as seated on the driver seat, any seating position in which the safety-
belt is unfastened.'' \108\ 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.\109\ This
warning may be canceled by the driver.\110\
---------------------------------------------------------------------------

    \106\ Section <IP_ADDRESS>; Section <IP_ADDRESS>.1.
    \107\ Section <IP_ADDRESS>.1; Sec.  <IP_ADDRESS>.2.
    \108\ Section <IP_ADDRESS>.
    \109\ Section <IP_ADDRESS>.
    \110\ Section <IP_ADDRESS>.
---------------------------------------------------------------------------

    Euro NCAP's rating protocol also requires a visual warning at the
start of a trip. The requirements are similar to ECE R16. Euro NCAP's
rating protocol does not require occupant detection but incentivizes
systems that use occupant detection by awarding additional points for
this feature. For systems without occupant detection, the visual signal
must show belts in use and not in use.\111\ 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 active as
long as the seat belts remain unfastened on any of the occupied seats
in the rear; \112\ no visual signal is required if no rear occupants
are detected.\113\ Systems with occupant detection must also provide a
30-second audible signal at the start of the trip before specified
speed or distance thresholds have been crossed.\114\ Alternatively, if
occupant detection is provided the manufacturer may use the same
warning strategy as specified for the front seats.\115\
---------------------------------------------------------------------------

    \111\ Section <IP_ADDRESS>.4.
    \112\ Section <IP_ADDRESS>.3.
    \113\ Section <IP_ADDRESS>.1.
    \114\ Section <IP_ADDRESS>.3. The thresholds are (at the choice of
the OEM) either a forward speed of 25 km/h or forward motion for 500
m.
    \115\ Section <IP_ADDRESS>.3. For front seat belts, the assessment
protocol requires both a visual and an audible warning signal (see
Section 3.4.2). The visual signal must remain active until the seat
belt is fastened. The audible signal has two stages, an initial and
final audible signal, which have different onset criteria. The
initial audible signal must not exceed 30 seconds and the final
audible signal must be at least 90 seconds. To prevent unnecessary
signals, the system must also be capable of detecting whether the
front passenger seats are occupied.
---------------------------------------------------------------------------

Comments
    Most commenters explicitly endorsed a warning on start-up, and none
opposed it, although the comments differed on whether it should have an
audible component. Two comments recommended harmonizing with the ECE
R16 requirement for a visual-only warning on start-up. A commenter
stated that NHTSA should provide flexibility in terms of the type of
information that is required to be communicated by the reminder system,
including positive-only, negative-only, and full-status systems, with
consideration for both occupant-detection and non-occupant-detection
centric approaches. Based on the definitions provided within the ANPRM,
the baseline standard for R16 could be met through a non-occupant
detection, positive-only system, but would not prohibit additional
technology features to provide additional functionality. Another
commenter agreed that positive-only, negative-only, and full-status
systems each could have strengths and limitations; the priority should
be that all of these variations effectively allow the driver to
identify which seats are unfastened (in the case without occupant
detection), or if any occupied seats are unfastened (with occupant
detection). The commenter noted that R16 does not establish such
definitions of systems, but rather specifies the base requirement that
the driver should be able to identify which seats are unfastened. The
comment stated that NHTSA should not set criteria too broadly, which
could restrict manufacturers to implementing a full-vehicle display,
even if occupant detection is applied, in which case a single seat belt
telltale indicator is sufficient.
    Three commenters recommended a visual-only warning. A commenter
stated that a visual warning, such as a telltale, should exist as an
initial warning, and a combination of audible and visual warnings could
exist as a ``second-level'' warning. Another commenter stated that
visual displays are efficient at conveying information that is complex,
that deals with locations in space, or that does not require immediate
action. The comment stated that, while audio-visual warnings are more
effective than visual-only warnings, visual displays are less intrusive
and perceived as less annoying than audible warnings, so that a visual-
only warning would minimize the impact of false warnings that could
negatively impact consumer acceptance. The commenter also stated that,
while visual displays alone have not been found to be effective for
motivating occupants to use a seat belt, the driver may use this
information to encourage unbuckled rear occupants to use a seat belt.
    Several commenters favored requiring an audio-visual warning at the
start of the trip. Four commenters supported the specification of the
most effective warnings and noted that audio-visual warnings are more
effective than visible warnings alone. Two commenters stated that a
visual-only warning would be easily missed by a driver who is focused
on driving safely.
    Three commenters recommended requiring a ``negative'' warning with
occupant detection. A commenter said that such systems would reduce
false signals and annoyance. Another commenter similarly supported a
warning on startup and commented that while a positive-only warning
icon at the start of a ride would be helpful, it would not be as
valuable as a warning triggered by negative-only status as a way to
change the behavior of those occupants who are lax or reluctant to
buckle up.
Agency Response
    This rule proposes to require a visual warning (without an audible
component) upon vehicle start-up. NHTSA decided to propose the three
compliance options identified in the ANPRM for the type of information
the warning must convey. Each proposed system has strengths and
limitations. The positive-only system would be the least technically
complex of the three proposed options. Since it would only need to
detect whether a seat belt is in use, it would only require a seat belt
latch sensor. With a positive-only system, the driver would need to
determine how many rear seat occupants there are and then determine if
that number equals the number of seat belts that are reported by the
warning system as buckled. This compliance option would not necessitate
occupant detection; we tentatively believe that there are still design
and technological challenges associated with implementing occupant
detection technology in rear seats (this is discussed in more detail in
Section XIII, Regulatory Alternatives).
    The negative-only and full-status systems would provide the driver
with more information, and thus might be more effective than the
positive-only system for at least two reasons. First, they would
directly inform the driver whether any rear seat occupants were
unbuckled, without the driver having to compare the number or location
of occupants and fastened belts. Second, as discussed in more detail
below, warning systems equipped with occupant

detection are more amenable to audible warnings and enhanced warning
features. However, we tentatively believe that systems such as these
that provide a negative warning--that is, a warning for an unfastened
belt--are only appropriate for systems utilizing occupant detection.
This is because we tentatively believe that it is not appropriate to
provide a warning for an unfastened seat belt at an unoccupied seat
because such ``false positives'' could be a nuisance for the driver and
might either desensitize the driver to the warning signal or lead them
to circumvent or defeat the system--especially since the majority of
trips do not have rear seat occupants. The proposal would therefore
permit a warning for an unfastened belt only if the seating position
were equipped with occupant detection. Accordingly, it would not, for
example, permit a system without occupant detection that displayed the
status of all the rear seat belts to be certified as a positive-only
system coupled with a voluntary warning for unfastened seat belts.
    With respect to comments in favor of requiring audio-visual
warnings, we agree that warnings with an audible component are
generally more effective. However, requiring an audio-visual warning
would necessitate requiring occupant detection because the resulting
``false positives''--having an audible warning activate for an
unfastened belt at an unoccupied seat--would annoy the driver and could
decrease the effectiveness of the warning. Thus, this NPRM does not
require an audible warning on startup. However, manufacturers would be
free to provide an audible warning on startup if they so choose,
especially if the vehicle is equipped with occupant detection in the
rear. This approach harmonizes with R16 and Euro NCAP.
    We acknowledge that there are systems currently deployed in both
the United States and Europe that would not comply with the proposed
compliance options. In particular, manufacturers appear to be deploying
systems without occupant detection that provide a warning for an
unfastened belt. When the ANPRM was published, the rear seat belt
warning systems in vehicles sold in the United States used what would
be classified in this proposal as a positive-only warning system. Our
current, preliminary review, however, indicates that manufacturers are
now providing visual warnings that indicate unfastened seat belts, and
not necessarily with occupant detection. For example, the visual
warning displays on some MY2022 Honda and Porsche vehicles appear to
indicate the status of all the rear seat belts, but the owner's manual
does not indicate that the vehicle is equipped with occupant detection
in the rear seats. This information is consistent with Honda's comment
that the compliance options should allow the driver to identify which
seats are unfastened (in the case without occupant detection).
    Similarly, it appears that, as suggested in the comments, European
vehicle manufacturers are deploying systems that indicate seat belts
that are fastened, seat belts that are not fastened, or the status of
all rear seat belts, both with and--importantly--without occupant
detection.\116\ For example, the MY 2021 Peugeot 3008 appears to have a
system that indicates the status of all the rear seat belts but does
not indicate in its owner's manual that it has occupant detection in
the rear seats. Both ECE R16 and Euro NCAP appear to permit a broad
range of systems, including those providing warnings for unfastened
belts at unoccupied seats. R16 requires that the visual warning
``indicate 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.'' Euro NCAP
similarly requires systems without occupant detection to provide a
visual warning showing both the belts in use and not in use.
Nevertheless, we tentatively believe that the proposed deviation from
R16 and some current United States and European systems is warranted
because we tentatively believe it is not appropriate to provide a
warning for an unfastened belt at an unoccupied seat.
---------------------------------------------------------------------------

    \116\ Approximately 70% of Euro NCAP-tested vehicles had
occupant detection in the rear seats.
---------------------------------------------------------------------------

    Although the three proposed compliance options are not identical to
the R16 and Euro NCAP requirements, we believe that a system that
complies with the proposed requirements could also comply with R16 and
Euro NCAP. With respect to R16, each of the three proposed compliance
options would ``allow the driver to identify, while facing forward as
seated on the driver seat, any seating position in which the safety-
belt is unfastened.'' While the reference to an ``unfastened'' belt
might be read to preclude a positive-only system--that is, it might be
read to mean that the system must explicitly inform the driver of an
unfastened belt, such as would be the case in the systems we are
calling ``negative-only'' or ``full-status''--after reviewing the types
of systems available in the European market we believe this is not the
case. Similarly, the negative-only and full-status compliance options
appear consistent with Euro NCAP because they would provide a warning
for an unfastened seat belt at an occupied seat.\117\ However, the
positive-only compliance option does 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.\118\
---------------------------------------------------------------------------

    \117\ Section <IP_ADDRESS>.3.
    \118\ See Euro NCAP section <IP_ADDRESS>.4.
---------------------------------------------------------------------------

    NHTSA seeks comment on all of these issues. While we have
tentatively concluded that the proposed compliance options would help
mitigate false warnings and the possibly attendant consumer acceptance
issues, we are considering altering the proposed compliance options to
accommodate systems that are currently being deployed, or that
manufacturers may wish to deploy in the future. For example, we are
considering allowing visual warnings that indicate which seat belts are
unfastened without occupant detection. We therefore seek comment on
what visual warnings vehicle manufacturers are using in the United
States and Europe and whether they employ occupant detection. We also
seek comment on why vehicle manufacturers have decided to use visual
warnings that indicate unfastened seat belts without the use of
occupant detection and whether they have received complaints from
consumers about false warnings, or requests to deactivate the system.
Is there any consumer acceptance data to support or oppose allowing
visual warnings that indicate unfastened seat belts without the use of
occupant detection in the rear seats? We also seek comment on whether
there are any other aspects of the proposed compliance options with
which current or anticipated future systems would not comply. Is there
a preferable set of options that is sufficiently objective to satisfy
the Safety Act? NHTSA also seeks comment on how manufacturers interpret
the R16 requirements, to the extent that the agency's characterization
of them is contrary to industry understanding or practice. NHTSA also
seeks comment on whether the proposed regulatory text is sufficiently
objective and unambiguous.
b. Triggering Conditions
    In the ANPRM we indicated that requiring the warning at the
beginning of each journey or trip the vehicle makes is intuitively
appealing because it

would help assure that occupants are safely restrained prior to any
potential vehicle crash. However, we sought comment on the possible
advantages of delaying the warning to a time when the driver or
occupants are less distracted and therefore might pay more attention to
the warning.
    R16 requires that the visual warning activate when a belt is not
fastened and the ignition or master control switch activated.\119\ Euro
NCAP similarly requires that the warning start at the commencement of a
journey when the ignition switch is engaged (whether or not the engine
is running) and any of the rear belts are not fastened.\120\ 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.\121\ For both R16 and Euro NCAP, for vehicles
that have occupant detection in the rear seats, the visual warning does
not need to indicate unfastened seat belts for unoccupied seating
positions.\122\
---------------------------------------------------------------------------

    \119\ Section <IP_ADDRESS>.1.
    \120\ Section 3.4.1; Section <IP_ADDRESS>.1.
    \121\ Section 3.4.1.
    \122\ Section <IP_ADDRESS> (R16; section <IP_ADDRESS>.1 (Euro NCAP).
---------------------------------------------------------------------------

Comments
    Many ANPRM commenters either specifically recommended harmonizing
with R16 or recommended triggers that harmonized with R16. Three
commenters specifically recommended harmonizing with R16. Many other
commenters recommended that the trigger be based on the ignition
switch. One commenter explained that this would provide flexibility for
novel approaches for classifying vehicle motion. A few commenters
stated that it was necessary for the warning to activate before the
vehicle was in motion; for example, it was noted that vehicle crashes
can happen quickly (e.g., backing out of a parking spot), so vehicle
occupants should be buckled up anytime the vehicle is in motion. A
commenter also stated that delaying the warning until the vehicle is in
drive mode could leave drivers unable to ensure all passenger belts are
fastened. Delaying the warning might warrant additional study, but if
the study suggests changing the warning timing, it should do so for all
vehicle occupants. A commenter stated that any triggering condition
other than initiation at the beginning of a trip when the ignition
switch is moved to the ``on'' or ``start'' position would necessitate
occupant detection.
    However, a few commenters suggested alternative approaches. One
commenter recommended against requiring a warning before a driver
shifts a vehicle into drive because a transmission-less electric
vehicle can quickly shift to drive. Requiring the warning before the
vehicle is shifted to drive would potentially amount to a seat belt
drive interlock and potentially delay shifting into drive. The
commenter believed this is unnecessary, could result in driver
frustrations that diminish acceptance, and lead to hasty detection that
increases the potential for error. Another commenter stated that the
warning would be most effective if it were triggered when the seat is
occupied, the belt is unfastened, and the vehicle's power is on. Yet
another commenter stated that the triggering condition should be
vehicle unlocking and for a period following relocking. Finally a
commenter stated that the warning should be deactivated or disallowed
if all occupants are properly buckled.
Agency Response
    NHTSA proposes that the warning begin when the vehicle's ignition
switch is moved to the ``on'' or ``start'' position. This same
condition appears in the existing driver seat belt warning requirements
and is similar to ECE R16 and Euro NCAP. We are not proposing to follow
R16 and refer to a ``master control switch'' because we do not believe
it is necessary to introduce this new term into FMVSS No. 208 for the
proposed amendments to the standard. Also similar to those protocols,
if the system has occupant detection, no warning is required for
unoccupied seats under the full-status and negative-only compliance
options. As a commenter suggests, this would likely lead to more
effective warnings because it mitigates false warnings and eases the
burden on the driver to reconcile what the warning depicts with the
actual status of the rear seat passengers. 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.\123\
---------------------------------------------------------------------------

    \123\ See DOT 2009 Seat Belt Study at 65.
---------------------------------------------------------------------------

    With respect to the commenter on transmission-less electric
vehicles quickly shifting to drive, the warning is triggered by the
ignition, not the transmission gear position and would not impede the
driver from shifting to drive. NHTSA also disagrees with the commenter
that the system would be triggered by the vehicle being unlocked. This
could require a warning before any occupants had entered the vehicle,
and thus would likely not serve its purpose of warning the driver and
occupants given the limited duration of the warning. Such a requirement
would also not harmonize with the existing driver belt warning system
and the ECE R16 and Euro NCAP requirements.
    For the negative-only system, we propose to require a visual
warning indicating which occupied seats have an unfastened seat belt
for the required duration or until the belts at all occupied rear
seating positions are in use. Therefore, like the R16 requirement, if
all occupied seats have fastened seat belts no visual warning would be
required.
c. Seat Occupancy Criteria and Interaction With Child Restraint Systems
    The negative-only and full-status compliance options would require
the warning system to determine whether a seat position is occupied.
Because the existing seat belt warning requirements in FMVSS No. 208,
S7.3 apply only to the driver seat, they do not contemplate an occupant
detection system (because driver seat occupancy could traditionally be
assumed).
    There are three main detection scenarios an occupant detection
system would be exposed to in the rear seats: adults, teenagers, and
older children of various heights and weights; children seated in a
child restraint system (CRS); and objects such as packages, pets, or
unoccupied CRSs. This section will discuss how the occupant detection
capability for negative-only and full-status systems should perform for
these different scenarios and our proposed weight and height criteria
for compliance testing of rear seat belt warning systems certified to
either the negative-only or full-status compliance options.
    The ANPRM identified a need to objectively specify when a seat is
occupied for the purposes of testing negative-only and full-status rear
seat belt warning systems for compliance. The ANPRM requested comment
on several options for seat occupancy criteria based on those specified
in FMVSS No. 208 for compliance testing of low-risk deployment and
suppression air bag systems in the presence of children or small-
stature adults. These fall into three main categories. First, FMVSS No.
208 specifies 1-, 3-, and 6-year-old child anthropomorphic test devices
(test dummies) (weighing, respectively, 22 lb [10 kg], 36 lb [16.3 kg],
and 52 lb [23.6 kg]). Second, it

specifies a 5th percentile female test dummy (weighing 108 lb [50 kg]).
Third, it specifies height and weight requirements for a child used as
an alternative for the 6-year-old child test dummy for compliance
testing of advanced air bag systems utilizing static suppression
(weighing between 46.5 lb and 56.5 lb [21 kg and 25.6 kg] and between
45 in and 49 in [114 cm and 124.5 cm] tall).\124\
---------------------------------------------------------------------------

    \124\ FMVSS No. 208 S29.1(e).
---------------------------------------------------------------------------

    ECE R16 specifies three alternative methods for testing rear seats
with occupant detection: placing a load of 40 kg (88 lb) on the seat;
placing an object or human representing a 5th percentile adult female
(the HIII-5F specified in 49 CFR part 572, as adjusted for the ECE
test); or an alternative method specified by the vehicle
manufacturer.\125\ Euro NCAP defines occupancy as the use by an
occupant larger, taller, or heavier than a 5th percentile female.\126\
---------------------------------------------------------------------------

    \125\ Annex 18.
    \126\ Section <IP_ADDRESS>.
---------------------------------------------------------------------------

    The ANPRM also sought comment on whether a rear seat belt warning
would reliably detect a child restraint system attached by a child
restraint anchorage system, or LATCH. The intent of this question was
to determine whether a seat belt warning system might register a false
alarm for a LATCH-installed CRS. Neither R16 nor Euro NCAP have
requirements with respect to the system's interaction with LATCH-
installed CRSs.
Comments
    We received a number of comments related to seat occupancy criteria
and the detection capabilities the system should have.
    With respect to seat occupancy criteria, several commenters
supported harmonizing with ECE R16 and/or basing the criteria on a 5th
female dummy (88 lb-105 lb). Several commenters suggested harmonizing
with the ECE R16 criteria. A commenter stated that the occupant size
that the system is required to detect should not be less than the
occupant size that would use the seat belt as the only restraint.
Another commenter stated that for children seated in booster seats or
high-back boosters (with belt positioning guides), the CRS often
directly utilizes the belt provided in the vehicle. In these cases, a
rear belt reminder system may be useful for reminding the driver to
ensure the child seated in that seating position is either restrained
or providing an alert that the restraint status has changed during a
trip (i.e., belt became unbuckled). A commenter recommended specifying
the 5th percent female detection criteria for several reasons: starting
with the 5th female would cover a large share of the target population;
belt usage is high for children as long as they are in a CRS (so a
warning system appears less needed); the 5th percent female includes a
large share of the teenage population; it would harmonize with FMVSS
No. 208 and international NCAP programs; and it would result in more
robust systems with respect to false positives.
    On the other hand, various commenters recommended that the
occupancy criteria be based on children that might reasonably be
expected to use seat belts. Two commenters suggested that the occupancy
criteria be based on the smallest weight of a child that can reasonably
be expected to be restrained by a seat belt rather than a CRS. One of
the commenters stated that a weight of 20 lb (9 kg) is consistent with
all state laws for CRS use. Another commenter stated that the criteria
should reflect a minimum weight equal to that of a Hybrid III 6-year
old child (about 52 lb). However, as noted below, commenters believed
that using weight alone was not enough. A commenter did not agree with
criteria based on a 6-year-old, and instead suggested the HIII 3-year-
old dummy (36 pounds, or 16 kg) as the minimum weight threshold,
stating that this dummy's weight roughly represents the 95th percentile
2-year-old and the 5th percentile 5-year-old. The commenter stated a 6-
year-old was not appropriate as nearly 60% of 4- and 5-year-old
children do not ride in a CRS with a harness, so many of the most
vulnerable seat belt users (very young children using the belt alone or
in conjunction with a booster) would fail to trigger the alarm if
unbuckled. A commenter stated that the specifications should represent
the occupant population at risk from non-use of rear seat belts, and
stated that NHTSA's 2017 passenger vehicle fatality data indicates that
restraint non-use exceeds the national average (47%) in the population
of occupants starting at age 8-12; the unrestrained percentage for
younger occupants is 36% for 4-7-year-olds and 22% for occupants less
than 4 years old. A commenter suggested that the criteria should
register children that would presumably be placed in a child restraint
system (i.e., children as young as 4 years old). Another commenter
recommended that NHTSA's testing reflect the full range of body types
as well as child restraint systems that could be present in rear seats.
    We also received a variety of comments about the detection
capabilities the system should have. Several commenters argued that the
system should be required to detect CRSs. Three commenters supported
requiring LATCH detection. Two of those commenters stated that the
reminder system should be able to recognize when a car safety seat is
installed with LATCH instead of the seat belt and should not activate
under those conditions in order to avoid nuisance (false) warnings. A
commenter said that when a CRS is installed using the lower anchors of
the LATCH system, the seat belt is typically not in use, so a non-
discerning sensor would conclude that an unbuckled occupant is present
(because a CRS is heavy enough to be classified as an occupant by an
occupant detection system).\127\ A commenter recommended that the
occupant detection system provide a warning if the CRS is improperly
latched.
---------------------------------------------------------------------------

    \127\ Safe Ride News also appeared to suggest that in
conjunction or in the alternative, the system should be able to be
deactivated or allow the driver to dismiss (acknowledge) the
warning. NHTSA's tentative conclusion to not adopt these approaches
is explained in Section X.E, Resistance to intentional and
inadvertent defeat and deactivation.
---------------------------------------------------------------------------

    On the other hand, several commenters believed that the system
should not be required to detect a CRS. Three commenters stated that
the system should not be required to detect a CRS, with two of the
commenters noting variation in CRS designs and the fact that neither
ECE R16 nor Euro NCAP require CRS detection capabilities. These three
commenters opposed requiring LATCH detection because it would provide
little benefit with significant added costs. One of the commenters
added that LATCH systems are not typically latched/unlatched
frequently, so it is far more uncommon to be in the unlatched state.
Additionally, as only the latch could potentially be detected, and yet
the remaining parts of the child restraint are unmonitored, it may give
a false assurance to the user that the child is fully restrained. Two
of the commenters said that if this were required, the system would
need to distinguish different types of CRS available in the market,
which would be difficult to implement. A commenter that opposed
requiring occupant detection on buses, commented that buses with LATCH
seats would require a detection system capable of differentiating
whether an occupant is unbuckled or secured using the LATCH
attachments; whether an occupant is unbuckled or secured using the
securement harness provided with the seat; and between removed seats
and those with incorrect electrical connections. Another commenter
stated that CRSs pose a challenge to occupant

detection systems, which would need to account for all of the different
uses of the rear seat; a false-positive warning on a child properly
restrained using the LATCH system (who would not be buckled in with the
seat belt) could discourage the consumer from using LATCH.
    Finally, some commenters advocated requiring more sophisticated
detection capabilities in order to limit false positives. Two of these
commenters suggested that the system should be able to discern the
difference between an occupant and objects such as packages. Another
commenter said that NHTSA should also limit false activations when
seats are occupied by child seats or other items. A commenter stated
that NHTSA should allow for a child seat mode that suppresses the
warning.
Agency Response
    As an initial matter, it is important to understand the different
types of CRSs, how seat belts are used with them, and the size/age of
the children for which each type of CRS is typically appropriate.\128\
---------------------------------------------------------------------------

    \128\ All 50 states, the District of Columbia, and all United
States territories have laws requiring children to be secured in the
appropriate car seats or booster seats for their ages and sizes
while riding in vehicles. Most states now require children to ride
in appropriate car seats or booster seats until as old as age eight
(Alaska covers children up to 15 years old as long as they fall
within their specified height and weight criteria).
---------------------------------------------------------------------------

    There are essentially three types of CRSs: rear-facing CRSs,
forward-facing CRSs, and booster seats.\129\ Rear-facing and forward-
facing CRSs are child seats that are installed using either LATCH \130\
or a seat belt to secure it in place.\131\ Booster seats raise and
position a child so the vehicle's lap-and-shoulder belt fits properly.
---------------------------------------------------------------------------

    \129\ Within these types are CRS designs that can be used for
multiple purposes, such as convertible CRSs that can be used as a
rear-facing and forward-facing CRS and combination CRSs that can be
used as a forward-facing CRS and booster seat.
    \130\ Many in the child passenger safety community refer to the
child restraint anchorage system as the ``LATCH'' system, an
abbreviation of the phrase ``Lower Anchors and Tethers for
Children.'' The term was developed by a group of manufacturers and
retailers for use in educating consumers on the availability and use
of the anchorage system and for marketing purposes.
    \131\ Some boosters can also be secured to the seat with LATCH
so that it stays in place when in use and not in use.
---------------------------------------------------------------------------

    NHTSA recommends that children remain in a rear-facing CRS until
they reach the top height or weight limit allowed by the CRS
manufacturer.\132\ NHTSA also recommends that children remain in a
forward-facing car seat with a harness and tether until they reach the
top height or weight limit allowed by the car seat's manufacturer. Most
forward-facing CRS are rated for children up to 49 in (124 cm) and 65
lb (29 kg).\133\ Once a child outgrows the forward-facing car seat with
a harness, the child can travel in a booster seat and use a seat belt.
NHTSA identifies an age range of 4-7 years old for when this transition
to a booster typically occurs, depending on the height and weight of
the child and the respective limits of their forward-facing car seat.
Once a child outgrows the booster seat they can sit directly in the
seat and use the seat belt alone; NHTSA identifies an age range of
eight to thirteen and older for when this typically occurs.
---------------------------------------------------------------------------

    \132\ For the NHTSA recommendations discussed here, see https://www.nhtsa.gov/equipment/car-seats-and-booster-seats (last accessed
Apr. 7, 2022).
    \133\ See https://www.healthychildren.org/English/safety-prevention/on-the-go/Pages/Car-Safety-Seats-Product-Listing.aspx.
---------------------------------------------------------------------------

    In the remainder of this section we discuss, first, the proposed
weight and height criteria NHTSA proposes to use in compliance testing
of rear seat belt warning systems certified to the negative-only or
full-status compliance options and, second, what ability (if any) such
systems should have to detect a CRS.
Weight and Height Criteria
    NHTSA believes the rear seat belt warning system should be able to
detect an occupant that should be restrained with a seat belt alone and
provide seat belt use information to the driver that is appropriate for
that type of system. This target population is comprised of adults,
teenagers, and children in booster seats. Children in booster seats are
part of the target population because they should be restrained with
the seat belt and so would benefit from a seat belt reminder. As
mentioned above, the transition to a booster seat typically occurs from
ages 4-7 years. Children in rear-facing and forward-facing CRSs are not
part of the target population because these children are restrained by
the CRS harness, not the seat belt. The intent of the reminder is not
to warn of CRS misuse, but to warn of occupants not restrained by a
belt alone.
    Accordingly, we are proposing 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 six-year-old child,
which roughly corresponds to a typical age at which a child would
transition from a forward-facing CRS to a booster seat. We have taken
these criteria from FMVSS No. 208, which uses them 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. The proposed
test does not specify the use of a booster seat because we are aware
that children can be prematurely transitioned to a seat belt without
the use of a booster,\134\ 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. As we explain
below in Section XII.B, Test Procedures, the agency proposes using
either a person or any anthropomorphic test device specified in part
572 that meets these proposed weight and height criteria.\135\
---------------------------------------------------------------------------

    \134\ About 16.6 percent of children 4 to 7 years old were
prematurely transitioned to seat belts in the ``2019 National Survey
of the Use of Booster Seats'' (DOT HS 813 033).
    \135\ For anthropomorphic test devices, this would include the
50th percentile male, 5th percentile female, and the 6-year-old and
10-year-old child dummies.
---------------------------------------------------------------------------

    These criteria specify a smaller occupant than does R16. We
tentatively believe that harmonizing with R16 and using a heavier dummy
would not capture the child segment of the population that is in
booster seats; that is, seat belt use may occur for occupants smaller
than the criteria specified by R16. We also do not believe it is
necessary to use a larger-size occupant because a system capable of
recognizing a six-year-old should also be capable of recognizing larger
occupants.
    At the same time, we tentatively believe that the proposed criteria
are 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
three-year-old), but we believe it would not be appropriate to specify
the use of the 3-year-old because a child represented by this ATD
should be seated in a forward- or rear-facing CRS, not a booster seat.
Ability of the System To Detect a CRS
    NHTSA also does not propose to require any sort of CRS detection
capabilities at this time.
    We tentatively believe that a forward- or rear-facing CRS installed
with the seat belt would not cause problematic false warnings; rather
it would just register the CRS as a buckled passenger.
    Similarly, we believe 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. There
are a few reasons for this. First, we do not believe

LATCH-installed CRSs would lead to false warnings or driver confusion
about the belt status of any rear occupants, because NHTSA recommends
buckling unused seat belts that are within reach of children to prevent
seat belt entanglement and/or strangulation.\136\ This includes, for
forward- or rear-facing CRSs installed with LATCH, buckling the unused
belt behind the CRS. (Fastening the unused seat belt behind the CRS
when installing a CRS with LATCH should not be mistaken for installing
a CRS with both the seat belt and LATCH; a CRS installed with LATCH is
not also installed with the seat belt unless it is approved by both the
car seat and vehicle manufacturers.) If users follow NHTSA's
recommendation and buckle the belt behind the CRS, the positive-only
system would simply consider those belts to be fastened, and the
negative- and full-status systems would not register a false warning.
If the belt is not buckled as NHTSA recommends, with a positive-only
system, the driver would simply see that there were no buckled belts,
so there would be no false warnings. For the negative-only and full-
status systems (which utilize occupant detection), the system could
register the child in the CRS as an occupant depending on the weight of
the child and CRS. We are aware of at least one vehicle manufacturer
that uses occupant detection for its rear seat belt warnings and it
recommends fastening the unused seat belt if the CRS is installed with
LATCH to avoid such a false warning. (In the owner's manual section of
this preamble we seek comment on including such guidance in the owner's
manual, which includes information provided by the vehicle manufacturer
to the consumer, whether in digital or printed form.) Again, if the
belt is not buckled as NHTSA recommends, the driver would need to take
these facts into account when comparing the number of rear seat
occupants against how many or which rear seat belts are reported to be
in use by the warning system. Second, we are not proposing to require a
warning for CRSs improperly attached to the LATCH because the focus of
this rulemaking is on providing a seat belt warning, not on providing
warnings for improperly installed LATCH child seats. Third, this
approach is consistent with ECE R16 and Euro NCAP, neither of which
have provisions for addressing LATCH-installed child restraints.
Finally, requiring LATCH sensors would add extra complexity and cost.
---------------------------------------------------------------------------

    \136\ https://www.nhtsa.gov/road-safety/child-safety.
---------------------------------------------------------------------------

    We also do not believe a booster seat would present any special
challenges to a seat belt warning system. If an (un)belted child is in
a booster seat, the system would register the belt as not (un)fastened
and (if equipped with occupant detection) that the seat was occupied.
This would not necessitate the system 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 criteria (roughly equivalent to a 6-year-old) is heavier than
an unoccupied booster seat.
    We are also not proposing to require more sophisticated features to
test how well the system avoids false positives--e.g., the ability of
the system to distinguish packages or pets from occupants or a child
seat mode. A detection system that can differentiate between cargo and
occupants would require additional sensor technology in comparison to a
weight-based sensor and would be more costly. This issue can be
mitigated by moving the cargo to the floor or trunk of the vehicle or
by buckling the unused belt and would not be an issue for the positive-
only compliance option. Tesla's ``child seat mode'' allows the driver
to acknowledge the warning triggered by a CRS installed with LATCH for
that trip. With respect to Tesla's comment regarding a child seat mode,
neither ECE R16 nor Euro NCAP contemplate this and we are not aware of
other manufacturers that have employed this feature. Given that a child
seat mode feature could be used to circumvent the warning (i.e., a belt
use warning could be prevented or dismissed by use of the child seat
mode), and the limited information NHTSA has on it, we have tentatively
decided not to permit this feature.
    We seek comment on all these issues.
d. Minimum Duration
    The ANPRM also sought comment on the minimum duration of the
warning. NHTSA's front seat belt warning research suggests that longer-
duration warnings are more effective, but also more annoying.\137\ The
current driver's seat belt visual warning in FMVSS No. 208 is required
to last at least 60 seconds under the second compliance option in FMVSS
No. 208, S7.3(a)(2). Both R16 and Euro NCAP specify a 60-second visual
warning (which may end sooner if the belt is fastened or the seat
becomes unoccupied).
---------------------------------------------------------------------------

    \137\ DOT 2009 Belt Warning Study, supra n. 36.
---------------------------------------------------------------------------

Comments
    Many commenters recommended harmonizing with R16 and adopting 60
seconds.\138\
---------------------------------------------------------------------------

    \138\ Global suggested not adopting the Euro NCAP duration
requirement (90 seconds) because the warning must balance
effectiveness and consumer acceptance, but NHTSA understands the
Euro NCAP minimum duration to be 60 seconds.
---------------------------------------------------------------------------

    A few commenters advocated a longer warning. Two commenters
recommended the warning should last until all occupants are buckled.
One commenter said that systems with long single-cycle durations and
those that cycle audible/visual reminders throughout the entirety of
the drive are more effective than systems that cycle for a limited
number of times.\139\
---------------------------------------------------------------------------

    \139\ NSC cited an IIHS study finding that an indefinite
reminder and a 100 second constant reminder increased seat belt use
by 30-34 percent over an intermittent reminder.
---------------------------------------------------------------------------

    Another commenter said that the visual warning duration should be
based on evidence of effectiveness while maintaining a balance with
annoyance.
Agency Response
    NHTSA is proposing that the warning last for at least 60 seconds.
We believe 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.\140\ This would be a shorter warning than we
are proposing for the front outboard seats (see Section XI.C). There
are a couple of reasons for our tentative decision that a shorter
warning is warranted for the rear seats. First, we are not proposing 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 think that it is not necessary to require that this 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 if they wished. The proposed compliance

options requiring occupant detection would not require a warning for
occupants with fastened belts.
---------------------------------------------------------------------------

    \140\ We are also proposing that these visual displays should
not be overridden by other visual warnings for the required
duration.
---------------------------------------------------------------------------

    This is consistent with ECE R16 and Euro NCAP and with systems
currently deployed in the United States. Our preliminary analysis found
that, of the 15 manufacturers that provide vehicle models with a rear
seat belt warning system in the United States, 8 appear to provide
systems with initial visual warnings that are active for at least 60
seconds. An additional three manufacturers appear to provide visual
warnings until the seat belt is fastened.
2. Audio-Visual Change-of-Status Warning
    The ANPRM sought comment on requiring a change-of-status warning
for when a fastened seat belt is unfastened, including an audio-visual
change-of-status warning. We also sought comment with respect to
potential requirements for an audible warning, including the duration
of the warning and whether NHTSA should specify additional warning
characteristics (such as sound level).
    R16 specifies an audio-visual change-of-status warning for the rear
seats. If a fastened rear belt becomes unfastened when the vehicle is
in ``normal operation,'' \141\ 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.\142\ The additional
thresholds are distance traveled (not to exceed 500 meters), vehicle
speed (not to exceed 25 km/h, 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.\143\ This warning may not be canceled by the driver.
---------------------------------------------------------------------------

    \141\ Defined as forward motion at a speed greater than 10 km/h.
Sec.  2.47.
    \142\ Section <IP_ADDRESS>.
    \143\ These summaries simplify the requirements somewhat. They
will be discussed in greater detail later in the preamble where
relevant.
---------------------------------------------------------------------------

    Euro NCAP also requires (in order to earn bonus points) an audio-
visual change-of-status warning at vehicle speeds of 25 km/h and
above.\144\ If the change-of-status occurs below 25 km/h 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.\145\ 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).\146\ 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.\147\ 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,\148\ 30 seconds have elapsed,\149\ or the vehicle speed falls
below 10 km/h.\150\
---------------------------------------------------------------------------

    \144\ Section <IP_ADDRESS>.
    \145\ Section <IP_ADDRESS>.
    \146\ Section <IP_ADDRESS>.
    \147\ Section <IP_ADDRESS>.1.
    \148\ Section <IP_ADDRESS>.
    \149\ Section <IP_ADDRESS>.
    \150\ Section <IP_ADDRESS>. The audio signal must resume when the
speed goes above 25 km/h 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.
---------------------------------------------------------------------------

Comments
    Many commenters specifically supported requiring an audio-visual
change-of-status warning. One commenter cited a survey of adult
passengers who do not routinely use a seat belt in the rear in which
62% of respondents said they would be more likely to use a seat belt if
there was an audible warning compared with only 50% who said the same
about a visual warning.
    With respect to the triggers for the warning, two commenters stated
that a change-of-status warning should activate regardless of the
speed.
    Several comments also discussed the duration of an audible alert.
Several commenters recommended harmonizing with the 30 seconds required
by R16. Other commenters argued for a longer audible warning,
including: 60 seconds, 90 seconds, and until all occupants are buckled.
One comment noted that audio-visual warnings that continue to cycle
throughout the drive are more effective than limited-duration warnings.
Another commenter recommended consistency with existing FMVSS No. 208
audible warning systems for front occupants. Commenters stated that the
duration should be based on evidence of effectiveness while maintaining
a balance with annoyance. A commenter stated that, while information
about the effect of an audio-visual rear seat belt warning on rear seat
belt use is sparse, research on front seat belt warning systems
suggests that an audio-visual warning lasting longer than 8 seconds
would be expected to motivate an unbelted rear occupant to refasten the
seat belt.
    With respect to other warning characteristics, three commenters
recommended that the audible warning be heard throughout the vehicle. A
commenter suggested following R16's requirement that the warning
``consist of a continuous or an intermittent (pauses shall not exceed 1
second) sound signal or of continuous vocal information.'' \151\ Two
commenters said that specifying additional audible warning
characteristics would be burdensome and unnecessary. A commenter said
that there should be a balance of the sound level so that consumers
would accept and react positively to the warning, and suggested it be
the same as that for the driver. Another commenter recommended that the
audible warning specification be based on evidence of effectiveness and
suggested that maintaining consistency with other seat belt warning
signals would be desirable. A commenter recommended consistency with
existing FMVSS No. 208 audible warning systems for front occupants. And
yet another commenter recommended a warning that is enhanced but does
not rattle the driver.
---------------------------------------------------------------------------

    \151\ Section <IP_ADDRESS>.1.
---------------------------------------------------------------------------

Agency Response
    The agency proposes to require an audio-visual warning when a rear
seat belt is unbuckled during a trip. We propose that when the
vehicle's ignition switch is in the ``on'' or ``start'' position, the
vehicle's transmission selector is in a forward or reverse gear, and a
rear seat belt in use changes to not being in use, the vehicle must
activate a continuous or flashing visual warning consisting of icons
\152\ or text visible to the driver, as well as a continuous or
intermittent audible signal for a period of not less than 30 seconds,
beginning when a seat belt in use changes to not being in use. The
warnings could cut off sooner if the belt is refastened before the
minimum time limit has been reached. Comments from vehicle
manufacturers were largely in support of harmonizing with the ECE R16
requirements, and the proposed requirements are comparable to the
change-of-status warnings on vehicles currently equipped with rear seat
belt warnings. For example, Volvo vehicles provide an audio-visual
warning lasting until the belt is refastened.
---------------------------------------------------------------------------

    \152\ In the proposed regulatory text, we use the term
``symbol'' instead of ``icon'' in order to be consistent with the
current usage in FMVSS Nos. 101 and 208.
---------------------------------------------------------------------------

    We believe this warning will be an effective way to reduce the risk
of injury

to rear seat occupants by alerting the driver when a passenger
unbuckles during a trip. NHTSA's 2015 consumer survey found that a
change-of-status warning is effective in getting passengers to refasten
their seat belt.\153\ This may be an especially beneficial feature for
drivers transporting children in the back seat. Such a warning may
reduce the risk of injury to children by alerting the driver that a
child has unbuckled his or her seat belt, providing the driver an
opportunity to direct the child to re-buckle the belt. Fifty-five
percent of the drivers surveyed by NHTSA who transport children in the
rear seat and who said their children do not always use seat belts,
have had the experience of their child unbuckling during a trip.\154\
---------------------------------------------------------------------------

    \153\ Paul Schroeder & Melanie Wilbur. 2015. Survey of Principal
Drivers of Vehicles with a Rear Seat Belt Reminder System.
Washington, DC: National Highway Traffic Safety Administration,
[Found in the docket for this ANPRM.]
    \154\ Id. at 10. This percentage is based on a fairly small
number (15) of drivers who reported that their children do not
always use seat belts.
---------------------------------------------------------------------------

    The proposed requirements follow ECE R16 and Euro NCAP in that both
of those protocols include an audio-visual rear belt change-of-status
warning with specified trigger criteria.\155\ We tentatively agree with
a commenter that a duration longer than 8 seconds is warranted because
it will be more effective and believe that a 30-second minimum duration
appropriately balances effectiveness and acceptance. We note that this
is shorter than the duration we are proposing for the change-of-status
warning for the front outboard seats (until the belt is re-fastened--
see Section XI.C.2) because we tentatively believe that a longer
warning for the rear seats is more likely to lead to driver
distraction, especially with children in the rear seats.
---------------------------------------------------------------------------

    \155\ Features of the change-of-status warning that are common
with the start of trip warning--for example, the telltale
characteristics--are discussed later in the preamble.
---------------------------------------------------------------------------

    The proposal differs from R16 and Euro NCAP in a few ways:
     Triggers. The warning would be required as long as the
ignition is on and the transmission selector is in the drive or reverse
position, with no additional thresholds or triggers, such as the
vehicle having to reach a forward speed of 25 km/h. We tentatively
believe this departure from R16 and Euro NCAP is justified. 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. We do not adopt 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 this would require a delay in the activation of the change-of-
status warning; also, these types of events are likely limited and
require very little time so exposure to the warning would be very
limited. We do, however, adopt the Euro NCAP requirement that if a
change-of-status occurs and a door is open, the system should consider
that as the start of a new trip. This would allow for passengers to
exit the vehicle when the driver does not shift into the park gear
without activating the change-of-status warning for the full duration
requirement.
     Duration. The proposed 30-second duration harmonizes with
ECE R16 (though it is 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 propose that the audible signal
may be ``intermittent'' (i.e., not continuous), which mirrors the
longstanding requirements for the driver's seat belt warning. ECE R16
\156\ and Euro NCAP \157\ do not count periods in which the warning
stops for longer than 3 seconds as part of the overall duration, and we
have tentatively decided to propose a similar requirement for the rear
audible change-of-status warning. (In contrast, we are specifying
additional signal characteristics for the front seat belt change-of-
status warning because we are proposing to require a longer duration
for that warning. This is discussed in Section XI.C.2)
---------------------------------------------------------------------------

    \156\ Section <IP_ADDRESS>.1.
    \157\ Section <IP_ADDRESS>.3.
---------------------------------------------------------------------------

     Audible warning characteristics. ECE R16 specifies that
for intermittent audible warnings, the pauses shall not exceed 1
second, and that gaps longer than 3 seconds would not count toward the
required 30 second duration. Euro NCAP specifies that there must be no
gaps greater than 10 seconds, and that gaps longer than 3 seconds would
also not count toward their required duration. We have tentatively
decided to propose a requirement that specifies that periods of time
when the audible warning is not active for longer than 3 seconds would
not count toward the required 30 second duration. Given the very
limited duration of the rear seat change-of-status audible warning for
the rear seats we believe this is a sufficient constraint for achieving
an adequate warning. We have not further specified audible warning
characteristics, such as volume or tone, in order to provide
manufacturers design flexibility. The standard has required an audible
driver's seat belt warning with no additional audible warning
requirements since the early 1970s, so we believe manufacturers are
familiar with designing and implementing optimal audible seat belt
warnings. As mentioned above, we are specifying additional signal
characteristics for the front seat belt change-of-status warning
because we are proposing to require an indefinite duration for that
warning, which requires more thought about the warning characteristics
to mitigate the use of ineffective audible warnings (See Section
XI.C.2).
    We seek comment on all aspects of the proposed change-of-status
warning. Are there situations when the warning at a low speed would
result in an unnecessary or unwanted warning, and how frequently would
such situations occur? Are any of the deviations from R16 and/or Euro
NCAP unwarranted, and what is the basis for such a conclusion? We
acknowledge that the proposed requirements may still trigger the
change-of-status warning for a short period of time until a door is
opened when a passenger exits the vehicle and the vehicle is not in the
park gear; however, we believe exposure to a very limited warning in
these scenarios is necessary in order to capture other change-of-status
events that occur when a vehicle is stopped but not in the park gear.
We seek comment on how vehicle manufacturers are currently handling
(e.g., what type of warning if any is provided) rear seat change-of-
status events that occur when the vehicle is stopped, but not in the
park gear, or at low speeds (e.g., what type of warning, if any, is
provided when passengers exit the vehicle without the vehicle being in
the park gear)? As will be discussed later, we are proposing that the
change-of-status warning for the front outboard seats be active until
the seat belt that triggered the warning is refastened, so we seek
comment on whether the proposed limited duration change-of-status
warning for the rear seats should

also be required to last indefinitely until the rear seat belt is
refastened.
3. Telltale Location
    A seat belt warning can function by alerting the driver that a rear
seat belt is unbuckled, leaving it to the driver to request the rear
passenger to buckle up. However, many other strategies are possible.
For example, in addition to warning the driver, the front seat
passenger could also be warned on the premise that, if the driver was
occupied by other matters, the front seat passenger could direct the
rear seat passengers to buckle up. Another strategy could be to warn
the rear passenger(s) directly that their belt is unbuckled. Finally,
in addition to warning the rear passenger(s), the driver and/or the
front passenger could be warned. Some research suggests that having the
warning visible to the unbelted occupant may increase
effectiveness.\158\
---------------------------------------------------------------------------

    \158\ DOT 2007 Acceptability Study, supra n.78.
---------------------------------------------------------------------------

    ECE R16 requires that the visual warning be visible to the driver
when they are facing forward,\159\ and Euro NCAP similarly requires
that the visual signal be clearly visible to the driver without the
need for the head to be moved from the normal driving position.\160\
---------------------------------------------------------------------------

    \159\ Section <IP_ADDRESS>.1.
    \160\ Section <IP_ADDRESS>.
---------------------------------------------------------------------------

Comments
    Most commenters recommended that the signal be visible to the
driver, while one suggested the signal be visible to the rear seat
passengers to avoid relying on the driver to enforce belt use,
especially as rear-seat occupancy increases due to the increased use of
for-hire vehicles (and, possibly at some time in the future, autonomous
vehicles).
    Another commenter stated that it is impractical to provide a
warning to rear passengers on buses due to wiring costs, customization,
and FMVSS No. 222 requirements for head impact performance (for school
buses).
Agency Response
    We agree with the majority of commenters and propose that the
warning signal be visible to the driver. Although some research may
suggest that having the warning visible to the unbelted occupant may
increase effectiveness, we tentatively believe that the increased cost,
complexity, and re-design such a requirement would entail would not be
justified. However, manufacturers would have the flexibility to place
the visual warning where it would be seen by some or all rear seat
occupants. In Section XII.C we discuss the implications of the telltale
location as it relates to automated vehicles.
4. Telltale Characteristics
    The ANPRM sought comment on whether we should propose requirements
for telltale characteristics such as color and required text.
    For the current driver's seat belt warning, FMVSS No. 208 requires
a continuous or flashing warning light displaying (at the choice of the
manufacturer) either the telltale specified in FMVSS No. 101 (see
Figure 2) or the words ``Fasten Seat Belts'' or ``Fasten Belts.'' \161\
The telltale must be visible to the driver \162\ in both daytime and
nighttime.\163\ There are no color or illumination requirements for the
telltale.\164\ The seat belt telltale may share a common space with
other telltales except several specific telltales identified in FMVSS
No. 101.\165\ Telltales in the same common space, however, may not be
displayed simultaneously.\166\ 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.\167\ Supplementary
symbols or words may be used in conjunction with the required telltale
or words.\168\
---------------------------------------------------------------------------

    \161\ FMVSS No. 208 S7.3(a) and FMVSS No. 101, table 2.
    \162\ FMVSS No. 208 S7.3; FMVSS No. 101 S5.1.2.
    \163\ FMVSS No. 101, S5.3.3(a).
    \164\ See Table 2.
    \165\ S5.5.2. These are: air bag malfunction, low tire pressure,
electronic stability control malfunction, passenger air bag off,
high beam, turn signal, and any brake system malfunction required by
table 1 to be red.
    \166\ See FMVSS No. 101 S4 (``Common space'' is ``an area on
which more than one telltale, indicator, identifier, or other
message may be displayed, but not simultaneously'').
    \167\ FMVSS No. 101, S5.5.5.
    \168\ FMVSS No. 101, S5.2.3.
---------------------------------------------------------------------------

Figure 2--Seat Belt Telltale From FMVSS No. 101
[GRAPHIC] [TIFF OMITTED] TP07SE23.001

    The rear reminder requirements in ECE R16 mirror the FMVSS driver's
warning requirements in several respects: the telltale may be flashing
or steady; \169\ it must be recognizable in the daylight and at
nighttime and distinguishable from other alerts; \170\ and there are no
color requirements.\171\ However, R16 differs from the FMVSS
requirements in that there is no required telltale symbol.\172\ R16
also appears to require a visual warning that depicts all the rear
seating positions.\173\
---------------------------------------------------------------------------

    \169\ Section <IP_ADDRESS>.2.
    \170\ Section <IP_ADDRESS>.1.
    \171\ Section <IP_ADDRESS>.
    \172\ Section <IP_ADDRESS>. A common telltale may be used for both
the front and rear seat belt reminders. Section <IP_ADDRESS>. The front
reminder is required to utilize the symbol specified in Regulation
121, which is the same symbol specified in FMVSS No. 101 and
depicted in Figure 2.
    \173\ Section <IP_ADDRESS> (``The visual warning shall indicate at
least al 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.'').
---------------------------------------------------------------------------

    Euro NCAP specifies that as soon as the audible part of the seat
belt reminder signal starts, the visual signal needs to flash and be
synchronized with the audible part.\174\
---------------------------------------------------------------------------

    \174\ Section <IP_ADDRESS>.
---------------------------------------------------------------------------

Comments
    Several commenters favored standardized warnings. Two commenters
stated that standardized telltales would help drivers recognize the
icons when driving different/multiple vehicles (rentals, etc.).
    In contrast, other commenters urged NHTSA to provide manufacturers
with

flexibility and not require a specific telltale. Two commenters
specifically suggested harmonizing with ECE R16, in addition to the
many commenters who generally urged harmonization with R16. A commenter
requested flexibility to choose the indication method for each seating
position, such as a telltale or a graphic or rendering of the vehicle
seating positions in a more advanced display screen.\175\ Another
commenter urged NHTSA to defer regulatory action on the establishment
of a specific symbol and simply require that any telltale provided be
communicated in the owner's manual because additional research is
needed to determine which approaches may be most effective in
communicating reminder status for a particular row or specific
designated seating position, and emphasized its belief that NHTSA
should not mandate specific indicators or display characteristics in
order to provide OEMs with flexibility. Two commenters similarly
suggested allowing the telltales for the rear seat belt reminder to
differ (e.g., different colors, symbols) from those currently used for
the front.
---------------------------------------------------------------------------

    \175\ Honda's comment seems ambiguous. It urges harmonization
with R16, which does not require a specific telltale, but also
states that the existing seat belt telltale in FMVSS No. 101 is a
universally-recognized warning that can be used to provide a
consistent link to additional seat belt information, and advocates
using the FMVSS No. 101 telltale as a ``baseline warning'' to ensure
that an active safety belt warning continues to be provided if an
additional seat belt warning visual display needs to give priority
to a more important safety warning.
---------------------------------------------------------------------------

    On the other hand, some commenters did not oppose requiring use of
the current driver's seat belt telltale. A commenter said that a
typical approach for rear seat belt warnings is to include a separate
area on the instrument panel for separate telltale(s) for the rear
seating position. These telltales could be specific to the actual
seating position to inform the driver of the actual position that is
buckled or unbuckled.
    A commenter said that the rear seat warning system should be
coordinated with the driver warning, and that an ideal approach would
be to provide a pictogram of the vehicle that has icons showing the
seat belt status for each seating position. The commenter suggested
this dashboard image could be combined with the door-ajar image, and it
could even be enhanced to indicate whether a door's child safety lock
feature is engaged. Similarly, a commenter stated that the warning
should convey the location of each unbuckled occupant
(negative[hyphen]only system for which occupant detection would be
necessary).
Agency Response
    We are proposing 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 propose that icon(s) must be green; if icons are used to indicate to
the driver how many or which belts are not in use, we propose 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 propose that the
text contain the words ``rear belt(s) in use'' or ``rear belt(s) not in
use.'' We also propose 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. We also
propose to amend able 1 in FMVSS No. 101 by adding in a row for the
proposed rear seat belt warning. We agree with the merits of
standardized warnings, but also seek to provide manufacturers
flexibility to address their vehicle designs.
    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 R16. However, we propose to depart from the
current driver's warning and from 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
believe that standardized colors and text will facilitate the
interpretation of the signal. We are departing from the current
driver's warning requirements and following 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; this NPRM provides manufacturers
flexibility in choosing which icons to use.
    Another difference between the proposal and R16 is that R16
requires that the visual warning ``indicate at least all rear seating
positions.'' We understand this to mean that the visual warning must
depict all the rear seating positions. For instance, on some vehicles,
Peugeot employs a visual warning that uses a schematic of the whole
vehicle to indicate seat belt non-use or change-of-status for each
seating position.\176\ Another manufacturer, Cupra, uses a visual
warning, on some of its European vehicles, which depicts the status of
all the seat belts in the rear seats without using a schematic of the
whole vehicle.\177\
---------------------------------------------------------------------------

    \176\ https://public.servicebox.peugeot.com/APddb/modeles/3008/eGuide_ed02-16/pdfs/9999_9999_091_en-GB.pdf, pg. 144.
    \177\ https://www.cupraofficial.com/content/dam/public/cupra-website/owners/cupra-car-model-manuals/brochures/CUPRA_FORMENTOR_06_21_EN.pdf, pg. 17.
---------------------------------------------------------------------------

    In order to give manufacturers design flexibility, we do not
propose to require that the warning depict all rear seating positions.
Our 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 as recommended by Safe Ride News. We
are not requiring this because we believe it would be difficult to
implement on vehicles such as passenger vans with many rear seats. (We
also note that R16, which requires the visual warning to indicate all
rear seats, does not apply to vehicles that transport more than eight
passengers.) We acknowledge that vehicles with a larger number of rear
seats, such as passenger vans/buses, may encounter visual signal
complexities; however, we are not dictating specific types of signals
in the proposed requirements in order to ensure manufacturers have
adequate flexibility to address these types of issues. We think these
vehicles, in particular, would benefit from the option to indicate how
many rear seats are fastened.
    We seek comment on all of these issues, including the type of
visual warnings that rear seat belt reminder systems employ currently
or may employ in the future. We also seek comment on whether we should
consider further aligning with R16 by requiring the visual warning to
indicate all rear seating positions, which features of a visual warning
would be appropriate for buses, and whether any further amendments to
FMVSS No. 101 are necessary (e.g., the common space requirements in
S5.5).
5. Belt Use Criteria
    The ANPRM sought comment on whether NHTSA should retain, for a rear
seat belt warning, the criteria used for the current driver's seat belt
warning to determine if the occupant is belted. 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.\178\
---------------------------------------------------------------------------

    \178\ S7.3(c). These are the definitions for manual belts. For
automatic belts, see infra Section XII.A.
---------------------------------------------------------------------------

    ECE R16 defines an ``unfastened'' belt to mean ``either the safety-
belt buckle of any occupant is not engaged or the length of the pulled
out webbing is less than the length of the webbing which is needed to
buckle an un-occupied seat in the rear most seating position.'' \179\
Euro NCAP does not specify a webbing spool-out criteria, and only
refers to the status of the belt buckle.
---------------------------------------------------------------------------

    \179\ Section 2.46.
---------------------------------------------------------------------------

Comments
    Three commenters supported using the existing FMVSS No. 208
criteria.
    A commenter suggested harmonizing with ECE R16, regardless of the
type of system, in order to provide flexibility for vehicles that may
have different characteristics with respect to rear row seating
positions; for example, for rear seats that can be removed from a
vehicle, providing an option whereby belt spooling can be used as an
alternative to buckle latching may reduce challenges associated with
any electrical connections that might be otherwise needed to provide
functionality.
    Other commenters suggested using different belt use criteria
considering the wide range of possible occupants, devices (e.g., car
seats), and objects in rear seats, but did not offer possible
solutions. One commenter stated that any seat belt use criteria should
take into account whether a bypass system for CRS installation would be
employed to prevent false warnings caused by using the lower anchors.
Another commenter stated that the prolific use of LATCH seats and
integrated child seats on buses will necessitate an alternate means of
seat belt use detection.
Agency Response
    The current FMVSS No. 208 belt use criteria for the driver's seat
belt warning requirements have been in place since 1974 and allow for
the use of a belt latch or spool-out sensor. While these criteria would
be effective for determining belt use for the initial seat belt
warning, we believe the use of a spool-out sensor would not allow for
an objective or reliable criterion for the proposed change-of-status
warning. 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. Therefore, we are proposing amending the belt use criteria in
FMVSS No. 208, for the seat belt warning requirements, to rely on the
use of a belt latch sensor, and not provide requirements that would
accommodate the use of a spool-out sensor. We believe this is
consistent with Euro NCAP. We invite comment on this tentative decision
to not accommodate the use of spool-out sensors for the belt use
criterion and request any data on the prevalence of the use of spool-
out sensors in the fleet.
    Concerns about false alarms triggered by LATCH use for the
installation of child restraints are already addressed by the simple
approach, in line with NHTSA's recommendations, that parents and
caregivers fasten and lock the unused seat belts for the seat where the
child restraint is being installed. This is an already existing agency
recommendation to prevent seat belt entanglement and would prevent
false warnings related to LATCH use.
6. Electrical Connections
    In the ANPRM, we explained that a rear seat belt warning system
might require an electrical connection between the seat and the vehicle
to relay the information gathered by a belt latch or webbing spool-out
sensor to the rest of the warning system. A rear-belt warning system
may therefore, as several commenters to the RFC noted,\180\ present
potential wiring complexities, particularly in vehicles with removable,
folding, rotating, or stowable seats. These types of seats might
present an issue for a rear seat belt warning system because the
electrical connection might not be automatically reestablished for
these seats when the seat is reinstalled. There could be instances with
manual connection seats where the driver either forgets to make the
connection or makes an improper connection. Even for seats where the
connections are automatically established when the seat is reinstalled,
the automatic connectors might malfunction. If the electrical
connection is not reestablished, the warning system could malfunction
or provide inaccurate information. Removable seats are mainly found in
the second row of minivans.\181\ Foldable, rotating or otherwise
stowable seats (e.g., Stow-n-Go, Flip and Fold) are prominent in the
third row of minivans or large SUVs. Foldable or stowable seats in the
second row are not as prominent in minivans.
---------------------------------------------------------------------------

    \180\ See Docket No. NHTSA-2010-0061 (comments of IEE S.A.,
Alliance of Automobile Manufacturers, Association of Global
Automakers, and Automotive Safety Council).
    \181\ We consider readily removable seats to be seats designed
to be easily removed and replaced by means installed by the
manufacturer for that purpose (see FMVSS No. 208 S<IP_ADDRESS>.2.), and
do not require any special tools for their removal.
---------------------------------------------------------------------------

    Neither Euro NCAP nor ECE R16 have any requirements that address
the potential for improper electrical connections for such seats. The
ECE regulations provide that the rear seat belt warning requirements
would not apply to folding rear seats or to seats fitted with an s-type
belt (including a harness belt) until September 2022.\182\ Euro NCAP
does not exclude folding seats and includes all seating positions
including optional and removable seats, but does not require the
monitoring of the buckle status for rear seat belt secondary buckles
that require a tool to unlock.
---------------------------------------------------------------------------

    \182\ See Sections <IP_ADDRESS> and 15.4.2.
---------------------------------------------------------------------------

Comments
    Three commenter stated that removable, suspension and folding seats
are complex and raise reliability and technological readiness concerns
and should be exempted from the warning requirements until it would be
practicable. Two of these commenters said that if a seat belt warning
were required for such seats, significant lead time or a phase-in
(e.g., until the vehicle platform was updated) would be necessary.
    Commenters stated that a rule should include some or all of these
seat types. A commenter stated that, although these seats may present
challenges for rear seat belt warning systems, NHTSA has provided no
evidence that, in cases other than removable seats, the challenges
would be insurmountable, or quantified the portion of the target
population represented by occupants of these types of seats, which
likely includes many children. Another commenter stated that removable
seats would not need to be exempted from the requirements (as they
currently are from ECE R16) if specific types of electrical connections
or technology (e.g., wired buckle switch, wireless buckle switch, belt
extension) were not required.
    Commenters said that electrical connections for removable,
rotating, flipping and folding seats should not require any action on
the part of the consumer because vehicles with these seats frequently
transport children, and believed that NHTSA should also consider
requiring wireless connections and a warning for an improper
connection.
    Commenters were against any prescriptive design requirements
related to the connection between the vehicle

and any removeable, folding, rotating, or stowable seats, and in favor
of a robust set of compliance options to facilitate new technology
(although one commenter also said that any additional time it would
take NHTSA to develop such options would not be justified by the
limited benefits and relatively small number of affected vehicles). A
commenter said that NHTSA should instead include a reliability
requirement (e.g., lifetime warranty).
    Two commenters expressed concerns with wiring complexities
associated with buses. One of these commenters specifically noted
track-mounted seats, which can be repositioned by the end user, which
are also subject to improper connections and for which wireless
communication technology is not currently available.
Agency Response
    We have tentatively decided not to exempt any of these seat types
from the proposed requirements. We are not exempting suspension and/or
folding seats; the electrical connections should not be disturbed
because these seats are not readily removable, and they would
potentially just require additional wiring to accommodate the folding
or stowing process. We are also not exempting removable seats because
we tentatively believe that concerns with improper electrical
connections will be addressed by the proposed warning requirement
discussed below. Applying the requirements to these seats also
harmonizes with ECE R16 (which will soon fully phase in the rear belt
requirements for these seats) and Euro NCAP. We do not consider a
phase-in necessary for suspension and/or folding seats because we
believe the solution for these seats is simple. For removable seats a
phase-in is unnecessary because readily attachable electrical
connections appear feasible. We do not believe buses would be subject
to these requirements, given our definition of readily removable seats.
    We have 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 are, however, proposing two
requirements related to the electrical connections for readily
removable seats.
    First, we are proposing that readily removable seats must either
automatically connect the electrical connections when the seat is put
in place (i.e., not require the vehicle user to take any additional
action to reconnect the electrical connections other than re-installing
the seat) or, if a manual connection is required (i.e., the user must
reconnect the electrical system), the connectors must be readily-
accessible.\183\ By readily-accessible connectors we mean connectors
that are easy for an ordinary consumer to see and access. A system
utilizing 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. We agree with the
commenters who recommended no prescriptive requirements in order to
ensure OEMs have flexibility in system design. We think the proposal
balances flexibility and the need to ensure that a proper connection is
made.
---------------------------------------------------------------------------

    \183\ As we note in Section X.C.7 below, we also propose that
the owner's manual (which includes information provided by the
vehicle manufacturer to the consumer, whether in digital or printed
form) include instructions on how to make any manual electric
connections for readily removable seats.
---------------------------------------------------------------------------

    Second, we are proposing that vehicles utilizing 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. We are concerned that consumers could reinstall removable seats
(with either automatic or manual connections) without making a proper
electrical connection. There could be instances for manual connection
seats where the driver either forgets to make the connection or makes
an improper connection. Even for seats where the connections are
automatically established when the seat is reinstalled, the automatic
connectors might malfunction (e.g., debris, broken connector) and a
proper connection may not be made. If the electrical connection is not
reestablished, the warning system could malfunction or provide
inaccurate information. We are only proposing to require the warning
for negative-only systems because a faulty connection would result in
the system not triggering any warning of an unbelted rear seat
occupant. Moreover, 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.
    These potentially serious problems are not present in full-status
or positive-only warning systems. First, it is our expectation that a
faulty connection for a full-status system would affect both the
occupant detection and belt status. However, if for some reason this is
not the case and the occupant detection of a full-status system is
working properly, but the seat belt buckle sensor is not connected
properly, then no visual warning should activate without input from the
buckle sensor and the driver should easily recognize the system is not
working properly. If for this same scenario, the system interprets a
lack of input from the seat belt sensor as an unbuckled seat belt when
the driver verifies or requests the rear seat occupant to buckle their
seat belt and the occupant is already buckled, then the driver would
again be aware the system is not working properly. If the occupant
detection sensors are not connected properly, the driver would be aware
of the number of rear seat occupants being transported, and would thus
be aware that the system is not operating correctly when there is not a
warning for each occupant. Similarly, if there were not a good
connection in a vehicle with a positive-only system, an unbelted rear
seat occupant would not register as belted, which would be accurate; a
belted passenger would also not register as belted, but since the
passenger would be belted, there would be no adverse consequences from
the system error if a crash were to occur.
    We believe that both of these requirements would mainly affect
minivans, which make up a small percentage of the fleet.\184\ We
believe it might be possible to utilize the rear seat belt visual
warning signal, with slight modifications (e.g., a different color).
The agency seeks comments on this proposal, particularly on the safety
need for such warnings, costs, and feasibility of the proposed warning.
We also seek comment on whether this telltale should be added to table
2 of FMVSS No. 101, Controls and displays.
---------------------------------------------------------------------------

    \184\ We estimate that minivans make up 3.6% of vehicles
produced based on MY 2015 WardsAuto production data. The number of
minivans that would potentially be affected by this proposed
requirement is less than 3.6%, because some minivans only have
foldable/stowable rear seats, not removable seats.
---------------------------------------------------------------------------

    None of the regulations or statutes administered by NHTSA require
manufacturers to provide a lifetime warranty. However, if a vehicle or
item of equipment is determined (by the manufacturer or NHTSA) to have
a safety-related defect or fails to meet an applicable FMVSS, the
Safety Act requires the manufacturer to notify the owner of the defect
or noncompliance and (if the vehicle or item is not more than 15 years
old) remedy the vehicle or item without charge to the vehicle owner.
7. Owner's Manual Instructions
    The ANPRM sought comment on requiring the owner's manual to provide

information on the warning system's features, including the location,
format, and meaning of the visual warnings. Because the owner's manual
readership may be relatively low,\185\ we also sought comment on
whether this information should be displayed in the vehicle instead of
(or in addition to) the owner's manual.
---------------------------------------------------------------------------

    \185\ The National Child Restraint Use Special Study found that
only 13 percent of drivers reported reading the vehicle owner's
manual. Nathan K. Greenwell. 2015. DOT HS 812 142. Washington, DC:
U.S. Department of Transportation, National Highway Traffic Safety
Administration, p. 10.
---------------------------------------------------------------------------

Comments
    None of the commenters opposed such a requirement. Several
commenters supported including such information in the owner's manual.
Some commenters requested flexibility in describing the functionality
of the system. One commenter suggested that the owner's manual could
include information on the seating positions where a rear-seat reminder
is provided, a description of the visual and audible warning(s), an
indication of whether the system incorporates driver monitoring
(including any limitations), instructions for deactivating or
cancelling any warning(s), any limitations related to CRS, and
information related to the connection of removable, folding, rotating,
or stowable seats.
    A commenter believed that information should also be displayed in-
vehicle, especially for one-time vehicle users (renters, friends,
family), and especially with respect to electrical connections for
removable/stowable seats. Another commenter believed that more research
on the best way to communicate this to owners is needed.
    A commenter stated that information on how a rear seat belt
reminder affects CRS installation should be provided, including whether
the system is able to detect a CRS (and avoid false warnings).
Agency Response
    We propose 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 propose that the owner's manual include instructions on how to
make any manual electrical connections for readily removable seats.
This will provide manufacturers flexibility for how they describe the
functionality of the system. These proposed additions to the owner's
manual requirements in FMVSS No. 208 would require a revision to the
approved collection of information OMB No. 2127-0541. Later in this
proposed rule, we seek comment on this revision.
    With regard to including system functionality information in the
vehicle itself, these types of vehicle features are not normally
explained visually in the vehicle, other than information on air bags
which pose safety risks. This level of detail is best described in the
owner's manual.
    We are aware of at least one manufacturer that provides information
in the owner's manual on how their rear belt warning system with
occupant detection functions when a CRS is installed with LATCH and
guidance on how to avoid activating the warning (for example, it
informs the consumer that fastening the seat belt prior to installing a
CRS with LATCH will avoid activating the warning system for that
seat).\186\ We seek comment on whether we should require including such
information in the owner's manual (which includes information provided
by the vehicle manufacturer to the consumer, whether in digital or
printed form).
---------------------------------------------------------------------------

    \186\ As noted earlier, NHTSA recommends buckling unused seat
belts that are within reach of children to prevent seat belt
entanglement and/or strangulation.
---------------------------------------------------------------------------

8. Interaction With Other Vehicle Warnings
    The ANPRM also solicited comment on whether a rear seat belt
warning could conflict with other in-vehicle warnings, and how this
might be addressed.
Comments
    A few commenters believed that the rear belt reminder could
conflict with other warnings. One commenter believed that there are
conflicts and that the rear seat belt warnings should be given priority
over other warnings. Two commenters recommended that NHTSA provide
flexibility for rear-seat reminder system alerts (or aspects of the
alert) to be temporarily suppressed or paused where it is necessary to
alert or redirect the driver's attention to higher-priority warnings--
for example, related to the operation of the vehicle or a potential
safety risk within the external roadway environment, such as an alert
provided by an advanced driver assistance system (ADAS), crash
avoidance system or automated driving system (ADS) request to
intervene. Another commenter recommended that the existing FMVSS No.
101 Seat Belt Unfastened Telltale be utilized as a persistent
``baseline'' warning when there is an active seat belt warning for any
occupant, even in the event that the display of detailed seat belt
information is prevented by a higher priority warning.
    Other commenters did not believe there would be conflicts with
other warnings, and one manufacturer did not believe there would be a
conflict if the audible warning is accompanied by a visual warning.
Agency Response
    NHTSA is proposing that the rear seat belt reminder telltale must
not be overridden by other visual warnings for the required duration.
This is consistent with the current requirements in FMVSS No. 101 for
the driver's seat belt warning 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 do not believe that the seat belt warning
requirements will interfere with other warnings for safety systems
since they have dedicated warning signals. This should give
manufacturers the flexibility to determine the best way to implement
their warnings. For instance, warnings for a potential safety risk can
be more aggressive than those for the seat belts. With regard to
available space, the visual signal might be displayed as a telltale
light on the instrument panel or on the vehicle's information display
screen. Manufacturers will also have to determine whether the driver
and rear passenger seat belt visual warning will be treated the same.
---------------------------------------------------------------------------

    \187\ FMVSS No. 101, S5.5.5. See discussion supra, Section
X.C.4, Telltale characteristics.
---------------------------------------------------------------------------

D. Alternative Warning Signals

    The ANPRM 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.
Alternatives to a visual warning on vehicle start-up could include an
audible signal, either electronic or mechanical, or a haptic warning
(e.g., steering wheel or seat vibration). Similarly, an audible or
visual warning of a change in the status of rear seat belts could be
either electronic or mechanical and could include a haptic signal. We
also sought comment on alternative solutions that would alert the
driver when a rear seat passenger buckles and/or unbuckles (e.g.,
mirrors to see whether belts are buckled, or the sound of the latch
plate clicking into the buckle).
Comments
    Many commenters recommended requiring the traditional audio-visual

warnings currently used for the front seats. One commenter stated that
warning specifications should be based on effectiveness and that audio-
visual warnings would likely be highly effective given occupants'
familiarity with them; it did not believe that a less-sophisticated
warning, such as a specialized system of mirrors, would be sufficient
to inform the driver about the status of the rear seat belts. Two
commenters noted the potential for confusion/distraction if an
alternative warning were used. A commenter stated that the ``click'' of
the belt buckle, while certainly evidence of a buckled seat belt, can
easily be missed by the driver and other occupants, as it could be
masked not only by the drivers' own belt clicking, but also by ambient
noise in the vehicle, and that, given the research supporting the
effectiveness of an audio-visual signal, an alternative warning system
would not be acceptable. Two commenters said that an alternate warning
is not necessary because ECE R16's requirements are adequate.
    A commenter said that, in addition to requiring an audio-visual
warning, the proposed rule should require a notification on the
instrument cluster if a seat belt is unbuckled that must be
acknowledged by the driver before any other use of the instrument panel
is permitted.
    A commenter stated that rear seat belt warnings are not practicable
for buses, but if they were used, an audible alarm similar to that
required for emergency exits would be necessary to provide an effective
notice to the driver. The commenter believed that the interior mirror
on buses designed to permit the driver to view the passengers, while
not as effective in determining proper seat belt use as an electronic
monitoring system, has been effective in aiding the driver to observe
passengers that were obviously not properly belted. The commenter did
not support the use of haptic signals on buses. A public commenter
suggested use of cameras.
Agency Response
    We agree with the commenters who believe that an alternative
warning is not necessary and that an audio-visual warning would be
appropriate.\188\ Cameras would be unnecessary and would add cost. The
agency believes that mirrors alone would not be as effective as an
audio-visual warning and may pose risks, as drivers would have to study
the view to determine belt status, assuming they could clearly see the
belts. In addition, as explained above, the proposed rule would not
apply to school buses.
---------------------------------------------------------------------------

    \188\ With respect to Blue Bird's argument regarding the
practicability of a rear warning for buses, see Section X.B,
Applicability.
---------------------------------------------------------------------------

    We are specifying minimum performance requirements in order to
balance the effectiveness and acceptability of these systems.
Manufacturers can 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.

E. Resistance to Intentional and Inadvertent Defeat and Deactivation

    The ANPRM sought comment on whether NHTSA should propose
requirements to address circumvention. We pointed to agency research on
the development of a seat belt misuse detection system that identified
a number of ways in which a rear seat belt warning system might be
intentionally defeated, as well as potential countermeasures.\189\ For
example, a warning system could be defeated if:
---------------------------------------------------------------------------

    \189\ 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). Washington, DC:
National Highway Traffic Safety Administration.
---------------------------------------------------------------------------

     The belt is buckled before the occupant sits in the seat.
This could be addressed by requiring a sequential logic system. A
sequential logic system would require that the belt be buckled after
the seat has been occupied in order for the system to recognize the
seat belt as being buckled.
     An occupant buckles the seat belt behind themselves. This
could be addressed by utilizing both seat belt latch and spool-out
sensors and deactivating the warning only if the webbing were spooled
out more than a predetermined length. However, even these sensors could
be defeated by pulling out additional webbing and clipping it off to
prevent retraction.
     The seat belt and/or occupant detection sensors utilized
by the rear warning system in vehicles with removable rear seats are
intentionally disconnected.
    We also noted some ways in which the warning could be inadvertently
circumvented (for example, when the driver uses a remote engine starter
so that the initial warning activates before the driver is in the
vehicle).
    We also sought comment on whether a feature allowing single-trip
manual deactivation would diminish the likelihood of circumvention. The
ECE regulations allow the rear seat belt warning system to incorporate
a short-term and/or a long-term deactivation feature for the audible
change-of-status warning.\190\ Under those regulations, a short-term
deactivation may only be effectuated by specific controls that are not
integrated in the safety-belt buckle, and only when the vehicle is
stationary.\191\ When the ignition or master control switch is
deactivated for more than 30 minutes and activated again, a short-term
deactivated safety-belt reminder must reactivate. A long-term
deactivation may only be effectuated by a sequence of operations that
are detailed only in the manufacturer's technical manual or which
require tools that are not provided with the vehicle. It must not be
possible to provide either short- or long-term deactivation of the
visual warning. Under Euro NCAP, the system may allow the driver to
acknowledge the signal and switch it off for that unique event, except
for change-of-status events; a new trigger of the warning should not be
prevented.\192\ We therefore understand there to be two distinct but
related concepts in the ECE regulations and Euro NCAP: acknowledgement
and deactivation. The former allows the driver to turn off the signal
once it is activated, while the latter prevents the signal from
activating altogether. In addition, FMVSS No. 101 provides that
telltales for several functions (such as high beams), but not including
the driver's seat belt warning, must not be cancelable while the
underlying condition for their activation exists.\193\
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    \190\ Section 8.4.5.
    \191\ Section <IP_ADDRESS>.
    \192\ Section <IP_ADDRESS>.2.
    \193\ S5.5.6(b).
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Comments
    Several commenters supported addressing intentional and/or
inadvertent defeat. A commenter stated that, given the relatively small
proportion of hard-core nonusers, the proportion of the potential
target population seeking to intentionally defeat the systems is
relatively small. Nonetheless, the commenter stated that, if mitigation
strategies can be built into the systems, such an advance would likely
help address at least some portion of ``hard-core nonusers'' as well as
those exhibiting inadvertent misuse. Commenters believed that the cost
of the potential countermeasures would be minimal, and they should be
required to the extent feasible. A commenter stated that the rear
warning system should include appropriate requirements for inadvertent
defeat, but not intentional defeat. Another commenter supported
investigating the possibility of eliminating the ``false comply''

condition of buckling behind the back or extracting and ``pinning'' the
belt without buckling. One potential option is to replicate current
systems used to identify seat belt use for front seated occupants, as
occupant detection systems can also assist with identifying misuse.
They also commented that sensor technology that identifies belt
pullout, occupant location, and buckle switches can add redundancy and
reduce the risk of intentional and inadvertent defeat.
    Other commenters disagreed with hardening the system against
circumvention because it would be burdensome and unnecessary (minimal
benefits). One commenter noted the relatively small proportion of
drivers who circumvent the seat belt warning.
    With respect to deactivation, three commenters supported following
R16, and IEE supported following R16 and/or Euro NCAP. Three other
commenters opposed allowing deactivation because it would drastically
weaken system effectiveness.
    We also received comments on the interaction with a remote engine
starter and the warning. A commenter believed that adopting the
requirements of R16 should help address this issue, as warnings must be
provided when the ignition switch (or master control switch) is
activated (i.e., capable of being driven). The commenter also believed
that the current driver's warning requirements (where the warning is
provided beginning when the vehicle ignition switch is moved to the
``on'' or the ``start'' position) address this issue. Another commenter
recommended that NHTSA specify the start of the drive as the moment
when the ignition is activated in the mode where the vehicle is capable
of being driven. A commenter stated that this potential issue can
easily be avoided with occupant detection, because the warning cycle
would only be triggered based on the actual presence of occupants.
Agency Response
    We have tentatively decided not to propose any system-hardening
features. In drafting this proposal, the agency focused on extending
the rear seat belt warning technologies currently in a relatively small
proportion of vehicles to the rest of the fleet. These existing systems
generally do not provide mechanisms to limit circumvention. We decided
not to include requirements to address circumvention for a variety of
reasons. Most importantly, doing so would increase cost and complexity.
For example, since we are not proposing to require occupant detection
technology, we are not proposing a sequential logic system. We also
believe that because the proposed warnings are minimally intrusive--a
relatively short-duration visual warning on start-up, and an additional
short audio-visual warning for a seat belt that is subsequently
unbuckled--attempts to defeat the system will be rare.
    We have also tentatively decided not to allow acknowledgement or
deactivation of the required warning signals. While some commenters
suggested adopting the R16 requirements, they did not offer further
information on the need or use of these options, except for one
commenter that noted it would diminish the safety value of the system.
Therefore, we believe that proposing to allow an acknowledgment, short-
term deactivation, and or long-term deactivation option would have a
net negative impact on the effectiveness of the proposed warning system
(the driver would not get the full benefit of the warning). As
discussed earlier in this proposed rule, we believe that the proposed
warnings are minimally intrusive and have relatively short durations
(visual-only at start-up and audio-visual for a change-of-status), and
the positive-only compliance option would mitigate warnings for
unoccupied seats. In addition, we believe that allowing the driver to
turn off the change-of-status warning would not meet the need for
safety. Since we cannot justify allowing such options from a safety
perspective (allowing it would negatively impact the effectiveness of
the systems) or consumer acceptance perspective (warning signals are
unobtrusive and vehicle manufacturers could opt for the positive-only
option), we have tentatively decided not to allow either a deactivation
or acknowledgment option. For this reason, we also propose amending
FMVSS No. 101 S5.5.6(b) by adding the seat belt telltale to the list of
telltales that may not be cancellable while the underlying condition
for the telltale exists. This would apply to both the front and rear
seat belt warnings. This would mean that the seat belt warning telltale
would not be allowed to be acknowledged (i.e., cancelled) until the
minimum warning duration had been reached.
    We seek comment on vehicle manufacturers' desire to provide such
options, and, if they currently offer such options, how they have
implemented them. We also seek comment on whether allowing such options
would affect manufacturers' choice of compliance option (e.g., if we
allowed acknowledging or deactivating the warning signals, would they
be more inclined to choose the negative-only or full-status compliance
options?). We also seek comment on our proposed revision of FMVSS No.
101.
    In vehicles with a remote engine starter, the driver would
potentially not be present to witness the initial warning signals if
they are designed to meet our minimum requirements. This could
potentially be addressed by programming the system to require input
from the door sensors or occupant sensors to verify that the driver is
in the vehicle, or by requiring the signals to initiate when the
transmission is moved out of the park mode. We have chosen not to
propose a strategy for this scenario, but request comments on
practicable solutions to this problem that could be implemented in the
final rule and the potential cost impacts. New technologies or
solutions may be available that may address these scenarios without
limiting the design flexibility of manufacturers or significantly
increasing the cost.

F. Consumer Acceptance

    In the ANPRM we explained that in order for the proposed rear seat
belt warning to have a lasting impact on seat belt use, it must balance
effectiveness and acceptability. For a seat belt warning system to
induce an unbelted occupant to buckle up, the warning must be
noticeable enough to attract the occupant's attention, or, for a
warning directed at the driver, the driver's attention. However, if the
warning is overly intrusive, consumers may not accept the
technology.\194\ Therefore, the warning must be noticeable enough to
prompt occupants to buckle their seat belts, but not so intrusive that
the public does not accept the warning system, or that an occupant will
circumvent or disable it. Consumer acceptance of any eventual seat belt
warning requirements is an important consideration, given the potential
safety benefits of rear seat belt warnings, the history of seat belt
warning technologies, and the fact that consumers have not yet had
widespread exposure to rear seat belt warnings. NHTSA is especially
aware of this concern, given the agency's experience with public and
Congressional backlash in the 1970s over the ignition interlock and
continuous warning buzzer regulations.
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    \194\ DOT 2009 Seat Belt Study at 2; Transportation Research
Board Study at 8.
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    We also noted research by NHTSA and others suggesting that
consumers would accept the new technology. The 2004 Transportation
Research Board Report observed that ``the data available to date
provide strongly converging

evidence in support of both the potential effectiveness and consumer
acceptance of many new seat belt use technologies[.]'' \195\ As part of
the research for the report, NHTSA conducted focus-group interviews
with part-time and hard-core nonusers. The report noted that ``many
part-time users interviewed by NHTSA--the primary target group for the
technology--were receptive to the new systems. Nearly two-thirds rated
the reminders ``acceptable,'' and approximately 80 percent thought that
they would be ``effective.'' \196\ The ANPRM also pointed to a
telephone survey of drivers of vehicles with and without a rear seat
belt warning system that NHTSA conducted in 2015.\197\ The rear warning
systems in those vehicles had characteristics that were similar to the
proposed requirements: a visual warning on start-up and an audio-visual
change-of-status warning. The survey found, among other things, that
81% of drivers of vehicles with a rear seat belt warning were ``very
satisfied'' with the system; less than 2% were dissatisfied. Among
drivers of vehicles without a rear seat belt warning, attitudes towards
rear belt warnings were generally positive as well: a majority (55%)
indicated that it was important to them that their next vehicle be
equipped with a rear belt warning system.
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    \195\ Transportation Research Board Study at 75-76.
    \196\ Id. at pg. 10.
    \197\ 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). The vehicles with seat belt warning systems were Volvos and
certain Cadillac and Chevrolet models.
---------------------------------------------------------------------------

Comments
    Several commenters believed that consumers would accept rear seat
belt warnings. Commenters said that NHTSA's research shows that a large
proportion of the consumer population will accept rear seat belt
warnings and it noted that at the time of the interlock issue in the
1970s, seat belt use rates were much lower than today, and a larger
proportion of the population were hard-core nonusers. A commenter
stated that its survey of 2,000 drivers showed that 70 percent favored
a law requiring seat belt reminders that continuously chime until the
seat belt is buckled, including rear seat passengers.\198\ Another
commenter noted a 2012 IIHS survey showing that most motorists
supported enhanced belt reminders that were ``more persistent and
intense'' than what most automakers offered at the time.\199\ The
commenter also noted the results of NHTSA's 2015 survey. Another
commenter said that IIHS has found that the majority of drivers in the
U.S. who transport passengers would accept a rear seat belt reminder
system.\200\ This study found that parents believed an audible alert to
be especially useful in alerting the driver to a child unbuckling in
the back seat during a trip. A commenter suggested that consumers would
accept R16-conforming systems.
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    \198\ Citing www.norc.org/Research/Projects/Pages/underutilized-strategies-in-traffic-safety-results-of-a-nationally-representative-survey.aspx (last accessed Oct. 25, 2021).
    \199\ Citing 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), available at www.iihs.org/api/datastoredocument/status-report/pdf/52/5 (last accessed Oct. 25,
2021).
    \200\ Citing David G. Kidd & Anne T. McCartt (2014) Drivers'
Attitudes Toward Front or Rear Child Passenger Belt Use and Seat
Belt Reminders at These Seating Positions, Traffic Injury
Prevention, 15:3, 278-286, DOI: 10.1080/15389588.2013.810333.
---------------------------------------------------------------------------

    One commenter said that further studies are necessary because there
is insufficient data on consumer acceptance.
Agency Response
    NHTSA has tentatively concluded that the proposed warning system
would be acceptable to consumers in light of the specific
characteristics of the proposed warning signals, real-world experience
with seat belt reminder systems, and research and consumer surveys by
NHTSA and others.
    We believe that the proposed requirements are specified so that the
potential for consumer disapproval is minimized. Our intent was to
specify minimum warning requirements that would result in an effective
yet acceptable warning. With respect to the warning on start-up, we
propose requiring only a visual warning, and not a more intrusive
audible alert. The 60-second duration is comparable to the visual rear
seat belt warnings provided by currently deployed systems. For example,
the visual rear belt warning in some MY2022 vehicles lasts for at least
60 seconds.\201\ The change-of-status warning would involve an audio-
visual alert lasting at least 30 seconds. While most vehicle models
currently available in the U.S. with rear seat belt warning systems
have a change-of-status warning that meets this 30-second minimum
duration, we are aware of two available models that exceed this
duration for the rear change-of-status warning. False positives would
also be minimized because the positive-only compliance option only
necessitates a buckle sensor, not occupant detection, which is more
prone to false positives.
---------------------------------------------------------------------------

    \201\ We identified three manufacturers that produce vehicles
with visual warnings that last for at least 60 seconds. One
manufacturer provides vehicles where the visual warning stays active
until the belt is fastened.
---------------------------------------------------------------------------

    Recent field experience also suggests that consumers would accept
the proposed requirements. As noted earlier, an increasing number of
vehicles sold in the United States have rear seat belt warning systems;
based on 2022 Purchasing with Safety in Mind: What to Look For When
Buying a Vehicle information, 46.9% of the total vehicle projected
sales are equipped with rear SBWS.\202\ Moreover, in connection with
the 2010 RFC, GM commented that it has not received any complaints
about its rear seat belt warning system in either the United States or
Europe,\203\ and Volvo indicated that it had found a high level of
acceptance for its system.\204\ In addition to this, many OEMs have
implemented enhanced seat belt warnings for the front outboard seats
over the past two decades. Consumers' acceptance of these warnings also
suggests that they would accept warnings for the rear seats.
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    \202\ In the ANPRM it was 13% based on MY2019 vehicle data.
    \203\ See Docket No. NHTSA-2010-0061 (GM comment).
    \204\ See Docket No. NHTSA-2010-0061 (Volvo comment).
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    Finally, in addition to the research noted in the ANPRM we note the
studies cited by the commenters that support our tentative conclusion
that consumers would accept the proposed warnings. In 2012, IIHS
conducted a national telephone survey of drivers and passengers about
seat belt use. Using this survey data, it proceeded to conduct several
studies.
    One study, cited by the commenters, was on the attitudes towards
seat belt use and in-vehicle technologies for encouraging seat belt
use.\205\ All respondents were asked questions regarding their belt use
habits and perceptions of different types of seat belt interlocks.
Part-time belt users and nonusers were additionally questioned about
different types of reminders and reminder strategies. The survey found
that enhanced reminders are more acceptable than seat belt interlocks
and are viewed as having the potential to be as effective as interlocks