[Federal Register Volume 69, Number 239 (Tuesday, December 14, 2004)]
[Rules and Regulations]
[Pages 74848-74891]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-26641]



[[Page 74847]]

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Part III





Department of Transportation





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National Highway and Traffic Safety Administration



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49 CFR Part 571



Federal Motor Vehicle Safety Standards; Head Restraints; Final Rule

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

[[Page 74848]]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2004-19807]
RIN 2127-AH09


Federal Motor Vehicle Safety Standards; Head Restraints

AGENCY: National Highway Traffic Safety Administration (NHTSA), DOT.

ACTION: Final rule.

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SUMMARY: This final rule upgrades NHTSA's head restraint standard in 
order to reduce whiplash injuries in rear collisions. For front seats, 
the rule establishes a higher minimum height requirement, a requirement 
limiting the distance between the back of an occupant's head and the 
occupant's head restraint, as well as a limit on the size of gaps and 
openings within head restraints. The rule also establishes new strength 
and dynamic compliance requirements, and amends most existing test 
procedures. In addition, the rule establishes requirements for head 
restraints voluntarily installed in rear outboard designated seating 
positions. The upgraded standard becomes mandatory for all vehicles 
manufactured on or after September 1, 2008. Until that time, the 
manufacturers may comply with the existing NHTSA standard, the upgraded 
NHTSA standard or the current European regulations.

DATES: Effective Date: This rule is effective March 14, 2005.
    Incorporation by reference: The incorporation by reference of 
certain publications listed in the regulations is approved by the 
Director of the Federal Register as of March 14, 2005.
    Petitions: Petitions for reconsideration must be received by 
January 28, 2005.

ADDRESSES: Petitions for reconsideration should refer to Docket No. 
NHTSA-2004-19807 and be submitted to: Administrator, Room 5220, 
National Highway Traffic Safety Administration, 400 Seventh Street, 
SW., Washington, DC 20590. Please see the Privacy Act heading under 
Regulatory Notices.

FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may contact 
Louis Molino of the Office of Rulemaking, Office of Crashworthiness 
Standards, Light Duty Vehicle Division, NVS-112, (Phone: (202) 366-
2264; Fax: (202) 366-4329; E-mail: <a href="/cdn-cgi/l/email-protection#95d9fae0fce6bbd8faf9fcfbfad5fbfde1e6f4bbf1fae1bbf2fae3"><span class="__cf_email__" data-cfemail="c28eadb7abb1ec8fadaeabacad82acaab6b1a3eca6adb6eca5adb4">[email protected]</span></a>).
    For legal issues, you may contact George Feygin of the Office of 
Chief Counsel, NCC-112, (Phone: (202) 366-2992; Fax (202) 366-3820; E-
mail: <a href="/cdn-cgi/l/email-protection#fcbb99938e9b99d2ba99859b9592bc9294888f9dd2989388d29b938a"><span class="__cf_email__" data-cfemail="0f486a607d686a21496a766866614f61677b7c6e216b607b21686079">[email protected]</span></a>).
    You may send mail to both of these officials at the National 
Highway Traffic Safety Administration, 400 7th Street, SW., Washington, 
DC 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary
II. Background
    a. The Safety Concern
    b. Understanding Whiplash
III. Notice of Proposed Rulemaking
IV. Summary of Comments on the NPRM
V. Summary of the Final Rule
VI. Height and Width Requirements
    a. Requirements for Front Seats
    b. Requirements for Rear Seats Equipped with Head Restraints
VII. Backset Requirements for Front Seats
VIII. Measurement of Backset and Height
IX. Maximum Gap Allowance and Removability
    a. Maximum Gap Allowance
    b. Removability
    c. Non-use Positions
X. Position Retention
XI. Energy Absorption
XII. Issues Unique to Rear Head Restraints
    a. Optional Head Restraints for Rear Seating Positions
    b. Exception for Seats Adjacent to an Aisle
    c. Potential Interference with Child Restraints and Tethers
XIII. Dynamic Test Alternative
XIV. Consumer Information
XV. Effective Date and Interim Compliance Options
XVI. Costs and Benefits Associated with the Final Rule
XVII. Rulemaking Analyses and Notices
    a. Executive Order 12866 and DOT Regulatory Policies and 
Procedures
    b. Regulatory Flexibility Act
    c. National Environmental Policy Act
    d. Executive Order 13132 (Federalism)
    e. Unfunded Mandates Reform Act
    f. Executive Order 12988 (Civil Justice Reform)
    g. Paperwork Reduction Act
    h. Executive Order 13045
    i. National Technology Transfer and Advancement Act
    j. Privacy Act
Appendix A: Efforts to Harmonize with ECE 17
Appendix B: Cervigard Suggestion

I. Executive Summary

    This final rule upgrades Federal Motor Vehicle Safety Standard No. 
202, Head Restraints (FMVSS No. 202). The standard, which seeks to 
reduce whiplash injuries in rear collisions, currently requires head 
restraints for front outboard designated seating positions in passenger 
cars and in light multipurpose passenger vehicles, trucks and buses.
    To provide better whiplash protection for a wider range of 
occupants, this rule requires that front outboard head restraints meet 
more stringent height requirements. Fixed front head restraints must be 
not less than 800 mm. In their lowest adjustment position, adjustable 
head restraints must not be lower than 750 mm, and in their highest 
position, they must be at least 800 mm. To reduce the distance that a 
vehicle occupant's head can be whipped backward in a rear end crash, 
this rule establishes new requirements limiting backset in front seats, 
i.e., the distance between the back of a person's head and his or her 
head restraint, and limiting the size of gaps and openings in the 
restraints. The rule also establishes new strength and position 
retention requirements. Finally, it significantly amends the dynamic 
compliance test option currently in the standard to encourage continued 
development and use of ``active'' head restraint systems because the 
test is designed to allow a manufacturer the flexibility necessary to 
offer innovative active head restraint designs while still ensuring a 
minimal level of head restraint performance.
    After a careful consideration of the public comments and further 
analysis of our proposal to require head restraints in each rear 
outboard designated seating position, we have decided not to adopt that 
proposal. In the Notice of Proposed Rulemaking (NPRM),\1\ we expressed 
concern that the proposal had a high cost per equivalent life saved. We 
have now made a more refined estimate of costs and benefits and found 
that the cost per equivalent life saved for such a requirement is even 
greater than originally thought. In response to the NPRM, several 
manufacturers raised visibility concerns associated with mandatory rear 
head restraints in all vehicles. While not a universal problem, we 
believe reduced visibility is a legitimate problem in some vehicles. 
Finally, in commenting on the NPRM, vehicle manufacturers expressed 
concern that adoption of the requirement would reduce vehicle utility 
by interfering with or even reducing the ability to provide the sort of 
folding seats currently available in ``multi-configuration'' vehicles 
such as vans and multipurpose vehicles. We believe that those concerns 
may have some merit.
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    \1\ See 66 FR 968 (January 4, 2001).
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    However, in order to ensure that head restraints voluntarily 
installed in rear outboard seating positions do not pose a risk of 
exacerbating whiplash injuries, this final rule requires that those 
head restraints meet certain height, strength, position retention, and 
energy absorption requirements. NHTSA notes that the head restraint 
regulation of the United Nations/Economic Commission

[[Page 74849]]

for Europe (UN/ECE) similarly does not mandate rear seat head 
restraints, but does regulate the performance of voluntarily installed 
ones. The ECE regulation is discussed at greater length several 
paragraphs below and in Appendix A.
    In the future stages of our efforts to improve occupant protection 
in rear impacts,\2\ NHTSA intends to evaluate the performance of head 
restraints and seat backs as a single system to protect occupants, just 
as they work in the real world, instead of evaluating their performance 
separately as individual components. Accordingly, in making our 
decisions about the upgraded requirements for head restraints in this 
final rule, we sought, e.g., through upgrading our dynamic test 
procedure option, to make those requirements consistent with the 
ultimate goal of adopting a method of comprehensively evaluating the 
seating system.
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    \2\ As part of this effort, NHTSA issued a final rule upgrading 
the performance of vehicle fuel systems in rear impacts. (68 FR 
67068, December 1, 2003).
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    This final rule harmonizes the FMVSS requirements for head 
restraints with the head restraint regulation of the UN/ECE, except to 
the extent needed to provide increased safety for vehicle occupants or 
to facilitate enforcement.\3\ In some instances, a desire to achieve 
increased safety in a cost effective manner made it necessary for us to 
go beyond or take an approach different from that in the ECE 
regulation.
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    \3\ The regulation, adopted by the UN/ECE's Working Party 29, 
World Forum for Harmonization of Vehicle Regulations, is ECE 17, 
Uniform Provisions Concerning the Approval of Vehicles With Regard 
to the Seats, Their Anchorages, and Any Head Restraints (http://www.unece.org/trans/main/wp29/wp29regs/r017r4e.pdf). A comparison of 
this final rule with ECE 17 is in Appendix A.
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    While some of the requirements of this final rule are more 
stringent than those of the ECE regulation, the latter is functionally 
equivalent to the current FMVSS No. 202.\4\ For this reason, in the 
interim before the mandatory compliance date of this rule (September 1, 
2008), the agency is giving manufacturers the option of complying with 
any of three alternatives: the existing FMVSS No. 202, the ECE 17, or 
the new, upgraded FMVSS No. 202, designated as FMVSS No. 202a.\5\
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    \4\ We determined that the current FMVSS No. 202 is functionally 
equivalent to the applicable ECE regulation using the method 
described in Appendix B of 49 CFR part 553.
    \5\ Once the FMVSS No. 202a becomes fully effective on September 
1, 2008, it will be re-designated as FMVSS No. 202.
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    The agency estimates that approximately 272,464 whiplash injuries 
occur annually. This final rule will result in approximately 16,831 
fewer whiplash injuries, 15,272 involving front seat occupants and 
1,559 involving rear seat occupants. The estimated average cost in 2002 
dollars, per vehicle, of meeting this rule will be $4.51 for front 
seats, and $1.13 for rear seats currently equipped with head 
restraints, for a combined cost of $5.42.\6\ The cost per year is 
estimated to be $70.1 million for front head restraints and $14.1 
million for optional rear head restraints, for a combined annual cost 
of $84.2 million. This final rule is economically significant because 
we estimate that the final rule will result in economic benefits in 
excess of $100 million.
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    \6\ Because this rule does not require head restraints in rear 
outboard designated seating positions, it does not impose any costs 
associated with installing head restraints where none were 
previously installed.
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II. Background

    Vehicle manufacturers currently use three types of head restraints 
to meet the requirements of FMVSS No. 202. The first type is the 
``integral head restraint,'' which is non-adjustable and is built into 
the seat. It typically consists of a seat back that extends high enough 
to meet the height requirement of the standard. The second type is the 
``adjustable'' head restraint, which consists of a separate cushion 
that is attached to the seat back, typically by a two sliding metal 
shafts. Adjustable head restraints typically adjust vertically to 
accommodate different occupant seating heights. Some also provide 
adjustments to allow the head restraint to be moved closer to the 
occupant's head. The third type is the active head restraint system, 
which deploys in the event of a collision to minimize the potential for 
whiplash. During the normal vehicle operation, the active head 
restraint system is retracted.

a. The Safety Concern

    Whiplash injuries are a set of common symptoms that occur in motor 
vehicle crashes and involve the soft tissues of the head, neck and 
spine. Symptoms of pain in the head, neck, shoulders, and arms may be 
present along with damage to muscles, ligaments and vertebrae, but in 
many cases lesions are not evident. The onset of symptoms may be 
delayed and may only last a few hours; however, in some cases, effects 
of the injury may last for years or even be permanent. The relatively 
short-term symptoms are associated with muscle and ligament trauma, 
while the long-term ones are associated with nerve damage.
    Based on National Analysis Sampling System (NASS) data, we estimate 
that between 1988 and 1996, 805,581 whiplash injuries \7\ occurred 
annually in crashes involving passenger cars and LTVs (light trucks, 
multipurpose passenger vehicles, and vans). Of these whiplash injuries, 
272,464 occurred as a result of rear impacts. For rear impact crashes, 
the average cost of whiplash injuries in 2002 dollars is $9,994 (which 
includes $6,843 in economic costs and $3,151 in quality of life 
impacts, but not property damage), resulting in a total annual cost of 
approximately $2.7 billion.
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    \7\ Non-contact Abbreviated Injury Scale (AIS) 1 neck.
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b. Understanding Whiplash

    Although whiplash injuries can occur in any kind of crash, an 
occupant's chances of sustaining this type of injury are greatest in 
rear-end collisions. When a vehicle is struck from behind, typically 
several things occur in quick succession to an occupant of that 
vehicle. First, from the occupant's frame of reference, the back of the 
seat moves forward into his or her torso, straightening the spine and 
forcing the head to rise vertically. Second, as the seat pushes the 
occupant's body forward, the unrestrained head tends to lag behind. 
This causes the neck to change shape, first taking on an S-shape and 
then bending backward. Third, the forces on the neck accelerate the 
head, which catches up with--and, depending on the seat back stiffness 
and if the occupant is using a shoulder belt, passes--the restrained 
torso. This motion of the head and neck, which is like the lash of a 
whip, gives the resulting neck injuries their popular name.
    Previous regulatory approach. As discussed in the NPRM preceding 
this final rule, a historical examination of head restraint standards 
in this country indicates that the focus has been the prevention of 
neck hyperextension (the rearward movement of the head and neck over a 
large range of motion relative to the torso), as opposed to controlling 
lesser amounts of head and neck movement in a crash. The predecessor to 
FMVSS No. 202 was General Services Administration (GSA) Standard 515/
22, which applied to vehicles purchased by the U.S. Government and went 
into effect on October 1, 1967. GSA 515/22 required that the top of the 
head restraint achieve a height 700 mm (27.5 inches (in)) above the H-
point.\8\ Also in 1967, research

[[Page 74850]]

using staged 48 kilometer per hour (kph) (30 mile per hour, mph) 
crashes concluded that a head restraint 711 mm (28 in) above the H-
point was adequate to prevent neck hyperextension of a 95th percentile 
male. FVMSS No. 202, which became effective on January 1, 1969, 
required that head restraints be at least 700 mm (27.5 in) above the 
seating reference point or limit the relative angle between the head 
and the torso to 45 degrees or less during a dynamic test.
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    \8\ The H-point is defined by a test machine placed in the 
vehicle seat (Society of Automotive Engineers (SAE) J826, July 
1995). From the side, the H-point represents the pivot point between 
the torso and upper leg portions of the test machine. It can be 
thought of, roughly, as the hip joint of a 50th percentile male 
occupant viewed laterally.
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    Current knowledge. There are many hypotheses as to the mechanisms 
of whiplash injuries. Despite a lack of consensus with respect to 
whiplash injury biomechanics, there is research indicating that reduced 
backset will result in reduced risk of whiplash injury. For example, 
one study of Volvo vehicles reported that, when vehicle occupants 
involved in rear crashes had their heads against the head restraint (an 
equivalent to 0 mm backset) during impact, no whiplash injury 
occurred.\9\ By contrast, another study showed significant increase in 
injury and duration of symptoms when occupant's head was more than 100 
mm away from the head restraint at the time of the rear impact.\10\
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    \9\ Jakobsson et al., Analysis of Head and Neck Responses in 
Rear End Impacts--A New Human-Like Model. Volvo Car Corporation 
Safety Report (1994).
    \10\ Olsson et al., An In-depth Study of Neck Injuries in Rear-
end Collisions. International IRCOBI Conference, pp 269-280 (1990).
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    In addition, the persistence of whiplash injuries in the current 
fleet of vehicles indicates that the existing height requirement is not 
sufficient to prevent excessive movement of the head and neck relative 
to the torso for some people. Specifically, the head restraints do not 
effectively limit rearward movement of the head of a person at least as 
tall as the average occupant. Research indicates that taller head 
restraints would better prevent whiplash injuries because at heights of 
750 to 800 mm, the head restraint can more effectively limit the 
movement of the head and neck.
    In a recent report from the Insurance Institute for Highway Safety 
(IIHS), Farmer, Wells, and Lund examined automobile insurance claims to 
determine the rates of neck injuries in rear end crashes for vehicles 
with the improved geometric fit of head restraints (reduced backset and 
increased head restraint height).\11\ Their data indicate that these 
improved head restraints are reducing the risk of whiplash injury. 
Specifically, there was an 18 percent reduction in injury claims. 
Similarly, NHTSA computer generated models have shown that the 
reduction of the backset and an increase in the height of the head 
restraint reduces the level of neck loading and relative head-to-torso 
motion that may be related to the incidence of whiplash injuries.\12\
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    \11\ Farmer, Charles, Wells, JoAnn, Lund, Adrian, ``Effects of 
Head Restraint and Seat Redesign on Neck Injury Risk in Rear--End 
Crashes,'' Insurance Institute For Highway Safety, October 2002.
    \12\ ``Effect of Head Restraint Position on Neck Injury in Rear 
Impact,'' World Congress of Whiplash-Associated Disorders (1999), 
Vancouver, British Columbia.
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    With respect to impact speeds, research and injury rate data 
indicate that whiplash may occur as a result of head and neck movements 
insufficient to cause hyperextension. Staged low speed impacts indicate 
that mild whiplash symptoms can occur without a person's head exceeding 
the normal range of motion. This means that our previous focus on 
preventing neck hyperextension is insufficient to adequately protect 
all rear impact victims from risks of whiplash injuries. Instead, to 
effectively prevent whiplash, the head restraint must control smaller 
amounts of rapid head and neck movement relative to the torso.
    In sum, in light of recent evidence that whiplash may be caused by 
smaller amounts of head and neck movements relative to the torso, and 
that reduced backset and increased height of head restraints help to 
better control these head and neck movements, we conclude that head 
restraints should be higher and positioned closer to the occupant's 
head in order to be more effective in preventing whiplash.
    Further, information about consumer practices regarding the 
positioning of adjustable head restraints indicates that there is a 
need to improve consumer awareness and knowledge of importance of 
properly adjusted head restraints. Specifically, in 1995, NHTSA 
surveyed 282 vehicles to examine how well head restraints were adjusted 
and if the restraints should have been adjusted higher. Approximately 
50 percent of adjustable head restraints were left in the lowest 
adjustable position. Three quarters of these could have been raised to 
decrease whiplash potential by bringing the head restraint higher in 
relation to the center of gravity of the occupant's head.

III. Notice of Proposed Rulemaking

    Using the new information gained about the effectiveness of head 
restraints, NHTSA published the NPRM for this final rule to improve on 
the effectiveness of head restraints. The continued persistence of high 
numbers of whiplash injuries indicated a need for the rulemaking.
    The NPRM proposed new height and backset requirements, and other 
requirements, described below. NHTSA also proposed that head restraints 
be required in the rear outboard seating positions.
    In the proposed FMVSS No. 202a, manufacturers were given the option 
of meeting either of two sets of requirements. The first set is a 
comprehensive group of dimension and strength requirements, compliance 
with which is measured statically. The second set was made of 
requirements that would have to be met in a dynamic test.\13\
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    \13\ The current version of FMVSS No. 202 also features two sets 
of requirements; one applies to statically tested head restraints 
and the other to dynamically tested head restraints.
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    Proposed requirements for head restraints tested statically. To 
ensure that head restraints would be properly used in a position high 
enough to limit hyperextension, the NPRM proposed the following height 
requirements. The top of the front integral head restraint would have 
to reach the height of at least 800 mm above the H-point. The top of 
the front adjustable head restraint would have to reach the height of 
at least 800 mm above the H-point, and could not be adjusted below 750 
mm. The top of the rear mandatory head restraint would have to reach 
the height of at least 750 mm above the H-point. The NPRM also proposed 
that adjustable head restraints must lock in their adjustment 
positions. NHTSA proposed to retain existing requirements for head 
restraint width.\14\ To control even smaller amounts of rapid head and 
neck movement relative to the torso than the amount of relative motion 
resulting in neck hyperextension, the NPRM proposed also to limit the 
amount of backset to 50 mm (2 in). In addition, the NPRM also proposed 
maximum gap requirements for head restraints openings within the 
perimeter of the restraint, and for height adjustable head restraints, 
between the seat and head restraint. Head restraints must remain locked 
in specific positions after being set by the user.
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    \14\ 254 mm (10 in) for restraints on bench-type seats, and 171 
mm (6.75 in) for restraints on individual seats.
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    The agency also proposed to prohibit head restraints in the front 
seats from being removable solely by hand, i.e., without use of tools. 
Comments were requested on applying such a requirement to rear seat 
head restraints. Rear seat head restraints could be folded or retracted 
to ``non-use'' positions if

[[Page 74851]]

they give the occupant an ``unambiguous physical cue'' that the 
restraint is not properly positioned by altering the normal torso angle 
of the seat occupant or automatically returning to a ``use'' position 
when the seat is occupied.
    In addition, the NPRM proposed that these statically-tested head 
restraints would have to meet a new energy absorption requirement, 
compliance with which would be measured using a free-motion impactor. 
Additionally, the agency proposed placing a minimum on the radius of 
curvature for the front surface of the vehicle seat and head restraint. 
The NPRM proposed modifications to the existing strength versus 
displacement test procedure to require simultaneous loading of the back 
pan \15\ and the head restraint, and to remove the allowance for seat 
back failure.
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    \15\ The back pan is the portion of the SAE J826 manikin (July 
1995) that comes in contact with the seat back. Its shape is 
intended to simulate the shape of an occupant's back and thus allow 
for a realistic load distribution.
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    Proposed requirements for head restraints tested dynamically. The 
NPRM proposed a dynamic test alternative and said that the purpose was 
to ensure that the final rule does not discourage or preclude 
continuing development and implementation of active head restraints and 
other advanced seat back/head restraint systems designed to minimize 
rear impact injuries. Specifically, the NPRM proposed that head 
restraints tested dynamically would have to meet a Head Injury 
Criterion (HIC) limit of 150 with a 15 millisecond (ms) window. In 
addition, NHTSA proposed a head-to-torso rotation limit of 20 degrees 
when testing with a 95th percentile male dummy in front outboard seats, 
and of 12 degrees when testing with a 50th percentile male dummy in all 
outboard seats.\16\ Further, the NPRM proposed that the head restraints 
must have the same lateral width specified for statically tested 
restraints. Comments were requested on whether dynamically tested 
restraints should be subject to the width requirement or any of the 
other dimensional requirements used in the static test option.
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    \16\ Changes to the dynamic test procedures were also proposed, 
including a new sled pulse corridor. Also, the entire vehicle would 
be mounted on the test sled, not merely the seat.
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IV. Summary of Comments on the NPRM

    The agency received approximately 50 comments on the NPRM, from 
motor vehicle manufacturers, seat suppliers, members of the engineering 
and research community, insurance companies, consumer groups, and 
governments and members of Congress. Overall, commenters supported 
upgrading FMVSS No. 202 while expressing concerns about and 
recommending changes to various proposals made in the NPRM.
    A majority of the commenters generally supported the new height 
proposal, particularly as applied to head restraints for front seats. 
While few commenters had knowledge of any specific data regarding 
benefits of the proposed height increase, most commenters agreed that 
the new height requirement is potentially beneficial in reducing 
whiplash injury and had merit in harmonizing with ECE 17. Nonetheless, 
some concerns were expressed. Some comments supported the position that 
increasing the height of head restraints would not obstruct a driver's 
rearward visibility, but there were concerns expressed that the new 
height requirements would reduce the ability of a driver in following 
vehicles to ``see through'' a vehicle in front of him or her. There was 
concern that the taller head restraints could make it more difficult to 
install seats during vehicle assembly. Several manufacturers commented 
that the taller head restraints might not be able to fit in the rear 
seats of some vehicles or may impede seat folding, thus limiting cargo 
capacity.
    As to the proposed width of head restraints, all of the vehicle 
manufacturers believed that a 254 mm width requirement for rear seat 
head restraints would reduce rearward visibility and is unwarranted. In 
contrast, Advocates for Highway Safety (Advocates) believed that the 
current widths of head restraints do not protect occupants in offset 
collisions and should be increased.
    Commenters expressed differing opinions with regard to the proposed 
backset requirement. Insurers, consumer groups and Transport Canada 
supported 50 mm as the maximum allowable backset. A majority of the 
seat and vehicle manufacturers supported a backset of more than 50 mm, 
because they believed that a backset of 50 mm could result in occupant 
discomfort, particularly to smaller occupants who, commenters 
maintained, tend to use steeper seat back angles. Some manufacturers 
suggested that NHTSA allow for an adjustable backset of up to 100 mm. 
Manufacturers also generally wanted to measure backset with the seat 
back at the manufacturer's design seating angle rather than placed at a 
25-degree angle. Some had concerns about the suitability of the head 
restraint measuring device for measuring backset.
    There were no significant objections to the 60 mm gap limit for 
gaps within the perimeter of head restraints. However, manufacturers 
and others had questions about the proposal that adjustable head 
restraints in their lowest position must have some position of backset 
adjustment at which the gap between the seat and the head restraint is 
less than 25 mm.
    A majority of industry commenters opposed the prohibition against 
the removability of head restraints. Some suggested allowing 
removability by hand, particularly of rear seat head restraints. 
Manufacturers stated that no limitations should be placed on non-use 
positions.
    Several manufacturers and suppliers objected to the proposed height 
retention test requirement. Some believed current head restraints do 
not move downward during crashes. Others were concerned that the 
requirement does not account for the compression of head restraint 
foam. In contrast, some non-industry commenters believed that the 
height retention requirement is needed to prevent designs that tend to 
``fall'' to their lowest position during normal vehicle operation.
    With regard to the energy absorption test, all manufacturers 
suggested use of a pendulum impactor instead of the free-motion head 
form. Most manufacturers expressed concerns about the need for or wide-
reaching application of the proposed limit on the radius of curvature 
of vehicle seats or head restraints (proposed S4.2(b)(8)).
    Most manufacturers and suppliers believed that rear seat head 
restraints should not be required. Concerns were raised about the 
safety need for them, and about possible interference of the head 
restraints with child restraint use in rear seats. Honda, Advocates and 
others believed that rear seat head restraints should be mandated.
    Concerning the proposed changes to the dynamic compliance test 
procedures, some commenters believed that the proposals should not be 
adopted at this time. Commenters disagreed on the most appropriate 
dummy to use for the dynamic test. Most vehicle manufacturers and some 
seat suppliers objected to the proposed HIC<INF>15</INF> 150 limit, 
seeing no correlation between HIC and the reduction of neck injuries. 
Some commenters stated that the dynamic test should be with the seat 
attached to a test buck, instead of the actual vehicle.
    In response to the NPRM's request for comments on the need to 
require vehicle manufacturers to provide

[[Page 74852]]

information in vehicle owners' manuals on how to properly adjust head 
restraints, the Insurance Corporation of British Columbia (ICBC) 
commented that it believed that consumer education has a positive 
influence on proper head restraint adjustment. Several manufacturers 
commented that most manufacturers already provide information in 
vehicle owners' manuals about proper head restraint use.

V. Summary of the Final Rule

    Based on our consideration of the comments and other available 
information, the agency is issuing a final rule that upgrades existing 
FMVSS No. 202. As noted above, the new upgraded version of the standard 
is designated as FMVSS No. 202a.
    Under this final rule, the top of the front outboard integral head 
restraint must reach the height of at least 800 mm above the H-point, 
instead of the 700 mm above the seating reference point (SgRP) \17\ 
currently required. The top of the front outboard adjustable head 
restraint must be adjustable to at least 800 mm above the H-point, and 
cannot be adjusted below 750 mm. Rear outboard head restraints are 
optional. However, if a manufacturer chooses to install head restraints 
in rear outboard seating positions, these head restraints must meet 
certain height,\18\ strength, position retention, and energy absorption 
requirements. The rear outboard head restraint is defined as a rear 
seat back, or any independently adjustable seat component attached to 
or adjacent to the rear seat back, that has a height equal to or 
greater than 700 mm, in any position of backset and height adjustment, 
as measured with the J826 manikin.\19\ Accordingly, any rear outboard 
seat back or any independently adjustable component attached or 
adjacent to that seat back that exceeds 700 mm above the H-point, must 
meet the above requirements.
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    \17\ The term ``seating reference point'' is fully defined in 49 
CFR 571.3. It represents a unique design H-point. The H-point is the 
mechanically hinged hip point of an SAE J826 (July 1995) three-
dimensional manikin (SAE J826 manikin), which simulates the actual 
pivot center of the human torso and thigh.
    \18\ Exceptions to the height requirements for rear head 
restraints are discussed in Sections VI(b) and IX.
    \19\ Section XII(a) explains how we arrived at our definition of 
rear head restraints.
---------------------------------------------------------------------------

    In recognition of the manufacturing and measurement variability 
concerns highlighted by the industry commenters, the agency has 
increased the maximum allowable backset for front head restraints from 
the proposed 50 mm to 55 mm. Backset adjustment to less than 55 mm is 
permitted. However, the backset may not be adjustable to greater than 
55 mm when the top of the front head restraint is positioned between 
750 and 800 mm, inclusive, above the H-point. There is no backset limit 
for optional rear head restraints. The agency will use an HRMD, 
consisting of a head form developed by ICBC attached to the SAE J826 
manikin (rev. Jul 95), for measuring backset compliance.
    The minimum width requirement for front outboard head restraints in 
vehicles without a front center seating position, and for optional rear 
head restraints is 170 mm. The minimum width requirement for front 
outboard head restraints in vehicles with a center seating position 
between the outboard positions is 254 mm. For integral head restraints, 
there is a limit of 60 mm on the maximum gap between the head restraint 
and the top of the seat. The gap limit for adjustable head restraints 
in their lowest position of adjustment and any position of backset 
adjustment is similarly 60 mm. The final rule does not adopt the 
proposed 25 mm limitation for adjustable head restraints in their 
lowest position of adjustment and single position of backset adjustment 
proposed in the NPRM. For all head restraints, gaps within the 
restraint are limited to not more than 60 mm.
    Under today's rule, an adjustment retention mechanism that locks 
into place is mandatory for all adjustable head restraints. NHTSA will 
test retention of the head restraint in its vertical position using a 
loading cylinder measuring 165 mm in diameter and 152 mm in length. The 
rearward (with respect to the seat direction) position retention 
testing will be conducted using a loading sphere, with the seat back 
braced. Under both tests, the head restraint must return to within 13 
mm of the initial reference point, an increase from the proposed 10 mm 
return requirement.
    The energy absorption test procedure will be conducted using a 
linear impactor, rather than the proposed free-motion impactor or the 
pendulum impactor used in ECE 17.
    The dynamic compliance option will utilize a Hybrid III 50th 
percentile adult male test dummy only, as the 95th percentile Hybrid 
III dummy is not yet available for compliance purposes. The head-to-
torso rotation is limited to 12 degrees, and the maximum 
HIC<INF>15</INF> is limited to 500 instead of 150 in the NPRM. These 
performance limits must be met with the head restraint midway between 
the lowest and the highest position of adjustment.
    Between the effective date of today's rule and September 1, 2008, 
manufacturers may comply with FMVSS No. 202 by meeting: (1) All the 
requirements of the current FMVSS No. 202, (2) the specified 
requirements of ECE 17, or (3) all the requirements of FMVSS No. 202a. 
NHTSA has found that ECE 17 is functionally equivalent to the existing 
FMVSS No. 202, so we are permitting compliance with ECE 17 during the 
interim.
    The ECE has two regulations applicable to head restraints, ECE 17 
and ECE 25.\20\ The two regulations have similar requirements. However, 
the provisions of ECE 17 supersede the requirements of ECE 25 for most 
vehicles subject to this final rule. Specifically, as amended in July 
2002, ECE 17 applies to vehicles in the following categories:
---------------------------------------------------------------------------

    \20\ ECE 25, Uniform Provisions Concerning the Approval of Head 
Restraints (Head Rests), whether or not Incorporated in Vehicle 
Seats (http://www.unece.org/trans/main/wp29/wp29regs/r025r1e.pdf).
---------------------------------------------------------------------------

    1. Passenger vehicles, including multipurpose passenger vehicles 
(MPVs) with 9 or fewer designated seating positions (``M1'').
    2. Passenger vehicles, MPVs and buses with more than 9, but less 
than 17 designated seating positions (``M2'' and ``M3'').\21\
---------------------------------------------------------------------------

    \21\ We note that buses with at least 17 designated seating 
positions are still classified as M2, M3. However, ECE 17 
specifically excludes these vehicles.
---------------------------------------------------------------------------

    3. Trucks (``N'').
    This final rule applies to passenger cars, MPVs, trucks and buses 
with a GVWR of 4,536 kg or less. Accordingly, the only vehicles that 
will be subject to this final rule, but will not fall under the 
requirements of ECE 17, are buses with at least seventeen designated 
seating positions. Because of the GVWR limit, it is unlikely that such 
buses will be subject to this final rule. Nevertheless, we note that 
the requirements of ECE 25 are more stringent than those of this final 
rule because they mandate rear head restraints. Since we want to 
provide a compliance option for the interim period that is functionally 
equivalent to the current standard, we decided that all vehicles, 
including large capacity buses subject to this final rule, may certify 
to the specified ECE 17 requirements instead of ECE 25.\22\
---------------------------------------------------------------------------

    \22\ We note that ECE 17, Paragraph 5.3.1 expressly allows other 
categories of vehicles equipped with head restraints to be certified 
to ECE 17.
---------------------------------------------------------------------------

    During this interim period, manufacturers must irrevocably elect 
one of the compliance options in its entirety and may not certify under 
an alternative compliance option, if there is a noncompliance. This 
restriction is necessary because each certification option addresses 
the risks associated

[[Page 74853]]

with poor head restraint design differently, and because individual 
parts of each of the compliance options provide different levels of 
safety. We note, however, that the manufacturer may select different 
compliance options for different designated seating positions.
    Major differences between this final rule and the NPRM. The 
following highlights the major differences between the NPRM and the 
final rule:
    <bullet> This final rule does not require head restraints in rear 
outboard designated seating positions. However, if a manufacturer 
chooses to install head restraints in rear outboard seating positions 
(as defined in FMVSS No. 202a.), these head restraints must meet the 
new height, strength, position retention, and energy absorption 
requirements, but not backset requirements.
    <bullet> The maximum allowable backset for front head restraints 
has been increased from 50 mm to 55 mm;
    <bullet> The 25 mm gap limit for adjustable head restraints in 
their lowest height position and a single position of backset 
adjustment has been eliminated, leaving the 60 mm limit at any position 
of backset adjustment;
    <bullet> With respect to position retention, the head restraint 
must return to within 13 mm of the initial reference point, instead of 
to within 10 mm, as proposed;
    <bullet> The proposed radius of curvature requirement has not been 
adopted;
    <bullet> The energy absorption testing procedure will be conducted 
using a linear impactor, instead of the proposed free-motion impactor;
    <bullet> The dynamic compliance option will require that the head-
to-torso rotation be limited to 12 degrees, when tested with a 50th 
percentile male Hybrid III dummy with the head restraint midway between 
the lowest and the highest position of adjustment (there will be no 
test with a 95th percentile dummy);
    <bullet> The dynamic compliance option mandates a maximum 
HIC<INF>15</INF> limit of 500, as opposed to 150 proposed in the NPRM, 
and;
    <bullet> Vehicle owner's manual must include information describing 
the vehicle's head restraint system, how to properly adjust head 
restraints, and how to remove and re-install head restraints.

VI. Height and Width Requirements

a. Requirements for Front Seats

    Height of front seat head restraints. FMVSS No. 202 currently 
requires that front head restraints be capable of reaching a height of 
at least 700 mm above the SgRP. The NPRM proposed amending the standard 
to increase the minimum height of front integral head restraints to 800 
mm above the H-point. It proposed that if the head restraints were 
adjustable, they must adjust up to at least 800 mm, and not below 750 
mm, with respect to the H-point. This adjustment range was estimated to 
ensure that the top of the head restraint exceeded the head C.G. 
(center of gravity) for an estimated 93 percent of all adults.
    A majority of the manufacturers and other commenters, among them 
the Alliance of Automobile Manufacturers (Alliance), General Motors 
North America (GM), TRW Automotive (TRW), the Association of 
International Automobile Manufacturers, Inc. (AIAM) and IIHS, generally 
supported the new height proposal. IIHS's support was based, in part, 
on a new standard for evaluating head restraints promulgated by the 
Research Council for Automobile Repairs (RCAR), which deems taller head 
restraints to be superior to shorter ones.\23\ In contrast, Advocates 
commented that fixed and adjustable head restraints should be subject 
to the same height requirements. According to Advocates, the NPRM did 
not justify allowing a 750 mm height for adjustable restraints in front 
seats.
---------------------------------------------------------------------------

    \23\ RCAR is an international organization intended to reduce 
insurance costs by improving automotive damageability, 
repairability, safety and security (www.RCAR.org). Under the RCAR 
standards, the head restraint is tested with the HRMD to evaluate 
the restraint geometry and then is rated as good, acceptable, 
marginal, or poor. These types of rating systems do not contain the 
level of objectivity or specificity to translate easily into a 
regulatory requirement.
---------------------------------------------------------------------------

    There were some concerns expressed about the effect of taller front 
outboard head restraints on driver visibility through the 
backlight,\24\ and on the ability of drivers in following vehicles to 
see through the backlight of a vehicle in front of them. Honda and Ford 
also said that taller front seats would contribute to rear seat 
occupants feeling closed-in.
---------------------------------------------------------------------------

    \24\ Backlight is the window located at the rear of the roof 
panel (SAE J953).
---------------------------------------------------------------------------

    Several manufacturers also stated that the taller head restraints 
could make it more difficult to install seats during vehicle assembly.
    Agency response: The persistence of high numbers of whiplash 
injuries in the current fleet of vehicles indicates that the height 
requirement currently in effect for front outboard head restraints is 
not preventing excessive movement of the head and neck relative to the 
torso. The current requirement allows head restraints that do not 
effectively limit rearward movement of an average occupant's head at 
its center of gravity, resulting in continuing high numbers of 
whiplash. Research indicates that a minimum height of 800 mm above the 
H-point for integral head restraints, and a minimum height of 750 mm 
for adjustable head restraints in their full down position and at least 
800 mm in their full upward position, will prevent whiplash injuries 
because at this height the head restraints can effectively limit the 
movement of the head and neck.
    We have decided against adopting Advocates' suggestion that 
adjustable head restraints should not be allowed to have an adjustment 
position below the minimum 800 mm requirement set for integral head 
restraints.\25\ Advocates' argument was based on the possibility that 
occupants will not adjust their head restraints to an effective 
position. We acknowledge that head restraint misuse has been a problem 
in the past and that some consumers may not receive the full benefit of 
an adjustable head restraint if they leave them in the lowest possible 
position of adjustment. However, we believe that misuse will decrease 
as consumers become more aware of the merit of raising their head 
restraints.
---------------------------------------------------------------------------

    \25\ We note that heights greater than 800 mm are permitted for 
both integral and adjustable head restraints.
---------------------------------------------------------------------------

    Further, prohibiting any position less than 800 mm for adjustable 
head restraints would likely result in a substantial increase in the 
overall height of the seat back. (The gap between the top of the seat 
back and the head restraint in its lowest position could not be widened 
substantially, because of the restrictions in today's rule that 
restricts such gaps to 60 mm.) The practical effect of adopting 
Advocates' suggestion would be to require integral head restraints, 
which we believe is unwarranted and overly design restrictive. 
Adjustable head restraints may allow shorter and very tall occupants to 
position their head restraints more optimally. Further, even occupants 
of average size may benefit from certain adjustment features, such as 
head restraint backset adjustment to positions closer than 55 mm, if 
they find it comfortable. Finally, when properly designed to maintain 
their position, adjustable head restraints can provide protection 
comparable to that provided by integral head restraints.
    We note that integral head restraints have in the past been 
considered more effective than adjustable head restraints, largely 
because many occupants do not properly position adjustable head 
restraints. In 1982, NHTSA assessed the performance of head restraints 
installed

[[Page 74854]]

pursuant to FMVSS No. 202 and reported that integral head restraints 
are 17 percent effective at reducing neck injuries in rear impacts and 
adjustable head restraints are 10 percent effective at doing so. The 
difference was due to integral head restraints' being higher with 
respect to the occupant's head than adjustable head restraints, which 
were normally left down. More recently, however, the Preliminary 
Economic Assessment (PEA) for the NPRM found no statistical difference 
in the protection offered by adjustable and integral head restraints. 
This may be attributable to increases in the height of adjustable head 
restraints relative to integral head restraints since the 1982 NHTSA 
study.
    With respect to comments on visibility concerns, we do not believe 
that the greater height of front seat head restraints will decrease 
rearward visibility. Numerous vehicles currently produced for the U.S. 
market already have head restraints reaching 800 mm without reports of 
visibility problems. In its comment, Transport Canada referred to a 
study conducted by Biokinetics & Associates entitled, ``The Effects of 
Increased Head Restraint Height on Driver Visibility,'' in support of 
its suggestion that increasing the height of head restraints would not 
result in any major visual obstruction. The study indicated that a 
fixed head restraint tall enough to accommodate a 95th percentile male 
would have a negligible effect on driver visibility in 83 percent of 
vehicles in the fleet, as compared to an adjustable head restraint in 
the lowest position.
    With regard to concerns about the difficulty of manufacturing 
vehicles with taller head restraints, we do not believe this is a major 
manufacturing obstacle. Numerous manufacturers already comply with 
ECE17, which requires front head restraints to be as tall as in this 
rule.\26\ Further, the manufacturers will have ample opportunity to 
address vehicle assembly processes during the interim period before the 
final rule becomes effective.
---------------------------------------------------------------------------

    \26\ We also note that some vehicles already feature rear seat 
head restraints that would comply with the new height, backset, 
strength, position retention, and energy absorption requirements for 
optional rear outboard head restraints.
---------------------------------------------------------------------------

    Some commenters believed that taller front seat head restraints 
will make rear seat passengers feel ``closed in'' and claustrophobic. 
There has been no indication of such problems from the European markets 
where rear seat passengers are already subjected to taller head 
restraints in the front outboard seating positions. We are unable to 
conclude, without supporting data, that a head restraint that is less 
than 100 mm (4 inches) higher than current restraints is generally 
likely to have this effect on passengers.
    Nissan and ICBC requested that height and backset requirements, as 
applied to active or dynamically deployed head restraints, be measured 
when such head restraints are fully activated. Unless the system is 
tested when fully activated, Nissan claimed that the active head 
restraint system currently featured in several Nissan and Infiniti 
vehicles would not pass under the new static testing requirements.
    We believe that it may be difficult to deploy these systems 
manually and to keep them deployed while making static measurements, 
unless the actual seat is partially disassembled. Further, this 
artificially deployed position may not accurately represent position of 
the head restraint when the occupant's head comes in contact with it 
during a rear impact. The agency knows of no practicable way to address 
these issues in the context of a static test nor did any commenter 
present one. Accordingly, this rule requires that front outboard active 
head restraint systems be tested for height in their un-deployed 
position. We note that there are practical limitations of any static 
test procedure on a system with dynamic properties.\27\ However, if an 
active head restraint were to meet the static test procedure 
requirements, this would not eliminate the value of the active nature 
of those head restraints since further gains in controlling the 
occupant's head-to-torso motion and energy absorption could be 
achieved.
---------------------------------------------------------------------------

    \27\ We note that the manufacturers' concerns are alleviated by 
the availability of the dynamic compliance option. The dynamic 
compliance option provides an alternative for those manufacturers 
who are now utilizing active or dynamic head restraint systems. 
Agency testing and other published research have shown that an 
active head restraint system can be designed to meet dynamic testing 
requirements with a comfortable compliance margin. Further, a 
manufacturer electing to certify compliance via dynamic testing is 
relieved from multiple static performance requirements. Our analysis 
also indicates that several active head restraint systems currently 
on the market would pass our static compliance requirements in their 
normal or non-deployed position. Accordingly, we believe most head 
restraints will be able to meet today's static test requirements. 
For those that cannot, the dynamic compliance option remains 
available.
---------------------------------------------------------------------------

    Front head restraints in low roofline vehicles. This rule permits a 
lower minimum height for head restraints for front outboard-designated 
seating positions to allow a maximum of 25 mm of vertical clear space 
between the top of the front head restraint and the roofline. The NPRM 
proposed to permit a similar exception during the interim period as 
part of the option of complying with ECE 17. ECE 17, paragraph 5.5.4 
allows for up to 25 mm of clear space between front head restraint and 
any fixed vehicle structure, provided that use of the exception does 
not result in a height lower than 700 mm.
    For front head restraints, DaimlerChrysler, Nissan, Alliance, 
Volkswagen, and Porsche requested that the 25 mm clearance exemption 
remain in the final rule to accommodate the possible situation in which 
the 800 mm head restraint may not clear the roof or front header when 
the seat back is folded for egress to or ingress from the rear seat 
area. In response to these comments we decided to adopt a 25 mm height 
allowance in this final rule. As in ECE 17, paragraph 5.5.4, the 25 mm 
height allowance is limited to the extent that the resulting front head 
restraint height cannot fall below 700 mm. However, this rule permits 
the 25 mm height allowance only in situations in which a full height 
front head restraint would interfere with the roofline, but not with 
any fixed vehicle structure, as allowed by ECE. We believe adopting the 
full ECE exception could provide relief in instances in which none may 
be needed. For example, an upper seat belt anchorage or the side of the 
vehicle's interior could be within 25 mm of the head restraint and yet 
would likely not create any compliance difficulties for vehicle 
manufacturers or unduly restrict visibility.
    The 25 mm height allowance for rear head restraints is described in 
the next section.
    Width of front seat head restraints: The NPRM proposed to maintain 
the existing width requirements of FMVSS No. 202: i.e., that both front 
and rear outboard seat head restraints must be at least 171 mm (6.7 in) 
wide on single seats and 254 mm (10 in) wide on bench seats.\28\ We 
note that ECE 17 regulation provides a 170 mm minimum width requirement 
for all head restraints. In the NPRM, we stated that bench seat head 
restraints should be wider because occupants seated on bench seats are 
freer than occupants of single seats to position themselves so that 
they are not directly in front of the head restraint.
---------------------------------------------------------------------------

    \28\ A bench seat is a seat that has a center designated seating 
position between the two outboard designated seating positions.
---------------------------------------------------------------------------

    AIAM called the proposed 254 mm head restraint width for bench 
seats unreasonable, stating that NHTSA should instead adopt the same 
170 mm width for bench seat head restraints. AIAM asserted that comfort 
factors and seat belt placement on most bench seats help place 
occupants in the proper seating positions. In contrast, Advocates

[[Page 74855]]

expressed concern that requiring a 254 mm width for bench head 
restraints and a 170 mm width for non-bench head restraints would 
protect only target occupants in centered, perpendicular rear impacts, 
not occupants in offset collisions, causing head/neck excursion to one 
side of the restraint. Given those concerns, Advocates stated it did 
not understand why all restraints, especially front head restraints, 
should not have a minimum width of 254 mm.
    For front bench seats we disagree with AIAM that the width 
requirement should be reduced. The 254 mm width requirement for these 
head restraints on bench seats has been in effect since January 1, 
1969. We are not aware of any evidence showing that the present level 
of protection should be reduced. We decided to maintain wider head 
restraints for front bench-type seats because wider head restraints 
tend to better reduce relative head-to-torso motion in off-axis 
impacts. However, rather than use the term ``bench,'' which some 
commenters felt required further clarification, we have defined the 
requirement in terms of front outboard designated seating positions in 
vehicles that have a front center designated seating position.
    With regard to Advocates' comment, NHTSA declines to require all 
head restraints to have a minimum width of 254 mm. With respect to 
front outboard seating positions, we note that front outboard non-bench 
seats have a defined contour that, in addition to belt use, better 
prescribe occupant seating position relative to the head restraint. 
Therefore, the front non-bench head restraints can be narrower than the 
front bench seat head restraints. With respect to rear outboard seating 
positions, we believe that the rearward visibility concerns associated 
with wider rear head restraints outweigh an unquantified off-axis rear 
impact benefit of wider restraints in all seats at this time.

b. Requirements for Rear Seats Equipped With Head Restraints

    In the NPRM, we proposed to require head restraints in rear 
outboard seating positions. Presently, neither FMVSS No. 202 nor ECE 17 
requires head restraints in rear outboard seating positions. Based on 
further analysis of the proposal and submitted comments, we have 
decided not to require head restraints in rear outboard designated 
seating positions. For a more detailed discussion of our decision not 
to require head restraints, please see section XII.
    While rear head restraints are not required, this final rule does 
impose certain requirements on head restraints voluntarily installed in 
outboard designated seating positions. The strength, position 
retention, and energy absorption requirements are the same for front 
outboard and optional rear head restraints. However, the requirements 
for height and width differ from those applicable to front outboard 
head restraints.
    Height of rear seat head restraints. The NPRM proposed that rear 
restraints have a minimum height of 750 mm if integral and, if 
adjustable, not be adjustable to a height below 750 mm.
    DaimlerChrysler, GM, Honda, and the Alliance expressed concern 
about diminished visibility and decreased functionality of rear seat 
storage due to the taller rear seat head restraints. As a result of 
this expected decline in visibility and utility, DaimlerChrysler 
indicated that customer dissatisfaction with the restraints could 
trigger misuse or removal. Johnson Controls expressed concerns 
pertaining to reduced rearward visibility (particularly for shorter 
drivers), as well as feasibility issues, including difficult ingress/
egress for third-row SUV or van seating, inability to fold and install 
all rows of seats, and lack of clearance between head restraints and 
the rear backlight area for sport coupes with rear seating.
    Porsche objected to the 750 mm rear head restraint height, claiming 
impracticability and lack of safety need. Porsche indicated that some 
of its current fleet would be unable to meet the new height 
requirements for rear head restraints. Specifically, Porsche presented 
their computer aided design data showing that several models, including 
the 911, have less than 750 mm of distance between the rear seat H-
point and the roofline, making compliance with the proposed 
requirements impossible.\29\ Accordingly, Porsche asked that the final 
rule either not require rear head restraints, or provide an exception 
for low roofline vehicles. Magna and Volkswagen also requested that a 
25 mm clearance between the top of head restraint and the roofline be 
allowed regardless of the actual head restraint height measurement. 
Such a provision would be similar to an ECE 17, Paragraph 5.5.4, which 
allows head restraints to have a lower maximum height in order to 
provide 25 mm of clear space between the head restraint and the 
roofline. Nissan suggested allowing a 25 mm clearance between the head 
restraint and interior vehicle structures as necessitated by vehicle 
design.
---------------------------------------------------------------------------

    \29\ The distance from the H-point to the point 25 mm below the 
roofline for 911 Coupe, Targa, and Cabrio models is 693, 666, and 
691 mm, respectively. Porsche also noted that requiring rear head 
restraints in such vehicles would create an almost 100 percent rear 
window obstruction (Docket No. NHTSA-2000-8570-39).
---------------------------------------------------------------------------

    In contrast, Advocates argued for an 800 mm minimum height for rear 
seat head restraints, in order to include (according to the commenter) 
sufficient whiplash protection for 95th percentile male adults.
    Agency response: As discussed above, NHTSA has concluded that any 
voluntarily installed rear head restraints must meet the height 
requirements proposed in the NPRM. Specifically, the optional rear head 
restraints must reach a minimum height of not less than 750 mm above 
the H-point.
    In the NPRM, we indicated that the 750 mm minimum head restraint 
height would reach above the head center of gravity of approximately 93 
percent of all adults. We note that with respect to the rear seat head 
restraint target population, the 750 mm height would sufficiently 
protect an even higher percentage of rear seat passengers because 
larger occupants typically sit in front seats.
    Some manufacturers stated that a taller rear head restraint might 
interfere with seat mechanisms designed to provide access to and from 
third row seats. Because we have decided not to require rear head 
restraints, a manufacturer concerned with functionality of these 
mechanisms need not install a head restraint in the affected seats. 
Additionally, as will be discussed in sections IX.b. and c., the 
manufacturers will be allowed to install removable rear outboard head 
restraints or rear outboard head restraints with ``non-use positions.''
    Several commenters discussed the possible effects of the proposed 
head restraint height increases on vehicle utility with respect to seat 
folding and cargo capacity. The Alliance, DaimlerChrysler, Honda and GM 
commented that the rear head restraint heights proposed in the NPRM 
could impede seat folding, thus limiting cargo capacity, or otherwise 
limit interior configuration possibilities.
    Since rear outboard head restraints will not be mandatory, vehicle 
manufacturers need not equip their rear seats with head restraints. 
Further, as will be discussed in section IX, if the manufacturers 
provide rear outboard head restraints, they will be allowed to make 
them removable and to design them so that they can be moved into ``non-
use positions.'' As a result, manufacturers will have ample design 
flexibility to address the cargo carrying needs of their customers.

[[Page 74856]]

    Rear head restraints in low roofline vehicles. This rule permits a 
lower minimum height for rear outboard seating positions equipped with 
optional head restraints to allow a maximum of 25 mm of vertical clear 
space between the top of the rear head restraint and the roofline or 
the backlight. The NPRM proposed to permit a similar exception during 
the interim period as part of the option of complying with ECE 17. ECE 
17, paragraph 5.5.4 allows for up to 25 mm of clear space between rear 
head restraint and any fixed vehicle structure, provided that use of 
the exception does not result in a height lower than 700 mm.
    We decided to adopt a similar provision for the long term. However, 
this rule permits the 25 mm height allowance only in situations in 
which the rear head restraint interferes with the roofline or the rear 
window, but not with any fixed vehicle structure as allowed by ECE. 
Further, the 25 mm height allowance is permitted only if the 
interference occurs when seats are positioned as intended for occupant 
use.\30\
---------------------------------------------------------------------------

    \30\ The term ``intended for occupant use'' has been defined in 
the final rule to apply to seat positions other than those intended 
solely for the purpose of allowing ease of ingress and egress of 
occupants and access to cargo storage areas of a vehicle.
---------------------------------------------------------------------------

    In their comments, DaimlerChrysler, Nissan, Alliance, Volkswagen, 
and Porsche asked for a permanent 25 mm height allowance and suggested 
that the clearance should apply in situations where the seat interferes 
with all fixed vehicle structures, including roof liners, seat backs, 
headers, and rear windows. Further, they stated the clearance should be 
allowed regardless of whether the seats are placed in either upright or 
folded down positions.
    This final rule does not permit a 25 mm height allowance in 
situations in which the rear head restraint interferes with fixed 
vehicle structures other than the roofline or the backlight. We believe 
adopting the full ECE exception could provide relief in instances in 
which remedies other than changing the basic vehicle structure are 
available.
    As previously stated, the rear seat 25 mm height allowance in this 
final rule applies only to seat adjustment positions intended for 
occupant use.\31\ That is, if a second row seat folds forward to permit 
ingress and egress and would hit the seat in front of it or some other 
vehicle structure, the 25 mm height allowance is not available for that 
situation. In situations in which interference occurs when a seat is 
not in a position intended for occupant use, the manufacturers may 
choose to utilize the ``non-use'' head restraint positions described 
later in this document, or redesign the seat fold-down mechanisms. We 
note that redesigning the fold down mechanism, though not necessitated 
by this final rule, can provide a practicable resolution at a 
reasonable cost.
---------------------------------------------------------------------------

    \31\ We note that both front and rear optional head restraints 
must meet the applicable height requirements with the seat 
positioned as intended for occupant use.
---------------------------------------------------------------------------

    The ECE 25 mm height allowance is limited to the extent that the 
resulting head restraint height cannot fall below 700 mm. As a 
practical matter, however, this requirement is moot with respect to the 
upgraded standard because the rear seat backs and attached or adjacent 
components that have a height of less than 700 mm are not considered 
rear head restraints under this final rule.
    Width requirements for rear head restraints. The agency tentatively 
concluded in the NPRM that a 171 mm width for single seats and a 254 mm 
width for bench seats were the appropriate specifications for all 
outboard seating positions. These proposed widths differed from ECE 17, 
Paragraph 5.10, which provides a 170 mm minimum width requirement for 
all head restraints. The NPRM asked whether NHTSA should implement 
specific requirements for rear seat head restraints in order to 
alleviate problems associated with potential visibility losses.
    All industry commenters agreed that the appropriate width 
requirement for rear seat head restraints should be 170 mm, and that 
254 mm is overly wide. Honda commented that the 254 mm bench seat width 
requirement could reduce rearward visibility and was unwarranted, given 
the unknown safety problems of rearward visibility reduction and the 
unidentified need for wider head restraints. Honda attached the results 
of a simulation it conducted to show the decreased visibility created 
when 750 mm high, 254 mm wide head restraints are installed in a coupe 
and a hatchback vehicle. When 254 mm wide head restraints were 
installed on a second row rear bench seat of a coupe model, Honda's 
simulation showed a 40 percent decline in rearward visibility. 
Similarly, when installed on a hatchback model, the 254 mm wide head 
restraints produced a 60 percent loss of rearward visibility. To 
rectify this reduction of rearward visibility, Honda suggested a head 
restraint minimum width requirement of 170 mm for both bench seats and 
individual seats. Honda based this 170 mm requirement for both types of 
seats on ECE 25.
    Ford presented data from a study it conducted, showing that rear 
head restraints with widths of 171 mm trimmed backlight visibility by 
10-12 percent, while 254 mm wide rear head restraints reduced 
visibility by 15-17 percent.
    In contrast, Advocates stated that it believed that all restraints 
should have a minimum width of 254 mm.
    Upon reviewing the comments, NHTSA has decided to require a 170 mm 
minimum width for all voluntarily installed rear head restraints. This 
decision was made to further reduce the effects of this rule on 
rearward visibility. In order to harmonize our requirements with that 
of ECE 17, we are adopting a 170 mm minimum width, as opposed to the 
171 mm proposed in the NPRM.

VII. Backset Requirements for Front Seats

    In the NPRM, we proposed that the front and rear outboard head 
restraints have a backset of no more than 50 mm, as measured by HRMD. 
``Backset'' means the minimum horizontal distance between the back of a 
representation of the head of a seated 50th percentile male occupant 
and the head restraint (i.e., the back of the ICBC head form and the 
head restraint). The 50 mm maximum backset requirement was to be met at 
all head restraint heights between 750 mm and 800 mm. We solicited 
comments on whether a maximum 50 mm backset limit would be effective in 
preventing whiplash injuries; whether 50 mm backset would provide 
sufficient comfort for the occupants; and whether an adjustable backset 
would be more appropriate.
    Commenters offered a range of opinions about the need for, and 
acceptable level of, a maximum backset requirement. Several commenters, 
including ICBC, IIHS, Transport Canada, and Advocates, supported 
establishing 50 mm as the maximum allowable backset. ICBC and Magna 
Seating Systems argued that Mathematical Dynamic Model (MADYMO) 
simulations performed by NHTSA confirm the decreasing safety benefit of 
head restraints with backsets greater than 50 mm. Therefore, ICBC 
believes 50 mm is sufficient to reduce whiplash significantly.
    ICBC provided data showing 49 of 164 vehicles manufactured in 2001 
by 19 different manufacturers have a backset of 50 mm or less.\32\ IIHS 
stated that a group of model year (MY) 2001 vehicles,

[[Page 74857]]

among them Jeep Cherokee, Ford Ranger, Toyota Camry, and Volvo S80 
already have 50 mm or smaller backsets. Because many newer vehicles 
already have backsets of 50 mm, these commenters claimed it was evident 
that the 50 mm requirement provides sufficient head clearance and that 
passenger comfort would not be compromised in a significant manner. 
IIHS stated that it was unaware of any significant comfort issues.
---------------------------------------------------------------------------

    \32\ We note that the ICBC evaluated backset using the 
measurement technique and seat back angle identical to that of this 
final rule.
---------------------------------------------------------------------------

    In opposition, a majority of the manufacturers, among them GM, 
Magna, Johnson Controls, AIAM, the Alliance, Nissan, Porsche, 
DaimlerChrysler, and Ford, suggested that vehicle occupants would 
prefer a head restraint backset of more than 50 mm. Specifically, they 
maintained that smaller female occupants tend to utilize steeper seat 
back angles. According to these commenters, a backset of 50 mm may 
cause significant intrusions into the space where these occupants 
typically place their heads, forcing their heads into an unnatural 
forward-tilting position. DaimlerChrysler indicated that a recent 
decrease in the backset to 50 mm in one of its models yielded four 
times as many warranty claims for the new head restraint. It did not 
elaborate on the basis for these claims. Autoliv commented that even a 
50 mm backset is not a guarantee to prevent whiplash, and that it will 
lead to discomfort for more than 20 percent of the occupants. General 
Motors and Ford suggested that an 80 mm backset is more appropriate to 
accommodate consumer comfort.
    Some commenters stated that IIHS rates backsets of 70 to 90 mm 
``acceptable'' and so that backset requirement should be increased to 
that range.
    The University of Michigan Transportation Research Institute 
(UMTRI) commented that it had conducted an extensive study of vehicle 
occupants' posture and position. Based on its research, a 50 mm backset 
would result in head restraint interference for 13 percent of the 
driving public.\33\ The head restraint would actually come in contact 
with the hair of approximately 33 percent of drivers, assuming a hair 
margin of 25 mm. Based on their calculations, the individuals who 
preferred seat back angles more upright than 25 degrees (usually small 
stature people) were most likely to be subject to the head restraint 
interference. UMTRI estimated that with current seat designs, a backset 
of 91 mm would accommodate the preferred head positions of 99 percent 
of the population and a 70 mm maximum backset would accommodate all but 
a small percentage of the population.
---------------------------------------------------------------------------

    \33\ The UMTRI evaluated backset of 50 mm at the seat back angle 
of 25 degrees, using a CAD representation of a HRMD and a typical 
seat.
---------------------------------------------------------------------------

    Ford cited 3 studies by Eichberger et al.,\34\ Szabo et al.,\35\ 
and Davidsson et al.,\36\ which used sled-mounted seats to simulate low 
speed rear impacts. Eichberger et al. tested volunteers on 9 different 
seat types at simulated impact speed changes (delta Vs) of 8 and 11 km/
h. When the measured backset was less than 70 mm, none of the 
volunteers complained of any discomfort or pain. Szabo et al. tested 5 
volunteers at delta Vs of 8-10 km/h under two conditions: an unmodified 
head restraint, and the same head restraint with 50 mm of additional 
padding. Backsets for the volunteers ranged between 76 to 114 mm with 
the unmodified head restraint, and by assumption between 26 to 64 mm 
with the modified head restraints. None of the volunteers reported any 
discomfort or pain after either test. Davidsson et al. subjected 13 
volunteers to multiple sled tests (2-4) with delta Vs of 5 to 7 km/h. 
The measured backsets ranged from 70 to 160 mm. The head restraint 
position was not varied during the test so the variation in backset for 
the different occupants was due to occupant size differences. Only one 
subject reported any symptoms. The symptom was a headache, which 
occurred after his third run, and desisted within 36 hours.
---------------------------------------------------------------------------

    \34\ Eichberger A, Geigl BC, Moser A, Fachbach B, Steffan H, 
Hell W, Langwieder K; Comparison of Different Car Seats Regarding 
Head-Neck Kinematics of Volunteers During Rear End Impact; 
Proceedings of the 1996 International IROCBI Conference on the 
Biomechanics of Impact; September 1996; pp. 153-164.
    \35\ Szabo TJ, Welcher JB; Human Subject Kinematics and 
Electromyographic Activity during Low Speed Rear Impacts, 
Proceedings of the 40th Stapp Car Crash Conference; November 1996, 
962432, pp. 235-315.
    \36\ Davidsson J, Deutscher C, Hell W, Linder A, Lovsund P, 
Svensson: Proceedings of the 1998 International IRCOBI Conference of 
the Biomechanics of Impact: September 1998; pp. 289-301.
---------------------------------------------------------------------------

    We also received a comment from Cervigard, Inc., which has designed 
a head restraint that incorporates a contoured shape intended to match 
the curvature of the head and cervical spine, which is essentially a 
neck bolster. In Appendix B of this NPRM, we discuss our reasons for 
not adopting a requirement for a neck bolster.
    Agency response: This final rule requires that front outboard head 
restraints meet the backset requirements described below. Because of 
occupant comfort countermeasure issues unique to rear seats, the agency 
decided not to regulate backset in the rear designated seating 
positions voluntarily equipped with head restraints. We concluded that 
comfort-related issues are not insurmountable in front seats because 
front seat backs can be adjusted to alleviate discomfort. Further, as 
explained further below, our Final Regulatory Impact Analysis (FRIA) 
does not attribute any safety benefits to vehicle occupants as a result 
of regulating backset in rear seats.
    For front outboard designated seating positions, we have decided to 
increase the maximum allowable backset to 55 mm, with the seat back 
positioned at an angle that gives the HRMD a torso reference line angle 
of 25 degrees. Our decision to relax the maximum allowable backset 
requirement is based on the <plus-minus> 5 mm tolerance of the 
measuring device. This tolerance is discussed more fully in the next 
section. Briefly stated, a 5 mm increase beyond the 50 mm limit 
proposed in the NPRM represents the variability associated with 
measuring backset with the ICBC measuring device.
    In sum, under today's rule, the backset for front outboard head 
restraints must not be adjustable beyond the new maximum allowable 
distance of 55 mm when the head restraint is at a height between 750 mm 
and 800 mm, inclusive. Backset adjustment to distances below 55 mm is 
allowed. Also, backset adjustment of above 55 mm at head restraint 
positions higher than 800 mm is allowed. For manufacturers of active 
head restraint systems who choose to certify to the static dimension 
and strength requirements, the backset measurements will be taken with 
the head restraints in non-deployed position because we believe that 
the artificially deployed position may not accurately represent the 
actual position of the head restraint when the occupant's head comes in 
contact with it.
    Necessity for a limited backset. Our decision to propose a 50 mm 
backset was based on published research, testing, computer modeling, 
and real world crash data.
    The consensus within the biomechanics community is that the backset 
dimension has an important influence on forces applied to the neck and 
the length of time a person is disabled by an injury. As early as 1967, 
Mertz and Patrick first showed that reducing the initial separation 
between the head restraint and head minimizes loading on the head 
during a rear impact.\37\ More recently, the Olsson

[[Page 74858]]

study, which examined neck injuries in rear end collisions and the 
correlation between the severity of injuries and vehicle parameters, 
showed that the duration of neck symptoms was correlated to the head 
restraint backset. Specifically, reduced backset, coupled with greater 
head restraint height, results in lower injury severity and shorter 
duration of symptoms.\38\
---------------------------------------------------------------------------

    \37\ Mertz, H.J.; Patrick, L.M.: ``Investigation of the 
Kinematics and Kinetics of Whiplash,'' Proceedings of the 11th Stapp 
Car Crash Conference, Anaheim, California, 1967; pp. 267-317.
    \38\ Olsson, I., Bunketorp, O., Carlsson G., Gustafsson, C., 
Planath, I., Norin, H., Ysander, L. An In-Depth Study of Neck 
Injuries in Rear End Collisions, 1990 International Conference on 
the Biomechanics of Impacts, September, 1990, Lyon, France. See 
Table IV and the Appendix.
---------------------------------------------------------------------------

    A different study examined sled tests to determine the influence of 
seat back and head restraint properties on head-neck motion in rear 
impacts. The study concluded that the head restraint backset had the 
largest influence on the head-neck motion among all the seat properties 
examined. With a smaller backset, the rearward head motion was stopped 
earlier by the head restraint, resulting in a smaller head to torso 
displacement. The findings indicated that a reduction in backset from 
100 mm to 40 mm would result in a significant reduction in whiplash 
injury risk.\39\
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    \39\ Svensson, M., Lovsund, P., Haland, Y., Larsson, S. The 
Influence of Seat-Back and Head-Restraint Properties on the Head-
Neck Motion During Rear-Impact, 1993 International Conference on the 
Biomechanics of Impacts, September, 1993, Eindhoven, Netherlands.
---------------------------------------------------------------------------

    A study conducted by Eichberger examined real world rear crashes 
and sled tests with human volunteers to determine whiplash injury risk 
and vehicle design parameters that influence this risk. The study found 
a positive correlation between head restraint backset and head to torso 
rotation of the volunteers and to the reported whiplash injury 
complaints. The most important design parameters were a low horizontal 
distance between the head and head restraint as well as the head 
restraint height.\40\
---------------------------------------------------------------------------

    \40\ Eichberger A, Geigl BC, Moser A, Fachbach B, Steffan H, 
Hell W, Langwieder K. Comparison of Different Car Seats Regarding 
Head-Neck Kinematics of Volunteers During Rear End Impact, 
International IRCOBI Conference on the Biomechanics of Impact, 
September, 1996, Dublin.
---------------------------------------------------------------------------

    A study conducted by Dr. Allan Tencer, PhD, used rigid occupant 
body models enhanced with finite element models of the cervical spine 
for simulating rear impacts in order to examine the effect of backset 
on neck kinematics and forces and moments in the neck. The study 
concluded larger backset correlates to greater displacement between 
cervical vertebrae and shearing at the facet capsules that are likely 
associated with whiplash injury. With the head initially closer to the 
head restraint, the time difference between the occurrences of the peak 
upper and lower neck shear forces are smaller. At 50 mm backset and 
lower, the head moved more in phase with the torso and extension of the 
head was reduced indicating a lower risk of whiplash injury.\41\ IIHS, 
in its studies of head restraints, considers a backset of 70 mm (2.8 
inches) or less to be ``good.'' \42\
---------------------------------------------------------------------------

    \41\ Tencer, A., Mirza, S., Bensel, K. Internal Loads in the 
Cervical Spine During Motor Vehicle Rear-End Impacts, SPINE, Vol. 
27, No. 1 pp 34-42, 2002.
    \42\ The IIHS head restraint rating criteria is discussed at: 
http://www.iihs.org/vehicle_ratings/head_restraints/head.htm.
---------------------------------------------------------------------------

    NHTSA used computer modeling described in the NPRM to verify our 
assumption regarding the benefits of a smaller backset. Our research 
indicates that lower head-to-torso rotation values were seen when the 
backset was approximately 50 mm in comparison to head restraints with 
large backset values. As discussed further in this notice, lower head-
to-torso rotation values are predicted to result in a lower probability 
of whiplash injury. Therefore, we continue to conclude that 50 mm of 
backset is an appropriate upper limit for all outboard seating 
positions. No data presented in the comments have indicated that a 
higher backset value is more appropriate from the occupant safety-
standpoint. Other than Ford's comments, all of the comments opposing 
the proposed 50 mm maximum backset were related to comfort issues and 
the repeatability of placement of the proposed test device. In sum, 
research indicates that limiting backset is critical to reducing 
whiplash injuries occurring in rear impacts.
    In its comments, Ford referred to three crash studies conducted at 
delta V's ranging from 5 to 11 km/h with varying degrees of backset and 
occupant size. Ford emphasized that there were no occupant injuries 
both with and without the backset reduction. We note that all of these 
tests utilized volunteers and therefore, the impact delta Vs were 
intended to be below the injury threshold. The primary goal of these 
studies was to understand occupant kinematics. The same research also 
indicated that when backset was reduced from 76 mm to 26 mm and from 
114 mm to 64 mm, the head acceleration, rearward head displacement and 
cervical extension were all reduced. These data confirm our contention 
that injury measures, including head-to-torso rotation, decrease with 
smaller backset and predict a lower probability of injury. While some 
of the data supplied by Ford seems to suggest that smaller backsets 
have no bearing on the occurrence of whiplash injuries at low speeds, 
we note that if all impacts in the real world were limited to this very 
slow speed, the backset limit indeed might not be as critical. The same 
data seem to support our rulemaking efforts, as Eichberger observed 
that backset ``is very important for a good seat design. Even a head 
restraint placed high enough can only prevent neck injuries when the 
head is sustained as soon as possible by the head restraint during rear 
end collision.'' \43\
---------------------------------------------------------------------------

    \43\ See Eichberger at pp. 153-164.
---------------------------------------------------------------------------

    Finally, we note that other seat parameters beyond the head 
restraint geometry play a role in risk of injury in rear impacts. 
Specifically, seat back frame force deflection characteristics and seat 
upholstery compliance characteristics can influence the occupant's 
kinematics. Thus, the head restraint geometric requirements specified 
in this final rule should be thought of as an interim step in the 
agency's goal of a unified seat/head restraint standard.
    Comfort of the seat occupant. In selecting a backset limit, we have 
attempted to balance comfort, safety and measurement variability 
concerns. As noted above, no commenter disputed scientific data 
indicating that the closer the head restraint is to the occupant's head 
at the time of impact, the better the protection the head restraint 
offers. Numerous commenters, however, stated that occupants may be 
intolerant of head restraints very close to the back of their head. 
Further, because of differences in the occupant size, posture and seat 
angle preference, the same head restraint can yield different amounts 
of backset clearance for different individuals.
    Several manufacturers argued that some occupants would select a 
steeper or more upright front seat back angle, thus causing the backset 
distance to be below 50 mm. They contend that a backset of less than 50 
mm will interfere with the normal position of the head. However, since 
ICBC reported that 49 of 164 vehicles from model year 2001 met the 50 
mm backset limit, it appears that occupant discomfort in front seats is 
not an insurmountable obstacle. Accordingly, we conclude that the 
available information does not substantiate the industry concerns 
associated with discomfort from front seat back adjustment to a more 
upright position.
    UMTRI commented that a 50 mm backset causes interference with 13 
percent of drivers ``preferred'' head position. Generally, these tend 
to be smaller occupants, who prefer a more

[[Page 74859]]

upright seat back angle. The ``preferred'' backset position, as 
articulated by UMTRI, may merely refer to a position that the drivers 
are most accustomed to. The term does not necessarily mean that the 
position is the only acceptable one or even the safest one for a given 
occupant. We note that the driving population as a whole is accustomed 
to a backset position that is, while comfortable, not optimal to 
prevent whiplash injuries.
    We believe that no significant deviation from our proposed backset 
limit of 50 mm is necessary to provide an overwhelming majority of 
front seat occupants with an acceptable backset position. Further, any 
potential discomfort can be reduced by a slight increase in seat back 
angle. We believe that most front seat occupants can increase the seat 
back angle slightly without compromising their ability to reach the 
steering wheel comfortably or see the road ahead. For every additional 
degree of inclination, approximately 3 mm of additional backset 
clearance would be obtained. For example, a 2-degree increase in seat 
back angle will result in additional 6 mm of backset.
    In addition to potential ways to alleviate potential discomfort, we 
note that our own measurements of 14 vehicles showed that the front 
seat head restraints in the MY 1999 Toyota Camry, Chevy C1500, Chevy 
S10, Saab 9-5, and Chevy Malibu, all had backsets within the proposed 
50 mm limit. This supports comments by ICBC and IIHS that many vehicles 
already have a 50 mm backset. We think the seat manufacturers can 
provide a front seating system design, such as a different head 
restraint shape, that would allow for better comfort.
    With respect to rear seats, however, the agency believes that 
potential occupant discomfort cannot be as easily reduced because most 
rear seat backs in passenger cars are not adjustable. In many vehicles, 
the rear seat back angle cannot be changed to provide additional 
backset clearance. Consequently, some vehicle occupants may experience 
interference with the normal position of their head, and could decide 
to completely remove the optional rear head restraints. NHTSA believes 
that it is preferable that the rear head restraints remain in the 
vehicle instead of being removed due to occupant discomfort, because we 
estimate that the increased height of optional rear head restraints 
will result in 1559 fewer whiplash injuries each year. Further, we are 
concerned that some manufacturers may choose not to install optional 
rear head restraints due to concerns of customer dissatisfaction with 
uncomfortable rear head restraints.
    Because of rear seat occupant comfort concerns, the agency decided 
not to limit the amount of backset in the rear designated seating 
positions equipped with optional head restraints.\44\ Because of 
abundant scientific evidence showing that smaller backset reduces 
instances of whiplash injuries, we believe that the vehicle 
manufacturers will install optional rear head restraints in a manner 
that will strike a proper balance between rear seat occupant safety and 
comfort.
---------------------------------------------------------------------------

    \44\ We note that the decision not to regulate the backset of 
rear head restraints has the effect of making our upgraded standard 
consistent with the ECE regulation on this point.
---------------------------------------------------------------------------

    In addition to rear occupant comfort concerns, we note that our 
FRIA does not attribute any safety benefits to vehicle occupants as a 
result of regulating backset in rear seats. By contrast, we estimated 
that for front seats, the limit on backset would result in 15,272 fewer 
whiplash injuries each year. As explained in Section XVI of this 
notice, we based our estimates of benefits on either increased height 
or reduced backset, but not both. We could not combine effectiveness of 
increased height and reduced backset because this, in some instances, 
would result in ``double-counted'' benefits. For front seats, we 
attribute the benefits to the backset limit. We estimate that greater 
share of the safety benefits will come from the backset limit because 
many current vehicles already include taller front seat head 
restraints. For rear seats, we attribute the benefits to height because 
we anticipate that the greater share of the benefits will come from 
regulating the height of optional head restraints.
    Adjustable backset suggestion. Several seat and automobile 
manufacturers argued that, to accommodate occupant comfort, a 50 mm 
backset requirement should be supplemented with an allowance for 
backset to be adjustable to distances of up to 100 mm, so long as it 
could also be adjustable to a minimum setting of 50 mm. In contrast, 
most consumer groups voiced opposition to allowing a backset distance 
of up to 100 mm, even if it would be adjustable to a shorter distance 
of 50 mm. Advocates argued that the backset should be limited to 50 mm 
or less, and there should not be an allowance for an adjustable 100 mm 
backset, because it is commonly known that most occupants will not 
properly adjust their head restraints. Florida International University 
(FIU) students claimed that most occupants would simply leave their 
head restraints adjusted at a backset of 100 mm because of the lack of 
adequate consumer awareness. Johnson Controls was similarly opposed to 
an adjustable backset, stating that it is evident that most head 
restraints would be misadjusted. Johnson Controls stated that 60 to 80 
percent of occupants do not properly adjust their head restraints. ICBC 
was similarly opposed to head restraints with adjustability beyond 50 
mm, stating that it would lead to misadjustment and reduced 
effectiveness.
    We were not persuaded to allow a head restraint system featuring 
adjustable backset mechanism that would allow as much as 100 mm of 
backset, even if such mechanism would be capable of achieving a 50 mm 
backset measurement. We agree with arguments put forth by ICBC and 
Advocates that the possibility of misadjustment is too great. In case 
of vertical adjustment, the height between the ears and the top of the 
head provides a clear target zone for adjustment. There is no such 
clear target adjustment zone for backset. Further, if a vertically 
adjustable front head restraint is adjusted to its lowest position, it 
still provides an acceptable level of protection at a height of 750 mm. 
If the head restraint is adjusted too high, it provides an obvious 
visual cue to the seat occupant. In the case of backset misadjustment, 
there would not be a minimally acceptable level of protection at 100 mm 
of backset, because such measurement does not provide sufficient 
protection against excessive head-to-torso rotation. Further, a head 
restraint with a misadjusted backset would not provide an occupant with 
an obvious visual cue, as most occupants are unaware of the necessity 
for proper backset adjustment. In sum, we conclude that allowing for an 
adjustable backset could end up defeating the purpose of the new 
backset requirement.
    Seat back angle for backset measurement. We are aware of certain 
variability concerns associated with backset measurement using the HRMD 
device with a SAE J826 manikin torso reference line angle of 25 
degrees. We will refer to the torso reference line angle of the J826 
manikin and seat back angle interchangeably. Concerns associated with 
the use of HRMD device are discussed in Section IX. The seat back angle 
of 25 degrees was chosen because it is on the edge of the range of 
normally selected seat back angles and would most likely be selected by 
larger occupants. ICBC, which developed the HRMD, designed it to be 
used at 25 degrees. Of course, for some fixed

[[Page 74860]]

position rear seats, this is not possible. The 25-degree angle is also 
consistent with the methods used by IIHS and RCAR for measurement of 
height and backset. ECE 17 does not specify a limit on backset, but for 
height measurement the seat back is set to 25 degrees unless the 
manufacturer's recommended seat back angle is specified. While several 
manufacturers stated that measuring head restraint height at steeper 
(i.e., smaller) seat back angles result in smaller measured height, our 
own data indicate that reducing seat back angle by one degree results 
only in a 2 to 3 mm reduction in head restraint height measurement. We 
also find persuasive the information provided by ICBC stating that a 
<plus-minus>1-degree error in torso angle results in a change in 
backset measurement of only <plus-minus>3 mm.
    We note that the 25-degree seat back angle in comparison to steeper 
angles represents a more stringent requirement for backset measurements 
because it maximizes the distance between the head and head restraint. 
However, a 25-degree angle is less stringent for measuring head 
restraint height. Indeed, if we decided to adopt the manufacturer's 
design seat back angle, typically around 23 degrees,\45\ we would in 
fact be requiring even taller head restraints. Although we considered 
measuring height at a steeper angle than 25 degrees, we decided against 
it. Rather, we are adopting a single measurement angle for both height 
and backset in order to reduce unnecessary complexity in measurements 
and increase accuracy of testing results. We believe the 25-degree 
specification will not compromise safety for shorter or taller 
occupants. Finally, using the same angle for the measurement of backset 
and height for every seat, rather than the manufacturer's design seat 
back angle, will allow comparison of height and backset measurement 
from seat to seat.
---------------------------------------------------------------------------

    \45\ SAE J1100--Motor Vehicle Dimensions. All 1999-2000 make and 
model data submitted to NHTSA. The data ranged from 18 to 28 
degrees.
---------------------------------------------------------------------------

VIII. Measurement of Backset and Height

    NHTSA proposed that compliance with the backset and height 
requirements be measured through use of the ICBC HRMD. The HRMD 
consists of a SAE J826 three-dimensional manikin with a head form 
designed by ICBC attached. The ICBC head form contains a probe that 
slides rearward until contact is made with the head restraint, thus 
allowing a backset measurement. For height measurement, the SAE J826 
manikin is used without the HRMD. The SAE J826 manikin provides a scale 
that gives the distance from the H-point along the torso line, thus 
allowing a height measurement.\46\ If the seat cushion adjusts 
vertically independently of the seat back, the measurements will be 
taken with the seat cushion adjusted to the most unfavorable position; 
i.e., the position that minimizes head restraint height.
---------------------------------------------------------------------------

    \46\ Although HRMD has a probe that makes it possible to measure 
head restraint height vertically down from the top of the HRMD, this 
probe will not be used because it is not consistent with measurement 
along the torso line.
---------------------------------------------------------------------------

    Most vehicle manufacturers and seat suppliers opposed the use of 
the HRMD. Generally, they questioned the accuracy and repeatability of 
head restraint geometry measurements made using that device. Further, 
the HRMD was deemed too sensitive to foam, trim, actual H-point, 
temperature, and humidity variations. Johnson Controls, Nissan, Magna, 
Ford, VW, and GM commented that the HRMD was not appropriate for 
compliance testing because repeated testing on the same seat assembly 
yielded different results. For example, Ford noted that the 2000 Ford 
Taurus and 2000 Mercury Sable received different ratings despite the 
fact that they are manufactured on the same platform and have identical 
front seats. Additionally, DaimlerChrysler commented that NHTSA's own 
compliance procedure for Standard No. 208, involving the J826 manikin, 
allows for variability of <plus-minus>12.5 mm for the Hybrid III test 
dummy's H-point in comparison to the J826 H-point and that the Hybrid 
III is a more biofidelic representation of a seated occupant. Ford 
stated that when measuring a head restraint reaching 800 mm, a manikin 
torso angle variation of <plus-minus>1 degree produced a 28 mm 
variation in the backset measurement. Porsche stated that the HRMD 
device could not be properly positioned in the seats that have strong-
contoured shape, therefore preventing accurate measurements. Honda 
provided data showing repeated backset measurement of a single seat by 
3 test technicians. The largest range for any technician was 10 mm and 
the overall range of backset was 17 mm.
    On the other hand, Transport Canada reported that a study 
commissioned by several Canadian insurance companies, conducted by Rona 
Kinetics and Associates, Ltd., entitled ``Head Restraint Field Study,'' 
concludes that HRMD is repeatable and an effective predictor of head 
restraint positions. Transport Canada has used HRMD for years and finds 
it to be a convenient and accurate tool.
    In addressing accuracy concerns, ICBC said that the HRMD yields a 
level of accuracy of <plus-minus>5 mm when used by competent, well-
trained operators. ICBC stated further that manufacturers have 
historically had to accommodate similar tolerance levels with other 
compliance testing based on the H-point machine. Further, according to 
ICBC, 1 degree in seat back variance yields a deviation of no more than 
3 mm as opposed to 13-28 mm as suggested by some commenters. In 
addressing Ford's comments on different measurement results for 
virtually identical vehicles, ICBC stated that the two seats, while 
identical in theory, had different upholstery materials (leather and 
cloth) and also had different stitching patterns. As a result, the 
deviation between two seat measurements was 5 mm, which ICBC noted was 
enough to warrant awarding two different vehicle head restraint 
ratings.
    The SAE cautioned that the current H-point machine is undergoing 
considerable revision and the ICBC device could not be mounted on the 
new manikin. It argued that if the ICBC device were mandated, the 
manufacturers would be forced to use an otherwise outdated compliance 
device. Magna suggested that we consider the ASPECT (Automotive Seat 
and Package Evaluation and Comparison Tools) manikin as a compliance 
tool, instead of the HRMD.
    According to several manufacturers, including Magna, Porsche and 
Honda, a more appropriate measurement methodology would utilize SgRP. 
The SgRP is a theoretical point in the vehicle, usually representing 
the most rearward normal riding or driving H-point, as determined by 
the manufacturer. Further, they requested that a CAD drawing be used to 
obtain the most precise height and backset measurements. Specifically, 
Magna recommended that we use a CAD design tool to measure the required 
head restraint height. Similarly, Porsche has asked us to consider 
virtual measurement methods using Ramsis software. Honda suggested that 
the HRMD assembly be translated into electronic data and the 
measurements be taken electronically.
    UMTRI also recommended a height and backset measurement technique 
that uses the H-point as the reference. Once the H-point is 
established, a 165 mm sphere would be rolled vertically. The most 
rearward part of the sphere would map a path. From this path, the 
height of the head restraint and backset can be calculated at any 
height. The procedure could be done at any position of head restraint 
adjustment.
    In response to the suggestion of alternative measuring devices, 
ICBC

[[Page 74861]]

commented that it developed the HRMD because there were no similar 
tools available to produce accurate and repeatable measurements. It 
claimed the HRMD is more biofidelic than other similar or proposed 
devices, because it has an articulating neck joint that approximates 
the C7-T1 joint (i.e., the location on the spine between the most 
inferior cervical vertebra and the most superior thoracic vertebra). 
This allows the operator to approximate human posture at any seat back 
angle. The ICBC noted that there are 35 HRMD devices now in use, 
arguing this makes it a well-accepted compliance tool; the device is 
readily available from ICBC. Further, the HRMD represents a small cost 
for demonstrating compliance.
    ICBC further stated that despite industry comments to the contrary, 
the ICBC device does not add extra weight to the H-point machine. The 
ICBC weight closely approximates the weight of the 50th percentile head 
and neck. No extra weight is added to the H-point machine because some 
upper torso weights are removed from the manikin to compensate for the 
ICBC device. Specifically, the HRMD with two ``replacement weights'' 
substitutes for 4 out of 8 H-point machine weights.
    Generally, ICBC suggested that the HRMD device be used instead of a 
computer-based method of determining compliance. However, if some sort 
of electronic compliance were implemented, it believes Honda's proposal 
is preferable because it contemplates the use of ``virtual'' HRMD, 
which most closely replicates actual human seating positions. In 
response to SAE's concern with the forthcoming development of the 
revised J826 H-point machine, ICBC pledged full cooperation to ensure 
that HRMD can fit the future H-point machine.
    RCAR submitted a test procedure it developed for head restraint 
measurement that uses the HRMD. It recommended using its measurement 
procedures in determining compliance with the new criteria.
    Agency response: Despite the objections of numerous commenters, we 
have decided to adopt the HRMD for our compliance tests. Under the 
current version of FMVSS No. 202, the manufacturers provide NHTSA with 
the theoretical location of the SgRP with respect to some vehicle 
reference point. The new rule eliminates the need for obtaining a 
theoretical point from the vehicle manufacturer, determined by a CAD 
technique, because the HRMD defines the H-point of the specific seat 
being measured. In addition, the H-point can be found for any position 
of seat cushion adjustment, thus allowing the worst-case head restraint 
height to be measured.
    We conclude that the ICBC comments related to a CAD technique for 
determining head restraint geometry are the most compelling. 
Specifically, ICBC noted that various techniques suggested by the 
manufacturers all have the limitation of not measuring the actual seat, 
as it exists in the real world. Instead, they rely upon measurements 
made in a virtual or computer generated environment. The current FMVSS 
No. 202 height measurement technique has the same weakness, as it uses 
the SgRP determined by drawing techniques and a seat position defined 
by the manufacturer. While we appreciate the numerous benefits 
associated with CAD techniques in the design of vehicles and their 
components, we believe these techniques are not yet appropriate for a 
regulatory environment. Any CAD method would not only have to rely on 
an adequate model of the J826 manikin, but, even more importantly, an 
accurate representation of the vehicle seats. Each seat model would 
require extensive validation to assure that the CAD results would match 
the results achieved by direct measurement. A design change such as new 
upholstery foam or covering material would likely require a re-
validation of the model. This type of process is appropriate for 
research or product development, but is not yet ready for regulatory 
purposes.
    In regard to the backset and height measurement technique suggested 
by UMTRI, we conclude that the technique is useful to the extent it 
allows backset to be calculated for an occupant of any height rather 
than just for a 50th percentile male. However, we are not aware of any 
physical device currently available to map out the continuous backset. 
Thus, in order for the agency to adopt the UMTRI method, a CAD 
technique would have to be adopted, unless a new physical testing 
device is developed. We have rejected the use of CAD methods for the 
reasons specified above.
    Numerous commenters questioned the accuracy of the HRMD device. 
Specifically, the manufacturers questioned repeatability of 
measurements and stated that the HRMD is incapable of accounting for 
foam, trim, actual H-point, temperature, and humidity variations. 
However, ICBC submitted data showing accuracy of <plus-minus>5 mm. 
Because ICBC has a significant amount of experience in using the HRMD, 
its assertion that the overall level of repeatability of its device is 
within a <plus-minus>5 mm, when used correctly, is persuasive.
    We also conclude that ICBC provided adequate explanation for the 
discrepancy between the measurement results for Ford Taurus and Mercury 
Sable, a discrepancy that would not have been found using a CAD 
technique. Different upholstery and stitching patterns can result in 
different measurements. If these differences are significant, the 
difference in both height and backset may be significant. Further, a 
Transport Canada study concluded that the HRMD is repeatable and an 
effective predictor of head restraint position of humans. Transport 
Canada has used the HRMD for years and finds it to be a convenient and 
accurate tool. There are at least 35 HRMDs now in use, and the head 
form is readily available from ICBC.
    We found that while measuring head restraint geometries with the 
HRMD for use in a cost study, the backset measurements varied by a 
total of 10 mm when NHTSA's Vehicle Research and Test Center (VRTC) 
repeated the measurement of a single vehicle seat 3 times. This is 
consistent with the ICBC statements showing <plus-minus>5 mm accuracy. 
Further, experience indicates that greater familiarity with the device 
reduces the variability of measurements. Thus, the measurement variance 
shown in the Honda data (10 mm for 1 operator and 17 mm for 3 
operators) may have been due to a lack of familiarity with HRMD.
    Porsche stated that the HRMD device could not be properly 
positioned in the seats that have ``strong-contoured shape,'' therefore 
preventing accurate measurements. However, Porsche did not provide any 
data comparing the position of HRMD head form to the position of an 
actual occupant's head in one of its ``strong-contoured shape'' seats. 
We believe that Porsche must currently use the SAE J826 manikin to find 
the reference H-point position of the Hybrid III 50th percentile 
manikin for frontal barrier tests in FMVSS No. 208, and therefore has 
some familiarity with how to properly position the device. Generally, 
we believe that experienced operators will not encounter any 
difficulties in measuring seating structures with HRMD.
    Several comments suggested that the HRMD device is insufficiently 
biofidelic. However, we are persuaded by ICBC's comments that HRMD is 
more biofidelic than other similar devices because it has an 
articulating neck joint that approximates the C7-T1 joint. This design 
feature allows the operator to level HRMD's head regardless of the seat 
back angle, similar to the posture of a human occupant, resulting in 
superior accuracy of backset measurement. While

[[Page 74862]]

we are aware that the SAE has updated the J826 manikin in the form of 
the ASPECT manikin in July 2002, this new device has yet to be 
evaluated by the agency for incorporation into FMVSS.
    Based on the comments and analysis presented above, we have decided 
that the HRMD will be the measurement tool.

IX. Maximum Gap Allowance and Removability

a. Maximum Gap Allowance

    The NPRM proposed allowing for gaps within the perimeter of the 
front (anterior) surface of head restraints in order to provide for 
better rearward visibility for drivers.\47\ The NPRM proposed two types 
of maximum gap allowances. First, for both integral and adjustable head 
restraints, a gap within the perimeter of the head restraint could not 
exceed 60 mm. Because there may not be a clear distinction between the 
end of the seat back and the beginning of the head restraint in 
integral head restraints, compliance with this first gap limit is 
determined by measuring any point on the front surface of the seat back 
540 mm above the H-point and within the minimum head restraint width. 
We note that ECE 17, Paragraph 5.8, similarly regulates gaps at heights 
above 540 mm.
---------------------------------------------------------------------------

    \47\ The gap limits are applied between two vertical 
longitudinal planes, which are one half the minimum head restraint 
width from the head restraint centerline. Thus, any part of the 
front surface of the head restraint outside of the minimum width 
requirement is excluded from the gap limits.
---------------------------------------------------------------------------

    The second type of gap allowance was between an adjustable head 
restraint in its lowest position and the seat. There were two levels of 
requirements. First, an adjustable head restraint in its lowest 
position must have some backset position in which the gap between the 
seat and the head restraint was less than 25 mm. Second, an adjustable 
head restraint in its lowest position, with the backset in any position 
of adjustment, must not have a gap between the head restraint and the 
seat back of greater than 60 mm.
    The HRMD used for measuring backset has a probe that slides out of 
the center of the back of the head form. The probe is relatively thin 
laterally, and cannot adequately measure gaps within the perimeter of 
the head restraints and between the head restraint and the seat. 
Accordingly, the gaps were to be measured with a 165 mm diameter sphere 
placed against them.
    Gaps within the perimeter of the restraint. Nearly all industry 
commenters concurred with the proposal for a 60 mm limit for gaps 
within the perimeter of any head restraint, because it was consistent 
with ECE 17 requirements. There were no significant objections to the 
specific value of 60 mm. The Alliance indicated that while it did not 
know of any data supporting the need for the 60 mm gap limit for a seat 
with an integral head restraint, it did not object because the 
dimension matched the ECE limit. Honda, GM and DaimlerChrysler stated 
that they did not have any data addressing the 60 mm gap limits but 
supported harmonizing the requirement with ECE 25.
    In contrast, Advocates argued against allowing gaps of any size, as 
it was not convinced by the NPRM's arguments pertaining to the proposed 
gap allowances.
    Agency response: NHTSA has adopted the 60 mm gap limit rather than 
allowing for gaps of any size in the perimeter of the head restraint, 
as is the case under the current standard. In doing so, NHTSA does not 
harmonize the final rule with the ECE regulation merely for the sake of 
harmonization, as Advocates alleged. Rather, the agency is harmonizing 
the requirement because while we believe that some gaps are beneficial 
for visibility, we also believe that gaps of excessive size can 
significantly reduce effectiveness of head restraints through 
effectively increasing backset. Absent evidence that the ECE 17, 
Paragraph 5.7 requirement is ineffective at balancing the need for 
adequate rearward visibility and a reduction in injuries, NHTSA is 
adopting the same 60 mm gap limit.
    Gaps between seat back and adjustable restraint. The Alliance 
stated that it did not understand why a limit of 25 mm would be placed 
on any gap between the top of the seat and the bottom of the head 
restraint. It stated that while the 25 mm gap limit is identical to the 
ECE 17 limit, the measurement procedure utilizing the 165 mm diameter 
sphere differs from that in the ECE regulation. ECE 17 only measures 
the distance directly between the bottom of the head restraint and the 
top of the seat back. The Alliance recommended NHTSA adopt a linear 
measurement technique employed by ECE 17.
    Honda commented on gap requirements in ECE 25 instead of ECE 17, 
and the gap limits proposed in the NPRM. Specifically, Honda submitted 
a figure showing that its Accord sedan with the head restraint in its 
lowest position complies with ECE 25 with no gap between the top of the 
seat back and the bottom of the head restraint. However, the Accord 
would not meet the proposed gap limit, because its gap would measure 
44.8 mm. That is, the Accord head restraint in its lowest position has 
a 44.8 mm gap in the front surface between the seat back and head 
restraint when measured with the 165 mm diameter sphere. Accordingly, 
Honda requested complete harmonization with the gap requirements in ECE 
25, which would exclude use of the 165 mm sphere for this gap limit. 
Honda stated that some of its current seat designs would need drastic 
modifications in order to comply with the 25 mm gap limit, as measured 
with the 165 mm sphere.
    GM remarked that if NHTSA considers gaps of 60 mm acceptable within 
a restraint, the need for a 25 mm gap limit between the top of the seat 
and the bottom of the head restraint is unclear. DaimlerChrysler said 
that the 25 mm gap limit, as applied to rear head restraints, could 
lead to an additional loss in visibility. DaimlerChrysler also stated 
that a head restraint making direct contact with the seat back with a 
15 mm radius at the head restraint's bottom front contour and seat 
back's top front contour would create a gap of more than 25 mm. AIAM 
expressed its support for all the proposed gap limits except for the 25 
mm limit on gaps between the seat and the head restraint for adjustable 
head restraints with adjustable backsets. In view of this, AIAM argued 
that unless NHTSA could show a safety necessity for backset 
adjustability, NHTSA should only mandate the head restraint 
specifications independent of backset adjustability, provided that the 
adjustability does not have a material effect on height. AIAM 
advocated, then, that the final rule should require that the gap be 
less than 25 mm at any position of backset adjustment, which is more 
stringent than the NPRM.
    In contrast, Advocates opposed allowing gaps of any size between an 
adjustable head restraint and seat back in any position of adjustment. 
Johnson Controls expressed support for a universal 25 mm gap limit 
between the lower edge of a head restraint and the seat for both 
adjustable and integral head restraints.
    Agency response: In consideration of comments submitted by GM and 
other manufacturers, we have decided not to adopt the 25 mm maximum gap 
limit for adjustable head restraints in their lowest height position 
and a single position of backset adjustment. After considering the 
comments, NHTSA does not believe there is a safety benefit in measuring 
the smallest space between the bottom of an adjustable head restraint 
and top of the seat back because an occupant's head does not 
necessarily come into contact

[[Page 74863]]

with these areas. Instead, a limit on gaps will focus on gaps in the 
front surface of the head restraint, i.e., the area designed to 
restrain an occupant's head in a rear impact collision. The maximum gap 
limit for adjustable head restraints in their lowest position and any 
backset position will be 60 mm. Thus, there is a single requirement for 
this type of gap, regardless of backset adjustability.\48\
---------------------------------------------------------------------------

    \48\ We note that all head restraints subject to this final rule 
must meet the backset limit of 55 mm irrespective of 60 mm gap 
allowances.
---------------------------------------------------------------------------

    Gaps between seat back and raised restraint. Comments were 
requested on whether there should be a maximum gap allowance between 
adjustable head restraints and the seat back when the restraint is in a 
raised position. NHTSA indicated in the NPRM that if such a maximum gap 
limit were adopted, most adjustable head restraints currently on the 
market would not meet it.
    The Alliance and Johnson Controls said that they did not know of 
any data supporting the need for this limit or any data indicating that 
such a requirement would be appropriate. DaimlerChrysler commented that 
there is not any known safety benefit related to such a limit. When 
head restraints are misadjusted, DaimlerChrysler said, they are most 
often in the full down position. Because a maximum gap limit between 
the seat and head restraint in its highest position potentially would 
only benefit shorter drivers who would most likely be positioned in a 
seat with a head restraint in the lowest position, DaimlerChrysler 
surmised that the maximum gap allowance is unnecessary. Taller drivers, 
according to DaimlerChrysler, would face no risks from this gap because 
their potential risks exist in head restraints not positioned high 
enough, not in head restraints adjusted too high.
    AIAM also commented with respect to the effect of a maximum gap 
limit on taller or shorter drivers. It commented that if a seat 
represents the lower stop of a head restraint for which the highest 
possible position is 800 mm, the gap could only be 50 mm unless a head 
restraint provides for positions higher than 800 mm. If higher 
positions are possible, AIAM asserted that such a head restraint would 
only be positioned higher than 800 mm when a taller person occupies the 
seat. AIAM acknowledged that there might be instances in which a 
shorter person sits in a seat with a head restraint adjusted in the 
higher position, but it commented that in such instances, the 
likelihood of injury to shorter occupants is unknown.
    Advocates believed that NHTSA should require adjustable head 
restraint designs such that no gap would exist when the head restraint 
is placed in its uppermost position.
    Agency response: After considering the comments, NHTSA concludes 
that there is no need to adopt a maximum gap limit when the head 
restraint is in its uppermost position. Transport Canada data indicate 
that head restraints are usually improperly adjusted too low rather 
than too high. AIAM's comment suggests that any minimum gap limit could 
have the effect of eliminating head restraint designs providing 
positions higher than 800 mm, which would adversely affect the 
protection offered for taller adults.

b. Removability

    The NPRM proposed prohibiting the removability of head restraints 
in front seats ``solely by hand,'' but allowed removability of rear 
seat head restraints in this manner. The NPRM noted that, given the 
lower occupancy rate of rear seats than of front seats, a rule allowing 
rear seat head restraints to be removed by hand might be warranted if 
it would have a positive effect on visibility.
    A number of commenters opposed any prohibition against the 
removability of head restraints, front or rear. AIAM asserted that all 
head restraints should be removable by hand in order to improve rear 
vision, cargo carrying, and overall functionality. In addition, it 
contended that allowing removability by hand would help prevent 
permanent damage to head restraint mountings caused when occupants use 
tools to temporarily remove head restraints that are non-removable by 
hand. Nissan asserted that there are potential production difficulties 
arising from front head restraint non-removability. Installing a large 
seat fitted with a head restraint into a small vehicle, Nissan 
asserted, might be an arduous task.
    Honda wanted all restraints to be removable by hand, out of concern 
that non-removable head restraints would limit seat design flexibility. 
Honda believed that a non-removability prohibition would prevent it 
from offering the ``fully flat seat'' option in its CRV model 
vehicle.\49\
---------------------------------------------------------------------------

    \49\ In alternative, Honda recommended that we allow head 
restraint removal by use of some tool included with the vehicle.
---------------------------------------------------------------------------

    In contrast, some commenters supported prohibiting head restraints 
from being removable by hand. Magna expressed concern that if head 
restraints were removable, they might not be replaced or correctly 
reinstalled. Advocates believed that head restraint removal and misuse 
would be similar to occupants placing both arms over shoulder belts or 
placing shoulder belts behind their torsos, effectively defeating the 
safety purposes of the safety system. DaimlerChrysler concurred with 
making front seat head restraints more difficult to remove than rear 
seat restraints because of their safety benefits and the absence of a 
need to remove them for visibility and functionality reasons. 
DaimlerChrysler also agreed that there should be some means to remove 
front head restraints for purposes such as seat cover installation. 
However, DaimlerChrysler wanted the word ``tool'' to be interpreted as 
including the mechanism in their current vehicles requiring two hands 
to operate.
    A majority of industry commenters wanted NHTSA to allow 
removability of rear head restraints in the final rule. Ford believed 
that removability of rear head restraints would allow occupants to fold 
seats to increase space and would reduce possible incompatibility with 
child restraints. Ford stated that while many vehicles are currently 
designed with head restraints that are removable by hand, Ford does not 
know of any data regarding misuse or improper adjustment of head 
restraints caused by hand removability. DaimlerChrysler believed that 
NHTSA should permit rear seat head restraint removability to facilitate 
increased vehicle utility and rearward visibility.
    Agency response to comments on head restraint removability: After 
considering comments, NHTSA decided to allow removability of head 
restraints solely by hand. However, for both front and rear optional 
head restraints, removal must be by means of a deliberate action that 
is distinct from any act necessary for adjustment. That is, the 
``action'' required for removal must be distinct from that required for 
adjustment. For example, the head restraint may be removed by 
depressing a special button or operating a lever located somewhere on 
the head restraint or the seat back. However, the action involved in 
adjusting head restraints must be different. This insures that head 
restraints are not accidentally removed when being adjusted. The new 
removability requirement uses language very similar to that in ECE 17, 
Paragraph 5.13.
    We are establishing the new head restraint requirements to ensure 
that vehicle occupants receive better protection from whiplash and 
related injuries. To achieve this purpose, the agency wants to take 
reasonable steps to increase the likelihood that a head restraint is 
available when needed. If head restraints were too easily

[[Page 74864]]

removable, chances are greater that they will be removed. That, in 
turn, increases the chances that the restraints might not be 
reinstalled correctly, if at all. By prohibiting removability without 
the use of deliberate action distinct from any act necessary for 
adjustment, the likelihood of inadvertent head restraint removal will 
be reduced, thus increasing the chances that vehicle occupants will 
receive the benefits of properly positioned head restraints.
    While NHTSA wants to increase the likelihood that a head restraint 
is available when needed, we also want to ensure that head restraints, 
especially in the rear outboard designated seating positions, can be 
removed in order to improve rear visibility, child restraint 
accommodation, and cargo carrying capacity. In certain very limited 
circumstances discussed by DaimlerChrysler, it may also be necessary to 
remove front head restraints. We are also persuaded by AIAM's comments 
concerning potential damage to head restraint mountings and locking 
mechanism that could be caused by occupants using a tool to temporarily 
remove the head restraints. Further, we believe that unforeseen 
problems could arise if the tool provided by the manufacturer for the 
purpose of removing head restraints is lost or otherwise unavailable at 
the time the head restraint must be removed. Because of these concerns, 
we decided not to adopt a proposed requirement that would have mandated 
that head restraints could not be removed without the use of a tool.
    We have considered Advocates' comments that head restraint removal 
would defeat the purpose of the safety device. We believe that out 
approach strikes a balance between the need to ensure that a head 
restraint is available when needed and the need to improve rear 
visibility, cargo carrying capacity and accommodate child restraints. 
Further, with respect to rear seats, prohibiting head restraint removal 
when no head restraint is required could have the effect of encouraging 
manufacturers to design vehicles without rear head restraints. Our 
preference is that when possible, manufacturers install optional rear 
head restraints.

c. Non-use Positions

    In connection with its proposal to mandate rear head restraints, 
NHTSA proposed to address concerns about the potential effect of those 
head restraints on the driver's view to the rear by allowing them to be 
foldable or retractable if they met certain requirements. Specifically, 
if a head restraint was adjusted to a ``non-use'' position (any 
position in which a head restraint's minimum height was less than the 
proposed 750 mm height or its backset was more than the 50 mm proposed 
backset), it would have been required to either return automatically to 
its proper use position when a dummy representing a person was placed 
in the seat, or give a person who occupied the seat an ``unambiguous 
physical cue'' of the improper head restraint position by significantly 
altering the torso angle of the occupant. If the head restraint was 
designed to return automatically from a non-use position to a normal 
use position, this had to occur when either a 5th percentile female or 
a 50th percentile male test dummy was placed in the seating position. 
To determine if the head restraint in a non-use position provided an 
``unambiguous physical cue,'' the SAE J826 manikin was to be placed in 
the seat position. The torso angle of the manikin would have been 
required to be at least 10 degrees closer to the vertical than when the 
head restraint was in a normal use position.
    Industry commenters uniformly favored a final rule permitting non-
use positions for rear head restraints. However, many stated that 
because non-use positions in current vehicle designs are obvious to 
occupants, NHTSA need not condition allowance of those positions upon 
either automatic repositioning or 10-degree torso angle displacement. 
GM contended that designing head restraints to fold forward into non-
use positions is not always feasible, especially given the proposed 254 
mm minimum rear head restraint width for bench seats. GM, Honda and 
others remarked that folding or retractable head restraints with 
automatic return capabilities might not be practical and could result 
in excessive cost.
    Other commenters asked NHTSA to permit methods different from the 
10-degree torso displacement angle to alert vehicle occupants to non-
use head restraint positioning. Specifically, VW and Honda advocated 
harmonization with ECE 17, Paragraph 5.5.3.3, which allows for head 
restraints to be retracted into non-use positions as long as this 
position is ``clearly recognizable to the occupant.'' Similarly, Ford 
stated it believed that the NPRM's 10-degree proposed displacement rule 
would be excessively burdensome and would require substantial redesign 
of seating systems.
    Several commenters opposed allowing non-use positions. State Farm 
suggested that NHTSA should only permit non-use positions for rear head 
restraints if NHTSA determines either visibility or child restraint 
incompatibility are issues meriting consideration. Advocates noted that 
automatically retracting or manually folding head restraints might 
malfunction or become stuck in a non-use position. Advocates opposed 
the proposal to the extent that it did not specifically require that 
non-use positions for rear head restraints remain limited to ones 
achieved by folding or retracting. Moreover, Advocates expressed doubt 
about the objectivity of the ``unambiguous physical cue'' as an 
occupant's indication of a non-use position, stating that the 
subjective standard would create the potential for ambiguous designs 
that would give rise to misuse.
    Transport Canada and Honda asserted that forward-folding head 
restraint designs might be misused in that an occupant may sit in the 
seat without returning the head restraint to an in-use position. Honda 
commented that smaller occupants might not recognize that the seating 
position moved 10 degrees closer to vertical is a warning of a non-use 
position. Instead, according to Honda, smaller stature occupants might 
consider the more upright position comfortable without understanding 
that the head restraint was positioned for non-use. In addition, 
Transport Canada stated that the proposal to require manufacturers to 
design their head restraints so that the torso angle of the SAE J826 
manikin at least 10 degrees changes when the head restraint is in a 
non-use position might bring about a low fulcrum, which would increase 
neck injury in a rear impact collision.
    Agency response: NHTSA does not believe that non-use positions for 
rear head restraints should be allowed without any limitations. 
Instead, there must be objective performance requirements established 
to reduce the chances of injuries stemming from misused head 
restraints. Accordingly, the final rule adopts non-use position 
requirements proposed in the NPRM, but with some modifications. 
Further, this rule changes the test procedure and the test device to be 
used in determining compliance. Specifically, we are adopting the 
following: (1) A head restraint in a non-use position must 
automatically return to a normal ``use position'' when the seat is 
occupied by a 5th percentile female dummy whose midsagittal plane is 
aligned within 15 mm of the head restraint centerline; or (2) a head 
restraint must be capable of manually rotating at least 60 degrees 
forward or rearward in a vehicle vertical longitudinal plane between 
the ``use position'' and the non-use position.

[[Page 74865]]

    The final rule does not require that the non-use positions cause a 
10-degree change of the torso angle of the J826 manikin. Our proposal 
was based on the premise that the non-use position should give the 
occupant an obvious physical cue when the head restraint is not 
properly positioned. We have reassessed this requirement in light of 
our decision not to mandate rear head restraints and to allow head 
restraints to be removable without the use of tools. Given those 
decisions, it would be incongruous to mandate a possibly complex seat 
mechanism to ensure that non-use positions provide a physical cue to 
the occupant in the form of a 10-degree change to the torso reference 
angle. The changes to the non-use position requirements will also 
address comments made by Ford, GM and Transport Canada with respect to 
complexity, inconvenience and possible neck injury risk increase 
associated with the proposed requirement of 10 degree change in the 
torso reference angle.
    We note that our requirements remain consistent with the ECE 17, 
Paragraph 5.5.3.3 to the extent that it mandates that a head restraint 
be capable of achieving a non-use position that is ``clearly 
recognizable to the occupant.'' With respect to Advocates' concerns 
that the ``unambiguous physical cue'' language in the NPRM was 
subjective, we note that unlike the ECE requirements, this rule 
provides an objective test procedure to assess the ``clearly 
recognizable'' factor. Specifically, if the head restraint is capable 
of rotating forward or rearward by at least 60 degrees to achieve a 
non-use position, it is deemed ``clearly'' in a non-use position. This 
restriction is necessary to clearly inform the occupant that the head 
restraint is available, but out of place.
    The final rule does not require that the rear head restraint 
automatically rotates the full 60 degrees or that the head restraint 
remains in this fully retracted position. In order to meet the strength 
requirements of this final rule, a head restraint that rotates rearward 
would likely need to have some mechanism that releases the head 
restraint from the position intended for occupant use. Accordingly, the 
head restraint would only be placed in a non-use position because of a 
particular need. It is possible that some vehicle operators may not 
rotate such head restraint fully. However, we believe in most instances 
the rear head restraint would be rotated the entire 60 degrees because 
this would best accommodate the vehicle operator's particular interest 
in adjusting the head restraint to a non-use position.
    For head restraints that automatically return to a use position 
when occupied, the final rule does not require the use of a 50th 
percentile male dummy in addition to the 5th percentile female dummy, 
as was the case in the NPRM. Based on our review of current sensing 
technology, we assume the head restraint systems that will be designed 
to automatically return to a normal use position when a seat becomes 
occupied will use weight or optically based occupant-sensing 
technology. Thus, the use of the taller and heavier 50th percentile 
male dummy would be redundant since it would be more difficult to 
detect the shorter and lighter 5th percentile female dummy.\50\
    In response to Transport Canada and Honda's concern with respect to 
fold-forward designs, we note that non-use positions can be achieved by 
means other than fold-forward head restraints. Further, in allowing 
this type of design, we anticipate that a forward-folded head restraint 
will provide both a physical and visual cue to the occupant to properly 
position the head restraint.\51\
---------------------------------------------------------------------------

    \50\ We believe Advocates' statement that automatic return head 
restraints may fail to function overstates the safety concern. 
Although such failures are possible, they can occur with any safety 
mechanism.
    \51\ We note that Volvo uses such a design in their S60 and S80 
sedans.
---------------------------------------------------------------------------

    NHTSA concludes that the allowing for non-use positions will 
facilitate better rearward visibility because the manufacturers will be 
able to design optional rear head restraints that fold or retract when 
rear seats are unoccupied, encouraging manufacturers to install rear 
head restraints.

X. Position Retention

    In the NPRM, we proposed two loading test procedures to ensure that 
the head restraints remain in their position of adjustment (lock) upon 
application of force. These test procedures ensure that the head 
restraints can withstand the forces associated with normal pressure 
applied upon the head restraint during ingress and egress, as well as 
in the event of a crash. We note that while the ECE 17, Paragraph 5.1.1 
requires locks on adjustable head restraints, it does not mandate that 
these locks meet vertical and horizontal position retention 
requirements to insure their functionality. In contrast, we proposed 
vertical and horizontal position retention requirements to ensure test 
objectivity associated with retention lock requirements.
    The first test provided for the vertical, downward application of 
force upon a head restraint when placed at its highest position of 
adjustment and not less than, but closest to 800 mm for front seats and 
750 mm for rear seats. A head restraint with an adjustable backset must 
meet the height retention requirements in any position of adjustment. 
Under the proposed procedure, a small, 50 N initial load would first be 
applied to the head restraint to provide a reference position for the 
head restraint. The reference position would be measured to eliminate 
variability associated with the soft upholstery of the head restraint. 
Next, a larger load would be applied to test the locking mechanism. The 
load would be increased to 500 N and held for 5 seconds. The load would 
then be reduced to the level of 50 N, at which point the head restraint 
would be required to return to within 13 mm of the initial reference 
position.
    The second test procedure provided for a rear (posterior--rear with 
respect to the direction that the seat is facing) application of force 
perpendicular to the torso line. Testing for this position retention 
requirement to the rear is performed in the context of the displacement 
and ultimate strength requirements. This test is performed at any 
position of backset adjustment (if applicable) with the height adjusted 
to not less than, but closest to 800 mm for front seats and 750 mm for 
rear seats. In this instance, the NPRM proposed that a load producing a 
373 Nm moment be applied to the back pan about the H-point to establish 
a displaced torso reference line. Next, a force producing 37 Nm would 
be applied to the head restraint to provide a reference position. The 
load would then be increased until it produced 373 Nm moment about the 
H-point and this load would be held for 5 seconds. At this point, any 
displacement beyond the displaced torso reference line would be limited 
to 102 mm. The head restraint load would then be reduced back to the 
level of 37 Nm, at which point the head restraint must return to within 
13 mm of the initial reference position. To satisfy the ultimate 
strength requirement, the head restraints must be capable of providing 
resistance to an 890 N load for a period of 5 seconds.
    We stated in the NPRM that the 500 N downward force and 373 Nm \52\ 
rearward moment are representative of the peak loads likely to be 
encountered in moderate to severe rear impacts. The agency has reviewed 
upper neck shear loading from 33 rigid moving barrier,

[[Page 74866]]

rear impact (48 km/h (30 mph)) FMVSS No. 301 tests and found the 
average maximum load caused by the head being loaded in the forward 
direction with respect to the torso is 351 N. This direction of shear 
load is a good indicator of head restraint loading on the head and, 
therefore, head loading on the head restraint. Thus, the 373 Nm 
rearward moment and 500 N downward force are representative of the peak 
loads likely to be encountered in moderate to severe rear impacts. We 
asked for comments on the appropriateness of load values proposed for 
the two tests as well as the role of the retention locks in preventing 
head restraint maladjustment.
---------------------------------------------------------------------------

    \52\ For an 800 mm high head restraint, the 373 Nm moment is 
achieved by applying a load 65 mm below the top of the head 
restraint. Thus the applied load is 507 N = 373 Nm/0.735 m.
---------------------------------------------------------------------------

    Several commenters disagreed with the proposed height retention 
test requirement. Johnson Controls commented that it is unaware of any 
situations in which head restraints would move downward during 
accidents and thus does not understand the need for the vertical 
position retention test. In its opinion, the new requirement would 
unnecessarily complicate the locking adjustment mechanism, which 
consumers already find hard to use. Other commenters requested that 
NHTSA alter or simplify its height retention requirement. GM 
recommended that the testing criteria require that the head restraints 
simply ``remain in their adjusted position'' after an application of 
the required loads. According to GM, a more specific requirement that 
the head restraint be within 10 mm of its initial position, after 
position retention tests, might be difficult to meet because of 
possible compression of the head restraint foam. Similarly, 
DaimlerChrysler stated that the proposed height-retention test is 
inadequate to account for low recovery rate of crushable ``friendly'' 
materials designed to cushion an occupant's head upon contact.
    Both Magna Seating Systems and DaimlerChrysler submitted the same 
test data showing a vertical load test in which an upholstered head 
restraint returned to within 22 mm of its initial position. The same 
head restraint with the upholstery removed returned to within 1 mm of 
its initial position. According to DaimlerChrysler, instead of testing 
the adjustment mechanism integrity, the proposed test indirectly 
measures the entire seating system, which includes energy-absorbing 
components. Therefore, a more appropriate solution is to simply measure 
head restraint position at the adjuster mechanism. Additionally, 
DaimlerChrysler stated that 500 N vertical load for position retention 
test may be excessive and unnecessarily harsh, and may end up requiring 
manufacturers to produce seats that are unnecessarily rigid and would 
result in potential harm to the passengers.
    The Alliance generally agreed with most aspects of the proposed 
head restraint loading procedure. However, it was not aware of any 
reasons for the 5-second ``hold'' requirement in the position retention 
test. The Alliance recommended that the ``hold'' requirement be 
completely stricken or, in the alternative, limited to one second. AIAM 
was likewise of the opinion that the stringent height retention 
requirements would in fact discourage adjustability, because a 
mechanism meeting such requirements would be unduly difficult to design 
and use. Therefore, it recommended that the height retention 
requirement be eliminated from the proposed rule.
    Honda commented that the problem with the vertical load test 
procedure is the shape and initial position of the loading device. 
Honda believed that this would cause the loading sphere to slip off of 
the head restraint. Honda recommended that loading test for height 
retention requirement be performed using a flat plate as opposed to a 
head form. Honda commented that no further height retention position 
testing (other than upper most position) should be tested, because the 
upper most position can be regarded as the worst position.
    VW stated, ``[s]ome Volkswagen and Audi vehicles provide head 
restraint adjustment above 800 mm to accommodate tall occupants, but in 
this situation a locking system at the maximum height is not 
provided.'' They requested that the height retention requirement not be 
applied to position of adjustment above 800 mm. They contended that 
when a seat back is folded the head restraint might interfere with the 
roof and cause damage to a locked head restraint.\53\
---------------------------------------------------------------------------

    \53\ Volkswagen also commented on the backset retention 
requirement. They asked that the agency clarify their interpretation 
that the initial reference position to which that the test device 
must return within 10 mm (now 13 mm in the final rule) is the 
position the test device obtains after the 37 Nm reference load. The 
agency confirms this interpretation of the test procedure.
---------------------------------------------------------------------------

    In contrast, IIHS commented that the height retention test is 
necessary to prevent poor head restraint designs that, for example, 
tend to ``fall'' to their lowest position during normal road movement. 
IIHS cautioned that many occupants place their hand or arm on the head 
restraints in getting into and out of the vehicles, thus applying 
vertical and non-vertical pressure on the restraint mechanism.
    There were no comments regarding the likelihood of misadjustment 
due to the absence of retention locks. There were no comments regarding 
the horizontal displacement requirement, other than the IIHS comment 
that the NPRM did not propose a horizontal loading requirement.
    Agency response: We have decided to adopt the position retention 
tests, both in the vertical and rearward directions, largely as 
proposed. As previously stated, ECE 17 requires locks on adjustable 
head restraints but does not mandate that these locks meet vertical and 
horizontal position retention requirements to insure their 
functionality. However, we find it necessary to require a certain 
minimal level of performance to ensure that the retention locks perform 
their function. Accordingly, the vertical and horizontal position 
retention requirements of this final rule apply to all front outboard 
head restraints and voluntarily installed rear outboard head 
restraints.
    We proposed performance requirements for adjustable head restraints 
to assure that they remain locked in a specific position and are not 
unduly difficult to properly adjust. A 1982 NHTSA study found that the 
effectiveness of integral head restraints was greater than adjustable 
head restraints. The study concluded that the difference in 
effectiveness was due, in part, to adjustable head restraints being 
improperly positioned. Furthermore adjustable restraints can be pushed 
down inadvertently during occupant ingress and egress, and can collapse 
in a collision. Adjustment retention locks can mitigate this problem by 
helping to retain the adjusted position. Our new height and backset 
requirements are expected to improve performance of all head 
restraints. The performance of adjustable head restraints will be 
further improved if steps are taken to ensure that a restraint remains 
locked in a position selected by the user.
    Today's rule requires that the head restraints remain within 13 mm 
of their vertical and horizontal position under the application of a 
downward and rearward force. For front seats, the height position 
retention requirements must be met at any backset position of 
adjustment and with the head restraint at a height not less than, but 
closest to 800 mm, and at the highest position of vertical adjustment. 
For optional rear seats, the height position retention requirements 
must be satisfied at a height not less than, but closest to 750 mm and 
at the highest position of vertical adjustment. The horizontal position 
retention requirements must be met at the height of 800 mm for front

[[Page 74867]]

head restraints and 750 mm for rear head restraints.
    We are not persuaded by the arguments presented by GM and the 
Alliance related to the load hold time of five seconds. These 
commenters argue that a 5 second hold time is not consistent with ECE 
17 requirements. Instead, they suggest a one second limit. We believe 
the ECE requirements are insufficient in this regard in that they do 
not specify a loading rate or hold time. Despite our attempts to bring 
the new rule into harmony with the ECE regulations when adopting a 
requirement already covered by the ECE, there are instances in which we 
need to further clarify the test compliance procedure to provide an 
objective measurement, as required by statute. This is one of those 
instances. We do not believe a 5 second hold period is onerous and have 
adopted it as part of the final rule. We further note availability of 
strong and properly functioning retention locks should not have any 
negative effect on occupants' ability to properly adjust their head 
restraints.
    We disagree with VW's objection to head restraints locking in the 
highest adjusted position above 800 mm. To the extent that such an 
adjustment position is provided, it would be intended to protect the 
tallest occupants. However, without the ability to lock in this 
position, the head restraint could slip down to the 800 mm position or 
perhaps even lower during normal use, or in a rear impact. Thus, the 
head restraint would not offer the intended protection, while giving 
these taller occupants the impression that they are well protected. We 
are not persuaded by Volkswagen's argument that the locking mechanism 
may be damaged if the front seat head restraint comes in contact with 
the vehicle roof when folded forward for rear seat access. We 
acknowledge that in some vehicles this interference between the roof 
and head restraint may exist. In fact, such interference may exist 
between rear seat head restraints and more forward seats. However, we 
are not convinced that such contact would be damaging to the locking 
mechanism. If a manufacturer were concerned about damage to their 
locking mechanism, two solutions would be to either increase the 
robustness of the lock or to decrease the spring load in the seat back 
folding mechanism. Another design alternative discussed above in the 
context of non-use positions, although more mechanically involved, 
would be a design that disengages both the seat back and head restraint 
simultaneously.
    We proposed a 10 mm performance limit on the return position of the 
actual loading device to the reference point because we considered this 
to be the most objective method of determining the actual performance 
of locks. Some vertical loading data provided by the industry indicated 
a return position as much as 22 mm from the initial position. No 
similar data were provided for the horizontal loading test. In order to 
verify that the performance value selected for the position retention 
requirement is reasonable, we performed a series of static tests on 
several seats. The tests were performed at General Testing Laboratories 
(GTL), under the FMVSS No. 202 compliance-testing contract. The tests 
were performed in January 2002, on five MY 2001 vehicles.\54\
    The test program assessed the ability of current head restraint 
designs to comply with the position retention requirements. We tested 
feasibility of the 10 mm limit on displacement from the initial 
position. Both the height retention and backset retention were tested. 
(See Table 1.) All head restraints were vertically adjustable and one 
(Mercedes E320) had rotational adjustment.
---------------------------------------------------------------------------

    \54\ For complete test results, please see Docket No. NHTSA-
2000-8570-60, 61, 62, 63, 64.
---------------------------------------------------------------------------

    Table 1 shows the results of the height position retention tests 
and Table 2 shows the result of the backset position retention tests. 
One determination made by analysis of the test results was that the 
head restraint should not be allowed to displace more than 25 mm during 
the application of a pre-load to account for foam compression and other 
mechanical tolerances in the head restraint attachment as well as the 
situation in which the locking mechanism is so weak it cannot resist 
the preload.
    The test results suggest that the backset displacement is less than 
the height displacement if the characteristics of the vehicle seat are 
accounted for. Therefore, if a single compliance value is selected for 
both the backset and height retention, we believe it is reasonable to 
allow the results of the height retention tests to drive the selection. 
However, if one does not account for seat characteristics, the 
horizontal displacement may be larger because of those characteristics.
    Based on this limited data set, we believe that it is reasonable to 
alter the position retention tests to allow the seat back frame to be 
braced. Further, we have determined that the displacement limit after 
full load and return to preload should be increased to 13 mm from 10 
mm. We believe using the limit of 13 mm would allow most vehicles to 
comfortably meet the requirement for both the height and backset 
retention. Therefore, we do not agree with DaimlerChysler's comments 
that suggested the 500 N vertical load for the position retention test 
is excessive.

   Table 1.--Height Position Retention, Final Displacement Values (mm)
------------------------------------------------------------------------
                                                      Final displacement
         Reference load              Vehicle model            (mm)
------------------------------------------------------------------------
50 N--not braced................  Mercedes E320.....  6.4
50 N--not braced................  Honda Civic.......  21.8
50 N--braced....................  Toyota Echo.......  11.4
100 N--not braced...............  Dodge Stratus.....  24.0
100 N--braced...................  Buick LeSabre*....  Moved at Reference
                                                       Load[dagger]
------------------------------------------------------------------------
* Detents but no locking mechanism.
[dagger] No lock.


[[Page 74868]]


  Table 2.--Backset Position Retention, Final Displacement Values (mm)
------------------------------------------------------------------------
                                                                Final
           Reference load                Vehicle model      displacement
                                                                 (mm)
------------------------------------------------------------------------
50 N--not braced...................  Mercedes 320.          10.9[Dagger]
50 N--not braced...................  Honda Civic.                   10.6
50 N--braced.......................  Toyota Echo.                    6.9
100 N--not braced..................  Dodge Stratus.                 24.0
100 N--braced......................  Buick LeSabre*.        20.3[dagger]
 
------------------------------------------------------------------------
[Dagger] Rotational Adjustment.
* Detents but no locking mechanism.
[dagger] No Lock.

    In response to comments provided by Honda, we believe that the 
vertical load test can be improved by replacing the loading sphere with 
a loading cylinder measuring 165 mm in diameter and 152 mm in length. 
We believe that any potential slippage of the head restraint with 
respect to the loading sphere, if it were to occur, would be primarily 
in the longitudinal direction. Since the long axis of the cylinder will 
be oriented in the vehicle longitudinal direction, the potential of 
slippage will be substantially reduced. Further, we have no experience 
with using a flat plate as the loading device, while the loading 
cylinder is currently an option in FMVSS No. 202. The cylinder is to be 
loaded at the point on the head restraint with the greatest vertical 
position, rather than at the ``top'' as previously defined in the 
standard. The term ``top'' has been defined as the highest point of the 
head restraint at which a plane that is perpendicular to the torso 
reference line of the J826 manikin intersects the head restraint. For 
the backset position retention loading test, however, the lower edge of 
the cylinder may inhibit the return of the head restraint during the 
unloading phase. Therefore the loading sphere, positioned perpendicular 
to the torso line, will be kept for this test.
    We believe that DaimlerChrysler's comments related to upholstery 
crush and Honda's comments related to the loading sphere slipping might 
have merit. However, we disagree with the commenters who have suggested 
that these issues can be resolved by simply specifying that the head 
restraint stay in its pre-load adjusted position. Although similar 
wording is used in other regulations, including Standard No. 207, such 
a performance requirement can in certain instances be difficult to 
enforce. We acknowledge that removing the head restraint upholstery and 
loading only the underlying structure would make it easier to determine 
lock failure and would remove the foam variability from the test. 
However, this would not be a realistic way of loading the head 
restraint and may, in fact, change the path of loading. We also note 
that measuring the movement of the loading device instead of directly 
measuring the head restraint (pre- and post-condition) produces more 
accurate measurements for compliance purposes.
    We believe that the proposed height and backset position retention 
requirements are comprehensive and that requirements for other 
positions than those mentioned above are unnecessary and would not 
result in significant additional safety benefits. We note, however, 
that manufacturers are not precluded from providing additional lockable 
positions within the range of the head restraint adjustment.

XI. Energy Absorption

    The NPRM proposed that a specified area of the head restraint would 
have to limit the deceleration of a 6.8 kg mass impactor, traveling at 
24.1 km/h, to 80 g's. The impactor was a free-motion head form. In 
addition, we proposed that any portion of the head restraint that was 
outside of the impact area and that had a radius of curvature of less 
than 5 mm would be required to pass the energy absorption test. We 
requested comments on whether a free-motion head form was an 
appropriate testing device and whether the radius of curvature 
requirement was necessary.
    Impactor. Industry commenters were unanimous in their desire for 
the use of the pendulum impactor instead of the free-motion head form. 
Johnson Controls and Honda suggested that the use of a pendulum 
impactor, as specified in ECE 17, Paragraph 5.1.3, is preferable to the 
use of a free-motion impactor for the energy absorption compliance 
testing. According to Honda, the primary reason for the desirability of 
the pendulum impactor is that conducting testing using this device 
would allow the manufacturers to use existing testing facilities and 
equipment.
    Agency response: In proposing the free-motion head form, we 
intended to simplify the ECE energy absorption test by making the 
impactor similar to that used for the upper interior impact portion of 
Standard No. 201. We also attempted to assure consistency with the ECE 
testing results by making the mass of the proposed free-motion impactor 
identical to that of the ECE 17 pendulum impactor (6.8 kg).
    We have decided to adopt a linear impactor, as opposed to a 
pendulum impactor or free-motion head form, as the compliance tool. Our 
decision was based on several factors. First, the use of a pendulum 
impactor could prevent us from running compliance tests on the actual 
vehicle without significant vehicle alteration, because of the 
interference of the vehicle interior with that type of impactor. If, as 
suggested by the manufacturers, a pendulum impactor were used, the 
seats would either have to be removed to allow for the pendulum swing 
or the roof of the vehicle would have to be cut open. Because of the 
cost involved, we often use the same vehicle to run multiple compliance 
tests. Removing seats or cutting into the vehicle to accommodate test 
equipment would limit our ability to run subsequent compliance tests 
for other standards.
    Second, the differences between the linear impactor and free-motion 
impactor are insignificant in terms of their ability to measure 
compliance with the energy absorption requirement. The linear impactor 
is constrained so that it moves along a line, while the free-motion 
impactor is free to rotate upon impact or to have a rotation imposed 
upon it at the time of launch. This unconstrained motion is beneficial 
for use with types of impactors that have an irregular surface, such as 
a surface simulating a human face. However, since the impactor for the 
energy absorption test is spherical, there is no need for the free 
motion.
    Third, the linear impactor is easier to target than the free motion 
head form, leading to more repeatable results. Currently, a linear 
impactor is used for the instrument panel and seat back impact testing 
under Standard No. 201. Fourth, we believe that the results obtained 
from a linear impactor will in fact be very similar to the results 
obtained from a pendulum impactor or free-motion impactor because the 
impactors have the same mass and impact velocity.
    Radius of curvature. We proposed an energy absorption requirement 
for all surfaces with less than a 5 mm radius of curvature to eliminate 
potential sources of high-pressure contacts between occupants and head 
restraints. We have decided against adopting this requirement.
    The Alliance stated that it is unaware of a need for a ``radius of 
curvature of less than 5 mm requirement,'' and recommended its 
deletion. Honda commented that the ECE 25 requirement for 5 mm radius 
of curvature limit is intended to apply to unpadded structures or 
structures padded with material softer than 50 Shore A hardness.

[[Page 74869]]

    Agency response: In our opinion, the burden associated with the 
enforcement of this requirement outweighs its benefits. In order to 
determine that structures with the soft upholstery have radii of less 
than 5 mm, we would be forced to remove the soft upholstery. 
Thereafter, a second, upholstered head restraint would have to be 
subjected to the impact test. No commenter provided information 
supporting such a requirement. Accordingly, we are not adopting our 
proposal regarding areas on the front surface of the head restraint 
that are outside of the impact area.
    As previously discussed, this final rule does not mandate rear 
outboard head restraints. However, this rule does require that the 
voluntarily installed rear outboard head restraints meet the energy 
absorption requirements discussed above.

XII. Issues Unique to Rear Head Restraints

a. Optional Head Restraints for Rear Seating Positions

    The NPRM proposed mandating head restraints for all rear outboard 
seating positions, but asked whether NHTSA should limit the final rule 
to front seating positions. This question was based on visibility 
concerns as well as the lower safety benefits that would be obtained 
from rear seat head restraints, as compared to those from front seat 
head restraints, given lower occupancy rates for rear seats. Most of 
the industry commenters stated that, consistent with ECE 17, rear head 
restraints should remain optional. ECE 17 treats rear head restraints 
as an option, but regulates them if they are installed in a vehicle. 
Johnson Controls reasoned that because the dangers for rear seat 
occupants are less than those for front seat occupants, rear head 
restraints should not be mandated. GM, the Alliance, and others 
believed that rear head restraints should be an option because of rear 
seats' lower occupancy rates, occupancy of rear seats usually by 
shorter individuals, potential child seat interference with rear head 
restraints, and the potential reduction of direct and indirect rear 
vision. In supplemental comments, GM stated its concern that rear seat 
head restraints will affect its ability to comply with the requirements 
of FMVSS No. 111, Rear View Mirrors.\55\
---------------------------------------------------------------------------

    \55\ GM's concern that rear head restraints will affect 
compliance with FMVSS No. 111 is not warranted because head 
restraints are an allowable obstruction. In addition, if the rear 
window field of view requirements are not met, compliance could be 
achieved by adding passenger side outside mirrors. These side 
mirrors are standard equipment on most vehicles.
---------------------------------------------------------------------------

    In contrast, Magna, Honda, Advocates, and the FIU students 
commented that NHTSA should mandate rear seat head restraints in 
addition to front seat head restraints. Magna stated that rear seats 
are designed to accommodate occupants ranging in size from the 5th 
percentile female to the 95th percentile male. Accordingly, Magna 
maintained that head restraints should support the entire range of rear 
seat occupants. Honda requested an additional three years of lead time 
to comply with the rear head restraint mandate, beyond the NPRM's 
proposed three-year lead time.\56\
---------------------------------------------------------------------------

    \56\ As discussed in a later section, the rule does not provide 
Honda's suggested additional lead time.
---------------------------------------------------------------------------

    Agency response: As noted previously in this document, this final 
rule does not mandate head restraints in rear outboard designated 
seating positions. Instead, this final rule regulates only voluntarily 
installed rear head restraints. Our decision was based on the several 
factors described below.
    First, additional analysis produced a more refined estimate of 
costs and benefits associated with mandating head restraints. 
Specifically, the benefits derived from: (a) Designing and installing 
compliant rear head restraints where none were previously provided, and 
(b) redesigning vehicles featuring multiple seating configurations 
(usually SUVs and minivans) that feature head restraints that do not 
meet the proposed requirements, are lower than originally estimated. 
The relationship of costs to benefits is represented as a cost per 
equivalent life saved. In the NPRM, the agency estimated that the cost 
per equivalent life saved for rear outboard head restraints was $9 
million as compared to $3 million for front outboard head 
restraints.\57\ We now estimate the cost per equivalent life saved for 
mandatory rear outboard head restraints to be greater than $13.8 
million, as compared to approximately $2.4 million for front outboard 
head restraints.\58\ The primary reason for the difference in the cost 
per equivalent life saved for front and rear seat head restraints is 
the difference in the numbers of front and rear seat occupants exposed 
to risk of whiplash injury in rear impacts and the difference between 
the costs of upgrading front head restraints and the costs of 
installing or upgrading rear head restraints.
---------------------------------------------------------------------------

    \57\ See 66 FR 963 at 981.
    \58\ By contrast, the cost per equivalent life saved for 
voluntarily installed rear head restraints is $4.71 million.
---------------------------------------------------------------------------

    Fewer rear seat occupants are exposed to risks in rear impacts 
because rear seats are much less likely to be occupied than front 
seats. An analysis of the distribution of occupants by seating position 
for all vehicle types in 2001 to 2003 NASS shows that 10 percent of all 
occupants sit in the second (or higher) row of outboard seats. We note 
that children and small adults derive less benefit from taller head 
restraints because their head center of gravity often does not reach 
the height of 750 mm above the H point. Therefore, if we further refine 
these data to include only occupants who are 13 years or older, the 
relevant percentage is reduced to approximately 5.1.\59\ Our 
conclusions about rear seat occupancy are further supported by the FRIA 
data, which indicate that out of a total of 272,464 annually occurring 
whiplash injuries, approximately 21,429 (7.8%) occur to the rear seat 
occupants. In sum, only a small percentage of occupants who are tall 
enough to benefit from taller head restraints sit in rear outboard 
seating positions.
---------------------------------------------------------------------------

    \59\ We further note that approximately 2 percent of rear seat 
occupants sit in the center seating positions.
---------------------------------------------------------------------------

    We have also reevaluated our compliance cost estimates. The cost of 
upgrading or installing rear head restraints in response to a mandate 
would have been significantly greater than the cost of upgrading front 
head restraints.\60\ Our data indicate that, on average, front seats 
were closer to meeting the proposed front head restraint requirements 
than the rear seats were to meeting proposed rear head restraint 
requirements. In fact, some vehicles currently in production already 
comply with the front head restraint height requirement because they 
were manufactured to comply with ECE 17. However, because ECE 17 does 
not require rear head restraints, we are not aware of any passenger 
vehicles that comply with the proposed requirements for rear seats.
---------------------------------------------------------------------------

    \60\ We estimated that equipping rear seats with head restraints 
would result in the annual costs of approximately $103 million.
---------------------------------------------------------------------------

    In addition to cost effectiveness, our decision not to require rear 
head restraints was influenced by comments indicating that rear head 
restraints would significantly reduce a driver's view through the rear 
view mirror in some vehicles. Although we are not able to estimate the 
associated adverse effects that might result from the rearward 
visibility losses, it is the likely that the effect would not be safety 
neutral for some vehicles.
    Finally, based on submitted comments, we conclude that mandating 
rear outboard head restraints could either decrease availability of 
certain

[[Page 74870]]

utility features currently available in ``multi-configuration'' 
vehicles such as minivans and SUVs, or make it necessary for vehicle 
manufacturers to alter interior or seat designs to maintain these 
features. At least initially, these alterations could significantly 
increase the cost of manufacturing these ``multi-configuration'' 
vehicles. Alternatively, such designs would necessitate the ability to 
remove the rear head restraints to allow seat folding.
    As previously discussed, we were aware of low occupancy rates and 
potentially detrimental effect on rearward visibility when we proposed 
to require head restraints at each rear outboard designated seating 
position. These factors alone, however, were not decisive enough to 
convince us that we should not to propose requirements for mandatory 
rear head restraints and obtain public comment before making a final 
judgment on the merits. At the time, we tentatively concluded that the 
philosophy that commonly used seating positions should offer similar 
levels of protection to their occupants warranted further exploration 
of the merits of a mandate. However, in light of the newly refined, 
higher estimates of the cost per equivalent life saved, we conclude 
that rear head restraints should not be mandated.\61\
---------------------------------------------------------------------------

    \61\ As the agency noted in its 1995 final rule establishing 
upper interior head impact protection requirements, the application 
of the philosophy of providing similar levels of protection in all 
seating positions is subject to the limits of reasonableness:
    While the costs per equivalent life saved still vary according 
to seating position, the conclusive factor in determining whether to 
regulate a particular seating position should not be the existence 
of such variations, but the reasonableness of the cost for that 
particular position. * * * So long as the cost per equivalent life 
is reasonable, NHTSA believes that a vehicle should be designed to 
offer the same level of protection to all occupants, regardless of 
the occupant's choice of seat. 60 FR 43031, at 43046; Aug. 18, 1995.
---------------------------------------------------------------------------

    Nevertheless, in order to ensure that voluntarily installed rear 
seat head restraints do not pose a risk of exacerbating whiplash 
injuries, this final rule requires that those head restraints meet 
certain height, strength, position retention and energy absorption 
requirements proposed in the NPRM. We are considering inclusion in our 
annual ``Buying a Safer Car'' brochure, and on our web site, the list 
of vehicles equipped with rear head restraints. We believe this could 
provide an added incentive for the manufacturers to equip their 
vehicles with optional rear head restraints.
    The definition of a rear head restraint: This final rule provides 
an objective definition and a test procedure for determining the 
presence of a rear head restraint. We decided that a vehicle seat will 
be considered to have a rear head restraint if the seat back, or any 
independently adjustable seat component attached to or adjacent to the 
rear seat back, that has a height equal to or greater than 700 mm, in 
any position of backset and height adjustment, as measured with the 
J826 manikin.
    We chose this method for the following reasons. Based on the survey 
of vehicles used to determine the cost effectiveness of this 
regulation, we found that a 700 mm threshold captured all of the seats 
that had adjustable cushion components at the top of the seat back; 
i.e., what the general public would probably consider being a head 
restraint.\62\ Further, this definition of the rear head restraint will 
allow the manufacturers to provide a relatively tall seat back (up to 
700 mm) without having to comply with rear head restraint requirements. 
We anticipate that such taller seat backs might offer some safety 
benefits to a certain portion of rear seat occupants. We note that the 
current head restraint standards do not require a height of above 700 
mm even for front head restraints.
---------------------------------------------------------------------------

    \62\ The survey included twelve 1999 model year vehicles (9 
passenger cars, 1 minivan, and 2 SUVs). Five of the twelve vehicles 
featured rear seating systems that fell under our definition of the 
rear head restraint.
---------------------------------------------------------------------------

    Because rearward visibility remains a concern, we note that the 
manufacturer will be able to determine whether providing a seat back 
structure above 700 mm would be consistent with the amount of rearward 
visibility they wish to provide.
    As discussed previously, the agency has made significant 
accommodations to mitigate possible visibility losses associated with 
rear head restraints. First, the agency is making their installation 
voluntary. Second, the agency allows non-use positions that can move 
the head restraints out of view when the seat is unoccupied. Third, the 
agency allows rear head restraints to be removable. Fourth, the maximum 
required head restraint width for rear bench seats is 84 mm less than 
for front bench seats. Fifth, gaps as large as 60 mm can be provided 
within the perimeter of the head restraint.

b. Exception for Seats Adjacent to an Aisle

    Johnson Controls expressed a concern that the NPRM's proposed 
heights for head restraints for third-row seating in vehicles would 
create a problem for outboard designated seating positions that are 
next to an aisle. The commenter suggested that the 750 mm proposed head 
restraint height requirement could create ingress and egress 
difficulties for people using these third-row seats, which could pose a 
safety problem in certain vehicle emergencies.
    NHTSA believes that these concerns are now addressed by making the 
head restraints optional for rear outboard seating positions. If a 
manufacturer believes that it is better not to place the head 
restraints in designated seating positions adjacent to the aisles in 
order to facilitate ingress and egress into third and higher rows, it 
may act accordingly.

c. Potential Interference With Child Restraints and Tethers

    The NPRM solicited comments related to safety concerns arising from 
potential interference of rear seat head restraints with the attachment 
of upper tethers of child restraint systems. The NPRM asked for test 
data and related comments regarding whether the passage of tethers over 
or under adjustable head restraints would affect the amount of head 
excursion of child restraint occupants in a crash or the lateral 
stability of child restraints.
    Interaction between tethers and head restraints. NHTSA received 
numerous responses to these requests and questions. Advocates believed 
that the performance of child seat tethers would not be negatively 
affected by the proposed FMVSS No. 202 amendments. Nevertheless, 
Advocates recommended that NHTSA's final rule prohibit child seat 
tethers from being designed so that their use necessitates either 
removing rear head restraints or placing them in the non-use position.
    Some industry commenters expressed concerns about, but did not 
provide any specific test data on, the safety impact of 
incompatibilities between child restraint tethers and rear seat head 
restraints. Johnson Controls asserted that safety concerns exist with 
respect to integral or adjustable head restraints and the proper 
management of child tether placement and loading. Johnson Controls 
commented that misuse or improper installation could occur. 
DaimlerChrysler suggested that a tether routed over the top of a head 
restraint would provide less effective safety protection in a side 
impact, given the longer tether length and routing. Honda believed that 
the perceived potential safety concern pertained to misuse that could 
occur when the tether strap is positioned over the head restraint and 
attached to the tether anchor when the head restraint is not positioned 
in the lowest possible adjustment position.
    Ford acknowledged its lack of information regarding any head 
excursion effects of child restraint routing over or under a head 
restraint.

[[Page 74871]]

Ford indicated that in some frontal sled tests it conducted, it 
discovered a degree of tether slippage to the side of the head 
restraint when the tether was routed over head restraints. Ford assumed 
this slippage would increase head excursion, although Ford's tests did 
not produce evidence of excessive head excursions. Ford stated that 
increased head restraint heights also might increase the effects of 
slippage on chest acceleration, neck loads, and HIC.
    Transport Canada said that it has investigated whether interference 
between head restraints and child restraint tethers might alter the 
angle at which the tethers depart the child restraint, or create slack 
in the strap, in a manner that would affect the performance of the 
child restraint. Transport Canada conducted numerous sled tests to 
discern any effects of varying strap angles and slack on child seat 
tether performance. Transport Canada's data indicated that tethers 
remained effective even at rather large strap angles. The data 
additionally showed that tethers retained their effectiveness up to the 
point at which large amounts of slack were incorporated into the tests.
    The Alliance commented that the extent of head restraint and tether 
interference varies depending on the exit point of the tether from the 
child restraint, as--the commenter believed--a lower exiting tether 
will produce greater interference. With respect to the NPRM's 
suggestion that a Y-shaped tether strap design might be used to go 
around the head restraint, the Alliance maintained that no child 
restraints currently on the market are equipped with Y-shaped tethers. 
However, it noted the availability of a V-shaped tether strap design on 
a few high-priced child restraints.
    Less of a snug fit between child restraint and vehicle seat because 
of head restraints.
    Several commenters believed that the proposed backset and gap 
requirements could interfere with proper child restraint and booster 
seat installation.
    The Partners for Child Passenger Safety (PCPS) said that there is 
an existing incompatibility between rear head restraints and some high-
back convertible child restraints and boosters. In particular, PCPS 
asserted that a rear head restraint might affect the tightness of a 
hybrid child restraint's \63\ fit on the seat when the child restraint 
is used as a forward-facing seat. The Alliance commented that many 
existing child restraint systems have higher and straighter backs that 
could interfere with head restraints meeting the proposed 50 mm backset 
limit, thus causing child restraint fit problems. The Alliance further 
indicated that head restraint interference causes tipping and sliding 
of high-back boosters during cornering due to the lack of contact 
between the back of the booster and the vehicle's seat back. The 
Alliance asserted that the interference of head restraints with reduced 
backsets with high-back belt-positioning boosters could push the 
booster seat forward, causing an adverse effect on the positioning of 
lap and shoulder belts.
---------------------------------------------------------------------------

    \63\ A hybrid child restraint is one that can be used as a 
forward facing seat below a certain child weight and a belt 
positioning booster seat above.
---------------------------------------------------------------------------

    Effect of new head restraints on child restraint anchorage systems. 
Several commenters raised concerns about the effect that the new head 
restraints might have on the design and testing of child restraint 
anchorage systems (pursuant to FMVSS No. 225). DaimlerChrysler 
expressed concern about the issue of interference with the child 
restraint and the Child Restraint Fixture (CRF) used by NHTSA to test 
the strength and positioning of child restraint anchorage systems in 
vehicles under FMVSS No. 225. Less desirable relocation of lower 
anchors for child seats, the Alliance contended, might also result from 
reduced backset due to head restraint interference with the CRF design.
    Agency response regarding child restraints and tethers: NHTSA 
reviewed the comments submitted with respect to potential child 
restraint and/or tether interference. These comments pertain 
exclusively to rear seats. Since the final rule does not require rear 
seat head restraints, any incompatibility can be addressed by the 
manufacturers. Therefore, we have concluded that the final rule's head 
restraint requirements will not adversely affect child restraint 
safety. In addition, we believe that optional rear head restraints will 
not have a significantly negative effect on child restraint 
compatibility. Below we provide responses specific to several areas of 
commenters' concern if a head restraint is present.
    Agency response regarding tethers: As the agency stated in the 
NPRM, tethered child restraint requirements have been in effect for 
quite some time in Canada and Australia, and vehicles with rear head 
restraints meeting requirements similar to those of today's final rule 
are relatively common in those countries. Transport Canada indicates 
that interference between rear head restraints and child restraint 
tethers has not created any significant problems. To the extent that 
interference occurs, it creates incentives for child restraint 
manufacturers to design child restraints to assure maximum child 
protection. For example, a demand would likely develop for Y- or V-
shaped tethers, if such tethers make attaching to a tether anchor 
easier.
    As indicated above, Johnson Controls, Honda, DaimlerChrysler, and 
Ford suggested that routing tethers over head restraints might lead to 
increased head excursions. However, industry commenters did not provide 
any data on this issue, while Transport Canada's data indicate that 
tethers remain effective up to the point at which large amounts of 
slack are introduced.
    NHTSA assumes that the worst-case tether location is floor mounting 
because floor-mounted tethers have the potential to introduce the most 
slack in a collision, while deck-mounted and roof-mounted tethers 
likely would not produce significant slack because of their shorter 
distance to the child restraint. If current voluntarily installed rear 
seat head restraints are an indication of future systems, NHTSA 
anticipates manufacturers will install adjustable systems, in which 
case the tether could be routed under the adjustable head restraints, 
reducing the potential for excessive amounts of slack.
    Vehicle manufacturers are required to provide instructions for 
proper attachment of the child restraint tether under FMVSS No. 225. 
Manufacturers must determine how child restraint tethers should be 
routed with respect to the particular head restraints in their 
vehicles, and how the head restraint should be adjusted. In some 
instances, a manufacturer may recommend that the head restraint be 
temporarily removed.
    Agency response regarding fit of child restraints: With respect to 
comments pertaining to the potential incompatibility between rear head 
restraints and some high-back hybrid child restraints and boosters, 
NHTSA notes that high-back child restraints are used in Europe with no 
reports of incompatibilities. As Magna commented, rear seat head 
restraints are much more common in Europe due to competitive pressures. 
Nonetheless, if incompatibilities arise in this country, they can be 
resolved by several means. First, we believe that an adjustable head 
restraint is likely to have a position that does not interfere with 
high back hybrid child restraints. That is, raising the head restraint 
may alleviate the potential interference. Second, the high-back child 
restraint can be installed in a seating position for which a head 
restraint is not provided, removable, or has a non-use position. We 
note that even where rear outboard head restraints are provided, many 
vehicles do not provide a head restraint in the

[[Page 74872]]

center seating position.\64\ We recognize that, even with the 
flexibility afforded to the manufacturers with respect to rear seat 
head restraints, there may be isolated situations where certain high 
back child restraints are not compatible with specific seating 
positions in certain vehicles. However, we expect this to be relatively 
infrequent. In short, the agency does not believe that the possible 
incompatibilities are insurmountable even in situations in which rear 
seats are equipped with optional head restraints. The agency will 
monitor these and other issues associated with the implementation of 
this final rule.
---------------------------------------------------------------------------

    \64\ NHTSA has issued an NPRM that would mandate installation of 
lap/shoulder belt restraint systems in the center rear seating 
position (68 FR 46546), which will ensure availability of restraints 
for use with an older child in a belt positioning booster.
---------------------------------------------------------------------------

    Agency response regarding testing of child restraint anchorage 
system: NHTSA disagrees with the Alliance's comments asserting that 
rear head restraints will cause interference with the CRF, thereby 
resulting in unfavorable positioning of lower anchors. In an earlier 
rulemaking on FMVSS No. 225, the agency modified the CRF so that it can 
be broken down into a short-back configuration, eliminating the 
potential for head restraint interference.

XIII. Dynamic Test Alternative

    In the NPRM, we proposed a dynamic compliance option for forward 
facing seats as an alternative to static requirements of this final 
rule. The dynamic compliance option was proposed primarily for two 
reasons. First, the dynamic test better represents ``real-world'' 
injury-causing events and thus produces greater assurance than the 
static measurement option of effective real world performance. Second, 
as explained below, we believe that the dynamic test will help to 
encourage continued development and use of ``active'' head restraint 
systems because the test is designed to allow a manufacturer the 
flexibility necessary to offer innovative active head restraint designs 
while still ensuring a minimal level of head restraint performance.
    Active head restraint systems deploy \65\ in the event of a 
collision to minimize the potential for whiplash. During the normal 
vehicle operation, the active head restraint system is ``retracted.'' 
Because an active head restraint system requires a certain range of 
motion to work effectively, an ``un-deployed'' active head restraint 
system might not meet the static measurement requirements of FMVSS No. 
202a.
---------------------------------------------------------------------------

    \65\ Besides mechanical deployment, some systems use other 
methods. For example, BMW 760Li uses a pyrotechnic head restraint 
system that utilizes a gas discharge to deploy head restraints.
---------------------------------------------------------------------------

    Several manufacturers now offer active head restraints. For 
example, Volvo offers the Whiplash Head Impact Protection System 
(WHIPS) in which the seat back recliner is designed to control the 
rearward motion of the seat back relative to the seat base in a rear 
impact. Volvo believes that this allows the head and torso to be more 
uniformly supported. A number of other vehicle models including Saab, 
Infiniti, and BMW also offer active head restraints in their vehicles.
    Although the dynamic compliance option is intended to ensure that 
the final rule encourages continuing development of active head 
restraint systems, the option is available to both active and 
conventional, or ``static'' head restraint systems. That is, both types 
of head restraints can be certified to either static requirements or 
the dynamic compliance option. As explained above in the discussion of 
the height requirements for front seat head restraints, if the choice 
were made to certify to the static requirements, an active head 
restraint would have to meet these requirements in its undeployed 
state. If an active head restraint were unable to do this, the dynamic 
compliance option provides an alternative means of certification. Head 
restraints certified to the dynamic compliance option must still meet 
the static width requirements of this final rule. As discussed below, a 
manufacturer's selection of a compliance option would be irrevocable. 
However, the manufacturer may select different compliance options for 
different designated seating positions.
    The current dynamic test in FMVSS No. 202 accelerates a seat to an 
8 g half sine acceleration pulse over 80 ms. The NPRM proposed a new 
dynamic compliance test option involving a sled test with a target 
pulse of 86 m/s<SUP>2</SUP> over an 88 ms duration and a 17.3 <plus-
minus> 0.6 km/h change of velocity.
    Most commenters on the NPRM agreed with maintaining an alternative 
dynamic compliance option. However, as IIHS noted, that there has been 
no strong interest in the industry to take advantage of a dynamic 
compliance option. Because the dynamic test requirements are based on 
the static location requirements, the AIAM commented that there is 
little incentive to use the dynamic testing option. King \66\ commented 
in favor of dynamic testing. The final rule adopts the proposed dynamic 
compliance option, with modification, because we believe it desirable 
and necessary to encourage continued development and use of ``active'' 
head restraint systems. Especially as modified, the test is designed to 
allow a manufacturer the flexibility necessary to offer innovative 
active head restraint designs while still ensuring a minimal level of 
head restraint performance.
---------------------------------------------------------------------------

    \66\ Albert I. King, PhD, Bioengineering Center, Wayne State 
University.
---------------------------------------------------------------------------

    Test Dummies. For the dynamic compliance test option, the NPRM 
proposed the use of a 95th percentile male dummy in a front seat with 
the head restraint at a single manufacturer selected position, and a 
50th percentile male dummy in the front and rear seats with the head 
restraint midway between the lowest and the highest position of 
vertical adjustment. In vehicles in which the seat cushion adjusts 
independently of the seat back, the dynamic measurements were to be 
taken with the seat cushion adjustment in the most unfavorable 
position.\67\
---------------------------------------------------------------------------

    \67\ If the seat cushion adjusts independently of the seat back, 
the seat cushion would be positioned such that the highest H-point 
position is achieved with respect to the seat back, as measured by 
the HRMD.
---------------------------------------------------------------------------

    The Alliance commented that there are many potential test dummy 
candidates, but no consensus on the most appropriate one to use for a 
dynamic head restraint test. Magna argued in favor of using 5th 
percentile female, 50th percentile male and 95th percentile male 
dummies. Honda stated that the 95th percentile male dummy should have 
priority in testing. DaimlerChrysler said that a 5th percentile female 
dummy is not needed for testing because if a head restraint is high 
enough for a 50th percentile male, it will also be high enough for a 
5th percentile female. Tencer suggested that in order to be certain 
that a smaller occupant's head contacts the intended surface of the 
head restraint, there should be some indication of how a small female 
would fit the seat. Autoliv commented that since the most common neck-
injured occupant is an average size female, a 50th percentile female 
dummy should be used in dynamic testing. Autoliv also said that a 
BioRID \68\

[[Page 74873]]

dummy, with its flexible spine, should be used in dynamic testing 
instead of the Hybrid III dummy. IIHS commented that the Hybrid III 
dummies are not biofidelic for rear impacts, that they represent large 
adult males, and that dynamic testing based on them may lead to dynamic 
head restraint designs that are not effective for smaller occupants 
such as children and females. King agreed that there is not any truly 
biofidelic dummy now available for rear impacts, but recommended use of 
the Hybrid III dummy as the best alternative currently available. He 
specifically recommended against the use of the BioRID dummy, stating 
that it had not been validated against cadaveric data in detail and 
that relative displacements between the pinned joints are not 
available. Advocates supported dynamic testing with 5th percentile 
female dummies to limit the negative effects of head restraints that 
are adjusted too high. Advocates also stated that the 95th percentile 
male dummy should be used in the rear seat as well as the front seat.
---------------------------------------------------------------------------

    \68\ BioRID 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.
---------------------------------------------------------------------------

    Agency Response: There was no consensus among the commenters on the 
use of the Hybrid III dummy or the range of dummy sizes to be utilized. 
NHTSA is aware of the criticism associated with Hybrid III. 
Specifically, many commenters assert that the 50th percentile male 
Hybrid III neck lacks sufficient biofidelity to be a useful tool for 
rear impact testing. Because of likely design similarities, the same 
criticism could be made of the 95th percentile male and 5th percentile 
female dummy necks. We are aware of a newly developed test devices, 
BioRID II and RID 2, which purport to model a human neck more 
accurately. We are also familiar with a paper by Ford (SAE 973342), 
which argues that the 50th percentile male Hybrid III neck is 
sufficiently biofidelic in the rearward direction. Another recent 
publication indicated that the overall flexibility of the Hybrid III 
dummy is comparable to that of a tensed volunteer, while the 
flexibility of the BioRID II and RID 2 are greater than those of tensed 
volunteers and embalmed cadavers.\69\ We are likely to revisit the 
decisions made in this final rule about dynamic performance values and 
the test device as more advanced dummies are developed and the injury 
criteria achieve broader consensus.
---------------------------------------------------------------------------

    \69\ Kim, A., Anderson, K., Berliner, J., Hassan, J., Jensen, J, 
Mertz, H., Pietzch, H., Rao, A., Schere, R., Sutterfield, A, (2003) 
Stapp Car Crash Journal, Vol. 47, pp. 489-523.
---------------------------------------------------------------------------

    Any consensus advancement in adaptation of a new, more biofidelic 
dummy will be welcomed by the agency and considered as part of future 
possible modifications to the standard. However, we believe the 
introduction of a modified dynamic test alternative should not be 
delayed, even if it is only an interim step toward a more advanced test 
procedure. We find especially persuasive King's comments, stating that 
the Hybrid III dummy is the only reasonable option at this time.
    In our opinion, the 95th male dummy in the front, and 50th 
percentile male dummy in the rear, provide for a relatively worst-case 
scenario in terms of potential occupants and assure that the head 
restraint has sufficient height. However, the 95th percentile male 
dummy is not yet available and thus has not been incorporated into 49 
CFR part 572, Anthropomorphic Test Devices. Therefore, the final rule 
does not use the 95th percentile male dummy in the dynamic compliance 
option for front seats. Instead, as discussed further below, this final 
rule requires that the head-to-torso rotation be limited to 12 degrees 
with the 50th percentile male dummy with the head restraint midway 
between the lowest and the highest position of vertical adjustment. 
Ideally, it would be preferable that the dynamic testing be performed 
with the 5th percentile female and 95th percentile male dummy. However, 
we conclude that the 50th percentile male dummy with the 12-degree 
head-to-torso rotation performance limit is sufficient to discern 
between acceptably safe head restraint systems and those that allow 
unacceptable levels of head-to-torso rotation for the taller occupants. 
We note that sled testing performed by the agency and described further 
below shows that the 50th percentile male dummy is capable of 
discerning the difference between 800 mm and 750 mm high head 
restraints. This data set did not vary backset. However, previous 
agency modeling results presented in the NPRM and sled testing by Viano 
have shown the 50th percentile male Hybrid III dummy to be sensitive to 
changes in backset as well.\70\ Thus, the 50th percentile male Hybrid 
III can, for the time being, be used as to determine the adequacy of 
head restraints for taller occupants.
---------------------------------------------------------------------------

    \70\ Viano, D., Davidsson, J., ``Neck Displacement of 
Volunteers, BioRid P3 and Hybrid III in Rear Impacts: Implications 
to Whiplash Assessment by a Neck Displacement Criterion (NDC),'' 
Traffic Injury Prevention, 3:105-116, 2002.
---------------------------------------------------------------------------

    In regard to commenters who preferred testing with a 5th percentile 
female dummy, we conclude that it is not necessary to use such a dummy 
to determine if the tested head restraint has the height and backset 
required to protect most occupants. Recent agency testing of several 
modified seat designs showed that dummy head-to-torso rotation is lower 
for a 5th percentile female than for a 50th percentile male dummy. 
Accordingly, a test featuring the 50th percentile male dummy captures 
the injury criteria associated with a 5th percentile female. We note, 
however, that this may not be the case for all seat designs. Any future 
upgrade proposals for dynamic rear impact testing in general, and the 
development of more refined injury criteria in particular, should 
consider incorporation of a small female dummy.\71\
---------------------------------------------------------------------------

    \71\ In response to Autoliv's suggestion that we test with a 
50th percentile adult female dummy, we note that there currently is 
no test dummy representing a 50th percentile female.
---------------------------------------------------------------------------

    Injury criteria. In the NPRM, we proposed two criteria for the 
dynamic performance option: A maximum head-to-torso rotation criterion 
and a maximum HIC15 level. Johnson Controls commented that the criteria 
should bear a direct relationship to whiplash injury prevention. Magna, 
along with AIAM, requested that a performance corridor be established 
for the dynamic testing alternative.
    Maximum head-to-torso rotation: The NPRM proposed a maximum head-
to-torso rotation of 20 degrees for a 95th percentile male test dummy 
in front outboard seats and 12 degrees for a 50th percentile male test 
dummy in all outboard seats. With the 95th percentile male dummy, the 
head restraint could be at a single manufacturer selected position of 
adjustment. With the 50th percentile dummy, the head restraint could be 
at any position of adjustment.
    Tencer and King both suggested time-dependent limits in their 
comments regarding the head-to-torso rotation performance criterion. 
Tencer believes that the extent of ``S'' shape curve correlates to the 
magnitude and time difference in the forward shear of the upper and 
lower neck. King believes that facet capsule stretch between the 
vertebrae could be a source of injury. In low speed impacts with a 
rigid seat back, the measured peak stretch occurs 100-120 ms after 
impact. He suggested that head restraint contact should be made within 
50 ms. AIAM recommended that the head-to-torso rotation be tested only 
at maximum backset. GM commented that because there is not yet a 
consensus on neck injury criteria, a limit of 12 degrees should not yet 
be established. The Alliance expressed concerns because the specified 
head rotation limits may be too restrictive. Advocates voiced

[[Page 74874]]

concerns that the 20-degree rotation limit for the 95th percentile male 
dummy in front seats is too large.
    Under today's rule, we are adopting a maximum relative head-to-
torso rotation value of 12 degrees with the 50th percentile male dummy 
in all outboard seats, with the head restraint adjusted vertically 
midway between the lowest and the highest position of adjustment.\72\
---------------------------------------------------------------------------

    \72\ We note that the manufacturer may select different 
compliance options for different designated seating positions to 
which the requirements of this section are applicable.
---------------------------------------------------------------------------

    We decided to require that the head restraint be positioned at one 
middle position of vertical adjustment instead of requiring that the 
head restraint meet the dynamic compliance option requirements at all 
positions of head restraint vertical adjustment because we are 
concerned with the effects of this final rule on active head restraint 
systems. As previously stated, we want to ensure that the dynamic 
compliance option encourages continuing development of active head 
restraint systems. As discussed below, research indicates that current 
head restraint systems can easily meet the head-to-torso rotation limit 
in this final rule when the head restraint is adjusted midway between 
the lowest and the highest position of adjustment.
    Using published data of low speed rear impact testing of original 
equipment manufacturer (OEM) seats with Hybrid III 50th percentile male 
dummies (Viano et al., 2002), and information on whiplash injuries 
sustained by occupants of these seats, the agency used logistic 
regression to develop a probability of whiplash injury as a function of 
dummy head-to-torso rotation. The function is shown below:
[GRAPHIC] [TIFF OMITTED] TR14DE04.149

    A 12-degree head-to-torso rotation corresponds to a 7.3 percent 
probability of whiplash. This criterion was selected to ensure adequate 
protection for occupants who range in stature from shorter females up 
to and including taller males, for all outboard seats. In evaluating 
the head-to-torso rotation limit, we note that in the past there has 
not been a consensus among the biomechanics community on how best to 
measure the potential for whiplash injury. This lack of consensus is 
evidenced by the related, yet different, criteria recommended by King 
and Tencer. In our opinion, the relative head-to-torso rotation is 
presently the best criterion available, and will assure early head 
restraint interaction consistent with King's recommendation. Our goal 
in selecting performance criterion limits for the dynamic compliance 
option was to provide a level of safety similar to that provided by the 
static requirements. Our research shows that it is feasible to meet 
these limits with both active and static head restraints.
    The agency performed sled testing as specified in the dynamic 
compliance option on a specially designed seat to explore how various 
seat characteristics affect relative head rotation and other dummy 
injury measures.\73\ An OEM seat with an adjustable head restraint was 
modified by removing the original recliner mechanism and replacing it 
with a pin joint free to rotate. The seat back was also reinforced with 
steel channels that provided the attachment points for a spring and 
damper system on each side of the seat. Seat back strength in the 
rearward direction was modified by changing the springs and/or their 
location of attachment relative to the hinge joint. In addition to seat 
back strength, sensitivity analyses to head restraint attachment 
strength and seat back upholstery compliance were also performed. Tests 
were performed with belted 5th percentile female, 50th percentile male 
and 95th percentile male Hybrid III dummies.
---------------------------------------------------------------------------

    \73\ For full details of these tests, please see Docket No. 
NHTSA-2002-8570-57, 58, 59.

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

[[Page 74875]]

    The head restraint height was either 750 mm or 800 mm and the 
backset was always 50 mm as measured by the HRMD. However, the majority 
of tests (20 tests) were performed with the 50th percentile male dummy 
with a 750 mm high head restraint. For all seat back parameters tested 
with this configuration of dummy and head restraint height, the range 
of relative head-to-torso rotation was 6 to 16 degrees. 
HIC<INF>15</INF> was measured for half of these tests and ranged from 
40 to 75. Nearly half of the seat configurations (9 of 20) met the 12-
degree limit placed on the dynamic compliance option for a head 
restraint in the lowest adjustment position (750 mm). In general, the 
smallest relative rotations were seen for the baseline seat back 
strength \74\ and non-rotating seat backs irrespective of the other 
seat/head restraint parameters. From these tests, we conclude that the 
head rotation and HIC limits selected can be met with typical seat 
back/head restraint designs when appropriate consideration is given to 
design in terms of height, backset and strength of head restraint 
attachment.
---------------------------------------------------------------------------

    \74\ The baseline seat back strength was obtained through static 
testing of OEM seats and modeling to determine the corresponding 
amount of seat back rotation. The static testing can be found in 
Docket NHTSA-1998-4064-26.
---------------------------------------------------------------------------

    In a separate set of tests, the agency subjected a MY 2000 Saab 9-3 
seat to the sled pulse of the dynamic compliance option. A 95th 
percentile male Hybrid III dummy occupied the seat. The Saab 9-3 has an 
active head restraint system, and the head restraint was set to its 
highest position of adjustment. The maximum head-to-torso rotation was 
9 degrees. Viano and Davidsson (2002) also sled tested a 9-3 head 
restraint at a slightly lower, 16 km/h [Delta]V, with the seat occupied 
by a 50th percentile male Hybrid III dummy. With the head restraint in 
the up position, the relative head rotation was measured at 6.5 
degrees. With the head restraint midway between the lowest and the 
highest position of adjustment, the relative head rotation was 10 
degrees at 23.5 km/h [Delta]V. We believe that this configuration would 
yield an even smaller head rotation at the 17.2 km/h [Delta]V.\75\
---------------------------------------------------------------------------

    \75\ Viano, D., Olsen, S., ``The Effectiveness of Active Head 
Restraint in Preventing Whiplash,'' Journal of Trauma, Injury, 
Infection, and Critical Care, Vol. 51, No. 5, 2001; and Viano, D., 
``Role of the Seat in Rear Crash Safety,'' Society of Automotive 
Engineers Inc., Warrendale, PA, 2002.

                                   Table 3.--Viano Rear Impact Sled Test Data
----------------------------------------------------------------------------------------------------------------
                                                                                                       Head-to-
                                                 DeltaV km/               HR position in                 torso
          Test type                 Vehicle           h      Backset mm       height         HIC15     rotation
                                                                                                         (deg)
----------------------------------------------------------------------------------------------------------------
Sled.........................  Saab 9-5 + SAHR.       12.8          35   up.............         11           1
Sled.........................  Saab 9-3 SAHR...         16       41-43   up.............  ..........    4.6-6.5
Sled.........................  Saab 9-5 + SAHR.         30          35   up.............         39          11
Sled.........................  Saab 9-3 SAHR...       23.5          46   mid............         35          10
Sled.........................  Saab 9-3 SAHR...         16       48-65   down...........  ..........    13.3-16
----------------------------------------------------------------------------------------------------------------

    In sum, research indicates that the head-to-torso rotation limit of 
12 degrees will not discourage the development of active head restraint 
systems. Current systems, such as the one in 2000 Saab 9-3, can readily 
meet the head-to-torso rotation limit in this final rule. Agency 
testing has also shown that current static head restraints/seats need 
more extensive modification to meet the head-to-torso rotation limits. 
These changes might include increasing the strength of attachment to 
the seat for adjustable head restraints and optimization of the seat 
back upholstery for compliance.
    We also considered performance criteria other than head-to-torso 
rotation for the dynamic compliance option. Alternative criteria 
included N<INF>ij</INF>, which is a combination of upper neck moments 
and forces introduced in the Advanced Air Bag Rulemaking (Docket NHTSA-
98-4405); and NIC, which was developed by Chalmers University and has 
been used by IIHS in testing active head restraints; and individual 
values of force, moment and acceleration. We have decided in favor of 
head-to-torso rotation because, in the absence of generally accepted 
injury criteria specifically applicable to whiplash injuries, we 
believe that a head restraint's ability to prevent whiplash is 
primarily due to its ability to prevent the rearward translation and 
rotation of the occupant's head with respect to the torso. The sled 
tests showed that rearward head rotation seemed to correlate with head 
restraint position. Other biomechanics researchers have found a similar 
correlation and used head-to-torso rotations for the evaluation of 
whiplash injury.\76\ The agency is willing to reconsider the dynamic 
performance criteria if and when more advanced whiplash injury criteria 
become available.
---------------------------------------------------------------------------

    \76\ Geigl et al. (1994) The Movement of Head and Cervical Spine 
During Rear-end Impact, IRCOBI, pp 127-137.
---------------------------------------------------------------------------

    HIC<INF>15</INF> criterion: The NPRM proposed a HIC<INF>15</INF> 
limit of 150 for the dynamic compliance option. Johnson Controls, GM 
and the Alliance opposed the 150 HIC<INF>15</INF> limit. They saw no 
correlation between HIC and the reduction of neck injuries. AIAM 
recommended that we adopt an ``acceleration limit,'' instead of 150 
HIC<INF>15</INF> limit requirement. Advocates supported the 
HIC<INF>15</INF> limit as a prudent safeguard against head restraints 
that may meet a head rotation limit, but still inflict cranial trauma. 
The FIU students commented that the current 150 limit of 
HIC<INF>15</INF> is sufficient for testing. No comments were made in 
favor of using a 36 ms window.
    We are adopting a HIC<INF>15</INF> window to be consistent with the 
new HIC criterion in Standard No. 208 (65 FR 30680; May 12, 2000). The 
agency did not propose the HIC<INF>15</INF> limit as a means of 
limiting whiplash, but instead as a surrogate for the 80 g energy 
absorption test required for the static compliance option. If we were 
to eliminate the HIC<INF>15</INF> limit from the dynamic compliance 
test, we would need to re-introduce the 80 g limit energy absorption 
test required for static compliance. Because HIC<INF>15</INF> is easily 
measured during dynamic testing, it appears to be a more appropriate 
measuring tool. However, we have decided to specify a limit of 500 in 
the final rule rather than the 150 limit proposed in the NPRM. We 
raised the limit because of concerns that the 150 level is at a 
location on the injury risk curve that indicates a very small 
probability of injury. Thus, requiring head restraints not to exceed 
this level might inhibit innovative whiplash protection. The 
HIC<INF>15</INF> level of 500 is associated with an 18.8 percent 
probability (95 percent confidence: 1.8

[[Page 74876]]

to 32.5 percent) of moderate (AIS 2+) head injury.\77\ While the 80 g 
limit and the HIC<INF>15</INF> limit of 500 are not necessarily 
equivalent, the two requirements do share the same intent of mitigating 
potential injury related to the head's striking a rigid or 
insufficiently padded head restraint. We analyzed data from FMVSS No. 
201 impactor tests on the back of head restraints and also vehicle seat 
sled test data. We superimposed a 80 g half sine acceleration on the 
time duration of the impacts from these tests. This resulted in range 
of HIC<INF>15</INF> values from approximately 425 to 800. Accordingly, 
we believe a limit of 500 is appropriate. The greatest HIC<INF>15</INF> 
value obtained in testing sled testing using a 50th percentile male 
dummy was 57. Thus, the HIC<INF>15</INF> limit of 500 is practicable. 
The 500 HIC<INF>15</INF> limit will give a strong indication of 
deleterious effects on the occupant's head and/or neck from deploying 
head restraints.
---------------------------------------------------------------------------

    \77\ Eppinger, R., et al. (1999) Development of Improved Injury 
Criteria for the Assessment of Advanced Automotive Restraint 
Systems--II. Available at http://www-nrd.nhtsa.dot.gov/pdf/nrd-11/airbags/rev_criteria.pdf.
---------------------------------------------------------------------------

    Summary of injury criteria: Table 4 summarizes the injury criteria 
to be met for the dynamic compliance option. Our research indicates 
that currently available dynamic head restraints can readily meet the 
requirements of this final rule. We believe that the dynamic compliance 
option is sufficiently flexible to encourage continuing development of 
dynamic head restraint systems. However, the agency remains open to 
alternative suggestions on dynamic criteria that would further 
encourage innovative active head restraint designs.

                                             Table 4.--Testing Parameters for the Dynamic Compliance Option
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                             HIC15
        Seating position               Dummy size         Rotation limit     limit   Height adjustment     Backset adjustment      Head restraint width
--------------------------------------------------------------------------------------------------------------------------------------------------------
Front & Rear....................  50th Male Hybrid     12 Deg.............     500  Midway between the  Any position of          170 mm except 254 mm
                                   III.                                              lowest and the      adjustment               for front bench seats.
                                                                                     highest position
                                                                                     of adjustment.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Other dynamic compliance option issues. There were three additional 
aspects of the dynamic compliance option that the agency discussed in 
the NPRM.
    Minimum width requirement: The NPRM proposed that the same head 
restraint width requirement in the static compliance option be 
applicable to the dynamic compliance option as well. As discussed 
above, the final rule requires that all head restraints on front bucket 
seats and all voluntarily installed rear head restraints certified to 
the static compliance option have a minimum width of 170 mm. The bench 
seat head restraints located in the front outboard seating positions 
must have a minimum width of 254 mm. The final rule adopts the same 
width requirement for head restraint systems certified to the dynamic 
compliance option.
    GM commented that the width requirement would be inappropriate, 
especially for active or deployable head restraints. Honda also stated 
that the requirement would be unnecessary. DaimlerChrysler had no 
concerns related to the width requirement in the dynamic option, except 
for the same visibility issues it had raised in the discussion of the 
static test requirements. Ford and the Alliance commented that the 
width requirement is necessary, and repeated their desire for a single 
170 mm width for all seat types. Advocates commented in favor of adding 
the width criteria to the dynamic option.
    There appears to be no industry consensus as to whether the width 
requirement should be included in the dynamic compliance option. We 
disagree with GM's assertion that the width requirement is 
inappropriate for deployable systems. Regardless of whether the head 
restraint pivots forward to contact the head in a collision or is 
permanently situated behind the head, the head restraint should be 
sufficiently wide to provide protection. We note that unlike height and 
backset, the dynamic test does not assure sufficient width because it 
decelerates the vehicle in the longitudinal plane which causes the 
occupant to move in that plane, rather to one side of the other as 
might occur in an off-axis impact.\78\ Therefore, we have decided that 
vehicles certified to the dynamic compliance option must also meet the 
width requirements of the static compliance option. For reasons 
discussed in Section VI.a., we decline to adopt a single 170 mm width 
requirement for all head restraints.
---------------------------------------------------------------------------

    \78\ The test procedure specifies that the midsagittal plane of 
the dummy must be aligned within 15 mm of the head restraint 
centerline as opposed to off-center as a vehicle occupant might be 
positioned.
---------------------------------------------------------------------------

    Seating procedure: The seating procedure for the dynamic compliance 
option is set forth in S10 of Standard No. 208, with additional details 
added to address lateral positioning of the dummy. Since the 
manufacturers are already familiar with these procedures, they should 
not encounter any seating procedure difficulties while conducting the 
dynamic compliance test. Since testing of the head restraint is the 
focus of this procedure, we found it necessary to add provisions 
specifying that the dummy torso be placed within 15 mm of the head 
restraint centerline. In the event that the dummy cannot be seated 
because of space limitations, such as might be the case in the outboard 
rear seat of a vehicle, the dynamic option would not be available for 
that seating position.
    Test fixture: For the dynamic compliance option, the NPRM proposed 
mounting the entire vehicle on a sled.
    The Alliance, among other commenters, asked the agency to consider 
allowing the use of a seat attached to a test buck, instead of an 
actual vehicle for the dynamic compliance option. GM commented that no 
one would certify to the dynamic performance option because mounting 
the whole vehicle on the sled, instead of just the seat, imposes an 
undue level of complexity.
    NHTSA concludes that attaching the seat to a test buck is 
problematic for compliance tests. NHTSA cannot use a vehicle for 
further testing involving a seat if we remove the seat for the purposes 
of dynamic compliance option testing. Accordingly, NHTSA will conduct 
its compliance testing using the whole vehicle. The manufacturers are, 
of course, free to conduct their

[[Page 74877]]

development and certification testing on a buck. To assure that any 
certification is in good faith, we would expect such a manufacturer to 
show a correlation between buck testing and full vehicle testing.

XIV. Consumer Information

    In the NPRM, we asked for comments regarding whether vehicle users 
understand how to properly adjust head restraints and, if not, whether 
the rule should require manufacturers to provide information on this 
subject to consumers in vehicle owners' manuals or elsewhere. In 
addition, the NPRM solicited comments regarding whether vehicle users 
intentionally misadjust head restraints for reasons related to comfort, 
visibility, or other factors.
    ICBC provided extensive comments on these issues. According to 
ICBC, most motorists are not aware of the need to properly adjust their 
head restraints. Results from focus group studies commissioned by ICBC 
in 1996 suggest that drivers do not perceive a head restraint as a 
safety device and do not understand how a head restraint protects them. 
Consumer education programs, ICBC asserted, can increase the rate of 
proper adjustment, and manufacturers should play a role in educating 
consumers through owners' manuals, advertising, and in vehicle 
showrooms. ICBC initiated media information and direct intervention 
with vehicle users at various locations, including emissions testing 
stations, ferry terminals, and insurance offices. Education at ferry 
terminals alone resulted in 79,000 of 190,000 vehicle drivers adjusting 
their head restraints. ICBC cited these results, as well as similar 
studies of Transport Canada, in support of its effort to show that 
consumer education programs can positively influence proper head 
restraint adjustment. Transport Canada relied on ICBC data and 
suggested that the public does not properly adjust head restraints in 
the absence of consumer information programs.
    Johnson Controls and the Alliance noted that they knew of no data 
suggesting whether head restraints are intentionally or inadvertently 
misadjusted. Based on consumer surveys conducted by Johnson Controls, 
users adjust their head restraint height at most only once, in order to 
increase comfort, not to improve safety.
    DaimlerChrysler believed vehicle users intentionally misadjust head 
restraints for reasons related to comfort, visibility, convenience, and 
a lack of knowledge about proper positioning. However, DaimlerChrysler 
indicated it did not have any data to show why this intentional 
misadjustment occurs as opposed to inadvertent misadjustment. 
DaimlerChrysler commented in favor of requiring additional literature, 
either in owners' manuals or elsewhere, to educate consumers about the 
proper use and positioning of head restraints. The Alliance stated that 
vehicle users generally do not fully understand the appropriate use and 
purpose of head restraints. The Alliance and GM stated that a consumer 
information program coordinated between NHTSA and industry members 
could substantially reduce the problem of improper head restraint 
adjustment.
    Ford indicated that it voluntarily includes head restraint 
adjustment information in its owners' manuals and that such information 
is adequate to educate consumers about proper head restraint 
positioning. State Farm expressed support for requiring manufacturers 
to include head restraint positioning information in owners' manuals.
    Agency response: NHTSA believes proper adjustment of head 
restraints is necessary to ensure that vehicle occupants realize the 
maximum whiplash protection from head restraints. In order to address 
head restraint misadjustment, this final rule requires that vehicle 
manufacturers include in owners' manuals information about appropriate 
head restraint adjustment. We note that most manufacturers already 
provide some of this information in their owners' manuals.

XV. Effective Date and Interim Compliance Options

    In the NPRM, we proposed that compliance with the upgraded standard 
would be mandatory on the first September 1 that occurred following the 
three-year period that began with the publication of the final rule. We 
asked for comments on the appropriateness of the three-year lead time.
    Today's final rule becomes mandatory for all vehicles manufactured 
on or after September 1, 2008. We decided to extend the lead time by 
one additional year in order to allow vehicle manufacturers to phase in 
the new head restraint requirements in conjunction with their natural 
product cycle. The four-year lead time will, in most instances, allow 
vehicle manufacturers to design compliant head restraints for newly 
introduced vehicles, as opposed to redesigning existing seating systems 
for vehicles currently in production.
    Between March 14, 2005, the effective date of today's rule, and 
September 1, 2008, manufacturers have five compliance options. First, 
manufacturers may comply with ECE 17, except that they must meet the 
current width requirements of FMVSS No. 202. Second, manufacturers may 
comply with either dynamic or static requirements of the existing FMVSS 
No. 202. Third, they may comply with either dynamic or static 
requirements of the new FMVSS No. 202a. Consistent with our approach in 
other standards in which there are compliance options, the manufacturer 
must irrevocably elect a particular option prior to certification of 
the vehicle. However, the manufacturer may select different compliance 
options for different designated seating positions.
    There were relatively few comments related to the proposed lead 
time or compliance choices during that time. Honda commented that an 
additional three years of lead time should be added for rear seat head 
restraint compliance, in addition to the three years for front seat 
head restraints. Magna requested that an additional 3-year phase-in 
period be included along with the proposed 3-year lead time period, to 
allow for proper product development. Porsche commented that limited 
line manufacturers should be provided additional lead time, or if a 
phase-in is utilized, they should be given until the end of the phase-
in period to comply. The Alliance argued that the final rule 
implementation should be postponed, and compliance with the current 
version of FMVSS No. 202 be allowed until at least 2005. The Alliance 
also recommended a phase-in period of 3 years after the rule is finally 
published. DaimlerChrysler believed four years of lead time was in 
order, in light of significant deviations from the ECE standards. 
Advocates strongly supported the 3-year interim period followed by 
complete implementation of the new standard.
    We believe that the requests for lead time in addition to the four 
years provided in this final rule are unwarranted. Unlike the NPRM 
proposal, this final rule does not require head restraints in rear 
outboard designated seating positions. With respect to height, this 
final rule harmonizes our head restraint requirements with those 
already in effect under the ECE 17 regulation. Accordingly, a 
significant number of vehicles for sale in the United States already 
meet the European height requirement. Finally, we believe the four-year 
lead time provides sufficient time to resolve any problems associated 
with the new backset requirement.
    As previously discussed, most of the commenters agreed that the new 
requirements for head restraints that are

[[Page 74878]]

taller and closer to the head are likely to reduce the instances of 
whiplash injuries. According to ICBC, numerous vehicles currently in 
production already satisfy the 55 mm backset requirement. Similarly, we 
believe that numerous vehicles currently in production satisfy the 800 
mm requirement. Most of the manufacturers who requested additional lead 
time sell cars in Europe and, therefore, are already in compliance with 
the ECE regulation requiring similar head restraint height. In light of 
the aforementioned circumstances, we conclude that a four-year lead 
time allows ample opportunity to redesign head restraints in order to 
comply with the new standard.
    In regard to comments made by Porsche on behalf of small, 
independent automobile manufacturers, we note that Porsche and other 
small line European manufacturers are, presumably, already 
manufacturing vehicles that are in compliance with ECE 17. Further, 
rear head restraints are optional, and the final rule does not consider 
a seat back lower than 700 mm above the H-point as a head restraint. 
Therefore, Porsche can continue to produce the 911 vehicle line without 
installing rear head restraints.\79\ Moreover, we have allowed 25 mm 
clearance between the rear head restraint and the roofline, thus 
alleviating some of the concerns raised by Porsche. Accordingly, 
Porsche can take advantage of the 25 mm height allowance if they choose 
to equip the rear seats in their 911 vehicle line with head restraints.
---------------------------------------------------------------------------

    \79\ A survey of 2004 model year Porsche 911 vehicles (911, 911 
Targa, 911 4S, 911 Cabriolet, 911 Turbo, 911 GT2, 911 GT3) indicates 
that none currently feature rear head restraints.
---------------------------------------------------------------------------

    We received a number of comments pertaining to the interim 
compliance options. Advocates called NHTSA's interim compliance 
proposals ``an eminently reasonable compromise'' and supported this 
approach in lieu of allowing a phase-in. TRW also supported the interim 
compliance options set forth in the NPRM, stating that allowing 
compliance options would spur the growth of better technologies.
    AIAM disagreed with the requirement that a manufacturer must choose 
a particular compliance option prior to certification. For reasons 
explained in other rulemakings, the agency will not allow manufacturer 
to recertify under an alternative compliance option, if there is a 
noncompliance with the option to which the manufacturer initially 
certified.\80\
---------------------------------------------------------------------------

    \80\ See, e.g., 64 FR 10786 at 10808 (March 15, 1999) and 64 FR 
69665 at 69668 (December 14, 1999).
---------------------------------------------------------------------------

    The Alliance argued against the interim compliance option approach, 
instead favoring a phase-in schedule after NHTSA better identified the 
causes of soft tissue neck injuries. This phase-in approach, the 
Alliance contended, should give manufacturers credit for early 
compliance. DaimlerChrysler asserted that NHTSA should allow compliance 
with the interim options indefinitely or at least until NHTSA gained a 
better understanding of whiplash injuries.
    Based on our consideration of ECE 17, and the existing version of 
FMVSS No. 202 under the functional equivalence process defined in 
Appendix B of 49 CFR Part 553, we have concluded that ECE 17 offers 
greater safety benefits than the existing version of FMVSS No. 202. The 
most notable differences between FMVSS No. 202 and ECE 17 are that 
while FMVSS No. 202 currently does not address head restraints for rear 
seating positions or contain any requirements for energy absorption, 
ECE 17 specifies requirements for head restraints that are voluntarily 
installed in rear seating positions and for energy absorption.
    Accordingly, we will permit interim compliance with the specified 
requirements of ECE 17. As stated above, the final rule also permits 
certification using either of the existing FMVSS No. 202 requirements 
or either of the upgraded FMVSS No. 202a requirements. Upon expiration 
of the four-year interim period, however, manufacturers must comply 
with upgraded FMVSS No. 202a.

XVI. Costs and Benefits Associated With the Final Rule

    The NPRM estimated that the proposed rule would reduce the annual 
number of whiplash injuries by 14,247 (9,575 for front outboard seats 
and 4,672 for rear outboard seats).\81\ The cost of raising the front 
head restraint was estimated to be $4.21 per vehicle, resulting in a 
fleet cost of $65.5 million.\82\ Installing two rear head restraints in 
vehicles that previously did not have rear head restraints was 
estimated at $12.34 per vehicle, resulting in a fleet cost of $74.8 
million. Raising the rear head restraints in vehicles already equipped 
with rear head restraints was estimated at $3.61 per vehicle, resulting 
in a fleet cost of $19.6 million. Adding a locking mechanism would cost 
$0.15 per vehicle, for a total fleet cost of $5.9 million. The total 
estimated fleet cost for all changes required by the new rule was 
$171.9 million. The cost per equivalent life saved was estimated at $3 
million for front seats and $9 million for rear seats.
---------------------------------------------------------------------------

    \81\ For details on the PEA, please see Docket No. NHTSA-2000-
8570-4.
    \82\ The NPRM costs were estimated in 1999 dollars.
---------------------------------------------------------------------------

    The sole commenter on the estimated costs of the upgrade was 
DaimlerChrysler, which estimated the cost of the proposal to be as high 
as $12 per head restraint. No commenter provided an estimate of 
potential benefits. The Alliance stated that the potential benefits are 
unproven. AIAM commented that general lack of understanding of the 
injury mechanism makes it nearly impossible to calculate the benefits 
of the proposal or any modifications to it.
    ICBC stated that any figures pertaining to whiplash injury costs 
are underestimated because whiplash injury symptoms do not manifest 
themselves until 12 to 72 hours after the accident. Additionally, 
unlike other spinal injuries, whiplash has no linear relationship to 
crash severity. Low speed crashes may nevertheless result in whiplash. 
Many low speed rear end collisions resulting in whiplash are never 
reported to the police, because of little physical damage to the actual 
vehicles and lack of immediate injury symptoms. Advocates stated that 
the proposed rule would be a cost-effective advance in vehicle occupant 
safety, even if forecasted benefits were reduced to more conservative 
figures and costs of compliance were substantially higher. The FIU 
students stated that the rear outboard head restraint cost for 
equivalent lives saved would be approximately $9 million.
    In support of this final rule, the agency has prepared and docketed 
a FRIA that contains a thorough analysis of the benefits and the costs 
associated with the new FMVSS No. 202a, as well as our response to the 
NPRM comments on our initial cost and benefits estimates.\83\
---------------------------------------------------------------------------

    \83\ See Docket No. NHTSA-2004-19807.
---------------------------------------------------------------------------

    Costs: In the NPRM, we estimated the yearly costs of the proposed 
rule at approximately $171 million. Accordingly, the NPRM was deemed to 
be economically significant. As previously noted, the final rule will 
not require head restraints at each rear outboard designated seating 
position. Consequently, the costs associated with this final rule are 
significantly lower than the costs estimated in the NPRM. Specifically, 
the cost per year is estimated to be $70.1 million for front head 
restraints and $14.1 million for optional rear head restraints for a 
total yearly cost of $84.2 million. However,

[[Page 74879]]

the final rule remains economically significant because we estimate the 
benefits of this final rule to be in excess of $100 million. The 
average cost per vehicle is estimated to be:
    (a) $4.51 for front seats
    (b) $1.13 for rear seats previously equipped with head restraints
    The cost per equivalent life saved is estimated to be:
    (a) $2.39 million for front seats
    (b) $4.71 million for rear seats equipped with optional rear head 
restraints
    (c) $2.61 million for front seats and optional rear seats combined
    Benefits: We estimate the annual number of whiplash injuries to be 
approximately 272,464. 251,035 of these injuries involve occupants of 
front outboard seats, 21,429 injuries involve occupants of rear 
outboard seats. The average economic cost of each whiplash injury 
resulting from a rear impact collision is $9,994,\84\ which includes 
$6,843 in economic costs and $3,151 in quality of life impacts. The 
total annual cost of rear impact whiplash injuries is approximately 
$2.7 billion.
---------------------------------------------------------------------------

    \84\ The cost is estimated in 2002 dollars.
---------------------------------------------------------------------------

    Based on a study conducted by Kahane in 1982, the agency estimates 
that current integral head restraints are 17 percent effective in 
reducing whiplash injury in rear impact crashes for adult occupants, 
while current adjustable head restraints are 10 percent effective in 
reducing whiplash injury in rear impact crashes for adult 
occupants.\85\ The overall effectiveness of current head restraints for 
passenger cars is estimated to be 13.1 percent.
---------------------------------------------------------------------------

    \85\ Kahane, C., ``An Evaluation of Head Restraints, Federal 
Motor Vehicle Safety Standard 202.'' NHTSA, February 1982, DOT HS-
806-108.
---------------------------------------------------------------------------

    In the FRIA, we estimate that upgrading the head restraint 
requirements would yield the following benefits:
    (a) For front seats, reducing the backset to 55 mm increases the 
head restraint effectiveness by 5.83 percent, resulting in 15,272 fewer 
whiplash injuries for front seat occupants each year.
    (b) For rear seats, increasing the height of voluntarily installed 
rear head restraints increases the effectiveness of these head 
restraints by 17.45 percent, resulting in 1,559 fewer whiplash injuries 
for rear seat occupants each year.\86\
---------------------------------------------------------------------------

    \86\ In computing benefits, we based our estimates on the 
effectiveness of either increased height or reduced backset, but not 
both. We could not combine effectiveness of increased height and 
reduced backset because this, in some instances, would result in 
``double-counted'' benefits. Since determining combined 
effectiveness is not possible, the agency notes that these estimates 
may underestimate the true effectiveness.
---------------------------------------------------------------------------

    (c) The total annual reduction in rear impact whiplash injuries is 
thus estimated at (15,272 + 1,559) 16,831 or 6 percent of the annual 
number of whiplash injuries (272,464).\87\
---------------------------------------------------------------------------

    \87\ For the full details of how the agency arrived at these 
estimates, please see FRE, in subsection entitled ``Benefits Accrued 
From Increasing Height and Reducing Backset.''
---------------------------------------------------------------------------

    In sum, we estimate that this rulemaking will further reduce the 
incidence of whiplash by an additional [ap]6 percent (272,464 *.0618 = 
16,831). We note that with respect to whiplash injuries, a 6 percent 
reduction in the incidence of whiplash is a significant step forward 
because the current head restraints only prevent 13.1 percent of 
whiplash injuries occurring in rear impact crashes. The agency 
anticipates further improvements in head restraint effectiveness if we 
decide, in the future, to combine evaluation of the head restraints and 
the seats in a single standard.
    As was the case in the PEA, no estimate was made for potential 
injury mitigation other than for whiplash. Further, the agency has not 
prepared an analysis of the potential benefits of the position 
retention requirement. Although we have some estimates on the 
percentage of misadjusted head restraints, we have no data on how the 
availability of a lock would reduce this maladjustment.
    We have several reasons to believe that the potential benefits of 
this regulation are understated. First, for the reason stated above, we 
did not perform a separate analysis of benefits associated with reduced 
position retention requirement. Second, we agree with the ICBC comments 
regarding inherent underestimation of whiplash injury costs due to the 
underreporting of such injuries. As previously stated, whiplash 
injuries are often underreported because of late onset of symptoms. 
Third, no estimate of the potential reduction of higher-level neck 
injury (>AIS 1) was made. Although such injuries are much less 
frequent, their associated costs are much greater.

XVII. Rulemaking Analyses and Notices

a. Executive Order 12866 and DOT Regulatory Policies and Procedures

    NHTSA has considered the impact of this rulemaking action under 
Executive Order 12866 and the Department of Transportation's regulatory 
policies and procedures. The Office of Management and Budget reviewed 
rulemaking document under E.O. 12866, ``Regulatory Planning and 
Review.'' This rulemaking action has been determined to be significant 
under DOT Policies and Procedures and Executive Order 12866 because of 
public interest. Further, this rulemaking action is economically 
significant because the agency estimates yearly economic cost savings 
of approximately $127 million ($2.61 million x 48.79 equivalent 
fatalities). NHTSA is placing in the public docket a Final Regulatory 
Evaluation describing the costs and benefits of this rulemaking action. 
The costs and benefits are summarized in the previous section of this 
document. The total estimated recurring fleet cost for all changes 
required by the new rule is $84.2 million. The average economic cost of 
a whiplash injury (excluding quality of life values) in a rear impact 
is estimated be $9,994 in 2002 dollars, resulting in a total annual 
cost of approximately $2.707 billion for 272,464 whiplash injuries.\88\ 
We estimate that when the new rule is fully implemented, it will reduce 
yearly instances of whiplash injuries by 6 percent or 16,831, resulting 
in yearly economic cost savings of approximately $127 million.
---------------------------------------------------------------------------

    \88\ Unless otherwise specified, all dollar alues in this 
document are represented in 2002 dollars.
---------------------------------------------------------------------------

b. Regulatory Flexibility Act

    NHTSA has considered the effects of this rulemaking action under 
the Regulatory Flexibility Act (5 U.S.C. 601 et seq.) The final rule 
will affect motor vehicle manufacturers, alterers, and seating 
manufacturers. NHTSA has determined that this action will not have a 
significant economic impact on a substantial number of small entities.
    First, NHTSA estimates that there are only four small passenger car 
and light truck manufacturers in the United States. These companies buy 
their seats from a seat manufacturer and install them in their 
vehicles. Accordingly, the necessary changes to seat design will be 
accomplished by seat manufacturers and not these small businesses.
    Second, there are approximately 30 seat manufacturers in the U.S. 
Many of these fall under the category of small businesses. The final 
rule will have some effect on these small businesses by changing the 
requirements for head restraints. However, raising the height of an 
integral or adjustable head restraint or changing the design of a head 
restraint to meet the new backset limit is not a novel or complex task 
that would require significant financial expenditures. Further, 
numerous vehicles currently in production already meet the new 
requirements. Consequently, the agency does not believe that this 
rulemaking will have a

[[Page 74880]]

significant impact on small seat manufacturers.
    Third, this rulemaking could affect final stage vehicle 
manufacturers and vehicle alterers. Many final stage manufacturers and 
alterers install supplier-constructed seating systems. Some of those 
seats and head restraints will have to be redesigned to meet the new 
requirements. However, final stage manufacturers or alterers most often 
purchase seats that have already been tested by the seat manufacturers 
and rely on that testing to certify to the requirements of FMVSS No. 
202. Accordingly, the agency does not believe that this rulemaking will 
have a significant impact on final stage manufacturers and vehicle 
alterers.
    For the reasons discussed above, the small entities that will most 
likely be affected by the new rule are seat manufacturers. While these 
seat manufacturers will face additional compliance costs, the agency 
believes that raising the height of a head restraint is not a novel or 
complex engineering task. The agency notes that, in the unlikely event 
that a small vehicle manufacturer did face substantial economic 
hardship, it could apply for a temporary exemption for up to three 
years.\89\ Additional information concerning the potential impacts of 
the new rule on small entities is presented in the FRIA.

c. National Environmental Policy Act
---------------------------------------------------------------------------

    \89\ See 49 CFR part 555.
---------------------------------------------------------------------------

    NHTSA has analyzed the final rule for the purposes of the National 
Environmental Policy Act. The agency has determined that implementation 
of this action will not have any significant impact on the quality of 
the human environment.

d. Executive Order 13132 (Federalism)

    The agency has analyzed this rulemaking in accordance with the 
principles and criteria contained in Executive Order 13132 and has 
determined that it does not have sufficient federalism implications to 
warrant consultation with State and local officials or the preparation 
of a federalism summary impact statement. The final rule has no 
substantial effects on the States, or on the current Federal-State 
relationship, or on the current distribution of power and 
responsibilities among the various local officials. The final rule is 
not intended to preempt State tort civil actions.

e. Unfunded Mandates Reform Act

    Section 202 of the Unfunded Mandates Reform Act of 1995 (UMRA) 
requires Federal agencies to prepare a written assessment of the costs, 
benefits, and other effects of proposed or final rules that include a 
Federal mandate likely to result in the expenditure by State, local, or 
tribal governments, in the aggregate, or by the private sector, of more 
than $100 million in any one year ($120,700,000 as adjusted for 
inflation with base year of 1995).
    The total estimated fleet cost for all changes required by the new 
rule is $84.2 million. Because this final rule will not have a $100 
million effect, no Unfunded Mandates assessment has been prepared. A 
full assessment of the rule's costs and benefits is provided in the 
FRIA.

f. Executive Order 12988 (Civil Justice Reform)

    This final rule will not have any retroactive effect. Under 49 
U.S.C. 30103, whenever a Federal motor vehicle safety standard is in 
effect, a State may not adopt or maintain a safety standard applicable 
to the same aspect of performance which is not identical to the Federal 
standard, except to the extent that the State requirement imposes a 
higher level of performance and applies only to vehicles procured for 
the State's use. 49 U.S.C. 30161 sets forth a procedure for judicial 
review of final rules establishing, amending or revoking Federal motor 
vehicle safety standards. That section does not require submission of a 
petition for reconsideration or other administrative proceedings before 
parties may file suit in court.

g. Paperwork Reduction Act

    This final rule includes the following ``collections of 
information,'' as that term is defined in 5 CFR part 1320 Controlling 
Paperwork Burdens on the Public: The final rule requires that vehicle 
manufacturers include in owners' manuals information about appropriate 
head restraint adjustment. At present, OMB has approved NHTSA's 
collection of owner's manual requirements under OMB clearance No. 2127-
0541 Consolidated Justification of Owner's Manual Requirements for 
Motor Vehicles and Motor Vehicle Equipment. This clearance will expire 
on 1/31/2005. NHTSA anticipates renewal of OMB clearance no. 2127-0541 
before the requirements established by today's rule become mandatory.

h. Executive Order 13045

    Executive Order 13045 \90\ applies to any rule that: (1) Is 
determined to be ``economically significant'' as defined under E.O. 
12866, and (2) concerns an environmental, health or safety risk that 
NHTSA has reason to believe may have a disproportionate effect on 
children. If the regulatory action meets both criteria, we must 
evaluate the environmental health or safety effects of the planned rule 
on children, and explain why the planned regulation is preferable to 
other potentially effective and reasonably feasible alternatives 
considered by us.
---------------------------------------------------------------------------

    \90\ 62 FR 19885, April 23, 1997.
---------------------------------------------------------------------------

    This rule is economically significant. However, this rule will not 
have a disproportionate effect on children. Most children do not need a 
head restraint because they are short enough for the seat back to 
adequately address a risk of whiplash injury. Once a child is tall 
enough to need a head restraint, this rule will provide additional 
protection because rear seats will now be equipped with head 
restraints, thus providing a new level of safety to taller children.

i. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act (NTTAA) requires NHTSA to evaluate and use existing voluntary 
consensus standards in its regulatory activities unless doing so would 
be inconsistent with applicable law (e.g., the statutory provisions 
regarding NHTSA's vehicle safety authority) or otherwise impractical. 
In meeting that requirement, we are required to consult with voluntary, 
private sector, consensus standards bodies. Examples of organizations 
generally regarded as voluntary consensus standards bodies include the 
American Society for Testing and Materials (ASTM), the Society of 
Automotive Engineers (SAE), and the American National Standards 
Institute (ANSI). If NHTSA does not use available and potentially 
applicable voluntary consensus standards, we are required by the Act to 
provide Congress, through OMB, an explanation of the reasons for not 
using such standards.
    Voluntary consensus standards are technical standards developed or 
adopted by voluntary consensus standards bodies. Technical standards 
are defined by the NTTAA as ``performance-based or design-specific 
technical specifications and related management systems practices.'' 
They pertain to ``products and processes, such as size, strength, or 
technical performance of a product, process or material.''
    We have incorporated a Society of Automotive Engineers (SAE) 
Recommended Practice J211/1 (rev. Mar 95), ``Instrumentation for Impact 
Test--

[[Page 74881]]

Part 1--Electronic Instrumentation.'' We have incorporated a three-
dimensional manikin from the Society of Automotive Engineers (SAE) J826 
(rev. Jul 95). None of the voluntary consensus standards incorporated 
into this final rule provides a comprehensive head restraint geometry 
standard that could replace this rule in its entirety. Instead, certain 
specific components of the final rule were adopted from available 
voluntary consensus standard.
    In sum, while two specific voluntary consensus standards are 
incorporated in the final rule, the overall need for extensive and 
precise new head restraint safety requirement precludes us from 
adopting of such voluntary consensus standards as a complete substitute 
for the final rule. No other voluntary consensus standards are 
addressed by this rulemaking. We were also were unable to identify any 
other relevant voluntary consensus standards.

j. Privacy Act

    Anyone is able to search the electronic form of all comments 
received into any of our dockets by the name of the individual 
submitting the comment (or signing the comment, if submitted on behalf 
of an association, business, labor union, etc.). You may review DOT's 
complete Privacy Act Statement in the Federal Register published on 
April 11, 2000 (65 FR 19477 at 19478).

Appendix A: Efforts To Harmonize With ECE 17

    In proposing to upgrade FMVSS No. 202, we sought to harmonize 
with existing ECE regulations, except to the extent needed to 
increase safety of vehicle occupants and to facilitate enforcement. 
The ECE has two regulations pertinent to our efforts on upgrading 
FMVSS No. 202. ECE 17 and ECE 25 both regulate head restraints. 
However, the provisions of ECE 17 supersede the requirements of ECE 
25 for most vehicles subject to this final rule. Specifically, ECE 
17 governs the head restraint requirements in all passenger 
vehicles, light trucks, and buses with fewer than 17 designated 
seating positions. The ECE 25 applies only to buses with 17 or more 
designated seating positions. Because this final rule applies to 
vehicles with a GVWR equal or less than 4536 kg, it is unlikely that 
any buses subject to this final rule would fall under ECE 25. 
Accordingly, we sought to harmonize certain aspects of this final 
rule with ECE 17, and not ECE 25.
    In some instances, achieving improved safety has made it 
necessary for us to go beyond or take an approach different from 
that in ECE 17. For example, this final rule limits the backset, 
while ECE 17 does not. We note that in most instances in which this 
rule is harmonized with the substance of the ECE requirements, the 
actual regulatory language is nevertheless drafted differently in 
order to facilitate enforcement. Specifically, we have found it 
necessary to specify different compliance procedures to facilitate 
their enforcement under our statutory provisions. For example, there 
are differences in the way in which gaps within head restraints are 
measured.
    In response to the NPRM, industry commenters generally advocated 
harmonizing the new FMVSS No. 202 with ECE 17, which applies to most 
vehicles subject to this final rule, although Honda requested 
harmonization with ECE 25. GM and Volkswagen suggested that it would 
be more appropriate to harmonize with ECE 17, rather than ECE 25, 
because ECE 17 is utilized for the type approval of vehicles, while 
ECE 25 is used for the type approval of head restraints only.
    As previously stated, this final rule is not fully harmonized 
with the ECE requirements. Instead, the rule adopts or modifies 
certain portions of ECE 17. Several of our newly adopted 
requirements do not have any counterparts in the ECE regulations. 
Among those is a limit on backset and position retention requirement 
for adjustable head restraints. In addition, our limit on gaps in 
adjustable restraints is different from that in the ECE regulations.
    The discussions that follow provide a brief description of those 
instances in which the final rule does or does not harmonize with 
the ECE regulations.

A. Areas in Which the Final Rule Requirements and Procedures Are 
Harmonized With Those of the ECE Regulations

    Neither this final rule nor ECE 17 requires head restraints for 
rear outboard seating positions. Although we proposed mandatory rear 
head restraints in the NPRM, we have decided against requiring head 
restraints in rear outboard seating positions because a more refined 
estimate of the cost effectiveness expressed as cost per equivalent 
life saved no longer supported this requirement and because we were 
concerned about potential visibility issues and with potential loss 
of certain features currently available in some ``multi-
configuration'' vehicles.
    This final rule and ECE 17 specify theoretically identical front 
and optional rear head restraint height requirements. For integral 
head restraints, the ECE 17, Paragraph 5.5.2 requires that front 
head restraints reach a height of 800 mm and rear head restraints 
reach the height of 750 mm. For adjustable head restraints, the ECE 
17, Paragraph 5.5.3.1 requires that front head restraints be capable 
of reaching a height of 800 mm, and have no ``use positions'' with a 
height of less than 750 mm. The optional rear adjustable head 
restraints must reach the height of at least 750 mm and cannot have 
any ``use position'' below that height. Additionally, ECE 17, 
Paragraph 5.5.4 allows for a 25 mm exception to the head restraint 
height requirement for head restraints installed in low roofline 
vehicles.
    This final rule likewise requires that the front integral head 
restraints reach a height of 800 mm above the H-point. The optional 
rear integral head restraints must reach the height of 750 mm above 
the H-point. For adjustable head restraints, the front head 
restraint must be capable of reaching the height of at least 800 mm 
above the H-point, and both front and optional rear head restraints 
cannot have an adjustment position below 750 mm above the H-point, 
unless it is a ``non-use'' position described above in Section IX c.
    Additionally, the final rule allows for a 25 mm height exception 
for head restraints installed in low roofline vehicles. However, the 
application of the 25 mm height exception is narrower in this final 
rule. Specifically, ECE 17 allows for a 25 mm height exception if 
the head restraint interferes with any interior vehicle structure. 
By contrast, this final rule limits the 25 mm exception to 
situations in which a head restraint would interfere with the 
roofline or the backlight (for rear head restraint). The 25 mm 
height exception for low roofline vehicles is discussed in Section 
VI a. and b.
    For height measurement ECE17, Paragraph 6.5.4 uses the R-point 
as the point of reference, while the final rule uses the H-point. 
Theoretically, these points are the same if the seat is placed in 
its rearmost normal riding or driving position, as specified by the 
vehicle manufacturer. The chief difference between the two points is 
that the H-point is referenced to the seat, while the R-point is 
referenced to the vehicle. NHTSA prefers the H-point as the point of 
reference because it takes into consideration the characteristics of 
the actual seat being tested.
    The final rule and ECE 17 Paragraph 5.1.3 both have an energy 
absorption test procedure. However, the final rule specifies using a 
linear impactor, while ECE 17, Annex 6, Paragraph 1.2.1 specifies a 
pendulum impactor. Nonetheless, NHTSA believes that the compliance 
testing methods are substantially similar because the mass and 
velocity of the impactor specified in this final rule is the same as 
the impactor specified in ECE 17. We chose to test using the linear 
impactor in order to facilitate enforcement. For a more detailed 
explanation of our rationale with respect to the choice of impactor, 
please see Section XI.
    ECE 17, Paragraph 5.10 mandates that the head restraint for a 
seat must extend at least 85 mm to each side of the centerline of 
the seat. In other words, a head restraint width must be at least 
170 mm. This ECE 17 minimum width requirement applies to both bench 
seats and bucket seats. This final rule specifies identical 
requirements of 170 mm,\91\ except for bench seats in the front 
outboard seating positions where the head restraint width must not 
be less than 254 mm.
---------------------------------------------------------------------------

    \91\ We note that the NPRM proposed a value of 171 mm rather 
than 170, which is consistent with the current regulation. We have 
reduced this value by 1 mm for consistency with ECE 17.
---------------------------------------------------------------------------

    Some of the head restraint gap allowances incorporated into the 
final rule harmonize with ECE 17. The final rule and ECE 17, 
Paragraphs 5.7, 5.8 all limit gaps within the perimeter of a head 
restraint to 60 mm. Similarly, for integral head restraints, the gap 
between the head restraint and the seat is limited to 60 mm in both 
regulations. However, the final rule requires different gap

[[Page 74882]]

limits between the seat and the adjustable head restraint. The 
details of these requirements are discussed in the next section.
    The ECE 17, Paragraph 5.1.1 requires locks on adjustable head 
restraints, but does not mandate that these locks meet vertical and 
horizontal position retention requirements to insure their 
functionality. By contrast, this rule requires that adjustable head 
restraints meet vertical and horizontal position retention 
requirements described above in Section X. We note, however, that 
both ECE 17, Paragraphs 5.11, 5.12 and this final rule impose 
horizontal displacement limits and strength requirements on all 
seating position equipped with head restraints.
    Finally, both this final rule and ECE 17, Paragraph 5.13 allow 
removability of head restraints with a deliberate action distinct 
from any act necessary for adjustment. For a more detailed 
discussion on removability of front and rear head restraints, please 
see Section IX b.

B. Areas in Which the Final Rule Requirements and Procedures Differ 
From Those in the ECE Regulations

    The chief difference between ECE 17 and this final rule is that 
we are requiring a backset limit of 55 mm for front seat head 
restraints. The ECE regulation does not limit the amount of backset. 
Studies show that a head restraint that is close to the back of an 
occupant's head reduces the potential for whiplash.\92\ Further, 
backset is a critical component of head restraint geometry. For 
these reasons and those outlined in Section VII above, NHTSA 
believes it is necessary to depart from the ECE regulations and set 
a limit on backset.
---------------------------------------------------------------------------

    \92\ See ICBC comments and attached research papers (Docket No. 
NHTSA-2000-8570-16).
---------------------------------------------------------------------------

    To measure height of head restraints, the final rule specifies 
the use of SAE J826 manikin. To measure front seat backset, the 
final rule specifies the use of the Head Restraint Measurement 
Device (HRMD). ECE 17 does not specify any device for height 
measurement and, as noted above, has no backset requirement. We 
chose the SAE J826 manikin and HRMD instead of certain Computer 
Aided Design (CAD) programs, as suggested by the manufacturers, 
because the HRMD and SAE J826 manikin measure the actual seating 
system, instead of relying on the computer-generated seat model 
utilized by other computer-aided measuring techniques.
    In addition to the measuring device, the height measuring 
procedure in this final rule in some circumstances differs from the 
measuring procedure of ECE 17. Specifically, this final rule 
specifies that the seat back angle for height measurement be as 
close as possible to 25 degrees. ECE 17, Paragraph 6.1.1 similarly 
specifies the 25-degree seat back angle if there is no manufacturer 
specified seat back angle. However, if there is a manufacturer 
specified seat back angle, the manufacturer specified angle is used 
instead of the 25-degree angle. Further, this final rule specifies 
that the seat cushion be adjusted to its most unfavorable position, 
i.e., the highest position. ECE 17, Annex 3, Paragraph 2.13 
specifies that the cushion is to be placed in the manufacturer 
specified position of adjustment. Positioning the cushion in the 
highest position of adjustment allows us to measure the height of 
head restraints in the ``worst case scenario.'' That is, the minimum 
required height would be assured even if the seat occupant adjusts 
the seat cushion all the way up.
    ECE 17, Paragraph 5.7 limits the gap between the lower edge of 
an adjustable head restraint and the top of the seat back to 25 mm 
when the head restraint is in its lowest position. The final rule, 
however, adopts a 60 mm gap limit between the seat back and the head 
restraint. Further, the final rule differs from the ECE requirements 
in that it specifies measuring this gap with a 165 mm diameter 
sphere placed on the front of the head restraint in lieu of 
measuring the smallest gap between the top of a seat back and the 
bottom of a head restraint. For a more detailed discussion on why we 
chose to adopt a different gap requirement and different measuring 
device, please see Section IX a.
    ECE 17, Paragraph 5.5.3.4 permits non-use positions (resulting 
in a height of less than 750 mm) for front head restraints, provided 
that the head restraints automatically return from those positions 
to their proper use positions when the seats become occupied. With 
respect to rear head restraints, ECE 17, Paragraph 5.5.3.3 allows 
displacement to a position below 750 mm as long as the non-use 
position is ``clearly recognizable to the occupant.'' In contrast, 
this final rule does not permit non-use positions for front head 
restraints. NHTSA believes non-use positions in front seats are 
unnecessary since the front head restraints do not raise the same 
visibility concern as the rear head restraints.
    While we permit non-use positions for optional rear head 
restraints, our requirements differ from those of the ECE. That is, 
the final rule allows rear head restraint to be in non-use positions 
when seats are unoccupied, subject to meeting certain requirements. 
Specifically, a manually folding optional rear head restraint must 
rotate forward or rearward by at least 60 degrees between the 
``proper use position'' and the ``non-use position.'' No other 
``non-use positions'' are allowed unless the head restraint returns 
automatically to its ``proper use position when the seat becomes 
occupied'' (as tested by placing a 5th percentile female dummy in 
the rear outboard seat with the optional head restraint in a ``non-
use position''). As with other procedural differences between this 
final rule and the ECE, this test procedure is necessary in order to 
facilitate enforcement.
    The final rule also features a dynamic compliance option not 
found in ECE 17. For front outboard and optional rear outboard head 
restraints, with the head restraint midway between the lowest and 
the highest position of adjustment, the final rule requires a head-
to-torso rotation limit of 12 degrees using the 50th percentile male 
Hybrid III dummy. The final rule limits HIC<INF>15</INF> to 500 for 
all the dynamic compliance option tests.
    The final rule specifies that adjustable head restraints must 
remain within 13 mm of their vertical and horizontal position under 
the application of force. Although ECE 17 requires locks on 
adjustable head restraints, the horizontal and vertical position 
retention requirements do not have a counterpart in the ECE 
regulations. However, we find it necessary to require a certain 
minimal level of performance to ensure that the retention locks 
perform their function.
    Both ECE 17, Paragraphs 5.11, 5.12 and this final rule have 
limits on the horizontal displacement and strength requirements. The 
purpose of this requirement is to ensure that the head restraint can 
withstand the application of rearward force and will not fail when 
the occupant's head makes contact with the head restraint during a 
rear impact to the vehicle. The final rule and ECE both maintain a 
373 Nm moment on the vehicle seat, applied through the back pan, as 
the head restraint is loaded. However, the head restraint loading 
sequence differs in the two standards. In the final rule, the 
loading device's reference position is located by first applying a 
force producing 37 Nm moment about the H-point. Then, the load is 
increased at a rate of 187 Nm/minute, until a 373 Nm moment is 
generated. This moment is held for 5 seconds and then reduced to 37 
Nm. While the 373 Nm moment applied to the head restraint is being 
maintained, the head restraint must not allow the loading device to 
displace more than 102 mm. When the moment is reduced, the head 
restraint loading device must return to within 13 mm of the initial 
reference position. This horizontal position retention requirement 
is unique to our final rule. While the ECE regulations do contain a 
similar rearward displacement test that limits displacement to 102 
mm, they do not require that the head restraint loading device 
return to within 13 mm of its reference position. Further, the ECE 
regulations do not specify a loading rate and hold time. NHTSA 
believes the 5-second hold time and loading rate specifications are 
a necessary clarification of the test procedure.
    Finally, the ECE 17, Paragraph 5.5.4 allows a 25 mm height 
allowance in those instances in which the front or rear head 
restraint would otherwise interfere with any fixed vehicle 
structure, when the seat is in the ``use'' or ``non-use'' position 
of adjustment. This final rule permits a 25 mm height allowance only 
in situations in which the head restraint interferes with either the 
roofline or the backlight. We decided against allowing a 25 mm 
height allowance in situations in which the head restraint 
interferes with other fixed vehicle structures because we believe 
that such an exception would provide relief in instances in which 
none is needed. For a more detailed explanation of our rationale 
with respect to the 25 mm height allowance please see Section VI a. 
and b.

Appendix B: Cervigard Suggestion

    Cervigard, Inc. is a New Jersey based company that designed a 
head restraint incorporating a contoured shape intended to match the 
curvature of the head and cervical spine. The portion of the head 
restraint that protrudes forward adjacent to the neck is referred to 
as a neck bolster.
    Cervigard submitted two sets of test data, comparing 
conventional head restraints

[[Page 74883]]

against the Cervigard Head Restraint System using a special neck-
bolstering contour. The first set came from an experiment that was 
conducted by Cadillac and Lear, which used Hybrid III dummies 
representing a 5th percentile female, 50th percentile male, and 95th 
percentile male in sled tests at 16 and 24 km/h delta-Vs. Specific 
positions of the test head restraints relative to the occupants were 
not given. Instead, they were designated as ``Full Up'' or ``Full 
Down.'' These were described as being ``In-Position'' or ``Out-of-
Position.'' HIC, NIC,\93\ upper neck shear and moment were provided. 
``Out-of-Position'' results were provided for the 5th percentile 
female, 50th percentile male and 95th percentile male. ``In-
Position'' results were provided for the 50th percentile male only. 
In general, the results provided indicated lower injury measures for 
the Cervigard head restraint tests.
---------------------------------------------------------------------------

    \93\ NIC is a whiplash criterion developed by Adman and Bostrom 
et al. NIC = 0.2 a<INF>rel</INF> + v<INF>rel</INF>2, where 
a<INF>rel</INF> is the resultant relative acceleration between first 
thoracic vertebra (T1) and first cervical vertebra (C1), 
v<INF>rel</INF> is the resultant relative velocity between T1 and 
C1.
---------------------------------------------------------------------------

    The second set of tests was performed by Wayne State University 
using a computer simulation model. The model appeared to be of a 
head and neck without a torso. A standard OEM head restraint was 
compared to what was called the Cervigard head restraint. Both 
restraints were modeled with the backsets shown in the table below. 
The height measurement of the head restraint relative to the head 
was not disclosed. Thus, it is unclear whether the head restraint 
height was within the range specified in the NPRM. The commenter 
states that, according to a researcher from Wayne State University, 
the Cervigard head restraint performed much better, better, or as 
good as a standard head restraint.

------------------------------------------------------------------------
                Head restraint                          Backset
------------------------------------------------------------------------
Standard Down................................  70 mm
Standard Up..................................  70 mm
Cervigard Down...............................  75 mm
Cervigard Up.................................  30 mm
------------------------------------------------------------------------

    Based on their submissions, Cervigard requested that the new 
rule require a neck-bolstering device. According to an engineering 
report from Cervigard, the Cervigard head restraint exhibited 23 
percent to 38 percent lower NIC and neck shear forces compared to 
samples of presently used head restraints, modified to comply with 
the proposed rule. Cervigard commented that a 50 mm backset position 
without neck-bolstering device might actually be too close to the 
head, which could result in potentially exacerbating the injury. We 
note that no other commenter or research source indicated that a 50 
mm backset position may prove to be too close to the head, as it 
relates to occupant safety, or somehow dangerous to the occupant.
    In support of its recommendation, Cervigard asserted that the 
additional costs of adding a neck-bolster device would be minimal if 
the requirement were added to the new rulemaking immediately, 
because seat manufacturers will be retooling for a new standard 
anyway. Specifically, Cervigard provided an estimate of $3.50 per 
each head restraint.
    Several lawmakers, among them Senator Torricelli of New Jersey, 
Congressman Bill Pascrell Jr. of the 8th District of New Jersey, New 
Jersey State Senator Anthony R. Bucco, and New Jersey Assemblyman 
Alex DeCroce submitted comments in support of Cervigard. 
Collectively, they urged NHTSA to incorporate a neck-bolstering 
requirement into the new rule, in light of minimal additional cost 
to manufacturers, support from safety and medical experts, and the 
societal benefit of reducing instances of neck trauma.
    Several chiropractors and other medical professionals submitted 
comments to support the addition of a requirement for the Cervigard 
device to the upgraded head restraint standard. In general, most 
commented that the Cervigard device reduces facet joint injury in 
the lower cervical region by maintaining normal curvature of the 
spine at time of impact.
    In contrast, according to the comments submitted by Lear 
Corporation and General Motors, Cervigard has put forth an 
incomplete and inaccurate summary of tests performed by Lear using 
the Cervigard device. Evaluations of the Cervigard device were 
conducted with the head restraints improperly positioned. Lear has 
never compared Cervigard head restraints to optimally positioned 
head restraints or latest head restraint designs and never stated 
that Cervigard head restraints performed ``as good'' or ``better'' 
than conventional head restraints. Indeed, GM opines that any 
improvement was due to decreased backset distance and not 
necessarily to Cervigard contour (See David E. Calder Engineering 
Report No. 2, top graph, Docket NHTSA-00-8570-42). GM further stated 
that any assertion indicating that Cervigard head restraints passed 
the ``do no harm'' criteria is false because no such criteria 
exists.
    Lear cautioned that the submitted data results were based on 
preliminary, unapproved data that have since been revised. 
Additionally, Cervigard omitted data showing that its device 
consistently increased certain injury parameters. Lear also 
indicated that what was reported by Cervigard as upper neck 
extension moment was actually lateral bending moment, which one 
would expect to be much lower than the extension moment. In fact, 
the Cervigard device often increased neck tension. Lear's own 
research indicated that the Cervigard device increased risk of neck 
injury in 62.5 percent of ``Out of Position'' head restraint 
conditions tested.
    In examining the test data from Wayne State, we conclude that 
the results confirm our position that the backset is a critical 
parameter in head restraint performance. It is not surprising that 
the Cervigard device tested with a 30 mm backset was able to limit 
the head's rearward motion to a much greater degree, compared to 
other configurations, with a much greater backset. Because the rest 
of the Wayne State testing was performed with backset greater than 
70 mm, it is impossible to draw any conclusions about the benefits 
of a head restraint with a neck bolster in comparison to those of a 
conventional head restraint, positioned, as we will require.
    In regard to the sled testing performed by Lear for GM, the 
docket submission by Cervigard did not provide positioning 
information. Additionally, as the proprietors of the data (Lear and 
GM) have indicated, the comparative sled testing between 
conventional head restraints and Cervigard did not take place with 
the same backset values. Our conclusion is that there is no way to 
determine from this information whether the neck bolster was 
actually helpful. In sum, we believe that a head restraint meeting 
the new height and backset requirements will serve to restrain the 
head with respect to the torso. The proposed neck bolster has not 
yet been shown to provide any additional benefit.
    We have an additional concern about a neck bolster. Unless the 
bolstered head restraint is precisely positioned at the appropriate 
height, the neck bolster will not support the neck. Currently, 
adjustable head restraints need only be adjusted such that the top 
is at least as high as the occupant's head C.G. If the adjustable 
restraint were supplemented by a neck bolster, positioning would 
need to be more precise. It appears that, for integral or fixed head 
restraints, the bolstered restraint would only fit an individual of 
a specific height. Thus, any neck bolster requirement would by 
necessity eliminate integral head restraint designs. We also 
conclude that it would be difficult to require a specific neck 
bolster contour that would fit a majority of occupants. Further, we 
note that we did not propose to adopt a neck bolster in the NPRM. 
Therefore, adopting such a requirement in this final rule would fall 
outside the scope of notice. Based on the comments and analysis 
presented above, we are not adopting any requirements for a neck 
bolster.

List of Subjects in 49 CFR Part 571

    Imports, Incorporation by Reference, Motor Vehicle Safety, Motor 
Vehicles, and Tires.

0
In consideration of the foregoing, 49 CFR part 571 is amended as 
follows:

PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS

0
1. The authority citation for part 571 of title 49 continues to read as 
follows:

    Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.50.


0
2. Section 571.202 is amended as follows:
0
A. Revise the section heading, S2, S3, S4, and S4.1 through S4.3;
0
B. Add S4.4, S4.5, and S4.6; and
0
C. Revise S5, S5.1 introductory text, S5.1(a)(2), (a)(3), and (b), S5.2 
introductory text, and S5.2(b) to read as follows:

[[Page 74884]]

Sec.  571.202  Standard No. 202; Head restraints; Applicable at the 
manufacturers option until September 1, 2008.

* * * * * *
    S2. Application. This standard applies to passenger cars, and to 
multipurpose passenger vehicles, trucks and buses with a 4,536 kg or 
less, manufactured before September 1, 2008. Until September 1, 2008, 
manufacturers may comply with the standard in this Sec.  571.202, with 
the European regulations referenced in S4.3 of this Sec.  571.202, or 
with the standard in Sec.  571.202a.
* * * * * *
    S3. Definitions.
    Head restraint means a device that limits rearward displacement of 
a seated occupant's head relative to the occupant's torso.
    Height means, when used in reference to a head restraint, the 
distance from the H-point, measured parallel to the torso reference 
line defined by the three dimensional SAE J826 (rev. Jul 95) manikin, 
to a plane normal to the torso reference line.
    Top of the head restraint means the point on the head restraint 
with the greatest height.
    S4. Requirements.
    S4.1 Each passenger car, and multipurpose passenger vehicle, truck 
and bus with a 4,536 kg or less, must comply with, at the 
manufacturer's option, S4.2, S4.3 or S4.4 of this section.
    S4.2 Except for school buses, a head restraint that conforms to 
either S4.2 (a) or (b) of this section must be provided at each 
outboard front designated seating position. For school buses, a head 
restraint that conforms to either S4.2 (a) or (b) of this section must 
be provided at the driver's seating position.
    (a) When tested in accordance with S5.1 of this section, limit 
rearward angular displacement of the head reference line to 45 degrees 
from the torso reference line; or
    (b) When adjusted to its fully extended design position, conform to 
each of the following:
    (1) When measured parallel to the torso line, the top of the head 
restraint must not be less than 700 mm above the seating reference 
point;
    (2) When measured either 64 mm below the top of the head restraint 
or 635 mm above the seating reference point, the lateral width of the 
head restraint must be not less than:
    (i) 254 mm for use with bench-type seats; and
    (ii) 170 mm for use with individual seats;
    (3) When tested in accordance with S5.2 of this section, any 
portion of the head form in contact with the head restraint must not be 
displaced to more than 102 mm perpendicularly rearward of the displaced 
extended torso reference line during the application of the load 
specified in S5.2 (c) of this section; and
    (4) When tested in accordance with S5.2 of this section, the head 
restraint must withstand an increasing load until one of the following 
occurs:
    (i) Failure of the seat or seat back; or,
    (ii) Application of a load of 890N.
    S4.3 Incorporation by reference.
    The English language version of the Economic Commission for Europe 
(ECE) Regulation 17: ``Uniform Provisions Concerning the Approval of 
Vehicles with Regard to the Seats, their Anchorages and any Head 
Restraints'' ECE 17 Rev. 1/Add. 16/Rev. 4 (31 July 2002) is 
incorporated by reference in S4.4(a) of this section. The Director of 
the Federal Register has approved the incorporation by reference of 
this material in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. A 
copy of ECE 17 Rev. 1/Add. 16/Rev. 4 (31 July 2002) may be obtained 
from the ECE Internet site: http://www.unece.org/trans/main/wp29/wp29regs/r017r4e.pdf, or by writing to: United Nations, Conference 
Services Division, Distribution and Sales Section, Office C.115-1, 
Palais des Nations, CH-1211, Geneva 10, Switzerland. A copy of ECE 17 
Rev. 1/Add. 16/Rev. 4 (31 July 2002) may be inspected at NHTSA's 
Technical Information Services, 400 Seventh Street, SW., Plaza Level, 
Room 403, Washington, DC, or at the National Archives and Records 
Administration (NARA). For information on the availability of this 
material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
    S4.4. Except for school buses, a head restraint that conforms to 
S4.4 (a) and (b) of this section must be provided at each outboard 
front designated seating position. For school buses, a head restraint 
that conforms to S4.4 (a) and (b) of this section must be provided at 
the driver's seating position.
    (a) The head restraint must comply with Paragraphs 5.1.1, 5.1.3, 
5.3.1, 5.5 through 5.13, 6.1.1, 6.1.3, and 6.4 through 6.8 of the 
English language version of the Economic Commission for Europe (ECE) 
Regulation 17: ECE 17 Rev. 1/Add. 16/Rev. 4 (31 July 2002).
    (b) The head restraint must meet the width requirements specified 
in S4.2(b)(2) of this section.
    S4.5 Except for school buses, head restraints that conform to the 
requirements of Sec.  571.202a must be provided at each front outboard 
designated seating position. If a rear head restraint (as defined in 
Sec.  571.202a) is provided at a rear outboard designated seating 
position, it must conform to the requirements of Sec.  571.202a 
applicable to rear head restraints. For school buses, a head restraint 
that conforms to the requirements of Sec.  571.202a must be installed 
at the driver's seating position.
    S4.6 Where manufacturer options are specified in this section or 
Sec.  571.202a, the manufacturer must select an option by the time it 
certifies the vehicle and may not thereafter select a different option 
for that vehicle. The manufacturer may select different compliance 
options for different designated seating positions to which the 
requirements of this section are applicable. Each manufacturer must, 
upon request from the National Highway Traffic Safety Administration, 
provide information regarding which of the compliance options it has 
selected for a particular vehicle or make/model.
    S5. Demonstration procedures.
    S5.1 Compliance with S4.2(a) of this section is demonstrated in 
accordance with the following with the head restraint in its fully 
extended design position:
    (a) * * *
    (2) Rotate the head of the dummy rearward until the back of the 
head contacts the flat horizontal surface specified in S5.1(a)(1) of 
this section.
    (3) Position the SAE J-826 two-dimensional manikin's back against 
the flat surface specified in S5.1(a)(1) of this section, alongside the 
dummy with the H-point of the manikin aligned with the H-point of the 
dummy.
* * * * *
    (b) At each designated seating position having a head restraint, 
place the dummy, snugly restrained by Type 2 seat belt, in the 
manufacturer's recommended design seating position.
* * * * *
    S5.2 Compliance with S4.2(b) of this section is demonstrated in 
accordance with the following with the head restraint in its fully 
extended design position:
* * * * *
    (b) Establish the displaced torso reference line by applying a 
rearward moment of 373 Nm about the seating reference point to the seat 
back through the test device back pan specified in S5.2(a) of this 
section.
* * * * *
0
3. Section 571.202a is added to read as follows:

[[Page 74885]]

Sec.  571.202a  Standard No. 202a; Head restraints; Mandatory 
applicability begins on September 1, 2008.

    S1. Purpose and scope. This standard specifies requirements for 
head restraints to reduce the frequency and severity of neck injury in 
rear-end and other collisions.
    S2. Application & incorporation by reference.
    S2.1 Application. This standard applies to passenger cars, and to 
multipurpose passenger vehicles, trucks and buses with a GVWR of 4,536 
kg or less, manufactured on or after September 1, 2008. Mandatory 
applicability begins on September 1, 2008. Until September 1, 2008, 
manufacturers may comply with the standard in this Sec.  571.202a, with 
the standard in Sec.  571.202, or with the European regulations 
referenced in S4.3(a) of Sec.  571.202.
    S2.2 Incorporation by reference.
    (a) Society of Automotive Engineers (SAE) Recommended Practice 
J211/1 rev. Mar 95, ``Instrumentation for Impact Test--Part 1--
Electronic Instrumentation,'' SAE J211/1 (rev. Mar 95) is incorporated 
by reference in S5.2.5(b), S5.3.8, S5.3.9, and 5.3.10 of this section. 
The Director of the Federal Register has approved the incorporation by 
reference of this material in accordance with 5 U.S.C. 552(a) and 1 CFR 
part 51. A copy of SAE J211/1 (rev. Mar 95) may be obtained from SAE at 
the Society of Automotive Engineers, Inc., 400 Commonwealth Drive, 
Warrendale, PA 15096. A copy of SAE J211/1 (rev. Mar 95) may be 
inspected at NHTSA's Technical Information Services, 400 Seventh 
Street, SW., Plaza Level, Room 403, Washington, DC, or at the National 
Archives and Records Administration (NARA). For information on the 
availability of this material at NARA, call 202-741-6030, or go to: 
http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
    (b) Society of Automotive Engineers (SAE) Standard J826 ``Devices 
for Use in Defining and Measuring Vehicle Seating Accommodation,'' SAE 
J826 (rev. Jul 95) is incorporated by reference in S3, S5, S5.1, 
S5.1.1, S5.2, S5.2.1, S5.2.2, and S5.2.7 of this section. The Director 
of the Federal Register has approved the incorporation by reference of 
this material in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. A 
copy of SAE J826 (rev. Jul 95) may be obtained from SAE at the Society 
of Automotive Engineers, Inc., 400 Commonwealth Drive, Warrendale, PA 
15096. A copy of SAE J826 (rev. Jul 95) may be inspected at NHTSA's 
Technical Information Services, 400 Seventh Street, SW., Plaza Level, 
Room 403, Washington, DC or at the National Archives and Records 
Administration (NARA). For information on the availability of this 
material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
    S3. Definitions.
    Backset means the minimum horizontal distance between the rear of a 
representation of the head of a seated 50th percentile male occupant 
and the head restraint, as measured by the head restraint measurement 
device.
    Head restraint means a device that limits rearward displacement of 
a seated occupant's head relative to the occupant's torso.
    Head restraint measurement device (HRMD) means the Society of 
Automotive Engineers (SAE) (rev. Jul 95) J826 three-dimensional manikin 
with a head form attached, representing the head position of a seated 
50th percentile male, with sliding scale at the back of the head for 
the purpose of measuring backset. The head form is designed by and 
available from the ICBC, 151 West Esplanade, North Vancouver, BC V7M 
3H9, Canada (www.icbc.com).
    Height means, when used in reference to a head restraint, the 
distance from the H-point, measured parallel to the torso reference 
line defined by the three dimensional SAE J826 (rev. Jul 95) manikin, 
to a plane normal to the torso reference line.
    Intended for occupant use means, when used in reference to the 
adjustment of a seat, positions other than that intended solely for the 
purpose of allowing ease of ingress and egress of occupants and access 
to cargo storage areas of a vehicle.
    Rear head restraint means, at any rear outboard designated seating 
position, a rear seat back, or any independently adjustable seat 
component attached to or adjacent to a seat back, that has a height 
equal to or greater than 700 mm, in any position of backset and height 
adjustment, as measured in accordance with S5.1.1.
    Top of the head restraint means the point on the head restraint 
with the greatest height.
    S4. Requirements. Except as provided in S4.4 and S.4.2.1(b)(2) of 
this section, each vehicle must comply with S4.1 of this section with 
the seat adjusted as intended for occupant use. Whenever a range of 
measurements is specified, the head restraint must meet the requirement 
at any position of adjustment within the specified range.
    S4.1 Performance levels. In each vehicle other than a school bus, a 
head restraint that conforms to either S4.2 or S4.3 of this section 
must be provided at each front outboard designated seating position. In 
each vehicle equipped with rear head restraints, the rear head 
restraint must conform to either S4.2 or S4.3 of this section. In each 
school bus, a head restraint that conforms to either S4.2 or S4.3 of 
this section must be provided for the driver's seating position. At 
each designated seating position incapable of seating a 50th percentile 
male Hybrid III test dummy specified in 49 CFR Part 572, subpart E, the 
applicable head restraint must conform to S4.2 of this section.
    S4.2 Dimensional and static performance. Each head restraint 
located in the front outboard designated seating position and each head 
restraint located in the rear outboard designated seating position must 
conform to paragraphs S4.2.1 through S4.2.7 of this section:
    S4.2.1 Minimum height.
    (a) Front outboard designated seating positions. (1) Except as 
provided in S4.2.1(a)(2) of this section, when measured in accordance 
with S5.2.1(a)(1) of this section, the top of a head restraint located 
in a front outboard designated seating position must have a height not 
less than 800 mm in at least one position of adjustment.
    (2) Exception. The requirements of S4.2.1(a)(1) do not apply if the 
vehicle roofline physically prevents a head restraint, located in the 
front outboard designated seating position, from attaining the required 
height. In those instances in which this head restraint cannot attain 
the required height, when measured in accordance with S5.2.1(a)(2), the 
maximum vertical distance between the top of the head restraint and the 
roofline must not exceed 25 mm. Notwithstanding this exception, when 
measured in accordance with S5.2.1(a)(2), the top of a head restraint 
located in a front outboard designated seating position must have a 
height not less than 700 mm in the lowest position of adjustment.
    (b) All outboard designated seating positions equipped with head 
restraints. (1) Except as provided in S4.2.1(b)(2) of this section, 
when measured in accordance with S5.2.1(b)(1) of this section, the top 
of a head restraint located in an outboard designated seating position 
must have a height not less than 750 mm in any position of adjustment.
    (2) Exception. The requirements of S4.2.1(b)(1) do not apply if the 
vehicle

[[Page 74886]]

roofline or backlight physically prevent a head restraint, located in 
the rear outboard designated seating position, from attaining the 
required height. In those instances in which this head restraint cannot 
attain the required height, when measured in accordance with 
S5.2.1(b)(2), the maximum vertical distance between the top of the head 
restraint and the roofline or the backlight must not exceed 25 mm.
    S4.2.2 Width. When measured in accordance with S5.2.2 of this 
section, 65 <plus-minus> 3 mm below the top of the head restraint, the 
lateral width of a head restraint must be not less than 170 mm, except 
the lateral width of the head restraint for front outboard designated 
seating positions in a vehicle with a front center designated seating 
position, must be not less than 254 mm.
    S4.2.3 Front Outboard Designated Seating Position Backset. When 
measured in accordance with S5.2.3 of this section, the backset must 
not be more than 55 mm, when the seat is adjusted in accordance with 
S5.1. For adjustable restraints, the requirements of this section must 
be met with the top of the head restraint in any height position of 
adjustment between 750 mm and 800 mm, inclusive. If the top of the head 
restraint, in its lowest position of adjustment, is above 800 mm, the 
requirements of this section must be met at that position. If the head 
restraint position is independent of the seat back inclination 
position, the head restraint must not be adjusted such that backset is 
more than 55 mm when the seat back inclination is positioned closer to 
vertical than the position specified in S5.1.
    S4.2.4 Gaps within head restraint and between the head restraint 
and seat. When measured in accordance with S5.2.4 of this section using 
the head form specified in that paragraph, there must not be any gap 
greater than 60 mm within or between the anterior surface of the head 
restraint and anterior surface of the seat, with the head restraint 
adjusted to its lowest height position and any backset position.
    S4.2.5 Energy absorption. When the anterior surface of the head 
restraint is impacted in accordance with S5.2.5 of this section by the 
head form specified in that paragraph at any velocity up to and 
including 24.1 km/h, the deceleration of the head form must not exceed 
785 m/s\2\ (80 g) continuously for more than 3 milliseconds.
    S4.2.6 Height retention. When tested in accordance with S5.2.6 of 
this section, the cylindrical test device specified in S5.2.6(b) must 
return to within 13 mm of its initial reference position after 
application of at least a 500 N load and subsequent reduction of the 
load to 50 N <plus-minus> 1 N. During application of the initial 50 N 
reference load, as specified in S5.2.6(b)(2) of this section, the 
cylindrical test device must not move downward more than 25 mm.
    S4.2.7 Backset retention, displacement, and strength.
    (a) Backset retention and displacement. When tested in accordance 
with S5.2.7 of this section, the described head form must:
    (1) Not be displaced more than 25 mm during the application of the 
initial reference moment of 37 <plus-minus> 0.7 Nm;
    (2) Not be displaced more than 102 mm perpendicularly and posterior 
of the displaced extended torso reference line during the application 
of a 373 <plus-minus> 7.5 Nm moment about the H-point; and
    (3) Return to within 13 mm of its initial reference position after 
the application of a 373 <plus-minus> 7.5 Nm moment about the H-point 
and reduction of the moment to 37 <plus-minus> 0.7 Nm.
    (b) Strength. When the head restraint is tested in accordance with 
S5.2.7 (b) of this section with the test device specified in that 
paragraph, the load applied to the head restraint must reach 890 N and 
remain at 890 N for a period of 5 seconds.
    S4.3 Dynamic performance and width. At each forward-facing outboard 
designated seating position equipped with a head restraint, the head 
restraint adjusted midway between the lowest and the highest position 
of adjustment, and at any position of backset adjustment, must conform 
to the following:
    S4.3.1 Injury criteria. When tested in accordance with S5.3 of this 
section, during a forward acceleration of the dynamic test platform 
described in S5.3.1, the head restraint must:
    (a) Angular rotation. Limit posterior angular rotation between the 
head and torso of the 50th percentile male Hybrid III test dummy 
specified in 49 CFR Part 572, Subpart E to 12 degrees for the dummy in 
all outboard designated seating positions;
    (b) Head injury criteria. Limit the maximum HIC<INF>15</INF> value 
to 500. HIC<INF>15</INF> is calculated as follows: for any two points 
in time, t<INF>1</INF> and t<INF>2</INF>, during the event which are 
separated by not more than a 15 millisecond time interval and where 
t<INF>1</INF> is less than t<INF>2</INF>, the head injury criterion 
(HIC<INF>15</INF>) is determined using the resultant head acceleration 
at the center of gravity of the dummy head, a<INF>r</INF>, expressed as 
a multiple of g (the acceleration of gravity) and is calculated using 
the expression:
[GRAPHIC] [TIFF OMITTED] TR14DE04.150

    4.3.2 Width. The head restraint must have the lateral width 
specified in S4.2.2 of this section.
    S4.4 Folding or retracting rear head restraints. A rear head 
restraint may be adjusted to a position at which its height does not 
comply with the requirements of S4.2.1 of this section. However, in any 
such position, the head restraint must meet either S4.4 (a) or (b) of 
this section.
    (a) The head restraint must automatically return to a position in 
which its minimum height is not less than that specified in S4.2.1(b) 
of this section when a test dummy representing a 5th percentile female 
Hybrid III test dummy specified in 49 CFR Part 572, Subpart O is 
positioned according to S5.4(a); or
    (b) The head restraint must, when tested in accordance with S5.4(b) 
of this section, be capable of manually rotating forward or rearward by 
not less than 60 degrees from any position of adjustment in which its 
minimum height is not less than that specified in S4.2.1(b) of this 
section.
    S4.5 Removability of head restraints. The head restraint must not 
be removable without a deliberate action distinct from any act 
necessary for adjustment.
    S4.6 Compliance option selection. Where manufacturer options are 
specified in this section, the manufacturer must select an option by 
the time it certifies the vehicle and may not thereafter select a 
different option for that vehicle. The manufacturer may select 
different compliance options for different designated seating positions 
to which the requirements of this section are applicable. Each 
manufacturer must, upon request from the National Highway Traffic 
Safety Administration, provide information regarding which of the 
compliance options it has selected for a particular vehicle or make/
model.
    S4.7 Information in owner's manual.
    S4.7.1 The owner's manual for each vehicle must emphasize that all 
occupants, including the driver, should not operate a vehicle or sit in 
a vehicle's seat until the head restraints are placed in their proper 
positions in order to minimize the risk of severe injury in the event 
of a crash.
    S4.7.2 The owner's manual for each vehicle must--
    (a) Include an accurate description of the vehicle's head restraint 
system in an easily understandable format. The owner's manual must 
clearly identify

[[Page 74887]]

which seats are equipped with head restraints;
    (b) If the head restraints are removable, the owner's manual must 
provide instructions on how to remove the head restraint by a 
deliberate action distinct from any act necessary for adjustment, and 
how to reinstall head restraints;
    (c) Warn that all head restraints must be reinstalled to properly 
protect vehicle occupants.
    (d) Describe in an easily understandable format the adjustment of 
the head restraints and/or seat back to achieve appropriate head 
restraint position relative to the occupant's head. This discussion 
must include, at a minimum, accurate information on the following 
topics:
    (1) A presentation and explanation of the main components of the 
vehicle's head restraints.
    (2) The basic requirements for proper head restraint operation, 
including an explanation of the actions that may affect the proper 
functioning of the head restraints.
    (3) The basic requirements for proper positioning of a head 
restraint in relation to an occupant's head position, including 
information regarding the proper positioning of the center of gravity 
of an occupant's head in relation to the head restraint.
    S5. Procedures. Demonstrate compliance with S4.2 through S4.4 of 
this section with any adjustable lumbar support adjusted to its most 
posterior nominal design position. If the seat cushion adjusts 
independently of the seat back, position the seat cushion such that the 
highest H-point position is achieved with respect to the seat back, as 
measured by SAE J826 (rev. Jul 95) manikin, with leg length specified 
in S10.4.2.1 of Sec.  571.208.
    S5.1 Except as specified in S5.2.3 of this section, if the seat 
back is adjustable, it is set at an initial inclination position 
closest to 25 degrees from the vertical, as measured by SAE J826 
manikin (rev. Jul 95). If there is more than one inclination position 
closest to 25 degrees from vertical, set the seat back inclination to 
the position closest to and rearward of 25 degrees.
    S5.1.1 Procedure for determining presence of head restraints in 
rear outboard seats. Measure the height of the top of a rear seat back 
or the top of any independently adjustable seat component attached to 
or adjacent to the rear seat back in its highest position of adjustment 
using the scale incorporated into the SAE J826 (rev. Jul 95) manikin or 
an equivalent scale, which is positioned laterally within 15 mm of the 
centerline of the rear seat back or any independently adjustable seat 
component attached to or adjacent to the rear seat back.
    S5.2 Dimensional and static performance procedures. Demonstrate 
compliance with S4.2 of this section in accordance with S5.2.1 through 
S5.2.7 of this section. Position the SAE J826 (rev. Jul 95) manikin 
according to the seating procedure found in SAE J826 (rev. Jul 95).
    S5.2.1 Procedure for height measurement. Demonstrate compliance 
with S4.2.1 of this section in accordance with S5.2.1 (a) and (b) of 
this section, using the scale incorporated into the SAE J826 (rev. Jul 
95) manikin or an equivalent scale, which is positioned laterally 
within 15 mm of the head restraint centerline. If the head restraint 
position is independent of the seat back inclination position, 
compliance is determined at a seat back inclination position closest to 
25 degrees from vertical, and each seat back inclination position less 
than 25 degrees from vertical.
    (a)(1) For head restraints in front outboard designated seating 
positions, adjust the top of the head restraint to the highest position 
and measure the height.
    (2) For head restraints located in the front outboard designated 
seating positions that are prevented by the vehicle roofline from 
meeting the required height as specified in S4.2.1(a)(1), measure the 
clearance between the top of the head restraint and the roofline, with 
the seat adjusted to its lowest vertical position intended for occupant 
use, by attempting to pass a 25 mm sphere between them. Adjust the top 
of the head restraint to the lowest position and measure the height.
    (b)(1) For head restraints in all outboard designated seating 
positions equipped with head restraints, adjust the top of the head 
restraint to the lowest position other than allowed by S4.4 and measure 
the height.
    (2) For head restraints located in rear outboard designated seating 
positions that are prevented by the vehicle roofline or rear backlight 
from meeting the required height as specified in S4.2.1(b)(1), measure 
the clearance between the top of the head restraint or the seat back 
and the roofline or the rear backlight, with the seat adjusted to its 
lowest vertical position intended for occupant use, by attempting to 
pass a 25 mm sphere between them.
    S5.2.2 Procedure for width measurement. Demonstrate compliance with 
S4.2.2 of this section using calipers to measure the maximum dimension 
perpendicular to the vehicle vertical longitudinal plane of the 
intersection of the head restraint with a plane that is normal to the 
torso reference line of SAE J826 (rev. Jul 95) manikin and 65 <plus-
minus> 3 mm below the top of the head restraint.
    S5.2.3 Procedure for backset measurement. Demonstrate compliance 
with S4.2.3 of this section using the HRMD positioned laterally within 
15 mm of the head restraint centerline. Adjust the front head restraint 
so that its top is at any height between and inclusive of 750 mm and 
800 mm and its backset is in the maximum position other than allowed by 
S4.4. If the lowest position of adjustment is above 800 mm, adjust the 
head restraint to that position. If the head restraint position is 
independent of the seat back inclination position, compliance is 
determined at each seat back inclination position closest to and less 
than 25 degrees from vertical.
    S5.2.4 Procedures for gap measurement. Demonstrate compliance with 
S4.2.4 of this section in accordance with the procedures of S5.2.4 (a) 
through (c) of this section, with the head restraint adjusted to its 
lowest height position and any backset position.
    (a) The area of measurement is anywhere on the anterior surface of 
the head restraint or seat with a height greater than 540 mm and within 
the following distances from the centerline of the seat--
    (1) 127 mm for seats required to have 254 mm minimum head restraint 
width; and
    (2) 85 mm for seats required to have a 170 mm head restraint width.
    (b) Applying a load of no more than 5 N against the area of 
measurement specified in S5.2.4(a) of this section, place a 165 <plus-
minus> 2 mm diameter spherical head form against any gap such that at 
least two points of contact are made within the area. The surface 
roughness of the head form is less than 1.6 [mu]m, root mean square.
    (c) Determine the gap dimension by measuring the vertical straight 
line distance between the inner edges of the two furthest contact 
points, as shown in Figures 2 and 3 of this section.
    S5.2.5 Procedures for energy absorption. Demonstrate compliance 
with S4.2.5 of this section in accordance with S5.2.5 (a) through (e) 
of this section, with the seat back rigidly fixed and the adjustable 
head restraints in any height and backset position of adjustment.
    (a) Use an impactor with a semispherical head form and a 165 <plus-
minus> 2 mm diameter and a surface roughness of less than 1.6 [mu]m, 
root mean square. The head form and associated base have a combined 
mass of 6.8 <plus-minus> 0.05 kg.

[[Page 74888]]

    (b) Instrument the impactor with an acceleration sensing device 
whose output is recorded in a data channel that conforms to the 
requirements for a 600 H<INF>z</INF> channel class as specified in SAE 
Recommended Practice J211/1 (rev. Mar 95). The axis of the 
acceleration-sensing device coincides with the geometric center of the 
head form and the direction of impact.
    (c) Propel the impactor toward the head restraint. At the time of 
launch, the longitudinal axis of the impactor is within 2 degrees of 
being horizontal and parallel to the vehicle longitudinal axis. The 
direction of travel is posteriorly.
    (d) Constrain the movement of the head form so that it travels 
linearly along the path described in S5.2.5(c) of this section for not 
less than 25 mm before making contact with the head restraint.
    (e) Impact the anterior surface of the seat or head restraint at 
any point with a height greater than 635 mm and within a distance of 
the head restraint vertical centerline of 70 mm.
    S5.2.6 Procedures for height retention. Demonstrate compliance with 
S4.2.6 of this section in accordance with S5.2.6 (a) through (d) of 
this section.
    (a) Adjust the adjustable head restraint so that its top is at any 
of the following height positions at any backset position--
    (1) For front outboard designated seating positions--
    (i) The highest position; and
    (ii) Not less than, but closest to 800 mm; and
    (2) For rear outboard designated seating positions equipped with 
head restraints--
    (i) The highest position; and
    (ii) Not less than, but closest to 750 mm.
    (b)(1) Orient a cylindrical test device having a 165 <plus-minus> 2 
mm diameter in plane view (perpendicular to the axis of revolution), 
and a 152 mm length in profile (through the axis of revolution) with a 
surface roughness of less than 1.6 [mu]m, root mean square, such that 
the axis of the revolution is horizontal and in the longitudinal 
vertical plane through the longitudinal centerline of the head 
restraint. Position the midpoint of the bottom surface of the cylinder 
in contact with the head restraint.
    (2) Establish initial reference position by applying a vertical 
downward load of 50 <plus-minus> 1 N.
    (c) Increase the load at the rate of 250 <plus-minus> 50 N/minute 
to at least 500 N and maintain this load for not less than 5 seconds.
    (d) Reduce the load at the rate of 250 <plus-minus> 50 N/minute to 
50 <plus-minus> 1 N and determine the position of the cylindrical 
device with respect to its initial reference position.
    S5.2.7 Procedures for backset retention, displacement, and 
strength. Demonstrate compliance with S4.2.7 of this section in 
accordance with S5.2.7 (a) and (b) of this section. The load vectors 
that generate moment on the head restraint are initially contained in a 
vertical plane parallel to the vehicle longitudinal centerline.
    (a) Backset retention and displacement--
    (1) Adjust the head restraint so that its top is at a height 
closest to and not less than:
    (i) 800 mm for front outboard designated seating positions (or the 
highest position of adjustment for head restraints subject to 
S4.2.1(a)(2)); and
    (ii) 750 mm for rear outboard designated seating positions equipped 
with head restraints (or the highest position of adjustment for rear 
head restraints subject to S4.2.1(b)(2)).
    (2) Adjust the head restraint to any backset position.
    (3) In the seat, place a test device having the back pan dimensions 
and torso reference line (vertical center line), when viewed laterally, 
with the head room probe in the full back position, of the three 
dimensional SAE J826 (rev. Jul 95) manikin;
    (4) Establish the displaced torso reference line by creating a 
posterior moment of 373 <plus-minus> 7.5 Nm about the H-point by 
applying a force to the seat back through the back pan at the rate of 
187 <plus-minus> 37 Nm/minute. The initial location on the back pan of 
the moment generating force vector has a height of 290 mm <plus-minus> 
13 mm. Apply the force vector normal to the torso reference line and 
maintain it within 2 degrees of a vertical plane parallel to the 
vehicle longitudinal centerline. Constrain the back pan to rotate about 
the H-point. Rotate the force vector direction with the back pan.
    (5) Maintain the position of the back pan as established in S5.2.7 
(4) of this section. Using a 165 <plus-minus> 2 mm diameter spherical 
head form with a surface roughness of less than 1.6 [mu]m, root mean 
square, establish the head form initial reference position by applying, 
perpendicular to the displaced torso reference line, a posterior 
initial load at the seat centerline at a height 65 <plus-minus> 3 mm 
below the top of the head restraint that will produce a 37 <plus-minus> 
0.7 Nm moment about the H-point. Measure the posterior displacement of 
the head form during the application of the load.
    (6) Increase the initial load at the rate of 187 <plus-minus> 37 
Nm/minute until a 373 <plus-minus> 7.5 Nm moment about the H-point is 
produced. Maintain the load level producing that moment for not less 
than 5 seconds and then measure the posterior displacement of the head 
form relative to the displaced torso reference line.
    (7) Reduce the load at the rate of 187 <plus-minus> 37 Nm/minute 
until a 37 <plus-minus> 0.7 Nm moment about the H-point is produced. 
While maintaining the load level producing that moment, measure the 
posterior displacement of the head form position with respect to its 
initial reference position; and
    (b) Strength. Increase the load specified in S5.2.7(a)(7) of this 
section at the rate of 250 <plus-minus> 50 N/minute to at least 890 N 
and maintain this load level for not less than 5 seconds.
    S5.3 Procedures for dynamic performance. Demonstrate compliance 
with S4.3 of this section in accordance with S5.3.1 though S5.3.9 of 
this section with a 50th percentile male Hybrid III test dummy 
specified in 49 CFR part 572 subpart E, with the head restraint midway 
between the lowest and the highest position of adjustment, and at any 
position of backset adjustment.
    S5.3.1 Mount the vehicle on a dynamic test platform at the vehicle 
attitude set forth in S13.3 of Sec.  571.208, so that the longitudinal 
centerline of the vehicle is parallel to the direction of the test 
platform travel and so that movement between the base of the vehicle 
and the test platform is prevented. Instrument the platform with an 
accelerometer and data processing system. Position the accelerometer 
sensitive axis parallel to the direction of test platform travel.
    S5.3.2 Remove the tires, wheels, fluids, and all unsecured 
components. Remove or rigidly secure the engine, transmission, axles, 
exhaust, vehicle frame and any other vehicle component necessary to 
assure that all points on the acceleration vs. time plot measured by an 
accelerometer on the dynamic test platform fall within the corridor 
described in Figure 1 and Table 1.
    S5.3.3 Place any moveable windows in the fully open position.
    S5.3.4 Seat adjustment. At each outboard designated seating 
position, using any control that primarily moves the entire seat 
vertically, place the seat in the lowest position. Using any control 
that primarily moves the entire seat in the fore and aft directions, 
place the seat midway between the forwardmost and rearmost position. If 
an adjustment position does not exist midway between the forwardmost 
and rearmost positions, the closest adjustment position to the rear of 
the midpoint is used. Adjust the seat cushion and seat back, without 
using any controls that move the entire seat,

[[Page 74889]]

as required by S5 and S5.1 of this section. If the specified position 
of the H-point can be achieved with a range of seat cushion inclination 
angles, adjust the seat inclination such that the most forward part of 
the seat cushion is at its lowest position with respect to the most 
rearward part. If the head restraint is adjustable, adjust the top of 
the head restraint to a position midway between the lowest position of 
adjustment and the highest position of adjustment. If an adjustment 
position midway between the lowest and the highest position does not 
exist, adjust the head restraint to a position below and nearest to 
midway between the lowest position of adjustment and the highest 
position of adjustment.
    S5.3.5 Seat belt adjustment. Prior to placing the Type 2 seat belt 
around the test dummy, fully extend the webbing from the seat belt 
retractor(s) and release it three times to remove slack. If an 
adjustable seat belt D-ring anchorage exists, place it in the 
adjustment position closest to the mid-position. If an adjustment 
position does not exist midway between the highest and lowest position, 
the closest adjustment position above the midpoint is used.
    S5.3.6 Dress and adjust each test dummy as specified in S8.1.8.2 
through S8.1.8.3 of Sec.  571.208.
    S5.3.7 Test dummy positioning procedure. Place a test dummy at each 
outboard designated seating position equipped with a head restraint.
    S5.3.7.1 Head. The transverse instrumentation platform of the head 
is level within \1/2\ degree. To level the head of the test dummy, the 
following sequences is followed. First, adjust the position of the H 
point within the limits set forth in S10.4.2.1 of Sec.  571.208 to 
level the transverse instrumentation platform of the head of the test 
dummy. If the transverse instrumentation platform of the head is still 
not level, then adjust the pelvic angle of the test dummy. If the 
transverse instrumentation platform of the head is still not level, 
then adjust the neck bracket of the dummy the minimum amount necessary 
from the non-adjusted ``0'' setting to ensure that the transverse 
instrumentation platform of the head is horizontal within \1/2\ degree. 
The test dummy remains within the limits specified in S10.4.2.1 of 
Sec.  571.208 after any adjustment of the neck bracket.
    S5.3.7.2 Upper arms and hands. Position each test dummy as 
specified in S10.2 and S10.3 of Sec.  571.208.
    S5.3.7.3 Torso. Position each test dummy as specified in S10.4.1.1, 
S10.4.1.2, and S10.4.2.1 of Sec.  571.208, except that the midsagittal 
plane of the dummy is aligned within 15 mm of the head restraint 
centerline. If the midsagittal plane of the dummy cannot be aligned 
within 15 mm of the head restraint centerline then align the 
midsagittal plane of the dummy as close as possible to the head 
restraint centerline.
    S5.3.7.4 Legs. Position each test dummy as specified in S10.5 of 
Sec.  571.208, except that final adjustment to accommodate placement of 
the feet in accordance with S5.3.7.4 of this section is permitted.
    S5.3.7.5 Feet. Position each test dummy as specified in S10.6 of 
Sec.  571.208, except that for rear outboard designated seating 
positions the feet of the test dummy are placed flat on the floorpan 
and beneath the front seat as far forward as possible without front 
seat interference. For rear outboard designated seating position, if 
necessary, the distance between the knees can be changed in order to 
place the feet beneath the seat.
    S5.3.8 Accelerate the dynamic test platform to 17.3 <plus-minus> 
0.6 km/h. All of the points on the acceleration vs. time curve fall 
within the corridor described in Figure 1 and Table 1 when filtered to 
channel class 60, as specified in the SAE Recommended Practice J211/1 
(rev. Mar 95). Measure the maximum posterior angular displacement.
    S5.3.9 Calculate the angular displacement from the output of 
instrumentation placed in the torso and head of the test dummy and an 
algorithm capable of determining the relative angular displacement to 
within one degree and conforming to the requirements of a 600 
H<INF>z</INF> channel class, as specified in SAE Recommended Practice 
J211/1, (rev. Mar 95). No data generated after 200 ms from the 
beginning of the forward acceleration are used in determining angular 
displacement of the head with respect to the torso.
    S5.3.10 Calculate the HIC<INF>15</INF> from the output of 
instrumentation placed in the head of the test dummy, using the 
equation in S4.3.1(b) of this section and conforming to the 
requirements for a 1000 H<INF>z</INF> channel class as specified in SAE 
Recommended Practice J211/1 (rev. Mar 95). No data generated after 200 
ms from the beginning of the forward acceleration are used in 
determining HIC.
    S5.4 Procedures for folding or retracting head restraints for 
unoccupied rear outboard designated seating positions.
    (a) Demonstrate compliance with S4.4 (a) of this section, using a 
5th percentile female Hybrid III test dummy specified in 49 CFR part 
572, subpart O, in accordance with the following procedure--
    (1) Position the test dummy in the seat such that the dummy's 
midsaggital plane is aligned within the 15 mm of the head restraint 
centerline and is parallel to a vertical plane parallel to the vehicle 
longitudinal centerline.
    (2) Hold the dummy's thighs down and push rearward on the upper 
torso to maximize the dummy's pelvic angle.
    (3) Place the legs as close as possible to 90 degrees to the 
thighs. Push rearward on the dummy's knees to force the pelvis into the 
seat so there is no gap between the pelvis and the seat back or until 
contact occurs between the back of the dummy's calves and the front of 
the seat cushion such that the angle between the dummy's thighs and 
legs begins to change.
    (4) Note the position of the head restraint. Remove the dummy from 
the seat. If the head restraint returns to a retracted position upon 
removal of the dummy, manually place it in the noted position. 
Determine compliance with the height requirements of S4.2.1 of this 
section by using the test procedures of S5.2.1 of this section.
    (b) Demonstrate compliance with S4.4 (b) of this section in 
accordance with the following procedure:
    (1) Place the rear head restraint in any position meeting the 
requirements of S4.2 of this section;
    (2) Strike a line on the head restraint. Measure the angle or range 
of angles of the head restraint reference line as projected onto a 
vertical longitudinal vehicle plane;
    (3) Fold or retract the head restraint to a position in which its 
minimum height is less than that specified in S4.2.1 (b) of this 
section or in which its backset is more than that specified in S4.2.3 
of this section;
    (4) Determine the minimum change in the head restraint reference 
line angle as projected onto a vertical longitudinal vehicle plane from 
the angle or range of angles measured in S5.4(b)(2) of this section.

    Table 1 of Sec.   571.202a.--Sled Pulse Corridor Reference Point
                               Locations.
------------------------------------------------------------------------
                                                   Time    Acceleration
                Reference point                    (ms)      (m/s\2\)
------------------------------------------------------------------------
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
------------------------------------------------------------------------


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    Dated: November 28, 2004.
Jeffrey W. Runge,
Administrator.
[FR Doc. 04-26641 Filed 12-7-04; 11:50 am]
BILLING CODE 4910-59-P


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