`[Federal Register Volume 90, Number 2 (Friday, January 3, 2025)]
[Rules and Regulations]
[Pages 390-468]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-30340]



[[Page 389]]

Vol. 90

Friday,

No. 2

January 3, 2025

Part II





Department of Transportation





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National Highway Traffic Safety Administration





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49 CFR Part 571





Federal Motor Vehicle Safety Standards; Occupant Crash Protection, Seat 
Belt Reminder Systems, Controls and Displays; Final Rule

  Federal Register / Vol. 90 , No. 2 / Friday, January 3, 2025 / Rules 
and Regulations  

[[Page 390]]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2024-0071]
RIN 2127-AL37


Federal Motor Vehicle Safety Standards; Occupant Crash 
Protection, Seat Belt Reminder Systems, Controls and Displays

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

ACTION: Final rule.

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SUMMARY: This document amends Federal Motor Vehicle Safety Standard 
(FMVSS) No. 208, ``Occupant crash protection,'' to require a seat belt 
use warning system for rear seats. The rule also updates and enhances 
the current seat belt warning requirements for the driver's seat belt 
and extends these requirements to the front outboard passenger seat. 
The final rule applies (with some exceptions) to passenger cars, 
trucks, most buses, and multipurpose passenger vehicles with a gross 
vehicle weight rating of 4,536 kilograms (10,000 pounds) or less. This 
document also makes related amendments to FMVSS No. 101, ``Controls and 
displays.''

DATES: Effective date: The effective date of this final rule is March 
4, 2025.
    Compliance date: The compliance date of this final rule is 
September 1, 2026, for the front seat belt warning system requirements 
and September 1, 2027, for the rear seat belt warning system 
requirements, with optional early compliance permitted. Multi-stage 
manufacturers and alterers would have an additional year to comply.
    Petitions for reconsideration: Petitions for reconsideration of 
this final rule must be received not later than February 18, 2025.

ADDRESSES: Petitions for reconsideration of this final rule must refer 
to the docket and notice number set forth above and be submitted to the 
Administrator, National Highway Traffic Safety Administration, 1200 New 
Jersey Avenue SE, Washington, DC 20590. Note that all petitions 
received will be posted without change to www.regulations.gov, 
including any personal information provided.
    Privacy Act: Petitions will be placed in the docket. Anyone is able 
to search the electronic form of all documents received into any of our 
dockets by the name of the individual submitting the comment (or 
signing the comment, if submitted on behalf of an association, 
business, labor union, etc.). You may review DOT's complete Privacy Act 
Statement in the Federal Register published on April 11, 2000 (Volume 
65, Number 70; Pages 19477-78) or you may visit https://www.transportation.gov/individuals/privacy/privacy-act-system-records-notices.

FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may contact 
Ms. Carla Rush, Office of Crashworthiness Standards, Telephone: (202) 
366-4583; Email: [email protected]; Facsimile: (202) 493-2739. For 
legal issues, you may contact Mr. John Piazza ([email protected]) or 
Eli Wachtel ([email protected]), Office of Chief Counsel, Telephone: 
(202) 366-2992; Facsimile: (202) 366-3820. The address of these 
officials is: the National Highway Traffic Safety Administration, 1200 
New Jersey Avenue SE, Washington, DC, 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary
II. Background
III. Other Seat Belt Reminder Requirements and Protocols
IV. Statutory Authority
V. Summary of the NPRM
VI. Final Rule and Response to Comments
    A. Rear Seat Belt Warning Requirements
    1. Applicability
    2. Requirements
    a. Visual Warning on Vehicle Start-Up
    i. Type of Information Conveyed by the Visual Warning and 
Whether Occupant Detection Should Be Required
    ii. Lack of an Audible Warning
    iii. Triggering Conditions for Start-of-Trip Warning (Not 
Including Occupant Detection Criteria)
    iv. Seat Occupancy Criteria and Interaction With Child Restraint 
Systems
    v. Duration
    vi. Other Aspects
    b. Audio-Visual Change-of-Status Warning
    c. Electrical Connections/Removable Seats
    d. Owner's Manual Instructions
    e. Telltale Location
    3. Alternative Warning Signals
    B. Front Seat Belt Warning Requirements
    1. Applicability
    2. Driver's Seat Belt Warning for Light Buses
    3. Visual and Audible Warning Duration and Activation
    4. Visibility of Visual Warning for Front Outboard Passenger 
Seat Belt
    5. Front Seat Occupant Detection and Seat Occupancy Criteria
    C. Issues Common to the Front and Rear Seat Belt Warning 
Requirements
    1. Modification of Start-of-Trip Warning Trigger Related 
Ignition Switch Position To Accommodate EVs
    2. Belt Use Criteria
    3. Visual Warning Characteristics
    4. Interaction With Other Vehicle Warnings
    5. Audible Warning Characteristics (Other Than Duration)
    6. Warning Deactivation and Acknowledgement and Hardening
    7. Vehicles With Automated Driving Systems
    8. Test Procedures
VII. Regulatory Alternatives
VIII. Overview of Benefits and Costs
    A. Final Rule Requirements
    1. Rear Seat Belt Warning System
    2. Front Seat Belt Warning System
    3. Overall Benefits and Costs of the Final Rule
    B. Regulatory Alternatives
    1. Occupant Detection in Rear Seats
    2. 90-Second Front Outboard Seat Belt Warning
    3. Seat Belt Warning for Front Center Seat
IX. Compliance Dates
X. Regulatory Analyses
Appendix A. List of Comments Cited in Preamble

I. Executive Summary

    This final rule amends Federal Motor Vehicle Safety Standard (FMVSS 
or Standard) No. 208, ``Occupant crash protection,'' to require a seat 
belt use warning system for rear seats. This rule completes NHTSA's 
response to a mandate in the Moving Ahead for Progress in the 21st 
Century Act (MAP-21) that directed NHTSA to initiate a rulemaking to 
require a seat belt warning for the rear seats in motor vehicles; it 
also completes NHTSA's action on a rulemaking petition from Public 
Citizen and Advocates for Highway and Auto Safety for the same rule. 
The final rule also updates and enhances the current seat belt warning 
requirements for the driver's seat belt and extends these requirements 
to the front outboard passenger seat. The final rule applies (with some 
exceptions) to passenger cars, trucks, most buses, and multipurpose 
passenger vehicles (MPVs) with a gross vehicle weight rating (GVWR) of 
4,536 kilograms (10,000 pounds) or less. NHTSA is issuing this final 
rule under the National Traffic and Motor Vehicle Safety Act (Safety 
Act), 49 U.S.C. chapter 301, Motor Vehicle Safety (49 U.S.C. 30101 et 
seq.).

Safety Need for the Final Rule

    Using a seat belt is one of the most effective ways a motor vehicle 
occupant can prevent death and injury in a crash. Seat belts prevent 
occupants from being ejected from the vehicle, provide ``ride-down'' by 
gradually decelerating the occupant as the vehicle deforms and absorbs 
energy, and reduce occupant contact with harmful interior surfaces and 
other occupants. Seat belts are effective in most types of crashes and

[[Page 391]]

greatly reduce the risk of fatal and non-fatal injuries compared to the 
risk faced by unrestrained occupants.
    While seat belt use is meaningfully higher than it was a decade 
ago, there is room for improvement. Usage rates for seat belts in rear 
seats have consistently been below those for the front seats; and while 
front seat belt use rates increased in the early 2010s, for the last 
several years they have plateaued. According to data from NHTSA's 
annual study of observed seat belt use, in every year from 2013 through 
2022, seat belt use was lower in the rear seats than in the front 
seats, ranging from a difference of about 9 percentage points in 2013 
(78 percent vs. 87 percent) to about 14 percentage points in 2017 (75 
percent vs. 89 percent). In 2022, front seat belt use was about 91.6 
percent and rear seat belt use was about 81.7 percent.
    Every year, thousands of unrestrained motor vehicle occupants are 
killed in crashes and tens of thousands of unrestrained occupants are 
injured (additional details on the target population are provided in 
the summary of benefits and costs later in this executive summary). 
Seat belt warning systems (also referred to as seat belt reminder 
systems) encourage seat belt use by reminding unbuckled occupants to 
fasten their belts and/or by informing the driver that a passenger is 
unbelted so that the driver can request the unbelted occupant to buckle 
up. The warnings provided by seat belt warning systems typically 
consist of visual and/or audible signals. Research by NHTSA and others 
shows that seat belt warning systems are effective at getting unbuckled 
occupants to fasten their seat belts.
    FMVSS No. 208 currently requires a short-duration audio-visual seat 
belt warning for the driver's seat belt in passenger cars, most trucks 
and MPVs with a GVWR of 4,536 kg (10,000 lb) or less, and buses with a 
GVWR of 3,855 kg (8,500 lb) or less. Under these current requirements, 
the visual component of the warning generally must be at least 60 
seconds long, and the audible component must be at least four seconds 
long.
    Voluntary adoption by vehicle manufacturers of warnings that go 
beyond this regulatory minimum, while considerable, has been mixed. 
Although the regulations do not require seat belt warnings for any 
seating position other than the driver's seat, almost all model year 
(MY) 2022 vehicles have a voluntarily provided seat belt warning for 
the front outboard passenger seat. However, voluntary adoption for rear 
seats has been much slower, as only about 47 percent of MY 2022 
vehicles come equipped with a voluntarily provided rear seat belt 
warning system. Most vehicles already provide a seat belt warning for 
both front outboard seats that is much longer than the minimal required 
warning for the driver's seat belt, with the vast majority of vehicles 
including an alert that is at least 90 seconds. This widespread 
adoption suggests that the front seat belt warning minimum requirements 
in the FMVSS are outdated, as consumers accept audio-visual reminders 
that are far longer than the required minimums.
    As discussed above, rear seat belt use rates have persistently been 
below those for the front seats, and progress on front seat belt use 
rates has slowed. Moreover, unbuckled occupants, in the front and rear 
seats, continue to be overrepresented in fatal crashes (51 percent), 
given the lower exposure of unbelted occupants relative to belted 
occupants (because front seat belt use is about 90 percent and rear 
seat belt use is 80 percent). Despite the effectiveness of seat belts 
and seat belt warnings, most new vehicles continue to lack a rear seat 
belt warning. Additionally, while most vehicles provide some level of 
enhanced reminders for the front seats, this level of enhanced 
protection has not occurred for all vehicles and is not standardized. 
This gap in protection suggests a need for a beneficial safety 
technology that is not being met in the vehicle market. This final rule 
is intended to meet this safety need.

Legal Authority and Prior Regulatory History

    NHTSA is issuing this final rule pursuant to the National Traffic 
and Motor Vehicle Safety Act (49 U.S.C. 30101 et seq.) (Safety Act), 
which authorizes NHTSA to establish FMVSSs. That statute requires 
safety standards to be objective, practicable, and meet the need for 
safety, among other things. NHTSA has concluded that the finalized 
requirements satisfy these statutory criteria.
    This final rule completes NHTSA's response to a rulemaking mandate 
in MAP-21. MAP-21 required DOT (NHTSA, by delegation) to initiate a 
rulemaking proceeding to require rear seat belt warnings and directed 
the agency to issue a final rule unless the rule would not meet the 
Safety Act requirements for an FMVSS.
    This final rule also completes NHTSA's action on a rulemaking 
petition from Public Citizen and Advocates for Highway and Auto Safety. 
The petition requested that NHTSA issue a rule requiring a seat belt 
warning system for rear seats on passenger cars and MPVs with a GVWR of 
4,536 kg (10,000 lb) or less.

Summary of the Final Rule

    This final rule amends the existing seat belt warning provisions in 
FMVSS No. 208. The final rule has two main components. The first 
requires a seat belt warning for the rear seats. The second amends and 
enhances the seat belt warning requirements for the front outboard 
seats. The requirements apply (with some exceptions) to passenger cars 
and trucks, most buses, and multipurpose passenger vehicles with a GVWR 
of 4,536 kg (10,000 lb) or less.
1. Rear Seat Belt Reminder Requirements
    The first component of this final rule is a set of requirements for 
a seat belt warning for rear seats. The new requirements have four main 
elements.
     Visual warning on vehicle start-up to inform the driver of 
the status of the rear seat belts. The final rule requires a visual 
warning that informs the driver how many or which rear seat belts are 
in use and/or not in use. The warning must activate when the ignition 
(or, for electric vehicles (EVs), propulsion system) is activated, and 
last for at least 60 seconds. No visual warning is required if the 
system can determine that there are no occupied rear seats or if there 
are no occupied rear seats with a seat belt that is not in use.
     Audio-visual change-of-status warning. The final rule 
requires an audio-visual warning whenever a fastened rear seat belt is 
unfastened while the vehicle is in forward or reverse drive mode. (The 
warning is not required if the system can determine that a rear 
passenger has unfastened the seat belt in order to exit the vehicle or 
switch seats.) The warning must last for at least 30 seconds or until 
the seat belt that triggered the warning is re-fastened. The audible 
portion of the warning may be temporarily paused to allow another 
audible safety warning alerting the driver to take immediate action.
     Requirements related to electrical connections. Readily 
removable rear seats must either automatically establish the electrical 
connections when the seat is put in place or, if a manual connection is 
required, the connectors must be readily accessible. Vehicles equipped 
with certain types of seat belt warning systems are additionally 
required to provide a visual warning to the driver if a proper 
electrical connection has not been established.
     Owner's manual requirements. The vehicle owner's manual 
(which includes information provided by the vehicle manufacturer to the 
consumer, whether

[[Page 392]]

in digital or printed form) must describe the warning system's 
features, including the location and format of the visual warnings. It 
must also include instructions on how to make any manual electrical 
connections for readily removable seats.
2. Front Outboard Seat Belt Warning Requirements
    The final rule includes several changes and enhancements to the 
seat belt warning requirements for the front outboard seats. The new 
requirements have two main elements.
     Seat belt warning now required for front outboard 
passenger seat. This final rule requires a seat belt warning for the 
front outboard passenger seat. It does not require one for front center 
seats because, among other things, doing so would not be cost-
effective. Currently, only the driver's seat is required to have a seat 
belt warning, although almost all vehicles now provide a seat belt 
warning for the front outboard passenger seat as well.
     Enhanced audio-visual seat belt warning. The final rule 
requires a longer-duration audio-visual warning than is currently 
required for the driver's seat belt. The final requirements for this 
warning differ from the proposal, which would have required (with some 
exceptions) an audio-visual warning lasting until the belt at any 
occupied front outboard seat was fastened. This included a warning at 
the start of a trip and if a belt was unfastened during a trip. The 
proposal did not include any other warning triggers, such as vehicle 
speed. The final rule requires a visual warning and a two-phase audible 
warning that is based, in part, on vehicle speed.
    Visual warning. Under the final rule, a visual warning is required 
whenever the ignition switch is in the ``on'' or ``start'' position (or 
the propulsion system is activated), the seat is occupied, and the seat 
belt is not in use. The warning must be visible to the driver.
    Audible warning. The final rule requires a two-phase audible 
warning. The first phase warning must activate when the ignition/
propulsion system is activated, the seat is occupied, and the belt is 
not in use. The first phase warning must last for at least 30 seconds, 
unless the seat belt that triggered the warning is fastened or the 
second phase audible warning is activated within that time. The second 
phase audible warning must activate, and remain active, whenever the 
seat is occupied, the seat belt is not in use, and the vehicle speed is 
at least 10 km/h (6.2 mph). The audible warning may be temporarily 
paused to allow another audible safety warning alerting the driver to 
take immediate action.
    The final rule also contains requirements for the visual and 
audible warnings as well as for other system features.

Compliance Date

    This final rule establishes a compliance date for the amendments to 
FMVSS No. 208, ``Occupant crash protection,'' as follows. Manufacturers 
must comply with the amendments as of September 1, 2026 for the front 
seat belt warning system requirements and September 1, 2027 for the 
rear seat belt warning system requirements, with optional early 
compliance (see Section IX for details). Consistent with 49 CFR 
571.8(b), multi-stage manufacturers and alterers have an additional 
year to comply.

Regulatory Alternatives

    NHTSA considered a wide range of alternatives to the proposed 
requirements. The main alternatives NHTSA considered were the seat belt 
warning requirements in Economic Commission for Europe (ECE) Regulation 
No. 16 (R16) and Euro New Car Assessment Programme (Euro NCAP). The 
finalized requirements are identical or similar to ECE R16 and Euro 
NCAP in many respects but differ from them in several ways. For 
instance, while under ECE R16 the smallest occupant a rear seat belt 
system with occupant detection must be capable of detecting is a small-
statured adult female, under the final rule such systems must be 
capable of detecting occupants as small as a 6-year-old child and 
activating the warning accordingly. Another way the proposal differs 
from ECE R16 is the duration of the front seat belt warning on vehicle 
start-up: R16 generally requires only a 30-60 second audio-visual 
warning; the final rule requires, under certain conditions, an audio-
visual warning that lasts until the seat belt is buckled. The final 
regulatory analysis quantifies the costs and benefits of three specific 
regulatory alternatives: requiring occupant detection for the rear seat 
belt warning system; requiring (for the front outboard seats) an audio-
visual warning on vehicle start-up with a duration of 90 seconds; and 
requiring a seat belt warning for front center seats.

Benefits and Costs of the Proposed Requirements

    This final rule is significant and was reviewed by the Office of 
Management and Budget under Executive Order 12866, as amended by 
Executive Order 14094.
    NHTSA estimates the target population and the benefits and costs of 
the final rule requirements in the stand-alone final regulatory impact 
analysis (FRIA) that is being placed in the docket with this final rule 
and is summarized in this document.
    Based on NHTSA's data on fatalities and injuries from motor vehicle 
crashes, adjusted to account for the benefits of other mandatory safety 
technologies, there are, on average, 822 fatalities and 11,409 injuries 
to unrestrained rear seat occupants and 8,383 fatalities and 154,739 
injuries to unrestrained front outboard seat occupants each year. The 
final rule requirements are aimed at reducing these deaths and 
injuries.
    NHTSA estimates the benefits it expects from the final rule seat 
belt warning requirements. The benefits are the fatalities and injuries 
that would be prevented by these requirements. The benefits depend, 
principally, on the expected increase in seat belt use and the 
effectiveness of seat belts in preventing deaths and injuries.
    For the rear seat belt warning system analysis, NHTSA used a 
``low'' and a ``high'' estimate for the increase in rear belt use with 
the warning system. For occupants 11 years and older, these were 3 and 
5 percentage points, respectively, and for occupants from 6 to 10 years 
old, 0.3 and 0.4 percentage points respectively.\1\ For simplicity, 
NHTSA refers to these scenarios as ``Low'' and ``High.'' The estimated 
annual benefits for rear seat belt warning systems are presented in 
table 1.\2\
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    \1\ Children in booster seats are part of the target population 
for this final rule because they should be restrained with the seat 
belt and so would benefit from a seat belt reminder. The transition 
to a booster seat typically occurs from ages 4-7 years, and 
recommendations to remain in a booster seat exist until age 12 
years.https://www.nhtsa.gov/vehicle-safety/car-seats-and-booster-seats#find-the-right-car-seat-car-seat-recommendations.
    \2\ The Abbreviated Injury Scale (AIS) is a classification 
system for assessing impact injury severity developed and published 
by the Association for the Advancement of Automotive Medicine and is 
used for coding single injuries, assessing multiple injuries, or for 
assessing cumulative effects of more than one injury. MAIS 
represents the maximum injury severity of an occupant at an AIS 
level, i.e., the highest single AIS for a person with one or more 
injuries. MAIS 1 & 2 injuries are considered minor injuries and MAIS 
3-5 are considered serious injuries.

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 Table 1--Estimated Annual Benefits--Potential Lives Saved and Injuries
  Prevented for Rear Seat Belt Warning Systems (SBWS) Without Occupant
Detection, With Estimated ``Low'' and ``High'' Percentage Point Increase
                               in Belt Use
------------------------------------------------------------------------
              Injury level                      Low            High
------------------------------------------------------------------------
MAIS 1..................................              36              54
MAIS 2..................................              80             120
MAIS 3..................................              26              38
MAIS 4..................................               4               6
MAIS 5..................................               1               2
                                         -------------------------------
    Total Injuries......................             148             221
------------------------------------------------------------------------
Fatal...................................              26              39
------------------------------------------------------------------------

    Another way to measure benefits is by calculating equivalent lives 
saved (ELS). Equivalent lives saved are the number of prevented 
fatalities added to the number of prevented injuries, with the 
prevented injuries expressed in terms of fatalities (that is, with an 
injury expressed as a fraction of a fatality, so that the more serious 
the injury, the higher the fraction). The estimated equivalent lives 
saved assuming either a 3 percent or 7 percent discount rate are 
presented in table 2.

 Table 2--Estimated Annual Benefits--Equivalent Lives Saved (ELS)--Rear
                     SBWS Without Occupant Detection
------------------------------------------------------------------------
                                           3 Percent        7 Percent
           Belt use increase             discount rate    discount rate
------------------------------------------------------------------------
Low...................................            29.98            24.31
High..................................            45.09            36.55
------------------------------------------------------------------------

    NHTSA also estimates the costs of the final rule requirements for 
rear seat belt warnings. NHTSA estimates that the minimum cost to 
comply with the rear seat belt warning requirements is $166.44 million 
(M). This is based on a per-vehicle cost of $19.59 for 53.1 percent of 
16M affected new vehicles.
    Based on the foregoing, NHTSA performed benefit-cost and cost-
effectiveness analyses. A benefit-cost analysis calculates the net 
benefits, which is the difference between the benefits flowing from 
injury and fatality reductions and the cost of the rule. The net 
benefit estimates are presented in table 3. The cost-effectiveness 
analysis derives the cost per equivalent life saved, which is equal to 
the total cost of the rule divided by the total fatal equivalents that 
it prevents. These estimates are presented in table 4.

                           Table 3--Net Benefits--Rear SBWS Without Occupant Detection
                                           [2020 Dollars, in millions]
----------------------------------------------------------------------------------------------------------------
                                       Benefits 3      Benefits 7                Net benefits 3   Net benefits 7
         Belt use increase               percent         percent        Cost        percent          percent
                                        discount        discount                 discount rate    discount rate
----------------------------------------------------------------------------------------------------------------
Low................................         $357.78         $290.05     $166.4          $191.34          $123.62
High...............................          538.00          436.16      166.4           371.56           269.72
----------------------------------------------------------------------------------------------------------------


   Table 4--Cost-Effectiveness Analysis (Cost per Equivalent Life Saved)--Rear SBWS Without Occupant Detection
                                           [2020 Dollars, in Millions]
----------------------------------------------------------------------------------------------------------------
                                              ELS 3        ELS 7                    Cost/ELS 3      Cost/ELS 7
            Belt use increase                percent      percent        Cost         percent         percent
                                             discount     discount                   discount        discount
----------------------------------------------------------------------------------------------------------------
Low......................................        29.98        24.31       $166.4           $5.55           $6.85
High.....................................        45.09        36.55        166.4            3.69            4.55
----------------------------------------------------------------------------------------------------------------

    This final rule also enhances the driver seat belt warning 
requirements by requiring an indefinite visual warning and a two-phase 
audible warning that is based, in part, on vehicle speed that remains 
active until the driver's seat belt is buckled and extending these 
enhanced driver's seat belt warning requirements to the front outboard 
passenger seat. NHTSA estimates the annual benefits of a seat belt 
warning for the driver and outboard front passenger that remains active 
until the occupant's seat belt is buckled as shown in table 5 and table 
6.

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Table 5--Estimated Annual Benefits--Lives Saved and Injuries Prevented--Indefinite Duration SBWS (Front Outboard
                                                     Seats)
----------------------------------------------------------------------------------------------------------------
                                                                                       Front
                          Injury level                                Driver         passenger         Total
----------------------------------------------------------------------------------------------------------------
MAIS 1..........................................................             129              14             143
MAIS 2..........................................................             151              19             170
MAIS 3..........................................................              62               8              69
MAIS 4..........................................................               9               1              10
MAIS 5..........................................................               3               0               3
                                                                 -----------------------------------------------
    Total Injuries..............................................             354              42             395
----------------------------------------------------------------------------------------------------------------
Fatal...........................................................              20               2              22
----------------------------------------------------------------------------------------------------------------


   Table 6--Estimated Annual Benefits--Equivalent Lives Saved--Indefinite Duration SBWS (Front Outboard Seats)
----------------------------------------------------------------------------------------------------------------
                                                                                   3 Percent        7 Percent
                                                                 Undiscounted    discount rate    discount rate
----------------------------------------------------------------------------------------------------------------
Driver........................................................           42.26            34.98            28.36
Front Passenger...............................................            4.44             3.68             2.99
                                                               -------------------------------------------------
    Total.....................................................           46.70            38.66            31.35
----------------------------------------------------------------------------------------------------------------

    NHTSA estimates that the incremental cost of the enhanced seat belt 
warning for the driver's seat and the front outboard passenger seat 
would be no greater than the currently available seat belt warning. 
Although a seat belt warning is currently not required for the front 
outboard passenger seats, we estimate that 96 percent of new vehicles 
are equipped with them.\3\ NHTSA estimates that the cost for equipping 
a front outboard passenger seat with a seat belt warning system is 
about $2.13 per vehicle. To equip a seat belt warning system in the 
front outboard passenger seat positions on the remaining four percent 
of the new vehicle fleet (16 million) without such a warning is $1.36 
million (= $2.13 x 0.04 x 16 million).
---------------------------------------------------------------------------

    \3\ Based on data on total projected vehicle sales in the United 
States for MY 2022 from the agency's New Car Assessment Program 
Purchasing with Safety in Mind: What to Look For When Buying a 
Vehicle program.
---------------------------------------------------------------------------

    The total monetized benefits, costs, and net benefits (total 
monetized benefits--total cost) of the enhanced seat belt warning 
system for the driver and front passenger are shown in table 7. Table 8 
presents the results of the cost effectiveness analysis--cost per 
equivalent lives saved from enhanced SBWS for the driver and front 
outboard passenger.

       Table 7--Annual Monetized Benefits, Costs, and Net Benefits--Indefinite SBWS (Front Outboard Seats)
                                           [2020 Dollars, in Millions]
----------------------------------------------------------------------------------------------------------------
                                             Driver                Front passenger          Driver and front
                                   ----------------------------------------------------         passenger
                                                                                       -------------------------
                                     3 Percent    7 Percent    3 Percent    7 Percent    3 Percent    7 Percent
----------------------------------------------------------------------------------------------------------------
Passenger Car Benefits............      $188.89      $154.12       $22.86       $18.65      $211.75      $172.77
Light Truck & Van Benefits........       228.51       184.29        21.05        16.97       249.56       201.26
                                   -----------------------------------------------------------------------------
    Total Benefits................       417.41       338.41        43.90        35.62       461.31       374.03
    Total Costs...................            0            0         1.36         1.36         1.36         1.36
----------------------------------------------------------------------------------------------------------------
Net Benefits......................       417.41       338.41        42.54        34.26       459.95       372.67
----------------------------------------------------------------------------------------------------------------


  Table 8--Cost-Effectiveness Analysis (Cost per Equivalent Life Saved)--Indefinite SBWS (Front Outboard Seats)
                                           [2020 Dollars, in millions]
----------------------------------------------------------------------------------------------------------------
                          Discount rate                                 ELS            Cost          Cost/ELS
----------------------------------------------------------------------------------------------------------------
3 percent.......................................................           38.66           $1.36           $0.04
7 percent.......................................................           31.35            1.36            0.04
----------------------------------------------------------------------------------------------------------------

    The net benefits of the final rule requiring seat belt warning for 
rear seating positions and the enhanced seat belt warning for the front 
outboard seats are shown in table 9. The net benefits are positive for 
both 3 percent and 7

[[Page 395]]

percent discount rates and for both the low and high effectiveness 
estimates for rear seat SBWS.

    Table 9--Net Benefits From the Final Rule (SBWS Without Occupant
   Detection for Rear Seating Positions and Indefinite SBWS for Front
                       Outboard Seating Positions)
                       [2020 Dollars, in millions]
------------------------------------------------------------------------
                                             3 Percent       7 Percent
                                           discount rate   discount rate
------------------------------------------------------------------------
Front Outboard Seats....................         $459.95         $372.67
Rear Seats (low increase in rear seat             191.34          123.62
 belt use)..............................
Rear Seats (high increase in rear seat            371.56          269.72
 belt use)..............................
                                         -------------------------------
    Total Net Benefits (low increase in           651.29          496.28
     rear belt use).....................
    Total Net Benefits (high increase in          831.51          642.39
     rear belt use).....................
------------------------------------------------------------------------

II. Background

    On September 7, 2023, NHTSA published a notice of proposed 
rulemaking (NPRM) to amend FMVSS No. 208, ``Occupant crash 
protection,'' to require a seat belt use warning system for rear seats 
and to enhance the existing front seat belt warning requirements, 
including requiring a seat belt warning for the front outboard 
passenger seat and increasing the duration of the warning.\4\ This 
section provides an abbreviated background on the subject matter and 
regulatory history of the proposed requirements. For a fuller 
discussion, the reader is referred to the NPRM.\5\
---------------------------------------------------------------------------

    \4\ 88 FR 61674.
    \5\ Id. at pgs. 61680-61686.
---------------------------------------------------------------------------

Seat Belts and Seat Belt Warning Systems
    Using a seat belt is one of the most effective actions a motor 
vehicle occupant can take to prevent death and injury in a crash.\6\ 
Seat belts protect occupants in various ways. They prevent occupants 
from being ejected from the vehicle, gradually decelerate the occupant 
as the vehicle deforms and absorbs energy, and reduce the occurrence of 
occupant contact with harmful interior surfaces and other occupants.\7\ 
Research has found that seat belts greatly reduce the risk of fatal and 
non-fatal injuries compared to the risk faced by unrestrained 
occupants. For rear seat occupants, seat belts reduce the risk of 
fatality by 55 percent (for passenger cars) and 74 percent (for light 
trucks and vans). For drivers, seat belts reduce the risk of fatality 
by 48 percent (for passenger cars) and 61 percent (for light trucks and 
vans) and reduce the risk of moderate to greater severity injuries by 
65 percent. For front outboard passengers, seat belts reduce the risk 
of fatality by 37 percent (for passenger cars) and by 58 percent (for 
light trucks and vans) and reduce the risk of moderate to greater 
severity injuries by 65 percent.\8\
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    \6\ See, e.g., 68 FR 46262 (Aug. 5, 2003). See also Buckling Up: 
Technologies to Increase Seat Belt Use. Special Report 278 at 18, 
Committee for the Safety Belt Technology Study, Transportation 
Research Board of The National Academies (2003).
    \7\ Charles J. Kahane, Lives Saved by Vehicle Safety 
Technologies and Associated Federal Motor Vehicle Safety Standards, 
1960 to 2012--Passenger Cars and LTVs--With Reviews of 26 FMVSS and 
the Effectiveness of Their Associated Safety Technologies in 
Reducing Fatalities, Injuries, and Crashes. 89 DOT HS 812 069 at 89, 
Department of Transportation, National Highway Traffic Safety 
Administration (2015).
    \8\ See the Final Regulatory Impact Analysis (FRIA) (in the 
docket for this rulemaking) for these effectiveness estimates.
---------------------------------------------------------------------------

    While seat belt use is meaningfully higher than it was a decade 
ago, there is room for improvement. Usage rates for rear seat belts 
have consistently been below those for the front seats, and while front 
seat belt use rates increased early in the previous decade, for the 
last several years they have plateaued. According to data from NHTSA's 
National Occupant Protection Use Survey (NOPUS), from 2013 to 2022, 
seat belt use was lower in the rear seat than in the front seat, 
ranging from a difference of 8.8 percentage points in 2013 (78.3 
percent vs. 87.1 percent) to 14.3 percentage points in 2017 (75.4 
percent vs. 89.7 percent).\9\ In 2022, front seat belt use was 91.6 
percent and rear seat belt use was 81.7 percent.\10\ See Figure 1.
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    \9\ Boyle, L.L. (2022, August). Occupant restraint use in 2021: 
Results from the NOPUS Controlled Intersection Study (Report No. DOT 
HS 813 344). National Highway Traffic Safety Administration. NOPUS 
is the only nationwide probability-based observational survey of 
seat belt use in the United States. The survey observes seat belt 
use as it actually occurs at randomly-selected roadway sites, and 
involves a large number of occupants (68,804 in 2021). NOPUS 
observations are made during daylight hours and are not necessarily 
representative of high-risk driving times when belt use may be 
lower.
    \10\ Boyle, L.L. (2023, November). Occupant restraint use in 
2022: Results from the NOPUS Controlled Intersection Study (Report 
No. DOT HS 813 523). National Highway Traffic Safety Administration.

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[[Page 396]]

[GRAPHIC] [TIFF OMITTED] TR03JA25.000

    NHTSA has, over time, implemented a variety of strategies to 
increase seat belt use. These have included sponsoring national media 
campaigns, supporting the enactment of state seat belt use laws and 
high-visibility enforcement, and facilitating or requiring vehicle-
based strategies.\11\ While such measures have helped make enormous 
progress, the persistent gaps in seat belt use suggest that additional 
approaches may be necessary.
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    \11\ For example, NHTSA runs a Congressionally mandated High 
Visibility Enforcement annual campaign focused on increasing seat 
belt use. The Click It or Ticket nationwide campaign has been in 
effect for about 20 years. It runs every year from mid-May through 
the Memorial Day weekend, into the first week in June.
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    Seat belt warning systems (also referred to as seat belt reminder 
systems) are a vehicle-based strategy to increase belt use. Seat belt 
warning systems encourage seat belt use by reminding unbuckled 
occupants to fasten their belts and/or by informing the driver that a 
passenger is unbelted, so that the driver can request the unbelted 
occupant buckle up. The warnings provided by seat belt warning systems 
typically consist of visual and audible signals. An optimized warning 
system balances effectiveness and annoyance, so that the warning is 
noticeable enough that the occupants will be motivated to fasten their 
belts, but not so intrusive that an occupant may attempt to circumvent 
or disable it or the public will not accept it. Research by NHTSA and 
others shows that seat belt warning systems are effective at getting 
unbuckled occupants to fasten their seat belts. (We take a closer look 
at this research in Section VIII, Overview of Benefits and Costs, and 
the FRIA.) \12\
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    \12\ See also Section V of the NPRM (pgs. 61684-61685).
---------------------------------------------------------------------------

    FMVSS No. 208 currently requires a short audio-visual seat belt 
warning for the driver's seat belt on passenger cars; \13\ trucks and 
MPVs with a GVWR of 4,536 kg (10,000 lb) or less (except for some 
compliance options which do not require the warning); \14\ and buses 
with a GVWR of 3,855 kg (8,500 lb) or less and an unloaded weight less 
than or equal to 2,495 kg (5,500 lb).\15\ The standard does not require 
seat belt warnings for any seating position other than the driver's 
seat.\16\
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    \13\ S4.1.5.1(a)(3); S7.3.
    \14\ S4.2.6; S7.3.
    \15\ S4.2.6 (with the exception of some compliance options).
    \16\ See, e.g., Interpretation Letter from NHTSA to R. Lucki, 
July 24, 1985 (``Thus, the intent was to require a warning system 
for only the driver's position.''). All NHTSA interpretation letters 
cited in this preamble are available at https://www.nhtsa.gov/nhtsa-interpretation-file-search.
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    Manufacturers have two compliance options for the driver's 
warning.\17\ The first option requires that if the key is in the ``on'' 
or ``start'' position and the seat belt is not in use, the vehicle must 
provide a visual warning for at least 60 seconds, and an audible 
warning that lasts 4 to 8 seconds. Under the second option, when the 
key is turned to the ``on'' or ``start'' position, the vehicle must 
provide a visual warning for 4 to 8 seconds (regardless of whether the 
driver seat belt is fastened) and an audible warning lasting 4 to 8 
seconds if the driver seat belt is not in use.\18\ The current seat 
belt warning requirements (i.e., for the driver's seat only) have been 
in the standard since 1974.\19\
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    \17\ 49 CFR 571.208, S7.3.
    \18\ The warning requirements for automatic belts in S4.5.3 
mirror, with some differences, the first compliance option. 
Automatic belts are rarely, if ever, installed in current production 
vehicles, and NHTSA's regulations limit the seating positions for 
which automatic belts may be used to rear seats.
    \19\ 39 FR 42692 (Dec. 6, 1974).
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    Although not required by NHTSA's regulations, most currently 
produced vehicles have a seat belt warning for the front outboard 
passenger seat. Based on data on total projected vehicle sales in the 
United States for MY 2022 from the agency's New Car Assessment Program 
(NCAP) Purchasing with Safety in Mind: What to Look For When Buying a 
Vehicle program, almost all (about 97 percent) MY 2022 vehicles offered 
for sale in the United States were equipped with a seat belt warning 
for the front outboard passenger seat.\20\ Further, almost all vehicles 
already provide an audio-visual seat belt warning for both front 
outboard seats that is longer than the minimum warning for the driver's 
seat belt currently required in FMVSS No. 208. However, the persistence 
of the front seat belt warning, while often greater than the minimal 
durations required by FMVSS No. 208, is not consistent across new 
vehicles. Specifically, a little over half of MY 2022 vehicles provide 
a visual warning that lasts until the belts at any occupied front 
outboard seat are fastened, and almost all (about 93 percent) have an 
audible warning lasting at least a minute and a half; however, less 
than half have an audible warning lasting at least two minutes.\21\ 
This means that while many new vehicles have significantly enhanced 
reminders, many do not. This disparity, along with the plateauing front 
seat belt use numbers, suggests that the current regulatory minima are

[[Page 397]]

too short, and that in the absence of a requirement, persistent audible 
reminders that could improve front seat belt use are not widely 
available in the market.22 23 24
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    \20\ Through the NCAP program, NHTSA sends annual requests for 
safety information about new vehicles to vehicle manufacturers. This 
includes specific questions on seat belt reminder systems. The focus 
of this request for information is for vehicle models that will be 
sold in the upcoming model year that have a GVWR of 4,536 kg (10,000 
lb) or less, and this data generally covers all such vehicles 
offered for sale in the U.S. for MY 2022. Throughout this document 
we will refer to this data as our ``NCAP data'' or ``Purchasing with 
Safety in Mind: What to Look For When Buying a Vehicle'' data or 
information.
    \21\ See NPRM, pgs. 61709-61711, and appendix A.
    \22\ Mark Freedman et al. The Effectiveness of Enhanced Seat 
Belt Reminder Systems Draft Report: Observational Field Data 
Collection Methodology and Findings. 2007. DOT HS-810-844. 
Washington, DC: National Highway Traffic Safety Administration.
    \23\ N. Lerner et al. 2007. Acceptability and Potential 
Effectiveness of Enhanced Seat Belt Reminder System Features. DOT HS 
810 848. Washington, DC: National Highway Traffic Safety 
Administration [hereinafter DOT 2007.
    \24\ Transportation Research Board Study at 8, 25; Mark Freedman 
et al., Effectiveness and Acceptance of Enhanced Seat Belt Reminder 
Systems: Characteristics of Optimal Reminder Systems Final Report. 
DOT HS 811 097.
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    While almost all MY 2022 vehicles have a seat belt warning for the 
front outboard passenger seat, under half come equipped with a rear 
seat belt warning system. Rear seat belt warnings were first introduced 
in the United States by Volvo around 2009. About 47 percent of MY 2022 
vehicles, from 15 vehicle manufacturers, are equipped with a rear seat 
belt warning system. Thus, while rear seat belt warnings have become 
more widely deployed in recent years, the majority of the current fleet 
still is not equipped with them.
    In short, front seat belt use rates appear to have plateaued, and 
rear seat belt use rates have persistently been below those for the 
front seats. Moreover, unbuckled occupants continue to be 
overrepresented in fatal crashes (51 percent), given the lower exposure 
of unbelted occupants relative to belted occupants (because front seat 
belt use was about 90 percent and rear seat belt use was 80 percent for 
the period in question). In spite of the effectiveness of seat belts 
and seat belt warnings, most new vehicles continue to lack a rear seat 
belt warning, and, while many vehicles provide significantly enhanced 
reminders for the front seats, many do not. This suggests a need for a 
beneficial safety technology that is not being met in the vehicle 
market. This final rule is intended to meet that need.
Rulemaking Petition, MAP-21 Mandate, and Prior Rulemaking Notices for 
This Action
    On November 21, 2007, Public Citizen and Advocates for Highway and 
Auto Safety (Advocates, and, collectively, petitioners) petitioned 
NHTSA to amend FMVSS No. 208 to require a seat belt warning system for 
rear seats on passenger cars and MPVs with a GVWR of 4,536 kg (10,000 
lb) or less.\25\ On June 29, 2010, the agency published a Request for 
Comments document (RFC) on the petition.\26\ The RFC discussed the 
agency's research and findings regarding rear seat belt warnings and 
solicited comments. NHTSA subsequently granted the petition.
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    \25\ Docket No. NHTSA-2010-0061-0002.
    \26\ 75 FR 37343 (June 29, 2010) (Docket No. NHTSA-2010-0061).
---------------------------------------------------------------------------

    In 2012, Congress passed the Moving Ahead for Progress in the 21st 
Century Act (MAP-21).\27\ That legislation contained two provisions 
regarding seat belt warning systems. First, it repealed the 8-second 
durational limit for the driver's seat belt audible warning.\28\ 
Second, it required the Secretary of Transportation to initiate a 
rulemaking proceeding to amend FMVSS No. 208 to provide a safety belt 
use warning system for designated seating positions in the rear 
seat.\29\ It directed the Secretary to either issue a final rule, or, 
if the Secretary determines that such an amendment does not meet the 
requirements and considerations of 49 U.S.C. 30111,\30\ to submit a 
report to Congress describing the reasons for not prescribing such a 
standard.
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    \27\ Public Law 112-141 (2012).
    \28\ Id. at section 31202(a)(2) (repealing portion of 49 U.S.C. 
30124).
    \29\ Id. at section 31503. Authority has been delegated to 
NHTSA. 49 CFR 1.95.
    \30\ Section 30111 requires that a Motor Vehicle Safety Standard 
meet the need for safety, be stated in objective terms, and be 
practicable, among other requirements. See infra Section IV.
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    In 2019, NHTSA published an Advance Notice of Proposed Rulemaking 
(ANPRM) seeking comment on a variety of issues related to potential 
rear seat belt warning requirements.\31\ NHTSA published the NPRM on 
September 7, 2023.\32\
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    \31\ 84 FR 51076 (Sept. 27, 2019) (Docket No. NHTSA-2019-0093).
    \32\ 88 FR 61674.
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III. Other Seat Belt Reminder Requirements and Protocols

    The Economic Commission for Europe (ECE) has instituted seat belt 
warning requirements, and the European New Car Assessment Programme 
(Euro NCAP) and the Insurance Institute for Highway Safety (IIHS) have 
also included seat belt reminder systems in their respective ratings 
protocols. Below we briefly summarize the seat belt reminder provisions 
in each of these.
ECE Requirements
    The ECE has issued an updated version of Regulation No. 16 \33\ 
(R16) that requires seat belt reminder systems in all front and rear 
seats on new cars.\34\ The seat belt reminder system is required to 
have both a start-of-trip warning and a change-of-status warning for 
both the rear and front seats, though the exact requirements differ 
somewhat for rear and front seats.
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    \33\ ECE Regulation No. 16, Revision 10.
    \34\ The regulation was introduced in two phases: September 1, 
2019 for new vehicle types (i.e., all vehicle models with a new type 
approval) and September 1, 2021 for all newly-produced and 
registered vehicles.
---------------------------------------------------------------------------

    Rear seat requirements. R16 specifies a two-level warning. The 
first-level warning is a visual warning and the second-level warning is 
an audio-visual warning. The first-level warning applies at the start 
of a trip and the second-level warning applies when a fastened belt 
becomes unfastened during a trip. The first-level warning must activate 
when the seat belt of any of the rear seats is not fastened and the 
ignition switch or master control switch is activated. The first-level 
warning must last at least 60 seconds or until the belt is fastened (or 
the seat is no longer occupied, if equipped with occupant detection). 
The second-level warning must activate when a belt becomes unfastened 
and certain specified speed or distance thresholds are met and must 
last for 30 seconds unless other specified criteria are met (e.g., the 
belt is re-fastened).
    Front seat requirements. The front seat belt warning requirements 
are similar to the rear seat warnings, with some differences. First, 
the first-level visual warning is only required to last 30 seconds, not 
60 seconds. Second, the second-level audio-visual warning applies to 
unfastened belts at the start of the trip as well as to changes in belt 
status (i.e., a fastened belt that becomes unfastened).
    The regulation also contains a variety of other requirements 
relating to the seat belt warning systems (e.g., telltales, exemptions 
for certain vehicles and seating positions). R16 also allows for short- 
and long-term deactivation of both front and rear warnings.
    The ECE requirements are discussed in more detail where relevant in 
later sections of this preamble.

Euro NCAP

    Euro NCAP introduced seat belt warnings in their assessment 
protocol in 2002. The Euro NCAP protocol for Safety Assist systems 
describes which features a seat belt reminder must have to qualify for 
points in this area of assessment,\35\ which is then used to calculate 
the overall vehicle rating.\36\
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    \35\ Euro NCAP's overall safety rating is based on four areas of 
assessment (Adult Occupant Protection, Child Occupant Protection, 
Vulnerable Road Users, and Safety Assist).
    \36\ European New Car Assessment Programme Assessment Protocol--
Safety Assist, Safe Driving, Version 10.3, December 2023.

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[[Page 398]]

    Rear seat warnings. For rear seats, a visual signal must start once 
the ignition switch is engaged. The visual signal must be at least 60 
seconds long. Occupant detection is required for rear seats to be 
eligible for a score; this is a new requirement that was instituted 
after NHTSA published the NPRM. For systems without occupant 
detection,\37\ the visual signal must clearly indicate to the driver 
which seat belts are in use and not in use. For systems with occupant 
detection on all rear seating positions, the visual signal does not 
need to indicate the number of seat belts in use or not in use, but the 
signal must remain active if a seat belt remains unfastened on any of 
the occupied seats in the rear. No visual signal is required if all the 
rear occupants are belted. For systems with rear seat occupant 
detection, a 30-second audible signal needs to activate before the 
vehicle reaches a speed of 25 km/h (15.5 mph) or before it travels 500 
meters when any occupied seat has an unbuckled belt. When any seat belt 
experiences a change of status at vehicle speeds above 25 km/h (15.5 
mph), an audio-visual signal is required, with the visual signal 
lasting 60 seconds and the audible warning lasting 30 seconds, unless 
certain conditions are met.
---------------------------------------------------------------------------

    \37\ This language remains in the protocol as a precondition for 
receiving a score for seats with occupant detection. In a vehicle 
where not all the rear seats are equipped with occupant detection, 
if seats without occupant detection do not meet these requirements 
the seats with occupant detection would not receive a score.
---------------------------------------------------------------------------

    Front seat warnings. The Euro NCAP protocol requires that, to 
receive points, at the start of a trip the system must provide a visual 
seat belt warning that lasts until the belt is fastened \38\ and an 
audible warning that activates when certain conditions are met and 
generally must last at least about 90 seconds (the exact duration 
depends on a variety of specified criteria, such as vehicle speed or 
distance travelled). It also specifies an audio-visual change-of-status 
warning that meets the requirements of the initial start-of-trip 
warning.
---------------------------------------------------------------------------

    \38\ Section 3.4.2.1.
---------------------------------------------------------------------------

Insurance Institute for Highway Safety (IIHS) Protocol
    On December 2021, IIHS released its Seat Belt Reminder System Test 
and Rating protocol.\39\ It sets out general requirements for the seat 
belt reminder visual and audible signals for front outboard and rear 
seating positions. It specifies that a visual signal must be displayed 
in the instrument panel, overhead panel, or center console, indicating 
an unfastened belt. The audible warning must begin if the seat belt is 
unfastened at ignition and for change-of-status, and can cease when the 
seat belt is unfastened, the vehicle is no longer in motion, or the 
seat is no longer occupied. The protocol also has sound pressure level 
and frequency requirements for the audible warning.
---------------------------------------------------------------------------

    \39\ Insurance Institute for Highway Safety. (April 2024.) Seat 
Belt Reminder System Test and Rating Protocol, Version III, 
available at https://www.iihs.org/media/f15e5be9-ac62-4ea6-a88d-7511105bfff5/H3hGKQ/Ratings/Protocols/current/Seat%20Belt%20Reminder%20Test%20Protocol.pdf (last accessed May 16, 
2024).
---------------------------------------------------------------------------

    For the rear seats, the IIHS protocol specifies that the visual 
signal must activate within 10 seconds of the ignition being turned on, 
that the signal must indicate whether the seat belt at each rear 
seating position is fastened or unfastened, and that it must last at 
least 60 seconds. It does not require a visual signal if the seat belts 
at all occupied rear seats are fastened or if no rear occupants are 
present. It allows the visual signal to be cancelled by the driver. For 
a seat belt change-of-status in the rear seats when the vehicle is in 
motion, it requires an audible and visual signal that lasts at least 30 
seconds. It further specifies that the audible and visual signal can 
stop when seat belts at the occupied rear seats are fastened, the 
vehicle is no longer in motion, or the seats are no longer occupied.
    For the front seats, under the IIHS ratings protocol, the primary 
audible reminder signal for the front outboard seats must be at least 
90 seconds in total duration to obtain an ``acceptable'' or ``good'' 
rating.
    Unlike Euro NCAP, the IIHS rating system provides ratings (Poor, 
Marginal, Acceptable, and Good) instead of points. For instance, if the 
front-passenger seat has an audible signal that lasts less than 8 
seconds it would be given a ``Poor'' rating. For a ``Good'' rating both 
the driver and front-passenger belt reminder must have an audible 
signal that lasts at least 90 seconds and meet the rest of the belt 
reminder system requirements for an ``Acceptable'' rating, including 
the requirements for a rear seat belt reminder system. Accordingly, a 
vehicle cannot receive a ``Good'' rating without having a rear seat 
belt reminder system, and a rear seat belt reminder system is not 
required for all the other ratings. The protocol does not specify 
occupancy criteria (that is, the smallest occupant (or the size and 
weight corresponding to the smallest occupant)) that the system must be 
able to detect.

IV. Statutory Authority

    NHTSA is issuing this final rule pursuant to its authority under 
the National Traffic and Motor Vehicle Safety Act (Safety Act). Under 
49 U.S.C. chapter 301, Motor Vehicle Safety (49 U.S.C. 30101 et seq.), 
the Secretary of Transportation is responsible for prescribing motor 
vehicle safety standards. The responsibility for promulgation of FMVSS 
is delegated to NHTSA.\40\
---------------------------------------------------------------------------

    \40\ See 49 CFR 1.95.
---------------------------------------------------------------------------

    Section 30111 of the Safety Act requires that an FMVSS be 
practicable, meet the need for motor vehicle safety, and be stated in 
objective terms.\41\ The Safety Act defines ``motor vehicle safety'' as 
``the performance of a motor vehicle or motor vehicle equipment in a 
way that protects the public against unreasonable risk of accidents 
occurring because of the design, construction, or performance of a 
motor vehicle, and against unreasonable risk of death or injury in an 
accident, and includes nonoperational safety of a motor vehicle.'' \42\ 
``Motor vehicle safety standard'' means a minimum performance standard 
for motor vehicles or motor vehicle equipment.\43\ When prescribing 
safety standards, the Secretary must consider all relevant, available 
motor vehicle safety information.\44\ The Secretary must also consider 
whether a proposed standard is reasonable, practicable, and appropriate 
for the types of motor vehicles or motor vehicle equipment for which it 
is prescribed, and the extent to which the standard will further the 
statutory purpose of reducing traffic accidents and associated 
deaths.\45\
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    \41\ 49 U.S.C. 30111(a).
    \42\ 49 U.S.C. 30102(a)(9).
    \43\ Section 30102(a)(10).
    \44\ Section 30111(b)(1).
    \45\ Section 30111(b)(3)-(4).
---------------------------------------------------------------------------

    The statutory criterion of practicability is multidimensional. Most 
relevant to this rule, it means that in issuing this final rule, NHTSA 
must balance benefits and costs, with safety as the preeminent 
consideration.\46\ This requirement means that NHTSA ought not simply 
choose the least costly regulatory option.\47\ It also means that

[[Page 399]]

the final rule must be reasonably feasible, both economically \48\ and 
technologically.\49\ Importantly, however, the Safety Act does allow 
NHTSA to issue technology-forcing safety standards.\50\ NHTSA must also 
consider the public acceptability of safety standards \51\ and provide 
adequate lead time.\52\
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    \46\ See, e.g., Motor Vehicle Mfrs. Ass'n of U.S., Inc. v. State 
Farm Mut. Auto. Ins. Co., 463 U.S. 29, 55 (1983) (``The agency is 
correct to look at the costs as well as the benefits of Standard 208 
. . . When the agency reexamines its findings as to the likely 
increase in seatbelt usage, it must also reconsider its judgment of 
the reasonableness of the monetary and other costs associated with 
the Standard. In reaching its judgment, NHTSA should bear in mind 
that Congress intended safety to be the preeminent factor under the 
Motor Vehicle Safety Act.'').
    \47\ See, e.g., Public Citizen, Inc. v. Mineta, 340 F.3d 39, 58 
(2nd Cir. 2003) (``The notion that `cheapest is best' is contrary to 
State Farm. There the Court instructed NHTSA `to look at the costs 
as well as the benefits' of motor vehicle safety standards, and to 
``bear in mind that Congress intended safety to be the pre-eminent 
factor under the [Safety Act.] Thus, when NHTSA issues standards 
under the Safety Act, State Farm requires that the agency weigh 
safety benefits against economic costs; moreover, State Farm 
instructs the agency to place a thumb on the safety side of the 
scale.'') (quoting Motor Vehicle Mfrs. Ass'n of U.S., Inc., 463 U.S. 
at 54) (citations omitted).
    \48\ See, e.g., Public Citizen, Inc. v. Mineta, 340 F.3d at 58 
(2nd Cir. 2003) (``The committee recognizes . . . that the Secretary 
will necessarily consider reasonableness of cost, feasibility and 
adequate lead time.'') (quoting H. Rep. No. 1776, at 16 (1966)).
    \49\ See, e.g., Paccar, Inc. v. Nat'l Highway Traffic Safety 
Admin., 573 F.2d 632, 635 n.5 (9th Cir. 1978) (``Practicable is 
defined to require consideration of all relevant factors, including 
technological ability to achieve the goal of a particular 
standard[.]'') (citations and quotations omitted) (quoting H.R. Rep. 
No. 1776, 89th Cong., 2d Sess. 16 (1966)).
    \50\ Chrysler Corp. v. Dep't of Transp., 472 F.2d 659, 673 (6th 
Cir. 1972) (``[T]he Agency is empowered to issue safety standards 
which require improvements in existing technology or which require 
the development of new technology, and it is not limited to issuing 
standards based solely on devices already fully developed.'').
    \51\ Pac. Legal Found. v. Dep't of Transp., 593 F.2d 1338, 1345-
46 (D.C. Cir. 1979) (``We believe that the agency cannot fulfill its 
statutory responsibility unless it considers popular reaction. 
Without public cooperation there can be no assurance that a safety 
system can meet the need for motor vehicle safety.'') (quotations 
and citations omitted).
    \52\ 2 U.S. Code Cong. & Adm. News, 89th Cong., 2d Sess., 1966, 
p. 2714, quoted in H & H Tire Co. v. U. S. Dep't of Transp., 471 
F.2d 350, 353 (7th Cir. 1972). (``The committee recognizes . . . 
that the Secretary will necessarily consider [in the issuance of 
standards] reasonableness of cost, feasibility and adequate lead 
time.'').
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    In developing this final rule, the agency carefully considered 
these statutory requirements and has concluded that it meets them. They 
are discussed in more detail throughout the preamble and in the 
regulatory analyses where relevant.

V. Summary of the NPRM

    The NPRM had two main components. The first proposed requiring a 
seat belt reminder for the rear seats. The second proposed changes and 
enhancements to the seat belt warning requirements for the front 
outboard seats, most notably an audio-visual warning that persists 
until the seat belt at any occupied front outboard seat is fastened. 
These proposed requirements would apply to passenger cars and trucks, 
buses (except school buses), and MPVs with a GVWR of 4,536 kg (10,000 
lb) or less.

Rear Seat Belt Reminder Requirements

    The first component of the NPRM was a set of proposed requirements 
for a seat belt warning for rear seats. The proposed requirements had 
four main elements.
     Visual warning on vehicle start-up to inform the driver of 
the status of the rear seat belts. We proposed three different 
compliance options from which manufacturers could choose for the rear 
seat belt warning system. The first would require the system to 
indicate how many or which rear seat belts are in use (the ``positive-
only'' option). The second would require the system to indicate, for 
the occupied rear seats, how many or which rear seat belts are not in 
use (the ``negative-only'' option). The third would require the system 
to indicate, for the occupied rear seats, how many or which rear seat 
belts are in use and how many or which rear seat belts are not in use 
(the ``full-status'' option). Certain features would be required of all 
the options. Each system would have to provide a continuous or flashing 
visual warning, consisting of either icons or text, visible to the 
driver. The visual warning would have to last for at least 60 seconds, 
beginning when the vehicle's ignition switch is moved to the ``on'' or 
``start'' position. All the systems would require that the vehicle be 
equipped with technology to determine that the belt latch is 
fastened.\53\ The negative-only and full-status compliance options 
would additionally have required that the vehicle be equipped with an 
occupant detection system (which facilitates these more informative 
warnings).
---------------------------------------------------------------------------

    \53\ We note the preamble language imprecisely indicated the 
necessity for a belt latch sensor. As discussed later in this 
document, it was not our intention to require a specific technology.
---------------------------------------------------------------------------

     Audio-visual change-of-status warning. We proposed an 
audio-visual warning whenever a fastened rear seat belt is unfastened 
while the ignition switch is in the ``on'' or ``start'' position and 
the vehicle's transmission selector is in a forward or reverse gear. 
The warning would have to last for at least 30 seconds. We did not 
propose any requirements for the volume or tone of the warning. The 
intent of this warning was to alert the driver or other occupants to a 
change in belt status during a trip. The warning would not be required 
if a door is open, which would be the case if a rear passenger 
unfastened their belt in order to exit the vehicle.
     Requirements related to electrical connections. We 
proposed to require that readily removable rear seats either 
automatically re-establish the necessary electrical connections, or, if 
a manual connection is required, have readily accessible connectors. 
Further, vehicles with the negative-only compliance option would be 
required to provide a visual warning to the driver if a proper 
electrical connection has not been established for a readily removable 
rear seat.
     Owner's manual requirements. We proposed that the vehicle 
owner's manual (which includes information provided by the vehicle 
manufacturer to the consumer, whether in digital or printed form) 
describe the warning system's features (including the location and 
format of the visual warnings) and include instructions on how to make 
any manual electrical connections for readily removable seats.

Front Outboard Seat Belt Warning Requirements

    The NPRM included several enhancements to the seat belt warning 
requirements for the front outboard seats. We proposed three main 
changes.
     Audio-visual warning on vehicle start-up for front 
outboard passenger seat. We proposed to require a seat belt warning for 
the front outboard passenger seat.
     Increasing the duration of the audio-visual warning on 
vehicle start-up. We proposed enhancing the front seat warning 
requirements by requiring an audio-visual warning that remains active 
until the seat belt at any occupied front outboard seat is fastened. 
Vehicle manufacturers could adjust the characteristics of the auditory 
warning signal (such as frequency and volume) to make the warning both 
effective and acceptable to consumers. The proposal included specific 
duty cycle characteristics.
     Audio-visual change-of-status warning. We also proposed to 
require an audio-visual change-of-status warning whenever a front 
outboard seat belt is unbuckled during a trip (unless a front door is 
open, to account for an occupant unfastening the belt to exit the 
vehicle). The warning would be required to remain active until the seat 
belt is refastened.

Proposed Compliance Date

    We proposed a compliance date for the amendments to FMVSS No. 208, 
``Occupant crash protection,'' as follows. Manufacturers would be 
required to comply with the amendments as of the first September 1 that 
is one year after the publication of the final rule for the front seat 
belt warning system requirements and the first September 1 that is two 
years after the publication of the final rule for the rear seat belt 
warning system requirements, with optional early

[[Page 400]]

compliance. Multi-stage manufacturers and alterers would have an 
additional year to comply.

Regulatory Alternatives

    NHTSA considered alternatives to the proposed requirements. The 
main alternatives NHTSA considered were the seat belt warning 
requirements in ECE R16 and Euro NCAP. The proposed requirements were 
identical or similar to ECE R16 and Euro NCAP in many respects but 
differed from them in several ways. For instance, while the ECE rear 
seat belt warning regulations allow a warning for an unfastened seat 
belt at an unoccupied seat, the proposal would not allow this, because 
we tentatively believed that the resulting ``false'' warning would 
potentially annoy drivers and lead to behaviors that would decrease 
system effectiveness. Another way the proposal differed from ECE R16 is 
the duration of the front seat belt warning on vehicle start-up: R16 
generally requires only a 30-60 second audio-visual warning; NHTSA 
proposed a warning that lasts until the seat belt is buckled.

VI. Final Rule and Response to Comments

A. Rear Seat Belt Warning Requirements

1. Applicability
    The proposal applied to all rear designated seating positions in 
passenger cars and all rear designated seating positions certified to a 
compliance option requiring a seat belt in trucks, buses, and MPVs with 
a GVWR of 4,536 kg (10,000 lb) or less, except for school buses and law 
enforcement vehicles. NHTSA's regulations define a bus as a vehicle 
designed for carrying more than ten persons.\54\ The proposal included 
small buses, which refers to buses with a GVWR not more than 10,000 lb; 
this therefore includes high-capacity vans. However, the proposal did 
not include medium-sized buses (with a GVWR 10,000 lb-26,000 lb) or 
large buses (with a GVWR greater than 26,000 lb). We proposed to apply 
the proposed requirements to the specified categories of vehicles 
because these vehicles are required to have seat belts at all rear 
designated seating positions and (except for some buses) a seat belt 
warning for the driver's seat. We noted that some types of trucks and 
MPVs (motor homes, walk-in van-type trucks, vehicles designed to be 
sold exclusively to the U.S. Postal Service, or vehicles with a GVWR 
between 8,500-10,000 lb carrying a chassis-mount camper) \55\ and over-
the-road buses that are also prison buses \56\ are not required to have 
rear seat belts. In the NPRM we explained that we did not propose to 
exempt special-purpose vehicle types such as ambulances because NHTSA 
believed that they are typically customized after first sale.
---------------------------------------------------------------------------

    \54\ 49 CFR 571.3 (``Bus means a motor vehicle with motive 
power, except a trailer, designed for carrying more than 10 
persons.'') (italics in original).
    \55\ S4.2.7.1.
    \56\ S4.4.3.3; S4.4.5.1.
---------------------------------------------------------------------------

    The proposed applicability was largely consistent with ECE R16, 
with a few differences. The rear seat belt reminder requirements in R16 
do not include vehicles that carry more than nine persons (including 
the driver).\57\ There is also no weight specification for the 
passenger vehicles to which R16 applies. R16 also exempts ``ambulances, 
hearses, and motor-caravans as well as for all seats for vehicles used 
for transport of disabled persons, vehicles intended for use by the 
armed services, civil defense, fire services and forces responsible for 
maintaining public order.'' \58\
---------------------------------------------------------------------------

    \57\ Section 8.4.1.2 (rear seat belt warning requirements apply 
to M1 and N1 category vehicles); Consolidated 
Resolution on the Construction of Vehicles (R.E.3) Revision 6, 
Section 2.2.1 (category M1 vehicles) (``Vehicles used for 
the carriage of passengers and comprising not more than eight seats 
in addition to the driver's seat.'') and Section 2.3.1 (category 
N1 vehicles) (``Vehicles used for the carriage of goods 
and having a maximum mass not exceeding 3.5 tonnes [7,716 lb].'').
    \58\ Section 8.4.1.3.
---------------------------------------------------------------------------

Comments
    NHTSA received comments that supported the proposal; comments that 
recommended expanding the applicability; and comments that recommended 
excluding additional vehicle types.
    Some commenters specifically supported various aspects of the 
proposal. Freedman Seating Company (FSC) and Mr. Koo supported the 
vehicles covered by the proposal and Ms. Tombrello supported including 
van-like buses because she believed some have been prone to misloading 
of passengers and baggage. Mr. Stange agreed that the final rule should 
exclude medium and large buses, due to the distraction the system would 
create for the driver; problems with maintenance and sensor 
reliability; and the fact that bus passengers are not required to wear 
seat belts in some states.
    Some commenters argued for including additional higher-capacity 
vehicles that the proposal excluded. The National Safety Council (NSC) 
and Ms. Tombrello supported including school buses (regardless of 
weight) and Mr. Koo supported including school buses with a GVWR 10,000 
lb and under. FSC supported extending the requirements to over-the-road 
buses with a GVWR between 10,000 and 26,000 lb (except school, 
perimeter seating and transit buses). NSC commented that the final rule 
should include limousines. Relatedly, InterMotive Vehicle Controls 
(InterMotive) commented that it manufactures an aftermarket seat belt 
reminder system for buses and vans with a GVWR both below and above 
10,000 lb.
    On the other hand, some comments argued for excluding additional 
vehicles from the requirements. The Alliance for Automotive Innovation 
(Auto Innovators) and Mercedes-Benz and Mercedes-Benz Research and 
Development North America (Mercedes) recommended exempting vehicles 
with more than six rear seats or more than two rear rows, pointing to 
challenges with providing the driver with the status information on all 
seating positions via the instrument panel (or other in-vehicle 
display) due to the number of seats that may need to be displayed. Auto 
Innovators further commented that for high-occupancy vehicles with 
removeable seats, an electronic control unit and other hardware are 
needed, which leads to practicability concerns, including increased 
costs for customers. Mercedes reiterated these practicability concerns.
    The Recreational Vehicle Industry Association (RVIA) similarly 
commented that this final rule should harmonize with R16 and not apply 
to motor homes. RVIA raised several different issues specific to motor 
homes. First, it explained that motor homes are used in unique ways 
because they are used both for transportation and for temporary, 
recreational, and seasonal use. As an example, RVIA discussed a 
scenario where occupants are seated in a rear seating position with the 
motor home turned on, but where the vehicle remains stationary, leading 
to a false warning. Second, it commented that motor homes' rear seats 
are often used for storage, which could again lead to false warnings. 
Third, RVIA commented that, because motor homes are often equipped with 
non-conventional seats that convert into a bed, developing wiring and 
sensors that would not be damaged in the conversion process would be 
challenging if not impossible. Fourth, RVIA commented that the rear 
portion of a motor home also has its own electrical system with very 
little interface with the chassis electronics. This lack of interface 
between electrical systems is unique in comparison to other types of 
vehicles that typically have seats installed in standard

[[Page 401]]

configurations in the same factory as the vehicle is assembled, 
completed, and shipped. RVIA stated that there is currently not a way 
to provide electronic signals from the seating positions in the rear 
portion of the motor home to the sophisticated electronics controls 
that are proprietary to the chassis manufacturers.
    Finally, Braun Northwest (BNW) commented that the final rule should 
exempt ambulances, giving essentially two different reasons. First, BNW 
commented that the reason NHTSA gave for not exempting ambulances--that 
they are typically customized after first sale--was factually 
inaccurate. BNW commented that while some special-purpose vehicles may 
be customized after first sale, that is not the case with ambulances. 
BNW explained that data from the Ambulance Manufacturer's Division of 
the National Truck Equipment Association indicates that van ambulances 
with a GVWR under 10,000 lb, which would be affected by this NPRM, 
comprise more than 20 percent of the annual production of United States 
ambulance manufacturers. Second, BNW pointed out that, while circuited 
buckles needed for seat belt buckle status indication are commonly 
available and simple to install on the two- and three-point seat belts 
commonly used on most vehicles, they are inherently problematic on the 
four, five, and six-point belts needed on ambulances. BNW explained 
that recent work facilitated by NHTSA resulted in a new SAE 
International (SAE) recommended practice, SAE J3026 Ambulance Patient 
Compartment Seating Integrity and Occupant Restraint, developed 
specifically for testing occupant restraint systems in ambulances. All 
three national ambulance standards (KKK-A-1822F, Federal Specification: 
Star-Of-Life Ambulance; NFPA 1917 Standard for Automotive Ambulances; 
and CAAS Ground Vehicle Standard) now require compliance with SAE 
J3026. BNW indicated that the critical ramification of SAE J3026 for 
the NPRM was that side-facing ambulance bench seats must be fitted with 
four-point, five-point, or six-point seat belts. BNW commented that 
there are practicability concerns with enabling buckle status 
indication for these seat belts, including the problem of getting wires 
from an emergency locking seat belt retractor to a circuited buckle 
located at the center front of the occupant's torso. Additionally, BNW 
argued that seat belt reminders may prevent medical personnel from 
administering medical care, as changes in occupant position required to 
render patient care would cause alarm indications that add distraction 
and confusion in an environment where such distractions can have dire 
consequences.
Agency Response
    NHTSA is adopting the proposal except that the final rule contains 
an additional exemption for ambulances.
    The major difference between the vehicles to which R16 and the 
final rule apply is that the final rule applies to small buses, which 
typically include buses with up to about four rear rows--mainly high-
capacity passenger vans (10 to 15-passengers), such as Chevrolet 
Express, Ford Transit, GMC Savana, and Mercedes Sprinter passenger 
vans. However, because the rule applies only to vehicles with a GVWR 
less than 10,000 lb, it would generally not include vehicles with more 
than four rows.
    We believe that including small buses such as these high-capacity 
vans addresses an important safety need. As we explained in the NPRM, 
we believe it is particularly important to include vehicles with a GVWR 
greater than 3,855 kg (8,500 lb), but less than or equal to 4,536 kg 
(10,000 lb), because this range includes high-occupancy vehicles. 
Including these vehicles is important because an increasing number of 
high-occupancy vehicles are used as personal vehicles and are not 
solely used for work-related purposes.\59\ In addition, multiple rear 
seats or rows make it more difficult for the driver to ascertain rear 
seat belt use, so a warning could prove especially useful in these 
vehicles. We think this requirement would be especially beneficial for 
15-passenger vans, for which there is both an increased risk of 
rollover (related to the occupancy level of these vehicles) and lower 
seat belt use rates compared to other passenger vehicles.\60\
---------------------------------------------------------------------------

    \59\ See, e.g., https://media.ford.com/content/fordmedia/fna/us/en/news/2016/07/29/nothing-mini-about-this-van--ford-transit-attracts-large-familie.html (last accessed May 16, 2024).
    \60\ Belt use rates among occupants in 15-passenger vans 
involved in fatal crashes are significantly lower compared to other 
passenger vehicles. See Subramanian, R. (2008). Fatalities to 
Occupants of 15-Passenger Vans, 1997-2006. (Report No. DOT-HS 810 
947). National Highway Traffic Safety Administration.
---------------------------------------------------------------------------

    Providing a reminder in vehicles with multiple rear rows is 
technically feasible. As we noted above, because the final rule applies 
to vehicles with a GVWR 10,000 lb or less, it generally would not 
include vehicles with more than four rear rows of seats, which should 
make it easier to implement a reminder. We are unaware of any currently 
produced full-size passenger vans having a rear seat belt reminder 
system. We did find aftermarket solutions from abroad for medium to 
large buses,\61\ and InterMotive commented that a seat belt warning 
system already exists for multipurpose passenger vehicles with a GVWR 
both below and above 10,000 lb. They currently manufacture an after-
market solution, SeatLink, for the bus and van market, including seats 
supplied by Freedman Seating Company (Freedman). However, we do not 
have any information on the performance and reliability of these 
systems.
---------------------------------------------------------------------------

    \61\ See https://www.phoenixseating.com/our-products/all-buckled-up and https://www.fsrtek.com/applications/bus-seat-belt-alarm-system (last accessed May 16, 2024).
---------------------------------------------------------------------------

    We do acknowledge that vehicles such as high-capacity vans may 
encounter visual signal complexities. Accordingly, our intent was to 
propose performance requirements that provide manufacturers with the 
flexibility to design a warning system that is appropriate for each 
vehicle type (for example, the final rule does not require a full 
schematic of the rear seats). For example, a visual warning option for 
vehicles with multiple rows could be the seat belt icon with an 
adjacent number corresponding to how many rear seat belts are fastened. 
In addition, as we explain in more detail below (see Section 
VI.A.2.a.i), in response to the comments, we have expanded the 
compliance options to allow additional types of visual warning systems. 
This too should help address any concerns related to feasibility.
    The final rule, however, also follows the proposal in excluding 
school buses and medium and large buses. As we explained in the NPRM, 
extending the requirements to school buses would place additional cost 
burden on school systems and may result in reductions in service; would 
place additional burdens on the driver; and raises liability issues and 
the potential for buses being out of service due to malfunctioning 
systems. Many of these concerns were raised by commenters to the ANPRM 
and we believe these concerns are still valid. Moreover, as we also 
pointed out in the NPRM, school buses use compartmentalization, which 
provides protection even to unbelted occupants. Similarly, the final 
rule also excludes medium and large buses because of issues such as 
those noted by Mr. Stange, including cost, reliability, and driver 
burden.
    The final rule also follows the proposal by including motor homes. 
As an initial matter, we note that some motor homes are not required to 
have

[[Page 402]]

rear seat belts so the requirements will not necessarily apply to all 
motor homes. In addition, the seat belt requirements do not apply to 
seats in motor homes with a GVWR over 10,000 lb and classified as MPVs 
which the manufacturer designates and conspicuously labels as not 
intended for occupancy while the vehicle is in motion.\62\ Accordingly, 
such vehicles are not subject to the requirements in this rule. 
Although we recognize that R16 exempts motor homes (motor caravans), we 
see no reason to exclude from this rule designated seating positions 
(DSPs) in motor homes that are required to have seat belts. Those DSPs 
are designed to have passengers while the vehicle is in motion. Such 
occupants would benefit from a seat belt and therefore, from a seat 
belt reminder. We note that if the motor home is turned on for other 
purposes than driving, the start-up warning is a 30-second visual 
warning that should not be unduly annoying.
---------------------------------------------------------------------------

    \62\ 49 CFR 571.3 (definition of ``designated seating 
position''); FMVSS No. 207 S4.4.
---------------------------------------------------------------------------

    Limousines, depending on their characteristics, may also be covered 
by the rule. Limousines are not currently a vehicle class defined in 
the FMVSS. Depending on its characteristics, a limousine might be 
classified as a passenger car, MPV, or bus.\63\ Generally, a passenger 
car is designed for carrying 10 or fewer persons, an MPV is a vehicle 
carrying 10 or fewer persons which is constructed either on a truck 
chassis or with certain special features, and a bus is designed to 
carry more than 10 persons. The final rule encompasses all these 
vehicle types, so a limousine would be covered by the requirements as 
long as it weighed 10,000 lb or less. At the same time, the FMVSS 
generally apply to new vehicles, including new vehicles that are 
altered, or vehicles manufactured in more than one stage. Limousines 
(such as ``stretch'' limousines) that are the result of modifications 
made to a vehicle after first purchase other than for resale would not 
be required to be certified to the seat belt reminder requirements for 
seating positions that are added in the modification process.\64\
---------------------------------------------------------------------------

    \63\ 49 CFR 571.3.
    \64\ The Infrastructure, Investment and Jobs Act, H.R. 3684, 
Sections 23015, 23023 (117th Congress) (2021), contains two 
provisions that direct NHTSA to conduct research and issue rules (if 
such rules would meet the criteria in section 30111 of the Safety 
Act) related to various aspects of limousine crashworthiness and 
occupant protection. NHTSA's research in these areas is ongoing. 
See, e.g., DOT Regulatory Agenda, Fall 2023, RIN 2127-AM48, ``Seat 
Belts in Limousines,'' available at https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202310&RIN=2127-AM48 (last accessed 
December 16, 2024). The law also directs that the rules issued 
pursuant to it apply to modified vehicles. However, that law also 
defines the term ``limousine'' to, among other things, refer to 
vehicles weighing between 10,000 and 26,000 lb. This would therefore 
not include any limousines that are covered by this final rule, 
which is limited to vehicles up to 10,000 lb. GVWR.
---------------------------------------------------------------------------

    The one way the final rule does depart from the proposal with 
respect to the applicability is by including an exemption for 
ambulances from the rear seat belt warning system requirements.\65\ 
Given the information provided by BNW, the original intent of the rule 
not applying to ambulances, and the fact that excluding ambulances 
harmonizes with ECE R16, the final rule exempts ambulances. Although 
neither FMVSS No. 208 nor 49 CFR 571.3 defines ``ambulance,'' FMVSS No. 
201, ``Occupant protection in interior impact,'' defines it to mean ``a 
motor vehicle designed exclusively for the purpose of emergency medical 
care, as evidenced by the presence of a passenger compartment to 
accommodate emergency medical personnel, one or more patients on 
litters or cots, and equipment and supplies for emergency care at a 
location or during transport.'' \66\ We are including a cross-reference 
to this definition in the regulatory text. However, we have not 
included a broader carve-out for emergency vehicles. We did not receive 
any comments indicating that such a carve-out was necessary. Moreover, 
there are a number of ways that owners and purchasers of emergency 
vehicles for official purposes could disable the warnings. These owners 
and purchasers already sometimes alter vehicles significantly.\67\
---------------------------------------------------------------------------

    \65\ This does not exempt ambulances from the front seat belt 
warning requirements.
    \66\ FMVSS No. 201, S3 (definitions).
    \67\ Although section 30122 of the Safety Act prohibits making 
inoperative required safety devices, this prohibition does not apply 
to vehicle owners. See infra n. 91 and accompanying text.
---------------------------------------------------------------------------

2. Requirements
    The NPRM proposed a 60-second visual warning on vehicle start-up; a 
30-second audio-visual warning if a buckled belt is unfastened during a 
trip; and requirements or criteria related to readily removable seats, 
the owner's manual instructions, the location of the telltale, and how 
NHTSA would determine that a belt was or was not in use. We discuss 
these requirements in turn below.
a. Visual Warning on Vehicle Start-Up
    The NPRM proposed a 60-second visual warning on vehicle start-up 
that would inform the driver of how many or which seat belts are and/or 
are not in use. We proposed three different compliance options for the 
type of information conveyed to the driver. Occupant detection would 
not be required for one of the three compliance options. The warning 
would be triggered when the ignition is placed in the ``on'' or 
``start'' position. When testing a system certified to one of the 
compliance options necessitating occupant detection, NHTSA would seat a 
dummy or human occupant corresponding to a 6-year-old. We discuss these 
proposed requirements below in more detail.
i. Type of Information Conveyed by the Visual Warning and Whether 
Occupant Detection Should Be Required
    The proposed requirements for the rear seat belt warning system 
(RSBWS) included a visual warning that would activate on vehicle start-
up to inform the driver of the status of the rear seat belts. We 
proposed three different compliance options. The first would require 
the system to indicate how many or which rear seat belts are in use 
(the ``positive-only'' option). The second would require the system to 
indicate, for the occupied rear seats, how many or which rear seat 
belts are not in use (the ``negative-only'' option). The third would 
require the system to indicate, for the occupied rear seats, how many 
or which rear seat belts are in use and how many or which rear seat 
belts are not in use (the ``full-status'' option). The negative-only 
and full-status compliance options would require that the rear seats be 
equipped with a mechanism to determine when a belt latch is fastened 
and an occupant detection system (which facilitates these more-
informative warnings), while the positive-only option would only 
require that the rear seats be equipped with a mechanism to determine 
when a belt latch is fastened.
    In the NPRM we stated that we had tentatively decided not to 
require occupant detection in the rear seats because occupant detection 
continued to present technical challenges which could reduce the 
effectiveness and/or acceptance of these systems. This tentative 
decision was also based on factors such as the needed increase in seat 
belt use for this regulatory alternative to have positive net benefits. 
Because we did not propose to require occupant detection, we also did 
not propose requiring enhanced warnings (such as an audible warning on 
vehicle start-up).
    The proposal harmonized with ECE R16 and Euro NCAP in a variety of 
ways, but also deviated from them in some respects.

[[Page 403]]

    ECE R16 requires a visual warning at the start of a trip. That 
warning ``indicate[s] at least all rear seating positions to allow the 
driver to identify, while facing forward as seated on the driver seat, 
any seating position in which the safety-belt is unfastened.'' \68\ 
Occupant detection is not required, but in vehicles that do have 
occupant detection the warning does not need to indicate unfastened 
belts for unoccupied seating positions.\69\
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    \68\ Section 8.4.4.2.
    \69\ Section 8.4.4.2.
---------------------------------------------------------------------------

    The Euro NCAP rating protocol also requires a visual warning at the 
start of a trip. The requirements are similar to ECE R16. However, Euro 
NCAP's rating protocol was recently revised to require occupant 
detection in the rear seat to receive points for this feature. For 
systems without occupant detection, the visual signal must clearly 
indicate to the driver the seating positions showing the rear seat 
belts in use and not in use. (These seats would not be eligible for 
points, but in order for seats with occupant detection to receive 
points the seats without occupant detection would have to meet these 
requirements.) For systems with occupant detection, the visual signal 
does not need to indicate the number of seat belts in use or not in 
use, but the signal must remain as long as the seat belt remains 
unfastened on any of the occupied seats in the rear.\70\ No signal is 
required if all of the rear occupants are belted \71\ or no rear 
occupants are detected.\72\
---------------------------------------------------------------------------

    \70\ Section 3.4.3.1.3.
    \71\ Section 3.4.3.1.4.
    \72\ Section 3.4.3.1.1.
---------------------------------------------------------------------------

    The IIHS rating protocol requires a visual signal indicating 
``whether the seat belt at each rear seating position is fastened or 
unfastened.'' \73\
---------------------------------------------------------------------------

    \73\ Seat Belt Reminder System Test and Rating Protocol, Version 
III at pg. 7.
---------------------------------------------------------------------------

    The NPRM acknowledged that the proposed compliance options were not 
consistent with all seat belt warning systems currently deployed in the 
U.S. and Europe or with Euro NCAP's requirements. Specifically, we 
noted that manufacturers appeared to be deploying systems that would be 
categorized as either positive-only or negative-only except without 
occupant detection, the latter of which would not be permitted under 
the proposed compliance options. We also noted that the positive-only 
compliance option did not appear to be consistent with Euro NCAP 
because Euro NCAP requires that systems without occupant detection show 
the rear seat belts in use and not in use, and the positive-only 
compliance option would not permit a visual signal for an unfastened 
seat belt.
    Accordingly, while we tentatively concluded that the proposed 
compliance options would help mitigate false warnings and the possibly 
attendant consumer acceptance issues, we explained that we were 
considering altering the proposed compliance options to accommodate 
systems that are currently being deployed, or that manufacturers may 
wish to deploy in the future.
Comments
    Auto Innovators, General Motors (GM), American Honda Motor Co. 
(Honda), and Hyundai America Technical Center, Inc. (HATCI) generally 
supported including multiple compliance options in the final rule. 
Freedman, Automotive Safety Council (ASC), Tesla, Advocates and Public 
Citizen, and the National Automobile Dealers Association (NADA) 
generally supported the proposed compliance options, although as noted 
below some of these commenters preferred certain compliance options or 
requested that additional compliance options be added.
    Several commenters (Consumer Reports, Safe Kids Worldwide (SKW), 
Paradise, NSC, Safe Ride News (SRN), Cross, and Ms. Tombrello) argued 
that NHTSA should require occupant detection in the rear seats. Other 
commenters (Freedman, IEE,\74\ ASC), while not explicitly recommending 
that occupant detection be required, either preferred options requiring 
occupant detection or focused on the benefits and feasibility of rear-
seat occupant detection. These commenters made a variety of arguments.
---------------------------------------------------------------------------

    \74\ A supplier of automotive sensing systems.
---------------------------------------------------------------------------

    Some commenters argued that the necessary technology for occupant 
detection is feasible. Consumer Reports commented that occupant 
detection does not pose unreasonable technical challenges, and is not 
prohibitively expensive (see Section VIII, Overview of Costs and 
Benefits). Consumer Reports and Mr. Paradise commented that rear-seat 
occupant detection technology is already widely available; Mr. Paradise 
also noted that 7 percent of vehicles already have the technological 
capability of occupant detection in rear seats. NSC commented that 
challenges with false positives (e.g., transportation of cargo and 
pets) can be addressed through a relatively small investment, such as 
with low-cost 2-D or digital cameras, and that costs would further 
decrease over time if it were required. Consumer Reports noted that 
occupant detection is already widely deployed in the front outboard 
passenger seats. Relatedly, although not recommending that occupant 
detection be required, IEE commented that today's occupant detection 
sensors, predominantly designed for a detection of 5th percentile adult 
female, can reliably differentiate occupants from cargo.
    Several commenters focused on the benefits of requiring occupant 
detection. Consumer Reports, Mr. Paradise, SKW, SRN, ASC, Ms. Cross, 
NSC, and Ms. Tombrello commented that warning systems using occupant 
detection would be more effective than those without it. Consumer 
Reports, Paradise, Ms. Cross, and NSC noted that occupant detection 
would enable enhanced warnings, which are more effective.
    Accordingly, some of these commenters recommended requiring the 
proposed full-status and/or negative-only options that required 
occupant detection. Consumer Reports argued that NHTSA should require 
the full-status compliance option because the ``positive-only'' and 
``negative-only'' compliance options are insufficient to incentivize 
rear seat belt use. Consumer Reports commented that the positive-only 
option would be the least technically complex, but it would also be the 
least effective type of warning system (because it creates unnecessary 
mental work for the driver and allows room for human error). Consumer 
Reports further explained that the positive-only system would be a 
departure from Euro NCAP, which requires that systems without occupant 
detection show both the rear seat belts in use and those not in use. 
Consumer Reports also commented that given that both the negative-only 
and the full-status options require a belt latch sensor and an occupant 
detection system, the negative-only option should be eliminated because 
the full-status option is more informative and effective. SRN, ASC, 
NSC, and Ms. Cross similarly commented that NHTSA should require 
negative-only or full-status systems, which would be more effective in 
alerting caregivers to an unbuckled rear passenger than ``positive-
only'' systems. Ms. Cross commented that negative-only and full-status 
systems can inform the driver whether any rear seat occupants are 
unbuckled without having to make a comparison between number of seats 
to the number of occupants and an audible component can be added. ASC 
also noted that permitting only negative-only and full-status systems 
would harmonize with the requirements in Europe.

[[Page 404]]

    Consumer Reports, Cross, and SKW also recommended requiring 
occupant detection because that feature could eventually be used for 
other safety functions such as rear occupant alerts for vehicular 
heatstroke prevention and air bag suppression. SKW and Ms. Cross 
pointed to the potential to detect children or other vulnerable 
occupants in child safety seats, booster seats, or seat belts.
    On the other hand, vehicle manufacturers commented that the final 
rule should not require occupant detection. Toyota Motor North America, 
Inc. and Toyota Motor Corporation (Toyota) and Auto Innovators 
commented that an occupant detection system can introduce false 
positives. Several manufacturers requested removing the requirement for 
occupant detection from one or both of the proposed compliance options 
that required it (full-status and negative-only).
    Toyota argued that NHTSA should allow negative-only systems without 
occupant detection because an occupant detection system does not 
provide any additional safety benefit for the negative-only system. 
Toyota explained that it is reasonable to anticipate that a driver 
knows whether a rear occupant is in the vehicle, and, as with a 
positive-only system, can combine that knowledge with the information 
from the visual indicator. Toyota also commented that a telltale 
indicating a seat belt is not fastened at an unoccupied seat is not a 
false positive, but is instead useful information for the driver.
    More generally, several manufacturers and trade groups (Auto 
Innovators, Ford Motor Company (Ford), Nissan North America (Nissan), 
NADA, Honda, Hyundai Motor Company (Hyundai)) commented that NHTSA 
should permit manufacturers to convey information on positive belt 
status information (i.e., when belt is in use) and/or negative belt 
status information (i.e., when the belt is not in use) without occupant 
detection--that is, NHTSA should expand the proposed compliance options 
to permit negative-only systems without occupant detection and/or full-
status systems without occupant detection.\75\ NADA argued that these 
options would provide better contextual information for drivers than 
the proposed full[hyphen]status option because they would provide seat 
belt status information for all seating positions regardless of 
occupancy. Nissan, Ford, and Auto Innovators argued that presenting 
information on the seat belt status regardless of whether the seat is 
occupied or not should not be deemed as misleading but rather as 
furnishing the driver with pertinent contextual information concerning 
seat belt usage across all positions. Nissan and Ford argued that this 
information would empower the driver to distinguish easily between 
buckled and unbuckled seat belts, particularly when compared to the 
locations where known passengers are situated in the rear row. Auto 
Innovators, Nissan, NADA and Ford commented that this approach would be 
consistent with European regulations. Nissan, NADA, and Ford indicated 
that this approach would align with ECE R16, and Ford and Auto 
Innovators commented that the approach aligns with the IIHS approach. 
Honda commented that systems without occupant detection that provide 
visual information on both fastened and unfastened seat belts have been 
in use in Europe for many years and are well understood by those that 
use it regularly. Auto Innovators and NADA commented that not expanding 
the compliance options in this way would require development and 
deployment of new systems and increase cost and lead time for some 
original equipment manufacturers (OEMs), which ultimately harms 
consumers and hinders achievement of NHTSA's safety objective. Auto 
Innovators further commented that it was unaware aware of any data that 
would support NHTSA's claim that a visual indication of an unfastened 
seat belt at an unoccupied seat would annoy drivers and argued that if 
driver annoyance is a concern, NHTSA should consider allowing a 
dismissible initial warning, as is the case with both IIHS and R16.
---------------------------------------------------------------------------

    \75\ Some of the comments were ambiguous with respect to whether 
they were referring to full-status systems, negative-only systems, 
or both.
---------------------------------------------------------------------------

    In addition, Ford, Toyota, and Honda raised concerns with the 
proposed positive-only compliance option. Ford and Toyota commented 
that it conflicts with R16 and the IIHS protocol. Honda commented that 
if all rear occupants are unbuckled and there is no indication of their 
status, the driver may remain unaware of the system's ability to 
support the determination of the statuses of the belts for the rear 
occupants.
Agency Response
    In response to the comments, the final rule follows the proposal in 
not requiring occupant detection, but modifies the proposal by revising 
the requirements to allow full-status and negative-only reminder 
systems without occupant detection.
    The final rule follows the proposal in not requiring that rear seat 
belt reminder systems be equipped with occupant detection. There are a 
few reasons for this decision.
    One reason is that we believe rear-seat occupant detection 
continues to present technical challenges. This is especially the case 
because we have concluded that rear-seat occupant detection systems 
should be able to detect, at a minimum, occupant characteristics 
matching a 6-year-old for determining whether a rear seat is occupied. 
This standard differs from ECE R16 and Euro NCAP, both of which base 
their requirements for occupant detection-equipped rear seat belt 
reminder systems on the 5th percentile female. This difference is 
discussed in more detail in Section VI.A.2.a.iv, Seat Occupancy 
Criteria and Interaction with Child Restraint Systems. Rear-seat belt 
reminder systems with occupant detection have only been recently 
deployed in vehicles sold in the U.S. (starting in MY 2021 based on our 
available data) and are currently offered on only a small proportion of 
new vehicles.\76\ Based on the projected sales for MY 2022, 
approximately 7 percent of vehicles were equipped with rear-seat 
occupant detection. We have no data on how the occupant detection in 
these vehicles is working.
---------------------------------------------------------------------------

    \76\ NHTSA does not have any specific information on the size of 
occupant these systems are designed to detect. However, based on the 
manufacturer comments requesting that NHTSA require occupant 
detection systems to detect a 5th percentile female occupant, it is 
likely that these systems are designed to detect occupants as small 
as the 5th percentile female.
---------------------------------------------------------------------------

    While occupant detection technology is readily available and 
standard equipment in most front outboard passenger seats, the occupant 
detection technology used for the front outboard passenger seat does 
not necessarily translate directly to the rear seats. By comparison, 
vehicles subject to advanced air bag requirements comply using either 
suppression or low-risk deployment for different size child dummies, 
including the 6-year-old child dummy, in the front outboard passenger 
seat. Vehicles with a suppression system use some type of occupant 
detection technology in addition to other inputs (e.g., seat belt use, 
seat position, etc.) to determine whether or not to deploy the air bag. 
Vehicles using low-risk deployment, however, do not necessarily need to 
use occupant detection to meet the advanced air bag requirements for 
that option. The vast majority of vehicles use the suppression option 
in the front outboard passenger

[[Page 405]]

seat for at least one child dummy, and therefore use occupant 
detection.77 78
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    \77\ There is also an option to use a dynamic automatic 
suppression system. To date, no manufacturer has attempted to 
certify using this option.
    \78\ With respect to the driver's seat, while it is subject to 
certain advanced air bag requirements, those particular requirements 
do not necessitate occupant detection.
---------------------------------------------------------------------------

    Vehicle manufacturers that opt to use a rear seat belt warning 
system with occupant detection will have to develop and implement 
occupant detection solutions that work for the unique seat designs and 
configurations found in rear seats (e.g., bench seats, folding seats, 
different types of seat cushions, etc.) and validate the performance to 
ensure that they meet the new requirements and mitigate the potential 
for false positives. Among other challenges, rear seats create more 
potential for false positives than the front seats. As we explained in 
the NPRM and ANPRM, while occupant detection can reduce false warnings 
for unoccupied seats, it can also result in false warnings, due to the 
limitations of the sensors and different use scenarios in the rear 
seats (e.g., transportation of cargo and pets). In addition, rear seats 
may be less well-defined than front seats (most rear seat rows, unlike 
the front seat rows, are comprised of three closely spaced seating 
positions), which could impede accurate detection. This deficiency 
could negatively affect consumer acceptance and/or effectiveness.
    Another reason the final rule does not require occupant detection 
is that it adds non-trivial costs to the seat belt warning system. 
While we agree with Consumer Reports that rear-seat occupant detection 
is not prohibitively expensive in the sense that this is true for some 
vehicle lines, our cost-benefit analysis shows that occupant detection 
would be cost-beneficial only if rear seat belt use increased 
substantially more than we estimate it would for a warning system 
without occupant detection. Our teardown analysis indicates that 
occupant detection components cost $39.74 per vehicle, which, added to 
the $19.59 per vehicle cost of the buckle sensor, results in a combined 
warning system cost of $59.33 per vehicle (2020 $). We estimate that 
the total new fleet cost of a rear seat belt warning system with 
occupant detection would be about $802 million (2020 $). With respect 
to benefits, there is uncertainty with respect to how much more 
effective systems with occupant detection are compared to systems 
without it. Because of this uncertainty, our regulatory analysis does 
not attempt to estimate the net benefits or cost-effectiveness of rear 
seat belt reminder systems that use an occupant detection system. The 
regulatory analysis does, however, include a break-even analysis for a 
rear seat belt reminder system that requires occupant detection. For 
benefits and costs to break even (be equal) for this regulatory option, 
seat belt use for rear seat occupants 11 years and older would need to 
increase by approximately 5.2 percent when discounted at 3 percent and 
6.4 percent when discounted at 7 percent. Furthermore, NHTSA considered 
the increase in seat belt use for rear seat occupants that would be 
required to match the net benefits under the final rule, which does not 
require occupant detection. When discounted at three and seven percent, 
seat belt use for rear seat occupants 11 years and older would need to 
increase by 6.43 percent to 8.57 percent to match the net benefits 
(taking into account the Low and High estimates) under the final rule. 
This is about two to three times greater than that estimated for the 
compliance option without occupant detection. (For more details, see 
Section VIII.B.1 and the FRIA.) Accordingly, while we agree with the 
commenters who supported a requirement for occupant detection because 
there may be benefits to having occupant detection (such as 
facilitating enhanced or more effective warnings) \79\ and would expect 
some potential increase in seat belt use from that specific 
functionality, an effectiveness increase of this order of magnitude 
seems unlikely. Therefore, we do not expect this regulatory alternative 
to be net beneficial and would not generate the same level of net 
benefits as the final rule. Manufacturers may voluntarily equip 
vehicles with occupant detection if they so choose. Our hope is that 
over time, as the systems evolve and penetrate the fleet, the 
technology will mature and per-unit costs will decrease.
---------------------------------------------------------------------------

    \79\ With respect to SKW's comments about the benefits of 
monitoring children in forward- or rear-facing CRSs, as we explained 
in the NPRM, children restrained by child restraint systems are not 
part of the target population for this rule.
---------------------------------------------------------------------------

    With respect to the comment from Mr. Paradise concerning what he 
believed was an inconsistency between NHTSA's statements that a single-
digit percentage of vehicles with rear-seat occupant detection being a 
small percentage of the fleet, and weighing in favor of not requiring 
it, and a single-digit percentage of vehicles with an indefinite 
reminder being non-trivial and supporting our proposal to require an 
indefinite reminder for the front seat belt start-of-trip warning, we 
do not believe these statements are inconsistent. In the context of 
occupant detection, we are referring to technological feasibility and 
likely regulatory cost; in the front seat belt warning section, we are 
referring solely to the optimum duration, as there is no question about 
feasibility. That is, a single-digit percentage has a different meaning 
in the two contexts.
    Because we have decided not to require occupant detection, we 
disagreed with commenters who recommended requiring one or both of the 
proposed options that required occupant detection (full-status with 
occupant detection or negative-only with occupant detection). We 
continue to believe, as we explained in the NPRM, that while the full-
status system (with occupant detection) does provide the driver with 
the most information, the other allowable types of systems, including 
those without occupant detection, will provide the driver with 
sufficient information to easily determine whether and where there are 
any unbuckled occupants and request that they fasten their seat belts.
    Accordingly, the final rule allows the proposed positive-only 
option. These systems, while not providing information on the occupancy 
status of each seat, do provide information on which seat belts are 
buckled. The driver can combine this information with knowledge of the 
other occupants in the vehicle and determine if there are any unbuckled 
occupants and request them to fasten their belts. While this does 
require mental work on the part of the driver, and may not be as 
effective as a full-status system, we believe it is not so burdensome 
as to render such systems ineffectual to such a degree that we see a 
basis for prohibiting them. While such systems are not permitted under 
ECE R16 or Euro NCAP, manufacturers could select another type of system 
if they wished to harmonize with those protocols. (The positive-only 
system without occupant detection does conform with the IIHS protocol.) 
With respect to Honda's comment that the proposed positive-only option 
could potentially leave the driver unaware that the vehicle was 
equipped with a seat belt reminder system, we acknowledge that is a 
possibility, but it would not be a long-term problem. This would be 
limited to times when a driver is driving a vehicle new to them (unless 
the driver always reads owner's manuals first) and would only be an 
issue until a rear passenger buckles up. Once a rear passenger buckles 
up the driver would become aware of the existence of the warning.
    We have modified the proposal so that the final rule does not 
dictate

[[Page 406]]

specific compliance options for the information conveyed by the visual 
warning; the finalized requirements for the visual warning allow all of 
the systems that would have been allowed under the proposed rule, as 
well as additional systems that would not have been allowed under the 
proposal, such as a negative-only system without occupant detection, 
and a full-status system without occupant detection. Both the negative-
only system without occupant detection and the full-status system 
without occupant detection are consistent with ECE R16 and the IIHS 
protocol (they would not be eligible for points under Euro NCAP). One 
factor underlying this choice is the lack of firm research data that 
could lead NHTSA to meaningfully compare the effectiveness of the 
different types of systems,\80\ coupled with the fact that rear seat 
belt reminder systems conforming to the finalized requirements have 
already been deployed on vehicles sold in the United States.\81\ These 
factors make us reluctant to prohibit particular design choices and 
inhibit manufacturer flexibility and ability to optimize system 
characteristics. We believe that the finalized regulatory text (``A 
visual warning indicating how many or which rear seat belts are in use 
and/or not in use must activate when the ignition switch is placed in 
the `on' or `start' position (or upon manual activation of the 
propulsion system, but prior to the vehicle being placed in ``possible 
active driving mode'' as defined by FMVSS No. 305))'' \82\ includes all 
of the systems manufacturers are currently deploying, but is specific 
enough to be objective and enforceable. For example, if there is one 
rear occupant, and that occupant is belted, a positive-only system 
without occupant detection that accurately indicates one buckled rear 
belt, and a full-status system with occupant detection that accurately 
indicates one rear occupant with a fastened belt, would both comply 
with the finalized regulatory text.
---------------------------------------------------------------------------

    \80\ See Mark Freedman et al., Effectiveness and Acceptance of 
Enhanced Seat Belt Reminder Systems: Characteristics of Optimal 
Reminder Systems Final Report. DOT HS 811 097 at pg. 49 (Feb. 2009) 
(hereinafter ``DOT 2009 Seat Belt Study'').
    \81\ An exception is a positive-only system with occupant 
detection, which is not prohibited by the finalized requirements and 
has yet to be deployed on vehicles sold in the United States. 
However, we believe it would be unlikely that a manufacturer would 
deploy such a system because the presence of occupant detection 
allows for more informative reminders--for example, a full-status 
reminder--than provided by a positive-only system. This is reflected 
in the fact that while we are aware of production versions of 
positive-only systems without occupant detection, negative-only and 
full-status systems with and without occupant detection, we are not 
aware of any vehicle equipped with both occupant detection and a 
positive-only reminder system.
    \82\ The language relating to EVs is discussed in Section 
VI.C.1.
---------------------------------------------------------------------------

    We agree with Toyota and Honda that the negative-only system 
requires the same cognitive effort on the part of the driver as the 
proposed positive-only option, and that it would still be effective and 
beneficial, even without occupant detection. We no longer agree with 
the view we expressed in the NPRM that such a signal is a false 
positive that might either desensitize the driver to the warning signal 
or lead them to circumvent or defeat the system. We now agree with 
Toyota that this is instead more accurately considered relevant 
information on seat belt status that the driver can use to determine 
whether there are any unbuckled occupants and request them to fasten 
their seat belts.
    We reached a similar conclusion with respect to full-status systems 
without occupant detection. As we discussed above for the negative-only 
systems without occupant detection, we agree that while this system 
does not provide as much information as would a system with occupant 
detection, the information it does provide on the seat belt status at 
every seating position (occupied or not) is useful information for the 
driver. We also agree with the commenters who argued that allowing this 
option would support the introduction of systems that are already in 
widespread use, without adding in additional cost and complexity.
ii. Lack of an Audible Warning
    The NPRM recognized that warnings with an audible component are 
generally more effective than visual-only warnings. However, we also 
recognized that requiring an audio-visual warning would necessitate 
requiring occupant detection because, without occupant detection, an 
audible warning would activate every time a rear seat is empty. These 
``false positives'' would annoy the driver (as well as other occupants) 
and would decrease the effectiveness of the warning. Thus, the NPRM did 
not propose an audible warning on start-up. However, manufacturers 
would be free to provide an audible warning on start-up if they so 
choose. This approach is also consistent with ECE R16, Euro NCAP, and 
IIHS.
Comments
    Many of the commenters who supported requiring occupant detection 
also supported requiring an audible warning (NSC, Consumer Reports, 
SRN, Karleigh Cross, and an anonymous commenter). SRN, Consumer 
Reports, and Ms. Cross commented that audible warnings are more 
effective than visual-only warnings. Consumer Reports also commented 
that requiring an audible component to the rear seat start-up warning 
would also make start-up warnings more consistent throughout a vehicle, 
regardless of the seating position.
Agency Response
    The final rule does not require a rear seat audible start-of-trip 
warning, for the reasons articulated in the proposal. Because the final 
rule does not require occupant detection in the rear seats, it does not 
require an audible warning. We acknowledge that audio-visual warnings 
are more effective than visual warnings alone, and we believe that 
consumers would accept them. However, we believe that a visual warning 
alone will still be effective. While we cannot precisely estimate 
effectiveness, we have used a three to five percent belt use rate 
increase range (``lower'' and ``higher'' scenario) in our analysis 
based on the available research. This analysis is explained in detail 
in the FRIA. We agree that in general, consistency between the rear 
reminder and front reminder requirements (which do require an audio-
visual start-of-trip warning) is desirable, but do not believe that not 
requiring an audible component to the rear start-of-trip warning will 
create an issue in practice. In this context, the relevant potential 
concern with this inconsistency is that the driver--the recipient of 
the warning--would be confused or annoyed by any differences in the two 
warnings. Ultimately, we do not believe this inconsistency is a 
significant problem. The front seat belt warnings have been in vehicles 
for many years. Rear seat belt warnings will be new to most drivers, so 
drivers will have to become accustomed to them. In addition, the rear 
reminder will be a fairly prominent visual warning. If the driver is 
unsure of how the warnings operate, this rule also requires that the 
owner's manual include an accurate and easily understandable 
description of system features and operation.
iii. Triggering Conditions for Start-of-Trip Warning (Not Including 
Occupant Detection Criteria)
    The NPRM proposed that the rear seat start-of-trip warning (which, 
as discussed above, is only required to be a visual warning) activate 
when the ignition switch is placed in the ``on'' or ``start'' position, 
except for negative-only systems when there are no occupied rear seats 
with a seat belt not

[[Page 407]]

in use (for which we proposed that a warning not be required to 
activate). The activation criteria were modeled on the existing driver 
seat belt warning requirements and are also similar to those in ECE 
R16, Euro NCAP, and the IIHS protocol.
    ECE R16 requires that the rear seat belt visual warning activate 
when a belt is not fastened and the ignition or master control switch 
activated.\83\ It also provides that for vehicles with rear seat 
occupant detection, the visual signal does not need to indicate 
unfastened belts at unoccupied seats.\84\
---------------------------------------------------------------------------

    \83\ Section 8.4.2.3.1.
    \84\ Section 8.4.4.2.
---------------------------------------------------------------------------

    Euro NCAP similarly requires that the warning ```start' at the 
commencement of each `journey' that the vehicle makes.'' \85\ More 
specifically, the Euro NCAP protocol specifies that the visual signal 
be activated ``when the ignition switch is engaged (engine running or 
not) and a seatbelt is not fastened.'' \86\ However, Euro NCAP allows 
for short breaks in the journey (up to 30 seconds) to account for 
events such as engine stalling where the reminder is not required to 
start again.\87\ Euro NCAP also provides that for systems with rear 
seat occupant detection, the visual signal does not need to indicate 
the number of rear seat belts in use or not in use.\88\
---------------------------------------------------------------------------

    \85\ Section 3.4.1.
    \86\ Section 3.4.2.1 (front); Sec.  3.4.3.1.1 (rear).
    \87\ Section 3.4.1.
    \88\ Section 3.4.3.1.3.
---------------------------------------------------------------------------

    For the rear seats, the IIHS protocol permits a 10-second delay 
between the ignition being turned on and the activation of the visual 
signal. Similar to ECE R16 and Euro NCAP, no visual signal is required 
for the rear seat belts if there are no unfastened belts at occupied 
seats.
    The major differences between the proposal and other approaches 
were that, unlike ECE R16, we did not propose to refer to a ``master 
control switch'' because we did not believe it is necessary to 
introduce this new term into FMVSS No. 208; unlike Euro NCAP we 
proposed not allowing for short breaks in the journey; and unlike IIHS 
we did not propose allowing any delay after the ignition was turned on.
Comments
    Commenters differed on whether the start-of-trip warning should be 
permitted to be delayed. HATCI and Ford supported the proposed trigger 
conditions (which did not permit a delay). On the other hand, Auto 
Innovators, NADA, Freedman, and Nissan recommended allowing a delay. 
Nissan, Auto Innovators, and NADA recommended aligning with the IIHS 
protocol and permitting a 10-second delay, while Freedman favored a 30-
second delay. Auto Innovators also commented that while it generally 
supports the agency harmonizing with ECE R16, the agency should 
maintain flexibility for when these warnings are displayed on startup 
and allow for a brief delay for when the alert is provided. Freedman 
also commented that certain systems, such as an electronic system 
separate from that of the OEM system, will require a powerup and boot 
cycle which can take several seconds.
    Auto Innovators also requested that the final rule allow the visual 
warning to be suppressed if all rear row seating positions are belted 
or determined to be empty based on occupant detection.
    Lastly, RVIA explained that motor homes can be used in many ways 
other than for transportation, such that the ignition may be turned on 
with occupants seated in the rear accessing the vehicle's amenities, 
but with no intention of placing the vehicle in motion. RVIA was 
concerned that such use of the rear seats would trigger the rear seat 
belt visual warning, even though the motor homeowner has no intention 
of operating the vehicle. RVIA concluded that a visual warning system 
on vehicle start-up would often go unnoticed in this scenario, creating 
a requirement not suitable for the application of the start-up trigger 
in a motor home.
Agency Response
    The final rule adopts the proposal for the warning to activate on 
start-up, with no provision for a delay. We continue to believe that 
basing the trigger on the ignition switch is preferable to delaying the 
warning until the vehicle is placed in gear because with a delay, there 
could be instances where a driver would pull out onto the road before 
the warning starts and before passengers have belted. The finalized 
requirements increase the likelihood that the occupants fasten their 
belts before the vehicle is in motion.\89\ With respect to mitigating 
interaction with other vehicle warnings, NHTSA does not believe this 
will be an issue at vehicle start-up because critical safety warnings 
that activate at start-up would likely have dedicated space on the 
display. Interactions between warnings is discussed in more detail in 
Section VI.C.4. We believe consumers will accept this start-up warning. 
The longstanding current front seat belt warning is based on similar 
triggers and has not caused any issues. In addition, the rear start-of-
trip warning is visual-only, so any potential annoyance is minimized. 
This factor distinguishes the rear-seat warning from the front seat 
belt warning, which we are requiring to be both audio-visual and to 
have two phases. We acknowledge there may be some scenarios during a 
trip where a rear seat belt warning is not required for an unbuckled 
occupant; for example, a passenger pickup scenario when the car is not 
turned off. In such a scenario, we are not requiring a warning because 
we are not requiring occupant detection, which would be necessary to 
detect the new occupant (and potentially avoid a false warning). 
Manufacturers of vehicles with rear-seat occupant detection may choose 
to provide warnings for such situations.
---------------------------------------------------------------------------

    \89\ See DOT 2009 Seat Belt Study at pg. 65.
---------------------------------------------------------------------------

    In addition, we are modifying the proposed trigger condition 
related to the vehicle ignition being in the ``on'' or ``start'' 
position for both the front and rear seat belt warning to better 
account for EVs. This change is discussed in Section VI.C.1. This 
modification generally harmonizes with ECE R16, Euro NCAP, and the IIHS 
protocol, so that a vehicle that complies with the finalized trigger 
requirements can still meet these requirements; some exceptions are 
discussed immediately below.
    In addition, we have also modified the proposal so that the final 
rule does not require a visual warning in three circumstances: (1) for 
an unoccupied seat if the system is able to determine whether a seat is 
occupied; (2) for a seat belt that is in use in a system designed to 
indicate to the driver how many or which rear seat belts are not in 
use; and (3) for a seat belt that is not in use in a system designed to 
indicate to the driver how many or which rear seat belts are in use. 
This regulatory text is intended to clarify two things.
    First, that, depending on the type of seat belt reminder system and 
belt use/occupancy scenario, a visual signal may not be necessary for a 
particular DSP, or may not be necessary for any DSP. So, for example, 
no visual warning would be required for a negative-only system when 
every rear seat is occupied by a belted occupant. Another example: if 
no rear seats are occupied, no visual signal is required for negative-
only, positive-only, or full-status systems with occupant detection; a 
visual warning would, however, be required in this case for a negative-
only system without occupant detection (assuming that no rear belts 
were in use) and a full-status system without occupant detection.

[[Page 408]]

This requirement is consistent with ECE R16, Euro NCAP, and IIHS.
    Second, this also clarifies, in response to the comments, that 
systems utilizing symbols or numbers may utilize colors other than 
green or red to indicate unoccupied seats or seating positions for 
which the system is not providing information on belt use. Accordingly, 
a negative-only system would be permitted to display a pictogram that 
denotes a seating position with an in-use belt as grayed-out (to give 
one example).\90\
---------------------------------------------------------------------------

    \90\ See also Section VI.C.3, Visual Warning Characteristics.
---------------------------------------------------------------------------

    Freedman's comment regarding certain vehicles requiring more time 
to boot up appears to be referring to accommodating aftermarket 
systems. Because the final requirements apply to vehicles before first 
purchase other than for resale, they do not directly apply to 
aftermarket systems that are installed later on. However, Sec.  30122 
of the Safety Act prohibits a vehicle modifier from taking a vehicle 
out of compliance with an applicable FMVSS.\91\ (The vehicle owner is 
not subject to the make inoperative provision). Therefore, a vehicle 
modification performed after the compliance date of this final rule on 
a vehicle with a rear seat belt warning system certified to the 
requirements in this rule that modifies the vehicle such that the rear 
seat belt visual warning does not activate when the ignition is in the 
``on'' or ``start'' position (or upon manual activation of the 
propulsion system, but prior to the vehicle being placed in ``possible 
active driving mode'' as defined by FMVSS No. 305) \92\ would violate 
Sec.  30122 and would therefore not be permitted.
---------------------------------------------------------------------------

    \91\ 49 U.S.C. 30122(b) (``A manufacturer, distributor, dealer, 
rental company, or motor vehicle repair business may not knowingly 
make inoperative any part of a device or element of design installed 
on or in a motor vehicle or motor vehicle equipment in compliance 
with an applicable motor vehicle safety standard prescribed under 
this chapter unless the manufacturer, distributor, dealer, rental 
company, or repair business reasonably believes the vehicle or 
equipment will not be used (except for testing or a similar purpose 
during maintenance or repair) when the device or element is 
inoperative.''); section 30122(a) (``(a) Definition. In this 
section, ``motor vehicle repair business'' means a person holding 
itself out to the public to repair for compensation a motor vehicle 
or motor vehicle equipment.'').
    \92\ See Section VI.C.1.
---------------------------------------------------------------------------

    The final rule does not incorporate RVIA's request to accommodate 
use scenarios specific to Recreational Vehicles (RVs). We agree that in 
the scenarios identified by RVIA the warning would activate when the 
vehicle was turned on with no intent to drive (thus obviating the need 
for a seat belt). A speed or motion trigger could address this issue, 
but we believe that such a trigger is undesirable because there is a 
safety benefit to having occupants belted before the vehicle is in 
motion or when it is travelling at lower speeds. Moreover, because the 
rear seat belt start-of-trip warning is visual-only, there are not the 
same consumer acceptance concerns that led us to include a speed 
criterion like we have included for the second-phase front seat belt 
audible warning. (See Section VI.B.3.) We could also potentially 
address this concern by either exempting RVs or crafting trigger 
criteria specific to RVs. We conclude the former is undesirable due to 
the significant safety benefit of belts when the vehicle is in motion, 
and that the latter would be overly complex. In addition, the rear seat 
belt start-of-trip warning is a mild visual warning that should not 
cause meaningful consumer annoyance (or condition them to ignore the 
warning) in these use cases.
iv. Seat Occupancy Criteria and Interaction With Child Restraint 
Systems
    For rear seat belt warning systems that manufacturers voluntarily 
choose to equip with occupant detection, NHTSA proposed the occupancy 
criteria for the test dummy (or human, at the manufacturer's option) 
that NHTSA would position in the seat to conduct compliance testing of 
the system. NHTSA proposed that a rear designated seating position 
would be considered ``occupied'' when an occupant who weighs at least 
46.5 lb (21 kg), and is at least 45 in (114 cm) tall, is seated there. 
These criteria are proxies for a 6-year-old child, which roughly 
corresponds to a typical age at which a child would begin using a seat 
belt (with a booster seat), transitioning from a forward-facing child 
restraint system (CRS). These are the same criteria used in FMVSS No. 
208 to specify the smallest child that may be used as an alternative to 
the 6-year-old dummy in static suppression tests under FMVSS No. 208. 
We proposed using either a human being, at the manufacturer's option, 
or any anthropomorphic test device specified in 49 CFR part 572 that 
meets these proposed weight and height criteria (Section VI.C.8., Test 
Procedures).
    The proposed criteria corresponded to a smaller occupant than ECE 
R16 or Euro NCAP, each of which essentially specifies an occupant (or 
load) no smaller than a 5th percentile adult female (e.g., the HIII-5F 
specified in 49 CFR part 572). In the NPRM we explained that we 
believed that harmonizing with ECE R16 and using a heavier dummy would 
not capture the child segment of the population that could be 
restrained with a seat belt. We also did not believe it was necessary 
to use a larger-size occupant because a system capable of recognizing a 
6-year-old should also be capable of recognizing larger occupants.
    At the same time, we tentatively believed that the proposed 
criteria were preferable to criteria reflecting a younger occupant 
(lower weight). The smallest dummy that would meet the proposed weight 
and height criteria is the 6-year-old dummy specified in part 572. The 
next smallest dummy represents a 3-year-old child (i.e., the Hybrid III 
3-year-old); we believed it would not be appropriate to specify the use 
of the 3-year-old because a child represented by this dummy should be 
seated in a forward- or rear-facing CRS, not restrained with a seat 
belt.
    NHTSA did not propose to require any sort of CRS detection 
capabilities. As explained in the NPRM, there are essentially three 
types of CRSs: rear-facing CRSs, forward-facing CRSs, and booster 
seats. Rear-facing and forward-facing CRSs are child seats that are 
installed using either Lower Anchors and Tethers for Children (LATCH) 
or a seat belt to secure it in place. Booster seats raise and position 
a child so the vehicle's lap-and-shoulder belt fits properly. We 
tentatively believed that a forward- or rear-facing CRS installed with 
the seat belt would not cause problematic false warnings; rather the 
system would just register the CRS as a buckled passenger. Similarly, 
we believed that a forward- or rear-facing CRS installed with LATCH 
would not pose issues necessitating any specific requirements related 
to the LATCH system, such as LATCH sensors.
    We also did not believe a booster seat would present any special 
challenges to a seat belt warning system. If an unbelted child is in a 
booster seat, the system would register the belt as not fastened and, 
if equipped with occupant detection, that the seat was occupied. The 
system would not have to specifically detect the booster seat because 
the performance criteria are weight-based. In addition, we would not 
expect an occupant detection system to provide a false warning for an 
unoccupied booster seat because the proposed seat occupancy criterion 
(roughly equivalent to a 6-year-old) is heavier than an unoccupied 
booster seat. We did not propose to specify the use of a booster seat 
for testing because children may be prematurely transitioned to a seat 
belt without the use of a booster, and we believe it is desirable to 
test the lower end of the

[[Page 409]]

possible weight range that encompasses children that could conceivably 
be restrained with a seat belt.
Comments
    A number of commenters (Auto Innovators, Mercedes, GM, NADA, IEE, 
Honda, HATCI, and Consumer Reports) disagreed with the proposal and 
recommended harmonizing with ECE R16 and Euro NCAP and specifying 
occupancy criteria based on a 5th-percentile adult female occupant. 
These commenters made a variety of arguments.
    Auto Innovators commented that harmonizing with the ECE 
requirements would avoid introducing unnecessary complexity and reduce 
the need for additional lead time to develop U.S.-specific designs. IEE 
commented that the proposed detection criterion would entail 
significant additional costs.
    IEE also commented that a detection criterion based on the 5th 
percentile female would address the key target population of unbelted 
teenagers and adults. Relatedly, IEE noted that the NPRM analysis 
investigated potential benefits for the age group 6 to 10 years old and 
only found a very small belt usage increase (by only 0.27 percent to 
0.41 percent) and concluded that members of this age group already have 
high rates of seat belt use (98 percent according to the preliminary 
regulatory impact analysis).
    Consumer Reports, IEE, Auto Innovators, Honda, HATCI, NADA, RVIA, 
and GM raised concerns regarding feasibility. Consumer Reports agreed 
with NHTSA on the importance of testing the lower end of the possible 
weight range that encompasses children that could conceivably be 
restrained with a seat belt alone, but believed that it would be 
premature to require the detection of dummies smaller than the 5th 
percentile adult female because the ability to detect occupants smaller 
than the 5th percentile adult female is limited. IEE commented that 
while detecting a 5th percentile female is well-established in the 
market and would not present any design or technical challenges, it was 
not aware of any car on the market that would be able to meet the 
proposed detection of the 6-year-old child scenarios, with or without a 
booster cushion. IEE commented that the 5th percentile female is the 
state-of-the art in contemporary sensing technology for seat belt 
reminder-related occupant detection and that no realistic alternative 
technologies are readily available at comparably low costs. IEE stated 
that it believed that the 7 percent of U.S. MY 2022 vehicles with rear 
seat occupant detection all meet the 5th percentile female detection 
criterion, not the one 6-year-old proposed in the NPRM.
    IEE also commented that the proposal assumed that a 6-year-old 
child on the booster seat would be automatically covered and detected 
as it has a higher total weight than the weight proposed for the 
occupancy criteria. IEE stated that this assumption is wrong: rear 
occupant detection systems are designed to detect a load that is 
generating a pressure profile on the seat foam that matches the 
pressure profile of a human buttocks. IEE commented that the pressure 
profile generated by a booster seat is different and would not be 
classified by the system as an occupant; contemporary occupant 
detection sensors used for seat belt reminder systems are not designed 
to detect booster seats, and child seats are considered as non-
detection objects. IEE indicated that this distinction is also required 
to differentiate between humans and objects, to avoid objects that 
would be likely to trigger false positives. Auto Innovators similarly 
commented that the contact area between a booster seat and a seat 
cushion can vary, causing some of the occupant's weight to be 
distributed to the seat itself or to the LATCH system, rather than to 
the weight sensor.
    Auto Innovators also pointed out that child occupants are also more 
likely to be out-of-position compared to an adult, further contributing 
to uneven weight transfer. Auto Innovators argued that if the weight of 
a child in a booster seat is not transferred to the weight sensor, the 
proposed system could misclassify the seat as empty. If this 
misclassification occurs, coupled with the lack of a visual warning for 
an unfastened seat belt at an unoccupied seat, Auto Innovators argued 
there would be no visual warning for cases where an age-appropriate 
child is sitting in a booster seat and not wearing a belt. Relatedly, 
IEE commented that more advanced detection technologies (such as 
cameras or radar sensors) are not currently used in the context of a 
seat belt reminder function, and that these technologies would still 
have to prove their reliability and robustness for the occupant 
detection needs of a seat belt reminder system. IEE explained that 
while future developments may enable the support of seat belt reminder 
functionalities with these technologies, it is too early to consider 
such a potential innovation in a regulatory pass/fail scenario.
    Honda, HATCI, Auto Innovators, NADA, IEE, RVIA, Honda, and GM 
commented that specifying criteria matching a 6-year-old would 
exacerbate the problem of false positives. HATCI and IEE commented that 
behavioral alternatives to avoid false positives, such as moving cargo 
to the floor of the vehicle or buckling the belt before loading heavy 
cargo onto seats, may not always be feasible or reliable. Auto 
Innovators and Honda argued that the proposed criteria would 
potentially discourage manufacturers from implementing occupant 
detection systems due to the potential for false warnings.
    IEE similarly commented that if the agency were to adopt the 6-
year-old criterion proposed in the NPRM, manufacturers would be 
disincentivized from implementing occupant detection in rear seats. IEE 
explained that because the proposed detection threshold is not 
technically feasible today within a regulatory pass/fail context, the 
threshold proposed in the NPRM would fail advanced rear seat belt 
reminder systems that have already entered the U.S. market and that 
offer a seat belt warning functionality that exceeds the proposed legal 
minimum. IEE stated that this requirement would force vehicle 
manufacturers to withdraw these advanced seat belt reminder systems 
from the market and downgrade the seat belt reminder systems features 
to the legal minimum (the positive-only compliance option). IEE argued 
that this result would be counterproductive from a safety perspective.
    IEE and Consumer Reports commented that manufacturers could 
voluntarily detect occupants smaller than the 5th percentile female. 
IEE argued that making such detection voluntary would provide 
flexibility for innovation. Consumer Reports recommended that NHTSA 
incorporate detection of dummies smaller than the 5th percentile female 
into NCAP ratings for rear seat belt reminders, which would award 
manufacturers for going above and beyond the regulatory minimum and 
drive innovation.
    On the other hand, NSC and SRN suggested a 3-year-old child for the 
occupancy criterion. NSC commented that data from the National Digital 
Car Seat Check Form show that many children are not riding in the 
appropriate CRS based on their height and weight, so specifying 
criteria corresponding to a 3-year-old child would protect children. 
SRN similarly noted that the weight of a 3-year-old dummy, though 
average for a toddler, is also the weight of many older children in the 
lower growth chart percentiles. SRN argued that since nearly all 
school-age children ride in seat belts or boosters (including these 
lighter-weight

[[Page 410]]

children, regardless of NHTSA best-practice recommendations), families 
would benefit from warnings about the belt-use status of those 
children. SRN explained that this is especially true for warnings that 
a passenger has unbuckled during a ride, which younger, less mature 
children may be prone to do. SRN explained that, as proposed, a system 
with occupant detection would not recognize some of the youngest 
booster/belt users, may provide inadequate warnings to families, and 
may cause caregivers some frustration in interpreting status 
indicators. SRN also commented that in comments to the ANPRM, SRN had 
voiced the concern that LATCH-installed car seats could trigger false 
alarms. SRN was less concerned that the proposed system will rise to 
the level of nuisance and is more concerned that false warnings will 
happen, such as when relatively heavy car seats are installed using 
LATCH. SRN argued that owners will need clear guidance in owner's 
manuals on how to interpret warnings when traveling with children, and 
that these instructions should be included (or at least referenced) in 
the child passenger section of the manual.
    Consumer Reports, HATCI, and Freedman agreed with NHTSA that a CRS 
detection requirement was not necessary. Consumer Reports stated that 
consumers might be better served by incorporating CRS detection into a 
component of NCAP for rear seat belt reminder systems to help drive 
safety innovation. Freedman commented that the easiest and most 
effective solution for LATCH-installed CRS is to continue recommending 
the seat belt be fastened behind the CRS.
    Auto Innovators and GM recommended that NHTSA ensure a technology-
neutral approach that includes consideration of compliance options that 
permit the use of camera- or vision-based sensors, or other 
technologies that may be adopted in lieu of weight-based sensors, as a 
means for determining occupant presence at a given designated seating 
position. Advocates and Public Citizen commented that the final rule 
should not preclude or discourage the use of existing state-of-the-art 
technology.
Agency Response
    After considering the comments, NHTSA has decided to adopt the 
proposal to use (at the option of the manufacturer) either a 
anthropomorphic test device at least as large as a 49 CFR part 572, 
subpart N 6-year-old child dummy or a person, at the manufacturer's 
option, that is at least 21 kg in weight and 114 cm in height to define 
an occupied rear designated seating position for the purposes of 
testing the rear seat belt reminder system. These criteria represent a 
50th percentile 6-year-old child, and only specify the low end of the 
occupancy criteria used for compliance testing. Therefore, when we 
refer to a 6-year-old as our occupancy criteria, this includes 
occupants or dummies that are larger.
    Before addressing the specific issues raised by the commenters, it 
is important to recognize that this final rule does not require or 
necessitate occupant detection. Moreover, we recognize that a 
manufacturer currently deploying reminder systems with occupant 
detection based on the 5th percentile female would likely need some 
time and effort to develop and implement new sensor solutions in the 
rear. Based on MY 2022 NCAP data, approximately 7 percent of vehicles 
sold in the U.S. are equipped with rear seat belt reminders using 
occupant detection. The commenters, however, did not provide specific 
information on what additional development would be necessary to meet 
the requirements when tested with a 6-year-old.
    Further, as explained above (Section VI.A.2.a.i) we have revised 
the proposed requirements to provide greater flexibility for systems 
without occupant detection. The proposal only included one compliance 
option (the positive-only compliance option) without occupant 
detection. In response to the comments, the final rule would allow for 
additional warning systems without occupant detection (e.g., negative-
only and full-status). Given this flexibility, manufacturers can simply 
use reminder systems without occupant detection if they believe they 
cannot deploy a reminder system using occupant detection that would 
comply with the requirements when tested with a 6-year-old.
    Given the above, NHTSA has concluded that it would fulfill the MAP-
21 mandate, meet the need for safety, and be practicable and 
appropriate to require that an occupant detection system be capable of 
detecting at least a 6-year-old. There are several reasons for this 
decision.
    First, section 31503 of MAP-21 directs NHTSA to initiate (and 
finalize, if the Sec.  30111 criteria are met) a rulemaking proceeding 
``to provide a safety belt use warning system for designated seating 
positions in the rear seat.'' Section 31503 itself does not refer to 
particular classes of occupants or identify a target population. 
``Subtitle E--Child Safety Standards'', in which Sec.  31503 is 
located, however, contains four mandates related to child passenger 
safety: improving the protection seated in CRSs during side impact 
crashes; improving the ease of use for LATCH systems; providing seat 
belt reminders for rear seats; and researching the risk of hyper- or 
hypothermia to children or other unattended passengers in rear seating 
positions.93 94
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    \93\ See, e.g., Norman J. Singer & Shambie Singer, 2b Sutherland 
Statutory Construction section 46:5 (7th ed.) (``[E]ach part or 
section of a statute should be construed in connection with every 
other part or section to produce a harmonious whole. Thus, it is not 
proper to confine interpretation to the one section to be 
construed.''); section 47:3 (explaining that while legislative 
titles cannot control a statute's plain words they ``may help 
resolve uncertainty'' and ``illuminat[e] statutory meaning''). See 
also id. section 47:6 (``Courts give effect to all the language of a 
purview as a harmonious whole, in light of the statute's purpose, 
and regardless of sectional formatting, unless to do so is plainly 
contrary to legislative intent.'').
    \94\ MAP-21, Division C, Title I, ``MOTOR VEHICLE AND HIGHWAY 
SAFETY IMPROVEMENT ACT OF 2012.''
---------------------------------------------------------------------------

    In addition, the Safety Act gives NHTSA the discretionary authority 
to issue safety standards to address specific safety needs, provided 
that the standard is objective, practicable, and appropriate for the 
type(s) of vehicles to which it applies.\95\ NHTSA has concluded that 
requiring a rear seat belt warning system equipped with occupant 
detection be able to detect unbelted children smaller than the size 
represented by the 5th percentile female crash test dummy meets a 
safety need and is practicable and appropriate.
---------------------------------------------------------------------------

    \95\ 49 U.S.C. 30111.
---------------------------------------------------------------------------

    Specifying occupant characteristics corresponding to a 5th 
percentile female would not address rear seat belt usage by children 
because the vast majority of children are smaller than the 5th 
percentile female test dummy. The population of children seated in the 
rear who should be restrained with a seat belt is comprised of children 
seated in a booster seat and children who have transitioned out of a 
booster seat to sit directly on the vehicle seat. As we explained in 
the NPRM, children typically begin sitting in a booster seat 
(transitioning out of a forward-facing CRS) around 4-7 years old 
(depending on the height and weight of the child and the respective 
limits of their forward-facing car seat). Children typically transition 
out of a booster seat between the ages of about eight and thirteen 
(again, exactly when depends on the child's height and weight). The 
Hybrid III 5th percentile female crash test dummy weighs 108 lb (50 
kg). This weight corresponds (approximately) to a 50th percentile 
fourteen-year-old girl and a 50th percentile thirteen-and-a-half-year-
old boy.\96\ This means that if

[[Page 411]]

NHTSA were to specify criteria matching the 5th percentile female, it 
would essentially be ignoring a large percentage of children ages 6-14, 
and likely some 15-18 year old children with weight lower than that of 
a 5th percentile female. That is, if NHTSA specified the 5th percentile 
female, the rear seat belt warning requirements would only be targeting 
older children, not younger children.\97\ This disparity strongly 
suggests that NHTSA should specify a smaller occupant for testing if 
doing so would be practicable.
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    \96\ Center for Disease Control Growth Charts for Children 2-20 
years of age: Boys Stature-for-age and Weight-for-age percentiles 
and Girls Stature-for-age and Weight-for-age percentiles, published 
in May 2000 (modified in November 2000) and available at https://www.cdc.gov/growthcharts/data/set1clinical/cj41c022.pdf and https://www.cdc.gov/growthcharts/data/set1clinical/cj41c021.pdf, 
respectively. (last accessed September 10, 2024).
    \97\ A booster seat augments the total weight on the rear seat. 
However, as we explained in the NPRM--and as we adopt in this final 
rule--we will not be testing with a booster seat because we are 
aware that children can be prematurely transitioned to a seat belt 
without the use of a booster, and we believe it is desirable to test 
the lower end of the possible weight range that encompasses children 
that could conceivably be restrained with a seat belt alone. We 
discuss the issue of booster seats in our discussion regarding 
feasibility later in this section.
---------------------------------------------------------------------------

    Although NHTSA has concluded that specifying occupant 
characteristics matching those of a 6-year-old child would meet a 
safety need and be fully consistent with MAP-21, MAP-21 directs NHTSA 
to issue a final rule only if the rule would meet the criteria set out 
in Sec.  30111 of the Safety Act. These criteria include that the rule 
be practicable. As noted earlier, the statutory criterion of 
practicability is multidimensional (see Section IV. Statutory 
Authority). After considering the comments, NHTSA agrees that most 
currently deployed rear seat belt warning systems utilizing occupant 
detection are not able (or designed) to reliably detect a 6-year-old 
occupant. NHTSA also agrees with the commenters who indicated that 
there are a number of challenges to rear-seat occupant detection, 
related both to false negatives and false positives. However, while 
many or most currently deployed rear occupant detection systems used 
for seat belt warnings may not comply with the requirements in the 
final rule, we believe that OEMs are capable of improving the 
technology and meeting these challenges. Further, NHTSA believes that 
selecting a 6-year-old child instead of the 5th percentile female 
appropriately balances benefits and costs. We explain this conclusion 
in more detail below.
    NHTSA believes that while current occupant detection systems might 
not reliably detect a 6-year-old child, or a booster seat, such a 
requirement is feasible. NHTSA acknowledges the commenters who argued 
that many or most rear occupant detection systems that are currently 
deployed may not be able to reliably detect a 6-year-old occupant, 
either seated directly on the seat or in a booster seat. NHTSA has not 
tested current systems to verify or refute this claim, so we have no 
firm basis on which to agree or disagree with these comments. NHTSA 
has, though, noted that some owner's manuals inform consumers that if 
they place lightweight objects (such as a briefcase) on the rear seat, 
it may trigger the seat belt warning; this suggests that some rear seat 
belt occupant detection systems may be capable of detecting younger 
(and therefore lighter) occupants. For example, the owner's manual for 
the MY 2024 Cadillac Escalade states that ``[t]he rear passenger seat 
belt reminder light and chime may come on if an object is put on the 
seat such as a briefcase, handbag, grocery bag, laptop, or other 
electronic device. To turn off the reminder light and/or chime, remove 
the object from the seat or buckle the seat belt.'' \98\ In most cases 
the weights of these listed items would be less than the weight of a 6-
year-old. Furthermore, we understand (although again, have not been 
able to verify) that at least one manufacturer's system may be able to 
detect a 6-year-old not in a booster.\99\
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    \98\ Page 114. As another example, the owner's manual for the MY 
2024 Tesla Model Y states: ``If all occupants are buckled up and the 
[seat belt] reminder stays on, . . . remove any heavy objects (such 
as a briefcase) from an unoccupied seat.''
    \99\ NHTSA is not disclosing further details about this finding 
because this information is confidential.
---------------------------------------------------------------------------

    We also acknowledge that some rear-seat occupant detection systems 
may not be able to reliably classify a young child seated in a booster 
seat as an occupant. We explained in the NPRM that children start using 
belts (with a booster seat) at about 6 years old, and typically 
transition out of a booster seat around 8 to 13 years old. We 
acknowledge, as IEE commented, that some rear detection systems may not 
simply classify objects/occupants based on weight, but may also base 
the classification on other information, such as the pressure profile, 
so that a child seated in a booster seat may not be classified as a 
human occupant, regardless of the child's weight and height. We 
recognize that manufacturers would have to develop a solution to this 
issue. We also acknowledge other issues pointed out by the commenters 
that make accurate detection a challenge, such as out-of-position 
children.
    Nevertheless, we believe that it is feasible to develop this 
technology. We agree with IEE that more advanced technologies (such as 
radar sensors) are not yet proven. However, occupant detection 
technology similar to that used for advanced air bag testing in the 
front that is used to detect different sized dummies in different test 
scenarios,\100\ including 6-year-old dummies, could potentially be 
reprogrammed to address our occupancy criteria needs and this would 
also address the comments about not being able to detect children in 
boosters. Testing with a 6-year-old should also be compatible with the 
requirements in ECE R16 and Euro NCAP; if a system can recognize a 6-
year-old occupant, it should also be able to recognize an occupant with 
the characteristics of the 5th percentile female. Moreover, to give 
manufacturers flexibility, we have kept the requirements as technology-
neutral as possible in order to facilitate innovation. We acknowledge 
that requiring an occupant detection system to meet the final 
requirements when tested with a dummy or human representing a 6-year-
old could increase the cost of the system and may take some time to 
implement and test, but again, the final rule does not require occupant 
detection. We are also providing two years of lead time, so current 
occupant detection systems could be offered until then (See Section IX, 
Compliance Date).
---------------------------------------------------------------------------

    \100\ The Advanced Air Bag rule was targeted at protecting all 
individuals from potential harm from air bags; specific requirements 
were included that were targeted at protecting children. See Section 
VI.A.2.a.1.
---------------------------------------------------------------------------

    With respect to the comments on cargo (or pets) leading to false 
warnings based on the relatively low weight specification for the 
occupancy criteria, while this is a potential issue, we believe that it 
is mitigated in a variety of ways. First, potential consumer annoyance 
should be mitigated by the relatively short duration of the warning (60 
sec) and the fact that it does not have an audible component. The 
weight of the types of objects typically placed on the rear seats (such 
as briefcases, water bottles, and groceries) would also likely be well 
under the weight of a 6-year-old (46.5 lb).
    There may also be technical solutions to mitigate false warnings. 
Several comments referred to complications with detection related to 
the weight of the occupant or object placed on the seat. However, 
occupant detection technology reliant solely on weight-based sensors 
may not necessarily be the only technology solution to meet the 
performance requirements in this final

[[Page 412]]

rule. We also note that, based on the comments alone, it appears that 
there are presently issues with false alarms for current systems which 
are presumably based on detecting a 5th percentile female occupant. 
(However, no specific data were provided on the performance of these 
systems with relation to false warnings or how such false warnings have 
affected acceptance.)
    If technical solutions to mitigating any remaining consumer 
acceptance concerns are not readily available, NHTSA continues to 
believe the behavioral solutions we suggested in the NPRM (such as 
placing objects on the floor instead of the seat, or buckling the belt 
if cargo is placed on the seat) are viable. Although Honda and HATCI 
did not believe such behavioral solutions were viable, as noted 
earlier, at least some manufacturers are already providing such 
guidance in the owner's manual. We acknowledge that there may be some 
trade-off in effectiveness if consumers frequently buckle the belt when 
cargo is placed on the seat or become accustomed to ignoring the 
warning. (We are not aware of any data or research on such trade-offs.) 
Nevertheless, we believe that this concern would not meaningfully 
affect the warning's effectiveness, and that any lessening in 
effectiveness should be offset by the system being able to detect the 
full range of occupants that should be using a seat belt.
    With respect to interactions between the occupant detection system 
and CRSs, we agree with the commenters that the final rule should not 
require that the occupant detection system be able to detect a forward- 
or rear-facing CRS installed with LATCH. We agree with Freedman and 
Honda that the easiest and most effective solution to avoid false 
warnings for LATCH-installed CRSs is to continue recommending the seat 
belt be fastened behind the CRS. We encourage this practice on our 
website \101\ and some manufacturers are already providing consumers 
with this guidance.\102\
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    \101\ See www.nhtsa.gov/road-safety/child-safety (last accessed 
May 16, 2024).
    \102\ For example, the owner's manual for the MY 2024 Subaru 
Forester advises the consumer that ``[t]he seatbelt warning system 
of the rear seats detects if any of the seats are occupied by a 
passenger. Installing a child restraint system in the rear seating 
area, using the LATCH anchors, may result in the activation of the 
passenger seatbelt warning light and chime. Fastening the rear 
seatbelt prior to installing the child restraint system will avoid 
activating the passenger seatbelt warning light and chime.''
---------------------------------------------------------------------------

    NHTSA also considered the relative costs and benefits of specifying 
a 6-year-old child as opposed to the 5th percentile female. In 
particular, we considered some commenters' assertions that specifying 
the 6-year-old would discourage manufacturers from adopting systems 
with occupant detection or would force manufacturers to downgrade their 
systems to the positive-only option (which did not require occupant 
detection). We have concluded that specifying a 6-year-old as opposed 
to the 5th percentile female appropriately balances costs and benefits. 
There are several reasons for this conclusion.
    First, and most important, a system that does not monitor child 
occupants smaller than a 5th percentile female does not monitor the 
entire population of children who can and should be using seat belts. 
As we noted above, the height and weight of the 5th percentile female 
dummy correspond, approximately, to that of a 14-year-old. Because the 
5th percentile female dummy would not represent most younger children, 
the system would not work accurately for these children. This is 
especially worrisome given that children 12 years old and younger 
represent more than half of the rear seat occupant population.\103\
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    \103\ See https://www.nhtsa.gov/crashworthiness/child-safety-
crashworthiness-
research#:~:text=Since%20children%2012%2Dyears%2Dold,booster%20seats%
20and%20seat%20belts (last accessed May 16, 2024).
---------------------------------------------------------------------------

    Accordingly, specifying the 5th percentile female could result in 
unbelted child occupants in the rear not benefiting from the seat belt 
warning. For instance, if a negative-only system with occupant 
detection did not detect an unbelted child smaller than the 5th 
percentile female seated in a rear seat, the visual warning would not 
indicate an unbelted occupant at an occupied seat (e.g., for systems 
with a pictogram that indicates which seat are not in use, the 
pictogram would likely display something like a ``grayed-out'' seat to 
indicate that the system was registering a seat as unoccupied). In this 
scenario, the driver may not realize that the system was not detecting 
the child occupant and may think the child is buckled when they are 
not. This concern is not hypothetical. The owner's manual for the MY 
2024 Subaru Forester states that ``[t]he driver must check that all the 
passengers have fastened their seatbelts properly since the seatbelt 
warning system may not detect passengers under the following 
circumstances.--When cushions or child restraint systems, etc., are 
used--When a child or small adult is sitting in the seat.'' The fact 
that the system does not work for some classes of occupants could also 
lead the driver to be less likely to respond to accurate warnings. 
These shortcomings could also affect consumer acceptance of the system.
    Second, the concern about downgrading to a positive-only system is 
alleviated because we have modified the proposal so that the final rule 
does not dictate specific compliance options for the information 
conveyed by the visual warning; the finalized requirements for the 
visual warning allow all of the systems that would have been allowed 
under the proposed rule, as well as additional systems that would not 
have been allowed under the proposal.
    Third, a very small percentage of vehicles currently sold in the 
U.S. is equipped with rear-seat occupant detection. Based on the 2022 
NCAP data, approximately seven percent of light vehicles have SBWS with 
occupant detection for the rear seats. Relatedly, rear systems with 
occupant detection are a relatively new feature in the U.S. vehicle 
market. So even if some manufacturers were to stop offering occupant 
detection, it would affect a relatively new feature on a small fraction 
of vehicles offered for sale in the U.S. and would not be a meaningful 
reduction in the choices presently offered to consumers.
    Fourth, this trade-off may or may not materialize. The trade-off 
would not occur if manufacturers develop and deploy rear-seat occupant 
detection systems capable of detecting a 6-year-old within the allotted 
lead time (two years).
    Fifth, the possibility that some manufacturers may choose to forgo 
occupant detection because the final rule specifies the 6-year-old does 
not lead us to conclude that it would be preferable to specify the 5th 
percentile female. We considered the relative benefits and costs of 
specifying each of these systems.
    The target population addressed by this rule will necessarily be 
larger if we specify the 6-year-old--and, importantly, this addition to 
the target population consists of children. Due to a lack of data, the 
FRIA was unable to establish how much more effective a rear seat belt 
reminder system with occupant detection would be relative to a seat 
belt reminder system without occupant detection. However, it is 
important to note that the baseline seat belt use rate for rear seat 
occupants ages 6 to 10 years is already very high. As it is unlikely 
that the seat belt use rate would reach 100 percent, this leaves very 
little room for improvement. Accordingly, the children who will benefit 
from the rule if we specify the 6-year-old is effectively children from 
about ages 11-18. This is still a larger

[[Page 413]]

target population than if we specified the 5th percentile female. 
Targeting this population points towards greater benefits.
    On the other hand, if NHTSA specifies the 6-year-old, at least some 
manufacturers may offer fewer rear seat belt reminder systems with 
occupant detection. However, we are unable to estimate the overall 
impact of this potential reduction because of several unknowns: how 
many fewer systems with occupant detection will be offered; the 
difference in effectiveness between systems with occupant detection and 
systems without occupant detection; \104\ and the seat belt use rates, 
injuries, or fatalities for children ages 11-18.\105\ We also believe 
that any short-term decrease in net benefits (if that should in fact 
materialize) is outweighed by what we anticipate to be the greater 
benefits in the medium-to-long term for children. Moreover, specifying 
the 6-year-old would result in seat belt reminder systems that are able 
to reliably inform the driver of unbelted children in the rear seat. 
While our regulatory analysis is not able to quantify these benefits to 
an especially vulnerable occupant population, we recognize the 
importance of these unquantified benefits. NHTSA therefore concludes 
that specifying the 6-year-old appropriately balances benefits and 
costs compared to specifying the 5th percentile female.
---------------------------------------------------------------------------

    \104\ The NPRM explained that while the main advantage is more 
informative warnings and that it can reduce false warnings for 
unoccupied seats, it can also (as pointed out by some commenters) 
result in false warnings.
    \105\ Because of data limitations, NHTSA was unable to break out 
this information for this age group specifically. NHTSA was only 
able to segment the analysis into occupants ages 6-10 and occupants 
11 and older.
---------------------------------------------------------------------------

v. Duration
    NHTSA proposed that the start-of-trip warning last for at least 60 
seconds. We believed that 60 seconds would be sufficient to capture the 
driver's attention and appropriately balanced effectiveness and 
acceptance.
    60 seconds is a shorter warning than we proposed for the front 
outboard seats. There were a couple of reasons for our tentative 
decision that a shorter warning is warranted for the rear seats. First, 
we did not propose to require occupant detection for the rear seat belt 
warning system; the positive-only compliance option would require that 
the driver be informed of which rear seat belts are fastened. This type 
of ``warning'' functions more to provide information to the driver, 
rather than a true warning (because it will be providing information to 
the driver even if all rear occupants have fastened their seat belts), 
so we tentatively believed that it is not necessary to require that it 
be particularly long-lasting. Second, and related, even for the 
compliance options that would entail occupant detection, the 
complexities of occupant detection in the rear seats and the 
possibilities for false positives provide another reason for not 
requiring an extremely long-lasting warning. Manufacturers would be 
free to provide a longer warning.
    This duration was consistent with ECE R16, Euro NCAP, and the IIHS 
protocol, each of which requires a visual warning at the start of the 
trip for the rear seat belts lasting at least 60 seconds. It is also 
consistent with many of the rear seat belt warning systems currently 
deployed in the United States. In the NPRM we noted that, of the 
fifteen manufacturers that provide vehicle models with a rear seat belt 
warning system in the United States, eight appeared to provide systems 
with initial visual warnings that are active for at least 60 seconds. 
An additional three manufacturers appeared to provide visual warnings 
until the seat belt is fastened.
Comments
    Auto Innovators, Freedman, Honda, HATCI, and Consumer Reports 
supported a 60-second minimum requirement. Auto Innovators and HATCI 
commented that this requirement would align with ECE R16.
    SRN requested a longer-duration warning requirement. It argued that 
the proposed warning would be only moderately effective (especially for 
occupants of rideshare vehicles) because it could be easily ignored. 
SRN also commented that caregivers, who may have children in car seats 
and boosters, may need more time to interpret the warning. SRN also 
suggested that a seat belt status indicator could be valuable as a 
constant readout on the dashboard, as warning lights are sometimes 
dismissed or ignored.
Agency Response
    The final rule adopts the proposed 60-second minimum duration. We 
believe this requirement appropriately balances effectiveness and 
acceptance. A 2015 survey of drivers of vehicles with RSBWSs found that 
28 percent of GM drivers noticed an increase in rear seat belt usage, 
and 23 percent of Volvo drivers reported an increase in rear seat belt 
usage.\106\ The GM system used a 30-second visual warning at start-up 
and the Volvo system provided a short message at start-up, suggesting 
that a 60-second warning would be at least as effective. The 60-second 
minimum duration also harmonizes with ECE R16, Euro NCAP, and the IIHS 
protocol.
---------------------------------------------------------------------------

    \106\ Paul Schroeder & Melanie Wilbur, Survey of Principal 
Drivers of Vehicles with a Rear Seat Belt Reminder System. 
Washington, DC: National Highway Traffic Safety Administration 
(2015).
---------------------------------------------------------------------------

    A longer warning then 60 seconds could be annoying (in particular 
for systems without occupant detection that display unfastened belts). 
We also believe that 60 seconds is long enough to interpret the 
warning. This is what some current systems use, and we have no 
information to suggest that consumers have had difficulty interpreting 
the warning. This is a minimum performance requirement so manufacturers 
may voluntarily provide warnings lasting longer than 60 seconds. On the 
other hand, we are aware of vehicles that provide shorter warnings, so 
having a 60-second requirement will ensure a minimum level of 
performance.
vi. Other Aspects
    NHTSA also received comments on other aspects of the proposed rear 
seat belt warning requirements.
Comments
    Tesla requested that NHTSA clarify whether the ``rear rows'' 
reference includes all designated rear seating positions. Tesla also 
commented asking if the agency had a plan to also address integrated 
child seats that have seat belt reminder technology. Auto Innovators 
commented that the proposed S7.5(c)(1)(ii), requiring a visual and 
audible change of status warning, and S7.5(c)(2)(ii), prohibiting a 
visual warning that a seat belt is not in use for an unoccupied seat, 
are inconsistent and require clarification.
Agency Response
    The final rule retains the reference to ``all rear designated 
seating positions.'' The proposed regulatory text did not refer to 
``rows''; it simply referred to ``rear designated seating positions.'' 
Accordingly, it applies to all rear designated seating positions in 
applicable vehicles.
    It is not necessary that the rule specifically address integrated 
child seats. Integrated child seats are CRSs or booster seats that are 
built into the vehicle seat. A child seated in an integrated child seat 
is secured with either a seat belt or a harness. If the child is 
secured with a seat belt, then the seat belt warning should monitor 
belt use as with any seat belt. If the child is secured with a harness, 
the seat belt reminder would not be required for the harness, because 
children in an integrated seat with a harness are not part of the 
target population for this rule

[[Page 414]]

just as children in rear- and forward-facing CRSs are not part of the 
target population. In addition, we were unable to identify any new 
vehicles with integrated child seats that use a harness. Integrated 
booster seats would not pose an issue for the seat belt warning system, 
and we are aware of only one vehicle manufacturer that offers 
integrated booster seats on some vehicles as an option.\107\ Regarding 
Auto Innovators comment, the final rule does not include the proposed 
requirement that the warning is not permitted to indicate a seat belt 
is not in use for an unoccupied seat because we do not believe this is 
necessary.
---------------------------------------------------------------------------

    \107\ See https://www.volvocars.com/lb/support/car/xc90/article/3212aabb4f810a77c0a8015146e81cc9 (last accessed May 16, 2024).
---------------------------------------------------------------------------

b. Audio-Visual Change-of-Status Warning
    NHTSA proposed requiring an audio-visual warning when a rear seat 
belt is unbuckled during a trip. We proposed that an audio-visual 
warning must activate when the ignition switch is in the ``on'' or 
``start'' position, the vehicle is in forward or reverse drive mode, 
and the status of the seat belt changes from in use to not in use, 
unless any rear door is open, in which case a change-of-status warning 
would not be required. The exception for an open rear door was intended 
to allow for passengers to exit the vehicle when the driver does not 
shift into park without activating the change-of-status warning.
    The audio-visual warning would have to last for at least 30 seconds 
or until the seat belt that triggered the warning is in use. We 
proposed that the audible signal may be ``intermittent'' (i.e., not 
continuous), which mirrors the longstanding requirements for the 
driver's seat belt warning. If intermittent, we proposed that inactive 
periods longer than three seconds would not be counted toward the total 
minimum duration of the audible warning. Because the required minimum 
duration was relatively short, we did not propose additional audible 
signal characteristics, such as a duty cycle. (In contrast, we proposed 
additional signal characteristics for the front seat belt change-of-
status warning because of the required longer duration for that 
warning. The final rule decisions on these aspects of the front seat 
warning are discussed in Section VI.B.3).
    ECE R16 similarly specifies an audio-visual change-of-status 
warning for rear seats. Specifically, if a fastened belt becomes 
unfastened when the vehicle is in ``normal operation'' (defined as 
forward motion at a speed greater than 10 km/h (6.2 mph)),\108\ ECE R16 
specifies an audio-visual warning (second level) when certain distance, 
time, and/or speed threshold(s) (at the choice of the manufacturer) are 
exceeded.\109\ The additional thresholds are distance traveled (not to 
exceed 500 meters), vehicle speed (not to exceed 25 km/h (15.5 mph), 
and/or travel time (not to exceed 60 sec). This warning must last for 
at least 30 seconds unless the unfastened belt becomes fastened, the 
seat associated with the unfastened belt is no longer occupied, or the 
vehicle is no longer in normal operation.\110\ This warning may not be 
canceled by the driver.
---------------------------------------------------------------------------

    \108\ Section 2.47.
    \109\ Section 8.4.3.3 (front seat belts) and section 8.4.4.5 
(rear seat belts).
    \110\ These summaries simplify the requirements somewhat. They 
will be discussed in greater detail later in the preamble where 
relevant.
---------------------------------------------------------------------------

    Euro NCAP also requires (to earn points) an audio-visual change-of-
status warning at vehicle speeds of 25 km/h (15.5 mph) and above.\111\ 
If the change of status occurs below 25 km/h (15.5 mph) and no doors 
are opened, the signal may be delayed until the vehicle has been in 
forward motion for 500 meters or has reached a forward speed of 25 km/h 
(15.5 mph).\112\ A warning is not required if the system has occupant 
detection as long as all doors remain closed and the number of buckled 
positions remains the same, in order to minimize the number of false 
positives (e.g., children remaining in the vehicle but swapping seats 
in the rear while at a traffic light).\113\ The warning duration 
differs for the visual and audible warnings. With respect to the visual 
warning, if the system does not have occupant detection, the warning 
must last until the seat belt is fastened or 60 seconds have 
elapsed.\114\ If the system does have occupant detection, the signal 
must remain on until the belt is fastened. The audible warning must 
last until the belt is fastened,\115\ 30 seconds have elapsed,\116\ or 
the vehicle speed falls below 10 km/h (6.2 mph).\117\
---------------------------------------------------------------------------

    \111\ Section 3.4.1.5.
    \112\ Section 3.4.1.5.
    \113\ Section 3.4.1.5.
    \114\ Section 3.4.3.1.1.
    \115\ Section 3.4.1.6.
    \116\ Section 3.4.3.2.
    \117\ Section 3.4.1.6. The audio signal must resume when the 
speed goes above 25 km/h (15.5 mph) and no doors have been opened 
and the seat belt(s) remain unbuckled. In addition, the audible 
signal may instead meet the requirements for the front seating 
positions, if the vehicle is equipped with occupant detection.
---------------------------------------------------------------------------

    ECE R16 \118\ and Euro NCAP \119\ do not count periods in which the 
warning stops for longer than three seconds as part of the overall 
duration.
---------------------------------------------------------------------------

    \118\ Section 8.4.2.4.1.
    \119\ Section 3.4.3.2.3.
---------------------------------------------------------------------------

    The IIHS protocol also requires an audio-visual change-of-status 
warning lasting at least 30 seconds when the vehicle is in motion. The 
exact trigger depends on vehicle speed. When vehicle speed is between 
10 and 40 km/h (6.2 and 24.9 mph), the audio-visual warning must start 
within 30 seconds of continuous forward motion, and when the speed 
exceeds 40 km/h (24.9 mph), the audio-visual warning must begin within 
two seconds if the signal has not already begun. The warning can 
deactivate when the seat belt that triggered the warning is fastened; 
the vehicle is no longer in forward motion above 10 km/h (6.2 mph); or 
the seat or seats that triggered the warning are no longer occupied. 
Similar to Euro NCAP, the thresholds to trigger the primary audible 
signal and visual signal may be reset if any doors have been opened 
when the vehicle is not in motion.
    The proposal differed from ECE R16, Euro NCAP, and the IIHS 
protocol in some respects. The proposed 30-second duration was shorter 
than the 60-second duration for the visual signal specified in Euro 
NCAP, but consistent with the 30-second duration for the audible 
signal. We also did not propose any speed, distance, or time triggers. 
And we did not propose the Euro NCAP allowance for not requiring a 
change-of-status warning when all doors remain closed and the number of 
buckled positions remains the same because it would require a delay in 
the activation of the change-of-status warning; also, these types of 
events are likely uncommon and require very little time to complete, so 
exposure to the warning would be very limited.
Comments
    Consumer Reports agreed with the agency's decision to require the 
change-of-status warning to include both audible and visual components. 
It also supported departing from ECE R16 and Euro NCAP and requiring a 
warning whether or not a vehicle is in motion because a stopped vehicle 
presents the best opportunity for the driver to ensure that the 
occupants are belted.
    On the other hand, Honda, Nissan, NADA, Tesla, Ford, Auto 
Innovators, and HATCI commented that reminder trigger conditions should 
harmonize with ECE R16 and/or Euro NCAP and be based on vehicle motion. 
Auto Innovators and Honda commented that the proposed requirements for 
providing an audible alert may result in widespread consumer acceptance 
issues. For example, Auto Innovators argued that establishing a trigger

[[Page 415]]

threshold based solely on the ignition being on, absent vehicle motion, 
will result in scenarios where an unbelted condition that may otherwise 
be viewed as reasonably acceptable would result in an audible alarm, 
including those where the vehicle is either stopped (and in drive) or 
slowing in anticipation of an upcoming stop (e.g., in a rideshare 
scenario or school drop-off). Auto Innovators recommended that NHTSA 
harmonize with ECE R16, which requires the audio-visual warning to be 
provided only when there is a change in seat belt status when the 
vehicle is traveling above 25 km/h (15.5 mph) or moving below 25 km/h 
(15.5 mph) for a period of 60 seconds.
    Auto Innovators further commented that the agency did not 
articulate why it has proposed that an audible alert occur when the 
vehicle is in reverse. Auto Innovators explained that such maneuvers 
are typically low-speed events, and that the agency has not provided 
clear justification for why an audible alert is needed in these 
scenarios.
    Honda commented that if NHTSA does not adopt a speed threshold, it 
could consider an alternative approach that would allow a single chime 
when the change of status occurs (assuming the vehicle is stationary) 
and then resume the full alarm when the vehicle begins moving. Honda 
commented this modification would minimize intrusive and annoying 
alarms, ensuring that the system still provides a warning but does not 
cause excessive consumer annoyance.
    We also received comments both in support of the proposed warning 
duration, as well as comments that recommended alternative durations. 
Auto Innovators, HATCI, and Honda support the proposed 30 second 
duration and harmonizing with ECE R16. Tesla encouraged harmonizing 
with either ECE R16 or Euro NCAP.
    Some commenters favored a longer minimum duration. Freedman argued 
that the audio warning should be the same as that for the driver seat 
(indefinite). Consumer Reports commented that the warning should last 
at least 60 seconds unless the belt is buckled, to be consistent with 
the start-of-trip visual warning. Ms. Cross proposed requiring at least 
a 90 second minimum duration, pointing to, for example, consumer 
surveys showing that many consumers favor persistent warnings.
    Honda and Auto Innovators recommended that NHTSA allow the change-
of-status warning to cease if a different belt is buckled (and the 
total number of buckled seats is restored) to allow the driver to 
recognize that a rear occupant has changed seats and refastened the 
belt.
    Tesla requested that NHTSA define the start time to measure the 30 
seconds duration. Tesla further commented that if the warning continues 
after the seat belt is fastened, it may lead to a potential confusion 
on system functionality, which could lead to occupants ignoring future 
warnings.
Agency Response
    In response to the comments, the final rule adds a provision to 
accommodate occupants switching seats. However, we are declining to 
adopt additional trigger conditions, such as a speed criterion. The 
final rule also includes the proposed 30-second duration. Our reasoning 
for these and other choices is detailed below.
    The final rule includes the proposed exception from activation when 
a rear door is opened, i.e., for a drop-off scenario: a change-of-
status warning is not required if a rear passenger unbuckles and exits 
the vehicle. However, the final rule omits the additional proposed 
language that ``the system may consider this situation as a new trip 
with respect to that seat belt and reset the warning system.'' This 
language is vague and superfluous. The exception is based on the door 
opening, and there is no need to permit the system to ``reset''; 
manufacturers can program the system logic for the state of the system 
after a belt is unfastened and a door is opened as they deem 
appropriate, as long as the system complies with the finalized 
requirements.
    The final rule implements the recommendation from Auto Innovators 
and Honda to follow Euro NCAP and allow the change-of-status warning to 
deactivate if the system is able to recognize passenger(s) switching 
seats when all the doors are closed and the number of buckled positions 
remains the same. This change would limit the exposure to the warning 
if the occupant(s) changes seats and refastens the belt in another 
seat. Without this allowance, the warning would remain activated when 
all occupants were belted and would be unnecessarily annoying. This 
condition will also accommodate situations where a passenger buckles 
into a wrong buckle and corrects it. The additional regulatory text is 
based on Euro NCAP.\120\
---------------------------------------------------------------------------

    \120\ Section 3.4.1.5 (``Where the system is able to track the 
number of buckled positions in the rear, no change of status signal 
(for the rear seats) is required as long as all doors remain closed, 
and the number of buckled positions remains the same. This is to 
minimize the number of false positives (ex: children remaining in 
the vehicle but swapping seats in the rear while at a traffic 
light.'')).
---------------------------------------------------------------------------

    However, we are declining to add the additional requested trigger 
conditions, or to simply require a single chime when a change of status 
occurs because, as we explained in the NPRM, seat belts provide a 
safety benefit even at lower speeds, and regardless of the direction of 
motion. We also believe a warning would be beneficial even if the 
vehicle is not moving. A driver may want to know if any rear seat 
occupants--especially children--have been unbuckled while the vehicle 
is temporarily stopped (e.g., at a traffic light) or slowed (e.g., in a 
parking lot), because the vehicle could soon be resuming travel. In 
addition, providing a warning when the vehicle is stationary would 
allow the driver to attend to the unbuckled passengers before having to 
focus attention on the driving task. We similarly believe that a 
warning would be useful before the vehicle has reached any distance or 
trip time threshold. The final rule also includes the reverse driving 
mode as a trigger as proposed. We believe this trigger is beneficial 
because it will require a warning before a vehicle begins driving on 
the road (e.g., before pulling out on to the road). We believe the 
benefits of having a warning activate in these circumstances outweighs 
the potential drawbacks identified by the commenters (for example, when 
the vehicle is stopped and the belt is unbuckled before a door is 
opened). In addition, we have eliminated the condition that the 
ignition switch be in the ``on'' or ``start'' position because it was 
redundant with the condition that the vehicle be in a forward or 
reverse drive mode.
    We do not believe that a visual warning alone, without an audible 
component, would be sufficient; a change of status is a serious event, 
due to the higher risk that comes with riding unbelted, and we believe 
this risk warrants a more effective audio-visual warning. In addition, 
the relatively short duration of the warning (30 seconds) should help 
minimize consumer annoyance in other scenarios that might result in an 
unbelted occupant in very low-risk scenarios. We therefore believe that 
consumers will accept the warning.
    NHTSA is also finalizing the proposal that the audio-visual change-
of-status warning last at least 30 seconds (or until a rear door is 
opened). As we explained in the NPRM, this requirement is comparable to 
the change-of-status warnings on vehicles currently equipped with rear 
seat belt warnings.

[[Page 416]]

While we recognize that longer warnings may be more effective, we are 
not requiring a longer warning for the rear change-of-status warning. 
This requirement differs from the front seat, for which we are 
requiring a visual warning that lasts until the belt is re-buckled and 
a speed threshold for the indefinite audible warning. The main reason 
we are not requiring a longer rear change-of-status warning is to 
mitigate driver distraction. Because the majority of rear passengers 
are children, the driver would not necessarily be able to address the 
issue immediately and a longer warning could distract from the driving 
task.\121\ With respect to Ms. Cross's comment, the survey on consumer 
acceptance for rear warnings does not support a specific duration, just 
that the majority found the feature acceptable, and the data on the 
majority of vehicles having at least a 90 second warning is for the 
front seat belt warning at the start of a trip, not a change-of-status 
warning, so they are not necessarily directly comparable.
---------------------------------------------------------------------------

    \121\ The change-of-status warning does not present the same 
concerns with false warnings as does the start-of-trip warning 
because the change-of-status warning is not triggered by occupancy.
---------------------------------------------------------------------------

    With respect to Tesla's question about start time, the 30-second 
clock commences when the trigger conditions specified in the rule are 
met. The warning is permitted to stop if the occupant of the seat with 
the belt triggering the warning buckles within 30 seconds.
c. Electrical Connections/Removable Seats
    In the NPRM we explained that we had tentatively decided not to 
propose any requirements with respect to the electrical connections for 
folding, rotating, or stowable seats. Because these seats are not 
readily removable, the electrical connections should not be disturbed 
and could be accommodated with additional wiring. We did, however, 
propose two requirements related to the electrical connections for 
readily removable seats.
    First, we proposed that readily removable seats must either 
automatically connect the electrical connections when the seat is put 
in place or, if a manual connection is required, the connectors must be 
readily accessible. A system using a wireless connection could be 
classified as either automatic or manual, depending on whether the user 
needs to take any additional actions to establish the wireless 
connection when the seat is installed. We agreed with the commenters 
who recommended no prescriptive requirements to ensure manufacturers 
have flexibility in system design.
    Second, we proposed that vehicles using the negative-only 
compliance option provide a visual warning to the driver if a proper 
electrical connection has not been established for a readily removable 
seat because we were concerned that consumers could reinstall removable 
seats without making a proper electrical connection. We proposed 
requiring a visual warning for negative-only systems only because a 
faulty connection would result in the system not triggering any warning 
of an unbelted rear seat occupant. Moreover, for a negative-only 
system, the driver would otherwise have no reason to suspect that the 
system was malfunctioning, and so might mistake the lack of a warning 
as an indication that the rear seat occupant was belted. In the NPRM we 
explained why we believed that these issues were not present in full-
status or positive-only warning systems.
    In the NPRM we stated our belief that both requirements would 
mainly affect minivans, which make up a small percentage of the fleet, 
but further explained that it might be possible to use the rear seat 
belt visual warning signal, with slight modifications (e.g., a 
different color) to comply.
Comments
    Freedman, ASC, Honda, and Consumer reports commented that they 
agree that readily removable seats should not be exempt from the 
proposed requirements.
    ASC also commented on potential challenges in establishing reliable 
electrical connections, explaining that seat belt technology to support 
seat belt reminder systems in the field today is contained within an 
electrical switch inside the buckle. According to ASC, this 
functionality presents two challenges. First, since the removal and 
reattachment of the seat will result in disconnecting/reconnecting the 
buckle wiring to the vehicle wire harness, the reliability of this 
connection needs to be studied to ensure it is robust against 
malfunction considering its use case. (RVIA also raised this concern in 
its comment.) Second, a user's handling of the electrical interface 
presents an opportunity for accidental damage. ASC recommended further 
study to determine the robustness of this connection in these systems.
    RVIA commented that motor homes are also often equipped with non-
conventional, custom-made rear seating, so that developing wiring and 
sensors for the seat belt warning system that are not damaged in the 
conversion process from seat to bed would be challenging if not 
impossible. RVIA further commented that the NPRM does not consider 
convertible seats.
    IEE recommended that a visual warning be required for all systems, 
not just the negative-only system.
Agency Response
    The final rule includes the proposed electrical connection 
requirements for readily removable seats. We agree with the commenters 
who supported including these requirements that doing so would provide 
important safety benefits by helping to ensure that proper electrical 
connections are made and the warning system operates correctly, and, in 
the case of negative-only systems, warns users that a proper connection 
has not been made. We agree with ASC that there is a foreseeable 
possibility that users can accidentally damage the system. This risk is 
why the final rule requires a warning that alerts the driver if a 
connection has not been properly made or if there is a malfunction for 
negative-only systems (where there is a risk of the driver not being 
aware of the issue).
    We acknowledge the potential challenges associated with electrical 
connections pointed out by some of the commenters, but we believe the 
requirements are feasible. NHTSA's understanding is that removable rear 
seats are relatively rare, and typically only installed in the second 
row of passenger vans (a very small percentage of the fleet). In the 
vehicles in which they are present, it is likely that the seats are not 
frequently removed, which would suggest that the electrical connections 
would not be exposed to constant removal and re-installation that could 
increase the likelihood of damage. Moreover, the fact that the seat is 
removable does not necessarily mean that removing the seat means 
disturbing the electrical connection. NHTSA is aware of one minivan 
model with a rear seat belt reminder and a removable seat (MY 2024 
Toyota Sienna Hybrid); in that vehicle, the seat belt anchors--which 
contain the wiring necessary for the rear reminder signal to function--
remain in place when the seat is removed, obviating any need to re-
establish any electrical connections when the seat is re-installed.
    Furthermore, the technology at issue here is not complex; re-
installing the seats simply would require re-establishing a connection. 
If a seat is designed to be removable, it would not be unreasonable to 
expect that the seat, when re-installed, continues to have the same 
functionality it had before it was

[[Page 417]]

removed. The fact that removable seats are not exempted by ECE R16 or 
Euro NCAP strongly suggests that this requirement is not 
unreasonable.\122\ Accordingly, we do not believe more study is 
necessary to determine the robustness of the connection. Electrical 
connections may not be necessary for every removable seat and only a 
limited number of vehicles are equipped with removable rear seats. It 
is also unlikely that seats are removed and reinstalled frequently. 
Therefore, this issue does not appear to warrant further study. In 
addition, the requirement for a warning if there is a malfunction also 
addresses safety risks associated with potential damage over time.
---------------------------------------------------------------------------

    \122\ NHTSA did some limited market research of European models 
with removable rear seats. In one (MY 2023 Peugeot 5008) the seat 
belt anchors did not appear to be affected by the removal of the 
seat. In another (MY 2023 Ford Tourneo Connect), visual indicators 
where the seat locks in place were used to confirm proper 
installation, but not pertaining to electrical connections 
specifically.
---------------------------------------------------------------------------

    With respect to RVIA's comment regarding seating specific to motor 
homes, such as dinette seating, it is unlikely the requirements apply 
to motor home convertible seats. Motor homes not greater than 10,000 lb 
GVWR are generally not required to have rear seat belts.\123\ And 
NHTSA's regulations exempt motor home seating locations labeled in 
accordance with S4.4 of FMVSS No. 207 from being classified as 
``designated seating positions,'' so that the seat belt and seat belt 
reminder requirements do not apply to motor home seats so labeled.\124\
---------------------------------------------------------------------------

    \123\ FMVSS No. 208 S4.2.7.
    \124\ 49 CFR 571.3(b) (definition of ``designated seating 
position'').
---------------------------------------------------------------------------

    The final rule does not expand the connection warning requirements 
to systems beyond the negative-only system. As mentioned in the NPRM, 
we only think this issue would pose a serious risk for negative-only 
systems.
d. Owner's Manual Instructions
    NHTSA proposed that the owner's manual (which includes information 
provided by the vehicle manufacturer to the consumer, whether in 
digital or printed form) describe the warning system's features, 
including the location, format, and meaning of the visual warnings. We 
also proposed that the owner's manual include instructions on how to 
make any manual electrical connections for readily removable seats. 
These proposed additions would require a revision to the approved 
collection of information in OMB No. 2127-0541.
Comments
    We received comments both in support of and in opposition to the 
proposed owner's manual instructions.
    ASC agreed with the proposal to include information regarding seat 
belt reminder systems in the owner's manual instructions. NSC commented 
that the owner's manual instructions should include instructions on how 
to make any manual electrical connections for readily removable seats, 
like child passenger safety seats. NSC urged NHTSA to consider 
standardizing generic nomenclature as well as standardizing warning and 
icon symbols to reduce driver confusion. SRN requested that 
instructions regarding false warnings, such as when relatively heavy 
car seats are installed using LATCH, be provided.
    Auto Innovators opposed any specific owner's manual requirements, 
particularly if the required language is not relevant or applicable to 
all vehicles. Auto Innovators commented that the extent to which 
guidance may need to be included in the owner's manual is a function of 
how the system is designed; if there are certain aspects of the system 
design that may require additional instruction, this information should 
be provided at the discretion of the manufacturer.
Agency Response
    The final rule includes, without any substantive changes, the 
proposed owner's manual requirements. We agree that these requirements 
will aid in public adoption of the warning systems and help to achieve 
their full safety potential. In addition, with increased system 
complexity, greater knowledge and understanding of the system is 
required. Including detailed information in the vehicle itself is not 
practical.
    The final rule to some extent standardizes nomenclature by defining 
some terms used in the regulation and by specifying requirements for 
the visual warning characteristics. However, we attempted to minimize 
such requirements to the extent possible to provide manufacturers with 
design flexibility. We agree with Auto Innovators not to require 
including specific information on how warning systems with occupant 
detection function when a CRS is installed with LATCH and guidance on 
how to avoid activating the warning (e.g., by fastening the seat belt). 
As Auto Innovators points out, the extent of the guidance needed to 
potentially limit false warnings depends on the type of system and its 
technology and should be left up to the discretion of the manufacturer. 
Manufacturers may include language in the child passenger section of 
their manuals for further guidance on potential false warnings that is 
specific to their system capabilities.
e. Telltale Location
    The NPRM proposed that the visual warning signal be required to be 
visible to the driver only and not the rear passengers.
Comments
    Auto Innovators supported the proposal to provide flexibility for 
manufacturers to specify the location of any necessary telltales 
related to rear row seat belt use, provided they are visible to the 
driver. On the other hand, Freedman commented it would be beneficial 
for passengers to see the seat belt status in those vehicles with 
multiple rows of rear seats, and indicated that this requirement could 
be accomplished with additional monitors in the passenger seating area.
Agency Response
    The final rule adopts the proposed requirement that the visual 
signal needs to be visible only to the driver. Although we agree with 
Freedman that it could be beneficial for rear passengers to see the 
warning, we conclude that the increased cost, complexity, and redesign 
such a requirement would entail would not be justified. However, 
manufacturers would have the flexibility to place the visual warning 
where it could be seen by some or all rear seat occupants. In Section 
VI.C.7. we discuss the implications of the telltale location as it 
relates to automated vehicles. This requirement harmonizes with ECE 
R16,\125\ Euro NCAP,\126\ and IIHS,\127\ all of which require that the 
rear seat belt visual warning be visible only to the driver.
---------------------------------------------------------------------------

    \125\ Section 8.4.4.2.
    \126\ Section 3.4.1.1.
    \127\ Insurance Institute for Highway Safety. (April 2024.) Seat 
Belt Reminder System Test and Rating Protocol, Version III, pg. 7.
---------------------------------------------------------------------------

3. Alternative Warning Signals
    In the NPRM, we noted that the ANPRM had sought comment on 
requiring or specifying as a compliance option a rear seat belt warning 
that differs from the type of audio-visual warning that is currently 
required for the driver's seat belt, such as a haptic warning. 
Commenters to the ANPRM generally argued that an alternative warning is 
not necessary and that an audio-visual warning would be appropriate.

[[Page 418]]

Comments
    We received one comment on this issue. Auto Innovators agreed that 
an alternative warning is not necessary in addition to the audio-visual 
warnings proposed. However, Auto Innovators commented that 
manufacturers should not be prohibited from using alternate warnings 
(in addition to the required alerts) if they choose to do so.
Agency Response
    We are moving forward with the originally proposed requirements for 
audio-visual warnings, while neither requiring nor prohibiting 
alternative warning signals. We are specifying minimum performance 
requirements to balance the effectiveness and acceptability of these 
systems. Manufacturers may go beyond our requirements, such as by 
providing a warning on the instrument panel that must be acknowledged 
by the driver before any other use of the instrument panel is 
permitted. Manufacturers interested in implementing supplementary 
alternative warnings signals should take steps to ensure that what is 
used will not cause unnecessary confusion or annoyance.

B. Front Seat Belt Warning Requirements

1. Applicability
    In the NPRM, NHTSA proposed to require an audio-visual seat belt 
warning for any front outboard seating positions in passenger cars, and 
all front outboard designated seating positions certified to a 
compliance option requiring seat belts in trucks, MPVs, and buses with 
a GVWR of 4,536 kg (10,000 lb) or less.\128\ NHTSA also proposed not to 
extend the seat belt warning requirements to front center seats. 
Additionally, in the NPRM the agency noted that the 2022 automated 
driving system (ADS) final rule \129\ also addresses situations where 
an ADS-equipped vehicle without manual driving controls has one or no 
outboard seats in the front row (e.g., an ADS-equipped vehicle with 
only two seats in the front row, one or both of which would be 
classified as inboard passenger seating positions under 49 CFR 571.3) 
and requires seat belt warnings for certain inboard seats in such 
vehicles. We proposed that these front inboard passenger seats have the 
same seat belt warnings as front outboard seats. However, although the 
proposed regulatory text for passenger cars addressed this ADS-related 
applicability issue, the regulatory text for trucks, MPVs, and buses 
did not have conforming revisions.
---------------------------------------------------------------------------

    \128\ There are some compliance options for certain trucks and 
MPVs that permit passive protection in lieu of seat belts at the 
front outboard seating positions. See FMVSS 208 S4.2.3 (compliance 
options for trucks and MPVs weighing between 8,500-10,000 lb); 
S4.2.6 & S4.2.1.1 (compliance options for walk-in van-type trucks 
and vehicles designed to be sold exclusively to the U.S. Postal 
Service 8,500 lb and less).
    \129\ 87 FR 18560 (Mar. 30, 2022).
---------------------------------------------------------------------------

    ECE R16 requires a warning for seats in the same row as the driver 
in passenger vehicles up to 5 tons (~11,000 lb) and vehicles used for 
carrying goods (e.g., pick-up trucks, vans, commercial trucks) up to 12 
tons (~26,000 lb).\130\ Euro NCAP awards points for warnings for all 
front row seating positions.
---------------------------------------------------------------------------

    \130\ Section 8.4.1.1. ECE R16 requires seat belt reminders in 
vehicle categories M (passenger vehicles) and N (vehicles carrying 
goods). Category M vehicles have a maximum mass of 5 tons 
(approximately 11,000 lb) and category N vehicles have a maximum 
mass of 12 tons (approximately 26,500 lb).
---------------------------------------------------------------------------

Comments
    Several commenters, including Consumer Reports, Ms. Freeman, Honda, 
Tesla, Mothers Against Drunk Driving (MADD), and Ms. Tombrello 
commented in support of requiring an audio-visual seat belt warning for 
front outboard passenger seats. Consumer Reports commented that most 
manufacturers already implement audible warnings for front outboard 
passenger seats that last more than eight seconds, and they agreed with 
updating the requirements to reflect marketplace changes that have 
resulted in more substantial audible warnings. Ms. Tombrello emphasized 
the value in mandating this technology to cover the remaining vehicles 
that have not yet incorporated it.
    IEE commented that NHTSA should consider mandating a seat belt 
reminder warning for the front row seats of vehicles with a GVWR beyond 
10,000 lb. IEE indicated that such vehicles are included in ECE R16, 
and it would be a safety relevant gain to cover the whole vehicle 
fleet. They also noted that ECE R16 includes some exemptions, such as 
foldable seats in entry areas of coaches, that could also be 
incorporated.
    Ms. Tombrello, MADD, Advocates and Public Citizen, and IEE 
supported extending the requirements to the front center seating 
position. Ms. Tombrello noted the high percentage of center-seat 
fatalities that were unrestrained and stated that many children may be 
seated in the front center seat. IEE commented that even with a 
possibly still negative cost-benefit analysis, NHTSA should consider 
including the front center seat because the market share of vehicles 
with front center seats can be expected to increase as EVs no longer 
have a transmission tunnel. IEE also noted that because ECE R16 
includes the front center seating position, established technical 
solutions are available.
Agency Response
    We are finalizing the applicability of the front seat warning 
requirements as proposed in the NPRM, except for a correction to the 
regulatory text for certain ADS-equipped vehicles. NHTSA appreciates 
IEE's concerns regarding the harmonization and safety benefits that 
could be gained by expanding this rule to cover vehicles with a GVWR 
over 10,000 lb. However, the agency will not do so in this final rule 
because we lack information on implementation cost to support such a 
requirement for heavy vehicles. The Safety Act requires that FMVSS be 
practicable, which includes appropriately weighting the benefits and 
costs of a requirement while ensuring that the standard meets the need 
for motor vehicle safety. As we explained in the NPRM, long duration or 
indefinite audio-visual warnings are typically appropriate only for 
occupied seats due to the nuisance and desensitization effects that 
occur when warnings are activated for unoccupied seats.\131\ We also 
noted several factors that enabled us to conclude that no cost is 
associated with requiring front outboard passenger seat occupant 
detection technology in the light vehicle fleet (the vehicles to which 
this rule applies). Specifically, light vehicles are covered by the 
advanced air bag requirements in FMVSS No. 208, so occupant detection 
in the front outboard passenger seat is already widely deployed as part 
of the air bag system. Additionally, passenger seat occupant detection 
systems are often installed in the light vehicle fleet in part for use 
in voluntary seat belt warning systems. Based on compliance and 
consumer information submitted to NHTSA, the agency was, and still is, 
unaware of any vehicles to which the requirements will apply which do 
not already have occupant detection for the front outboard passenger 
seating position.
---------------------------------------------------------------------------

    \131\ 88 FR 61674, 61691 (Sept. 7, 2023).
---------------------------------------------------------------------------

    However, we do not currently have such information regarding the 
heavy vehicle fleet and therefore cannot come to the same (or any) 
conclusion about the costs associated with implementation of a similar 
requirement for heavy vehicles, so we are not going to extend the 
requirements in this final rule. Heavy vehicles are not covered by the 
advanced air bag requirements in FMVSS No. 208 \132\ and we do not have

[[Page 419]]

data indicating the market penetration of occupant detection systems 
for front outboard passengers in the heavy vehicle fleet in the United 
States. Without this or other information indicating the adoption of 
occupant detection technology, NHTSA is unable to determine whether 
additional occupant detection systems may need to be incorporated into 
vehicle designs to support a seat belt reminder system and the 
associated cost, and therefore at this time cannot determine that such 
a requirement would be practicable. Given the safety problem associated 
with a lack of seat belt use in light vehicles, and the availability 
and strength of data for systems in light vehicles, delaying this rule 
to obtain information for heavy vehicles would not be prudent. Instead, 
we are finalizing this rule to cover light vehicles and achieve those 
safety benefits quickly. In the future, as more data regarding heavy 
vehicles is available, we may choose to extend these requirements. 
However, we are not doing so in this final rule.
---------------------------------------------------------------------------

    \132\ 49 CFR 571.208, S14.
---------------------------------------------------------------------------

    Additionally, NHTSA is finalizing this rule without a requirement 
for front center seats. As we explained in the NPRM, a system for the 
front center seat without occupant detection would provide limited 
benefit because it would be only a visible and not an audible warning, 
the low occupancy of the front center seat, and the limited number of 
vehicles in the fleet with a front center seat. In addition, we 
estimated that requiring a system with occupant detection for the front 
center seats would not be cost effective.\133\ This is discussed 
further in Section VIII.B.3 as well as in the docketed FRIA. While EVs 
present fewer technical barriers to having a front center seat, we do 
not have data suggesting that manufacturers of EVs are incorporating 
front center seats at higher rates, or that if they did so, the 
requirement would become cost effective.
---------------------------------------------------------------------------

    \133\ Due to lack of data, NHTSA was unable to establish seat 
belt use rates for front center seat passengers under the baseline. 
The analysis therefore used the use rates for front outboard 
passengers.
---------------------------------------------------------------------------

    Finally, NHTSA is correcting the regulatory text for trucks, MPVs, 
and buses to address the potential for ADS-equipped vehicles that may 
have one or no outboard seats in the front row. We discuss other 
considerations related to ADS vehicles in Section VI.C.7.
2. Driver's Seat Belt Warning for Light Buses
    In the NPRM we proposed to require buses with a GVWR greater than 
3,855 kg (8,500 lb) and less than or equal to 4,536 kg (10,000 lb), or 
with a GVWR less than or equal to 3,855 kg (8,500 lb) and an unloaded 
weight greater than 2,495 kg (5,500 lb), to be equipped with a driver 
seat belt warning. This requirement would close a loophole in FMVSS No. 
208.\134\
---------------------------------------------------------------------------

    \134\ In the NPRM, NHTSA mistakenly referred to these vehicles 
as ``medium-sized buses.'' This was incorrect. ``Medium-sized 
buses'' refers to buses with GVWRs between 10,000 lb and 26,000 lb.
---------------------------------------------------------------------------

Comments
    Consumer Reports supported NHTSA's efforts to close this regulatory 
gap.
Agency Response
    NHTSA is finalizing this provision as proposed without change.
3. Visual and Audible Warning Duration and Activation
    In the NPRM, we proposed two separate audio-visual warnings for the 
driver and front outboard passenger seats. First, we proposed an audio-
visual ``start-of-trip'' warning that must activate when the ignition 
switch is placed in the ``on'' or ``start'' position if the seat is 
occupied and the seat belt is not in use. This warning would be 
required to continue until the seat belt that triggered the warning is 
in use. Second, we proposed an audio-visual change-of-status warning 
that would be required to activate when the ignition switch is in the 
``on'' or ``start'' position, the vehicle is in forward or reverse 
drive mode, and the status of the seat belt changes from in use to not 
in use. We also proposed that if the change-of-status occurs and a 
front door on the same side of the vehicle as the belt triggering the 
warning is open, the system can consider that the start of a new trip. 
The warning would be required to continue until the seat belt that 
triggered the warning is in use. We also proposed that the audio-visual 
warning would otherwise not be permitted to activate.
    ECE R16 requires a first-level visual warning and a second level 
audio-visual warning. The first level visual warning is a start-of-trip 
warning that must activate for at least 30 seconds a front seat belt is 
not fastened and the ignition is activated. The second-level audio-
visual warning must activate when a seat belt at an occupied seat is or 
becomes unfastened when the vehicle is in ``normal operation'' (defined 
as forward motion at a speed greater than 10 km/h) and specific 
threshold criteria are met (distance traveled, speed, time). The 
second-level warning must remain activated for at least 30 seconds, 
unless the safety belt is fastened, the seat is no longer occupied, or 
the vehicle is no longer in ``normal operation.''
    The Euro NCAP specifications are largely similar to those in ECE 
R16, with some differences. For example, Euro NCAP requires a longer-
duration ``Loud and Clear'' audible warning (90 seconds) when an 
additional speed, time or distance threshold is met. The audio-visual 
signal must also immediately deploy if a change of status to unbuckled 
occurs at speeds over 25 km/h (15.5 mph). When the change of status 
occurs below 25 km/h and the doors are opened, the system may consider 
this a ``new journey.'' To prevent unnecessary signals, both ECE R16 
and Euro NCAP require that the system be capable of detecting whether 
the front passenger seat is occupied.
    The IIHS ratings protocol for the initial signal specifies that if 
a seat belt at an occupied outboard front-row seating position is 
unfastened at ignition and the vehicle achieves continuous forward 
motion (at least 10 km/h (6.2 mph)), the audible signal must begin 
within 30 seconds when the vehicle speed remains between 10 and 40 km/h 
(6.2 and 24.9 mph) and within 2 seconds once the vehicle speed exceeds 
40 km/h (24.9 mph), if not already active. For the change-of-status 
signal, IIHS specifies the following: If a fastened seat belt at an 
occupied outboard front-row seating position is unfastened when the 
vehicle's forward motion is between 10 and 40 km/h (6.2 and 24.9 mph), 
then the primary audible signal must begin within 30 seconds of 
continuous forward motion; if a seat belt at an occupied outboard 
front-row seating position is unfastened when the vehicle's forward 
motion exceeds 40 km/h (24.9 mph), then the primary audible signal must 
begin within 2 seconds if it has not already begun.
    In the NPRM, NHTSA proposed to require that the audio-visual 
reminder last indefinitely until the belts are fastened (or refastened, 
in the case of a change-of-status scenario) at any occupied front 
outboard seating position. We proposed that this requirement be both 
upon start-up as well as in a change-of-status scenario. We based this 
proposal on five reasons that supported our belief that the proposal 
would be practicable, objective, and meet the need for motor vehicle 
safety. First, the existing requirements are significantly exceeded by 
the warnings provided in current vehicles. Second, we tentatively found 
(in agreement with IIHS) that the current audible signal duration upper 
limit of eight seconds is ineffective for increasing seat belt use. 
Third, we tentatively believed that contemporary

[[Page 420]]

consumers would accept a longer warning. Fourth, the technology 
necessary to implement such an enhanced warning is already standard 
equipment on almost all light vehicles. Fifth, a longer duration would 
be consistent with seat belt warning durations required or encouraged 
in other markets and ratings programs.
    We also sought comment on other duration alternatives, including 
those specified in or by ECE R16, Euro NCAP, and the IIHS. ECE R16 
requires a 30 second visual warning when the front seat belts are not 
fastened and the ignition is activated as well as an audio-visual 
warning that must activate for at least 30 seconds if the seat belt 
remains unfastened and specific onset criteria are met (e.g., distance 
traveled, speed, etc.). The Euro NCAP assessment protocol requires a 
visual signal that remains active until the seat belt is fastened, and 
a two-stage audible signal; the initial audible signal must not exceed 
30 seconds and the final audible signal must be at least 90 seconds. 
Under the IIHS ratings protocol, the primary audible reminder signal 
for the front outboard seats must be at least 90 seconds in total 
duration to obtain an ``acceptable'' or ``good'' rating.
Comments
Duration
    NSC, Consumer Reports, and Ms. Freeman supported the proposed 
indefinite warning. NSC and GM cited IIHS studies estimating that 
audible reminders lasting at least 90 seconds were significantly more 
effective for increasing seat belt use than an intermittent audible 
reminder and could save up to 1,489 lives annually. NSC also noted IIHS 
research that suggests that indefinite and 100 second constant 
reminders increased seat belt use by 30-34 percent over an intermittent 
reminder. Consumer Reports agreed with updating the requirements to 
reflect that the marketplace now accepts more substantial audible 
warnings.
    Auto Innovators, Mercedes, Honda, NADA, GM, Tesla, Nissan, and 
Rivian Automotive (Rivian) opposed the proposed indefinite reminder. 
Commenters cited consumer acceptance concerns, and some, such as 
Mercedes, Ford, and Auto Innovators, expressed concern that vehicle 
owners might seek to circumvent use of the system in various ways. Auto 
Innovators also commented that requiring a persistent audible warning 
may distract the driver from the driving task and other relevant safety 
warnings and may also result in desensitization. Honda noted that these 
concerns may lead to consumer backlash if the triggering conditions 
fail to accurately target risky situations when trips commence or when 
trips are actively occurring.
    Auto Innovators commented that the proposal is inconsistent with 
the agency's assertions with respect to the rear seat where a 60-second 
visual warning would be effective. They argued that 60 seconds is 
sufficient to capture the driver's attention and that a longer warning 
would have the potential to become distracting or a nuisance.
    Commenters suggested a variety of alternative warning durations. 
Auto Innovators, Mercedes, NADA, and Nissan encouraged NHTSA to align 
the final requirement with the ECE R16 requirement of 30 seconds.
    Honda and General Motors both recommended adopting a 90-second 
continuous audio-visual warning because it would be the most effective 
and is sufficiently persistent to ensure that occupants buckle up. 
Honda also encouraged the agency to consider whether adopting a warning 
that is continuously active (i.e., 100 percent duty cycle) for a 
definite duration of 90 seconds would be as effective as the proposal 
to require an indefinite warning with a minimum duty cycle of 20 
percent. Honda comments that it believes that a continuous 90-second 
chime is sufficiently persistent and might offer greater effectiveness 
compared to an indefinite warning that delivers only a 6- second chime 
followed by a 24-second pause between chimes. GM cited the IIHS 
research mentioned above and an internal research study with the 
Virginia Tech Transportation Institute that they stated showed that 
even a seat belt reminder chime lasting only approximately 34 seconds 
could result in all vehicle occupants in the study buckling their seat 
belts.
    Tesla and Rivian suggested maintaining the current 4-second 
regulatory duration. Tesla noted that longer duration warnings may 
increase the risk of distraction if a sensor malfunctions as well as 
lead to defeat attempts. Rivian commented that, based on the proposed 
triggers, the proposed continuous audible warning would sound in EVs 
even if the occupant does not intend to initiate a trip but rather just 
sits in the vehicle. It explained that depressing the brake at ignition 
places the vehicle in ``Go'' power mode and provides access to the 
vehicle's full feature set. As a result, a driver occupying the vehicle 
and depressing the brake, even without shifting the vehicle into Drive 
mode, would initiate the continuous chime. Rivian suggested that the 
current requirement resolves this concern, or alternatively, NHTSA 
could allow a manual reset or discontinue feature.
Start-Up Warning Trigger
    NADA, Nissan, Auto Innovators, Ford, Mercedes, Rivian, Honda, and 
HATCI specifically disagreed with the proposed ignition trigger for the 
indefinite warning and argued that it would result in consumer 
annoyance.
    Some commenters, such as Auto Innovators, HATCI, and NADA, 
suggested that the agency should more closely align with the trigger 
requirements of ECE R16, which requires a first level visual warning on 
start-up but does not require an audible alert to be provided until the 
vehicle travels 500 m, the vehicle speed exceeds 25 km/h (15.5 mph), or 
the duration time (engine running, propulsion system activated, etc.) 
is more than 60 seconds (second level warning). Nissan, Ford, and Honda 
urged NHTSA to contemplate harmonization with Euro NCAP and ECE R16 by 
including a minimum speed criterion for the trigger.
    Mercedes made a similar comment and argued that harmonization would 
allow for new seat belt reminder technology/designs to be implemented 
faster in the U.S. market. It also commented that it would support 
implementing the approach taken in IIHS's protocol, which requires an 
audible warning to begin after driving for 30 seconds while exceeding 
10 km/h (6.2 mph) or within 2 seconds while exceeding 40 km/h (24.9 
mph). Rivian also suggested use of the 10 km/h (6.2 mph) IIHS threshold 
for the indefinite audible alert because it largely mitigates low speed 
crash concerns. Rivian also noted that this requirement would resolve 
concerns with activating the reminder during activation of Auto Hold, 
which applies the brakes when the vehicle is stopped even though the 
brake pedal is released. Ford supported using a visual warning when the 
vehicle is stationary because it offers the best balance of providing 
an important reminder before the start of a trip without the potential 
annoyance of a persistent audio warning, especially in use cases where 
an audio warning is not warranted.
    Several commenters, including Nissan, Ford, Auto Innovators, and 
Honda, had concerns regarding the proposed triggering conditions when 
it comes to consumer acceptance. Honda commented that the start-of-trip 
audio-visual warning should be triggered by vehicle motion (or, 
alternatively, by the vehicle being shifted into drive or reverse), not 
by the vehicle's ignition

[[Page 421]]

being turned on. Honda referred to consumer research suggesting 
desensitization regarding the intended purpose of the existing start-up 
alarm, which it argued might worsen under the proposed approach. Honda 
commented that most individuals do not comprehend why their car chimes 
at start-up and that consumers also often incorrectly identify this 
chime as being merely a normal start-up sound. Honda argued that an 
alarm should sound only when genuine need for the alarm exists.
    Honda also requested a clarification, if NHTSA were to retain the 
status of the ignition switch as a trigger. It pointed out that as 
proposed, the start-of-trip warning ``must activate when the ignition 
switch is placed in the `on' or `start' position'' (emphasis Honda's). 
Relatedly, the proposed trigger for the change-of-status warning was 
tied to the vehicle being in forward or reverse gear. Honda pointed to 
a scenario where the driver buckles after turning on the ignition, and 
then unbuckles while the vehicle is still in park. In such a case, a 
warning would not be required (either start-of-trip or change-of-
status). Accordingly, Honda suggested modifying the logic of the start-
of-trip and/or change-of-status warning to require a warning in this 
situation.
    A number of commenters, such as Ford, HATCI, and Mercedes, noted 
specific consumer acceptance concerns with an ignition trigger in 
circumstances where a vehicle has been started but a trip has not begun 
or is not going to occur or when a vehicle is going to be travelling at 
low speeds. Commenters described situations including: when idling, 
waiting for passenger(s), warming up or cooling down a vehicle prior to 
a trip (Honda), waiting out inclement weather inside a vehicle, sitting 
in a stationary vehicle listening to audio (Honda), and, in the case of 
EVs, keeping the vehicle ``ignition'' on for extended periods while 
charging to allow use of air conditioning (Mercedes and Honda).
    Honda also commented that the proposed trigger is excessively 
stringent to meet the safety need and asked that the agency reevaluate 
the trigger mechanism to ensure it aligns with safe consumer 
expectations and behavior. Auto Innovators commented similarly, noting 
that the proposed approach does not meet the need for safety. Auto 
Innovators noted customer complaints regarding overly aggressive start-
of-trip warnings that begin on start-up, before the driver even has the 
opportunity to put the belt on. Honda argued that crash data illustrate 
that crashes at sufficiently low speeds are not likely to lead to 
injury, and pointed to data indicating that occupants are highly 
unlikely to sustain injuries in crashes occurring below 10 mph. Honda 
also argued that speeds below 15 mph are typically not associated with 
regular roadway driving. The lowest posted speed limits on residential 
or urban roadways in the U.S. are typically set at 25 mph. Speed limits 
of 15 mph are more common in non-roadway settings like residential 
neighborhoods or parking lots.
    Some commenters suggested other alternatives beyond incorporation 
of a speed-based trigger. For example, HATCI and Honda suggested a 
trigger in which the audible warning begins when the transmission is 
placed into a forward or reverse gear. HATCI commented that this 
trigger would resolve some concerns with a stationary vehicle pre-trip 
or during pick-up and drop-off and for EVs. Auto Innovators posited a 
short visual warning as an alternative to an ECE R16 harmonization. It 
noted that this approach would be consistent with the IIHS requirements 
for front-row seating positions, which also predicate second level 
audible alerts based on forward motion of the vehicle. Additionally, 
Auto Innovators argued that for the front outboard passenger seat, the 
triggering conditions should provide for a delay before a visual 
warning is required. Auto Innovators argued that this delay would be 
consistent with the proposal to allow for a similar delay for rear row 
occupants. It expected that this delay would address challenges in 
detecting seat occupancy instantaneously upon ignition.
Change-of-Status Warning Trigger
    With regard to the change-of-status warning, commenters generally 
supported a requirement but several, including Mercedes, NADA, Honda, 
and Tesla, commented that the trigger for the change-of-status warning 
should include a minimum vehicle speed. Mercedes and NADA recommended 
NHTSA harmonize with the ECE R16 on this issue and require only a 
visual warning if the vehicle is stopped or travelling at slow speeds 
and incorporate an audio warning if the vehicle is travelling at speeds 
of 25 km/h (15.5 mph) or greater. Nissan emphasized that when the 
trigger for audio warnings is solely based on gear selection, and these 
warnings are activated even when the vehicle is stationary, it has the 
potential to be irritating for the occupants, especially in situations 
such as being stuck in heavy traffic or waiting in drop-off lines. 
Honda commented that using vehicle speed would be more aligned with 
safety needs, and that triggering the warning any time the vehicle is 
in the drive mode would result in unnecessary alarms for individuals 
who are otherwise consistent belt users. Honda commented that this 
trigger would reduce acceptance of the system among regular belt users 
and desensitize consumers to the alarm. Honda also suggested adding 
seat occupancy as one of the activation criteria for the change-of-
status warning to address use cases where an occupant buckles a seat 
belt for another seat that is unoccupied, and then unbuckles it.
    Nissan and HATCI emphasized consumer acceptance concerns with the 
proposed change of-status warning, in particular regarding drop-off. 
HATCI noted that the ECE R16 triggers are particularly useful for 
addressing these scenarios. It explained that in these drop-off 
scenarios, the proposed audible alert would sound until the passenger 
opens the door, which could be considered a nuisance to the occupants. 
Ford also noted that its vehicles tend to experience frequent ingress/
egress scenarios (e.g., work use of farmers, ranchers or construction 
workers) where a persistent warning is not warranted.
    Honda suggested that if the agency retains the drive mode trigger 
for the change-of-status warning, an alternative could be to use a 
single chime when the vehicle speed is below a certain threshold at the 
time of unbuckling that becomes a persistent reminder of indefinite 
duration once the vehicle resumes motion (if the door remains closed). 
Honda argued that if NHTSA believes that a notification is needed, the 
single-chime approach would adequately notify the occupants in a non-
intrusive manner.
    Mr. Gaal suggested that once a driver or front outboard seat 
passenger has unbuckled their seat belt during a trip, a visual change-
of-status warning should immediately appear along with a singular 
audible beep, followed by a two-minute gap allowed before the 
indefinite audible component of the change-of-status warning occurs 
again.
    In the NPRM, the agency sought comment on the possibility of 
allowing deactivation of the audio-visual system and the situations 
under which it would be warranted. While comments on this topic are 
discussed more broadly in Section VI.C.6, we note here that a few 
commenters, such as Rivian, suggested a manual reset or discontinue 
feature as an alternative to a speed-based trigger. Honda, however, 
commented that if deactivation requires a complicated procedure, it is 
impractical to deactivate nuisance warnings for short trips and 
therefore this approach does not effectively mitigate driver annoyance,

[[Page 422]]

especially in comparison to alternative triggers, like vehicle motion. 
Honda noted that the use of a motion-based trigger would eliminate the 
need for deactivation.
    Tesla requested clarification on the definition of ``during the 
trip.'' Tesla also asked how the front change-of-status warning is 
envisioned to be applied to vehicles in automated mode or full 
automation.
    Auto Innovators commented that NHTSA proposed unnecessary 
restrictions on when an audio-visual warning for a front outboard seat 
belt warning system is permitted to activate and requested that they be 
removed. It argued that there may be other circumstances, including 
those currently unforeseen by the agency, where a manufacturer may seek 
to provide a similar audio-visual warning. It also stated that it is 
unclear whether these restrictions prevent standardization of the 
audible alert used for both front and rear rows.
    AVIA observed, with regard to vehicles with automated driving 
systems, that the NPRM proposed that the front outboard seats be 
allowed to suppress and reset the change-of-status warning only when 
the front door being opened is on the same side of the vehicle as the 
seat belt triggering the warning. In contrast, the NPRM proposed that 
the rear seat belt warning system may suppress and reset the change-of-
status warning when any rear door is opened. AVIA commented that while 
this distinction makes sense for a conventional vehicle, some vehicles 
with automated driving systems may have interior configurations that 
allow for a front outboard occupant to exit through a door that is not 
adjacent to their seat. Further, AVIA indicated that autonomous ride 
hailing manufacturers or operators may implement safety measures that 
only permit the door(s) on a particular side to be opened to encourage 
safer egress, even though the door(s) may not be adjacent to the 
occupant's seat. AVIA noted that this scenario could lead to a seat 
belt change-of-status warning remaining active indefinitely after a 
front row occupant exits the vehicle. AVIA suggested the language of 
the change-of-status warnings (both front and rear) be updated to allow 
the change-of-status warning to be reset when any door designed to 
provide egress for the seat is opened.
Agency Response
    After considering the comments, NHTSA has decided to modify the 
proposed front seat belt warning requirements. The final rule requires 
a visual warning whenever a driver or front outboard occupant is 
unbelted, and a two-phase audible warning.\135\
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    \135\ The final rule also applies to any inboard designated 
seating position for which a seat belt warning is required in 
S4.1.5.6 (which concerns inboard designated seating positions in 
passenger cars without manually operated driving controls).
---------------------------------------------------------------------------

    The first-phase audible warning is required to activate whenever 
the ignition switch is placed in the ``on'' or ``start'' position (or 
upon manual activation of the propulsion system, but prior to the 
vehicle being placed in ``possible active driving mode'' as defined by 
FMVSS No. 305), the seat is occupied, and the seat belt is not in use. 
The first-phase audible warning must continue for 30 seconds, until the 
seat belt that triggered the warning is in use, until the seat is no 
longer occupied, or until the second-phase warning activates, whichever 
comes first.
    The second-phase audible warning must activate and remain active 
when the vehicle speed is equal to or greater than 10 km/h (6.2 mph), 
the seat is occupied, and the seat belt is not in use.
    Under this approach, there is a start-of-trip audio-visual warning, 
with the visual warning lasting until the driver and any front outboard 
passenger have fastened their belts, and the audible component lasting 
at least 30 seconds (regardless of vehicle speed) and remaining 
activated whenever the vehicle speed is 10 km/h or more. Thus, if the 
vehicle is on but not traveling at least 10 km/h (6.2 mph), the audible 
warning would end after 30 seconds, but would either continue or 
reactivate should the vehicle speed reach 10 km/h or more. Similarly, 
the final rule requires an audio-visual change-of-status warning, with 
the visual warning required to activate and remain activated as long as 
the occupant remains unbuckled, and the audible component required to 
activate and remain activated whenever the vehicle is traveling at 
least 10 km/h.
    We are making these accommodations to reduce the potential that 
frequent belt users will interact with the audible warning. 
Additionally, as explained later in Section VI.C.5 and in the NPRM, we 
are specifying a level of audible characteristics, i.e., 30 second 
warning cycle, 0.5 Hz chime frequency, and a 20 percent duty cycle, 
which we believe will allow manufacturers to optimize for acceptability 
while maintaining effectiveness.
    This brief summary only gives a high-level overview of the 
requirements; the final rule contains additional specifications and 
nuances. These, as well as a response to the comments, are covered in 
detail below. First, we discuss the audible warning; then we discuss 
the visual warning.
Audible Warning Duration
    NHTSA has chosen to finalize the indefinite warning (subject to 
certain triggers and conditions) because NHTSA has concluded that it 
strikes an appropriate balance between effectiveness and annoyance and 
meets the need for safety.
    As NHTSA explained in the NPRM and PRIA, and explains in the FRIA, 
over the years there have been a number of studies of reminder 
effectiveness by NHTSA and others. The results of these studies have 
been consistent though somewhat fragmentary. In general, longer 
warnings are more effective than shorter warnings, and audio-visual 
warnings are more effective than visual warnings alone. Overall, these 
studies provide evidence that the relative annoyance (e.g., longer 
duration, more frequent cycle) of a warning increases the 
effectiveness. The studies also suggest that annoyance and 
effectiveness are inversely related to acceptance, although not 
necessarily in the same way. Therefore, there is the potential to 
optimize systems so as to increase effectiveness and also enhance 
acceptance. However, NHTSA's research also found that the evidence to 
date was not sufficient to clearly identify which specific signal 
characteristics were optimal.
    The proposal explained that in developing our estimate of the 
effectiveness of a front seat belt reminder with an indefinite 
duration, we used the results of a study conducted by the Insurance 
Institute for Highway Safety (IIHS) by Kidd et al. (2019).\136\ We 
explained that the study found that, relative to a short intermittent 
reminder, an audio-visual seat belt warning with a 100-second audible 
component increased seat belt use by 30 percent, and an audio-visual 
seat belt warning with an indefinite audible component increased belt 
use by 34 percent. In the NPRM, we explained that there were several 
limitations in this study, the main one being that the number of study 
participants was small, and, consequently, there was limited 
statistical power when comparing the change in rate of belt use between 
the different vehicle technology conditions. We noted that the study 
further discusses this and other limitations, such as how the 
demographics of the

[[Page 423]]

study sample differs from part-time belt users nationwide.
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    \136\ ``The effects of persistent audible seat belt reminders 
and a speed-limiting interlock on the seat belt use of drivers who 
do not always use a seat belt,'' April 2019, David G. Kidd Insurance 
Institute for Highway Safety, Jeremiah Singer Westat, Inc.
---------------------------------------------------------------------------

    Another limitation in the study is that the confidence intervals 
for the reported estimates are large. The 34 percent effectiveness 
estimate for the indefinite reminder had a 95 percent confidence 
interval of (12.7, 59.9), and the 30 percent effectiveness estimate for 
the 100-second reminder had a 95 percent confidence interval of (10.9, 
52.4.). Not only are the confidence intervals large, they also 
substantially overlap.
    We also note that the Kidd study further adjusted these 
effectiveness estimates to account for potential circumvention by study 
participants (e.g., buckling the seat belt behind the driver's back). 
Four of the seventeen study participants assigned to the vehicle with 
the 100 second reminder and three of the sixteen participants assigned 
to the vehicle with the indefinite reminder circumvented the warning. 
Accordingly, ``due to concern that the rate of seat belt use for 
participants who circumvented the vehicle technologies could bias the 
comparisons being made,'' \137\ the study authors repeated the 
analysis, except this time excluding those individuals who circumvented 
the warning. With that adjustment, the indefinite reminder increased 
seat belt use by 23 percent (95 percent CI [6.5, 42.6]) and the 100 
second reminder increased seat belt use by 25 percent (95 percent C I 
[8.2, 44.3]).\138\
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    \137\ Id. at pg. 16.
    \138\ The study does not report how often these excluded 
participants circumvented the warning. Accordingly, this exclusion 
could lead the effectiveness estimate to be lower than it actually 
was. And to the extent that the rate of circumvention for the 
excluded BMW and Subaru participants differed, that could also 
affect the relative effectiveness of the indefinite and 100-second 
warnings.
---------------------------------------------------------------------------

    In addition to these limitations in the Kidd study, the estimation 
of the effectiveness in the regulatory analysis has several other 
limitations or assumptions. These are discussed in detail in the FRIA. 
Thus, while the research is clear that longer durations are generally 
more effective than shorter durations, there is no conclusive evidence 
regarding what duration will maximize effectiveness (recognizing, of 
course, that duration is not the only warning characteristic and that 
other attributes, such as duty cycle, also affect effectiveness as well 
as annoyance).
    Nevertheless, the evidence is such that we are able to easily 
reject some of the specific suggestions from commenters for shorter 
warning durations. The 4-second and 30-second warnings suggested by 
some commenters are well below the typical duration for an audible 
warning in current vehicles. Further, a 4- or 30-second reminder is 
shorter and less persistent than the intermittent Chevy Cruise reminder 
\139\ included in the Kidd study, compared to which both the 100-second 
and indefinite audible warnings were significantly more effective. We 
are similarly unable to agree with General Motors, which referred to 
internal research showing that an audible warning lasting 34 seconds 
would be sufficient. (In addition, NHTSA has not seen the underlying 
research or data.)
---------------------------------------------------------------------------

    \139\ This was an enhanced reminder with three cycles that 
occurred at ignition, 105 seconds after ignition, and 360 seconds 
after ignition. Each cycle was 20 seconds in duration.
---------------------------------------------------------------------------

    The available evidence also does not lead us to conclude with 
confidence that, as asserted by Honda and General Motors, a 90-second 
continuous warning would be most effective. As we explained earlier, 
the Kidd study, while informative, still leaves uncertainty about 
whether a 90-second or indefinite warning would be most effective. We 
are also unaware of any study, as suggested by Honda, comparing a 90-
second continuous warning to an indefinite 20 percent duty cycle 
warning. However, a study of indefinite warnings with 100 percent and 
20 percent duty cycles found no difference in their relative 
effectiveness, which suggests that a 90-second continuous warning would 
not necessarily be more effective than a 20 percent duty cycle 
indefinite warning.\140\ Similarly, we are not aware of--and the 
commenters did not present--any persuasive evidence that an audible 
warning lasting greater than 90 seconds and less than indefinite would 
be at least as effective as an indefinite warning.
---------------------------------------------------------------------------

    \140\ Kidd, D.G. (2012). Response of part-time belt users to 
enhanced seat belt reminder systems of different duty cycles and 
duration. Transportation Research Part F, 15, 525-534.
---------------------------------------------------------------------------

    In light of the available evidence, NHTSA has therefore concluded 
that requiring an audible warning that lasts until all front outboard 
occupants are belted best and appropriately balances effectiveness and 
annoyance, and will help to ensure that as many as possible occupants 
take advantage of one of the most safety-enhancing technologies, the 
seat belt. As we explained above, there is uncertainty about the most 
effective duration and the magnitude of the effectiveness. The 
commenters did not provide any persuasive evidence or data that a 
shorter audible warning would be at least as effective as an indefinite 
warning.
    At the same time, there is no uncertainty that seat belts save 
lives, and there would appear to be little uncertainty that, regardless 
of assumptions and estimates, the monetized net benefits of a long 
warning would almost certainly be positive, because almost all subject 
vehicles already provide a seat belt warning for the front outboard 
seats, and any necessary changes to implement a longer warning (such as 
re-programming to optimize the warning characteristics) would likely be 
quite low-cost. Moreover, although an indefinite-duration warning would 
likely require some re-engineering, audio-visual seat belt warnings are 
a longstanding and established technology, so there should be no 
concerns about the technical feasibility of such a warning.
    Of course, effectiveness and component cost are not the only 
considerations in deciding what duration to require. Consumer 
acceptance is also crucial, and the Safety Act requires NHTSA to 
consider it. NHTSA is cognizant of--and takes seriously--likely 
disbenefits from annoyance. Many of the commenters' criticisms relate 
to the potential for an indefinite warning being annoying. In the NPRM 
the agency acknowledged past studies that found a correlation between 
annoyance and warning effectiveness.141 142 Elsewhere in 
this preamble we discuss the modifications NHTSA has made to the 
proposal in response to the comments in order to address concerns 
related to consumer acceptance, such as including a speed threshold for 
the indefinite audible warning. However, despite the steps the agency 
is taking to make the audible warning acceptable, it is not 
unreasonable to expect that there will be some level of annoyance, 
particularly from hardcore non-belt users, for an effective reminder. 
Similarly, it would be expected that with annoyance would come some 
level of distraction. Consequently, we would expect some level of lack 
of acceptance from hardcore non-users.\143\ Additionally, we

[[Page 424]]

understand that this lack of acceptance could lead to some level of 
misuse or attempts to defeat the system for some in this same group. 
The agency has studied such potential misuse in previous research 
\144\, and, as noted earlier, some of the Kidd study participants 
circumvented both the indefinite and 90 second audible warnings.
---------------------------------------------------------------------------

    \141\ N. Lerner et al. (2007). Acceptability and Potential 
Effectiveness of Enhanced Seat Belt Reminder System Features. 
(Report No. DOT HS 810 848). National Highway Traffic Safety 
Administration.
    \142\ Kidd, D.G. (2012). Response of part-time belt users to 
enhanced seat belt reminder systems of different duty cycles and 
duration. Transportation Research Part F, 15, 525-534.
    \143\ The Kidd study excluded from participation individuals who 
reported never using a seat belt from participating in the study. As 
we explain in Section VIII, Overview of Benefits and Costs and the 
FRIA, our benefits estimates conservatively assume that an 
indefinite audible warning will not cause occupants who ``never'' 
use a seat belt to begin using a seat belt. This is a change from 
the PRIA, which assumed that the indefinite reminder would be 
effective for such occupants. We note that the NPRM incorrectly 
stated that ``for the purposes of our effectiveness (and benefits) 
analysis, we conservatively assume that the increase in belt use 
would be due entirely to part-time nonusers'' (pg. 61711, n.231).
    \144\ Mazzae, E.N., Baldwin, G.H.S., & Andrella, A.T. (2018, 
October). Performance assessment of prototype seat belt misuse 
detection system. (Report No. DOT HS 812 593). National Highway 
Traffic Safety Administration. NHTSA has chosen not to implement 
measures to harden the systems against misuse at this time, for the 
reasons expressed in the NPRM. However, the agency will monitor this 
situation and act in the future if need be.
---------------------------------------------------------------------------

    NHTSA, however, believes that the population of occupants who will 
not respond to the warning by fastening the belt will be relatively 
small in number; as noted earlier, about 5.4 percent of occupants never 
or seldom use a seat belt. Moreover, we note that NHTSA's survey data 
does suggest that even though ``[s]eat belt reminder systems are likely 
to have little effect on hard-core nonusers who choose not to buckle 
up'',\145\ some individuals who report never using a belt would likely 
be responsive to a reminder. When asked about their reasons for not 
using a seat belt, many people who report never using a seat belt give 
reasons suggestive of some amenability to a reminder (for example, only 
driving a short distance or forgetting), as opposed to reasons that 
indicate general opposition to belts (such as e.g., ``don't like being 
told what to do'' or ``belts sometimes cause injuries'').\146\ In 
addition, many of those who never or rarely used a belt do not 
necessarily hold strongly negative beliefs about seat belts or seat 
belt use. For example, of drivers who never or rarely used a belt, 43 
percent do not report disliking seat belts or finding them annoying; 
\147\ about half do not believe that the belt is just as likely to harm 
them as help them; \148\ and only 20 percent report that putting on a 
seat belt makes them worry.\149\ And, when asked whether they would 
want a belt on in a crash, 63 percent of drivers who never or rarely 
use a belt strongly or somewhat agreed that they would want to be 
wearing a belt in a crash.\150\ This is consistent with NHTSA's other 
research, which acknowledges that occupants who sometimes use belts are 
the primary target for seat belt reminders, but not necessarily the 
only target.\151\ Therefore, while our benefits analysis excludes 
occupants who never use a seat belt, we would expect at least some of 
these nonusers to begin using a seat belt. Accordingly, overall we 
believe that the public will accept the required reminder, and that it 
will not negatively impact public acceptance of warnings in general.
---------------------------------------------------------------------------

    \145\ Buckling Up: Technologies to Increase Seat Belt Use. 
Special Report 278, Committee for the Safety Belt Technology Study, 
Transportation Research Board of The National Academies (2003), pg. 
40.
    \146\ 2016 MVOSS, pg. 71(Fig. 53).
    \147\ 2016 MVOSS, pg. 79 (Fig. 55).
    \148\ 2016 MVOSS, pg. 89 (Fig. 64).
    \149\ 2016 MVOSS, pg. 90 (Fig. 65).
    \150\ 2016 MVOSS, pg. 88 (Fig. 63).
    \151\ For example, as we stated in the NPRM (pg. 61705), the 
2004 Transportation Research Board Report notes that part-time belt 
users are the primary (not sole) target group for seat belt 
warnings.
---------------------------------------------------------------------------

    On the whole, in light of the uncertainty about the duration that 
will be most beneficial; the unquestioned benefit and effectiveness of 
seat belts; the relatively small proportion of users who will choose 
not to use the belt and will either experience annoyance from the 
reminder or choose to circumvent it; and recognizing that in MAP-21 
Congress removed the statutory limitation on the required duration for 
an audible seat belt warning, NHTSA is choosing to require an audible 
warning that lasts until the front outboard occupants are belted 
(again, subject to additional triggering criteria, such as the 10 km/h 
speed threshold).
    The other points raised by the commenters also do not persuade us 
to require a shorter warning. Commenters opposed to the indefinite 
warning also argued that it would be desensitizing. This conclusion 
does not seem to be consistent with the IIHS study where the findings 
indicate that a long duration warning may have a greater impact on seat 
belt use,\152\ and the comments by Honda and GM that warnings lasting 
90 or 34 seconds (respectively) may be more effective than an 
indefinite warning. As to the comments that a seat belt warning will 
cause other warnings to not be recognized, we address this in the 
Section VI.C.4. As to the comment by Auto Innovators that an indefinite 
warning in the front would be inconsistent with the agency's conclusion 
to limit the rear seat warning to 60 seconds because a longer warning 
could be distracting, the commenter did not provide the full context of 
the rationale for the agency's conclusion. Our conclusion was partially 
based on the fact that the rear seat warning system does not require 
occupant detection. Because of this, the rear seat belt warnings 
(particularly what the NPRM referred to as positive-only or full-status 
systems, which provide information on belted, as well as unbelted, 
occupants) function more as a source of information for the driver, 
rather than as a true ``warning'' for an unbelted occupant. It was for 
this reason that we believed that it was not necessary to require a 
particularly long-lasting warning for the rear. This logic does not 
apply to the front seats, for which occupant detection is either 
required or (for a driver's seat) can be assumed. Accordingly, the 
audio-visual signal functions more as a warning than as a source of 
information, because it is not activated for a belted occupant.
---------------------------------------------------------------------------

    \152\ Kidd, D.G., and Singer, J. (2019, April) The effects of 
persistent audible seat belt reminders and a speed-limiting 
interlock on the seat belt use of drivers who do not always use a 
seat belt. Insurance Institute for Highway Safety, Westat, Inc.
---------------------------------------------------------------------------

Audible Warning Activation
    The final rule incorporates a two-phased audible warning. The 
first-phase audible warning is required to activate whenever the 
ignition switch is placed in the ``on'' or ``start'' position (or upon 
manual activation of the propulsion system, but prior to the vehicle 
being placed in ``possible active driving mode'' as defined by FMVSS 
No. 305),\153\ the seat is occupied, and the seat belt is not in use. 
The first-phase audible warning must continue for 30 seconds, until the 
seat belt that triggered the warning is in use, until the seat is no 
longer occupied, or until the second-phase warning activates, whichever 
comes first. The second-phase audible warning must activate and remain 
active when the vehicle speed is equal to or greater than 10 km/h (6.2 
mph), the seat is occupied, and the seat belt is not in use.
---------------------------------------------------------------------------

    \153\ This EV-specific language is discussed in Section VI.C.1.
---------------------------------------------------------------------------

    The agency believes that this change in the triggering strategy 
from that specified in the NPRM will address many of the concerns 
expressed by the commenters related to potential user annoyance such as 
when the vehicle occupant is in a stationary vehicle, e.g., interacting 
with non-driving aspects of the vehicle or waiting for the vehicle's 
climate control. This change will also ameliorate the concerns related 
to EVs triggering the indefinite warning while being on, but stationary 
(Auto Hold applied).
    We are rejecting advice from commenters suggesting requiring only a 
visual warning upon vehicle start. Such

[[Page 425]]

a requirement would not even be consistent with the 4-8 second audible 
warning requirement currently in FMVSS No. 208. The initial 30-second 
audible warning remains important for the reasons expressed in the NPRM 
for why we want such a warning to initiate at vehicle start. We believe 
basing the trigger on the ignition switch is preferable to delaying the 
warning until the vehicle is placed in gear because the proposed 
requirement would make it more likely that the occupants fasten their 
belts before the vehicle is in motion.\154\
---------------------------------------------------------------------------

    \154\ DOT 2009 Seat Belt Study at pg. 65.
---------------------------------------------------------------------------

    The selection of 30 seconds is consistent with the ECE R16 start-up 
visual warning duration and the rear seat change-of-status audible 
warning for this final rule. We believe the 30-second audible warning 
will maintain the agency's goal of an effective warning at the start of 
a trip, while increasing the level of acceptance from what might be the 
case if the start-up warning remained indefinitely active. The initial 
30-second audible warning will have the same characteristics as the 
rear seat change-of-status audible warning, i.e., the warning may be 
continuous or intermittent. If intermittent, inactive periods longer 
than 3 seconds will not be counted toward the total duration of the 
warning and no gap longer than 10 seconds is allowed. These are also 
characteristics required by the ECE R16 audible warning, except for the 
10-second gap limit, which is required by Euro NCAP.
    The second-phase audible warning is important to encourage belt use 
for occupants that would otherwise wait out a finite warning and not 
buckle their belt. The 30-second start-up warning alone would have very 
little additional safety benefit, given that nearly all new vehicles 
already have audible warnings of this length or greater. Additionally, 
the agency agrees with commenters that a speed-based approach for the 
indefinite audible warning should address pick-up and drop-off 
situations that could lead to consumer backlash, particularly for 
frequent belt users.
    The selected speed threshold (10 km/h (6.2 mph)) is aligned with 
the IIHS rating system and Rivian's recommendation. ECE R16 also uses a 
10 km/h (6.2 mph) threshold for its definition of when a vehicle is in 
normal operation, and 10 km/h (6.2 mph) is within its maximum allowed 
speed threshold (25 km/h (15.5 mph)). The selected speed threshold is 
meant to address such scenarios as where the vehicle is parked, driving 
to a mailbox, on a long driveway, driving in a parking lot/garage, or 
dropping off passengers, but is not high enough that vehicles will be 
able to drive on roadways and not get a warning. Once the vehicle is 
traveling below 10 km/h (6.2 mph), the warning may deactivate. We are 
not allowing for any delay in the warning after the speed threshold is 
reached as is allowed by the IIHS rating,\155\ as we do not believe 
such a delay is necessary to achieve our goal of limiting the 
activation of the audible warning for regular belt users and would be 
counterproductive (i.e., increase the amount of time at which unbelted 
occupants do not get a warning).
---------------------------------------------------------------------------

    \155\ IIHS allows for a 30-second delay at speeds between 10 and 
40 km/h (6.2 and 24.9 mph) and a 2-second delay at speeds at and 
above 40 km/h (24.9 mph).
---------------------------------------------------------------------------

    The agency is not allowing manufacturers the choice to initiate the 
warning based on a combination of speed, timing, or distance traveled, 
such as is the case for the second level ECE R16 warning. We believe 
that vehicle speed is the most relevant parameter and that 10 km/h (6.2 
mph) limit is sufficiently low to achieve the agency's safety goals. 
Analysis of agency field data indicates that a 10 km/h (6.2 mph) delta 
V frontal crash shows a 28 percent probability of MAIS1 and 1.7 percent 
MAIS2 injuries and essentially no risk of higher level injury, whereas 
at 20 km/h (12.4 mph) there is a 39 percent probability of MAIS1 and 
4.0 percent MAIS2.\156\ Though still low probability, this is a 2.4-
fold increase in the risk of MAIS2.\157\ Although equating vehicle 
travel speed to delta V would tend to overestimate occupant injury, the 
results are directionally correct, and a higher speed threshold (or 
delay in initiating a particular speed threshold) would tend to 
increase injury risk.
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    \156\ Wang, J.-S. (2022, May). MAIS(05/08) injury probability 
curves as functions of delta V (Report No. DOT HS 813 219). National 
Highway Traffic Safety Administration.
    \157\ At 25 km/h (15.5 mph) there is a 41 percent probability of 
MAIS1 and 4.3 percent MAIS2.
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    We acknowledge that the data show that MAIS1 and MAIS2 injuries, 
which are meaningful safety concerns, occur frequently in collisions 
with delta V at 10 km/h, and that this final rule appears to depart 
from the NPRM's stated belief that seat belts provide a safety benefit 
even at lower speeds, regardless of the direction of motion. We also 
grant that in rare cases a vehicle traveling at a speed below 10 km/h 
(6.2 mph) may be struck by another vehicle traveling at a higher speed 
and that seat belt protection would be beneficial in such cases. 
However, we believe that the resulting increase in the warning systems' 
overall level of acceptability (which is an important consideration for 
both meeting the safety need and practicability), particularly for 
those that regularly wear seat belts, will outweigh the negative 
effects from non-activation of the warning system below 10 km/h.
    The second phase indefinite audible warning will also serve as a 
change-of-status warning, except that now that the indefinite audible 
warning is speed based, there is no need to relate activation to the 
gear selection or door opening status as was proposed. The fact that 
the speed threshold is exceeded is a sufficient reason for the audible 
warning to be active.
    With respect to AVIA's comment about modifying the provision for 
resetting the system when a door is opened for the front seats to 
address novel seating configurations, NHTSA believes these types of 
vehicles, specifically vehicles without a driver's seating position 
where all seats in the front and/or rear rows may be accessed via a 
common door, are beyond the scope of this rule. The agency did not 
develop the finalized seat belt warning requirements with these 
specific vehicles in mind. In any case, AVIA's concern about exposure 
to the proposed audio-visual change-of-status warning in these vehicles 
under the scenario it described in its comment is largely addressed by 
the finalized requirements for the front seat for change-of-status 
events, which only requires the activation of a visual warning in a 
drop-off scenario given the speed trigger criteria for the audible 
component.
Visual Warning
    The final rule requires that a visual warning activate and remain 
active whenever the ignition switch is in the ``on'' or ``start'' 
position (or the propulsion system is activated), the seat is occupied, 
and the seat belt is not in use. The final rule condenses the proposed 
``start of trip'' and ``change-of-status'' visual warnings into a 
single requirement and changes the proposed activation triggers in a 
few ways.
    We agreed with Honda's comment that under the proposed rule, if an 
occupant unbuckled while the vehicle was in park, no warning would be 
required to activate, even if the vehicle were subsequently placed in 
gear and commenced moving. We therefore believe that a ``change-of-
status'' visual warning should not be limited to when the vehicle is in 
a forward or reverse drive mode. Accordingly, for the visual warning, 
we removed the activation triggers that referred to the ignition switch 
being placed in the ``on'' or ``start'' position and to the 
transmission

[[Page 426]]

gear position. (We have also made analogous changes to the regulatory 
text related to EVs. These changes are discussed in Section VI.C.1.) 
These changes will ensure that a warning is activated whenever the 
vehicle is on and a driver or front outboard passenger is in the seat 
and not belted. Because this only applies to the visual warning--and 
not the audible warning--we do not believe this will lead to issues 
with consumer acceptance, because a visual warning is not nearly as 
intrusive as an audible warning. (On the other hand, as we explain in 
the preceding section, we have modified the proposed triggers for the 
audible warning to limit the scenarios in which it will activate to 
address concerns with consumer acceptance.) Concerns with consumer 
acceptance are further allayed by the fact that the warning requirement 
is tied to seat occupancy, so there will not be nuisance alarms for an 
unfastened belt at an unoccupied seat.
    The finalized regulatory text also adopts Honda's suggestion that 
the proposed change-of-status warning include seat occupancy as one of 
the triggering conditions. Because the front seats are either equipped 
with occupant detection or (for the driver's seat) occupancy can be 
assumed,\158\ there is no reason to require a visual warning for an 
unoccupied seat. This also addresses the misuse case Honda identifies. 
Including seat occupancy as a trigger also allows us to further 
simplify the triggering logic for the visual warning by deleting the 
exception to the proposed change-of-status warning for when a front 
door on the same side of the vehicle as the seat belt triggering the 
warning is open. This language is now unnecessary because seat 
occupancy is one of the triggers for the visual warning--in a scenario 
where a driver or front outboard passenger unbuckles and disembarks, a 
visual warning is not required because the seat is no longer occupied, 
and any reference to a door opening is unnecessary.
---------------------------------------------------------------------------

    \158\ See Section VI.B.5.
---------------------------------------------------------------------------

    We also implemented Auto Innovators' recommendation to delete the 
proposed restriction that the audio-visual warning is permitted to 
activate only to comply with the requirements in this rule.
    The finalized requirements for the visual warning are also 
generally consistent with the broad tenor of the comments on the 
proposed audio-visual warning, which, as we discussed earlier, were 
primarily concerned with the proposed indefinite audible warning and 
the proposed triggers for that warning. For example, we agreed with 
Mercedes and NADA that the change-of-status warning should better 
harmonize with ECE R16 and now require only a visual warning if the 
vehicle is stationary or travelling at low speeds. We did disagree with 
the commenters who suggested a shorter visual warning (at or below the 
30 seconds required in ECE R16) because, among other things, we believe 
both that a longer visual warning will be more effective than a shorter 
warning and also that a long visual warning does not pose the same 
consumer acceptance concerns as does a long audible warning.
4. Visibility of Visual Warning for Front Outboard Passenger Seat Belt
    We proposed requiring that if there is a driver's designated 
seating position, the visual warning for the driver's seat belt must be 
visible from the driver's seat and the visual warning for the front 
outboard passenger seat belt must be visible from both the driver's 
seat and the front outboard passenger seat. We did not propose to 
specify more detailed criteria for location or visibility of the 
telltale. (For discussion of vehicles with no driver's designated 
seating position, such as ADS-equipped vehicles without any manual 
driving controls, see Section VI.C.7.) We proposed requiring that the 
visual warning for the front outboard passenger seat belt be visible to 
both the driver and the front outboard passenger because NHTSA's study 
on front seat belt warning systems suggests that visual warnings for 
front outboard passenger seat belts are more effective when they are 
visible to the passenger as well as the driver.\159\ We tentatively 
believed it would be practicable for manufacturers to comply with this 
requirement; for example, the warning could be located in the center 
console display (which might be a salient place to present visual 
displays, both because of its location and because it may allow larger 
size icons or text).\160\ Some manufacturers already provide a 
passenger seat belt warning in close proximity to the passenger air bag 
status indicator, which is visible to both the driver and front 
passenger.
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    \159\ See DOT 2009 Seat Belt Study at pgs. 67-68.
    \160\ Id.
---------------------------------------------------------------------------

    We did not propose more detailed criteria for the location or 
visibility of the telltale as, for example, are provided in FMVSS No. 
208 S19.2.2 for the passenger air bag telltale. A visual warning for 
the driver's seat belt has been required since the early 1970s and we 
are not aware of any issues with the visibility of that telltale, so we 
tentatively believed more detailed requirements to be unnecessary.
    IIHS's ratings system specifies for the front outboard passenger 
seat that a visual signal must be displayed in the instrument panel, 
overhead panel, or center console, indicating an unfastened belt.
    ECE R16 specifies only that the visual warning must be readily 
visible and recognizable in the daylight and at nighttime by the driver 
and distinguishable from other alerts.\161\ Euro NCAP recommends that 
the visual signal must be clearly visible to the driver, without the 
need for the head to be moved from the normal driving position (such as 
in the instrument panel, head-up display, rear-view mirror, or center 
console).\162\
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    \161\ Section 8.4.2.1.1.
    \162\ Section 3.4.1.1. We note that the NPRM incorrectly 
referenced a prior version of the Euro NCAP protocols which 
specified visibility to the passenger. NHTSA appreciates Auto 
Innovators' comment noting that the referenced material was removed 
in v8.0 of the assessment protocol.
---------------------------------------------------------------------------

Comments
    A number of commenters, such as Auto Innovators, Mercedes, Ford, 
Nissan, HATCI, NADA, Toyota, and Honda, commented that the rule should 
require only that the front outboard passenger seat visual warning be 
visible to the driver. Mercedes noted that the agency did not provide 
any insight on how to achieve the passenger visibility requirement. 
Ford commented that a visual warning for front row passenger belt use 
that is visible to both driver and passenger may be unnecessary, overly 
complex to implement, and delay implementation. Auto Innovators and 
Mercedes commented that requiring passenger visibility of the visual 
reminder would be inconsistent with ECE R16 and Euro NCAP.
    Auto Innovators, Nissan, HATCI, Mercedes, Ford, and NADA all 
commented that the driver has primary responsibility to notify and 
ensure occupants fasten their seat belts and that the occupant in the 
front passenger seat will be alerted by the audible warning if the seat 
belt is not fastened. Honda noted that the primary mechanism for 
encouraging seat belt use is the audible alarm, and that the visual 
indicator primarily serves to explain the cause of the alarm. Honda 
stated that because the driver can hear the audible alarm and interpret 
the visual alarm, the passenger telltale becomes a matter of 
convenience.
    Honda also commented that the proposed outboard passenger 
visibility requirements have questionable merit because the DOT 2009 
Seat Belt Study, the research upon which much of the expected benefits 
of the requirement

[[Page 427]]

was based, has limitations. Honda noted aspects of the study and the 
design of the warnings used in the study, such as unusually large and 
aggressive indicators, which may limit the effectiveness conclusions 
that can be drawn from the study. Honda commented the study noted that 
in actual tests the most effective seat belt warning modality was the 
audible chime that repeated at a frequent interval, which suggested 
that the placement of the passenger telltale being visible to the 
passenger is of questionable efficacy.
    Auto Innovators, HATCI, Nissan, Mercedes, Ford, NADA, and Honda all 
commented that requiring that a warning also be visible to the front 
outboard passenger would require significant interior redesign of 
displays. Auto Innovators commented that this requirement would likely 
require either all visual warnings be in a central position (outside of 
the instrument cluster) so that they are visible to both the driver and 
right front passenger, or a second visual warning located in a central 
position to solely communicate the status of the passenger seat belt. 
Several of the commenters stated that this requirement would 
necessitate additional lead time.
    Toyota, Auto Innovators, and Honda commented that requiring front 
outboard passenger visibility would be unnecessary and inconsistent 
with the agency's proposed approach to the rear seat reminder 
requirements. They emphasized that the agency did not propose a 
requirement that visual warnings/indicators be visible to rear seat 
occupants, and that the agency is being inconsistent by proposing a 
requirement that the front seat visual reminder must be visible to the 
passenger, while the rear seat visual reminder only must be visible to 
the driver. These commenters expressed that the visual alert visible to 
the driver combined with the required audible alert would be sufficient 
to ensure that occupants in both the rear and the front passenger seats 
know their belt status.
    Auto Innovators and Honda commented that while FMVSS No. 208 
specifies requirements for a telltale to indicate the status of the 
passenger air bag for those seated in the front outboard passenger 
seat, this does not create a precedent, or support the need for, a 
similar front outboard passenger belt reminder telltale. Auto 
Innovators and Honda argued that with respect to seat belt use, the 
passenger can verify, based on a visual or manual check, whether their 
seat belt is buckled. This is not the case for air bag systems.
Agency Response
    The final rule requires that the front outboard passenger seat belt 
visual warning be visible only to the driver, with two exceptions 
related to ADS-equipped vehicles. In response to comments, we have 
decided not to require that the visual warning for the front outboard 
passenger seat belt be visible from the front outboard passenger seat. 
Retaining this requirement for the driver is critical for generating a 
communication dynamic between the driver and passenger, which is 
discussed further in this section and in Section VI.C.3 below. 
Manufacturers retain the flexibility to incorporate a visual signal 
that is visible to both the driver and front outboard passenger (or an 
additional signal visible to the passenger), and many already do. The 
final rule harmonizes with ECE R16 and Euro NCAP. It also matches the 
requirements for the visibility of alerts for the front passenger and 
rear seat belt reminders.
    Although there is limited information available on the safety 
benefits and compliance costs of a passenger visibility requirement, 
what information we have suggests that both would likely be low, at 
least in the context of this final rule. In this instance we feel that 
the relatively minimal benefits do not justify the costs that could be 
realized.
    With respect to benefits, because this final rule requires an 
audible alert, it (along with the visual warning provided to the 
driver) can serve the role provided by a visual warning to the 
passenger. The primary study we used to support this proposal does 
suggest that visual alerts may be more effective when the passenger 
sees them. It also notes that the visual alert may present an 
opportunity for communication between driver and passenger to prompt 
passenger belt usage.\163\ However, given that this rule requires an 
audible warning which can initiate this communication, the visual alert 
for the passenger would likely serve a supporting role, limiting its 
added benefit.\164\
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    \163\ DOT 2009 Seat Belt Study at pg. 66.
    \164\ We also note that this research noted the efficacy of 
audible alerts, but suggested not using an alert audible to drivers 
for the passenger's belt due to consumer acceptance concerns. 
However, as discussed in the NPRM and elsewhere in this final rule, 
research shows that consumers are now far more accepting of audible 
alerts. Therefore, the audible alert required by this final rule may 
serve to more effectively perform the communication role that this 
research suggested the visual alert to the passenger did. See DOT 
2009 Seat Belt Study at pgs. 67-68.
---------------------------------------------------------------------------

    It is also worth noting that under the requirements of this final 
rule there are only rare scenarios in which a visual alert is the only 
alert required to be active. We are requiring an indefinite audible 
alert if the vehicle is traveling at or over 10 km/h (6.2 mph) and a 30 
second minimum start-of-trip audible warning if there is an unbelted 
front passenger. Therefore, the only situation in which the visual 
alert is the only active warning is when the vehicle is traveling under 
10 km/h (6.2 mph) (or stopped) and the start-of-trip warning has 
elapsed. These situations are limited, and field data shows only small 
risks of injuries with severity above MAIS1 and almost no risk of 
injuries with severity above MAIS2 in frontal crashes at these speeds. 
Therefore, while research suggests the proposed visibility requirement 
might generate some safety benefits, given the structure of this final 
rule those additional benefits are hard to determine and may only be 
minor.\165\
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    \165\ Other research referenced in the NPRM that suggested a 
passenger visibility requirement might increase effectiveness was 
preliminary on this point and precluded firm conclusions. For 
example, some research noted that it is not evident to what extent 
improved effectiveness is due to direct message effects on the 
passenger and to what extent it may be due to more complex social 
dynamics between the driver and the passenger. We also cited studies 
that suggest that center console display locations might be more 
effective than dashboard display locations but were not conclusive 
due to other differentiating factors in the visual designs, such as 
character size, display size, and color, which may be covaried. See 
N. Lerner et al. (2007). Acceptability and Potential Effectiveness 
of Enhanced Seat Belt Reminder System Features. (Report No. DOT HS 
810 848). National Highway Traffic Safety Administration; DOT 2009 
Seat Belt Study.
---------------------------------------------------------------------------

    Regarding costs, we disagree with commenters about the size and 
scope of the costs associated with incorporating a signal visible to 
the passenger. However, we understand that, depending on how 
manufacturers decided to implement the proposed requirement, there 
could be more than de minimis costs for certain vehicles and these 
costs may outweigh the benefits of this requirement.\166\ Given this 
potential imbalance and our belief that most if not all of the desired 
benefits will be achieved by the indefinite audible warning, we are 
only finalizing that the front passenger's visual seat belt warning be 
visible to the driver.
---------------------------------------------------------------------------

    \166\ Given that many manufacturers currently provide visual 
alerts in the center console or in proximity to the passenger 
advanced air bag signal, we maintain our confidence that in many 
cases the cost would be limited and encourage manufacturers to 
voluntarily provide visual warnings to the passenger.
---------------------------------------------------------------------------

    This approach is consistent with the approach we took for the rear 
seat belt warning. In the NPRM, we did not propose that the rear seat 
visual warning be visible to the rear passenger because

[[Page 428]]

we did not believe that the benefits would outweigh the costs (viewed 
qualitatively). On the other hand, the NPRM did propose this for the 
front outboard passenger seat belt warning, because in that case we did 
expect the benefits to be greater than the costs. We now agree with the 
commenters, however, that because of the relatively low benefits; 
potentially non-de minimis costs for at least some vehicles; and the 
interplay between the visual and audible signals, that it is 
appropriate not to require that the visual warning for the front 
outboard passenger be visible to that passenger.
    We also wish to clarify the purpose of our reference, in the NPRM, 
to the advanced air bag visual signal because Honda's and Auto 
Innovators' comments suggest it may have caused some confusion. In the 
context of visibility, we referenced the advanced air bag telltale for 
the passenger only to indicate that it provides a location some 
manufacturers already use for a visual signal that is visible to the 
passenger. We did not intend to make any statements about the purpose 
of these signals within the structure of the FMVSS, their relative 
safety benefits, or the meanings they convey.
    Finally, we believe it is important to address two potential future 
situations where only requiring the visual warning to be visible to the 
driver would not be sufficient. The first is for dual-mode ADS-equipped 
vehicles that still have a driver's seat and driving controls.\167\ For 
such vehicles the driver's seat could remain unoccupied throughout the 
vehicle's operation. In this situation, limiting the visibility of the 
front seat warnings to the driver's seat would result in the passenger 
not seeing the warning. The second is for ADS-equipped vehicles without 
a driver's designated seating position. For the former, the final rule 
requires that the visual warning for the front outboard passenger seat 
belt must be visible from the front outboard passenger seat, and for 
the latter the final rule requires that the visual warning for each 
outboard designated seating position be visible from each outboard 
passenger seating position.
---------------------------------------------------------------------------

    \167\ An ADS-Equipped Dual-Mode Vehicle is defined as ``[a] type 
of ADS-equipped vehicle designed for both driverless operation and 
operation by a conventional driver for complete trips.'' SAE 
J3016_201806 Taxonomy and Definitions for Terms Related to Driving 
Automation Systems for On-Road Motor Vehicles.
---------------------------------------------------------------------------

5. Front Seat Occupant Detection and Seat Occupancy Criteria
    In the NPRM, we proposed a single compliance option that requires a 
start-of-trip audio-visual warning that lasts until the seat belt at 
any occupied front outboard seat is fastened. We proposed that the 
warning system consider the front outboard passenger seating position 
``occupied'' when an occupant or dummy that weighs at least 46.7 kg 
(103 lb) and is at least 139.7 cm (55 in) tall is seated in the seat, 
which matches the specification in FMVSS No. 208 for a person who is 
used as an alternative for the 5th percentile adult female test dummy 
for compliance testing of advanced air bag systems using static 
suppression. The NPRM also proposed giving the manufacturers the option 
to use a human being instead of using test dummies for testing 
purposes. Requiring occupant detection for front outboard passenger 
seating is consistent with Euro NCAP and IIHS ratings protocols, and 
the specification is consistent with Euro NCAP and the ECE R16 test 
procedures. IIHS does not specify any occupancy criteria for either 
front outboard seating positions.
    However, the NPRM was unclear about the occupancy requirements 
pertaining to the driver's designated seating position. The proposal 
included occupancy as a condition to trigger the warning for the 
driver's seat. The proposed test procedures also specified they applied 
to ``front designated seating positions.'' Thus, the test procedures 
would have applied to both front outboard seating positions and 
therefore may have required NHTSA to place a dummy or a human being in 
the driver's seat to establish occupancy for the test. However, we did 
not propose to define ``occupied'' for the driver's seat.\168\
---------------------------------------------------------------------------

    \168\ Occupant detection systems are currently used for front 
outboard passenger seating positions to comply with the advanced air 
bag requirements in FMVSS No. 208. However, this is not the case for 
driver's designated seating positions, which do not have the same 
considerations.
---------------------------------------------------------------------------

    Euro NCAP and IIHS allow occupancy for the driver's seat to be 
assumed. ECE R16 does not require the driver's seat to be occupied in 
its test procedures for the start-of-trip warning.
    For the change-of-status warning for the front outboard passenger 
seat, NHTSA did not propose that the seat must be occupied when the 
buckle is unfastened to trigger the alarm. On the other hand, IIHS 
protocol requires occupancy to trigger the change-of-status warning and 
ECE R16 allows the warning to be discontinued if the seat which 
triggered the warning is no longer occupied. This is also true of 
IIHS's and ECE R16's specification for the driver's seat.
Comments
    IEE, Honda, and Consumer Reports expressed support for requiring 
occupant detection for the front outboard passenger seat and for using 
occupancy as an element of the trigger for the front outboard passenger 
seat warning. Consumer Reports commented that it agrees with NHTSA's 
decision to align with Euro NCAP and require an occupant detection 
system for the front outboard passenger seat. Consumer Reports further 
explained that occupant detection is already widely deployed in these 
seats, either as part of an advanced air bag system or as part of a 
voluntary seat belt warning system, reinforcing the feasibility of 
equipping vehicles with occupant detection technology. IEE commented 
that it supports NHTSA's proposal to use the 5th percentile female as 
occupant detection criteria for the front outboard passenger seat 
because it aligns with the requirements for the sensors installed in 
the front passenger seats of vehicles complying with the advanced air 
bag requirements of FMVSS No. 208 and the same sensors are widely used 
for the voluntary front passenger seat belt warning systems.
    Honda commented requesting clarification on occupant detection for 
the driver's seat. Honda explained that the NPRM proposed that the 
start-of-trip warning for front outboard seats must activate ``if the 
seat is occupied,'' among other conditions. It commented that while 
this language is an appropriate condition for the front outboard 
passenger seat, it is unnecessary for the driver seat. Honda further 
commented that FMVSS No. 208 does not contemplate an occupant detection 
system because a driver is assumed to be present in a conventional 
vehicle. Honda recommended that this language be revised so that 
occupant detection requirements are not unintentionally prescribed for 
the driver's seat.
    Honda commented that if a speed threshold is not adopted for the 
change-of-status warning and the proposed transmission trigger is 
retained, NHTSA should also use occupant detection as a trigger.\169\ 
Honda believes this recommendation would resolve a

[[Page 429]]

misuse case in which someone buckles an empty seat and then unbuckles 
it. Honda expressed concern that under the proposal this type of 
scenario would require an unending alarm until the seat is re-buckled 
or the door is opened.
---------------------------------------------------------------------------

    \169\ Specifically, Honda recommended the change-of-status 
warning should be revised to read as follows: ``An audio-visual 
warning must activate when the ignition switch is in the `on' or 
`start' position, the vehicle is in forward or reverse drive mode, 
the seat is occupied (other than the driver's seat for vehicles with 
a designated driver seating position), and the status of the seat 
belt changes from in use to not in use, unless a front door on the 
same side of the vehicle as the seat belt triggering the warning is 
open, in which case a warning is not required and the system may 
consider this as a new trip with respect to that seat belt and reset 
the warning system.''
---------------------------------------------------------------------------

Agency Response
    NHTSA appreciates IEE's, Honda's, and Consumer Reports' support for 
requiring occupant detection for the front outboard passenger seat and 
for using occupant detection as an element of the trigger for the front 
outboard passenger seat warning. In addition, NHTSA received no 
comments in opposition to requiring vehicles to have occupant detection 
capability for front outboard passenger seats or for including front 
outboard passenger seat occupancy as one of the trigger conditions for 
the start-of-trip front outboard passenger seat belt warning. Likewise, 
NHTSA received no comments in opposition to specifying that the warning 
system consider a front outboard passenger seating position 
``occupied'' when an occupant or dummy that weighs at least 46.7 kg 
(103 lb) and is at least 139.7 cm (55 in) tall is seated in the seat. 
We are finalizing these provisions proposed in the NPRM with some 
revisions to the final regulatory text for clarity.
    With respect to a driver's seat, we have modified the proposal to 
clarify that the final rule does not require occupant detection for the 
driver's seat. The final rule does specify seat occupancy as one of the 
criteria for activation of all of the required front seat belt warnings 
(the visual warning and first- and second-phase audible warnings). 
However, the final rule also provides manufacturers with three 
compliance options for certifying that a driver's seat belt warning 
complies with these requirements. First, a manufacturer may certify 
that the system meets the requirements when the 5th percentile female 
test dummy described in part 572 \170\ of this chapter, as well as any 
larger dummy described in part 572, is seated in the seat. Second, a 
manufacturer may certify that the system meets the requirements when 
any human occupant that weighs 46.7 kg (103 lb) or more and is 139.7 cm 
(55 inches) tall or taller is seated in the seat.\171\ Third, a 
manufacturer may certify that the system meets the requirements when, 
instead of seating a dummy or human, the seat is considered occupied 
when the ignition switch is in the ``on'' or ``start'' position (or the 
propulsion system is activated). Similar to the front outboard 
passenger seat, the first two options would necessitate occupant 
detection technology and is technology-neutral with respect to the type 
of occupant detection technology used. The third option is consistent 
with our understanding of how these systems currently work as well as 
the approaches taken by Euro NCAP and ECE R16, and essentially allows 
the vehicle to infer that the driver's seat is occupied based on the 
fact that the vehicle has been turned on.\172\
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    \170\ 49 CFR part 572, subpart O.
    \171\ These are the bottom of the ranges specified in FMVSS 208 
S29.1(f) for the weight and weight of a human female who may be used 
in certain of the advanced air bag testing in place of the 5th 
percentile female dummy.
    \172\ To be clear, although a vehicle might be placed in these 
conditions without an occupant in the driver's seat, this is not a 
typical or likely scenario in the field because it is the driver 
that initiates these conditions (other than for vehicles without a 
driver's designated seating position).
---------------------------------------------------------------------------

    We are finalizing the rule this way for three reasons. First, 
requiring that the system activates only when the seating positions are 
occupied reduces false activations, which is important both for 
effectiveness and consumer acceptance. Although this is a larger 
concern for long or indefinite reminders, it is also relevant for the 
start-of-trip 30-second audible warning.
    Second, requiring occupancy for the driver's seat aligns the 
activation criteria for the front outboard passenger and driver's 
seating positions. Although Honda suggested that regulatory language is 
not necessary because driver's seat occupancy can be inferred, 
including it avoids confusion about when the warning needs to or can 
activate that could come from specifying different activation criteria.
    Third, the first and second compliance options provide 
manufacturers the flexibility to optimize systems for vehicles with a 
driver's designated seating position, but which may be ``on'' without a 
driver in the vehicle, such as dual-mode vehicles equipped with ADS but 
which still have a driver's seat and driving controls, as well as 
vehicles which use remote start. Because dual-mode vehicles could 
operate without an occupant in the driver's seat, we do not believe 
that inferring or assuming occupancy (which Euro NCAP and ECE R16 do) 
fully accounts for these vehicles. Without the option to use occupant 
detection, these vehicles could be required to initiate the driver's 
seat start-of-trip audible warning when the ignition switch is placed 
in the ``on'' position (or for an EV, when the propulsion system is 
activated. Such scenarios would therefore result in false positives. By 
allowing manufacturers to select the occupancy method, our approach is 
similar in application to the inference approach taken by Euro NCAP and 
ECE R16 for conventional vehicles, while being forward-looking for 
vehicles with ADS.
    To clarify, although adding an activation condition that the seat 
is occupied is a change to the current driver's seat belt warning 
requirements in FMVSS No. 208, we do not intend it to increase the 
stringency of the existing requirement for the driver's seat. The 
activation criteria for the current driver's seat belt warning do not 
include seat occupancy.\173\ Although the final rule introduces an 
occupancy criterion, it does not require occupant detection technology 
for the driver's seat. Indeed, we are not defining occupancy for the 
driver's seat as we have for the front outboard passenger seat, and the 
test procedure for the third compliance option does not require placing 
a test dummy (or human) in the driver's seat. Instead, under this final 
rule, manufacturers will have the discretion to choose the method by 
which the seat belt warning system determines whether the driver's seat 
is occupied in the context of seat belt warning activation. The third 
option enables systems that do not use occupant detection to certify to 
occupancy, while the first and second options enable manufacturers, if 
they so choose, to certify using a test dummy or a person 
(respectively), which may enable them to optimize a system for vehicles 
which may not have a person in the driver's seat at start-up.
---------------------------------------------------------------------------

    \173\ The activation criteria are (1) the vehicle's ignition 
switch is moved to the ``on'' position or to the ``start'' position; 
and (2) the driver's lap belt is not in use, as determined either by 
the belt latch mechanism not being fastened, or by the belt not 
being extended at least 4 inches from its stowed position.
---------------------------------------------------------------------------

    Finally, in response to a comment from Honda and to incorporate 
considerations for certain vehicles with ADS, the finalized regulatory 
text implements Honda's suggestion that the proposed change-of-status 
warning have occupancy as one of the triggering conditions. Because in 
the final rule, the visual warning and the second-phase audible warning 
function as a change-of-status warning, the regulatory text for these 
warnings includes seat occupancy as one of the triggering conditions.

C. Issues Common to the Front and Rear Seat Belt Warning Requirements

1. Modification of Start-of-Trip Warning Trigger Related Ignition 
Switch Position To Accommodate EVs
    As noted earlier, the NPRM proposed that the activation of both the 
front and rear seat belt warnings be triggered

[[Page 430]]

when, among other things, ``the ignition switch is placed in the `on' 
or `start' position.'' We also stated that this same condition appears 
in the existing driver seat belt warning requirements and is similar to 
ECE R16 and Euro NCAP.
    ECE R16 specifies that the first-level visual warning activates 
``when the safety-belt of any of the seats is not fastened and the 
ignition switch or master control switch is activated.'' \174\ In the 
NPRM we explained that we were not proposing to follow ECE R16 and 
refer to a ``master control switch'' because we did not believe it 
necessary to introduce this new term into FMVSS No. 208. The second-
level warning and the change-of-status warning have different triggers 
that are all based on the vehicle being in motion.
---------------------------------------------------------------------------

    \174\ Section 8.4.2.3.1.
---------------------------------------------------------------------------

    Euro NCAP similarly specifies that the visual signal activate 
``when the ignition switch is engaged (engine running or not)'' and the 
seatbelt is not fastened.'' \175\ Like ECE R16, the audible and change-
of-status warnings have different triggers, mostly related to the 
vehicle being in motion.
---------------------------------------------------------------------------

    \175\ Section 3.4.2.1 (front); section 3.4.3.1.1 (rear).
---------------------------------------------------------------------------

    The IIHS protocol similarly links the start-of-trip visual signal 
to the vehicle engine being ``turned on (i.e., powered and capable of 
propulsion).''
Comments
    Tesla requested that NHTSA broaden the definition of ``ignition 
switch'' to cover, for example, EVs which do not have one. As an 
example, Tesla noted that the ``ignition switch'' definition could be 
expanded to the moment when power is delivered to wheels to initiate 
vehicle motion. Tesla also requested clarity on the definition of 
``vehicle start-up.'' Tesla noted that this clarification is especially 
important for EVs.
    Honda had similar concerns, noting that electrified vehicles may 
differ from traditional internal combustion vehicles in that they may 
not have a distinct moment when the ignition switch is turned ``on'' or 
``started.'' Instead, Honda explained that these vehicles typically use 
automatic ``wake'' and ``sleep'' modes, which are activated based on 
various sensing and detection algorithms. While Honda preferred that 
NHTSA reconsider using the ignition switch as a trigger, it requested 
clarification on the start-of-trip warning if it is retained.
Agency Response
    We agree with Tesla and Honda that it would be helpful to provide 
clarity regarding warning activation for vehicles that do not have a 
traditional ignition switch or button with ``on'' and ``start'' 
positions or conditions, which could be the case for EVs. Therefore, we 
are adding regulatory text to address these vehicles.
    The start-of-trip warnings (front seat belt visual and first-phase 
audible warnings and rear seat belt warning) are required to activate 
when (among other things) the ignition switch is ``placed in'' the 
``on'' or ``start'' position or upon manual activation of the 
propulsion system, but before the vehicle is placed in ``possible 
active driving mode'' as defined by FMVSS No. 305.\176\ In developing 
this language, our goal was to specify a time in the start-up process 
to begin the start-of-trip warning for EVs that is roughly the same as 
the time we specified for vehicles with a conventional ignition switch 
such that the safety benefits for EVs would be the same as for 
ignition-equipped vehicles. For an ignition-equipped vehicle, while in 
the ``on'' position the vehicle electrical systems have been powered. 
While in the ``start'' position, the engine has been started and in 
this state a conventional vehicle is ready to be placed in a drive 
mode. An additional consideration is that, for an ignition-equipped 
vehicle certified to the option that the system determines the driver's 
seat is occupied through movement of the ignition switch to both the 
``on'' or ``start'' position, the driver is presumed to be in the 
vehicle to initiate the action. However, what actions by the driver 
initiate these modes, and whether a vehicle even has an analogous state 
to ``on,'' varies widely across EV models. For instance, some EVs, upon 
the door being opened, may activate some systems without providing 
electrical power to the motors, and may not be ready to be moved into a 
drive mode until another action is taken (such as depressing the brake 
pedal) which would typically entail the driver being seated. Others, 
however, may provide power to the motors upon the door being opened. 
Therefore, the agency attempted to incorporate language that 
approximates the following moment in a start-up sequence for an EV: an 
occupied outboard seat, ready to drive, but not yet in a drive mode. 
(This condition also closely approximates when the ignition of a 
conventional vehicle, certified to the option which uses the ignition 
switch ``on'' or ``start'' to indicate occupancy, is moved to the 
``start'' position). These requirements should equalize the safety 
benefits of the start-of-trip warning across vehicles with and without 
ignition switches.
---------------------------------------------------------------------------

    \176\ More specifically, the ``placed in'' language is used to 
specify the rear seat belt start-of-trip warning and the front seat 
belt first-phase audible warning but not the front seat belt visual 
warning. The front seat belt visual warning is required to 
``activate and remain active whenever the ignition switch is in the 
``on'' or ``start'' position (or the propulsion system is 
activated), the seat is occupied, and the seat belt is not in use'' 
(emphasis added). Because this visual warning is also serving as a 
change-of-status warning, this text refers to the ignition switch 
being ``in'' the on or start position, not being ``placed in'' on or 
start. However, in order for the ignition switch to be ``in'' the on 
or start position, it must first be ``placed in'' that position. 
Accordingly, this language necessarily includes the start of the 
trip. Similar reasoning applies to the EV-specific language for the 
front seat belt visual warning.
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    To accomplish this objective, we are adding language from FMVSS No. 
305; ``Electric-powered vehicles: electrolyte spillage and electrical 
shock protection.'' That standard defines ``possible active driving 
mode'' as ``the vehicle mode when application of pressure to the 
accelerator pedal (or activation of an equivalent control) or release 
of the brake system causes the electric power train to move the 
vehicle.'' \177\ As such, the mode is analogous to the vehicle being 
placed in a drive gear. Additionally, FMVSS No. 305, S5.4.6.1 Indicator 
of possible active driving mode, states that ``[a]t least a momentary 
indication shall be given to the driver each time the vehicle is first 
placed in possible active driving mode after manual activation of the 
propulsion system.'' This language implies that ``manual activation of 
the propulsion system'' precedes the ``possible active driving mode.'' 
In the final rule that added this language to FMVSS No. 305, we 
explained that the phrase ``when the vehicle is first placed in 
possible active driving mode after manual activation of the propulsion 
system'' was meant to indicate ``start up.'' \178\ Thus, we believe 
that the appropriate time in the start-up sequence of an EV (which is 
roughly analogous to the movement of the ignition of a conventional 
vehicle to the ``start'' position) is upon manual activation of the 
propulsion system, but prior to the vehicle being placed in ``possible 
active driving mode'' as defined by FMVSS No. 305. We understand that 
the process of driving system activation could vary from vehicle to 
vehicle but believe that the criteria in the final rule encompass all 
or most EV start-up sequences.\179\
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    \177\ NHTSA recently proposed to establish FMVSS No. 305a to 
replace FMVSS No. 305. The proposed FMVSS No. 305a refers to this 
state as ``active driving possible mode.'' However, the definition 
is the same. The terminology is originally from Global Technical 
Regulation No. 13.
    \178\ 82 FR 44945, 44956.
    \179\ We also anticipate that if a vehicle activates the 
propulsion system before the driver is inside the vehicle, the 
warning will be delayed until the driver has entered the vehicle to 
comply with the occupancy requirement, even if such a vehicle is 
certified to the first option.

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[[Page 431]]

2. Belt Use Criteria
    The current driver's belt warning requirements specify that a belt 
is ``not in use'' when, at the option of the manufacturer, either the 
seat belt latch mechanism is not fastened or the belt is not extended 
at least 10.16 centimeters (cm) (4 inches (in)) from its stowed 
position.\180\
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    \180\ S7.3(c). These are the definitions for manual belts. For 
automatic belts, see supra n.18.
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    We proposed amending these current criteria by specifying criteria 
related only to the seat belt latch mechanism. Specifically, we 
proposed that a manual seat belt would be considered ``not in use'' 
when the seat belt latch mechanism is not fastened, and ``in use'' when 
the seat belt latch mechanism is fastened. We proposed eliminating the 
spool-out sensor requirements because we tentatively believed that 
accommodating the use of a spool-out sensor would not allow for an 
objective or reliable criterion for the proposed change-of-status 
warning. For instance, there may be instances where the webbing may not 
readily spool back in when the seat belt is unbuckled (e.g., due to the 
use of shoulder belt routing features or the use of a belt positioning 
booster seat), and thus would not reliably trigger the change-of-status 
warning.
    The proposal differed from ECE R16,\181\ which gives manufacturers 
the option of using either a belt latch or spool-out sensor.\182\ Euro 
NCAP does not specify webbing spool-out criteria, and only refers to 
the status of the belt buckle. The IIHS protocol does not specify such 
criteria.
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    \181\ Section 2.46.
    \182\ Section 2.46.
---------------------------------------------------------------------------

Comments
    We received one comment from Auto Innovators, which generally 
agreed with the agency's proposal to enable compliance with the 
regulation through the use of seat belt latch sensors. Auto Innovators 
indicated that this proposal is consistent with ECE R16 and avoids 
introducing unnecessary complexity in redesigning rear belt reminder 
systems for the U.S. market. However, Auto Innovators requested that 
NHTSA update the definitions for S7.5 to ensure the regulation supports 
additional compliance options for classifying seat belt use, including 
systems that rely on camera-based sensors (or other advanced sensor 
technology). Auto Innovators commented that, currently, these options 
would not be permitted unless the belt use reminder system also 
included a belt latch mechanism.
Agency Response
    In the NPRM we stated that the current FMVSS No. 208 belt use 
criteria for the driver's seat belt warning requirements allow for the 
use of a belt latch or spool-out sensor, and that we were proposing to 
amend the belt use criteria to rely solely on the use of a belt latch 
sensor, and not provide requirements that would accommodate the use of 
a spool-out sensor. These statements were imprecise. The intent of the 
NPRM was not to restrict the types of technology manufacturers may use 
to determine whether or not an occupant is belted. The proposal was 
intended to identify objective criteria that NHTSA would use to 
determine whether or not a belt is in use. A manufacturer may use 
whatever technology it chooses to detect whether a belt is in use or 
not. However, regardless of the technology a manufacturer uses--whether 
it is a latch sensor or a camera--NHTSA, for the purposes of its 
compliance test, will consider a belt to be ``not in use'' when the 
belt latch is not fastened. Suppose, for example, that NHTSA tests a 
seating position equipped with a spool-out sensor for compliance with 
the change-of-status warning requirements. Suppose further that, in the 
test, a fastened belt is unfastened, but the spool-out sensor 
malfunctions so that the change-of-status warning does not activate. 
This would be considered an apparent test failure because the warning 
system did not activate when the status of the belt changed from in use 
to not in use (i.e., the belt latch became unfastened).
3. Visual Warning Characteristics
    NHTSA proposed different requirements for the rear and front seat 
belt visual warnings.
Rear Seat Belt Visual Warning
    We proposed that the visual warning be continuous or flashing and 
consist of icons or text and indicate how many or which rear seat belts 
are in use or not in use depending on the type of warning system. If 
icons are used to indicate how many or which rear belts are in use, we 
proposed that the icon(s) must be green; if icons are used to indicate 
to the driver how many or which belts are not in use, we proposed that 
the icon(s) be red. If text is used to indicate to the driver how many 
or which rear seat belts are in use or not in use, we proposed that the 
text contain the words ``rear belt(s) in use'' or ``rear belt(s) not in 
use.'' We also proposed to amend table 2 in FMVSS No. 101, ``Controls 
and displays,'' to clarify that the ``Seat Belt Unfastened Telltale'' 
depicted there does not apply to the rear seat belt reminder and to 
amend table 1 by adding in a row for the proposed rear seat belt 
warning.
    The requirement that the visual warning be continuous or flashing 
mirrors the current driver's seat belt visual warning requirement and 
is also consistent with ECE R16. However, we proposed to depart from 
the current driver's warning and from ECE R16 and standardize the color 
of the icons and text for the warnings to increase the likelihood that 
consumers would notice, recognize, and respond to the warnings. We 
believed that standardized colors and text will facilitate the 
interpretation of the signal. We departed from the current driver's 
warning requirements and followed ECE R16 by not requiring specific 
icons because we believe the choice of icons would largely depend on 
whether the system displayed the number of seat belts in use or which 
seat belts are in use.
    Another difference between the proposal and ECE R16 was that ECE 
R16 requires that the visual warning ``indicate at least all rear 
seating positions.'' We understood this requirement to mean that the 
visual warning must depict all the rear seating positions. To give 
manufacturers design flexibility, we did not propose to require that 
the warning depict all rear seating positions. Instead, the proposed 
requirements would allow the visual warning to consist of text or icons 
indicating how many or which rear seats are fastened or unfastened. For 
example, the warning text might consist of ``Middle and Right rear seat 
belts fastened.'' Another visual warning option would be the seat belt 
icon with an adjacent numeral indicating the number of rear seat belts 
fastened. Accordingly, the proposal would allow, but not require, use 
of a pictogram.
Front Seat Belt Visual Warning
    The current requirements for the driver telltale differ from those 
we proposed for the rear seat belts. As noted earlier in this document, 
some vehicles already equipped with a rear seat belt warning system in 
addition to a front seat belt warning system combine the two (such as 
with a pictogram depicting all seating positions). These vehicles also 
must continue to meet the current requirements for the driver seat belt 
telltale. These require that the warning be continuous or intermittent 
(flashing) and display either the identifying symbol or the words 
(``Fasten Belts'' or ``Fasten Seat belts'') specified in table 2 of 
FMVSS No. 101. Thus, vehicles that

[[Page 432]]

currently have a rear seat belt warning system using a pictogram also 
provide a separate, FMVSS No. 101-compliant telltale for the driver's 
seat belt warning.
    We proposed generally retaining, for both front outboard seats, the 
current visual warning requirement for the symbols or text specified in 
FMVSS No. 101 because these visual warnings have been in place for 
decades and we believe that consumers are accustomed to them. Removing 
the requirement may have unintended negative effects if drivers and 
front passengers are not accustomed to new visual warnings or do not 
find the new visual warnings as effective. This means that if a 
manufacturer chose to use a pictogram format to comply with the new 
rear seat belt warning requirements, it could--as many manufacturers 
are already doing--include the front seat belts in this pictogram, but 
it would also have to provide the telltale specified in FMVSS No. 101, 
table 2. As we explained earlier, we proposed that the telltale for the 
front outboard passenger seat would also have to be visible to that 
passenger. We also proposed to require that for telltales associated 
with multiple front outboard seats, the seat with which each telltale 
is associated must be clearly recognizable to the driver and front 
outboard passenger.
Comments
    Regarding the rear seat belt warning telltale, several commenters 
suggested that NHTSA should require visual warnings that indicated all 
rear seating positions. Consumer Reports encouraged NHTSA to align with 
ECE R16 by requiring that visual warnings indicate all rear seating 
positions. It argued that although a seating map may require a somewhat 
more sophisticated display, it is preferable because it offers the 
driver complete information while facing forward. Auto Innovators and 
HATCI commented that contextual displays or pictograms are generally 
feasible and useful. Auto Innovators also added that several automakers 
have already implemented seat belt warning systems that use a 
contextual display diagram to provide the driver with information on 
the status of passenger belt use.
    Some commenters such as HATCI and NADA also explicitly requested 
flexibility in telltale design. Rivian requested flexibility in 
choosing icons for the front and rear seat belt reminder warnings and 
that NHTSA not require the FMVSS No. 101 icon for the front seat belt 
reminder warning icon. HATCI supported providing manufacturers 
flexibility in the rear seat telltale and commented that the use of a 
pictogram for the rear seat belt warning will allow for more 
flexibility for different vehicles and vehicle sizes. Consumer Reports 
also commented that, within a seating map, easily recognizable icons 
are preferable to text, as icons enable a driver to assess seating 
usage at a quick glance, without having to read. Consumer Reports also 
argued that easily recognizable icons are also useful for drivers for 
whom English is not a first language.
    NSC commented that seat belt warning systems have different 
operational parameters, generic names, and limitations across 
manufacturers and sometimes even across the same manufacturer's varying 
models. It urged NHTSA to consider standardizing generic nomenclature 
as well as standardizing warning and icon symbols to reduce driver 
confusion.
    Mercedes commented that, based on the requirements in the proposal, 
there would be technical challenges with providing the driver seat belt 
status information within the instrument cluster for seating 
configurations that can hold up to 13 rear passengers.
    Auto Innovators commented that in addition to issues related to the 
symbol, standardizing the text to say ``Rear belt(s) in use'' or ``rear 
belt(s) not in use'' may be difficult to package on the instrument 
cluster. Auto Innovators requested that the agency permit the use of 
either the word ``Rear'' or a corresponding number next to the seat 
belt icon referencing which seating position is unbuckled as an 
acceptable alternative. It noted that this request is similar to the 
number 2 notation used next to the air bag symbol for specifying the 
icon is relevant to the passenger-side air bag.
    Auto Innovators and Rivian supported harmonizing the telltale 
symbol with ECE R16. However, Auto Innovators, Mercedes, Honda, NADA, 
and HATCI requested that the agency also permit the use of a neutral 
color (e.g., gray) that could be used to display either an unoccupied 
seat or, for positive only systems, a seat that remained in the 
unbuckled condition. For negative only and full-status systems, the 
symbol would be required to be red to indicate occupancy in an unbelted 
condition. Auto Innovators commented that this approach is being widely 
adopted in the U.S. and other markets and is understood by consumers. 
Accordingly, Auto Innovators requested aligning the color requirements 
with ECE R16. Mercedes expressed concern that red icons should not be 
used if the buckle has not changed status because there is no critical 
information to be shared with the driver, and red could provide a false 
alarm and lead to desensitization if it is always on. Hyundai also 
noted that it is not aware of consumer complaints or requests to 
deactivate existing visual seat belt displays.
    Auto Innovators and Rivian argued that, given the prevalence of 
red-green color vision deficiency among the U.S. population, the 
requirement should not limit the ability of manufacturers to implement 
approaches that may be more easily understood or recognized by 
consumers. Auto Innovators indicated that the rule should include 
allowances for providing a visual diagram of all seating positions 
whereby belt use can either be communicated through the presence or 
absence of the belted symbol or through the use of a bi- or tri-color 
scheme consisting of green and red symbols to indicate belt status, and 
either gray or white symbols to denote either unoccupied seats (for 
systems with occupant detection) or unbelted seats (for systems without 
occupant detection) at the manufacturer's discretion.
    Rivian and GM also noted that permitting the use of other icons, 
such as a checkmark to indicate belts in-use and a ``x'' to indicate 
belts not-in use for both front and rear occupants seat belt status, 
could help mitigate the challenges with red and green coloration if 
manufacturers were permitted flexibility in the use of different icons 
for both the front and rear locations. Rivian further commented that 
the agency proposed that the ``Seat Belt Unfastened Telltale'' 
requirement, depicted in table 2 in FMVSS 101, Controls and displays, 
does not apply to the rear seat belt reminder. Rivian stated that its 
interpretation of the proposal is that manufacturers may use other 
icons such as a checkmark to indicate belts in-use and a ``x'' to 
indicate belts not in use. Rivian recommended that for consistency and 
occupant recognition, NHTSA allow this design flexibility for the front 
and rear belt reminders. It stated that this commonality is 
particularly important for pictogram designs driven by other protocols, 
such as IIHS, and would help address the color issue.
    GM also indicated that glanceability can be significantly improved 
through redundancy, which involves combining both color and forms as 
cues. It cited several studies in support of this assertion. GM argued 
that the symbols, along with the colors of green representing success, 
red representing failure, and gray representing an empty seat, can 
ensure clear communication of the belt status to the customers.
    Honda commented requesting clarification on the proposed

[[Page 433]]

requirement that for telltales associated with multiple front outboard 
seats, the seat with which each telltale is associated must be clearly 
recognizable to a driver and to any front outboard passenger. Honda 
indicated that it understands the final rule to require the telltale to 
use the identifying symbol or words specified in table 2 of FMVSS No. 
101 and to also allow the use of a single telltale to be associated 
with multiple front outboard seats. However, Honda suggested that the 
``clearly recognizable'' language may be contrary to Honda's 
understanding. Honda commented that it is not aware of any consumer 
concerns with distinguishing the front seat positions to which this 
single telltale is associated and believes that maintaining this 
standardized approach will facilitate continued consumer understanding. 
Honda also expressed concern about the cost burden if this requirement 
cannot be met with a single telltale and concern about the extra visual 
indicator overriding other warnings. Honda provided a list of telltale 
designs and requested clarity regarding whether they would meet the 
``clearly recognizable'' language. Honda also requested that the rule 
allow for a single telltale to display all seating positions.
Agency Response
    NHTSA generally agrees with the commenters who recommended that the 
rule provide manufacturers flexibility, but we do believe that some 
standardization of the visual warning would provide safety benefits. We 
note that while many of the requirements discussed below apply only to 
the rear seat belt warning, manufacturers may choose to integrate the 
warnings for the front and rear, so we are presenting this material 
together.
Requirements for the Rear Seat Belt Visual Warning
    We disagreed with Consumer Reports and have decided to depart from 
ECE R16 and not require that all rear seating positions be depicted. 
While such a requirement would provide the driver with more 
information, we have decided to give manufacturers design flexibility 
(such as by using text, number of seats buckled/unbuckled, etc.) so 
that they can decide how to optimize design for each particular 
vehicle.
    One situation in which this flexibility would be particularly 
important is for buses and vans with many rear seats. As we explain 
above (see Section VI.A.1, Applicability) one difference between the 
final rule and ECE R16 is that the final rule applies to small buses 
such as 15-passenger vans, while the ECE R16 rear seat belt warning 
requirements do not apply to vehicles with more than 9 seats (including 
the driver). As we acknowledged in the NPRM, vehicles with a larger 
number of rear seats, such as passenger vans and buses, may encounter 
visual signal complexities; not dictating specific types of signals 
should provide manufacturers with adequate flexibility to address these 
types of issues. We believe these vehicles, in particular, would 
benefit from the option to indicate how many rear seats are fastened; 
for example, a visual warning option for vehicles with multiple rows 
would be the seat belt icon with an adjacent numeral indicating the 
number of rear seat belts fastened. We recognize that such a 
requirement would require more space if a manufacturer decides to 
display a warning with multiple rear rows and may entail redesign of 
the instrument panel or display space. We note that while one commenter 
(InterMotive) indicated that it has an aftermarket solution for a rear 
warning system for such higher-occupancy vehicles, NHTSA is not aware 
of any new vehicles equipped with such systems. In light of the current 
state of the market, we are providing two years of lead time and have 
attempted to specify the final requirements in such a way as to provide 
manufacturers as much flexibility as possible so that they can devise 
solutions for their specific vehicles.
    Similarly, with respect to the visual warning for the rear seat 
belts, we have decided to finalize the proposal and permit both icons 
(symbols) and text. However, we are modifying the proposal and not 
specifying standardized text. We are also clarifying that numbers may 
also be used in addition to symbols, and are finalizing the proposal to 
standardize colors for symbols (and numbers). While we recognize that 
standardized icons would help drivers recognize the icon when driving 
different (multiple) vehicles, we believe there are even greater 
benefits to providing manufacturers with flexibility; manufacturers can 
optimize the visual warning based on the vehicle design and consumer 
preferences, particularly since there are a range of different 
approaches being used already. (Icons appear to be prevalent in newer 
vehicles.) We have also decided to allow the use of text and/or numbers 
other than what we proposed for the rear seat belt warning to afford 
manufacturers as much flexibility as possible. We note that the 
effectiveness of numbers depends on how well the design is executed; 
for example, one commenter provided an example showing that it can be 
confusing. Accordingly, manufacturers should not assume drivers will be 
familiar with seat numbers when developing their warning. On the other 
hand, as discussed below, we are standardizing colors to facilitate the 
interpretation of the signal.
    We have decided to finalize the requirements for the color of 
symbols or numbers if used to indicate how many or which rear seat 
belts are (not) in use. After considering the comments, NHTSA concludes 
that the advantages of standardizing colors outweigh the drawbacks. We 
believe that standardizing colors limits confusion and allows for 
faster interpretation. We note that the FMVSS generally do not address 
color blindness. Importantly, however, this requirement does not 
prevent manufacturers from designing the visual warning so that it can 
be perceived by colorblind consumers. For example, OEMs could design 
systems using a combination of color and a positive/negative symbol. 
Moreover, we agree with GM that such redundancy can aid in rapid 
interpretation of the warning (glanceability). Use of a symbol without 
a color would be prohibited but we believe this requirement is 
warranted because use of a color would aid in faster identification of 
buckled/unbuckled seats for most users. Similarly, the final rule 
provides that the change-of-status visual warning may use the same 
telltale as the start of trip warning, provided that the color of an 
illuminated symbol or number used to indicate to the driver how many or 
which rear seat belts experienced a change of status from in use to not 
in use is red.
    NHTSA is, however, clarifying that the proposed requirements were 
not intended to prohibit the use of gray or other neutral colors or 
signifiers (such as a non-illuminated indicator) to denote seats that 
are unoccupied or to denote a seating position for which information 
about buckle status is not being conveyed (e.g., using gray to indicate 
seating positions at which the belt is fastened in a negative-only 
system that does not use occupant detection). This approach is being 
widely adopted in the U.S. and other markets and, in our view, is 
understood by consumers. To more clearly convey our intent here, the 
final rule explicitly provides that a visual warning is not required 
for (1) an unoccupied seat if the system is able to determine whether 
or not a seat is occupied; (2) a seat belt that is in use in a system 
designed to indicate to the driver how many or

[[Page 434]]

which rear seat belts are not in use; and (3) a seat belt that is not 
in use in a system designed to indicate to the driver how many or which 
rear seat belts are in use. Therefore, the color requirements will not 
apply to symbols or numbers that are conveying any of these three types 
of information, because such information is not considered part of the 
required warning.
Requirements for the Front Outboard Seat Belt Visual Warning
    We have decided to finalize the proposal to maintain the FMVSS No. 
101 icon for the driver's seat belt warning and extend it to the front 
outboard passenger seat belt warning. We continue to believe, as we 
explained in the NPRM, that this requirement is beneficial because 
these visual warnings have been in place for decades and we believe 
that consumers are accustomed to them. It is also in line with ECE R16, 
which requires the same icon for the front seats.\183\ At this time we 
therefore do not see a need to remove this requirement.
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    \183\ Section 8.4.3.2.
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    As stated in Section VI.B.4, in response to the comments, NHTSA has 
modified the proposal so that the final rule requires that the front 
outboard passenger visible warning be visible only to the driver, 
except for two potential future situations where only requiring the 
visual warning to be visible to the driver would not be sufficient. The 
first is for dual-mode ADS-equipped vehicles that still have a driver's 
seat and driving controls. For such vehicles the driver's seat could 
remain unoccupied throughout the vehicle's operation. In this 
situation, limiting the visibility of the front seat warnings to the 
driver's seat would result in the passenger not seeing the warning. The 
second is for ADS-equipped vehicles without a driver's designated 
seating position. For the first, the final rule requires that the 
visual warning for the front outboard passenger seat belt must be 
visible from the front outboard passenger seat, and for the second the 
final rule requires that the visual warning for each outboard 
designated seating position be visible from each outboard passenger 
seating position.
    Accordingly, while we proposed that for telltales associated with 
multiple front outboard seats the seat with which each telltale is 
associated must be clearly recognizable to a driver and to ``any front 
outboard passenger,'' the final rule instead requires that a visual 
warning associated with multiple front outboard seats must ``clearly 
identify the seating positions for which the warnings are intended.'' 
Honda's comment concerned the proposed ``clearly recognizable'' 
language. NHTSA clarifies that this final rule does not require a 
separate telltale (i.e., a telltale with the identifying symbol 
specified in table 2 of FMVSS No. 101) for each front seating position 
nor does it require any particular visual warning design. We believe 
that one telltale which distinguishes which position is unbuckled would 
be acceptable, as would separate telltales, as long as the visual 
warning clearly identifies the seating position(s) for which the 
warning(s) is intended. We leave it to manufacturers to design their 
systems such that they can certify in good faith that they meet the 
standard, and the final rule does not further specify how to do so to 
preserve that design flexibility.184 185
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    \184\ It is possible to design single telltales that comply both 
with FMVSS No. 101, Table 2 and the requirement that for telltales 
associated with multiple front outboard seats, the seat with which 
each telltale is associated must be clearly identified because FMVSS 
No. 101 allows supplemental symbols and information. See S5.2.3 
(``Supplementary symbols, words, or abbreviations may be used at the 
manufacturer's discretion in conjunction with any symbol, word, or 
abbreviation specified in Table 1 or Table 2.'').
    \185\ We note that the proposed ``clearly recognizable'' 
language was identical to language currently found in S19.2.2 of 
FMVSS 208. That language was added to the standard in a 2022 final 
rule on Occupant Protection for Vehicles with Automated Driving 
Systems. In the preamble to that final rule, we explained that that 
provision would not permit a single telltale for both front outboard 
seating positions: ``[t]he Alliance and GM requested allowing a 
single telltale for both front outboard seating positions. It is 
NHTSA's position that, while a single telltale unit that 
distinguishes both indicators would be acceptable, a single light 
indicating the suppression status of both air bag systems, but not 
distinguishing their individual state of suppression would not. 
Separate suppression telltales clarify which associated seating 
position is suppressed, allowing the corresponding passenger to 
respond to the information with appropriate action.'' 87 FR 18560. 
While NHTSA continues to believe that requiring separate telltales 
for two front seating positions was justified for the reasons given 
in that rulemaking, after considering the comments, we believe that 
it would be appropriate for this final rule to allow a single 
telltale for two seating positions, as long as the visual warning 
clearly identifies the seating position(s) for which the warning is 
intended.
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4. Interaction With Other Vehicle Warnings
    NHTSA proposed that neither the visual nor the audible component of 
the seat belt warning for the both the front and rear seat belts could 
be overridden by other warnings for the required durations.\186\ This 
proposal was consistent with the current requirements in FMVSS No. 101 
for the driver's seat belt telltale which specify, among other things, 
that the seat belt telltale must displace any other symbol or message 
in that common space while the underlying condition for the telltale's 
activation exists.\187\ We did not believe that the seat belt warning 
requirements would interfere with warnings for other safety systems 
because we believed that those other warnings have dedicated warning 
signals, and that manufacturers would have enough flexibility to 
determine the best way to implement the various warnings. For instance, 
warnings for another potential safety risk may be more aggressive than 
those for the seat belts. With regard to available space, we proposed 
that the visual signal might be displayed as a telltale on the 
instrument panel or on the vehicle's information display screen. We 
noted that manufacturers would also have to determine whether the 
driver and rear passenger seat belt visual warning would be treated the 
same. Neither ECE R16 nor Euro NCAP address interaction with other 
vehicle warnings.
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    \186\ 88 FR 61674 61742-43 (Sept. 7, 2023) (proposed front and 
rear warnings at S7.5(b)(5) and S7.5(c)(5), respectively). Proposed 
S7.5(c)(1)(v), which also required that the rear seat belt visual 
warning not be overridden, was redundant. This issue is discussed 
later in this document.
    \187\ 49 CFR 571.101, S5.5.5. See also S5.5.2 (``The telltales 
for any brake system malfunction required by Table 1 to be red, air 
bag malfunction, low tire pressure, electronic stability control 
malfunction (as of September 1, 2011), passenger air bag off, high 
beam, turn signal, and seat belt must not be shown in the same 
common space.'')
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Comments
    A number of commenters expressed concern about the proposed 
requirement that the visual warning could not be overridden. HATCI, for 
example, commented that if manufacturers display the rear telltale in 
the visual information screen, they would display the rear seat 
pictogram in the same location often used to display advanced safety 
feature warnings such as Forward Collision Warning (FCW) or Automatic 
Emergency Braking (AEB) and may impede or prevent those warnings. Auto 
Innovators commented that several automakers currently have warning 
systems that use a contextual display diagram to provide the driver 
with information on the status of passenger belt use. However, they 
noted that these displays can be relatively large and necessitate 
sharing limited display space in the instrument panel, and therefore 
may need to be temporarily overridden to convey other safety urgent 
warnings.
    To address this concern, Auto Innovators, NADA, Nissan, Rivian, 
Honda, and HATCI requested that NHTSA remove the proposed override 
requirements, or provide a general

[[Page 435]]

exception that manufacturers have discretion to prioritize other safety 
relevant warnings as needed. Auto Innovators commented that NHTSA 
should harmonize with ECE R16 and remove the override requirements for 
both front and rear row seating positions to provide flexibility for 
manufacturers to implement in-vehicle displays such that important 
information can temporarily override the reminder alert on an as-needed 
basis.
    Specific to the front reminder, HATCI recommended allowing a 
warning displayed in the vehicle's information display screen to be 
temporarily suppressed when it is necessary to alert or redirect the 
driver's attention to an advanced safety warning related to vehicle 
operation. On the other hand, Honda commented that the front seat belt 
unfastened telltale, as currently specified in FMVSS 101, should remain 
a dedicated warning that cannot be interrupted.
    Auto Innovators supported providing manufacturers with the 
flexibility to prioritize safety alerts for the duration that other 
safety critical warnings may be required. Honda and Mercedes commented 
that it is not essential for the rear seat belt visual warning to be 
provided uninterrupted 100 percent of the time because it is 
supplemental to the audible warning. Because of this redundancy, in 
Auto Innovators' view, other critical information should be allowed to 
be presented to the driver.
    Honda and Auto Innovators urged NHTSA to allow visual warnings, 
with the exception of the dedicated telltale currently specified in 
table 2 of FMVSS No. 101, to be temporarily overridden by system 
failure warnings and warnings requiring an urgent response. Honda 
stated that doing so would allow existing high-visibility display 
locations to convey the most urgent warning to the driver, while 
retaining a baseline warning that would convey whether there is an 
unbelted occupant. Honda and Auto Innovators argued that this approach 
would also align with the current FMVSS No. 101 requirements prescribed 
in section 5.5 where the seat belt unfastened symbol or text (``Fasten 
Seat Belts'') must have a dedicated telltale, but other supplemental 
warnings may be displayed in a common display space. Auto Innovators 
requested additional clarification on the applicability of the override 
prohibition and whether it applies to suppression of the visual 
warning, audible warning, or both. It requested that both be able to be 
overridden.
    Honda and Auto Innovators also commented that the proposal would 
necessitate several changes to systems currently deployed without any 
substantiated benefit. First, Honda explained that the visible display 
space for the driver, particularly the instrument cluster, is already 
allocated. Therefore, the proposal would require either the 
implementation of a new standalone indicator, dedicated to only the 
rear seating positions, or repositioning the warning to a less ideal 
area of the instrument cluster. Honda indicated an example in which it 
may become necessary to minimize the seat belt warning size in order 
for the warning to have a dedicated space. Honda and Auto Innovators 
argued that these changes would require substantial redevelopment and 
that implementing such a system within the proposed time frame would be 
impractical.
    Rivian commented that the proposal does not contain volume or tone 
requirements for the chime. Rivian inquired about whether a change in 
volume for the audible chimes during the required duration of the 
warning to increase the volume of a competing safety-critical warning 
would or would not constitute an override.
    Finally, InterMotive commented that the proposed requirements 
should not create interaction issues between different vehicle systems. 
InterMotive noted that it has a product in the market that would comply 
with the proposed requirements and that there have been no issues with 
the product interacting with other warning systems.
Agency Response
    NHTSA has decided to finalize the proposal that the visual seat 
belt warning not be overridden by other vehicle warnings. However, in 
response to the comments we have decided to modify the proposal and 
permit the audible component of the front and rear seat belt warnings 
to be overridden by certain safety-critical warnings that require the 
driver to take some immediate action.
Visual Warning
    We are finalizing the proposal that the visual seat belt warnings 
not be overridden by other vehicle warnings. FMVSS No. 101 has long 
required that the driver's seat belt visual warning not be displaced by 
other warnings. We do not believe that these amendments to the seat 
belt warning requirements should lead us to alter this 
requirement.\188\ There are several reasons for this conclusion.
---------------------------------------------------------------------------

    \188\ The final rule does not prohibit manufacturers from 
designing vehicles so that a crash-imminent visual warning, or other 
visual warning that alerts the driver to take some immediate action, 
is more prominent than the seat belt warning.
---------------------------------------------------------------------------

    First, while the final rule requires an additional telltale for the 
rear seat belt warning, we believe that there is sufficient room on the 
vehicle's instrument panel or on the vehicle's information display 
screen. Most safety telltales have a dedicated icon and display space. 
In particular, we believe most critical safety warnings have dedicated 
space for their respective icons/symbols. NHTSA's understanding of 
contemporary vehicle designs is that they are more likely to feature a 
larger combined display instead of separate instrument panels and 
center stack displays, so there should be sufficient space to present 
two simultaneous visual warning signals separately. Whether prohibiting 
override of the seat belt warning would require redesign of the display 
area depends on whether the competing warnings are supplemental. If 
they are, then not allowing the seat belt warning to be overridden 
would not necessarily require redesign; while the supplemental warning 
could not be displayed in the space common to the seat belt warning, 
the primary warning could still be displayed. However, if the competing 
warning were not simply supplemental, then we acknowledge that redesign 
would be necessary. If an OEM chose to redesign in such a way as to 
have dedicated space for all the different warnings, we believe it 
would be possible, but acknowledge it might be burdensome. However, we 
believe the final rule provides manufacturers with ample flexibility in 
terms of what types of warnings are allowed and not dictating a 
specific location for the warning.\189\
---------------------------------------------------------------------------

    \189\ With respect to InterMotive's comment, its aftermarket 
product has a separate display, so it is not relevant to this 
discussion.
---------------------------------------------------------------------------

    Second, it would likely be rare for the seat belt warning and other 
warnings to occur at the same time. With respect to the front seat belt 
warning, because these systems have been in place for decades, and 
because FMVSS No. 101 has long required that the driver's seat belt 
visual warning not be displaced by other warnings, we believe these 
visual warnings have their dedicated display space already and thus do 
not warrant allowing override for other safety critical warnings 
because the warnings can activate simultaneously. With respect to the 
rear seat belt start-of-trip warning, given the relatively short 
duration (30 seconds) and timing (ignition on or start), it should be 
relatively unlikely for another safety-critical warning to be necessary 
in that time. With respect to the rear seat belt change-of-status 
warning, because we are requiring that the start-of-trip visual

[[Page 436]]

warning not be overridden, we believe that although a safety critical 
warning may need to activate at the same time as the change-of-status 
warning, the warnings will have been designed to not be in the same 
space and they can both activate simultaneously.
    Third, extinguishing the seat belt reminder visual warning during 
other warnings might confuse drivers. If they notice that the warning 
deactivates and then re-activates with no corresponding change in seat 
belt status, they may believe the system is malfunctioning.
    We are also declining to adopt Honda's suggestion to allow override 
of the larger warning and rely on the use of the single FMVSS No. 101 
front seat belt warning telltale for all seats. We believe that this 
would confuse the driver, because the driver would not know what seat 
the warning applies to. The current FMVSS No. 101 seat belt warning 
requirements apply only to the driver's seat belt warning (with this 
final rule extending them to the front outboard passenger's seat and 
the rear seats), and not to other seating positions.
Audible Warning
    The final rule, however, does permit the audible component of the 
seat belt warnings to be overridden by certain safety-critical warnings 
that require the driver to take an immediate action. As an initial 
matter, we clarify that the proposal would have prohibited the audible 
component of the reminder from being overridden as well as the visual 
component.\190\ The proposed regulatory text contained a redundant 
provision that required that the rear seat belt visual warning not be 
overridden by other visual warnings that was likely the source of 
confusion.\191\ However, in response to the comments, NHTSA has decided 
to permit the seat belt audible warning to be overridden by certain 
warnings. Specifically, NHTSA believes it is reasonable to allow a 
pause in the audible seat belt warning to allow for a safety critical 
warning that requires the driver to take some immediate action. This 
includes crash avoidance warnings that require immediate action by the 
driver, such as braking or steering. With respect to Rivian's comment, 
a change in volume of the chime would not constitute an override of the 
warning because the final rule does not regulate audible warning 
volume. See Section VI.C.5, Audible Warning Characteristics.
---------------------------------------------------------------------------

    \190\ See 88 FR 61674, 61742 (Sept. 7, 2023) (Proposed 
S7.5(b)(5) and S7.5(c)(5)).
    \191\ See 88 FR at pg. 61743 (Proposed S7.5(c)(v)).
---------------------------------------------------------------------------

5. Audible Warning Characteristics (Other Than Duration)
    The NPRM proposed a variety of specifications for the audible 
warnings. The proposed requirements were different for the front and 
rear audible warnings.
    For the rear change-of-status warning (which had a minimum required 
duration of 30 seconds), we proposed that the audible signal could be 
intermittent or continuous and that if intermittent, inactive periods 
longer than 3 seconds would not be counted toward the total duration of 
the audible warning. We did not propose to specify minimum duty cycle, 
chime frequency, or warning cycle.
    For the front seat belt audible component of the start-of-trip and 
change-of-status warnings, we proposed more detailed requirements than 
for the rear seat belt audible warning because the minimum duration was 
much longer (essentially until all front outboard occupants were 
belted, for both the start-of-trip and change-of-status warnings). We 
proposed that the front seat belt audible warning may be continuous or 
intermittent. If intermittent, we proposed that, when active, the 
audible warning must be continuous or have a chime frequency of at 
least 0.5 Hz and a duty cycle of at least 0.2. The proposal defined, 
for an intermittent audible warning, the terms warning cycle, chime 
frequency, and duty cycle. The proposal defined ``warning cycle'' as 
consisting of period(s) when the warning is active at the chime 
frequency or continuously, and inactive period(s). A warning cycle 
would begin with an active period and would be 30 seconds in duration. 
``Chime Frequency'' meant the repetition rate for an intermittent 
audible warning when the warning is active. ``Duty Cycle'' meant the 
total amount of time an intermittent audible warning is active during a 
warning cycle at the chime frequency or continuously, divided by the 
total warning cycle duration (30 seconds). These requirements were 
largely based on the results of a 2012 IIHS study on duty cycles.\192\ 
IIHS test protocols do not specify a duty cycle. We proposed that the 
same audible warning may be used for all seats. We did not propose a 
limit on the maximum duration of audible gaps for the purposes of 
determining the warning's total duration because we did not propose a 
finite minimum duration.
---------------------------------------------------------------------------

    \192\ Kidd, D.G. (2012). Response of part-time belt users to 
enhanced seat belt reminder systems of different duty cycles and 
duration. Transportation Research Part F, 15, 525-534.
---------------------------------------------------------------------------

    These proposals deviated from Euro NCAP and ECE R16's 
specifications in some ways. Euro NCAP specifies that for the front 
seats the audible signal must not have gaps greater than 10 seconds, 
and that gaps longer than 3 seconds would not count toward the 
warning's total duration. The final audible signal must be ``loud and 
clear'' for the driver. The 10 second limit, in addition to its 
specification of a 3 second gap limit toward the calculation of the 
warning's total duration, would not be sufficient to ensure a 0.20 duty 
cycle warning. ECE R16 also does not count warning gaps longer than 3 
seconds toward the required minimum warning duration requirement.
Comments
    Auto Innovators and NADA requested that NHTSA harmonize with ECE 
R16, which provides increased flexibility for manufacturers determining 
the characteristics of both front and rear row belt reminder alerts.
    Auto Innovators recommended that the agency avoid defining 
characteristics (such as the warning and duty cycles) that would 
prevent a manufacturer from implementing different alerts such as 
escalating alerts.
    Mercedes commented that its current seat belt reminder system 
design starts a baseline alert once the criteria have been met; if the 
conditions of the seat belts at the occupied seats have not changed 
after 30 seconds, the system will escalate the warning. Mercedes stated 
that this approach does not cause excessive annoyance to drivers and 
does not negatively affect the efficacy of the warning system. Mercedes 
urged NHTSA to remove the continuous series requirement for 
manufacturers to develop systems with effective escalating alerts. 
Consumer Reports also commented that audible warnings should escalate.
    Honda sought clarity on the ``warning cycle'' requirements as 
proposed. Additionally, it encouraged the agency to consider whether 
adopting a warning that is continuously active (i.e., 100 percent duty 
cycle) for a definite duration of 90 seconds would be as effective as 
the proposal to require an indefinite warning with a minimum duty cycle 
of 20 percent. Honda explained that its experience is that a continuous 
90-second chime is sufficiently persistent and might offer greater 
effectiveness compared to an indefinite warning that delivers only a 6-
second chime followed by a 24-second pause between chimes. IIHS, 
identifying the same concern, urged NHTSA to require auditory signals 
to be separated by no more than 3 seconds in addition

[[Page 437]]

to requiring a minimum 20 percent duty cycle.
    IIHS, supported by MADD, Advocates and Public Citizen, and the 
National Association of Mutual Insurance Companies (NAMIC), requested 
that NHTSA set minimum requirements for the volume and fundamental 
frequency of an auditory reminder to ensure it is ``loud and clear'' 
and will be noticed by vehicle occupants. IIHS provided supporting 
materials for the volume and fundamental frequency minimums that it 
requires. It also commented that NHTSA should require the same auditory 
reminder characteristics (e.g., volume, fundamental frequency, gap 
between signals, duty cycle) for the front and rear rows. It stated 
that consistency makes the requirements easier to implement for 
automakers, easier for consumers to understand, and would align with 
current practice.
Agency Response
    After reviewing comments, we are finalizing the proposed audible 
warning requirements for both the front and the rear warnings with 
minor changes. The first change is that the front start-of-trip warning 
now must meet only the same minimum requirements as the rear change-of-
status warning, because both are time-defined. The second change is 
that we are adding a 10-second maximum gap limitation, similar to Euro 
NCAP, to both of these warnings. Because this final rule requires that 
gaps longer than 3 seconds do not count toward the required duration 
for these two warnings, without a maximum gap limitation there would be 
no limit on the amount of time it would take for the warning to reach 
the 30 second minimum cumulative warning duration. Allowing audible 
warnings that take too long to meet the 30 second minimum cumulative 
warning duration could degrade the effectiveness of the warning. We 
also believe that this requirement will not impede the manufacturer's 
design flexibility significantly and that these parameters meet the 
need for safety, are objective, and are practicable, because they 
provide an acceptable minimum level of effectiveness while allowing 
manufacturers latitude to optimize the warning for effectiveness and 
vehicle occupant acceptance. We continue to believe that the parameters 
stated for the front second phase warning--warning cycle, duty cycle, 
and chime frequency--are essential for an indefinite warning to meet 
the need for safety. Similarly, we believe that the 30-second front 
start-of trip-warning and rear change-of-status warning will be 
effective with the specified signal gap limitations.
    We have concluded that specifying minimum requirements for chime 
frequency and duty cycle for the second phase front audible warning is 
critical for ensuring a minimum baseline of effectiveness. This 
approach is based on the existing research which suggests that warning 
signal characteristics--such as duty cycle, frequency, volume, or 
timbre--can be adjusted to balance effectiveness and consumer 
acceptance but also shows that there is a minimum level of 
effectiveness provided by requiring a 30-second repeating warning 
cycle, with a minimum 0.5 Hz chime frequency and a 20 percent duty 
cycle.\193\ Because ECE R16 requires very short time-defined alerts for 
the front seat belt warning (30 seconds), a duty cycle requirement is 
not necessary. We are incorporating a duty cycle requirement because in 
the context of an indefinite warning this requirement ensures a minimum 
time that the audible warning chime will be active. Additionally, we 
are not incorporating one of the approaches taken by ECE R16 and Euro 
NCAP to limit gaps in the audible warning (that gaps longer than 3 
seconds would not count toward the warning's total duration) because we 
do not have research suggesting that it would increase effectiveness. 
Additionally, a sole requirement that gaps longer than 3 seconds would 
not count toward the warning's total duration would be inadequate in 
the context of an indefinite warning. Therefore, at this time, the 
agency is making the judgement that specifying a maximum signal gap of 
3 seconds, either with or without a duty cycle, unnecessarily limits 
manufacturer's flexibility for the speed-initiated warning. Finally, 
this final rule does not prevent the design of escalating alerts, as 
some manufacturers such as Mercedes suggested in their comments. The 
duty cycle and chime frequency are minimum requirements, and the 
warning cycle specification does not require each cycle to be 
identical. Manufacturers may design escalating alerts within the 
minimum requirements of this final rule.
---------------------------------------------------------------------------

    \193\ Id.
---------------------------------------------------------------------------

    Additionally, given the required duty cycle for the front 
indefinite warning, we do not need to incorporate a maximum signal gap 
(i.e., no gaps longer than 10 seconds) like the one used by Euro NCAP. 
Some comments suggested that the proposal contained a flaw: that given 
the 20 percent duty cycle and 30 second warning cycle requirements, 
this rule would allow a warning that was active for 6 seconds, with a 
24-second gap. However, this was not an error. Commenters did not 
demonstrate that the proposed warning would be ineffective, and that 
notion is inconsistent with available data. Increasing the duty cycle 
would, after a point, cause a reduction in signal gaps, even if no 
specific signal gap limitation were required. Therefore, if those 
commenters were correct, and the gap in the signal were a meaningful 
characteristic, we would expect higher duty cycles to increase 
effectiveness. However, the 2012 IIHS study on duty cycles, referenced 
in the NPRM, indicated that there was not a statistically significant 
difference in effectiveness between the 20 percent, 50 percent, and 100 
percent duty cycles, which cycled over 30 second warning periods. This 
suggests that beyond the maximum gap established by a 20 percent duty 
cycle, reducing the gap does not increase effectiveness. Without 
demonstrable safety benefits, such a limit would unnecessarily restrict 
manufacturers' design flexibility. Therefore, we are not specifying a 
maximum signal gap in this final rule for the front seat belt 
indefinite warning. Only the time-defined front start-of-trip warning 
and the rear change-of-status warning have a signal gap rule (that gaps 
longer than 3 seconds would not count toward the warning's total 
duration) and maximum signal gap requirement (10 seconds). Importantly, 
meeting the requirements of this rule does not preclude designing an 
alert that complies with the signal gap rules in ECE R16. As an 
example, with a 20 percent duty cycle requirement and a gap duration of 
3 seconds, a compliant alert could be active for at least 0.75 seconds 
regardless of the chime frequency.\194\
---------------------------------------------------------------------------

    \194\ This was calculated as follows: (0.2 = 0.75/(3 + 0.75) 
(duty cycle is the total amount of time an intermittent audible 
warning is active (.75 seconds) divided by the total warning cycle 
duration (time active plus the duration of the gap)).
---------------------------------------------------------------------------

    With regard to requests to harmonize the requirements for the front 
and rear audible alerts, we do not believe it is necessary to require 
that the alerts have the same minimum characteristics across seating 
positions. Instead, we structured this final rule so that 
manufacturers, if they choose, may design one audible alert that 
complies with the requirements for both the front and rear alerts. We 
also continue to believe that given the short duration of the rear 
change-of-status warning, it is not necessary to specify 
characteristics such as duty cycle, chime frequency, and warning cycle. 
As we stated in the

[[Page 438]]

NPRM, we believe establishing minimums for these characteristics is 
primarily needed for longer or indefinite alerts to ensure that the 
warnings have at least a minimum level of persistence. As such, since 
we have revised the requirements for the front seats so that the start-
of-trip warning is required only to be at least 30 seconds long, we 
have decided that the audible portion of the start-of-trip warning 
should be subject to the same characteristics as the rear change-of-
status warning. Therefore, as mentioned above, for consistency we are 
finalizing for both the front start-of-trip warning and the rear 
change-of-status warning only that inactive periods longer than 3 
seconds would not be counted toward the total duration of the audible 
warning and that there be no gaps in the warning greater than 10 
seconds. The proposed minimum characteristics for the audible component 
of the front seat belt warning, as finalized, will now only apply to 
the audible front seat second phase warning.
    Finally, we are not incorporating the specifications for volume and 
frequency IIHS suggested. We have designed the final requirements to 
give manufacturer the flexibility to design warnings that are both 
effective and acceptable to consumers. We believe that sound volume and 
frequency can be used by manufacturers to make their warnings more 
effective and/or more acceptable, which is particularly important for 
an indefinite warning. Similarly, we are skeptical that a volume 
specification is needed because it has never been needed in the past. 
Since the early 1970s, FMVSS No. 208 has required an audible driver's 
seat belt warning with no additional audible warning requirements and 
manufacturers have been designing and implementing warnings under that 
structure without issue. Additionally, regarding frequency, IIHS 
indicated that nearly all systems tested already meet their suggested 
specification, so a regulatory requirement may not be needed. 
Nonetheless, as the new requirements are implemented, the agency will 
monitor these characteristics and assess whether additional rulemaking 
action is warranted.\195\
---------------------------------------------------------------------------

    \195\ Accordingly, we explain in Section VI.C.4, Interaction 
with other vehicle warnings, that a change in the volume of the 
audible warning would not constitute an override of the warning.
---------------------------------------------------------------------------

6. Warning Deactivation and Acknowledgement and Hardening
    In the NPRM, we proposed not to allow features which would permit 
the driver to acknowledge the warning and cancel it before the end of 
the required duration or to deactivate the warning for an entire trip 
or for a specified time period (thus preventing it from activating in 
the first place).\196\ We also did not propose requiring features to 
harden the system against circumvention due to concerns about the cost 
and effectiveness of such features. We sought comment on both issues 
and whether these features would impact the effectiveness of the rule.
---------------------------------------------------------------------------

    \196\ 88 FR 61674, 61704 (Sept. 7, 2023).
---------------------------------------------------------------------------

    ECE R16 allows both short-term and long-term deactivation of the 
audible warning (with a variety of restrictions, such as that it be 
more difficult to effectuate a short-term deactivation than to buckle 
the belt). Euro NCAP does not provide any specifications for 
deactivation or acknowledgement of the warnings for the front seats; it 
allows acknowledgement only of warnings for rear seats, except for 
change-of-status warnings. Neither ECE R16 nor Euro NCAP requires 
hardening features.
Comments
    Some commenters suggested making the visual warning, audible 
warning, or both dismissible, and presented a variety of approaches. 
For example, Auto Innovators and HATCI suggested harmonization with 
IIHS and ECE R16. HATCI specified making the dismissal procedure more 
complex than buckling the belt. NADA noted that dismissal or 
suppression would help address consumer acceptance concerns with the 
indefinite warning. Auto Innovators also suggested allowing 
deactivation of the audible rear seat warning. Auto Innovators believes 
that this approach would minimize potential consumer acceptance issue 
in circumstances where there may be a frequent change in the status of 
rear row occupancy and movement of occupants between seating positions 
such as ridesharing. Rivian recommended that NHTSA permit a reset or 
discontinue feature for instances in which a system with occupant 
detection detects that a seat becomes or is unoccupied to clear the 
audio-visual warning for front and rear occupants who exit the vehicle. 
Consumer Reports commented that it would be reasonable to allow drivers 
to ``acknowledge and dismiss'' warnings on a trip-by-trip basis to 
address drop-off situations, seat position changes, and situations 
involving fastening the wrong buckle.
    Anonymous #24 and Anonymous #33 commented that a potential issue 
with the rear seat belt warning systems is the frequency with which 
individuals use rear seat space for storage or transportation of items 
large enough to trigger a seat belt warning system. Accordingly, 
Anonymous #24 argued that there should be an option for the vehicle 
operator to dismiss the warning in situations in which the seat belt 
reminder system is triggered by items other than people in the rear 
seat.
    Regarding hardening features, Auto Innovators and HATCI did not 
support additional hardening features due to the added technical 
complexity and implementation cost that would be required to reduce the 
potential for intentional and inadvertent defeat and activation.
    On the other hand, Ms. Tombrello commented that it is important to 
address occupants who may intentionally try to circumvent seat belt 
reminder systems such as a scenario in which seat belts are buckled 
while passengers sit on top of the belt.
    GM commented that NHTSA should also consider allowing suppression 
or dismissal of the front seat reminder audible warning in specialty 
vehicles such as police cars to allow for cases where the officer needs 
to communicate, whether with other law enforcement, first responders, 
or on radio devices, without the interference of background chimes in 
the vehicle.
Agency Response
    The final rule does not allow deactivation or acknowledgement and 
dismissal of the front or rear seat belt warnings. As 87.7 percent of 
front seat occupants already always use their seat belts, the large 
majority of the overall population will not encounter the indefinite 
warning and, therefore, are unlikely to find it annoying. Furthermore, 
based on the Kidd and Chu study, we have at the very most only 8.4 
percent (5.4 percent (never users) + 3.0 percent (44 percent x 6.9 
percent of sometimes users)) of the total population that would not be 
accepting of this as a standard feature. Therefore, allowing 
deactivation or acknowledgement and dismissal, would reduce safety 
benefits of the final rule even though there is general acceptance of 
this feature. Even temporary dismissal can reduce effectiveness by 
increasing the time before a change-of-status situation is addressed. 
Additionally, warnings lose effectiveness if drivers regularly dismiss 
the warning. Instead of deactivation or dismissal, this final rule 
contains multiple provisions and changes from the NPRM designed to 
maximize consumer acceptance while retaining the effectiveness of the 
belt warnings. The alerts required are now either short duration (for 
which driver annoyance is low) or are active in situations where

[[Page 439]]

belt use is critical. For instance, the start-of-trip audible warning 
system for the front seats and the change-of-status audible warning 
system for the rear seats now only have a 30 second minimum duration, 
which is short enough to have only a limited consumer annoyance impact. 
An indefinite duration audible warning is required only for front seats 
for speeds at or over 10 km/h (6.2 mph), at which point allowing 
deactivation or dismissal not only reduces effectiveness but defeats 
the purpose of an indefinite alert. There is also a variety of 
research, cited throughout this document and in the NPRM, regarding the 
high level of consumer acceptance for seat belt warning systems.
    Additionally, a few commenters such as Consumer Reports brought up 
scenarios that may generate false warnings, such as passenger pick-up 
and drop-off, or rear seat occupants switching seats during a trip, for 
which they argued that driver deactivation (or dismissal) is the 
appropriate response. This comment does not convince the agency that 
deactivation or dismissal is needed because in this final rule we have 
addressed many of these scenarios through other means. Regarding 
passenger pick-up and drop-off, this final rule allows systems to treat 
a door opening as the start of a new trip, resetting the change-of-
status warning for the rear seats. For the front seats, the finalized 
requirements require only a visual change-of-status warning (assuming 
that, because the vehicle is stopped in a pick-up and drop-off 
scenario, the second phase warning would not activate), but the door 
reset provision would still apply to that visual change-of-status 
warning. For seat-switching in the rear, this final rule now contains a 
provision allowing a system to deactivate the warning if the system has 
determined that rear occupants have switched seats.
    We also received comments regarding items placed on the rear seat, 
which is addressed elsewhere in this final rule. We note here that this 
rule does not preclude designs that do not activate a passenger seat 
belt warning if the seat belt is fastened and no one is in the seat. 
Thus, nuisance warnings due to cargo could be prevented by buckling the 
seat belt or placing the cargo somewhere else. NHTSA understands that 
these provisions may not account for all scenarios and warnings may 
still cause some unneeded annoyance. However, we believe that this rule 
properly balances effectiveness with consumer acceptance. Therefore, 
NHTSA is not going to allow deactivation or dismissal in this final 
rule.
    We also note two items in response to some commenters' requests to 
harmonize with ECE R16 to allow deactivation and dismissal of front 
warnings. First, regarding the visual alert, this final rule is 
harmonized with ECE R16 in that it does not allow dismissal. This is in 
part because visual warnings cause little annoyance to the driver and 
have a low impact on consumer acceptance. Second, commenters such as 
NADA stated that their reasons for seeking harmonization on 
deactivation or dismissal centered on consumer acceptance grounds. As 
noted, these concerns have largely been addressed through other means. 
Additional harmonization may reduce this rule's effectiveness even if, 
as some commenters suggested and ECE R16 requires, the rule were to 
require a short-term deactivation to be more difficult than buckling 
the belt. Therefore, we have determined not to harmonize on 
deactivation or dismissal of the audible warnings.
    We have also decided not to incorporate required hardening features 
or features to prevent circumvention of the system because, as some 
commenters pointed out, they increase the cost and complexity of 
warning systems without providing corresponding benefits. Although 
these requirements could increase benefits for the hardcore belt non-
users, these benefits are unclear because most rear seat belt non-users 
are not hardcore and are less likely to intentionally circumvent the 
warning system.\197\ We note that manufacturers do have the discretion 
to incorporate such features if they choose to. This decision 
harmonizes with ECE R16 and Euro NCAP, which do not require such 
features.
---------------------------------------------------------------------------

    \197\ Highway Loss Data Inst., Ins. Inst. for Highway Safety, 
Unbelted: Adults Admit They Often Skip Belts in Rear Seat, 52 Status 
Rep. 1, 3 (Aug. 3, 2017).
---------------------------------------------------------------------------

    Finally, we are not including a deactivation provision for the 
front seat belt warning specific to law enforcement vehicles. FMVSS No. 
208 has required a warning system for the driver's seat in law 
enforcement vehicles for many years without issue. Commenters did not 
suggest that extending the requirement to the front outboard passenger 
seat would create a concern. NHTSA understands that there may be 
additional considerations for law enforcement vehicles given some of 
the changes to the audible alert itself in this rule. However, 
currently NHTSA does not believe these considerations are sufficient to 
change the requirements specific to such vehicles. Like emergency 
vehicles, these vehicles are often modified by the purchaser to 
accommodate specific concerns, and the FMVSS do not prohibit such 
purchaser modifications. As with emergency vehicles, NHTSA will also 
monitor the situation and can modify this approach in future rulemaking 
actions, if necessary.
7. Vehicles With Automated Driving Systems
    In the NPRM, NHTSA proposed incorporating certain language to 
tailor aspects of this rule to vehicles with ADS, which may be designed 
differently, to maintain the same level of occupant protection in 
vehicles equipped with ADS as in conventional vehicles. For example, 
such vehicles may not have a driver's designated seating position or 
may have multiple front outboard passenger seating positions. 
Therefore, we proposed that the front passenger warning apply to 
``any'' front outboard passenger. The addition of the term ``any'' 
makes it clear that, in some vehicles, there may be more than one front 
outboard passenger seating position. We also noted that in a dual-mode 
vehicle, the left front seat is still by definition a driver's seat, 
regardless of the operational status of the vehicle, so a provision to 
just have a warning for the driver and right outboard passenger would 
be sufficient to assure that all front seat outboard occupants receive 
a warning. Additionally, because some ADS-equipped vehicles have one or 
no front outboard passenger seats, we also proposed to align this final 
rule with the 2022 final rule updating occupant protection standards to 
incorporate considerations for vehicles with ADS and apply the same 
seat belt warnings for front inboard passenger seats as front outboard 
seats. Finally, we noted that NHTSA was not prepared to propose a 
solution for the visibility of rear seat belt warnings for ADS-equipped 
vehicles and that it was beyond the scope of the proposed rule.
Comments
    AVIA commented that as NHTSA continues to promulgate safety 
standards to integrate emerging technologies into motor vehicles, AVIA 
encourages the agency to ensure that any new regulatory requirements 
include considerations for how autonomous vehicles can meet those 
standards.
    Tesla supported the proposed warning on vehicle start up for front 
outboard passenger seats because it aligns with manually driven 
vehicles as well as partial and full automation, but

[[Page 440]]

asked how the change-of-status warning for front seats requirement will 
be applied to autonomous vehicles.
Agency Response
    We have added language to tailor aspects of the rule for vehicles 
with automated driving systems in order to maintain the same level of 
occupant protection as this final rule requires for conventional 
vehicles. Some of these elements are discussed in other sections of 
this document specific to aspects of the rule. For example, in Section 
VI.B.4 we discuss an exception to the front seat visual warning 
visibility requirement that is necessary for dual-mode ADS and in 
Section VI.B.5 we address occupant detection as it relates to dual-mode 
ADS. Here, we note a few additional items.
    First, we are finalizing without change two items from the NPRM: 
one, to apply the front seat belt warning requirements to ``any'' front 
outboard designated seating position and two, to apply the same seat 
belt warnings for certain front inboard passenger seats as front 
outboard seat. We did not receive comment specific to these items 
intended to accommodate vehicles with ADS that may not have 
conventional seating configurations.
    Second, to accommodate other changes in the final rule, we have 
included language regarding telltale visibility as applied to certain 
vehicles with ADS to maintain the same level of occupant protection as 
this rule requires for conventional vehicles. As noted in Section 
VI.B.4, this rule requires the front outboard passenger seat belt 
visual warning to be visible only to the driver. Additionally, this 
final rule requires that for telltales associated with multiple front 
outboard seats, the seat with which each telltale is associated must 
clearly identify the seating positions for which the warnings are 
intended. This requirement is discussed further in Section VI.C.3. As 
many commenters pointed out and we explained, in vehicles with a 
driver, the front outboard passenger can receive the audible signal and 
the driver can communicate the additional information provided by a 
visual signal to the front outboard passenger. However, in vehicles 
with ADS, there may not be a driver's designated seating position with 
a human driver who can receive and communicate this information. 
Instead, as we noted in the NPRM, in a vehicle without manually 
operated driving controls, one of the front passengers may be 
performing the management role for the duration of a trip, such as in 
the case of a parent and children. In this circumstance, the most 
appropriate recipient of the visual warning is likely to be a front 
passenger.
    For these reasons, we are finalizing two provisions. First, we are 
finalizing as proposed that for vehicles that do not have a driver's 
designated seating position, the visual warning for each front outboard 
passenger designated seating position must be visible from each front 
outboard passenger designated seating position. Second, we are now 
requiring that for vehicles without a driver's designated seating 
position, for telltales associated with multiple front outboard seats, 
the seats with which each telltale is associated must clearly identify 
the seating positions for which the warnings are intended. These 
requirements maintain the same level of occupant protection as is 
required for conventional vehicles and is also consistent with the 
logic of the NPRM.\198\
---------------------------------------------------------------------------

    \198\ As discussed in Section VI.B.4, many commenters expressed 
concerns with redesign costs associated with a requirement that the 
telltale be visible to the passenger. Although NHTSA sought comment 
on aspects of the NPRM regarding vehicles with ADS, commenters 
focused their concerns on conventional vehicles. Therefore, NHTSA 
does not believe that such concerns are present to the same degree 
with vehicles without a driver's designated seating position.
---------------------------------------------------------------------------

    As we stated in the 2022 final rule on occupant protection for 
vehicles with ADS, these requirements are intended to apply only to 
ADS-equipped vehicles that have seating configurations similar to non-
ADS vehicles, i.e., forward-facing front seating positions 
(conventional seating). As we stated in the 2022 final rule, additional 
research is necessary (some of which is currently underway) to 
understand and address different safety risks posed by vehicles with 
unconventional seating arrangements (e.g., rear-facing seats or 
campfire seating), including with regards to seat belt reminder 
systems.\199\ Therefore, as we stated in Section VI.B.3 of this 
document in response to AVIA's comment about front seat occupants 
exiting through a door not adjacent to their seat, considerations for 
vehicles with unconventional seating (and other related considerations, 
such as bi-directional vehicles) are out of scope of this final rule. 
Additionally, as noted in the NPRM, the visibility of rear seat belt 
warnings for ADS-equipped vehicles is also out of scope of this final 
rule because further research is needed before the agency proposes a 
solution. Research on this topic is underway.
---------------------------------------------------------------------------

    \199\ 87 FR 18560.
---------------------------------------------------------------------------

    Finally, we believe the final rule has addressed in prior sections 
Tesla's concern about change-of-status warnings for front seats in 
vehicles operating in an automated state.
8. Test Procedures
    In the NPRM, NHTSA proposed that NHTSA could test any system under 
any combination of seat occupancy or seat belt use status. The proposed 
test procedures also specified how the agency would test a seat belt 
warning system with a designated seating position that is occupied. The 
finalized occupancy criteria (the test dummies and the height and 
weight criteria for human beings, to be used instead of test dummies at 
the manufacturer's option, that will be used to determine occupancy) 
are discussed in Sections VI.A.2.a.iv (rear) and VI.B.5 (front 
passenger). The NPRM also proposed that to pass the test, the human 
beings or test dummies used would be seated, the seat belt use and 
ignition conditions would be applied, and the required signals must 
operate (that is, either activate or not activate) accordingly. The 
test could be conducted with the seat and adjustable belt anchorages in 
any position. The NPRM also noted that for rear designated seating 
positions with occupant detection, the agency would perform the test 
with the seat in any position, the seat back in the manufacturer's 
nominal design riding position, and any adjustable anchorages in any 
position.
Comments
    Auto Innovators requested that NHTSA publish the proposed test 
procedures used to evaluate vehicle compliance before issuance of the 
final rule. Auto Innovators stated that this request is particularly 
relevant given the differences in the requirements in the NPRM when 
compared to the current requirements of ECE R16, and stakeholders' 
desire for the opportunity to address any technical concerns before the 
rule or test procedure is finalized. In particular, Auto Innovators 
sought additional information regarding how NHTSA will evaluate the 
performance of an indefinite alert.
    Auto Innovators also commented that the agency should more closely 
align its requirements with ECE R16 and Annex 18 to reduce test burden 
costs, in particular regarding the process for evaluating the 
conditions for warning activation. Auto Innovators also commented that 
the proposal increases the complexity of evaluating vehicle compliance 
and may require specialized equipment or similar measurement devices to 
verify the characteristics of the proposed audible warning.
    Finally, Auto Innovators recommended that NHTSA ensure a technology 
neutral approach, both for performance requirements and test

[[Page 441]]

procedures, towards the means used to determine occupant detection.
Agency Response
    The final rule incorporates several changes to the proposed 
regulatory text for the test procedures:
     Definition of ``seat centerline''--Both the proposed and 
finalized test procedures specify the seating of the test dummy by 
reference to the ``seat centerline.'' The final regulatory text 
includes a definition of this term.
     Occupancy criteria--The proposed regulatory text specified 
these in the definitions section. In the final rule these have been 
moved to the test procedures section and edited for clarity.
     Test procedures--The final rule clarifies several aspects 
of how the test may be carried out. The final rule does not include the 
proposed specification that if a human occupant is used for testing, 
that they be dressed in a cotton T-shirt, full length cotton trousers, 
and sneakers, instead we are specifying that the dummy or human 
occupant may be clothed in any manner because clothing should not 
change the performance of the system. With respect to carrying out 
testing, the proposed regulatory text simply stated, ``Place the 
ignition switch in the ``on'' or ``start'' position and verify that the 
seat belt warnings function as specified in S7.5(b) and S7.5(c), for 
any combination of seat belt use or seat occupancy at any designated 
seating position(s).'' The final rule clarifies that NHTSA could test 
any of a number of test parameters: ``Verify that the seat belt 
warnings function as specified in S7.5(b) and S7.5(c), for any 
combination of seat belt use (at any seating position), seat occupancy 
(at any seating position), removable seat electrical connection status 
(connected or not connected, for any removable seat), vehicle speed, 
and door status (open or closed, for any door), except that the door 
shall not be opened when the vehicle is in motion.''
    NHTSA is not publishing the compliance laboratory test procedures 
before publishing this final rule as requested by Auto Innovators. To 
investigate whether specific vehicles or products comply with the 
FMVSS, NHTSA's Office of Vehicle Safety Compliance (OVSC) contracts 
with labs to conduct compliance testing. OVSC laboratory test 
procedures are prepared for the limited purpose of use by contracted 
independent laboratories conducting compliance tests for the OVSC. OVSC 
laboratory test procedures are distinct from regulatory test procedures 
that are included as part of most FMVSS. OVSC laboratory test 
procedures are generally based off of the regulatory test procedures in 
specific FMVSS but are prepared by the agency to give contracted labs 
specific instructions on how to conduct a specific test. The OVSC 
laboratory test procedures are simply agency guidance for contracted 
labs and do not constitute official agency action (e.g., a rule). In 
some cases, the OVSC laboratory test procedure, or the report produced 
as a result of the work performed by the contracted laboratory, does 
not include all of the various FMVSS minimum performance requirements. 
Because the OVSC laboratory test procedures are not part of the 
regulation, NHTSA is not required to publish them prior to or with this 
final rule. Typically, NHTSA will publish the OVSC laboratory test 
procedures on its website for transparency. NHTSA plans to publish the 
OVSC test procedures for this rule in the future.
    NHTSA also declines to specify in the FMVSS the exact amount of 
time that it will test the indefinite front outboard seat belt 
warnings. NHTSA believes that specifying a finite testing duration 
would weaken the rule by enabling systems that are not indefinite to 
meet the test. Manufacturers must certify that their products comply 
with all applicable FMVSS, and they determine what steps are necessary 
to ensure that every product manufactured meets the applicable 
requirements. The procedures in this rule are sufficiently detailed and 
objective for manufacturers to self-certify that their systems meet the 
indefinite warning requirement.
    NHTSA agrees with Auto Innovators that this final rule should be 
technology neutral toward occupant detection, and this rule is 
technology neutral. As discussed in Section VI.B.5, this final rule 
does not require occupant detection capability for the driver's 
designated seating position. It provides manufacturers the flexibility 
to optionally choose to certify compliance to the same occupant 
detection criteria applied to the outboard passenger seats. 
Additionally, while the final rule requires occupant detection 
capability for the front outboard passenger designated seating position 
and specifies seat occupant criteria for testing front outboard 
passenger designated seating positions and rear designated seating 
positions, it does not specify the methods that must be used to detect 
occupancy. Manufacturers may choose occupant detection technologies at 
their discretion, so long as they can certify that the vehicle meets 
the requirements of this final rule and the test procedure it 
specifies. The same is true for the technology that OEMs may use to 
detect whether the seat belt is in use.
    Throughout this final rule NHTSA has considered harmonization and 
has taken care, where possible, to incorporate performance requirements 
and test procedures that can enable systems to also meet ECE R16 
requirements to minimize testing and compliance costs for 
manufacturers. Therefore, while this final rule does not fully align 
with the test procedures in ECE R16 Annex 18, they are largely 
compatible. As noted in the NPRM, ECE R16 operates in a type approval 
regime, while the FMVSS use self-certification and must be objective. 
For this reason, the final rule departs from Annex 18 when necessary to 
ensure that it is objective. Because of these necessary differences to 
meet statutory obligations, full alignment of the test procedures is 
not achievable.\200\
---------------------------------------------------------------------------

    \200\ The Safety Act establishes a self-certification process in 
which vehicle and equipment manufacturers certify that their 
products comply with all applicable FMVSS, which establish minimum 
performance standards that the product must meet. It is up to 
manufacturers to determine what steps are necessary to ensure that 
every product manufactured meets or exceeds the applicable 
requirements before the products are imported, sold, offered for 
sale, or introduced into interstate commerce in the United States.
---------------------------------------------------------------------------

    Finally, with respect to Auto Innovators' concern about specialized 
test equipment needed to verify compliance with the required audible 
warning characteristics, this final rule does not establish test 
procedures that necessitate specialty equipment that laboratory test 
facilities would not already have readily available (e.g., a stopwatch) 
to verify compliance of the audible warnings.

VII. Regulatory Alternatives

    In the proposal, NHTSA considered several major alternatives: 
harmonizing with the standards set in ECE R16 and Euro NCAP; requiring 
occupant detection and enhanced warning signals for the rear seat belt 
warning; requiring a warning for the front center seat; requiring an 
audio-visual seat belt warning for the front outboard seating positions 
with a duration not less than 90 seconds; and a few non-regulatory 
alternatives. For three of these alternatives (rear-seat occupant 
detection, front center seat warning, and 90-second front warning), 
NHTSA quantified the costs and benefits (see Section VIII.B). Although 
the proposal followed ECE R16 and Euro NCAP in a variety of ways, it 
also deviated from them in some important respects. The NPRM explained 
this deviation in detail. The NPRM also explained NHTSA's tentative 
reasoning for not

[[Page 442]]

selecting the other regulatory alternatives.

Comments

    NHTSA received many comments concerning the regulatory 
alternatives. Comments regarding alternatives for specific aspects of 
the proposal are discussed throughout the preceding sections of the 
preamble. Many of these comments concerned harmonization with the 
relevant provisions in ECE R16, Euro NCAP, and the IIHS protocol. 
Safety advocates in several instances favored final requirements that 
would be more stringent or demanding than those requirements or 
protocols. On the other hand, industry commenters generally--although 
not always--commented in support of greater alignment with them. In 
this section, NHTSA summarizes and addresses comments that concerned 
harmonization generally, as well as comments concerning non-regulatory 
alternatives.
    In addition to the more specific comments already addressed in this 
document, several industry commenters commented more generally in favor 
of harmonization with ECE R16 and Euro NCAP. Auto Innovators, Hyundai, 
HATCI, IEE, NAMIC, and Nissan commented in support of harmonizing the 
requirements with ECE R16 and Euro NCAP. Auto Innovators commented that 
harmonization with ECE R16 provides the agency with the greatest 
opportunity to ensure an objective and practical approach that meets 
the need for safety, while also minimizing regulatory burden and 
corresponding delays associated with developing region-specific 
features for the U.S. market. Auto Innovators expressed concerns with 
several areas where the agency has proposed alternatives to the 
requirements of ECE R16, which have already been widely adopted and 
implemented in other global markets. Auto Innovators argued that 
several fundamental aspects of the proposal (such as the triggering 
conditions) differ from the systems that consumers may have experienced 
in both previous and current model year vehicles and would result in 
significant negative pushback from the public if the final rule is 
adopted without change.
    Hyundai similarly commented that although it supported the 
proposal, its largest caveat to full support was the proposal's 
departure from ECE R16's requirements. Hyundai characterized these 
differences as minor in the sense that they do not represent any 
fundamental change to the core elements or safety benefits of NHTSA's 
proposal but stated that these ``minor'' differences could have 
significant adverse implications with respect to safety benefits, 
customer acceptance, unnecessary country-specific designs, costs, and 
required lead times. Hyundai commented that the benefits of 
international regulatory harmonization have been recognized and 
espoused by government and industry organizations, including NHTSA, for 
many years. Hyundai argued that these benefits include improved 
regulatory and NCAP provisions that reflect the international consensus 
of leading government and industry experts, more efficient development 
and timely enactment of state-of-the-art vehicle safety provisions, 
enabling international trade and cooperation by reducing nontariff 
barriers, more effective use of finite government and industry 
resources, avoidance of country-specific requirements, and 
significantly reduced consumer costs.
    HATCI also noted that the requirements that the agency has proposed 
would require significant interior redesign which would require longer 
design lead time. HATCI encouraged the agency to further harmonize with 
established international regulations and rating programs, allow for 
more flexible telltale design, and extend the effective dates.
    GM, NSC, SRN, Hyundai, HATCI, and an individual commenter also 
supported the inclusion of seat belt reminder ratings in NCAP. Hyundai 
recommended that NHTSA coordinate its FMVSS and NCAP initiatives to 
pursue maximum safety benefits in the shortest feasible timeframes; by 
virtue of being voluntary, NCAP enables vehicle safety technology to be 
socialized in a non-compulsory way to enhance consumer acceptance. 
Hyundai suggested that a follow-on NCAP action might incentivize some 
form of a so-called ``Seat Belt Assurance System'' (e.g., limiting 
infotainment functionality or constraining vehicle speed when an 
occupant is unbuckled) to further motivate buckling up. Hyundai stated 
that this suggested NCAP update could also specify requirements 
regarding bypassing/disablement to obtain credit for the specified Seat 
Belt Assurance System. Hyundai argued that a timely progression of 
FMVSS and NCAP actions by NHTSA could appreciably improve seat belt use 
rates and consumer acceptance of these vehicle interventions. SRN 
commented that if NHTSA did not require the full-status rear seat 
warning system, it could reward vehicles with these more effective 
systems with NCAP points.
    Consumer Reports agreed with NHTSA's decision not to pursue either 
of the non-regulatory alternatives presented in the ANPRM.

Agency Response

    Because NHTSA is amending FMVSS No. 208 to include these new 
requirements, it is not necessary to incorporate these requirements 
into NCAP. To help consumers make purchasing decisions, NHTSA currently 
indicates on a vehicle's NCAP safety rating web page if the vehicle has 
a seat belt reminder system for the front and/or rear passengers. NHTSA 
may at a later date, as suggested by some commenters, consider using 
NCAP to incentivize enhanced rear seat belt reminder systems. NHTSA 
also concurs with Consumer Reports not to pursue either of the non-
regulatory alternatives presented in the ANPRM.
    In developing the requirements in this final rule, NHTSA considered 
the requirements in ECE R16, as well as materials published by Euro 
NCAP and IIHS. NHTSA agrees with the commenters that harmonization is 
an important goal and agrees that in some specific instances that the 
proposal should be modified to align more closely with ECE R16, Euro 
NCAP, and IIHS.
    Executive Order 13609 provides that international regulatory 
cooperation can reduce, eliminate, or prevent unnecessary differences 
in regulatory requirements. Similarly, the Infrastructure, Investment, 
and Jobs Act directs that ``[t]he Secretary [of Transportation] shall 
cooperate, to the maximum extent practicable, with foreign governments, 
nongovernmental stakeholder groups, the motor vehicle industry, and 
consumer groups with respect to global harmonization of vehicle 
regulations as a means for improving motor vehicle safety.'' \201\ 
(These directives are also discussed in the Regulatory Analyses 
section.) At the same time, the Safety Act authorizes NHTSA to 
establish motor vehicle safety standards that, among other things, meet 
the need for safety and are practicable.
---------------------------------------------------------------------------

    \201\ H.R. 3684 (117th Congress) (2021) section 24211.
---------------------------------------------------------------------------

    Consistent with these directives, and after NHTSA has carefully 
considered the comments, the final rule more closely aligns with those 
regulatory alternatives where warranted but continues to deviate from 
them where necessary. The preceding sections of this document discuss 
in detail the ways in which the final rule follows and differs from 
these regulatory alternatives and explains why we believe the

[[Page 443]]

departures are justified. The major provisions in the final rule and 
the regulatory alternatives, including the differences between them, 
are summarized in table 10.
---------------------------------------------------------------------------

    \202\ The final rule makes no distinction between start-of-trip 
and change-of-status visual warnings. It has been combined into one 
single visual warning requirement, so the triggering and duration 
characteristics summarized here are for the single visual warning 
requirement.

                         Table 10--Comparison of Final Rule With Regulatory Alternatives
----------------------------------------------------------------------------------------------------------------
              Topic                   Final rule          UN ECE R16           Euro NCAP             IIHS
----------------------------------------------------------------------------------------------------------------
                                       Rear Seat Belt Warning Requirements
----------------------------------------------------------------------------------------------------------------
Applicability...................  Excludes small      Excludes all small  Excludes            N/A.
                                   school buses, law   buses and more      commercial
                                   enforcement         categories of       vehicles and most
                                   vehicles, and       special-purpose     vehicles over
                                   ambulances.         vehicles.           3,500 kg.
Occupant detection..............  Not required......  Not required......  Awards points only  Not required.
                                                                           for systems with
                                                                           occupant
                                                                           detection.
Visual Warning on vehicle
 startup:
    Type of information conveyed  How many or which   Indicates at least  Indicates the rear  Whether the seat
     by visual signal.             seat belts are in   all rear seats to   seat belts in use   belt at each rear
                                   use and/or not in   allow the driver    and not in use.     seating position
                                   use.                to identify any                         is in use or not
                                                       seat where the                          in use.
                                                       belt is not in
                                                       use.
    Triggering Conditions.......  Ignition switch on/ Master control      Ignition switch is  Engine/motor on;
                                   start or (for       switch activated.   engaged (engine     allows 10-second
                                   EVs) propulsion                         running or not).    delay.
                                   activation.
    Seat Occupancy Criteria.....  6-year-old........  5th percentile      5th percentile      Seated human or
                                                       female.             female.             dummy in front
                                                                                               passenger seat
                                                                                               and human in rear
                                                                                               seat (unspecified
                                                                                               size).
    Duration....................  60 seconds........  60 seconds........  60 seconds........  60 seconds.
Audio-Visual Change-of-status
 warning:
    Duration....................  30 seconds........  30 seconds........  60 second visual    30 seconds.
                                                                           warning; 30
                                                                           second audible
                                                                           warning.
    Triggering Conditions.......  Fastened belt       Fastened belt       Fastened belt       Fastened belt
                                   becomes             becomes             becomes             becomes
                                   unfastened, the     unfastened and      unfastened,         unfastened,
                                   vehicle is in       certain distance,   certain distance,   certain distance,
                                   forward or          time and/or speed   time and/or speed   time and speed
                                   reverse, and all    threshold(s) are    threshold(s) are    threshold(s) are
                                   rear doors remain   exceeded.           exceeded, and all   exceeded, and all
                                   closed.                                 rear doors remain   rear doors remain
                                                                           closed.             closed.
----------------------------------------------------------------------------------------------------------------
                                      Front Seat Belt Warning Requirements
----------------------------------------------------------------------------------------------------------------
Applicability...................  Excludes all heavy  Does not exclude    N/A...............  N/A.
                                   vehicles.           heavy vehicles
                                                       used for carrying
                                                       goods.
Front Seating Positions.........  Front outboard      All positions in    All front row       Front outboard.
                                   passenger and       the same row as     positions.
                                   driver (not         the driver.
                                   center seat).
Visual Warning--start-of-trip:
 \202\
    Triggering Conditions.......  Seat occupied,      Belt unfastened,    Belt unfastened,    Concurrent with
                                   belt unfastened,    ignition or         ignition switch     audible.
                                   ignition on/start   master control      engaged.
                                   or (for EVs)        switch engaged.
                                   propulsion
                                   activation.
    Duration....................  Until belt is       30 seconds........  Until belt is       Concurrent with
                                   fastened.                               fastened.           audible.
Visual Warning--Change-of-
 Status:
    Triggering Conditions.......  Seat occupied,      If belt remains     Belt unfastened,    Concurrent with
                                   belt unfastened,    unfastened and      speed over 25 km/   audible.
                                   ignition on/start   certain distance,   h (15.5 mph).
                                   or (for EVs)        time, and/or
                                   propulsion          speed threshold
                                   activation.         (25 km/h (15.5
                                                       mph)) are
                                                       exceeded.
    Duration....................  Until belt is       At least 30         Until belt is       Concurrent with
                                   Fastened.           seconds not         fastened.           audible.
                                                       counting gaps
                                                       over 3 seconds.
Audible Warning--First Phase:
    Triggering Conditions.......  Seat occupied,      If belt remains     Must be deployed    Seat occupied,
                                   belt unfastened,    unfastened and      before and          belt unfastened
                                   ignition on/start   certain distance,   certain distance,   at ignition,
                                   or (for EVs)        time, and/or        time, and/or        continuous
                                   propulsion          speed threshold     speed threshold     forward motion of
                                   activation.         (25 km/h (15.5      (25 km/h (15.5      at least 10 km/h
                                                       mph)) are           mph)) are           (6.2 mph).
                                                       exceeded.           exceeded
                                                                           (``final'' signal
                                                                           if other, higher
                                                                           thresholds are
                                                                           met).
    Duration....................  30 seconds........  At least 30         May not exceed 30   90 seconds.
                                                       seconds.            seconds
                                                                           (``final'' signal
                                                                           at least 90
                                                                           seconds).
Audible Warning--Second Phase:
    Triggering Conditions.......  Seat occupied,      Fastened belt       Fastened belt       Occupied seat,
                                   belt unfastened,    becomes             becomes             belt unfastened,
                                   and a speed >=10    unfastened and      unfastened,         continuous
                                   km/h (6.2 mph).     certain distance,   vehicle speed       forward motion of
                                                       time and/or speed   over 25 km/h        at least 10 km/h
                                                       threshold(s) (25    (15.5 mph)          (6.2 mph).
                                                       km/h (15.5 mph))    (``final audible
                                                       are exceeded.       signal'' if over
                                                                           40 km/h (24.9
                                                                           mph)).
    Duration....................  Until belt is       At least 30         At least 90         90 seconds.
                                   fastened or speed   seconds.            seconds.
                                   <10 km/h.

[[Page 444]]

 
Visual Warning Characteristics..  Must provide        Specifies image     N/A...............  Indicate an
                                   telltale            identical to                            outboard front-
                                   specified in        FMVSS No. 101,                          row seating
                                   FMVSS No. 101,      Table 2.                                position with an
                                   Table 2, the seat                                           unfastened belt.
                                   to which the
                                   telltale is
                                   associated must
                                   be clearly
                                   identified.
----------------------------------------------------------------------------------------------------------------
                                               Other Requirements
----------------------------------------------------------------------------------------------------------------
Audible Warning Characteristics:
    Cycle, Chime Frequency,       Front First Phase   Gap limitations...  Gap limitations...  Gap limitations.
     Signal Gaps.                  and Rear: Gap
                                   limitations.
                                  Front Second
                                   Phase: Specifies
                                   duty cycle,
                                   warning cycle,
                                   and chime
                                   frequency. No gap
                                   limitations.
    Volume......................  No volume           ``easily            Final audible       Must be between 20
                                   requirement.        recognizable by     warning must be     and 20,000 Hz and
                                                       the driver''.       ``loud and          must include at
                                                                           clear''.            least one
                                                                                               dominant
                                                                                               frequency between
                                                                                               500 and 2,250 Hz.
Warning Deactivation,             Not permitted.....  Short and long-     Acknowledgement     Rear visual signal
 Acknowledgement, and Dismissal.                       term deactivation   allowed for rear    may be cancelled
                                                       of the audible      seats but not for   by the driver.
                                                       warning with        the change-of-
                                                       limitations,        status warning.
                                                       including that it
                                                       must be more
                                                       difficult to
                                                       effectuate a
                                                       short-term
                                                       deactivation than
                                                       to buckle the
                                                       belt.
----------------------------------------------------------------------------------------------------------------

VIII. Overview of Benefits and Costs

    NHTSA has prepared a Final Regulatory Impact Analysis (FRIA) that 
assesses the benefits, costs, and other impacts of this final 
rule.\203\ For a more detailed discussion, please refer to the FRIA. 
The following sections present the benefits and costs of the final rule 
requirements for the rear and front SBWSs and the three major 
regulatory alternatives considered. It is important to note that the 
incremental benefits presented in the section stem not from the SBWS's 
function itself, but instead result from the increase in seat belt use 
brought about by the SBWS. Therefore, the incremental benefits 
associated with the final rule are comprised of the fatalities and non-
fatal injuries prevented as a result of the increase in seat belt use 
from the SBWS.
---------------------------------------------------------------------------

    \203\ The FRIA is available in the docket for this final rule 
and may be obtained by downloading it or by contacting Docket 
Management at the address or telephone number provided in the 
ADDRESSES section of this document.
---------------------------------------------------------------------------

A. Final Rule Requirements

    NHTSA quantified the benefits and costs of the final rule 
requirements. This section presents a summary of the benefits and costs 
for the requirements on rear seat belt warning systems, front outboard 
seat belt warning systems, and the combined costs and benefits for both 
warning systems.
1. Rear Seat Belt Warning System
    The September 2023 NPRM sought comment on the potential 
effectiveness, benefits, and costs of a rear seat belt warning.
Comments
    1. Safety benefits for rear SBWS are underestimated: Consumer 
Reports commented in support of the proposed rule stating that the 
preliminary regulatory impact analysis (PRIA) likely underestimates the 
safety benefits associated with the requirements for the rear seats. 
Consumer Reports commented that the analysis did not factor in the 
technological advancements of current vehicle fleets which will likely 
increase the rate of injury for unrestrained rear seat passengers. More 
specifically, Consumer Reports noted that crash avoidance systems that 
are associated with hard braking and pre-crash maneuvers may result in 
an increased rate of injury to unrestrained rear seat passengers.
Agency Response
    Regarding Consumer Reports' comment on underestimating the benefits 
associated with rear SBWS, NHTSA has updated the target population in 
the final rule using the most recently available data along with 
adjustments to account for safety impacts of new required safety 
technologies that have yet to be applied to the fleet. These updates in 
the final rule correctly reflect the benefits for rear SBWS. This 
analysis does not project changes in ridership between front and rear 
seat occupants as such projections would introduce uncertainty into the 
analysis. However, if ride sharing services increase rear seat 
occupancy, it is possible that benefits for rear seat occupants could 
be greater than those estimated in this FRIA.
    2. Require occupant detection for rear seats: Commentors including 
Consumer Reports and NSC urged NHTSA to require SBWS with occupant 
detection for rear seats. These commenters also requested that the 
agency estimate benefits of the case that manufacturers would choose to 
implement negative-only or full-status warning system stating that the 
projected increases in seat belt use from the rule would likely be 
greater if NHTSA required the full-status compliance option for all 
applicable vehicles. Consumer Reports, citing findings of an IIHS 
study,\204\ noted that benefits for rear seat occupants may be 
underestimated as NHTSA did not account for increases in rear seat 
passengers resulting from consumers increasingly using ride sharing 
services in recent years.
---------------------------------------------------------------------------

    \204\ Kidd and O'Malley titled ``Increasing seat belt use in the 
United States by promoting and requiring more effective seat belt 
reminder systems.'' https://pubmed.ncbi.nlm.nih.gov/37267012/
#:~:text=If%20every%20vehicle%20in%20the,85.9%25%20in%20the%20rear%20
row.
---------------------------------------------------------------------------

Agency Response
    The final rule does not require occupant detection for the rear 
SBWS but permits it. Based on comments received, the final rule differs 
from the proposed rear SBWS requirements by permitting positive-only, 
negative-only,

[[Page 445]]

and full-status SBWS without the use of occupant detection. We believe 
that while the full-status system (with occupant detection) does 
provide the driver with the most information, as we explained in the 
NPRM, we continue to believe that the other allowable types of systems 
without occupant detection would provide the driver with sufficient 
information to easily determine whether and where there are any 
unbuckled occupants and request that they fasten their seat belts. 
Although some vehicle manufacturers may implement warning systems with 
occupant detection, NHTSA estimated benefits based on vehicle 
manufacturers meeting the minimum requirements. Therefore, NHTSA 
estimated the incremental benefits and costs associated with the least 
costly compliance option, which is a rear SBWS without occupant 
detection.
    The study by Kidd and O'Malley, cited by Consumer Reports, compares 
the effectiveness of SBWS with different warning durations and system 
interlocks in increasing seat belt use. The study found that enhanced 
reminders, in particular more persistent reminders, are more effective 
in increasing seat belt use. Although system interlocks are effective 
in increasing seat belt use, they are found to be much less acceptable 
than audible reminders and more likely to be circumvented. The 2019 
IIHS study by Kidd (used in the PRIA and in this final rule) found that 
moving from a 7-second warning to either a 90-second or indefinite 
duration warning increased seat belt use for part-time users by 30 
percent and 34 percent respectively. Overall, these studies provide 
evidence that the relative annoyance or duration of a warning increases 
the effectiveness of a SBWS. However, they do not provide any data that 
can be used to estimate the increase in seat belt use generated by 
adding occupant detection to the rear seat SBWS.
    Due to a lack of data, NHTSA is unable to estimate the increase in 
seat belt use for a SBWS with occupant detection compared with a SBWS 
without occupant detection. Therefore, the agency is unable to estimate 
incremental benefits for the regulatory alternative with occupant 
detection. Instead, NHTSA considered how much more effective a SBWS 
with occupant detection would need to be to generate the same net 
benefits as the final rule, which allows for a SBWS without occupant 
detection in the rear seat. Overall, a SBWS with occupant detection 
would need to increase seat belt use by approximately two to three 
times that of a SBWS without occupant detection to generate the same 
level of net benefits. As it is not likely that a SBWS would be two or 
three times as effective as one without occupant detection, this 
regulatory alternative was not selected. However, while occupant 
detection was not included as a requirement in the final rule, the 
finalized requirements do allow systems that have occupant detection.
    3. Cost burden for requiring SBWS on rear seats for high occupancy 
vehicles: Mercedes-Benz AG commented on the cost burden of implementing 
SBWS for rear seats in high occupancy vans. The commenter noted that 
for each removeable seat, an electronic control unit (ECU) would be 
required along with other hardware components and corresponding 
software. Additionally, one commenter indicated concern that the agency 
did not fully account for the potential burden on industry; in 
particular, in cases in which businesses will incur the cost of adding 
SBWS to vehicles with a large number of rear seats, such as vans and 
buses.
Agency Response
    In estimating the costs associated with the final rule, the agency 
made use of end-user costs estimates from a teardown study. Those unit 
costs were then applied on a per-seat basis to the average number of 
seats per vehicle and average number of new light vehicles sold 
annually to estimate the total annual cost. NHTSA did not estimate 
costs on a per-manufacturer or per-business basis but instead provided 
the total annual cost to end users. This estimate reflects not only the 
cost of materials and labor incurred by manufacturers, but also non-
production costs and profit reflected in the price passed down to 
consumers. Additionally, while the per-vehicle cost may vary based on 
the number of seats per vehicle, in vehicles with more rear seats, both 
costs and benefits will increase. While costs increase based on the 
number of seats in a vehicle, benefits increase not only based on both 
the number of restrained occupants that avoid injury due to their use 
of seat belts, but also due to the reduction in potential injuries from 
harmful interactions between unrestrained occupants.
    4. Lack of harmonization with existing standards increases cost: 
Commenters, including Auto Innovators and Tesla, encouraged harmonizing 
with other regulatory and safety ratings requirements. More 
specifically, Auto Innovators stated that the agency should consider 
potential costs associated with redesign due to misalignment with ECE 
R16.
    Agency Response: Throughout this final rule NHTSA has considered 
harmonization and has taken care to incorporate performance 
requirements and test procedures that can, in many cases, enable 
systems to also meet ECE R16 requirements to minimize testing and 
compliance costs for manufacturers. However, NHTSA declines to fully 
harmonize with the test procedures in ECE R16 Annex 18. Since NHTSA's 
regulations follow a self-certification approach, it is important to 
include certain information in the FMVSS test procedures to ensure that 
they are objective and properly test for compliance with this final 
rule, which may not be necessary for ECE R16 testing.
    In general, the rear seat belt warning system requirements in this 
final rule are consistent with those in ECE R16 and Euro NCAP. One 
major difference is that ECE R16 evaluates occupant detection using the 
5th percentile female dummy while the final rule specifies using a 50th 
percentile 6-year-old child or equivalent. For the reasons explained in 
a previous section, this final rule addresses a MAP-21 mandate and 
requires, if an occupant detection system is provided, that the system 
be able to detect children in the rear seats. The weight of a 5th 
percentile female dummy is greater than that of many children aged 6 to 
16 years old and so it is not an appropriate surrogate for evaluating 
child occupancy.
Summary of Analysis and Results
    Based on the Fatality Analysis Reporting System (FARS) and the 
Crash Investigation Sampling System (CISS) data from 2017 through 
2021,\205\ on average 930 unrestrained rear seat occupants were killed 
in crashes and 15,380 were injured annually.\206\ After adjusting these 
to account for future decreases in fatalities and injuries projected to 
occur in the absence of the finalized requirements due to the 
introduction of other mandatory safety technologies (e.g., electronic 
stability control), the analysis estimates a baseline of, on average, 
822 fatalities and 11,409 injuries to unrestrained rear seat occupants 
each year.\207\ This is the overall target population for rear seat 
occupants--the annual deaths and

[[Page 446]]

injuries that the final rule requirements are aimed at reducing.
---------------------------------------------------------------------------

    \205\ The target population in the PRIA reflected the 2011-2015 
FARS and 2011-2015 NASS/CDS data. The FRIA updated the target 
population to reflect more recent data. The NASS/CDS data previously 
used did not reflect injury data for vehicles older than ten years 
which may have underestimated injuries.
    \206\ See FRIA, appendix A.7.
    \207\ See FRIA, tables 25 and 26.
---------------------------------------------------------------------------

    We estimated the benefits resulting from the final rule rear seat 
belt warning requirements. The benefits are the fatalities and injuries 
that we estimate would be prevented by the finalized requirements. The 
benefits depend, principally, on the effectiveness of seat belts in 
preventing deaths and injuries and the expected increase in seat belt 
use due to the finalized rear seat belt warning system requirements. 
Seat belt effectiveness in mitigating fatalities for rear seat 
occupants 11 years of age and older is 56 percent for passenger cars 
and 74 percent for light trucks and vans.\208\
---------------------------------------------------------------------------

    \208\ See FRIA, table 33.
---------------------------------------------------------------------------

    NHTSA believes that the minimum required warning signal 
characteristics would be effective at informing the driver of the use 
status of the rear seat belts and facilitating the driver to request 
that a rear passenger fasten an unfastened belt. A seat belt warning 
system can increase rear seat belt use in two ways: it can remind an 
occupant to fasten the occupant's belt, and it can inform the driver 
that a passenger is unbuckled, so that the driver can request the 
occupant fasten the occupant's belt.\209\ Without a rear seat belt 
warning, the driver must turn around to ascertain whether a rear seat 
occupant is using a seat belt (or ask the occupant); in some vehicles, 
belt use may not be evident to the driver, even if he or she turns 
around, due to line-of-sight limitations. As noted above, in NHTSA's 
2015 survey, 65 percent of drivers of vehicles equipped with rear seat 
belt reminders reported that the rear seat belt reminder made it easier 
to encourage the rear seat passengers to buckle up.\210\ Also, as noted 
earlier, part-time seat belt users--the predominant non-user group--are 
amenable to seat belt warnings. In addition, children, who might be 
particularly compliant with driver requests, are proportionally much 
more likely to be rear seat passengers than are adults.\211\
---------------------------------------------------------------------------

    \209\ Motoyuki Akamatsu et al., Assessment Method of 
Effectiveness of Passenger Seat Belt Reminder. 2012-01-0050, SAE 
International (2012).
    \210\ Survey of Principal Drivers of Vehicles with a Rear Seat 
Belt Reminder System at 47.
    \211\ Matthew J. Trowbridge & Richard Kent, Rear-Seat Motor 
Vehicle Travel in the U.S.: Using National Data to Define a 
Population at Risk. Am. J. Prev. Med. 37(4), at 322 (2009).
---------------------------------------------------------------------------

    We believe that any of the allowable rear seat belt reminder 
systems would be effective at accomplishing this goal. While some 
systems provide more information than others, and some would require 
the driver to fill in some informational gaps, even the most basic 
system (a RSBWS without occupant detection) would inform the driver 
about which belts are or are not fastened; the driver would readily be 
able to determine whether there were any unbelted occupants. We also 
believe that the 60-second visual warning would be effective. NHTSA 
could have proposed a more intrusive warning signal, such as an audible 
warning and/or a longer-duration visual warning. However, because such 
warnings necessitate occupant detection and we are not requiring 
occupant detection, we are also not requiring more aggressive warnings.
    NHTSA estimated the effectiveness of the rear seat belt warnings. 
Available research regarding seat belt use indicates that seat belt 
warning systems are effective at increasing seat belt use; however, 
estimates of the amount of increased belt usage that can be attributed 
to warning systems vary. In arriving at our estimates of increased seat 
belt usage from SBWS for rear seats, we examined current seat belt use 
rate in rear seats and the results of research conducted by NHTSA and 
others on percent increase in seat belt use for different types of 
warning systems for front seat occupants, as well as information 
submitted in response to the request for comments. For rear seat 
passengers 11 years old and older, we used a ``low'' estimate of 3.4 
percent increase in seat belt use, and a ``high'' estimate of 5.1 
percent increase in seat belt use. For rear seat passengers from six to 
ten years old, we used a low estimate of 0.27 percent and a high 
estimate of 0.41 percent. (The estimated increases for younger 
passengers are much lower because they already have high rates of seat 
belt use). For simplicity, we refer to these scenarios as ``Low'' and 
``High.'' \212\
---------------------------------------------------------------------------

    \212\ See FRIA section 4.2, ``Effect of SBWS on Seat Belt Use 
Rates for Rear Seat Occupants.''
---------------------------------------------------------------------------

    Based on these belt and warning system effectiveness estimates, we 
estimate that the rear seat belt warning requirements would prevent 26 
fatalities and 148 injuries annually under the ``Low'' scenario. Under 
the ``High'' scenario, we estimate that 39 fatalities and 221 injuries 
would be prevented annually.\213\ See table 11. Another way to measure 
benefits is by calculating equivalent lives saved. Equivalent lives 
saved are the number of prevented fatalities added to the number of 
prevented injuries, with the prevented injuries expressed in terms of 
equivalent fatalities (that is, with an injury expressed as a fraction 
of a fatality, so that the more serious the injury, the higher the 
fraction). The estimated equivalent lives saved are presented in table 
12 at the 3 percent and 7 percent discount rate.\214\
---------------------------------------------------------------------------

    \213\ See FRIA table 47.
    \214\ The 3 percent and 7 percent discount rates are in 
accordance with OMB Circular A-4. https://www.whitehouse.gov/wp-content/uploads/2023/11/CircularA-4.pdf.

 Table 11--Estimated Annual Benefits--Lives Saved and Injuries Prevented
for SBWS Without Occupant Detection (Rear Seats), With Estimated Low and
               High Percentage Point Increase in Belt Use
------------------------------------------------------------------------
              Injury level                      Low            High
------------------------------------------------------------------------
MAIS 1..................................              36              54
MAIS 2..................................              80             120
MAIS 3..................................              26              38
MAIS 4..................................               4               6
MAIS 5..................................               1               2
                                         -------------------------------
    Total Injuries......................             148             221
                                         -------------------------------
    Fatal...............................              26              39
------------------------------------------------------------------------


[[Page 447]]


 Table 12--Estimated Annual Benefits--Equivalent Lives Saved--SBWS Without Occupant Detection (Rear Seats) \215\
----------------------------------------------------------------------------------------------------------------
                                                                                   3 Percent        7 Percent
                       Belt use increase                         Undiscounted    discount rate    discount rate
----------------------------------------------------------------------------------------------------------------
Low...........................................................           36.22            29.98            24.31
High..........................................................           54.47            45.09            36.55
----------------------------------------------------------------------------------------------------------------

    We also estimated the costs of the finalized requirements. To 
comply with the minimum requirements (a positive-only system or 
negative-only/full-status system without occupant detection), the 
system would need to have seat belt buckle sensors (to determine if the 
belt is fastened) and wiring and wire conduits to provide information 
on the belt buckle status from the rear seats to the computer processor 
controlling the warning system.\216\ Based on the results of NHTSA's 
teardown analysis, we estimate a cost of $6.28 per seat. Given an 
average of 3.12 rear seats per vehicle, this yields a final cost of 
$19.59 per vehicle. Based on this per-vehicle cost, the cost to the 
fleet to comply with the finalized minimum requirements is $166.4 
million.
---------------------------------------------------------------------------

    \215\ See FRIA tables 68 and 70.
    \216\ The final rule is based on performance requirements, and 
as discussed previously, vehicle manufacturers are not restricted to 
using seat belt buckle sensors to determine belt usage. For example, 
spool-out sensors could be used instead of seat belt buckle sensors, 
but for the purposes of its compliance test NHTSA will consider a 
belt to be ``not in use'' when the belt latch is not fastened. We 
assume most manufacturers will likely use buckle sensors and that 
the cost is the same for seat belt buckle sensors as for spool-out 
sensors.
---------------------------------------------------------------------------

    Based on the forgoing, we performed benefit-cost and cost-
effectiveness analyses. A benefit-cost analysis calculates net 
benefits, which is the difference between the benefits flowing from 
injury and fatality reductions and the cost of the rule. Our net 
benefit estimates are presented in table 13. The cost-effectiveness 
analysis derives the cost per equivalent life saved, which is equal to 
the total cost of the rule divided by the total fatal equivalents that 
it prevents. These estimates are presented in table 14.
---------------------------------------------------------------------------

    \217\ See FRIA table 82.
    \218\ See FRIA table 74.

                    Table 13--Annual Monetized Benefits, Costs, and Net Benefits--SBWS Without Occupant Detection (Rear Seats) \217\
                                                               [2020 Dollars, in millions]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      3 percent discount rate                         7 percent discount rate
                 Seat belt use increase                  -----------------------------------------------------------------------------------------------
                                                             Benefits          Cost        Net benefits      Benefits          Cost        Net benefits
--------------------------------------------------------------------------------------------------------------------------------------------------------
Low.....................................................         $357.78         $166.44         $191.34         $290.05         $166.44         $123.62
High....................................................          538.00          166.44          371.56          436.16          166.44          269.72
--------------------------------------------------------------------------------------------------------------------------------------------------------


  Table 14--Cost-Effectiveness Analysis (Cost per Equivalent Life Saved)--SBWS Without Occupant Detection (Rear
                                                  Seats) \218\
                                           [2020 Dollars, in millions]
----------------------------------------------------------------------------------------------------------------
                Seat position & belt use increase                       ELS            Cost          Cost/ELS
----------------------------------------------------------------------------------------------------------------
                                             3 Percent Discount Rate
----------------------------------------------------------------------------------------------------------------
Low.............................................................           29.98          $166.4           $5.55
High............................................................           45.09           166.4            3.69
----------------------------------------------------------------------------------------------------------------
                                             7 Percent Discount Rate
----------------------------------------------------------------------------------------------------------------
Low.............................................................           24.31          $166.4           $6.85
High............................................................           36.55           166.4            4.55
----------------------------------------------------------------------------------------------------------------

2. Front Seat Belt Warning System
    Based on FARS and CISS data from 2017 through 2021, on average 
8,345 unrestrained drivers and 1,447 unrestrained front outboard 
passengers of passenger cars and light trucks were killed annually in 
traffic crashes. Additionally, 132,416 unrestrained drivers and 25,046 
unrestrained front outboard passengers were, on average, injured 
annually. After adjusting these to account for future decreases in 
fatalities and injuries projected to occur in the absence of the 
finalized requirements due to the introduction of other mandatory 
safety technologies (e.g., electronic stability control), the analysis 
estimates a baseline of, on average, 8,383 fatalities and 150,739 
injuries to unrestrained front seat occupants each year. This is the 
overall target population--the annual deaths and injuries that the 
final requirements are aimed at reducing.
    According to the NOPUS, 90.6 percent of drivers used their seat 
belt in 2021, and 89.4 percent of passengers in the right-front seating 
position used their seat belt.\219\ To estimate the percentage of 
drivers and front passengers who do not always use a seat belt, we used 
the results from a 2004 analysis using data from the Household

[[Page 448]]

Component of the 2002 Medical Expenditure Panel Survey (MEPS-HC) \220\ 
that found that among persons 16-64 years of age, 87.7 percent reported 
always or nearly always using seat belts when driving or riding in a 
car. Another 6.9 percent reported sometimes using seat belts, while 5.4 
percent reported seldom or never using seat belts when driving or 
riding in a car. These results are summarized in table 15. This means, 
when an observation is made about the percentage of drivers who use the 
seat belts, the observed belt use rate is higher than 87.7 percent 
since the other groups would contribute to the observed belt use rate 
although they are not always using the seat belts. NHTSA recognizes 
that driving habits may or may not have changed since 2002 as seat belt 
use rates have increased and as new generations of drivers and 
passengers are on the road. NHTSA considered, but tentatively decided 
not to use, the results of more recent studies, such as the (2016) 
Motor Vehicle Occupant Safety Survey (MVOSS) \221\ to estimate the 
percentage of drivers and front passengers who do not always use a seat 
belt. While the 2016 MVOSS is more recent, we decided to use the 2004 
study because we tentatively concluded that the data provided by the 
2004 study best suited the needs of our analysis. Although most data on 
seat belt use is self-reported, including the data in the 2004 study, 
the 2004 study has a high sample size (approximately 25,000) \222\ and 
provides robust categorizations of seat belt use that fit the needs of 
our analysis. Furthermore, when comparing this data to the findings of 
the 2016 MVOSS, we did not find evidence that seat belt use trends have 
significantly changed over time.\223\
---------------------------------------------------------------------------

    \219\ National Center for Statistics and Analysis. (2021, 
December). Seat belt use in 2021--Overall results (Traffic Safety 
Facts Research Note. Report No. DOT HS 813 241). National Highway 
Traffic Safety Administration.
    \220\ May Chu, ``Statistical brief #62: Characteristics of 
Persons Who Seldom or Never Wear Seat Belts 2002.'' https://meps.ahrq.gov/data_files/publications/st62/stat62.pdf.
    \221\ Spado, D., Schaad, A., & Block, A. (2019, December). 2016 
motor vehicle occupant safety survey; Volume 2: Seat belt report 
(Report No. DOT HS 812 727). National Highway Traffic Safety 
Administration.
    \222\ Compared to the 2016 MVOSS, which had, depending on the 
question, sample sizes of approximately 5,000 to 10,000.
    \223\ For example, the 2016 MVOSS found that about 6 percent of 
drivers reported using their belt most of the time or some of the 
time. See pg. 7 (Fig. 5) in the MVOSS.

                 Table 15--Seat Belt Use Characteristics
------------------------------------------------------------------------
               Belt user and related items                Rate (percent)
------------------------------------------------------------------------
Reported ``sometimes using seat belts''.................             6.9
Reported ``seldom or never using seat belts when driving             5.4
 or riding in a car''...................................
Reported always use seat belts..........................            87.7
                                                         ---------------
    Total...............................................           100.0
------------------------------------------------------------------------

    As we did for the rear seats, NHTSA estimated the effectiveness and 
benefits associated with requiring a seat belt warning system that 
remains activated until the seat belts are buckled for the driver and 
front outboard passenger seats. In developing this estimate, NHTSA used 
the results of a 2019 study conducted by IIHS by Kidd et al.\224\ In 
the Kidd et al. (2019) study, part-time belt users (who had a recent 
seat belt citation and reported not always using a seat belt) drove two 
vehicles for a certain period of time, a Chevrolet with three 
intermittent 7-second audible warnings followed by either a BMW with a 
100-second audible warning (n=17) or a Subaru with an audible warning 
that continues until the seat belt is buckled (n=16). (All of the 
vehicles provided a visual warning that lasted until the seat belt was 
buckled.) Kidd et al. found that, relative to the intermittent reminder 
(i.e., 7-second audible reminder), the BMW warning with the 100-second 
audible reminder increased seat belt use by 30 percent and the Subaru 
warning with the indefinite audible warning increased belt use by 34 
percent.\225\ The Kidd Study also found that some participants 
circumvented the enhanced warning systems by misusing the seat belt 
(sitting on a buckled seat belt or routing the buckled seat belt behind 
their back). Hard core ``never users'' of seat belts may similarly 
choose to circumvent the enhanced seat belt warning system. Therefore, 
NHTSA assumed that the ``never and seldom users'' of seat belts (5.4 
percent from the Chu study) could potentially circumvent the enhanced 
SBWS, so the analysis conservatively assumes no increase in seat belt 
use with enhanced SBWS for ``never and seldom users.''
---------------------------------------------------------------------------

    \224\ Kidd, D.G., and Singer, J. (2019, April) The effects of 
persistent audible seat belt reminders and a speed-limiting 
interlock on the seat belt use of drivers who do not always use a 
seat belt. Insurance Institute for Highway Safety, Westat, Inc.
    \225\ There were several limitations in this study, the main one 
being that the number of study participants was small, and, 
consequently, there was limited statistical power when comparing the 
change in rate of belt use between the different vehicle technology 
conditions. The study further discusses this and other limitations, 
such as how the demographics of the study sample differ from part-
time belt users nationwide. See also the discussion supra, Section 
VI.B.3.
---------------------------------------------------------------------------

    NHTSA also reviewed manufacturer data for MY 2020 vehicles to 
determine the market penetration of seat belt warning systems of 
various durations in the front outboard seats and obtained the 
estimates in table 16.

  Table 16--Market Penetration of Different Duration Seat Belt Audible
                             Warning Systems
------------------------------------------------------------------------
                                                           Percentage of
                       SBWS system                             sales
------------------------------------------------------------------------
<90 second warning......................................             7.6
90 second and 90+ but not indefinite....................            85.2
Enhanced--Warning until seat belt is buckled............             7.2
------------------------------------------------------------------------


[[Page 449]]

    For drivers, seat belts reduce the risk of fatality by 48 percent 
(for passenger cars) and 61 percent (for light trucks and vans) and 
reduce the risk of moderate to greater severity injuries by up to 65 
percent.\226\ For front outboard passengers, seat belts reduce the risk 
of fatality by 37 percent (for passenger cars) and by 58 percent (for 
light trucks and vans) and reduce the risk of moderate to greater 
severity injuries by 65 percent.\227\
---------------------------------------------------------------------------

    \226\ See FRIA table 31.
    \227\ See FRIA table 32.
---------------------------------------------------------------------------

    Based on the estimated seat belt warning system effectiveness in 
increasing seat belt use, the market penetration of different duration 
seat belt audible warning systems, and the effectiveness of seat belts 
in mitigating fatalities and injuries, NHTSA estimates that requiring 
an audio-visual seat belt warning \228\ that remains activated until 
the seat belt is buckled (indefinite duration) would prevent 20 driver 
fatalities, 2 front outboard passenger fatalities, and a total of 395 
injuries annually, as shown in table 17. This rule results in 46.7 
undiscounted equivalent lives saved, as shown in table 18. The 
estimated discounted annual benefits in terms of equivalent lives saved 
are also shown in table 18.
---------------------------------------------------------------------------

    \228\ The final rule differs from the proposed indefinite audio-
visual warning on vehicle start-up, because while the visual warning 
will be indefinite it is no longer specific to the ``start-of-trip'' 
and the audible warning will only be required to activate for at 
least 30 seconds and after the 30 seconds it will be a speed-
initiated indefinite audible warning. However, in the benefits and 
costs sections we will continue to refer to the front seat belt 
warning system as an indefinite warning because both the audible and 
visual warnings will be required to be active until the seat belt is 
fastened, if the respective trigger criteria are met.
    \229\ See FRIA table 60.
    \230\ See FRIA table 73.

 Table 17--Estimated Annual Benefits--Lives Saved and Injuries Prevented--Indefinite SBWS (Front Outboard Seats)
                                                      \229\
----------------------------------------------------------------------------------------------------------------
                         Injury level                              Driver       Front passenger        Total
----------------------------------------------------------------------------------------------------------------
MAIS 1.......................................................             129                 14             143
MAIS 2.......................................................             151                 19             170
MAIS 3.......................................................              62                  8              69
MAIS 4.......................................................               9                  1              10
MAIS 5.......................................................               3                  0               3
                                                              --------------------------------------------------
    Total Injuries...........................................             354                 42             395
----------------------------------------------------------------------------------------------------------------
Fatal........................................................              20                  2              22
----------------------------------------------------------------------------------------------------------------
Note: Values may not sum due to rounding.


    Table 18--Estimated Annual Benefits--Equivalent Lives Saved--Indefinite SBWS (Front Outboard Seats) \230\
----------------------------------------------------------------------------------------------------------------
                                                                                     3 Percent       7 Percent
                                                                   Undiscounted    discount rate   discount rate
----------------------------------------------------------------------------------------------------------------
Driver..........................................................           42.26           34.98           28.36
Front Passenger.................................................            4.44            3.68            2.99
                                                                 -----------------------------------------------
    Total.......................................................           46.70           38.66           31.35
----------------------------------------------------------------------------------------------------------------

    We also estimated the costs of the finalized requirements. Since 
all driver seats are already required to have at least the basic 
warning system, the incremental cost of enhanced seat belt warning for 
the driver seat is zero. We assume there would be some labor costs 
associated with software updates needed to extend the warning. However, 
as this is a simple programming change, this cost would be amortized 
over each vehicle's production and is therefore considered de minimis. 
Though there are no current requirements for a seat belt warning system 
for the front outboard passenger seat, NHTSA estimates that 96 percent 
of vehicles have seat belt warning systems on the front outboard 
passenger seat. NHTSA estimated the cost of equipping a seat belt 
warning system in the front outboard passenger seat to be $2.13 per 
seat. Therefore, the cost of equipping the remaining 4 percent of the 
16 million new vehicle fleet is $1.36 million (= 16 million x 4 percent 
x $2.13).
    Based on the foregoing, we performed benefit-cost and cost-
effectiveness analyses. The estimated net benefits, based on a 3 
percent and 7 percent discount, are presented in table 19 and the cost-
effectiveness estimates are presented in table 20.
---------------------------------------------------------------------------

    \231\ See FRIA, tables 80, 81, and 82.

                        Table 19--Annual Monetized Benefits, Costs and Net Benefits--Indefinite SBWS (Front Outboard Seats) \231\
                                                               [2020 Dollars, in millions]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      Driver                      Front passenger           Driver and front passenger
                                                         -----------------------------------------------------------------------------------------------
                                                             3 Percent       7 Percent       3 Percent       7 Percent       3 Percent       7 Percent
--------------------------------------------------------------------------------------------------------------------------------------------------------
Passenger car Benefits..................................         $188.89         $154.12          $22.86          $18.65         $211.75         $172.77
Light Truck & Van Benefits..............................          228.51          184.29           21.05           16.97          249.56          201.26
                                                         -----------------------------------------------------------------------------------------------

[[Page 450]]

 
    Total Benefits......................................          417.41          338.41           43.90           35.62          461.31          374.03
    Total Costs.........................................               0               0            1.36            1.36            1.36            1.36
--------------------------------------------------------------------------------------------------------------------------------------------------------
Net Benefits............................................          417.41          338.41           42.54           34.26          459.95          372.67
--------------------------------------------------------------------------------------------------------------------------------------------------------


 Table 20--Cost-Effectiveness Analysis (Cost per Equivalent Life Saved)--Indefinite SBWS (Front Outboard Seats)
                                                      \232\
                                           [2020 Dollars, in millions]
----------------------------------------------------------------------------------------------------------------
                          Discount rate                                 ELS            Cost          Cost/ELS
----------------------------------------------------------------------------------------------------------------
3 percent.......................................................           38.66           $1.36           $0.04
7 percent.......................................................           31.35           $1.36           $0.04
----------------------------------------------------------------------------------------------------------------

3. Overall Benefits and Costs of the Final Rule
---------------------------------------------------------------------------

    \232\ See FRIA, table 74.
---------------------------------------------------------------------------

    In table 21, we combine the benefits and costs for the finalized 
rear and front seat belt warning requirements. We estimate positive net 
benefits under all discount rates and effectiveness estimates.

    Table 21--Net Benefits From the Final Rule (SBWS for Rear Seating
   Positions and Indefinite SBWS for Front Outboard Seating Positions)
                    [2020 Dollars, in millions] \233\
------------------------------------------------------------------------
                                             3 Percent       7 Percent
                                           discount rate   discount rate
------------------------------------------------------------------------
Front Outboard Seats....................         $459.95         $372.67
Rear Seats..............................          191.34          123.62
(low increase in rear seat belt use)....
Rear Seats..............................          371.56          269.72
(high increase in rear seat belt use)...
                                         -------------------------------
    Total Net Benefits..................          651.29          496.28
    (low increase in rear belt use).....
    Total Net Benefits..................          831.51          642.39
    (high increase in rear belt use)....
------------------------------------------------------------------------

    In table 22, we combine the equivalent lives saved and cost for the 
finalized rear and front seat belt warning requirements to determine 
the cost per equivalent life saved.
---------------------------------------------------------------------------

    \233\ See FRIA, table 82.
    \234\ See FRIA, table 74.

Table 22--Cost per Equivalent Lives Saved from the Final Rule (SBWS for Rear Seating Positions and Indefinite SBWS for Front Outboard Seating Positions)
                                                                          \234\
                                                               [2020 Dollars, in millions]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                             Discounted at 3 percent                     Discounted at 7 percent
                                                                  --------------------------------------------------------------------------------------
                             Category                                                              Cost per                                    Cost per
                                                                     Equivalent        Cost       Equivalent     Equivalent       Cost        Equivalent
                                                                     Lives Saved                  Live Saved    Lives Saved                   Live Saved
--------------------------------------------------------------------------------------------------------------------------------------------------------
Rear Seat:
    Low..........................................................           29.98      $166.44           $5.55        24.31         $166.44        $6.85
    High.........................................................           45.09                         3.69        36.55                         4.55
Front Seat.......................................................           38.66         1.36            0.04        31.35            1.36         0.04
                                                                  --------------------------------------------------------------------------------------
    Total:.......................................................
        Low......................................................           68.65        167.8            2.44        55.66           167.8         3.01
        High.....................................................           83.75                         2.00        67.90                         2.47
--------------------------------------------------------------------------------------------------------------------------------------------------------


[[Page 451]]

B. Regulatory Alternatives

    In the preceding sections of this document, we discussed various 
alternatives for different aspects of the finalized requirements. We 
quantified the costs and benefits of three of these alternatives (rear-
seat occupant detection, a 90-second front outboard seat belt warning, 
and front center seat belt warning). Below, we briefly summarize our 
results. For a more detailed discussion, the reader is referred to the 
Final Regulatory Impact Analysis in the docket for this rulemaking.
1. Occupant Detection in Rear Seats
    For the rear seat belt reminder, NHTSA is not requiring occupant 
detection in the rear seats but permits occupant detection in rear 
seats. As a regulatory alternative, NHTSA estimated the costs and 
benefits of requiring a SBWS with occupant detection in the rear seats.
    NHTSA's teardown analysis indicates that occupant detection 
components cost $39.75 per vehicle, which, added to the $19.59 per 
vehicle cost of the buckle sensor, results in a combined warning system 
cost of $59.33 per vehicle (2020 $). NHTSA estimates that about 47 
percent of new vehicles have a SBWS for the rear seating positions and 
7 percent of new vehicles have occupant detection in rear seats. If 
NHTSA selected the regulatory alternative that required occupant 
detection, this rule would result in a total cost of $802 million. As 
with the final rule, this cost estimate assumed that 53 percent of new 
vehicles would need to install a seat belt sensor in the rear seats. 
And as discussed, rear seat occupant detection systems would need to be 
installed in all new vehicles. Although seven percent of light vehicles 
already have rear seat occupant detection, those SBWSs may not meet the 
requirements specified in this regulatory alternative.\235\ As a 
result, this analysis accounts for the cost of adding occupant 
detection in the rear seats in all new light vehicles to comply with 
this regulatory alternative. The total cost for this regulatory 
alternative is about $802 million.\236\
---------------------------------------------------------------------------

    \235\ The rear seat occupant detection in current vehicles is 
likely only able to detect a 5th percentile female and heavier 
occupants, but not children who weigh less than the 5th percentile 
female as is required for rear seat occupant detection in this final 
rule.
    \236\ See FRIA, table 119.
---------------------------------------------------------------------------

    Because there is uncertainty in how much more effective a SBWS with 
occupant detection would be in increasing seat belt use compared to the 
already estimated increase in seat belt use with SBWSs without occupant 
detection, NHTSA did not conduct a cost-effectiveness and net benefits 
analysis. Instead, NHTSA estimated the minimum increase in seat belt 
use for this regulatory alternative that would result in overall 
benefits equal to the overall costs (zero net benefits). Furthermore, 
for a direct comparison to the final rule requirements, NHTSA also 
considered how much greater the benefits from this regulatory 
alternative would have to be for the net benefits to be equal to those 
from the final rule, which does not require occupant detection.
    The agency estimated that seat belt use for rear seat occupants 11 
years and older would have to increase by approximately 5.4 percent 
when discounted at 3 percent and 6.7 percent when discounted at 7 
percent for this regulatory alternative to result in zero net benefits. 
Moreover, for this regulatory alternative to match the net benefits 
(taking into account the Low and High estimates of increased seat belt 
usage) from the final rule, seat belt use for rear seat occupants 11 
years and older would have to increase by 7.8 to 9.0 percent when 
discounted at 3 percent, and by 9.1 to 10.2 percent when discounted at 
7 percent.
    Under the final rule, which does not require occupant detection, 
seat belt use for rear seat occupants 11 years and older is estimated 
to increase from 75.12 percent to approximately 76.93 percent in the 
Low estimate and 77.84 percent in the High estimate. These increases 
reflect an approximately 2.4 percent and 3.6 percent increase in seat 
belt use under the final rule.
    Therefore, in this regulatory alternative requiring occupant 
detection for the rear seats, SBWS for rear seat occupants would need 
to be approximately 2.5 to 3.8 times more effective than the final rule 
at increasing seal belt usage to generate the same level of net 
benefits as the final rule. The SBWSs considered under this regulatory 
alternative are capable of informing the driver either which occupants 
are not using their seat belts or how many of the rear seat occupants 
are not using their seat belts. While we would expect some possible 
increase in seat belt use from that specific functionality, it is 
doubtful that it would double to quadruple the increase in seat belt 
use estimated for SBWSs without occupant detection. Therefore, based on 
the available information, the agency did not choose this regulatory 
alternative.
2. 90-Second Front Outboard Seat Belt Warning
    NHTSA also estimated the costs and benefits if it were to require a 
90-second audio-visual warning for the front outboard seats instead of 
the finalized requirement for a warning that lasts until the belt and 
any occupied seat is buckled. NHTSA estimated the benefits in a similar 
manner as that for the finalized seat belt warning for front seat 
occupants where the warning remains on until the seat belt is buckled. 
The main difference is that this alternative only affects the 7.6 
percent of the vehicle fleet with a front seat occupant seat belt 
warning with duration less than 90 seconds.
    The benefits of this alternative are presented in table 23.\237\
---------------------------------------------------------------------------

    \237\ See FRIA, tables 134 and 138.

  Table 23--Injuries Prevented, Lives Saved, and Equivalent Lives Saved in Front Outboard Seats by a 90 Second
                                                  Duration SBWS
----------------------------------------------------------------------------------------------------------------
                                            Injuries and Fatalities Prevented        Equivalent Lives Saved
               Injury Level                ---------------------------------------------------------------------
                                                Driver       Front Passenger       Driver       Front Passenger
----------------------------------------------------------------------------------------------------------------
MAIS 1....................................              43                4.7            0.19               0.02
MAIS 2....................................              44                5.7            1.82               0.23
MAIS 3....................................              18                2.3            3.26               0.41
MAIS 4....................................               3                0.3            0.83               0.08
MAIS 5....................................               1                0.1            0.47               0.05
Fatal.....................................               6                0.6            6.07               0.57
                                           ---------------------------------------------------------------------
    Total.................................  ..............  .................           12.66               1.37
----------------------------------------------------------------------------------------------------------------


[[Page 452]]

    About 14 equivalent lives are saved by this alternative, which is 
significantly lower than the nearly 47 equivalent lives saved by a 
warning that remains on until the seat belt is buckled. The cost of 
this alternative is the same as that for the warning required by this 
final rule. The only cost is that for the 4 percent of vehicles without 
a seat belt warning system in the front outboard passenger seat (cost = 
$1.36 million). The annual monetized benefits, costs, and net benefits 
of this alternative are shown in table 24.
---------------------------------------------------------------------------

    \238\ See FRIA, tables 142 and 143.

   Table 24--Annual Monetized Benefits, Costs and Net Benefits for a 90 Second Duration SBWS in Front Outboard
                                                   Seats \238\
                                           [2020 Dollars, in millions]
----------------------------------------------------------------------------------------------------------------
                                             Driver                Front Passenger          Driver and Front
                                   ----------------------------------------------------         Passenger
                                                                                       -------------------------
                                     3 Percent    7 Percent    3 Percent    7 Percent    3 Percent    7 Percent
----------------------------------------------------------------------------------------------------------------
Passenger car Benefits............       $58.69       $47.89        $7.25        $5.92       $65.94       $53.81
Light Truck & Van Benefits........        66.34        53.50         6.25         5.04        72.59        58.54
                                   -----------------------------------------------------------------------------
    Total Benefits................       125.03       101.39        13.50        10.96       138.54       112.35
Total Costs.......................            0            0         1.36         1.36         1.36         1.36
----------------------------------------------------------------------------------------------------------------
    Net Benefits..................       125.03       101.39        12.14         9.59       137.18       110.99
----------------------------------------------------------------------------------------------------------------

    While this regulatory alternative has positive net benefits, the 
benefits and net benefits are significantly lower than the indefinite 
duration SBWS for front seat occupants in the final rule (net benefits 
of $459.95 million and $372.67 million when discounted to 3 and 7 
percent, respectively).
3. Seat Belt Warning for Front Center Seat
    The agency also considered requiring a seat belt warning system for 
the front center seating position. To estimate incremental benefits, 
NHTSA used the 2017-2021 FARS data and CISS data, and the adjustment 
factors to account for safety impacts of new required safety 
technologies to establish the target population addressed by this 
regulatory alterative (Table 25).
---------------------------------------------------------------------------

    \239\ See FRIA, table 122.

        Table 25--Annual Adjusted Fatalities and Non-Fatal Injuries to Front Center Seat Passengers \239\
----------------------------------------------------------------------------------------------------------------
                         Injury severity                            Restrained     Unrestrained        Total
----------------------------------------------------------------------------------------------------------------
MAIS 1..........................................................             190             100             290
MAIS 2..........................................................               0               0               0
MAIS 3..........................................................               0               0               0
MAIS 4..........................................................               0               0               0
MAIS 5..........................................................               0               0               0
                                                                 -----------------------------------------------
    Total Injuries..............................................             190             100             290
    (MAIS 1-5)..................................................
----------------------------------------------------------------------------------------------------------------
Fatal...........................................................               6              13              19
----------------------------------------------------------------------------------------------------------------

    Due to a lack of data, NHTSA is unable to establish the seat belt 
use rate for front center passengers under the baseline. As front 
center seat passengers are most similar to front outboard passengers, 
this analysis makes use of the established seat belt use rate for front 
outboard passengers to establish the baseline seat belt use rates for 
front center seat occupants. Based on the 2021 NOPUS data, the baseline 
seat belt use rate is 89.40 percent and the corresponding seat belt use 
rate in potentially fatal crashes is 76.88 percent.
    In order to estimate the change in seat belt use for front center 
seat passengers as a result of the SBWS, this analysis makes use of the 
linear regression model used to estimate the impact of the SBWS on the 
seat belt use rates of rear seat occupants. Under this regulatory 
alternative, the seat belt use rate for front center seat passengers 
using the high estimate is 91.58 percent and the corresponding seat 
belt use rate in potentially fatal crashes is 79.69 percent.
    The cost for front center passenger seats would include the cost 
for a buckle sensor and occupant detection. Therefore, the cost per 
vehicle for this regulatory alternative is $14.86 in 2020 dollars. This 
cost estimate reflects a cost of $2.13 to add a buckle sensor and the 
cost to add occupant detection of $12.73.
    In assessing the number of vehicles that would be impacted by this 
regulatory alternative, we consider that the front center seat is not a 
common feature in new light vehicles. Based on our engineering 
judgement, we expect that approximately 800,000 vehicles or 5 percent 
of the new vehicle fleet include a center seating position. Table 26 
presents the total cost to meet the requirements under this regulatory 
alternative for an indefinite duration SBWS for front center passenger 
seats.

[[Page 453]]



             Table 26--Total Cost of Indefinite Duration SBWS for Front Center Passenger Seats \240\
----------------------------------------------------------------------------------------------------------------
     Number of vehicles impacted                Per vehicle cost                         Total cost
----------------------------------------------------------------------------------------------------------------
                      800,000                                $14.86                           $11,888,000
----------------------------------------------------------------------------------------------------------------

    Table 27 presents the of the cost-effectiveness analysis and table 
28 presents the benefit-cost analysis for this regulatory 
alternative.\241\ When discounted at three and seven percent, the cost 
per ELS is approximately $40.9 million and $50.6 million, respectively 
and the net benefits are negative for this regulatory alternative. 
Because the cost per ELS is higher than the comprehensive cost of a 
fatality and the net benefits are negative, this regulatory alternative 
is not cost-effective.
---------------------------------------------------------------------------

    \240\ See FRIA, table 128.
    \241\ See FRIA, tables 129 and 130.

                                       Table 27--Cost-Effectiveness Analysis for SBWS Front Center Seat Passengers
                                                                       [Millions]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                 Discounted at 3 percent                            Discounted at 7 percent
                                                   -----------------------------------------------------------------------------------------------------
                     Category                                                             Cost per                                           Cost per
                                                       Equivalent          Cost       equivalent live     Equivalent          Cost       equivalent live
                                                      lives saved                          saved         lives saved                          saved
--------------------------------------------------------------------------------------------------------------------------------------------------------
Front Center Seat.................................            0.29           $11.89           $40.91             0.23           $11.89           $50.63
--------------------------------------------------------------------------------------------------------------------------------------------------------


                                          Table 28--Benefit-Cost Analysis for SBWS Front Center Seat Passengers
                                                                       [Millions]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                 Discounted at 3 percent                            Discounted at 7 percent
                                                   -----------------------------------------------------------------------------------------------------
                     Category                          Monetized                                          Monetized
                                                        benefits           Cost         Net benefits       benefits           Cost         Net benefits
--------------------------------------------------------------------------------------------------------------------------------------------------------
Front Center Seat.................................           $3.47           $11.89           -$8.42            $2.80           $11.89           -$9.09
--------------------------------------------------------------------------------------------------------------------------------------------------------

IX. Compliance Dates

    NHTSA proposed that vehicles be required to comply with the 
requirements of this rule the first September 1 that is one year after 
the publication of the final rule for the front seat belt warning 
system requirements and the first September 1 that is two years after 
the publication of the final rule for the rear seat belt warning system 
requirements, with optional early compliance permitted. Consistent with 
49 CFR 571.8(b), multi-stage manufacturers and alterers would have an 
additional year to comply.
    We estimated it would take two years for manufacturers to equip 
their vehicles with the necessary technologies, redesign hardware and 
software components, and validate their systems to comply with the 
requirements for the rear seat belt reminder systems. Regarding front 
passenger outboard seat belt warning requirements, we noted that 
because of the market penetration of such systems (96 percent of new 
vehicles), the majority of vehicle manufacturers would simply have to 
make software adjustments necessary to ensure they meet the proposed 
requirements.\242\
---------------------------------------------------------------------------

    \242\ 88 FR 61674. This figure is based on data on total 
projected vehicle sales in the United States for MY 2022 from the 
agency's New Car Assessment Program Purchasing with Safety in Mind: 
What to Look For When Buying a Vehicle program.
---------------------------------------------------------------------------

Comments
    The National Transportation Safety Board (NTSB) supported the 
proposed lead time and emphasized the timeline of this rulemaking 
activity related to seat belt warning systems.
    Several commenters suggested shorter lead times. MADD and Advocates 
and Public Citizen supported a compliance deadline as soon as is 
feasible. MADD stated that given the state and availability of current 
technology, a one-year deadline for compliance is likely reasonable. 
Advocates and Public Citizen stated that one year should be sufficient 
for rear systems, noting that IIHS testing has demonstrated that this 
deadline is achievable and that delaying will cost lives.
    SRN commented that, depending on the date on which the final rule 
is published, the rear seat compliance deadline could be closer to 3 
years, and urged NHTSA to ensure that compliance is required within 
close to a 2-year window.
    IIHS and NAMIC commented that the requirements should be 
implemented immediately. IIHS noted research suggesting that increasing 
seat belt use of unbuckled occupants throughout the vehicle by up to 34 
percent would save about 1,600 lives each year (Kidd & O'Malley, 2023), 
and that delaying the implementation of the upgraded standard would 
unnecessarily delay its life-saving benefits. IIHS explained that 
according to its evaluations, since 2022 adoption of rear reminder 
systems has increased and manufacturers have responded quickly in the 
past to their requirements, suggesting that less lead time is needed.
    Consumer Reports agreed with IIHS that manufacturers have 
demonstrated they can make improvements quickly and suggested that both 
rear and front reminders be required within 1 year. They also noted 
that in 2012, Congress mandated that NHTSA issue a final rule by 2015, 
and that the ANPRM for this rulemaking was published in 2019. They 
argued that given this timeline, compliance should be required sooner.
    Other commenters requested that the compliance dates be extended. 
Auto Innovators contended that the proposed lead time is not reasonable 
or practical for implementing the proposed changes.

[[Page 454]]

In particular, they emphasized that the lack of harmonization with ECE 
R16 may result in design changes for vehicles that are in the final 
stages of preproduction and manufacturers may no longer be able to use 
hardware and software systems currently deployed in other markets. 
Honda provided a list of changes that it would undertake to meet the 
requirements proposed in the NPRM and suggested that the lead time 
proposed is inadequate to accomplish them.
    Nissan also requested additional lead time, especially if it is 
necessary to relocate the front outboard passenger telltale. Auto 
Innovators and Honda noted that if NHTSA harmonized the rule further 
with ECE R16, less lead time would be needed to meet the requirements.
    Auto Innovators, HATCI, Ford, and Honda requested a synchronized 
two-year phase-in for both the front and rear row seating position 
requirements that begins three years after publication of the final 
rule. In their proposal, a set percentage of vehicles would be required 
to meet the requirements of the rule beginning the first September 1st 
that is at least 3 years after publication of the final rule; a higher 
percentage by the first September 1st after 4 years; with full 
compliance by the first September 1st that is at least five years after 
publication of the final rule. HATCI specified that the first phase-in 
threshold should be no more than 50 percent of vehicles. Ford and Honda 
emphasized that this approach would allow manufacturers to account for 
differences in implementation across models with varied development 
cycles. Auto Innovators and Honda argued that this approach would unify 
the lead time for front and rear systems because there would not be a 
benefit to having different lead times for front and rear systems due 
to the limitations of production schedules. Auto Innovators commented 
that there is no benefit or regulatory relief provided by NHTSA's 
proposal for one year of lead time for the front and two years for the 
rear because it is both highly impractical and unlikely that 
manufacturers will be able to adjust production schedules to account 
for changes to the front row and rear row seating positions 
independently of each other, and only one year apart. Additionally, 
some commenters, such as Auto Innovators and Nissan, commented that if 
the rule does not allow for the reminder to be overridden, it will 
likely result in the need for significant changes to the instrument 
cluster that will require additional time and resources to implement. 
Nissan commented that additional lead time becomes more critical if 
relocating the front outboard passenger telltale indicator beyond the 
vehicle's current meter display is required.
    A few commenters, such as Auto Innovators and Consumer reports, 
requested that optional early compliance be allowed.
    Auto Innovators urged the agency to announce whether the lead time 
will be changed through the docket, other such notice, or to publish a 
second NPRM within one year of its original filing, to ensure that 
manufacturers do not waste time, money, and effort to develop products 
that align with the proposal, but which need to be changed to meet the 
final rule.
Agency Response
    NHTSA is finalizing the compliance dates as proposed in the NPRM. 
These dates properly balance the practical realities of bringing 
systems into compliance with maximizing the safety benefits of this 
rule. We are allowing optional early compliance.
    NHTSA disagrees with commenters who argue that compliance can be 
required immediately or who seek to shorten the compliance timeline. 
NHTSA understands that any allowed time to bring systems into 
compliance risks reducing some of the benefits of the rule. However, we 
must balance maximizing effectiveness with considerations of 
feasibility and practicability. Although commenters correctly point out 
that the necessary technologies for both front and rear systems are 
available, they underestimate the time some manufacturers may need to 
integrate components into vehicles for the rear seat reminder as well 
as incorporate visual signals and validate system performance for both 
front and rear positions. Although some manufacturers may have been 
able to rapidly adapt their systems to changes in IIHS ratings, this 
fact does not support the notion that doing so would be practicable for 
the entire industry. For example, a small number of vehicles do not yet 
have voluntary front passenger seat belt warnings, and these vehicles 
would need hardware integration. We also disagree with NAMIC and 
Consumer Reports that the duration of this rulemaking effort warrants 
shortening the date schedule. Our determination regarding the proper 
compliance dates is based on current information and when the rule is 
finalized. The option of early compliance may realize earlier safety 
benefits for vehicles with earlier development schedules.
    NHTSA also disagrees with commenters seeking to extend the dates. 
In particular, a three-year compliance date with a two-year phase-in, 
suggested by Auto Innovators, HATCI, Honda, and Ford, dramatically 
exceeds the amount of time that manufacturers should need to implement 
the changes required by this rule. As noted, the technology for these 
systems already exists. For front systems in particular, the vast 
majority of vehicles already incorporate the necessary technology, and 
only software changes will be needed to bring systems into compliance.
    Additionally, we have made changes from the NPRM which should 
significantly reduce the time needed to bring systems into compliance. 
For example, this final rule no longer dictates specific compliance 
options for the information conveyed by the rear seat belt warning 
visual warning; the finalized requirements for the visual warning allow 
all of the systems that would have been allowed under the proposed 
rule, as well as additional systems that would not have been allowed 
under the proposed rule, such as a negative-only system without 
occupant detection and a full-status system without occupant detection. 
It also does not require the front passenger seat belt visual warning 
to be visible to the front passenger (except for certain ADS-equipped 
vehicles), which was an element of the proposal about which certain 
commenters, such as Nissan, expressed significant cost and time 
concerns. Indeed, in the NPRM we sought comment, and received no 
detailed comments, regarding which types of vehicles might need 
additional lead time to accommodate the proposed visibility 
requirement. Additionally, Auto Innovators noted that less time would 
be needed to implement requirements that harmonize with ECE R16. We 
have also incorporated changes from the NPRM which increase 
harmonization with ECE R16 significantly. Finally, we do not believe it 
is necessary to grant additional time to accommodate that warnings are 
not allowed to be overridden because this rule provides a large amount 
of flexibility for manufacturers to design and locate the visual alerts 
to resolve this issue.\243\ Because these elements resolve many of the 
concerns raised by

[[Page 455]]

commenters about the compliance timeline, we are not extending the 
compliance dates.
---------------------------------------------------------------------------

    \243\ While the final rule requires that the visual warning must 
not be overridden by other visual warnings, it does allow the 
audible warning to be paused during the activation of another 
audible safety warning that is designed to alert the driver to take 
immediate action; in this case, however, the seat belt audible 
warning must be resumed for the remainder of the required duration 
after the other audible warning deactivates.
---------------------------------------------------------------------------

    We are also not implementing a unified lead time for front and rear 
systems. As we pointed out in the NPRM, 96 percent of vehicles already 
have a front outboard passenger seat belt warning system, while market 
penetration for rear systems is much lower. The acquisition and 
integration of additional hardware for rear seats, which is not needed 
for the vast majority of front passenger systems, warrants additional 
lead time for the rear systems.
    Finally, because we are not changing the lead time from the 
proposal, we are not publishing the notice of changes regarding the 
lead time requested by Auto Innovators.

X. Regulatory Analyses

Executive Order 12866, Executive Order 14094, Executive Order 13563, 
and DOT Regulatory Policies and Procedures

    NHTSA has considered the impact of this rule under Executive Order 
12866, Executive Order 14094, Executive Order 13563, DOT Order 2100.6A, 
and the Department of Transportation's regulatory policies and 
procedures.\244\ The Office of Management and Budget determined that 
this rule is a significant regulatory action and was reviewed under 
Section 3(f)(1) of E.O. 12866, as amended by E.O. 14094. Pursuant to 
E.O. 12866 and the Department's policies, we have identified the 
problem this rule addresses, assessed the benefits and costs, and 
considered alternatives. These analyses have been summarized in Section 
VII, Regulatory Alternatives and Section VIII, Overview of Benefits and 
Costs and are discussed in more detail in the docketed final regulatory 
impact analysis.
---------------------------------------------------------------------------

    \244\ 49 CFR, Part 5, Subpart B; Department of Transportation 
Order 2100.6A, Rulemaking and Guidance Procedures, June 7, 2021.
---------------------------------------------------------------------------

Promoting International Regulatory Cooperation

    The policy statement in section 1 of Executive Order 13609 provides 
that the regulatory approaches taken by foreign governments may differ 
from those taken by the United States to address similar issues, and 
that in some cases the differences between them might not be necessary 
and might impair the ability of American businesses to export and 
compete internationally. It further recognizes that in meeting shared 
challenges involving health, safety, and other issues, international 
regulatory cooperation can identify approaches that are at least as 
protective as those that are or would be adopted in the absence of such 
cooperation and can reduce, eliminate, or prevent unnecessary 
differences in regulatory requirements.
    In addition, section 24211 of the Infrastructure, Investment, and 
Jobs Act (IIJA; Pub. L. 117-58), Global Harmonization, provides that 
DOT ``shall cooperate, to the maximum extent practicable, with foreign 
governments, nongovernmental stakeholder groups, the motor vehicle 
industry, and consumer groups with respect to global harmonization of 
vehicle regulations as a means for improving motor vehicle safety.'' 
\245\
---------------------------------------------------------------------------

    \245\ H.R. 3684 (117th Congress) (2021).
---------------------------------------------------------------------------

    As discussed in Section VII and through this preamble, this rule 
harmonizes with ECE R16, Euro NCAP, and the IIHS protocol as much as 
possible, but deviates where we believed it was justified with respect 
to the Safety Act criteria (need for safety, objectivity, and 
practicability). The reasons for following or deviating in any of these 
respects are explained in detail in the relevant section of the 
preamble. In general, we believe that although this rule deviates from 
these requirements or protocols in some ways, it is not incompatible 
with them, so that it is possible to design a seat belt reminder system 
that complies with both this rule and protocols such as R16. Further, 
almost all international NCAP programs, including those in Europe, 
Japan, China, Korea, Latin America, Southeast Asia, and Australia and 
New Zealand, award points to vehicles that are equipped with seat belt 
warning systems for passenger seating positions. Thus, the requirements 
in this rule are consistent with these international programs and 
complement those international efforts to increase seat belt use by all 
vehicle occupants.

Regulatory Flexibility Act

    Pursuant to the Regulatory Flexibility Act (5 U.S.C. 601 et seq., 
as amended by the Small Business Regulatory Enforcement Fairness Act 
(SBREFA) of 1996), whenever an agency is required to publish an NPRM or 
final rule, it must prepare and make available for public comment a 
regulatory flexibility analysis (RFA) that describes the effect of the 
rule on small entities (i.e., small businesses, small organizations, 
and small governmental jurisdictions). The Small Business 
Administration's regulations at 13 CFR part 121 define a small 
business, in part, as a business entity ``which operates primarily 
within the United States.'' 13 CFR 121.105(a). No regulatory 
flexibility analysis is required if the head of an agency certifies 
that the rule will not have a significant economic impact on a 
substantial number of small entities. SBREFA amended the Regulatory 
Flexibility Act to require Federal agencies to provide a statement of 
the factual basis for certifying that a rule will not have a 
significant economic impact on a substantial number of small entities.
    I certify that this final rule would not have a significant 
economic impact on a substantial number of small entities. According to 
13 CFR 121.201, the Small Business Administration's size standards 
regulations used to define small business concerns, manufacturers of 
the vehicles covered by this final rule would fall under North American 
Industry Classification System (NAICS) No. 336211, Automobile 
Manufacturing, which has a size standard of 1,000 employees or fewer.
    NHTSA estimates that there are three small light vehicle 
manufacturers in the U.S. As noted in Section 11.1 of the docketed 
final regulatory impact analysis, the estimated annual vehicle sales 
for these three manufacturers range from 25 to 100 vehicles with a 
sales price range $24,000 to $750,000 and estimated annual revenue 
between $2 million and $4 million. We estimate that there are several 
hundred second-stage or final-stage manufacturers and alterers that 
could be impacted by this final rule. The agency has analyzed the 
economic impact on these entities. For the reasons discussed below and 
detailed in the final regulatory impact analysis, we conclude that this 
rule would not have a significant economic impact on a substantial 
number of small entities.
    The rule would directly affect motor vehicle manufacturers, 
including small light vehicle manufacturers. However, we believe that 
the rule will not have a significant economic impact on these entities. 
Small manufacturers are already certifying their vehicle's compliance, 
for the driver position, with FMVSS No. 208's seat belt warning system 
requirements. The means they use to certify to the current requirements 
would be similar to or the same as those they would use to certify to 
the rear seat belt warning requirements and front outboard passenger 
seat belt warning requirements under the final rule.
    Further, the compliance test is a relatively simple test, involving 
a test technician positioning a person or test dummy in a seat and 
checking if the requisite signals activate. Checking to see if visual 
and audible warnings activate for the driver seat belt warning

[[Page 456]]

system has been a part of FMVSS No. 208 compliance testing for many 
years, and manufacturers are knowledgeable about conducting such tests.
    Small manufacturers have options available to certify compliance, 
none of which will result in a significant economic impact on these 
entities. The manufacturers can and do obtain seating systems from seat 
suppliers and install the seats on the body following the instructions 
of the seat supplier. Seat and seat belt suppliers are large entities 
with resources available to assist small manufacturers in incorporating 
the seat belt warning systems, if manufacturers need technical 
assistance (which we do not think they will need, given the simplicity 
of the systems, particularly those rear systems that do not involve 
occupant detection). We do not believe that current manufacturing 
practices will have to change significantly because of this rule.
    In addition, we also believe that the rule will not have a 
significant impact on small and limited-line vehicle manufacturers 
because the market for the vehicles produced by these entities is 
highly inelastic. Purchasers of these vehicles are attracted by the 
desire to have an unusual vehicle. Further, all light vehicles would 
have to comply with the requirements. Since the price of complying with 
the rule will likely be passed on to the final consumer, the price of 
competitor's models would increase by similar amounts. Further, we do 
not believe that raising the price of a vehicle to account for the 
incremental costs estimated for this final rule ($2.13 for the front 
outboard passenger seat and $19.59 for the rear seats) would have much, 
if any, effect on vehicle sales.
    There are a significant number (several hundred) of second-stage or 
final-stage manufacturers and alterers that would be impacted by a 
final rule. These manufacturers buy incomplete vehicles to finish as 
complete vehicles or modify previously certified vehicles. Many of 
these latter vehicles are van conversions; there are a variety of 
vehicles affected.
    To produce a vehicle, a final-stage manufacturer can either stay 
within the incomplete vehicle document (IVD) furnished by the 
incomplete vehicle manufacturer (which are typically large vehicle 
manufacturers, such as GM or Ford), or the final-stage manufacturer can 
work with incomplete vehicle manufacturers to enable the final-stage 
manufacturer to certify to the new requirements.\246\ The final-stage 
manufacturer can also certify to the standard using due care based on 
an assessment of the information available to the manufacturer.
---------------------------------------------------------------------------

    \246\ For a discussion of NHTSA's certification regulations for 
final stage manufacturers, see 71 FR 28168, May 15, 2006, Docket No. 
NHTSA-2006-24664, Response to petitions for reconsideration of a 
final rule implementing regulations pertaining to multi-stage 
vehicles and to altered vehicles. The Background section of that 
document provides concepts and terminology relating to the 
certification of multi-stage vehicles.
---------------------------------------------------------------------------

    While there are a substantial number of multi-stage manufacturers 
that could be impacted by the final rule, we believe that the impact on 
them would not be significant. We note that these manufacturers are 
already certifying their vehicles to FMVSS No. 208's seat belt warning 
system requirements that apply to the driver seating position. They are 
already familiar with the equipment and manufacturing processes 
involved to certify their vehicles to seat belt warning system 
requirements. Further, we anticipate that final-stage manufacturers 
will base their vehicles on incomplete vehicles that already have the 
seat belt reminder system installed rather than install the systems 
themselves.
    For final-stage manufacturers working with incomplete vehicles that 
do not have rear seats or seat belt reminder systems already installed, 
we believe that completing vehicles to meet the requirements would be 
practicable. The manufacturers can obtain seats and seat belt systems 
(with seat belt warning system) from suppliers. NHTSA recognizes that 
the suppliers might be supplying larger vehicle manufacturers during 
the development and lead time period, and do not have the capabilities 
to handle all of the smaller manufacturers, including final-stage 
manufacturers. The rulemaking accounts for this limitation by allowing 
final-stage manufacturers an additional year to comply with the 
requirements, to provide flexibility to these small entities and reduce 
the economic impact of the rule on them. (See also 49 CFR 571.8(b).)
    For an alterer (a person who alters by addition, substitution or 
removal of components, other than readily attachable components, a 
certified vehicle before the first purchase of the vehicle other than 
for resale), the impacts of the rule will not be significant. The final 
rule allows alterers an additional year to comply with the 
requirements. For example, if an alterer is removing rear seats, the 
person making the alteration would simply have to be careful not to 
render non-compliant the seat belt warning system for the remaining 
seats. (See 49 CFR 571.8(b).)
    An alterer that is adding rear seats could obtain seating systems 
with seat belt warning systems from seat suppliers and install the 
seats on the body following the instructions of the seat supplier. 
Changes may have to be made to the instrument panel area to add the 
requisite visual signal, but the final rule provides flexibility to 
manufacturers in providing the visual signal.

Executive Order 13132 (Federalism)

    NHTSA has examined this rule pursuant to Executive Order 13132 (64 
FR 43255; Aug. 10, 1999) and concluded that no additional consultation 
with States, local governments, or their representatives is mandated 
beyond the rulemaking process. The agency has concluded that the rule 
does not have sufficient federalism implications to warrant 
consultation with State and local officials or the preparation of a 
federalism summary impact statement. The rule does not have 
``substantial direct effects on the States, on the relationship between 
the national government and the States, or on the distribution of power 
and responsibilities among the various levels of government.''
    NHTSA rules can have preemptive effect in two ways. First, the 
National Traffic and Motor Vehicle Safety Act contains an express 
preemption provision: When a motor vehicle safety standard is in effect 
under this chapter, a State or a political subdivision of a State may 
prescribe or continue in effect a standard applicable to the same 
aspect of performance of a motor vehicle or motor vehicle equipment 
only if the standard is identical to the standard prescribed under this 
chapter. 49 U.S.C. 30103(b)(1). It is this statutory command by 
Congress that preempts any non-identical State legislative and 
administrative law address the same aspect of performance.
    The express preemption provision described above is subject to a 
savings clause under which ``[c]compliance with a motor vehicle safety 
standard prescribed under this chapter does not exempt a person from 
liability at common law.'' 49 U.S.C. 30103(e). Pursuant to this 
provision, State common law tort causes of action against motor vehicle 
manufacturers that might otherwise be preempted by the express 
preemption provision are generally preserved.
    NHTSA rules can also preempt State law is if complying with the 
FMVSS would render the motor vehicle manufacturers liable under State 
tort law. Because most NHTSA standards established by an FMVSS are 
minimum

[[Page 457]]

standards, a State common law tort cause of action that seeks to impose 
a higher standard on motor vehicle manufacturers will generally not be 
preempted. However, if and when such a conflict does exist--for 
example, when the standard at issue is both a minimum and a maximum 
standard--the State common law tort cause of action is impliedly 
preempted. See Geier v. American Honda Motor Co., 529 U.S. 861 (2000).
    Pursuant to Executive Order 13132, NHTSA has considered whether 
this rule could or should preempt State common law causes of action. 
The agency's ability to announce its conclusion regarding the 
preemptive effect of one of its rules reduces the likelihood that 
preemption will be an issue in any subsequent tort litigation.
    To this end, the agency has examined the nature (e.g., the language 
and structure of the regulatory text) and objectives of this rule and 
finds that this rule, like many NHTSA rules, would prescribe only a 
minimum safety standard. NHTSA does not intend that this rule preempt 
state tort law that would effectively impose a higher standard on motor 
vehicle manufacturers than that established by this rule. Establishment 
of a higher standard by means of State tort law would not conflict with 
the standards in this final rule. Without any conflict, there could not 
be any implied preemption of a State common law tort cause of action.

National Environmental Policy Act

    NHTSA has analyzed this rule for the purposes of the National 
Environmental Policy Act. In accordance with 49 CFR 1.81, 42 U.S.C. 
4336, and DOT NEPA Order 5610.1C, NHTSA has determined that this rule 
is categorically excluded pursuant to 23 CFR 771.118(c)(4) (planning 
and administrative activities, such as promulgation of rules, that do 
not involve or lead directly to construction). This rulemaking, which 
amends Federal Motor Vehicle Safety Standard (FMVSS) No. 208, 
``Occupant crash protection,'' to require a seat belt use warning 
system for rear seats, updates and enhances the current seat belt 
warning requirements for the driver's seat belt, and extends these 
requirements to the front outboard passenger seat, is not anticipated 
to result in any environmental impacts, and there are no extraordinary 
circumstances present in connection with this rulemaking.

Executive Order 12988 (Civil Justice Reform)

    With respect to the review of the promulgation of a new regulation, 
section 3(b) of Executive Order 12988, ``Civil Justice Reform'' (61 FR 
4729, February 7, 1996) requires that Executive agencies make every 
reasonable effort to ensure that the regulation: (1) Clearly specifies 
the preemptive effect; (2) clearly specifies the effect on existing 
Federal law or regulation; (3) provides a clear legal standard for 
affected conduct, while promoting simplification and burden reduction; 
(4) clearly specifies the retroactive effect, if any; (5) adequately 
defines key terms; and (6) addresses other important issues affecting 
clarity and general draftsmanship under any guidelines issued by the 
Attorney General. This document is consistent with that requirement.
    Pursuant to Executive Order 12988, NHTSA notes as follows. The 
issue of preemption is discussed above in connection with Executive 
Order 13132. NHTSA notes further that there is no requirement that 
individuals submit a petition for reconsideration or pursue other 
administrative proceeding before they may file suit in court.

Paperwork Reduction Act

    Under the procedures established by the Paperwork Reduction Act of 
1995 (PRA) (44 U.S.C. 3501, et seq.), a Federal agency must request and 
receive approval from the Office of Management and Budget (OMB) before 
it collects certain information from the public and a person is not 
required to respond to a collection of information by a Federal agency 
unless the collection displays a valid OMB control number. In 
compliance with these requirements, NHTSA is submitting an information 
collection request (ICR) to OMB for approval for modifications to a 
currently approved information collection titled ``Consolidated Vehicle 
Owner's Manual Requirements for Motor Vehicles and Motor Vehicle 
Equipment'' (OMB Control No. 2127-0541, Current Expiration Date: 03/31/
2026).
    This final rule amends 49 CFR 571.208 to, among other things, add 
new owner's manual requirements. NHTSA submitted an ICR to OMB for 
review when the NPRM was published.\247\ OMB deferred review until 
after receiving NHTSA's summary and response to all comments related to 
the information collection requirements contained in this rulemaking. 
Accordingly, NHTSA is resubmitting the ICR for this final rule.
---------------------------------------------------------------------------

    \247\ https://www.reginfo.gov/public/do/PRAViewICR?ref_nbr=202308-2127-002#.
---------------------------------------------------------------------------

    NHTSA's ICR describes the nature of the information collections and 
their expected burden. The ICR is for fifteen mandatory and voluntary 
disclosure requirements for manufacturers of motor vehicles and items 
of motor vehicle equipment. Pursuant to 49 U.S.C. 30117, the Secretary 
(NHTSA by delegation) is authorized to require manufacturers to provide 
information to first purchasers of motor vehicles or items of motor 
vehicle equipment related to performance and safety in printed 
materials that are attached to or accompany the motor vehicle or item 
of motor vehicle equipment. NHTSA has exercised this authority to 
require manufacturers to provide certain specified safety information 
to be readily available to consumers and purchasers of motor vehicles 
and items of motor vehicle equipment. This information is most often 
provided in vehicle owners' manuals and the requirements are found in 
49 CFR parts 563, 571, and 575. Some of these requirements are 
contained in the Federal Motor Vehicle Safety Standards (FMVSS) that 
set performance requirements for motor vehicles and items of motor 
vehicle equipment. The other requirements are contained in separate 
regulations. Manufacturers must comply with these requirements whenever 
they manufacture a vehicle or equipment item that is subject to the 
requirements. The purpose of the required disclosures is to provide 
important safety information to vehicle owners.
    This final rule makes changes to existing an information collection 
requiring that the owner's manual describe the vehicle's seat belt 
warning system features, including the location, format, and meaning of 
the visual warnings. It also requires that the owner's manual include 
instructions on how to make any manual electrical connections for 
readily removable seats. These changes are finalized without any 
substantive changes from those proposed in the NPRM.
    We received comments on the proposed changes. ASC supported the 
proposed changes to the owner's manual requirements. NSC suggested 
standardizing generic nomenclature and warning and icon symbols to 
reduce driver confusion. Regarding installation of child restraint 
systems, Auto Innovators emphasized that additional information about 
system design can be included at the discretion of the manufacturer, 
and SRN suggested that instructions regarding how to interpret certain 
warnings should be included in

[[Page 458]]

the child passenger section of the manual. These comments are discussed 
in Section VI.A.2.d.
    As described in the NPRM, NHTSA estimates that the total burden of 
the ICR is approximately 10,172 hours and $8,726,501 annually. This 
burden represents an increase in estimated burden hours of 1,544 hours 
(8,628 hours to 10,172 hours) and an increase in costs of $755,040 
($7,971,461 to $8,726,501), compared with existing requirements. The 
change in burden reflects changes as a result of the rulemaking 
requiring the development and publication of new information for the 
owner's manual. Printing costs have increased due to accounting for the 
estimated number of vehicles that will be equipped with seat belt 
reminder systems and will therefore need to comply with the 
requirements to provide system information and operating instructions. 
We did not receive comments on these burden estimates or other aspects 
of the proposed revision to the information collection. These burden 
estimates did not change between the NPRM and final rule.

National Technology Transfer and Advancement Act

    Under the National Technology Transfer and Advancement Act of 1995 
(NTTAA) (Pub. L. 104-113), ``all Federal agencies and departments shall 
use technical standards that are developed or adopted by voluntary 
consensus standards bodies, using such technical standards as a means 
to carry out policy objectives or activities determined by the agencies 
and departments.'' Voluntary consensus standards are technical 
standards (e.g., materials specifications, test methods, sampling 
procedures, and business practices) that are developed or adopted by 
voluntary consensus standards bodies, such as SAE (formerly, the 
Society of Automotive Engineers). The NTTAA directs this agency to 
provide Congress, through OMB, explanations when the agency decides not 
to use available and applicable voluntary consensus standards.
    While the agency is not aware of any voluntary standards that exist 
regarding the seat belt warnings contemplated in this rule, the agency 
has examined relevant regulations in other countries, such as the 
European Union standard ECE R16. As discussed above, although we are 
not aware of any foreign regulations that require seat belt warnings 
for the front outboard passenger or rear seat belts or for the driver 
seat on small buses, we believe that requiring seat belt warnings for 
these seating positions and for the driver seats on small buses meets a 
safety need and is practicable.

Severability

    The issue of severability of FMVSS is addressed in 49 CFR 571.9. It 
provides that if any FMVSS or its application to any person or 
circumstance is held invalid, the remainder of the part and the 
application of that standard to other persons or circumstances is 
unaffected.

Unfunded Mandates Reform Act

    The Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4) (UMRA) 
requires agencies to prepare a written assessment of the costs, 
benefits, and other effects of proposed or final rules that include a 
Federal mandate likely to result in the expenditures by States, local 
or tribal governments, in the aggregate, or by the private sector, of 
$100 million or more (adjusted annually for inflation with base year of 
1995) in any one year. Adjusting this amount by the implicit gross 
domestic product price deflator for 2022 results in $177 million 
(111.416/75.324 = 1.48). The assessment may be included in conjunction 
with other assessments, as it is here.
    UMRA requires the agency to select the ``least costly, most cost-
effective or least burdensome alternative that achieves the objectives 
of the rule.'' As discussed above, the agency considered alternatives 
to the final rule and has concluded that the requirements are the most 
cost-effective alternatives that achieve the objectives of the rule.
    This rule on seat belt reminder systems is not likely to result in 
expenditures by State, local or tribal governments of more than $177 
million annually. However, it is estimated to result in the expenditure 
by automobile manufacturers and/or their suppliers by approximately 
$168 million annually. The estimated costs are discussed in Section 
VIII, Overview of Benefits and Costs, and the docketed final regulatory 
impact analysis.
    We have concluded that the requirements in this rule are the most 
cost-effective alternatives that achieve the objectives of the rule.

Plain Language

    Executive Order 12866 and E.O. 13563 require each agency to write 
all rules in plain language. Application of the principles of plain 
language includes consideration of the following questions:
     Have we organized the material to suit the public's needs?
     Are the requirements in the rule clearly stated?
     Does the rule contain technical language or jargon that 
isn't clear?
     Would a different format (grouping and order of sections, 
use of headings, paragraphing) make the rule easier to understand?
     Would more (but shorter) sections be better?
     Could we improve clarity by adding tables, lists, or 
diagrams?
     What else could we do to make the rule easier to 
understand?
    NHTSA has considered these questions and attempted to use plain 
language in writing this rule. Please inform the agency if you can 
suggest how NHTSA can improve its use of plain language.

Regulation Identifier Number (RIN)

    The Department of Transportation assigns a regulation identifier 
number (RIN) to each regulatory action listed in the Unified Agenda of 
Federal Regulations. The Regulatory Information Service Center 
publishes the Unified Agenda in April and October of each year. You may 
use the RIN contained in the heading at the beginning of this document 
to find this action in the Unified Agenda.

    Note: The following appendix will not appear in the Code of 
Federal Regulations.

Appendix A. List of Comments Cited in Preamble

----------------------------------------------------------------------------------------------------------------
                        Commenter                                                Comment ID
----------------------------------------------------------------------------------------------------------------
Advocates for Highway and Auto Safety and Public Citizen   NHTSA-2023-0032-0040
 (Advocates and Public Citizen).
Alliance for Automotive Innovation (Auto Innovators).....  NHTSA-2023-0032-0048
Automotive Safety Council (ASC)..........................  NHTSA-2023-0032-0015
Autonomous Vehicle Industry Association (AVIA)...........  NHTSA-2023-0032-0029
Braun Northwest, Inc. (BNW)..............................  NHTSA-2023-0032-0050
Consumer Reports.........................................  NHTSA-2023-0032-0049
Cross, Karleigh..........................................  NHTSA-2023-0032-0013
Dorey, Rivers............................................  NHTSA-2023-0032-0008

[[Page 459]]

 
Ford Motor Company (Ford)................................  NHTSA-2023-0032-0045
Freedman Seating Company (Freedman)......................  NHTSA-2023-0032-0041
Freeman, Paige...........................................  NHTSA-2023-0032-0017
Gaal, Edward.............................................  NHTSA-2023-0032-0010
General Motors (GM)......................................  NHTSA-2023-0032-0026
American Honda Motor Co. (Honda).........................  NHTSA-2023-0032-0039
Hyundai America Technical Center, Inc. (HATCI)...........  NHTSA-2023-0032-0053
Hyundai Motor Company (Hyundai)..........................  NHTSA-2023-0032-0047
IEE......................................................  NHTSA-2023-0032-0032
Insurance Institute for Highway Safety (IIHS)............  NHTSA-2023-0032-0020
InterMotive Vehicle Controls (InterMotive)...............  NHTSA-2023-0032-0016
Koo, John................................................  NHTSA-2023-0032-0012
Mothers Against Drunk Driving (MADD).....................  NHTSA-2023-0032-0055
Mercedes-Benz and Mercedes-Benz Research and Development   NHTSA-2023-0032-0025
 North America (Mercedes).
National Association of Mutual Insurance Companies         NHTSA-2023-0032-0034
 (NAMIC).
National Automobile Dealers Association (NADA)...........  NHTSA-2023-0032-0042
National Safety Council (NSC)............................  NHTSA-2023-0032-0038
Nissan North America.....................................  NHTSA-2023-0032-0043
National Transportation Safety Board (NTSB)..............  NHTSA-2023-0032-0019
Paradise, John...........................................  NHTSA-2023-0032-0009
Recreational Vehicle Industry Association (RVIA).........  NHTSA-2023-0032-0028
Rivian Automotive........................................  NHTSA-2023-0032-0044
Safe Kids Worldwide (SKW)................................  NHTSA-2023-0032-0046
Safe Ride News (SRN).....................................  NHTSA-2023-0032-0036
Stange, Trenton..........................................  NHTSA-2023-0032-0018
Tesla....................................................  NHTSA-2023-0032-0035
Tombrello, Stephanie.....................................  NHTSA-2023-0032-0030
Toyota Motor North America, Inc. and Toyota Motor          NHTSA-2023-0032-0054
 Corporation (Toyota).
Anonymous #5.............................................  NHTSA-2023-0032-0005
Anonymous #24............................................  NHTSA-2023-0032-0024
Anonymous #33............................................  NHTSA-2023-0032-0033
----------------------------------------------------------------------------------------------------------------

List of Subjects in 49 CFR Part 571

    Imports, Motor vehicle safety, Motor vehicles.

    In consideration of the foregoing, NHTSA amends 49 CFR part 571 as 
set forth below.

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 1.95.


0
2. Amend Sec.  571.101 by revising paragraph S5.5.6 and tables 1 and 2 
to read as follows.


Sec.  571.101  Standard No. 101; Controls and displays.

* * * * *
    S5.5.6(a) Except as provided in S5.5.6(b) and (c), messages 
displayed in a common space may be cancelable automatically or by the 
driver.
    (b) Telltales for high beams, turn signal, low tire pressure, and 
passenger air bag off, and telltales for which the color red is 
required in table 1 to this section must not be cancelable while the 
underlying condition for their activation exists.
    (c) Telltales for the seat belts must not be cancelable by the 
driver before the minimum durations are satisfied but may be 
cancellable automatically as specified in FMVSS No. 208 (Sec.  
571.208).
* * * * *
BILLING CODE 4910-59-P

[[Page 460]]

Table 1 to Sec.  571.101
[GRAPHIC] [TIFF OMITTED] TR03JA25.001


[[Page 461]]


[GRAPHIC] [TIFF OMITTED] TR03JA25.002


[[Page 462]]


[GRAPHIC] [TIFF OMITTED] TR03JA25.003


[[Page 463]]


[GRAPHIC] [TIFF OMITTED] TR03JA25.004


[[Page 464]]


[GRAPHIC] [TIFF OMITTED] TR03JA25.005


[[Page 465]]



Table 2 to Sec.  571.101
[GRAPHIC] [TIFF OMITTED] TR03JA25.006

BILLING CODE 4910-59-C

0
3. Amend Sec.  571.208 by:
0
a. Adding paragraphs S4.1.5.7, S4.1.5.7.1, S4.1.5.8, S4.1.5.8.1, 
S4.2.8, S4.2.8.1, S4.2.9, S4.2.9.1, S4.4.3.4, S4.4.3.4.1, S4.4.3.5, 
S4.4.3.5.1, and S4.5.1.(f)(3);
0
b. Revising paragraph S4.5.3.3(b); and
0
c. Adding paragraph S7.5.
    The additions and revisions read as follows:


Sec.  571.208  Standard No. 208; Occupant crash protection.

* * * * *
    S4.1.5.7. Front seat belt warnings for passenger cars manufactured 
on or after September 1, 2026.
    S4.1.5.7.1 Any front outboard designated seating position and any 
inboard designated seating position for which a seat belt warning is 
required in S4.1.5.6 shall comply with S7.5 of this standard.
    S4.1.5.8. Rear seat belt warnings for passenger cars manufactured 
on or after September 1, 2027.
    S4.1.5.8.1. All rear designated seating positions, except in law 
enforcement vehicles, shall comply with S7.5 of this standard.
* * * * *
    S4.2.8 Front seat belt warnings for trucks and multipurpose 
passenger vehicles manufactured on or after September 1, 2026 with a 
GVWR of 4,536 kg (10,000 lb) or less.
    S4.2.8.1. Any front outboard designated seating position certified 
to a compliance option requiring a seat belt and any inboard designated 
seating position for which a seat belt warning is required by S4.2.6.4 
shall comply with S7.5 of this standard.

[[Page 466]]

    S4.2.9 Rear seat belt warnings for trucks and multipurpose 
passenger vehicles manufactured on or after September 1, 2027 with a 
GVWR of 4,536 kg (10,000 lb) or less.
    S4.2.9.1. All rear designated seating positions certified to a 
compliance option requiring a seat belt, except ambulances, as defined 
by FMVSS No. 201 (Sec.  571.201), and law enforcement vehicles, shall 
comply with S7.5 of this standard.
* * * * *
    S4.4.3.4 Front seat belt warnings for buses manufactured on or 
after September 1, 2026 with a GVWR of 4,536 kg (10,000 lb) or less.
    S4.4.3.4.1 All front outboard designated seating positions and any 
inboard designated seating position for which a seat belt warning is 
required by S4.2.6.4 shall comply with S7.5 of this standard.
    S4.4.3.5 Rear seat belt warnings for buses manufactured on or after 
September 1, 2027 with a GVWR of 4,536 kg (10,000 lb) or less.
    S4.4.3.5.1 All rear designated seating positions certified to a 
compliance option requiring a seat belt, except for school buses and 
law enforcement vehicles, shall comply with S7.5 of this standard.
* * * * *
    S4.5.1 * * *
    (f) * * *
    (3) The owner's manual (which includes information provided by the 
vehicle manufacturer to the consumer, whether in digital or printed 
form) for any vehicle equipped with a seat belt warning system must 
include an accurate description of the system features and warning 
signals, including the location and format of the visual warnings, in 
an easily understandable format. The description shall include 
information on when the different features of the warning system will 
activate and how to interpret the visual warnings. For vehicles with 
any rear designated seating position that is a readily-removable seat 
(a seat designed to be easily removed and replaced by means installed 
by the manufacturer for that purpose) equipped with manual electrical 
connections that are utilized by the rear seat belt warning system, the 
owner's manual must include a description of the purpose of the 
connection, instructions on how to achieve a proper connection, and a 
description of how not achieving a proper connection may affect the 
proper functioning of the system.
* * * * *
    S4.5.3.3 * * *
    (b) Conform to the seat belt warning system requirements of S7.3 or 
S7.5 of this standard, as applicable.
* * * * *
    S7.5 Seat belt warning systems for front outboard seat belt 
assemblies in vehicles manufactured on or after September 1, 2026 
provided in accordance with the requirements of S4.1.5.7, S4.2.8, 
S4.4.3.4, and S4.5.3.3 of this standard, and rear seat belt assemblies 
in vehicles manufactured on or after September 1, 2027 provided in 
accordance with the requirements of S4.1.5.8, S4.2.9, S4.4.3.5, and 
S4.5.3.3 of this standard.
    (a) Definitions for S7.5. (1) A manual seat belt is not in use when 
the seat belt latch mechanism is not fastened. A seat belt is in use 
when the seat belt latch mechanism is fastened. An automatic seat belt 
is not in use when the seat belt latch mechanism is not fastened or, if 
the automatic belt is non-detachable, the emergency release mechanism 
is in the released position. If the automatic seat belt is motorized, 
whether the seat belt is in use is determined when the seat belt 
webbing is in its locked protective mode at the anchorage point.
    (2) A warning cycle for an intermittent audible warning consists of 
period(s) when the warning is active at the chime frequency or 
continuously, and of inactive period(s). A warning cycle begins with an 
active period and is 30 seconds in duration.
    (3) Chime frequency means the repetition rate for an intermittent 
audible warning when the warning is active.
    (4) Duty cycle means the total amount of time an intermittent 
audible warning is active during a warning cycle at the chime frequency 
or continuously, divided by the total warning cycle duration (30 
seconds).
    (5) A readily-removable seat means a seat designed to be easily 
removed and replaced by means installed by the manufacturer for that 
purpose.
    (6) Seat centerline means the line formed by the intersection of 
the seating surface and the vertical plane that passes through the 
``seating reference point'' (as defined at 49 CFR 571.3) and is 
parallel to the direction that the seat faces.
    (b) Front seat belt warning system. A driver's designated seating 
position and any front outboard passenger designating seating position 
must be equipped with an audio-visual seat belt warning meeting the 
requirements of S7.5(b)(1) through (4) when tested in accordance with 
S7.5(d).
    (1) Visual warning. (i) A visual warning must activate and remain 
active whenever the ignition switch is in the ``on'' or ``start'' 
position (or the propulsion system is activated), the seat is occupied, 
and the seat belt is not in use.
    (ii) Vehicles with a driver's designated seating position. The 
visual warning for the driver's seat belt and the visual warning for 
the front outboard passenger seat belt must be visible from the 
driver's seat. If the vehicle has a mode of driverless operation, the 
visual warning for the front outboard passenger seat belt must also be 
visible from the front outboard passenger seat.
    (iii) Vehicles without a driver's designated seating position. The 
visual warning for each outboard passenger designated seating position 
must be visible from each outboard passenger designated seating 
position.
    (iv) The visual warning may be continuous or intermittent and must 
display the identifying symbol or the words specified in table 2 of 
FMVSS No. 101 (Sec.  571.101).
    (v) For a visual warning associated with multiple front outboard 
seats, the visual warning must clearly identify the seating positions 
for which the warnings are intended.
    (vi) The visual warning must not be overridden by other warnings.
    (2) Audible warning--first phase. (i) An audible warning must 
activate when the ignition switch is placed in the ``on'' or ``start'' 
position (or upon manual activation of the propulsion system, but prior 
to the vehicle being placed in ``possible active driving mode'' as 
defined by FMVSS No. 305 (Sec.  571.305)), the seat is occupied, and 
the seat belt is not in use.
    (ii) The audible warning must continue for 30 seconds, until the 
seat belt that triggered the warning is in use, until the seat is no 
longer occupied, or until the second-phase warning activates, whichever 
comes first. The audible warning may be paused during the activation of 
another audible safety warning that is designed to alert the driver to 
take immediate action, but the seat belt audible warning must be 
resumed for the remainder of the required duration after the other 
audible warning deactivates.
    (iii) The audible warning may be continuous or intermittent. If 
intermittent, inactive periods longer than 3 seconds will not be 
counted toward the total duration of the audible warning, and there 
must be no inactive periods greater than 10 seconds. The same audible 
warning may be used for all front and rear seats.
    (3) Audible warning--second phase. (i) The audible warning must 
activate and remain active when the vehicle

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speed is equal to or greater than 10 km/h (6.2 mph), the seat is 
occupied, and the seat belt is not in use. The audible warning may be 
paused during the activation of another audible safety warning that is 
designed to alert the driver to take immediate action, but the seat 
belt audible warning must be resumed after the other audible warning 
deactivates.
    (ii) The audible warning may be continuous or intermittent. If 
intermittent, the audible warning when active must be continuous or 
have a chime frequency of at least 0.5 Hz and a duty cycle of at least 
0.2. The same audible warning may be used for all front and rear seats.
    (4) Cancellation. The warning must not be able to be canceled or 
deactivated.
    (c) Rear passenger seat belt warning system. All rear designated 
seating positions must be equipped with a warning system meeting the 
requirements of S7.5(c)(1) through (7) when tested in accordance with 
S7.5(d).
    (1) Start-of-trip warning. A visual warning indicating how many or 
which rear seat belts are in use and/or not in use must activate when 
the ignition switch is placed in the ``on'' or ``start'' position (or 
upon manual activation of the propulsion system, but prior to the 
vehicle being placed in ``possible active driving mode'' as defined by 
FMVSS No. 305 (Sec.  571.305)) and continue for at least 60 seconds.
    (i) No visual warning is required for:
    (A) an unoccupied seat if the system is able to determine whether 
or not a seat is occupied;
    (B) a seat belt that is in use in a system designed to indicate to 
the driver how many or which rear seat belts are not in use; and
    (C) a seat belt that is not in use in a system designed to indicate 
to the driver how many or which rear seat belts are in use.
    (2) Change-of-status warning. An audio-visual warning indicating 
how many or which rear seat belts have undergone a change of status 
from in use to not in use must activate when the status of any rear 
seat belt changes from in use to not in use and the vehicle is in 
forward or reverse drive mode, unless any rear door is open. The 
warning must continue for at least 30 seconds or until the seat belt 
that triggered the warning is in use. The warning may deactivate if the 
system is able to determine that the number of seat belts in use is 
restored and all the doors remained closed.
    (3) Additional visual warning requirements. (i) The warning may be 
continuous or intermittent and may consist of text, symbols, and/or 
numbers.
    (ii) The warning must be visible from the driver's seat.
    (iii) If the warning is designed to indicate how many or which rear 
seat belts are in use, the color of the symbols or numbers indicating 
seat belts in use must be green. If the warning is designed to indicate 
to the driver how many or which rear seat belts are not in use, the 
color of the symbols or numbers indicating seat belts not in use must 
be red.
    (iv) The change-of-status visual warning may use the same telltale 
as the start of trip warning, provided that the color of an illuminated 
symbol or number used to indicate to the driver how many or which rear 
seat belts have undergone a change of status from in use to not in use 
is red.
    (v) The warning must not be overridden by other visual warnings for 
the required duration.
    (4) Audible warning requirements. (i) The audible warning may be 
continuous or intermittent. If intermittent, inactive periods longer 
than 3 seconds will not be counted toward the total duration of the 
warning, and there must be no inactive periods greater than 10 seconds.
    (ii) The audible warning may be paused during the activation of 
another audible safety warning that is designed to alert the driver to 
take immediate action, but the seat belt audible warning must be 
resumed for the remainder of the required duration after the other 
audible warning deactivates.
    (iii) The same audible warning may be used for all front and rear 
seats.
    (5) Cancellation. The warning must not be able to be canceled or 
deactivated.
    (6) Seat electrical connection requirements. Any rear designated 
seating position consisting of a readily-removable seat that is 
equipped with electrical connections utilized by the rear seat belt 
warning system must either--
    (i) Automatically connect the electrical connections when the seat 
is put in place; or
    (ii) If a manual electrical connection is required, the connectors 
must be readily accessible.
    (7) Electrical connection warning signal. Vehicles that provide a 
visual warning designed to indicate to the driver how many or which 
rear seat belts are not in use and are equipped with any readily 
removable rear seats must, when the ignition switch is placed in the 
``on'' or ``start'' position (or upon manual activation of the 
propulsion system, but prior to the vehicle being placed in ``possible 
active driving mode'' as defined by FMVSS No. 305 (Sec.  571.305)) 
provide a visual warning visible from the driver's seat if a seat has 
been installed and a proper electrical connection has not been made. 
The visual warning may be intermittent but must remain active until all 
rear seat electrical connections are properly made.
    (d) Test procedures. (1) Occupied designated seating positions. If 
testing with a designated seating position occupied, the following 
apply, at the option of the manufacturer:
    (i) Front outboard seating positions. (A) Seat the 5th percentile 
female test dummy described in part 572, subpart O of this chapter, as 
well as any larger dummy described in part 572 of this chapter; or
    (B) Seat any human occupant that weighs 46.7 kg (103 lb) or more 
and is 139.7 cm (55 inches) tall or taller.
    (ii) Driver's seating position. (A) Seat the 5th percentile female 
test dummy described in part 572, subpart O of this chapter, as well as 
any larger dummy described in part 572 of this chapter;
    (B) Seat any human occupant that weighs 46.7 kg (103 lb) or more 
and is 139.7 cm (55 inches) tall or taller; or
    (C) The seat may be considered occupied when the ignition switch is 
in the ``on'' or ``start'' position (or the propulsion system is 
activated).
    (iii) Rear seating positions. (A) Seat the 6-year-old child dummy 
described in part 572, subpart N of this chapter, as well as any larger 
dummy described in part 572 of this chapter; or
    (B) Seat any human occupant that weighs 21 kg (46.5 lb) or more and 
is 114 cm (45 inches) tall or taller.
    (iv) Compliance option selection. The manufacturer shall select a 
compliance option by the time it certifies the vehicle and may not 
thereafter select a different option for the vehicle. Each manufacturer 
shall provide information to NHTSA regarding which of the compliance 
options it has selected for a particular vehicle or make/model upon 
request.
    (2) Seating procedures--(i) Seat adjustment. If adjustable, the 
seat back shall be placed in the manufacturer's nominal design riding 
position, with any other seat adjustments in any position, and any 
adjustable seat belt anchorages in any position.
    (ii) Test dummy. Seat the test dummy such that the midsagittal 
plane of the dummy is vertical and within 10 mm of the seat 
centerline, with the torso and pelvis in contact with the seat back. 
The dummy may be clothed in any manner.
    (iii) Human occupant. The occupant shall assume, to the extent 
possible, the

[[Page 468]]

final physical position specified for the test dummy. The occupant may 
be clothed in any manner.
    (3) Verify that the seat belt warnings function as specified in 
S7.5(b) and (c) for any combination of seat belt use (at any seating 
position), seat occupancy (at any seating position), removable seat 
electrical connection status (connected or not connected, for any 
removable seat), vehicle speed, and door status (open or closed, for 
any door), except that the door shall not be opened when the vehicle is 
in motion.

    Issued in Washington, DC, under authority delegated in 49 CFR 
1.95 and part 501.
Adam Raviv,
Chief Counsel.
[FR Doc. 2024-30340 Filed 1-2-25; 8:45 am]
BILLING CODE 4910-59-P`