968 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

1Summary of the highlights of Traffic Safety and

Auto Engineering Stream, World Congress on

Whiplash-Associated Disorders, February 1999,

Vancouver, Canada http://www.whiplash99.org/

highlights/index.htm.

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety

Administration

49 CFR Part 571

[Docket No. NHTSA–2000–8570]

RIN 2127–AH09

Federal Motor Vehicle Safety

Standards; Head Restraints

AGENCY: National Highway Traffic

Safety Administration (NHTSA), DOT.

ACTION: Notice of proposed rulemaking.

SUMMARY: Consistent with this agency’s

policy of seeking to adopt those

regulatory requirements that produce

the highest benefits at reasonable costs,

this document proposes to upgrade the

standard for head restraints for

passenger cars and for light

multipurpose vehicles, trucks and

buses. The proposal would establish

higher minimum height requirements

for head restraints, and add a

requirement limiting backset, i.e., the

distance between a person’s head and

his or her head restraint. The proposal

would also extend the requirement for

head restraints to rear outboard

designated seating positions; establish

new strength requirements for head

restraints; and place limits on the size

of gaps and openings in head restraints.

In addition, it would modify the

dynamic compliance test and amend

test procedures. The proposal would

harmonize the standard with the

counterpart regulation of the Economic

Commission for Europe (ECE) to an

extent, but would set different

requirements for head restraint width

and gap measurement for adjustable

restraints. Further, it would add two

requirements not found in the ECE

regulation, i.e., one for backset and one

for adjustment retention locks. The goal

of these proposed changes is to improve

the protection that head restraints

provide in rear-end collisions.

This document also proposes that

before compliance with the upgraded

requirements becomes mandatory on the

first September 1, three years following

publication of the final rule, the

manufacturers could chose to comply

with any of three sets of requirements:

the existing requirements of Standard

202, the ECE regulation, or the upgraded

requirements of Standard 202. The

proposal to allow compliance with the

ECE regulation during the interim

responds to a petition for rulemaking by

the American Automobile

Manufacturers Association (AAMA) and

the Association of International

Automobile Manufacturers (AIAM)

requesting that we consider the benefits

of complying with the European

regulation to be at least equivalent to

those of complying with the existing

requirements of Standard 202.

DATES: You should submit your

comments early enough to ensure that

Docket Management receives them not

later than March 5, 2001.

ADDRESSES: You should mention the

docket number of this document in your

comments and submit your comments

in writing to: Docket Management,

Room PL–401, 400 Seventh Street, SW.,

Washington, DC, 20590. Comments may

also be submitted to the docket

electronically by logging onto the

Dockets Management System website at

http://dms.dot.gov. Click on ‘‘Help &

Information’’ or ‘‘Help/Info’’ to obtain

instructions for filing the document

electronically.

You may call Docket Management at

202–366–9324. You may visit the

Docket from 10 a.m. to 5 p.m., Monday

through Friday.

FOR FURTHER INFORMATION CONTACT: For

non-legal issues, you may contact Louis

Molino of the Office of Safety

Performance Standards, Vehicle

Crashworthiness Standards, Light Duty

Vehicle Division, NPS–11, (Phone: 202–

366–2264; fax: 202–366–4329; E-mail:

lmolino@nhtsa.dot.gov).

For legal issues, you may contact Otto

Matheke of the Office of Chief Counsel,

NCC–20, (Phone: 202–366–5263; Fax

202–366–3820).

You may send mail to both of these

officials at the National Highway Traffic

Safety Administration, 400 Seventh St.,

SW., Washington, DC, 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. The Safety Problem

II. Background

A. Studies of Head Restraint Effectiveness

B. December 1996 Request for Comments

C. AIAM/AAMA Petition

III. Overview of Proposal

IV. Proposed Upgraded Requirements

A. Height Requirements

B. Backset Requirement

C. Height Adjustment Retention

Requirement

D. Rear Outboard Seating Positions

E. Removability of Head Restraints

F. Head Restraint Configuration

Requirements

1. Width

2. Gaps

G. Energy Absorption

H. Test Procedures

1. Displacement Test Procedure

2. Dynamic Sled Test Procedure

V. Interim Compliance Options Before

Upgraded Requirements Become

Mandatory

VI. Benefits

VII. Costs

VIII. Effective Date

IX. Rulemaking Analyses and Notices

X. Submission of Comments

XI. Proposed Regulatory Text

I. The Safety Problem

Whiplash injuries, a set of common

symptoms involving the soft tissues of

the head, neck and spine, are believed

to be associated with rapid motion of

the head and neck relative to the torso

in a crash. 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 be permanent. The relatively

short-term symptoms are associated

with muscle and ligament trauma, while

the long-term ones are associated with

nerve damage.1

Although whiplash injuries can occur

in any kind of crash, they occur most

often 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 occupant’s body is

pushed forward by the seat, 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, which is like the lash of a whip,

gives the resulting neck injuries their

popular name. However, at what point

in this motion the injury occurs is still

a matter of debate.

We estimate from National Analysis

Sampling System (NASS) data that

between 1988 and 1996, 805,581

whiplash injuries (non-contact

Abbreviated Injury Scale (AIS) 1 neck)

occurred annually in all crashes in

passenger cars (PCs), and in LTV’s (light

trucks, multipurpose passenger vehicles

and vans). The average cost (excluding

property damage) of such an injury is

$6,485, resulting in a total annual cost

of $5.2 billion.

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 969

2Severy et al. (1968) Backrest and Head Restraint

Design for Rear-End Collision Protection. SAE

680029.

3McConnell et al. (1995) Human Head and Neck

Kinematics After Low Velocity Rear-End Impacts—

Understanding ‘‘Whiplash.’’ SAE 952724.

4Mertz and Patrick (1967) Investigation of the

Kinematics and Kinetics of Whiplash. Proceedings

of the 11th STAPP Car Crash Conference, pp. 267–

317.

5 Jacobsson et al. (1994) Analysis of Head and

Neck Responses in Rear End Impacts—A New

Human-Like Model. Volvo Car Corporation Safety

Report.

6Olsson et al. (1990) An In-depth Study of Neck

Injuries in Rear-end Collisions. IRCOBI, pp. 269–

280.

7Svensson et al. (1993) Pressure Effects in the

Spinal Canal During Whiplash Extension Motion: A

Possible Cause of Injury to the Cervical Spinal

Ganglia. IRCOBI, pp. 189–200.

8 Yoganandan et al. (1998) Biomechanical

Assessment of Whiplash. In: Frontiers in Head and

Neck Trauma: Clinical and Biomechanical, pp. 344–

373.

9 Kaneoka and Ono (1998) Human Volunteer

Studies on Whiplash Injury Mechanisms. In:

Frontiers in Head and Neck Trauma: Clinical and

Biomechanical, pp. 313–325.

The potential for whiplash injuries is

influenced by the ability of several

aspects of vehicle design, including

vehicle structure, seats and head

restraints, to absorb and control crash

forces. In addition to integral and

adjustable head restraints, which are

designed to maintain their position

relative to the seat back during a crash,

several manufacturers have recently

introduced new seat and head restraint

designs that allow the head restraints to

actively move closer to the occupant’s

head during a rear impact of the vehicle.

Volvo has introduced a system it has

labeled as WHIPS (Whiplash Head

Impact Protection System) in which the

seat back recliner is designed to give a

controlled rearward motion of the seat

back relative to the seat base in a rear

impact—allowing the torso to move

backward. In the first phase the seat

back translates rearward for the purpose

of reducing relative motion of the seat

back—reducing relative motion of the

head and torso and allowing the head to

move closer to the head restraint. The

second phase involves rearward folding

of the seat back, with the center of

motion in the recliner. This reduces

acceleration of the occupant while

absorbing energy. Saab has incorporated

an active and adjustable head restraint

into the front seat backs of its 9–3 and

9–5 models. Known as the Saab Active

Head Restraint System, it moves the

head restraint forward and upward as

the seat occupant moves backward

during and after a rear impact. Model

year 2000 Infiniti I30s, Buick LeSabres

and Pontiac Bonnevilles also have

active front seat head restraints. The

Insurance Institute for Highway Safety

(IIHS) has attempted to determine the

potential contributions of the advanced

seats like the Volvo seat and of active

head restraints through dynamic testing

of those designs. More information on

these tests is discussed in the

Background section of this document.

Two suppliers, TRW and Breed Siemens

Restraint Systems, are each in the

process of developing an inflatable head

restraint that is activated in rear

impacts.

This notice focuses on the potential

for reducing whiplash through requiring

improvements in head restraints. 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 Federal

Motor Vehicle Safety Standard 202

(Standard 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) above the H-point. The H-point

is defined by a test machine placed in

the vehicle seat (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 thought of, roughly, as the hip

joint of a 50th percentile male occupant

viewed laterally. Also in 1967, research

using staged 48.3 kph (30 mph) crashes

concluded that a head restraint 711 mm

(28 inches) above the H-point was

adequate to prevent neck

hyperextension of a 95th percentile

male.2 Standard 202, which became

effective on January 1, 1969, required

that head restraints be at least 700 mm

(27.5 inches) 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 research indicates that

whiplash may occur as a result of head

and neck movements insufficient to

cause hyperextension. Low speed staged

impacts indicate that mild whiplash

symptoms can occur without exceeding

the normal range of motion.3 Other

research shows that 70.8 kph (44 mph)

impacts can be sustained without injury

if no relative motion occurs between the

head and torso.4 A Volvo study reported

that, when vehicle occupants involved

in rear crashes had their heads against

the head restraint during impact, no

injury occurred.5 The same study

related a rear impact simulation

computer model to actual crash data

and identified the rate of volume change

in the cervical spinal canal as a possible

predictor of whiplash injury. Other

predictors identified were neck shear

force, neck tensile force and head

angular acceleration. A study of Volvo

vehicles involved in rear impacts

showed that a significant increase in

injury duration occurred when the

occupant’s head was more than 100 mm

(4 inches) away from the head restraint

at the time of the rear impact.6

Although there seems to be no clear

consensus in the biomechanics

community about the mechanism for

whiplash injuries, several hypotheses

have been proposed based on

investigations using animals,

volunteers, and human surrogates.

Animal research at Chalmers University

suggests that rapid head/neck motion,

within the normal range, can cause

spinal canal pressures to damage nerve

ganglia.7 Other studies have attributed

whiplash injuries to damage to the

highly innervated cervical facet joints.

Researchers at the Medical College of

Wisconsin propose that local

compression in the lower cervical spine

and sliding along the facet joint may

cause the excitation of local pain fibers,

micro-damage to the cartilage plates and

squeezing of the synovial space in the

facet joints.8 Similarly, a study

performed in Japan using

cineradiography (x-ray motion pictures)

on human volunteers to study vertebral

motion, hypothesized that the upward

ramping of the torso due to the

straightening of the natural spine

lordotic curvature causes compression

of the cervical spine and an unnatural

S-shape of the cervical spine.9 At the

mid-portion of this unnatural S-shape,

large rotations may occur which stretch

the ligaments or damage the facet joint.

In 1995, the National Highway Traffic

Safety Administration (NHTSA)

performed a survey of the relative

position of occupants’ heads and head

restraints on 282 vehicles. The survey

examined relative position of the head

to the restraint, how the head restraint

was adjusted and if the head restraint

could potentially have been adjusted

higher. The tops of 59 percent of

adjustable and 77 percent of integral

head restraints were at or above the

occupant’s ear—a point equivalent to

the head center of gravity. NHTSA also

estimated the backset of these head

restraints—the horizontal distance from

the back of the occupant’s head to the

head restraint. Sixty-nine percent of

adjustable head restraints and 77

970 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

10This study is summarized in the May 22, 1999

edition of IIHS’ Status Reports (http://

www.hwysafety.org).

percent of integral head restraints had a

backset of less than 100 mm (4 inches).

When combined height and backset

position was assessed, 53 percent of

adjustable and 70 percent of integral

head restraints were both above the ear

and less than 100 mm (4 inches) from

the head. Half of adjustable head

restraints were left in the lowest

adjustable position and three quarters of

these could have been raised to decrease

whiplash potential by bringing the head

restraint higher in relation to the

occupant’s head height.

The continued persistence of

whiplash injuries indicates that

Standard 202 should be revised. The

current state of knowledge indicates that

limiting hyperextension of the neck

does not prevent the occurrence of

whiplash and that controlling even

smaller amounts of rapid head and neck

movement relative to the torso would be

more effective. The current regulation

requires a head restraint height of 700

mm (27.5 inches) to prevent

hyperextension and has been shown to

accomplish this for occupants as large

as 95th percentile males. However, the

current regulation has no lower limit on

head restraint position. Therefore, if an

adjustable head restraint is not raised to

the 700 mm (27.5 inch) level,

hyperextension may be more likely for

some occupants. Additionally, if an

existing head restraint is not designed to

exceed the current height requirement

and to also limit backset distance, it will

not be capable of controlling small

amounts of head and neck movement

relative to the torso for many occupants.

These factors may be playing a large role

in the persistence of whiplash. NHTSA

has tentatively concluded that an

upgrade to Standard 202 is required to

foster further gains in neck injury

protection in rear impacts.

II. Background

A. Studies of Head Restraint

Effectiveness

Since January 1, 1969, passenger cars

have been required by Standard 202 to

have head restraints in the front

outboard seating positions. Head

restraints must either (a) be at least 700

mm (27.5 inches) above the seating

reference point in their highest position

and not deflect more than 100 mm (4

inches) under a 373 Nm (3,300 inchpounds) moment, or (b) limit the

relative angle of the head and torso of

a 95th percentile dummy to not exceed

45 degrees when exposed to an 8 g

acceleration. Standard 202 was

extended to light trucks and vans under

10,000 pounds, effective September 1,

1991.

In 1982, NHTSA assessed the

performance of head restraints installed

pursuant to Standard 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.

IIHS evaluated and rated head

restraints in 1995, 1997 and 1999. In

1998, in conjunction with the State

Farm Insurance Company (State Farm),

IIHS compared the conclusions from the

1995 and 1997 evaluations to crash

data.10 In the 1997 evaluation, the head

restraints of 214 1997 model year (MY)

vehicles were rated based on their

position relative to the 50th percentile

male head. The restraints were ranked

according to the prevailing view of the

biomechanics community that head

restraints that are in close proximity,

both horizontally and vertically, to the

center of gravity of the head are more

effective. The vertical reference value

used in the evaluation of each head

restraint was the distance from the top

of the head to the head’s center of

gravity. The vertical reference

measurement of 90 mm (3.5 inches) was

taken from the 50th percentile adult

male dummy drawing produced by the

University of Michigan. The height of a

head restraint was rated as ‘‘marginal’’

if the restraint’s top was 90 ± 10 mm (3.5

± 0.4 inches) below the top of the head

form. The vertical rating was ‘‘good’’ if

the distance from the top of the head

form to the top of the restraint was less

than 60 mm (2.36 inches) (i.e., the top

of the head restraint was at least 30 mm

(1.2 inches) above the head’s center of

gravity).

The reference value used to evaluate

backset, 100 mm (4 inches), was based

on a 1990 study showing a statistical

relationship between the backset larger

than 100 mm (4 inches) and the

duration of neck symptoms. The backset

of a restraint was rated as ‘‘marginal’’ if

the horizontal distance between the

head form and restraint was 100 ± 10

mm (4 ± 0.4 inches). The backset was

rating as ‘‘good’’ if the distance was less

than 70 mm (2.8 inches). A restraint’s

overall rating was the lower of the

height and backset scores. The results of

the IIHS study and the rating criteria are

presented in Table 1.

TABLE 1.—1999 IIHS HEAD RESTRAINT STUDY

IIHS rating Number of

vehicles Percent Distance down from top of head Backset

Good .................................................. 10 5.4 60 mm (2.36 in.) or less ................... 70 mm (2.76 in.) or less.

Acceptable ......................................... 50 26.9 60–80 mm (2.36–3.15 in.) ................ 70–90 mm (2.76–3.54 in.).

Marginal ............................................. 60 32.3 80–100 mm (3.15–3.94 in.) .............. 90–110 mm (3.54–4.33 in.)

Poor ................................................... 66 35.5 100 mm (3.94 in.) or greater ............ 110 mm (4.33 in.) or greater.

Total ........................................ 186 100

Scores were reduced for adjustable

head restraints since IIHS contends that

field observations have shown that they

typically are not adjusted properly.

Adjustable head restraints without locks

were evaluated based on their lowest

and most rearward position of

adjustment. For adjustable head

restraints with locks, IIHS rated the

restraint according to its locked

position, but downgraded the rating by

one category based on data establishing

that few users properly adjust head

restraints.

Because of variations in the shapes of

head restraints, it is not possible to

accurately correlate head restraint

height as measured by IIHS and the

height as measured by the method in

Standard 202. The IIHS method

evaluates head restraint height by

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 971

measuring the difference in vertical

height between the top of a special (50th

percentile male) head form mounted on

a standard H-point machine and the top

of the head restraint. The Standard 202

method measures along the torso line

(which has an angle θ with respect to

the vertical—see Figure A) from the Hpoint on the vehicle seat to the point at

which the torso line intersects with the

upper surface of the head restraint.

Assuming an idealized head restraint

shape, a simple relationship between

the two measurement methods can be

developed as shown in Figure A. The

dimension of this figure assume a torso

angle (θ) of 25 degrees from the vertical

and a distance from the H-point to the

top of the head of 755 mm (29.7 inches).

Figure B is a graphical depiction of how

head restraints of 700 mm (27.5 inches),

750 mm (29.5 inches) and 800 mm (31.5

inches) fare with respect to the IIHS

dimensional rating technique. For any

backset up to 70 mm (2.8 inches), the

800 mm (31.5 inches) high head

restraint is always rated ‘‘good.’’ A 700

mm (27.5 inches) high head restraint

can never be rated better than ‘‘poor’’ for

any backset. A 750 mm (29.5 inch) high

head restraint is ‘‘good’’ for backsets up

to 30 mm (1.2 inches) and ‘‘acceptable’’

for backsets up to 73 mm (2.9 inches).

972 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

The 1998 joint State Farm-IIHS study

compared the ratings applied in the

1995 and 1997 IIHS evaluations to

actual whiplash claims. The new study,

based on detailed analyses of more than

5,000 State Farm claims involving

midsize cars struck in the rear by other

vehicles, indicates that head restraints

rated ‘‘good’’ in the 1995 and 1997 IIHS

evaluations offered better protection in

real-world crashes than those rated

‘‘poor.’’ According to the State FarmIIHS study, drivers in cars with head

restraints rated ‘‘good’’ by IIHS are 24

percent less likely to suffer neck injuries

in rear-end crashes than drivers with

head restraints rated ‘‘poor.’’

Percentages of drivers with neck injuries

ranged from 22 percent of those with

‘‘good’’ head restraints to 27 percent of

those with ‘‘poor’’ head restraints. The

State Farm-IIHS study also found that

female drivers have higher neck injury

rates overall than male drivers—30

percent versus 23 percent, but that the

likelihood of neck injury was 36 percent

lower among female drivers with

‘‘good’’ head restraints than among

females with ‘‘poor’’ restraints. Among

male drivers, the State Farm-IIHS study

found that the risk reduction was 10

percent with ‘‘good’’ head restraints.

However, it should be noted that there

were a limited number of ‘‘good’’ head

restraints in the study (3 vehicles, all

Volvos). Thus, the results are not

conclusive.

The State Farm-IIHS study appears to

verify that higher head restraints that

are also closer to the back of an

occupant’s head (i.e., have less backset)

reduce the risk of whiplash. The study

also found measurable improvement as

the ratings increased between head

restraints in the four categories

established by IIHS—poor, marginal,

acceptable and good. The State FarmIIHS study does not, however, allow for

analysis of the virtues of increases in

height with no change in backset or

reductions in backset independent of

changes in height. Further, the IIHS

methodology accounted for the fact that

adjustable restraints are often not placed

in their highest and closest position,

resulting in only integral restraints

being rated as ‘‘good.’’

IIHS reported in its 1999 head

restraint evaluation that it dynamically

tested two advanced head restraint

designs and applied the Chalmers

University NIC criterion to the results.

These were moving rigid barrier to full

vehicle impacts at barrier speed of 24

kph (15 mph). IIHS tested the Saab

Active Head Restraint System and the

Volvo WHIPS seat. The two designs had

significantly lower NIC values than even

‘‘good’’ non-deploying designs.

B. December 1996 Request for

Comments

In 1996, NHTSA issued a Technical

Report entitled, ‘‘Head Restraints—

Identification of Issues Relevant to

Regulation, Design and Effectiveness.’’

This report identified and examined

issues related to the biomechanics of

neck injury, whiplash rates, occupant

and head restraint positioning and the

state of contemporary and future head

restraint designs. On December 19,

1996, NHTSA published a document in

the Federal Register (61 FR 66992)

alerting the public to the existence of

the report and that the agency was

interested in obtaining information and

comments about the performance of

head restraints and potential

modifications to Standard 202. The

December 1996 document contained

questions regarding:

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 973

11Economic Commission for Europe (ECE)

Regulation 25—Uniform Provisions Concerning the

Approval of Head Restraints (HeadRests), Whether

or Not Incorporated in Vehicle Seats is similar to

Standard 202 in that the same strength/

displacement test procedure and performance

values are required. The head restraint height is

measured in the same way by both regulations, but

the required heights differ. ECE 25 specifies that

head restraints he higher than the current version

of Standard 202. In addition, the current ECE 25

requires all forward facing outboard seats to have

head restraints.

(1) The effectiveness of current

designs and the potential for

improvements to reduce injury;

(2) The adequacy of Standard 202’s

height requirements and the efficacy of

new requirements such as backset and

adjustable head restraint locks;

(3) The continued need for and

possible changes to the existing

dynamic test procedure;

(4) Potential conflicts between

visibility and revised head restraint

requirements;

(5) Whether NHTSA should

harmonize its regulations with ECE

requirements;

(6) Whether changes to Standard 202

should be synchronized with changes to

Standard 207, Seating Systems; and

(7) The costs of whiplash injury in the

United States and the costs and benefits

of modifying Standard 202.

The agency received comments from

four manufacturers (Volkswagen,

Toyota, Volvo, and Ford), three safety

advocacy organizations (Consumers

Union (CU), Advocates for Highway

Safety (Advocates) and IIHS), one

equipment manufacturer, Cerviguard,

one insurance company, Insurance

Corporation of British Columbia (ICBC),

and the Chalmers University of

Technology (Chalmers).

None of the respondents submitting

comments stated that current head

restraint designs were sufficiently

effective at preventing neck injuries.

While Ford indicated that current

‘‘designs have been shown to be

effective at reducing the risk of neck

injuries in vehicle crashes,’’ it also

stated that improved designs will

require additional research and testing.

Chalmers, ICBC, CU and Advocates

stated that they believed current head

restraint designs were not sufficiently

protective against neck injuries. None of

the commenters stated that the current

required height for head restraints of

700 mm (27.5 inches) is sufficient. IIHS,

whose comments were submitted prior

to the completion of the 1998 State

Farm-IIHS report, referred to its 1995

and 1997 studies of head restraints.

These studies, based on an examination

of the head restraint positions relative to

the head, concluded that the majority of

head restraints were inadequate.

According to IIHS, only 2.3 percent of

1997 vehicles evaluated had ‘‘good’’

head restraints, thus indicating that the

current dimensional requirements are

not sufficient.

Advocates indicated that most head

restraint designs allow too much backset

and that this should be limited to

‘‘considerably’’ less than four inches.

CU stated that head restraints should

have a minimum height of 737 mm (29

inches) to 762 mm (30 inches), but

should be able to adjust even higher.

Advocates urged the agency to require

adjustable head restraints to lock in

position, considering this ‘‘a crucial

aspect of restraint design and

performance.’’ It stated that it believes

many of the current designs allow

vertical collapse of the head restraints in

rear crashes especially when the top of

the head restraint is below the head’s

C.G. Chalmers and CU also endorsed

adjustable head restraints having locks.

Toyota said it believes that, at a

minimum, the vertical adjustment

should lock.

In reference to changes to test

procedures, Chalmers stated that a

dynamic test procedure is a necessity

for new designs known as ‘‘active’’ head

restraints. These head restraints move

forward and/or higher in a crash.

Chalmers also stated that this test

should use a Rear Impact Dummy (RID)

neck (developed by Chalmers) mounted

on a Hybrid III dummy. The RID neck

was developed at Chalmers because

they thought the Hybrid III neck was too

stiff in the midsagittal plane. Advocates,

Toyota and Cervigard also expressed

concern about the biofidelity of the

Hybrid III neck. Volvo advised ‘‘that the

present 8g alternate standard in

Standard 202 should be deleted and no

new dynamic performance standard

should be adopted until more

knowledgeable injury mechanisms have

been acquired and until relevant test

procedures and improved test dummies

have been developed.’’ This would

include a change to the dummy spine as

well as the neck.

Comments on the impact of potential

changes to head restraint requirements

included concerns about effectiveness

and degradation in visibility. Volvo

stated that head restraint designs may

not be optimal for occupant protection

because manufacturers must also

consider occupant comfort and visibility

through the vehicle from the rear.

Advocates noted that increasing the

protective value of head restraints will

be affected by comfort considerations as

well as lateral and rear visibility issues.

Chalmers said it believes that head

restraints which are ‘‘actively

positioned during impact, would solve

both the problems of visibility and

injury prevention.’’

The comments also indicated support

for harmonizing Standard 202 with

Economic Commission for Europe (ECE)

Regulation 25.11 Advocates favored

harmonization, but said that the

modified Standard 202 must go further.

The organization said it believes the

agency should investigate the merits of

requiring head restraints in rear seats, as

is required by ECE 25. However, it also

mentions that this might conflict with

tethered child safety seats and rear

window visibility. CU recommended

harmonization with ECE 25 as a move

towards the goal of improving head

restraints. This includes the provision

for head restraints in the rear seats.

However, it also endorsed other changes

to the standard. Volkswagen endorsed

harmonization with ECE Commission

Directive 96/37/EC which combines

ECE 25 (Head Restraints) and ECE 17

(Seats). Toyota stated that if the agency

raises the required height for head

restraints, it should match ECE 25.

Volvo asked that NHTSA simply

‘‘monitor’’ the European standard. Ford

stated that it ‘‘strongly supports

harmonization with other world

regulations to promote world trade,

providing it does not compromise safety

or the integrity of the vehicle.’’ It

supported modification of Standard 202

on this basis.

Most of the commenters also favored

coordinating changes to Standard 202

with changes to Standard 207 on the

basis that seat and head restraint

performance are closely linked because

the longitudinal stiffness of a seat back

will have an impact on the relative

movement of the head and torso in the

event of a crash. Chalmers indicated

that their dynamic test proposal

inherently coordinates changes to

Standards 202 and 207. Advocates said

that it believes coordinating the head

restraint standard with any seat back

standard is worthy of exploration and

urged NHTSA to give explicit attention

to the relationship between head

restraints and integrated seat/head

restraint systems. Volvo stated that in

the short term no change should be

made to either Standard 202 or 207 until

more research has been done. At the

same time, it provided information on

its Whiplash Protection Study (WHIPS)

in which Volvo modified its standard

seat to optimize it for whiplash

protection.

Only one commenter, ICBC,

submitted data on the costs of whiplash

and the benefits of reducing whiplash

974 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

12NHTSA observes that the 1998 State Farm-IIHS

study revealed that the overall neck injury rate in

Michigan, the study’s only no-fault state, was 13

percent compared with 26 percent in other states,

without no-fault liability systems. This suggest that

the availability of fault-based compensation systems

may lead to higher reported rates of whiplash.

13The European regulations, EEC 74/408, as

amended by Directive 96/37/EC, promulgated by

the European Union, and ECE 17.04, established by

the UN Economic Commission for Europe (ECE),

apply to vehicles with a seating capacity of nine

passengers or less. These regulations, which

principally govern seats and seating systems, are

identical to each other. ECE 25, which applies to

head restraints, is incorporated into ECE 17.04.

Therefore, for the purposes of head restraints, ECE

17.04 and ECE 25 may be considered to be one and

the same.

injuries. ICBC stated that 45,437 British

Columbians suffered whiplash in 1996.

Since the population of British

Columbia is about 1 percent of the U.S.

population, extrapolating this figure to

the U.S. would imply that there were

4,543,700 whiplash injuries in the U.S.

during 1996. This figure is more than

five times NHTSA’s estimate of the

number of whiplash injuries in the U.S.

ICBC estimates that each whiplash costs

$8,199 U.S. If this figure were

multiplied by the number of

extrapolated injuries, this would suggest

a total cost of $37 billion U.S. That is

more than seven times greater than

NHTSA’s estimate. NHTSA does not

know why the number of whiplashes

estimated from the ICBC figures are so

much higher than the NHTSA estimate.

While the agency has not examined the

methodology used by ICBC to calculate

its estimate, it is possible that the

number of insurance reported

whiplashes may overstate the actual

incidence of injury.12 The agency’s

whiplash estimate is based on crash

data generated by police reported

crashes where one or all of the vehicles

involved are towed away from the

scene. Since many whiplashes occur in

crashes where no vehicle is towed and

no police report is made, a correction

factor was used to adjust the estimate

for these non-towed crashes.

C. AIAM/AAMA Petition

On August 13, 1997, the American

Automobile Manufacturers Association

(AAMA) and the Association of

International Automobile Manufacturers

(AIAM) submitted a joint petition for

rulemaking requesting that NHTSA

consider the possibility of amending

five safety standards so that these

standards would be ‘‘functionally

equivalent’’ to corresponding ECE

standards. The petition defined

‘‘functional equivalence’’ through

comparison with harmonization:

A harmonized regulation would contain

and define either (1) a single set of

performance requirements that a vehicle

could be ‘‘certified’’ to and sold anywhere in

the world or (2) common test conditions and

procedures, common test devices and

measurement techniques, and common test

criteria limits. A functionally equivalent

regulation may have any number of

‘‘technical’’ differences but would provide an

equivalent level of real world performance

despite these differences.

The petition did not offer any further

illumination of what ‘‘technical’’

differences may exist between two

regulatory schemes that are

‘‘functionally equivalent.’’ The AAMA/

AIAM petition implies that two

standards should be considered as

functionally equivalent if they are

similar and offer equivalent levels of

performance.

AAMA/AIAM indicated that the

European standards, ECE 17 and ECE

17.04,13 differ from Standard 202 in the

requirements for the height and width of

head restraints, the energy absorption

characteristics of the front surface of

restraints and in the requirement for

rear head restraints. The petition

requested that NHTSA amend S4.3 of its

standard to require that the top of a fully

extended head restraint be not less than

800 mm above the seating reference

point and that the top of a head

restraint, when adjusted to its lowest

adjustment position, be not less than

750 mm above the seating reference

point. The addition of these proposed

amendments, in AAMA/AIAM’s view,

would make Standard 202 functionally

equivalent to the European regulations.

Further, AAMA/AIAM requested that a

new provision be added to Standard 202

indicating that head restraints meeting

the requirements of ECE 17.05 or ECE

25.04 or EEC 74/408 be deemed to have

met the requirements of Standard 202.

In order to accommodate the product

cycles of their members, AAMA/AIAM

suggested that the upgraded Standard

202 have an effective date of September

1, 2004.

III. Overview of Proposal

NHTSA is proposing a series of

amendments to upgrade Standard 202 to

improve the protection provided to

occupants. The agency anticipates that

these amendments will provide safety

benefits in all crashes. However, we are

limiting our benefits analysis to rear end

collisions only. These new requirements

would require that head restraints,

when adjusted to their lowest possible

adjustment position, be at least 50 mm

(2 inches) higher than they are currently

required to be. (Note: This proposal is

presented in the International System of

Units (SI) with the English Units

conversion provided in parenthesis for

convenience. A final rule will be

presented in only SI units.) It would

also require front seat head restraints to

be able to achieve a height 100 mm (4

inches) higher than currently required,

and lock in this adjustment position as

well as lock at the highest adjustment

position. Rear seat head restraints

would also be required to lock in the

highest adjustment position. Head

restraints would also be subject to a new

requirement limiting the amount of

backset, i.e., distance between the back

of an occupant’s head and the front of

the head restraint, to 50 mm (2 inches).

NHTSA is also proposing that head

restraints be required in the rear

outboard seating positions. These

upgraded requirements appear in the

portion of the regulatory text which

would apply to vehicles manufactured

after the first occurrence of September 1,

three years after publication of the final

rule.

The agency proposal for upgrading

Standard 202 would harmonize

Standard 202 with the requirements for

head restraints in ECE Regulation 25 in

some respects. The proposed height

requirements are identical to those in

ECE 25. The agency proposal also

contains provisions establishing

performance criteria for energy

absorption by the front surface of head

restraints. Finally, as amended,

Standard 202 would require rear seat

head restraints.

However, the proposal would set

different requirements for head restraint

width and gap measurement for

adjustable restraints than those found in

ECE 25. Further, it would add

requirements for backset and adjustment

retention locks. It would also include a

dynamic compliance option not found

in ECE 25. In the current and proposed

Standard 202, compliance may be

measured in one of two ways. The first

way is to meet all static dimension and

strength requirements, while the second

way is to meet a dynamic test. The

proposal would modify the required

level of performance in the dynamic

compliance option to reflect the

proposed height and backset

requirements.

Prior to the first occurrence of

September 1, three years after

publication of the final rule on which

compliance with the upgraded

requirements becomes mandatory, the

manufacturers would be given the

option of complying with any of three

different sets of requirements: the

existing requirements of Standard 202,

the existing requirements of ECE 25, or

the upgraded requirements of Standard

202. Consistent with other recent

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 975

amendments to our Safety Standards,

the compliance option would have to be

selected prior to certification of the

vehicle, and the selection could not be

changed thereafter.

IV. Proposed Upgraded Requirements

A. Height Requirements

Standard 202 currently requires that

all head restraints be capable of

achieving a height where the top of the

head restraint must be at least 700 mm

(27.5 inches) above the seating reference

point measured parallel to the torso

reference line. For vehicles produced on

or after the first occurrence of

September 1, three years after

publication of the final rule, NHTSA

proposes to change this requirement to

800 mm (31.5 inches) above the H-point

for front seat head restraints. The

proposal adds a lower limit on all

required head restraints including those

in the rear outboard seats, requiring that

head restraints may not be less than 750

mm (29.5 inches) above the H-point.

Therefore, under the proposal, front

integral head restraints must have a

minimum height of 800 mm (31.5

inches) and front adjustable head

restraints must be capable of achieving

a height of at least 800 mm (31.5 inches)

and cannot be adjusted below 750 mm

(29.5 inches). Rear integral restraints

must have a minimum height of 750 mm

(29.5 inches) and rear adjustable head

restraints must not be adjustable to a

height below 750 mm (29.5 inches).

Research indicates that, for many

occupants, in order to prevent

hyperextension or lesser movements of

the head and neck in relation to the

torso that result in injury, head

restraints must be higher than currently

required by Standard 202 and close to

the rear of the head.

The proposed alterations in the height

requirements are intended to prevent

whiplash injuries by requiring that head

restraints be high enough to limit the

movement of the head and neck, even

if such movements do not result in

hyperextension of the neck. The

persistence of whiplash injuries in

current vehicles indicates that current

designs are not preventing whiplash

injuries from occurring. Research has

led to the conclusion that prevention of

hyperextension alone does not stop

whiplash from occurring. Since a 700

mm (27.5 inch) high head restraint is

capable of preventing hyperextension in

many occupants, it seems likely that the

persistence of whiplash may be the

result of the inability of current head

restraints to be positioned to sufficiently

limit relative head and neck motion in

the normal range of motion. Research

conducted since the implementation of

the current height requirement has

shown that head restraints should be at

least as high as the center of gravity

(C.G.) of the occupant’s head to

adequately control motion of the head

and neck relative to the torso. This does

not mean that there would be no

additional benefits for a head restraint

with a height greater than the height of

the head C.G. However, this is likely to

be controlled by other factors such as

backset, head restraint shape and the

underlying structure of the head

restraint under the upholstery.

Therefore, the head restraint height

relative to the head C.G. height will be

used here as an indication of the

adequacy of the proposed height

dimension.

A 750 mm (29.5 inch) high head

restraint would have a height above the

C.G. of a 50th percentile male if the

backset were 125 mm (5 inches) or less,

and assuming a head C.G. 105 mm from

the top of the head (See Figure B). The

difference in erect seating height

between a 50th and 95th percentile male

is 58 mm (2.3 inches). The size of most

adult heads is essentially the same. The

difference between the base of the neck

and the top of the head of a 50th and

95th percentile male is only 6 mm (0.2

inches). Therefore it is reasonable to

assume that the vertical dimensions

from the top of the head to the C.G. is

nearly the same at 105 mm (4.1 inches).

A 95th percentile male with a torso

angle of 25 degrees will have the top

and C.G. of the head 53 mm (2.1 inches)

higher than a 50th percentile male.

It is also reasonable to assume that the

back of the 95th and 50th percentile

male heads are essentially aligned

vertically with each other. Therefore,

they would have the same distance from

a head restraint with a flat vertical face.

This is because the longer torso of the

95th male would tend to place it closer

to the head restraint and the larger

lower back and buttocks would push the

H-point away from the back of the seat,

resulting in no net change in backset

(see Figure C). These assumptions about

backset are consistent with the agency’s

laboratory observations and a 1998

Experimental Safety of Vehicles (ESV)

Conference paper by Toyota.

Based on these assumptions, a 750

mm (29.5 inch) high head restraint

would be as high as the 95th percentile

male head C.G. if the backset were 13

mm (0.5 inches) or less (see Figure D).

It would be 17 mm (0.7 inches) below

the 95th percentile male head C.G. at 50

mm of backset. A 800 mm (31.5 inch)

high head restraint would be as high as

the 95th percentile male C.G. if the

backset were 133 mm (5.3 inches) or

less. It would be 38 mm (1.5 inches)

above the 95th percentile male head

C.G. at 50 mm of backset.

The proposal for the front seat of

requiring head restraints to be capable

of achieving an 800 mm height and have

a backset no greater than 50 mm should

assure that the top of the head restraint

is above the head C.G. of virtually all

front seat occupants. The proposal for

front and rear seats requiring a

minimum height of 750 mm and backset

no greater than 50 mm will provide

head restraints higher than the head

C.G. of about 86 percent of the adult

males (assuming a normal distribution

of height). The C.G. height of a 99th

percentile female reclined at 25 degrees

is about 19 mm below a 750 mm (29.5

inches) high head restraint at a 50 mm

(2 inch) backset. Therefore, this will

provide head restraints higher than the

head C.G. of nearly all adult females and

93 percent of all adults. In term of the

rear seat target population, this proposal

will cover an even higher percentage of

rear seat occupants than it would of the

entire population of occupants. This is

because more children occupy the rear

seats and larger occupants rarely sit in

the rear where there is generally less

room.

976 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 977

The recent State Farm-IIHS study also

suggests that head restraints that are

higher in relation to the head center of

gravity and closer to the back of the

head provide greater protection against

whiplash. The agency notes that head

restraints rated ‘‘good’’ by IIHS—

integral restraints with a height less

than 60 mm (2.36 inches) below the top

to the head and within 70 mm of the

rear of the head—reduced the likelihood

of whiplash by 36 percent in females

and 10 percent in males. Figure B shows

that an 800 mm (31.5 inches) high head

restraint is likely to be high enough to

be rated as ‘‘good’’ at all backsets within

the ‘‘good’’ range. NHTSA believes that

the proposed requirement for backset, in

conjunction with the proposed height

requirements, would lead to a

significant improvement in safety.

Although the agency tentatively

concludes that its proposed 800 mm

(31.5 inches) height requirement would

offer significant benefits for people

taller than 50th percentile males, the

agency wishes to know if additional

safety benefits could be realized by

requiring head restraints to be capable

of achieving a somewhat greater height.

Therefore, NHTSA requests comments

on:

1. The marginal benefits and costs of

requiring head restraints to be capable of

achieving a height greater than the one

proposed in this notice.

2. Other issues that may be raised by a

height requirement greater than the proposed

one, including those associated with the

potential effects on visibility, seat

adjustability and compliance with other

safety standards, e.g., Standard 201, ‘‘Head

Protection in Interior Impact.’’

B. Backset Requirement

NHTSA is also proposing to add, for

vehicles produced on or after the first

occurrence of September 1, three years

after publication of the final rule, a

backset requirement of no more than 50

mm (2 inches) for front and rear head

restraints. The consensus of the

biomechanics community is that the

backset dimension has an important

influence on the forces felt by the neck

and the length of time a person is

disabled by injury. This judgment is

based on testing, computer modeling

and real world crash data. As far back

as 1967, Mertz and Patrick showed that

loading on the head during a rear

impact is minimized by reducing the

initial separation between the head

restraint and head. With the head

initially against the head restraint, a

volunteer test subject endured a 71 kph

(44 mph) rear impact without

discomfort. Research presented at the

1990 International Research Council on

the Biomechanics of Impact (IRCOBI)

examined 25 rear impacts involving 33

occupants of Volvo cars. The study

results showed a statistically significant

increase in neck injury duration when

there was more than 100 mm (4 inches)

of backset. A 1994 study conducted by

Volvo found additional potential injury

reduction as the backset approaches

zero, allowing no relative motion

between the head and torso upon rear

impact. IIHS, in its studies of head

restraints, considered a backset of 70

mm (2.8 inches) or less to be ‘‘good.’’

NHTSA has tentatively concluded

that adding a requirement specifying a

limit on backset would result in reduced

angular displacement between the head

and torso in a crash. One method the

agency used to assess the potential

benefits of a backset limit was through

a computer modeling study in which

the backset dimension was defined as

the distance between two vertical lateral

978 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

planes; one plane passing through the

rearmost point on the headform and the

other passing through the forwardmost

part of the head restraint at its

centerline. A seat model intended to

represent a 1986–1994 Pontiac Grand

Am was used with the head restraint

positioned in 21 different configurations

with varying heights and backsets. The

vehicle seat, as modeled, was relatively

stiff in the longitudinal direction in

comparison to those currently on the

market. Another set of data was

generated with the hinge joint kept

completely rigid. This was intended to

simulate a rear seat that has its seat back

structure rigidly attached to the vehicle

body, such as is the case for many

passenger cars. A model of a Hybrid III

50th percentile male was the seat

occupant.

For both seat stiffnesses, no head-totorso angular rotation was greater than

2 degrees for head restraints above 750

mm (29.5 inches) and backsets 50 mm

(2 inches) and closer. At backsets up to

100 mm (4 inches), all head-to-torso

angular rotations were less than 21

degrees for head restraints above 750

mm (29.5 inches). At a backset of 150

mm (6 inches), head rotations of 27 and

44 degrees occurred at head restraint

heights of 750 mm (29.5) and 800 mm

(31.5 inches), respectively.

The computer modeling indicates that

the lowest head-to-torso rotation value

was seen when the backset was

approximately 50 mm (2 inches).

NHTSA tentatively concludes that this

amount of backset is appropriate for all

outboard seating positions.

The agency understands that there are

differences in the way occupants adjust

and sit in seats and that the backset

measurement device being used may not

capture this variety completely since it

attempts to represent the head position

of a 50th percentile male in a seat with

a 25 degree inclination from the vertical.

A steeper seat back inclination will

further reduce the backset.

The agency also believes that physical

differences in seat design may

contribute to seat performance. In fact,

National Automotive Sampling Systems

(NASS) crash data indicate that the

whiplash rate for rear seat occupants is

significantly lower than that of front

seat occupants. One explanation may be

that many rear seats are often configured

differently than front seats and

frequently do not have adjustable backs.

Adjustable seat backs allow wide

variations in location of the head

restraint relative to the user as the

seatback angle changes through the

range of adjustment.

In making the backset proposal, the

agency has attempted to balance the

need for both occupant safety and

comfort while considering potential

misadjustment. The agency believes the

backset requirement is practicable—the

majority of occupants should

comfortably fit in seats with a 50 mm (2

inch) backset and it is well within the

capability of manufacturers to produce

seats with this backset.

The agency measured 14 MY 1999

vehicles and found that the front seats

of the Toyota Camry, Chevy C1500,

Chevy S10, Saab 9–5, and Chevy Malibu

had backsets within the proposed 50

mm (2 inch) limit. Saab 9–5 rear seats

also meet that proposal. For the entire

fleet of new vehicles, we estimate that

front seats are an average of 23 mm (0.9

inches) away from meeting the proposal

and rear seats are an average of 47 mm

(1.8 inches) away from the proposal.

These fleet estimates were derived by

using the sales weighted averages of the

14 MY 1999 vehicles measured. More

details can be found in the PEA for this

proposed rule.

Further, based on IIHS’ rating of head

restraints in MY 1999 vehicles, it

appears that there are at least some

models in all classes of vehicles that

already meet or come close to meeting

the proposed backset limit. As noted

above, IIHS rates the backset of a

vehicle’s head restraints as good if it is

not more than 70 mm (2.6 inches).

According to IIHS, cars with head

restraints rated good overall (i.e., both

backset and height) include the BMW

Z3 Coupe, Saab 9–3 and 9–5,

Volkswagen New Beetle (some seat

options), and Volvo C70/S70/V70 and

S80 models. Among pickups, the

Chevrolet S10 and GMC Sonoma have

good restraints. And among utility

vehicles, the Chevrolet Blazer (some

seat options) and Mitsubishi Montero

earn good ratings.

Nonetheless, NHTSA solicits

comments on whether this proposed

backset limitation is appropriate. In

particular, the agency seeks information

and comments on:

3. Whether limiting backset to 50 mm (2

inches) is sufficient to prevent excessive

relative motion between the occupant’s head

and torso. Does 50 mm (2 inches) of backset

provide sufficient head clearance and

comfort for most occupants?

4. Would it be appropriate to allow a

greater maximum backset (e.g., 100 mm (4

inches)) while requiring that head restraints

with more than 50 mm (2 inches) of backset

be adjustable so that backset can be reduced

to 50 mm (2 inches)? Please provide data on

the amount of safety disbenefit that would be

associated with allowing a backset of 75 or

100 mm (3 or 4 inches), instead of 50 mm

(2 inches).

NHTSA is proposing that compliance

with the backset requirement be

measured through use of the ICBC Head

Restraint Measuring Device. Under the

proposed rule, all outboard seat head

restraints must have a backset of not

more than 50 mm (2 inches). This 50

mm (2 inches) backset must not be

exceeded at any height between 750–

800 mm (29.5–31.5 inches). Although

no height adjustment beyond 750 mm

(29.5 inches) is required for rear seats,

if these higher height positions exist,

backset must be limited to 50 mm (2

inches). Figure E is a graph of the zones

of adjustment for front and rear head

restraints relative to the head C.G. of a

50th and 95th percentile male dummy.

These positions are based on the

assumptions stated in Section IV.A.,

Height Requirements and shown in

Figures C and D.

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 979

The agency believes that the ICBC

measuring device is an appropriate tool

for measuring backset. However, the

agency solicits comments on:

5. Other devices that may be used to

perform the same function as the ICBC device

and whether such devices would be more

appropriate.

NHTSA observes that the ECE 25

requirements do not include a

specification for backset. The agency

believes, however, that the proposed

backset requirement, which the agency

believes offers significant safety

benefits, would not prevent

manufacturers from producing designs

meeting ECE 25.

Both the height and backset

measurements are accomplished

through the use of the SAE J826

manikin (June 1992) or H-point

machine. The positioning procedure for

this device is explicitly defined in SAE

J826 in order to maximize repeatability.

This in turn maximizes the repeatability

of the height and backset measurements.

C. Height Adjustment and Backset Limit

Retention Requirements

The agency is also proposing, for

vehicles produced on or after the first

occurrence of September 1, three years

after publication of the final rule, that

performance requirements for adjustable

head restraints be added to Standard

202 which are intended to assure that

the front head restraints remain locked

in specific positions. A 1982 NHTSA

study found that the effectiveness of

integral head restraints was greater than

adjustable head restraints. The study

concluded that this difference in

effectiveness was due, in part, to

adjustable head restraints not being

properly positioned. Although one

reason for improper positioning is a lack

of understanding on the part of the

occupant on where to place the head

restraint, it also could be due to the

head restraint’s moving out of position

either during normal vehicle use or in

a crash. Adjustment locks can mitigate

this problem by helping to retain the

adjusted position. IIHS has also been

critical of adjustable head restraints,

especially when they do not provide

locks, in their evaluation of head

restraints. This criticism has manifested

itself in that IIHS, in its rating of head

restraints, automatically gave adjustable

restraints a lower rating on the

assumption that these restraints would

not be properly adjusted. In addition, it

only evaluated adjustable head

restraints without locks in their lowest

position. In comments on the agency’s

1996 technical report, Advocates stated

that adjustable restraints should be

required to lock. Toyota also stated that,

at a minimum, head restraints should

lock vertically.

The modifications to the existing

height requirements and the addition of

a backset requirement that are now

being proposed are expected to improve

the performance of all adjustable head

restraints. The performance of

adjustable head restraints may be

further improved if steps are taken to

ensure that a restraint remains in

position after it has been set by the user.

In making this proposal, the agency

has no desire to require specific

methods for adjustment and locking. A

typical adjustable head restraint design

allows manual adjustment by sliding the

head restraint in and out of the seat back

on posts attached to the head restraint.

Position locking is achieved by notches

in the shaft allowing for a detent

mechanism. There are also powered

adjustable head restraints which are

infinitely adjustable within a specific

range. When the adjustment mechanism

is inactive, the head restraint is, in

effect, locked in position. Under the

980 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

current proposal, these and other

locking methods would be permissible

as long as the performance criteria

below are met.

Therefore, we are proposing that

adjustable head restraints for the front

outboard seating positions must

maintain their height (i.e., lock) in

several height positions under

application of a downward force. In

addition to locking at a position of not

less than 800 mm (31.5 inches), they

must also lock at the highest adjustment

positions. It may be that, for some

designs, the highest position is at 800

mm (31.5 inches). Adjustable head

restraints for the rear outboard seating

positions must lock at the highest

position of adjustment above 750 mm

(29.5 inches), if this position exists. In

addition to locking at these specified

positions of height adjustment, both

front and rear head restraints must be

capable of retaining the minimum

height of 750 mm (29.5 inches) under

application of a downward force.

The height position retention

requirements must be met at any backset

position of adjustment. The agency

believes that this is important for

designs which adjust vertically as well

as rotate for backset adjustment.

Although there may be no backset

position more than 50 mm (2 inches), a

change in the backset position may

change the height of the head restraint.

We are also proposing to adopt the

following backset retention requirement.

Under application of a rearward

moment, with the head restraint

adjusted to 800 mm (31.5 inches) for

front outboard seats and 750 mm (29.5

inches) for rear outboard seats, the head

restraint must maintain any position of

backset adjustment.

The agency believes that the proposed

height and backset position retention

requirements are very comprehensive

and that requirements for other

positions than those mentioned above

are unnecessary and would not result in

significant additional safety benefits.

The agency notes, however, that

manufacturers would not be precluded

from providing additional lockable

positions within the range of the head

restraint’s adjustment.

The proposed height adjustment

retention lock and backset limiter

compliance tests begin by applying a

small initial load to the head restraint.

A headform is used to apply the load

and a reference position is recorded.

The head form reference position is

measured with this load applied to

eliminate variability associated with the

soft upholstery of the head restraint. A

larger load is then applied through the

headform to test the locking mechanism.

Finally, the load is then reduced to the

initial value and the head form is

checked against its initial position. In

order to comply, the locking and limiter

mechanisms must not have allowed the

headform to have moved more than 10

mm (0.4 inches) from the initial

reference position. First, to test the

vertical lock, a load is of 500 N (112

pounds) is applied vertically

downward. Then, to test the backset

limiter, a force is applied sufficient to

generate a 373 Nm moment (3,300 inchpounds) perpendicular and rearward to

the torso reference line about the Hpoint. A force of approximately 500 N

(112 pounds) is required to generate this

moment. The agency has reviewed

upper neck shear loading from 33 rigid

moving barrier, rear impact (48 kph (30

mph)) FMVSS 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 (78.9 pounds). 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 (3,300 inch-pounds) rearward

moment and 500 N (112) downward

force are representative of the peak

loads likely to be encountered in

moderate to severe rear impacts.

NHTSA remains concerned, however,

that while the addition of the proposed

locking and limiter requirements will

help ensure that properly adjusted head

restraint remain in position, the

requirements cannot do anything to

ensure that adjustable head restraints

are actually put in that position in the

first place. The agency requests

comments on:

6. The appropriateness of the load values

used to assess the position retention

capability of head restraints. Should other

height and adjustment positions such as a

mid-height position be tested and/or

required?

7. Do vehicle users understand how to

properly adjust head restraints? If not, should

manufacturers be required to provide

information on this subject to consumers in

the vehicle owner’s manual or elsewhere?

8. The extent to which misadjustment of

head restraints is due to the absence of

adjustment retention locks versus intentional

misadjustment by occupants.

9. Do vehicle users intentionally misadjust

head restraints for reasons related to comfort,

visibility, or other factors?

10. Are adjustable head restraints with

adjustment retention locks significantly less

likely to be misadjusted than ones without

such locks?

11. Would equipping restraints with locks

discourage misadjustment? If not, should

other requirements be adopted to address the

problem of misadjustment? The agency has

previously addressed issues of misuse, nonuse and adjustment in several contexts,

including manual seat belts and child seats.

Would the measure adopted in these contexts

be appropriate with respect to head

restraints?

12. What would the costs and benefits be

of requiring that the height of front seat head

restraints be fixed at 800 mm (31.5 inches)

or at some other single height? What would

the costs and benefits be of adopting such a

fixed head restraint requirement for rear seat

head restraints?

D. Rear Outboard Seating Positions

In addition to modifying requirements

for head restraints for front outboard

seating positions, NHTSA is also

proposing to add head restraint

requirements for rear outboard seating

positions for vehicles produced on or

after the first September 1 that occurs

three years after publication of the final

rule. The agency has tentatively

concluded that the addition of head

restraints for these seating positions

would reduce whiplash injuries to rear

seat occupants and harmonize Standard

202 with the ECE 25 head restraint

requirements. Data obtained from NASS

for non-rollover towaway rear crashes

for passenger cars and LTV’s for the

years 1988 through 1996 shows that

there were 5,440 whiplash injuries

reported annually for occupants of rear

outboard seating positions.

The whiplash rate (number of

occupants with whiplash divided by the

number in crashes) for these seating

positions is less than that for front

outboard seating positions, but is still

significant. The reasons for a lower rear

seat whiplash rate are not clear, but

probably cannot be attributed solely to

the fact that rear seat occupants are on

average shorter than front seat

occupants. Occupants may sit

differently in rear seats—their posture

may place the head closer to the head

restraint and reduce or eliminate

backset. Although rear seat head

restraints are on average 33 mm (1.3

inches) lower than front seat head

restraints, the reason for the relatively

low occurrence of whiplash in rear seats

may be the existing configuration of rear

seats and rear seat head restraints.

NHTSA is proposing that rear

outboard seat head restraints must have

a minimum height of 750 mm (29.5

inches) above the H-point. As noted

above in the backset requirement

section, the rear outboard head

restraints must also meet backset

requirements and have a backset of 50

mm (2 inches) or less.

NHTSA sampled the head restraint

heights and backsets of 12 1999 MY

vehicles which had front and rear head

restraints. Three of the vehicles had rear

seats of sufficient height and one

vehicle met the backset limit proposed

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 981

for rear seats. One of the twelve vehicles

would meet both the height and backset

proposal.

The agency’s proposal to require head

restraints in the rear outboard seating

positions is, in part, based on a

philosophy that commonly used seating

positions should offer similar levels of

protection to their occupants. This

philosophy has guided the agency in

requiring a test dummy to be placed in

the rear seat for the dynamic

performance test in FMVSS 214; Side

Impact Protection, and in the provision

of FMVSS 208; Occupant Crash

Protection, requiring lap/shoulder seat

belts to be installed in forward facing

rear outboard seating positions. In

establishing the FMVSS 208 and 214

requirements for both front and rear

seats, we realized that, because of the

significantly lower rear seat occupancy

rates, the ratio of cost to benefit was

inherently higher than similar front

seating position requirements. In this

case, there are again lesser safety

benefits from rear seat head restraint

protection because of lower rear seat

occupancy rates. However, when people

are sitting in the rear seat, they will gain

safety benefits from improved head

restraints.

Assessment of the relative merits of

requiring enhanced protection for rear

seats must also reflect the fact that

NHTSA has recommended that all

children 12 and under sit in the rear.

Given that we have provided this advice

to parents, NHTSA feels particularly

obligated to provide similar levels of

protection in the rear. Older children

are large enough to benefit from a rear

seat head restraint particularly in family

vehicles with bench type seats such as

minivans and SUVs. Also, rear seat

occupancy should rise as more children

sit there, thereby increasing the at-risk

population and the corresponding

benefits of rear seat head restraints. For

these reasons, we have decided to

propose upgrading whiplash protection

in outboard rear seats notwithstanding

lower cost-effectiveness for improved

head restraints at those positions.

NHTSA is especially interested in

public comments on this approach.

The agency is not proposing to require

front or rear center seat head restraints

because of significant costs, much

higher cost per equivalent fatality than

outboard positions, and visibility

concerns. The combined total cost of

front and rear center seats head

restraints would be $52 million (front)

+ $94 million (rear) = $146 million. We

estimate that this substantial investment

would result in reducing the annual

number of whiplash injuries in the front

center seat by 440 and in the rear center

seat by 1,276. The combination of these

cost and benefit figures would be a cost

per equivalent life saved (at 7 percent

discount) of $52 million for front center

seat head restraints, based on the

effectiveness for increasing the height of

head restraints and assuming no benefit

for backset. For rear center seat head

restraints, the cost would be $33

million. For both front and rear center

seats combined, the cost per equivalent

life saved would be $38 million. All of

those figures are much higher than the

cost per equivalent life saved for front

outboard seats ($3 million) and that for

rear outboard seats ($9 million).

Finally, having center seat head

restraints limits to some extent the

driver’s ability to see following traffic

using the inside rearview mirror. When

a vehicle is in reverse, front and rear

center head restraints limit visibility

when the driver turns his/her head to

back up. In addition, a front center seat

head restraint can limit vision through

the right side second seat window when

the driver is considering a lane change

maneuver to the right. The agency can

not quantify these potential losses in

visibility, nor the potential impact that

this loss in visibility could have on

safety.

The agency is aware of rear seat head

restraint designs which have the goal of

lessening the rearview obstruction.

Some designs provide open areas in the

head restraint so the driver can see

through them. Other head restraints fold

out of the way into non-use positions.

The agency’s current proposal does not

contain any requirements to specifically

compensate for the potential rearview

obstruction. However, the agency is

proposing language in S4.3 which will

allow for folding or retractable head

restraints for rear seats if they meet

specific criteria. If such a head restraint

is adjusted to a non-use position, i.e.,

any position in which its minimum

height is less than that proposed in this

document or in which its backset is

more than that proposed in this

document, it must give the occupant an

unambiguous physical cue that the head

restraint is not properly positioned by

altering the normal torso angle of the

occupant or it must automatically return

to a position where it would comply

with all provisions of the regulation

when the seat is occupied. To determine

if the head restraint in a non-use

position alters the torso angle of an

occupant, the SAE J826 manikin is

placed in the seat position. The torso

angle of the manikin when the head

restraint is in a non-use position must

be at least 10 degrees closer to the

vertical than when the head restraint is

in a normal use position. Alternately, if

the head restraint is designed to return

automatically from a non-use position to

a normal use position, this must occur

when a 5th female and 50th male

Hybrid III test dummy in placed in the

seating position.

The agency would like commenters to

address the issues surrounding rear seat

head restraints and their impact on

rearward visibility. Specifically, the

agency would like to know the

following:

13. Are data available related to safety

risks, if any, associated with decreased

visibility caused by rear seat head restraints?

14. Should the agency place specific design

requirements on rear seat head restraints to

compensate for any potential visibility

losses?

15. Should Standard 202 allow rear head

restraints to have non-use positions? If so,

how should such positions be defined and

limited?

16. Are the proposed requirements for nonuse positions sufficiently objective? Are they

sufficient to alert occupants that the head

restraint is not in a normal use position?

17. Given the lesser safety from rear seat

head restraint protection because of lower

rear seat occupancy rates, and given the

visibility issues, should the agency limit the

application of any final rule to front seating

positions?

An additional concern raised by the

required installation of outboard rear

seat head restraints is the impact of such

restraints on child restraints that use top

mounted tether straps. The agency notes

that tethered child restraint

requirements have just been instituted

in the United States and have been

required for some time in Canada and

Australia—where vehicles with rear

head restraints are relatively common.

Inquiries to Transport Canada, NHTSA’s

Canadian counterpart, indicate that

interference between rear head

restraints and child seat tethers has not

posed significant problems. NHTSA also

wishes to point out that on March 5,

1999, the agency published the final

rule for Standard 225, ‘‘Child Restraint

Anchorage System’’ (64 FR 10785). The

standard requires an independent

system which has two lower

anchorages, and one upper anchorage.

Each lower anchorage includes a rigid

round rod or bar onto which a hook, a

jaw-like buckle or other connector can

be snapped. The bars will be located

near the intersection of the vehicle seat

cushion and seat back. The upper

anchorage will be a ring-like object to

which the upper tether of a child

restraint system can be attached.

In its examination of the potential for

interference between tethers and rear

seat head restraints conducted prior to

the issuance of that final rule, the

agency agreed that compatibility

982 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

problems between the tether and rear

seat head restraints could occur in some

situations but concluded that this did

not present an unsurmountable design

problem. NHTSA concluded that ‘‘Y’’

shaped tether strap designs that encircle

the head restraint might be used where

the tether could not pass over or under

the head restraint. Furthermore, as the

final rule amending Standard 213,

‘‘Child Restraint Systems,’’ requires the

use of a fixture for testing tether

strength, manufacturers should be able

to identify and correct for potential

compatibility problems between the

tether system and head restraints.

Nonetheless, the agency solicits

comments on the following:

18. Are there potential safety concerns

caused by interference between rear seat

head restraints and child seat tethers?

19. The existence or significance of test

data showing whether passing the top tether

over the top of the head restraint or

underneath an adjustable head restraint has

any effect on head excursion or lateral

stability of a child restraint.

E. Removability of Head Restraints

The agency is aware that some current

head restraints, both front and rear, can

be manually removed solely by hand

(i.e., without the assistance of any hand

held object). Such a design is not

currently prohibited by Standard 202.

The agency believes strongly that all

occupied outboard seats should have a

properly positioned head restraint in

place. However, for seats which are

often unoccupied, which is usually the

case for rear seats, there may be a

potential benefit to allow head restraints

to be removable for the sake of

increasing a driver’s field of view

towards the rear. The proposed rule

would prohibit removable head

restraints in the front seats, but would

not prohibit removable head restraints

in the rear seats. The agency believes

that a rear seat which has its head

restraint removed gives a strong visual

cue to a prospective occupant unlike a

head restraint which may be in a subtle

non-use position. Front seats must be

designed so that they cannot be

removed solely by hand.

20. Should Standard 202 continue to allow

any head restraints to be removable by hand?

If so, should this be limited to rear seat head

restraints?

21. Should there be some type of indicator

to warn a prospective occupant that the head

restraint has been removed, or is the visual

cue of a seat without a head restraint

sufficient?

F. Head Restraint Configuration

Requirements

1. Width

NHTSA has tentatively concluded

that the requirements for head restraints

on vehicles produced on or after the

first occurrence of September 1, three

years after publication of the final rule,

should maintain the existing width

requirements contained in Standard

202. These provisions require that head

restraints be at least 170 mm (6.7

inches) wide on single seats and 254

mm (10 inches) wide on bench seats.

The agency believes that doing

otherwise will degrade the level of

safety currently available. 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. This is

especially true if they do not use their

seat belts—a concern that is more

relevant in the United States than in

Europe. Thus, the head restraint needs

to be wider to assure that, in the event

of a crash, the head restraint will be

positioned behind an occupant’s head.

This proposal differs from the ECE 25

regulations in specifying a different

width requirement for bench seats than

for other seats. As noted above, the

agency is concerned that because seats

other than bucket seats, i.e., bench and

split bench seats, are more widely used

in the United States than in Europe,

Standard 202 should dictate different

width requirements than those found in

ECE 25.

2. Gaps

NHTSA is proposing the addition of

maximum gap requirements for head

restraint designs incorporating openings

within the perimeter of the restraint.

Gaps may be provided to allow for sight

through the head restraint. However,

gaps which are too large may defeat the

purpose of the head restraint by

allowing the head to displace too far

before contact with the head restraint.

The agency used ECE 25 as a model for

the gap requirement in the NPRM. The

agency proposal for integral restraints

allows a maximum 60 mm (2.36 inches)

gap in the head restraint and an

identical maximum gap between the

head restraint and seat. For height

adjustable head restraints, 60 mm (2.36

inches) gaps are allowed in the head

restraint. When adjustable head

restraints are in their lowest position

they must have some position of backset

adjustment where the gap between the

seat and head restraint is less than 25

mm (1 inch). However, this gap cannot

be greater than 60 mm (2.36 inches).

The agency believes that a 25 mm (1

inch) gap requirement between the seat

and head restraint would essentially

require the seat back to provide the

travel stop for head restraint adjustment

downward. This would eliminate

significant discontinuities between the

seat back and head restraint when the

head restraint is in its lowest position,

which may be a benefit to short

occupants. The maximum 60 mm (2.36

inches) gap between the seat back and

head restraint when the head restraint is

in the lowest adjustment position is

allowed in anticipation of designs that

have rotational backset adjustment. It

may not be possible for this type of

design to meet the 25 mm (1 inch) limit

in all rotational positions.

Finally, it should be noted that the

gap requirements would place no limit

on the size of the gap between the seat

back and head restraint that is produced

when the head restraint is raised. The

establishment of such a limit would

eliminate from the market place most

existing adjustable head restraints. The

agency anticipates that occupants will

not adjust their head restraints such that

the rear portion of their head would be

between the top of the seat and bottom

of the head restraint. Nonetheless, the

agency would like comments on this

issue.

For harmonization purposes, NHTSA

notes that the proposed gap

requirements are identical to the ECE 25

specifications with two exceptions.

First, the proposed NHTSA limit on the

distance between the head restraint and

the seat when the head restraint is in its

lowest position applies only at a single

position of backset adjustment. The ECE

requirement does not contemplate head

restraints that may be adjustable for

backset and simply allows no more than

a 25 mm (1 inch) gap. Second, the ECE

standard allows an alternate compliance

option of application of a load to the gap

area rather than limiting the gap to 60

mm (2.36 inches). The agency assumes

that the concept behind this option is

that if pushing on the gap area with a

head form does not cause deflection of

more than 102 mm (4 inches), the gap

is acceptable. The agency sees no need

for permitting this alternate method of

compliance.

22. The agency requests comments on the

need for a requirement limiting the gap

between the lower edge of an adjustable head

restraint and the seat to 25 mm (1 inch) when

the restraint is in its lowest position.

23. NHTSA requests comments on whether

60 mm (2.36 inches) is an appropriate value

for the maximum size of the gap between a

seat and the lower edge of an integral head

restraint and the maximum allowable gap in

any head restraint.

24. The agency also requests comments on

whether a limit should be placed on the gap

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 983

between adjustable head restraints and the

seat back when the head restrain is in a

raised position.

G. Energy Absorption

For vehicles produced on or after the

first occurrence of September 1, three

years after publication of the final rule,

the agency is also proposing an energy

absorption requirement specifying that

when the front of the head restraint is

impacted by a head form at a velocity

of 24.1 kilometers per hour (15 mph),

the deceleration of the head form must

not exceed 80g continuously for more

than 3 milliseconds. The impactor

would be a free-motion head form with

a 6.8 kg (15 pound) mass. The proposal

would require the head restraint to

comply in any position of adjustment.

The area of the head restraint subject to

impact in the compliance test would

differ depending on the seat

configuration. The proposal limits this

area to within 70 mm (2.8 inches) of the

head restraint vertical centerline for

single seats, but increases the impact

area to within 105 mm (4.1 inches) of

the centerline for bench seats because of

the potential for occupants to be seated

farther from the centerline in bench

seats. The point of impact must be at

least 635 mm (25 inches) above the Hpoint.

The agency proposal is similar, but

not identical, to the requirements of ECE

25. ECE 25 requires the use of a

pendulum impactor. The agency’s

proposal specifies the use of a freemotion head form impactor. NHTSA

believes the results from a pendulum or

head form impactor would be the same.

In order to increase the level of

harmonization with ECE 25, the agency

is not at this time proposing the use of

the free-motion head form in Part 572

Subpart L. This head form is required

for upper interior impacts in Standard

201; Occupant Protection in Interior

Impacts. The Part 572(L) head form has

a 4.5 kg mass (10 pound) rather than a

6.8 kg (15 pound) mass. However the

mass and impact speed of the head form

in ECE 25 and being proposed here are

the same as required by Section 5 of

Standard 201.

The agency proposal also differs from

ECE 25 in the dimensions of the area of

impact. ECE 25 specifies a single size for

the impact area regardless of the seat

configuration. As bench seating is more

common in vehicles produced for the

North American market, the agency

believes that the variance between the

two regulations is justified.

The proposal also contains a

minimum radius of curvature

requirement for the front surface of the

head restraint. In order to protect rear

seat occupants from injuries caused by

impact with the head restraint in frontal

crashes and all occupants in rollovers or

similar crashes, any part of the head

restraint outside of the impact zone for

the energy absorption requirement must

not have a radius smaller than 5 mm

(0.2 inches) unless it can pass the

energy absorption requirement. This

requirement is intended to eliminate

potential sources of high pressure

contacts between occupants and head

restraints. NHTSA is not aware of any

surfaces on current head restraint

designs that have such a small radius of

curvature and believes that most, if not

all, would be in compliance.

Nonetheless, NHTSA is proposing this

requirement in the interest of increasing

the level of harmonization with ECE 25.

25. The agency requests comment on the

need for the requirement for limiting the

radius of curvature outside of the impact

zone to no less than 5 mm (0.2 inches).

26. NHTSA would also like comments

whether the Part 572 Subpart L free-motion

head form should be proposed rather than

the head form in the current proposal which

more closely harmonizes with ECE 25.

H. Test Procedures

1. Displacement Test Procedure

The agency is also proposing changes

to the existing displacement test

procedure contained in Standard 202. In

this procedure, the head restraint’s

ability to resist deflection is measured

by applying a load to the back pan of the

seat and applying a load to the head

restraint after the load on the back pan

of the seat is released. A 102 mm (4

inch) displacement is allowed with a

373 Nm (3,300 inch-pounds) moment

applied. The applied load is then

increased until the seat or seat back fails

or the load reaches 890 N (200 pounds)

and the head restraint withstands this

load.

The proposal modifies this test

procedure to require that the back pan

of the seat and the head restraint be

subjected to simultaneous loading. The

agency proposal also removes the

current standard’s provision allowing

seats or seat backs to fail when the head

restraint is subjected to the 890 N (200

pounds) load. Lastly, the proposal

modifies the existing test procedure to

clarify the direction of the loads placed

on the restraint, seat and seat back. The

proposal maintains the 4 inch

displacement limit. The exact SI

conversion to 102 mm is used rather

than rounding the value to 100 mm

because it is an existing requirement.

Data provided by the AAMA and

AIAM indicate that loading the seat

back pan and the head restraint at the

same time results in a more severe test.

These data were contained in a petition

submitted to the agency in support of

harmonizing the existing Standard 202

test with the ECE 25 test. AAMA/AIAM

provided data from one 1998 model year

vehicle seat that showed a 64 mm (2.5

inch) displacement for the Standard 202

method and a 89 mm (3.5 inch)

displacement for the ECE method.

NHTSA’s review of the AAMA/AIAM

data indicates that the AAMA/AIAM

position appears to be correct. Because

the back pan position is maintained

while the head restraint is loaded, some

amount of load may be applied through

the back pan to the seat. This load,

along with the load applied to the head

restraint, results in the total applied seat

moment and contributes to head

restraint deflection. Thus, the head

restraint deflection may be greater than

if the back pan load is removed before

application of the head restraint load.

The agency believes that applying loads

to both the back pan and the head

restraint simultaneously better reflects

the stresses that occur in rear end

crashes.

This change, if adopted, will

harmonize the Standard 202

displacement test procedure with that

contained in the ECE 25 regulation. In

both test procedures, the back pan of the

SAE J826 test device is used to apply a

373 Nm (3,300 inch-pounds) moment to

the seat back. Currently, the difference

in the two test procedures is that

Standard 202 specifies that the back pan

load is removed before application of

the moment to the head restraint and

ECE 25 specifies that the back pan

position is maintained while the head

restraint moment is applied.

Additional text has been added to the

displacement test procedure to clarify

the direction of loading on the head

restraint and seat back. The proposal

would require that the back pan be

constrained so that as pressure is

applied, it rotates about the H-point and

the moment producing force, which is

initially perpendicular to the torso line,

rotates with the back pan. However, the

proposal also would require that the

moment-producing force on the head

restraint initially be applied

perpendicular to the displaced torso

reference line and that the orientation

be maintained with respect to the

ground throughout the testing.

Finally, the existing displacement

procedure allows the seat back to fail

without consequence under application

of 890 N (200 pounds) to the head

restraint. Yet, from the perspective of an

occupant, if the head restraint is

displaced during loading, the

consequences may be equally severe

regardless of the reason for the

984 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

displacement. Therefore, the NPRM

removes the allowance for seat back

failure. The head restraint must be able

to apply a resistive force of 890 N (200

pounds) to the load applying head form.

If the head restraint is displaced out of

the path of the head form prior to

achievement of the 890 N (200 pounds)

load, the head restraint has failed,

regardless of whether failure was due to

weakness in the seat or the head

restraint components.

2. Dynamic Sled Test Procedure

The agency is also proposing changes

to the existing Standard 202 dynamic

test option. Currently, Standard 202’s

dynamic compliance option specifies

that the seat structure must be

accelerated such that the acceleration

pulse lies between two half sine waves.

The lower boundary half sine wave is

represented by the expression a = 78

Sin(πt/80) and the upper boundary is

represented by a = 94 Sin(πt/96), where

t is in milliseconds and a has the units

of m/s 2. Figure F shows these sled pulse

boundaries along with the target sled

pulse between them (represented by a =

86 Sin(πt/88)). It can be seen from this

figure that at the beginning of the pulse

there is very little area in the corridor.

NHTSA believes that as a practical

matter the existing corridor cannot be

met. For this reason, a new sled pulse

corridor has been developed. Its

dimensions are derived from a scaled

down corridor now used in the FMVSS

208 sled test procedure. The new

corridor is wider than the existing

corridor until about 40 ms and narrower

from about 60 ms on. However, the

target sled pulse remains the same.

In addition to modifying the corridor

shape, we have revised the test

procedure to specify that the vehicle,

instead of simply the seat, is mounted

on the sled. The agency believes this is

necessary because both front and rear

seats are now required to have head

restraints and could be dynamically

tested. This also simplifies the test setup

because the dummies are required to be

restrained by a Type 2 belt which is

often attached to the B-pillar. The

agency believes existing sled designs

can stay within the specified

acceleration corridor with a vehicle

mounted to them. Finally, SAE J211/1

(March 1995) has been referenced to

indicate the use of channel filter class

(CFC) 60 for data processing.

The agency is also proposing to alter

the performance requirements for the

dynamic compliance test option due to

the proposal’s alteration of the existing

head restraint height requirements. The

current dynamic test accelerates a seat

loaded with a 95th percentile dummy to

an 8g half sine acceleration pulse over

80 ms. In order to pass this test, the

dummy neck must not rotate rearward

with respect to the torso more than 45

degrees. The 45 degree performance

limit was developed such that a 700 mm

(27.5 inch) high head restraint would

pass the dynamic test.

The proposal also alters the

specifications for one aspect of the

seating procedure for the dynamic test.

Standard 202 currently specifies that the

test device shall be secured by a Type

1 seat belt in the design seating position

of each designated seating position with

a head restraint. The proposal changes

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 985

14The Saab active head restraint is purely

mechanical. When the vehicle is struck from the

rear (at speeds equivalent to 16 km/h or greater in

a crash involving a barrier), the driver and front seat

passenger’s bodies move rearward into the seat

cushion. A padded pressure plate is moved

rearward as a result, and through a linkage moves

the head restraint upwards and forward to support

the head. The precise activation of the system is

determined by the force with which the driver or

passenger’s back is propelled against the backrest,

the magnitude of the crash forces and the

occupant’s weight.

this requirement by substituting a Type

2 seat belt for a Type 1. This change is

being instituted to more accurately

reflect current requirements for the

installation of Type 2 belts in outboard

seating positions.

If the agency’s proposal did not alter

the dummy head rotation requirement,

manufacturers could pass the standard

using the dynamic test with 700 mm

(27.5 inch) high head restraints even

though the new proposed minimum

height requirement is 750 mm (29.5

inches). To avoid this, we are proposing

to alter the dynamic test procedure and

injury criteria for front outboard seating

positions so that when the 95th

percentile male test dummy is used,

only head restraints at least 800 mm

(31.5 inches) high with a maximum 50

mm (2 inch) backset could pass. We are

also proposing requirements using a

50th percentile male test dummy at all

outboard seating positions.

In their comments to the agencies

1996 Technical Report discussed in

Section II.B, Volvo favored the

elimination of the dynamic test option.

It believed that there was insufficient

knowledge about injury mechanisms

and that test dummies needed to be

improved. However, Volvo has

developed a seat design to specifically

reduce whiplash injuries, indicating

that it believes that it has enough

knowledge to change the way it designs

seats. In their comments to the

Technical Report, Chalmers supported a

dynamic test using either a BioRID or

Hybrid III dummy and suggested that

the Neck Injury Criterion (NIC) be used

to evaluate performance. Chalmers also

believes a dynamic test procedure is

needed to measure the performance of

active head restraints.

There are several reasons why the

agency does not wish to eliminate the

dynamic compliance option. Some of

these became apparent when NHTSA

proposed deleting this option in 1995.

In October 1995, under the ‘‘Regulatory

Reinvention Initiative,’’ the agency

published an NPRM which proposed to

eliminate the dynamic options because

it believed neither manufacturers nor

the agency used this option to

determine compliance. Comments on

the Reinvention NPRM by vehicle

manufacturers favored deleting the

options, but Advocates and recreational

vehicle (RV) manufacturers and a seat

supplier opposed the deletion because it

would limit compliance options.

IIHS wanted to keep the dynamic test

because not having it might limit the

development of active head restraint

systems designed to deploy upon rear

impact. For example, as noted above,

the Saab 9–5 is equipped with active

head restraints which operate by use of

a lever.14 We measured a head restraint

in a MY 1999 model 9–5 to determine

its height and backset. It meets the

current height requirement by 95 mm

(3.8 inches). Therefore, there is no need

for the manufacturer to certify to the

current dynamic compliance option.

However, the current design would not

meet the requirements in this proposal

by 6 mm (0.3 inches). However, if the

proposed requirements were in place,

the manufacturer could choose to certify

to the dynamic compliance option.

NHTSA believes that the dynamic test

option should be retained and

upgraded. The dynamic test option

provides the means to assess the many

seat design parameters which affect

whiplash reduction. However, as it is

clear that limiting hyperextension alone

does not prevent whiplash injury, the

agency proposes to modify the dynamic

test procedure by adopting new

performance values of relative head-totorso rearward rotation for determining

compliance with Standard 202. The

proposed performance requirement for

front seating positions is a maximum of

12 degrees of relative head-to-torso

rotation with the 50th percentile

dummy and a maximum of 20 degrees

of head-to-torso rotation with a 95th

percentile dummy. For rear seating

positions no more than 12 degrees of

head-to-torso rotation is permissible

with a 50th percentile dummy as the

measurement device. The current

standard allows head-to-torso rotation of

45 degrees with a 95th percentile

dummy for the front seating positions

and does not regulate the rear seating

positions.

The proposed values were selected to

be consistent with the height and

backset requirements in the proposed

static compliance option. The head

restraints would need to comply at any

position of height and backset

adjustment when the 50th percentile

dummy is used in the front and rear

seats. The manufacturer would have the

option of selecting a single height

position for the 95th percentile dummy

in the front seats. The key testing

parameters associated with each seating

position are shown in Table 3.

TABLE 3.—PROPOSED TESTING PARAMETERS FOR EACH SEATING POSITION FOR THE DYNAMIC COMPLIANCE OPTION

Seating position Dummy size Rotation

limit (deg.)

Head restraint adjustment

Backset Height

Front ........................................................................ 50th male ............................................................... 12 Any .......... Any

Front ........................................................................ 95th male ............................................................... 20 Any .......... One *

Rear ........................................................................ 50th male ............................................................... 12 Any .......... Any

* Position selected at the manufacturer’s option.

The criteria were developed primarily

through sled testing of a modified

production vehicle seat. A preliminary

report on the experimental results is

available in the docket for this notice.

The seat used was not optimized to

limit head rotation, but was modified to

allow positioning of the head restraint

to specified locations and stiffened to

eliminate seat back rotation with respect

to the seat base. Stiffening of the seat

back was believed to create a worst case

situation for head rotation. Table 4

shows the rearward angular head-totorso rotation of a 50th and 95th

percentile Hybrid III dummy when

exposed to a sled acceleration such that

the change in velocity was about 20—

25 percent greater than that in both the

current and proposed regulation.

Rotation was not measured beyond 200

986 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

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

Cervical Spine During Rear-end Impact. IRCOBI, pp

127–137.

milliseconds because the dummy torso

has rebounded away from the seat at

that point in time. The backset values

listed were as measured by the ICBC

device prior to testing.

TABLE 4.—50TH AND 95TH PERCENTILE MALE HYBRID III DUMMY MAXIMUM HEAD-TO-TORSO ROTATION (DEG.) AS A

FUNCTION OF HEAD RESTRAINT BACKSET AND HEIGHT

Height

Backset

0 mm (0 in.) 50 mm (2 in.) 100 mm (4 in.)

50th 95th 50th 95th 50th 95th

750 mm (29.5 in.) ............................................................ 11 * 25 18 45 41 61

800 mm (31.5 in.) ............................................................ * 13 * 20 23 34 44 56

* Maximum value prior to 200 ms after start of acceleration.

The sled test data for the 50th

percentile dummy show that the 750

mm (29.5 inches) high head restraint

had lower head rotation than the 800

mm (31.5 inches) high restraint. This

may have been because of the shape of

the head restraint caused the dummy

head to contact the head restraint above

the rearmost portion of the head. Thus,

the tested head restraint was more

optimally fit to the 50th percentile

dummy head when positioned at a

height of 750 mm (29.5 inches). This

phenomenon illustrates why the

proposed regulation would also specify

the use of a 95th percentile male

dummy. If only the 50th dummy were

specified, complying head restraints

could have heights of no more than 750

mm (29.5 inches). This would be

inconsistent with the static height

requirement of 800 mm (31.5 inches) for

front seats. The agency believes that

compliance with performance

requirements with both the 50th and

95th percentile dummies is needed to

assure that all occupants in the front

seating positions up to and including

the tallest are protected. To be

consistent with the rear seat static

requirement, where only a minimum

height of 750 mm (29.5 inches) required,

only the 50th percentile dummy is

specified for rear seat dynamic

compliance.

Based on the sled testing, the agency

believes that head restraints 800 mm

(31.5 inches) high with a backset of 50

mm (2 inches) could restrict head-totorso rearward rotation of a 95th

percentile dummy to 20 degrees in the

proposed dynamic test. Similarly, head

restraint at least 750 mm (29.5 inch)

high with a 50 mm (2 inch) backset

could restrict head-to-torso rearward

rotation of a 50th percentile dummy to

12 degrees. The proposed performance

values are as shown in Table 3.

In selecting performance criteria for

the dynamic compliance option, the

agency’s goal was to provide a level of

safety similar to that provided by the

static requirements and provide a

method of compliance appropriate for

both static and active head restraint

designs. Although the modified seat

tested by the agency had greater headto-torso rotation than the proposed

performance values in some of the head

restraint positions that are proposed for

the static compliance option, the agency

believes these test data provide insight

into the worst case head-to-torso

rotation at each head restraint position

tested. As stated above, this was

partially due to the rigid nature of the

seat back, which provided very firm

restraint to the dummy torso and

therefore accentuated the effect of any

gap between the dummy head and the

head restraint. It was also due to the

sled pulse velocity change being 20–25

percent greater than the target of 17.3

kph in about the same time period.

Finally, the method used to attach the

head restraint to the seat back, which in

some situations allowed significant

movement of the head restraint when in

contact with the dummy head, added to

head-to-torso rotation. As an example of

this movement, when the 95th male

dummy was tested at the 800 mm (31.5

inch) high and 50 mm (2 inch) backset

head restraint position, the dummy

head rotated an additional 10 degrees

after the head restraint began to deform

due to contact with the dummy head. A

similar situation occurred at the 750

mm (29.5 inch) high and 50 mm (2 inch)

backset head restraint position when the

50th percentile dummy was tested.

Therefore, the agency believes that it

would be practicable for manufacturers

to achieve head-to-torso rotations below

those proposed when tested within the

proposed acceleration corridor.

The agency plans to perform

additional sled tests before the

publication of the final rule to assure

that the head rotation performance

values selected are appropriate.

The agency considered performance

criteria other than head rotation for the

dynamic compliance options. These

included Nij, which is a combination of

upper neck moments and forces

introduced in the Advanced Air Bag

Rulemaking (Docket NHTSA–98–4405);

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. In the absence of generally

accepted injury criteria specifically

applicable to whiplash injuries, the

agency must still assume 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 to head restraint position.

Other biomechnics researchers have

found a similar correlation and used

head-to-torso rotations for the

evaluation of whiplash injury.15 Such a

correlation indicates there are similar

safety benefits between the dynamic and

static requirements of the proposed

regulation. The agency is willing to

reconsider the dynamic performance

criteria when more advanced whiplash

injury criteria become available.

The agency requests comments on:

27. Are the performance criteria and values

tentatively selected for the dynamic

performance option the most appropriate

criteria and values?

28. Should a limit also be placed on

forward head rotation or neck loading so that

any potential negative effects of active head

restraints would be minimized?

In the current standard the dynamic

test procedure specifies only a 95th

percentile dummy, but not the specific

type. This proposal rectifies this

ambiguity by proposing the use of the

Hybrid III 50th and 95th percentile

dummy. The 95th percentile male

dummy is not currently incorporated in

49 CFR Part 572, Anthropomorphic Test

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 987

16BioRID 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

capable of producing the S-shape observed in

human necks during rear crashes.

Devices. However, we anticipate issuing

an NPRM to incorporate this dummy

into 49 CFR Part 572 within 12 to 18

months, which will probably be several

years prior to the proposed effective

date of the upgraded Standard 202.

The positioning procedure for the

95th Hybrid III dummy is essentially the

same as for the 50th Hybrid III except

for the positioning of dummy’s H-point

in reference to the seat H-point. The

offset specified is 9 mm (0.35 inches)

above and 15 mm (0.60 inches) forward

of the seat H-point.

NHTSA is aware of criticism that the

50th percentile Hybrid III neck lacks

sufficient biofidelity to be a useful tool

for rear impact testing and, since it is

likely to be very similar in design, the

same criticism could be extended to the

95th percentile dummy neck. NHTSA is

also aware of a newly developed test

device, BioRID,16 which purports to

more accurately models the human

neck, and of a recent paper by Ford

(SAE 973342) which argues that the

50th percentile Hybrid III neck is

sufficiently biofidelic in the rearward

direction. The agency is likely to revisit

both the dynamic performance values

and the proposed test device as more

advanced dummies are developed and

as injury criteria based on human

studies achieve broader consensus. The

agency would like commenters to

address the following issues related to

the test dummy selected for the

dynamic compliance option:

29. Should the agency consider the use of

the 5th percentile female in addition to the

50th and 95th percentile male dummies in

the dynamic test or is it reasonable to assume

that designs which are adequate for the 50th

and 95th males will be adequate for the 5th

female?

30. Which advanced dummy neck designs

should be considered for future use in the

dynamic test and are they likely to be

available prior to the effective date of the

proposal?

Currently, the dynamic compliance

test option requires only that the head

rotation criteria be met. The agency is

now proposing that, in addition to head

rotation, a Head Injury Criterion (HIC)

(15 ms) limit of 150 must not be

exceeded. We are proposing a 15 ms

HIC window to be consistent with the

new HIC criterion in Standard 208. The

HIC level of 150 is associated with a 1.1

to 4.3 percent probability of moderate

(MAIS 2+) head injury. It is the agency’s

view that inclusion of this requirement

would serve as an equivalent to the 80g

energy absorption limit found in the

static test option.

NHTSA has tentatively concluded

that the addition of the HIC requirement

to the dynamic compliance option

would not place an undue burden on

manufacturers while ensuring that head

restraints certified to this option have

adequate impact absorption

characteristics. The HIC values

measured in sled testing of a modified

production vehicle seat are shown in

Table 5. The greatest HIC value in Table

5 is for the 50th percentile dummy with

a head restraint position of 50 mm (2

inches) of backset and 750 mm (29.5

inches) of height. This HIC of 157

exceeds the proposed limit of 150.

However, the sled pulse for this test had

a velocity change of 4.3 kph (25 percent)

greater than the proposed velocity

change of 17.3 kph and, as mentioned

previously the head restraint was not

optimized in any way. The agency

believes that for a more optimally

designed head restraint tested within

the proposed acceleration corridor the

150 HIC limit can be met without great

difficulty and is needed to provide

assurance that head restraints will be

sufficiently padded.

31. The agency solicits comments on the

proposed HIC 15 limit of 150. Should a

different upper limit be specified? Should a

36 ms window be used? If so, should the

maximum allowable HIC value be increased?

TABLE 5.—50TH AND 95TH PERCENTILE MALE HYBRID III DUMMY MAXIMUM HEAD-TO-TORSO ROTATION (DEG.) AS A

FUNCTION OF HEAD RESTRAINT BACKSET AND HEIGHT

Height

Backset

0 mm (0 in.) 50 mm (2 in.) 100 mm (4 in.)

50th 95th 50th 95th 50th 95th

750 mm (29.5 in.) ............................................................ 11 * 25 18 45 41 61

800 mm (31.5 in.) ............................................................ * 13 * 20 23 34 44 56

The agency believes that head

restraints certified to the dynamic

compliance option should also be

required to meet the head restraint

width provisions proposed for the static

test. These provisions require that head

restraints be at least 170 mm (6.7

inches) wide on single seats and 254

mm (10 inches) wide on bench seats.

The agency notes that because the

motion of the sled used in the dynamic

test is unimodal—in a single

longitudinal direction—the proposed

test would not address the performance

of head restraints in off-axis impacts.

The proposed width requirements are

the only dimensional criteria offered for

inclusion in the dynamic test option.

The agency believes that the gap limits

proposed in the static test option are not

necessary, as head rotation limits would

be exceeded if gap sizes were excessive.

NHTSA is, however, soliciting

comments relating to certain aspects of

the proposed dynamic test option:

32. Is the head restraint width requirement

appropriate for the dynamic compliance

option? Should any of the other dimensional

requirements used in the static test option be

inserted into the dynamic test requirements?

V. Interim Compliance Options Before

Upgraded Requirements Become

Mandatory

The August 13, 1997 petition

submitted by AAMA/AIAM urged

NHTSA to consider compliance with

European head restraint regulations to

be functionally equivalent to

compliance with the current Standard

202. There are three European

regulations applicable to head

restraints—EEC 96/37/EU, promulgated

by the European Union, and ECE 17.05,

and ECE 25.04, both issued by the

Economic Commission for Europe. Of

these three regulations, both 96/37/EU

988 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

and ECE 17.05 are applicable to seats

and seat backs, but incorporate the head

restraint provisions found in ECE 25.

Each establishes a performance

requirement for energy absorption

which is slightly more stringent than

that now in Standard 202. Further, the

requirements for height, allowable gaps,

rear seat head restraints, energy

absorption and the procedure for

rearward displacement testing are

identical to those now being proposed

by NHTSA for incorporation in

Standard 202. However, the agency’s

proposal contains backset requirements

and adjustment retention lock

provisions not found in the European

regulations and retains the existing

minimum width provisions currently

incorporated into Standard 202. The

European regulations also do not

contain a separate width requirement

for bench seats found in the current

version of Standard 202 and specify a

slightly smaller minimum width for

head restraints for non-bench seats.

NHTSA’s policies and procedures for

evaluating the functional equivalence of

foreign safety standards are contained in

Appendix B of 49 CFR Part 553, the

agency’s rulemaking procedures,

published in the Federal Register on

May 13, 1998 (63 FR 26508). Under the

policy and procedures enunciated in

that final rule, a determination by this

agency that a foreign standard is

functionally equivalent to a counterpart

U.S. standard is dependent upon this

agency’s concluding that the functional

performance or safety benefits

associated with compliance with the

foreign standard is at least as great as

those associated with the current U.S.

standard.

The first step in the procedures is the

determination of whether the U.S.

regulation and the foreign directive are

intended to address the same safety

problem. In the instant case, ECE 25 and

Standard 202 are intended to address

neck and other injuries to occupants in

rear impacts. Having identified both

standards as addressing the same safety

need, the agency then performed further

analysis.

Under the agency’s procedures, the

next step in evaluating functional

equivalence is a comparison of the

requirements, test conditions and test

procedures found in the two standards.

If the differences between the two

standards are not insignificant, the next

step involves the examination of the real

world safety data to examine the relative

benefits of the two standards. If this

safety data show the foreign standard

offers greater benefits, the agency will

begin rulemaking to upgrade the U.S.

standard to the level of the foreign

standard or beyond. If the real world

data show the performance of the two

standards to be equal, the agency may

initiate rulemaking to add the foreign

standard as an alternative means of

compliance.

NHTSA recognizes that the

differences in requirements, test

conditions, and test procedures between

the U.S. regulation and the ECE 25 may

have safety consequences. Therefore,

the agency must make some effort to

compare the relative benefits and

effectiveness of each regulation. The

preferred means of determining if

foreign standard produces at least as

much benefit are real world crash data

from some vehicles meeting one

standard and from other vehicles

meeting the other standard.

When an attempt was made to

examine crash data to compare the

relative benefits of Standard 202 and

ECE 25, NHTSA determined that the

crash data available relating to the

actual performance of ECE 25 was not

sufficient to allow the agency to draw

any meaningful conclusions. Similarly,

the agency has determined that since

ECE 25 and Standard 202 compliance

data are primarily dimensional in

nature, these data are not useful in

comparing the relative safety benefits of

each.

Completion of this initial phase of

data analysis placed NHTSA at a major

decision point in the functional

equivalence process (i.e., Are there

sufficient data to assess the functional

equivalency of the two standards? If not,

could additional research be conducted

to generate data?). Rather than

embarking on a research program of its

own, the agency surveyed existing

biomedical and safety research to

determine if this information could be

used to assess the relative merits of ECE

25 and the existing provisions of

Standard 202.

As noted above, there is a general

consensus in the safety and biomedical

community that head restraints that are

both higher and closer to the head offer

increased protection against whiplash

injuries in rear impacts. ECE 25

specifies a greater minimum height

which is 50 mm (2 inches) greater than

the height that must currently be

achieved in Standard 202. That

difference suggests that compliance

with ECE 25 provides greater safety

benefits than the existing provisions of

Standard 202. Also, the maximum

height that must be achieved in ECE 25

is 100 mm (4 inches) greater than that

required by Standard 202. ECE 25

differs from the existing version of

Standard 202 in ways other than height

requirements. Standard 202 currently

does not require head restraints for rear

seating positions or contain any

requirements for energy absorption. ECE

25 contains requirements for energy

absorption and applies to head

restraints in rear seating positions.

Therefore, the agency has tentatively

concluded that ECE 25 offers greater

safety benefits than the existing version

of Standard 202 under the functional

equivalence process defined in Part 553,

Appendix B. Therefore, the agency is

proposing that in the period between 90

days following the publication of any

final rule that is derived from this

proposal and the first occurrence of

September 1, three years after

publication of the final rule (the date on

which new cars must meet the upgraded

Standard 202 requirements),

manufacturers may certify their vehicles

using the existing ECE 25 requirements,

with one exception. Standard 202 now

requires that restraints on vehicles

equipped with bench seats must be at

least 254 mm (10 inches) wide and other

seats must have head restraints that are

171 mm (6.75 inches) wide while ECE

25 specify a 170 mm (6.70 inch)

minimum width for all head restraints.

The agency has tentatively concluded

that the continued use of bench and

split bench seats in vehicles

manufactured for the U.S. market makes

it necessary maintain this portion of

FMVSS 202.

The agency is not simply proposing

that compliance with ECE 25 be

considered to be the equivalent of

compliance with the existing version of

Standard 202 but is also proposing an

upgrade to Standard 202. The proposed

upgrade to Standard 202 requires the

agency to make a second functional

equivalence assessment comparing ECE

25 to the new Standard 202. As outlined

above, the agency’s functional

equivalence assessment in this case has,

due to the lack of European crash and

compliance test data, focused on

existing research regarding the

performance of head restraints in

reducing whiplash injuries.

The backset, vertical adjustment

retention, and existing bench seat head

restraint width requirements proposed

for the upgrade to Standard 202 do not

have counterparts in the European

regulations. In performing its functional

equivalence assessment, NHTSA found

that current research indicates that these

requirements are important factors in

the safety performance of head

restraints. If those new requirements

were adopted, ECE 25 could no longer

be said to be equivalent to the upgraded

Standard. Accordingly, we are not

proposing to allow compliance with

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 989

ECE 25 as an option after the upgraded

requirements go into effect.

VI. Benefits

In support of this rulemaking action,

the agency has prepared a Preliminary

Economic Assessment (PEA) which

contains a thorough analysis of both the

benefits and the costs of the changes

this document proposes for Standard

202. The analysis contained in the PEA

estimates that full implementation of

the proposed changes would result in,

on an annual basis, 9,575 fewer

whiplash injuries for front seat

occupants and 4,672 fewer whiplash

injuries for rear seat occupants,

providing a total of 14,247 fewer

whiplash injuries for both front and rear

seating positions in rear impacts.

NHTSA estimates from National

Automotive Sampling System (NASS)

data that, between 1988 and 1996, there

were 805,581 occupants with whiplash

injuries (non-contact AIS 1 neck

injuries) annually in the outboard

seating positions of passenger cars

(PCs), light trucks, and vans (LTVs) in

police reported and unreported

towaway and non-towaway nonrollover

impacts. However, since the agency

believes head restraints will have their

greatest effectiveness in rear impacts,

the benefits analysis will be restricted to

that crash mode only. Based on this

same 1988 to 1996 NASS data, the

average number of whiplash injuries in

rear impacts annually was 272,088. The

number of vehicles with head restraints

in the rear outboard seats has increased

dramatically over the last several years.

An estimated 41 percent of the MY 1999

fleet have rear seat head restraints and

20 percent have no rear seat. Because of

the increase in the numbers of rear seat

head restraints, it is estimated that for

the 1999 model year the total

population of whiplash injures will be

270,815 (251,035 front seat occupant

injuries and 19,780 rear seat occupant

injuries).

The average economic cost (excluding

property damage) of a whiplash injury

in a rear impact, in 1998 dollars, is

estimated to be $6,485, resulting in a

total annual cost of approximately $1.75

billion for 272,088 whiplash injuries.

The $6,485 estimate is based on the

assumption that the maximum injury

per occupant is an AIS 1 injury. The

agency believes that this is a reasonable

assumption because very few occupants

in the rear impact crashes used to

develop our estimate had injuries higher

than AIS 1. Further, in such impacts, a

whiplash injury is likely to be the most

costly AIS 1 injury and the longest

lasting one.

The characteristics of adjustable head

restraints and their use have changed as

well. A 1982 survey of adjustable head

restraints indicated that at the lowest

position in the range of adjustment, the

lowest head restraint was 635 mm (25

inches) high. In a survey conducted for

this rulemaking, the agency determined

that, at the lowest position of

adjustment, the lowest head restraint

observed had a height of 712 mm (28

inches). Therefore, the lowest

adjustment height for these restraints

has increased by three inches.

Examination of survey data for the

highest position of adjustment indicates

that adjustable head restraints are also

40 mm (1.6 inches) higher now at the

uppermost range of adjustment than

they were in 1982. At the lowest

observed position, contemporary

adjustable restraints are now 13 mm (.5

inches) lower than integral restraints

observed in 1982.

Adjustable restraints are not only

higher now than they were in 1982, but

they are also more likely to be properly

adjusted. While the majority of

adjustable head restraints are still not

properly adjusted, agency data indicates

that 47 percent of current head

restraints are properly positioned as

opposed to 27 percent in 1982.

The agency believes that about 30

percent of all occupants involved in

towaway rear impacts receive a

whiplash injury. However, injury rates

do not appear to vary significantly

between integral and adjustable head

restraints. The changes in head restraint

configurations and use discussed above

may explain why. The data available for

front and rear head restraints combined

are not sufficient to make statistically

valid comparisons between restraint and

vehicle types. This data indicated that

the average whiplash injury rate for

passenger cars with integral head

restraints (31.75 per hundred occupants

in towaway rear impacts) was higher

than the whiplash injury rate (27.99 per

hundred) for adjustable head restraints.

For LTVs, the data indicated that the

average whiplash rate (30.57 per

hundred) for adjustable head restraints

was slightly higher than the whiplash

injury rate (30.53 per hundred) for

integral head restraints. Comparing

integral restraints by vehicle type shows

that the injury rate for cars (31.75 per

hundred) exceeds that for trucks (30.53

per hundred) while for adjustable head

restraints, the rate for cars is lower

(27.99 per hundred) than it is for trucks

(30.57 per hundred).

Two sets of data were statistically

significant for front occupants only and

indicate that integral restraints are

performing differently in cars and trucks

and in trucks depending on occupant

height. For shorter occupants of front

outboard seats, the injury rate for trucks

with integral restraints was much lower

(17.14 per hundred) than the rate for

cars (37.94 per hundred). When

comparing short drivers with taller

drivers in trucks with integral restraints,

the taller drivers were injured at a much

greater rate (56.71 per hundred) than the

shorter (17.14 per hundred). This may

indicate that integral head restraints in

trucks are better positioned to perform

well in preventing injury to short

drivers and not as well in protecting tall

drivers. Estimates of annual whiplash

injury rates by vehicle and restraint type

are shown in Table 6.

TABLE 6.—WHIPLASH RATES FOR NONROLLOVER REAR IMPACTS 1988–1996 NASS ANNUALIZED DATA IN TOWAWAY

CRASHES

Front and Back Outboard Occupants

Vehicle Type: Integral Adjustable

Car ............................................................................. 31.75 27.99

Truck .......................................................................... 30.53 30.57

Head Restraint Type: Car: Truck:

Integral ....................................................................... 31.75 30.53

Adjustable .................................................................. 27.99 30.57

Front Outboard Only

Vehicle Type: Occupant Height: Integral Adjustable

Car ............................................................................. Short .......................................................................... 37.94 31.00

990 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

TABLE 6.—WHIPLASH RATES FOR NONROLLOVER REAR IMPACTS 1988–1996 NASS ANNUALIZED DATA IN TOWAWAY

CRASHES—Continued

Car ............................................................................. Tall ............................................................................ 35.72 28.04

Vehicle Type: Head Restraint Type: Short Tall

Car ............................................................................. Integral ...................................................................... 37.94 35.72

Car ............................................................................. Adjustable ................................................................. 31.00 28.04

Vehicle Type: Occupant Height: Integral Adjustable

Truck .......................................................................... Short .......................................................................... 17.14 20.65

Truck .......................................................................... Tall ............................................................................ 56.71 30.19

Vehicle Type: Head Restraint Type: Short: Tall:

Truck .......................................................................... Integral ...................................................................... 17.14 *56.71

Truck .......................................................................... Adjustable ................................................................. 20.65 30.19

Head Restraint Type: Occupant Height: Car Truck

Integral ....................................................................... Short .......................................................................... 37.94 *17.14

Integral ....................................................................... Tall ............................................................................ 35.72 56.71

Adjustable .................................................................. Short .......................................................................... 31.00 20.65

Adjustable .................................................................. Tall ............................................................................ 28.04 30.19

* Difference is significant at 0.05.

NHTSA estimates that the present

fleet of vehicles has an average front

seat outboard head restraint maximum

height of 768 mm (30.2 inches), which

is 32 mm (1.3 inches) less than the

proposed minimum height capability of

800 mm (31.5 inches). As outlined in

the PEA, the agency believes that raising

the height of the front seat outboard

head restraint from the present average

to 800 mm (31.5 inches) will result in

a 1.1 percentage point increase in

effectiveness for all rear impact injuries

and a 1.83 percentage point increase for

whiplash injuries alone.

In examining the effectiveness of the

proposed changes, the agency

considered the differences between

integral and adjustable head restraints.

For integral head restraints and those

adjustable head restraints properly

adjusted in the fully up position (which

the agency estimates would be 53

percent of such restraints), the average

increase in effectiveness would be a

1.68 percentage points. For the

remaining percentage of adjustable head

restraints, the 47 percent that would be

adjusted in the lowest adjustment

position, we estimated that the

proposed minimum height of 750 mm

(29.5 inches) would result in a 3.50

percentage point increase in

effectiveness for all rear impact injuries

and 5.83 percentage point increase in

effectiveness for whiplash injuries.

Calculating the benefits of the

proposed requirements for rear seat

head restraints poses several challenges.

The baseline heights of rear seats are

different than those of front seats. In

addition, rear seats are less frequently

occupied. When they are occupied, the

occupant is often a child. The present

fleet also includes vehicles with and

without rear seat head restraints.

Agency survey data indicate that, in

vehicles with rear seat head restraints,

the average lowest head restraint height

is 653 mm (25.7 inches), which is 97

mm (3.8 inches) lower than the

proposed minimum height of 750 mm

(29.5 inches). In models with rear seat

adjustable head restraints, the average

head restraint height is 655 mm (25.8

inches) and the average seatback height

in vehicles without rear seat head

restraints is 650 mm (25.6 inches). As

outlined in the PEA, an increase in head

restraint height from 25.7 inches to the

29.5 inches for front seats would

increase effectiveness by 12.35

percentage points. After correcting for

the different occupancy rates and

occupant heights in rear seats, the

average effectiveness for the rear seat

would be 13 percent.

Taking into account the differing

degrees of effectiveness for each type of

head restraint available for front seat

occupants, i.e., integral, adjustable in

the highest position, and adjustable in

the lowest position, the agency

estimates that the increase in minimum

head restraint height for integral head

restraints would result in 1,588 fewer

injuries per year. For adjustable head

restraints adjusted to the highest

position, it is anticipated that the

proposed increase in minimum height

would result in 1,959 fewer front seat

occupant injuries per year. Reductions

in injuries for adjustable head restraints

in the lowest position would be 6,028

front seat occupant injuries annually.

The total reduction in injuries

attributable to the proposed front seat

head restraint requirements would be

9,575 fewer injuries per year.

For the rear seat, the proposed head

restraint requirement, which would

require head restraints to be installed at

locations where they were not

previously required, would result in

4,642 fewer injuries per year.

Adding the benefits from the rear seat

requirements to those calculated for the

front seat results in rear impact crashes

alone a total reduction of 14,247

whiplash injuries each year.

The agency has not prepared an

analysis of the potential benefits of two

other new requirements contained in

this proposal—the backset requirement

and the adjustment lock requirement. It

should be noted that while there is a

general consensus among safety

researchers that a smaller backset will

result in a reduction of injuries, NHTSA

has not yet developed a methodology for

quantitatively assessing this benefit.

Similarly, the benefits of adding a

height locking requirement have also

not been calculated. The agency has not

determined how many vehicles in the

current fleet have height locks for their

head restraints. Therefore, a baseline for

calculating benefits has not been

developed. Further, the benefits of such

locks will depend entirely on the rate at

which they are employed. As NHTSA

does not have access to such data at this

time, no estimation of the benefits of the

height lock requirement has been

prepared.

VII. Costs

In estimating the costs of the

proposed requirements, the agency

relied on a 1992 NHTSA tear down

study of a variety of vehicles. As

outlined in the PEA, this study, adjusted

to 1998 dollar values, revealed that the

sales weighted average cost of integral

head restraints is $30.12 per restraint.

The same analysis applied to adjustable

head restraints indicated an average cost

of $29.13 per restraint. The average cost

for both adjustable and integral is

$29.44 per restraint. As the proposal

contains provisions requiring that head

restraints be higher than the existing

ones in the front and rear seats, we used

data from the 1992 study also to

calculate the cost per inch of head

restraint. Using the same tear-down

study and distinguishing between

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 991

integral and adjustable head restraints,

the agency calculated a cost per inch of

$1.40 for integral head restraints and

$1.46 per inch for adjustable head

restraints. As these calculations

indicated little difference in cost

between integral and adjustable head

restraints, the agency estimated that the

sales weighted average cost per inch of

head restraints for all restraints, in 1998

dollars, was $1.54. In determining the

overall cost of compliance with the

proposed regulations both in situations

where existing head restraints must be

raised or a head restraint must be added

to the rear seat, we have tentatively

concluded that an average cost of $1.54

per additional inch of head restraint

height is appropriate.

To evaluate the cost of the proposed

minimum height requirements, NHTSA

assumed that the cost increase

associated with this new requirement is

the cost of increasing the highest head

restraint position up to 800 mm (31.5

inches) in the front seat or to 750 mm

(29.5 inches) in the rear seat. As we

believe that the cost of head restraints

would be very similar for adjustable and

integral head restraints, we assume that

the true cost would be to raise the

highest height of the head restraint and

that changes in design, at no additional

variable cost, could be accomplished to

comply with the minimum height

requirements.

The agency believes that the backset

requirements would not add cost to the

vehicle. There would be some redesign

costs to both increase the height and

reduce the backset, but the agency

believes that the backset requirement is

a design change that could be

implemented at the same time as height

is increased, with no increase in head

restraint cost.

Light vehicle sales in the U.S. totaled

15.55 million units in 1998. There were

8.14 million car sales and 7.40 million

truck sales in the U.S. in 1998. All of

these vehicles would be required to

have higher front seat head restraints.

The cost of raising front seat head

restraints would be $4.21 per vehicle,

resulting in a fleet cost of $65.5 million.

In regard to rear seats without head

restraints, raising the seat back to create

an integral restraint would cost $12.34

per vehicle, resulting in a fleet cost of

$74.8 million. Raising the rear seat head

restraints in vehicles already equipped

with rear head restraints costs $3.61 per

vehicle, resulting in a fleet cost of $19.6

million. There would be a small cost to

add locking mechanisms to those head

restraints that do not currently have

such mechanisms. Our studies indicate

that approximately half of the existing

fleet with adjustable head restraints has

locking mechanisms. Adding locking

mechanisms to the rest of the fleet with

adjustable head restraints at a cost of

$0.15 per vehicle is projected to result

in costs of $3.3 million for front seat

restraints and $2.6 million for rear seats

for a combined total is $5.9 million. The

total estimated costs of the vehicle

changes that would be required by this

proposal would be $160.5 million ($65.5

million for the front seat and $95.0

million for the rear seat).

VIII. Effective Date

As noted above, the agency is

proposing two amended versions of

Standard 202. The first version would

become effective 90 days after issuance

of the final rule. It would allow three

options for compliance. The first option

would be compliance with the

requirements of the existing Standard

202. The second option would allow

manufacturers to comply with the

requirements of ECE 25 as

supplemented by the current width

requirements. The third option would

allow manufacturers to comply with the

new upgraded Standard 202

requirements, which would apply to

vehicles manufactured on or after the

first occurrence of September 1, three

years after the publication of the final

rule, before that date. Between the

effective date of the final rule and

August 31, 2004, manufacturers may

choose one of the foregoing three

options when certifying their vehicles.

However, the election of the option used

by the manufacturer in certifying the

vehicle, including the choice between

the static and dynamic test options,

must be made at or before the time of

certification, and the manufacturer may

not thereafter rely on any other test

option to establish compliance.

The agency is proposing that

compliance with the upgraded version

of the standard become mandatory on

the first occurrence of September 1,

three years after publication of the final

rule. NHTSA believes that this date will

provide manufacturers with sufficient

leadtime to redesign seats and seating

systems in production vehicles and to

incorporate new elements of head

restraint design in new models.

IX. 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. This rulemaking document

was reviewed by the Office of

Management and Budget under

Executive Order 12866, ‘‘Regulatory

Planning and Review.’’ The rulemaking

action has been determined to be

economically significant. NHTSA is

placing in the public docket a

Preliminary Economic Assessment

(PEA) describing the costs and benefits

of this rulemaking action. The costs and

benefits are summarized earlier in this

document.

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.) I hereby certify that the

proposed amendment would not have a

significant economic impact on a

substantial number of small entities.

The proposed rule would affect motor

vehicle manufacturers, alterers, and

seating manufacturers.

NHTSA estimates that there are only

about four small passenger car and light

truck manufacturers in the United

States. These manufacturers serve a

niche market. The agency believes that

small manufacturers manufacture less

than 0.1 percent of total U.S. passenger

car and light truck production per year.

There are about 30 seating

manufacturers in the U.S. Many of these

are small businesses. The proposed rule

would affect these small businesses by

changing the requirements for head

restraints. Raising the height of and

integral seat or of an adjustable head

restraint is not a new or novel idea. The

agency does not believe that this will

have a significant impact on these

manufacturers.

NHTSA notes that final stage vehicle

manufacturers and alterers could also be

affected by this proposal. Many final

stage manufacturers and alterers install

supplier constructed seating systems in

vehicles they produce. The proposal

would not have any significant effect on

final stage manufacturers or alterers,

however, since the seats they purchase

should be tested and certified by the

seat manufacturer.

Small organizations and small

governmental units would not be

significantly affected since the potential

cost impacts associated with this

proposed action should only slightly

affect the price of new motor vehicles.

For the reasons discussed above, the

small entities that would most likely be

affected by this proposal are small

vehicle manufacturers, seating

manufacturers, final stage

manufacturers and alterers.

The agency believes, further, that the

economic impact on these

manufacturers would be small. While

the small vehicle manufacturers would

face additional compliance costs, the

992 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

agency believes that seating

manufacturers would likely provide

much of the engineering expertise

necessary to meet the new requirements.

Raising the height of a head restraint is

not a new or novel engineering task.

However, doing so for many makes and

models at the same time could present

a challenge. The agency also notes that,

in the unlikely event that a small

vehicle manufacturer or alterer did face

substantial economic hardship, it could

apply for a temporary exemption for up

to three years. See 49 CFR Part 555. It

could subsequently apply for a renewal

of such an exemption. However, the

agency requests comments concerning:

32. The economic impact of the proposed

rule on small vehicle manufacturers, seating

manufacturers, final stage manufacturers and

vehicle alterers.

Additional information concerning

the potential impacts of the proposed

requirements on small entities is

presented in the PEA.

C. National Environmental Policy Act

NHTSA has analyzed this proposal for

the purposes of the National

Environmental Policy Act. The agency

has determined that implementation of

this action would not have any

significant impact on the quality of the

human environment.

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.

E. Unfunded Mandates Act

The Unfunded Mandates Reform Act

of 1995 requires agencies to prepare a

written assessment of the costs, benefits

and other effects of proposed or final

rules that include a Federal mandate

likely to result in the expenditure by

State, local or tribal governments, in the

aggregate, or by the private sector, of

more than $100 million annually

(adjusted for inflation with base year of

1995). This assessment is included in

the PEA.

F. Civil Justice Reform

This proposal would not have any

retroactive effect. Under 49 U.S.C.

21403, 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. 21461 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. National Technology Transfer and

Advancement Act

Under the National Technology

Transfer and Advancement Act of 1995

(NTTAA)(Public Law 104–113), ‘‘all

Federal agencies and departments shall

use technical standards that are

developed or adopted by voluntary

consensus standards bodies, using such

technical standards as a means to carry

out policy objectives or activities

determined by the agencies and

departments.’’ This action proposes to

modify performance requirements for

head restraints to allow, on an interim

basis, compliance with either U.S. or

ECE requirements. After the end of the

interim period, head restraints must

comply with the proposed U.S.

requirements. Certain technical

standards developed by the Society of

Automotive Engineers (SAE) and other

bodies have been incorporated into this

proposal but the overall need for safety

precludes, in NHTSA’s view, the

adoption of such voluntary standards as

a substitute for this proposal.

H. Paperwork Reduction Act

This rule does not contain any

collection of information requirements

requiring review under the Paperwork

Reduction Act of 1995 (Public Law 104–

13).

X. Submission of Comments

How Can I Influence NHTSA’s Thinking

on This Proposed Rule?

In developing this proposal, we tried

to address the concerns of all our

stakeholders. Your comments will help

us improve this rule. We invite you to

provide different views on options we

propose, new approaches we haven’t

considered, new data, how this

proposed rule may affect you, or other

relevant information. We welcome your

views on all aspects of this proposed

rule, but request comments on specific

issues throughout this notice. We

grouped these specific requests near the

end of the sections in which we discuss

the relevant issues. Your comments will

be most effective if you follow the

suggestions below:

• Explain your views and reasoning

as clearly as possible.

• Provide solid technical and cost

data to support your views.

• If you estimate potential costs,

explain how you arrived at the estimate.

• Tell us which parts of the proposal

you support, as well as those with

which you disagree.

• Provide specific examples to

illustrate your concerns.

• Offer specific alternatives.

• Refer your comments to specific

sections of the proposal, such as the

units or page numbers of the preamble,

or the regulatory sections.

• Be sure to include the name, date,

and docket number with your

comments.

How Do I Prepare and Submit

Comments?

Your comments must be written and

in English. To ensure that your

comments are correctly filed in the

Docket, please include the docket

number of this document in your

comments.

Your comments must not be more

than 15 pages long. (49 CFR 553.21). We

established this limit to encourage you

to write your primary comments in a

concise fashion. However, you may

attach necessary additional documents

to your comments. There is no limit on

the length of the attachments.

Please submit two copies of your

comments, including the attachments,

to Docket Management at the address

given above under ADDRESSES.

Comments may also be submitted to

the docket electronically by logging onto

the Dockets Management System

website at http://dms.dot.gov. Click on

‘‘Help & Information’’ or ‘‘Help/Info’’ to

obtain instructions for filing the

document electronically.

How Can I Be Sure That My Comments

Were Received?

If you wish Docket Management to

notify you upon its receipt of your

comments, enclose a self-addressed,

stamped postcard in the envelope

containing your comments. Upon

receiving your comments, Docket

Management will return the postcard by

mail.

How Do I Submit Confidential Business

Information?

If you wish to submit any information

under a claim of confidentiality, you

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 993

should submit three copies of your

complete submission, including the

information you claim to be confidential

business information, to the Chief

Counsel, NHTSA, at the address given

above under FOR FURTHER INFORMATION

CONTACT. In addition, you should

submit two copies, from which you

have deleted the claimed confidential

business information, to Docket

Management at the address given above

under ADDRESSES. When you send a

comment containing information

claimed to be confidential business

information, you should include a cover

letter setting forth the information

specified in our confidential business

information regulation. (49 CFR Part

512.)

Will the Agency Consider Late

Comments?

We will consider all comments that

Docket Management receives before the

close of business on the comment

closing date indicated above under

DATES. To the extent possible, we will

also consider comments that Docket

Management receives after that date. If

Docket Management receives a comment

too late for us to consider it in

developing a final rule (assuming that

one is issued), we will consider that

comment as an informal suggestion for

future rulemaking action.

How Can I Read the Comments

Submitted by Other People?

You may read the comments received

by Docket Management at the address

given above under ADDRESSES. The

hours of the Docket are indicated above

in the same location.

You may also see the comments on

the Internet. To read the comments on

the Internet, take the following steps:

(1) Go to the Docket Management

System (DMS) Web page of the

Department of Transportation (http://

dms.dot.gov/).

(2) On that page, click on ‘‘search.’’

(3) On the next page (http://

dms.dot.gov/search/), type in the fourdigit docket number shown at the

beginning of this document. Example: If

the docket number were ‘‘NHTSA–

1998–1234,’’ you would type ‘‘1234.’’

After typing the docket number, click on

‘‘search.’’

(4) On the next page, which contains

docket summary information for the

docket you selected, click on the desired

comments. You may download the

comments. However, since the

comments are imaged documents,

instead of word processing documents,

the downloaded comments are not word

searchable.

Please note that even after the

comment closing date, we will continue

to file relevant information in the

Docket as it becomes available. Further,

some people may submit late comments.

Accordingly, we recommend that you

periodically check the Docket for new

material.

Plain Language

Executive Order 12866 and the

President’s memorandum of June 1,

1998, require each agency to write all

rules in plain language. Application of

the principles of plain language

includes consideration of the following

questions:

• Have we organized the material to

suit the public’s needs?

• Are the requirements in the rule

clearly stated?

• Does the rule contain technical

language or jargon that isn’t clear?

• Would a different format (grouping

and order of sections, use of headings,

paragraphing) make the rule easier to

understand?

• Would more (but shorter) sections

be better?

• Could we improve clarity by adding

tables, lists, or diagrams?

• What else could we do to make the

rule easier to understand?

If you have any responses to these

questions, please include them in your

comments on this proposal.

List of Subjects in 49 CFR Part 571

Imports, Motor vehicle safety, Motor

vehicles.

In consideration of the foregoing, it is

proposed that 49 CFR part 571 be

amended as follows:

PART 571—FEDERAL MOTOR

VEHICLE SAFETY STANDARDS

1. The authority citation for part 571

of title 49 would be revised 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 would be revised

to read as follows:

§ 571.202 Standard No. 202; Head

restraints.

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. This standard

applies to passenger cars, and to

multipurpose passenger vehicles, trucks

and buses with a GVWR of 4,536 kg

(10,000 pounds) or less manufactured

before [Insert a date which is the first

occurrence of September 1, three years

after publication of the final rule].

S3. Definitions.

Head restraint means a device that

limits rearward displacement of a seated

occupant’s head relative to the

occupant’s torso.

S4. Requirements.

S4.1 Each passenger car must comply

with, at the manufacturer’s option,

either S4.3, S4.4 or S4.5 of this section.

S4.2 Each truck, multipurpose

passenger vehicle and bus with a GVWR

of 4,536 kg (10,000 pounds) or less must

comply with, at the manufacturer’s

option, either S4.3, S4.4 or S4.5 of this

section.

S4.3 Except for school buses, a head

restraint that conforms to either S4.3 (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

S4.3 (a) or (b) of this section must be

provided for the driver’s seating

position.

(a) It must, 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) It must, when adjusted to its fully

extended design position, conform to

each of the following—

(1) When measured parallel to 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) 171 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.

S4.4 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 for

the driver’s seating position.

994 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

(a) The head restraint must comply

with paragraphs 6.1 through 6.6.3, 6.8

through 6.10, 7, and 8 of the following

English language version of the

Economic Commission for Europe

Regulation 25: E/ECE/324–E/ECE/

TRANS/505/Rev.1/Add.24/Rev.1, as

amended by E/ECE/324–E/ECE/TRANS/

505/Rev.1/Add.24/Rev.1/Corr.1, E/ECE/

324–E/ECE/TRANS/505/Rev.1/Add.24/

Rev.1/Amend.1, and E/ECE/324–E/ECE/

TRANS/505/Rev.1/Add.24/Rev.1/

Amend.2. (A copy of paragraphs 2, 6.1

through 6.6.3 and 6.8 through 6.10, 7,

and 8 may be reviewed at the DOT

Docket Management Facility, U.S.

Department of Transportation, Room

PL–01, 400 Seventh Street, SW.,

Washington, DC 20590–0001. Copies of

E/ECE/324–E/ECE/TRANS/505, Rev.1/

Add.24/Rev.1/Amend.2, 16 April 1997

may be obtained from the ECE Internet

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

main/wp29/wp29regs.html or by

writing to the United Nations,

Conference Services Division,

Distribution and Sales Section, Office

C.115–1, Palais des Nations, CH–1211,

Geneva 10, Switzerland); and

(b) The head restraint must meet the

width requirements specified in

S4.3(b)(2) of this section.

S4.5 Head restraints that comply with

the requirements of § 571.202a of this

part, becoming effective on [Insert a date

which is the first occurrence of

September 1, three years after

publication of the final rule], must be

provided at each outboard designated

seating position.

S4.6 Whenever this standard provides

an option for compliance the

manufacturer must select the option no

later than the time it certifies the vehicle

and may not thereafter select a different

option for the vehicle.

S5. Demonstration procedures.

S5.1 Compliance with S4.3(a) of this

section is demonstrated in accordance

with the following with the head

restraint in its fully extended design

position:

(a) On the exterior profile of the head

and torso of a dummy having the weight

and seated height of a 95th percentile

adult male with an approved

representation of a human, articulated

neck structure, or an approved

equivalent test device, establish

reference lines by the following method:

(1) Position the dummy’s back on a

horizontal flat surface with the lumbar

joints in a straight line.

(2) Rotate the head of the dummy

rearward until the back of the head

contacts the same flat horizontal surface

in paragraph (a)(1) of S5.1 of this

section.

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

flat surface 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.

(4) Establish the torso line of the

manikin as defined in SAE AerospaceAutomotive Drawing Standards, sec.

2.3.6, P.E1.01, September 1963.

(5) Establish the dummy torso

reference line by superimposing the

torso line of the manikin on the torso of

the dummy.

(6) Establish the head reference line

by extending the dummy torso reference

line onto the head.

(b) At each designated seating

position having a head restraint, place

the dummy, snugly restrained by a Type

2 seat belt, in the manufacturer’s

recommended design seated position.

(c) During forward acceleration

applied to the structure supporting the

seat as described in this paragraph,

measure the maximum rearward angular

displacement between the dummy torso

reference line and head reference line.

When graphically depicted, the

magnitude of the acceleration curve

must not be less than that of a half-sine

wave having the amplitude of 78 m/s2

and a duration of 80 milliseconds and

not more than that of a half-sine wave

curve having an amplitude of 94 m/s2

and a duration of 96 milliseconds.

S5.2 Compliance with S4.3(b) of this

section is demonstrated in accordance

with the following with the head

restraint in its fully extended design

position:

(a) Place a test device, having the back

plan dimensions and torso line

(centerline of the head room probe in

full back position), of the three

dimensional SAE J826 manikin, at the

manufacturer’s recommended design

seated position.

(b) Establish the displaced torso

reference line by applying a rearward

moment of 373 Nm moment about the

seating reference point to the seat back

through the test device back pan located

in paragraph S5.2(a) of this section.

(c) After removing the back pan, using

a 165 mm diameter spherical head form

or cylindrical head form having a 165

mm diameter in plan view and a 152

mm height in profile view, apply,

perpendicular to the displaced torso

reference line, a rearward initial load 64

mm below the top of the head restraint

that will produce a 373 Nm moment

about the seating reference point.

(d) Gradually increase this initial load

to 890 N or until the seat or seat back

fails, whichever occurs first.

* * * * *

3. On [Insert a date which is the first

occurrence of September 1, three years

after publication of the final rule],

§ 571.202(a) would be added to read as

follows:

§ 571.202(a) Standard 202; Head restraints.

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. This standard

applies to passenger cars, and to

multipurpose passenger vehicles, trucks

and buses with a GVWR of 4526 kg

(10,000 pounds) or less.

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.

Head restraint means a device that

limits rearward displacement of a seated

occupant’s head relative to the

occupant’s torso.

Height means the distance from the Hpoint to a point measured parallel to the

torso reference line defined by the three

dimensional SAE J826 (July 1995)

manikin.

Top means the point on the head

restraint with the greatest height.

S4. Requirements.

S4.1 Except as provided in S4.3 of

this section, each vehicle must comply

with S4 of this section.

S.4.2 Performance levels. In vehicles

other than school buses, a head restraint

that conforms to either S4.2(a) or (b) of

this section must be provided at each

outboard designated seating position. In

school buses, a head restraint that

conforms to either S4.2(a) or (b) of this

section must be provided for the driver’s

seating position.

(a) Dynamic performance and width.

Each head restraint must conform to the

following—

(1) When tested in accordance with

S5.1 of this section, during a forward

acceleration of the dynamic test

platform described in S5.1(a), the head

restraint must—

(i) Limit the rearward angular

displacement between the dummy’s

head and torso to 12 degrees for the 50th

percentile male dummy in front and

rear seating positions and 20 degrees for

the 95th percentile male dummy in

front seating positions; and

(ii) Limit HIC to 150, when calculated

in accordance with the following

formula:

HIC

t t

adt t t

t

t

= ( ) −















 ( ) − ∫ 1

2 1

2 5

2 1

1

2

.

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 995

Where the term a is the resultant head

acceleration expressed as a multiple of

g (the acceleration of gravity), and t1

and t2 are any two points in time during

the impact which are separated by not

more than a 15 millisecond time

interval; and

(2) The head restraint must have the

lateral width specified in S4.2(b)(3) of

this section.

(b) Dimensional and static

performance. Each head restraint must

conform to each of paragraphs S4.2(b)

(1) through (12) of this section:

(1) Minimum height capability. When

measured in accordance with S5.2(a) of

this section, the top of head restraints in

front seating positions must be capable

of being positioned at a height not less

than 800 mm (31.5 inches).

(2) Minimum height limit. When

measured in accordance with S5.2(b) of

this section, the top of the head restraint

must have a height not less than 750

mm (29.5 inches) in any position of

adjustment.

(3) Width. When measured 64 ± 3 mm

(2.5 ± 0.1 inches) below the top of the

head restraint, the lateral width of the

head restraint must be not less than—

(i) 254 mm (10 inches), in the case of

head restraints on bench-type seats; and

(ii) 171 mm (6.75 inches), in the case

of head restraints on individual seats.

(4) Backset. When measured in

accordance with S5.2(c) of this section,

the head restraint backset must be not

more than 50 mm (1.97 inches), with the

top of adjustable head restraints in any

height position of adjustment between

750 mm (29.5 inches) and 800 mm (31.5

inches).

(5) Gaps. Except as provided in

S4.2(b)(6) of this section, when

measured in accordance with S5.3 of

this section using the described head

form, there must not be any gap greater

than 60 mm (2.36 inches) in the front

surface of the head restraint or between

the front surface of the head restraint

and the front surface of the seat.

(6) Gaps. For adjustable head

restraints, when measured in

accordance with S5.3 of this section

using the described head form, there

must be no gap greater than 25 mm (1

inch) between the front surface of the

head restraint and the front surface of

the seat.

(7) Energy absorption. When the front

surface of the head restraint is impacted

in accordance with S5.4 of this section

by the described head form at any

velocity up to and including 24.1

kilometers per hour (15 mph), the

deceleration of the head form must not

exceed 785 m/s2 (80g) continuously for

more than 3 milliseconds.

(8) Radius of curvature. Any portion

of the front surface of the seat or head

restraint that has a height greater than

635 mm (25 inches) and that is outside

of the impact area described in S5.4(c)

of this section must either have a radius

of curvature of not less than 5 mm (0.2

inches) or meet the requirement of

S4.2(b)(7) of this section when tested

outside the impact area.

(9) Height retention. When tested in

accordance with S5.5 of this section, the

lowest portion of the described head

form must return to within 10 mm (0.4

inches) of its initial reference position

after application of at least a 500 N (112

pound) load and reduction of the load

to 50 ± 1 N (11.2 ± 0.2 pounds).

(10) Displacement. When tested in

accordance with S5.6(a) through (f) of

this section, the rearmost portion of the

described head form must not be

displaced to more than 102 mm (4

inches) perpendicularly rearward of the

displaced extended torso reference line

during the application of a 373 ± 7.5 Nm

(3,300 ± 66 inch-pounds) moment about

the H-point.

(11) Backset retention. When tested in

accordance with S5.6 of this section, the

rearmost portion of the described head

form must return to within 10 mm (0.39

inches) of its initial reference position

after application of a 373 ± 7.5 Nm

(3,300 ± 66 inch-pounds) moment about

the H-point and reduction of the

moment to 37 ± 0.7 Nm (327 ± 6.5 inchpounds).

(12) Strength. When tested in

accordance with S5.6 of this section, the

head restraint must provide a resistance

to the test device of at least 890 N (200

pounds).

S4.3 Folding or retracting head

restraints for unoccupied seats. A rear

seat head restraint may be adjustable by

folding or retracting to a position in

which its minimum height is less than

that specified in S4.2(b)(2) of this

section or in which its backset is more

than that specified in S4.2(b)(4) of this

section. In any such position, the head

restraint must meet either S4.3(a) or (b)

of this section.

(a) The head restraint must

automatically return to a position in

which its height is not less than that

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

and its backset is not more than that

specified in S4.2(b)(4) of this section

when a test dummy representing a 5th

percentile female is positioned in the

seat and when a test dummy

representing 50th percentile male is

positioned in the seat and the

midsagittal plane of the test dummy is

aligned within 15 mm (0.6 inches) of the

head restraint centerline; or

(b) The head restraint must, when

tested in accordance with S5.7 of this

section, cause the torso reference line

angle to be at least 10 degrees closer to

vertical than when the head restraint is

in any position of adjustment in which

its height is not less than that specified

in S4.2(b)(2) of this section and its

backset is not more than that specified

in S4.2(b)(4) of this section.

S4.4 Removability of head restraints.

A front seat head restraint must not be

removable from the seat solely by hand.

A rear seat head restraint may be

removable from the seat solely by hand.

S4.5 Compliance option selection.

Whenever this standard provides an

option for compliance, the manufacturer

must select the option not later than the

time it certifies the vehicle and may not

thereafter select a different option for

the vehicle.

S5. Procedures. Demonstrate

compliance with S4.2 and S4.3 of this

section with any adjustable lumbar

support adjusted to its rearwardmost

nominal design position in forward

facing seats and its forwardmost

nominal design position in rear facing

seats. Except for S5.1 of this section, if

the seat back is adjustable, it shall be set

at an initial inclination position closest

to 25 degrees from the vertical, as

measured by the three dimensional SAE

J826 manikin (July 1995) equipped with

the ICBC Head Restraint Measuring

Device (available from the Insurance

Corporation of British Columbia, 151

West Esplanade, North Vancouver, BC

V7M 3H9, Canada. www.icbc.com). The

order of test performance is S5.7 and

S5.1 to S5.6 of this section, in numerical

order.

S5.1 Procedures for dynamic

performance. Demonstrate compliance

with S4.2(a) of this section in

accordance with S5.1(a) though (i) of

this section with the head restraints in

any backset position of adjustment. For

all seating positions demonstrate

compliance with a 50th percentile male

Hybrid III test dummy specified in 49

CFR part 572, subpart E. For front

seating positions demonstrate

compliance with a 95th percentile male

Hybrid III test dummy specified in 49

CFR part 572. When testing with the

95th percentile dummy demonstrate

compliance with the head restraint at

one height position of adjustment, at the

option of the manufacturer. When

testing with the 50th percentile

demonstrate compliance with the head

restraint at any height position of

adjustment.

(a) Mount the vehicle on a dynamic

test platform at the vehicle attitude set

forth in S13.3 of § 571.208 of this part,

so that the longitudinal centerline of the

996 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

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 having a frequency response of

channel class 60 as specified in the

Society of Automotive Engineers (SAE)

Recommended Practice J211/1, March

1995. Position the accelerometer

sensitive axis parallel to the direction of

test platform travel.

(b) Remove the tires, wheels, battery,

fluids, and all unsecured components.

Remove or rigidly secure the engine,

transmission, axles, exhaust, vehicle

frame, etc. in order to assure that all

points on the acceleration vs. time plot

measured by an accelerometer on the

floor pan fall within the corridor

described in Figure 1 and Table 1.

(c) Place any moveable windows in

the fully open position.

(d) At each outboard designated

seating position, place the test dummy

with the seat adjusted as specified in

S8.1.2 through S8.1.3 of § 571.208 of

this part. Prior to placing the Type 2

seat belt around the test dummy,

exercise the seat belt retractor(s) three

times to remove slack.

(e) Dress and adjust each test dummy

as specified in S8.1.8.2 through S8.1.8.3

of § 571.208 of this part.

(f) Position each test dummy as

specified in S10.1 through S10.3 of

§ 571.208 of this part and S7.1 through

S7.4 of § 571.214 of this part, except for

the following:

(1) If it is not possible to position the

test dummy so that the midsagittal

plane is aligned within 15 mm (0.6

inches) of the head restraint centerline,

follow the positioning procedure in S7.1

through S7.4 of § 571.214 of this part.

(2) The H-point of the 95th percentile

male test dummy coincides within 13

mm (0.5 inches) in the vertical

dimension and 13 mm (0.5 inches) in

the horizontal dimension of a point 9

mm (0.4 inches) above and 15 mm (0.6

inches) forward of the H-point of the

seat.

(g) Accelerate the dynamic test

platform such that it experiences a

forward velocity change of 17.3 ± 0.6

kph (10.8 ± 0.37 mph) and all of the

points on the acceleration vs. time curve

fall within the corridor described in

Figure 1 and Table 1. Measure the

maximum rearward angular

displacement between the head and

torso of each dummy.

(h) 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 for a 600 Hz channel class

as specified in SAE Recommended

Practice J211/1 (March 1995). No data

generated after 200 ms from the

beginning of the forward acceleration

are used in determining angular

displacement.

(i) Calculate the HIC from the output

of instrumentation placed in the head of

the test dummy using the equation in

S4.2(a)(1)(ii) of this section and

conforming to the requirements for a

1000 Hz channel class as specified in

SAE Recommended Practice J211/1

(March 1995). No data generated after

200 ms from the beginning of the

forward acceleration are used in

determining angular displacement.

S5.2 Procedures for height and

backset. Demonstrate compliance with

S4.2(b)(1), (2), and (4) of this section in

accordance with S5.2(a) through (c) of

this section.

(a) For adjustable head restraints in

front seating positions, adjust the top of

the head restraint to its highest position

and measure the height. For all other

head restraints in front seating

positions, measure the height.

(b) For adjustable head restraints,

adjust the top of the head restraint to its

lowest position and measure the height.

For all other head restraints, measure

the height.

(c) For adjustable head restraints,

adjust the head restraint so that its top

is at any height between 750 mm (29.5

inches) and 800 mm (31.5 inches) and

to the maximum backset position at that

height, and measure the backset. For all

other head restraints, measure the

backset.

S5.3 Procedures for measuring gaps.

Demonstrate compliance with S4.2(b)(5)

and (6) of this section in accordance

with the requirements of S5.3(a) through

(c) of this section. For adjustable head

restraints, demonstrate compliance with

the head restraint adjusted to its

minimum height position. Demonstrate

compliance with S4.2(b)(5) of this

section at any backset position of

adjustment. Demonstrate compliance

with S4.2(b)(6) of this section at one

backset position of adjustment, at the

option of the manufacturer.

(a) The area of measurement is

anywhere on the front surface of the

head restraint or seat with a height

greater than 540 mm (21.3 inches) and

within a distance of the head restraint

vertical centerline of—

(1) 127 mm (5 inches) for bench-type

seats; and

(2) 85 mm (3.4 inches) for individual

seats.

(b) Place a 165 ± 2 mm (6.5 ± 0.1

inches) diameter spherical head form

against any gap such that only two

points of contact are made. The surface

roughness of the head form is less than

1.6 μm, root mean square.

(c) Determine the gap dimension by

measuring the straight line distance

between the two contact points, as

shown in Figures 2 and 3.

S5.4 Procedures for energy

absorption. Demonstrate compliance

with S4.2(b)(7) of this section in

accordance with S5.4(a) through (e) of

this section, with the seatback rigidly

fixed and adjustable head restraints in

any height and backset position of

adjustment.

(a) Propel a semispherical head form

with a 165 ± 2 mm (6.5 ± 0.1 inches)

diameter and a surface roughness of less

than 1.6 μm, root mean square, into the

head restraint. The head form and

associated base have a combined mass

of 6.8 ± 0.05 kg (15 ± 0.1 pound).

(b) Instrument the head form 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 (March

1995). The axis of the acceleration

sensing device coincides with the

geometric center of the head form and

the direction of impact.

(c) At the time of launch, the

longitudinal axis of the head form is

within 2 degrees of being horizontal and

parallel to the vehicle longitudinal axis.

The direction of travel is rearward.

(d) The headform travels freely

through the air along the path described

in S5.4(b) of this section not less than

25 mm (1 inch) before making contact

with the head restraint.

(e) Impact the front surface of the seat

or head restraint at any point with a

height greater than 635 mm (25 inches)

and within a distance of the head

restraint vertical centerline of—

(1) 105 mm (4.1 inches) for benchtype seats; and

(2) 70 mm (2.8 inches) for individual

seats.

S5.5 Procedures for height retention.

Demonstrate compliance with S4.2(b)(9)

of this section in accordance with S5.5

(a) through (d) of this section.

(a) Adjust adjustable head restraints

so that the top of the head restraint is

at any of the following height positions

at any backset position—

(1) For front seating positions—

(i) The highest position;

(ii) Not less than, but closest to 800

mm (31.5 inches);

(iii) Not less than, but closest to 750

mm (29.5 inches); and

(2) For rear seating positions—

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 997

(i) The highest position; and

(ii) Not less than, but closest to 750

mm (29.5 inches).

(b) Establish the head form initial

reference position by applying a vertical

downward load of 50 N ± 1 (11.2 ± 0.2

pounds) to the top of the head restraint

at the head restraint centerline using a

165 ± 2 mm (6.5 ± 0.1 inch) diameter

spherical head form with a surface

roughness of less than 1.6 μm, root

mean square.

(c) Increase the load at the rate of 250

± 50 N/minute (50.6 ± 10 pounds/

minute) to at least 500 N (112 pounds)

and maintain this load level for not less

than 5 seconds.

(d) Reduce the load at the rate of 250

± 50 N/minute (50.6 ± 11.2 pounds/

minute) to 50 ± 1 N (11.2 ± 0.22 pounds)

and determine the head form position

with respect to its initial reference

position.

S5.6 Procedures for displacement,

backset retention and strength.

Demonstrate compliance with

S4.2(b)(10) through (12) of this section

in accordance with S5.6(a) through (h)

of this section. The angular orientation

of the load vectors generating the

specified moments on the head restraint

are initially within 2 degrees of a

vertical plane parallel to the vehicle

longitudinal centerline and do not

deviate more than 2 degrees from their

initial orientation.

(a) Adjust adjustable head restraints

so that the top of the head restraint is

at the height not less than, but closest

to—

(1) 800 mm (31.5 inches) for front

seating positions; and

(2) 750 mm (29.5 inches) for rear

seating positions;

(b) Adjust adjustable head restraints

to any backset position;

(c) Place a test device, having the back

pan dimensions and torso line (vertical

centerline), when viewed laterally, of

the head room probe in full back

position, of the three dimensional SAE

J826 manikin, in the seat;

(d) Establish the displaced torso

reference line by creating a rearward

moment of 373 ± 7.5 Nm (3,300 ± 66

inch-pounds) about the H-point by

applying a force to the seat back through

the test device back pan located as

specified in S5.6(c) of this section at the

rate of 187 ± 37 Nm/minute (1,655 ± 327

inch-pounds/minute). The initial

location on the back pan of the moment

generating force vector has a height of

290 mm ± 13 mm (11.4 ± 0.5 inches).

Apply the force vector normal to the

torso 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;

(e) Maintain the position of the test

device back pan as established in

S5.6(d) of this section. Using a 165 ± 2

mm (6.5 ± 0.1 inch) 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

rearward initial load on the head

restraint centerline 65 ± 3 mm (2.6 ± 0.1

inches) below the top of the head

restraint that will produce a 37 ± 0.7 Nm

(327 ± 6.5 inch-pounds) moment about

the H-point;

(f) Increase this initial load at the rate

of 187 ± 37 Nm/minute (1,655 ± 327

inch-pounds/minute) until a 373 ± 7.5

Nm (3,300 ± 66 inch-pound) moment

about the H-point is produced. Maintain

the load level producing that moment

for not less than 5 seconds and then

determine the head form position with

respect to the displaced torso reference

line;

(g) Reduce the load at the rate of 187

± 37 Nm/minute (1655 ± 327 inchpounds/minute) until a 37 ± 0.7 Nm

(327 ± 6.5 in-pound) moment about the

H-point is produced. While maintaining

the load level producing that moment,

determine the head form position with

respect to its initial reference position;

and

(h) Increase the load at the rate of 250

± 50 N/minute (50.6 ± 10 pounds/

minute) to at least 890 N (200 pounds)

and maintain this load level for not less

than 5 seconds.

S5.7 Procedures for folding or

retracting head restraints for

unoccupied rear seats. Demonstrate

compliance with S4.3(b) of this section

in accordance with S5.7(a) through (d)

of this section:

(a) Place the head restraint into any

position meeting the requirements of

S4.2 of this section;

(b) Measure the torso reference line

angle with the three dimensional SAE

J826 manikin;

(c) Fold or retract the head restraint to

any position in which its minimum

height is less than that specified in

S4.2(b)(2) of this section or in which its

backset is more than that specified in

S4.2(b)(4) of this section; and

(d) Again measure the torso reference

line angle.

998 Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules

TABLE 1.—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

Federal Register / Vol. 66, No. 3 / Thursday, January 4, 2001 / Proposed Rules 999

Issued on December 22, 2000.

Stephen R. Kratzke,

Associate Administrator for Safety

Performance Standards.

[FR Doc. 01–136 Filed 1–3–01; 8:45 am]

BILLING CODE 4910–59–P