74848 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

1See 66 FR 968 (January 4, 2001).

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety 

Administration 

49 CFR Part 571 

[Docket No. NHTSA–2004–19807] 

RIN 2127–AH09 

Federal Motor Vehicle Safety 

Standards; Head Restraints

AGENCY: National Highway Traffic 

Safety Administration (NHTSA), DOT.

ACTION: Final rule.

SUMMARY: This final rule upgrades 

NHTSA’s head restraint standard in 

order to reduce whiplash injuries in rear 

collisions. For front seats, the rule 

establishes a higher minimum height 

requirement, a requirement limiting the 

distance between the back of an 

occupant’s head and the occupant’s 

head restraint, as well as a limit on the 

size of gaps and openings within head 

restraints. The rule also establishes new 

strength and dynamic compliance 

requirements, and amends most existing 

test procedures. In addition, the rule 

establishes requirements for head 

restraints voluntarily installed in rear 

outboard designated seating positions. 

The upgraded standard becomes 

mandatory for all vehicles manufactured 

on or after September 1, 2008. Until that 

time, the manufacturers may comply 

with the existing NHTSA standard, the 

upgraded NHTSA standard or the 

current European regulations.

DATES: Effective Date: This rule is 

effective March 14, 2005. 

Incorporation by reference: The 

incorporation by reference of certain 

publications listed in the regulations is 

approved by the Director of the Federal 

Register as of March 14, 2005. 

Petitions: Petitions for reconsideration 

must be received by January 28, 2005.

ADDRESSES: Petitions for reconsideration 

should refer to Docket No. NHTSA–

2004–19807 and be submitted to: 

Administrator, Room 5220, National 

Highway Traffic Safety Administration, 

400 Seventh Street, SW., Washington, 

DC 20590. Please see the Privacy Act 

heading under Regulatory Notices.

FOR FURTHER INFORMATION CONTACT: For 

non-legal issues, you may contact Louis 

Molino of the Office of Rulemaking, 

Office of Crashworthiness Standards, 

Light Duty Vehicle Division, NVS–112, 

(Phone: (202) 366–2264; Fax: (202) 366–

4329; E-mail: 

Louis.Molino@nhtsa.dot.gov). 

For legal issues, you may contact 

George Feygin of the Office of Chief 

Counsel, NCC–112, (Phone: (202) 366–

2992; Fax (202) 366–3820; E-mail: 

George.Feygin@nhtsa.dot.gov). 

You may send mail to both of these 

officials at the National Highway Traffic 

Safety Administration, 400 7th Street, 

SW., Washington, DC 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents 

I. Executive Summary 

II. Background 

a. The Safety Concern 

b. Understanding Whiplash 

III. Notice of Proposed Rulemaking 

IV. Summary of Comments on the NPRM 

V. Summary of the Final Rule 

VI. Height and Width Requirements

a. Requirements for Front Seats 

b. Requirements for Rear Seats Equipped 

with Head Restraints 

VII. Backset Requirements for Front Seats 

VIII. Measurement of Backset and Height 

IX. Maximum Gap Allowance and 

Removability 

a. Maximum Gap Allowance 

b. Removability 

c. Non-use Positions 

X. Position Retention 

XI. Energy Absorption 

XII. Issues Unique to Rear Head Restraints 

a. Optional Head Restraints for Rear 

Seating Positions 

b. Exception for Seats Adjacent to an Aisle 

c. Potential Interference with Child 

Restraints and Tethers 

XIII. Dynamic Test Alternative 

XIV. Consumer Information 

XV. Effective Date and Interim Compliance 

Options 

XVI. Costs and Benefits Associated with the 

Final Rule 

XVII. Rulemaking Analyses and Notices 

a. Executive Order 12866 and DOT 

Regulatory Policies and Procedures 

b. Regulatory Flexibility Act 

c. National Environmental Policy Act 

d. Executive Order 13132 (Federalism) 

e. Unfunded Mandates Reform Act 

f. Executive Order 12988 (Civil Justice 

Reform) 

g. Paperwork Reduction Act 

h. Executive Order 13045 

i. National Technology Transfer and 

Advancement Act 

j. Privacy Act 

Appendix A: Efforts to Harmonize with ECE 

17 

Appendix B: Cervigard Suggestion

I. Executive Summary 

This final rule upgrades Federal 

Motor Vehicle Safety Standard No. 202, 

Head Restraints (FMVSS No. 202). The 

standard, which seeks to reduce 

whiplash injuries in rear collisions, 

currently requires head restraints for 

front outboard designated seating 

positions in passenger cars and in light 

multipurpose passenger vehicles, trucks 

and buses. 

To provide better whiplash protection 

for a wider range of occupants, this rule 

requires that front outboard head 

restraints meet more stringent height 

requirements. Fixed front head 

restraints must be not less than 800 mm. 

In their lowest adjustment position, 

adjustable head restraints must not be 

lower than 750 mm, and in their highest 

position, they must be at least 800 mm. 

To reduce the distance that a vehicle 

occupant’s head can be whipped 

backward in a rear end crash, this rule 

establishes new requirements limiting 

backset in front seats, i.e., the distance 

between the back of a person’s head and 

his or her head restraint, and limiting 

the size of gaps and openings in the 

restraints. The rule also establishes new 

strength and position retention 

requirements. Finally, it significantly 

amends the dynamic compliance test 

option currently in the standard to 

encourage continued development and 

use of ‘‘active’’ head restraint systems 

because the test is designed to allow a 

manufacturer the flexibility necessary to 

offer innovative active head restraint 

designs while still ensuring a minimal 

level of head restraint performance. 

After a careful consideration of the 

public comments and further analysis of 

our proposal to require head restraints 

in each rear outboard designated seating 

position, we have decided not to adopt 

that proposal. In the Notice of Proposed 

Rulemaking (NPRM),1 we expressed 

concern that the proposal had a high 

cost per equivalent life saved. We have 

now made a more refined estimate of 

costs and benefits and found that the 

cost per equivalent life saved for such 

a requirement is even greater than 

originally thought. In response to the 

NPRM, several manufacturers raised 

visibility concerns associated with 

mandatory rear head restraints in all 

vehicles. While not a universal problem, 

we believe reduced visibility is a 

legitimate problem in some vehicles. 

Finally, in commenting on the NPRM, 

vehicle manufacturers expressed 

concern that adoption of the 

requirement would reduce vehicle 

utility by interfering with or even 

reducing the ability to provide the sort 

of folding seats currently available in 

‘‘multi-configuration’’ vehicles such as 

vans and multipurpose vehicles. We 

believe that those concerns may have 

some merit.

However, in order to ensure that head 

restraints voluntarily installed in rear 

outboard seating positions do not pose 

a risk of exacerbating whiplash injuries, 

this final rule requires that those head 

restraints meet certain height, strength, 

position retention, and energy 

absorption requirements. NHTSA notes 

that the head restraint regulation of the 

United Nations/Economic Commission 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74849

2As part of this effort, NHTSA issued a final rule 

upgrading the performance of vehicle fuel systems 

in rear impacts. (68 FR 67068, December 1, 2003).

3The regulation, adopted by the UN/ECE’s 

Working Party 29, World Forum for Harmonization 

of Vehicle Regulations, is ECE 17, Uniform 

Provisions Concerning the Approval of Vehicles 

With Regard to the Seats, Their Anchorages, and 

Any Head Restraints (http://www.unece.org/trans/

main/wp29/wp29regs/r017r4e.pdf). A comparison 

of this final rule with ECE 17 is in Appendix A.

4We determined that the current FMVSS No. 202 

is functionally equivalent to the applicable ECE 

regulation using the method described in Appendix 

B of 49 CFR part 553.

5Once the FMVSS No. 202a becomes fully 

effective on September 1, 2008, it will be redesignated as FMVSS No. 202.

6Because this rule does not require head 

restraints in rear outboard designated seating 

positions, it does not impose any costs associated 

with installing head restraints where none were 

previously installed.

7Non-contact Abbreviated Injury Scale (AIS) 1 

neck.

8The H-point is defined by a test machine placed 

in the vehicle seat (Society of Automotive Engineers 

(SAE) J826, July 1995). From the side, the H-point 

represents the pivot point between the torso and 

upper leg portions of the test machine. It can be 

Continued

for Europe (UN/ECE) similarly does not 

mandate rear seat head restraints, but 

does regulate the performance of 

voluntarily installed ones. The ECE 

regulation is discussed at greater length 

several paragraphs below and in 

Appendix A. 

In the future stages of our efforts to 

improve occupant protection in rear 

impacts,2 NHTSA intends to evaluate 

the performance of head restraints and 

seat backs as a single system to protect 

occupants, just as they work in the real 

world, instead of evaluating their 

performance separately as individual 

components. Accordingly, in making 

our decisions about the upgraded 

requirements for head restraints in this 

final rule, we sought, e.g., through 

upgrading our dynamic test procedure 

option, to make those requirements 

consistent with the ultimate goal of 

adopting a method of comprehensively 

evaluating the seating system.

This final rule harmonizes the FMVSS 

requirements for head restraints with 

the head restraint regulation of the UN/

ECE, except to the extent needed to 

provide increased safety for vehicle 

occupants or to facilitate enforcement.3

In some instances, a desire to achieve 

increased safety in a cost effective 

manner made it necessary for us to go 

beyond or take an approach different 

from that in the ECE regulation.

While some of the requirements of 

this final rule are more stringent than 

those of the ECE regulation, the latter is 

functionally equivalent to the current 

FMVSS No. 202.4 For this reason, in the 

interim before the mandatory 

compliance date of this rule (September 

1, 2008), the agency is giving 

manufacturers the option of complying 

with any of three alternatives: the 

existing FMVSS No. 202, the ECE 17, or 

the new, upgraded FMVSS No. 202, 

designated as FMVSS No. 202a.5

The agency estimates that 

approximately 272,464 whiplash 

injuries occur annually. This final rule 

will result in approximately 16,831 

fewer whiplash injuries, 15,272 

involving front seat occupants and 1,559 

involving rear seat occupants. The 

estimated average cost in 2002 dollars, 

per vehicle, of meeting this rule will be 

$4.51 for front seats, and $1.13 for rear 

seats currently equipped with head 

restraints, for a combined cost of $5.42.6

The cost per year is estimated to be 

$70.1 million for front head restraints 

and $14.1 million for optional rear head 

restraints, for a combined annual cost of 

$84.2 million. This final rule is 

economically significant because we 

estimate that the final rule will result in 

economic benefits in excess of $100 

million.

II. Background 

Vehicle manufacturers currently use 

three types of head restraints to meet the 

requirements of FMVSS No. 202. The 

first type is the ‘‘integral head restraint,’’

which is non-adjustable and is built into 

the seat. It typically consists of a seat 

back that extends high enough to meet 

the height requirement of the standard. 

The second type is the ‘‘adjustable’’

head restraint, which consists of a 

separate cushion that is attached to the 

seat back, typically by a two sliding 

metal shafts. Adjustable head restraints 

typically adjust vertically to 

accommodate different occupant seating 

heights. Some also provide adjustments 

to allow the head restraint to be moved 

closer to the occupant’s head. The third 

type is the active head restraint system, 

which deploys in the event of a 

collision to minimize the potential for 

whiplash. During the normal vehicle 

operation, the active head restraint 

system is retracted. 

a. The Safety Concern 

Whiplash injuries are a set of common 

symptoms that occur in motor vehicle 

crashes and involve the soft tissues of 

the head, neck and spine. Symptoms of 

pain in the head, neck, shoulders, and 

arms may be present along with damage 

to muscles, ligaments and vertebrae, but 

in many cases lesions are not evident. 

The onset of symptoms may be delayed 

and may only last a few hours; however, 

in some cases, effects of the injury may 

last for years or even be permanent. The 

relatively short-term symptoms are 

associated with muscle and ligament 

trauma, while the long-term ones are 

associated with nerve damage. 

Based on National Analysis Sampling 

System (NASS) data, we estimate that 

between 1988 and 1996, 805,581 

whiplash injuries 7 occurred annually in 

crashes involving passenger cars and 

LTVs (light trucks, multipurpose 

passenger vehicles, and vans). Of these 

whiplash injuries, 272,464 occurred as a 

result of rear impacts. For rear impact 

crashes, the average cost of whiplash 

injuries in 2002 dollars is $9,994 (which 

includes $6,843 in economic costs and 

$3,151 in quality of life impacts, but not 

property damage), resulting in a total 

annual cost of approximately $2.7 

billion.

b. Understanding Whiplash 

Although whiplash injuries can occur 

in any kind of crash, an occupant’s 

chances of sustaining this type of injury 

are greatest in rear-end collisions. When 

a vehicle is struck from behind, 

typically several things occur in quick 

succession to an occupant of that 

vehicle. First, from the occupant’s frame 

of reference, the back of the seat moves 

forward into his or her torso, 

straightening the spine and forcing the 

head to rise vertically. Second, as the 

seat pushes the occupant’s body 

forward, the unrestrained head tends to 

lag behind. This causes the neck to 

change shape, first taking on an S-shape 

and then bending backward. Third, the 

forces on the neck accelerate the head, 

which catches up with—and, depending 

on the seat back stiffness and if the 

occupant is using a shoulder belt, 

passes—the restrained torso. This 

motion of the head and neck, which is 

like the lash of a whip, gives the 

resulting neck injuries their popular 

name. 

Previous regulatory approach. As 

discussed in the NPRM preceding this 

final rule, a historical examination of 

head restraint standards in this country 

indicates that the focus has been the 

prevention of neck hyperextension (the 

rearward movement of the head and 

neck over a large range of motion 

relative to the torso), as opposed to 

controlling lesser amounts of head and 

neck movement in a crash. The 

predecessor to FMVSS No. 202 was 

General Services Administration (GSA) 

Standard 515/22, which applied to 

vehicles purchased by the U.S. 

Government and went into effect on 

October 1, 1967. GSA 515/22 required 

that the top of the head restraint achieve 

a height 700 mm (27.5 inches (in)) above 

the H-point.8 Also in 1967, research 

74850 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

thought of, roughly, as the hip joint of a 50th 

percentile male occupant viewed laterally.

9 Jakobsson et al., Analysis of Head and Neck 

Responses in Rear End Impacts—A New HumanLike Model. Volvo Car Corporation Safety Report 

(1994).

10Olsson et al., An In-depth Study of Neck 

Injuries in Rear-end Collisions. International 

IRCOBI Conference, pp 269–280 (1990).

11Farmer, Charles, Wells, JoAnn, Lund, Adrian, 

‘‘Effects of Head Restraint and Seat Redesign on 

Neck Injury Risk in Rear—End Crashes,’’ Insurance 

Institute For Highway Safety, October 2002.

12 ‘‘Effect of Head Restraint Position on Neck 

Injury in Rear Impact,’’ World Congress of 

Whiplash-Associated Disorders (1999), Vancouver, 

British Columbia.

13The current version of FMVSS No. 202 also 

features two sets of requirements; one applies to 

statically tested head restraints and the other to 

dynamically tested head restraints.

14 254 mm (10 in) for restraints on bench-type 

seats, and 171 mm (6.75 in) for restraints on 

individual seats.

using staged 48 kilometer per hour (kph) 

(30 mile per hour, mph) crashes 

concluded that a head restraint 711 mm 

(28 in) above the H-point was adequate 

to prevent neck hyperextension of a 

95th percentile male. FVMSS No. 202, 

which became effective on January 1, 

1969, required that head restraints be at 

least 700 mm (27.5 in) above the seating 

reference point or limit the relative 

angle between the head and the torso to 

45 degrees or less during a dynamic test.

Current knowledge. There are many 

hypotheses as to the mechanisms of 

whiplash injuries. Despite a lack of 

consensus with respect to whiplash 

injury biomechanics, there is research 

indicating that reduced backset will 

result in reduced risk of whiplash 

injury. For example, one study of Volvo 

vehicles reported that, when vehicle 

occupants involved in rear crashes had 

their heads against the head restraint (an 

equivalent to 0 mm backset) during 

impact, no whiplash injury occurred.9

By contrast, another study showed 

significant increase in injury and 

duration of symptoms when occupant’s 

head was more than 100 mm away from 

the head restraint at the time of the rear 

impact.10

In addition, the persistence of 

whiplash injuries in the current fleet of 

vehicles indicates that the existing 

height requirement is not sufficient to 

prevent excessive movement of the head 

and neck relative to the torso for some 

people. Specifically, the head restraints 

do not effectively limit rearward 

movement of the head of a person at 

least as tall as the average occupant. 

Research indicates that taller head 

restraints would better prevent 

whiplash injuries because at heights of 

750 to 800 mm, the head restraint can 

more effectively limit the movement of 

the head and neck. 

In a recent report from the Insurance 

Institute for Highway Safety (IIHS), 

Farmer, Wells, and Lund examined 

automobile insurance claims to 

determine the rates of neck injuries in 

rear end crashes for vehicles with the 

improved geometric fit of head 

restraints (reduced backset and 

increased head restraint height).11 Their 

data indicate that these improved head 

restraints are reducing the risk of 

whiplash injury. Specifically, there was 

an 18 percent reduction in injury 

claims. Similarly, NHTSA computer 

generated models have shown that the 

reduction of the backset and an increase 

in the height of the head restraint 

reduces the level of neck loading and 

relative head-to-torso motion that may 

be related to the incidence of whiplash 

injuries.12

With respect to impact speeds, 

research and injury rate data indicate 

that whiplash may occur as a result of 

head and neck movements insufficient 

to cause hyperextension. Staged low 

speed impacts indicate that mild 

whiplash symptoms can occur without 

a person’s head exceeding the normal 

range of motion. This means that our 

previous focus on preventing neck 

hyperextension is insufficient to 

adequately protect all rear impact 

victims from risks of whiplash injuries. 

Instead, to effectively prevent whiplash, 

the head restraint must control smaller 

amounts of rapid head and neck 

movement relative to the torso. 

In sum, in light of recent evidence 

that whiplash may be caused by smaller 

amounts of head and neck movements 

relative to the torso, and that reduced 

backset and increased height of head 

restraints help to better control these 

head and neck movements, we conclude 

that head restraints should be higher 

and positioned closer to the occupant’s 

head in order to be more effective in 

preventing whiplash. 

Further, information about consumer 

practices regarding the positioning of 

adjustable head restraints indicates that 

there is a need to improve consumer 

awareness and knowledge of importance 

of properly adjusted head restraints. 

Specifically, in 1995, NHTSA surveyed 

282 vehicles to examine how well head 

restraints were adjusted and if the 

restraints should have been adjusted 

higher. Approximately 50 percent of 

adjustable head restraints were left in 

the lowest adjustable position. Three 

quarters of these could have been raised 

to decrease whiplash potential by 

bringing the head restraint higher in 

relation to the center of gravity of the 

occupant’s head. 

III. Notice of Proposed Rulemaking 

Using the new information gained 

about the effectiveness of head 

restraints, NHTSA published the NPRM 

for this final rule to improve on the 

effectiveness of head restraints. The 

continued persistence of high numbers 

of whiplash injuries indicated a need for 

the rulemaking. 

The NPRM proposed new height and 

backset requirements, and other 

requirements, described below. NHTSA 

also proposed that head restraints be 

required in the rear outboard seating 

positions. 

In the proposed FMVSS No. 202a, 

manufacturers were given the option of 

meeting either of two sets of 

requirements. The first set is a 

comprehensive group of dimension and 

strength requirements, compliance with 

which is measured statically. The 

second set was made of requirements 

that would have to be met in a dynamic 

test.13

Proposed requirements for head 

restraints tested statically. To ensure 

that head restraints would be properly 

used in a position high enough to limit 

hyperextension, the NPRM proposed the 

following height requirements. The top 

of the front integral head restraint 

would have to reach the height of at 

least 800 mm above the H-point. The 

top of the front adjustable head restraint 

would have to reach the height of at 

least 800 mm above the H-point, and 

could not be adjusted below 750 mm. 

The top of the rear mandatory head 

restraint would have to reach the height 

of at least 750 mm above the H-point. 

The NPRM also proposed that 

adjustable head restraints must lock in 

their adjustment positions. NHTSA 

proposed to retain existing requirements 

for head restraint width.14 To control 

even smaller amounts of rapid head and 

neck movement relative to the torso 

than the amount of relative motion 

resulting in neck hyperextension, the 

NPRM proposed also to limit the 

amount of backset to 50 mm (2 in). In 

addition, the NPRM also proposed 

maximum gap requirements for head 

restraints openings within the perimeter 

of the restraint, and for height adjustable 

head restraints, between the seat and 

head restraint. Head restraints must 

remain locked in specific positions after 

being set by the user.

The agency also proposed to prohibit 

head restraints in the front seats from 

being removable solely by hand, i.e., 

without use of tools. Comments were 

requested on applying such a 

requirement to rear seat head restraints. 

Rear seat head restraints could be folded 

or retracted to ‘‘non-use’’ positions if 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74851

15The back pan is the portion of the SAE J826 

manikin (July 1995) that comes in contact with the 

seat back. Its shape is intended to simulate the 

shape of an occupant’s back and thus allow for a 

realistic load distribution.

16Changes to the dynamic test procedures were 

also proposed, including a new sled pulse corridor. 

Also, the entire vehicle would be mounted on the 

test sled, not merely the seat.

they give the occupant an 

‘‘unambiguous physical cue’’ that the 

restraint is not properly positioned by 

altering the normal torso angle of the 

seat occupant or automatically returning 

to a ‘‘use’’ position when the seat is 

occupied. 

In addition, the NPRM proposed that 

these statically-tested head restraints 

would have to meet a new energy 

absorption requirement, compliance 

with which would be measured using a 

free-motion impactor. Additionally, the 

agency proposed placing a minimum on 

the radius of curvature for the front 

surface of the vehicle seat and head 

restraint. The NPRM proposed 

modifications to the existing strength 

versus displacement test procedure to 

require simultaneous loading of the 

back pan 15 and the head restraint, and 

to remove the allowance for seat back 

failure.

Proposed requirements for head 

restraints tested dynamically. The 

NPRM proposed a dynamic test 

alternative and said that the purpose 

was to ensure that the final rule does 

not discourage or preclude continuing 

development and implementation of 

active head restraints and other 

advanced seat back/head restraint 

systems designed to minimize rear 

impact injuries. Specifically, the NPRM 

proposed that head restraints tested 

dynamically would have to meet a Head 

Injury Criterion (HIC) limit of 150 with 

a 15 millisecond (ms) window. In 

addition, NHTSA proposed a head-totorso rotation limit of 20 degrees when 

testing with a 95th percentile male 

dummy in front outboard seats, and of 

12 degrees when testing with a 50th 

percentile male dummy in all outboard 

seats.16 Further, the NPRM proposed 

that the head restraints must have the 

same lateral width specified for 

statically tested restraints. Comments 

were requested on whether dynamically 

tested restraints should be subject to the 

width requirement or any of the other 

dimensional requirements used in the 

static test option.

IV. Summary of Comments on the 

NPRM 

The agency received approximately 

50 comments on the NPRM, from motor 

vehicle manufacturers, seat suppliers, 

members of the engineering and 

research community, insurance 

companies, consumer groups, and 

governments and members of Congress. 

Overall, commenters supported 

upgrading FMVSS No. 202 while 

expressing concerns about and 

recommending changes to various 

proposals made in the NPRM. 

A majority of the commenters 

generally supported the new height 

proposal, particularly as applied to head 

restraints for front seats. While few 

commenters had knowledge of any 

specific data regarding benefits of the 

proposed height increase, most 

commenters agreed that the new height 

requirement is potentially beneficial in 

reducing whiplash injury and had merit 

in harmonizing with ECE 17. 

Nonetheless, some concerns were 

expressed. Some comments supported 

the position that increasing the height of 

head restraints would not obstruct a 

driver’s rearward visibility, but there 

were concerns expressed that the new 

height requirements would reduce the 

ability of a driver in following vehicles 

to ‘‘see through’’ a vehicle in front of 

him or her. There was concern that the 

taller head restraints could make it more 

difficult to install seats during vehicle 

assembly. Several manufacturers 

commented that the taller head 

restraints might not be able to fit in the 

rear seats of some vehicles or may 

impede seat folding, thus limiting cargo 

capacity. 

As to the proposed width of head 

restraints, all of the vehicle 

manufacturers believed that a 254 mm 

width requirement for rear seat head 

restraints would reduce rearward 

visibility and is unwarranted. In 

contrast, Advocates for Highway Safety 

(Advocates) believed that the current 

widths of head restraints do not protect 

occupants in offset collisions and 

should be increased. 

Commenters expressed differing 

opinions with regard to the proposed 

backset requirement. Insurers, consumer 

groups and Transport Canada supported 

50 mm as the maximum allowable 

backset. A majority of the seat and 

vehicle manufacturers supported a 

backset of more than 50 mm, because 

they believed that a backset of 50 mm 

could result in occupant discomfort, 

particularly to smaller occupants who, 

commenters maintained, tend to use 

steeper seat back angles. Some 

manufacturers suggested that NHTSA 

allow for an adjustable backset of up to 

100 mm. Manufacturers also generally 

wanted to measure backset with the seat 

back at the manufacturer’s design 

seating angle rather than placed at a 25-

degree angle. Some had concerns about 

the suitability of the head restraint 

measuring device for measuring backset. 

There were no significant objections 

to the 60 mm gap limit for gaps within 

the perimeter of head restraints. 

However, manufacturers and others had 

questions about the proposal that 

adjustable head restraints in their lowest 

position must have some position of 

backset adjustment at which the gap 

between the seat and the head restraint 

is less than 25 mm.

A majority of industry commenters 

opposed the prohibition against the 

removability of head restraints. Some 

suggested allowing removability by 

hand, particularly of rear seat head 

restraints. Manufacturers stated that no 

limitations should be placed on non-use 

positions. 

Several manufacturers and suppliers 

objected to the proposed height 

retention test requirement. Some 

believed current head restraints do not 

move downward during crashes. Others 

were concerned that the requirement 

does not account for the compression of 

head restraint foam. In contrast, some 

non-industry commenters believed that 

the height retention requirement is 

needed to prevent designs that tend to 

‘‘fall’’ to their lowest position during 

normal vehicle operation. 

With regard to the energy absorption 

test, all manufacturers suggested use of 

a pendulum impactor instead of the 

free-motion head form. Most 

manufacturers expressed concerns about 

the need for or wide-reaching 

application of the proposed limit on the 

radius of curvature of vehicle seats or 

head restraints (proposed S4.2(b)(8)). 

Most manufacturers and suppliers 

believed that rear seat head restraints 

should not be required. Concerns were 

raised about the safety need for them, 

and about possible interference of the 

head restraints with child restraint use 

in rear seats. Honda, Advocates and 

others believed that rear seat head 

restraints should be mandated. 

Concerning the proposed changes to 

the dynamic compliance test 

procedures, some commenters believed 

that the proposals should not be 

adopted at this time. Commenters 

disagreed on the most appropriate 

dummy to use for the dynamic test. 

Most vehicle manufacturers and some 

seat suppliers objected to the proposed 

HIC15 150 limit, seeing no correlation 

between HIC and the reduction of neck 

injuries. Some commenters stated that 

the dynamic test should be with the seat 

attached to a test buck, instead of the 

actual vehicle. 

In response to the NPRM’s request for 

comments on the need to require 

vehicle manufacturers to provide 

74852 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

17The term ‘‘seating reference point’’ is fully 

defined in 49 CFR 571.3. It represents a unique 

design H-point. The H-point is the mechanically 

hinged hip point of an SAE J826 (July 1995) threedimensional manikin (SAE J826 manikin), which 

simulates the actual pivot center of the human torso 

and thigh.

18Exceptions to the height requirements for rear 

head restraints are discussed in Sections VI(b) and 

IX.

19Section XII(a) explains how we arrived at our 

definition of rear head restraints.

20ECE 25, Uniform Provisions Concerning the 

Approval of Head Restraints (Head Rests), whether 

or not Incorporated in Vehicle Seats (http://

www.unece.org/trans/main/wp29/wp29regs/

r025r1e.pdf).

21We note that buses with at least 17 designated 

seating positions are still classified as M2, M3. 

However, ECE 17 specifically excludes these 

vehicles.

22We note that ECE 17, Paragraph 5.3.1 expressly 

allows other categories of vehicles equipped with 

head restraints to be certified to ECE 17.

information in vehicle owners’ manuals 

on how to properly adjust head 

restraints, the Insurance Corporation of 

British Columbia (ICBC) commented 

that it believed that consumer education 

has a positive influence on proper head 

restraint adjustment. Several 

manufacturers commented that most 

manufacturers already provide 

information in vehicle owners’ manuals 

about proper head restraint use. 

V. Summary of the Final Rule 

Based on our consideration of the 

comments and other available 

information, the agency is issuing a final 

rule that upgrades existing FMVSS No. 

202. As noted above, the new upgraded 

version of the standard is designated as 

FMVSS No. 202a. 

Under this final rule, the top of the 

front outboard integral head restraint 

must reach the height of at least 800 mm 

above the H-point, instead of the 700 

mm above the seating reference point 

(SgRP) 17 currently required. The top of 

the front outboard adjustable head 

restraint must be adjustable to at least 

800 mm above the H-point, and cannot 

be adjusted below 750 mm. Rear 

outboard head restraints are optional. 

However, if a manufacturer chooses to 

install head restraints in rear outboard 

seating positions, these head restraints 

must meet certain height,18 strength, 

position retention, and energy 

absorption requirements. The rear 

outboard head restraint is defined as a 

rear seat back, or any independently 

adjustable seat component attached to 

or adjacent to the rear seat back, that has 

a height equal to or greater than 700 

mm, in any position of backset and 

height adjustment, as measured with the 

J826 manikin.19 Accordingly, any rear 

outboard seat back or any 

independently adjustable component 

attached or adjacent to that seat back 

that exceeds 700 mm above the H-point, 

must meet the above requirements.

In recognition of the manufacturing 

and measurement variability concerns 

highlighted by the industry 

commenters, the agency has increased 

the maximum allowable backset for 

front head restraints from the proposed 

50 mm to 55 mm. Backset adjustment to 

less than 55 mm is permitted. However, 

the backset may not be adjustable to 

greater than 55 mm when the top of the 

front head restraint is positioned 

between 750 and 800 mm, inclusive, 

above the H-point. There is no backset 

limit for optional rear head restraints. 

The agency will use an HRMD, 

consisting of a head form developed by 

ICBC attached to the SAE J826 manikin 

(rev. Jul 95), for measuring backset 

compliance. 

The minimum width requirement for 

front outboard head restraints in 

vehicles without a front center seating 

position, and for optional rear head 

restraints is 170 mm. The minimum 

width requirement for front outboard 

head restraints in vehicles with a center 

seating position between the outboard 

positions is 254 mm. For integral head 

restraints, there is a limit of 60 mm on 

the maximum gap between the head 

restraint and the top of the seat. The gap 

limit for adjustable head restraints in 

their lowest position of adjustment and 

any position of backset adjustment is 

similarly 60 mm. The final rule does not 

adopt the proposed 25 mm limitation 

for adjustable head restraints in their 

lowest position of adjustment and single 

position of backset adjustment proposed 

in the NPRM. For all head restraints, 

gaps within the restraint are limited to 

not more than 60 mm. 

Under today’s rule, an adjustment 

retention mechanism that locks into 

place is mandatory for all adjustable 

head restraints. NHTSA will test 

retention of the head restraint in its 

vertical position using a loading 

cylinder measuring 165 mm in diameter 

and 152 mm in length. The rearward 

(with respect to the seat direction) 

position retention testing will be 

conducted using a loading sphere, with 

the seat back braced. Under both tests, 

the head restraint must return to within 

13 mm of the initial reference point, an 

increase from the proposed 10 mm 

return requirement. 

The energy absorption test procedure 

will be conducted using a linear 

impactor, rather than the proposed freemotion impactor or the pendulum 

impactor used in ECE 17. 

The dynamic compliance option will 

utilize a Hybrid III 50th percentile adult 

male test dummy only, as the 95th 

percentile Hybrid III dummy is not yet 

available for compliance purposes. The 

head-to-torso rotation is limited to 12 

degrees, and the maximum HIC15 is 

limited to 500 instead of 150 in the 

NPRM. These performance limits must 

be met with the head restraint midway 

between the lowest and the highest 

position of adjustment. 

Between the effective date of today’s 

rule and September 1, 2008, 

manufacturers may comply with 

FMVSS No. 202 by meeting: (1) All the 

requirements of the current FMVSS No. 

202, (2) the specified requirements of 

ECE 17, or (3) all the requirements of 

FMVSS No. 202a. NHTSA has found 

that ECE 17 is functionally equivalent to 

the existing FMVSS No. 202, so we are 

permitting compliance with ECE 17 

during the interim.

The ECE has two regulations 

applicable to head restraints, ECE 17 

and ECE 25.20 The two regulations have 

similar requirements. However, the 

provisions of ECE 17 supersede the 

requirements of ECE 25 for most 

vehicles subject to this final rule. 

Specifically, as amended in July 2002, 

ECE 17 applies to vehicles in the 

following categories:

1. Passenger vehicles, including 

multipurpose passenger vehicles 

(MPVs) with 9 or fewer designated 

seating positions (‘‘M1’’). 

2. Passenger vehicles, MPVs and 

buses with more than 9, but less than 17 

designated seating positions (‘‘M2’’ and 

‘‘M3’’).21

3. Trucks (‘‘N’’). 

This final rule applies to passenger 

cars, MPVs, trucks and buses with a 

GVWR of 4,536 kg or less. Accordingly, 

the only vehicles that will be subject to 

this final rule, but will not fall under the 

requirements of ECE 17, are buses with 

at least seventeen designated seating 

positions. Because of the GVWR limit, it 

is unlikely that such buses will be 

subject to this final rule. Nevertheless, 

we note that the requirements of ECE 25 

are more stringent than those of this 

final rule because they mandate rear 

head restraints. Since we want to 

provide a compliance option for the 

interim period that is functionally 

equivalent to the current standard, we 

decided that all vehicles, including 

large capacity buses subject to this final 

rule, may certify to the specified ECE 17 

requirements instead of ECE 25.22

During this interim period, 

manufacturers must irrevocably elect 

one of the compliance options in its 

entirety and may not certify under an 

alternative compliance option, if there is 

a noncompliance. This restriction is 

necessary because each certification 

option addresses the risks associated 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74853

23RCAR is an international organization intended 

to reduce insurance costs by improving automotive 

damageability, repairability, safety and security 

(www.RCAR.org). Under the RCAR standards, the 

head restraint is tested with the HRMD to evaluate 

the restraint geometry and then is rated as good, 

acceptable, marginal, or poor. These types of rating 

systems do not contain the level of objectivity or 

specificity to translate easily into a regulatory 

requirement.

24Backlight is the window located at the rear of 

the roof panel (SAE J953).

25We note that heights greater than 800 mm are 

permitted for both integral and adjustable head 

restraints.

with poor head restraint design 

differently, and because individual parts 

of each of the compliance options 

provide different levels of safety. We 

note, however, that the manufacturer 

may select different compliance options 

for different designated seating 

positions. 

Major differences between this final 

rule and the NPRM. The following 

highlights the major differences between 

the NPRM and the final rule: 

• This final rule does not require 

head restraints in rear outboard 

designated seating positions. However, 

if a manufacturer chooses to install head 

restraints in rear outboard seating 

positions (as defined in FMVSS No. 

202a.), these head restraints must meet 

the new height, strength, position 

retention, and energy absorption 

requirements, but not backset 

requirements. 

• The maximum allowable backset for 

front head restraints has been increased 

from 50 mm to 55 mm; 

• The 25 mm gap limit for adjustable 

head restraints in their lowest height 

position and a single position of backset 

adjustment has been eliminated, leaving 

the 60 mm limit at any position of 

backset adjustment; 

• With respect to position retention, 

the head restraint must return to within 

13 mm of the initial reference point, 

instead of to within 10 mm, as 

proposed; 

• The proposed radius of curvature 

requirement has not been adopted; 

• The energy absorption testing 

procedure will be conducted using a 

linear impactor, instead of the proposed 

free-motion impactor; 

• The dynamic compliance option 

will require that the head-to-torso 

rotation be limited to 12 degrees, when 

tested with a 50th percentile male 

Hybrid III dummy with the head 

restraint midway between the lowest 

and the highest position of adjustment 

(there will be no test with a 95th 

percentile dummy); 

• The dynamic compliance option 

mandates a maximum HIC15 limit of 

500, as opposed to 150 proposed in the 

NPRM, and; 

• Vehicle owner’s manual must 

include information describing the 

vehicle’s head restraint system, how to 

properly adjust head restraints, and how 

to remove and re-install head restraints. 

VI. Height and Width Requirements 

a. Requirements for Front Seats 

Height of front seat head restraints.

FMVSS No. 202 currently requires that 

front head restraints be capable of 

reaching a height of at least 700 mm 

above the SgRP. The NPRM proposed 

amending the standard to increase the 

minimum height of front integral head 

restraints to 800 mm above the H-point. 

It proposed that if the head restraints 

were adjustable, they must adjust up to 

at least 800 mm, and not below 750 mm, 

with respect to the H-point. This 

adjustment range was estimated to 

ensure that the top of the head restraint 

exceeded the head C.G. (center of 

gravity) for an estimated 93 percent of 

all adults. 

A majority of the manufacturers and 

other commenters, among them the 

Alliance of Automobile Manufacturers 

(Alliance), General Motors North 

America (GM), TRW Automotive (TRW), 

the Association of International 

Automobile Manufacturers, Inc. (AIAM) 

and IIHS, generally supported the new 

height proposal. IIHS’s support was 

based, in part, on a new standard for 

evaluating head restraints promulgated 

by the Research Council for Automobile 

Repairs (RCAR), which deems taller 

head restraints to be superior to shorter 

ones.23 In contrast, Advocates 

commented that fixed and adjustable 

head restraints should be subject to the 

same height requirements. According to 

Advocates, the NPRM did not justify 

allowing a 750 mm height for adjustable 

restraints in front seats.

There were some concerns expressed 

about the effect of taller front outboard 

head restraints on driver visibility 

through the backlight,24 and on the 

ability of drivers in following vehicles 

to see through the backlight of a vehicle 

in front of them. Honda and Ford also 

said that taller front seats would 

contribute to rear seat occupants feeling 

closed-in.

Several manufacturers also stated that 

the taller head restraints could make it 

more difficult to install seats during 

vehicle assembly. 

Agency response: The persistence of 

high numbers of whiplash injuries in 

the current fleet of vehicles indicates 

that the height requirement currently in 

effect for front outboard head restraints 

is not preventing excessive movement of 

the head and neck relative to the torso. 

The current requirement allows head 

restraints that do not effectively limit 

rearward movement of an average 

occupant’s head at its center of gravity, 

resulting in continuing high numbers of 

whiplash. Research indicates that a 

minimum height of 800 mm above the 

H-point for integral head restraints, and 

a minimum height of 750 mm for 

adjustable head restraints in their full 

down position and at least 800 mm in 

their full upward position, will prevent 

whiplash injuries because at this height 

the head restraints can effectively limit 

the movement of the head and neck.

We have decided against adopting 

Advocates’ suggestion that adjustable 

head restraints should not be allowed to 

have an adjustment position below the 

minimum 800 mm requirement set for 

integral head restraints.25 Advocates’

argument was based on the possibility 

that occupants will not adjust their head 

restraints to an effective position. We 

acknowledge that head restraint misuse 

has been a problem in the past and that 

some consumers may not receive the 

full benefit of an adjustable head 

restraint if they leave them in the lowest 

possible position of adjustment. 

However, we believe that misuse will 

decrease as consumers become more 

aware of the merit of raising their head 

restraints.

Further, prohibiting any position less 

than 800 mm for adjustable head 

restraints would likely result in a 

substantial increase in the overall height 

of the seat back. (The gap between the 

top of the seat back and the head 

restraint in its lowest position could not 

be widened substantially, because of the 

restrictions in today’s rule that restricts 

such gaps to 60 mm.) The practical 

effect of adopting Advocates’ suggestion 

would be to require integral head 

restraints, which we believe is 

unwarranted and overly design 

restrictive. Adjustable head restraints 

may allow shorter and very tall 

occupants to position their head 

restraints more optimally. Further, even 

occupants of average size may benefit 

from certain adjustment features, such 

as head restraint backset adjustment to 

positions closer than 55 mm, if they find 

it comfortable. Finally, when properly 

designed to maintain their position, 

adjustable head restraints can provide 

protection comparable to that provided 

by integral head restraints. 

We note that integral head restraints 

have in the past been considered more 

effective than adjustable head restraints, 

largely because many occupants do not 

properly position adjustable head 

restraints. In 1982, NHTSA assessed the 

performance of head restraints installed 

74854 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

26We also note that some vehicles already feature 

rear seat head restraints that would comply with the 

new height, backset, strength, position retention, 

and energy absorption requirements for optional 

rear outboard head restraints.

27We note that the manufacturers’ concerns are 

alleviated by the availability of the dynamic 

compliance option. The dynamic compliance 

option provides an alternative for those 

manufacturers who are now utilizing active or 

dynamic head restraint systems. Agency testing and 

other published research have shown that an active 

head restraint system can be designed to meet 

dynamic testing requirements with a comfortable 

compliance margin. Further, a manufacturer 

electing to certify compliance via dynamic testing 

is relieved from multiple static performance 

requirements. Our analysis also indicates that 

several active head restraint systems currently on 

the market would pass our static compliance 

requirements in their normal or non-deployed 

position. Accordingly, we believe most head 

restraints will be able to meet today’s static test 

requirements. For those that cannot, the dynamic 

compliance option remains available.

28A bench seat is a seat that has a center 

designated seating position between the two 

outboard designated seating positions.

pursuant to FMVSS No. 202 and 

reported that integral head restraints are 

17 percent effective at reducing neck 

injuries in rear impacts and adjustable 

head restraints are 10 percent effective 

at doing so. The difference was due to 

integral head restraints’ being higher 

with respect to the occupant’s head than 

adjustable head restraints, which were 

normally left down. More recently, 

however, the Preliminary Economic 

Assessment (PEA) for the NPRM found 

no statistical difference in the protection 

offered by adjustable and integral head 

restraints. This may be attributable to 

increases in the height of adjustable 

head restraints relative to integral head 

restraints since the 1982 NHTSA study. 

With respect to comments on 

visibility concerns, we do not believe 

that the greater height of front seat head 

restraints will decrease rearward 

visibility. Numerous vehicles currently 

produced for the U.S. market already 

have head restraints reaching 800 mm 

without reports of visibility problems. 

In its comment, Transport Canada 

referred to a study conducted by 

Biokinetics & Associates entitled, ‘‘The 

Effects of Increased Head Restraint 

Height on Driver Visibility,’’ in support 

of its suggestion that increasing the 

height of head restraints would not 

result in any major visual obstruction. 

The study indicated that a fixed head 

restraint tall enough to accommodate a 

95th percentile male would have a 

negligible effect on driver visibility in 

83 percent of vehicles in the fleet, as 

compared to an adjustable head restraint 

in the lowest position.

With regard to concerns about the 

difficulty of manufacturing vehicles 

with taller head restraints, we do not 

believe this is a major manufacturing 

obstacle. Numerous manufacturers 

already comply with ECE17, which 

requires front head restraints to be as 

tall as in this rule.26 Further, the 

manufacturers will have ample 

opportunity to address vehicle assembly 

processes during the interim period 

before the final rule becomes effective.

Some commenters believed that taller 

front seat head restraints will make rear 

seat passengers feel ‘‘closed in’’ and 

claustrophobic. There has been no 

indication of such problems from the 

European markets where rear seat 

passengers are already subjected to 

taller head restraints in the front 

outboard seating positions. We are 

unable to conclude, without supporting 

data, that a head restraint that is less 

than 100 mm (4 inches) higher than 

current restraints is generally likely to 

have this effect on passengers. 

Nissan and ICBC requested that height 

and backset requirements, as applied to 

active or dynamically deployed head 

restraints, be measured when such head 

restraints are fully activated. Unless the 

system is tested when fully activated, 

Nissan claimed that the active head 

restraint system currently featured in 

several Nissan and Infiniti vehicles 

would not pass under the new static 

testing requirements. 

We believe that it may be difficult to 

deploy these systems manually and to 

keep them deployed while making static 

measurements, unless the actual seat is 

partially disassembled. Further, this 

artificially deployed position may not 

accurately represent position of the 

head restraint when the occupant’s head 

comes in contact with it during a rear 

impact. The agency knows of no 

practicable way to address these issues 

in the context of a static test nor did any 

commenter present one. Accordingly, 

this rule requires that front outboard 

active head restraint systems be tested 

for height in their un-deployed position. 

We note that there are practical 

limitations of any static test procedure 

on a system with dynamic properties.27

However, if an active head restraint 

were to meet the static test procedure 

requirements, this would not eliminate 

the value of the active nature of those 

head restraints since further gains in 

controlling the occupant’s head-to-torso 

motion and energy absorption could be 

achieved.

Front head restraints in low roofline 

vehicles. This rule permits a lower 

minimum height for head restraints for 

front outboard-designated seating 

positions to allow a maximum of 25 mm 

of vertical clear space between the top 

of the front head restraint and the 

roofline. The NPRM proposed to permit 

a similar exception during the interim 

period as part of the option of 

complying with ECE 17. ECE 17, 

paragraph 5.5.4 allows for up to 25 mm 

of clear space between front head 

restraint and any fixed vehicle structure, 

provided that use of the exception does 

not result in a height lower than 700 

mm. 

For front head restraints, 

DaimlerChrysler, Nissan, Alliance, 

Volkswagen, and Porsche requested that 

the 25 mm clearance exemption remain 

in the final rule to accommodate the 

possible situation in which the 800 mm 

head restraint may not clear the roof or 

front header when the seat back is 

folded for egress to or ingress from the 

rear seat area. In response to these 

comments we decided to adopt a 25 mm 

height allowance in this final rule. As in 

ECE 17, paragraph 5.5.4, the 25 mm 

height allowance is limited to the extent 

that the resulting front head restraint 

height cannot fall below 700 mm. 

However, this rule permits the 25 mm 

height allowance only in situations in 

which a full height front head restraint 

would interfere with the roofline, but 

not with any fixed vehicle structure, as 

allowed by ECE. We believe adopting 

the full ECE exception could provide 

relief in instances in which none may be 

needed. For example, an upper seat belt 

anchorage or the side of the vehicle’s 

interior could be within 25 mm of the 

head restraint and yet would likely not 

create any compliance difficulties for 

vehicle manufacturers or unduly restrict 

visibility. 

The 25 mm height allowance for rear 

head restraints is described in the next 

section. 

Width of front seat head restraints:

The NPRM proposed to maintain the 

existing width requirements of FMVSS 

No. 202: i.e., that both front and rear 

outboard seat head restraints must be at 

least 171 mm (6.7 in) wide on single 

seats and 254 mm (10 in) wide on bench 

seats.28 We note that ECE 17 regulation 

provides a 170 mm minimum width 

requirement for all head restraints. In 

the NPRM, we stated that bench seat 

head restraints should be wider because 

occupants seated on bench seats are 

freer than occupants of single seats to 

position themselves so that they are not 

directly in front of the head restraint.

AIAM called the proposed 254 mm 

head restraint width for bench seats 

unreasonable, stating that NHTSA 

should instead adopt the same 170 mm 

width for bench seat head restraints. 

AIAM asserted that comfort factors and 

seat belt placement on most bench seats 

help place occupants in the proper 

seating positions. In contrast, Advocates 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74855

29The distance from the H-point to the point 25 

mm below the roofline for 911 Coupe, Targa, and 

Cabrio models is 693, 666, and 691 mm, 

respectively. Porsche also noted that requiring rear 

head restraints in such vehicles would create an 

almost 100 percent rear window obstruction 

(Docket No. NHTSA–2000–8570–39).

expressed concern that requiring a 254 

mm width for bench head restraints and 

a 170 mm width for non-bench head 

restraints would protect only target 

occupants in centered, perpendicular 

rear impacts, not occupants in offset 

collisions, causing head/neck excursion 

to one side of the restraint. Given those 

concerns, Advocates stated it did not 

understand why all restraints, especially 

front head restraints, should not have a 

minimum width of 254 mm. 

For front bench seats we disagree with 

AIAM that the width requirement 

should be reduced. The 254 mm width 

requirement for these head restraints on 

bench seats has been in effect since 

January 1, 1969. We are not aware of 

any evidence showing that the present 

level of protection should be reduced. 

We decided to maintain wider head 

restraints for front bench-type seats 

because wider head restraints tend to 

better reduce relative head-to-torso 

motion in off-axis impacts. However, 

rather than use the term ‘‘bench,’’ which 

some commenters felt required further 

clarification, we have defined the 

requirement in terms of front outboard 

designated seating positions in vehicles 

that have a front center designated 

seating position. 

With regard to Advocates’ comment, 

NHTSA declines to require all head 

restraints to have a minimum width of 

254 mm. With respect to front outboard 

seating positions, we note that front 

outboard non-bench seats have a 

defined contour that, in addition to belt 

use, better prescribe occupant seating 

position relative to the head restraint. 

Therefore, the front non-bench head 

restraints can be narrower than the front 

bench seat head restraints. With respect 

to rear outboard seating positions, we 

believe that the rearward visibility 

concerns associated with wider rear 

head restraints outweigh an 

unquantified off-axis rear impact benefit 

of wider restraints in all seats at this 

time.

b. Requirements for Rear Seats 

Equipped With Head Restraints 

In the NPRM, we proposed to require 

head restraints in rear outboard seating 

positions. Presently, neither FMVSS No. 

202 nor ECE 17 requires head restraints 

in rear outboard seating positions. Based 

on further analysis of the proposal and 

submitted comments, we have decided 

not to require head restraints in rear 

outboard designated seating positions. 

For a more detailed discussion of our 

decision not to require head restraints, 

please see section XII. 

While rear head restraints are not 

required, this final rule does impose 

certain requirements on head restraints 

voluntarily installed in outboard 

designated seating positions. The 

strength, position retention, and energy 

absorption requirements are the same 

for front outboard and optional rear 

head restraints. However, the 

requirements for height and width differ 

from those applicable to front outboard 

head restraints. 

Height of rear seat head restraints.

The NPRM proposed that rear restraints 

have a minimum height of 750 mm if 

integral and, if adjustable, not be 

adjustable to a height below 750 mm. 

DaimlerChrysler, GM, Honda, and the 

Alliance expressed concern about 

diminished visibility and decreased 

functionality of rear seat storage due to 

the taller rear seat head restraints. As a 

result of this expected decline in 

visibility and utility, DaimlerChrysler 

indicated that customer dissatisfaction 

with the restraints could trigger misuse 

or removal. Johnson Controls expressed 

concerns pertaining to reduced rearward 

visibility (particularly for shorter 

drivers), as well as feasibility issues, 

including difficult ingress/egress for 

third-row SUV or van seating, inability 

to fold and install all rows of seats, and 

lack of clearance between head 

restraints and the rear backlight area for 

sport coupes with rear seating. 

Porsche objected to the 750 mm rear 

head restraint height, claiming 

impracticability and lack of safety need. 

Porsche indicated that some of its 

current fleet would be unable to meet 

the new height requirements for rear 

head restraints. Specifically, Porsche 

presented their computer aided design 

data showing that several models, 

including the 911, have less than 750 

mm of distance between the rear seat Hpoint and the roofline, making 

compliance with the proposed 

requirements impossible.29

Accordingly, Porsche asked that the 

final rule either not require rear head 

restraints, or provide an exception for 

low roofline vehicles. Magna and 

Volkswagen also requested that a 25 mm 

clearance between the top of head 

restraint and the roofline be allowed 

regardless of the actual head restraint 

height measurement. Such a provision 

would be similar to an ECE 17, 

Paragraph 5.5.4, which allows head 

restraints to have a lower maximum 

height in order to provide 25 mm of 

clear space between the head restraint 

and the roofline. Nissan suggested 

allowing a 25 mm clearance between the 

head restraint and interior vehicle 

structures as necessitated by vehicle 

design.

In contrast, Advocates argued for an 

800 mm minimum height for rear seat 

head restraints, in order to include 

(according to the commenter) sufficient 

whiplash protection for 95th percentile 

male adults. 

Agency response: As discussed above, 

NHTSA has concluded that any 

voluntarily installed rear head restraints 

must meet the height requirements 

proposed in the NPRM. Specifically, the 

optional rear head restraints must reach 

a minimum height of not less than 750 

mm above the H-point. 

In the NPRM, we indicated that the 

750 mm minimum head restraint height 

would reach above the head center of 

gravity of approximately 93 percent of 

all adults. We note that with respect to 

the rear seat head restraint target 

population, the 750 mm height would 

sufficiently protect an even higher 

percentage of rear seat passengers 

because larger occupants typically sit in 

front seats. 

Some manufacturers stated that a 

taller rear head restraint might interfere 

with seat mechanisms designed to 

provide access to and from third row 

seats. Because we have decided not to 

require rear head restraints, a 

manufacturer concerned with 

functionality of these mechanisms need 

not install a head restraint in the 

affected seats. Additionally, as will be 

discussed in sections IX.b. and c., the 

manufacturers will be allowed to install 

removable rear outboard head restraints 

or rear outboard head restraints with 

‘‘non-use positions.’’

Several commenters discussed the 

possible effects of the proposed head 

restraint height increases on vehicle 

utility with respect to seat folding and 

cargo capacity. The Alliance, 

DaimlerChrysler, Honda and GM 

commented that the rear head restraint 

heights proposed in the NPRM could 

impede seat folding, thus limiting cargo 

capacity, or otherwise limit interior 

configuration possibilities. 

Since rear outboard head restraints 

will not be mandatory, vehicle 

manufacturers need not equip their rear 

seats with head restraints. Further, as 

will be discussed in section IX, if the 

manufacturers provide rear outboard 

head restraints, they will be allowed to 

make them removable and to design 

them so that they can be moved into 

‘‘non-use positions.’’ As a result, 

manufacturers will have ample design 

flexibility to address the cargo carrying 

needs of their customers. 

74856 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

30The term ‘‘intended for occupant use’’ has been 

defined in the final rule to apply to seat positions 

other than those intended solely for the purpose of 

allowing ease of ingress and egress of occupants 

and access to cargo storage areas of a vehicle.

31We note that both front and rear optional head 

restraints must meet the applicable height 

requirements with the seat positioned as intended 

for occupant use.

32We note that the ICBC evaluated backset using 

the measurement technique and seat back angle 

identical to that of this final rule.

Rear head restraints in low roofline 

vehicles. This rule permits a lower 

minimum height for rear outboard 

seating positions equipped with 

optional head restraints to allow a 

maximum of 25 mm of vertical clear 

space between the top of the rear head 

restraint and the roofline or the 

backlight. The NPRM proposed to 

permit a similar exception during the 

interim period as part of the option of 

complying with ECE 17. ECE 17, 

paragraph 5.5.4 allows for up to 25 mm 

of clear space between rear head 

restraint and any fixed vehicle structure, 

provided that use of the exception does 

not result in a height lower than 700 

mm. 

We decided to adopt a similar 

provision for the long term. However, 

this rule permits the 25 mm height 

allowance only in situations in which 

the rear head restraint interferes with 

the roofline or the rear window, but not 

with any fixed vehicle structure as 

allowed by ECE. Further, the 25 mm 

height allowance is permitted only if the 

interference occurs when seats are 

positioned as intended for occupant 

use.30

In their comments, DaimlerChrysler, 

Nissan, Alliance, Volkswagen, and 

Porsche asked for a permanent 25 mm 

height allowance and suggested that the 

clearance should apply in situations 

where the seat interferes with all fixed 

vehicle structures, including roof liners, 

seat backs, headers, and rear windows. 

Further, they stated the clearance 

should be allowed regardless of whether 

the seats are placed in either upright or 

folded down positions.

This final rule does not permit a 25 

mm height allowance in situations in 

which the rear head restraint interferes 

with fixed vehicle structures other than 

the roofline or the backlight. We believe 

adopting the full ECE exception could 

provide relief in instances in which 

remedies other than changing the basic 

vehicle structure are available. 

As previously stated, the rear seat 25 

mm height allowance in this final rule 

applies only to seat adjustment 

positions intended for occupant use.31

That is, if a second row seat folds 

forward to permit ingress and egress and 

would hit the seat in front of it or some 

other vehicle structure, the 25 mm 

height allowance is not available for that 

situation. In situations in which 

interference occurs when a seat is not in 

a position intended for occupant use, 

the manufacturers may choose to utilize 

the ‘‘non-use’’ head restraint positions 

described later in this document, or 

redesign the seat fold-down 

mechanisms. We note that redesigning 

the fold down mechanism, though not 

necessitated by this final rule, can 

provide a practicable resolution at a 

reasonable cost.

The ECE 25 mm height allowance is 

limited to the extent that the resulting 

head restraint height cannot fall below 

700 mm. As a practical matter, however, 

this requirement is moot with respect to 

the upgraded standard because the rear 

seat backs and attached or adjacent 

components that have a height of less 

than 700 mm are not considered rear 

head restraints under this final rule. 

Width requirements for rear head 

restraints. The agency tentatively 

concluded in the NPRM that a 171 mm 

width for single seats and a 254 mm 

width for bench seats were the 

appropriate specifications for all 

outboard seating positions. These 

proposed widths differed from ECE 17, 

Paragraph 5.10, which provides a 170 

mm minimum width requirement for all 

head restraints. The NPRM asked 

whether NHTSA should implement 

specific requirements for rear seat head 

restraints in order to alleviate problems 

associated with potential visibility 

losses. 

All industry commenters agreed that 

the appropriate width requirement for 

rear seat head restraints should be 170 

mm, and that 254 mm is overly wide. 

Honda commented that the 254 mm 

bench seat width requirement could 

reduce rearward visibility and was 

unwarranted, given the unknown safety 

problems of rearward visibility 

reduction and the unidentified need for 

wider head restraints. Honda attached 

the results of a simulation it conducted 

to show the decreased visibility created 

when 750 mm high, 254 mm wide head 

restraints are installed in a coupe and a 

hatchback vehicle. When 254 mm wide 

head restraints were installed on a 

second row rear bench seat of a coupe 

model, Honda’s simulation showed a 40 

percent decline in rearward visibility. 

Similarly, when installed on a 

hatchback model, the 254 mm wide 

head restraints produced a 60 percent 

loss of rearward visibility. To rectify 

this reduction of rearward visibility, 

Honda suggested a head restraint 

minimum width requirement of 170 mm 

for both bench seats and individual 

seats. Honda based this 170 mm 

requirement for both types of seats on 

ECE 25. 

Ford presented data from a study it 

conducted, showing that rear head 

restraints with widths of 171 mm 

trimmed backlight visibility by 10–12 

percent, while 254 mm wide rear head 

restraints reduced visibility by 15–17 

percent. 

In contrast, Advocates stated that it 

believed that all restraints should have 

a minimum width of 254 mm. 

Upon reviewing the comments, 

NHTSA has decided to require a 170 

mm minimum width for all voluntarily 

installed rear head restraints. This 

decision was made to further reduce the 

effects of this rule on rearward 

visibility. In order to harmonize our 

requirements with that of ECE 17, we 

are adopting a 170 mm minimum width, 

as opposed to the 171 mm proposed in 

the NPRM. 

VII. Backset Requirements for Front 

Seats 

In the NPRM, we proposed that the 

front and rear outboard head restraints 

have a backset of no more than 50 mm, 

as measured by HRMD. ‘‘Backset’’

means the minimum horizontal distance 

between the back of a representation of 

the head of a seated 50th percentile 

male occupant and the head restraint 

(i.e., the back of the ICBC head form and 

the head restraint). The 50 mm 

maximum backset requirement was to 

be met at all head restraint heights 

between 750 mm and 800 mm. We 

solicited comments on whether a 

maximum 50 mm backset limit would 

be effective in preventing whiplash 

injuries; whether 50 mm backset would 

provide sufficient comfort for the 

occupants; and whether an adjustable 

backset would be more appropriate. 

Commenters offered a range of 

opinions about the need for, and 

acceptable level of, a maximum backset 

requirement. Several commenters, 

including ICBC, IIHS, Transport Canada, 

and Advocates, supported establishing 

50 mm as the maximum allowable 

backset. ICBC and Magna Seating 

Systems argued that Mathematical 

Dynamic Model (MADYMO) 

simulations performed by NHTSA 

confirm the decreasing safety benefit of 

head restraints with backsets greater 

than 50 mm. Therefore, ICBC believes 

50 mm is sufficient to reduce whiplash 

significantly. 

ICBC provided data showing 49 of 164 

vehicles manufactured in 2001 by 19 

different manufacturers have a backset 

of 50 mm or less.32 IIHS stated that a 

group of model year (MY) 2001 vehicles, 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74857

33The UMTRI evaluated backset of 50 mm at the 

seat back angle of 25 degrees, using a CAD 

representation of a HRMD and a typical seat.

34Eichberger A, Geigl BC, Moser A, Fachbach B, 

Steffan H, Hell W, Langwieder K; Comparison of 

Different Car Seats Regarding Head-Neck 

Kinematics of Volunteers During Rear End Impact; 

Proceedings of the 1996 International IROCBI 

Conference on the Biomechanics of Impact; 

September 1996; pp. 153–164.

35Szabo TJ, Welcher JB; Human Subject 

Kinematics and Electromyographic Activity during 

Low Speed Rear Impacts, Proceedings of the 40th 

Stapp Car Crash Conference; November 1996, 

962432, pp. 235–315.

36 Davidsson J, Deutscher C, Hell W, Linder A, 

Lovsund P, Svensson: Proceedings of the 1998 

International IRCOBI Conference of the 

Biomechanics of Impact: September 1998; pp. 289–

301.

37Mertz, H.J.; Patrick, L.M.: ‘‘Investigation of the 

Kinematics and Kinetics of Whiplash,’’ Proceedings 

of the 11th Stapp Car Crash Conference, Anaheim, 

California, 1967; pp. 267–317.

among them Jeep Cherokee, Ford 

Ranger, Toyota Camry, and Volvo S80 

already have 50 mm or smaller backsets. 

Because many newer vehicles already 

have backsets of 50 mm, these 

commenters claimed it was evident that 

the 50 mm requirement provides 

sufficient head clearance and that 

passenger comfort would not be 

compromised in a significant manner. 

IIHS stated that it was unaware of any 

significant comfort issues.

In opposition, a majority of the 

manufacturers, among them GM, Magna, 

Johnson Controls, AIAM, the Alliance, 

Nissan, Porsche, DaimlerChrysler, and 

Ford, suggested that vehicle occupants 

would prefer a head restraint backset of 

more than 50 mm. Specifically, they 

maintained that smaller female 

occupants tend to utilize steeper seat 

back angles. According to these 

commenters, a backset of 50 mm may 

cause significant intrusions into the 

space where these occupants typically 

place their heads, forcing their heads 

into an unnatural forward-tilting 

position. DaimlerChrysler indicated that 

a recent decrease in the backset to 50 

mm in one of its models yielded four 

times as many warranty claims for the 

new head restraint. It did not elaborate 

on the basis for these claims. Autoliv 

commented that even a 50 mm backset 

is not a guarantee to prevent whiplash, 

and that it will lead to discomfort for 

more than 20 percent of the occupants. 

General Motors and Ford suggested that 

an 80 mm backset is more appropriate 

to accommodate consumer comfort.

Some commenters stated that IIHS 

rates backsets of 70 to 90 mm 

‘‘acceptable’’ and so that backset 

requirement should be increased to that 

range. 

The University of Michigan 

Transportation Research Institute 

(UMTRI) commented that it had 

conducted an extensive study of vehicle 

occupants’ posture and position. Based 

on its research, a 50 mm backset would 

result in head restraint interference for 

13 percent of the driving public.33 The 

head restraint would actually come in 

contact with the hair of approximately 

33 percent of drivers, assuming a hair 

margin of 25 mm. Based on their 

calculations, the individuals who 

preferred seat back angles more upright 

than 25 degrees (usually small stature 

people) were most likely to be subject to 

the head restraint interference. UMTRI 

estimated that with current seat designs, 

a backset of 91 mm would accommodate 

the preferred head positions of 99 

percent of the population and a 70 mm 

maximum backset would accommodate 

all but a small percentage of the 

population.

Ford cited 3 studies by Eichberger et 

al.,34 Szabo et al.,35 and Davidsson et 

al.,36 which used sled-mounted seats to 

simulate low speed rear impacts. 

Eichberger et al. tested volunteers on 9 

different seat types at simulated impact 

speed changes (delta Vs) of 8 and 11 

km/h. When the measured backset was 

less than 70 mm, none of the volunteers 

complained of any discomfort or pain. 

Szabo et al. tested 5 volunteers at delta 

Vs of 8–10 km/h under two conditions: 

an unmodified head restraint, and the 

same head restraint with 50 mm of 

additional padding. Backsets for the 

volunteers ranged between 76 to 114 

mm with the unmodified head restraint, 

and by assumption between 26 to 64 

mm with the modified head restraints. 

None of the volunteers reported any 

discomfort or pain after either test. 

Davidsson et al. subjected 13 volunteers 

to multiple sled tests (2–4) with delta Vs 

of 5 to 7 km/h. The measured backsets 

ranged from 70 to 160 mm. The head 

restraint position was not varied during 

the test so the variation in backset for 

the different occupants was due to 

occupant size differences. Only one 

subject reported any symptoms. The 

symptom was a headache, which 

occurred after his third run, and 

desisted within 36 hours.

We also received a comment from 

Cervigard, Inc., which has designed a 

head restraint that incorporates a 

contoured shape intended to match the 

curvature of the head and cervical 

spine, which is essentially a neck 

bolster. In Appendix B of this NPRM, 

we discuss our reasons for not adopting 

a requirement for a neck bolster. 

Agency response: This final rule 

requires that front outboard head 

restraints meet the backset requirements 

described below. Because of occupant 

comfort countermeasure issues unique 

to rear seats, the agency decided not to 

regulate backset in the rear designated 

seating positions voluntarily equipped 

with head restraints. We concluded that 

comfort-related issues are not 

insurmountable in front seats because 

front seat backs can be adjusted to 

alleviate discomfort. Further, as 

explained further below, our Final 

Regulatory Impact Analysis (FRIA) does 

not attribute any safety benefits to 

vehicle occupants as a result of 

regulating backset in rear seats. 

For front outboard designated seating 

positions, we have decided to increase 

the maximum allowable backset to 55 

mm, with the seat back positioned at an 

angle that gives the HRMD a torso 

reference line angle of 25 degrees. Our 

decision to relax the maximum 

allowable backset requirement is based 

on the ± 5 mm tolerance of the 

measuring device. This tolerance is 

discussed more fully in the next section. 

Briefly stated, a 5 mm increase beyond 

the 50 mm limit proposed in the NPRM 

represents the variability associated 

with measuring backset with the ICBC 

measuring device. 

In sum, under today’s rule, the 

backset for front outboard head 

restraints must not be adjustable beyond 

the new maximum allowable distance of 

55 mm when the head restraint is at a 

height between 750 mm and 800 mm, 

inclusive. Backset adjustment to 

distances below 55 mm is allowed. 

Also, backset adjustment of above 55 

mm at head restraint positions higher 

than 800 mm is allowed. For 

manufacturers of active head restraint 

systems who choose to certify to the 

static dimension and strength 

requirements, the backset measurements 

will be taken with the head restraints in 

non-deployed position because we 

believe that the artificially deployed 

position may not accurately represent 

the actual position of the head restraint 

when the occupant’s head comes in 

contact with it. 

Necessity for a limited backset. Our 

decision to propose a 50 mm backset 

was based on published research, 

testing, computer modeling, and real 

world crash data. 

The consensus within the 

biomechanics community is that the 

backset dimension has an important 

influence on forces applied to the neck 

and the length of time a person is 

disabled by an injury. As early as 1967, 

Mertz and Patrick first showed that 

reducing the initial separation between 

the head restraint and head minimizes 

loading on the head during a rear 

impact.37 More recently, the Olsson 

74858 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

38Olsson, I., Bunketorp, O., Carlsson G., 

Gustafsson, C., Planath, I., Norin, H., Ysander, L. An 

In-Depth Study of Neck Injuries in Rear End 

Collisions, 1990 International Conference on the 

Biomechanics of Impacts, September, 1990, Lyon, 

France. See Table IV and the Appendix.

39Svensson, M., Lovsund, P., Haland, Y., Larsson, 

S. The Influence of Seat-Back and Head-Restraint 

Properties on the Head-Neck Motion During RearImpact, 1993 International Conference on the 

Biomechanics of Impacts, September, 1993, 

Eindhoven, Netherlands.

40Eichberger A, Geigl BC, Moser A, Fachbach B, 

Steffan H, Hell W, Langwieder K. Comparison of 

Different Car Seats Regarding Head-Neck 

Kinematics of Volunteers During Rear End Impact, 

International IRCOBI Conference on the 

Biomechanics of Impact, September, 1996, Dublin.

41Tencer, A., Mirza, S., Bensel, K. Internal Loads 

in the Cervical Spine During Motor Vehicle RearEnd Impacts, SPINE, Vol. 27, No. 1 pp 34–42, 2002. 42The IIHS head restraint rating criteria is 

discussed at: http://www.iihs.org/vehicle_ratings/

head_restraints/head.htm. 43See Eichberger at pp. 153–164.

study, which examined neck injuries in 

rear end collisions and the correlation 

between the severity of injuries and 

vehicle parameters, showed that the 

duration of neck symptoms was 

correlated to the head restraint backset. 

Specifically, reduced backset, coupled 

with greater head restraint height, 

results in lower injury severity and 

shorter duration of symptoms.38

A different study examined sled tests 

to determine the influence of seat back 

and head restraint properties on headneck motion in rear impacts. The study 

concluded that the head restraint 

backset had the largest influence on the 

head-neck motion among all the seat 

properties examined. With a smaller 

backset, the rearward head motion was 

stopped earlier by the head restraint, 

resulting in a smaller head to torso 

displacement. The findings indicated 

that a reduction in backset from 100 mm 

to 40 mm would result in a significant 

reduction in whiplash injury risk.39

A study conducted by Eichberger 

examined real world rear crashes and 

sled tests with human volunteers to 

determine whiplash injury risk and 

vehicle design parameters that influence 

this risk. The study found a positive 

correlation between head restraint 

backset and head to torso rotation of the 

volunteers and to the reported whiplash 

injury complaints. The most important 

design parameters were a low horizontal 

distance between the head and head 

restraint as well as the head restraint 

height.40

A study conducted by Dr. Allan 

Tencer, PhD, used rigid occupant body 

models enhanced with finite element 

models of the cervical spine for 

simulating rear impacts in order to 

examine the effect of backset on neck 

kinematics and forces and moments in 

the neck. The study concluded larger 

backset correlates to greater 

displacement between cervical vertebrae 

and shearing at the facet capsules that 

are likely associated with whiplash 

injury. With the head initially closer to 

the head restraint, the time difference 

between the occurrences of the peak 

upper and lower neck shear forces are 

smaller. At 50 mm backset and lower, 

the head moved more in phase with the 

torso and extension of the head was 

reduced indicating a lower risk of 

whiplash injury.41 IIHS, in its studies of 

head restraints, considers a backset of 

70 mm (2.8 inches) or less to be 

‘‘good.’’ 42

NHTSA used computer modeling 

described in the NPRM to verify our 

assumption regarding the benefits of a 

smaller backset. Our research indicates 

that lower head-to-torso rotation values 

were seen when the backset was 

approximately 50 mm in comparison to 

head restraints with large backset 

values. As discussed further in this 

notice, lower head-to-torso rotation 

values are predicted to result in a lower 

probability of whiplash injury. 

Therefore, we continue to conclude that 

50 mm of backset is an appropriate 

upper limit for all outboard seating 

positions. No data presented in the 

comments have indicated that a higher 

backset value is more appropriate from 

the occupant safety-standpoint. Other 

than Ford’s comments, all of the 

comments opposing the proposed 50 

mm maximum backset were related to 

comfort issues and the repeatability of 

placement of the proposed test device. 

In sum, research indicates that limiting 

backset is critical to reducing whiplash 

injuries occurring in rear impacts. 

In its comments, Ford referred to 

three crash studies conducted at delta 

V’s ranging from 5 to 11 km/h with 

varying degrees of backset and occupant 

size. Ford emphasized that there were 

no occupant injuries both with and 

without the backset reduction. We note 

that all of these tests utilized volunteers 

and therefore, the impact delta Vs were 

intended to be below the injury 

threshold. The primary goal of these 

studies was to understand occupant 

kinematics. The same research also 

indicated that when backset was 

reduced from 76 mm to 26 mm and from 

114 mm to 64 mm, the head 

acceleration, rearward head 

displacement and cervical extension 

were all reduced. These data confirm 

our contention that injury measures, 

including head-to-torso rotation, 

decrease with smaller backset and 

predict a lower probability of injury. 

While some of the data supplied by 

Ford seems to suggest that smaller 

backsets have no bearing on the 

occurrence of whiplash injuries at low 

speeds, we note that if all impacts in the 

real world were limited to this very 

slow speed, the backset limit indeed 

might not be as critical. The same data 

seem to support our rulemaking efforts, 

as Eichberger observed that backset ‘‘is 

very important for a good seat design. 

Even a head restraint placed high 

enough can only prevent neck injuries 

when the head is sustained as soon as 

possible by the head restraint during 

rear end collision.’’ 43

Finally, we note that other seat 

parameters beyond the head restraint 

geometry play a role in risk of injury in 

rear impacts. Specifically, seat back 

frame force deflection characteristics 

and seat upholstery compliance 

characteristics can influence the 

occupant’s kinematics. Thus, the head 

restraint geometric requirements 

specified in this final rule should be 

thought of as an interim step in the 

agency’s goal of a unified seat/head 

restraint standard. 

Comfort of the seat occupant. In 

selecting a backset limit, we have 

attempted to balance comfort, safety and 

measurement variability concerns. As 

noted above, no commenter disputed 

scientific data indicating that the closer 

the head restraint is to the occupant’s 

head at the time of impact, the better the 

protection the head restraint offers. 

Numerous commenters, however, stated 

that occupants may be intolerant of 

head restraints very close to the back of 

their head. Further, because of 

differences in the occupant size, posture 

and seat angle preference, the same 

head restraint can yield different 

amounts of backset clearance for 

different individuals. 

Several manufacturers argued that 

some occupants would select a steeper 

or more upright front seat back angle, 

thus causing the backset distance to be 

below 50 mm. They contend that a 

backset of less than 50 mm will interfere 

with the normal position of the head. 

However, since ICBC reported that 49 of 

164 vehicles from model year 2001 met 

the 50 mm backset limit, it appears that 

occupant discomfort in front seats is not 

an insurmountable obstacle. 

Accordingly, we conclude that the 

available information does not 

substantiate the industry concerns 

associated with discomfort from front 

seat back adjustment to a more upright 

position. 

UMTRI commented that a 50 mm 

backset causes interference with 13 

percent of drivers ‘‘preferred’’ head 

position. Generally, these tend to be 

smaller occupants, who prefer a more 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74859

44We note that the decision not to regulate the 

backset of rear head restraints has the effect of 

making our upgraded standard consistent with the 

ECE regulation on this point.

upright seat back angle. The ‘‘preferred’’

backset position, as articulated by 

UMTRI, may merely refer to a position 

that the drivers are most accustomed to. 

The term does not necessarily mean that 

the position is the only acceptable one 

or even the safest one for a given 

occupant. We note that the driving 

population as a whole is accustomed to 

a backset position that is, while 

comfortable, not optimal to prevent 

whiplash injuries.

We believe that no significant 

deviation from our proposed backset 

limit of 50 mm is necessary to provide 

an overwhelming majority of front seat 

occupants with an acceptable backset 

position. Further, any potential 

discomfort can be reduced by a slight 

increase in seat back angle. We believe 

that most front seat occupants can 

increase the seat back angle slightly 

without compromising their ability to 

reach the steering wheel comfortably or 

see the road ahead. For every additional 

degree of inclination, approximately 3 

mm of additional backset clearance 

would be obtained. For example, a 2-

degree increase in seat back angle will 

result in additional 6 mm of backset. 

In addition to potential ways to 

alleviate potential discomfort, we note 

that our own measurements of 14 

vehicles showed that the front seat head 

restraints in the MY 1999 Toyota Camry, 

Chevy C1500, Chevy S10, Saab 9–5, and 

Chevy Malibu, all had backsets within 

the proposed 50 mm limit. This 

supports comments by ICBC and IIHS 

that many vehicles already have a 50 

mm backset. We think the seat 

manufacturers can provide a front 

seating system design, such as a 

different head restraint shape, that 

would allow for better comfort. 

With respect to rear seats, however, 

the agency believes that potential 

occupant discomfort cannot be as easily 

reduced because most rear seat backs in 

passenger cars are not adjustable. In 

many vehicles, the rear seat back angle 

cannot be changed to provide additional 

backset clearance. Consequently, some 

vehicle occupants may experience 

interference with the normal position of 

their head, and could decide to 

completely remove the optional rear 

head restraints. NHTSA believes that it 

is preferable that the rear head restraints 

remain in the vehicle instead of being 

removed due to occupant discomfort, 

because we estimate that the increased 

height of optional rear head restraints 

will result in 1559 fewer whiplash 

injuries each year. Further, we are 

concerned that some manufacturers may 

choose not to install optional rear head 

restraints due to concerns of customer 

dissatisfaction with uncomfortable rear 

head restraints. 

Because of rear seat occupant comfort 

concerns, the agency decided not to 

limit the amount of backset in the rear 

designated seating positions equipped 

with optional head restraints.44 Because 

of abundant scientific evidence showing 

that smaller backset reduces instances of 

whiplash injuries, we believe that the 

vehicle manufacturers will install 

optional rear head restraints in a 

manner that will strike a proper balance 

between rear seat occupant safety and 

comfort.

In addition to rear occupant comfort 

concerns, we note that our FRIA does 

not attribute any safety benefits to 

vehicle occupants as a result of 

regulating backset in rear seats. By 

contrast, we estimated that for front 

seats, the limit on backset would result 

in 15,272 fewer whiplash injuries each 

year. As explained in Section XVI of 

this notice, we based our estimates of 

benefits on either increased height or 

reduced backset, but not both. We could 

not combine effectiveness of increased 

height and reduced backset because 

this, in some instances, would result in 

‘‘double-counted’’ benefits. For front 

seats, we attribute the benefits to the 

backset limit. We estimate that greater 

share of the safety benefits will come 

from the backset limit because many 

current vehicles already include taller 

front seat head restraints. For rear seats, 

we attribute the benefits to height 

because we anticipate that the greater 

share of the benefits will come from 

regulating the height of optional head 

restraints. 

Adjustable backset suggestion.

Several seat and automobile 

manufacturers argued that, to 

accommodate occupant comfort, a 50 

mm backset requirement should be 

supplemented with an allowance for 

backset to be adjustable to distances of 

up to 100 mm, so long as it could also 

be adjustable to a minimum setting of 50 

mm. In contrast, most consumer groups 

voiced opposition to allowing a backset 

distance of up to 100 mm, even if it 

would be adjustable to a shorter 

distance of 50 mm. Advocates argued 

that the backset should be limited to 50 

mm or less, and there should not be an 

allowance for an adjustable 100 mm 

backset, because it is commonly known 

that most occupants will not properly 

adjust their head restraints. Florida 

International University (FIU) students 

claimed that most occupants would 

simply leave their head restraints 

adjusted at a backset of 100 mm because 

of the lack of adequate consumer 

awareness. Johnson Controls was 

similarly opposed to an adjustable 

backset, stating that it is evident that 

most head restraints would be 

misadjusted. Johnson Controls stated 

that 60 to 80 percent of occupants do 

not properly adjust their head restraints. 

ICBC was similarly opposed to head 

restraints with adjustability beyond 50 

mm, stating that it would lead to 

misadjustment and reduced 

effectiveness. 

We were not persuaded to allow a 

head restraint system featuring 

adjustable backset mechanism that 

would allow as much as 100 mm of 

backset, even if such mechanism would 

be capable of achieving a 50 mm backset 

measurement. We agree with arguments 

put forth by ICBC and Advocates that 

the possibility of misadjustment is too 

great. In case of vertical adjustment, the 

height between the ears and the top of 

the head provides a clear target zone for 

adjustment. There is no such clear target 

adjustment zone for backset. Further, if 

a vertically adjustable front head 

restraint is adjusted to its lowest 

position, it still provides an acceptable 

level of protection at a height of 750 

mm. If the head restraint is adjusted too 

high, it provides an obvious visual cue 

to the seat occupant. In the case of 

backset misadjustment, there would not 

be a minimally acceptable level of 

protection at 100 mm of backset, 

because such measurement does not 

provide sufficient protection against 

excessive head-to-torso rotation. 

Further, a head restraint with a 

misadjusted backset would not provide 

an occupant with an obvious visual cue, 

as most occupants are unaware of the 

necessity for proper backset adjustment. 

In sum, we conclude that allowing for 

an adjustable backset could end up 

defeating the purpose of the new 

backset requirement. 

Seat back angle for backset 

measurement. We are aware of certain 

variability concerns associated with 

backset measurement using the HRMD 

device with a SAE J826 manikin torso 

reference line angle of 25 degrees. We 

will refer to the torso reference line 

angle of the J826 manikin and seat back 

angle interchangeably. Concerns 

associated with the use of HRMD device 

are discussed in Section IX. The seat 

back angle of 25 degrees was chosen 

because it is on the edge of the range of 

normally selected seat back angles and 

would most likely be selected by larger 

occupants. ICBC, which developed the 

HRMD, designed it to be used at 25 

degrees. Of course, for some fixed 

74860 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

45SAE J1100—Motor Vehicle Dimensions. All 

1999–2000 make and model data submitted to 

NHTSA. The data ranged from 18 to 28 degrees.

46Although HRMD has a probe that makes it 

possible to measure head restraint height vertically 

down from the top of the HRMD, this probe will 

not be used because it is not consistent with 

measurement along the torso line.

position rear seats, this is not possible. 

The 25-degree angle is also consistent 

with the methods used by IIHS and 

RCAR for measurement of height and 

backset. ECE 17 does not specify a limit 

on backset, but for height measurement 

the seat back is set to 25 degrees unless 

the manufacturer’s recommended seat 

back angle is specified. While several 

manufacturers stated that measuring 

head restraint height at steeper (i.e., 

smaller) seat back angles result in 

smaller measured height, our own data 

indicate that reducing seat back angle by 

one degree results only in a 2 to 3 mm 

reduction in head restraint height 

measurement. We also find persuasive 

the information provided by ICBC 

stating that a ±1-degree error in torso 

angle results in a change in backset 

measurement of only ±3 mm.

We note that the 25-degree seat back 

angle in comparison to steeper angles 

represents a more stringent requirement 

for backset measurements because it 

maximizes the distance between the 

head and head restraint. However, a 25-

degree angle is less stringent for 

measuring head restraint height. Indeed, 

if we decided to adopt the 

manufacturer’s design seat back angle, 

typically around 23 degrees,45 we would 

in fact be requiring even taller head 

restraints. Although we considered 

measuring height at a steeper angle than 

25 degrees, we decided against it. 

Rather, we are adopting a single 

measurement angle for both height and 

backset in order to reduce unnecessary 

complexity in measurements and 

increase accuracy of testing results. We 

believe the 25-degree specification will 

not compromise safety for shorter or 

taller occupants. Finally, using the same 

angle for the measurement of backset 

and height for every seat, rather than the 

manufacturer’s design seat back angle, 

will allow comparison of height and 

backset measurement from seat to seat.

VIII. Measurement of Backset and 

Height 

NHTSA proposed that compliance 

with the backset and height 

requirements be measured through use 

of the ICBC HRMD. The HRMD consists 

of a SAE J826 three-dimensional 

manikin with a head form designed by 

ICBC attached. The ICBC head form 

contains a probe that slides rearward 

until contact is made with the head 

restraint, thus allowing a backset 

measurement. For height measurement, 

the SAE J826 manikin is used without 

the HRMD. The SAE J826 manikin 

provides a scale that gives the distance 

from the H-point along the torso line, 

thus allowing a height measurement.46

If the seat cushion adjusts vertically 

independently of the seat back, the 

measurements will be taken with the 

seat cushion adjusted to the most 

unfavorable position; i.e., the position 

that minimizes head restraint height.

Most vehicle manufacturers and seat 

suppliers opposed the use of the HRMD. 

Generally, they questioned the accuracy 

and repeatability of head restraint 

geometry measurements made using 

that device. Further, the HRMD was 

deemed too sensitive to foam, trim, 

actual H-point, temperature, and 

humidity variations. Johnson Controls, 

Nissan, Magna, Ford, VW, and GM 

commented that the HRMD was not 

appropriate for compliance testing 

because repeated testing on the same 

seat assembly yielded different results. 

For example, Ford noted that the 2000 

Ford Taurus and 2000 Mercury Sable 

received different ratings despite the 

fact that they are manufactured on the 

same platform and have identical front 

seats. Additionally, DaimlerChrysler 

commented that NHTSA’s own 

compliance procedure for Standard No. 

208, involving the J826 manikin, allows 

for variability of ±12.5 mm for the 

Hybrid III test dummy’s H-point in 

comparison to the J826 H-point and that 

the Hybrid III is a more biofidelic 

representation of a seated occupant. 

Ford stated that when measuring a head 

restraint reaching 800 mm, a manikin 

torso angle variation of ±1 degree 

produced a 28 mm variation in the 

backset measurement. Porsche stated 

that the HRMD device could not be 

properly positioned in the seats that 

have strong-contoured shape, therefore 

preventing accurate measurements. 

Honda provided data showing repeated 

backset measurement of a single seat by 

3 test technicians. The largest range for 

any technician was 10 mm and the 

overall range of backset was 17 mm. 

On the other hand, Transport Canada 

reported that a study commissioned by 

several Canadian insurance companies, 

conducted by Rona Kinetics and 

Associates, Ltd., entitled ‘‘Head 

Restraint Field Study,’’ concludes that 

HRMD is repeatable and an effective 

predictor of head restraint positions. 

Transport Canada has used HRMD for 

years and finds it to be a convenient and 

accurate tool. 

In addressing accuracy concerns, 

ICBC said that the HRMD yields a level 

of accuracy of ±5 mm when used by 

competent, well-trained operators. ICBC 

stated further that manufacturers have 

historically had to accommodate similar 

tolerance levels with other compliance 

testing based on the H-point machine. 

Further, according to ICBC, 1 degree in 

seat back variance yields a deviation of 

no more than 3 mm as opposed to 13–

28 mm as suggested by some 

commenters. In addressing Ford’s 

comments on different measurement 

results for virtually identical vehicles, 

ICBC stated that the two seats, while 

identical in theory, had different 

upholstery materials (leather and cloth) 

and also had different stitching patterns. 

As a result, the deviation between two 

seat measurements was 5 mm, which 

ICBC noted was enough to warrant 

awarding two different vehicle head 

restraint ratings. 

The SAE cautioned that the current Hpoint machine is undergoing 

considerable revision and the ICBC 

device could not be mounted on the 

new manikin. It argued that if the ICBC 

device were mandated, the 

manufacturers would be forced to use 

an otherwise outdated compliance 

device. Magna suggested that we 

consider the ASPECT (Automotive Seat 

and Package Evaluation and 

Comparison Tools) manikin as a 

compliance tool, instead of the HRMD. 

According to several manufacturers, 

including Magna, Porsche and Honda, a 

more appropriate measurement 

methodology would utilize SgRP. The 

SgRP is a theoretical point in the 

vehicle, usually representing the most 

rearward normal riding or driving Hpoint, as determined by the 

manufacturer. Further, they requested 

that a CAD drawing be used to obtain 

the most precise height and backset 

measurements. Specifically, Magna 

recommended that we use a CAD design 

tool to measure the required head 

restraint height. Similarly, Porsche has 

asked us to consider virtual 

measurement methods using Ramsis 

software. Honda suggested that the 

HRMD assembly be translated into 

electronic data and the measurements 

be taken electronically. 

UMTRI also recommended a height 

and backset measurement technique 

that uses the H-point as the reference. 

Once the H-point is established, a 165 

mm sphere would be rolled vertically. 

The most rearward part of the sphere 

would map a path. From this path, the 

height of the head restraint and backset 

can be calculated at any height. The 

procedure could be done at any position 

of head restraint adjustment. 

In response to the suggestion of 

alternative measuring devices, ICBC 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74861

commented that it developed the HRMD 

because there were no similar tools 

available to produce accurate and 

repeatable measurements. It claimed the 

HRMD is more biofidelic than other 

similar or proposed devices, because it 

has an articulating neck joint that 

approximates the C7–T1 joint (i.e., the 

location on the spine between the most 

inferior cervical vertebra and the most 

superior thoracic vertebra). This allows 

the operator to approximate human 

posture at any seat back angle. The ICBC 

noted that there are 35 HRMD devices 

now in use, arguing this makes it a wellaccepted compliance tool; the device is 

readily available from ICBC. Further, the 

HRMD represents a small cost for 

demonstrating compliance.

ICBC further stated that despite 

industry comments to the contrary, the 

ICBC device does not add extra weight 

to the H-point machine. The ICBC 

weight closely approximates the weight 

of the 50th percentile head and neck. No 

extra weight is added to the H-point 

machine because some upper torso 

weights are removed from the manikin 

to compensate for the ICBC device. 

Specifically, the HRMD with two 

‘‘replacement weights’’ substitutes for 4 

out of 8 H-point machine weights. 

Generally, ICBC suggested that the 

HRMD device be used instead of a 

computer-based method of determining 

compliance. However, if some sort of 

electronic compliance were 

implemented, it believes Honda’s 

proposal is preferable because it 

contemplates the use of ‘‘virtual’’

HRMD, which most closely replicates 

actual human seating positions. In 

response to SAE’s concern with the 

forthcoming development of the revised 

J826 H-point machine, ICBC pledged 

full cooperation to ensure that HRMD 

can fit the future H-point machine. 

RCAR submitted a test procedure it 

developed for head restraint 

measurement that uses the HRMD. It 

recommended using its measurement 

procedures in determining compliance 

with the new criteria. 

Agency response: Despite the 

objections of numerous commenters, we 

have decided to adopt the HRMD for our 

compliance tests. Under the current 

version of FMVSS No. 202, the 

manufacturers provide NHTSA with the 

theoretical location of the SgRP with 

respect to some vehicle reference point. 

The new rule eliminates the need for 

obtaining a theoretical point from the 

vehicle manufacturer, determined by a 

CAD technique, because the HRMD 

defines the H-point of the specific seat 

being measured. In addition, the Hpoint can be found for any position of 

seat cushion adjustment, thus allowing 

the worst-case head restraint height to 

be measured. 

We conclude that the ICBC comments 

related to a CAD technique for 

determining head restraint geometry are 

the most compelling. Specifically, ICBC 

noted that various techniques suggested 

by the manufacturers all have the 

limitation of not measuring the actual 

seat, as it exists in the real world. 

Instead, they rely upon measurements 

made in a virtual or computer generated 

environment. The current FMVSS No. 

202 height measurement technique has 

the same weakness, as it uses the SgRP 

determined by drawing techniques and 

a seat position defined by the 

manufacturer. While we appreciate the 

numerous benefits associated with CAD 

techniques in the design of vehicles and 

their components, we believe these 

techniques are not yet appropriate for a 

regulatory environment. Any CAD 

method would not only have to rely on 

an adequate model of the J826 manikin, 

but, even more importantly, an accurate 

representation of the vehicle seats. Each 

seat model would require extensive 

validation to assure that the CAD results 

would match the results achieved by 

direct measurement. A design change 

such as new upholstery foam or 

covering material would likely require a 

re-validation of the model. This type of 

process is appropriate for research or 

product development, but is not yet 

ready for regulatory purposes. 

In regard to the backset and height 

measurement technique suggested by 

UMTRI, we conclude that the technique 

is useful to the extent it allows backset 

to be calculated for an occupant of any 

height rather than just for a 50th 

percentile male. However, we are not 

aware of any physical device currently 

available to map out the continuous 

backset. Thus, in order for the agency to 

adopt the UMTRI method, a CAD 

technique would have to be adopted, 

unless a new physical testing device is 

developed. We have rejected the use of 

CAD methods for the reasons specified 

above. 

Numerous commenters questioned 

the accuracy of the HRMD device. 

Specifically, the manufacturers 

questioned repeatability of 

measurements and stated that the 

HRMD is incapable of accounting for 

foam, trim, actual H-point, temperature, 

and humidity variations. However, ICBC 

submitted data showing accuracy of ±5 

mm. Because ICBC has a significant 

amount of experience in using the 

HRMD, its assertion that the overall 

level of repeatability of its device is 

within a ±5 mm, when used correctly, 

is persuasive. 

We also conclude that ICBC provided 

adequate explanation for the 

discrepancy between the measurement 

results for Ford Taurus and Mercury 

Sable, a discrepancy that would not 

have been found using a CAD 

technique. Different upholstery and 

stitching patterns can result in different 

measurements. If these differences are 

significant, the difference in both height 

and backset may be significant. Further, 

a Transport Canada study concluded 

that the HRMD is repeatable and an 

effective predictor of head restraint 

position of humans. Transport Canada 

has used the HRMD for years and finds 

it to be a convenient and accurate tool. 

There are at least 35 HRMDs now in use, 

and the head form is readily available 

from ICBC. 

We found that while measuring head 

restraint geometries with the HRMD for 

use in a cost study, the backset 

measurements varied by a total of 10 

mm when NHTSA’s Vehicle Research 

and Test Center (VRTC) repeated the 

measurement of a single vehicle seat 3 

times. This is consistent with the ICBC 

statements showing ±5 mm accuracy. 

Further, experience indicates that 

greater familiarity with the device 

reduces the variability of measurements. 

Thus, the measurement variance shown 

in the Honda data (10 mm for 1 operator 

and 17 mm for 3 operators) may have 

been due to a lack of familiarity with 

HRMD. 

Porsche stated that the HRMD device 

could not be properly positioned in the 

seats that have ‘‘strong-contoured 

shape,’’ therefore preventing accurate 

measurements. However, Porsche did 

not provide any data comparing the 

position of HRMD head form to the 

position of an actual occupant’s head in 

one of its ‘‘strong-contoured shape’’

seats. We believe that Porsche must 

currently use the SAE J826 manikin to 

find the reference H-point position of 

the Hybrid III 50th percentile manikin 

for frontal barrier tests in FMVSS No. 

208, and therefore has some familiarity 

with how to properly position the 

device. Generally, we believe that 

experienced operators will not 

encounter any difficulties in measuring 

seating structures with HRMD. 

Several comments suggested that the 

HRMD device is insufficiently 

biofidelic. However, we are persuaded 

by ICBC’s comments that HRMD is more 

biofidelic than other similar devices 

because it has an articulating neck joint 

that approximates the C7–T1 joint. This 

design feature allows the operator to 

level HRMD’s head regardless of the seat 

back angle, similar to the posture of a 

human occupant, resulting in superior 

accuracy of backset measurement. While 

74862 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

47The gap limits are applied between two vertical 

longitudinal planes, which are one half the 

minimum head restraint width from the head 

restraint centerline. Thus, any part of the front 

surface of the head restraint outside of the 

minimum width requirement is excluded from the 

gap limits.

we are aware that the SAE has updated 

the J826 manikin in the form of the 

ASPECT manikin in July 2002, this new 

device has yet to be evaluated by the 

agency for incorporation into FMVSS. 

Based on the comments and analysis 

presented above, we have decided that 

the HRMD will be the measurement 

tool.

IX. Maximum Gap Allowance and 

Removability 

a. Maximum Gap Allowance 

The NPRM proposed allowing for 

gaps within the perimeter of the front 

(anterior) surface of head restraints in 

order to provide for better rearward 

visibility for drivers.47 The NPRM 

proposed two types of maximum gap 

allowances. First, for both integral and 

adjustable head restraints, a gap within 

the perimeter of the head restraint could 

not exceed 60 mm. Because there may 

not be a clear distinction between the 

end of the seat back and the beginning 

of the head restraint in integral head 

restraints, compliance with this first gap 

limit is determined by measuring any 

point on the front surface of the seat 

back 540 mm above the H-point and 

within the minimum head restraint 

width. We note that ECE 17, Paragraph 

5.8, similarly regulates gaps at heights 

above 540 mm.

The second type of gap allowance was 

between an adjustable head restraint in 

its lowest position and the seat. There 

were two levels of requirements. First, 

an adjustable head restraint in its lowest 

position must have some backset 

position in which the gap between the 

seat and the head restraint was less than 

25 mm. Second, an adjustable head 

restraint in its lowest position, with the 

backset in any position of adjustment, 

must not have a gap between the head 

restraint and the seat back of greater 

than 60 mm. 

The HRMD used for measuring 

backset has a probe that slides out of the 

center of the back of the head form. The 

probe is relatively thin laterally, and 

cannot adequately measure gaps within 

the perimeter of the head restraints and 

between the head restraint and the seat. 

Accordingly, the gaps were to be 

measured with a 165 mm diameter 

sphere placed against them. 

Gaps within the perimeter of the 

restraint. Nearly all industry 

commenters concurred with the 

proposal for a 60 mm limit for gaps 

within the perimeter of any head 

restraint, because it was consistent with 

ECE 17 requirements. There were no 

significant objections to the specific 

value of 60 mm. The Alliance indicated 

that while it did not know of any data 

supporting the need for the 60 mm gap 

limit for a seat with an integral head 

restraint, it did not object because the 

dimension matched the ECE limit. 

Honda, GM and DaimlerChrysler stated 

that they did not have any data 

addressing the 60 mm gap limits but 

supported harmonizing the requirement 

with ECE 25. 

In contrast, Advocates argued against 

allowing gaps of any size, as it was not 

convinced by the NPRM’s arguments 

pertaining to the proposed gap 

allowances. 

Agency response: NHTSA has 

adopted the 60 mm gap limit rather than 

allowing for gaps of any size in the 

perimeter of the head restraint, as is the 

case under the current standard. In 

doing so, NHTSA does not harmonize 

the final rule with the ECE regulation 

merely for the sake of harmonization, as 

Advocates alleged. Rather, the agency is 

harmonizing the requirement because 

while we believe that some gaps are 

beneficial for visibility, we also believe 

that gaps of excessive size can 

significantly reduce effectiveness of 

head restraints through effectively 

increasing backset. Absent evidence that 

the ECE 17, Paragraph 5.7 requirement 

is ineffective at balancing the need for 

adequate rearward visibility and a 

reduction in injuries, NHTSA is 

adopting the same 60 mm gap limit. 

Gaps between seat back and 

adjustable restraint. The Alliance stated 

that it did not understand why a limit 

of 25 mm would be placed on any gap 

between the top of the seat and the 

bottom of the head restraint. It stated 

that while the 25 mm gap limit is 

identical to the ECE 17 limit, the 

measurement procedure utilizing the 

165 mm diameter sphere differs from 

that in the ECE regulation. ECE 17 only 

measures the distance directly between 

the bottom of the head restraint and the 

top of the seat back. The Alliance 

recommended NHTSA adopt a linear 

measurement technique employed by 

ECE 17. 

Honda commented on gap 

requirements in ECE 25 instead of ECE 

17, and the gap limits proposed in the 

NPRM. Specifically, Honda submitted a 

figure showing that its Accord sedan 

with the head restraint in its lowest 

position complies with ECE 25 with no 

gap between the top of the seat back and 

the bottom of the head restraint. 

However, the Accord would not meet 

the proposed gap limit, because its gap 

would measure 44.8 mm. That is, the 

Accord head restraint in its lowest 

position has a 44.8 mm gap in the front 

surface between the seat back and head 

restraint when measured with the 165 

mm diameter sphere. Accordingly, 

Honda requested complete 

harmonization with the gap 

requirements in ECE 25, which would 

exclude use of the 165 mm sphere for 

this gap limit. Honda stated that some 

of its current seat designs would need 

drastic modifications in order to comply 

with the 25 mm gap limit, as measured 

with the 165 mm sphere. 

GM remarked that if NHTSA 

considers gaps of 60 mm acceptable 

within a restraint, the need for a 25 mm 

gap limit between the top of the seat and 

the bottom of the head restraint is 

unclear. DaimlerChrysler said that the 

25 mm gap limit, as applied to rear head 

restraints, could lead to an additional 

loss in visibility. DaimlerChrysler also 

stated that a head restraint making 

direct contact with the seat back with a 

15 mm radius at the head restraint’s 

bottom front contour and seat back’s top 

front contour would create a gap of 

more than 25 mm. AIAM expressed its 

support for all the proposed gap limits 

except for the 25 mm limit on gaps 

between the seat and the head restraint 

for adjustable head restraints with 

adjustable backsets. In view of this, 

AIAM argued that unless NHTSA could 

show a safety necessity for backset 

adjustability, NHTSA should only 

mandate the head restraint 

specifications independent of backset 

adjustability, provided that the 

adjustability does not have a material 

effect on height. AIAM advocated, then, 

that the final rule should require that 

the gap be less than 25 mm at any 

position of backset adjustment, which is 

more stringent than the NPRM. 

In contrast, Advocates opposed 

allowing gaps of any size between an 

adjustable head restraint and seat back 

in any position of adjustment. Johnson 

Controls expressed support for a 

universal 25 mm gap limit between the 

lower edge of a head restraint and the 

seat for both adjustable and integral 

head restraints. 

Agency response: In consideration of 

comments submitted by GM and other 

manufacturers, we have decided not to 

adopt the 25 mm maximum gap limit for 

adjustable head restraints in their lowest 

height position and a single position of 

backset adjustment. After considering 

the comments, NHTSA does not believe 

there is a safety benefit in measuring the 

smallest space between the bottom of an 

adjustable head restraint and top of the 

seat back because an occupant’s head 

does not necessarily come into contact 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74863

48We note that all head restraints subject to this 

final rule must meet the backset limit of 55 mm 

irrespective of 60 mm gap allowances.

49 In alternative, Honda recommended that we 

allow head restraint removal by use of some tool 

included with the vehicle.

with these areas. Instead, a limit on gaps 

will focus on gaps in the front surface 

of the head restraint, i.e., the area 

designed to restrain an occupant’s head 

in a rear impact collision. The 

maximum gap limit for adjustable head 

restraints in their lowest position and 

any backset position will be 60 mm. 

Thus, there is a single requirement for 

this type of gap, regardless of backset 

adjustability.48

Gaps between seat back and raised 

restraint. Comments were requested on 

whether there should be a maximum 

gap allowance between adjustable head 

restraints and the seat back when the 

restraint is in a raised position. NHTSA 

indicated in the NPRM that if such a 

maximum gap limit were adopted, most 

adjustable head restraints currently on 

the market would not meet it. 

The Alliance and Johnson Controls 

said that they did not know of any data 

supporting the need for this limit or any 

data indicating that such a requirement 

would be appropriate. DaimlerChrysler 

commented that there is not any known 

safety benefit related to such a limit. 

When head restraints are misadjusted, 

DaimlerChrysler said, they are most 

often in the full down position. Because 

a maximum gap limit between the seat 

and head restraint in its highest position 

potentially would only benefit shorter 

drivers who would most likely be 

positioned in a seat with a head 

restraint in the lowest position, 

DaimlerChrysler surmised that the 

maximum gap allowance is 

unnecessary. Taller drivers, according to 

DaimlerChrysler, would face no risks 

from this gap because their potential 

risks exist in head restraints not 

positioned high enough, not in head 

restraints adjusted too high. 

AIAM also commented with respect 

to the effect of a maximum gap limit on 

taller or shorter drivers. It commented 

that if a seat represents the lower stop 

of a head restraint for which the highest 

possible position is 800 mm, the gap 

could only be 50 mm unless a head 

restraint provides for positions higher 

than 800 mm. If higher positions are 

possible, AIAM asserted that such a 

head restraint would only be positioned 

higher than 800 mm when a taller 

person occupies the seat. AIAM 

acknowledged that there might be 

instances in which a shorter person sits 

in a seat with a head restraint adjusted 

in the higher position, but it commented 

that in such instances, the likelihood of 

injury to shorter occupants is unknown. 

Advocates believed that NHTSA 

should require adjustable head restraint 

designs such that no gap would exist 

when the head restraint is placed in its 

uppermost position. 

Agency response: After considering 

the comments, NHTSA concludes that 

there is no need to adopt a maximum 

gap limit when the head restraint is in 

its uppermost position. Transport 

Canada data indicate that head 

restraints are usually improperly 

adjusted too low rather than too high. 

AIAM’s comment suggests that any 

minimum gap limit could have the 

effect of eliminating head restraint 

designs providing positions higher than 

800 mm, which would adversely affect 

the protection offered for taller adults. 

b. Removability 

The NPRM proposed prohibiting the 

removability of head restraints in front 

seats ‘‘solely by hand,’’ but allowed 

removability of rear seat head restraints 

in this manner. The NPRM noted that, 

given the lower occupancy rate of rear 

seats than of front seats, a rule allowing 

rear seat head restraints to be removed 

by hand might be warranted if it would 

have a positive effect on visibility. 

A number of commenters opposed 

any prohibition against the removability 

of head restraints, front or rear. AIAM 

asserted that all head restraints should 

be removable by hand in order to 

improve rear vision, cargo carrying, and 

overall functionality. In addition, it 

contended that allowing removability by 

hand would help prevent permanent 

damage to head restraint mountings 

caused when occupants use tools to 

temporarily remove head restraints that 

are non-removable by hand. Nissan 

asserted that there are potential 

production difficulties arising from 

front head restraint non-removability. 

Installing a large seat fitted with a head 

restraint into a small vehicle, Nissan 

asserted, might be an arduous task. 

Honda wanted all restraints to be 

removable by hand, out of concern that 

non-removable head restraints would 

limit seat design flexibility. Honda 

believed that a non-removability 

prohibition would prevent it from 

offering the ‘‘fully flat seat’’ option in its 

CRV model vehicle.49

In contrast, some commenters 

supported prohibiting head restraints 

from being removable by hand. Magna 

expressed concern that if head restraints 

were removable, they might not be 

replaced or correctly reinstalled. 

Advocates believed that head restraint 

removal and misuse would be similar to 

occupants placing both arms over 

shoulder belts or placing shoulder belts 

behind their torsos, effectively defeating 

the safety purposes of the safety system. 

DaimlerChrysler concurred with making 

front seat head restraints more difficult 

to remove than rear seat restraints 

because of their safety benefits and the 

absence of a need to remove them for 

visibility and functionality reasons. 

DaimlerChrysler also agreed that there 

should be some means to remove front 

head restraints for purposes such as seat 

cover installation. However, 

DaimlerChrysler wanted the word 

‘‘tool’’ to be interpreted as including the 

mechanism in their current vehicles 

requiring two hands to operate.

A majority of industry commenters 

wanted NHTSA to allow removability of 

rear head restraints in the final rule. 

Ford believed that removability of rear 

head restraints would allow occupants 

to fold seats to increase space and 

would reduce possible incompatibility 

with child restraints. Ford stated that 

while many vehicles are currently 

designed with head restraints that are 

removable by hand, Ford does not know 

of any data regarding misuse or 

improper adjustment of head restraints 

caused by hand removability. 

DaimlerChrysler believed that NHTSA 

should permit rear seat head restraint 

removability to facilitate increased 

vehicle utility and rearward visibility. 

Agency response to comments on 

head restraint removability: After 

considering comments, NHTSA decided 

to allow removability of head restraints 

solely by hand. However, for both front 

and rear optional head restraints, 

removal must be by means of a 

deliberate action that is distinct from 

any act necessary for adjustment. That 

is, the ‘‘action’’ required for removal 

must be distinct from that required for 

adjustment. For example, the head 

restraint may be removed by depressing 

a special button or operating a lever 

located somewhere on the head restraint 

or the seat back. However, the action 

involved in adjusting head restraints 

must be different. This insures that head 

restraints are not accidentally removed 

when being adjusted. The new 

removability requirement uses language 

very similar to that in ECE 17, Paragraph 

5.13. 

We are establishing the new head 

restraint requirements to ensure that 

vehicle occupants receive better 

protection from whiplash and related 

injuries. To achieve this purpose, the 

agency wants to take reasonable steps to 

increase the likelihood that a head 

restraint is available when needed. If 

head restraints were too easily 

74864 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

removable, chances are greater that they 

will be removed. That, in turn, increases 

the chances that the restraints might not 

be reinstalled correctly, if at all. By 

prohibiting removability without the 

use of deliberate action distinct from 

any act necessary for adjustment, the 

likelihood of inadvertent head restraint 

removal will be reduced, thus 

increasing the chances that vehicle 

occupants will receive the benefits of 

properly positioned head restraints. 

While NHTSA wants to increase the 

likelihood that a head restraint is 

available when needed, we also want to 

ensure that head restraints, especially in 

the rear outboard designated seating 

positions, can be removed in order to 

improve rear visibility, child restraint 

accommodation, and cargo carrying 

capacity. In certain very limited 

circumstances discussed by 

DaimlerChrysler, it may also be 

necessary to remove front head 

restraints. We are also persuaded by 

AIAM’s comments concerning potential 

damage to head restraint mountings and 

locking mechanism that could be caused 

by occupants using a tool to temporarily 

remove the head restraints. Further, we 

believe that unforeseen problems could 

arise if the tool provided by the 

manufacturer for the purpose of 

removing head restraints is lost or 

otherwise unavailable at the time the 

head restraint must be removed. 

Because of these concerns, we decided 

not to adopt a proposed requirement 

that would have mandated that head 

restraints could not be removed without 

the use of a tool. 

We have considered Advocates’

comments that head restraint removal 

would defeat the purpose of the safety 

device. We believe that out approach 

strikes a balance between the need to 

ensure that a head restraint is available 

when needed and the need to improve 

rear visibility, cargo carrying capacity 

and accommodate child restraints. 

Further, with respect to rear seats, 

prohibiting head restraint removal when 

no head restraint is required could have 

the effect of encouraging manufacturers 

to design vehicles without rear head 

restraints. Our preference is that when 

possible, manufacturers install optional 

rear head restraints. 

c. Non-use Positions 

In connection with its proposal to 

mandate rear head restraints, NHTSA 

proposed to address concerns about the 

potential effect of those head restraints 

on the driver’s view to the rear by 

allowing them to be foldable or 

retractable if they met certain 

requirements. Specifically, if a head 

restraint was adjusted to a ‘‘non-use’’

position (any position in which a head 

restraint’s minimum height was less 

than the proposed 750 mm height or its 

backset was more than the 50 mm 

proposed backset), it would have been 

required to either return automatically 

to its proper use position when a 

dummy representing a person was 

placed in the seat, or give a person who 

occupied the seat an ‘‘unambiguous 

physical cue’’ of the improper head 

restraint position by significantly 

altering the torso angle of the occupant. 

If the head restraint was designed to 

return automatically from a non-use 

position to a normal use position, this 

had to occur when either a 5th 

percentile female or a 50th percentile 

male test dummy was placed in the 

seating position. To determine if the 

head restraint in a non-use position 

provided an ‘‘unambiguous physical 

cue,’’ the SAE J826 manikin was to be 

placed in the seat position. The torso 

angle of the manikin would have been 

required to be at least 10 degrees closer 

to the vertical than when the head 

restraint was in a normal use position. 

Industry commenters uniformly 

favored a final rule permitting non-use 

positions for rear head restraints. 

However, many stated that because nonuse positions in current vehicle designs 

are obvious to occupants, NHTSA need 

not condition allowance of those 

positions upon either automatic 

repositioning or 10-degree torso angle 

displacement. GM contended that 

designing head restraints to fold forward 

into non-use positions is not always 

feasible, especially given the proposed 

254 mm minimum rear head restraint 

width for bench seats. GM, Honda and 

others remarked that folding or 

retractable head restraints with 

automatic return capabilities might not 

be practical and could result in 

excessive cost. 

Other commenters asked NHTSA to 

permit methods different from the 10-

degree torso displacement angle to alert 

vehicle occupants to non-use head 

restraint positioning. Specifically, VW 

and Honda advocated harmonization 

with ECE 17, Paragraph 5.5.3.3, which 

allows for head restraints to be retracted 

into non-use positions as long as this 

position is ‘‘clearly recognizable to the 

occupant.’’ Similarly, Ford stated it 

believed that the NPRM’s 10-degree 

proposed displacement rule would be 

excessively burdensome and would 

require substantial redesign of seating 

systems. 

Several commenters opposed 

allowing non-use positions. State Farm 

suggested that NHTSA should only 

permit non-use positions for rear head 

restraints if NHTSA determines either 

visibility or child restraint 

incompatibility are issues meriting 

consideration. Advocates noted that 

automatically retracting or manually 

folding head restraints might 

malfunction or become stuck in a nonuse position. Advocates opposed the 

proposal to the extent that it did not 

specifically require that non-use 

positions for rear head restraints remain 

limited to ones achieved by folding or 

retracting. Moreover, Advocates 

expressed doubt about the objectivity of 

the ‘‘unambiguous physical cue’’ as an 

occupant’s indication of a non-use 

position, stating that the subjective 

standard would create the potential for 

ambiguous designs that would give rise 

to misuse.

Transport Canada and Honda asserted 

that forward-folding head restraint 

designs might be misused in that an 

occupant may sit in the seat without 

returning the head restraint to an in-use 

position. Honda commented that 

smaller occupants might not recognize 

that the seating position moved 10 

degrees closer to vertical is a warning of 

a non-use position. Instead, according to 

Honda, smaller stature occupants might 

consider the more upright position 

comfortable without understanding that 

the head restraint was positioned for 

non-use. In addition, Transport Canada 

stated that the proposal to require 

manufacturers to design their head 

restraints so that the torso angle of the 

SAE J826 manikin at least 10 degrees 

changes when the head restraint is in a 

non-use position might bring about a 

low fulcrum, which would increase 

neck injury in a rear impact collision. 

Agency response: NHTSA does not 

believe that non-use positions for rear 

head restraints should be allowed 

without any limitations. Instead, there 

must be objective performance 

requirements established to reduce the 

chances of injuries stemming from 

misused head restraints. Accordingly, 

the final rule adopts non-use position 

requirements proposed in the NPRM, 

but with some modifications. Further, 

this rule changes the test procedure and 

the test device to be used in determining 

compliance. Specifically, we are 

adopting the following: (1) A head 

restraint in a non-use position must 

automatically return to a normal ‘‘use 

position’’ when the seat is occupied by 

a 5th percentile female dummy whose 

midsagittal plane is aligned within 15 

mm of the head restraint centerline; or 

(2) a head restraint must be capable of 

manually rotating at least 60 degrees 

forward or rearward in a vehicle vertical 

longitudinal plane between the ‘‘use 

position’’ and the non-use position. 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74865

50We believe Advocates’ statement that 

automatic return head restraints may fail to 

function overstates the safety concern. Although 

such failures are possible, they can occur with any 

safety mechanism.

51We note that Volvo uses such a design in their 

S60 and S80 sedans.

52For an 800 mm high head restraint, the 373 Nm 

moment is achieved by applying a load 65 mm 

below the top of the head restraint. Thus the 

applied load is 507 N = 373 Nm/0.735 m.

The final rule does not require that 

the non-use positions cause a 10-degree 

change of the torso angle of the J826 

manikin. Our proposal was based on the 

premise that the non-use position 

should give the occupant an obvious 

physical cue when the head restraint is 

not properly positioned. We have 

reassessed this requirement in light of 

our decision not to mandate rear head 

restraints and to allow head restraints to 

be removable without the use of tools. 

Given those decisions, it would be 

incongruous to mandate a possibly 

complex seat mechanism to ensure that 

non-use positions provide a physical 

cue to the occupant in the form of a 10-

degree change to the torso reference 

angle. The changes to the non-use 

position requirements will also address 

comments made by Ford, GM and 

Transport Canada with respect to 

complexity, inconvenience and possible 

neck injury risk increase associated with 

the proposed requirement of 10 degree 

change in the torso reference angle. 

We note that our requirements remain 

consistent with the ECE 17, Paragraph 

5.5.3.3 to the extent that it mandates 

that a head restraint be capable of 

achieving a non-use position that is 

‘‘clearly recognizable to the occupant.’’

With respect to Advocates’ concerns 

that the ‘‘unambiguous physical cue’’

language in the NPRM was subjective, 

we note that unlike the ECE 

requirements, this rule provides an 

objective test procedure to assess the 

‘‘clearly recognizable’’ factor. 

Specifically, if the head restraint is 

capable of rotating forward or rearward 

by at least 60 degrees to achieve a nonuse position, it is deemed ‘‘clearly’’ in 

a non-use position. This restriction is 

necessary to clearly inform the occupant 

that the head restraint is available, but 

out of place. 

The final rule does not require that 

the rear head restraint automatically 

rotates the full 60 degrees or that the 

head restraint remains in this fully 

retracted position. In order to meet the 

strength requirements of this final rule, 

a head restraint that rotates rearward 

would likely need to have some 

mechanism that releases the head 

restraint from the position intended for 

occupant use. Accordingly, the head 

restraint would only be placed in a nonuse position because of a particular 

need. It is possible that some vehicle 

operators may not rotate such head 

restraint fully. However, we believe in 

most instances the rear head restraint 

would be rotated the entire 60 degrees 

because this would best accommodate 

the vehicle operator’s particular interest 

in adjusting the head restraint to a nonuse position. 

For head restraints that automatically 

return to a use position when occupied, 

the final rule does not require the use 

of a 50th percentile male dummy in 

addition to the 5th percentile female 

dummy, as was the case in the NPRM. 

Based on our review of current sensing 

technology, we assume the head 

restraint systems that will be designed 

to automatically return to a normal use 

position when a seat becomes occupied 

will use weight or optically based 

occupant-sensing technology. Thus, the 

use of the taller and heavier 50th 

percentile male dummy would be 

redundant since it would be more 

difficult to detect the shorter and lighter 

5th percentile female dummy.50

In response to Transport Canada and 

Honda’s concern with respect to foldforward designs, we note that non-use 

positions can be achieved by means 

other than fold-forward head restraints. 

Further, in allowing this type of design, 

we anticipate that a forward-folded head 

restraint will provide both a physical 

and visual cue to the occupant to 

properly position the head restraint.51

NHTSA concludes that the allowing 

for non-use positions will facilitate 

better rearward visibility because the 

manufacturers will be able to design 

optional rear head restraints that fold or 

retract when rear seats are unoccupied, 

encouraging manufacturers to install 

rear head restraints. 

X. Position Retention 

In the NPRM, we proposed two 

loading test procedures to ensure that 

the head restraints remain in their 

position of adjustment (lock) upon 

application of force. These test 

procedures ensure that the head 

restraints can withstand the forces 

associated with normal pressure applied 

upon the head restraint during ingress 

and egress, as well as in the event of a 

crash. We note that while the ECE 17, 

Paragraph 5.1.1 requires locks on 

adjustable head restraints, it does not 

mandate that these locks meet vertical 

and horizontal position retention 

requirements to insure their 

functionality. In contrast, we proposed 

vertical and horizontal position 

retention requirements to ensure test 

objectivity associated with retention 

lock requirements. 

The first test provided for the vertical, 

downward application of force upon a 

head restraint when placed at its highest 

position of adjustment and not less 

than, but closest to 800 mm for front 

seats and 750 mm for rear seats. A head 

restraint with an adjustable backset 

must meet the height retention 

requirements in any position of 

adjustment. Under the proposed 

procedure, a small, 50 N initial load 

would first be applied to the head 

restraint to provide a reference position 

for the head restraint. The reference 

position would be measured to 

eliminate variability associated with the 

soft upholstery of the head restraint. 

Next, a larger load would be applied to 

test the locking mechanism. The load 

would be increased to 500 N and held 

for 5 seconds. The load would then be 

reduced to the level of 50 N, at which 

point the head restraint would be 

required to return to within 13 mm of 

the initial reference position. 

The second test procedure provided 

for a rear (posterior—rear with respect 

to the direction that the seat is facing) 

application of force perpendicular to the 

torso line. Testing for this position 

retention requirement to the rear is 

performed in the context of the 

displacement and ultimate strength 

requirements. This test is performed at 

any position of backset adjustment (if 

applicable) with the height adjusted to 

not less than, but closest to 800 mm for 

front seats and 750 mm for rear seats. In 

this instance, the NPRM proposed that 

a load producing a 373 Nm moment be 

applied to the back pan about the Hpoint to establish a displaced torso 

reference line. Next, a force producing 

37 Nm would be applied to the head 

restraint to provide a reference position. 

The load would then be increased until 

it produced 373 Nm moment about the 

H-point and this load would be held for 

5 seconds. At this point, any 

displacement beyond the displaced 

torso reference line would be limited to 

102 mm. The head restraint load would 

then be reduced back to the level of 37 

Nm, at which point the head restraint 

must return to within 13 mm of the 

initial reference position. To satisfy the 

ultimate strength requirement, the head 

restraints must be capable of providing 

resistance to an 890 N load for a period 

of 5 seconds. 

We stated in the NPRM that the 500 

N downward force and 373 Nm 52

rearward moment are representative of 

the peak loads likely to be encountered 

in moderate to severe rear impacts. The 

agency has reviewed upper neck shear 

loading from 33 rigid moving barrier, 

74866 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

53 Volkswagen also commented on the backset 

retention requirement. They asked that the agency 

clarify their interpretation that the initial reference 

position to which that the test device must return 

within 10 mm (now 13 mm in the final rule) is the 

position the test device obtains after the 37 Nm 

reference load. The agency confirms this 

interpretation of the test procedure.

rear impact (48 km/h (30 mph)) FMVSS 

No. 301 tests and found the average 

maximum load caused by the head 

being loaded in the forward direction 

with respect to the torso is 351 N. This 

direction of shear load is a good 

indicator of head restraint loading on 

the head and, therefore, head loading on 

the head restraint. Thus, the 373 Nm 

rearward moment and 500 N downward 

force are representative of the peak 

loads likely to be encountered in 

moderate to severe rear impacts. We 

asked for comments on the 

appropriateness of load values proposed 

for the two tests as well as the role of 

the retention locks in preventing head 

restraint maladjustment.

Several commenters disagreed with 

the proposed height retention test 

requirement. Johnson Controls 

commented that it is unaware of any 

situations in which head restraints 

would move downward during 

accidents and thus does not understand 

the need for the vertical position 

retention test. In its opinion, the new 

requirement would unnecessarily 

complicate the locking adjustment 

mechanism, which consumers already 

find hard to use. Other commenters 

requested that NHTSA alter or simplify 

its height retention requirement. GM 

recommended that the testing criteria 

require that the head restraints simply 

‘‘remain in their adjusted position’’ after 

an application of the required loads. 

According to GM, a more specific 

requirement that the head restraint be 

within 10 mm of its initial position, 

after position retention tests, might be 

difficult to meet because of possible 

compression of the head restraint foam. 

Similarly, DaimlerChrysler stated that 

the proposed height-retention test is 

inadequate to account for low recovery 

rate of crushable ‘‘friendly’’ materials 

designed to cushion an occupant’s head 

upon contact. 

Both Magna Seating Systems and 

DaimlerChrysler submitted the same test 

data showing a vertical load test in 

which an upholstered head restraint 

returned to within 22 mm of its initial 

position. The same head restraint with 

the upholstery removed returned to 

within 1 mm of its initial position. 

According to DaimlerChrysler, instead 

of testing the adjustment mechanism 

integrity, the proposed test indirectly 

measures the entire seating system, 

which includes energy-absorbing 

components. Therefore, a more 

appropriate solution is to simply 

measure head restraint position at the 

adjuster mechanism. Additionally, 

DaimlerChrysler stated that 500 N 

vertical load for position retention test 

may be excessive and unnecessarily 

harsh, and may end up requiring 

manufacturers to produce seats that are 

unnecessarily rigid and would result in 

potential harm to the passengers. 

The Alliance generally agreed with 

most aspects of the proposed head 

restraint loading procedure. However, it 

was not aware of any reasons for the 5-

second ‘‘hold’’ requirement in the 

position retention test. The Alliance 

recommended that the ‘‘hold’’

requirement be completely stricken or, 

in the alternative, limited to one second. 

AIAM was likewise of the opinion that 

the stringent height retention 

requirements would in fact discourage 

adjustability, because a mechanism 

meeting such requirements would be 

unduly difficult to design and use. 

Therefore, it recommended that the 

height retention requirement be 

eliminated from the proposed rule. 

Honda commented that the problem 

with the vertical load test procedure is 

the shape and initial position of the 

loading device. Honda believed that this 

would cause the loading sphere to slip 

off of the head restraint. Honda 

recommended that loading test for 

height retention requirement be 

performed using a flat plate as opposed 

to a head form. Honda commented that 

no further height retention position 

testing (other than upper most position) 

should be tested, because the upper 

most position can be regarded as the 

worst position.

VW stated, ‘‘[s]ome Volkswagen and 

Audi vehicles provide head restraint 

adjustment above 800 mm to 

accommodate tall occupants, but in this 

situation a locking system at the 

maximum height is not provided.’’ They 

requested that the height retention 

requirement not be applied to position 

of adjustment above 800 mm. They 

contended that when a seat back is 

folded the head restraint might interfere 

with the roof and cause damage to a 

locked head restraint.53

In contrast, IIHS commented that the 

height retention test is necessary to 

prevent poor head restraint designs that, 

for example, tend to ‘‘fall’’ to their 

lowest position during normal road 

movement. IIHS cautioned that many 

occupants place their hand or arm on 

the head restraints in getting into and 

out of the vehicles, thus applying 

vertical and non-vertical pressure on the 

restraint mechanism. 

There were no comments regarding 

the likelihood of misadjustment due to 

the absence of retention locks. There 

were no comments regarding the 

horizontal displacement requirement, 

other than the IIHS comment that the 

NPRM did not propose a horizontal 

loading requirement. 

Agency response: We have decided to 

adopt the position retention tests, both 

in the vertical and rearward directions, 

largely as proposed. As previously 

stated, ECE 17 requires locks on 

adjustable head restraints but does not 

mandate that these locks meet vertical 

and horizontal position retention 

requirements to insure their 

functionality. However, we find it 

necessary to require a certain minimal 

level of performance to ensure that the 

retention locks perform their function. 

Accordingly, the vertical and horizontal 

position retention requirements of this 

final rule apply to all front outboard 

head restraints and voluntarily installed 

rear outboard head restraints. 

We proposed performance 

requirements for adjustable head 

restraints to assure that they remain 

locked in a specific position and are not 

unduly difficult to properly adjust. A 

1982 NHTSA study found that the 

effectiveness of integral head restraints 

was greater than adjustable head 

restraints. The study concluded that the 

difference in effectiveness was due, in 

part, to adjustable head restraints being 

improperly positioned. Furthermore 

adjustable restraints can be pushed 

down inadvertently during occupant 

ingress and egress, and can collapse in 

a collision. Adjustment retention locks 

can mitigate this problem by helping to 

retain the adjusted position. Our new 

height and backset requirements are 

expected to improve performance of all 

head restraints. The performance of 

adjustable head restraints will be further 

improved if steps are taken to ensure 

that a restraint remains locked in a 

position selected by the user. 

Today’s rule requires that the head 

restraints remain within 13 mm of their 

vertical and horizontal position under 

the application of a downward and 

rearward force. For front seats, the 

height position retention requirements 

must be met at any backset position of 

adjustment and with the head restraint 

at a height not less than, but closest to 

800 mm, and at the highest position of 

vertical adjustment. For optional rear 

seats, the height position retention 

requirements must be satisfied at a 

height not less than, but closest to 750 

mm and at the highest position of 

vertical adjustment. The horizontal 

position retention requirements must be 

met at the height of 800 mm for front 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74867

54For complete test results, please see Docket No. 

NHTSA–2000–8570–60, 61, 62, 63, 64.

head restraints and 750 mm for rear 

head restraints. 

We are not persuaded by the 

arguments presented by GM and the 

Alliance related to the load hold time of 

five seconds. These commenters argue 

that a 5 second hold time is not 

consistent with ECE 17 requirements. 

Instead, they suggest a one second limit. 

We believe the ECE requirements are 

insufficient in this regard in that they do 

not specify a loading rate or hold time. 

Despite our attempts to bring the new 

rule into harmony with the ECE 

regulations when adopting a 

requirement already covered by the 

ECE, there are instances in which we 

need to further clarify the test 

compliance procedure to provide an 

objective measurement, as required by 

statute. This is one of those instances. 

We do not believe a 5 second hold 

period is onerous and have adopted it 

as part of the final rule. We further note 

availability of strong and properly 

functioning retention locks should not 

have any negative effect on occupants’

ability to properly adjust their head 

restraints. 

We disagree with VW’s objection to 

head restraints locking in the highest 

adjusted position above 800 mm. To the 

extent that such an adjustment position 

is provided, it would be intended to 

protect the tallest occupants. However, 

without the ability to lock in this 

position, the head restraint could slip 

down to the 800 mm position or 

perhaps even lower during normal use, 

or in a rear impact. Thus, the head 

restraint would not offer the intended 

protection, while giving these taller 

occupants the impression that they are 

well protected. We are not persuaded by 

Volkswagen’s argument that the locking 

mechanism may be damaged if the front 

seat head restraint comes in contact 

with the vehicle roof when folded 

forward for rear seat access. We 

acknowledge that in some vehicles this 

interference between the roof and head 

restraint may exist. In fact, such 

interference may exist between rear seat 

head restraints and more forward seats. 

However, we are not convinced that 

such contact would be damaging to the 

locking mechanism. If a manufacturer 

were concerned about damage to their 

locking mechanism, two solutions 

would be to either increase the 

robustness of the lock or to decrease the 

spring load in the seat back folding 

mechanism. Another design alternative 

discussed above in the context of nonuse positions, although more 

mechanically involved, would be a 

design that disengages both the seat 

back and head restraint simultaneously. 

We proposed a 10 mm performance 

limit on the return position of the actual 

loading device to the reference point 

because we considered this to be the 

most objective method of determining 

the actual performance of locks. Some 

vertical loading data provided by the 

industry indicated a return position as 

much as 22 mm from the initial 

position. No similar data were provided 

for the horizontal loading test. In order 

to verify that the performance value 

selected for the position retention 

requirement is reasonable, we 

performed a series of static tests on 

several seats. The tests were performed 

at General Testing Laboratories (GTL), 

under the FMVSS No. 202 compliancetesting contract. The tests were 

performed in January 2002, on five MY 

2001 vehicles.54

The test program assessed the ability 

of current head restraint designs to 

comply with the position retention 

requirements. We tested feasibility of 

the 10 mm limit on displacement from 

the initial position. Both the height 

retention and backset retention were 

tested. (See Table 1.) All head restraints 

were vertically adjustable and one 

(Mercedes E320) had rotational 

adjustment.

Table 1 shows the results of the height 

position retention tests and Table 2 

shows the result of the backset position 

retention tests. One determination made 

by analysis of the test results was that 

the head restraint should not be allowed 

to displace more than 25 mm during the 

application of a pre-load to account for 

foam compression and other mechanical 

tolerances in the head restraint 

attachment as well as the situation in 

which the locking mechanism is so 

weak it cannot resist the preload. 

The test results suggest that the 

backset displacement is less than the 

height displacement if the 

characteristics of the vehicle seat are 

accounted for. Therefore, if a single 

compliance value is selected for both 

the backset and height retention, we 

believe it is reasonable to allow the 

results of the height retention tests to 

drive the selection. However, if one 

does not account for seat characteristics, 

the horizontal displacement may be 

larger because of those characteristics. 

Based on this limited data set, we 

believe that it is reasonable to alter the 

position retention tests to allow the seat 

back frame to be braced. Further, we 

have determined that the displacement 

limit after full load and return to 

preload should be increased to 13 mm 

from 10 mm. We believe using the limit 

of 13 mm would allow most vehicles to 

comfortably meet the requirement for 

both the height and backset retention. 

Therefore, we do not agree with 

DaimlerChysler’s comments that 

suggested the 500 N vertical load for the 

position retention test is excessive.

TABLE 1.—HEIGHT POSITION RETENTION, FINAL DISPLACEMENT VALUES (MM) 

Reference load Vehicle model Final displacement

(mm) 

50 N—not braced .............................................. Mercedes E320 ................................................ 6.4 

50 N—not braced .............................................. Honda Civic ...................................................... 21.8 

50 N—braced .................................................... Toyota Echo ..................................................... 11.4 

100 N—not braced ............................................ Dodge Stratus .................................................. 24.0

100 N—braced .................................................. Buick LeSabre* ................................................. Moved at Reference Load†

* Detents but no locking mechanism. 

† No lock. 

74868 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

TABLE 2.—BACKSET POSITION RETENTION, FINAL DISPLACEMENT VALUES

(MM) 

Reference 

load Vehicle model 

Final displacement

(mm) 

50 N—not 

braced.

Mercedes 

320. 

10.9‡

50 N—not 

braced.

Honda Civic. 10.6 

50 N—braced Toyota Echo. 6.9 

100 N—not 

braced.

Dodge Stratus. 24.0 

100 N—

braced.

Buick 

LeSabre*. 

20.3†

‡ Rotational Adjustment. 

* Detents but no locking mechanism. 

† No Lock. 

In response to comments provided by 

Honda, we believe that the vertical load 

test can be improved by replacing the 

loading sphere with a loading cylinder 

measuring 165 mm in diameter and 152 

mm in length. We believe that any 

potential slippage of the head restraint 

with respect to the loading sphere, if it 

were to occur, would be primarily in the 

longitudinal direction. Since the long 

axis of the cylinder will be oriented in 

the vehicle longitudinal direction, the 

potential of slippage will be 

substantially reduced. Further, we have 

no experience with using a flat plate as 

the loading device, while the loading 

cylinder is currently an option in 

FMVSS No. 202. The cylinder is to be 

loaded at the point on the head restraint 

with the greatest vertical position, rather 

than at the ‘‘top’’ as previously defined 

in the standard. The term ‘‘top’’ has 

been defined as the highest point of the 

head restraint at which a plane that is 

perpendicular to the torso reference line 

of the J826 manikin intersects the head 

restraint. For the backset position 

retention loading test, however, the 

lower edge of the cylinder may inhibit 

the return of the head restraint during 

the unloading phase. Therefore the 

loading sphere, positioned 

perpendicular to the torso line, will be 

kept for this test. 

We believe that DaimlerChrysler’s 

comments related to upholstery crush 

and Honda’s comments related to the 

loading sphere slipping might have 

merit. However, we disagree with the 

commenters who have suggested that 

these issues can be resolved by simply 

specifying that the head restraint stay in 

its pre-load adjusted position. Although 

similar wording is used in other 

regulations, including Standard No. 207, 

such a performance requirement can in 

certain instances be difficult to enforce. 

We acknowledge that removing the head 

restraint upholstery and loading only 

the underlying structure would make it 

easier to determine lock failure and 

would remove the foam variability from 

the test. However, this would not be a 

realistic way of loading the head 

restraint and may, in fact, change the 

path of loading. We also note that 

measuring the movement of the loading 

device instead of directly measuring the 

head restraint (pre- and post-condition) 

produces more accurate measurements 

for compliance purposes. 

We believe that the proposed height 

and backset position retention 

requirements are comprehensive and 

that requirements for other positions 

than those mentioned above are 

unnecessary and would not result in 

significant additional safety benefits. 

We note, however, that manufacturers 

are not precluded from providing 

additional lockable positions within the 

range of the head restraint adjustment. 

XI. Energy Absorption

The NPRM proposed that a specified 

area of the head restraint would have to 

limit the deceleration of a 6.8 kg mass 

impactor, traveling at 24.1 km/h, to 80 

g’s. The impactor was a free-motion 

head form. In addition, we proposed 

that any portion of the head restraint 

that was outside of the impact area and 

that had a radius of curvature of less 

than 5 mm would be required to pass 

the energy absorption test. We requested 

comments on whether a free-motion 

head form was an appropriate testing 

device and whether the radius of 

curvature requirement was necessary. 

Impactor. Industry commenters were 

unanimous in their desire for the use of 

the pendulum impactor instead of the 

free-motion head form. Johnson 

Controls and Honda suggested that the 

use of a pendulum impactor, as 

specified in ECE 17, Paragraph 5.1.3, is 

preferable to the use of a free-motion 

impactor for the energy absorption 

compliance testing. According to 

Honda, the primary reason for the 

desirability of the pendulum impactor is 

that conducting testing using this device 

would allow the manufacturers to use 

existing testing facilities and equipment. 

Agency response: In proposing the 

free-motion head form, we intended to 

simplify the ECE energy absorption test 

by making the impactor similar to that 

used for the upper interior impact 

portion of Standard No. 201. We also 

attempted to assure consistency with 

the ECE testing results by making the 

mass of the proposed free-motion 

impactor identical to that of the ECE 17 

pendulum impactor (6.8 kg). 

We have decided to adopt a linear 

impactor, as opposed to a pendulum 

impactor or free-motion head form, as 

the compliance tool. Our decision was 

based on several factors. First, the use 

of a pendulum impactor could prevent 

us from running compliance tests on the 

actual vehicle without significant 

vehicle alteration, because of the 

interference of the vehicle interior with 

that type of impactor. If, as suggested by 

the manufacturers, a pendulum 

impactor were used, the seats would 

either have to be removed to allow for 

the pendulum swing or the roof of the 

vehicle would have to be cut open. 

Because of the cost involved, we often 

use the same vehicle to run multiple 

compliance tests. Removing seats or 

cutting into the vehicle to accommodate 

test equipment would limit our ability 

to run subsequent compliance tests for 

other standards. 

Second, the differences between the 

linear impactor and free-motion 

impactor are insignificant in terms of 

their ability to measure compliance with 

the energy absorption requirement. The 

linear impactor is constrained so that it 

moves along a line, while the freemotion impactor is free to rotate upon 

impact or to have a rotation imposed 

upon it at the time of launch. This 

unconstrained motion is beneficial for 

use with types of impactors that have an 

irregular surface, such as a surface 

simulating a human face. However, 

since the impactor for the energy 

absorption test is spherical, there is no 

need for the free motion. 

Third, the linear impactor is easier to 

target than the free motion head form, 

leading to more repeatable results. 

Currently, a linear impactor is used for 

the instrument panel and seat back 

impact testing under Standard No. 201. 

Fourth, we believe that the results 

obtained from a linear impactor will in 

fact be very similar to the results 

obtained from a pendulum impactor or 

free-motion impactor because the 

impactors have the same mass and 

impact velocity. 

Radius of curvature. We proposed an 

energy absorption requirement for all 

surfaces with less than a 5 mm radius 

of curvature to eliminate potential 

sources of high-pressure contacts 

between occupants and head restraints. 

We have decided against adopting this 

requirement. 

The Alliance stated that it is unaware 

of a need for a ‘‘radius of curvature of 

less than 5 mm requirement,’’ and 

recommended its deletion. Honda 

commented that the ECE 25 requirement 

for 5 mm radius of curvature limit is 

intended to apply to unpadded 

structures or structures padded with 

material softer than 50 Shore A 

hardness. 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74869

55 GM’s concern that rear head restraints will 

affect compliance with FMVSS No. 111 is not 

warranted because head restraints are an allowable 

obstruction. In addition, if the rear window field of 

view requirements are not met, compliance could 

be achieved by adding passenger side outside 

mirrors. These side mirrors are standard equipment 

on most vehicles.

56As discussed in a later section, the rule does 

not provide Honda’s suggested additional lead time. 57See 66 FR 963 at 981. 58By contrast, the cost per equivalent life saved 

for voluntarily installed rear head restraints is $4.71 

million.

59We further note that approximately 2 percent 

of rear seat occupants sit in the center seating 

positions.

60We estimated that equipping rear seats with 

head restraints would result in the annual costs of 

approximately $103 million.

Agency response: In our opinion, the 

burden associated with the enforcement 

of this requirement outweighs its 

benefits. In order to determine that 

structures with the soft upholstery have 

radii of less than 5 mm, we would be 

forced to remove the soft upholstery. 

Thereafter, a second, upholstered head 

restraint would have to be subjected to 

the impact test. No commenter provided 

information supporting such a 

requirement. Accordingly, we are not 

adopting our proposal regarding areas 

on the front surface of the head restraint 

that are outside of the impact area. 

As previously discussed, this final 

rule does not mandate rear outboard 

head restraints. However, this rule does 

require that the voluntarily installed 

rear outboard head restraints meet the 

energy absorption requirements 

discussed above. 

XII. Issues Unique to Rear Head 

Restraints 

a. Optional Head Restraints for Rear 

Seating Positions 

The NPRM proposed mandating head 

restraints for all rear outboard seating 

positions, but asked whether NHTSA 

should limit the final rule to front 

seating positions. This question was 

based on visibility concerns as well as 

the lower safety benefits that would be 

obtained from rear seat head restraints, 

as compared to those from front seat 

head restraints, given lower occupancy 

rates for rear seats. Most of the industry 

commenters stated that, consistent with 

ECE 17, rear head restraints should 

remain optional. ECE 17 treats rear head 

restraints as an option, but regulates 

them if they are installed in a vehicle. 

Johnson Controls reasoned that because 

the dangers for rear seat occupants are 

less than those for front seat occupants, 

rear head restraints should not be 

mandated. GM, the Alliance, and others 

believed that rear head restraints should 

be an option because of rear seats’ lower 

occupancy rates, occupancy of rear seats 

usually by shorter individuals, potential 

child seat interference with rear head 

restraints, and the potential reduction of 

direct and indirect rear vision. In 

supplemental comments, GM stated its 

concern that rear seat head restraints 

will affect its ability to comply with the 

requirements of FMVSS No. 111, Rear 

View Mirrors.55

In contrast, Magna, Honda, 

Advocates, and the FIU students 

commented that NHTSA should 

mandate rear seat head restraints in 

addition to front seat head restraints. 

Magna stated that rear seats are 

designed to accommodate occupants 

ranging in size from the 5th percentile 

female to the 95th percentile male. 

Accordingly, Magna maintained that 

head restraints should support the 

entire range of rear seat occupants. 

Honda requested an additional three 

years of lead time to comply with the 

rear head restraint mandate, beyond the 

NPRM’s proposed three-year lead 

time.56

Agency response: As noted previously 

in this document, this final rule does 

not mandate head restraints in rear 

outboard designated seating positions. 

Instead, this final rule regulates only 

voluntarily installed rear head 

restraints. Our decision was based on 

the several factors described below.

First, additional analysis produced a 

more refined estimate of costs and 

benefits associated with mandating head 

restraints. Specifically, the benefits 

derived from: (a) Designing and 

installing compliant rear head restraints 

where none were previously provided, 

and (b) redesigning vehicles featuring 

multiple seating configurations (usually 

SUVs and minivans) that feature head 

restraints that do not meet the proposed 

requirements, are lower than originally 

estimated. The relationship of costs to 

benefits is represented as a cost per 

equivalent life saved. In the NPRM, the 

agency estimated that the cost per 

equivalent life saved for rear outboard 

head restraints was $9 million as 

compared to $3 million for front 

outboard head restraints.57 We now 

estimate the cost per equivalent life 

saved for mandatory rear outboard head 

restraints to be greater than $13.8 

million, as compared to approximately 

$2.4 million for front outboard head 

restraints.58 The primary reason for the 

difference in the cost per equivalent life 

saved for front and rear seat head 

restraints is the difference in the 

numbers of front and rear seat 

occupants exposed to risk of whiplash 

injury in rear impacts and the difference 

between the costs of upgrading front 

head restraints and the costs of 

installing or upgrading rear head 

restraints.

Fewer rear seat occupants are exposed 

to risks in rear impacts because rear 

seats are much less likely to be occupied 

than front seats. An analysis of the 

distribution of occupants by seating 

position for all vehicle types in 2001 to 

2003 NASS shows that 10 percent of all 

occupants sit in the second (or higher) 

row of outboard seats. We note that 

children and small adults derive less 

benefit from taller head restraints 

because their head center of gravity 

often does not reach the height of 750 

mm above the H point. Therefore, if we 

further refine these data to include only 

occupants who are 13 years or older, the 

relevant percentage is reduced to 

approximately 5.1.59 Our conclusions 

about rear seat occupancy are further 

supported by the FRIA data, which 

indicate that out of a total of 272,464 

annually occurring whiplash injuries, 

approximately 21,429 (7.8%) occur to 

the rear seat occupants. In sum, only a 

small percentage of occupants who are 

tall enough to benefit from taller head 

restraints sit in rear outboard seating 

positions.

We have also reevaluated our 

compliance cost estimates. The cost of 

upgrading or installing rear head 

restraints in response to a mandate 

would have been significantly greater 

than the cost of upgrading front head 

restraints.60 Our data indicate that, on 

average, front seats were closer to 

meeting the proposed front head 

restraint requirements than the rear 

seats were to meeting proposed rear 

head restraint requirements. In fact, 

some vehicles currently in production 

already comply with the front head 

restraint height requirement because 

they were manufactured to comply with 

ECE 17. However, because ECE 17 does 

not require rear head restraints, we are 

not aware of any passenger vehicles that 

comply with the proposed requirements 

for rear seats.

In addition to cost effectiveness, our 

decision not to require rear head 

restraints was influenced by comments 

indicating that rear head restraints 

would significantly reduce a driver’s 

view through the rear view mirror in 

some vehicles. Although we are not able 

to estimate the associated adverse 

effects that might result from the 

rearward visibility losses, it is the likely 

that the effect would not be safety 

neutral for some vehicles. 

Finally, based on submitted 

comments, we conclude that mandating 

rear outboard head restraints could 

either decrease availability of certain 

74870 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

61As the agency noted in its 1995 final rule 

establishing upper interior head impact protection 

requirements, the application of the philosophy of 

providing similar levels of protection in all seating 

positions is subject to the limits of reasonableness: 

While the costs per equivalent life saved still vary 

according to seating position, the conclusive factor 

in determining whether to regulate a particular 

seating position should not be the existence of such 

variations, but the reasonableness of the cost for 

that particular position. * * * So long as the cost 

per equivalent life is reasonable, NHTSA believes 

that a vehicle should be designed to offer the same 

level of protection to all occupants, regardless of the 

occupant’s choice of seat. 60 FR 43031, at 43046; 

Aug. 18, 1995.

62The survey included twelve 1999 model year 

vehicles (9 passenger cars, 1 minivan, and 2 SUVs). 

Five of the twelve vehicles featured rear seating 

systems that fell under our definition of the rear 

head restraint.

utility features currently available in 

‘‘multi-configuration’’ vehicles such as 

minivans and SUVs, or make it 

necessary for vehicle manufacturers to 

alter interior or seat designs to maintain 

these features. At least initially, these 

alterations could significantly increase 

the cost of manufacturing these ‘‘multiconfiguration’’ vehicles. Alternatively, 

such designs would necessitate the 

ability to remove the rear head restraints 

to allow seat folding. 

As previously discussed, we were 

aware of low occupancy rates and 

potentially detrimental effect on 

rearward visibility when we proposed to 

require head restraints at each rear 

outboard designated seating position. 

These factors alone, however, were not 

decisive enough to convince us that we 

should not to propose requirements for 

mandatory rear head restraints and 

obtain public comment before making a 

final judgment on the merits. At the 

time, we tentatively concluded that the 

philosophy that commonly used seating 

positions should offer similar levels of 

protection to their occupants warranted 

further exploration of the merits of a 

mandate. However, in light of the newly 

refined, higher estimates of the cost per 

equivalent life saved, we conclude that 

rear head restraints should not be 

mandated.61

Nevertheless, in order to ensure that 

voluntarily installed rear seat head 

restraints do not pose a risk of 

exacerbating whiplash injuries, this 

final rule requires that those head 

restraints meet certain height, strength, 

position retention and energy 

absorption requirements proposed in 

the NPRM. We are considering 

inclusion in our annual ‘‘Buying a Safer 

Car’’ brochure, and on our web site, the 

list of vehicles equipped with rear head 

restraints. We believe this could provide 

an added incentive for the 

manufacturers to equip their vehicles 

with optional rear head restraints. 

The definition of a rear head restraint:

This final rule provides an objective 

definition and a test procedure for 

determining the presence of a rear head 

restraint. We decided that a vehicle seat 

will be considered to have a rear head 

restraint if the seat back, or any 

independently adjustable seat 

component attached to or adjacent to 

the rear seat back, that has a height 

equal to or greater than 700 mm, in any 

position of backset and height 

adjustment, as measured with the J826 

manikin. 

We chose this method for the 

following reasons. Based on the survey 

of vehicles used to determine the cost 

effectiveness of this regulation, we 

found that a 700 mm threshold captured 

all of the seats that had adjustable 

cushion components at the top of the 

seat back; i.e., what the general public 

would probably consider being a head 

restraint.62 Further, this definition of the 

rear head restraint will allow the 

manufacturers to provide a relatively 

tall seat back (up to 700 mm) without 

having to comply with rear head 

restraint requirements. We anticipate 

that such taller seat backs might offer 

some safety benefits to a certain portion 

of rear seat occupants. We note that the 

current head restraint standards do not 

require a height of above 700 mm even 

for front head restraints.

Because rearward visibility remains a 

concern, we note that the manufacturer 

will be able to determine whether 

providing a seat back structure above 

700 mm would be consistent with the 

amount of rearward visibility they wish 

to provide. 

As discussed previously, the agency 

has made significant accommodations to 

mitigate possible visibility losses 

associated with rear head restraints. 

First, the agency is making their 

installation voluntary. Second, the 

agency allows non-use positions that 

can move the head restraints out of view 

when the seat is unoccupied. Third, the 

agency allows rear head restraints to be 

removable. Fourth, the maximum 

required head restraint width for rear 

bench seats is 84 mm less than for front 

bench seats. Fifth, gaps as large as 60 

mm can be provided within the 

perimeter of the head restraint. 

b. Exception for Seats Adjacent to an 

Aisle 

Johnson Controls expressed a concern 

that the NPRM’s proposed heights for 

head restraints for third-row seating in 

vehicles would create a problem for 

outboard designated seating positions 

that are next to an aisle. The commenter 

suggested that the 750 mm proposed 

head restraint height requirement could 

create ingress and egress difficulties for 

people using these third-row seats, 

which could pose a safety problem in 

certain vehicle emergencies. 

NHTSA believes that these concerns 

are now addressed by making the head 

restraints optional for rear outboard 

seating positions. If a manufacturer 

believes that it is better not to place the 

head restraints in designated seating 

positions adjacent to the aisles in order 

to facilitate ingress and egress into third 

and higher rows, it may act accordingly. 

c. Potential Interference With Child 

Restraints and Tethers 

The NPRM solicited comments 

related to safety concerns arising from 

potential interference of rear seat head 

restraints with the attachment of upper 

tethers of child restraint systems. The 

NPRM asked for test data and related 

comments regarding whether the 

passage of tethers over or under 

adjustable head restraints would affect 

the amount of head excursion of child 

restraint occupants in a crash or the 

lateral stability of child restraints. 

Interaction between tethers and head 

restraints. NHTSA received numerous 

responses to these requests and 

questions. Advocates believed that the 

performance of child seat tethers would 

not be negatively affected by the 

proposed FMVSS No. 202 amendments. 

Nevertheless, Advocates recommended 

that NHTSA’s final rule prohibit child 

seat tethers from being designed so that 

their use necessitates either removing 

rear head restraints or placing them in 

the non-use position. 

Some industry commenters expressed 

concerns about, but did not provide any 

specific test data on, the safety impact 

of incompatibilities between child 

restraint tethers and rear seat head 

restraints. Johnson Controls asserted 

that safety concerns exist with respect to 

integral or adjustable head restraints 

and the proper management of child 

tether placement and loading. Johnson 

Controls commented that misuse or 

improper installation could occur. 

DaimlerChrysler suggested that a tether 

routed over the top of a head restraint 

would provide less effective safety 

protection in a side impact, given the 

longer tether length and routing. Honda 

believed that the perceived potential 

safety concern pertained to misuse that 

could occur when the tether strap is 

positioned over the head restraint and 

attached to the tether anchor when the 

head restraint is not positioned in the 

lowest possible adjustment position. 

Ford acknowledged its lack of 

information regarding any head 

excursion effects of child restraint 

routing over or under a head restraint. 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74871

63A hybrid child restraint is one that can be used 

as a forward facing seat below a certain child 

weight and a belt positioning booster seat above.

Ford indicated that in some frontal sled 

tests it conducted, it discovered a degree 

of tether slippage to the side of the head 

restraint when the tether was routed 

over head restraints. Ford assumed this 

slippage would increase head excursion, 

although Ford’s tests did not produce 

evidence of excessive head excursions. 

Ford stated that increased head restraint 

heights also might increase the effects of 

slippage on chest acceleration, neck 

loads, and HIC. 

Transport Canada said that it has 

investigated whether interference 

between head restraints and child 

restraint tethers might alter the angle at 

which the tethers depart the child 

restraint, or create slack in the strap, in 

a manner that would affect the 

performance of the child restraint. 

Transport Canada conducted numerous 

sled tests to discern any effects of 

varying strap angles and slack on child 

seat tether performance. Transport 

Canada’s data indicated that tethers 

remained effective even at rather large 

strap angles. The data additionally 

showed that tethers retained their 

effectiveness up to the point at which 

large amounts of slack were 

incorporated into the tests. 

The Alliance commented that the 

extent of head restraint and tether 

interference varies depending on the 

exit point of the tether from the child 

restraint, as—the commenter believed—

a lower exiting tether will produce 

greater interference. With respect to the 

NPRM’s suggestion that a Y-shaped 

tether strap design might be used to go 

around the head restraint, the Alliance 

maintained that no child restraints 

currently on the market are equipped 

with Y-shaped tethers. However, it 

noted the availability of a V-shaped 

tether strap design on a few high-priced 

child restraints. 

Less of a snug fit between child 

restraint and vehicle seat because of 

head restraints.

Several commenters believed that the 

proposed backset and gap requirements 

could interfere with proper child 

restraint and booster seat installation. 

The Partners for Child Passenger 

Safety (PCPS) said that there is an 

existing incompatibility between rear 

head restraints and some high-back 

convertible child restraints and 

boosters. In particular, PCPS asserted 

that a rear head restraint might affect the 

tightness of a hybrid child restraint’s 63

fit on the seat when the child restraint 

is used as a forward-facing seat. The 

Alliance commented that many existing 

child restraint systems have higher and 

straighter backs that could interfere with 

head restraints meeting the proposed 50 

mm backset limit, thus causing child 

restraint fit problems. The Alliance 

further indicated that head restraint 

interference causes tipping and sliding 

of high-back boosters during cornering 

due to the lack of contact between the 

back of the booster and the vehicle’s 

seat back. The Alliance asserted that the 

interference of head restraints with 

reduced backsets with high-back beltpositioning boosters could push the 

booster seat forward, causing an adverse 

effect on the positioning of lap and 

shoulder belts.

Effect of new head restraints on child 

restraint anchorage systems. Several 

commenters raised concerns about the 

effect that the new head restraints might 

have on the design and testing of child 

restraint anchorage systems (pursuant to 

FMVSS No. 225). DaimlerChrysler 

expressed concern about the issue of 

interference with the child restraint and 

the Child Restraint Fixture (CRF) used 

by NHTSA to test the strength and 

positioning of child restraint anchorage 

systems in vehicles under FMVSS No. 

225. Less desirable relocation of lower 

anchors for child seats, the Alliance 

contended, might also result from 

reduced backset due to head restraint 

interference with the CRF design.

Agency response regarding child 

restraints and tethers: NHTSA reviewed 

the comments submitted with respect to 

potential child restraint and/or tether 

interference. These comments pertain 

exclusively to rear seats. Since the final 

rule does not require rear seat head 

restraints, any incompatibility can be 

addressed by the manufacturers. 

Therefore, we have concluded that the 

final rule’s head restraint requirements 

will not adversely affect child restraint 

safety. In addition, we believe that 

optional rear head restraints will not 

have a significantly negative effect on 

child restraint compatibility. Below we 

provide responses specific to several 

areas of commenters’ concern if a head 

restraint is present. 

Agency response regarding tethers: As 

the agency stated in the NPRM, tethered 

child restraint requirements have been 

in effect for quite some time in Canada 

and Australia, and vehicles with rear 

head restraints meeting requirements 

similar to those of today’s final rule are 

relatively common in those countries. 

Transport Canada indicates that 

interference between rear head 

restraints and child restraint tethers has 

not created any significant problems. To 

the extent that interference occurs, it 

creates incentives for child restraint 

manufacturers to design child restraints 

to assure maximum child protection. 

For example, a demand would likely 

develop for Y- or V-shaped tethers, if 

such tethers make attaching to a tether 

anchor easier. 

As indicated above, Johnson Controls, 

Honda, DaimlerChrysler, and Ford 

suggested that routing tethers over head 

restraints might lead to increased head 

excursions. However, industry 

commenters did not provide any data on 

this issue, while Transport Canada’s 

data indicate that tethers remain 

effective up to the point at which large 

amounts of slack are introduced. 

NHTSA assumes that the worst-case 

tether location is floor mounting 

because floor-mounted tethers have the 

potential to introduce the most slack in 

a collision, while deck-mounted and 

roof-mounted tethers likely would not 

produce significant slack because of 

their shorter distance to the child 

restraint. If current voluntarily installed 

rear seat head restraints are an 

indication of future systems, NHTSA 

anticipates manufacturers will install 

adjustable systems, in which case the 

tether could be routed under the 

adjustable head restraints, reducing the 

potential for excessive amounts of slack. 

Vehicle manufacturers are required to 

provide instructions for proper 

attachment of the child restraint tether 

under FMVSS No. 225. Manufacturers 

must determine how child restraint 

tethers should be routed with respect to 

the particular head restraints in their 

vehicles, and how the head restraint 

should be adjusted. In some instances, 

a manufacturer may recommend that the 

head restraint be temporarily removed. 

Agency response regarding fit of child 

restraints: With respect to comments 

pertaining to the potential 

incompatibility between rear head 

restraints and some high-back hybrid 

child restraints and boosters, NHTSA 

notes that high-back child restraints are 

used in Europe with no reports of 

incompatibilities. As Magna 

commented, rear seat head restraints are 

much more common in Europe due to 

competitive pressures. Nonetheless, if 

incompatibilities arise in this country, 

they can be resolved by several means. 

First, we believe that an adjustable head 

restraint is likely to have a position that 

does not interfere with high back hybrid 

child restraints. That is, raising the head 

restraint may alleviate the potential 

interference. Second, the high-back 

child restraint can be installed in a 

seating position for which a head 

restraint is not provided, removable, or 

has a non-use position. We note that 

even where rear outboard head 

restraints are provided, many vehicles 

do not provide a head restraint in the 

74872 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

64NHTSA has issued an NPRM that would 

mandate installation of lap/shoulder belt restraint 

systems in the center rear seating position (68 FR 

46546), which will ensure availability of restraints 

for use with an older child in a belt positioning 

booster. 65Besides mechanical deployment, some systems 

use other methods. For example, BMW 760Li uses 

a pyrotechnic head restraint system that utilizes a 

gas discharge to deploy head restraints.

66Albert I. King, PhD, Bioengineering Center, 

Wayne State University.

67 If the seat cushion adjusts independently of the 

seat back, the seat cushion would be positioned 

such that the highest H-point position is achieved 

with respect to the seat back, as measured by the 

HRMD.

68BioRID stands for Biofidelic Rear Impact 

Dummy. It was developed by a consortium of 

Chalmers University of Technology in Sweden, 

Autoliv, Saab and Volvo to help safety engineers 

evaluate the relative motion of the head and torso 

in rear crashes. BioRID has a flexible spine with 24 

vertebra-like segments, the same number as in the 

human spine. It has joints that allow for forward 

and backward movement of the head, and integrates 

spring-loaded cables that simulate the action of 

human neck muscles. Its spine is said to interact 

with vehicle seats in a more humanlike way than 

the Hybrid III’s rigid spine. Further, its neck is 

center seating position.64 We recognize 

that, even with the flexibility afforded to 

the manufacturers with respect to rear 

seat head restraints, there may be 

isolated situations where certain high 

back child restraints are not compatible 

with specific seating positions in certain 

vehicles. However, we expect this to be 

relatively infrequent. In short, the 

agency does not believe that the 

possible incompatibilities are 

insurmountable even in situations in 

which rear seats are equipped with 

optional head restraints. The agency 

will monitor these and other issues 

associated with the implementation of 

this final rule.

Agency response regarding testing of 

child restraint anchorage system:

NHTSA disagrees with the Alliance’s 

comments asserting that rear head 

restraints will cause interference with 

the CRF, thereby resulting in 

unfavorable positioning of lower 

anchors. In an earlier rulemaking on 

FMVSS No. 225, the agency modified 

the CRF so that it can be broken down 

into a short-back configuration, 

eliminating the potential for head 

restraint interference. 

XIII. Dynamic Test Alternative 

In the NPRM, we proposed a dynamic 

compliance option for forward facing 

seats as an alternative to static 

requirements of this final rule. The 

dynamic compliance option was 

proposed primarily for two reasons. 

First, the dynamic test better represents 

‘‘real-world’’ injury-causing events and 

thus produces greater assurance than 

the static measurement option of 

effective real world performance. 

Second, as explained below, we believe 

that the dynamic test will help to 

encourage continued development and 

use of ‘‘active’’ head restraint systems 

because the test is designed to allow a 

manufacturer the flexibility necessary to 

offer innovative active head restraint 

designs while still ensuring a minimal 

level of head restraint performance.

Active head restraint systems 

deploy 65 in the event of a collision to 

minimize the potential for whiplash. 

During the normal vehicle operation, 

the active head restraint system is 

‘‘retracted.’’ Because an active head 

restraint system requires a certain range 

of motion to work effectively, an ‘‘undeployed’’ active head restraint system 

might not meet the static measurement 

requirements of FMVSS No. 202a.

Several manufacturers now offer 

active head restraints. For example, 

Volvo offers the Whiplash Head Impact 

Protection System (WHIPS) in which 

the seat back recliner is designed to 

control the rearward motion of the seat 

back relative to the seat base in a rear 

impact. Volvo believes that this allows 

the head and torso to be more uniformly 

supported. A number of other vehicle 

models including Saab, Infiniti, and 

BMW also offer active head restraints in 

their vehicles. 

Although the dynamic compliance 

option is intended to ensure that the 

final rule encourages continuing 

development of active head restraint 

systems, the option is available to both 

active and conventional, or ‘‘static’’

head restraint systems. That is, both 

types of head restraints can be certified 

to either static requirements or the 

dynamic compliance option. As 

explained above in the discussion of the 

height requirements for front seat head 

restraints, if the choice were made to 

certify to the static requirements, an 

active head restraint would have to meet 

these requirements in its undeployed 

state. If an active head restraint were 

unable to do this, the dynamic 

compliance option provides an 

alternative means of certification. Head 

restraints certified to the dynamic 

compliance option must still meet the 

static width requirements of this final 

rule. As discussed below, a 

manufacturer’s selection of a 

compliance option would be 

irrevocable. However, the manufacturer 

may select different compliance options 

for different designated seating 

positions. 

The current dynamic test in FMVSS 

No. 202 accelerates a seat to an 8 g half 

sine acceleration pulse over 80 ms. The 

NPRM proposed a new dynamic 

compliance test option involving a sled 

test with a target pulse of 86 m/s2 over 

an 88 ms duration and a 17.3 ± 0.6 km/

h change of velocity. 

Most commenters on the NPRM 

agreed with maintaining an alternative 

dynamic compliance option. However, 

as IIHS noted, that there has been no 

strong interest in the industry to take 

advantage of a dynamic compliance 

option. Because the dynamic test 

requirements are based on the static 

location requirements, the AIAM 

commented that there is little incentive 

to use the dynamic testing option. 

King 66 commented in favor of dynamic 

testing. The final rule adopts the 

proposed dynamic compliance option, 

with modification, because we believe it 

desirable and necessary to encourage 

continued development and use of 

‘‘active’’ head restraint systems. 

Especially as modified, the test is 

designed to allow a manufacturer the 

flexibility necessary to offer innovative 

active head restraint designs while still 

ensuring a minimal level of head 

restraint performance.

Test Dummies. For the dynamic 

compliance test option, the NPRM 

proposed the use of a 95th percentile 

male dummy in a front seat with the 

head restraint at a single manufacturer 

selected position, and a 50th percentile 

male dummy in the front and rear seats 

with the head restraint midway between 

the lowest and the highest position of 

vertical adjustment. In vehicles in 

which the seat cushion adjusts 

independently of the seat back, the 

dynamic measurements were to be taken 

with the seat cushion adjustment in the 

most unfavorable position.67

The Alliance commented that there 

are many potential test dummy 

candidates, but no consensus on the 

most appropriate one to use for a 

dynamic head restraint test. Magna 

argued in favor of using 5th percentile 

female, 50th percentile male and 95th 

percentile male dummies. Honda stated 

that the 95th percentile male dummy 

should have priority in testing. 

DaimlerChrysler said that a 5th 

percentile female dummy is not needed 

for testing because if a head restraint is 

high enough for a 50th percentile male, 

it will also be high enough for a 5th 

percentile female. Tencer suggested that 

in order to be certain that a smaller 

occupant’s head contacts the intended 

surface of the head restraint, there 

should be some indication of how a 

small female would fit the seat. Autoliv 

commented that since the most common 

neck-injured occupant is an average size 

female, a 50th percentile female dummy 

should be used in dynamic testing. 

Autoliv also said that a BioRID 68

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74873

capable of producing the S-shape observed in 

human necks during rear crashes. 69 Kim, A., Anderson, K., Berliner, J., Hassan, J., 

Jensen, J, Mertz, H., Pietzch, H., Rao, A., Schere, R., 

Sutterfield, A, (2003) Stapp Car Crash Journal, Vol. 

47, pp. 489–523.

70 Viano, D., Davidsson, J., ‘‘Neck Displacement of 

Volunteers, BioRid P3 and Hybrid III in Rear 

Impacts: Implications to Whiplash Assessment by a 

Neck Displacement Criterion (NDC),’’ Traffic Injury 

Prevention, 3:105–116, 2002.

71 In response to Autoliv’s suggestion that we test 

with a 50th percentile adult female dummy, we 

note that there currently is no test dummy 

representing a 50th percentile female.

dummy, with its flexible spine, should 

be used in dynamic testing instead of 

the Hybrid III dummy. IIHS commented 

that the Hybrid III dummies are not 

biofidelic for rear impacts, that they 

represent large adult males, and that 

dynamic testing based on them may 

lead to dynamic head restraint designs 

that are not effective for smaller 

occupants such as children and females. 

King agreed that there is not any truly 

biofidelic dummy now available for rear 

impacts, but recommended use of the 

Hybrid III dummy as the best alternative 

currently available. He specifically 

recommended against the use of the 

BioRID dummy, stating that it had not 

been validated against cadaveric data in 

detail and that relative displacements 

between the pinned joints are not 

available. Advocates supported dynamic 

testing with 5th percentile female 

dummies to limit the negative effects of 

head restraints that are adjusted too 

high. Advocates also stated that the 95th 

percentile male dummy should be used 

in the rear seat as well as the front seat.

Agency Response: There was no 

consensus among the commenters on 

the use of the Hybrid III dummy or the 

range of dummy sizes to be utilized. 

NHTSA is aware of the criticism 

associated with Hybrid III. Specifically, 

many commenters assert that the 50th 

percentile male Hybrid III neck lacks 

sufficient biofidelity to be a useful tool 

for rear impact testing. Because of likely 

design similarities, the same criticism 

could be made of the 95th percentile 

male and 5th percentile female dummy 

necks. We are aware of a newly 

developed test devices, BioRID II and 

RID 2, which purport to model a human 

neck more accurately. We are also 

familiar with a paper by Ford (SAE 

973342), which argues that the 50th 

percentile male Hybrid III neck is 

sufficiently biofidelic in the rearward 

direction. Another recent publication 

indicated that the overall flexibility of 

the Hybrid III dummy is comparable to 

that of a tensed volunteer, while the 

flexibility of the BioRID II and RID 2 are 

greater than those of tensed volunteers 

and embalmed cadavers.69 We are likely 

to revisit the decisions made in this 

final rule about dynamic performance 

values and the test device as more 

advanced dummies are developed and 

the injury criteria achieve broader 

consensus.

Any consensus advancement in 

adaptation of a new, more biofidelic 

dummy will be welcomed by the agency 

and considered as part of future possible 

modifications to the standard. However, 

we believe the introduction of a 

modified dynamic test alternative 

should not be delayed, even if it is only 

an interim step toward a more advanced 

test procedure. We find especially 

persuasive King’s comments, stating 

that the Hybrid III dummy is the only 

reasonable option at this time. 

In our opinion, the 95th male dummy 

in the front, and 50th percentile male 

dummy in the rear, provide for a 

relatively worst-case scenario in terms 

of potential occupants and assure that 

the head restraint has sufficient height. 

However, the 95th percentile male 

dummy is not yet available and thus has 

not been incorporated into 49 CFR part 

572, Anthropomorphic Test Devices.

Therefore, the final rule does not use the 

95th percentile male dummy in the 

dynamic compliance option for front 

seats. Instead, as discussed further 

below, this final rule requires that the 

head-to-torso rotation be limited to 12 

degrees with the 50th percentile male 

dummy with the head restraint midway 

between the lowest and the highest 

position of vertical adjustment. Ideally, 

it would be preferable that the dynamic 

testing be performed with the 5th 

percentile female and 95th percentile 

male dummy. However, we conclude 

that the 50th percentile male dummy 

with the 12-degree head-to-torso 

rotation performance limit is sufficient 

to discern between acceptably safe head 

restraint systems and those that allow 

unacceptable levels of head-to-torso 

rotation for the taller occupants. We 

note that sled testing performed by the 

agency and described further below 

shows that the 50th percentile male 

dummy is capable of discerning the 

difference between 800 mm and 750 

mm high head restraints. This data set 

did not vary backset. However, previous 

agency modeling results presented in 

the NPRM and sled testing by Viano 

have shown the 50th percentile male 

Hybrid III dummy to be sensitive to 

changes in backset as well.70 Thus, the 

50th percentile male Hybrid III can, for 

the time being, be used as to determine 

the adequacy of head restraints for taller 

occupants.

In regard to commenters who 

preferred testing with a 5th percentile 

female dummy, we conclude that it is 

not necessary to use such a dummy to 

determine if the tested head restraint 

has the height and backset required to 

protect most occupants. Recent agency 

testing of several modified seat designs 

showed that dummy head-to-torso 

rotation is lower for a 5th percentile 

female than for a 50th percentile male 

dummy. Accordingly, a test featuring 

the 50th percentile male dummy 

captures the injury criteria associated 

with a 5th percentile female. We note, 

however, that this may not be the case 

for all seat designs. Any future upgrade 

proposals for dynamic rear impact 

testing in general, and the development 

of more refined injury criteria in 

particular, should consider 

incorporation of a small female 

dummy.71

Injury criteria. In the NPRM, we 

proposed two criteria for the dynamic 

performance option: A maximum headto-torso rotation criterion and a 

maximum HIC15 level. Johnson 

Controls commented that the criteria 

should bear a direct relationship to 

whiplash injury prevention. Magna, 

along with AIAM, requested that a 

performance corridor be established for 

the dynamic testing alternative. 

Maximum head-to-torso rotation: The 

NPRM proposed a maximum head-totorso rotation of 20 degrees for a 95th 

percentile male test dummy in front 

outboard seats and 12 degrees for a 50th 

percentile male test dummy in all 

outboard seats. With the 95th percentile 

male dummy, the head restraint could 

be at a single manufacturer selected 

position of adjustment. With the 50th 

percentile dummy, the head restraint 

could be at any position of adjustment. 

Tencer and King both suggested timedependent limits in their comments 

regarding the head-to-torso rotation 

performance criterion. Tencer believes 

that the extent of ‘‘S’’ shape curve 

correlates to the magnitude and time 

difference in the forward shear of the 

upper and lower neck. King believes 

that facet capsule stretch between the 

vertebrae could be a source of injury. In 

low speed impacts with a rigid seat 

back, the measured peak stretch occurs 

100–120 ms after impact. He suggested 

that head restraint contact should be 

made within 50 ms. AIAM 

recommended that the head-to-torso 

rotation be tested only at maximum 

backset. GM commented that because 

there is not yet a consensus on neck 

injury criteria, a limit of 12 degrees 

should not yet be established. The 

Alliance expressed concerns because 

the specified head rotation limits may 

be too restrictive. Advocates voiced 

74874 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

72We note that the manufacturer may select 

different compliance options for different 

designated seating positions to which the 

requirements of this section are applicable.

73For full details of these tests, please see Docket 

No. NHTSA–2002–8570–57, 58, 59.

concerns that the 20-degree rotation 

limit for the 95th percentile male 

dummy in front seats is too large. 

Under today’s rule, we are adopting a 

maximum relative head-to-torso rotation 

value of 12 degrees with the 50th 

percentile male dummy in all outboard 

seats, with the head restraint adjusted 

vertically midway between the lowest 

and the highest position of 

adjustment.72

We decided to require that the head 

restraint be positioned at one middle 

position of vertical adjustment instead 

of requiring that the head restraint meet 

the dynamic compliance option 

requirements at all positions of head 

restraint vertical adjustment because we 

are concerned with the effects of this 

final rule on active head restraint 

systems. As previously stated, we want 

to ensure that the dynamic compliance 

option encourages continuing 

development of active head restraint 

systems. As discussed below, research 

indicates that current head restraint 

systems can easily meet the head-totorso rotation limit in this final rule 

when the head restraint is adjusted 

midway between the lowest and the 

highest position of adjustment. 

Using published data of low speed 

rear impact testing of original 

equipment manufacturer (OEM) seats 

with Hybrid III 50th percentile male 

dummies (Viano et al., 2002), and 

information on whiplash injuries 

sustained by occupants of these seats, 

the agency used logistic regression to 

develop a probability of whiplash injury 

as a function of dummy head-to-torso 

rotation. The function is shown below:

A 12-degree head-to-torso rotation 

corresponds to a 7.3 percent probability 

of whiplash. This criterion was selected 

to ensure adequate protection for 

occupants who range in stature from 

shorter females up to and including 

taller males, for all outboard seats. In 

evaluating the head-to-torso rotation 

limit, we note that in the past there has 

not been a consensus among the 

biomechanics community on how best 

to measure the potential for whiplash 

injury. This lack of consensus is 

evidenced by the related, yet different, 

criteria recommended by King and 

Tencer. In our opinion, the relative 

head-to-torso rotation is presently the 

best criterion available, and will assure 

early head restraint interaction 

consistent with King’s recommendation. 

Our goal in selecting performance 

criterion limits for the dynamic 

compliance option was to provide a 

level of safety similar to that provided 

by the static requirements. Our research 

shows that it is feasible to meet these 

limits with both active and static head 

restraints. 

The agency performed sled testing as 

specified in the dynamic compliance 

option on a specially designed seat to 

explore how various seat characteristics 

affect relative head rotation and other 

dummy injury measures.73 An OEM seat 

with an adjustable head restraint was 

modified by removing the original 

recliner mechanism and replacing it 

with a pin joint free to rotate. The seat 

back was also reinforced with steel 

channels that provided the attachment 

points for a spring and damper system 

on each side of the seat. Seat back 

strength in the rearward direction was 

modified by changing the springs and/

or their location of attachment relative 

to the hinge joint. In addition to seat 

back strength, sensitivity analyses to 

head restraint attachment strength and 

seat back upholstery compliance were 

also performed. Tests were performed 

with belted 5th percentile female, 50th 

percentile male and 95th percentile 

male Hybrid III dummies.


er14de04.149</GPH>
Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74875

74The baseline seat back strength was obtained 

through static testing of OEM seats and modeling 

to determine the corresponding amount of seat back 

rotation. The static testing can be found in Docket 

NHTSA–1998–4064–26.

75 Viano, D., Olsen, S., ‘‘The Effectiveness of 

Active Head Restraint in Preventing Whiplash,’’

Journal of Trauma, Injury, Infection, and Critical 

Care, Vol. 51, No. 5, 2001; and Viano, D., ‘‘Role of 

the Seat in Rear Crash Safety,’’ Society of 

Automotive Engineers Inc., Warrendale, PA, 2002.

76 Geigl et al. (1994) The Movement of Head and 

Cervical Spine During Rear-end Impact, IRCOBI, pp 

127–137.

The head restraint height was either 

750 mm or 800 mm and the backset was 

always 50 mm as measured by the 

HRMD. However, the majority of tests 

(20 tests) were performed with the 50th 

percentile male dummy with a 750 mm 

high head restraint. For all seat back 

parameters tested with this 

configuration of dummy and head 

restraint height, the range of relative 

head-to-torso rotation was 6 to 16 

degrees. HIC15 was measured for half of 

these tests and ranged from 40 to 75. 

Nearly half of the seat configurations (9 

of 20) met the 12-degree limit placed on 

the dynamic compliance option for a 

head restraint in the lowest adjustment 

position (750 mm). In general, the 

smallest relative rotations were seen for 

the baseline seat back strength 74 and 

non-rotating seat backs irrespective of 

the other seat/head restraint parameters. 

From these tests, we conclude that the 

head rotation and HIC limits selected 

can be met with typical seat back/head 

restraint designs when appropriate 

consideration is given to design in terms 

of height, backset and strength of head 

restraint attachment.

In a separate set of tests, the agency 

subjected a MY 2000 Saab 9–3 seat to 

the sled pulse of the dynamic 

compliance option. A 95th percentile 

male Hybrid III dummy occupied the 

seat. The Saab 9–3 has an active head 

restraint system, and the head restraint 

was set to its highest position of 

adjustment. The maximum head-totorso rotation was 9 degrees. Viano and 

Davidsson (2002) also sled tested a 9–

3 head restraint at a slightly lower, 16 

km/h DV, with the seat occupied by a 

50th percentile male Hybrid III dummy. 

With the head restraint in the up 

position, the relative head rotation was 

measured at 6.5 degrees. With the head 

restraint midway between the lowest 

and the highest position of adjustment, 

the relative head rotation was 10 

degrees at 23.5 km/h DV. We believe 

that this configuration would yield an 

even smaller head rotation at the 17.2 

km/h DV.75

TABLE 3.—VIANO REAR IMPACT SLED TEST DATA

Test type Vehicle DeltaV 

km/h 

Backset 

mm HR position in height HIC15 

Head-totorso rotation 

(deg) 

Sled .................................. Saab 9–5 + SAHR ............................... 12.8 35 up .................................... 11 1

Sled .................................. Saab 9–3 SAHR .................................. 16 41–43 up .................................... ................ 4.6–6.5 

Sled .................................. Saab 9–5 + SAHR ............................... 30 35 up .................................... 39 11 

Sled .................................. Saab 9–3 SAHR .................................. 23.5 46 mid .................................. 35 10 

Sled .................................. Saab 9–3 SAHR .................................. 16 48–65 down ................................ ................ 13.3–16 

In sum, research indicates that the 

head-to-torso rotation limit of 12 

degrees will not discourage the 

development of active head restraint 

systems. Current systems, such as the 

one in 2000 Saab 9–3, can readily meet 

the head-to-torso rotation limit in this 

final rule. Agency testing has also 

shown that current static head 

restraints/seats need more extensive 

modification to meet the head-to-torso 

rotation limits. These changes might 

include increasing the strength of 

attachment to the seat for adjustable 

head restraints and optimization of the 

seat back upholstery for compliance. 

We also considered performance 

criteria other than head-to-torso rotation 

for the dynamic compliance option. 

Alternative criteria included Nij, which 

is a combination of upper neck 

moments and forces introduced in the 

Advanced Air Bag Rulemaking (Docket 

NHTSA–98–4405); and NIC, which was 

developed by Chalmers University and 

has been used by IIHS in testing active 

head restraints; and individual values of 

force, moment and acceleration. We 

have decided in favor of head-to-torso 

rotation because, in the absence of 

generally accepted injury criteria 

specifically applicable to whiplash 

injuries, we believe that a head 

restraint’s ability to prevent whiplash is 

primarily due to its ability to prevent 

the rearward translation and rotation of 

the occupant’s head with respect to the 

torso. The sled tests showed that 

rearward head rotation seemed to 

correlate with head restraint position. 

Other biomechanics researchers have 

found a similar correlation and used 

head-to-torso rotations for the 

evaluation of whiplash injury.76 The 

agency is willing to reconsider the 

dynamic performance criteria if and 

when more advanced whiplash injury 

criteria become available.

HIC15 criterion: The NPRM proposed 

a HIC15 limit of 150 for the dynamic 

compliance option. Johnson Controls, 

GM and the Alliance opposed the 150 

HIC15 limit. They saw no correlation 

between HIC and the reduction of neck 

injuries. AIAM recommended that we 

adopt an ‘‘acceleration limit,’’ instead of 

150 HIC15 limit requirement. Advocates 

supported the HIC15 limit as a prudent 

safeguard against head restraints that 

may meet a head rotation limit, but still 

inflict cranial trauma. The FIU students 

commented that the current 150 limit of 

HIC15 is sufficient for testing. No 

comments were made in favor of using 

a 36 ms window. 

We are adopting a HIC15 window to be 

consistent with the new HIC criterion in 

Standard No. 208 (65 FR 30680; May 12, 

2000). The agency did not propose the 

HIC15 limit as a means of limiting 

whiplash, but instead as a surrogate for 

the 80 g energy absorption test required 

for the static compliance option. If we 

were to eliminate the HIC15 limit from 

the dynamic compliance test, we would 

need to re-introduce the 80 g limit 

energy absorption test required for static 

compliance. Because HIC15 is easily 

measured during dynamic testing, it 

appears to be a more appropriate 

measuring tool. However, we have 

decided to specify a limit of 500 in the 

final rule rather than the 150 limit 

proposed in the NPRM. We raised the 

limit because of concerns that the 150 

level is at a location on the injury risk 

curve that indicates a very small 

probability of injury. Thus, requiring 

head restraints not to exceed this level 

might inhibit innovative whiplash 

protection. The HIC15 level of 500 is 

associated with an 18.8 percent 

probability (95 percent confidence: 1.8 

74876 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

77Eppinger, R., et al. (1999) Development of 

Improved Injury Criteria for the Assessment of 

Advanced Automotive Restraint Systems—II. 

Available at http://www-nrd.nhtsa.dot.gov/pdf/nrd11/airbags/rev_criteria.pdf.

78The test procedure specifies that the 

midsagittal plane of the dummy must be aligned 

within 15 mm of the head restraint centerline as 

opposed to off-center as a vehicle occupant might 

be positioned.

to 32.5 percent) of moderate (AIS 2+) 

head injury.77 While the 80 g limit and 

the HIC15 limit of 500 are not 

necessarily equivalent, the two 

requirements do share the same intent 

of mitigating potential injury related to 

the head’s striking a rigid or 

insufficiently padded head restraint. We 

analyzed data from FMVSS No. 201 

impactor tests on the back of head 

restraints and also vehicle seat sled test 

data. We superimposed a 80 g half sine 

acceleration on the time duration of the 

impacts from these tests. This resulted 

in range of HIC15 values from 

approximately 425 to 800. Accordingly, 

we believe a limit of 500 is appropriate. 

The greatest HIC15 value obtained in 

testing sled testing using a 50th 

percentile male dummy was 57. Thus, 

the HIC15 limit of 500 is practicable. The 

500 HIC15 limit will give a strong 

indication of deleterious effects on the 

occupant’s head and/or neck from 

deploying head restraints.

Summary of injury criteria: Table 4 

summarizes the injury criteria to be met 

for the dynamic compliance option. Our 

research indicates that currently 

available dynamic head restraints can 

readily meet the requirements of this 

final rule. We believe that the dynamic 

compliance option is sufficiently 

flexible to encourage continuing 

development of dynamic head restraint 

systems. However, the agency remains 

open to alternative suggestions on 

dynamic criteria that would further 

encourage innovative active head 

restraint designs.

TABLE 4.—TESTING PARAMETERS FOR THE DYNAMIC COMPLIANCE OPTION

Seating position Dummy size Rotation limit HIC15

limit 

Height adjustment Backset adjustment Head restraint width 

Front & Rear ........ 50th Male Hybrid 

III.

12 Deg .............. 500 Midway between the 

lowest and 

the highest 

position of 

adjustment.

Any position of adjustment 170 mm except 254 mm for 

front bench seats. 

Other dynamic compliance option 

issues. There were three additional 

aspects of the dynamic compliance 

option that the agency discussed in the 

NPRM. 

Minimum width requirement: The 

NPRM proposed that the same head 

restraint width requirement in the static 

compliance option be applicable to the 

dynamic compliance option as well. As 

discussed above, the final rule requires 

that all head restraints on front bucket 

seats and all voluntarily installed rear 

head restraints certified to the static 

compliance option have a minimum 

width of 170 mm. The bench seat head 

restraints located in the front outboard 

seating positions must have a minimum 

width of 254 mm. The final rule adopts 

the same width requirement for head 

restraint systems certified to the 

dynamic compliance option. 

GM commented that the width 

requirement would be inappropriate, 

especially for active or deployable head 

restraints. Honda also stated that the 

requirement would be unnecessary. 

DaimlerChrysler had no concerns 

related to the width requirement in the 

dynamic option, except for the same 

visibility issues it had raised in the 

discussion of the static test 

requirements. Ford and the Alliance 

commented that the width requirement 

is necessary, and repeated their desire 

for a single 170 mm width for all seat 

types. Advocates commented in favor of 

adding the width criteria to the dynamic 

option. 

There appears to be no industry 

consensus as to whether the width 

requirement should be included in the 

dynamic compliance option. We 

disagree with GM’s assertion that the 

width requirement is inappropriate for 

deployable systems. Regardless of 

whether the head restraint pivots 

forward to contact the head in a 

collision or is permanently situated 

behind the head, the head restraint 

should be sufficiently wide to provide 

protection. We note that unlike height 

and backset, the dynamic test does not 

assure sufficient width because it 

decelerates the vehicle in the 

longitudinal plane which causes the 

occupant to move in that plane, rather 

to one side of the other as might occur 

in an off-axis impact.78 Therefore, we 

have decided that vehicles certified to 

the dynamic compliance option must 

also meet the width requirements of the 

static compliance option. For reasons 

discussed in Section VI.a., we decline to 

adopt a single 170 mm width 

requirement for all head restraints.

Seating procedure: The seating 

procedure for the dynamic compliance 

option is set forth in S10 of Standard 

No. 208, with additional details added 

to address lateral positioning of the 

dummy. Since the manufacturers are 

already familiar with these procedures, 

they should not encounter any seating 

procedure difficulties while conducting 

the dynamic compliance test. Since 

testing of the head restraint is the focus 

of this procedure, we found it necessary 

to add provisions specifying that the 

dummy torso be placed within 15 mm 

of the head restraint centerline. In the 

event that the dummy cannot be seated 

because of space limitations, such as 

might be the case in the outboard rear 

seat of a vehicle, the dynamic option 

would not be available for that seating 

position. 

Test fixture: For the dynamic 

compliance option, the NPRM proposed 

mounting the entire vehicle on a sled. 

The Alliance, among other 

commenters, asked the agency to 

consider allowing the use of a seat 

attached to a test buck, instead of an 

actual vehicle for the dynamic 

compliance option. GM commented that 

no one would certify to the dynamic 

performance option because mounting 

the whole vehicle on the sled, instead 

of just the seat, imposes an undue level 

of complexity.

NHTSA concludes that attaching the 

seat to a test buck is problematic for 

compliance tests. NHTSA cannot use a 

vehicle for further testing involving a 

seat if we remove the seat for the 

purposes of dynamic compliance option 

testing. Accordingly, NHTSA will 

conduct its compliance testing using the 

whole vehicle. The manufacturers are, 

of course, free to conduct their 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74877

development and certification testing on 

a buck. To assure that any certification 

is in good faith, we would expect such 

a manufacturer to show a correlation 

between buck testing and full vehicle 

testing. 

XIV. Consumer Information 

In the NPRM, we asked for comments 

regarding whether vehicle users 

understand how to properly adjust head 

restraints and, if not, whether the rule 

should require manufacturers to provide 

information on this subject to 

consumers in vehicle owners’ manuals 

or elsewhere. In addition, the NPRM 

solicited comments regarding whether 

vehicle users intentionally misadjust 

head restraints for reasons related to 

comfort, visibility, or other factors. 

ICBC provided extensive comments 

on these issues. According to ICBC, 

most motorists are not aware of the need 

to properly adjust their head restraints. 

Results from focus group studies 

commissioned by ICBC in 1996 suggest 

that drivers do not perceive a head 

restraint as a safety device and do not 

understand how a head restraint 

protects them. Consumer education 

programs, ICBC asserted, can increase 

the rate of proper adjustment, and 

manufacturers should play a role in 

educating consumers through owners’

manuals, advertising, and in vehicle 

showrooms. ICBC initiated media 

information and direct intervention 

with vehicle users at various locations, 

including emissions testing stations, 

ferry terminals, and insurance offices. 

Education at ferry terminals alone 

resulted in 79,000 of 190,000 vehicle 

drivers adjusting their head restraints. 

ICBC cited these results, as well as 

similar studies of Transport Canada, in 

support of its effort to show that 

consumer education programs can 

positively influence proper head 

restraint adjustment. Transport Canada 

relied on ICBC data and suggested that 

the public does not properly adjust head 

restraints in the absence of consumer 

information programs. 

Johnson Controls and the Alliance 

noted that they knew of no data 

suggesting whether head restraints are 

intentionally or inadvertently 

misadjusted. Based on consumer 

surveys conducted by Johnson Controls, 

users adjust their head restraint height 

at most only once, in order to increase 

comfort, not to improve safety. 

DaimlerChrysler believed vehicle 

users intentionally misadjust head 

restraints for reasons related to comfort, 

visibility, convenience, and a lack of 

knowledge about proper positioning. 

However, DaimlerChrysler indicated it 

did not have any data to show why this 

intentional misadjustment occurs as 

opposed to inadvertent misadjustment. 

DaimlerChrysler commented in favor of 

requiring additional literature, either in 

owners’ manuals or elsewhere, to 

educate consumers about the proper use 

and positioning of head restraints. The 

Alliance stated that vehicle users 

generally do not fully understand the 

appropriate use and purpose of head 

restraints. The Alliance and GM stated 

that a consumer information program 

coordinated between NHTSA and 

industry members could substantially 

reduce the problem of improper head 

restraint adjustment. 

Ford indicated that it voluntarily 

includes head restraint adjustment 

information in its owners’ manuals and 

that such information is adequate to 

educate consumers about proper head 

restraint positioning. State Farm 

expressed support for requiring 

manufacturers to include head restraint 

positioning information in owners’

manuals. 

Agency response: NHTSA believes 

proper adjustment of head restraints is 

necessary to ensure that vehicle 

occupants realize the maximum 

whiplash protection from head 

restraints. In order to address head 

restraint misadjustment, this final rule 

requires that vehicle manufacturers 

include in owners’ manuals information 

about appropriate head restraint 

adjustment. We note that most 

manufacturers already provide some of 

this information in their owners’

manuals. 

XV. Effective Date and Interim 

Compliance Options 

In the NPRM, we proposed that 

compliance with the upgraded standard 

would be mandatory on the first 

September 1 that occurred following the 

three-year period that began with the 

publication of the final rule. We asked 

for comments on the appropriateness of 

the three-year lead time. 

Today’s final rule becomes mandatory 

for all vehicles manufactured on or after 

September 1, 2008. We decided to 

extend the lead time by one additional 

year in order to allow vehicle 

manufacturers to phase in the new head 

restraint requirements in conjunction 

with their natural product cycle. The 

four-year lead time will, in most 

instances, allow vehicle manufacturers 

to design compliant head restraints for 

newly introduced vehicles, as opposed 

to redesigning existing seating systems 

for vehicles currently in production. 

Between March 14, 2005, the effective 

date of today’s rule, and September 1, 

2008, manufacturers have five 

compliance options. First, 

manufacturers may comply with ECE 

17, except that they must meet the 

current width requirements of FMVSS 

No. 202. Second, manufacturers may 

comply with either dynamic or static 

requirements of the existing FMVSS No. 

202. Third, they may comply with either 

dynamic or static requirements of the 

new FMVSS No. 202a. Consistent with 

our approach in other standards in 

which there are compliance options, the 

manufacturer must irrevocably elect a 

particular option prior to certification of 

the vehicle. However, the manufacturer 

may select different compliance options 

for different designated seating 

positions. 

There were relatively few comments 

related to the proposed lead time or 

compliance choices during that time. 

Honda commented that an additional 

three years of lead time should be added 

for rear seat head restraint compliance, 

in addition to the three years for front 

seat head restraints. Magna requested 

that an additional 3-year phase-in 

period be included along with the 

proposed 3-year lead time period, to 

allow for proper product development. 

Porsche commented that limited line 

manufacturers should be provided 

additional lead time, or if a phase-in is 

utilized, they should be given until the 

end of the phase-in period to comply. 

The Alliance argued that the final rule 

implementation should be postponed, 

and compliance with the current 

version of FMVSS No. 202 be allowed 

until at least 2005. The Alliance also 

recommended a phase-in period of 3 

years after the rule is finally published. 

DaimlerChrysler believed four years of 

lead time was in order, in light of 

significant deviations from the ECE 

standards. Advocates strongly 

supported the 3-year interim period 

followed by complete implementation 

of the new standard.

We believe that the requests for lead 

time in addition to the four years 

provided in this final rule are 

unwarranted. Unlike the NPRM 

proposal, this final rule does not require 

head restraints in rear outboard 

designated seating positions. With 

respect to height, this final rule 

harmonizes our head restraint 

requirements with those already in 

effect under the ECE 17 regulation. 

Accordingly, a significant number of 

vehicles for sale in the United States 

already meet the European height 

requirement. Finally, we believe the 

four-year lead time provides sufficient 

time to resolve any problems associated 

with the new backset requirement. 

As previously discussed, most of the 

commenters agreed that the new 

requirements for head restraints that are 

74878 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

79A survey of 2004 model year Porsche 911 

vehicles (911, 911 Targa, 911 4S, 911 Cabriolet, 911 

Turbo, 911 GT2, 911 GT3) indicates that none 

currently feature rear head restraints.

80See, e.g., 64 FR 10786 at 10808 (March 15, 

1999) and 64 FR 69665 at 69668 (December 14, 

1999).

81For details on the PEA, please see Docket No. 

NHTSA–2000–8570–4.

82The NPRM costs were estimated in 1999 

dollars. 83See Docket No. NHTSA–2004–19807.

taller and closer to the head are likely 

to reduce the instances of whiplash 

injuries. According to ICBC, numerous 

vehicles currently in production already 

satisfy the 55 mm backset requirement. 

Similarly, we believe that numerous 

vehicles currently in production satisfy 

the 800 mm requirement. Most of the 

manufacturers who requested additional 

lead time sell cars in Europe and, 

therefore, are already in compliance 

with the ECE regulation requiring 

similar head restraint height. In light of 

the aforementioned circumstances, we 

conclude that a four-year lead time 

allows ample opportunity to redesign 

head restraints in order to comply with 

the new standard. 

In regard to comments made by 

Porsche on behalf of small, independent 

automobile manufacturers, we note that 

Porsche and other small line European 

manufacturers are, presumably, already 

manufacturing vehicles that are in 

compliance with ECE 17. Further, rear 

head restraints are optional, and the 

final rule does not consider a seat back 

lower than 700 mm above the H-point 

as a head restraint. Therefore, Porsche 

can continue to produce the 911 vehicle 

line without installing rear head 

restraints.79 Moreover, we have allowed 

25 mm clearance between the rear head 

restraint and the roofline, thus 

alleviating some of the concerns raised 

by Porsche. Accordingly, Porsche can 

take advantage of the 25 mm height 

allowance if they choose to equip the 

rear seats in their 911 vehicle line with 

head restraints.

We received a number of comments 

pertaining to the interim compliance 

options. Advocates called NHTSA’s 

interim compliance proposals ‘‘an 

eminently reasonable compromise’’ and 

supported this approach in lieu of 

allowing a phase-in. TRW also 

supported the interim compliance 

options set forth in the NPRM, stating 

that allowing compliance options would 

spur the growth of better technologies. 

AIAM disagreed with the requirement 

that a manufacturer must choose a 

particular compliance option prior to 

certification. For reasons explained in 

other rulemakings, the agency will not 

allow manufacturer to recertify under an 

alternative compliance option, if there is 

a noncompliance with the option to 

which the manufacturer initially 

certified.80

The Alliance argued against the 

interim compliance option approach, 

instead favoring a phase-in schedule 

after NHTSA better identified the causes 

of soft tissue neck injuries. This phasein approach, the Alliance contended, 

should give manufacturers credit for 

early compliance. DaimlerChrysler 

asserted that NHTSA should allow 

compliance with the interim options 

indefinitely or at least until NHTSA 

gained a better understanding of 

whiplash injuries. 

Based on our consideration of ECE 17, 

and the existing version of FMVSS No. 

202 under the functional equivalence 

process defined in Appendix B of 49 

CFR Part 553, we have concluded that 

ECE 17 offers greater safety benefits than 

the existing version of FMVSS No. 202. 

The most notable differences between 

FMVSS No. 202 and ECE 17 are that 

while FMVSS No. 202 currently does 

not address head restraints for rear 

seating positions or contain any 

requirements for energy absorption, ECE 

17 specifies requirements for head 

restraints that are voluntarily installed 

in rear seating positions and for energy 

absorption. 

Accordingly, we will permit interim 

compliance with the specified 

requirements of ECE 17. As stated 

above, the final rule also permits 

certification using either of the existing 

FMVSS No. 202 requirements or either 

of the upgraded FMVSS No. 202a 

requirements. Upon expiration of the 

four-year interim period, however, 

manufacturers must comply with 

upgraded FMVSS No. 202a. 

XVI. Costs and Benefits Associated 

With the Final Rule 

The NPRM estimated that the 

proposed rule would reduce the annual 

number of whiplash injuries by 14,247 

(9,575 for front outboard seats and 4,672 

for rear outboard seats).81 The cost of 

raising the front head restraint was 

estimated to be $4.21 per vehicle, 

resulting in a fleet cost of $65.5 

million.82 Installing two rear head 

restraints in vehicles that previously did 

not have rear head restraints was 

estimated at $12.34 per vehicle, 

resulting in a fleet cost of $74.8 million. 

Raising the rear head restraints in 

vehicles already equipped with rear 

head restraints was estimated at $3.61 

per vehicle, resulting in a fleet cost of 

$19.6 million. Adding a locking 

mechanism would cost $0.15 per 

vehicle, for a total fleet cost of $5.9 

million. The total estimated fleet cost 

for all changes required by the new rule 

was $171.9 million. The cost per 

equivalent life saved was estimated at 

$3 million for front seats and $9 million 

for rear seats.

The sole commenter on the estimated 

costs of the upgrade was 

DaimlerChrysler, which estimated the 

cost of the proposal to be as high as $12 

per head restraint. No commenter 

provided an estimate of potential 

benefits. The Alliance stated that the 

potential benefits are unproven. AIAM 

commented that general lack of 

understanding of the injury mechanism 

makes it nearly impossible to calculate 

the benefits of the proposal or any 

modifications to it. 

ICBC stated that any figures 

pertaining to whiplash injury costs are 

underestimated because whiplash injury 

symptoms do not manifest themselves 

until 12 to 72 hours after the accident. 

Additionally, unlike other spinal 

injuries, whiplash has no linear 

relationship to crash severity. Low 

speed crashes may nevertheless result in 

whiplash. Many low speed rear end 

collisions resulting in whiplash are 

never reported to the police, because of 

little physical damage to the actual 

vehicles and lack of immediate injury 

symptoms. Advocates stated that the 

proposed rule would be a cost-effective 

advance in vehicle occupant safety, 

even if forecasted benefits were reduced 

to more conservative figures and costs of 

compliance were substantially higher. 

The FIU students stated that the rear 

outboard head restraint cost for 

equivalent lives saved would be 

approximately $9 million. 

In support of this final rule, the 

agency has prepared and docketed a 

FRIA that contains a thorough analysis 

of the benefits and the costs associated 

with the new FMVSS No. 202a, as well 

as our response to the NPRM comments 

on our initial cost and benefits 

estimates.83

Costs: In the NPRM, we estimated the 

yearly costs of the proposed rule at 

approximately $171 million. 

Accordingly, the NPRM was deemed to 

be economically significant. As 

previously noted, the final rule will not 

require head restraints at each rear 

outboard designated seating position. 

Consequently, the costs associated with 

this final rule are significantly lower 

than the costs estimated in the NPRM. 

Specifically, the cost per year is 

estimated to be $70.1 million for front 

head restraints and $14.1 million for 

optional rear head restraints for a total 

yearly cost of $84.2 million. However, 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74879

84The cost is estimated in 2002 dollars. 85 Kahane, C., ‘‘An Evaluation of Head Restraints, 

Federal Motor Vehicle Safety Standard 202.’’

NHTSA, February 1982, DOT HS–806–108. 86 In computing benefits, we based our estimates 

on the effectiveness of either increased height or 

reduced backset, but not both. We could not 

combine effectiveness of increased height and 

reduced backset because this, in some instances, 

would result in ‘‘double-counted’’ benefits. Since 

determining combined effectiveness is not possible, 

the agency notes that these estimates may 

underestimate the true effectiveness.

87For the full details of how the agency arrived 

at these estimates, please see FRE, in subsection 

entitled ‘‘Benefits Accrued From Increasing Height 

and Reducing Backset.’’

88Unless otherwise specified, all dollar alues in 

this document are represented in 2002 dollars.

the final rule remains economically 

significant because we estimate the 

benefits of this final rule to be in excess 

of $100 million. The average cost per 

vehicle is estimated to be: 

(a) $4.51 for front seats 

(b) $1.13 for rear seats previously 

equipped with head restraints 

The cost per equivalent life saved is 

estimated to be: 

(a) $2.39 million for front seats 

(b) $4.71 million for rear seats 

equipped with optional rear head 

restraints 

(c) $2.61 million for front seats and 

optional rear seats combined 

Benefits: We estimate the annual 

number of whiplash injuries to be 

approximately 272,464. 251,035 of these 

injuries involve occupants of front 

outboard seats, 21,429 injuries involve 

occupants of rear outboard seats. The 

average economic cost of each whiplash 

injury resulting from a rear impact 

collision is $9,994,84 which includes 

$6,843 in economic costs and $3,151 in 

quality of life impacts. The total annual 

cost of rear impact whiplash injuries is 

approximately $2.7 billion.

Based on a study conducted by 

Kahane in 1982, the agency estimates 

that current integral head restraints are 

17 percent effective in reducing 

whiplash injury in rear impact crashes 

for adult occupants, while current 

adjustable head restraints are 10 percent 

effective in reducing whiplash injury in 

rear impact crashes for adult 

occupants.85 The overall effectiveness of 

current head restraints for passenger 

cars is estimated to be 13.1 percent.

In the FRIA, we estimate that 

upgrading the head restraint 

requirements would yield the following 

benefits: 

(a) For front seats, reducing the 

backset to 55 mm increases the head 

restraint effectiveness by 5.83 percent, 

resulting in 15,272 fewer whiplash 

injuries for front seat occupants each 

year. 

(b) For rear seats, increasing the 

height of voluntarily installed rear head 

restraints increases the effectiveness of 

these head restraints by 17.45 percent, 

resulting in 1,559 fewer whiplash 

injuries for rear seat occupants each 

year.86

(c) The total annual reduction in rear 

impact whiplash injuries is thus 

estimated at (15,272 + 1,559) 16,831 or 

6 percent of the annual number of 

whiplash injuries (272,464).87

In sum, we estimate that this 

rulemaking will further reduce the 

incidence of whiplash by an additional 

≈6 percent (272,464 *.0618 = 16,831). 

We note that with respect to whiplash 

injuries, a 6 percent reduction in the 

incidence of whiplash is a significant 

step forward because the current head 

restraints only prevent 13.1 percent of 

whiplash injuries occurring in rear 

impact crashes. The agency anticipates 

further improvements in head restraint 

effectiveness if we decide, in the future, 

to combine evaluation of the head 

restraints and the seats in a single 

standard.

As was the case in the PEA, no 

estimate was made for potential injury 

mitigation other than for whiplash. 

Further, the agency has not prepared an 

analysis of the potential benefits of the 

position retention requirement. 

Although we have some estimates on 

the percentage of misadjusted head 

restraints, we have no data on how the 

availability of a lock would reduce this 

maladjustment. 

We have several reasons to believe 

that the potential benefits of this 

regulation are understated. First, for the 

reason stated above, we did not perform 

a separate analysis of benefits associated 

with reduced position retention 

requirement. Second, we agree with the 

ICBC comments regarding inherent 

underestimation of whiplash injury 

costs due to the underreporting of such 

injuries. As previously stated, whiplash 

injuries are often underreported because 

of late onset of symptoms. Third, no 

estimate of the potential reduction of 

higher-level neck injury (>AIS 1) was 

made. Although such injuries are much 

less frequent, their associated costs are 

much greater. 

XVII. Rulemaking Analyses and 

Notices 

a. Executive Order 12866 and DOT 

Regulatory Policies and Procedures 

NHTSA has considered the impact of 

this rulemaking action under Executive 

Order 12866 and the Department of 

Transportation’s regulatory policies and 

procedures. The Office of Management 

and Budget reviewed rulemaking 

document under E.O. 12866, 

‘‘Regulatory Planning and Review.’’

This rulemaking action has been 

determined to be significant under DOT 

Policies and Procedures and Executive 

Order 12866 because of public interest. 

Further, this rulemaking action is 

economically significant because the 

agency estimates yearly economic cost 

savings of approximately $127 million 

($2.61 million × 48.79 equivalent 

fatalities). NHTSA is placing in the 

public docket a Final Regulatory 

Evaluation describing the costs and 

benefits of this rulemaking action. The 

costs and benefits are summarized in 

the previous section of this document. 

The total estimated recurring fleet cost 

for all changes required by the new rule 

is $84.2 million. The average economic 

cost of a whiplash injury (excluding 

quality of life values) in a rear impact 

is estimated be $9,994 in 2002 dollars, 

resulting in a total annual cost of 

approximately $2.707 billion for 

272,464 whiplash injuries.88 We 

estimate that when the new rule is fully 

implemented, it will reduce yearly 

instances of whiplash injuries by 6 

percent or 16,831, resulting in yearly 

economic cost savings of approximately 

$127 million.

b. Regulatory Flexibility Act 

NHTSA has considered the effects of 

this rulemaking action under the 

Regulatory Flexibility Act (5 U.S.C. 601 

et seq.) The final rule will affect motor 

vehicle manufacturers, alterers, and 

seating manufacturers. NHTSA has 

determined that this action will not 

have a significant economic impact on 

a substantial number of small entities. 

First, NHTSA estimates that there are 

only four small passenger car and light 

truck manufacturers in the United 

States. These companies buy their seats 

from a seat manufacturer and install 

them in their vehicles. Accordingly, the 

necessary changes to seat design will be 

accomplished by seat manufacturers 

and not these small businesses. 

Second, there are approximately 30 

seat manufacturers in the U.S. Many of 

these fall under the category of small 

businesses. The final rule will have 

some effect on these small businesses by 

changing the requirements for head 

restraints. However, raising the height of 

an integral or adjustable head restraint 

or changing the design of a head 

restraint to meet the new backset limit 

is not a novel or complex task that 

would require significant financial 

expenditures. Further, numerous 

vehicles currently in production already 

meet the new requirements. 

Consequently, the agency does not 

believe that this rulemaking will have a 

74880 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

89See 49 CFR part 555. 90 62 FR 19885, April 23, 1997.

significant impact on small seat 

manufacturers. 

Third, this rulemaking could affect 

final stage vehicle manufacturers and 

vehicle alterers. Many final stage 

manufacturers and alterers install 

supplier-constructed seating systems. 

Some of those seats and head restraints 

will have to be redesigned to meet the 

new requirements. However, final stage 

manufacturers or alterers most often 

purchase seats that have already been 

tested by the seat manufacturers and 

rely on that testing to certify to the 

requirements of FMVSS No. 202. 

Accordingly, the agency does not 

believe that this rulemaking will have a 

significant impact on final stage 

manufacturers and vehicle alterers. 

For the reasons discussed above, the 

small entities that will most likely be 

affected by the new rule are seat 

manufacturers. While these seat 

manufacturers will face additional 

compliance costs, the agency believes 

that raising the height of a head restraint 

is not a novel or complex engineering 

task. The agency notes that, in the 

unlikely event that a small vehicle 

manufacturer did face substantial 

economic hardship, it could apply for a 

temporary exemption for up to three 

years.89 Additional information 

concerning the potential impacts of the 

new rule on small entities is presented 

in the FRIA. 

c. National Environmental Policy Act

NHTSA has analyzed the final rule for 

the purposes of the National 

Environmental Policy Act. The agency 

has determined that implementation of 

this action will not have any significant 

impact on the quality of the human 

environment. 

d. Executive Order 13132 (Federalism) 

The agency has analyzed this 

rulemaking in accordance with the 

principles and criteria contained in 

Executive Order 13132 and has 

determined that it does not have 

sufficient federalism implications to 

warrant consultation with State and 

local officials or the preparation of a 

federalism summary impact statement. 

The final rule has no substantial effects 

on the States, or on the current FederalState relationship, or on the current 

distribution of power and 

responsibilities among the various local 

officials. The final rule is not intended 

to preempt State tort civil actions. 

e. 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 

($120,700,000 as adjusted for inflation 

with base year of 1995). 

The total estimated fleet cost for all 

changes required by the new rule is 

$84.2 million. Because this final rule 

will not have a $100 million effect, no 

Unfunded Mandates assessment has 

been prepared. A full assessment of the 

rule’s costs and benefits is provided in 

the FRIA. 

f. Executive Order 12988 (Civil Justice 

Reform) 

This final rule will not have any 

retroactive effect. Under 49 U.S.C. 

30103, whenever a Federal motor 

vehicle safety standard is in effect, a 

State may not adopt or maintain a safety 

standard applicable to the same aspect 

of performance which is not identical to 

the Federal standard, except to the 

extent that the State requirement 

imposes a higher level of performance 

and applies only to vehicles procured 

for the State’s use. 49 U.S.C. 30161 sets 

forth a procedure for judicial review of 

final rules establishing, amending or 

revoking Federal motor vehicle safety 

standards. That section does not require 

submission of a petition for 

reconsideration or other administrative 

proceedings before parties may file suit 

in court. 

g. Paperwork Reduction Act 

This final rule includes the following 

‘‘collections of information,’’ as that 

term is defined in 5 CFR part 1320 

Controlling Paperwork Burdens on the 

Public: The final rule requires that 

vehicle manufacturers include in 

owners’ manuals information about 

appropriate head restraint adjustment. 

At present, OMB has approved 

NHTSA’s collection of owner’s manual 

requirements under OMB clearance No. 

2127–0541 Consolidated Justification of 

Owner’s Manual Requirements for 

Motor Vehicles and Motor Vehicle 

Equipment. This clearance will expire 

on 1/31/2005. NHTSA anticipates 

renewal of OMB clearance no. 2127–

0541 before the requirements 

established by today’s rule become 

mandatory. 

h. Executive Order 13045 

Executive Order 13045 90 applies to 

any rule that: (1) Is determined to be 

‘‘economically significant’’ as defined 

under E.O. 12866, and (2) concerns an 

environmental, health or safety risk that 

NHTSA has reason to believe may have 

a disproportionate effect on children. If 

the regulatory action meets both criteria, 

we must evaluate the environmental 

health or safety effects of the planned 

rule on children, and explain why the 

planned regulation is preferable to other 

potentially effective and reasonably 

feasible alternatives considered by us.

This rule is economically significant. 

However, this rule will not have a 

disproportionate effect on children. 

Most children do not need a head 

restraint because they are short enough 

for the seat back to adequately address 

a risk of whiplash injury. Once a child 

is tall enough to need a head restraint, 

this rule will provide additional 

protection because rear seats will now 

be equipped with head restraints, thus 

providing a new level of safety to taller 

children. 

i. National Technology Transfer and 

Advancement Act 

Section 12(d) of the National 

Technology Transfer and Advancement 

Act (NTTAA) requires NHTSA to 

evaluate and use existing voluntary 

consensus standards in its regulatory 

activities unless doing so would be 

inconsistent with applicable law (e.g.,

the statutory provisions regarding 

NHTSA’s vehicle safety authority) or 

otherwise impractical. In meeting that 

requirement, we are required to consult 

with voluntary, private sector, 

consensus standards bodies. Examples 

of organizations generally regarded as 

voluntary consensus standards bodies 

include the American Society for 

Testing and Materials (ASTM), the 

Society of Automotive Engineers (SAE), 

and the American National Standards 

Institute (ANSI). If NHTSA does not use 

available and potentially applicable 

voluntary consensus standards, we are 

required by the Act to provide Congress, 

through OMB, an explanation of the 

reasons for not using such standards.

Voluntary consensus standards are 

technical standards developed or 

adopted by voluntary consensus 

standards bodies. Technical standards 

are defined by the NTTAA as 

‘‘performance-based or design-specific 

technical specifications and related 

management systems practices.’’ They 

pertain to ‘‘products and processes, 

such as size, strength, or technical 

performance of a product, process or 

material.’’

We have incorporated a Society of 

Automotive Engineers (SAE) 

Recommended Practice J211/1 (rev. Mar 

95), ‘‘Instrumentation for Impact Test—

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74881

91We note that the NPRM proposed a value of 

171 mm rather than 170, which is consistent with 

the current regulation. We have reduced this value 

by 1 mm for consistency with ECE 17.

Part 1—Electronic Instrumentation.’’ We 

have incorporated a three-dimensional 

manikin from the Society of Automotive 

Engineers (SAE) J826 (rev. Jul 95). None 

of the voluntary consensus standards 

incorporated into this final rule 

provides a comprehensive head restraint 

geometry standard that could replace 

this rule in its entirety. Instead, certain 

specific components of the final rule 

were adopted from available voluntary 

consensus standard. 

In sum, while two specific voluntary 

consensus standards are incorporated in 

the final rule, the overall need for 

extensive and precise new head 

restraint safety requirement precludes 

us from adopting of such voluntary 

consensus standards as a complete 

substitute for the final rule. No other 

voluntary consensus standards are 

addressed by this rulemaking. We were 

also were unable to identify any other 

relevant voluntary consensus standards. 

j. Privacy Act 

Anyone is able to search the 

electronic form of all comments 

received into any of our dockets by the 

name of the individual submitting the 

comment (or signing the comment, if 

submitted on behalf of an association, 

business, labor union, etc.). You may 

review DOT’s complete Privacy Act 

Statement in the Federal Register

published on April 11, 2000 (65 FR 

19477 at 19478). 

Appendix A: Efforts To Harmonize 

With ECE 17

In proposing to upgrade FMVSS No. 202, 

we sought to harmonize with existing ECE 

regulations, except to the extent needed to 

increase safety of vehicle occupants and to 

facilitate enforcement. The ECE has two 

regulations pertinent to our efforts on 

upgrading FMVSS No. 202. ECE 17 and ECE 

25 both regulate head restraints. However, 

the provisions of ECE 17 supersede the 

requirements of ECE 25 for most vehicles 

subject to this final rule. Specifically, ECE 17 

governs the head restraint requirements in all 

passenger vehicles, light trucks, and buses 

with fewer than 17 designated seating 

positions. The ECE 25 applies only to buses 

with 17 or more designated seating positions. 

Because this final rule applies to vehicles 

with a GVWR equal or less than 4536 kg, it 

is unlikely that any buses subject to this final 

rule would fall under ECE 25. Accordingly, 

we sought to harmonize certain aspects of 

this final rule with ECE 17, and not ECE 25. 

In some instances, achieving improved 

safety has made it necessary for us to go 

beyond or take an approach different from 

that in ECE 17. For example, this final rule 

limits the backset, while ECE 17 does not. We 

note that in most instances in which this rule 

is harmonized with the substance of the ECE 

requirements, the actual regulatory language 

is nevertheless drafted differently in order to 

facilitate enforcement. Specifically, we have 

found it necessary to specify different 

compliance procedures to facilitate their 

enforcement under our statutory provisions. 

For example, there are differences in the way 

in which gaps within head restraints are 

measured. 

In response to the NPRM, industry 

commenters generally advocated 

harmonizing the new FMVSS No. 202 with 

ECE 17, which applies to most vehicles 

subject to this final rule, although Honda 

requested harmonization with ECE 25. GM 

and Volkswagen suggested that it would be 

more appropriate to harmonize with ECE 17, 

rather than ECE 25, because ECE 17 is 

utilized for the type approval of vehicles, 

while ECE 25 is used for the type approval 

of head restraints only. 

As previously stated, this final rule is not 

fully harmonized with the ECE requirements. 

Instead, the rule adopts or modifies certain 

portions of ECE 17. Several of our newly 

adopted requirements do not have any 

counterparts in the ECE regulations. Among 

those is a limit on backset and position 

retention requirement for adjustable head 

restraints. In addition, our limit on gaps in 

adjustable restraints is different from that in 

the ECE regulations. 

The discussions that follow provide a brief 

description of those instances in which the 

final rule does or does not harmonize with 

the ECE regulations. 

A. Areas in Which the Final Rule 

Requirements and Procedures Are 

Harmonized With Those of the ECE 

Regulations 

Neither this final rule nor ECE 17 requires 

head restraints for rear outboard seating 

positions. Although we proposed mandatory 

rear head restraints in the NPRM, we have 

decided against requiring head restraints in 

rear outboard seating positions because a 

more refined estimate of the cost 

effectiveness expressed as cost per equivalent 

life saved no longer supported this 

requirement and because we were concerned 

about potential visibility issues and with 

potential loss of certain features currently 

available in some ‘‘multi-configuration’’

vehicles.

This final rule and ECE 17 specify 

theoretically identical front and optional rear 

head restraint height requirements. For 

integral head restraints, the ECE 17, 

Paragraph 5.5.2 requires that front head 

restraints reach a height of 800 mm and rear 

head restraints reach the height of 750 mm. 

For adjustable head restraints, the ECE 17, 

Paragraph 5.5.3.1 requires that front head 

restraints be capable of reaching a height of 

800 mm, and have no ‘‘use positions’’ with 

a height of less than 750 mm. The optional 

rear adjustable head restraints must reach the 

height of at least 750 mm and cannot have 

any ‘‘use position’’ below that height. 

Additionally, ECE 17, Paragraph 5.5.4 allows 

for a 25 mm exception to the head restraint 

height requirement for head restraints 

installed in low roofline vehicles. 

This final rule likewise requires that the 

front integral head restraints reach a height 

of 800 mm above the H-point. The optional 

rear integral head restraints must reach the 

height of 750 mm above the H-point. For 

adjustable head restraints, the front head 

restraint must be capable of reaching the 

height of at least 800 mm above the H-point, 

and both front and optional rear head 

restraints cannot have an adjustment position 

below 750 mm above the H-point, unless it 

is a ‘‘non-use’’ position described above in 

Section IX c. 

Additionally, the final rule allows for a 25 

mm height exception for head restraints 

installed in low roofline vehicles. However, 

the application of the 25 mm height 

exception is narrower in this final rule. 

Specifically, ECE 17 allows for a 25 mm 

height exception if the head restraint 

interferes with any interior vehicle structure. 

By contrast, this final rule limits the 25 mm 

exception to situations in which a head 

restraint would interfere with the roofline or 

the backlight (for rear head restraint). The 25 

mm height exception for low roofline 

vehicles is discussed in Section VI a. and b. 

For height measurement ECE17, Paragraph 

6.5.4 uses the R-point as the point of 

reference, while the final rule uses the Hpoint. Theoretically, these points are the 

same if the seat is placed in its rearmost 

normal riding or driving position, as 

specified by the vehicle manufacturer. The 

chief difference between the two points is 

that the H-point is referenced to the seat, 

while the R-point is referenced to the vehicle. 

NHTSA prefers the H-point as the point of 

reference because it takes into consideration 

the characteristics of the actual seat being 

tested. 

The final rule and ECE 17 Paragraph 5.1.3 

both have an energy absorption test 

procedure. However, the final rule specifies 

using a linear impactor, while ECE 17, Annex 

6, Paragraph 1.2.1 specifies a pendulum 

impactor. Nonetheless, NHTSA believes that 

the compliance testing methods are 

substantially similar because the mass and 

velocity of the impactor specified in this final 

rule is the same as the impactor specified in 

ECE 17. We chose to test using the linear 

impactor in order to facilitate enforcement. 

For a more detailed explanation of our 

rationale with respect to the choice of 

impactor, please see Section XI. 

ECE 17, Paragraph 5.10 mandates that the 

head restraint for a seat must extend at least 

85 mm to each side of the centerline of the 

seat. In other words, a head restraint width 

must be at least 170 mm. This ECE 17 

minimum width requirement applies to both 

bench seats and bucket seats. This final rule 

specifies identical requirements of 170 mm,91

except for bench seats in the front outboard 

seating positions where the head restraint 

width must not be less than 254 mm.

Some of the head restraint gap allowances 

incorporated into the final rule harmonize 

with ECE 17. The final rule and ECE 17, 

Paragraphs 5.7, 5.8 all limit gaps within the 

perimeter of a head restraint to 60 mm. 

Similarly, for integral head restraints, the gap 

between the head restraint and the seat is 

limited to 60 mm in both regulations. 

However, the final rule requires different gap 

74882 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

92See ICBC comments and attached research 

papers (Docket No. NHTSA–2000–8570–16).

limits between the seat and the adjustable 

head restraint. The details of these 

requirements are discussed in the next 

section. 

The ECE 17, Paragraph 5.1.1 requires locks 

on adjustable head restraints, but does not 

mandate that these locks meet vertical and 

horizontal position retention requirements to 

insure their functionality. By contrast, this 

rule requires that adjustable head restraints 

meet vertical and horizontal position 

retention requirements described above in 

Section X. We note, however, that both ECE 

17, Paragraphs 5.11, 5.12 and this final rule 

impose horizontal displacement limits and 

strength requirements on all seating position 

equipped with head restraints. 

Finally, both this final rule and ECE 17, 

Paragraph 5.13 allow removability of head 

restraints with a deliberate action distinct 

from any act necessary for adjustment. For a 

more detailed discussion on removability of 

front and rear head restraints, please see 

Section IX b. 

B. Areas in Which the Final Rule 

Requirements and Procedures Differ From 

Those in the ECE Regulations 

The chief difference between ECE 17 and 

this final rule is that we are requiring a 

backset limit of 55 mm for front seat head 

restraints. The ECE regulation does not limit 

the amount of backset. Studies show that a 

head restraint that is close to the back of an 

occupant’s head reduces the potential for 

whiplash.92 Further, backset is a critical 

component of head restraint geometry. For 

these reasons and those outlined in Section 

VII above, NHTSA believes it is necessary to 

depart from the ECE regulations and set a 

limit on backset.

To measure height of head restraints, the 

final rule specifies the use of SAE J826 

manikin. To measure front seat backset, the 

final rule specifies the use of the Head 

Restraint Measurement Device (HRMD). ECE 

17 does not specify any device for height 

measurement and, as noted above, has no 

backset requirement. We chose the SAE J826 

manikin and HRMD instead of certain 

Computer Aided Design (CAD) programs, as 

suggested by the manufacturers, because the 

HRMD and SAE J826 manikin measure the 

actual seating system, instead of relying on 

the computer-generated seat model utilized 

by other computer-aided measuring 

techniques. 

In addition to the measuring device, the 

height measuring procedure in this final rule 

in some circumstances differs from the 

measuring procedure of ECE 17. Specifically, 

this final rule specifies that the seat back 

angle for height measurement be as close as 

possible to 25 degrees. ECE 17, Paragraph 

6.1.1 similarly specifies the 25-degree seat 

back angle if there is no manufacturer 

specified seat back angle. However, if there 

is a manufacturer specified seat back angle, 

the manufacturer specified angle is used 

instead of the 25-degree angle. Further, this 

final rule specifies that the seat cushion be 

adjusted to its most unfavorable position, i.e., 

the highest position. ECE 17, Annex 3, 

Paragraph 2.13 specifies that the cushion is 

to be placed in the manufacturer specified 

position of adjustment. Positioning the 

cushion in the highest position of adjustment 

allows us to measure the height of head 

restraints in the ‘‘worst case scenario.’’ That 

is, the minimum required height would be 

assured even if the seat occupant adjusts the 

seat cushion all the way up. 

ECE 17, Paragraph 5.7 limits the gap 

between the lower edge of an adjustable head 

restraint and the top of the seat back to 25 

mm when the head restraint is in its lowest 

position. The final rule, however, adopts a 60 

mm gap limit between the seat back and the 

head restraint. Further, the final rule differs 

from the ECE requirements in that it specifies 

measuring this gap with a 165 mm diameter 

sphere placed on the front of the head 

restraint in lieu of measuring the smallest gap 

between the top of a seat back and the bottom 

of a head restraint. For a more detailed 

discussion on why we chose to adopt a 

different gap requirement and different 

measuring device, please see Section IX a. 

ECE 17, Paragraph 5.5.3.4 permits non-use 

positions (resulting in a height of less than 

750 mm) for front head restraints, provided 

that the head restraints automatically return 

from those positions to their proper use 

positions when the seats become occupied. 

With respect to rear head restraints, ECE 17, 

Paragraph 5.5.3.3 allows displacement to a 

position below 750 mm as long as the nonuse position is ‘‘clearly recognizable to the 

occupant.’’ In contrast, this final rule does 

not permit non-use positions for front head 

restraints. NHTSA believes non-use positions 

in front seats are unnecessary since the front 

head restraints do not raise the same 

visibility concern as the rear head restraints. 

While we permit non-use positions for 

optional rear head restraints, our 

requirements differ from those of the ECE. 

That is, the final rule allows rear head 

restraint to be in non-use positions when 

seats are unoccupied, subject to meeting 

certain requirements. Specifically, a 

manually folding optional rear head restraint 

must rotate forward or rearward by at least 

60 degrees between the ‘‘proper use position’’

and the ‘‘non-use position.’’ No other ‘‘nonuse positions’’ are allowed unless the head 

restraint returns automatically to its ‘‘proper 

use position when the seat becomes 

occupied’’ (as tested by placing a 5th 

percentile female dummy in the rear 

outboard seat with the optional head restraint 

in a ‘‘non-use position’’). As with other 

procedural differences between this final rule 

and the ECE, this test procedure is necessary 

in order to facilitate enforcement. 

The final rule also features a dynamic 

compliance option not found in ECE 17. For 

front outboard and optional rear outboard 

head restraints, with the head restraint 

midway between the lowest and the highest 

position of adjustment, the final rule requires 

a head-to-torso rotation limit of 12 degrees 

using the 50th percentile male Hybrid III 

dummy. The final rule limits HIC15 to 500 for 

all the dynamic compliance option tests. 

The final rule specifies that adjustable 

head restraints must remain within 13 mm of 

their vertical and horizontal position under 

the application of force. Although ECE 17 

requires locks on adjustable head restraints, 

the horizontal and vertical position retention 

requirements do not have a counterpart in 

the ECE regulations. However, we find it 

necessary to require a certain minimal level 

of performance to ensure that the retention 

locks perform their function. 

Both ECE 17, Paragraphs 5.11, 5.12 and 

this final rule have limits on the horizontal 

displacement and strength requirements. The 

purpose of this requirement is to ensure that 

the head restraint can withstand the 

application of rearward force and will not fail 

when the occupant’s head makes contact 

with the head restraint during a rear impact 

to the vehicle. The final rule and ECE both 

maintain a 373 Nm moment on the vehicle 

seat, applied through the back pan, as the 

head restraint is loaded. However, the head 

restraint loading sequence differs in the two 

standards. In the final rule, the loading 

device’s reference position is located by first 

applying a force producing 37 Nm moment 

about the H-point. Then, the load is 

increased at a rate of 187 Nm/minute, until 

a 373 Nm moment is generated. This moment 

is held for 5 seconds and then reduced to 37 

Nm. While the 373 Nm moment applied to 

the head restraint is being maintained, the 

head restraint must not allow the loading 

device to displace more than 102 mm. When 

the moment is reduced, the head restraint 

loading device must return to within 13 mm 

of the initial reference position. This 

horizontal position retention requirement is 

unique to our final rule. While the ECE 

regulations do contain a similar rearward 

displacement test that limits displacement to 

102 mm, they do not require that the head 

restraint loading device return to within 13 

mm of its reference position. Further, the 

ECE regulations do not specify a loading rate 

and hold time. NHTSA believes the 5-second 

hold time and loading rate specifications are 

a necessary clarification of the test 

procedure. 

Finally, the ECE 17, Paragraph 5.5.4 allows 

a 25 mm height allowance in those instances 

in which the front or rear head restraint 

would otherwise interfere with any fixed 

vehicle structure, when the seat is in the 

‘‘use’’ or ‘‘non-use’’ position of adjustment. 

This final rule permits a 25 mm height 

allowance only in situations in which the 

head restraint interferes with either the 

roofline or the backlight. We decided against 

allowing a 25 mm height allowance in 

situations in which the head restraint 

interferes with other fixed vehicle structures 

because we believe that such an exception 

would provide relief in instances in which 

none is needed. For a more detailed 

explanation of our rationale with respect to 

the 25 mm height allowance please see 

Section VI a. and b.

Appendix B: Cervigard Suggestion

Cervigard, Inc. is a New Jersey based 

company that designed a head restraint 

incorporating a contoured shape intended to 

match the curvature of the head and cervical 

spine. The portion of the head restraint that 

protrudes forward adjacent to the neck is 

referred to as a neck bolster. 

Cervigard submitted two sets of test data, 

comparing conventional head restraints 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74883

93NIC is a whiplash criterion developed by 

Adman and Bostrom et al. NIC = 0.2 arel + vrel2, 

where arel is the resultant relative acceleration 

between first thoracic vertebra (T1) and first 

cervical vertebra (C1), vrel is the resultant relative 

velocity between T1 and C1.

against the Cervigard Head Restraint System 

using a special neck-bolstering contour. The 

first set came from an experiment that was 

conducted by Cadillac and Lear, which used 

Hybrid III dummies representing a 5th 

percentile female, 50th percentile male, and 

95th percentile male in sled tests at 16 and 

24 km/h delta-Vs. Specific positions of the 

test head restraints relative to the occupants 

were not given. Instead, they were designated 

as ‘‘Full Up’’ or ‘‘Full Down.’’ These were 

described as being ‘‘In-Position’’ or ‘‘Out-ofPosition.’’ HIC, NIC,93 upper neck shear and 

moment were provided. ‘‘Out-of-Position’’

results were provided for the 5th percentile 

female, 50th percentile male and 95th 

percentile male. ‘‘In-Position’’ results were 

provided for the 50th percentile male only. 

In general, the results provided indicated 

lower injury measures for the Cervigard head 

restraint tests.

The second set of tests was performed by 

Wayne State University using a computer 

simulation model. The model appeared to be 

of a head and neck without a torso. A 

standard OEM head restraint was compared 

to what was called the Cervigard head 

restraint. Both restraints were modeled with 

the backsets shown in the table below. The 

height measurement of the head restraint 

relative to the head was not disclosed. Thus, 

it is unclear whether the head restraint height 

was within the range specified in the NPRM. 

The commenter states that, according to a 

researcher from Wayne State University, the 

Cervigard head restraint performed much 

better, better, or as good as a standard head 

restraint.

Head restraint Backset 

Standard Down ................................ 70 mm 

Standard Up ..................................... 70 mm 

Cervigard Down ............................... 75 mm 

Cervigard Up .................................... 30 mm 

Based on their submissions, Cervigard 

requested that the new rule require a neckbolstering device. According to an 

engineering report from Cervigard, the 

Cervigard head restraint exhibited 23 percent 

to 38 percent lower NIC and neck shear 

forces compared to samples of presently used 

head restraints, modified to comply with the 

proposed rule. Cervigard commented that a 

50 mm backset position without neckbolstering device might actually be too close 

to the head, which could result in potentially 

exacerbating the injury. We note that no 

other commenter or research source 

indicated that a 50 mm backset position may 

prove to be too close to the head, as it relates 

to occupant safety, or somehow dangerous to 

the occupant. 

In support of its recommendation, 

Cervigard asserted that the additional costs of 

adding a neck-bolster device would be 

minimal if the requirement were added to the 

new rulemaking immediately, because seat 

manufacturers will be retooling for a new 

standard anyway. Specifically, Cervigard 

provided an estimate of $3.50 per each head 

restraint. 

Several lawmakers, among them Senator 

Torricelli of New Jersey, Congressman Bill 

Pascrell Jr. of the 8th District of New Jersey, 

New Jersey State Senator Anthony R. Bucco, 

and New Jersey Assemblyman Alex DeCroce 

submitted comments in support of Cervigard. 

Collectively, they urged NHTSA to 

incorporate a neck-bolstering requirement 

into the new rule, in light of minimal 

additional cost to manufacturers, support 

from safety and medical experts, and the 

societal benefit of reducing instances of neck 

trauma. 

Several chiropractors and other medical 

professionals submitted comments to support 

the addition of a requirement for the 

Cervigard device to the upgraded head 

restraint standard. In general, most 

commented that the Cervigard device reduces 

facet joint injury in the lower cervical region 

by maintaining normal curvature of the spine 

at time of impact. 

In contrast, according to the comments 

submitted by Lear Corporation and General 

Motors, Cervigard has put forth an 

incomplete and inaccurate summary of tests 

performed by Lear using the Cervigard 

device. Evaluations of the Cervigard device 

were conducted with the head restraints 

improperly positioned. Lear has never 

compared Cervigard head restraints to 

optimally positioned head restraints or latest 

head restraint designs and never stated that 

Cervigard head restraints performed ‘‘as 

good’’ or ‘‘better’’ than conventional head 

restraints. Indeed, GM opines that any 

improvement was due to decreased backset 

distance and not necessarily to Cervigard 

contour (See David E. Calder Engineering 

Report No. 2, top graph, Docket NHTSA–00–

8570–42). GM further stated that any 

assertion indicating that Cervigard head 

restraints passed the ‘‘do no harm’’ criteria is 

false because no such criteria exists.

Lear cautioned that the submitted data 

results were based on preliminary, 

unapproved data that have since been 

revised. Additionally, Cervigard omitted data 

showing that its device consistently 

increased certain injury parameters. Lear also 

indicated that what was reported by 

Cervigard as upper neck extension moment 

was actually lateral bending moment, which 

one would expect to be much lower than the 

extension moment. In fact, the Cervigard 

device often increased neck tension. Lear’s 

own research indicated that the Cervigard 

device increased risk of neck injury in 62.5 

percent of ‘‘Out of Position’’ head restraint 

conditions tested. 

In examining the test data from Wayne 

State, we conclude that the results confirm 

our position that the backset is a critical 

parameter in head restraint performance. It is 

not surprising that the Cervigard device 

tested with a 30 mm backset was able to limit 

the head’s rearward motion to a much greater 

degree, compared to other configurations, 

with a much greater backset. Because the rest 

of the Wayne State testing was performed 

with backset greater than 70 mm, it is 

impossible to draw any conclusions about 

the benefits of a head restraint with a neck 

bolster in comparison to those of a 

conventional head restraint, positioned, as 

we will require. 

In regard to the sled testing performed by 

Lear for GM, the docket submission by 

Cervigard did not provide positioning 

information. Additionally, as the proprietors 

of the data (Lear and GM) have indicated, the 

comparative sled testing between 

conventional head restraints and Cervigard 

did not take place with the same backset 

values. Our conclusion is that there is no way 

to determine from this information whether 

the neck bolster was actually helpful. In sum, 

we believe that a head restraint meeting the 

new height and backset requirements will 

serve to restrain the head with respect to the 

torso. The proposed neck bolster has not yet 

been shown to provide any additional 

benefit. 

We have an additional concern about a 

neck bolster. Unless the bolstered head 

restraint is precisely positioned at the 

appropriate height, the neck bolster will not 

support the neck. Currently, adjustable head 

restraints need only be adjusted such that the 

top is at least as high as the occupant’s head 

C.G. If the adjustable restraint were 

supplemented by a neck bolster, positioning 

would need to be more precise. It appears 

that, for integral or fixed head restraints, the 

bolstered restraint would only fit an 

individual of a specific height. Thus, any 

neck bolster requirement would by necessity 

eliminate integral head restraint designs. We 

also conclude that it would be difficult to 

require a specific neck bolster contour that 

would fit a majority of occupants. Further, 

we note that we did not propose to adopt a 

neck bolster in the NPRM. Therefore, 

adopting such a requirement in this final rule 

would fall outside the scope of notice. Based 

on the comments and analysis presented 

above, we are not adopting any requirements 

for a neck bolster.

List of Subjects in 49 CFR Part 571 

Imports, Incorporation by Reference, 

Motor Vehicle Safety, Motor Vehicles, 

and Tires.

■ In consideration of the foregoing, 49 

CFR part 571 is amended as follows:

PART 571—FEDERAL MOTOR 

VEHICLE SAFETY STANDARDS

■ 1. The authority citation for part 571 of 

title 49 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 571.202 is amended as 

follows:

■ A. Revise the section heading, S2, S3, 

S4, and S4.1 through S4.3;

■ B. Add S4.4, S4.5, and S4.6; and

■ C. Revise S5, S5.1 introductory text, 

S5.1(a)(2), (a)(3), and (b), S5.2 

introductory text, and S5.2(b) to read as 

follows:

74884 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

§ 571.202 Standard No. 202; Head 

restraints; Applicable at the manufacturers 

option until September 1, 2008.

* * * * * *

S2. Application. This standard 

applies to passenger cars, and to 

multipurpose passenger vehicles, trucks 

and buses with a 4,536 kg or less, 

manufactured before September 1, 2008. 

Until September 1, 2008, manufacturers 

may comply with the standard in this 

§ 571.202, with the European 

regulations referenced in S4.3 of this 

§ 571.202, or with the standard in 

§ 571.202a.

* * * * * *

S3. Definitions.

Head restraint means a device that 

limits rearward displacement of a seated 

occupant’s head relative to the 

occupant’s torso. 

Height means, when used in reference 

to a head restraint, the distance from the 

H-point, measured parallel to the torso 

reference line defined by the three 

dimensional SAE J826 (rev. Jul 95) 

manikin, to a plane normal to the torso 

reference line. 

Top of the head restraint means the 

point on the head restraint with the 

greatest height. 

S4. Requirements.

S4.1 Each passenger car, and 

multipurpose passenger vehicle, truck 

and bus with a 4,536 kg or less, must 

comply with, at the manufacturer’s 

option, S4.2, S4.3 or S4.4 of this section. 

S4.2 Except for school buses, a head 

restraint that conforms to either S4.2 (a) 

or (b) of this section must be provided 

at each outboard front designated 

seating position. For school buses, a 

head restraint that conforms to either 

S4.2 (a) or (b) of this section must be 

provided at the driver’s seating position. 

(a) When tested in accordance with 

S5.1 of this section, limit rearward 

angular displacement of the head 

reference line to 45 degrees from the 

torso reference line; or 

(b) When adjusted to its fully 

extended design position, conform to 

each of the following: 

(1) When measured parallel to the 

torso line, the top of the head restraint 

must not be less than 700 mm above the 

seating reference point; 

(2) When measured either 64 mm 

below the top of the head restraint or 

635 mm above the seating reference 

point, the lateral width of the head 

restraint must be not less than: 

(i) 254 mm for use with bench-type 

seats; and 

(ii) 170 mm for use with individual 

seats; 

(3) When tested in accordance with 

S5.2 of this section, any portion of the 

head form in contact with the head 

restraint must not be displaced to more 

than 102 mm perpendicularly rearward 

of the displaced extended torso 

reference line during the application of 

the load specified in S5.2 (c) of this 

section; and 

(4) When tested in accordance with 

S5.2 of this section, the head restraint 

must withstand an increasing load until 

one of the following occurs: 

(i) Failure of the seat or seat back; or, 

(ii) Application of a load of 890N. 

S4.3 Incorporation by reference.

The English language version of the 

Economic Commission for Europe (ECE) 

Regulation 17: ‘‘Uniform Provisions 

Concerning the Approval of Vehicles 

with Regard to the Seats, their 

Anchorages and any Head Restraints’’

ECE 17 Rev. 1/Add. 16/Rev. 4 (31 July 

2002) is incorporated by reference in 

S4.4(a) 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. A copy of ECE 

17 Rev. 1/Add. 16/Rev. 4 (31 July 2002) 

may be obtained from the ECE Internet 

site: http://www.unece.org/trans/main/

wp29/wp29regs/r017r4e.pdf, or by 

writing to: United Nations, Conference 

Services Division, Distribution and 

Sales Section, Office C.115–1, Palais des 

Nations, CH–1211, Geneva 10, 

Switzerland. A copy of ECE 17 Rev. 1/

Add. 16/Rev. 4 (31 July 2002) may be 

inspected at NHTSA’s Technical 

Information Services, 400 Seventh 

Street, SW., Plaza Level, Room 403, 

Washington, DC, 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.

S4.4. Except for school buses, a head 

restraint that conforms to S4.4 (a) and 

(b) of this section must be provided at 

each outboard front designated seating 

position. For school buses, a head 

restraint that conforms to S4.4 (a) and 

(b) of this section must be provided at 

the driver’s seating position. 

(a) The head restraint must comply 

with Paragraphs 5.1.1, 5.1.3, 5.3.1, 5.5 

through 5.13, 6.1.1, 6.1.3, and 6.4 

through 6.8 of the English language 

version of the Economic Commission for 

Europe (ECE) Regulation 17: ECE 17 

Rev. 1/Add. 16/Rev. 4 (31 July 2002). 

(b) The head restraint must meet the 

width requirements specified in 

S4.2(b)(2) of this section. 

S4.5 Except for school buses, head 

restraints that conform to the 

requirements of § 571.202a must be 

provided at each front outboard 

designated seating position. If a rear 

head restraint (as defined in § 571.202a) 

is provided at a rear outboard 

designated seating position, it must 

conform to the requirements of 

§ 571.202a applicable to rear head 

restraints. For school buses, a head 

restraint that conforms to the 

requirements of § 571.202a must be 

installed at the driver’s seating position. 

S4.6 Where manufacturer options 

are specified in this section or 

§ 571.202a, the manufacturer must 

select an option by the time it certifies 

the vehicle and may not thereafter select 

a different option for that vehicle. The 

manufacturer may select different 

compliance options for different 

designated seating positions to which 

the requirements of this section are 

applicable. Each manufacturer must, 

upon request from the National 

Highway Traffic Safety Administration, 

provide information regarding which of 

the compliance options it has selected 

for a particular vehicle or make/model. 

S5. Demonstration procedures.

S5.1 Compliance with S4.2(a) of this 

section is demonstrated in accordance 

with the following with the head 

restraint in its fully extended design 

position: 

(a) * * * 

(2) Rotate the head of the dummy 

rearward until the back of the head 

contacts the flat horizontal surface 

specified in S5.1(a)(1) of this section. 

(3) Position the SAE J–826 twodimensional manikin’s back against the 

flat surface specified in S5.1(a)(1) of this 

section, alongside the dummy with the 

H-point of the manikin aligned with the 

H-point of the dummy.

* * * * *

(b) At each designated seating 

position having a head restraint, place 

the dummy, snugly restrained by Type 

2 seat belt, in the manufacturer’s 

recommended design seating position.

* * * * *

S5.2 Compliance with S4.2(b) of this 

section is demonstrated in accordance 

with the following with the head 

restraint in its fully extended design 

position:

* * * * *

(b) Establish the displaced torso 

reference line by applying a rearward 

moment of 373 Nm about the seating 

reference point to the seat back through 

the test device back pan specified in 

S5.2(a) of this section.

* * * * *

■ 3. Section 571.202a is added to read as 

follows:

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74885

§ 571.202a Standard No. 202a; Head 

restraints; Mandatory applicability begins 

on September 1, 2008. 

S1. Purpose and scope. This standard 

specifies requirements for head 

restraints to reduce the frequency and 

severity of neck injury in rear-end and 

other collisions. 

S2. Application & incorporation by 

reference.

S2.1 Application. This standard 

applies to passenger cars, and to 

multipurpose passenger vehicles, trucks 

and buses with a GVWR of 4,536 kg or 

less, manufactured on or after 

September 1, 2008. Mandatory 

applicability begins on September 1, 

2008. Until September 1, 2008, 

manufacturers may comply with the 

standard in this § 571.202a, with the 

standard in § 571.202, or with the 

European regulations referenced in 

S4.3(a) of § 571.202. 

S2.2 Incorporation by reference.

(a) Society of Automotive Engineers 

(SAE) Recommended Practice J211/1 

rev. Mar 95, ‘‘Instrumentation for 

Impact Test—Part 1—Electronic 

Instrumentation,’’ SAE J211/1 (rev. Mar 

95) is incorporated by reference in 

S5.2.5(b), S5.3.8, S5.3.9, and 5.3.10 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. A copy of SAE J211/1 (rev. 

Mar 95) may be obtained from SAE at 

the Society of Automotive Engineers, 

Inc., 400 Commonwealth Drive, 

Warrendale, PA 15096. A copy of SAE 

J211/1 (rev. Mar 95) may be inspected 

at NHTSA’s Technical Information 

Services, 400 Seventh Street, SW., Plaza 

Level, Room 403, Washington, DC, 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.

(b) Society of Automotive Engineers 

(SAE) Standard J826 ‘‘Devices for Use in 

Defining and Measuring Vehicle Seating 

Accommodation,’’ SAE J826 (rev. Jul 95) 

is incorporated by reference in S3, S5, 

S5.1, S5.1.1, S5.2, S5.2.1, S5.2.2, and 

S5.2.7 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. A copy of SAE 

J826 (rev. Jul 95) may be obtained from 

SAE at the Society of Automotive 

Engineers, Inc., 400 Commonwealth 

Drive, Warrendale, PA 15096. A copy of 

SAE J826 (rev. Jul 95) may be inspected 

at NHTSA’s Technical Information 

Services, 400 Seventh Street, SW., Plaza 

Level, Room 403, Washington, DC 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.

S3. Definitions.

Backset means the minimum 

horizontal distance between the rear of 

a representation of the head of a seated 

50th percentile male occupant and the 

head restraint, as measured by the head 

restraint measurement device. 

Head restraint means a device that 

limits rearward displacement of a seated 

occupant’s head relative to the 

occupant’s torso. 

Head restraint measurement device 

(HRMD) means the Society of 

Automotive Engineers (SAE) (rev. Jul 

95) J826 three-dimensional manikin 

with a head form attached, representing 

the head position of a seated 50th 

percentile male, with sliding scale at the 

back of the head for the purpose of 

measuring backset. The head form is 

designed by and available from the 

ICBC, 151 West Esplanade, North 

Vancouver, BC V7M 3H9, Canada 

(www.icbc.com). 

Height means, when used in reference 

to a head restraint, the distance from the 

H-point, measured parallel to the torso 

reference line defined by the three 

dimensional SAE J826 (rev. Jul 95) 

manikin, to a plane normal to the torso 

reference line.

Intended for occupant use means, 

when used in reference to the 

adjustment of a seat, positions other 

than that intended solely for the 

purpose of allowing ease of ingress and 

egress of occupants and access to cargo 

storage areas of a vehicle. 

Rear head restraint means, at any rear 

outboard designated seating position, a 

rear seat back, or any independently 

adjustable seat component attached to 

or adjacent to a seat back, that has a 

height equal to or greater than 700 mm, 

in any position of backset and height 

adjustment, as measured in accordance 

with S5.1.1. 

Top of the head restraint means the 

point on the head restraint with the 

greatest height. 

S4. Requirements. Except as provided 

in S4.4 and S.4.2.1(b)(2) of this section, 

each vehicle must comply with S4.1 of 

this section with the seat adjusted as 

intended for occupant use. Whenever a 

range of measurements is specified, the 

head restraint must meet the 

requirement at any position of 

adjustment within the specified range. 

S4.1 Performance levels. In each 

vehicle other than a school bus, a head 

restraint that conforms to either S4.2 or 

S4.3 of this section must be provided at 

each front outboard designated seating 

position. In each vehicle equipped with 

rear head restraints, the rear head 

restraint must conform to either S4.2 or 

S4.3 of this section. In each school bus, 

a head restraint that conforms to either 

S4.2 or S4.3 of this section must be 

provided for the driver’s seating 

position. At each designated seating 

position incapable of seating a 50th 

percentile male Hybrid III test dummy 

specified in 49 CFR Part 572, subpart E, 

the applicable head restraint must 

conform to S4.2 of this section. 

S4.2 Dimensional and static 

performance. Each head restraint 

located in the front outboard designated 

seating position and each head restraint 

located in the rear outboard designated 

seating position must conform to 

paragraphs S4.2.1 through S4.2.7 of this 

section: 

S4.2.1 Minimum height.

(a) Front outboard designated seating 

positions. (1) Except as provided in 

S4.2.1(a)(2) of this section, when 

measured in accordance with 

S5.2.1(a)(1) of this section, the top of a 

head restraint located in a front 

outboard designated seating position 

must have a height not less than 800 

mm in at least one position of 

adjustment. 

(2) Exception. The requirements of 

S4.2.1(a)(1) do not apply if the vehicle 

roofline physically prevents a head 

restraint, located in the front outboard 

designated seating position, from 

attaining the required height. In those 

instances in which this head restraint 

cannot attain the required height, when 

measured in accordance with 

S5.2.1(a)(2), the maximum vertical 

distance between the top of the head 

restraint and the roofline must not 

exceed 25 mm. Notwithstanding this 

exception, when measured in 

accordance with S5.2.1(a)(2), the top of 

a head restraint located in a front 

outboard designated seating position 

must have a height not less than 700 

mm in the lowest position of 

adjustment. 

(b) All outboard designated seating 

positions equipped with head restraints.

(1) Except as provided in S4.2.1(b)(2) of 

this section, when measured in 

accordance with S5.2.1(b)(1) of this 

section, the top of a head restraint 

located in an outboard designated 

seating position must have a height not 

less than 750 mm in any position of 

adjustment. 

(2) Exception. The requirements of 

S4.2.1(b)(1) do not apply if the vehicle 

74886 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

roofline or backlight physically prevent 

a head restraint, located in the rear 

outboard designated seating position, 

from attaining the required height. In 

those instances in which this head 

restraint cannot attain the required 

height, when measured in accordance 

with S5.2.1(b)(2), the maximum vertical 

distance between the top of the head 

restraint and the roofline or the 

backlight must not exceed 25 mm. 

S4.2.2 Width. When measured in 

accordance with S5.2.2 of this section, 

65 ± 3 mm below the top of the head 

restraint, the lateral width of a head 

restraint must be not less than 170 mm, 

except the lateral width of the head 

restraint for front outboard designated 

seating positions in a vehicle with a 

front center designated seating position, 

must be not less than 254 mm. 

S4.2.3 Front Outboard Designated 

Seating Position Backset. When 

measured in accordance with S5.2.3 of 

this section, the backset must not be 

more than 55 mm, when the seat is 

adjusted in accordance with S5.1. For 

adjustable restraints, the requirements 

of this section must be met with the top 

of the head restraint in any height 

position of adjustment between 750 mm 

and 800 mm, inclusive. If the top of the 

head restraint, in its lowest position of 

adjustment, is above 800 mm, the 

requirements of this section must be met 

at that position. If the head restraint 

position is independent of the seat back 

inclination position, the head restraint 

must not be adjusted such that backset 

is more than 55 mm when the seat back 

inclination is positioned closer to 

vertical than the position specified in 

S5.1. 

S4.2.4 Gaps within head restraint 

and between the head restraint and seat.

When measured in accordance with 

S5.2.4 of this section using the head 

form specified in that paragraph, there 

must not be any gap greater than 60 mm 

within or between the anterior surface 

of the head restraint and anterior surface 

of the seat, with the head restraint 

adjusted to its lowest height position 

and any backset position. 

S4.2.5 Energy absorption. When the 

anterior surface of the head restraint is 

impacted in accordance with S5.2.5 of 

this section by the head form specified 

in that paragraph at any velocity up to 

and including 24.1 km/h, the 

deceleration of the head form must not 

exceed 785 m/s2 (80 g) continuously for 

more than 3 milliseconds. 

S4.2.6 Height retention. When tested 

in accordance with S5.2.6 of this 

section, the cylindrical test device 

specified in S5.2.6(b) must return to 

within 13 mm of its initial reference 

position after application of at least a 

500 N load and subsequent reduction of 

the load to 50 N ± 1 N. During 

application of the initial 50 N reference 

load, as specified in S5.2.6(b)(2) of this 

section, the cylindrical test device must 

not move downward more than 25 mm. 

S4.2.7 Backset retention, 

displacement, and strength.

(a) Backset retention and 

displacement. When tested in 

accordance with S5.2.7 of this section, 

the described head form must: 

(1) Not be displaced more than 25 mm 

during the application of the initial 

reference moment of 37 ± 0.7 Nm; 

(2) Not be displaced more than 102 

mm perpendicularly and posterior of 

the displaced extended torso reference 

line during the application of a 373 ±

7.5 Nm moment about the H-point; and 

(3) Return to within 13 mm of its 

initial reference position after the 

application of a 373 ± 7.5 Nm moment 

about the H-point and reduction of the 

moment to 37 ± 0.7 Nm. 

(b) Strength. When the head restraint 

is tested in accordance with S5.2.7 (b) 

of this section with the test device 

specified in that paragraph, the load 

applied to the head restraint must reach 

890 N and remain at 890 N for a period 

of 5 seconds.

S4.3 Dynamic performance and 

width. At each forward-facing outboard 

designated seating position equipped 

with a head restraint, the head restraint 

adjusted midway between the lowest 

and the highest position of adjustment, 

and at any position of backset 

adjustment, must conform to the 

following: 

S4.3.1 Injury criteria. When tested in 

accordance with S5.3 of this section, 

during a forward acceleration of the 

dynamic test platform described in 

S5.3.1, the head restraint must: 

(a) Angular rotation. Limit posterior 

angular rotation between the head and 

torso of the 50th percentile male Hybrid 

III test dummy specified in 49 CFR Part 

572, Subpart E to 12 degrees for the 

dummy in all outboard designated 

seating positions; 

(b) Head injury criteria. Limit the 

maximum HIC15 value to 500. HIC15 is 

calculated as follows: for any two points 

in time, t1 and t2, during the event 

which are separated by not more than a 

15 millisecond time interval and where 

t1 is less than t2, the head injury 

criterion (HIC15) is determined using the 

resultant head acceleration at the center 

of gravity of the dummy head, ar, 

expressed as a multiple of g (the 

acceleration of gravity) and is calculated 

using the expression:

HIC = 1

t

a t

2

r 2 ( ) −















 ( ) − ∫ t

dt t

t

t

1

2 5

1

1

2

.

4.3.2 Width. The head restraint must 

have the lateral width specified in 

S4.2.2 of this section. 

S4.4 Folding or retracting rear head 

restraints. A rear head restraint may be 

adjusted to a position at which its 

height does not comply with the 

requirements of S4.2.1 of this section. 

However, in any such position, the head 

restraint must meet either S4.4 (a) or (b) 

of this section. 

(a) The head restraint must 

automatically return to a position in 

which its minimum height is not less 

than that specified in S4.2.1(b) of this 

section when a test dummy representing 

a 5th percentile female Hybrid III test 

dummy specified in 49 CFR Part 572, 

Subpart O is positioned according to 

S5.4(a); or 

(b) The head restraint must, when 

tested in accordance with S5.4(b) of this 

section, be capable of manually rotating 

forward or rearward by not less than 60 

degrees from any position of adjustment 

in which its minimum height is not less 

than that specified in S4.2.1(b) of this 

section. 

S4.5 Removability of head restraints.

The head restraint must not be 

removable without a deliberate action 

distinct from any act necessary for 

adjustment. 

S4.6 Compliance option selection.

Where manufacturer options are 

specified in this section, the 

manufacturer must select an option by 

the time it certifies the vehicle and may 

not thereafter select a different option 

for that vehicle. The manufacturer may 

select different compliance options for 

different designated seating positions to 

which the requirements of this section 

are applicable. Each manufacturer must, 

upon request from the National 

Highway Traffic Safety Administration, 

provide information regarding which of 

the compliance options it has selected 

for a particular vehicle or make/model. 

S4.7 Information in owner’s manual.

S4.7.1 The owner’s manual for each 

vehicle must emphasize that all 

occupants, including the driver, should 

not operate a vehicle or sit in a vehicle’s 

seat until the head restraints are placed 

in their proper positions in order to 

minimize the risk of severe injury in the 

event of a crash. 

S4.7.2 The owner’s manual for each 

vehicle must—

(a) Include an accurate description of 

the vehicle’s head restraint system in an 

easily understandable format. The 

owner’s manual must clearly identify 


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Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74887

which seats are equipped with head 

restraints; 

(b) If the head restraints are 

removable, the owner’s manual must 

provide instructions on how to remove 

the head restraint by a deliberate action 

distinct from any act necessary for 

adjustment, and how to reinstall head 

restraints; 

(c) Warn that all head restraints must 

be reinstalled to properly protect 

vehicle occupants. 

(d) Describe in an easily 

understandable format the adjustment of 

the head restraints and/or seat back to 

achieve appropriate head restraint 

position relative to the occupant’s head. 

This discussion must include, at a 

minimum, accurate information on the 

following topics: 

(1) A presentation and explanation of 

the main components of the vehicle’s 

head restraints. 

(2) The basic requirements for proper 

head restraint operation, including an 

explanation of the actions that may 

affect the proper functioning of the head 

restraints.

(3) The basic requirements for proper 

positioning of a head restraint in 

relation to an occupant’s head position, 

including information regarding the 

proper positioning of the center of 

gravity of an occupant’s head in relation 

to the head restraint. 

S5. Procedures. Demonstrate 

compliance with S4.2 through S4.4 of 

this section with any adjustable lumbar 

support adjusted to its most posterior 

nominal design position. If the seat 

cushion adjusts independently of the 

seat back, position the seat cushion such 

that the highest H-point position is 

achieved with respect to the seat back, 

as measured by SAE J826 (rev. Jul 95) 

manikin, with leg length specified in 

S10.4.2.1 of § 571.208. 

S5.1 Except as specified in S5.2.3 of 

this section, if the seat back is 

adjustable, it is set at an initial 

inclination position closest to 25 

degrees from the vertical, as measured 

by SAE J826 manikin (rev. Jul 95). If 

there is more than one inclination 

position closest to 25 degrees from 

vertical, set the seat back inclination to 

the position closest to and rearward of 

25 degrees. 

S5.1.1 Procedure for determining 

presence of head restraints in rear 

outboard seats. Measure the height of 

the top of a rear seat back or the top of 

any independently adjustable seat 

component attached to or adjacent to 

the rear seat back in its highest position 

of adjustment using the scale 

incorporated into the SAE J826 (rev. Jul 

95) manikin or an equivalent scale, 

which is positioned laterally within 15 

mm of the centerline of the rear seat 

back or any independently adjustable 

seat component attached to or adjacent 

to the rear seat back. 

S5.2 Dimensional and static 

performance procedures. Demonstrate 

compliance with S4.2 of this section in 

accordance with S5.2.1 through S5.2.7 

of this section. Position the SAE J826 

(rev. Jul 95) manikin according to the 

seating procedure found in SAE J826 

(rev. Jul 95). 

S5.2.1 Procedure for height 

measurement. Demonstrate compliance 

with S4.2.1 of this section in accordance 

with S5.2.1 (a) and (b) of this section, 

using the scale incorporated into the 

SAE J826 (rev. Jul 95) manikin or an 

equivalent scale, which is positioned 

laterally within 15 mm of the head 

restraint centerline. If the head restraint 

position is independent of the seat back 

inclination position, compliance is 

determined at a seat back inclination 

position closest to 25 degrees from 

vertical, and each seat back inclination 

position less than 25 degrees from 

vertical. 

(a)(1) For head restraints in front 

outboard designated seating positions, 

adjust the top of the head restraint to the 

highest position and measure the height. 

(2) For head restraints located in the 

front outboard designated seating 

positions that are prevented by the 

vehicle roofline from meeting the 

required height as specified in 

S4.2.1(a)(1), measure the clearance 

between the top of the head restraint 

and the roofline, with the seat adjusted 

to its lowest vertical position intended 

for occupant use, by attempting to pass 

a 25 mm sphere between them. Adjust 

the top of the head restraint to the 

lowest position and measure the height. 

(b)(1) For head restraints in all 

outboard designated seating positions 

equipped with head restraints, adjust 

the top of the head restraint to the 

lowest position other than allowed by 

S4.4 and measure the height. 

(2) For head restraints located in rear 

outboard designated seating positions 

that are prevented by the vehicle 

roofline or rear backlight from meeting 

the required height as specified in 

S4.2.1(b)(1), measure the clearance 

between the top of the head restraint or 

the seat back and the roofline or the rear 

backlight, with the seat adjusted to its 

lowest vertical position intended for 

occupant use, by attempting to pass a 25 

mm sphere between them. 

S5.2.2 Procedure for width 

measurement. Demonstrate compliance 

with S4.2.2 of this section using calipers 

to measure the maximum dimension 

perpendicular to the vehicle vertical 

longitudinal plane of the intersection of 

the head restraint with a plane that is 

normal to the torso reference line of 

SAE J826 (rev. Jul 95) manikin and 65 

± 3 mm below the top of the head 

restraint. 

S5.2.3 Procedure for backset 

measurement. Demonstrate compliance 

with S4.2.3 of this section using the 

HRMD positioned laterally within 15 

mm of the head restraint centerline. 

Adjust the front head restraint so that its 

top is at any height between and 

inclusive of 750 mm and 800 mm and 

its backset is in the maximum position 

other than allowed by S4.4. If the lowest 

position of adjustment is above 800 mm, 

adjust the head restraint to that position. 

If the head restraint position is 

independent of the seat back inclination 

position, compliance is determined at 

each seat back inclination position 

closest to and less than 25 degrees from 

vertical. 

S5.2.4 Procedures for gap 

measurement. Demonstrate compliance 

with S4.2.4 of this section in accordance 

with the procedures of S5.2.4 (a) 

through (c) of this section, with the head 

restraint adjusted to its lowest height 

position and any backset position. 

(a) The area of measurement is 

anywhere on the anterior surface of the 

head restraint or seat with a height 

greater than 540 mm and within the 

following distances from the centerline 

of the seat—

(1) 127 mm for seats required to have 

254 mm minimum head restraint width; 

and 

(2) 85 mm for seats required to have 

a 170 mm head restraint width. 

(b) Applying a load of no more than 

5 N against the area of measurement 

specified in S5.2.4(a) of this section, 

place a 165 ± 2 mm diameter spherical 

head form against any gap such that at 

least two points of contact are made 

within the area. The surface roughness 

of the head form is less than 1.6 μm, 

root mean square. 

(c) Determine the gap dimension by 

measuring the vertical straight line 

distance between the inner edges of the 

two furthest contact points, as shown in 

Figures 2 and 3 of this section. 

S5.2.5 Procedures for energy 

absorption. Demonstrate compliance 

with S4.2.5 of this section in accordance 

with S5.2.5 (a) through (e) of this 

section, with the seat back rigidly fixed 

and the adjustable head restraints in any 

height and backset position of 

adjustment. 

(a) Use an impactor with a 

semispherical head form and a 165 ± 2 

mm diameter and a surface roughness of 

less than 1.6 μm, root mean square. The 

head form and associated base have a 

combined mass of 6.8 ± 0.05 kg. 

74888 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 

(b) Instrument the impactor with an 

acceleration sensing device whose 

output is recorded in a data channel that 

conforms to the requirements for a 600 

Hz channel class as specified in SAE 

Recommended Practice J211/1 (rev. Mar 

95). The axis of the acceleration-sensing 

device coincides with the geometric 

center of the head form and the 

direction of impact. 

(c) Propel the impactor toward the 

head restraint. At the time of launch, the 

longitudinal axis of the impactor is 

within 2 degrees of being horizontal and 

parallel to the vehicle longitudinal axis. 

The direction of travel is posteriorly. 

(d) Constrain the movement of the 

head form so that it travels linearly 

along the path described in S5.2.5(c) of 

this section for not less than 25 mm 

before making contact with the head 

restraint. 

(e) Impact the anterior surface of the 

seat or head restraint at any point with 

a height greater than 635 mm and 

within a distance of the head restraint 

vertical centerline of 70 mm. 

S5.2.6 Procedures for height 

retention. Demonstrate compliance with 

S4.2.6 of this section in accordance with 

S5.2.6 (a) through (d) of this section. 

(a) Adjust the adjustable head 

restraint so that its top is at any of the 

following height positions at any 

backset position—

(1) For front outboard designated 

seating positions—

(i) The highest position; and 

(ii) Not less than, but closest to 800 

mm; and 

(2) For rear outboard designated 

seating positions equipped with head 

restraints—

(i) The highest position; and 

(ii) Not less than, but closest to 750 

mm. 

(b)(1) Orient a cylindrical test device 

having a 165 ± 2 mm diameter in plane 

view (perpendicular to the axis of 

revolution), and a 152 mm length in 

profile (through the axis of revolution) 

with a surface roughness of less than 1.6 

μm, root mean square, such that the axis 

of the revolution is horizontal and in the 

longitudinal vertical plane through the 

longitudinal centerline of the head 

restraint. Position the midpoint of the 

bottom surface of the cylinder in contact 

with the head restraint. 

(2) Establish initial reference position 

by applying a vertical downward load of 

50 ± 1 N. 

(c) Increase the load at the rate of 250 

± 50 N/minute to at least 500 N and 

maintain this load for not less than 5 

seconds. 

(d) Reduce the load at the rate of 250 

± 50 N/minute to 50 ± 1 N and 

determine the position of the cylindrical 

device with respect to its initial 

reference position. 

S5.2.7 Procedures for backset 

retention, displacement, and strength.

Demonstrate compliance with S4.2.7 of 

this section in accordance with S5.2.7 

(a) and (b) of this section. The load 

vectors that generate moment on the 

head restraint are initially contained in 

a vertical plane parallel to the vehicle 

longitudinal centerline. 

(a) Backset retention and 

displacement—

(1) Adjust the head restraint so that its 

top is at a height closest to and not less 

than: 

(i) 800 mm for front outboard 

designated seating positions (or the 

highest position of adjustment for head 

restraints subject to S4.2.1(a)(2)); and 

(ii) 750 mm for rear outboard 

designated seating positions equipped 

with head restraints (or the highest 

position of adjustment for rear head 

restraints subject to S4.2.1(b)(2)). 

(2) Adjust the head restraint to any 

backset position.

(3) In the seat, place a test device 

having the back pan dimensions and 

torso reference line (vertical center line), 

when viewed laterally, with the head 

room probe in the full back position, of 

the three dimensional SAE J826 (rev. Jul 

95) manikin; 

(4) Establish the displaced torso 

reference line by creating a posterior 

moment of 373 ± 7.5 Nm about the Hpoint by applying a force to the seat 

back through the back pan at the rate of 

187 ± 37 Nm/minute. The initial 

location on the back pan of the moment 

generating force vector has a height of 

290 mm ± 13 mm. Apply the force 

vector normal to the torso reference line 

and maintain it within 2 degrees of a 

vertical plane parallel to the vehicle 

longitudinal centerline. Constrain the 

back pan to rotate about the H-point. 

Rotate the force vector direction with 

the back pan. 

(5) Maintain the position of the back 

pan as established in S5.2.7 (4) of this 

section. Using a 165 ± 2 mm diameter 

spherical head form with a surface 

roughness of less than 1.6 μm, root 

mean square, establish the head form 

initial reference position by applying, 

perpendicular to the displaced torso 

reference line, a posterior initial load at 

the seat centerline at a height 65 ± 3 mm 

below the top of the head restraint that 

will produce a 37 ± 0.7 Nm moment 

about the H-point. Measure the posterior 

displacement of the head form during 

the application of the load. 

(6) Increase the initial load at the rate 

of 187 ± 37 Nm/minute until a 373 ± 7.5 

Nm moment about the H-point is 

produced. Maintain the load level 

producing that moment for not less than 

5 seconds and then measure the 

posterior displacement of the head form 

relative to the displaced torso reference 

line. 

(7) Reduce the load at the rate of 187 

± 37 Nm/minute until a 37 ± 0.7 Nm 

moment about the H-point is produced. 

While maintaining the load level 

producing that moment, measure the 

posterior displacement of the head form 

position with respect to its initial 

reference position; and 

(b) Strength. Increase the load 

specified in S5.2.7(a)(7) of this section 

at the rate of 250 ± 50 N/minute to at 

least 890 N and maintain this load level 

for not less than 5 seconds. 

S5.3 Procedures for dynamic 

performance. Demonstrate compliance 

with S4.3 of this section in accordance 

with S5.3.1 though S5.3.9 of this section 

with a 50th percentile male Hybrid III 

test dummy specified in 49 CFR part 

572 subpart E, with the head restraint 

midway between the lowest and the 

highest position of adjustment, and at 

any position of backset adjustment. 

S5.3.1 Mount the vehicle on a 

dynamic test platform at the vehicle 

attitude set forth in S13.3 of § 571.208, 

so that the longitudinal centerline of the 

vehicle is parallel to the direction of the 

test platform travel and so that 

movement between the base of the 

vehicle and the test platform is 

prevented. Instrument the platform with 

an accelerometer and data processing 

system. Position the accelerometer 

sensitive axis parallel to the direction of 

test platform travel. 

S5.3.2 Remove the tires, wheels, 

fluids, and all unsecured components. 

Remove or rigidly secure the engine, 

transmission, axles, exhaust, vehicle 

frame and any other vehicle component 

necessary to assure that all points on the 

acceleration vs. time plot measured by 

an accelerometer on the dynamic test 

platform fall within the corridor 

described in Figure 1 and Table 1. 

S5.3.3 Place any moveable windows 

in the fully open position. 

S5.3.4 Seat adjustment. At each 

outboard designated seating position, 

using any control that primarily moves 

the entire seat vertically, place the seat 

in the lowest position. Using any 

control that primarily moves the entire 

seat in the fore and aft directions, place 

the seat midway between the 

forwardmost and rearmost position. If 

an adjustment position does not exist 

midway between the forwardmost and 

rearmost positions, the closest 

adjustment position to the rear of the 

midpoint is used. Adjust the seat 

cushion and seat back, without using 

any controls that move the entire seat, 

Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74889

as required by S5 and S5.1 of this 

section. If the specified position of the 

H-point can be achieved with a range of 

seat cushion inclination angles, adjust 

the seat inclination such that the most 

forward part of the seat cushion is at its 

lowest position with respect to the most 

rearward part. If the head restraint is 

adjustable, adjust the top of the head 

restraint to a position midway between 

the lowest position of adjustment and 

the highest position of adjustment. If an 

adjustment position midway between 

the lowest and the highest position does 

not exist, adjust the head restraint to a 

position below and nearest to midway 

between the lowest position of 

adjustment and the highest position of 

adjustment. 

S5.3.5 Seat belt adjustment. Prior to 

placing the Type 2 seat belt around the 

test dummy, fully extend the webbing 

from the seat belt retractor(s) and release 

it three times to remove slack. If an 

adjustable seat belt D-ring anchorage 

exists, place it in the adjustment 

position closest to the mid-position. If 

an adjustment position does not exist 

midway between the highest and lowest 

position, the closest adjustment position 

above the midpoint is used.

S5.3.6 Dress and adjust each test 

dummy as specified in S8.1.8.2 through 

S8.1.8.3 of § 571.208. 

S5.3.7 Test dummy positioning 

procedure. Place a test dummy at each 

outboard designated seating position 

equipped with a head restraint. 

S5.3.7.1 Head. The transverse 

instrumentation platform of the head is 

level within 1⁄2 degree. To level the head 

of the test dummy, the following 

sequences is followed. First, adjust the 

position of the H point within the limits 

set forth in S10.4.2.1 of § 571.208 to 

level the transverse instrumentation 

platform of the head of the test dummy. 

If the transverse instrumentation 

platform of the head is still not level, 

then adjust the pelvic angle of the test 

dummy. If the transverse 

instrumentation platform of the head is 

still not level, then adjust the neck 

bracket of the dummy the minimum 

amount necessary from the non-adjusted 

‘‘0’’ setting to ensure that the transverse 

instrumentation platform of the head is 

horizontal within 1⁄2 degree. The test 

dummy remains within the limits 

specified in S10.4.2.1 of § 571.208 after 

any adjustment of the neck bracket. 

S5.3.7.2 Upper arms and hands.

Position each test dummy as specified 

in S10.2 and S10.3 of § 571.208. 

S5.3.7.3 Torso. Position each test 

dummy as specified in S10.4.1.1, 

S10.4.1.2, and S10.4.2.1 of § 571.208, 

except that the midsagittal plane of the 

dummy is aligned within 15 mm of the 

head restraint centerline. If the 

midsagittal plane of the dummy cannot 

be aligned within 15 mm of the head 

restraint centerline then align the 

midsagittal plane of the dummy as close 

as possible to the head restraint 

centerline. 

S5.3.7.4 Legs. Position each test 

dummy as specified in S10.5 of 

§ 571.208, except that final adjustment 

to accommodate placement of the feet in 

accordance with S5.3.7.4 of this section 

is permitted. 

S5.3.7.5 Feet. Position each test 

dummy as specified in S10.6 of 

§ 571.208, except that for rear outboard 

designated seating positions the feet of 

the test dummy are placed flat on the 

floorpan and beneath the front seat as 

far forward as possible without front 

seat interference. For rear outboard 

designated seating position, if 

necessary, the distance between the 

knees can be changed in order to place 

the feet beneath the seat. 

S5.3.8 Accelerate the dynamic test 

platform to 17.3 ± 0.6 km/h. All of the 

points on the acceleration vs. time curve 

fall within the corridor described in 

Figure 1 and Table 1 when filtered to 

channel class 60, as specified in the 

SAE Recommended Practice J211/1 (rev. 

Mar 95). Measure the maximum 

posterior angular displacement. 

S5.3.9 Calculate the angular 

displacement from the output of 

instrumentation placed in the torso and 

head of the test dummy and an 

algorithm capable of determining the 

relative angular displacement to within 

one degree and conforming to the 

requirements of a 600 Hz channel class, 

as specified in SAE Recommended 

Practice J211/1, (rev. Mar 95). No data 

generated after 200 ms from the 

beginning of the forward acceleration 

are used in determining angular 

displacement of the head with respect to 

the torso. 

S5.3.10 Calculate the HIC15 from the 

output of instrumentation placed in the 

head of the test dummy, using the 

equation in S4.3.1(b) of this section and 

conforming to the requirements for a 

1000 Hz channel class as specified in 

SAE Recommended Practice J211/1 (rev. 

Mar 95). No data generated after 200 ms 

from the beginning of the forward 

acceleration are used in determining 

HIC. 

S5.4 Procedures for folding or 

retracting head restraints for 

unoccupied rear outboard designated 

seating positions. 

(a) Demonstrate compliance with S4.4 

(a) of this section, using a 5th percentile 

female Hybrid III test dummy specified 

in 49 CFR part 572, subpart O, in 

accordance with the following 

procedure— 

(1) Position the test dummy in the 

seat such that the dummy’s midsaggital 

plane is aligned within the 15 mm of the 

head restraint centerline and is parallel 

to a vertical plane parallel to the vehicle 

longitudinal centerline. 

(2) Hold the dummy’s thighs down 

and push rearward on the upper torso 

to maximize the dummy’s pelvic angle. 

(3) Place the legs as close as possible 

to 90 degrees to the thighs. Push 

rearward on the dummy’s knees to force 

the pelvis into the seat so there is no gap 

between the pelvis and the seat back or 

until contact occurs between the back of 

the dummy’s calves and the front of the 

seat cushion such that the angle 

between the dummy’s thighs and legs 

begins to change. 

(4) Note the position of the head 

restraint. Remove the dummy from the 

seat. If the head restraint returns to a 

retracted position upon removal of the 

dummy, manually place it in the noted 

position. Determine compliance with 

the height requirements of S4.2.1 of this 

section by using the test procedures of 

S5.2.1 of this section. 

(b) Demonstrate compliance with S4.4 

(b) of this section in accordance with 

the following procedure: 

(1) Place the rear head restraint in any 

position meeting the requirements of 

S4.2 of this section;

(2) Strike a line on the head restraint. 

Measure the angle or range of angles of 

the head restraint reference line as 

projected onto a vertical longitudinal 

vehicle plane; 

(3) Fold or retract the head restraint 

to a position in which its minimum 

height is less than that specified in 

S4.2.1 (b) of this section or in which its 

backset is more than that specified in 

S4.2.3 of this section; 

(4) Determine the minimum change in 

the head restraint reference line angle as 

projected onto a vertical longitudinal 

vehicle plane from the angle or range of 

angles measured in S5.4(b)(2) of this 

section.

TABLE 1 OF § 571.202A.—SLED PULSE

CORRIDOR REFERENCE POINT LOCATIONS. 

Reference point Time

(ms) 

Acceleration

(m/s2) 

A ........................... 0 10 

B ........................... 28 94 

C ........................... 60 94 

D ........................... 92 0 

E ........................... 4 0 

F ............................ 38.5 80 

G ........................... 49.5 80 

H ........................... 84 0 

74890 Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 


ER14DE04.151</GPH> ER14DE04.152</GPH>
Federal Register / Vol. 69, No. 239 / Tuesday, December 14, 2004 / Rules and Regulations 74891

Dated: November 28, 2004. 

Jeffrey W. Runge, 

Administrator.

[FR Doc. 04–26641 Filed 12–7–04; 11:50 am] 

BILLING CODE 4910–59–P


ER14DE04.153</GPH>