC telltale illumination 

strategy would be permissible: If the 

ESC is deactivated by the driver, 

illuminate the ESC symbol in the 

instrument panel (by which we assume 

Porsche means the ESC malfunction 

symbol and not the ‘‘ESC Off’’ symbol), 

provide a ‘‘PSM OFF’’ message in the 

message/information center, and 

illuminate a yellow light-emitting diode 

(LED) in the ‘‘ESC Off’’ button which is 

in clear view of the driver. 

In response to Porsche’s comment, we 

note that paragraph S5.3 of the NPRM 

states that the ESC malfunction telltale 

shall be illuminated ‘‘* * * after the 

occurrence of one or more 

malfunctions.’’ Manual disablement of 

the ESC by the driver does not 

constitute an ESC malfunction. 

Furthermore, paragraph S5.3.1(e) of 

FMVSS 101 requires, ‘‘A telltale must 

not emit light except when identifying 

the malfunction or vehicle condition it 

is designed to indicate, or during a bulb 

check.’’ Thus, the ESC malfunction 

telltale can only be used when a 

malfunction exists. 

NHTSA is concerned that if the ESC 

malfunction telltale were permitted to 

be presented simultaneously with the 

‘‘ESC Off’’ telltale, drivers would be 

unable to distinguish whether the 

system had been switched off or 

whether a malfunction had occurred. 

Therefore, presentation of the ESC 

malfunction telltale in addition to an 

‘‘ESC Off’’ indication when ESC has 

been disabled via the driver-selectable 


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58 71 FR 54729 (Sept. 18, 2006). 

59 Id. 

control and no system malfunction 

exists is prohibited. 

(v) Use of Two-Part Telltales 

Porsche stated that vehicle 

manufacturers should be permitted the 

flexibility to use two adjacent telltales, 

one containing the ISO symbol for the 

proposed yellow ESC malfunction 

indicator and another yellow telltale 

with the word ‘‘Off.’’ Porsche stated that 

given the limited space available on the 

instrument clusters in their vehicles, 

this dual-purpose combination should 

be permissible. The Alliance/AIAM 

offered the same comment, arguing that 

this approach would increase efficiency 

by allowing one lamp to be illuminated 

to indicate ESC malfunction and both to 

be illuminated to indicate that the 

system has been turned off or placed in 

a mode other than the ‘‘full on’’ mode. 

NHTSA acknowledges the 

commenters’’ concerns regarding 

limited instrument panel area available 

for locating telltales. However, we are 

not adopting the commenters’

recommendation, because allowing a 

two-part telltale in such manner would 

create conflicting regulatory 

requirements, as discussed below. 

Indication of a malfunction condition 

must always be the predominant visual 

indication provided to the driver by a 

telltale. As a result, if a two-part ESC 

telltale were used and an ESC 

malfunction occurred, only the 

malfunction portion of the telltale could 

be illuminated. Paragraphs S5.4.2 and 

S5.4.3 of the proposed regulatory text 

state that a telltale consisting of the 

symbol for ‘‘ESC Off’’ or substitute text 

(as indicated in Table 1 of FMVSS No. 

101) must be illuminated when a 

control input to the ESC switch (i.e., 

control) has been made by the driver to 

put the vehicle into a non-compliant 

ESC mode. If a two-part telltale were 

used, and an ESC malfunction condition 

occurred after the ESC had been turned 

off by the driver, the malfunction 

indication would take precedence over 

the ‘‘off’’ indication, thereby requiring 

that the ‘‘off’’ portion of the two-part 

telltale be extinguished. This situation 

would be in conflict with S5.4.2 of the 

proposed regulatory text. Due to this 

conflict, NHTSA has decided to deny 

the request to permit use of a two-part 

ESC telltale. 

(vi) Conditions for Illumination of the 

‘‘ESC Off’’ Telltale: Speed 

The Alliance/AIAM sought 

clarification that the ‘‘ESC Off’’ telltale 

(if provided) need not illuminate when 

the vehicle is traveling below the lowspeed threshold at which the ESC 

system becomes operational. 

We note that under paragraph S5.1.2, 

NHTSA’s proposal states that the ESC 

system must be ‘‘* * * operational 

during all phases of driving including 

acceleration, coasting, and deceleration 

(including braking), except when the 

driver has disabled ESC or when the 

vehicle is below a speed threshold 

where loss of control is unlikely.’’ Thus, 

NHTSA’s proposal provides that the 

ESC system need not be functional 

when the vehicle is traveling at low 

speeds. 

Paragraph S5.4.2 of FMVSS No. 126 

requires the vehicle manufacturer to 

illuminate the ‘‘ESC Off’’ telltale when 

the ‘‘vehicle has been put into a mode 

that renders it unable to satisfy the 

requirements of S5.2.1, S5.2.2 and 

S5.2.3.’’ Driving a vehicle at low speeds 

does not equate with the vehicle 

operator actively using a driverselectable control that places the ESC 

system ‘‘into a mode in which it will not 

satisfy the requirements of S5.2,’’ as 

stated in S5.4. Therefore, NHTSA 

believes that the proposed language 

does not imply that the ‘‘ESC Off’’

telltale must be illuminated when the 

vehicle is traveling at low speeds and is 

sufficiently clear in defining the 

conditions under which the ‘‘ESC Off’’

telltale must be illuminated. As a result, 

NHTSA has determined that no 

revisions to the proposed regulatory 

language are necessary to address this 

issue. 

(vii) Conditions for Illumination of the 

‘‘ESC Off’’ Telltale: Direction 

The Alliance/AIAM, Bosch, 

Continental, Delphi, and Nissan 

commented that the final rule should be 

modified to clarify that there is no need 

to illuminate the ‘‘ESC Off’’ telltale 

when the vehicle is driven in reverse, 

because triggering the telltale under 

those circumstances could result in 

driver confusion. 

As discussed under Section IV.C.6(f) 

above, NHTSA did not intend to require 

the ESC system to be operable when the 

vehicle is driven in reverse, because 

such a requirement would necessitate 

costly changes to current ESC systems 

with no anticipated safety benefit. 

Furthermore, we have decided in the 

final rule to modify the regulatory 

language in S4 of FMVSS No. 126 to 

clarify that ESC is intended to function 

‘‘over the full speed range of the vehicle 

(except at vehicle speeds less than 

15km/h (9.3 mph) or when being driven 

in reverse). In such instances, the ESC 

system has not been turned off, but 

instead, it has encountered a situation 

in which, by regulation, the ESC system 

need not operate; once the vehicle is 

returned to forward motion at a speed 

above the minimum threshold, one 

would presume that the ESC system 

would return to normal operation 

automatically. 

Requiring the ‘‘ESC Off’’ telltale to 

illuminate frequently (given that 

reversing the vehicle and low-speed 

driving are routine occurrences) would 

certainly be perceived as a nuisance by 

drivers and might even be mistaken for 

a system malfunction. Furthermore, we 

note that paragraph S5.4.2 of the 

NHTSA proposal comes under the 

heading and is in the context of the 

‘‘ESC Off’’ Switch and Telltale (see 

S5.4). Those provisions already stated 

that the ‘‘ESC Off’’ indicator must be 

illuminated when the ESC system is 

manually disabled (i.e., placed in a noncompliant mode) by the driver via the 

‘‘ESC Off’’ switch. For these reasons, the 

agency does not believe that any change 

to the regulatory text is necessary to 

clarify that the ‘‘ESC Off’’ telltale need 

not be illuminated when the vehicle is 

in reverse gear. 

(c) Alerting the Driver of ESC Activation 

As noted above, paragraph S5.3.7 of 

the NPRM stated that manufacturers 

may use the ESC malfunction telltale in 

a flashing mode to indicate ESC 

operation. However, as was also stated 

in the NPRM, NHTSA has not identified 

any safety need that would justify a 

requirement for provision of an ESC 

activation indicator to alert the driver 

that the ESC system is intervening 

during a loss-of-control situation.58 The 

NPRM also stated that the agency does 

not recommend use of an auditory 

indication of ESC activation.59

(i) Visual and Auditory Indications of 

ESC Activation 

Regarding the issue of provision of an 

indication of ESC activation to the 

driver, commenters offered a variety of 

viewpoints. In overview, the Alliance/ 

AIAM expressed support for a visual 

telltale. Consumers Union and Toyota 

expressed support for both visual and 

auditory indications. Advocates 

expressed support for a steady-burning 

telltale, and Public Citizen stated that an 

activation telltale is unnecessary and 

potentially distracting to the driver. 

These comments are summarized in 

detail below. 

The Alliance/AIAM expressed 

support for allowing the ESC telltale to 

be used, at the manufacturer’s option, to 

indicate an ESC operating or 

‘‘intervention’’ event to the driver. 

Consumers Union challenged the 

agency’s data suggesting that visual and 


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60Mazzae, E. et al., The Effectiveness of ESC and 

Related Telltales: NADS Wet Pavement Study, 

(Telltale Study) DOT HS 809 978, NHTSA 

(November 2005) (Docket No. NHTSA–2006–

25801–7). 61 Id. 62 Id. 

audible warnings to the driver when the 

ESC system has been activated provide 

little or no safety benefit. The 

organization stated that testing by its 

own engineers suggested that such 

warnings are helpful, in that they may 

alert drivers earlier regarding slippery 

road conditions, thereby causing the 

driver to slow down in anticipation of 

a potential hazard. Accordingly, 

Consumers Union requested that the 

agency either include a requirement for 

visual and audible warnings of ESC 

operation in the final rule or at least 

conduct additional research before 

deciding to exclude such requirement. 

In its comments, the Advocates stated 

that NHTSA should allow ESC telltales 

to be lit or not lit at the manufacturer’s 

discretion when ESC intervenes, but, if 

lit, the telltale should not be allowed to 

flash. The commenter cited the agency’s 

own study, which it interpreted as 

suggesting that flashing illumination 

increases driver distraction. The 

commenter also faulted the agency for 

making a tentative determination that a 

flashing ESC telltale was not shown to 

result in a measurable consequence in 

terms of roadway departures, arguing 

that the agency should have disclosed 

that the portion of the November 2005 

study 60 upon which it relied had data 

from only 20 subjects in a driving 

simulator. The Advocates opined that 

this small sample size results in low 

statistical power for generalization. 

The Advocates also expressed 

concern that a flashing telltale could 

elicit a panic reaction in some drivers or 

be confused with an ESC malfunction 

(since an increasing number of telltales 

are being wired to flash to indicate 

malfunction of the given system). The 

commenter expressed concern that ESC 

is not an ‘‘automatic’’ technology, in 

that it will only attempt to correct the 

vehicle’s path if the driver is actively 

steering. The Advocates argued that if a 

driver panics and fails to even attempt 

to steer the vehicle, then the ESC system 

cannot intervene to compensate for a 

loss of lateral stability. 

The Advocates argued that there is no 

support in the rulemaking record for 

allowing the ESC telltale to flash, but 

instead, that approach is arbitrary in 

that it contradicts the contrary evidence 

presented in NHTSA’s own limited 

study (i.e., one showing increased eye 

glance distributions away from the 

roadway). Instead, the commenter 

characterized this issue as the agency 

again seeking to permit continuation of 

certain current, suboptimal ESC 

systems. For these reasons, the 

commenter argued that a flashing ESC 

telltale could be detrimental to safety, so 

this aspect of the agency proposal 

should be reconsidered. 

Public Citizen commented that 

NHTSA’s position on telltales is sound. 

Public Citizen stated its belief that a 

telltale for ESC activation indication is 

unnecessary and argued that its position 

is supported by NHTSA’s own study, 

which did not show such indicators to 

provide any benefit. Further, Public 

Citizen stated concern that an ESC 

activation telltale may create a 

distraction for drivers or lead to 

annoyance, which may cause drivers to 

deactivate the ESC system. 

Toyota asked whether their current 

strategy of providing both visual 

(flashing) and auditory indications of 

ESC activation indication would be 

permissible. The commenter correctly 

stated NHTSA research results as 

showing that there were increased road 

departures and the average glance time 

was approximately twice as long for 

participants presented with an auditoryonly indication of ESC activation as 

compared to those presented with a 

steady-burning telltale, flashing telltale, 

or no telltale. Toyota postulated that 

those responses resulted from the driver 

searching for a visual indicator to 

explain the meaning of the auditory 

indicator. Toyota noted that the NHTSA 

study did not test a condition in which 

an auditory indication of ESC activation 

is presented in addition to the flashing 

ESC telltale, as they currently provide in 

their vehicles, and, therefore, the 

commenter believes that NHTSA’s 

recommendation not to use an auditory 

indicator refers to an auditory-only 

indication, and not to a system such as 

Toyota’s that provides both visual and 

auditory indications to the driver. 

After careful consideration of the 

numerous public comments raising this 

issue, the agency has decided to retain 

the approach toward ESC activation 

warnings presented in the NPRM for the 

reasons that follow. In a survey 

conducted in the early phases of 

NHTSA’s human factors research 

relating to ESC,61 we examined 28 

vehicles equipped with ESC systems 

and found that all manufacturers 

appeared to provide a visual indication 

of ESC activation. The study found that 

a majority of vehicle manufacturers 

provided such indication using a 

symbol, while a few indicated ESC 

activation using text. Each vehicle 

examined that used a symbol to indicate 

ESC activation did so by flashing the 

telltale. Owner’s manuals examined 

typically indicated that the purpose of 

the flashing telltale was to inform the 

driver that the ESC was ‘‘active’’ or 

‘‘working.’’

As discussed in NHTSA’s proposal, 

the safety need for an ESC activation 

indicator to alert the driver during an 

emergency situation that ESC is 

intervening is not obvious. It would 

seem that with ESC, as with anti-lock 

brake systems, vehicle stability would 

be increased regardless of whether 

feedback was provided to inform the 

driver that a safety system had 

intervened. No data have been provided 

to NHTSA to suggest that safety benefits 

are enhanced by alerting the driver of 

ESC activations. Nevertheless, the 

agency’s current research on the topic of 

ESC activation warnings supports the 

NPRM’s current approach (with which 

the Alliance/AIAM and Public Citizen 

agree) that an ESC activation indication 

should neither be prohibited nor 

required, as explained below. 

The results of recent NHTSA 

research 62 neither show that alerting a 

driver to ESC activation provides a 

safety benefit, nor that it may prove to 

be a source of distraction that could lead 

to adverse safety consequences. Our 

research shows that drivers presented 

with the flashing telltale were more 

likely to glance at the instrument panel 

and that these drivers typically glanced 

at the panel twice, rather than just once 

as for the steady-burning telltale or no 

telltale. Insofar as a flashing telltale 

draws a driver’s attention away from the 

road, where we believe it should be 

during an emergency loss-of-control 

situation, we cannot logically require it. 

Although the Consumers Union 

commented that ‘‘their own testing 

resulted in [their] engineers finding 

these warnings were helpful and alerted 

them earlier in their driving to the 

possibility of slippery conditions before 

an emergency situation may occur,’’ the 

commenter provided no indication of 

whether the telltale flashed because of 

the activation of the ESC system itself, 

or due to other traction control 

interventions, which are often 

connected with the ESC telltale. NHTSA 

agrees that it makes sense to alert 

drivers to slick road conditions when 

the driver is operating the vehicle on the 

roadway in a generally straight path, but 

disagrees that it would make sense to 

draw the driver’s attention away from 

the road when they are in the midst of 

assessing a crash-imminent situation 

and attempting to avoid a collision. 

While NHTSA’s research to date 

showed that drivers looked at a flashing 


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telltale twice as often, this did not result 

in significantly different rates for loss of 

control, road departures, and collisions 

than with steady-burning telltales or no 

telltales. Thus, despite the logical risk of 

looking away from the road during an 

ESC-worthy maneuver, we found no 

apparent detriment from the increased 

glances at a flashing telltale. NHTSA 

therefore cannot agree with Advocates’

comment that NHTSA should allow ESC 

telltales to be lit or not lit at the 

manufacturer’s discretion when ESC 

intervenes, but that lit telltales should 

not be allowed to flash, because the 

flashing might lead to driver distraction 

or panic. Currently available research 

results are insufficient to support 

prohibition of the existing practice of 

providing a visual indication of ESC 

activation, but neither do they support 

requiring it. Although Consumers Union 

engineers have performed their own 

informal study, the agency does not 

consider their results (without data 

being provided), to offer sufficient 

justification for requiring a visual 

indication of ESC activation. 

Consumers Union requested that the 

agency either include a requirement for 

visual and audible warnings of ESC 

operation in the final rule, or at least 

conduct additional research before 

deciding to exclude such a requirement. 

Advocates also criticized the small 

sample size of NHTSA’s existing 

research in this area. To both 

commenters, we respond that, while the 

existing research had statistically valid 

sample sizes, additional research is 

underway to examine driver behavior 

and crash-imminent situation outcomes 

as a function of whether a flashing ESC 

telltale is presented during ESC 

activation, versus presentation of the 

icon immediately following ESC 

activation. Data from this research are 

being analyzed, and NHTSA hopes that 

the study results will further clarify 

which strategy for notifying the driver of 

ESC activation is least likely to 

negatively impact the driver’s response 

to a loss-of-control situation. However, 

unless additional research provides 

strong, statistically-valid evidence of a 

benefit or detriment associated with 

presentation of an ESC activation 

indication, we will not require or 

prohibit such an indication. 

To NHTSA’s knowledge, Toyota is the 

only manufacturer that currently 

presents both a visual and an auditory 

indication of ESC activation. As Toyota 

correctly pointed out, NHTSA’s recent 

ESC study measured a negative 

consequence of the presentation of an 

auditory-only indicator of ESC 

activation, statistically significant for 

older drivers in terms of road 

departures. Approximately twice as 

many road departures were observed for 

participants presented with the auditory 

ESC activation indication as compared 

to those who were presented with a 

steady-burning telltale, flashing telltale, 

or no telltale. For this reason, NHTSA 

recommended against using an auditory 

ESC activation indicator in its proposal. 

Toyota postulated that increased 

instrument panel glances resulted from 

the driver searching for a visual 

indicator to explain the meaning of the 

auditory indicator. Given that study 

results showed drivers presented with 

no visual or auditory indication of ESC 

activation exhibited instrument panel 

glances lasting half the duration of those 

observed in conjunction with 

presentation of the Toyota auditory ESC 

indicator, one can only assume that the 

auditory alert produced the longer 

glance durations. Toyota has not 

provided any data to substantiate its 

apparent assertions that providing 

simultaneous visual and auditory 

indicators would result in: (1) 

Instrument panel glances of similar 

duration to those observed in the 

NHTSA study for participants presented 

with only a visual indicator, and (2) 

fewer road departures, as were observed 

in the other ESC activation indication 

conditions. 

Consistent with its research, NHTSA 

believes that auditory indications of 

ESC activation are not necessary and 

provide no apparent safety benefit. 

However, while NHTSA has conducted 

research showing that an auditory 

indication of ESC activation elicits 

longer instrument panel glances and 

may be associated with an increase in 

road departures, we do not consider 

these results from a single, simulator 

study to provide sufficient justification 

to prohibit use of an auditory ESC 

indicator. Therefore, while we would 

discourage Toyota’s use of an auditory 

ESC activation warning, even when 

combined with a visual indication, 

current data do not justify a prohibition 

of such approach. 

(ii) Flashing Telltale as Indication of 

Intervention by Related Systems/ 

Functions 

Honda and the Alliance/AIAM 

requested permission to flash the ESC 

malfunction telltale to indicate the 

intervention of other related systems, 

including traction control and trailer 

stability assist function. Honda reasoned 

that these functions are directly related 

to the ESC system and that the driver 

would experience the same sensations 

from the braking system actuator and 

throttle control triggered by operation of 

these related systems, as they would in 

the event of ESC activation. In addition 

to keeping the driver informed, Honda 

also reasoned that this strategy would 

aid in minimizing the number of 

telltales used for related functions. The 

commenter proposed revising paragraph 

S5.3.7 as follows: ‘‘The manufacturer 

may use the ESC malfunction telltale in 

a flashing mode to indicate ESC 

operation, or to indicate operation of 

functions directly related to stability 

control such as a traction control 

program.’’

Because NHTSA is not requiring an 

ESC activation indication, if vehicle 

manufacturers choose to provide one, 

they may use it to indicate interventions 

by additional related systems in their 

discretion. We expect that 

manufacturers would explain the 

meaning and scope of the activation 

indication in the vehicle owner’s 

manual, consistent with facilitating 

consumer understanding of important 

vehicle safety features. 

(d) Bulb Check 

Except when a starter interlock is in 

operation, the NPRM proposed to 

require that each ESC malfunction 

telltale and each ‘‘ESC Off’’ telltale must 

be activated as a check of lamp function 

either when the ignition locking system 

is turned to the ‘‘On’’ (‘‘Run’’) position 

when the engine is not running, or 

when the ignition locking system is in 

a position between ‘‘On’’ (‘‘Run’’) and 

‘‘Start’’ that is designated by the 

manufacturer as a check position (see 

S5.3.4 and S5.5.6). 

(i) Waiver of Bulb Check for Message/ 

Information Centers 

Regarding the NPRM’s proposed bulb 

check requirements, the Alliance/AIAM 

stated that while such requirements are 

appropriate for traditional telltales, 

those requirements are not appropriate 

for vehicle message/information centers 

which do not use bulbs and are 

illuminated whenever the vehicle is 

operating. According to the 

commenters, if there were a problem of 

this type, it would be readily apparent 

because the entire message/information 

center would be blank. Therefore, the 

Alliance/AIAM requested that in the 

final rule, the agency exclude ESC 

system status indications provided 

through a message/information center 

from the standard’s bulb check 

requirements. (Porsche provided a 

similar comment on this issue.) 

As indicated in paragraphs S5.3.4 and 

S5.5.6, any ESC status information 

presented via a telltale must have a bulb 

check performed for that telltale. 

However, NHTSA agrees with the 

commenters that a bulb check is not 


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63A. Houser, J. Pierowicz, Concept of Operations 

and Voluntary Operational Requirements for 

Vehicular Stability Systems (VSS) On-Board 

Commercial Motor Vehicles, FMCSA–MCRR–05–

006 (July 2005). 

relevant or necessary for the type of 

display technology utilized for 

information/message centers. 

Presumably, if an information/message 

center experiences a problem analogous 

to one which would be found by a 

telltale’s bulb check, the entire message 

center would be non-operational, a 

situation likely to be rapidly discovered 

by the driver. Therefore, we have 

decided to waive the bulb check 

requirement under FMVSS No. 126 for 

ESC system status indications provided 

via a message/information center. In 

response to these comments, we are 

adding new paragraphs S5.3.6 and 

S5.5.8 as follows: 

S5.3.6 The requirement S5.3.4 does not 

apply to telltales shown in a common space. 

* * * 

* * * * * 

S5.5.8 The requirement S5.5.6 does not 

apply to telltales shown in a common space. 

(ii) Clarification Regarding Bulb Check 

TRW Automotive recommended that 

as part of the final rule, the agency 

clarify that under paragraph S7.2, 

Telltale bulb check, of the proposed test 

procedures, the bulb check for the ESC 

malfunction telltale and ESC Off telltale 

(if provided) may be performed by any 

vehicle system and is not required to be 

conducted by the ESC system itself. 

According to TRW Automotive, many 

vehicle systems are able to perform this 

function, and most current vehicles are 

designed such that the instrument panel 

controls the telltales. Thus, the 

commenter recommended that the last 

sentence of S7.2 (consistent with 

paragraphs S5.3.4 and S5.4.6) be revised 

to read as follows: ‘‘The ESC 

malfunction telltale must be activated as 

a check of lamp function for the ESC 

malfunction telltale, and if equipped, 

the ‘‘ESC Off’’ telltale, as specified in 

S5.3.4 and S5.4.6.’’

NHTSA is not concerned with the 

precise mechanism of how the bulb 

check for an ESC-related telltale is 

accomplished, provided that this 

performance requirement is met. 

Accordingly, we have decided to modify 

S7.2 by adopting the language 

recommended by TRW Automotive. 

10. System Disablement and the ‘‘ESC 

Off’’ Control 

Under paragraph S5.4, the NPRM 

proposed to permit manufacturers to 

provide a driver-selectable switch that 

places the ESC system in a mode in 

which it will not satisfy the 

performance requirements of the 

standard. However, if an ‘‘ESC Off’’

switch is provided, the vehicle’s ESC 

system must always return to a mode 

that satisfies the requirements of the 

standard at the initiation of each new 

ignition cycle, regardless of what mode 

the driver had previously selected (see 

S5.4.1). If the system has more than one 

mode that satisfies these requirements, 

the default mode must be the mode that 

satisfies the performance requirements 

by the greatest margin (see S5.4.1). 

Under the proposal, if an ‘‘ESC Off’’

switch is provided, the vehicle 

manufacturer must also provide a 

telltale indicating that the vehicle has 

been put into a mode that renders it 

unable to satisfy the requirements of the 

standard (see S5.4.2). The ‘‘ESC Off’’

switch and telltale must be identified by 

the symbol shown for ‘‘ESC Off’’ in 

Table 1 of Standard No. 101 (49 CFR 

571.101) (see S5.4.3). (For further details 

of the telltales and symbols for the ‘‘ESC 

Off’’ switch and telltale (and issues 

relating thereto), see section IV.C.9 

above.) 

Commenters raised a number of issues 

regarding these provisions pertaining to 

system disablement and the ‘‘ESC Off’’

switch. Most commenters agreed that 

there may be a need to disengage the 

ESC system in certain driving situations 

(e.g., to gain traction in snow, mud). 

General comments on this issue (e.g., 

appropriateness and reach of the system 

disablement provision) are discussed 

immediately below, followed by more 

detailed, technical comments. 

(a) Provision of an ‘‘ESC Off’’ Control 

In its comments, IIHS supported 

inclusion of an ESC off switch, because 

it agreed that there are situations in 

which the system would need to be 

disabled (e.g., initiating movement in 

deep snow). IIHS also supported the 

proposal to have a default mode of ‘‘on’’

for the ESC each time the vehicle is 

started. 

Mr. Petkun supported the proposal’s 

tentative decision to permit vehicle 

manufacturers to install ESC off 

switches, stating that a driver may need 

to disable the ESC system when a 

vehicle is stuck in a deformable surface 

such as mud or snow, or when a 

compact spare tire, tires of mismatched 

sizes, or tires with chains are installed 

on the vehicle. He agreed that vehicle 

manufacturers should provide an easily 

identifiable telltale to indicate when the 

vehicle has been placed in a mode that 

completely disables the ESC system. 

In contrast to the comments above, 

the Advocates stated that the proposal’s 

policy for ESC on-off switches is too 

liberal and may place motorists at risk. 

Although it agreed that there may be 

justification for temporary ESC 

disablement where the vehicle needs 

full longitudinal tire traction for 

negotiating mud, gravel, or snow, the 

commenter did not support ESC 

disablement for the purpose of 

increasing ‘‘driving enjoyment’’ (similar 

comment from Public Citizen). The 

organization was particularly skeptical 

of the rationale related to racing, arguing 

that this small minority of drivers can 

disable their ESC systems by other 

(unspecified) means. The Advocates’

comments suggested that ESC 

disablement could result in the loss of 

benefits of an active ESC system for long 

distances or considerable periods of 

time until the start of the next ignition 

cycle. Furthermore, Advocates 

expressed concerns that turning off the 

ESC system could also disable ABS 

operation, thereby negatively impacting 

vehicle safety. 

In addition, the Advocates made an 

analogous argument that NHTSA’s sister 

agency, the Federal Motor Carrier Safety 

Administration (FMCSA), issued a 

report 63 in 2005 which recommended 

that in no case should drivers of 

vehicles greater than 10,000 pounds 

GVWR be allowed to disable a Vehicle 

Stability System (either roll stability 

control or ESC). The commenter argued 

that this is another reason for the agency 

to reconsider the ease with which a 

driver could use an ESC disabling 

switch for vehicles under 10,000 

pounds GVWR. 

Advocates suggested that it may be 

unnecessary to permit ESC disablement, 

if ESC systems can operate in 

conjunction with vehicle traction 

control systems. According to the 

Advocates, if the agency continues to 

believe that ESC disablement switches 

should be permitted, disablement 

should require either: (1) A long switch 

engagement period, or (2) sequential 

switch engagement actions. 

Despite the reservations of some 

commenters, NHTSA continues to 

believe that provision of a control for 

temporarily disabling ESC will enhance 

safety. The rationale for this position is 

detailed below. 

First, we acknowledge that driving 

situations exist in which ESC operation 

may not be helpful, most notably in 

conditions of winter travel (e.g., driving 

with snow chains, initiating movement 

in deep snow). ESC determines the 

speed at which the vehicle is traveling 

via the wheel speeds, rather than using 

an accelerometer or other sensor. While 

NHTSA is only requiring ESC to operate 

at travel speeds of 15 kph (9.3 mph) and 

greater, some manufacturers may choose 

to design their ESC systems to operate 


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at lower speeds. Thus, drivers trying to 

work their way out of being stuck in 

deep snow may induce wheel spinning 

that implies a high enough travel speed 

to engage the ESC to intervene, thereby 

hindering the driver’s ability to free the 

vehicle. 

Second, NHTSA is concerned that if 

a control is not provided to permit 

drivers to disable ESC when they choose 

to, some drivers may find their own, 

permanent way to disable ESC 

completely. This permanent elimination 

of this important safety system would 

likely result in the driver losing the 

benefit of ESC for the life of the vehicle. 

However, as currently designed, ESC 

systems retain some residual safety 

benefits when they are ‘‘switched off’’

and they also become operational again 

at the next ignition cycle of the vehicle. 

NHTSA feels that provision of this type 

of temporary ‘‘ESC Off’’ control is the 

best strategy for dealing with such 

situations. 

While we acknowledge FMCSA’s 

recommendation that drivers of vehicles 

with a GVWR greater than 10,000 

pounds should not be permitted to 

disable a Vehicle Stability System, those 

vehicles generally have very different 

handling characteristics than the light 

vehicles subject to today’s final rule. 

Furthermore, the operators of those 

vehicles in many cases may be expected 

to have different motivations for driving 

(i.e., driving for personal reasons, rather 

than work reasons). Accordingly, we do 

not believe that the referenced FMCSA 

recommendation would alter the 

identified safety need discussed above 

to allow vehicle manufacturers to 

include an ‘‘ESC Off’’ control on certain 

light vehicles equipped with an ESC 

system. 

In response to Advocates’ suggestion 

that it may be unnecessary to permit 

ESC disablement if ESC systems can 

operate in conjunction with traction 

control, NHTSA does not believe that 

ESC disablement should be prohibited 

on this basis. This rule mandates ESC, 

not traction control, for new vehicles. 

For vehicles equipped with ESC but not 

with traction control, ESC disablement 

may be necessary in certain situations, 

as described above. Mandating traction 

control as well as ESC, as Advocates’

suggestion would entail, is beyond the 

scope of this rulemaking. 

(b) Switch for Complete ESC 

Deactivation 

Consumers Union stated that for 

certain sporty models, NHTSA could 

permit a separate mode (perhaps 

activated with a switch) which would 

give the driver discretion to completely 

disable the ESC for race track use 

(similar comments by Mr. Cheah and 

Mr. Kiefer). Mr. Kiefer added that this 

disablement mechanism, which would 

fully and permanently disable the 

vehicle’s ESC system, should shut down 

any vehicle subsystem that intervenes in 

the vehicle’s performance, although he 

agreed that exceptions may be 

warranted (e.g., where the driver wishes 

to keep ABS operative). 

The proposed regulatory text states 

that the ‘‘manufacturer may include a 

driver-selectable switch that places the 

ESC system in a mode in which it will 

not satisfy the performance 

requirements’’ specified by NHTSA (see 

S5.4 of the NPRM). Because NHTSA is 

permitting, rather than requiring such a 

switch and is not specifying the extent 

to which ESC function must be reduced 

via the switch, manufacturers have the 

freedom to provide drivers with a 

switch that has the ability to completely 

disable ESC. Thus, NHTSA believes that 

the regulatory text as originally drafted 

sufficiently addresses the commenters’

concerns regarding this issue. 

(c) ESC Operation After Malfunction 

and ‘‘ESC Off’’ Control Override 

Honda expressed concern that when 

an ESC malfunction is detected, some 

drivers may respond by pressing the 

ESC Off control (if one is provided). 

According to Honda, not all ESC 

malfunctions may render the system 

totally inoperable, so there may be 

benefits to ensuring that the system 

remains active in those cases. Thus, the 

commenter urged the agency to permit 

manufacturers to disable the ESC Off 

control in those instances where an ESC 

malfunction has been indicated. Honda 

recommended adding a new provision 

to S5.4 stating, ‘‘Operation of the ESC 

off switch may be disabled when the 

ESC malfunction telltale is 

illuminated.’’

In addition, Honda’s comments also 

stated that the company’s current ESC 

system designs contain a logic that 

permits the system to override the ‘‘ESC 

Off’’ control in certain appropriate 

situations (e.g., when the TPMS system 

detects low tire pressure or a TPMS 

system malfunction such as when a 

spare tire is in use). Honda argued that 

at such times, the benefits of ESC 

operational availability are more 

important than the ability to disable the 

system. The company further argued 

that because the ESC Off control is 

permitted at the vehicle manufacturer’s 

option, the manufacturer should be 

accorded discretion to appropriately 

limit the operation of that off control. 

We agree with the commenter’s 

reasoning on both of these issues. It was 

never the agency’s intention to require 

that just because the manufacturer 

permits the ESC system to be disabled 

under some circumstances, the 

manufacturer must allow it to be 

disabled at all times. If the vehicle 

manufacturer believes a situation has 

occurred in which it should not be 

possible to turn ESC off, then the 

manufacturer should be permitted to 

override the operation of the ‘‘ESC Off’’

control. Honda’s example of an ESC 

system malfunction after which the 

driver triggers the ‘‘ESC Off’’ switch is 

illustrative of such a situation; in such 

cases, the vehicle operator presumably 

had desired to maintain ESC 

functionality while driving, so the 

driver’s action to turn the system off 

arguably reflects a reflex reaction that 

the system is unavailable and must be 

shut down, rather than a reasoned 

decision to forgo any residual ESC 

benefits that might remain in spite of 

the malfunction. 

Similarly, it was not the agency’s 

intention to require the ESC system to 

remain disabled if the vehicle 

manufacturer believes a situation has 

occurred in which ESC should again 

become functional. We do not believe 

that any changes to the regulatory text 

are necessary regarding this issue. 

(d) Default to ‘‘ESC On’’ Status 

Although Consumers Union 

acknowledged that there may be certain 

situations in which ESC disablement 

may be appropriate (e.g., vehicles stuck 

in snow or mud), it did not support the 

proposed requirement that the ESC 

system be permitted to remain disabled 

until the next ignition cycle (i.e., default 

mode upon vehicle start-up be ESC 

‘‘on’’). The commenter argued that the 

driver may inadvertently forget to 

reengage the ESC for the remainder of 

the current trip by turning the ignition 

off and then on again. Thus, Consumers 

Union recommended that the standard 

should require that, once disabled, the 

ESC system must again become 

operational once the vehicle has 

reached a speed of 25 mph. 

Public Citizen expressed support for a 

default setting of ‘‘on’’ for ESC systems 

at the start of each ignition cycle 

(similar comment by Mr. Petkun). 

However, Public Citizen argued that 

waiting for the next ignition cycle to 

require reengagement of the ESC system 

needlessly compromises potential safety 

benefits. Accordingly, Public Citizen 

urged the agency to consider other 

alternatives, such as a time-delay 

reminder to re-enable the system or 

some other means of automatic reenablement. 

In response to these comments, we 

note that while paragraph S5.4.1 of the 


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Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17281 

proposed regulation states that ‘‘[t]he 

vehicle’s ESC system must always 

return to a mode that satisfies the 

requirements of S5.1 and S5.2 at the 

initiation of each new ignition cycle,’’

manufacturers have the freedom to 

equip their vehicles with ESC systems 

that return to a compliant mode sooner, 

based upon an automatic speed trigger 

or timeout. 

As discussed in Section IV.C.10(a) 

above, NHTSA noted two situations in 

which drivers may desire to turn off 

ESC, specifically when a vehicle is 

stuck in the snow and when a driver 

chooses to engage in sporty driving or 

racing. The latter of these two situations 

is the only one that warrants a 

potentially more prolonged delay of ESC 

re-enablement until the next ignition 

cycle. However, if the agency were to 

require automatic reengagement of a 

fully-functional ESC mode after a 

certain time delay or upon the vehicle 

reaching a certain speed threshold, 

many vehicle operators might face a 

considerable obstacle if they wished to 

continue engaging in sports driving. As 

mentioned above, we believe that there 

could be safety disbenefits associated 

with sports drivers who try to 

permanently disable the ESC system 

themselves. 

Nevertheless, NHTSA believes that 

many vehicle manufacturers will equip 

vehicles that are not of a ‘‘sport’’ class 

with ESC systems that automatically reengage the operation of the ESC system 

based on some threshold reached during 

the ignition cycle. Given our assessment 

of the situation, NHTSA does not 

believe it necessary or advisable to 

specify more stringent requirements for 

returning ESC to a compliant mode. 

(e) Operation of Vehicle in 4WD Low 

Modes 

The Alliance/AIAM, Bosch, 

Continental, Delphi, and Nissan all 

stated that there are certain situation in 

which the ESC system would not be 

able to default to ‘‘on’’ status at the start 

of a new ignition cycle. As an example, 

Bosch stated that there are certain 

vehicle operational modes in which the 

driver intends to optimize traction, not 

stability (e.g., 4WD-locked high, 4WDlocked low, locking front/rear 

differentials). The commenters argued 

that an exception should be made in 

FMVSS No. 126 for when drivers select 

ESC modes for four-wheel drive low, 

has locked the vehicle’s differentials, or 

has placed the vehicle in other special 

off-road chassis modes. According to the 

commenters, transition to one of these 

modes is mechanical and cannot be 

automatically reverted to ‘‘on’’ status at 

the start of each new ignition cycle. 

The commenters suggested that this 

approach would be consistent with 

safety because the operating conditions 

for these vehicle modes tend to involve 

low-speed driving. The Alliance/AIAM 

added that in those cases, the ESC ‘‘Off’’

telltale should be illuminated, in order 

to remind the driver of the ESC system’s 

status as being unavailable. Bosch 

recommended modifying paragraph 

S5.4.1 to read as follows: ‘‘The vehicle’s 

stability control system must always 

return to a mode which satisfies the 

requirements of S5.1 and S5.2 at the 

initiation of each new ignition cycle, 

regardless of the mode the driver had 

previously selected, except if that mode 

was specifically for enhanced traction 

during low-speed, off-road driving.’’

We agree with the commenters that 

when a vehicle has been intentionally 

placed in a mode specifically intended 

for enhanced traction during low-speed, 

off-road driving via mechanical means 

(e.g., levers, switches) and in this mode 

ESC is always disabled, it is not sensible 

to require the ESC system to be returned 

to enabled status just because the 

ignition has been cycled. In these 

situations, keeping the ESC disabled 

and illuminating the ESC ‘‘Off’’ telltale, 

in order to remind the driver of the ESC 

system’s status as being unavailable, 

makes more sense. We agree with the 

comment that making this change to the 

regulatory text should have no 

substantial effect on safety because the 

operating conditions for these vehicle 

modes tend to involve low-speed 

driving. 

In revising the regulatory text 

pertaining to this issue, we have 

adopted Bosch’s recommended 

language, except that a clause has been 

added to limit applicability to situations 

where the vehicle’s mode transition is 

accomplished via mechanical means. 

We note that if the vehicle’s mode 

transition is accomplished via electronic 

means, then the vehicle can reset itself 

to a normal traction mode, and the ESC 

to active status, with each ignition 

cycle. Accordingly, paragraph S5.4.1 

has been revised to read as follows: 

S5.4.1 The vehicle’s ESC system must 

always return to a mode that satisfies the 

requirements of S5.1 and S5.2 at the 

initiation of each new ignition cycle, 

regardless of what mode the driver had 

previously selected, except if that mode is 

specifically for enhanced traction during 

low-speed, off-road driving and is entered by 

the driver using a mechanical control that 

cannot be automatically reset electrically. If 

the system has more than one mode that 

satisfies these requirements, the default mode 

must be the mode that satisfies the 

performance requirements of S5.2 by the 

greatest margin. 

(f) ‘‘ESC Off’’ Control Requirements 

Under paragraph S5.4.3 of the NPRM, 

the agency proposed to require the ‘‘ESC 

Off’’ control, if present, to be identified 

by the symbol shown for ‘‘ESC Off’’ in 

Table 1 of Standard No. 101 (i.e., the 

ISO symbol J.14 with the English word 

‘‘Off’’). 

(i) Labeling of the ‘‘ESC Off’’ Control 

While the Alliance/AIAM agreed that 

the ‘‘ESC Off’’ control should be 

identified, they argued that vehicle 

manufacturers should be granted 

flexibility in terms of how to identify 

the ‘‘ESC Off’’ control. The commenters 

stated that it is not necessary to 

standardize the identification of the 

control because vehicle manufacturers 

have been providing drivers with more 

detailed feedback on the ESC operating 

mode when the system is in other than 

the default ‘‘full on’’ mode. If the agency 

understands the comment correctly, the 

Alliance and AIAM are suggesting that 

because vehicle manufacturers are 

providing a telltale that would 

illuminate whenever the system is in a 

mode other than ‘‘full on,’’ they should 

be permitted discretion to optimize 

control labeling in ways that would 

facilitate driver understanding of 

variable ESC modes (i.e., permitting a 

message other than ‘‘ESC Off’’). 

NHTSA shares the commenters’

concern for ensuring driver 

understanding of ESC status. We also 

agree that it would be beneficial to 

encourage drivers to select ESC modes 

other than ‘‘full on’’ only when driving 

conditions warrant. We feel that 

standard control labeling of an actual 

‘‘ESC Off’’ control must be maintained 

and, therefore, manufacturers must 

identify the ‘‘ESC Off’’ control using the 

specified ‘‘ESC Off’’ symbol or ‘‘ESC 

Off’’ text (which may be supplemented 

with other text and symbols). However, 

we are distinguishing between an actual 

‘‘ESC Off’’ control (i.e., one whose 

function is to put the ESC system in a 

mode in which it no longer satisfies the 

requirements of an ESC system, and 

which accordingly must bear the 

required ‘‘ESC Off’’ labeling) and two 

other possible types of controls (which 

would not be required to bear the ‘‘ESC 

Off’’ labeling). 

The first control to be clarified as 

excluded is one which has a different 

primary purpose (e.g., a control for the 

selection of low-range 4WD that locks 

the axles), but which must turn off the 

ESC system as a consequence of an 

operational conflict with the function 

that it controls. In this case, such 

control would be made confusing by 

adding ‘‘ESC Off’’ to its functional label. 


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Nevertheless, in such situations, the 

‘‘ESC Off’’ telltale must illuminate to 

inform the driver of ESC system status. 

The second control to be clarified as 

excluded is one that changes the mode 

of ESC to a less aggressive mode than 

the default mode but which still 

satisfies the performance criteria of 

Standard No. 126. In such cases, the 

manufacturer may label such a control 

with an identifier other than ‘‘ESC Off,’’

and the manufacturer is permitted, but 

not required, to use the ‘‘ESC Off’’

telltale beyond the default mode to 

signify lesser modes that still satisfy the 

test criteria. 

Accordingly, paragraph S5.4 has been 

rewritten to address which vehicle 

controls must be identified with the 

‘‘ESC Off’’ symbol or ‘‘ESC Off’’ text. 

(ii) Location of the ‘‘ESC Off’’ Control 

Nissan stated its understanding that 

by including the optional ESC off switch 

in Table 1 of FMVSS No. 101, Controls 

and Displays, such switch is subject to 

the requirement of S5.3.2.1 that the 

control be visible to a restrained driver. 

However, the commenter requested that 

vehicle manufacturers be provided 

flexibility in the placement of the ESC 

off switch for the following reasons. 

First, Nissan believes that the ESC off 

switch would be infrequently used 

during normal driving. Second, the 

location of the ESC off switch would 

help ensure that disabling of the ESC 

reflects a deliberate act by the driver. 

Accordingly, Nissan requested that the 

final rule exclude the ESC off switch 

from the visibility requirements of 

FMVSS No. 101. 

For the reasons that follow, the 

agency has decided that the ‘‘ESC Off’’

switch location must meet the 

requirements of FMVSS No. 101 S5.1.1, 

which states that ‘‘[t]he controls listed 

in Table 1 and in Table 2 must be 

located so that they are operable by the 

driver under the conditions of S5.6.2 

[i.e., while properly restrained by the 

seat belt].’’ The commenter correctly 

understood the intent of FMVSS No. 

101, in noting the implicit requirement 

that both telltales and controls be 

located such that they are visible to a 

belted driver. We believe that handoperated controls should be mounted 

where they are easily visible to the 

driver so as to minimize visual search 

time, because safety may be diminished 

the longer a driver’s vision and attention 

are diverted from the roadway. 

Furthermore, relative consistency of 

location across vehicle platforms will 

promote easy identification of the 

switch when drivers encounter a new 

vehicle. Therefore, NHTSA believes 

that, consistent with S5.1.1 of FMVSS 

No. 101, it is necessary to require the 

‘‘ESC Off’’ switch to be located in a 

position where it is visible to a belted 

driver. 

11. Test Procedures 

(a) Accuracy Requirements 

Honda requested that the agency 

specify accuracy requirements for the 

following measurement instruments 

used in the ESC test procedures: (1) Yaw 

rate sensor; (2) steering machine, and (3) 

lateral acceleration sensor. The 

commenter stated that such 

specifications would assist in the selfcertification process and the agency’s 

own compliance testing. 

The agency has decided that it is not 

necessary to include sensor 

specifications as part of the regulatory 

text of FMVSS No. 126. NHTSA is 

including these sensor specifications in 

the NHTSA Laboratory Test Procedures 

for Standard No. 126. The Laboratory 

Test Procedures provide detailed 

instructions to personnel conducting 

compliance testing for the agency, 

including test equipment to be used and 

the limitations on equipment output 

variability. Including the acceptable 

equipment output variability parameters 

in the test procedures does not affect the 

substance of the standard’s 

requirements, and helps the agency 

respond as needed to factors affecting 

the availability of test equipment. The 

Laboratory Test Procedures will be 

made available to the public prior to the 

initiation of FMVSS No. 126 compliance 

testing, but for those interested, we note 

here that the sensor specifications of the 

instrumentation used by the agency’s 

ESC research program and currently 

planned for use in the compliance 

testing program are as follows: 

Yaw rate: Range ±100 degrees/s; 

Nonlinearity ≤0.05% of full scale. 

Steering machine encoder: Range ±720 

degrees; Resolution ±0.10 degrees 

(combined resolution of the encoder 

and D/A converter). 

Accelerometers: Range ±2 g; 

Nonlinearity <50μg/g.2

The agency emphasizes that there is 

considerable precedent on the question 

of what belongs in the regulatory text as 

compared to what belongs in the 

compliance test procedure. For 

example, neither FMVSS No. 138 (Tire 

Pressure Monitoring Systems) nor 

FMVSS No. 139 (New Pneumatic Radial 

Tires for Light Vehicles) contain 

accuracy requirements in the standard, 

but rather include them in the test 

procedures. 

Given how the agency knows that 

manufacturers design their vehicles to 

pass compliance tests (i.e., with some 

margin to allow for test inaccuracy), we 

anticipate that manufacturers should 

have no difficulty complying with 

specifications contained in the test 

procedures rather than in the standard 

itself. Manufacturers may base their 

margins on their own estimates of the 

repeatability and reproducibility of the 

Sine with Dwell test. NHTSA has 

recently completed a major round-robin 

study with industry examining the 

reproducibility and repeatability of the 

test. Industry, as well as NHTSA, has all 

of the raw data, and as the results are 

evaluated, we believe that 

manufacturers will have more than 

sufficient information to make these 

decisions. 

(b) Tolerances 

Under paragraph S7.4, Brake 

Conditioning, the NPRM’s proposed test 

procedures call for the vehicle to 

undertake a series of stops from either 

56 km/h (35 mph) or 72 km/h (45 mph) 

in order to condition the brakes prior to 

further testing under the standard (see 

S7.4). In addition, the NPRM called for 

the vehicle to undertake several passes 

with sinusoidal steering at 56 km/h (35 

mph) to condition the tires (see S7.5). 

Honda recommended that the agency 

outline specific tolerances for vehicle 

speed and deceleration to condition the 

tires and brakes prior to compliance 

testing, thereby helping to ensure 

consistent test conditions. 

The agency has decided not to make 

additional changes to the tire and brake 

conditioning provisions of the 

regulatory text based upon Honda’s 

recommendations, because, for the 

reasons discussed below, we believe the 

details currently specified in the 

proposed regulatory text for FMVSS No. 

126 are sufficient. The intent of tire 

conditioning is to wear away mold 

sheen and to help bring the tires up to 

test temperature. Minor fluctuations in 

the vehicle speeds specified in S7.5.1 

and S7.5.2 should not have any 

measurable effect on these objectives. 

Similarly, we believe minor fluctuations 

in the maneuver entrance speeds and 

deceleration specifications provided in 

S7.4.1 through S7.4.4 will not adversely 

affect the brake conditioning process. 

Accordingly, we believe that the 

commenter’s recommended tolerances 

for vehicle speed and deceleration are 

unnecessary. 

(c) Location of Lateral Accelerometer 

Honda recommended that the final 

rule’s test procedures should include 

detailed specifications on how to 

calculate lateral acceleration. According 

to Honda, the NPRM proposed to 

require calculation of lateral 


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displacement of the vehicle’s center of 

gravity based upon lateral acceleration 

of the vehicle’s center of gravity. 

However, the commenter stated that for 

some vehicles, it may not be possible to 

install a lateral acceleration sensor at 

the location of the vehicle’s actual 

center of gravity; in those cases, it 

reasoned, a correction factor will be 

necessary to accommodate this different 

sensor positioning. 

We agree with Honda’s comment that 

it may not be possible to install a lateral 

acceleration sensor at the location of the 

vehicle’s actual center of gravity. For 

this reason, it is important to provide a 

coordinate transformation to resolve the 

measured lateral acceleration values to 

the vehicle’s center of gravity location. 

The specific equations used to perform 

this operation, as well as those used to 

correct lateral acceleration data for the 

effect of chassis roll angle, will be 

incorporated into the laboratory test 

procedure. 

(d) Calculation of Lateral Displacement 

As noted above, the NPRM proposed 

that under each test performed under 

the test conditions of S6 and the test 

procedure of S7.9, the vehicle would be 

required to satisfy the responsiveness 

criterion of S5.2.3 during each of those 

tests conducted with a steering 

amplitude of 180 degrees or greater. 

Specifically, proposed paragraph S5.2.3 

provides that lateral displacement of the 

vehicle center of gravity with respect to 

its initial straight path must be at least 

1.83 m (6 feet) when computed 1.07 

seconds after initiation of steering. The 

NPRM further proposed that the 

computation of lateral displacement is 

performed using double integration with 

respect to time of the measurement of 

lateral acceleration at the vehicle center 

of gravity (see S5.2.3.1) and that time 

t=0 for the integration operation is the 

instant of steering initiation (see 

S5.2.3.2). 

Oxford Technical Solutions, Ltd. 

(Oxford) commented that the proposed 

ESC test procedures require refinement, 

because it believes that the same 

vehicle, when tested at different 

facilities and by different engineers, 

may experience differences in lateral 

displacement of up to 60 cm. 

Specifically, Oxford identified what it 

perceived to be problems with the 

proposed test procedures’ computation 

of lateral displacement and also the 

repeatability of those procedures. 

Regarding lateral displacement 

computation, Oxford argued that 

integrating the accelerometer into a 

rotating reference frame does not 

compute actual lateral displacement, 

because with this technique, a vehicle 

that rotates more (i.e., achieves a higher 

yaw angle compared to the original 

straight driving line) will yield a 

different result, even if the displacement 

is the same. Although the commenter 

acknowledged the need to set some 

value as part of the test (e.g., 1.83 

meters, as proposed), it suggested using 

some term to prevent confusion, such as 

‘‘NHTSA Displacement,’’ ‘‘ESC 

Displacement,’’ or ‘‘Spin 

Displacement.’’ On this point, Oxford 

recommended consideration of the 

following language: 

The ‘‘Spin Displacement’’ is a doubleintegration of a lateral accelerometer over a 

period of 1.071 seconds and the value has to 

be 1.83m. The test must be conducted uphill 

on your VDA to within 5 degrees of the 

uphill direction. The VDA should have an 

angle of no more than 2 degrees. The lateral 

acceleration must be measured to an 

accuracy of 0.03m/s2, including roll effects. 

Therefore roll must be measured to an 

accuracy of 0.2 degrees relative to gravity. 

The accelerometer must have a linearity and 

scale factor better than 0.3% and a 

bandwidth larger than 25 Hz. 

Regarding repeatability, Oxford stated 

that up to 60 cm of difference in lateral 

displacement could result from small 

differences in the conduct of testing, 

including: 

• Use of a true lateral displacement 

measurement (i.e., GPS), as opposed to 

the proposed accelerometer technique, 

could result in a 6 cm difference. 

• Failure to do a roll correction for 

the acceleration could result in up to an 

18 cm difference. 

• Variation for the linearity error of a 

low-cost accelerometer could result in 

up to a 2 cm difference. 

• Depending upon the rainwater runoff angle of the road, there could be up 

to a 6 cm difference. 

• Variations in the mounting angle of 

the accelerometer in the vehicle may 

result in about a 9 cm difference. 

• If there is a 20 ms timing error in 

acquisition, this could result in about an 

8 cm difference. 

• For accelerometers with a 10 Hz 

bandwidth, as compared to a wide 

bandwidth, there could be a difference 

of about 20 cm. 

• There may also be some variation in 

the natural drift of vehicles, which can 

vary by about 40 cm over 100 m. This 

may affect the results by a few 

centimeters in the 20 m traveled during 

the test. (Changing the tires, keeping the 

same tire model, would yield yet a 

different result.) 

Oxford also suggested that the test 

should be based upon ‘‘spin velocity’’

rather than ‘‘spin displacement.’’ The 

commenter reasoned that this approach 

would render timing less important, 

because spin velocity at 1.071 seconds 

is roughly constant, and it argued that 

measurements of ‘‘spin velocity’’ would 

be easier to repeat. 

Technically speaking, as Oxford 

points out, the lateral displacement 

evaluated under the proposed ESC rule 

is not the ‘‘lateral displacement of the 

vehicle’s center of gravity,’’ but an 

approximation of this displacement. In 

the context of the proposal, the location 

of the vehicle’s center of gravity 

corresponds to the longitudinal center 

of gravity, measured when the vehicle is 

at rest on a flat, uniform surface. 

The lateral displacement metric, as 

defined in the ESC NPRM, is based on 

the double integration of accurate lateral 

acceleration data. Lateral acceleration 

data are collected from an 

accelerometer, corrected for roll angle 

effects, and resolved to the vehicle’s 

center of gravity using coordinate 

transformation equations. The use of 

accelerometers is commonplace in the 

vehicle testing community, and 

installation is simple and well 

understood. Although the use of GPSbased measurements for vehicle 

dynamics testing is increasing, 

achieving high dynamic accuracy 

requires differential post-processing (a 

process the agency has found to be timeconsuming), a real-time differential 

service, or real-time kinematics base 

station correction of the data. Each of 

these options introduces significant cost 

and complexity to the testing effort. 

However, the system described by 

Oxford is approximately forty times 

more expensive than the calculation 

method prescribed by the final rule. 

For the purposes of the ESC 

performance criteria, we believe use of 

a calculated lateral displacement metric 

provides a simple, reasonably accurate, 

and cost-effective way to evaluate 

vehicle responsiveness. Since the 

integration interval is short (recall that 

lateral displacement is assessed 1.07 

seconds after initiation of the 

maneuver’s steering inputs), integration 

errors are expected to be small. Recent 

improvements to the agency’s data 

processing routines include refined 

signal offset and zeroing strategies that 

should minimize the confounding 

effects these factors may have on the test 

output, thereby ensuring repeatable 

results. 

These NHTSA-developed routines 

used to calculate lateral displacement 

during data post-processing will be 

made publicly available, in order to 

ensure that vehicle manufacturers and 

ESC suppliers know exactly how the 

responsiveness of their vehicle’s (or 

customer’s vehicles) will be evaluated. 

If the sensors used to measure the 


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17284 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

64As background, the frequency of the sinusoidal 

curve used to command the Sine with Swell 

maneuver steering input is 0.7 Hz. Use of this 

frequency causes the time from the completion of 

the initial steering input (the first peak) to the 

completion of the steering reversal (the second 

peak) to take approximately 714 ms, regardless of 

the commanded steering angle magnitude. We have 

performed multiple studies using double-lane 

change maneuvers to evaluate the upper limit of 

human driver steering capability, and we have 

found the results listed above. See Forkenbrock, 

Garrick J. and Devin Elsasser, ‘‘An Assessment of 

Human Driver Steering Capability,’’ NHTSA 

Technical Report, DOT HS 809 875, October 2005. 

Available at http://www-nrd.nhtsa.dot.gov/vrtc/ca/

capubs/NHTSA_forkenbrock_driversteering

capabilityrpt.pdf. 

65Schneider, L.W., Robbins, D.H., Pflug, M.A., 

and Synder, R.G., ‘‘Development of 

Anthropometrically Based Design Specifications for 

vehicle responses are of sufficient 

accuracy, and have been installed and 

configured correctly, use of the analysis 

routines provided by NHTSA are 

expected to minimize the potential for 

performance discrepancies among 

NHTSA and industry test efforts. The 

specifications of the accelerometers 

used by NHTSA are: (1) Bandwidth 

>300 Hz, (2) non-linearity <50 μg/g2, (3) 

resolution ≤10 μg, and (4) output noise 

≤7.0mV. An overview of all NHTSA 

instrumentation used during Sine with 

Dwell tests is provided in Table 5. 

TABLE 5.—NHTSA SENSOR SPECIFICATIONS

Data measured Type Range Manufacturer Accuracy Model No. 

Steering Wheel Angle Angle Encoder .......... ±720 degrees ............ Automotive Testing, 

Inc. 

±0.10 degrees1 .......... Integral with ATI 

Steering Machine. 

Longitudinal, Lateral, 

and Vertical Acceleration.

Multi-Axis Inertial 

Sensing System.

Accelerometers: ±2g

Angular Rate Sensors: ±100°/s.

BEI Technologies, 

Inc. 

Systron Donner Inertial Division.

Accelerometers:<50μg/g2 2.

Angular Rate Sensors: ≤0.05%.

MotionPak Multi-Axis 

Inertial Sensing 

System MP–1. 

Left and Right Side 

Vehicle Ride Height.

Ultrasonic Distance 

Measuring System.

4–40 inches ............... Massa Products Corp. 0.25% of maximum 

distance.

M–5000/220 kHz. 

Vehicle Speed ........... Radar Speed Sensor 0.1–125 mph ............. B+S Software und 

Messtechnik.

0.1 mph ..................... DRS–6. 

1 Combined resolution of the encoder and D/A converter. 

2 Non-linearity specifications. 

(e) Maximum Steering Angle 

For the Sine with Dwell test, the 

NPRM proposed to provide that ‘‘[t]he 

steering amplitude of the final run in 

each series is the greater of 6.5A or 270 

degrees.’’ (See S7.9.4) 

Toyota expressed concern that S7.9.4 

may allow the steering angle to be too 

large for vehicles that have a large 

steering gear ratio. Toyota stated its 

belief that the upper limit of an average 

driver’s steering velocity is 

approximately 1000°/sec; thus, the 

steering angle is 227° under a Sine with 

Dwell condition with a frequency of 0.7 

Hz. Similarly, Toyota stated that the 

steering angle of 270° is equal to the 

steering velocity of 1188°/sec, a value 

that exceeds the average driver’s 

steering velocity. Therefore, Toyota 

recommended revising S7.9.4 to state: 

‘‘The steering amplitude of the final run 

in each series is 270 degrees.’’

NHTSA disagrees with Toyota’s 

recommendation. Our own studies have 

shown that human drivers can sustain 

handwheel rates of up to 1189 degrees 

per second for 750 milliseconds. This 

steering rate corresponds to a steering 

angle magnitude of approximately 303 

degrees.64

We concede that the method used to 

determine maximum Sine with Dwell 

steering angles can produce very large 

steering angles. Of the 62 vehicles used 

to develop the Sine with Dwell 

performance criteria, the vehicle 

requiring the most steering was a 2005 

Ford F250. This vehicle required a 

maximum steering angle of 371 degrees 

(calculated by multiplying the average 

steering angle capable of producing a 

lateral acceleration of 0.3g in the Slowly 

Increasing Steer maneuver times a 

steering scalar of 6.5). Use of this 

steering wheel angle required an 

effective steering wheel rate of 1454 

degrees per second, a magnitude well 

beyond the steering capability of a 

human driver. 

Although we do not believe the 

maximum steering angle specified in 

S7.9.4 should be revised in the precise 

manner recommended by Toyota, we do 

believe revision of that specification is 

necessary. As such, we have updated 

the specification in S7.9.4 to read as 

follows: 

S7.9.4 The steering amplitude of the final 

run in each series is the greater of 6.5A or 

270 degrees, provided the calculated 

magnitude of 6.5A is less than or equal to 300 

degrees. If any 0.5A increment, up to 6.5A, 

is greater than 300 degrees, the steering 

amplitude of the final run shall be 300 

degrees. 

(f) Vehicle Test Weight 

Under S6.3.2, the NPRM proposed 

that the vehicle is to be loaded with the 

fuel tank filled to at least 75 percent of 

capacity, an total interior load of 168 kg 

(370 lbs) comprised of the test driver, 

approximately 59 kg (130 lbs) of test 

equipment (automated steering 

machine, data acquisition system and 

the power supply for the steering 

machine), and ballast as required by 

differences in the weight of test drivers 

and test equipment. 

TRW Automotive commented that the 

proposed vehicle test conditions for 

vehicle weight leave only 240 pounds as 

the maximum driver test weight. The 

commenter suggested that the total 

interior load should be increased to 400 

pounds, thereby permitting a maximum 

driver test weight of 270 pounds. 

According to TRW Automotive, this 

modification should not result in a 

substantive change to the intent of the 

regulation or test results, but it would 

provide greater flexibility in testing by 

accommodating a broader weight 

variance between drivers. 

The Alliance/AIAM recommended 

modifying S6.3.2 to clarify the location 

where ballast (if required) is to be 

placed in the vehicle. The commenters 

recommended substituting the following 

language: 

S6.3.2 Test Weight. The vehicle is loaded 

with the fuel tank filled to at least 75 percent 

of capacity, and total interior load of 168 kg 

(370 lbs.) comprised of the test driver, 

approximately 59 kg (130 lbs.) of test 

equipment (automated steering machine, data 

acquisition system and power supply for the 

steering machine), and ballast as required by 

differences in the weight of test drivers and 

test equipment. Where required, ballast shall 

be placed on the floor behind the passenger 

front seat or if necessary in the front 

passenger foot well area. 

In regard to the TRW Automotive 

comment, given that the weight of a 

95th percentile male is 225 pounds,65


ycherry on PROD1PC64 with RULES2
Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17285 

an Advanced Adult Anthropomorphic Dummy 

Family—Volume 1—Procedures, Summary 

Findings, and Appendices,’’ The University of 

Michigan Transportation Research Institute Report 

UMTRI–83–53–1, December 1983, Table 2–5 at 20. 

66We note that this is Alliance/AIAM’s term, not 

NHTSA’s. We believe they are referring to a rubber 

chemistry issue (i.e., that all rubbery polymers turn 

into glassy solids at characteristic low 

temperatures), which vary depending on the 

polymer composition of the tires. The Alliance/ 

AIAM seem to assert that because of their 

composition, for certain high performance tires, the 

‘‘glass transition range’’ (i.e., the temperature range 

between the glass temperature and the onset of fully 

rubber-like response) may include some of the 

lower bound of the proposed ambient test range. 

we believe that the maximum allowable 

weight allocated for the test driver, as 

presently specified in the NPRM for 

FMVSS No. 126, is conservative and 

should not impose an unreasonable 

testing burden on parties performing 

ESC compliance tests. As such, in this 

final rule, we are retaining the total 

interior load of 168 kg (370 lbs) 

specified in S6.3.2. 

In response to the Alliance/AIAM 

comment, we note that the standard 

does require ballast to be added to a test 

vehicle, if necessary, to account for 

varying weights of test drivers and test 

equipment. We agree with the Alliance/ 

AIAM comment additional clarification 

of where the ballast shall be positioned 

is necessary. The agency has decided to 

provide further direction in the 

standard’s test procedure to ensure 

required ballast is appropriately placed 

in the vehicle. We concur with the 

Alliance/AIAM recommendation, as it 

provides a reasonable way to evenly 

distribute the load of the driver, steering 

machine, and test equipment. 

Additionally, we also acknowledge the 

very abrupt vehicle motions imposed by 

the Sine with Dwell maneuver are 

capable of dislodging and/or relocating 

unsecured ballast while testing. So as to 

maximize driver safety, we have revised 

S6.3.2 to read: 

S6.3.2 Test Weight. The vehicle is loaded 

with the fuel tank filled to at least 75 percent 

of capacity, and total interior load of 168 kg 

(370 lbs.) comprised of the test driver, 

approximately 59 kg (130 lbs.) of test 

equipment (automated steering machine, data 

acquisition system and power supply for the 

steering machine), and ballast as required by 

differences in the weight of test drivers and 

test equipment. Where required, ballast shall 

be placed on the floor behind the passenger 

front seat or if necessary in the front 

passenger foot well area. All ballast shall be 

secured in a way that prevents it from 

becoming dislodged during test conduct. 

(g) Data Filtering 

According to the Alliance/AIAM, 

NHTSA usually incorporates 

specifications for its data filtering 

method as part of its test report 

(presumably referring to the agency’s 

laboratory test procedure). However, the 

commenters argued that given the 

potential for different filtering methods 

to significantly influence final results, 

the agency should specify its data 

filtering methods directly in FMVSS No. 

126. 

The Alliance/AIAM recommended 

the following filtering protocol for all 

channels (except steering wheel angle 

and steering wheel velocity): (a) Create 

a six-pole, low-pass Butterworth filter 

with a 6 Hz cut-off frequency, and (b) 

filter the data forwards and backwards 

so that no phase shift is induced. For 

the steering wheel angle channel, the 

commenters recommended using the 

same protocol, but with a 10 Hz cut-off 

frequency. For steering wheel velocity, 

the Alliance/AIAM recommended 

adoption of a specific calculation 

described in Appendix 1 of their 

comments. 

Data filtering methods can have a 

significant impact on final test results 

used for determining vehicle 

compliance with FMVSS No. 126. The 

agency agrees with the Alliance/AIAM 

that the same filtering and processing 

protocols must be followed in order to 

ensure consistent and repeatable test 

results. Therefore, the agency has 

decided to add a new paragraph S7.11 

to the test procedures section of the 

final rule’s regulatory text in order to 

specify critical test filtering protocols 

and techniques to be used for test data 

processing, as described in greater detail 

above in Section IV.C.7(e), Data 

Processing Issues. 

(h) Outriggers 

Under the proposed test condition in 

S6 of the NPRM, paragraph S6.3.4 

provides, ‘‘Outriggers must be used for 

tests of Sport Utility Vehicles (SUVs), 

and they are permitted on other test 

vehicles if deemed necessary for driver 

safety.’’

According to the Alliance/AIAM, 

although the use of outriggers may be 

appropriate, the final rule should 

explicitly clarify the vehicle classes that 

are to be equipped with outriggers 

under the standard and set forth the 

design specifications for those devices. 

The organizations suggested that 

requiring outriggers on sport utility 

vehicles and ‘‘other test vehicles if 

deemed necessary for driver safety’’ is 

too open-ended. The commenters 

argued that such clarification is 

necessary because outriggers can 

influence vehicle dynamics in the 

subject tests. Thus, the Alliance/AIAM 

recommended revising S6.3.4 to read as 

follows: ‘‘Outriggers meeting the 

specifications of [cite section] must be 

used for tests of trucks, multipurpose 

vehicles, and buses.’’ 

The agency agrees that the use of 

outriggers has the potential to influence 

vehicle dynamics during ESC testing. 

Therefore, in order to reduce test 

variability and increase the repeatability 

of test results, the agency is revising 

paragraph S6.3.4 in this final rule to 

specify that outriggers are to be used on 

all vehicles other than passenger cars. 

Furthermore, the agency has decided to 

include maximum weight and roll 

moment of inertia specifications for 

outriggers in paragraph S6.3.4, and we 

will also make available the detailed 

design specifications for the outriggers 

used by the agency as part of the 

NHTSA compliance test procedure for 

FMVSS No. 126. 

(i) Ambient Temperature Range 

Under the proposed test condition in 

S6 of the NPRM, paragraph S6.1.1 

provides, ‘‘The ambient temperature is 

between 0 °C (32 °F) and 40 °C (104 °F).’’

In their comments, the Alliance/ 

AIAM stated that their analysis has 

demonstrated test variability due to 

temperature. The Alliance/AIAM 

comments also suggested that certain 

high performance tires could enter their 

‘‘glass transition range’’ 66 which could 

introduce further variability at nearfreezing temperatures. For these 

reasons, the commenters expressed 

concern that the lower bound of the 

proposed ambient test range is too low. 

Accordingly, the Alliance/AIAM 

recommended increasing the lower 

bound of the temperature range to 50 

degrees F. In addition to reducing test 

variability, the commenters stated that 

their proposed modification to the 

temperature portion of the test 

procedures would permit virtually yearround testing at certain facilities (e.g., 

DRI Bakersfield), reduce burdens 

associated with confirming compliance 

at low temperatures, and avoid 

complications of snow and ice during 

testing. 

A vehicle’s ESC system is designed 

for and expected to address stability 

issues over a wide range of various 

environmental conditions. Testing 

conducted by Alliance/AIAM member 

companies indicates that lateral 

displacement for vehicles equipped 

with all-season tires varies with 

fluctuating ambient temperatures. 

According to the Alliance/AIAM, the 

data indicate that lateral displacement 

for test vehicles equipped with allseason tires increases as the ambient 

temperature decreased, suggesting that 

the displacement requirement could be 

met more easily at lower ambient 


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temperatures. However, this same 

relationship was not manifest for test 

vehicles equipped with high 

performance tires. (Some highperformance tires are not designed for 

operation under freezing conditions, 

and the performance variability of these 

tires under cold ambient temperatures is 

unknown, because in our repeatability 

studies, we only test tires in the 

temperature ranges in which they are 

designed to operate.) The Alliance 

recommended minimizing potential test 

variability by reducing the specified test 

condition ambient temperature range. 

To minimize test variability the agency 

has decided to increase the lower bound 

of the temperature range for compliance 

testing to 45 degrees F. The agency 

believes that 7 °C (45 °F) is appropriate 

because it is low enough to increase the 

length of the testing season at multiple 

testing sites, and also represents the low 

end of the relevant temperature range 

for at least one brand of high 

performance tires of which the agency is 

aware. 

(j) Brake Temperatures 

In their comments, the Alliance/ 

AIAM stated that several of their 

member companies assessed the affect 

of brake pad temperatures on ESC test 

results, particularly given the potential 

for drivers to use heavy braking between 

test runs. Included in their comments 

were charts based upon their research 

that purported to demonstrate variance 

in testing due to brake pad temperature 

would be an artifact of the test 

methodology, not a reflection of 

expected ESC performance in the real 

world. Therefore, in order to minimize 

non-representative test results, the 

Alliance/AIAM comments 

recommended that the standard’s test 

procedures should specify a minimum 

of 90 seconds between test runs in order 

to allow sufficient time for cooling of 

the brake pads. 

The test procedure specified in the 

NPRM did not address brake 

temperature issues that may arise from 

heavy braking between test runs. 

Because the agency agrees that excessive 

brake temperatures may have an effect 

on ESC test results, a minimum wait 

time between test runs has been 

incorporated into the test procedure to 

ensure brake temperatures are not 

excessive. We believe that 90 seconds, 

as proposed by the Alliance/AIAM, is a 

reasonable lower bound for the 

allowable time between runs. Note that 

the procedure specified in the NPRM 

does specify a maximum wait time of 5 

minutes between test runs to ensure that 

the brakes and tires remain at operating 

temperatures, a feature we believe is 

important since compliance test 

procedures endeavor to simulate real 

world driving conditions. For these 

reasons, the allowable range of time 

between Sine with Dwell tests will be 

90 seconds to 5 minutes. 

(k) Wind Speed 

Under the proposed test condition in 

S6 of the NPRM, paragraph S6.1.2 

provides, ‘‘The maximum wind speed is 

no greater than 10 m/s (22 mph).’’

The Alliance/AIAM expressed 

concern that the proposed maximum 

wind speed for testing (10 m/s (22mph)) 

could impact the performance of certain 

vehicle configurations (e.g., cube vans, 

15-passenger vans, vehicles built in two 

or more stages). The commenters 

estimated that a cross wind at 22 mph 

could reduce lateral displacement at 

1.07 s by 0.5 feet, compared to the same 

test conducted under calm conditions. 

Accordingly, the Alliance/AIAM 

recommended revising S6.1.2 to reduce 

the maximum allowable wind speed to 

5 m/s (11 mph), a figure consistent with 

other regulatory requirements (e.g., 

FMVSS No. 135, Light Vehicle Brake 

Systems) and ISO 7401. 

The agency agrees that wind speed 

could have some impact on the lateral 

displacement for certain vehicle 

configurations, including large sport 

utility vehicles and vans. However, we 

also believe that reducing the maximum 

wind speed to 5 m/s (11 mph) can 

impose additional burdens on our test 

labs by restricting the environmental 

conditions under which testing can be 

conducted. With these considerations in 

mind, we have decided to modify S6.1.2 

to reduce the wind speed requirement 

as recommended to 5 m/s (11 mph) for 

multipurpose passenger vehicles 

(including SUVs, vans, and trucks), but 

to keep the specified wind speed for 

passenger cars at 10 m/s (22 mph). This 

change will reduce test variability for 

those vehicles expected to be most 

effected by wind speed and to minimize 

any additional burdens on test 

laboratories. 

We note that if we set the wind speed 

requirement at 5 m/s (11 mph) for all 

light vehicles, that would unduly limit 

the number of days on which NHTSA 

could perform compliance testing, and 

we further believe that wind speed up 

to 10 m/s (22 mph) would not have an 

appreciable impact on the testing of 

passenger cars due to their smaller side 

dimensions. 

(l) Rounding of Steering Wheel Angle at 

0.3 g 

Under the proposed test procedure in 

S7 of the NPRM, paragraph S7.6.1 

provides, ‘‘From the Slowly Increasing 

Steer tests, the quantity ‘‘A’’ is 

determined. ‘‘A’’ is the steering wheel 

angle in degrees that produces a steady 

state lateral acceleration of 0.3 g for the 

test vehicle. Utilizing linear regression, 

A is calculated, to the nearest 0.1 

degrees, from each of the six Slowly 

Increasing Steer tests. The absolute 

value of the six A’s calculated is 

averaged and rounded to the nearest 

degree to produce the final quantity, A, 

used below.’’

The Alliance/AIAM recommended 

against rounding the steering wheel 

angle measurement at 0.3 g to the 

nearest whole number, because such 

methodology potentially increases 

variability across test runs. As 

demonstrated in a table included in 

their submission, the commenters stated 

that such an approach could also 

increase steering wheel angle variability 

at a scalar of 5.0 (where the proposed 

responsiveness metric starts) by a factor 

of five. They also argued that rounding 

to that proposed level of precision (i.e., 

to a whole number) does not simplify 

programming or control of the steering 

robot. Therefore, in order to eliminate 

this source of test variability, the 

Alliance/AIAM recommended rounding 

the steering wheel angle at 0.3 g to the 

nearest 0.1 degrees. 

The agency agrees with the Alliance 

and AIAM recommendation to round 

the steering wheel angle at 0.3 g to the 

nearest 0.1 degree, and we have 

modified the final rule’s regulatory text 

accordingly. Rounding to this level is 

not expected to complicate 

programming of the automated steering 

controller and will decrease the 

variability in the number of required 

test runs. 

(m) Vehicle Speed Specification for the 

Slowly Increasing Steer Test 

In their comments, the Alliance/ 

AIAM questioned whether the 

proposal’s failure to specify a vehicle 

speed for the slowly-increasing-steer 

test was an oversight. The commenters 

recommended adopting specifications 

for a test speed of 80 ± 1 km/h, which 

is consistent with the speed for the Sine 

with Dwell test. 

We agree that a speed tolerance 

should be specified for the Slowly 

Increasing Steer test, and we have 

determined that it should be the same 

as the speed tolerance specified for the 

Sine with Dwell test. However, we note 

that in this final rule, the proposed Sine 

with Dwell test speed tolerance has 

been revised to better reflect the manner 

in which testing is performed; as 

revised, the speed tolerance is 80 ± 2 

km/h (50 ±1 mph). This speed tolerance 


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67The adjectival ratings used to rate the test 

maneuvers were ‘‘Excellent,’’ ‘‘Good,’’ and ‘‘Fair,’’

with ‘‘Excellent’’ being the best and ‘‘Fair’’ being 

the worst. We considered an ‘‘Excellent’’ maneuver 

as one capable of adequately demonstrating 

whether a vehicle was, or was not, equipped with 

an ESC system that satisfied a preliminary version 

of our minimum performance criteria. Conversely, 

a maneuver assigned a ‘‘Fair’’ rating was unable to 

adequately demonstrate whether vehicles evaluated 

by NHTSA were, or were not, equipped with ESC 

systems capable of satisfying the preliminary 

minimum performance criteria. 

68 In an obstacle avoidance scenario, it is clearly 

conceivable that the second steering input may be 

larger than the first input. If the first steering input 

induces overshoot, the driver’s reversal will need to 

be equal to the first steering input plus enough 

steering to combat the yaw overshoot. 

will also be applicable to the Slowly 

Increasing Steer maneuver. 

(n) Alternative Test Procedures 

Public Citizen stated that in the 

NPRM, the agency noted that there is a 

trade-off between lateral stability and 

intervention magnitude, but the 

commenter challenged the agency’s 

determination as to where the 

appropriate balance should be set. 

Public Citizen stated that the agency 

should provide an assessment of other 

available alternative test procedures and 

the agency’s rationale for not adopting 

those procedures. The commenter 

further argued that the test procedures 

which the agency did propose may be 

inadequate, particularly if errors in 

measurement would allow vehicles to 

pass the performance test. 

We believe an appropriate balance 

between lateral stability and 

intervention magnitude is one in which 

a light vehicle is in compliance with the 

evaluation criteria of FMVSS No. 126, 

both in terms of lateral stability and 

responsiveness. Development of these 

criteria was the result of hundreds of 

hours of testing and data analysis. We 

are confident these criteria provide an 

extremely effective way of objectively 

assessing whether the lateral stability of 

ESC-equipped vehicle is adequate. 

We believe the responsiveness criteria 

proposed for use in FMVSS 126, that a 

vehicle must achieve at least 6 feet (5 

feet for vehicles with a GVWR of greater 

than 3500 kilograms) of lateral 

displacement when the Sine with Dwell 

maneuver is performed with normalized 

steering angles (normalized steering 

wheel angles account for differences in 

steering ratios between vehicles) greater 

than 5.0, adequately safeguards against 

implementation of overly aggressive 

ESC systems, even those specifically 

designed to mitigate on road untripped 

rollover (i.e., systems that may consider 

stability more important than path 

following capability). Achieving 

acceptable lateral stability is very 

important, but should not be 

accomplished by grossly diminishing a 

driver’s crash avoidance capability. 

Intervention intrusiveness can refer to 

how the vehicle manufacturer and its 

ESC vendor ‘‘tune’’ an ESC system for 

a particular make/model, specifically 

how apparent the intervention is to the 

driver. We do not believe it is 

appropriate to dictate this form of 

intervention magnitude, as it can be an 

extremely subjective specification. As 

long as a vehicle’s ESC (1) Satisfies our 

hardware and software definitions and 

(2) allows the vehicle to comply with 

our lateral stability and responsiveness 

performance criteria, we believe 

intervention intrusiveness should be a 

tuning characteristic best specified by 

the vehicle/ESC manufacturers. 

In response to the Public Citizen 

statement regarding maneuver selection, 

we evaluated twelve test maneuvers 

before ultimately selecting the Sine with 

Dwell maneuver to assess ESC 

performance. As explained below, this 

evaluation was performed in two stages, 

an initial reduction from twelve 

maneuvers to four, then from four to 

one. 

The first stage began with 

identification of three important 

attributes: (1) High maneuver severity 

(‘‘maneuver severity’’); (2) capability to 

produce highly repeatable and 

reproducible results using inputs 

relevant to real-world driving scenarios 

(‘‘face validity’’); and (3) ability to 

effectively evaluate both lateral stability 

and responsiveness (‘‘performability’’). 

To quantify the extent to which each 

maneuver possessed these attributes, 

adjectival ratings ranging from 

‘‘Excellent’’ to ‘‘Fair’’ were assigned to 

each of the twelve maneuvers, for each 

of the three maneuver evaluation 

criteria. Of the twelve test maneuvers, 

only four received ‘‘Excellent’’ ratings 67

for each of the maneuver evaluation 

criteria—the Increasing Amplitude Sine 

(0.7 Hz), Sine with Dwell (0.7 Hz), Yaw 

Acceleration Steering Reversal (YASR; 

500 deg/sec), and Yaw Acceleration 

Steering Reversal with Pause (YASR 

with Pause; 500 deg/sec steering rate). 

Stage two of the maneuver reduction 

process used data from 24 vehicles (a 

sampling of sports cars, sedans, 

minivans, small and large pickup 

trucks, and sport utility vehicles 

intended to represent a majority of the 

vehicles presently sold in the United 

States) to compare the maneuver 

severity, face validity, and 

performability of the four maneuvers 

selected in the first stage. The ability of 

the four maneuvers to satisfy these three 

evaluation criteria were compared and 

rank ordered. 

Of the four candidate maneuvers, we 

concluded the Sine with Dwell and 

YASR with Pause were the top 

performers in terms of evaluating the 

lateral stability component of ESC 

functionality. However, due to the fact 

that the Sine with Dwell maneuver 

required smaller steering angles to 

produce spinouts for five of the ten 

vehicles evaluated with left-right 

steering, and for two of the ten vehicles 

with right-left steering (with the 

remaining thirteen tests using the same 

steering angles), we assigned the Sine 

with Dwell maneuver a higher 

maneuver severity ranking than that 

assigned to the YASR with Pause 

maneuver. 

Generally speaking, the Increasing 

Amplitude Sine and YASR maneuvers 

required the most steering to produce 

spinouts, regardless of direction of steer. 

However, the Increasing Amplitude 

Sine maneuver also produced the lowest 

normalized second yaw rate peak 

magnitudes, implying the maneuver was 

the least severe for most of the 24 test 

vehicles used for maneuver comparison. 

For this reason, we assigned the worst 

severity ranking to the Increasing 

Amplitude Sine maneuver. 

Each of the four candidate maneuvers 

possessed inherently high face validity 

since they were each comprised of 

steering inputs similar to those capable 

of being produced by a human driver in 

an emergency obstacle avoidance 

maneuver. However, of the four 

maneuvers, we believed the Increasing 

Amplitude Sine maneuver possessed 

the best face validity. Conceptually, the 

steering profile of this maneuver was 

the most similar to that expected to be 

used by real drivers,68 and even with 

steering wheel angles as large as 300 

degrees, the maneuver’s maximum 

effective steering rate was a very 

reasonable 650 deg/sec. For these 

reasons, the Increasing Amplitude Sine 

maneuver received the top face validity 

rating. 

The two YASR maneuvers received 

the same face validity ratings, just lower 

than that assigned to the Increasing 

Amplitude Sine. The YASR steering 

profiles were comprised of very 

reasonable 500 deg/sec steering rates; 

however, their sharply defined, 

trapezoidal shapes reduce their 

similarity to inputs actually used by 

drivers in real world driving situations. 

The steering profile of the Sine with 

Dwell was deemed very reasonable; 

however, the maneuver can require 

steering rates very near what we believe 

is the maximum capability of a human 

driver. 


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17288 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

69Forkenbrock, Garrick J., Elsasser, Devin, 

O’Harra, Bryan C., ‘‘NHTSA’s Light Vehicle 

Handling and ESC Effectiveness Research 

Program,’’ ESV Paper Number 05–0221, June 2005. 

(Docket No. NHTSA–2006–25801–5) 

70Forkenbrock, Garrick J., Elsasser, Devin, 

O’Harra, Bryan C., Jones, Robert E., ‘‘Development 

of Electronic Stability Control (ESC) Performance 

Criteria,’’ NHTSA Technical Report, DOT HS 809 

974, September 2006. Available at http://wwwnrd.nhtsa.dot.gov/pdf/nrd-01/esv/esv19/05-0221- 

O.pdf. 

71The comments made by Mr. Watts are 

specifically addressed in Section IV.C.11(d) of this 

document. 

72See 71 FR 54712, 54718 (Sept. 18, 2006) 

footnote 11. 

73 Data were analyzed for the development of the 

rollover NCAP star ratings criteria. It is data for six 

States: Florida (1994–2001), Maryland (1994–2000), 

Missouri (1994–2000), North Carolina (1994–1999), 

Pennsylvania (1994–1997), and Utah (1994–2000). 

Only single-vehicle crashes for 100 make-models 

were included. Please consult the Rollover NCAP 

portion of the NHTSA Web site for further 

information (http:///www.nhtsa.dot.gov). 

The performability of the Sine with 

Dwell and the Increasing Amplitude 

Sine maneuvers were deemed to be 

excellent. These maneuvers are very 

easy to program into the steering 

machine, and their lack of rate or 

acceleration feedback loops simplifies 

the instrumentation required to perform 

the tests. Conversely, the YASR 

maneuvers require the use of 

specialized equipment (an angular 

accelerometer), and these maneuvers 

required an acceleration-based feedback 

loop that was sensitive to the 

accelerometer’s signal-to-noise ratio 

near peak yaw rate. Testing 

demonstrated that large steering angles 

can introduce dwell time variability 

capable of adversely reducing maneuver 

severity and test outcome. 

After considering the totality of the 

test result from our evaluation of the 

candidate maneuvers and for the 

reasons stated above, the agency 

concluded that the Sine with Dwell 

maneuver offers the best combination of 

maneuver severity, face validity, and 

performability. Additional details of the 

maneuver selection process are 

available in an Enhanced Safety of 

Vehicles (ESV) technical paper 69 and an 

NHTSA technical report.70

Turning to the statement in Public 

Citizen’s comments regarding the 

implication of measurement errors, the 

commenter stated that ‘‘* * * the error 

in measurements would allow vehicles 

to pass that did not even meet the * * * 

standard of the proposal.’’ This 

comment is in response to comments 

made by Brendan Watts from Oxford 

Technologies, a company that sells 

highly accurate (and very expensive) 

instrumentation.71 Many of the 

concerns expressed by Mr. Watts 

(stressing the importance of using 

accurate accelerometers and sound data 

processing techniques) are not 

specifically applicable to the manner in 

which we (NHTSA) will be performing 

our ESC compliance tests, in that such 

concerns have already been addressed 

by the agency. For example, the 

accelerometers that will be used in ESC 

compliance tests are more accurate than 

those Mr. Watts indicated may 

compromise test accuracy. We 

appreciate the data processing concerns 

expressed by Mr. Watts (e.g., correcting 

lateral acceleration for the effects of roll 

angle, or addressing offset from the 

vehicle’s center of gravity), but again, 

our post-processing routines already 

contain algorithms to resolve such 

concerns. 

We note that all test track evaluations 

inherently contain some degree of 

output variability, regardless of what 

aspect of vehicle performance they are 

being used to evaluate. In the context of 

ESC compliance, we concede this 

variability could result in a marginally 

non-compliant vehicle passing the 

proposed test, but it is important to 

recognize these situations would only 

affect a very small population of 

vehicles, and that that effect of 

instrumentation and/or calculation 

errors is likewise believed to be very 

small. Since the performance of most 

contemporary vehicles resides far 

enough away from the proposed 

compliance thresholds, we believe it is 

extremely unlikely that measurement 

complications will be solely responsible 

for having the performance of a noncompliant vehicle be deemed 

acceptable. 

(o) Representativeness of Real World 

Conditions 

Mr. Kiefer questioned the adequacy of 

the agency’s proposed ESC test 

procedures. Specifically, the commenter 

questioned how many tests are 

necessary to ensure that the system is 

robust, and how many different 

configurations of tires, loading, and 

trailering are needed to be 

representative of real world driving. 

Mr. Cheah also questioned whether it 

would be feasible for the ESC test 

procedures’ controlled conditions to 

adequately represent real world 

conditions. He argued that even though 

an ESC system may increase safety 

under certain conditions, in other cases, 

it may add ‘‘unpredictable and unusual 

characteristics to the vehicle.’’

NHTSA has reviewed many crash 

data studies quantifying real world ESC 

effectiveness.72 Regardless of the origin 

of the data used for these studies (i.e., 

whether from the United States, 

Germany, Japan, France, Sweden, etc.), 

all reported or estimated that ESC 

systems provide substantial benefits in 

‘‘loss of control’’ situations (see Section 

II.D). These studies reported that ESC is 

expected to be particularly effective in 

situations involving excessive oversteer, 

such as ‘‘fishtailing’’ or ‘‘spinout’’

which may result from sudden collision 

avoidance maneuvers (e.g., lane changes 

or off-road recovery maneuvers). 

We note that the Sine with Dwell 

maneuver is specifically designed to 

excite an oversteer response from the 

vehicle being evaluated. While this 

maneuver has been optimized for the 

test track (because objectivity, 

repeatability, and reproducibility are 

necessary elements of a regulatory 

compliance test), it is important to 

recognize that multiple studies have 

indicated that the steering angles and 

rates associated with the Sine with 

Dwell maneuver are within the 

capabilities of actual drivers, not just 

highly trained professional test drivers. 

NHTSA does not know of any 

‘‘unpredictable and unusual 

characteristics’’ imparted by any ESC 

system on the vehicle in which it is 

installed. ESC interventions occur in 

extreme driving situations where the 

driver risks losing control of the vehicle, 

not during ‘‘normal’’ day-to-day driving 

comprised of relatively small, slow, and 

deliberate steering inputs. In these 

extreme situations, the driver must still 

operate the vehicle by conventional 

means (i.e., use of steering and/or brake 

inputs are still required to direct the 

vehicle where the driver wants it to go); 

however, the mitigation strategies used 

by ESC to suppress excessive oversteer 

and understeer help improve the 

driver’s ability to successfully retain 

control of the vehicle under a broad 

range of operating conditions. 

The load configuration used during 

the conduct of our ESC performance 

tests is known as the ‘‘nominal’’ load 

configuration, consisting of a driver and 

test equipment. This configuration 

approximates a driver and one front seat 

occupant. We believe this configuration 

is highly representative of how the 

majority of vehicles driven on our 

nation’s roadways are loaded. Our 

analyses, based on results from a 

database 73 comprised of 293,000 singlevehicle crashes, indicate that the 

average number of passenger car 

occupants involved in a single-vehicle 

crash was 1.48 occupants per vehicle. 

Results for pickups, sport utility 

vehicles, and vans were similar (1.35, 


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1.54, and 1.81 occupants per vehicle, 

respectively). 

We believe it is important for an 

objective test procedure to be applicable 

to all light vehicles (i.e., vehicles with 

a GVWR of 10,000 pounds or less). The 

use of multiple load configurations was 

considered, but there are an infinite 

number of ways drivers can potentially 

load their vehicles, and not all vehicles 

can be subjected to the same load 

configurations. 

Although we do believe it is 

important to understand how vehicle 

loading can influence ESC effectiveness 

and presently have research programs 

designed to objectively quantify those 

effects, we believe requiring ESC on all 

light vehicles will save thousands of 

lives per year. Accordingly, we do not 

believe it is appropriate to delay the 

present mandate for ESC, and to thereby 

fail to maximize the benefits of this 

requirement, pending the outcome of 

this additional research. In sum, we 

believe that the available data strongly 

support our decision to mandate ESC 

installation on all light vehicles at this 

time. 

12. Lead Time and Phase-in 

In preparing its ESC proposal, the 

agency carefully considered the lead 

time necessary for expedient yet 

practicable incorporation of this 

important safety device. With minor 

exceptions discussed below, NHTSA 

proposed in the NPRM to require all 

light vehicles covered by this standard 

to be equipped with a FMVSS No. 126- 

compliant ESC system by September 1, 

2011 (see 8.4). However, the agency 

proposed to extend by one year the time 

for compliance by multi-stage 

manufacturers and alterers (i.e., until 

September 1, 2012) (see S8.8). 

In terms of the phase-in for ESC, the 

agency proposed that compliance would 

commence on September 1, 2008, which 

would mark the start of a three-year 

phase-in period (see S8.1 to S8.4). 

Subject to the special provisions 

discussed below, the agency proposed 

the following phase-in schedule for 

FMVSS No. 126: 30 percent of a vehicle 

manufacturer’s light vehicles 

manufactured during the period from 

September 1, 2008 to August 31, 2009 

would be required to comply with the 

standard; 60 percent of those 

manufactured during the period from 

September 1, 2009 to August 31, 2010; 

90 percent of those manufactured 

during the period from September 1, 

2010 to August 31, 2011, and all light 

vehicles thereafter. 

The agency proposed to exclude 

multi-stage manufacturers and alterers 

from the requirements of the phase-in 

and instead require full implementation 

at the special mandatory compliance 

date applicable to those manufacturers 

(i.e., September 1, 2012) (see S8.8). The 

NPRM also proposed to exclude small 

volume manufacturers (i.e., 

manufacturers producing less than 

5,000 vehicles for sale in the U.S. 

market in one year) from the phase-in, 

instead requiring such manufacturers to 

fully comply with the standard on 

September 1, 2011 (see S8.7). 

Under our proposal, vehicle 

manufacturers would be permitted to 

earn carry-forward credits for compliant 

vehicles, produced in excess of the 

phase-in requirements, which are 

manufactured between the effective date 

of the final rule and the conclusion of 

the phase-in period (see S8.5). In the 

NPRM, we noted that carry-forward 

credits would not be permitted to be 

used to defer the mandatory compliance 

date for all covered vehicles. 

(a) Lead Time for ESC Telltale(s) 

Vehicle manufacturers and their 

representatives generally did not object 

to the lead time provided for meeting 

the proposed ESC performance 

requirements, although they did request 

additional lead time to meet the control 

and telltale requirements. For example, 

the Alliance/AIAM comments argued 

that there is currently a lack of 

uniformity among ESC systems in terms 

of their labeling and telltales, such that 

most existing systems would not meet 

those requirements. In fact, the Alliance 

and AIAM stated that none of their 

members’ ESC systems would fully meet 

the proposed requirements. As a result, 

they suggested that these ESC systems 

may not be fully compliant with the 

standard and, therefore, may be 

ineligible for carry-forward credits 

under the standard. 

These commenters also argued that 

current ESC systems have a variety of 

special-purpose operating modes which 

may require specific context-related 

labeling. According to the commenters, 

these modes are not fully ‘‘off’’ and 

provide varying degrees of ESC 

intervention, but they will generally not 

comply with the proposal’s ‘‘full on’’

performance requirements. The 

Alliance/AIAM stated that in some 

cases, an ESC system may have more 

than one of these special-purpose 

modes, so they requested that 

manufacturers be given flexibility in 

terms of how relevant information is 

presented to vehicle operators. 

Accordingly, the Alliance/AIAM 

requested that the effective date for the 

ESC control and telltale requirements 

proposed to be contained in FMVSS 

Nos. 101 and 126 be postponed until the 

end of the phase-in (i.e., September 1, 

2011), with early compliance permitted, 

as was done in the agency’s TPMS 

rulemaking. The commenters also 

requested that ESC-equipped vehicles 

produced prior to that date which meet 

all other requirements of the standard be 

permitted to earn carry-forward credits 

under FMVSS No. 126 and the ESC 

phase-in reporting provisions of 49 CFR 

Part 585, because many manufacturers 

will need to use such carry-forward 

credits to meet the agency’s aggressive 

phase-in schedule. 

Honda stated that although it expects 

its ESC systems to already meet the 

proposed performance requirements, 

additional lead time is necessary to 

meet the proposed control and telltale 

requirements for ESC. As a result of the 

proposal, the commenter stated that 

every Honda and Acura vehicle would 

require a redesign of its instrument 

panel to accommodate the proposed 

telltale symbol and sizing (i.e., a vertical 

layout, which differs from the 

company’s current horizontal layout). 

According to Honda, the necessary 

tooling changes to the instrument panel 

assemblies and required 

reprogramming, testing, and validation 

to the electronic control unit would 

involve significant cost; Honda 

estimated these costs to range from 

$17,000 to $170,000 per model, with a 

total expenditure of over $1 million. 

Honda stated that in its proposal, the 

agency stated its expectation that 

approximately 98 percent of the ESC 

systems in current vehicles would 

already comply with the proposed 

requirements, and the remaining two 

percent would only require slight 

tuning. However, the commenter argued 

that the agency must have been focusing 

on the ESC performance requirements, 

because very few vehicles currently in 

production meet the proposed control 

and telltale requirements. Looking 

beyond the issue of cost, Honda stated 

that it would be difficult to make these 

changes in line with the proposed 

phase-in schedule. 

According to Honda, its request for a 

delay in implementation of the ESC 

control and telltale requirements is 

consistent with the approach adopted 

by NHTSA in its rulemaking 

establishing FMVSS No. 138, Tire 

Pressure Monitoring Systems (TPMS). 

Honda stated that this approach would 

allow the public to receive the 

immediate benefit of ESC systems, 

while providing the industry adequate 

time to ensure compliance with the 

entire regulation. Therefore, Honda 

requested lead time until the end of the 

phase-in period (i.e., September 1, 2011) 

to meet the proposed control and telltale 


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requirements. Alternatively, the 

company requested that the entire 

phase-in be delayed, beginning three 

years after publication of the final rule 

to establish FMVSS No. 126, in order to 

provide adequate lead time. 

Nissan stated that depending upon 

the design of the vehicle and the extent 

of the changes required, it would 

require an additional ten months to 

three years of lead time in order to meet 

the control and telltale requirements in 

the ESC proposal. Thus, Nissan also 

requested that the agency delay the 

effective date of the ESC control and 

telltale requirements until the end of the 

phase-in (i.e., September 1, 2011) 

(similar comment provided by the 

Toyota). Nissan stated that without an 

extension of the lead time for the 

control and telltale requirements, its 

current systems would not be eligible 

for the carry-forward credits upon 

which the company plans to rely in 

order to meet the aggressive phase-in 

schedule for ESC. The commenter 

further noted that the control and 

telltale requirements would not impact 

the dynamic performance of the ESC 

system and that the company has not 

received any reports of consumer 

confusion associated with its current 

ESC telltales and symbols. 

Porsche also requested additional lead 

time to meet the proposed control and 

telltale requirements for ESC, citing the 

company’s longer-than-average product 

life cycles which present unique 

challenges in terms of meeting standard 

phase-in schedules. The commenter 

stated that the telltale systems for its 

vehicles have already been developed, 

and it had planned on keeping those 

systems unchanged until the next 

product cycle (mid-2012 for some 

models). Porsche stated that the 

proposed ESC off telltale requirements 

would substantially disrupt this existing 

telltale production strategy. 

Accordingly, Porsche requested either 

an extension for compliance with the 

ESC-related control and display 

requirements for all manufacturers until 

September 1, 2012, or alternatively, it 

requested an extension from those 

requirements until that date for any 

manufacturer which would be able to 

equip 100 percent of their fleet with 

vehicles meeting the ESC performance 

requirements by September 1, 2008 (a 

schedule Porsche expects to meet). 

According to the VDA, indicator 

symbols and indicator algorithms for 

current ESC systems vary considerably 

across different vehicle manufacturers. 

The commenter stated that 

implementing the proposed telltale 

requirements within the proposed 

phase-in schedule would involve 

considerable effort, particularly in light 

of the long lead times associated with 

changes to vehicle cockpit designs. 

Therefore, the VDA recommended 

extending the lead time provided for 

implementing the ESC telltale 

requirements and to accord vehicle 

manufacturers flexibility in terms of 

ESC telltale designs for special modes 

(e.g., ones for deep snow, snow chains). 

In order to provide the public as 

rapidly as possible with what are 

expected to be the significant safety 

benefits of ESC systems, NHTSA has 

decided to require all light vehicles 

covered by this standard to be equipped 

with a FMVSS No. 126-compliant ESC 

system by September 1, 2011 (with 

certain exceptions discussed below). 

Consistent with our proposal, 

September 1, 2008 marks the start of a 

three-year phase-in period for FMVSS 

No. 126. 

After consideration of the numerous 

manufacturer comments on this issue, 

we have decided to defer the standard’s 

requirements related to the ESC telltales 

and controls until the end of the phasein (i.e., September 1, 2011 for most 

manufacturers; September 1, 2012 for 

final-stage manufacturers and alterers); 

however, at that point, all covered 

vehicles must meet all relevant 

requirements of the standard (i.e., no 

additional phase-in for the control and 

telltale requirements). This approach is 

consistent with vehicle manufacturers’

request for additional lead time until the 

end of the phase-in to bring their ESC 

systems into full compliance (including 

the control and telltale requirements). 

Manufacturers are encouraged to 

voluntarily install compliant ESC 

controls and displays prior to the 

mandatory compliance date. Our 

rationale for this change from our 

proposal is as follows. 

We now understand from the public 

comments that vehicle manufacturers 

currently employ a variety of 

approaches for ESC controls and 

telltales, many of which would not meet 

the requirements of the agency’s 

proposal, and that standardization of 

ESC controls and telltales will involve 

substantial design and production 

changes. We further understand from 

the comments that manufacturers’

inability to meet the proposed control 

and display requirements would 

prevent them from earning the carryforward credits, even though these ESC 

systems might otherwise meet the 

performance requirements of the 

standard. Vehicle manufacturers’

inability to earn carry-forward credits 

would likely jeopardize their ability to 

meet the standard’s phase-in schedule. 

We agree that it is the performance of 

the ESC systems themselves that impart 

safety benefits under the standard, and 

our analysis demonstrates that the safety 

benefits associated with early 

introduction of ESC systems, even 

without standardized controls and 

displays, far outweigh the benefits of 

delaying the standard until all systems 

can fully meet the control and display 

requirements (see FRIA’s lead time/ 

phase-in discussion). We do not believe 

that implementation of the entire 

standard should be delayed until 

technical changes related to the ESC 

controls and telltales can be fully 

resolved, because they would deny the 

public the safety benefits of ESC 

systems in the meantime. Accordingly, 

we believe that it is preferable to move 

rapidly to implement the standard, but 

to delay the compliance date only for 

the ESC control and telltale 

requirements. 

On a related matter, commenters 

pointed out that vehicle manufacturers 

may earn carry-forward credits for 

compliant vehicles, produced in excess 

of the phase-in requirements, which are 

manufactured between the effective date 

of the final rule and the conclusion of 

the phase-in period. In clarification, we 

would note that vehicles that meet the 

performance requirements of FMVSS 

No. 126, but do not meet the control and 

telltale requirements of the standard 

prior to the end of the phase-in are 

eligible for carry-forward credits and 

may be counted as part of the 

manufacturer’s required production 

under the phase-in. 

In response to the comments of the 

Alliance/AIAM and the VDA that the 

agency should accord vehicle 

manufacturers flexibility in terms of 

ESC telltale designs for special modes, 

we acknowledge that resolution of this 

issue is another factor supporting our 

decision to provide additional lead time 

for manufacturers to meet the ESC 

control and telltale requirements. 

However, in terms of the substantive 

issue of what message should be 

provided by those controls and telltale, 

this is a substantive matter which we 

are addressing under the public 

comment response for ESC telltales (see 

Section IV.C.9 of this document). 

(b) Phase-in Schedule 

Advocates for Highway and Auto 

Safety argued that in light of vehicle 

manufacturers’ current high level of 

installation of advanced ESC systems, 

the agency should accelerate is 

proposed timetable (similar comment by 

IIHS). Advocates argued that this 

acceleration should occur in terms of 

both the interim percentages within the 


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phase-in and the date for mandatory full 

compliance in order to bring this 

important safety feature to the whole 

market more quickly. The Advocates 

suggested that full implementation 

should occur by September 1, 2010 (i.e., 

one year earlier than proposed in the 

NPRM) (similar comment by Consumers 

Union, Mr. Petkun). Specifically, 

Advocates recommended adoption of 

the following implementation schedule 

for installation of ESC in the final rule: 

• 40 percent of model year (MY) 2008 

light vehicles by September 1, 2008. 

• 70 percent of MY 2009 light 

vehicles by September 1, 2009. 

• 100 percent of MY 2010 light 

vehicles by September 1, 2010. 

• 100 percent of light vehicles 

produced by multi-stage manufacturers, 

alterers, and small volume 

manufacturers by September 1, 2011. 

Advocates argued that its 

recommended phase-in schedule would 

be both realistic and achievable, because 

it would be consistent with the 

projected ESC installation rates 

predicted by vehicle manufacturers and 

the agency. The commenter also stated 

that given that the proposal would 

effectively permit compliance by 

currently existing ESC systems, a 

protracted phase-in schedule is 

unnecessary. 

Consumers Union stated that it would 

like to see the phase-in be vehicle-typespecific. It recommended that ESC first 

be required on all SUVs, followed by 

small cars (which the commenter stated 

tend to be driven by younger, less 

experienced drivers), and then on 

family and upscale sedans (which the 

commenter stated tend to be driven by 

older, more experienced drivers). 

Public Citizen argued that because 

ESC components are already welldefined and familiar to manufacturers, 

extensive research and development for 

these systems is not required, and that 

given the important life-saving potential 

of ESC technology, the agency should 

not provide a phase-in schedule slower 

than what the industry is already 

planning (citing statements by Ford, 

General Motors, and DaimlerChrysler). 

In addition, Public Citizen also 

suggested that the agency should 

consider adopting a more aggressive 

phase-in schedule for ESC on new light 

trucks and SUVs, because of these 

vehicles’ higher propensity to roll over. 

In order to provide the public as 

rapidly as possible with what are 

expected to be the significant safety 

benefits of ESC systems, NHTSA has 

decided to require all light vehicles 

covered by this standard to be equipped 

with a FMVSS No. 126-compliant ESC 

system by September 1, 2011 (with 

certain exceptions discussed below), 

with September 1, 2008 marking the 

start of a three-year phase-in. This 

implementation date for full, mandatory 

compliance is the same as that proposed 

in the NPRM. The agency continues to 

believe that this schedule for full 

implementation of the safety standard 

for ESC is appropriate, in order to 

provide manufacturers adequate lead 

time to make necessary production 

changes. Even though vehicle 

manufacturers are currently introducing 

ESC systems into an increasing 

percentage of their new vehicle fleets, 

that does not mean that these complex 

systems can be incorporated into 

vehicles without significant 

developmental efforts to tune them to 

and to incorporate them into a specific 

vehicle design. 

However, in response to public 

comments and upon further review of 

the production plans voluntarily 

submitted by vehicle manufacturers, we 

have determined that it would be 

practicable to increase the percentage of 

new light vehicles that must comply 

with Standard No. 126 under the phasein, thereby accelerating the benefits 

expected to be provided by ESC 

systems. Because ESC is so costeffective and has such high benefits in 

terms of potential fatalities and injuries 

that may be prevented, the agency 

agrees that it is important to require ESC 

installation in light vehicles as quickly 

as possible. Accordingly, under this 

final rule, we are requiring the following 

phase-in schedule for FMVSS No. 126: 

55 percent of a vehicle manufacturer’s 

light vehicles manufactured during the 

period from September 1, 2008 to 

August 31, 2009 would be required to 

comply with the standard; 75 percent of 

those manufactured during the period 

from September 1, 2009 to August 31, 

2010; 95 percent of those manufactured 

during the period from September 1, 

2010 to August 31, 2011, and all light 

vehicles thereafter. (This compares to 

the NPRM’s proposal for a 30/60/90/all 

phase-in schedule over the same time 

periods.) 

In order to ensure the financial and 

technological practicability of the final 

rule (in keeping with our statutory 

mandate), while at the same time 

facilitating ESC installation in the light 

vehicle fleet as expeditiously as 

possible, the agency analyzed the 

product plans submitted by six vehicle 

manufacturers, whose combined 

production accounts for approximately 

87 percent of the new light vehicle fleet. 

As explained in Chapter VII of the FRIA, 

we examined three different potential 

phase-in schedules to find the right 

balance among these competing 

concerns. Based upon this product plan 

information and the desire to provide 

manufacturers with flexibility by having 

a carry forward provision, we have 

chosen the most aggressive phase-in 

alternative that we believe is reasonable 

(i.e., 55/75/95%). 

Two factors were controlling in 

making the decision as to which 

alternative to choose: (1) The ability of 

manufacturers to change vehicles from 

being equipped with optional ESC to 

standard ESC for MY 2010 and MY 

2011; and (2) Not forcing any 

manufacturer to install ESC in any 

make/model for which it was not 

planned to be at least an option. The 

agency did not believe there was enough 

lead time to redesign such a make/ 

model to include ESC by MY 2009. 

While there may be enough time to 

redesign a make/model to include ESC 

by MY 2010, given the carry forward 

provisions this was not necessary for 

any of the six manufacturers for MY 

2010. The second consideration became 

a factor once again in MY 2011, in not 

going beyond 95 percent (thereby 

obviating the costly need to redesign 

and develop tooling for a few vehicle 

lines which will not be produced in MY 

2012). 

In general, we anticipate that vehicle 

manufacturers will be able to meet the 

requirements of the standard by 

installing ESC system designs currently 

in production (i.e., ones available in MY 

2006), and most vehicle lines would 

likely experience some level of redesign 

over the next three to four years, thereby 

providing an opportunity to incorporate 

an ESC system during the course of the 

manufacturer’s normal production 

cycle. Except for possibly some lowproduction-volume vehicles with 

infrequent design changes (addressed 

below), NHTSA believes that most other 

vehicles can reasonably be equipped 

with ESC within three to four model 

years. Furthermore, we do not believe 

that the final rule’s phase-in should 

pose ESC supply problems; public 

comments from vehicle manufacturers 

and ESC suppliers did not raise any 

such supply concerns, and our analysis 

of vehicle manufacturers’ production 

plans suggest that the selected phase-in 

schedule will result in an installation 

rate increase of only a few percentage 

points in any year of the phase-in. 

Overall, we have determined that the 

final rule’s phase-in schedule may be 

accomplished without disruptive 

changes in manufacturer and supplier 

production processes. 

As noted immediately above, we have 

decided to defer the standard’s 

requirements related to the ESC telltales 

and controls until the end of the phaseVerDate Aug<31>2005 18:57 Apr 05, 2007 Jkt 211001 PO 00000 Frm 00057 Fmt 4701 Sfmt 4700 E:\FR\FM\06APR2.SGM 06APR2

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74Although the benefit calculation is based on the 

annual impact for a full, on-road vehicle fleet, it 

would also represent the lifetime savings for a given 

model year’s fleet. 

75On January 10, 2007, SEMA officials and other 

representatives of the aftermarket industry met with 

agency staff to discuss their concerns with the 

potential impact of the ESC final rule on their 

businesses, consistent with SEMA’s November 17, 

2006 comments. However, despite the passage of 

almost two months, the industry representatives 

were still unable to provide any information 

regarding the nature and scope of the identified 

problem with aftermarket modifications impacting 

ESC system functionality, When asked, the industry 

representatives were not able verifiably identify any 

modifications that would or would not cause failure 

of the ESC systems. (For a record of this meeting, 

see Docket No. NHTSA–2006–25801–55.). 

in (i.e., September 1, 2011 for most 

manufacturers; September 1, 2012 for 

final-stage manufacturers and alterers. 

We have modified the final rule’s 

phase-in reporting requirements for ESC 

systems (contained in Subpart I of 49 

CFR Part 585) in a manner consistent 

with the phase-in schedule discussed 

above. 

We have decided not to adopt the 

suggestion by Consumers Union that the 

agency should specify phase-in 

requirements for ESC by vehicle type. 

We note that vehicle manufacturers 

have already been moving aggressively 

to include ESC systems in high-centerof-gravity vehicles (e.g., SUVs). 

Furthermore, we are concerned that 

such action would amount to 

unwarranted agency intervention into 

the details of manufacturers’ production 

plans. It is unclear how such 

intervention might impact 

implementation of the standard and 

installation of ESC systems overall. 

Given these concerns, we have decided 

not to change our traditional approach 

of affording vehicle manufacturers 

flexibility in terms of how (i.e., with 

which models) they will meet a safety 

standard’s phase-in requirements. 

13. Impacts on the Aftermarket 

The Specialty Equipment Market 

Association (SEMA), an aftermarket 

trade association representing the 

specialty automotive industry, 

expressed support for the ESC 

rulemaking as an important advance for 

automotive safety. However, the 

organization expressed concern 

regarding the interaction of ESC systems 

with products manufactured by its 

members (many of which are small 

businesses), arguing that current ESC 

systems seem to be largely vehiclespecific. According to SEMA, many of 

their members’ products (e.g., wheels, 

tires, suspension systems), installed 

either for repair or replacement of 

existing equipment, also increase motor 

vehicle safety, so it is imperative that 

these products remain available to 

consumers and that they operate in 

unison with the ESC system. 

SEMA explained that as a new and 

evolving technology, ESC systems could 

potentially be impacted by the 

installation of a variety of other 

automotive products (e.g.’’ wheels, tires, 

suspension systems, drive gear sets, 

brake parts/systems) during the life of 

the vehicle. The commenter cited the 

potential for such modifications to 

deactivate the ESC system, to cause its 

premature failure, or to reduce its 

effectiveness. However, SEMA stated its 

impression that neither vehicle 

manufacturers, ESC suppliers, nor the 

agency have answers to questions 

regarding ESC interaction with other 

equipment and systems, and SEMA is 

not aware of any available data on this 

topic or related testing. It argued that, as 

drafted, the agency’s proposal fails to 

contemplate the full range of 

downstream consequences associated 

with the required ESC installation. 

According to SEMA, the dearth of 

knowledge about how ESC systems will 

operate in conjunction with common 

vehicle modifications is a fundamental 

flaw in the agency’s rulemaking. 

In terms of its impact on automotive 

aftermarket manufacturers and the 

vehicle service industry, SEMA stated 

that there is a significant difference 

between voluntary installation of the 

ESC system and its mandatory 

installation under a Federal safety 

standard. Specifically, SEMA referred to 

the statutory prohibitions on 

manufacturing/selling/importing 

noncomplying motor vehicles and 

equipment (49 U.S.C. 30112) and on 

making safety devices and elements 

inoperative (49 U.S.C. 30122). 

Violations of these provisions can result 

in substantial civil penalties. 

Accordingly, the commenter cautioned 

the agency to fully investigate how the 

ESC rule will impact the aftermarket 

industry prior to establishing a 

mandatory safety standard. 

SEMA’s recommended solution is to 

either: (1) Delay issuance of a final rule 

until the interaction between ESC 

systems and aftermarket components is 

better understood, or (2) require ESC 

systems to be capable of adapting to 

subsequent vehicle modifications or 

otherwise be capable of being modified 

by installers to accommodate 

aftermarket equipment. According to 

SEMA, the agency should not feel 

rushed to issue a final rule, given that 

vehicle manufacturers are already ahead 

of NHTSA’s proposed phase-in schedule 

and that the statute only requires 

issuance of a final rule by April 1, 2009. 

In response, NHTSA emphasizes that 

we are issuing a final rule on ESC 

systems before the statutory deadline 

(i.e., April 2009) because of the 

tremendous safety benefits that we 

believe an ESC standard can achieve. If, 

as anticipated, an ESC standard can save 

thousands of lives each year, clearly we 

should establish that standard as soon 

as possible. As noted above, ESC 

systems were installed on 

approximately 29 percent of MY 2006 

light vehicles, and that percentage was 

expected to rise to 71 percent by MY 

2011, consistent with manufacturers’

production plans. However, given ESC’s 

estimated high effectiveness rate in 

preventing single-vehicle crashes (34 

percent for passenger cars and 59 

percent for SUVs) and rollovers (71 

percent for passenger cars and 84 

percent for SUVs), the agency decided 

that it was imperative to mandate ESC 

to ensure that all drivers receive the 

benefit of this important safety device 

(i.e., to close the gap between 

manufacturers’ planned installation 

rates and the requirement for ESC 

systems to be standard equipment on all 

light vehicles). For every year that the 

final rule is delayed (assuming 

consistent lead time and the same 

phase-in), we estimate that 1,547–2,534 

lives would be lost and 46,896–65,801 

injuries would occur over the lifetime of 

that model year fleet due to lower ESC 

installation rates (see FRIA Executive 

Summary, E–2 .74) We believe that result 

is unacceptable. Thus, NHTSA will not 

delay the issuance of this final rule 

simply because the statute allows us 

more time. 

Furthermore, NHTSA disagrees that 

the final rule should be delayed because 

it does not analyze all possible 

‘‘downstream consequences’’ or impacts 

on the aftermarket community to 

SEMA’s satisfaction. As discussed in 

Section IV.C.14 below, even though 

NHTSA has no legal obligation to 

analyze the impacts of a rulemaking on 

entities not directly regulated by the 

rule, we are nevertheless concerned 

about the impact our rules have on all 

affected parties. Accordingly, we have 

considered the effects that the ESC final 

rule might have on aftermarket motor 

vehicle equipment manufacturers and 

the motor vehicle service industry. The 

agency is not aware of any significant 

compatibility problems between ESC 

systems and other vehicle equipment, 

and SEMA has not provided any 

evidence to substantiate such problems, 

either in its comments or in a 

subsequent meeting 75 with the agency. 

So at this point, delay of the final rule 

would be based upon a speculative 

concern. Furthermore, we note that with 

any complex system, the agency cannot 


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76We should note that these modifications 

identified by SEMA, particularly any that would 

elevate the vehicle’s center of gravity, might affect 

the stability of the vehicle and raise safety issues 

that are distinct from those addressed by an ESC 

system. 

77 In a January 10, 2007 with the agency, SEMA 

and other representatives of the aftermarket 

industry stated that TRW Inc. has designed an ESC 

system capable of adaptive learning regarding 

changes in tire sizes (see Docket No. NHTSA–2006–

25801–55). However, even such system would not 

be expected to be capable of adaptive learning of 

the numerous aftermarket modifications that could 

potentially impact the vehicle’s ESC system. 

hypothesize on all possible interactions 

between required safety technologies 

and different vehicle equipment. 

Therefore, for all these reasons, 

NHTSA will not delay the final rule 

until all possible interactions are known 

and documented, because that would 

frustrate the agency’s purpose of saving 

lives as soon as possible. However, 

NHTSA recognizes that ESC systems 

vary from vehicle to vehicle, and that 

additional information will help the 

agency and industry to better 

understand how ESC systems interact 

with other vehicle equipment and 

systems. NHTSA will continue to 

monitor the data and testing information 

we receive on this issue, and we 

encourage all interested parties to share 

relevant information with the agency 

and the public as it becomes available. 

Additionally, should we later find 

significant safety risks associated with 

the interaction between ESC systems 

and other equipment and systems 

(whether aftermarket or otherwise), 

NHTSA will work toward adjusting the 

ESC standard to address these possible 

problems. 

Furthermore, NHTSA disagrees that it 

should require ESC systems to be 

capable of adapting to subsequent 

vehicle modifications, because we 

question the feasibility and 

practicability of such a requirement due 

to the varied and voluminous nature of 

the aftermarket vehicle equipment 

market. Likewise, NHTSA is not 

mandating a requirement that ESC 

systems be capable of being modified by 

installers to accommodate aftermarket 

equipment. NHTSA does not believe 

that such a requirement is necessary, 

given that the agency has not been 

presented with any evidence of a safety 

problem or a compatibility problem 

between ESC and other vehicle systems 

or equipment, and given the tendency 

for the market to respond to consumer 

demands that sufficient information be 

provided to permit third party vehicle 

servicing. Nonetheless, NHTSA strongly 

encourages SEMA and its members to 

develop relationships with vehicle and 

ESC system manufacturers to research 

and find solutions to these questions. 

(a) System Adaptability and Sharing 

ESC Information 

In describing the need for an ESC 

system to be ‘‘adjustable’’ to subsequent 

modifications (such as ones permitting 

enhanced towing capacity), SEMA 

stated that the ESC system should be 

sufficiently flexible to allow for 

relocated vehicle centers of gravity,76

and changes in roll rate, lateral 

acceleration, and related dynamics (e.g., 

changes that may accompany 

installation of an aftermarket 

suspension system). SEMA called upon 

NHTSA to require ESC systems with 

‘‘adaptive learning’’ capabilities, such 

that the ESC systems recognize 

subsequent vehicle modifications and 

make corresponding adjustments so that 

the vehicle is not taken out of 

compliance with FMVSS No. 126. In 

addition, the commenter stated that the 

agency should require a 

reprogrammability requirement as part 

of the final rule, in order to ensure 

ongoing ESC functionality after 

subsequent vehicle modifications. 

Furthermore, SEMA called for 

original equipment manufacturers (both 

ESC suppliers and vehicle 

manufacturers) to share relevant ESC 

information with aftermarket 

manufacturers (e.g., providing access to 

software used for ESC calibration). The 

commenter stated that aftermarket onboard computer re-programming 

companies will also need access to this 

information. SEMA commented that 

inability of these aftermarket 

manufacturers to gain access to ESC onboard communications software may 

render installers of these products 

unable to determine methods for 

keeping the ESC system operational. 

According to SEMA, ESC manufacturer 

estimates suggest that aftermarket 

suppliers will need to operate within 

three percent of the ESC’s 

predetermined control level, something 

currently beyond a majority of legal 

aftermarket products. Because these 

aftermarket businesses have no 

knowledge of the operational limits of 

typical ESC systems, SEMA argued that 

these businesses need to understand 

ESC systems’ failure modes, as well as 

the test protocols and standard for 

compliance (if any), in order to 

understand the design parameters 

within which the aftermarket parts must 

comply and to provide practical 

objectives for their own products to 

meet. 

NHTSA does not agree that requiring 

ESC systems to have ‘‘adaptive 

learning’’ capabilities or to be 

reprogrammable after all subsequent 

vehicle modifications is necessary or 

appropriate at this time. In its 

comments, SEMA has provided no 

evidence that current ESC systems are 

even capable of the ‘‘adaptive learning’’

or reprogramming, how that would be 

accomplished, or the cost of achieving 

such capability if it is possible.77 (The 

agency is not aware of any ESC systems 

with an adaptive learning capability of 

the type suggested by SEMA.) The 

requirements NHTSA has decided to 

mandate through this final rule are 

already being met by the vast majority 

of ESC-equipped vehicles in current 

production. NHTSA cannot mandate 

equipment or performance requirements 

without any indication that complying 

with them would even be possible. 

NHTSA agrees with the commenter 

that sharing of information between 

vehicle and ESC manufacturers and 

aftermarket businesses is important, but 

we do not believe that a requirement 

that OEMs share ESC information is 

necessary at this time. Vehicle and ESC 

system manufacturers undoubtedly 

realize that aftermarket alterations of 

vehicles that could affect ESC systems 

are happening and will continue to 

happen. NHTSA believes that OEMs 

will recognize it to be in their best 

interest to share as much nonproprietary information as possible with 

the aftermarket sales industry to avoid 

rendering ESC systems ineffective 

through subsequent vehicle alterations. 

Again, NHTSA strongly encourages 

OEMs and the aftermarket sales industry 

to work together in this regard, but for 

now, mandating such cooperation is 

beyond the scope of this rulemaking. 

Furthermore, we agree that consumers 

and the motor vehicle industry (OEM, 

aftermarket, and service/repair) should 

be vigilant in avoiding alterations which 

could render ESC systems inoperative or 

lessen their effectiveness. We note that, 

as mentioned, we do not yet have any 

reliable information on what these ESCdegrading alterations might be and what 

effects they might have. Still, to the 

extent they become aware of problems, 

as one possible measure, vehicle 

manufacturers might consider alerting 

purchasers to alterations that reasonably 

could render ESC systems inoperative or 

lessen their effectiveness. We believe 

that, to the extent needed, vehicle 

manufacturers are in the best position to 

communicate specific statements and to 

make recommendations about which 

alterations may reasonably be expected 

to impact ESC systems adversely. 


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17294 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

78We believe that the TPMS rulemaking is 

distinguishable from the present ESC rulemaking, 

because for TPMS, the agency had a reasonable 

degree of certainty that the malfunction indicator 

would be able to detect any aftermarket 

modifications (e.g., installation of replacement tires) 

likely to affect the system’s operation. In contrast, 

given the complexity of the ESC system and the 

greater number of modifications with the potential 

to impact its proper functioning, we do not have the 

same level of confidence that the driver would be 

accurately informed of the ESC system’s status in 

all cases. 

(b) ‘‘Make Inoperative’’ Prohibition 

SEMA argued that, provided the ESC 

malfunction lamp does not illuminate, 

installers of aftermarket equipment 

should not be required to undertake 

additional action to confirm that the 

vehicle remains in compliance with 

FMVSS No. 126. Stated another way, 

SEMA asserted that if the ESC 

malfunction telltale does not illuminate, 

the manufacturer, distributor, dealer, or 

motor vehicle repair business should be 

able to assume that the ESC system is 

operating properly and that the vehicle 

modifications in question have not 

violated the ‘‘make inoperative’’

prohibition of 49 U.S.C. 30122. The 

commenter stated that for the agency to 

hold otherwise would place an 

impossible burden on the aftermarket 

industry and have a strong negative 

impact on many small businesses. 

According to SEMA, installers generally 

lack knowledge as to the changes made 

to vehicles before they arrive at their 

shops, given the countless possibilities. 

Thus, SEMA recommended that 

NHTSA state in the final rule that when 

a vehicle has been modified and the 

malfunction telltale has not been 

disabled, one may assume that the 

vehicle remains in compliance with 

FMVSS No. 126 and that there has been 

no violation of the ‘‘make inoperative’’

prohibition (49 U.S.C. 30122). SEMA 

reasoned that if the ESC malfunction 

telltale does illuminate, it will have 

served its purpose of alerting the 

consumer as to a potential compatibility 

problem, thereby permitting corrective 

action to be taken. The commenter 

stated that NHTSA has adopted an 

identical approach for two other safety 

standards—FMVSS No. 110, Tire 

Selection and Rims for Motor Vehicles 

with a GVWR of 4,536 Kilograms 

(10,000 Pounds) or Less, and FMVSS 

No. 138, Tire Pressure Monitoring 

Systems. 

NHTSA recognizes that in previous 

rules (e.g., TPMS 78), we have allowed 

vehicle modifiers to assume that a 

vehicle remains in compliance with the 

relevant FMVSS if a malfunction telltale 

has not illuminated, but we decline to 

do so again for the ESC standard for the 

reasons that follow. SEMA has provided 

no evidence to establish that aftermarket 

modifications have already caused ESC 

system malfunctions or any indication 

whether such malfunction did or did 

not illuminate the ESC telltale. 

In most cases, we expect that 

replacement of motor vehicle 

equipment, such as tire and rims, with 

replacement or aftermarket equipment 

of the same size would not impact ESC 

functionality or result in ‘‘make 

inoperative’’ problems. Replacement of 

worn or damaged equipment with 

similar equipment would likely 

constitute a large majority of instances 

of aftermarket product usage. However, 

NHTSA believes that there may well be 

modifications to vehicles that negatively 

impact the ESC system without causing 

the telltale to illuminate (e.g., changing 

the steering ratio through modification 

to tie rods and steering arms). It would 

not be consistent with the agency’s 

safety mission to require drivers to 

unwittingly forgo the life-saving benefits 

of ESC, without any indication that the 

system is malfunctioning due to 

subsequent vehicle modifications. 

Therefore, we have decided not to grant 

SEMA’s request. However, NHTSA will 

seek relevant information, monitor this 

situation, and take appropriate action as 

necessary. And again, NHTSA 

encourages SEMA and its members to 

develop relationships with vehicle and 

ESC system manufacturers to research 

and find solutions to these questions. 

In the meantime, persons who modify 

vehicle may assume that their actions 

have made the ESC system inoperative 

if those action result in the ESC 

malfunction telltale being illuminated 

or, regardless of whether the telltale 

illuminates, they know based upon 

other sources of information that their 

actions are likely to make the system 

inoperative. 

(c) Pass-Through Certification 

Delphi stated that the NPRM 

indicated that final-stage manufacturers 

and alterers can rely on the original 

manufacturer’s certification of ESC 

compliance, provided they make no 

modifications to a vehicle’s brake 

system. Delphi commented that this 

cautionary statement by the agency is 

too narrow, suggesting that there should 

be clarification that any major 

modification to the vehicle’s dynamic 

characteristics (e.g., handling, 

propulsion) may influence ESC 

operation. According to Delphi, a brakebased ESC system is designed and 

‘‘tuned’’ or ‘‘calibrated’’ for a specific 

vehicle configuration with a specific 

dynamic response character (with such 

character being determined by factors 

such as mass, distribution of mass, size 

(length, width, height), tires, 

suspension/steering geometry, and 

suspension/steering components, among 

others, such as likely driving 

characteristics and conditions). Delphi 

stated that brake-based ESC systems are 

designed to accommodate routine 

variations, but not major modifications 

affecting a vehicle’s handling character. 

The commenter stated that major 

modifications of that nature could result 

in improper operation of the ESC 

system, causing either unwanted 

braking or a failure to intervene when 

needed. Delphi further recommended 

that the final-stage manufacturer or 

alterer should consult with the original 

manufacturer and/or the ESC supplier to 

determine whether there is a need for 

adjustments to the vehicle’s ESC system 

in response to the subsequent 

modifications. 

NHTSA recognizes that many 

different subsequent vehicle 

modifications have the potential to 

affect the ability of an ESC system to 

perform as originally designed. The 

agency agrees that vehicle/ESC 

manufacturers and final-stage 

manufacturers and alterers should 

communicate as to the effects that 

subsequent vehicle modifications may 

have on ESC systems, and we strongly 

encourage such communication to 

ensure proper functioning of the ESC 

system. As with other vehicle 

technologies that may be affected by 

final stages of manufacturing or 

subsequent alterations, NHTSA also 

encourages OEMs to be in contact with 

final-stage manufacturers and alterers, 

to the extent possible, to ensure that the 

certification of their vehicles under the 

ESC standard is not compromised. 

14. Compliance With Relevant Legal 

Requirements 

(a) Regulatory Flexibility Act 

SEMA argued that NHTSA’s 

Regulatory Flexibility Analysis did not 

consider how the rule would potentially 

impact manufacturers, installers, and 

retailers of aftermarket products that 

would have the potential to interact 

with the ESC system when installed on 

the vehicle. The commenter stated that 

the agency is obligated under the 

Regulatory Flexibility Act to consider 

all reasonable alternatives for crafting 

the least burdensome rule. SEMA 

suggested that the agency’s analysis was 

inadequate because it did not also focus 

on the aftermarket industry. Mr. 

Sparhawk also argued that the NPRM 

failed to adequately analyze the 

reasonably foreseeable impacts of the 

proposed ESC requirement on small 

businesses, as required by the 


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Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17295 

79Office of Advocacy, United States Small 

Business Administration, ‘‘A Guide for Government 

Agencies: How to Comply with the Regulatory 

Flexibility Act,’’ 2003, p. 20. 

80 Mid-Tex Electric Cooperative, Inc. v. Federal 

Energy Regulatory Commission (FERC), 773 F.2d 

327, 341 (DC Cir. 1985) (stating that ‘‘Congress did 

not intend to require that every agency consider 

every indirect effect that any regulation might have 

on small businesses in any stratum of the national 

economy.’’). 

81 Motor & Equipment Mfrs. Ass’n v. Nichols, 142 

F.3d 449, 467 (DC Cir. 1998) (holding that ‘‘Because 

the deemed-to-comply rule did not subject any 

aftermarket businesses to regulation, EPA was not 

required to conduct a flexibility analysis as to small 

aftermarket businesses. It was only obliged to 

consider the impact of the rule on small automobile 

manufacturers subject to the rule, and it met that 

obligation.’’). 

82 Id., fn 18, at 467 (describing 5 U.S.C. 603(b)(3) 

and (4)). 

Regulatory Flexibility Act, because it 

does not consider the impacts on 

vehicle repair businesses, instead only 

addressing the effects of the proposal on 

large manufacturers. 

In response, we note that NHTSA is 

not required to perform a regulatory 

flexibility analysis for entities not 

directly impacted by its rulemaking. In 

its 2003 publication titled ‘‘A Guide for 

Government Agencies: How to Comply 

with the Regulatory Flexibility Act’’

(‘‘RFA Guide’’), the Small Business 

Administration states that ‘‘[t]he courts 

have held that the RFA requires an 

agency to perform a regulatory 

flexibility analysis of small entity 

impacts only when a rule directly 

regulates them.’’ 79 The cases cited by 

the RFA Guide indicate that a rule 

‘‘directly regulates’’ only the entities to 

which the rule applies—for example, 

electric utilities but not independent 

electricity cooperatives in a FERC ratesetting regulation,80 or automobile 

manufacturers but not aftermarket 

businesses in an EPA ‘‘deemed-tocomply’’ rule.81 In Motor & Equipment 

Mfrs. Ass’n v. Nichols, the DC Circuit 

described the distinction as follows: 

‘‘The RFA itself distinguishes between 

small entities subject to an agency rule, 

to which its requirements apply, and 

those not subject to the rule, to which 

the requirements do not apply.’’ 82

This final rule establishes 

performance and equipment 

requirements for ESC systems. The only 

entities subject to these requirements 

are vehicle manufacturers and 

manufacturers of ESC systems. NHTSA 

has already analyzed the potential 

impacts of the rule on these directly 

affected entities, as the final regulatory 

flexibility analysis (contained within 

the FRIA) makes clear. Nothing in this 

rule subjects the entities described by 

SEMA and Mr. Sparhawk to NHTSA’s 

regulation. 

With that said, although NHTSA has 

no obligation to perform a regulatory 

flexibility analysis to consider the 

potential impacts of this final rule on 

such non-directly regulated entities, we 

are nevertheless concerned about the 

impact our rules have on all affected 

parties. Again, we have considered the 

effects that the ESC final rule might 

have on aftermarket motor vehicle 

equipment manufacturers and the motor 

vehicle service industry. The agency is 

not aware of any significant 

compatibility problems between ESC 

systems and other vehicle equipment. 

However, we note that with any 

complex system, the agency cannot 

hypothesize on all possible interactions 

between required safety technologies 

and different vehicle equipment. Again, 

we do not believe it appropriate to delay 

this final rule for ESC systems and the 

significant safety benefits accompanying 

them on the basis of speculative 

arguments regarding compatibility 

problems for which there is no 

evidence; we believe that this is 

particularly so in light of the substantial 

number of vehicles currently equipped 

with ESC systems—some portion of 

which it is expected would have had 

aftermarket modifications of the types 

suggested by SEMA—and given that 

there has been no indication of any 

problem to date. However, to the extent 

information suggesting such a problem 

exists, the agency will carefully 

consider it. 

(b) Executive Orders 12866 and 13258 

SEMA stated that Executive Order 

12866 (Regulatory Planning and 

Review), as amended by Executive 

Order 13258, requires agencies to write 

all rules in plain language, and it also 

stated that the Administrative Procedure 

Act (APA) requires agencies to include 

issues of consequence within a 

rulemaking and to provide the 

opportunity for public comment. SEMA 

argued that the agency’s ESC proposal 

did not properly assess the impact of the 

ESC rule on the aftermarket community 

and that any such impacts (e.g., how the 

‘‘make inoperative’’ prohibition applies 

to their activities) should be stated in 

plain language in the rule. 

NHTSA agrees that agencies are 

required to write rules in plain language 

and to address and provide an 

opportunity for public comment on the 

substance of the rulemaking, as well as 

its impact. However, for the reasons 

discussed in the response to the 

Regulatory Flexibility Act comment 

above, NHTSA disagrees that it is 

obligated to assess the indirect impact of 

the ESC rule on the aftermarket 

community (entities described by 

SEMA) or state any such impacts in the 

rule. Nevertheless, because we are 

concerned about the impact our rules 

have on all affected parties, we have 

considered the effects that the ESC final 

rule might have on aftermarket motor 

vehicle equipment manufacturers and 

the motor vehicle service industry. 

Again, the agency is not aware of any 

significant compatibility problems 

between ESC systems and other vehicle 

equipment. 

(c) Vehicle Safety Act 

SEMA asserted that NHTSA’s 

proposed rule does not meet the 

practicability requirement of the Safety 

Act, because it could ‘‘potentially lead 

to millions of [subsequently-modified] 

vehicles whose compliance with the 

ESC standard would be unknown.’’

SEMA also argued that the rule could 

‘‘deny consumers the right to 

accessorize their vehicles with products 

that may provide additional safety 

benefits beyond the ESC systems.’’

NHTSA disagrees with these 

comments. SEMA has provided no 

evidence that the final rule is 

impracticable under the Safety Act. 

Vehicles currently include many 

complex systems, and aftermarket 

suppliers are able to produce products 

compatible with those systems; 

similarly, motor vehicle repair 

businesses are currently able to obtain 

sufficient information to perform their 

work. We do not believe that the 

situation with ESC will be any different, 

and NHTSA anticipates that the 

aftermarket community will be able to 

work with OEMs and dealers as the 

phase-in progresses to avoid SEMA’s 

concern. Additionally, this final rule in 

no way denies consumers the right to 

modify their vehicles. Individual 

vehicle owners are not regulated under 

the Vehicle Safety Act nor under this 

final rule, and SEMA provided no 

evidence that these products would be 

incompatible with ESC systems. 

15. ESC Outreach Efforts 

(a) ESC Test Procedures Workshop 

Honda requested that the agency 

consider sponsoring a workshop on the 

ESC test procedures once a final rule 

has been issued, similar to the one the 

agency conducted for the TPMS 

standard. The commenter suggested that 

such a workshop would be useful to 

provide manufacturers the opportunity 

to understand important details of the 

test procedure and to clarify questions 

in a practical, hands-on setting. 

NHTSA agrees with this suggestion 

and will plan to have a workshop on the 

ESC test procedures in the near future. 


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83See http://isearch.nhtsa.gov/files/ 

21281.ztv.html. 

Details of this ESC workshop will be 

announced in a separate Federal 

Register notice at least 30 days prior to 

the scheduled date of the meeting. 

(b) Public Information Campaign 

SUVOA, an association representing 

owners of sport utility vehicles, pick-up 

trucks, and vans, encouraged the agency 

to undertake a strong public information 

campaign as part of the final rule for 

ESC. According to SUVOA, consumers 

need to understand how newly required 

safety equipment such as ESC works 

and how it enhances the safety of their 

vehicles, and automobile dealerships 

and their salespeople should similarly 

be educated regarding the lifesaving 

benefits of ESC. SUVOA offered to work 

with the agency to contribute to such 

communications efforts. 

NHTSA’s principal public 

information portals are its main agency 

Web site (www.nhtsa.dot.gov), the 

Safercar.gov Web site, and its 

publication ‘‘Buying a Safer Car.’’ In 

these information sources, consumers 

can already obtain information about 

what ESC systems do and which 

vehicles were equipped with ESC 

systems in 2005, 2006, and 2007. 

However, we agree with SUVOA about 

the general desirability of increased 

public information which could 

possibly drive demand for ESC systems 

during the phase-in period. We applaud 

the efforts of General Motors and Bosch 

in particular to educate dealers and 

salesman about ESC, and we encourage 

other interested parties to help spread 

the message regarding the important 

benefits provided by ESC systems. 

16. Miscellaneous Issues 

(a) Linking Brake Light Illumination to 

ESC Activation 

Consumers Union suggested that 

whenever the vehicle’s ESC system is 

activated and intervenes, the vehicle’s 

brake lights should be automatically 

illuminated in order to alert motorists to 

the rear of potentially slippery 

conditions and of a slowing vehicle 

ahead (similar comment by Mr. Petkun). 

The commenter urged the agency to 

undertake whatever ancillary 

amendments to other safety standards 

that may be necessary to effectuate this 

change (e.g., possible amendments to 

FMVSS No. 105, Hydraulic and Electric 

Brake Systems, and FMVSS No. 108, 

Lamps, Reflective Devices, and 

Associated Equipment). 

In our May 26, 2000 letter of 

interpretation 83 to Mr. C. Thomas Terry 

of General Motors, NHTSA has already 

established a policy regarding stop 

lamps and technologies that make use of 

the vehicles brakes (including ESC), and 

we intend to follow that interpretation 

with regard to FMVSS No. 126, as 

discussed below. Under our 

interpretation letter to Mr. Terry, only 

when a vehicle system operates in a way 

that is analogous to the driver using the 

brakes to slow the vehicle should the 

stop lamps activate. We believe that it 

is not desirable to change the meaning 

of the stop lamp signal. Traction 

control, for example, applies one brake 

on an axle at a time to limit wheel spin 

for the purpose of accelerating rather 

than decelerating the vehicle, so in such 

cases, stop lamps should not be 

activated. Adaptive cruise control, on 

the other hand, uses brakes in the same 

way as the driver and should activate 

the stop lamp. 

We understand that vehicle 

manufacturers consider the duration 

and mode of ESC operation to determine 

whether to activate the stop lamps (to 

avoid confusing blinks), but whenever 

the system augments the reduction of 

engine power with braking intended to 

further slow the vehicle (as opposed to 

a very short application of a single brake 

simply to change the vehicle’s heading), 

brake lamp activation would be 

expected to occur. 

(b) Vehicles With Dual Wheels on the 

Rear Axle 

According to the Alliance/AIAM, 

there are a small number (unspecified) 

of incomplete vehicles with a GVWR of 

10,000 pounds or less that are equipped 

with dual wheels on the rear axle 

(‘‘dualies’’), which are typically 

completed as commercial vehicles. The 

commenters stated that these vehicles 

require their own unique ESC 

calibration. Based upon the small 

number of ‘‘dualies’’ and their unusual 

calibration needs, the Alliance/AIAM 

requested that the agency exclude these 

vehicles from the present ESC 

rulemaking and instead consider them 

as part of any subsequent ESC 

rulemaking for heavy trucks (a category 

in which dualies’ ESC systems arguably 

more appropriately belong). 

In light of the agency’s statutory 

mandate under section 10301 of 

SAFETEA–LU, NHTSA does not believe 

it has the authority to exempt any 

vehicles with a GVWR of 10,000 pounds 

or less from the requirements of the 

Standard No. 126. Accordingly, this 

final rule applies to passenger cars, 

multipurpose vehicles, trucks and buses 

with a gross vehicle weight rating of 

4,536 Kg (10,000 pounds) or less, as 

originally proposed. 

(c) ESC Operation With Towed Trailers 

According to Mr. Feldhus, ESC 

systems must be required to have on/off 

controls for vehicles capable of towing 

a trailer, because current ESC systems 

do not communicate with the trailer 

when intervening to maintain stability. 

He stated that because the ESCequipped towing vehicle’s brake lights 

do not activate, the aftermarket trailer’s 

brake controllers cannot participate. He 

further stated that towing vehicles dive 

and trailer hitches rise during heavy 

braking, so unless care is taken, a twoto-four ton trailer could lift and 

overpower the towing vehicle. Thus, 

Mr. Feldhus stated that the agency 

should not mandate ESC systems until 

such time as it evaluates such effects 

using special trailer test rigs that have 

motor-controlled swinging masses and 

numerous hitch combinations. He also 

suggested additional tests simulating air 

disturbance from oncoming trucks on 

two-lane roads. Ultimately, Mr. Feldhus 

recommended adopting specific pass/ 

fail towing criteria that vehicle 

manufacturers must meet, as part of any 

safety standard for ESC. 

We have no evidence supporting the 

supposition that ESC intervention will 

adversely affect the safety of a vehicle 

hauling a trailer, nor has any vehicle or 

ESC manufacturer told us that lack of 

communication between a tow vehicle 

and trailer will negatively affect ESC 

functionality. ESC systems operate in 

extreme driving situations where a loss 

of control is anticipated (i.e., excessive 

oversteer or understeer situations). On 

some vehicles with high centers of 

gravity, ESC may also intervene during 

impending on-road, untripped rollover 

situations. In each of these loss-ofcontrol situations, we do not believe 

ESC stabilization of the tow vehicle 

would result in a subsequent loss of 

trailer stability. Accordingly, we see no 

reason to revise the regulatory text 

regarding this issue. 

However, tow vehicle/trailer safety is 

an area of ongoing interest to NHTSA, 

and the agency always welcomes 

information on ways new technology 

can improve it. For example, some ESC 

systems are now being offered with 

trailer stabilization assist (TSA) control 

algorithms. These algorithms are 

specifically designed to help mitigate 

yaw oscillations that can occur when 

the vehicle/trailer system is being 

operated in certain driving situations. 

These systems operate by using the tow 

vehicle ESC system to automatically 

brake the tow vehicle in a way that 

suppresses the trailer yaw oscillations 

before they become so large that a loss 

of control is evident. Evaluating TSA 


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Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17297 

84Note that estimates for the FMVSS No. 214 

rulemaking are from the agency’s preliminary 

regulatory analysis that accompanied the notice of 

proposed rulemaking. When the final rule is 

published, the revised regulatory analysis will 

reflect the impact of today’s ESC final rule, which 

will reduce the benefit of the FMVSS No. 214 rule. 

effectiveness is an area of research 

presently under consideration at 

NHTSA. 

(d) Wheelchair-Accessible Vehicles 

The National Mobility Equipment 

Dealers Association (NMEDA) 

commented that ESC system sensors are 

normally located under one of the front 

row seats. NMEDA argued that because 

ESC systems are position-sensitive, their 

relocation is likely to affect the 

accuracy, performance, and 

effectiveness of those systems. (The 

commenter pointed to the fact that yaw 

rate and sideslip are functions of the 

vehicle center of gravity, and also, the 

ESC’s horizontal plane of reference will 

likely be altered when an ESC system is 

relocated, further altering its 

performance.) The organization 

expressed concern that whenever the 

system sensors must be moved in the 

process of modifying vehicles to make 

them accessible to the disabled, the ESC 

system could generate potentially 

dangerous and unpredictable vehicle 

responses under certain driving 

conditions. 

Therefore, NMEDA recommended 

that the final rule should require an 

original equipment manufacturer to 

provide a means to permanently 

deactivate an ESC system for vehicles 

manufactured, altered, or modified after 

first sale to accommodate persons with 

disabilities. According to NMEDA, it 

would be possible to ensure that the 

ESC system is not accidentally activated 

by equipping the vehicle with a 

permanent, key-operated ‘‘off’’

mechanism and an associated warning 

lamp (similar to one provided on an air 

bag deactivation system). Alternatively, 

NMEDA stated that the agency could 

specify in the final rule that third 

parties are permitted to permanently 

deactivate the ESC system on vehicles 

that are manufactured, altered, or 

modified after first sale to be accessible 

to persons with disabilities. 

In response to the commenter’s 

concerns about vehicles modified to 

make them accessible to disabled 

individuals, NHTSA believes that no 

change is necessary as part of the ESC 

final rule. Parties who must certify that 

their vehicles are in compliance with 

Federal motor vehicle safety standards 

prior to first retail sale should have the 

capability to ensure the functionality of 

the ESC system installed in their 

vehicles. However, aftermarket 

modifiers who adapt vehicles for 

persons with disabilities would not 

likely be able to move ESC components 

without some level of assistance from 

vehicle manufacturers or ESC system 

suppliers. 

We strongly urge OEMs to work with 

vehicle modifiers to identify alternative 

locations or other modification methods 

so that the benefits of ESC may be 

retained for drivers of adapted vehicles. 

The number of vehicles that are popular 

for adaptations for persons with 

disabilities is quite limited, and we 

believe it is practical for manufacturers 

to provide assistance to modifiers who 

must remove OEM seats, supply 

alternative seats, or modify floors, so 

that the modifiers may relocate ESC 

components in a way that preserves the 

proper functioning of the system. (We 

understand that General Motors already 

provides some technical assistance to 

those adapting its vans for disabled 

persons.) NHTSA would be willing to 

host a technical session to be attended 

by OEM engineers, ESC manufacturer 

engineers, and representatives of 

aftermarket modifiers to facilitate this 

discussion. 

In addition, NHTSA will consider 

whether it is necessary to add language 

to 49 CFR 595 Subpart C, Vehicle 

Modifications to Accommodate People 

With Disabilities, to exempt the modifier 

from the ‘‘make inoperative’’

prohibition of 49 U.S.C 30122, as it 

applies to FMVSS No. 126 in the event 

that: (1) The ESC sensor must be moved 

in the modification of a vehicle after 

first retail sale to accommodate a person 

with a disability, and (2) the OEM has 

not provided an alterative position. 

V. Benefits and Costs 

A. Summary 

This section summarizes our analysis 

of the benefits, costs, and cost per 

equivalent life saved as a result of the 

ESC requirements contained in this final 

rule. As noted previously, the life- and 

injury-saving potential of ESC is very 

significant, both in absolute terms and 

when compared to prior agency 

rulemakings. We anticipate that this 

final rule for ESC, compared to a 

baseline of manufacturers’ plans of 

having 71 percent of the light vehicle 

fleet with ESC by MY 2011, will save 

1,547 to 2,534 lives and cause a 

reduction of 46,896 to 65,801 MAIS 1–

5 injuries annually once all passenger 

vehicles have ESC. This compares 

favorably with the Regulatory Impact 

Analyses for other important 

rulemakings such as FMVSS No. 208 

mandatory air bags (1,964 to 3,670 lives 

saved), FMVSS No. 214 side impact 

protection (690 to 1,030 lives saved 84), 

and FMVSS No. 201 upper interior head 

impact protection (870 to 1,050 lives 

saved). The ESC final rule is expected 

to also save $376 to $535 million 

annually in property damage and travel 

delay (undiscounted). The total cost of 

this final rule is estimated to be $985 

million. 

The ESC final rule is extremely costeffective. The cost per equivalent life 

saved is expected to range from $0.18 to 

$0.33 million at a 3 percent discount 

and $0.26 to $0.45 million at a 7 percent 

discount. Again, the cost-effectiveness 

for ESC compares favorably with the 

Regulatory Impact Analyses for other 

important rulemakings such as FMVSS 

No. 202 head restraints safety 

improvement ($2.61 million per life 

saved), FMVSS No. 208 center seat 

shoulder belts ($3.39 to $5.92 million 

per life saved), FMVSS No. 208 

advanced air bags ($1.9 to $9.0 million 

per life saved), and FMVSS No. 301 fuel 

system integrity upgrade ($1.96 to $5.13 

million per life saved). 

For a more complete discussion of the 

benefits and costs associated with this 

rulemaking for ESC, please consult the 

Final Regulatory Impact Analysis 

(FRIA), which is available in the docket 

for this rulemaking. 

B. ESC Benefits 

As discussed in detail in Chapter IV 

(Benefits) of the FRIA, we anticipate 

that, when all light vehicles have ESC, 

this rulemaking would prevent 67,466 

to 90,807 crashes (1,430 to 2,354 fatal 

crashes and 66,036 to 88,453 non-fatal 

crashes). Preventing these crashes 

entirely is the ideal safety outcome and 

would translate into 1,547 to 2,534 lives 

saved and 46,896 to 65,801 MAIS 1–5 

injuries prevented. 

The above figures include benefits 

related to rollover crashes, a subset of 

all crashes. However, in light of the 

relatively severe nature of crashes 

involving rollover, ESC’s contribution 

toward mitigating the problem 

associated with this subset of crashes 

should be noted. We anticipate that this 

rulemaking would prevent 35,680 to 

39,387 rollover crashes (1,076 to 1,347 

fatal crashes and 34,604 to 38,040 nonfatal crashes). This would translate into 

1,171 to 1,465 lives saved and 33,001 to 

36,420 MAIS 1–5 injuries prevented in 

rollovers. 

In addition, preventing crashes would 

also result in benefits in terms of travel 

delay savings and property damage 

savings. We estimate that this 

rulemaking would save $376 to $535 


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85The present discounted value of these savings 

ranges from $247 to $436 million (based on 3 

percent and 7 percent discount rates). 

86 49 U.S.C. 30111(a). 

87 49 U.S.C. 30102(a)(9). 

88 49 U.S.C. 30111(b). 

89 Id. 

million, undiscounted,85 in these two 

categories ($240 to $269 million of this 

savings is attributable to prevented 

rollover crashes). 

We further note that this rule also has 

the effect of causing all light vehicles to 

be equipped with anti-lock braking 

systems (ABS) as a foundation for ESC. 

We anticipate some level of benefits 

from improved brake performance on 

vehicles not currently equipped with 

ABS, but have not attempted to quantify 

them. However, the potential benefits of 

ABS did not influence our effectiveness 

estimates for ESC, because all of the 

non-ESC control vehicles in the study 

already had ABS. The measure of 

unquantified benefits relates to 

situations where the ABS system 

activates (but the ESC system does not 

need to) on vehicles that were not 

previously equipped with ABS. 

C. ESC Costs 

In order to estimate the cost of the 

additional components required to 

equip every vehicle in future model 

years with an ESC system, assumptions 

were made about future production 

volume and the relationship between 

equipment found in anti-lock brake 

systems (ABS), traction control (TC), 

and ESC systems. We assumed that in 

an ESC system, the equipment of ABS 

is a prerequisite. Thus, if a passenger car 

did not have ABS, it would require the 

cost of an ABS system plus the 

additional incremental costs of the ESC 

system to comply with an ESC standard. 

We assumed that traction control (TC) 

was not required to achieve the safety 

benefits found with ESC. We estimated 

a future annual production of 17 million 

light vehicles consisting of nine million 

light trucks and eight million passenger 

cars. 

An estimate was made of the MY 2011 

installation rates of ABS and ESC. It 

served as the baseline against which 

both costs and benefits are measured. 

Thus, the cost of the standard is the 

incremental cost of going from the 

estimated MY 2011 installations to 100 

percent installation of ABS and ESC. 

The estimated MY 2011 installation 

rates are presented in Table 6. 

TABLE 6.—MY 2011 PREDICTED

INSTALLATIONS

[Percent of the light vehicle fleet] 

ABS ABS + 

ESC 

Passenger Cars .... 86 65 

TABLE 6.—MY 2011 PREDICTED

INSTALLATIONS—Continued 

[Percent of the light vehicle fleet] 

ABS ABS + 

ESC 

Light Trucks .......... 99 77 

Based on the assumptions above and 

the data provided in Table 6, Table 7 

presents the percent of the MY 2011 

fleet that would need these specific 

technologies in order to equip all light 

vehicles with ESC. 

TABLE 7.—PERCENT OF THE LIGHT

VEHICLE FLEET REQUIRING TECHNOLOGY TO ACHIEVE 100% ESC INSTALLATION

None ABS + 

ESC 

ESC 

only 

Passenger Cars 65 14 21 

Light Trucks ...... 77 1 22 

The cost estimates developed for this 

analysis were taken from tear down 

studies that contractors have performed 

for NHTSA. This process resulted in 

estimates of the consumer cost of ABS 

at $368 and the incremental cost of ESC 

at $111. Thus, it would cost a vehicle 

that does not have ABS currently, $479 

to meet the requirements of this final 

rule. Combining the technology needs in 

Table 7 with the cost above and 

assumed production volumes yields the 

cost estimate in Table 8 for the ESC 

standard. Thus, for example, the average 

cost for passenger cars, including both 

those that require installation of an ESC 

system and those that already have it, is 

$90. 

TABLE 8.—SUMMARY OF VEHICLE

COSTS FOR THE ESC STANDARD

[2005$] 

Average 

vehicle 

costs 

Total costs 

(millions) 

Passenger Cars .... $90.3 $722.5 

Light Trucks .......... 29.2 262.7 

Total .................. 58.0 985.2 

In summary, Table 8 shows that 

requiring electronic stability control and 

anti-lock brakes will increase the cost of 

new light vehicles on average by $58, 

totaling $985 million annually across 

the new light vehicle fleet. 

In addition, we note that this final 

rule is expected to add weight to 

vehicles and consequently to increase 

their lifetime use of fuel. Most of the 

added weight is for ABS components 

and very little is for the ESC 

components. Since 99 percent of light 

trucks are predicted to have ABS in MY 

2011, the weight increase for light 

trucks is less than one pound and is 

considered negligible. The average 

weight gain for passenger cars is 

estimated to be 2.13 pounds, resulting 

in 2.6 more gallons of fuel being used 

over the lifetime of these vehicles. The 

present discounted value of the added 

fuel cost over the lifetime of the average 

passenger car is estimated to be $2.73 at 

a 7 percent discount rate and $3.35 at 

a 3 percent discount rate. 

We have not included in these cost 

estimates, allowances for ESC system 

maintenance and repair. Although all 

complex electronic systems will 

experience component failures from 

time to time necessitating repair, our 

experience to date with existing systems 

is that their failure rate is not outside 

the norm. Also, there are no routine 

maintenance requirements for ESC 

systems. 

VI. Regulatory Analyses and Notices 

A. Vehicle Safety Act 

As noted above, the agency is 

implementing the ESC language in 

SAFETEA–LU through promulgation of 

a Federal motor vehicle safety standard 

for ESC pursuant to 49 U.S.C. Chapter 

301, Motor Vehicle Safety. Thus, in 

developing this final rule for ESC, the 

agency carefully considered the 

statutory requirements of both 

SAFETEA–LU and 49 U.S.C. Chapter 

301. 

Under 49 U.S.C. Chapter 301, Motor 

Vehicle Safety (49 U.S.C. 30101 et seq.), 

the Secretary of Transportation is 

responsible for prescribing motor 

vehicle safety standards that are 

practicable, meet the need for motor 

vehicle safety, and are stated in 

objective terms.86 These motor vehicle 

safety standards set the minimum level 

of performance for a motor vehicle or 

motor vehicle equipment to be 

considered safe.87 When prescribing 

such standards, the Secretary must 

consider all relevant, available motor 

vehicle safety information.88 The 

Secretary also must consider whether a 

standard is reasonable, practicable, and 

appropriate for the type of motor vehicle 

or motor vehicle equipment for which it 

is prescribed and the extent to which 

the standard will further the statutory 

purpose of reducing traffic accidents 

and associated deaths.89 The 

responsibility for promulgation of 


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90 49 U.S.C. 105 and 322; delegation of authority 

at 49 CFR 1.50. 

91 515 F.2d 1053 (6th Cir. 1975) (holding that 

NHTSA’s specification of dimensional requirements 

for rectangular headlamps constitutes an objective 

performance standard under the Vehicle Safety 

Act). 

Federal motor vehicle safety standards 

has been delegated to NHTSA.90 We 

describe below our consideration of 

these provisions. 

First, in preparing this document, the 

agency carefully evaluated available 

research, testing results, and other 

information related to ESC technology. 

The agency performed extensive 

research on its own and made use of 

research performed by the Alliance of 

Automobile Manufacturers and its 

member companies, plus research from 

Hyundai/Kia. We also performed 

analyses of ESC using actual crash data 

to determine the effectiveness of ESC in 

reducing single-vehicle crashes and 

rollovers. Furthermore, the agency 

carefully considered all of the public 

comments submitted on the NPRM for 

ESC, along with any accompanying 

data, and responded to such information 

as part of this final rule. In sum, this 

document reflects our consideration of 

all relevant, available motor vehicle 

safety information. 

Second, to ensure that the ESC 

requirements are practicable, the agency 

research and the industry research 

documented the capabilities of current 

ESC systems and dynamic performance 

of model year 2005 vehicles equipped 

with them. ESC is a developed 

technology that is currently available on 

a wide variety of vehicle types and 

models. We have concluded that all 

current production vehicles equipped 

with ESC systems are capable of 

complying with the equipment 

requirements, that all but one current 

vehicle model are capable of complying 

with the performance tests, and that 

only minor software tuning would be 

required to bring that vehicle model into 

compliance. In sum, we believe that this 

final rule is practicable for fleet-wide 

implementation, in that it may be 

implemented with existing technology 

and is quite cost-effective, given its 

potential to prevent thousands of deaths 

and injuries each year, particularly 

those associated with single-vehicle 

crashes leading to rollover. 

Third, the regulatory text following 

this preamble is stated in objective 

terms in order to specify precisely what 

equipment constitutes an ESC system, 

what performance is required, and how 

performance is tested under the 

standard. The final rule’s definition of 

an ‘‘ESC System’’ is based on a 

voluntary consensus definition 

developed by the Society of Automotive 

Engineers (SAE). The rule also includes 

performance requirements and test 

procedures for the timing and intensity 

of the oversteer intervention by the ESC 

system (i.e., a lateral stability criterion) 

and the responsiveness of the vehicle 

(i.e., a vehicle responsiveness criterion). 

This test procedure involves a preciselydefined steering pattern performed by a 

robotic steering machine under a 

defined set of test conditions (e.g., 

ambient temperature, road test surface, 

vehicle load, vehicle speed). 

Performance is defined by objective 

measurements of yaw rate and lateral 

acceleration taken by scientific 

instruments at precise times with 

reference to the steering pattern. The 

standard’s test procedures carefully 

delineate how such testing is 

conducted. 

Historically, the agency has striven to 

set motor vehicle safety standards that 

are as performance-based as possible, 

but we have interpreted our mandate as 

permitting the adoption of more specific 

regulatory requirements when such 

action is in the interest of safety. In the 

present case, the agency cannot specify 

a practicable and repeatable dynamic 

understeer performance test at this time. 

As discussed in Section IV.C.4 above, 

there is no available test for effective 

understeer intervention in non-linearhandling, loss-of-control situations, and 

the agency’s own research efforts were 

not able to identify a broadly applicable 

test for understeer that would ensure 

intervention by the ESC system in all 

appropriate cases. However, as the court 

held in Chrysler Corporation v. DOT,91

NHTSA may specify equipment 

requirements as part of an FMVSS 

where development of a performance 

standard alone would not be practicable 

or meet the need for motor vehicle 

safety. Such is the case here, thereby 

necessitating our adoption of a 

definitional requirement for an ESC 

system (based upon the definition in 

SAE J2564) that has the components/ 

capabilities for effective understeer (and 

oversteer) intervention, consistent with 

current production systems. However, 

the agency will continue its research 

effort pertaining to ESC understeer 

intervention and will consider 

amending the standard in the future, as 

appropriate. 

In light of the above, the agency 

believes that the regulatory 

requirements and test procedures in this 

final rule are sufficiently objective and 

would not result in any uncertainty as 

to whether a given vehicle satisfies the 

requirements of the ESC standard. 

Finally, we believe that this final rule 

is reasonable and appropriate for motor 

vehicles subject to the applicable 

requirements. As discussed elsewhere 

in this notice, the agency is addressing 

Congress’ concern about rollover 

crashes resulting in fatalities and 

serious injuries. Under section 10301 of 

SAFETEA–LU, Congress mandated 

installation of stability enhancing 

technologies in new vehicles to reduce 

rollovers. NHTSA has determined that 

ESC systems meeting the requirements 

of this final rule offer an effective 

countermeasure to rollover crashes and 

to other single-vehicle and certain 

multi-vehicle crashes. Accordingly, we 

believe that this final rule is appropriate 

for vehicles subject to these provisions 

because it furthers the agency’s 

objective of preventing deaths and 

serious injuries, particularly those 

associated with rollover crashes. 

B. Executive Order 12866 and DOT 

Regulatory Policies and Procedures 

Executive Order 12866, ‘‘Regulatory 

Planning and Review’’ (58 FR 51735, 

October 4, 1993), provides for making 

determinations whether a regulatory 

action is ‘‘significant’’ and therefore 

subject to Office of Management and 

Budget (OMB) review and to the 

requirements of the Executive Order. 

The Order defines a ‘‘significant 

regulatory action’’ as one that is likely 

to result in a rule that may: 

(1) Have an annual effect on the 

economy of $100 million or more or 

adversely affect in a material way the 

economy, a sector of the economy, 

productivity, competition, jobs, the 

environment, public health or safety, or 

State, local, or Tribal governments or 

communities; 

(2) Create a serious inconsistency or 

otherwise interfere with an action taken 

or planned by another agency; 

(3) Materially alter the budgetary 

impact of entitlements, grants, user fees, 

or loan programs or the rights and 

obligations of recipients thereof; or 

(4) Raise novel legal or policy issues 

arising out of legal mandates, the 

President’s priorities, or the principles 

set forth in the Executive Order. 

We have considered the impact of this 

action under Executive Order 12866 and 

the Department of Transportation’s 

regulatory policies and procedures. This 

action has been determined to be 

economically significant under the 

Executive Order, and it is also a subject 

of congressional interest and a mandate 

under section 10301 of SAFETEA–LU. 

The agency has prepared and placed in 

the docket a Final Regulatory Impact 

Analysis. This rulemaking action is also 

significant within the meaning of the 


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Department of Transportation’s 

Regulatory Policies and Procedures (44 

FR 11034; February 26, 1979). 

Accordingly, this rulemaking document 

was reviewed by the Office of 

Management and Budget under 

Executive Order 12866, ‘‘Regulatory 

Planning and Review.’’ The agency has 

estimated that compliance with this rule 

would cost approximately $985 million 

per year and have net benefits as high 

as $11.4 billion per year. Thus, this rule 

would have greater than a $100 million 

effect. 

C. Regulatory Flexibility Act 

Pursuant to the Regulatory Flexibility 

Act of 1980 (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). 

However, no regulatory or flexibility 

analysis is required if the head of an 

agency certifies that the rule will not 

have a significant economic impact on 

a substantial number of small entities. 

SBREFA amended the Regulatory 

Flexibility Act to require Federal 

agencies to provide a statement of the 

factual basis for certifying that a rule 

will not have a significant economic 

impact on a substantial number of small 

entities. 

NHTSA has considered the effects of 

this rulemaking action under the 

Regulatory Flexibility Act and has 

included a final regulatory flexibility 

analysis in the FRIA. This analysis 

discusses potential regulatory 

alternatives that the agency considered 

that would still meet the identified 

safety need of reducing the occurrence 

of rollovers through stability enhancing 

technologies. Alternatives considered 

included (a) Applying the standard to 

light trucks but not to passenger cars 

and (b) permitting front-wheel-only ESC 

systems that are incapable of understeer 

intervention. The first alternative was 

rejected because passenger car ESC 

systems would save 945 lives and 

reduce 32,196 injuries annually at a cost 

per equivalent fatality that would easily 

justify a separate rule for passenger cars. 

The second alternative was rejected 

because front-wheel-only ESC systems 

would prevent 30 percent fewer singlevehicle crashes without producing a 

large cost saving. 

To summarize the conclusions of that 

analysis, the agency believes that the 

final rule will have a significant 

economic impact on a substantial 

number of small businesses. There are 

currently four small domestic motor 

vehicle manufacturers in the United 

States, each having fewer than 1,000 

employees. Although the cost for an 

ESC system is relatively high, we 

believe that these manufacturers should 

be able to pass the associated costs on 

to purchasers without decreasing sales 

volume, because the demand for the 

high-end, luxury vehicles produced by 

these manufacturers tends to be 

inelastic and the increase in total 

vehicle cost is expected to be only 0.2–

1.1 percent. 

There are a significant number of 

final-stage manufacturers and alterers 

likely to be impacted by the final rule 

for ESC, some of which buy incomplete 

vehicles. However, final-stage 

manufacturers and alterers typically do 

not modify the brake system of the 

vehicle (the modification most likely to 

impact ESC), so the original 

manufacturer’s certification of the ESC 

system should pass through for these 

vehicles. To the extent other subsequent 

vehicle modifications have the potential 

to affect the ability of an ESC system to 

perform as originally designed, we 

encourage vehicle/ESC manufacturers 

and final-stage manufacturers and 

alterers to communicate as to the effects 

that subsequent vehicle modifications 

may have on ESC systems in order to 

ensure continued proper functioning. 

As with other vehicle technologies that 

may be affected by final stages of 

manufacturing or subsequent 

alterations, NHTSA also encourages 

OEMs to be in contact with final-stage 

manufacturers and alterers, to the extent 

possible, to ensure that the certification 

of their vehicles under the ESC standard 

is not compromised. We believe that 

increased costs associated with ESC will 

impact all such final-stage 

manufacturers and alterers equally, and 

that such costs will be passed on to 

consumers. Furthermore, we have no 

reason to believe that an average cost of 

$90 per passenger car and $29 per truck 

will cause a significant decline in 

overall vehicle sales. 

We do not expect manufacturers of 

ESC systems to be classified as small 

businesses. 

The agency also received public 

comments from SEMA and Mr. 

Sparhawk arguing that the agency is 

bound to address the indirect effects 

that this regulation would have on 

installers of aftermarket vehicle 

equipment and motor vehicle repair 

businesses. 

Although our response to these 

commenters is discussed more fully 

under Section IV.C.14(a), we repeat that 

this final rule establishes performance 

and equipment requirements for ESC 

systems and that the only entities 

subject to and directly affected by these 

requirements are vehicle manufacturers 

and manufacturers of ESC systems. 

Nothing in this rule subjects the entities 

described by SEMA and Mr. Sparhawk 

to NHTSA’s regulation. However, 

NHTSA nevertheless considered the 

effects that the ESC final rule might 

have on aftermarket motor vehicle 

equipment manufacturers and the motor 

vehicle service industry, and based 

upon that analysis, the agency is not 

aware of any significant compatibility 

problems between ESC systems and 

other vehicle equipment. Although the 

agency will continue to monitor this 

issue, we do not believe it appropriate 

to delay this final rule for ESC systems 

and the significant safety benefits 

accompanying them on the basis of 

speculative arguments regarding 

compatibility problems for which there 

is no evidence. 

D. Executive Order 13132 (Federalism) 

NHTSA has examined today’s final 

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 rule does not have federalism 

implications, because the rule does 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 the 

responsibilities among the various 

levels of government.’’

Further, no consultation is needed to 

discuss the preemptive effect of today’s 

rule. NHTSA rules can have preemptive 

effect in at least two ways. First, the 

National Traffic and Motor Vehicle 

Safety Act contains an express 

preemptive 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. 

30102(b)(1). In addition, we note that 

this final rule establishing a safety 

standard for electronic stability control 

systems was mandated by Congress, 

pursuant to section 10301 of SAFETEA–

LU. It is this statutory command that 

preempts State law, not today’s 


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rulemaking, so consultation would be 

inappropriate. 

In addition to the express preemption 

noted above, the Supreme Court has 

also recognized that State requirements 

imposed on motor vehicle 

manufacturers, including sanctions 

imposed by State tort law, can stand as 

an obstacle to the accomplishment and 

execution of a NHTSA safety standard. 

When such a conflict is discerned, the 

Supremacy Clause of the Constitution 

makes their State requirements 

unenforceable. See Geier v. American 

Honda Motor Co., 529 U.S. 861 (2000). 

NHTSA has not outlined such potential 

State requirements in today’s 

rulemaking, however, in part because 

such conflicts can arise in varied 

contexts, but it is conceivable that such 

a conflict may become clear through 

subsequent experience with today’s 

standard and test regime. NHTSA may 

opine on such conflicts in the future, if 

warranted. See id. at 883–86. 

E. 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, 

February 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) 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 preemptive effect of this 

rule is discussed above. NHTSA notes 

further that there is no requirement that 

individuals submit a petition for 

reconsideration or pursue other 

administrative proceeding before they 

may file suit in court. 

F. Executive Order 13045 (Protection of 

Children From Environmental Health 

and Safety Risks) 

Executive Order 13045, ‘‘Protection of 

Children from Environmental Health 

and Safety Risks’’ (62 FR 19855, April 

23, 1997), applies to any rule that: (1) 

Is determined to be ‘‘economically 

significant’’ as defined under Executive 

Order 12866, and (2) concerns an 

environmental, health, or safety risk that 

the agency has reason to believe may 

have a disproportionate effect on 

children. If the regulatory action meets 

both criteria, the agency must evaluate 

the environmental health or safety 

effects of the planned rule on children, 

and explain why the planned regulation 

is preferable to other potentially 

effective and reasonably feasible 

alternatives considered by the agency. 

Although the rule for ESC has been 

determined to be an economically 

significant regulatory action under 

Executive Order 12866, the problems 

associated with loss of vehicle control 

equally impact all persons riding in a 

vehicle, regardless of age. Consequently, 

this final rule does not involve a 

decision based on environmental, 

health, or safety risks that 

disproportionately affect children and 

would not necessitate further analyses 

under Executive Order 13045. 

G. Paperwork Reduction Act 

Under the Paperwork Reduction Act 

of 1995 (PRA), 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 Department of 

Transportation is submitting the 

following information collection request 

to OMB for review and clearance under 

the PRA. 

Agency: National Highway Traffic 

Safety Administration (NHTSA). 

Title: Phase-In Production Reporting 

Requirements for Electronic Stability 

Control Systems. 

Type of Request: Routine. 

OMB Clearance Number: 2127-New. 

Form Number: This collection of 

information will not use any standard 

forms. 

Affected Public: The respondents are 

manufacturers of passenger cars, 

multipurpose passenger vehicles, 

trucks, and buses having a gross vehicle 

weight rating of 4,536 Kg (10,000 

pounds) or less. The agency estimates 

that there are about 21 such 

manufacturers. 

Estimate of the Total Annual 

Reporting and Recordkeeping Burden 

Resulting from the Collection of 

Information: NHTSA estimates that the 

total annual hour burden is 42 hours. 

Estimated Costs: NHTSA estimates 

that the total annual cost burden, in U.S. 

dollars, will be $2,100. No additional 

resources would be expended by vehicle 

manufacturers to gather annual 

production information because they 

already compile this data for their own 

uses. 

Summary of Collection of 

Information: This collection would 

require manufacturers of passenger cars, 

multipurpose passenger vehicles, 

trucks, and buses with a gross vehicle 

weight rating of 4,536 Kg (10,000 

pounds) or less to provide motor vehicle 

production data for the following three 

years: September 1, 2008 to August 31, 

2009; September 1, 2009 to August 31, 

2010; and September 1, 2010 to August 

31, 2011. 

Description of the Need for the 

Information and the Proposed 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. 126, Electronic 

Stability Control Systems, during the 

phase-in of those requirements. In the 

NPRM, NHTSA requested comments on 

the agency’s estimates of the total 

annual hour and cost burdens resulting 

from this collection of information. No 

comments were received on this issue. 

H. National Technology Transfer and 

Advancement Act 

Section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (NTTAA), Public Law 104–

113, section 12(d) (15 U.S.C. 272) 

directs NHTSA to use voluntary 

consensus standards in its regulatory 

activities unless doing so would be 

inconsistent with applicable law or 

otherwise impractical. Voluntary 

consensus standards are technical 

standards (e.g., materials specifications, 

test methods, sampling procedures, and 

business practices) that are developed or 

adopted by voluntary consensus 

standards bodies, such as the Society of 

Automotive Engineers (SAE). The 

NTTAA directs NHTSA to provide 

Congress, through OMB, explanations 

when the agency decides not to use 

available and applicable voluntary 

consensus standards. The NTTAA does 

not apply to symbols. 

The equipment requirements of this 

standard are based (with minor 

modifications) on the SAE Surface 

Vehicle Information Report on 

Automotive Stability Enhancement 

Systems J2564 Rev JUN2004 that 

provides an industry consensus 

definition of an ESC system. However, 

there is no voluntary consensus 

standard for ESC that contains any 

specifications for a performance test. 

The agency has also incorporated by 

reference two standards developed by 

the American Society for Testing and 

Materials (ASTM) in order to provide 

specifications for road test surface 

conditions for use in the standard’s test 

procedures. These are: (1) ASTM 

E1337–90 (rev. 1996), Standard Test 

Method for Determining Longitudinal 


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92As explained in Chapter VII of the FRIA, the 

agency assessed the following potential phase-in 

schedules for ESC: (A) 30%/60%/90% with carry 

forward credits (as proposed in the NPRM); (B) 

55%/75%/95% with carry forward credits; and (C) 

55%/75%/95% without carry forward credits. 

Peak Braking Coefficient of Paved 

Surfaces Using a STD Reference Test 

Tire; and (2) ASTM E1136–93, Standard 

Specification for a Radial Standard 

Reference Test Tire (1993). 

I. 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 in any one year 

(adjusted for inflation with base year of 

1995, currently $122 million in 2005 

dollars). Before promulgating a rule for 

which a written statement is needed, 

section 205 of the UMRA generally 

requires NHTSA to identify and 

consider a reasonable number of 

regulatory alternatives and adopt the 

least costly, most cost-effective, or least 

burdensome alternative that achieves 

the objectives of the rule. The 

provisions of section 205 do not apply 

when they are inconsistent with 

applicable law. Moreover, section 205 

allows NHTSA to adopt an alternative 

other than the least costly, most costeffective or least burdensome alternative 

if we publish with the final rule an 

explanation why that alternative was 

not adopted. 

This final rule is not expected to 

result in the expenditure by State, local, 

or tribal governments, in the aggregate, 

of more than $122 million annually, but 

it will result in the expenditure of that 

magnitude by vehicle manufacturers 

and/or their suppliers. 

As noted above, this rulemaking is 

being promulgated pursuant to section 

10301 of the Safe, Accountable, 

Flexible, Efficient Transportation Equity 

Act: A Legacy for Users of 2005 

(SAFETEA–LU). As part of this final 

rule, the agency is presenting not only 

its regulatory approach for ESC, but also 

the regulatory alternatives it considered; 

we also present a detailed discussion of 

the costs and benefits associated with 

the rule (see the FRIA and also Section 

V of this document). 

In terms of regulatory alternatives 

considered, the agency analyzed three 

possibilities: (1) Limiting the standard’s 

applicability to light trucks and vans 

(LTVs); (2) permitting use of 2-channel 

ESC systems; and (3) three different 

potential phase-in schedules.92 The 

following briefly explains the 

conclusions that the agency reached in 

analyzing these available alternatives. 

Although the first alternative reduces 

overall costs of the regulation and 

increases cost-effectiveness (based upon 

the higher propensity for LTVs to roll 

over), the agency rejected it because our 

analysis showed that requiring ESC for 

passenger cars would save 945 lives and 

reduce 32,196 non-fatal injuries. These 

benefits were substantial in their own 

right (a net benefit of $4.7 billion at a 

3 percent discount rate and $3.7 billion 

at a 7 percent discount rate). Further, 

ESC was found to be highly costeffective for passenger cars alone ($0.38 

million at a 3 percent discount rate and 

$0.50 million at a 7 percent discount 

rate). 

Although the second alternative 

would have reduced the cost of the 

regulation by approximately $10 per 

vehicle, the agency rejected that 

alternative because the agency’s 

research showed a potentially enhanced 

safety benefit from 4-channel ESC 

systems, as compared to 2-channel 

systems, and also because of the strong 

industry trend toward providing 4- 

channel systems. A more detailed 

analysis of the regulatory alternatives 

considered by the agency may be found 

in the FRIA (see FRIA Chapter VII). 

In terms of the alternative phase-in 

schedules, the agency analyzed a 

number of potential alternatives to 

identify the schedule that would 

facilitate ESC installation in the light 

vehicle fleet as expeditiously as 

possible, while at the same time ensure 

the financial and technological 

practicability of the final rule (in 

keeping with our statutory mandate). To 

this end, the agency analyzed the 

product plans submitted by six vehicle 

manufacturers, whose combined 

production accounts for approximately 

87 percent of the new light vehicle fleet. 

As explained in Chapter VII of the FRIA, 

we examined three different potential 

phase-in schedules to find the right 

balance among these competing 

concerns. 

Two factors were controlling in 

making the decision as to which 

alternative to choose: (1) The ability of 

manufacturers to change vehicles from 

being equipped with optional ESC to 

standard ESC for MY 2010 and MY 

2011; and (2) Not forcing any 

manufacturer to install ESC in any 

make/model for which it was not 

planned to be at least an option. The 

agency did not believe there was enough 

lead time to redesign such a make/ 

model to include ESC by MY 2009. 

While there may be enough time to 

redesign a make/model to include ESC 

by MY 2010, given the carry forward 

provisions, this was not necessary for 

any of the six manufacturers for MY 

2010. The second consideration became 

a factor once again in MY 2011, in not 

going beyond 95 percent (thereby 

obviating the costly need to redesign 

and develop tooling for a few vehicle 

lines which will not be produced in MY 

2012). 

Based upon this product plan 

information and the desire to provide 

manufacturers with flexibility, we chose 

the most aggressive phase-in alternative 

with a carry forward provision that we 

believe is reasonable (i.e., 55/75/95%). 

(We note that the estimates below are 

compared to a baseline of the NPRM’s 

proposed phase-in schedule of 30/60/ 

90% with carry-forward credits.) 

Although the 55/75/95% phase-in 

alternative was not the least costly 

(expected to increase total compliance 

costs by $295 million), it was 

nevertheless very cost-effective ($0.394 

to $0.640 million per equivalent life 

saved at a 3 percent discount rate; 

$0.496 to $0.802 million per equivalent 

life saved at a 7 percent discount rate). 

Further, this alternative also had the 

potential to substantially increase the 

number of prevented fatalities (336–550) 

and injuries (10,174–14,276) over the 

lifetime of the three model years in the 

phase-in period. Although the 55/75/ 

95% without carry-forward credits 

alternative theoretically had higher 

benefits and was more cost-effective, the 

agency determined that based upon 

available product plan information, it 

may not be practical for manufacturers 

to achieve such high installation rates in 

such a short timeframe without carryforward credits. Accordingly, the agency 

believes that the alternative chosen will 

provide the highest achievable level of 

incremental benefits among the 

schedules with a carry-forward 

provision, a feature the agency 

determined was necessary for 

reasonable implementation of the 

standard. 

Accordingly, in light of the 

substantial benefits in terms of fatalities 

and injuries prevented (discussed at 

length in the FRIA and elsewhere in this 

document), the agency decided to adopt 

an ESC requirement for all light 

vehicles, even though this alternative 

was not the least costly, most costeffective, or least burdensome available. 

In light of the demonstrated 

effectiveness of ESC in preventing 

single-vehicle crashes (including 

rollovers), the agency decided that it 

would be inappropriate to not make the 


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life-saving benefits of ESC available to 

all vehicle occupants and in the shortest 

timeframe that the agency determined to 

be both reasonable and practicable. As 

noted previously, we have determined 

that the final rule’s phase-in schedule 

may be accomplished without 

disruptive changes in manufacturer and 

supplier production processes. 

In addition, as part of the public 

comment process, the agency’s NPRM 

also invited suggestions regarding ways 

to promote flexibility and to minimize 

costs of compliance, while achieving the 

safety purposes of SAFETEA–LU. The 

overwhelming majority of public 

comments supported the ESC 

rulemaking and offered no suggested 

substitute. However, commenters did 

suggest numerous technical changes 

that might be characterized as 

promoting flexibility or minimizing 

costs. Each such issue is addressed in 

this final rule. 

J. National Environmental Policy Act 

NHTSA has analyzed this rulemaking 

action for the purposes of the National 

Environmental Policy Act. The agency 

has determined that implementation of 

this action would not have any 

significant impact on the quality of the 

human environment. 

K. 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. 

L. Privacy Act 

Please note that anyone is able to 

search the electronic form of all 

comments received into any of our 

dockets by the name of the individual 

submitting the comment (or signing the 

comment, if submitted on behalf of an 

association, business, labor union, etc.). 

You may review DOT’s complete 

Privacy Act Statement in the Federal 

Register published on April 11, 2000 

(Volume 65, Number 70; pages 19477–

78) or you may visit http://dms.dot.gov. 

BILLING CODE 4910–59–P 


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BILLING CODE 4910–59–C 


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List of Subjects in 49 CFR Parts 571 and 

585 

Imports, Incorporation by reference, 

Motor vehicle safety, Report and 

recordkeeping requirements, Tires. 

■ In consideration of the foregoing, 

NHTSA is amending 49 CFR parts 571 

and 585 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 1.50. 

■ 2. Section 571.101 is amended by 

revising the section heading, S5.5.2, 

S5.5.5, and Table 1 to read as follows: 

§ 571.101 Standard No. 101; Controls and 

displays. 

* * * * * 

S5.5.2. The telltales for any brake 

system malfunction required by Table 1 

to be red, air bag malfunction, low tire 

pressure, electronic stability control 

malfunction, passenger air bag off, high 

beam, turn signal, and seat belt must not 

be shown in the same common space. 

* * * * * 

S5.5.5. In the case of the telltale for a 

brake system malfunction, air bag 

malfunction, side air bag malfunction, 

low tire pressure, electronic stability 

control malfunction, passenger air bag 

off, high beam, turn signal, or seat belt 

that is designed to display in a common 

space, that telltale must displace any 

other symbol or message in that 

common space while the underlying 

condition for the telltale’s activation 

exists. 

* * * * * 

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* * * * * 

■ 3. Section 571.126 is added to read as 

follows: 

§ 571.126 Standard No. 126; Electronic 

stability control systems. 

S1. Scope. This standard establishes 

performance and equipment 

requirements for electronic stability 

control (ESC) systems. 

S2. Purpose. The purpose of this 

standard is to reduce the number of 

deaths and injuries that result from 

crashes in which the driver loses 

directional control of the vehicle, 

including those resulting in vehicle 

rollover. 

S3. Application and Incorporation by 

Reference. 

S3.1 Application. This standard 

applies to passenger cars, multipurpose 

passenger vehicles, trucks, and buses 

with a gross vehicle weight rating of 

4,536 kilograms (10,000 pounds) or less, 

according to the phase-in schedule 

specified in S8 of this standard. 

S3.2 Incorporation by reference. 

ASTM E1337–90 (Reapproved 1996), 

Standard Test Method for Determining 

Longitudinal Peak Braking Coefficient of 

Paved Surfaces Using a STD Reference 

Test Tire, and ASTM E1136–93 (1993), 

Standard Specification for a Radial 

Standard Reference Test Tire, are 

incorporated by reference in S6.2.2 of 

this section. The Director of the Federal 

Register has approved the incorporation 

by reference of this material in 

accordance with 5 U.S.C. 552(a) and 1 

CFR Part 51. Copies of ASTM E1337–90 

(rev. 1996) and ASTM E1136–93 (1993) 

may be obtained from the ASTM Web 

site at http://www.astm.org, or by 

contacting ASTM, 100 Barr Harbor 

Drive, West Conshohocken, PA 19428–

2959. Copies of ASTM E1337–90 

(Reapproved 1996) and ASTM E1136–

93 (1993) may be inspected at NHTSA’s 

Office of Rulemaking, 400 Seventh 

Street, SW., Washington, DC 20590, or 

at the National Archives and Records 

Administration (NARA). For 

information on the availability of this 

material at NARA, call 202–741–6030, 

or go to: http://www.archives.gov/ 

federal_register/ 

code_of_federal_regulations/ 

ibr_locations.html. 

S4. Definitions. 

Ackerman Steer Angle means the 

angle whose tangent is the wheelbase 

divided by the radius of the turn at a 

very low speed. 

Electronic Stability Control System or 

ESC System means a system that has all 

of the following attributes: 

(1) That augments vehicle directional 

stability by applying and adjusting the 

vehicle brake torques individually to 

induce a correcting yaw moment to a 

vehicle; 

(2) That is computer controlled with 

the computer using a closed-loop 

algorithm to limit vehicle oversteer and 

to limit vehicle understeer; 

(3) That has a means to determine the 

vehicle’s yaw rate and to estimate its 

side slip or side slip derivative with 

respect to time; 

(4) That has a means to monitor driver 

steering inputs; 

(5) That has an algorithm to determine 

the need, and a means to modify engine 

torque, as necessary, to assist the driver 

in maintaining control of the vehicle, 

and 

(6) That is operational over the full 

speed range of the vehicle (except at 

vehicle speeds less than 15 km/h (9.3 

mph) or when being driven in reverse). 

Lateral Acceleration means the 

component of the vector acceleration of 

a point in the vehicle perpendicular to 

the vehicle x axis (longitudinal) and 

parallel to the road plane. 

Oversteer means a condition in which 

the vehicle’s yaw rate is greater than the 

yaw rate that would occur at the 

vehicle’s speed as a result of the 

Ackerman Steer Angle. 

Sideslip or side slip angle means the 

arctangent of the lateral velocity of the 

center of gravity of the vehicle divided 

by the longitudinal velocity of the 

center of gravity. 

Understeer means a condition in 

which the vehicle’s yaw rate is less than 

the yaw rate that would occur at the 

vehicle’s speed as result of the 

Ackerman Steer Angle. 

Yaw rate means the rate of change of 

the vehicle’s heading angle measured in 

degrees/second of rotation about a 

vertical axis through the vehicle’s center 

of gravity. 

S5. Requirements. Subject to the 

phase-in set forth in S8, each vehicle 

must be equipped with an ESC system 

that meets the requirements specified in 

S5 under the test conditions specified in 

S6 and the test procedures specified in 

S7 of this standard. 

S5.1 Required Equipment. Vehicles 

to which this standard applies must be 

equipped with an electronic stability 

control system that: 

S5.1.1 Is capable of applying brake 

torques individually to all four wheels 

and has a control algorithm that utilizes 

this capability. 

S5.1.2 Is operational during all 

phases of driving including 

acceleration, coasting, and deceleration 

(including braking), except when the 

driver has disabled ESC, the vehicle 

speed is below 15 km/h (9.3 mph), or 

the vehicle is being driven in reverse. 

S5.1.3 Remains capable of activation 

even if the antilock brake system or 

traction control system is also activated. 

S5.2 Performance Requirements. 

During each test performed under the 

test conditions of S6 and the test 

procedure of S7.9, the vehicle with the 

ESC system engaged must satisfy the 

stability criteria of S5.2.1 and S5.2.2, 

and it must satisfy the responsiveness 

criterion of S5.2.3 during each of those 

tests conducted with a commanded 

steering wheel angle of 5A or greater, 

where A is the steering wheel angle 

computed in S7.6.1. 

S5.2.1 The yaw rate measured one 

second after completion of the sine with 

dwell steering input (time T0 + 1 in 

Figure 1) must not exceed 35 percent of 

the first peak value of yaw rate recorded 

after the steering wheel angle changes 

sign (between first and second peaks) 

(y« Peak in Figure 1) during the same test 

run, and 

S5.2.2 The yaw rate measured 1.75 

seconds after completion of the sine 

with dwell steering input must not 

exceed 20 percent of the first peak value 

of yaw rate recorded after the steering 

wheel angle changes sign (between first 

and second peaks) during the same test 

run. 

S5.2.3 The lateral displacement of 

the vehicle center of gravity with 

respect to its initial straight path must 

be at least 1.83 m (6 feet) for vehicles 

with a GVWR of 3,500kg (7,716 lb) or 

less, and 1.52 m (5 feet) for vehicles 

with a GVWR greater than 3,500 kg 

(7,716 lb) when computed 1.07 seconds 

after the Beginning of Steer (BOS). BOS 

is defined in S7.11.6. 

S5.2.3.1 The computation of lateral 

displacement is performed using double 

integration with respect to time of the 

measurement of lateral acceleration at 

the vehicle center of gravity, as 

expressed by the formula: 

Lateral dt Displacement = Ay ∫∫ C.G.

S5.2.3.2 Time t = 0 for the 

integration operation is the instant of 

steering initiation, known as the 

Beginning of Steer (BOS). BOS is 

defined in S7.11.6. 

S5.3 ESC Malfunction. The vehicle 

must be equipped with a telltale that 

provides a warning to the driver of the 

occurrence of one or more malfunctions 

that affect the generation or 

transmission of control or response 

signals in the vehicle’s electronic 

stability control system. The ESC 

malfunction telltale: 

S5.3.1 As of September 1, 2011, 

must be mounted inside the occupant 


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compartment in front of and in clear 

view of the driver; 

S5.3.2 As of September 1, 2011, 

must be identified by the symbol shown 

for ‘‘ESC Malfunction Telltale’’ or the 

specified words or abbreviations listed 

in Table 1 of Standard No. 101 (49 CFR 

571.101); 

S5.3.3 Except as provided in 

paragraph S5.3.4, the ESC malfunction 

telltale must illuminate only when a 

malfunction(s) exists and must remain 

continuously illuminated under the 

conditions specified in S5.3 for as long 

as the malfunction(s) exists, whenever 

the ignition locking system is in the 

‘‘On’’ (‘‘Run’’) position; and 

S5.3.4 As of September 1, 2011, 

except as provided in paragraph S5.3.5, 

each ESC malfunction telltale must be 

activated as a check of lamp function 

either when the ignition locking system 

is turned to the ‘‘On’’ (‘‘Run’’) position 

when the engine is not running, or 

when the ignition locking system is in 

a position between ‘‘On’’ (‘‘Run’’) and 

‘‘Start’’ that is designated by the 

manufacturer as a check position. 

S5.3.5 The ESC malfunction telltale 

need not be activated when a starter 

interlock is in operation. 

S5.3.6 The requirement S5.3.4 does 

not apply to telltales shown in a 

common space. 

S5.3.7 The ESC malfunction telltale 

must extinguish at the next ignition 

cycle after the malfunction has been 

corrected. 

S5.3.8 The manufacturer may use 

the ESC malfunction telltale in a 

flashing mode to indicate ESC 

operation. 

S5.3.9 Prior to September 1, 2011, a 

disconnection of the power to the ESC 

electronic control unit may be indicated 

by the ABS malfunction telltale instead 

of the ESC malfunction telltale, and a 

disconnection of the ‘‘ESC Off’’ control 

need not illuminate the ESC 

malfunction telltale. 

S5.4. ESC Off and Other System 

Controls. The manufacturer may include 

an ‘‘ESC Off’’ control whose only 

purpose is to place the ESC system in 

a mode in which it will no longer satisfy 

the performance requirements of S5.2.1, 

S5.2.2 and S5.2.3. Manufacturers may 

also provide controls for other systems 

that have an ancillary effect upon ESC 

operation. Controls of either kind that 

place the ESC system in a mode in 

which it will no longer satisfy the 

performance requirements of S5.2.1, 

S5.2.2 and S5.2.3 are permitted, 

provided that: 

S5.4.1 The vehicle’s ESC system 

must always return to a mode that 

satisfies the requirements of S5.1 and 

S5.2 at the initiation of each new 

ignition cycle, regardless of what mode 

the driver had previously selected 

except if that mode is specifically for 

enhanced traction during low-speed, 

off-road driving and is entered by the 

driver using a mechanical control that 

cannot be automatically reset 

electrically. If the system has more than 

one mode that satisfies these 

requirements, the default mode must be 

the mode that satisfies the performance 

requirements of S5.2 by the greatest 

margin. 

S5.4.2 As of September 1, 2011, a 

control whose only purpose is to place 

the ESC system in a mode in which it 

will no longer satisfy the performance 

requirements of S5.2.1, S5.2.2 and 

S5.2.3 must be identified by the symbol 

shown for ‘‘ESC Off’’ in Table 1 of 

Standard No. 101 (49 CFR 571.101) or 

the text, ‘‘ESC Off’’ as listed under 

‘‘Word(s) or Abbreviations’’ in Table 1 

of Standard No. 101 (49 CFR 571.101). 

S5.4.3 A control for another system 

that has the ancillary effect of placing 

the ESC system in a mode in which it 

no longer satisfies the performance 

requirements of S5.2.1, S5.2.2 and 

S5.2.3 need not be identified by the 

‘‘ESC Off’’ identifiers in Table 1 of 

Standard No. 101 (49 CFR 571.101), but 

the ESC status must be identified by the 

‘‘ESC Off’’ telltale in accordance with 

S5.5. 

S5.5 ESC Off Telltale 

S5.5.1 The vehicle manufacturer 

must provide a telltale indicating that 

the vehicle has been put into a mode 

that renders it unable to satisfy the 

requirements of S5.2.1, S5.2.2 and 

S5.2.3, if such a mode is provided. 

S5.5.2 As of September 1, 2011, the 

‘‘ESC Off’’ telltale must be identified by 

the symbol shown for ‘‘ESC Off’’ in 

Table 1 of Standard No. 101 (49 CFR 

571.101) or the text, ‘‘ESC Off’’ as listed 

under ‘‘Word(s) or Abbreviations’’ in 

Table 1 of Standard No. 101 (49 CFR 

571.101). 

S5.5.3 As of September 1, 2011, the 

‘‘ESC Off’’ telltale must be mounted 

inside the occupant compartment in 

front of and in clear view of the driver. 

S5.5.4 The ‘‘ESC Off’’ telltale must 

remain continuously illuminated for as 

long as the ESC is in a mode that 

renders it unable to satisfy the 

requirements of S5.2.1, S5.2.2 and 

S5.2.3, and 

S5.5.5 Notwithstanding S5.3.1(e) of 

49 CFR 571.101, the vehicle 

manufacturer may use the ‘‘ESC Off’’

telltale to indicate an ESC level of 

function other than the fully functional 

default mode even if the vehicle would 

meet S5.2.1, S5.2.2 and S5.2.3 at that 

level of ESC function. 

S5.5.6 As of September 1, 2011, 

except as provided in paragraph S5.5.7 

and S5.5.8, each ‘‘ESC Off’’ telltale must 

be activated as a check of lamp function 

either when the ignition locking system 

is turned to the ‘‘On’’ (‘‘Run’’) position 

when the engine is not running, or 

when the ignition locking system is in 

a position between ‘‘On’’ (‘‘Run’’) and 

‘‘Start’’ that is designated by the 

manufacturer as a check position. 

S5.5.7 The ‘‘ESC Off’’ telltale need 

not be activated when a starter interlock 

is in operation. 

S5.5.8 The requirement S5.5.6 does 

not apply to telltales shown in a 

common space. 

S5.5.9 The ‘‘ESC Off’’ telltale must 

extinguish after the ESC system has 

been returned to its fully functional 

default mode. 

S5.6 ESC System Technical 

Documentation. To ensure a vehicle is 

equipped with an ESC system that 

meets the definition of ‘‘ESC System’’ in 

S4, the vehicle manufacturer must make 

available to the agency, upon request, 

the following documentation: 

S5.6.1 A system diagram that 

identifies all ESC system hardware. The 

diagram must identify what components 

are used to generate brake torques at 

each wheel, determine vehicle yaw rate, 

estimated side slip or the side slip 

derivative and driver steering inputs. 

S5.6.2 A written explanation 

describing the ESC system basic 

operational characteristics. This 

explanation must include a discussion 

on the system’s capability to apply 

brake torques at each wheel and how 

the system modifies engine torque 

during ESC system activation. The 

explanation must also identify the 

vehicle speed range and the driving 

phases (acceleration, deceleration, 

coasting, during activation of the ABS or 

traction control) under which the ESC 

system can activate. 

S5.6.3 A logic diagram that supports 

the explanation provided in S5.6.2. 

S5.6.4 Specifically for mitigating 

vehicle understeer, a discussion of the 

pertinent inputs to the computer or 

calculations within the computer and 

how its algorithm uses that information 

and controls ESC system hardware to 

limit vehicle understeer. 

S6. Test Conditions. 

S6.1 Ambient conditions. 

S6.1.1 The ambient temperature is 

between 7 °C (45 °F) and 40 °C (104 °F). 

S6.1.2 The maximum wind speed is 

no greater than 10 m/s (22 mph) for 

passenger cars and 5 m/s (11 mph) for 

multipurpose passenger vehicles, trucks 

and buses. 

S6.2 Road test surface. 


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S6.2.1 The tests are conducted on a 

dry, uniform, solid-paved surface. 

Surfaces with irregularities and 

undulations, such as dips and large 

cracks, are unsuitable. 

S6.2.2 The road test surface must 

produce a peak friction coefficient (PFC) 

of 0.9 when measured using an 

American Society for Testing and 

Materials (ASTM) E1136–93 (1993) 

standard reference test tire, in 

accordance with ASTM Method E 1337–

90 (Reapproved 1996), at a speed of 64.4 

km/h (40 mph), without water delivery. 

(These standards are here incorporated 

by reference as explained in S3.2 

above.) 

S6.2.3 The test surface has a 

consistent slope between level and 1%. 

S6.3 Vehicle conditions. 

S6.3.1 The ESC system is enabled 

for all testing. 

S6.3.2 Test Weight. The vehicle is 

loaded with the fuel tank filled to at 

least 75 percent of capacity, and total 

interior load of 168 kg (370 lbs) 

comprised of the test driver, 

approximately 59 kg (130 lbs) of test 

equipment (automated steering 

machine, data acquisition system and 

the power supply for the steering 

machine), and ballast as required by 

differences in the weight of test drivers 

and test equipment. Where required, 

ballast shall be placed on the floor 

behind the passenger front seat or if 

necessary in the front passenger foot 

well area. All ballast shall be secured in 

a way that prevents it from becoming 

dislodged during test conduct. 

S6.3.3 Tires. The vehicle is tested 

with the tires installed on the vehicle at 

time of initial vehicle sale. The tires are 

inflated to the vehicle manufacturer’s 

recommended cold tire inflation 

pressure(s) specified on the vehicle’s 

placard or the tire inflation pressure 

label. Tubes may be installed to prevent 

tire de-beading. 

S6.3.4 Outriggers. Outriggers must 

be used for testing trucks, multipurpose 

passenger vehicles, and buses. Vehicles 

with a baseline weight under 2,722 kg 

(6,000 lbs) must be equipped with 

‘‘standard’’ outriggers and vehicles with 

a baseline weight equal to or greater 

than 2,722 kg (6,000 lbs) must be 

equipped with ‘‘heavy’’ outriggers. A 

vehicle’s baseline weight is the weight 

of the vehicle delivered from the dealer, 

fully fueled, with a 73 kg (160 lb) driver. 

Standard outriggers shall be designed 

with a maximum weight of 32 kg (70 lb) 

and a maximum roll moment of inertia 

of 35.9 kg-m2 (26.5 ft-lb-sec2). Heavy 

outriggers shall be designed with a 

maximum weight of 39 kg (86 lb) and 

a maximum roll moment of inertia of 

40.7 kg-m2 (30.0 ft-lb-sec2). 

S6.3.5 Automated steering machine. 

A steering machine programmed to 

execute the required steering pattern 

must be used in S7.5.2, S7.5.3, S7.6 and 

S7.9. The steering machine shall be 

capable of supplying steering torques 

between 40 to 60 Nm (29.5 to 44.3 lbft). The steering machine must be able 

to apply these torques when operating 

with steering wheel velocities up to 

1200 degrees per second. 

S7. Test Procedure. 

S7.1 Inflate the vehicles’ tires to the 

cold tire inflation pressure(s) provided 

on the vehicle’s placard or the tire 

inflation pressure label. 

S7.2 Telltale bulb check. With the 

vehicle stationary and the ignition 

locking system in the ‘‘Lock’’ or ‘‘Off’’

position, activate the ignition locking 

system to the ‘‘On’’ (‘‘Run’’) position or, 

where applicable, the appropriate 

position for the lamp check. The ESC 

malfunction telltale must be activated as 

a check of lamp function, as specified in 

S5.3.4, and if equipped, the ‘‘ESC Off’’

telltale must also be activated as a check 

of lamp function, as specified in S5.5.6. 

The telltale bulb check is not required 

for a telltale shown in a common space 

as specified in S5.3.6 and S5.5.8. 

S7.3 ‘‘ESC Off’’ control check. For 

vehicles equipped with an ‘‘ESC Off’’

control, with the vehicle stationary and 

the ignition locking system in the 

‘‘Lock’’ or ‘‘Off’’ position, activate the 

ignition locking system to the ‘‘On’’

(‘‘Run’’) position. Activate the ‘‘ESC 

Off’’ control and verify that the ‘‘ESC 

Off’’ telltale is illuminated, as specified 

in S5.5.4. Turn the ignition locking 

system to the ‘‘Lock’’ or ‘‘Off’’ position. 

Again, activate the ignition locking 

system to the ‘‘On’’ (‘‘Run’’) position 

and verify that the ‘‘ESC Off’’ telltale 

has extinguished indicating that the ESC 

system has been reactivated as specified 

in S5.4.1. 

S7.4 Brake Conditioning. Condition 

the vehicle brakes as follows: 

S7.4.1 Ten stops are performed from 

a speed of 56 km/h (35 mph), with an 

average deceleration of approximately 

0.5 g. 

S7.4.2 Immediately following the 

series of 56 km/h (35 mph) stops, three 

additional stops are performed from 72 

km/h (45 mph). 

S7.4.3 When executing the stops in 

S7.4.2, sufficient force is applied to the 

brake pedal to activate the vehicle’s 

antilock brake system (ABS) for a 

majority of each braking event. 

S7.4.4 Following completion of the 

final stop in S7.4.2, the vehicle is driven 

at a speed of 72 km/h (45 mph) for five 

minutes to cool the brakes. 

S7.5 Tire Conditioning. Condition 

the tires using the following procedure 

to wear away mold sheen and achieve 

operating temperature immediately 

before beginning the test runs of S7.6 

and S7.9. 

S7.5.1 The test vehicle is driven 

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. 

S7.5.2 Using a sinusoidal steering 

pattern at a frequency of 1 Hz, a peak 

steering wheel angle amplitude 

corresponding to a peak lateral 

acceleration of 0.5–0.6 g, and a vehicle 

speed of 56 km/h (35 mph), the vehicle 

is driven through four passes 

performing 10 cycles of sinusoidal 

steering during each pass. 

S7.5.3 The steering wheel angle 

amplitude of the final cycle of the final 

pass is twice that of the other cycles. 

The maximum time permitted between 

all laps and passes is five minutes. 

S7.6 Slowly Increasing Steer Test. 

The vehicle is subjected to two series of 

runs of the Slowly Increasing Steer Test 

using a constant vehicle speed of 80 ± 

2 km/h (50 ± 1 mph) and a steering 

pattern that increases by 13.5 degrees 

per second until a lateral acceleration of 

approximately 0.5 g is obtained. Three 

repetitions are performed for each test 

series. One series uses counterclockwise 

steering, and the other series uses 

clockwise steering. The maximum time 

permitted between each test run is five 

minutes. 

S7.6.1 From the Slowly Increasing 

Steer tests, the quantity ‘‘A’’ is 

determined. ‘‘A’’ is the steering wheel 

angle in degrees that produces a steady 

state lateral acceleration (corrected 

using the methods specified in S7.11.3) 

of 0.3 g for the test vehicle. Utilizing 

linear regression, A is calculated, to the 

nearest 0.1 degrees, from each of the six 

Slowly Increasing Steer tests. The 

absolute value of the six A’s calculated 

is averaged and rounded to the nearest 

0.1 degrees to produce the final 

quantity, A, used below. 

S7.7 After the quantity A has been 

determined, without replacing the tires, 

the tire conditioning procedure 

described in S7.5 is performed 

immediately prior to conducting the 

Sine with Dwell Test of S7.9. Initiation 

of the first Sine with Dwell test series 

shall begin within two hours after 

completion of the Slowly Increasing 

Steer tests of S7.6. 

S7.8 Check that the ESC system is 

enabled by ensuring that the ESC 

malfunction and ‘‘ESC Off’’ (if provided) 

telltales are not illuminated. 

S7.9 Sine with Dwell Test of 

Oversteer Intervention and 


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Responsiveness. The vehicle is 

subjected to two series of test runs using 

a steering pattern of a sine wave at 0.7 

Hz frequency with a 500 ms delay 

beginning at the second peak amplitude 

as shown in Figure 2 (the Sine with 

Dwell tests). One series uses 

counterclockwise steering for the first 

half cycle, and the other series uses 

clockwise steering for the first half 

cycle. The vehicle is provided a cooldown period between each test run of 

90 seconds to five minutes, with the 

vehicle stationary. 

S7.9.1 The steering motion is 

initiated with the vehicle coasting in 

high gear at 80 ±2 km/h (50 ±1 mph). 

S7.9.2 In each series of test runs, the 

steering amplitude is increased from run 

to run, by 0.5A, provided that no such 

run will result in a steering amplitude 

greater than that of the final run 

specified in S7.9.4. 

S7.9.3 The steering amplitude for 

the initial run of each series is 1.5A 

where A is the steering wheel angle 

determined in S7.6.1. 

S7.9.4 The steering amplitude of the 

final run in each series is the greater of 

6.5A or 270 degrees, provided the 

calculated magnitude of 6.5A is less 

than or equal to 300 degrees. If any 0.5A 

increment, up to 6.5A, is greater than 

300 degrees, the steering amplitude of 

the final run shall be 300 degrees. 

S7.9.5 Upon completion of the two 

series of test runs, post processing of 

yaw rate and lateral acceleration data is 

done as specified in S7.11. 

S7.10 ESC Malfunction Detection. 

S7.10.1 Simulate one or more ESC 

malfunction(s) by disconnecting the 

power source to any ESC component, or 

disconnecting any electrical connection 

between ESC components (with the 

vehicle power off). When simulating an 

ESC malfunction, the electrical 

connections for the telltale lamp(s) are 

not to be disconnected. 

S7.10.2 With the vehicle initially 

stationary and the ignition locking 

system in the ‘‘Lock’’ or ‘‘Off’’ position, 

activate the ignition locking system to 

the ‘‘Start’’ position and start the engine. 

Place the vehicle in a forward gear and 

obtain a vehicle speed of 48 ± 8 km/h 

(30 ± 5 mph). Drive the vehicle for at 

least two minutes including at least one 

left and one right turning maneuver. 

Verify that within two minutes of 

obtaining this vehicle speed the ESC 

malfunction indicator illuminates in 

accordance with S5.3. 

S7.10.3 Stop the vehicle, deactivate 

the ignition locking system to the ‘‘Off’’

or ‘‘Lock’’ position. After a five-minute 

period, activate the vehicle’s ignition 

locking system to the ‘‘Start’’ position 

and start the engine. Verify that the ESC 

malfunction indicator again illuminates 

to signal a malfunction and remains 

illuminated as long as the engine is 

running or until the fault is corrected. 

S7.10.4 Deactivate the ignition 

locking system to the ‘‘Off’’ or ‘‘Lock’’

position. Restore the ESC system to 

normal operation, activate the ignition 

system to the ‘‘Start’’ position and start 

the engine. Verify that the telltale has 

extinguished. 

S7.11 Post Data Processing—

Calculations for Performance Metrics. 

Yaw rate and lateral displacement 

measurements and calculations must be 

processed utilizing the following 

techniques: 

S7.11.1 Raw steering wheel angle 

data is filtered with a 12-pole phaseless 

Butterworth filter and a cutoff frequency 

of 10Hz. The filtered data is then zeroed 

to remove sensor offset utilizing static 

pretest data. 

S7.11.2 Raw yaw rate data is filtered 

with a 12-pole phaseless Butterworth 

filter and a cutoff frequency of 6Hz. The 

filtered data is then zeroed to remove 

sensor offset utilizing static pretest data. 

S7.11.3 Raw lateral acceleration data 

is filtered with a 12-pole phaseless 

Butterworth filter and a cutoff frequency 

of 6Hz. The filtered data is then zeroed 

to remove sensor offset utilizing static 

pretest data. The lateral acceleration 

data at the vehicle center of gravity is 

determined by removing the effects 

caused by vehicle body roll and by 

correcting for sensor placement via use 

of coordinate transformation. For data 

collection, the lateral accelerometer 

shall be located as close as possible to 

the position of the vehicle’s longitudinal 

and lateral centers of gravity. 

S7.11.4 Steering wheel velocity is 

determined by differentiating the 

filtered steering wheel angle data. The 

steering wheel velocity data is then 

filtered with a moving 0.1 second 

running average filter. 

S7.11.5 Lateral acceleration, yaw 

rate and steering wheel angle data 

channels are zeroed utilizing a defined 

‘‘zeroing range.’’ The methods used to 

establish the zeroing range are defined 

in S7.11.5.1 and S7.11.5.2. 

S7.11.5.1 Using the steering wheel 

rate data calculated using the methods 

described in S7.11.4, the first instant 

steering wheel rate exceeds 75 deg/sec 

is identified. From this point, steering 

wheel rate must remain greater than 75 

deg/sec for at least 200 ms. If the second 

condition is not met, the next instant 

steering wheel rate exceeds 75 deg/sec 

is identified and the 200 ms validity 

check applied. This iterative process 

continues until both conditions are 

ultimately satisfied. 

S7.11.5.2 The ‘‘zeroing range’’ is 

defined as the 1.0 second time period 

prior to the instant the steering wheel 

rate exceeds 75 deg/sec (i.e., the instant 

the steering wheel velocity exceeds 75 

deg/sec defines the end of the ‘‘zeroing 

range’’). 

S7.11.6 The Beginning of Steer 

(BOS) is defined as the first instance 

filtered and zeroed steering wheel angle 

data reaches ¥5 degrees (when the 

initial steering input is 

counterclockwise) or +5 degrees (when 

the initial steering input is clockwise) 

after time defining the end of the 

‘‘zeroing range.’’ The value for time at 

the BOS is interpolated. 

S7.11.7 The Completion of Steer 

(COS) is defined as the time the steering 

wheel angle returns to zero at the 

completion of the Sine with Dwell 

steering maneuver. The value for time at 

the zero degree steering wheel angle is 

interpolated. 

S7.11.8 The second peak yaw rate is 

defined as the first local yaw rate peak 

produced by the reversal of the steering 

wheel. The yaw rates at 1.000 and 1.750 

seconds after COS are determined by 

interpolation. 

S7.11.9 Determine lateral velocity by 

integrating corrected, filtered and 

zeroed lateral acceleration data. Zero 

lateral velocity at BOS event. Determine 

lateral displacement by integrating 

zeroed lateral velocity. Zero lateral 

displacement at BOS event. Lateral 

displacement at 1.07 seconds from BOS 

event is determined by interpolation. 

S8. Phase-in schedule. 

S8.1 Vehicles manufactured on or 

after September 1, 2008, and before 

September 1, 2009. For vehicles 

manufactured on or after September 1, 

2008, and before September 1, 2009, the 

number of vehicles complying with this 

standard must not be less than 55 

percent of: 

(a) The manufacturer’s average annual 

production of vehicles manufactured on 

or after September 1, 2005, and before 

September 1, 2008; or 

(b) The manufacturer’s production on 

or after September 1, 2008, and before 

September 1, 2009. 

S8.2 Vehicles manufactured on or 

after September 1, 2009, and before 

September 1, 2010. For vehicles 

manufactured on or after September 1, 

2009, and before September 1, 2010, the 

number of vehicles complying with this 

standard must not be less than 75 

percent of: 

(a) The manufacturer’s average annual 

production of vehicles manufactured on 

or after September 1, 2006, and before 

September 1, 2009; or 


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17314 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

(b) The manufacturer’s production on 

or after September 1, 2009, and before 

September 1, 2010. 

S8.3 Vehicles manufactured on or 

after September 1, 2010, and before 

September 1, 2011. For vehicles 

manufactured on or after September 1, 

2010, and before September 1, 2011, the 

number of vehicles complying with this 

standard must not be less than 95 

percent of: 

(a) The manufacturer’s average annual 

production of vehicles manufactured on 

or after September 1, 2007, and before 

September 1, 2010; or 

(b) The manufacturer’s production on 

or after September 1, 2010, and before 

September 1, 2011. 

S8.4 Vehicles manufactured on or 

after September 1, 2011. All vehicles 

manufactured on or after September 1, 

2011 must comply with this standard. 

S8.5 Calculation of complying 

vehicles. 

(a) For purposes of complying with 

S8.1, a manufacturer may count a 

vehicle if it is certified as complying 

with this standard and is manufactured 

on or after June 5, 2007, but before 

September 1, 2009. 

(b) For purpose of complying with 

S8.2, a manufacturer may count a 

vehicle if it: 

(1) (i) Is certified as complying with 

this standard and is manufactured on or 

after June 5, 2007, but before September 

1, 2010; and 

(ii) Is not counted toward compliance 

with S8.1; or 

(2) Is manufactured on or after 

September 1, 2009, but before 

September 1, 2010. 

(c) For purposes of complying with 

S8.3, a manufacturer may count a 

vehicle if it: 

(1)(i) Is certified as complying with 

this standard and is manufactured on or 

after June 5, 2007, but before September 

1, 2011; and 

(ii) Is not counted toward compliance 

with S8.1 or S8.2; or 

(2) Is manufactured on or after 

September 1, 2010, but before 

September 1, 2011. 

S8.6 Vehicles produced by more 

than one manufacturer. 

S8.6.1 For the purpose of calculating 

average annual production of vehicles 

for each manufacturer and the number 

of vehicles manufactured by each 

manufacturer under S8.1 through S8.4, 

a vehicle produced by more than one 

manufacturer must be attributed to a 

single manufacturer as follows, subject 

to S8.6.2: 

(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. 

S8.6.2 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 S8.6.1. 

S8.7 Small volume manufacturers. 

Vehicles manufactured during any of 

the three years of the September 1, 2008 

through August 31, 2011 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 S8.1, S8.2, S8.3, and 

S8.5. 

S8.8 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 

S8.1 through S8.5. Instead, all vehicles 

produced by these manufacturers on or 

after September 1, 2012 must comply 

with this standard. 

BILLING CODE 4910–59–P 


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17316 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

PART 585—PHASE-IN REPORTING 

REQUIREMENTS 

■ 4. The authority citation for part 585 

continues to read as follows: 

Authority: 49 U.S.C. 322, 30111, 30115, 

30117, and 30166; delegation of authority at 

49 CFR 1.50. 

■ 5. Subpart H is added and reserved. 

■ 6. Subpart I is added to read as 

follows: 

Subpart I—Electronic Stability Control 

System Phase-In Reporting Requirements 

Sec. 

585.81 Scope. 

585.82 Purpose. 

585.83 Applicability. 

585.84 Definitions. 

585.85 Response to inquiries. 

585.86 Reporting requirements. 

585.87 Records. 

585.88 Petition to extend period to file 

report. 

Subpart I—Electronic Stability Control 

System Phase In Reporting 

Requirements 

§ 585.81 Scope. 

This subpart establishes requirements 

for manufacturers of passenger cars, 

multipurpose passenger vehicles, 

trucks, and buses with a gross vehicle 

weight rating of 4,536 kilograms (10,000 

pounds) or less to submit a report, and 

maintain records related to the report, 

concerning the number of such vehicles 

that meet the requirements of Standard 

No. 126, Electronic stability control 

systems (49 CFR 571.126). 

§ 585.82 Purpose. 

The purpose of these reporting 

requirements is to assist the National 

Highway Traffic Safety Administration 

in determining whether a manufacturer 

has complied with Standard No. 126 (49 

CFR 571.126). 

§ 585.83 Applicability. 

This subpart applies to manufacturers 

of passenger cars, multipurpose 

passenger vehicles, trucks, and buses 

with a gross vehicle weight rating of 

4,536 kilograms (10,000 pounds) or less. 

However, this subpart does not apply to 

manufacturers whose production 

consists exclusively of vehicles 

manufactured in two or more stages, 

and vehicles that are altered after 

previously having been certified in 

accordance with part 567 of this 

chapter. In addition, this subpart does 

not apply to manufacturers whose 

production of motor vehicles for the 

United States market is less than 5,000 

vehicles in a production year. 

§ 585.84 Definitions. 

For the purposes of this subpart: 

Production year means the 12-month 

period between September 1 of one year 

and August 31 of the following year, 

inclusive. 

§ 585.85 Response to inquiries. 

At any time prior to August 31, 2011, 

each manufacturer must, 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 Standard No. 126 (49 

CFR 571.126). The manufacturer’s 

designation of a vehicle as a certified 

vehicle is irrevocable. Upon request, the 

manufacturer also must specify whether 

it intends to utilize carry-forward 

credits, and the vehicles to which those 

credits relate. 

§ 585.86 Reporting requirements. 

(a) General reporting requirements. 

Within 60 days after the end of the 

production years ending August 31, 

2009, August 31, 2010, and August 31, 

2011, each manufacturer must submit a 

report to the National Highway Traffic 

Safety Administration concerning its 

compliance with Standard No. 126 (49 

CFR 571.126) for its passenger cars, 

multipurpose passenger vehicles, 

trucks, and buses with a gross vehicle 

weight rating of less than 4,536 

kilograms (10,000 pounds) produced in 

that year. 

Each report must—

(1) Identify the manufacturer; 

(2) State the full name, title, and 

address of the official responsible for 

preparing the report; 

(3) Identify the production year being 

reported on; 

(4) Contain a statement regarding 

whether or not the manufacturer 

complied with the requirements of 

Standard No. 126 (49 CFR 571.126) for 

the period covered by the report and the 

basis for that statement; 

(5) Provide the information specified 

in paragraph (b) of this section; 

(6) Be written in the English language; 

and 

(7) Be submitted to: Administrator, 

National Highway Traffic Safety 

Administration, 400 Seventh Street, 

SW., Washington, DC 20590. 

(b) Report content. 

(1) Basis for statement of compliance. 

Each manufacturer must provide the 

number of passenger cars, multipurpose 

passenger vehicles, trucks, and buses 

with a gross vehicle weight rating of 

4,536 kilograms (10,000 pounds) or less, 

manufactured for sale in the United 

States for each of the three previous 

production years, or, at the 

manufacturer’s option, for the current 

production year. A new manufacturer 

that has not previously manufactured 

these vehicles for sale in the United 

States must report the number of such 

vehicles manufactured during the 

current production year. 

(2) Production. Each manufacturer 

must report for the production year for 

which the report is filed: the number of 

passenger cars, multipurpose passenger 

vehicles, trucks, and buses with a gross 

vehicle weight rating of 4,536 kilograms 

(10,000 pounds) or less that meet 

Standard No. 126 (49 CFR 571.126). 

(3) Statement regarding compliance. 

Each manufacturer must provide a 

statement regarding whether or not the 

manufacturer complied with the ESC 

requirements as applicable to the period 

covered by the report, and the basis for 

that statement. This statement must 

include an explanation concerning the 

use of any carry-forward credits. 

(4) Vehicles produced by more than 

one manufacturer. Each manufacturer 

whose reporting of information is 

affected by one or more of the express 

written contracts permitted by S8.6.2 of 

Standard No. 126 (49 CFR 571.126) 

must: 

(i) Report the existence of each 

contract, including the names of all 

parties to the contract, and explain how 

the contract affects the report being 

submitted. 

(ii) Report the actual number of 

vehicles covered by each contract. 

§ 585.87 Records. 

Each manufacturer must maintain 

records of the Vehicle Identification 

Number for each vehicle for which 

information is reported under 

§ 585.86(b)(2) until December 31, 2013. 

§ 585.88 Petition to extend period to file 

report. 

A manufacturer may petition for 

extension of time to submit a report 

under this Part. A petition will be 

granted only if the petitioner shows 

good cause for the extension and if the 

extension is consistent with the public 

interest. The petition must be received 

not later than 15 days before expiration 

of the time stated in § 585.86(a). The 

filing of a petition does not 

automatically extend the time for filing 

a report. The petition must be submitted 

to: Administrator, National Highway 

Traffic Safety Administration, 400 

Seventh Street, SW., Washington, DC 

20590. 

Issued: March 22, 2007. 

Nicole R. Nason, 

Administrator. 

[Note: The Following Appendix Will 

Not Appear in the Code of Federal 

Regulations.] 


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93 71 FR 54712, 54716–54718 (Sept. 18, 2006). 

94SAE J670e, ‘‘Vehicle Dynamics Terminology,’’

SAE Recommended Practice, Issued by the SAE 

Vehicle Dynamics Committee July 1952, last revised 

July 1976. 

95For the reader’s reference, ‘‘trim’’ is roughly 

defined as the vehicle’s weight distribution at a 

given time. For example, loading the vehicle’s trunk 

changes the trim. 

96A less technical way of describing ‘‘linear 

range’’ would be the normal situation of everyday 

driving, where a given turn by the driver of the 

steering wheel causes an expected amount of turn 

of the vehicle itself, because the vehicle is operating 

at the traction levels to which most drivers are 

accustomed. 97Milliken, W.F., and Milliken, D.L., p. 144, 

‘‘Race Car Vehicle Dynamics,’’ SAE International, 

1995 98 ‘‘Unconditionally stable’’ for a motor vehicle 

means that, regardless of the weight distribution, 

suspension configuration, tire cornering stiffness, or 

vehicle speed (provided the vehicle can be modeled 

by the Elementary Automobile or ‘‘bicycle’’ model), 

the vehicle will return to straight ahead driving 

after enough time (usually only a couple of seconds) 

has passed after the return of the steering wheel to 

the straight ahead position. 

99A simple test illustrates the concepts of 

understeer and oversteer. A vehicle is driven 

around a circle at a constant speed, then the speed 

is slowly increased. If the vehicle tends to go off 

the outside of the circle so that the driver must 

increase steering to maintain the circle, then the 

vehicle is considered to be an understeer vehicle. 

If the vehicle tends to go off the inside of the circle 

so that the driver must reduce steering to maintain 

the circle, then the vehicle is considered to be an 

oversteer vehicle. Understeer and oversteer can 

affect the stability of a vehicle; however, just 

because a vehicle is an oversteer vehicle does not 

mean that it is uncontrollable. A more detailed 

discussion of understeer and oversteer and their 

impact on stability and control is contained in (a) 

William F. Milliken and Douglas L. Milliken, 

‘‘Simplified Steady State Stability and Control,’’

Chapter 5, and ‘‘Simplified Transient Stability and 

Control,’’ Chapter 6 in Race Car Vehicle Dynamics 

(Warrendale, PA: Society of Automotive Engineers, 

1995) 123–229 and 231–277; and (b) Thomas D. 

Gillespie, ‘‘Rollover,’’ Chapter 9 in Fundamentals of 

Vehicle Dynamics (Warrendale, PA: Society of 

Automotive Engineers, 1992) 309–333. 

100Lateral responsiveness is defined here as how 

much a vehicle moves sideways in a given amount 

of time due to a specified rotation of the steering 

wheel. 

APPENDIX: Technical Explanation in 

Response to Comments on Understeer 

This appendix explains NHTSA’s 

reasoning regarding the issue raised by 

public comment on Understeer 

Requirements, as discussed in the Response 

to Comments section of the Final Rule (see 

Section IV.C.4). This is an area of ongoing 

research by vehicle dynamics researchers 

involving concepts that are beyond what is 

usually discussed in a first-year graduateschool-level course on vehicle dynamics. We 

have done our best to address this subject in 

a way that will be easily understandable by 

the general reader. Nevertheless, some 

aspects of the following discussion are 

unavoidably fairly technical. 

Explanation of Linear and Non-Linear 

Understeer 

First, we wish to clarify what we mean by 

linear and non-linear range understeer since 

some of the commenters did not appear to 

understand the fundamental issues 

associated with the agency’s decision to 

include an understeer requirement in the 

definition of ESC System. 

Understeer has proven to be an extremely 

useful concept for characterizing the lateral 

response of a vehicle. Section III.A, How ESC 

Prevents Loss of Vehicle Control 93 of the 

Notice of Proposed Rulemaking (NPRM) 

attempts to explain the concepts of 

understeer and oversteer to the reader in nontechnical terms. However, the full scientific 

definitions of understeer and oversteer are 

presented here in order to lay the technical 

groundwork for the discussions that follow. 

Many alternative definitions of understeer 

have been developed. The Society of 

Automotive Engineers’ (SAE) definitions of 

understeer and its opposite, oversteer, taken 

from SAE J670e,94 are: 

‘‘9.4.7 UNDERSTEER/OVERSTEER 

GRADIENT—The ratio of the steering wheel 

angle gradient to the overall steering ratio 

quantity obtained by subtracting the 

Ackerman steer angle gradient from the ratio 

of the steering wheel angle gradient to the 

overall steering ratio.’’

‘‘9.4.9 UNDERSTEER—A vehicle is 

understeer at a given trim 95 if the ratio of the 

steering wheel angle gradient to the overall 

steering ratio is greater than the Ackerman 

steer angle gradient.’’

‘‘9.4.10 OVERSTEER—A vehicle is 

oversteer at a given trim if the ratio of the 

steering wheel angle gradient to the overall 

steering ratio is less than the Ackerman steer 

angle gradient.’’

SAE J670e defines ‘‘steering wheel angle 

gradient’’ and ‘‘Ackerman steer angle 

gradient’’ as follows: 

‘‘9.4.5 STEERING WHEEL ANGLE 

GRADIENT—The rate of change in the 

steering wheel angle with respect to change 

in steady state lateral acceleration on a level 

road at a given trim and test conditions.’’

‘‘Note 14 ACKERMAN STEER ANGLE 

GRADIENT is equal to the wheelbase divided 

by the square of the vehicle speed (rad/ft/ 

sec2).’’

Consider the linear range of vehicle 

handling. The linear range is defined as the 

region of handling where the lateral 

acceleration versus steering wheel angle gain 

remains approximately constant (meaning 

that the understeer gradient is essentially 

constant).96 The boundaries of the linear 

range depend upon the friction of the surface 

being driven on. The linear range occurs for 

lateral accelerations between 0.1 and 0.4g on 

a high friction surface such as dry asphalt or 

concrete. For a slippery, moderately low 

friction surface such as a wet road, the linear 

range would be lower, perhaps between 

lateral accelerations of 0.05 and 0.2g 

(depending upon the surface of the road), 

while on ice the limits of the linear range 

would be still lower. 

All light vehicles (including passenger 

cars, pickups, vans, minivans, crossovers, 

and sport utility vehicles) are designed to 

understeer in the linear range of lateral 

acceleration, although operational factors 

such as loading, tire inflation pressure, and 

so forth can in rare situations make them 

oversteer in use. This is a fundamental 

design characteristic. Understeer provides a 

valuable, and benign, way for the vehicle to 

inform the driver of how the available 

roadway friction is being utilized. Multiple 

tests have been developed to objectively 

quantify linear-range understeer, including 

SAE J266 and ISO 4138. 

In the linear range of handling, ESC should 

never activate. ESC interventions occur when 

the driver’s intended path (calculated by the 

ESC control algorithms using a constant 

linear range understeer gradient) differs from 

the actual path of the vehicle as measured by 

ESC sensors. Since by definition, this 

relationship is not violated while driving in 

the linear range, ESC intervention will not 

occur. Therefore, ESC has no effect upon the 

linear-range understeer of a vehicle. 

Solving the linear range differential 

equations of motion for what the Millikens 97

refer to as the ‘‘Elementary Automobile’’ or 

‘‘bicycle’’ model reveals that the understeer 

gradient has some very interesting 

mathematical properties. 

First, the solutions to the linear range 

differential equations of motion are 

unconditionally stable 98 provided that the 

understeer gradient is positive (i.e., the 

vehicle is understeer). For an oversteer 

vehicle,99 solutions to the linear range 

differential equations of motion become 

unstable if the vehicle’s speed exceeds the 

critical speed. The value of the critical speed 

depends upon the degree of oversteer the 

vehicle exhibits (and on other vehicle 

properties); however, a vehicle with 

reasonable amounts of oversteer can easily 

exceed the critical speed and become 

unstable during normal driving. 

What does it mean when the solutions to 

the linear range differential equations of 

motion become unstable? It means that as 

soon as the unstable vehicle encounters a 

disturbance input (and in real driving, 

disturbance inputs such as small wind gusts 

or small bumps in the road occur very 

frequently), the actual solutions of the 

differential equation will rapidly diverge 

from the nominal solutions. In the real world, 

this means that the driver can no longer 

control the unstable vehicle by using the 

steering wheel. The unstable vehicle 

generally will rotate rapidly about a vertical 

axis (spin) and may change its direction of 

motion regardless of what the driver does 

with the steering wheel. From the safety 

point of view, a vehicle becoming unstable 

often has severe negative consequences, 

ranging from road departure to sideways 

impacts with off-road obstacles to tripped 

rollover. 

Returning to the mathematical properties 

of the understeer gradient, we find that it also 

is a key parameter in determining the lateral 

responsiveness 100 of the vehicle. According 

to the solutions to the linear range 

differential equations of motion, the more a 

vehicle understeers, the less lateral 

responsiveness it will have (assuming, of 

course, that all other parameters are held 

constant). 

For a vehicle to be safe, it must have 

adequate lateral responsiveness. Vehicles 

with too little lateral responsiveness will not 

be able to successfully maneuver around 

pedestrians, vehicles, or other objects that 


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17318 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

101Birkhoff, G. and Rota, G.C., pp 134–136, 

‘‘Ordinary Differential Equations,’’ Blaisdell 

Publishing Company, 1969. 

may suddenly intrude into the roadway. 

They will also be more difficult to steer 

around turns in the road, requiring the driver 

to initiate steering earlier than for vehicles 

with adequate lateral responsiveness. 

A safe vehicle, then, requires both stability 

and adequate lateral responsiveness. In the 

linear range of handling, this is achieved by 

having the vehicle understeer to a moderate 

degree. This explains why all light vehicles 

are designed to understeer in the linear range 

of lateral acceleration. 

Next, consider driving situations that are 

outside of the linear range of handling. In 

this situation, the differential equations of 

motion, even for the ‘‘Elementary 

Automobile’’ or ‘‘bicycle’’ model become 

non-linear, complicated, and beyond the 

ability of humans to solve analytically. 

Vehicle dynamics simulations have been 

developed that use numerical integration to 

predict the vehicle trajectories. 

Unfortunately, the prediction of vehicle 

trajectories is insufficient to determine the 

stability of the vehicle, although it can be 

used to determine the lateral responsiveness 

of the vehicle. 

To determine the stability of the solutions 

of the non-linear range differential equations 

of motion, the ‘‘Method of Liapunov’’ 101 is 

used. The Method of Liapunov consists of 

linearizing the non-linear differential 

equations about an operating point of the 

vehicle. Liapunov proved that the stability of 

the solutions of the linearized differential 

equations about an operating point is the 

same as the stability of the original nonlinear differential equations about that same 

operating point. The term that determines the 

stability of the solutions of the linearized 

differential equations about an operating 

point is called the non-linear understeer 

gradient. However, unlike the linear 

understeer gradient, the non-linear 

understeer gradient is no longer constant. It 

will vary as a function of the vehicle’s lateral 

acceleration. 

Just as is the case for the linear range 

vehicle, for a vehicle to be safe at an 

operating point in the non-linear range, we 

must have both stability and adequate lateral 

responsiveness. Again, this is achieved by 

designing the vehicle to understeer to a 

moderate degree. However, for reasons that 

are explained below, it is impossible to attain 

this desirable condition over the entire nonlinear operating range of the vehicle. 

What NHTSA Means by Mitigating Excessive 

Understeer 

All motor vehicles are limited as to how 

sharply they can turn. This fact has 

important implications for the non-linear 

understeer/oversteer of vehicles. 

The behavior of a vehicle when turning as 

sharply as possible is referred to as the limit 

behavior of the vehicle. For vehicles with 

four wheels and two axles, there are exactly 

four possible limit behaviors. Each of these 

cases, and its implications for limit 

understeer/oversteer are discussed below. 

Case 1—The vehicle plows out. For this 

case, how sharply the vehicle can turn is 

limited by the friction between the roadway 

and the tires on the vehicle’s front axle. 

When the tires on the vehicle’s front axle are 

producing as much side force as the road/tire 

friction permits, we say that the vehicle’s 

front tires are saturated. When the front tires 

saturate before the rear tires, the vehicle 

continues to travel forward in as tight a curve 

as it can manage. The turn will not become 

tighter, even if the driver turns the steering 

wheel requesting a sharper turn. We call this 

behavior vehicle plow-out. While from a 

safety point of view it is never good for a 

vehicle to reach limit behavior, plow-out is 

the most benign form of limit behavior. 

Mathematically, plow-out corresponds to the 

non-linear understeer gradient remaining 

positive and becoming infinite at the limit of 

handling. 

Case 2—The vehicle drifts out. For this 

case, the tires on both the vehicle’s front and 

rear axles saturate at exactly the same time. 

Drift-out is extremely rare; it is very hard to 

saturate both axles at the same time. When 

drift-out occurs, the vehicle continues to 

travel forward in as tight a curve as it can 

manage (similar to plow-out) except that the 

vehicle will slowly (far more slowly than for 

Case 3, below) rotate about its vertical axis. 

Due to this slow rotation of the vehicle, from 

a safety point of view drift-out is not as 

benign as plow-out but it is better than spinout (Case 3, below). Mathematically, drift-out 

corresponds to the non-linear understeer 

gradient remaining positive and becoming 

infinite at the limit of handling. 

Case 3—The vehicle spins out. For this 

case, the tires on the vehicle’s rear axle 

saturate first. When spin-out occurs, the 

vehicle continues to travel forwards in a 

curve while the rear of the vehicle rapidly 

rotates about its vertical axis. From the safety 

point of view, vehicle spin-out is very bad 

with negative consequences ranging from 

road departure to sideways impacts with offroad obstacles to tripped rollover. 

Mathematically, spin-out corresponds to the 

non-linear understeer gradient becoming 

negative and infinite (i.e., the vehicle 

oversteers to an extreme degree) at the limit 

of handling. 

Case 4—The vehicle rolls over. For this 

case, the tires on the vehicle’s front and rear 

axles do not reach saturation. Instead, before 

the friction limit is reached, the vehicle’s 

tires leave the roadway and the vehicle 

rotates rapidly about its longitudinal axis 

onto its side or roof. From the safety point 

of view, vehicle rollover is the worst type of 

limit behavior. It is also the only type of limit 

behavior in which the vehicle’s behavior at 

the limit does not determine the non-linear 

understeer gradient at the limit of handling. 

Either understeer or oversteer, and by any 

amount, is possible for this case. 

Summarizing the above cases, at the limit 

of handling a vehicle’s understeer gradient 

will either be positive and infinite (plow-out 

and drift-out), negative and infinite (spinout), or not determined (rollover). While both 

spin-out and rollover are major safety 

concerns, this discussion is concerned with 

mitigating excessive understeer. Therefore, in 

the following discussion, we will only deal 

with the case in which a vehicle’s understeer 

gradient is positive and infinite at the limit 

of handling. Vehicles that behave in this 

manner are called ‘‘terminally 

understeering.’’

A terminally understeering vehicle’s 

understeer gradient will then be a positive 

constant in its linear range and positive and 

infinite at the limit of handling. Between the 

upper limit of the linear handling range and 

the limit of handling, the non-linear 

understeer gradient will be positive and 

monotonically increasing. (Vehicles with 

local maxima in their non-linear understeer 

gradient usually become terminally oversteer 

although we are not aware of any proofs that 

this must occur.) Figure 1 shows a typical 

understeer gradient curve for a hypothetical 

vehicle without ESC (the curve marked 

‘‘Original’’). The goal of mitigating excessive 

understeer is to use the ESC to reduce the 

non-linear understeer gradient over the range 

from 40 to 95 percent friction utilization to 

closer to the linear range understeer gradient. 

The curve marked ‘‘Reduced’’ in Figure 1 

shows a hypothetical example of mitigation 

of excessive understeer. 


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Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17319 

Need for Care in Mitigating Excessive 

Understeer 

Conceptually, the idea of ESC understeer 

mitigation makes good physical sense. In a 

situation where the vehicle does not 

sufficiently respond to the driver’s steering 

input (e.g., ‘‘plowing’’ when the driver 

attempts to steer around a corner), the 

automatic application of single-wheel 

braking torque to reduce understeer and 

increase the vehicle’s lateral responsiveness, 

thereby tightening the turning radius, seems 

like a logical course of action. NHTSA 

researchers have participated in ESC 

demonstrations specifically designed to 

showcase understeer mitigation effectiveness, 

and acknowledge that in certain driving 

situations, performed with certain vehicles, 

at certain vehicle speeds, the technology can 

suppress excessive understeer, thereby 

improving the driver’s ability to control the 

vehicle. However, truly understanding both 

what understeer mitigation can and, equally 

importantly, cannot do, is deceptively 

complicated. In fact, there are certain 

situations where understeer mitigation could 

potentially produce safety disbenefits if not 

properly tuned. 

The technique used for mitigating 

excessive understeer is to apply unbalanced 

vehicle braking so as to generate an 

oversteering moment. Clearly, if too much 

oversteering moment is generated, then the 

vehicle may oversteer and spin out with 

obvious negative safety consequences. 

Another possible problem with understeer 

mitigation is that reducing the non-linear 

understeer gradient increases the lateral 

responsiveness of the vehicle. This increases 

the lateral acceleration the vehicle can attain. 

For vehicles with low static stability factors 

and/or soft (in roll) suspensions, this may 

result in untripped rollover. Keep in mind 

that the idea of roll stability control (RSC) is 

to prevent untripped rollover by momentarily 

inducing excessive understeer, thereby 

reducing the lateral responsiveness of the 

vehicle and decreasing the lateral 

acceleration. Excessive understeer mitigation 

acts like anti-RSC. Based on this concern, 

ESC manufacturers generally do not perform 

understeer mitigation on high-coefficient-offriction pavements for vehicles for which 

untripped rollover is possible (sport utility 

vehicles, pickup trucks, full sized vans). 

For the reasons discussed above, 

understeer mitigation must be performed 

with great care. Too much mitigation can 

create safety problems (spin out or rollover). 

Problems With Performance Tests for 

Mitigating Excessive Understeer 

All current ESC designs that NHTSA has 

studied appear to include provisions for 

mitigating excessive understeer. How do we 

know this? We know this from driving these 

vehicles in the sort of maneuvers in which 

understeer mitigation should be performed 

and evaluating the resultant vehicle 

performance. 

How are ESC algorithms for mitigating 

excessive understeer developed? Designers 

use a combination of analysis, vehicle 

dynamics simulation, and evaluation based 

on engineering judgment to develop the 

algorithms. 

NHTSA cannot rely upon analysis, vehicle 

dynamics simulation, or evaluation based on 

engineering judgment for ensuring 

compliance with NHTSA regulations. We 

need a performance test, one that is objective, 

repeatable, generates reproducible results, is 

practicable to perform, and has acceptable 

face validity (i.e., passing the test must 

enhance safety). 

Tests designed to measure linear range 

understeer gradient (e.g. SAE J266 and ISO 

4138) are not suitable to evaluate an ESC’s 

understeer mitigation performance. ESC 

interventions occur when the driver’s 

intended path differs from the actual path of 

the vehicle, as discussed above. Since this 

relationship is not violated during linear 

range driving, by the definition of linear 

range, ESC intervention will not occur. 

Without intervention, assessment of ESC 

performance is not possible. 

NHTSA has carefully examined the 

existing vehicle dynamics literature 

including both the SAE and ISO standards. 

We have been unable to find any test 

designed to measure the non-linear 

understeer gradient over the full non-linear 

range of vehicle handling. A variety of 

theoretical difficulties make it unlikely that 

such test will ever be developed. 

In order for ESC understeer mitigation to 

occur during a non-linear understeer 

mitigation scenario, differences between the 

calculated and actual paths of the vehicle 

must exceed a manufacturer-specified 

allowable threshold. NHTSA knows of no 

existing test protocol capable of objectively 

evaluating non-linear understeer mitigation. 

(Note that this is a somewhat different 

problem than that of measuring the nonlinear understeer gradient over the full nonlinear range of vehicle handling. The 

theoretical problems referred to above do not 

prevent the development of an objective test 

for evaluating non-linear understeer 

mitigation.) 

What are the principal challenges to 

developing a suitable, objective, non-linear 

understeer mitigation performance test? 

Dry Test Challenges 

Understeer mitigation is only possible for 

vehicles that are designed to exhibit nonlinear and terminal understeer. Although a 

reduction of understeer may allow the tires 

of these vehicles to better utilize the available 

friction, the subsequent increase in 

maximum lateral acceleration capacity is not 

desirable for all vehicles. Some vehicles, 

particularly those with low static stability 

factors such as sport utility vehicles, or those 

having soft (in roll) suspensions, understeer 


ycherry on PROD1PC64 with RULES2ER06AP07.007</GPH>
17320 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

102 It is important to note that the braking action 

present during ESC understeer mitigation 

intervention will help slow the vehicle somewhat, 

decreasing the amount of energy available to 

produce rollover. 

designed into the chassis helps reduce the 

risk of on-road untripped rollover. By 

attempting to remove understeer, it is 

possible ESC could increase the likelihood of 

on-road untripped rollover.102 Discussions 

with ESC manufacturers have indicated that 

tests performed on a high friction surface at 

moderate to high speeds may not trigger any 

understeer intervention from this type of 

vehicles’ ESC systems. For this reason, 

NHTSA has concluded that it would be 

inappropriate to require that understeer 

mitigation occur in situations where vehicles 

are being operated on high friction surfaces 

at high speeds. 

Unfortunately, the specific details of this 

potential compromise are not fully 

understood. NHTSA does not know of any 

vehicle whose understeer mitigation 

algorithms induce on-road untripped 

rollover, and therefore has no test data to 

objectively quantify the extent to which 

understeer mitigation may increase the 

likelihood of on-road untripped rollover 

beyond that realized with the same vehicle 

evaluated with ESC disabled. Nevertheless, if 

NHTSA were to require that understeer 

mitigation effectiveness be evaluated using a 

test performed on a dry high coefficient 

surface, the potential for achieving good 

understeer control on the test track at the 

expense of compromised real world driving 

safety cannot be ignored. 

NHTSA notes that ESC systems containing 

rollover mitigation control (RSC) algorithms 

present another reason that understeer 

mitigation should not be evaluated on high 

friction surfaces. To create a state of nonlinear understeer for testing purposes, large 

steering wheel angles and rates must be 

inputted. For vehicles with RSC, these severe 

inputs may be interpreted as a threat to the 

vehicle’s roll stability. If RSC intervention 

occurs, the effect will be a brief period of 

substantially increased understeer, where no 

understeer mitigation would occur. Although 

NHTSA has no crash data quantifying the 

safety benefits of RSC, we do not want to 

preclude implementation of RSC technology 

as the result of an inappropriate understeer 

mitigation test. 

In summary, performing tests designed to 

evaluate ESC understeer mitigation 

technology on dry, high friction surfaces 

presents too many problems. NHTSA then 

considered whether it could mandate such 

tests on low friction surfaces, as discussed 

below. 

Wet Test Challenges 

So as to avoid the problems associated 

with testing on dry, high-friction surfaces, 

NHTSA believes that ESC understeer 

mitigation performance testing must be 

performed on a low-friction test surface such 

as wet Jennite or wet basalt tiles. Use of low 

friction surfaces, where peak coefficient of 

friction would be expected to range between 

0.3 and 0.5, would prevent the development 

of lateral accelerations capable of inducing 

on-road untripped rollover. This fact alone 

resolves many of the issues that plague the 

use of high friction surfaces for understeer 

mitigation assessment. NHTSA does not 

expect any adverse repercussions for 

requiring a properly tuned ESC to invoke 

understeer mitigation on low friction 

surfaces, regardless of vehicle type. 

Furthermore, since on-road untripped 

rollover is not expected, RSC intervention 

should not confound understeer mitigation 

assessment on low friction surfaces, as 

activation of such interventions should not 

occur. 

Unfortunately, low friction tests have 

historically been plagued with high test 

variability when compared to otherwise 

equivalent tests performed on high friction 

surfaces. They can also be confounded by 

hydroplaning, and can be difficult-toimpossible to perform within the confines of 

the relatively small low friction test pads 

available at the various proving grounds. 

Resolution of these matters is imperative if 

understeer mitigation effectiveness is to be 

objectively assessed. 

NHTSA performed numerous low-friction 

tests during the 2006 testing season. Most of 

these tests were based on the ‘‘ramp steer’’

maneuver, a test NHTSA believes is its best 

candidate for objectively evaluating ESC 

understeer mitigation performance. This 

maneuver uses a steering ramp (input at one 

of eight steering velocities) from zero to a 

target steering wheel angle, a brief pause, and 

a return of the steering wheel back to zero 

degrees. Using the ramp steer maneuver, data 

were collected during tests performed with 

three passenger cars, one sports car, three 

sport utility vehicles, and one 15-passenger 

van. To compare how the maneuver output 

might change as a function of surface, tests 

were performed on the Transportation 

Research Center’s (TRC) Vehicle Dynamics 

Area Jennite pad, and on the General Motors 

Milford Proving Grounds basalt tile pad. 

Results from this testing will be provided in 

a detailed technical report, to be released 

spring 2007. 

NHTSA is presently evaluating two ways 

to reduce factors contributing to test 

variability on low friction surfaces, 

specifically in the realm of improved water 

delivery and optimized water delivery-totest-conduct timing. Preliminary results from 

NHTSA’s 2006 understeer mitigation 

research indicated similar variability for tests 

performed on Jennite and basalt. From a 

logistics standpoint, this is important since 

basalt test pads of dimensions appropriate for 

use in understeer mitigation are not common. 

NHTSA knows of only one basalt pad 

capable of supporting understeer mitigation 

tests (located at the General Motors Milford 

Proving Grounds), and considers even the 

dimensions of this pad to be only marginally 

adequate. Construction of a new basalt 

facility capable of supporting ramp steer tests 

is cost-prohibitive for NHTSA, as such 

facilities cost millions of dollars. TRC’s 

Jennite pad is also marginal for understeer 

mitigation testing. Again, increasing the size 

of the TRC Jennite pad will be extremely 

expensive, although not to the extent a basalt 

facility would be. 

In short, resolution of low friction testing 

issues is the topic of ongoing research, and 

the primary challenge in the development of 

an objective and repeatable way of assessing 

light vehicle understeer mitigation 

effectiveness. However, there are many issues 

that remain to be resolved, ranging from a 

lack of large-enough test surfaces to possible 

performance criteria before NHTSA could 

have a suitable low coefficient of friction 

understeer mitigation performance test. 

Based on preliminary results from 

NHTSA’s 2006 understeer mitigation 

research, we have investigated two possible 

types of low coefficient of friction understeer 

mitigation performance tests. The easier type 

of test to perform will be called the 

Understeer Presence test, the more difficult 

type, the Full Understeer Performance test. 

The Understeer Presence test would check 

that a vehicle is equipped with an ESC 

system that will limit vehicle understeer in 

at least some conditions. We are fairly 

confident that this test can be developed with 

one to two years of research. The drawback 

of this test is that it will accomplish nothing 

more than providing a means for NHTSA to 

check that a vehicle meets the understeer 

mitigation requirements of FMVSS 126. It is 

not clear that this test will be as robust as the 

method (see discussion below) that NHTSA 

intends to use in the absence of this test to 

check compliance with the understeer 

mitigation portion of FMVSS 126. In other 

words, having this test will do nothing to 

improve vehicle safety beyond the understeer 

requirement presently specified in FMVSS 

No. 126. Based on this fact, NHTSA’s has no 

plans at this time to expend further effort to 

develop the Understeer Presence test. 

The Full Understeer Performance test 

would actually impose further understeer 

mitigation requirements beyond those 

currently specified in FMVSS 126. We hope, 

but do not know, that these additional 

understeer mitigation requirements would 

further enhance vehicle safety. 

Unfortunately, development of the Full 

Understeer Performance test is expected to 

take at least five years and require provision 

of substantial financial resources. 

To summarize the above discussion, we do 

not know of any existing objective 

performance tests for understeer mitigation. 

We believe that it is not appropriate to 

perform an understeer mitigation 

performance test on a dry, high coefficient of 

friction test surface. NHTSA has been 

working on a low coefficient of friction 

understeer mitigation performance test and 

has found some approaches that its 

researchers believe to be promising. 

However, considerable work remains to 

develop such a performance test. 

How NHTSA Will Enforce FMVSS No. 126 

Requirements Without an Understeer 

Performance Test 

The final regulatory text for FMVSS No. 

126 requires light vehicles to be equipped 

with a system meeting the definition of ESC. 

A portion of the revised ESC definition from 

that standard is: 

Electronic Stability Control System or ESC 

System means a system that has all of the 

following attributes:* * * 

(2) That is computer controlled with the 

computer using a closed-loop algorithm to 


ycherry on PROD1PC64 with RULES2
Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 17321 

limit vehicle oversteer and to limit vehicle 

understeer; (emphasis added)* * * 

Without having a performance test for 

understeer mitigation, how will NHTSA 

ensure that light vehicles are equipped with 

a system that will limit vehicle understeer 

under these circumstances? This will be 

accomplished through a two part process: 

ensuring that vehicles have all of the 

hardware needed to limit vehicle understeer 

(as required by FMVSS No. 126), and 

checking engineering documentation 

provided by the vehicle and ESC 

manufacturers that the ESC algorithm is 

capable of recognizing and limiting excessive 

understeer. 

The regulatory text of FMVSS No. 126 

includes S5.1 Required Equipment. Under 

this section, S5.1.1 mandates that light 

vehicles must have an ESC system as follows: 

S5.1.1 Is capable of applying brake 

torques individually to all four wheels and 

has a control algorithm that utilizes this 

capability. 

Having the capability of applying all four 

brakes individually is necessary to allow the 

ESC to limit vehicle understeer when 

appropriate. ESC systems have been 

developed (called two-channel ESC systems) 

that are capable of applying only the 

vehicle’s front brakes. These two-channel 

ESC systems can prevent crashes from 

occurring in three of the four ways that fourchannel ESC systems can prevent crashes, 

although perhaps not as well. Two-channel 

ESC can: (1) Prevent the vehicle from 

becoming oversteer and spinning out, (2) 

preventing untripped vehicle rollovers by 

using RSC-type algorithms, and (3) slow the 

vehicle down. What two-channel ESC cannot 

do is mitigate excessive understeer. 

The development of an ESC algorithm is a 

large and complicated task. Development of 

the understeer mitigation portion of such an 

algorithm requires much analysis, vehicle 

dynamics simulation, and testing by 

engineers. We anticipate that ESC 

manufacturers will document the results of 

such analysis, simulation, and testing. This 

engineering documentation can be shown to 

NHTSA when it is necessary to demonstrate 

that an ESC algorithm is capable of limiting 

vehicle understeer when appropriate. 

In summary, we believe that the 

requirement that all light vehicles be 

equipped with an ESC system capable of 

applying all four brakes individually, 

combined with the engineering 

documentation developed by ESC 

manufacturers, will be sufficient to enforce 

the understeer requirements of the ESC 

definition in FMVSS No. 126. 

Responses to Other Understeer-Related 

Issues 

One commenter stated that some 

manufacturers might supply ESC systems 

that do not adequately compensate for 

understeer loss of control circumstances, 

arguing that there are already vast differences 

in tuning among various ESC systems. They 

predicted that failure of the agency to specify 

understeer performance requirements would 

maintain or expand differences between ESC 

performance from one vehicle make or model 

to another and could cause the standard to 

forgo prevention of additional fatalities and 

injuries. The commenter did not provide any 

data to support this ‘‘prediction.’’ NHTSA 

will continue to monitor the safety 

performance of vehicles equipped with 

different ESC systems. If we do see safety 

related differences between ESC 

performances from one vehicle make or 

model to another, we will use the 

information to require safer ESC systems. 

Unfortunately, we do not know today, and 

are unlikely to know for the next several 

years, what understeer performance 

requirements would improve safety. 

One commenter argued that since 

SAFETEA–LU directs the agency to establish 

performance criteria for stability enhancing 

technologies (i.e., noting the plural nature of 

that statutory provision, which they 

suggested requires something more than an 

oversteer criterion alone), including the 

understeer component that the agency has 

determined to be a necessary part of ESC 

systems from a safety perspective is also 

required from a legal perspective. We do not 

agree with this comment. While SAFETEA–

LU does direct the agency to establish 

performance criteria (which we agree is 

plural) for stability-enhancing technologies, 

having both lateral stability and lateral 

responsiveness criteria in the current FMVSS 

126 fulfills this Congressional requirement 

without adding an understeer performance 

test. 

Conclusions about Understeer Mitigation 

Multiple commenters have requested that 

we include a performance test for excessive 

understeer mitigation in FMVSS 126. A 

number of other questions about understeer 

mitigation were also asked in these 

comments. 

We have tried in our response to these 

comments to fully explain NHTSA’s position 

on this important issue. Unfortunately, 

mitigation of excessive understeer is an 

extremely complex technical problem, so our 

response has been long and technical. In this 

final section of the response, we will try to 

summarize the results of the previous 

discussion. 

First, excessive understeer mitigation 

involves the non-linear understeer gradient, 

a very different quantity than the linear 

understeer gradient (a calculation that is 

commonly mentioned in vehicle dynamics 

literature). While the non-linear understeer 

gradient shares many important properties 

with the linear understeer gradient, the nonlinear gradient is both theoretically and 

practically a far more complex concept. 

Figure 1, presented previously, probably 

gives the clearest idea as to what we mean 

by mitigation of excessive understeer. The 

goal is for ESC to change the non-linear 

understeer gradient of the vehicle from the 

higher to the lower curve. 

For reasons that were explained, mitigation 

of excessive understeer must be performed 

with great care. Too much mitigation can 

create safety problems (spin out or rollover). 

Tests designed to measure linear range 

understeer gradient (e.g. SAE J266 and ISO 

4138) are not suitable to evaluate an ESC’s 

understeer mitigation performance. ESC 

interventions occur when the driver’s 

intended path (i.e., that calculated by the 

ESC control algorithms) differs from the 

actual path of the vehicle (i.e., as measured 

by ESC sensors). Since by definition, this 

relationship is not violated during linear 

range driving, ESC intervention will not 

occur. Without intervention, assessment of 

ESC performance is not possible. 

NHTSA has carefully examined the 

existing vehicle dynamics literature 

including both the SAE and ISO standards. 

We have been unable to find any test 

designed to measure the non-linear 

understeer gradient over the full non-linear 

range of vehicle handling. A variety of 

theoretical difficulties make it unlikely that 

such test will ever be developed. 

In order for ESC understeer mitigation to 

occur during a non-linear understeer 

mitigation scenario, differences between the 

calculated and actual paths of the vehicle 

must exceed a manufacturer-specified 

allowable threshold. NHTSA knows of no 

existing test protocol capable of objectively 

evaluating non-linear understeer mitigation. 

(Note that this is a somewhat different 

problem than that of measuring the nonlinear understeer gradient over the full nonlinear range of vehicle handling. The 

theoretical problems referred to above do not 

prevent the development of an objective test 

for evaluating non-linear understeer 

mitigation.) 

Performing tests designed to evaluate ESC 

understeer mitigation technology on dry high 

friction surfaces presents too many problems. 

Rather, NHTSA believes it is much more 

appropriate to perform such tests on low 

friction surfaces. 

NHTSA would like to include a 

performance standard for understeer 

mitigation in FMVSS No. 126. Unfortunately, 

we do not know of any existing objective 

performance tests for understeer mitigation. 

We believe that it is not appropriate to 

perform an understeer mitigation 

performance test on a dry, high coefficient of 

friction test. NHTSA has been working on a 

low coefficient of friction understeer 

mitigation performance test and has found 

some approaches that its researchers believe 

to be promising. However, considerable effort 

remains to develop such a performance test. 

Based on expected costs and benefits, 

NHTSA is not currently developing such a 

test. 

Without having a performance test for 

understeer mitigation, how will NHTSA 

ensure that light vehicles are equipped with 

a system that will limit vehicle understeer 

when appropriate? This will be 

accomplished through a two part process: 

ensuring that vehicles have all of the 

hardware needed to limit vehicle understeer 

(as required by FMVSS No. 126), and 

checking engineering documentation 

provided by the vehicle and ESC 

manufacturers that the ESC algorithm is 

capable of limiting vehicle understeer when 

appropriate. 

In conclusion, while NHTSA would like to 

include a performance standard for 

understeer intervention in FMVSS No. 126, 

we unfortunately do not know of any suitable 

performance tests for mitigation of excessive 

understeer. We are unwilling to forgo the 


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17322 Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules and Regulations 

large safety benefits that ESC will provide to 

the American public in the near future just 

because we might, some years from now, be 

able to produce a better standard. If, in the 

future, we see ways to improve FMVSS No. 

126 to increase motoring safety, NHTSA 

would at that time undertake another 

rulemaking activity to gain those benefits. 

[FR Doc. 07–1649 Filed 4–5–07; 8:45 am] 

BILLING CODE 4910–59–P 


ycherry on PROD1PC64 with RULES2