[Federal Register Volume 79, Number 151 (Wednesday, August 6, 2014)]
[Proposed Rules]
[Pages 46089-46123]
[FR Doc No: 2014-18326]

Vol. 79

Wednesday,

No. 151

August 6, 2014

Part VI

 Department of Transportation

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National Highway Traffic Safety Administration

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49 CFR Part 571

Federal Motor Vehicle Safety Standards; Bus Rollover Structural
Integrity, Motorcoach Safety Plan; Proposed Rule

Federal Register / Vol. 79 , No. 151 / Wednesday, August 6, 2014 /
Proposed Rules

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2014-0085]
RIN 2127-AK96

Federal Motor Vehicle Safety Standards; Bus Rollover Structural
Integrity, Motorcoach Safety Plan

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

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: NHTSA is issuing this NPRM to propose a new Federal motor
vehicle safety standard to enhance the rollover structural integrity of
certain types of large buses (generally, over-the-road buses (of any
weight) and non-over-the-road buses with a gross vehicle weight rating
(GVWR) greater than 11,793 kilograms (kg) (26,000 pounds (lb)). The
agency is proposing performance requirements that new large buses of
these types must meet in a test in which the vehicle is tipped over
from an 800 millimeter (mm) raised platform onto a level ground
surface. The performance requirements would ensure that these vehicles
provide a sufficient level of survival space to restrained occupants in
rollover crashes. The performance requirements would also ensure that
seats and overhead luggage racks remain secured and window glazing
attached to its mounting during and after a rollover crash, and would
ensure that emergency exits remain closed during the rollover crash and
operable after the crash.
    This NPRM is among the rulemakings issued pursuant to NHTSA's 2007
Approach to Motorcoach Safety and DOT's Departmental Motorcoach Safety
Action Plan. In addition, establishing roof strength and crush
resistance requirements, to the extent warranted under the National
Traffic and Motor Vehicle Safety Act, would fulfill a statutory
provision of the Motorcoach Enhanced Safety Act of 2012 (incorporated
and passed as part of the Moving Ahead for Progress in the 21st Century
Act).

DATES: Comments must be received on or before October 6, 2014.

ADDRESSES: You may submit comments to the docket number identified in
the heading of this document by any of the following methods:
     Federal eRulemaking Portal: go to http://www.regulations.gov. Follow the online instructions for submitting
comments.
     Mail: Docket Management Facility, M-30, U.S. Department of
Transportation, West Building, Ground Floor, Rm. W12-140, 1200 New
Jersey Avenue SE., Washington, DC 20590.
     Hand Delivery or Courier: West Building Ground Floor, Room
W12-140, 1200 New Jersey Avenue SE., between 9 a.m. and 5 p.m. Eastern
Time, Monday through Friday, except Federal holidays.
     Fax:<PHONE_NUMBER>.
    Regardless of how you submit your comments, please mention the
docket number of this document.
    You may also call the Docket at<PHONE_NUMBER>.
    Instructions: For detailed instructions on submitting comments and
additional information on the rulemaking process, see the Public
Participation heading of the Supplementary Information section of this
document. Note that all comments received will be posted without change
to http://www.regulations.gov, including any personal information
provided.
    Privacy Act: Please see the Privacy Act heading under Rulemaking
Analyses and Notices.

FOR FURTHER INFORMATION CONTACT: For non-legal issues, Ms. Shashi
Kuppa, Office of Crashworthiness Standards (telephone:<PHONE_NUMBER>)
(fax:<PHONE_NUMBER>). Ms. Kuppa's mailing address is National Highway
Traffic Safety Administration, NVS-113, 1200 New Jersey Avenue SE.,
Washington, DC 20590.
    For legal issues, Mr. Jesse Chang, Office of the Chief Counsel
(telephone:<PHONE_NUMBER>) (fax:<PHONE_NUMBER>). Mr. Chang's mailing
address is National Highway Traffic Safety Administration, NCC-112,
1200 New Jersey Avenue SE., Washington, DC 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary
II. Background
    a. NHTSA's Statutory Authority
    b. NHTSA's 2007 Approach to Motorcoach Safety
    c. DOT's 2009 Task Force Action Plan
    d. NTSB Recommendations
    e. NHTSA's Seat Belt Final Rule
III. Safety Need
    a. FARS Data and Recent Crashes
    b. Rollover and Ejection Statistics
IV. NHTSA's Large Bus Rollover Structural Integrity Research
    a. Findings of the FMVSS No. 220-Based Tests
    b. Findings of the ECE R.66-Based Tests
V. Proposed Requirements
    a. Overview
    b. Applicability
    c. Test Procedure
    d. Survival Space
    e. Overhead Luggage Rack and Seat Retention
    f. Emergency Exits
    g. Side Window Glazing
VI. Regulatory Alternatives
    a. FMVSS No. 216
    b. FMVSS No. 220
    c. ECE R.66 Alternative Compliance Methods
    d. Comments Requested on Alternative Levels of Stringency
VII. Other Issues
    a. Retrofitting
    b. Lead Time
    c. Additional MAP-21 Considerations
VIII. Overview of Costs and Benefits
IX. Regulatory Analyses
X. Public Participation

I. Executive Summary

    This rulemaking is part of both NHTSA and DOT's continual effort to
improve safety in motorcoaches and other types of large buses. In 2007,
NHTSA published its Approach to Motorcoach Safety describing NHTSA's
comprehensive strategy to improve motorcoach safety.\1\ The plan was
developed to respond to several National Transportation Safety Board
(NTSB) recommendations, and also to address several crashes that
occurred after those recommendations were issued. In 2009, DOT issued a
Departmental Motorcoach Safety Action Plan, \2\ which outlined a
Department-wide strategy to enhance motorcoach safety, addressing
additional factors such as driver fatigue and operator maintenance
issues.
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    \1\ See Docket No. NHTSA-2007-28793, NHTSA's Approach to
Motorcoach Safety. In NHTSA's plan, ``motorcoach'' referred to
inter-city transport buses.
    \2\ An update to the 2009 plan was published in December 2012,
http://www.fmcsa.dot.gov/safety-security/pcs/Motorcoach-Safety-Action-Plan.aspx.
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    NHTSA's Approach to Motorcoach Safety identified four specific
areas where NHTSA could most effectively address open NTSB
recommendations and potentially improve motorcoach safety. The four
priority areas were: Reducing the risk of passenger ejection from the
motorcoach, improving rollover structural integrity, enhancing
emergency evacuation, and upgrading fire safety.
    NHTSA has published a final rule (RIN 2127-AK56) on the first area
detailed in NHTSA's Approach to Motorcoach Safety, requiring seat belts
for each passenger seating position in: (a) All new over-the-road buses
\3\; and (b) in new buses other than over-the-road buses, with a GVWR
greater than 11,793 kg (26,000 lb).\4\ Today's NPRM

builds on the seat belt final rule by proposing to require those buses
to meet increased structural integrity and other requirements to
protect both restrained and unrestrained occupants in rollover crashes.
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    \3\ An over-the-road bus is a bus characterized by an elevated
passenger deck located over a baggage compartment.
    \4\ Some buses are excluded from this latter category, such as
transit and school buses.
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    On July 6, 2012, the President signed the ``Moving Ahead for
Progress in the 21st Century Act'' (MAP-21).\5\ MAP-21 incorporates the
``Motorcoach Enhanced Safety Act of 2012'' (Motorcoach Enhanced Safety
Act) in Subtitle G (Sec. Sec.  32701 et seq.) Among other matters, the
Motorcoach Enhanced Safety Act requires DOT to ``establish improved
roof and roof support standards for motorcoaches that substantially
improve the resistance of motorcoach roofs to deformation and intrusion
to prevent serious occupant injury in rollover crashes involving
motorcoaches'' if such standards ``meet the requirements and
considerations set forth in subsections (a) and (b) of section 30111 of
title 49, United States Code.'' \6\ In addition, MAP-21\7\ directs DOT
to consider ``portal improvements to prevent partial and complete
ejection of motorcoach passengers, including children.'' Under MAP-21,
``motorcoach'' means an over-the-road bus, but does not include a bus
used in public transportation provided by, or on behalf of, a public
transportation agency, or a school bus.
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    \5\ Moving Ahead for Progress in the 21st Century Act, Pub. L.
112-141.
    \6\ See MAP-21, Sec. Sec.  32703(b)z6-(b)(1).
    \7\ Id., Sec. Sec.  32703(b)(2).
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    We have issued this NPRM in furtherance of NHTSA's goal to enhance
the safety of all heavy buses used in intercity bus transportation,
including over-the-road buses, which were the focus of the Motorcoach
Enhanced Safety Act of MAP-21. Similar to the seat belt rule, we are
not proposing that this standard apply to school buses and urban
transit buses.
    Transportation by over-the-road buses (and other similar large
buses) is an overall safe form of transportation. Over the ten year
period between 2000 and 2009, there were 87 fatal crashes involving the
large bus types covered by today's proposed rule. These crashes
resulted in 209 occupant fatalities (168 passenger and 41 driver
fatalities). During this period, on average, 21 fatalities have
occurred annually to occupants of these buses in crashes. Annually 17
of these fatalities were passengers and 4 were drivers. Nonetheless,
given the high occupancy of these vehicles, a significant number of
fatal or serious injuries can occur in a single crash. NHTSA
tentatively believes that standards improving structural integrity and
thereby side window glazing retention, issued pursuant to Sec. Sec.
32703(b)-(b)(2) of MAP-21 and the National Traffic and Motor Vehicle
Safety Act (``Motor Vehicle Safety Act''), would meet the need for
safety. Among the 87 fatal crashes (involving the bus types covered by
today's proposal) that occurred from 2000-2009, data from NHTSA's
Fatality Analysis Reporting System (FARS) indicate that 32 were
rollover crashes resulting in 114 fatalities. While fatal rollover
crashes were only one-third of all fatal crashes involving these bus
types, they represent more than half of all the occupant fatalities.
Further, approximately two-thirds of the rollover crash fatalities were
attributable to occupant ejections.
    In developing today's NPRM, the agency turned to United Nations
Economic Commission for Europe Regulation 66 (ECE R.66).\8\ Today's
NPRM proposes a test for rollover structural integrity based on the
complete vehicle rollover test of ECE R.66. We also examined the school
bus roof crush standard set forth in Federal Motor Vehicle Safety
Standard (FMVSS) No. 220, ``School bus rollover protection,'' but chose
to base our new standard on ECE R.66's complete vehicle test because
the latter appears to more closely simulate a real-world rollover crash
involving the large bus types that are associated with the highest
crash risk. Further, an ECE R.66-based test enables us to better
evaluate particular aspects of performance that are pertinent for
safety of these types of buses (e.g., the affixing of side glazing
panels--an area of concern of MAP-21--and attachment of overhead
luggage racks). Using a procedure based on ECE R.66 also furthers
NHTSA's efforts to harmonize with international standards when
feasible.
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    \8\ Uniform Technical Prescriptions Concerning the Approval of
Large Passenger Vehicles with Regard to the Strength of their
Superstructure, ECE R.66, February 2006, http://live.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r066r1e.pdf.
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    This NPRM proposes performance requirements that the buses must
meet when tested by NHTSA using an ECE R.66-based test. The vehicle is
placed on a tilting platform that is 800 mm above a smooth and level
concrete surface. One side of the tilting platform along the length of
the vehicle is raised at a steady rate of not more than 5 degrees/
second until the vehicle becomes unstable, rolls off the platform, and
impacts the concrete surface below.
    The rollover structural integrity test is illustrated below in
Figure 1.

[GRAPHIC] [TIFF OMITTED] TP06AU14.005

    The following are the main proposed performance requirements that
buses covered by this proposed rule must meet when subjected to the
rollover structural integrity test:
    (1) Intrusion into the ``survival space,'' demarcated in the
vehicle interior, by any part of the vehicle outside the survival space
is prohibited;
    (2) each anchorage of the seats and overhead luggage racks must not
completely separate from its mounting structure;
    (3) emergency exits must remain shut during the test and must be
operable in the manner required under FMVSS No. 217 after the test; and
    (4) each side window glazing opposite the impacted side of the
vehicle must remain attached to its mounting such that there is no
opening that will allow the passage of a 102 mm diameter sphere.
    We believe these proposed requirements would provide reasonable and
needed improvements to the types of buses with the greatest safety risk
in rollovers. They supplement the agency's final rule on passenger seat
belts. With passengers more likely to be retained in the bus interior
as a result of the agency's seat belt final rule, today's NPRM improves
the protective attributes of the occupant compartment in which they are
retained.
    The proposed requirements for maintaining the survival space and
ensuring that seats, overhead luggage racks, and window glazing remain
attached to their mounting structures would set a minimum level of
structural integrity for these buses, to help prevent dangerous
structural intrusions into the occupant survival space. The proposed
requirement that emergency exits remain closed during the rollover
structural integrity test and operable after the test is to increase
the likelihood that emergency exits do not become ejection portals
during rollover crashes. The requirement also helps ensure that the
emergency exits remain an effective means of egress after the crash.
    NHTSA believes that this rulemaking would be cost beneficial.\9\
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    \9\ NHTSA has developed a Preliminary Regulatory Evaluation
(PRE) that discusses issues relating to the potential costs,
benefits and other impacts of this regulatory action. The PRE is
available in the docket for this NPRM and may be obtained by
downloading it or by contacting Docket Management at the address or
telephone number provided at the beginning of this document.
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    The agency estimates the annual cost of this proposed rule to be
between $5.28 million and $13.26 million (see Table 1 below). The
countermeasures may include stronger roof structure, support pillars,
and side walls, shock resistant latches for emergency exits, stronger
seat and overhead luggage rack anchorages, and improved window
mounting, resulting in material costs for each bus covered under
today's proposed rule ranging from $282 to $507. We estimate the total
weight increase will range from 564 to 1,114 pounds (lb) for each of
these buses and cost an additional $2,118 to $5,523 in fuel per vehicle
over the lifetime of the vehicle.
    Beyond the benefits attributable to the agency's final rule on seat
belts and a potential final rule on electronic stability control (ESC)
that also may

apply to this universe of vehicles, \10\ we estimate that requiring new
buses of the aforementioned types to meet the proposed performance
criteria would save approximately 2 lives annually. In addition, we
expect that the proposed rule would reduce the number of seriously
injured occupants by approximately 4 annually. Thus, we estimate that
approximately 3.1 equivalent lives are saved annually if 15 percent of
occupants use seat belts, and approximately 2.3 equivalent lives are
saved annually (undiscounted) if 84 percent of occupants use seat belts
(see Table 2 below).
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    \10\ An ESC rulemaking for the buses is also included in MAP-21.
The statute directs us to consider requiring motorcoaches to be
equipped with stability enhancing technology, such as ESC, to reduce
the number and frequency of rollover crashes. See Sec.  32703(b)(3).
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    The cost per equivalent life saved is estimated to be $2.09 million
to $4.72 million when belt use is estimated to be 15 percent, and $2.91
million to $6.42 million when belt use is estimated to be 84 percent
(see Table 3 below). The net cost/benefit impact ranges from a net
benefit of $9.47 million to $19.35 million if seat belt usage is 15
percent. If the seat belt usage rate is 84 percent, the estimated net
cost/benefit impact ranges from a net benefit of $4.69 million to a net
benefit of $13.06 million (see Table 4 below). While the cost and
benefits of this rule will vary depending on the material/fuel costs
per vehicle and on the belt use rate, all the available information
indicate that this proposed rule--if made final--would be cost
beneficial.

                     Table 1--Estimated Annual Costs
                             [2010 Dollars]
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------------------------------------------------------------------------
Potential Costs:
    Material Costs Per Vehicle.  $282 to $507.
    Material Costs, Total New    $0.6 million to $1.1 million.
     Fleet.
Fuel Costs per Vehicle @3%.....  $2,814 to $5,523.
Fuel Costs per Vehicle @7%.....  $2,118 to $4,156.
Fuel Costs, Total New Fleet....  $4.7 million to $12.2 million.
                                ----------------------------------------
    Total Annual Cost..........  $5.3 million to $13.3 million.
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                   Table 2--Estimated Annual Benefits
                  [Undiscounted equivalent lives saved]
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15 percent belt usage................................                3.1
84 percent belt usage................................                2.3
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                 Table 3--Cost per Equivalent Life Saved
                [Across 3% and 7% discount, 2010 dollars]
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------------------------------------------------------------------------
15 percent belt usage..........  $2.09 million to $4.72 million.
84 percent belt usage..........  $2.91 million to $6.42 million
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                                     Table 4--Annualized Costs and Benefits
                                        [In millions (M) of 2010 dollars]
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                                             Annual costs           Annual benefits            Net benefits
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15% belt usage:
    3% Discount Rate.................  $6.81 M--$13.26 M......  $26.16 M...............  $12.9 M--$19.35 M.
    7% Discount Rate.................  $5.28 M--$10.26 M......  $19.73 M...............  $9.47 M--$14.45 M.
84% belt usage:
    3% Discount Rate.................  $6.81 M--$13.26 M......  $19.87 M...............  $6.61 M--$13.06 M.
    7% Discount Rate.................  $5.28 M--$10.26 M......  $14.95 M...............  $4.69 M--$9.67 M.
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    NHTSA has considered retrofit requirements. Based on our tests of
older buses, the agency believes that major structural changes to the
vehicle's entire sidewall and roof structure would be needed for some
existing buses (that are of the type covered by this rule) to meet the
rollover structural integrity requirements proposed in today's NPRM.
Such structural changes are likely to be cost-prohibitive, making
retrofitting for rollover structural integrity quite impractical. Thus,
the agency has tentatively not included roof structure retrofitting
requirements for existing vehicles in today's proposal.
    However, today's NPRM proposes requirements for emergency exit
integrity and operability and side window glazing retention through
enhanced structural integrity, aspects of performance included in Sec.
32703(b)(2) of MAP-21. Section 32703(e)(2)(A) of MAP-21 states that
``the Secretary may assess the feasibility, benefits, and costs with
respect to the application of any requirement established under [Sec.
32703(b)(2)] to motorcoaches manufactured before the date on which the
requirement applies to new motorcoaches.'' Subsection (e) states that
the Secretary shall submit a report on the assessment to Congress not
later than July 2014. Thus, the agency is requesting comments on the
feasibility, benefits, and costs of any potential requirement to
retrofit existing buses with stronger emergency exit mechanisms and
enhanced structural integrity to increase side window glazing retention
to afford a similar level

of anti-ejection protection for passengers riding in existing buses.

II. Background

    Each year, the motorcoach industry transports millions of people
for long and short distance travel, tours, school field trips,
commuter, and entertainment-related trips. According to the 2008
Motorcoach Census,\11\ there were 3,432 over-the-road bus carriers in
the United States and Canada in 2007. These carriers operated over
33,536 over-the-road buses,\12\ logged 751 million trips made by
passengers, and traveled over 1.8 billion miles yearly. The services
provided by over-the-road buses in 2007 included charter services (46.4
percent of the miles driven), moving people between cities or between
cities and rural areas (26.5 percent of the miles driven), transporting
people between home and work (10.3 percent of the miles driven), and
shuttle services to and from the airport (3.4 percent of the miles
driven). In 2007, each over-the-road bus was driven an average of
54,000 miles.
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    \11\ The ``2008 Motorcoach Census,'' funded by the American Bus
Association (ABA), defines a motorcoach as an over-the-road bus,
designed for long-distance transportation of passengers,
characterized by integral construction, and with an elevated
passenger deck located over a baggage compartment. See ``Motorcoach
Census 2008, A Benchmarking Study of the Size and Activity of the
Motorcoach Industry in the United States and Canada in 2007.'' Paul
Bourquin, Economist and Industry Analyst, December 18, 2008. The
buses included in the 2008 Motorcoach Census are over-the-road buses
that are at least 35 feet in length and have a capacity of more than
30 passengers. Traditionally, these over-the-road buses are
considered to be motorcoaches. We note that this rule would apply to
a larger set of vehicles than those within the ABA's definition of
motorcoach, and therefore the statistics from the 2008 Motorcoach
Census presented in this section are only applicable to over-the-
road buses.
    \12\ The 2008 Motorcoach Census defines motorcoaches to include
a smaller set of vehicles than those covered by this NPRM. Thus, we
have used the term ``over-the-road buses'' to describe the set of
vehicles referenced by the 2008 Motorcoach Census.
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    Over the ten year period between 2000 and 2009, there were 45 fatal
crashes of cross-country/intercity buses resulting in 134 occupant
fatalities \13\ according to the FARS data \14\ collected by the
agency. During this period, on average, 13 fatalities (11 passengers
and 2 drivers) have occurred annually to occupants of cross-country/
intercity buses. This field and market data suggest that over-the-road
(cross-country/intercity) bus transportation overall is a relatively
safe form of transportation.
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    \13\ There was one cross-country/intercity bus fire in 2005 in
Wilmer, Texas where 23 bus occupants died. The 134 occupant
fatalities in cross-country/intercity buses does not include the 23
fatalities from the bus fire since it did not occur as a result of a
bus crash or rollover.
    \14\ The FARS database categorizes the vehicle body type of
over-the-road buses as cross-country/intercity buses.
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    However, given the high occupancy of over-the-road buses (and the
other large buses considered in today's proposed rule) and the speed at
which they travel, a single crash can result in a significant number of
fatal or serious injuries. Therefore, in this NPRM, the agency is
proposing to enhance the safety of these vehicles by improving their
crashworthiness relative to crush resistance, structural integrity, and
reducing portal openings during rollover crashes.

a. NHTSA's Statutory Authority

    NHTSA is proposing today's NPRM pursuant to its authority under the
Motor Vehicle Safety Act and the relevant provisions of MAP-21.
National Traffic and Motor Vehicle Safety Act
    Under 49 U.S.C. Chapter 301, Motor Vehicle Safety (49 U.S.C. 30101
et seq.), the Secretary of Transportation is responsible for
prescribing motor vehicle safety standards that are practicable, meet
the need for motor vehicle safety, and are stated in objective terms.
``Motor vehicle safety'' is defined in the Motor Vehicle Safety Act as
``the performance of a motor vehicle or motor vehicle equipment in a
way that protects the public against unreasonable risk of accidents
occurring because of the design, construction, or performance of a
motor vehicle, and against unreasonable risk of death or injury in an
accident, and includes nonoperational safety of a motor vehicle.''
``Motor vehicle safety standard'' means a minimum performance standard
for motor vehicles or motor vehicle equipment. When prescribing such
standards, the Secretary must consider all relevant, available motor
vehicle safety information. The Secretary must also consider whether a
proposed standard is reasonable, practicable, and appropriate for the
types of motor vehicles or motor vehicle equipment for which it is
prescribed and the extent to which the standard will further the
statutory purpose of reducing traffic accidents and associated deaths.
The responsibility for promulgation of Federal motor vehicle safety
standards is delegated to NHTSA.15 16 In making the
proposals in today's NPRM, the agency carefully considered all the
aforementioned statutory requirements.
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    \15\ See 49 CFR 1.95.
    \16\ The Secretary also delegated to NHTSA the authority set out
for Section 101(f) of Public Law 106-159 to carry out, in
coordination with the Federal Motor Carrier Safety Administrator,
the authority vested in the Secretary by subchapter 311 and section
31502 of title 49, U.S.C., to promulgate safety standards for
commercial motor vehicles and equipment subsequent to initial
manufacture when the standards are based upon and similar to a
Federal Motor Vehicle Safety Standard promulgated, either
simultaneously or previously, under chapter 301 of title 49, U.S.C.
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Motorcoach Enhanced Safety Act of 2012 (Incorporated in MAP-21)
    On July 6, 2012, President Obama signed MAP-21, which incorporated
the ``Motorcoach Enhanced Safety Act of 2012'' into Subtitle G.\17\
Section 32703(b) of MAP-21 requires the Secretary to prescribe
standards that would address certain aspects of motorcoach crash
performance within two years if the Secretary determines that the
standards would meet the requirements and considerations of Sec. Sec.
30111(a) and (b) of the Motor Vehicle Safety Act.\18\ There are two
subsections of Sec.  32703(b) that are particularly relevant to this
NPRM. Subsection (b)(1) specifies that the Secretary is to establish
improved roof and roof support standards that ``substantially improve
the resistance of motorcoach roofs to deformation and intrusion to
prevent serious occupant injury in rollover crashes involving
motorcoaches.'' Subsection (b)(2) directs the Secretary to ``consider
advanced glazing standards for each motorcoach portal and [to] consider
other portal improvements to prevent partial and complete ejection of
motorcoach passengers, including children.'' \19\
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    \17\ See Moving Ahead for Progress in the 21st Century Act, Pub.
L. 112-141 (Jul. 6, 2012).
    \18\ See id. at Sec.  32703(b).
    \19\ While today's NPRM is mainly aimed at addressing the
rollover structural integrity of specific large bus types, the
proposed rule also addresses some of the safety risks associated
with occupant ejection through side window glazing retention and
emergency exit requirements. Thus, both subsection (b)(1) and
subsection (b)(2) are relevant to this notice.
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    MAP-21 contains various other provisions that are relevant to this
rulemaking. Section 32702 states that ``motorcoach'' has the meaning
given to the term ``over-the-road bus'' in section 3038(a)(3) of the
Transportation Equity Act for the 21st Century (TEA-21).\20\ Section
3038(a)(3) of TEA-21 (see 49 U.S.C. 5310 note) defines ``over-the-road
bus'' as ``a bus characterized by an elevated passenger deck located
over a baggage compartment.'' However, Sec.  32702 of MAP-21 excludes
transit buses and school buses from the ``motorcoach'' definition.\21\
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    \20\ See Moving Ahead for Progress in the 21st Century Act, Pub.
L. 112-141, Sec.  32702(6).
    \21\ See id. at Sec.  32702(6)(A)-(B).

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    MAP-21 further directs the Secretary to apply any regulation
prescribed in accordance with Sec.  32703(b) (and several other
subsections) to all motorcoaches manufactured more than 3 years after
the date on which the regulation is published.\22\ In addition, the
Secretary may assess the feasibility, benefits, and costs of applying
any requirement established under Sec.  32703 (b)(2) to ``motorcoaches
manufactured before the date on which the requirement applies to new
motorcoaches'' (retrofit).\23\ Finally, MAP-21 also authorizes the
Secretary to combine the required rulemaking actions as the Secretary
deems appropriate.\24\
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    \22\ See id. at Sec.  32703(e)(1).
    \23\ See id. at Sec.  32703(e)(2). ``Retrofit Assessment for
Existing Motorcoaches.''
    \24\ See id. at Sec.  32706.
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b. NHTSA's 2007 Approach to Motorcoach Safety

    In 2007, NHTSA undertook a comprehensive review of motorcoach
safety issues and the course of action that the agency could pursue to
address them. The agency considered various prevention, mitigation, and
evacuation approaches in developing the course of action. Many
considerations were factored into determining the priorities,
including: cost and duration of testing, development, and analysis
required; likelihood that the effort would lead to the desired and
successful conclusion; target population and possible benefits that
might be realized; and anticipated cost of implementing the ensuing
requirements into the motorcoach fleet.
    The result was NHTSA's 2007 plan, NHTSA's Approach to Motorcoach
Safety (Docket No. NHTSA-2007-28793-001), in which we identified the
following areas as the highest priorities for possible near term
regulatory action to enhance motorcoach safety: (1) Passenger ejection;
(2) rollover structural integrity; (3) emergency egress; and (4) fire
safety.
    For passenger ejection (action (1) above), we pursued the
incorporation of passenger seat belts as the most effective and
expeditious way to mitigate ejection. The agency's seat belt
rulemaking, discussed further below, began NHTSA's implementation of
our Motorcoach Safety Plan. Today's document advances the
implementation of the plan.

c. DOT's 2009 Task Force Action Plan

    In 2009, DOT issued a Departmental Motorcoach Safety Action Plan,
which outlined a Department-wide strategy to enhance motorcoach
safety.\25\ An update of the plan was issued on December 2012.\26\ In
addition to the four priority action items specified in NHTSA's 2007
plan, the 2009 DOT plan, and the 2012 updated plan identified
additional factors for enhancing motorcoach safety, such as electronic
stability control systems (ESC), event data recorders (EDRs), and
driver fatigue and operator maintenance issues. Various DOT agencies
are working on the motorcoach safety initiatives related to their
administrations.
---------------------------------------------------------------------------

    \25\ http://www.fmcsa.dot.gov/documents/safety-security/MotorcoachSafetyActionPlan_finalreport-508.pdf.
    \26\ http://www.fmcsa.dot.gov/safety-security/pcs/Motorcoach-Safety-Action-Plan.aspx.
---------------------------------------------------------------------------

d. NTSB Recommendations

    As a part of its motorcoach crash investigations, NTSB has issued
recommendations to NHTSA relating to actions that NTSB believes could
improve motorcoach safety. The following NTSB recommendations related
to motorcoach structural integrity pertain to this NPRM.
    In an NTSB Highway Special Investigation Report (1999), Bus
Crashworthiness Issues,\27\ NTSB cited an October 1971 rollover of a
1970 Motor Coach Industries (MCI) bus as justification for the
following recommendations:
---------------------------------------------------------------------------

    \27\ National Transportation Safety Board. 1999, Bus
Crashworthiness Issues. Highway Special Investigation Report NTSB/
SIR-99/04. Washington, DC.
---------------------------------------------------------------------------

    ``H-99-50 (MW): In 2 years, issue performance standards for
motorcoach roof strength that provide maximum survival space for all
seating positions and that take into account current typical motorcoach
window dimensions.''
    ``H-99-51: Once performance standards have been developed for
motorcoach roof strength, require newly manufactured motorcoaches to
meet those standards.''
    In November 2009, after investigating an August 2008 Sherman, Texas
bus crash,\28\ the NTSB issued two new safety recommendations. In this
rollover crash, the failure of the overhead luggage rack on the vehicle
impeded passenger egress and rescue efforts. Thus, NTSB stated that the
Sherman accident and NHTSA's motorcoach testing indicate that the lack
of standards for overhead luggage racks on motorcoaches leaves
passengers at risk of serious injury from interaction with overhead
luggage racks in a crash and made the following recommendations:
---------------------------------------------------------------------------

    \28\ NTSB/HAR-09/02 PB2009-916202; Motorcoach Run-Off-the-Bridge
and Rollover Sherman, Texas August 8, 2008; October 2009; http://www.ntsb.gov/doclib/reports/2009/HAR0902.pdf.
---------------------------------------------------------------------------

    ``H-09-23: Develop performance standards for newly manufactured
motorcoaches to require that overhead luggage racks remain anchored
during an accident sequence.''
    ``H-09-24: Develop performance standards for newly manufactured
motorcoaches that prevent head and neck injuries from overhead luggage
racks.''
    In June 2010, after investigating a 2009 motorcoach rollover crash
in Dolan Springs, the NTSB issued two additional recommendations:
    ``H-10-03: In your rulemaking to improve motorcoach roof strength,
occupant protection, and window glazing standards, include all buses
with a gross vehicle weight rating above 10,000 pounds, other than
school buses.''
    ``H-10-04: Develop performance standards for all newly manufactured
buses with a gross vehicle weight rating above 10,000 pounds to require
that overhead luggage racks are constructed and installed to prevent
head and neck injuries and remain anchored during an accident
sequence.''

e. NHTSA's Seat Belt Final Rule

    Completing the first initiative of NHTSA's 2007 ``NHTSA's Approach
to Motorcoach Safety'' plan and one of the principal undertakings of
DOT's 2009 Motorcoach Safety Action Plan, and fulfilling a statutory
mandate of the Motorcoach Enhanced Safety Act, NHTSA issued a final
rule amending FMVSS No. 208, ``Occupant crash protection.'' The final
rule required lap/shoulder seat belts for each passenger seating
position in: (a) All new over-the-road buses; and (b) in new buses
other than over-the-road buses, with a GVWR greater than 11,793 kg
(26,000 lb).\29\ (The notice of proposed rulemaking preceding the final
rule called buses with GVWR greater than 11,793 kg (26,000 lb)
``motorcoaches.'')
---------------------------------------------------------------------------

    \29\ Some buses are excluded from this latter category, such as
transit buses, school buses, and buses with perimeter-seating.
---------------------------------------------------------------------------

    NHTSA's safety research on seat belts in large buses (greater than
11,793 kg (26,000 lb) GVWR) completed in 2009, showed that the
installation of lap/shoulder belts on the vehicles is practicable and
effective and could reduce the risk of fatal injuries in rollover
crashes by 77 percent, primarily by preventing occupant ejection. Lap/
shoulder belts are also highly effective in preventing fatalities and
serious injuries in frontal crashes, and will

enhance protection in side crashes in the affected buses. By requiring
passenger lap/shoulder seat belts on (a) new over-the-road buses, and
(b) new buses, other than over the road buses, with a GVWR greater than
11,793 kg (26,000 lb), the final rule significantly reduces the risk of
fatality and serious injury in frontal crashes and the risk of occupant
ejection in rollovers, thus considerably enhancing the safety of these
vehicles.

III. Safety Need

    The rulemakings that are being conducted pursuant to the
requirements of the Motor Vehicle Safety Act and MAP-21, and as part of
NHTSA's Approach to Motorcoach Safety and the DOT Motorcoach Safety
Action Plan, explore whether there are unreasonable safety risks
associated with motorcoach transportation. If there are such risks, we
explore whether those safety risks can be reasonably reduced by having
minimum levels of performance specified for crashworthiness and crash
avoidance standards, such as a standard for rollover structural
integrity.
    NHTSA found in the seat belt final rule that, generally, a
significant majority of fatalities are attributable to rollovers.
Because more than three-quarters of rollover fatalities are
attributable to ejections, NHTSA issued a seat belt requirement to
mitigate those ejections. For purposes of today's proposal, we believe
that, hand-in-hand with that seat belt proposal, there is a need to
ensure enhanced structural integrity of the interior of these buses, to
better protect the restrained occupants who, due to the belts, will be
retained in the bus interior. Moreover, independent of a seat belt
requirement, we believe that more can be done to improve the vehicle
structure to reduce the likelihood of ejection of occupants who may not
be restrained at the time of the crash. For instance, emergency exits
should not open during a rollover crash (an open emergency exit forms a
portal through which occupants could be ejected). Today's NPRM proposes
requirements to meet these objectives.

a. FARS Data and Recent Crashes

    To determine the types of vehicles that should be covered by the
rulemakings conducted pursuant to the Motor Vehicle Safety Act and MAP-
21 and as part of the NHTSA's Approach to Motorcoach Safety plan and
the DOT Motorcoach Safety Action Plan, the agency examined FARS data
files to gain a better understanding of fatal crashes involving over-
the-road buses and other bus types.\30\ FARS contains data on a census
of fatal traffic crashes within the 50 States, the District of
Columbia, and Puerto Rico. To be included in FARS, a crash must involve
a motor vehicle traveling on a traffic way customarily open to the
public, and must result in the death of an occupant of a vehicle or a
non-occupant within 30 days of the crash.
---------------------------------------------------------------------------

    \30\ Previous discussions of the FARS data is set forth in the
seat belt final rule, and in the DOT 2009 Motorcoach Action Plan,
http://www.nhtsa.gov/staticfiles/DOT/NHTSA/reports/HS811177.pdf.
---------------------------------------------------------------------------

    For the seat belt rulemaking and other ``motorcoach'' rulemakings,
we analyzed 10 years of FARS data to assess what type of vehicle should
be covered by NHTSA's motorcoach safety plan initiatives. We analyzed
FARS data of high-occupancy vehicles (buses) that are in fatal crashes.
FARS data for fatalities of occupants in high occupancy vehicles (buses
with a GVWR greater than 4,536 kg (10,000 lb), other than school buses
and transit buses) over 10 years show that 83 percent of the occupant
fatalities were in buses with a GVWR greater than 11,793 kg (26,000
lb). Based on these data, NHTSA determined that the vehicles of
significance are those with a GVWR of greater than 11,793 kg (26,000
lb). These buses appear to have a higher risk of involvement in fatal
crashes involving passenger fatalities than buses with a GVWR of 11,793
kg (26,000 lb) or less.
    For the seat belt final rule and for purposes of today's NPRM, the
agency analyzed FARS data for vehicles coded in FARS as ``cross-
country/intercity buses,'' ``other buses,'' and ``unknown buses.'' \31\
Among these buses (cross-country/intercity buses, other buses, unknown
buses) with a GVWR greater than 11,793 kg (26,000 lb), there were a
total of 209 occupant fatalities \32\ in crashes during the 10-year
period between 2000-2009. This number includes 134 occupant fatalities
in cross-country/intercity buses, 47 in other buses, and 28 in unknown
buses (see Figure 1 and Table 5 below). In contrast, with regard to
buses with a GVWR less than 11,793 kg (26,000 lb), there were a total
of 44 fatalities in cross-country/intercity buses, other buses, and
unknown buses with a GVWR of 11,793 kg (26,000 lb) or less in the 2000-
2009 FARS data files. This is approximately one-fifth of the fatalities
in such buses with a GVWR greater than 11,793 kg (26,000 lb).
---------------------------------------------------------------------------

    \31\ The FARS database has five bus body type categories: (1)
Cross-country/intercity bus, (2) transit bus, (3) school bus, (4)
other bus, and (5) unknown bus. Transit bus and school bus body
types were excluded from the analysis because they are easily
recognized and categorized as such by crash investigators and those
coding the FARS data. Thus, those vehicles are unlikely to be
miscoded as other buses.
    \32\ There were 232 occupant fatalities in the large bus types
considered in today's NPRM during this 10-year period. However, 23
fatalities occurred due to a fire (Wilmer, Texas bus fire) and were
not related to a crash event and therefore are not included in the
fatality count resulting from crashes.

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

[GRAPHIC] [TIFF OMITTED] TP06AU14.006

               Table 5--Number of Bus Occupant Fatalities in Crashes by Bus Body Type, GVWR, and Occupant Type. FARS 2000-2009 Data Files
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Bus body type
                                                 -------------------------------------------------------------------------------------------------------
                    GVWR (lb)                           Cross-Country                 Other                    Unknown                    Total
                                                 -------------------------------------------------------------------------------------------------------
                                                     Driver        Pass        Driver        Pass        Driver        Pass        Driver        Pass
--------------------------------------------------------------------------------------------------------------------------------------------------------
10,000-26,000...................................            0            2            5           26            2            7            7           35
>26,000.........................................           22          112           11           36            8           20           41          168
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Among the 209 occupant fatalities in the 10-year period, the FARS
data show that 168 (80 percent) were passengers, and 41 (20 percent)
were drivers. In addition, the data show that 64 percent of the
fatalities were in cross-country/intercity buses and 36 percent were in
the other bus and unknown bus categories (see Table 5 above).
    As shown in Figure 1, fatalities in certain years are significantly
higher than average. There were more than 20 occupant fatalities in
2002, 2004, 2007, and 2008 in crashes involving these vehicles. We note
that such increases in fatality statistics were often attributable to a
small number of serious crashes during that year which caused a large
number of fatalities.
    For example, the majority of fatalities in 2004 resulted from a
crash in Arkansas, which involved a bus hitting a highway signpost and
subsequently rolling over. The rollover and partial detachment of the
roof resulted in the ejection of all 30 occupants. This crash resulted
in 15 fatalities, including the driver. All 14 passengers who died in
this crash were ejected.
    The 42 passenger fatalities in 2008 were mainly a result of 3
separate crashes. The first event was a rollover crash that occurred in
Mexican Hat, Utah, where the bus overturned as it departed the roadway
and rolled one full turn, striking several rocks in a drainage ditch
bed at the bottom of the embankment, and came to rest on its wheels.
The roof of the vehicle separated from the body, and 51 of the 53
occupants were ejected. Nine passengers were fatally injured and 43
passengers and the driver received various injuries.
    The second 2008 event was a crash in Sherman, Texas, where the bus
went through the bridge railing and off the bridge. As a result of the
accident, 17 passengers died. Among the NTSB findings, the report
concluded that the overhead luggage rack had detached from its mounting
and fell diagonally across the aisle onto the passengers and impeded
passenger egress and rescue efforts.
    The third 2008 event was a rollover crash near Williams,
California, where the bus flipped and rolled into a ditch, killing 9
people and injuring more than 30 others. According to a media
report,\33\ 30 to 38 people suffered critical injuries, while the rest
of the passengers received moderate to minor injuries. Approximately a
dozen passengers were ejected from the vehicle.
---------------------------------------------------------------------------

    \33\ http://www.kcra.com/news/17630435/detail.html.
---------------------------------------------------------------------------

    Separately, in 2009, a large number of fatalities were a result of
a January 30, 2009 crash in which a 29-passenger tour bus overturned on
a highway near the Hoover Dam, killing 7 occupants and injuring 10
others. According to the

NTSB report,\34\ the 29-passenger mid-size bus veered left out of its
lane. After the driver overcorrected, the bus rolled 1.25 times before
stopping. During the rollover, 15 of the 17 occupants were fully or
partially ejected.
---------------------------------------------------------------------------

    \34\ NTSB/HAR-10/01 PB2010-916201; Bus Loss of Control and
Rollover Dolan Springs, Arizona; January 30, 2009.
---------------------------------------------------------------------------

b. Rollover and Ejection Statistics

    Using the aforementioned FARS bus type categories, the agency
examined the FARS data to understand the proportion of occupant
fatalities that resulted from rollover crashes and occupant ejections.
The FARS data show that rollovers account for more than half of the
occupant fatalities in these bus types. Figure 2, below, shows the 209
fatalities categorized by rollover/first impact point for the 10-year
period 2000-2009. If a vehicle was involved in a rollover, it is
categorized as a rollover crash since it is generally the most harmful
event in a crash and results in most of these fatalities. Vehicles not
involved in a rollover are categorized by first impact point (front,
side, and rear).
[GRAPHIC] [TIFF OMITTED] TP06AU14.007

    Among the 209 occupant fatalities, rollovers accounted for 114
fatalities (55 percent). Also, 71 percent of crash fatalities in cross-
country buses were in rollover crashes, while 25 percent of the
fatalities in other and unknown buses were in rollover crashes. There
were no fatalities in rear and side impacts in cross-country and
unknown bus body type categories.
    The agency further examined these data and found that the vast
majority of fatalities in rollover crashes involve occupant ejections.
Figure 3 shows the distribution of fatalities in) rollover crashes
involving these bus types (cross-country, other, and unknown buses with
a GVWR greater than 11,793 kg (26,000 lb)) by occupant type and
ejection status. For the ten year period from 2000 to 2009, there were
32 fatal rollover crashes, resulting in 114 fatalities. In these
rollover crashes, two thirds (78 out of 114) of the fatalities were
occupants who were ejected. Three drivers (3 percent) involved in
rollover crashes were ejected.

[GRAPHIC] [TIFF OMITTED] TP06AU14.008

    While a large percentage of fatalities in rollover crashes are due
to the occupants being ejected, some fatalities can be attributed to
the collapse of structure during the rollover event. On May 31, 2011, a
2000 Setra bus carrying 58 passengers from Greensboro, North Carolina
to New York City on Interstate 95 departed the roadway near Doswell,
Virginia, rolled 180 degrees, and landed on its roof. NTSB, which is
investigating this accident, noted that there was considerable
deformation of the roof into the occupant survival space as evidenced
by the seat back deformation resulting from contact with the roof
structure. The passenger seats were not equipped with seat belts. Four
passengers were killed as a result of encroachment of the occupant
survival space by the roof and fourteen passengers sustained serious
injuries. The driver, restrained by a lap belt, was not injured.
    The agency is proposing the requirements in today's NPRM to improve
rollover safety in large buses. The aforementioned data show that
crashes involving rollovers and ejections present the greatest risk of
death to the occupants of these buses. The majority of fatalities occur
in rollovers, and two-thirds of rollover fatalities are associated with
occupant ejection, particularly passenger ejection. There is also real
world evidence that bus occupants retained in the bus during rollover
events may sustain serious to fatal injuries due to structural
collapse. The proposed requirements work in conjunction with the seat
belt requirements by enhancing the protection of restrained and
retained occupants in rollovers and reducing the risk of ejection of
occupants who are not restrained.

IV. NHTSA's Large Bus Rollover Structural Integrity Research

    In support of this rulemaking initiative, the agency evaluated two
existing roof crush/rollover standards: FMVSS No. 220, ``School bus
rollover protection,'' and ECE R.66, ``Uniform Technical Prescriptions
Concerning the Approval of Large Passenger Vehicles with Regard to the
Strength of their Superstructure.'' \35\ We sought to evaluate the
extent to which the standards would address the aforementioned safety
concerns, particularly as to providing a minimum level of protection
for vehicle occupants who are retained in the vehicle after a rollover.
---------------------------------------------------------------------------

    \35\ ECE R.66 defines ``superstructure'' as ``the load-bearing
components of the bodywork as defined by the manufacturer,
containing those coherent parts and elements which contribute to the
strength and energy absorbing capability of the bodywork, and
preserve the residual space in the rollover test.'' ``Bodywork''
means ``the complete structure of the vehicle in running order,
including all the structural elements which form the passenger
compartment, driver's compartment, baggage compartment and spaces
for the mechanical units and components.'' (Footnote added.)
---------------------------------------------------------------------------

    The agency purchased three different bus models for this test
program. Two older models were selected because they were
representative of the range of roof characteristics (such as design,
material, pillars, shape, etc.) of large bus roofs in the U.S. fleet.
The vehicles selected were two 12.2 meters (m) (40 feet) long MY 1992
MCI model MC-12, and two 12.2 m (40 feet) long MY 1991 Prevost model
(Prevost) LeMirage buses. The MCI and Prevost models were selected
because they were similar in size and weight but exhibited visible
differences in construction. The most discernible difference between
these two models was that of the two, the Prevost LeMirage had smaller
side windows and more roof support pillars.
    Many buses, newer than those MCI and Prevost models, are 13.7 m (45
feet) instead of 12.2 m (40 feet) in length. Thus, the agency believed
that manufacturers could have significantly redesigned their bus models
when introducing the longer designs. Thus, the agency also procured a
MY 2000 MCI bus, Model 102-EL3, that was 13.7 m (45 foot) in length.
    All five of the buses purchased were tested to requirements in
either FMVSS No. 220 or ECE R.66. For further information on the four
older buses tested, a detailed discussion of the tests and results are
available in the docket entry NHTSA-2007-28793-0019. For further
information on the newer vehicle tested, see the test report, ``ECE
Regulation 66 Based Research Test of Motorcoach Roof Strength, 2000 MCI
102-EL3 Series Motorcoach, NHTSA

No.: MY0800,'' October 1, 2009, Report No.: ECE 66-MGA-2009-001, which
can be found on NHTSA's Web site.\36\
---------------------------------------------------------------------------

    \36\ http://www-nrd.nhtsa.dot.gov/database/aspx/searchmedia2.aspx?database=v&tstno=6797&mediatype=r&r_tstno=6797,
Report 8. Step-by-step instructions on accessing the research report
can be found in a memorandum in Docket No. NHTSA-2007-28793-0025.
---------------------------------------------------------------------------

a. Findings of the FMVSS No. 220-Based Tests

    In evaluating FMVSS No. 220, the agency used one of the MY 1992 MCI
buses and one of the MY 1991 Prevost buses.
    The FMVSS No. 220 test applies a uniformly distributed compressive
load (equivalent to 1.5 times the unloaded vehicle weight (UVW) of the
bus), on the roof of the bus along the vehicle's longitudinal
centerline using a 915 mm (3 feet) wide platen that is 305 mm (1 foot)
shorter than the bus length. The requirements are that the bus roof
must not compress more than 130 mm (5.118 inches) and that the
emergency exits remain operable.
    Since there were some uncertainties regarding the strength of the
bus roofs and whether they could withstand a force of 1.5 times the
unloaded vehicle weight (UVW), we slightly changed how the FMVSS No.
220 test was conducted. In particular, when the applied force reached
the magnitude of 0.5 times UVW and 1.0 times UVW, the force was held
constant at that level for a period of time in order to examine the
operability of the emergency exits. In addition, survival space
templates \37\ (similar to those used in the ECE R.66 test) were
installed for comparison with the results with the ECE R.66 tests.
---------------------------------------------------------------------------

    \37\ The templates are used to delineate the occupant survival
space. The templates are 1,250 mm (50.2 inches) tall and are tapered
from the sidewall a distance of 150 mm (5.9 inches) at the bottom
and 400 mm (15.8 inches) at the top. Several templates are placed in
the bus passenger compartment. Encroachment of any bus structure
into the survival space, as delineated by the templates, would be
prohibited by ECE R.66.
---------------------------------------------------------------------------

    Neither the MY 1992 MCI nor the MY 1991 Prevost bus was able to
meet the 1.5 times the UVW required for school buses. For the MCI bus,
a peak load of 0.91 times UVW was achieved when the force application
device reached its maximum displacement range. Approximately 13 seconds
after the peak force was recorded, contact was made between the front
survival space template and the left and right overhead luggage racks.
The emergency exit windows were operable after the load reached 0.5
times UVW and after the test with the load removed.
    For the MY 1991 Prevost bus, a peak load of 1.17 times UVW was
achieved during the test. This peak load was reached when the force
application device reached its maximum displacement range.
Approximately 12 seconds after the peak load was reached, contact was
made between the front survival space template and the left and right
overhead luggage racks. The emergency exit windows were operable after
the load reached 0.5 times UVW and after the test with the load
removed. However, no measurements were made at 1.0 times UVW for safety
reasons.
    We made the following observations from the tests. Even though the
buses we tested were heavier, larger, and structurally different than
school buses,\38\ the testing demonstrated that FMVSS No. 220's test
protocol could be adapted to test these vehicles with only minor
changes to the test device and procedure for mounting and stabilizing
the bus on the test device. The testing further showed that the front
sections of these two bus models are weaker than the back. We believe
this is because the windshield and service door are located in the
front of the bus and offered little resistance to the compressive load.
The front of the MY 1992 MCI bus yielded to the compressive load at
0.91 times UVW, while the front of the MY 1991 Prevost bus yielded at
1.17 times UVW.
---------------------------------------------------------------------------

    \38\ Generally, large bus designs are integral constructions
whereas school buses are the traditional body-on-chassis designs.
The loads specified in FMVSS No. 220 are applied to the frame
structure of the school bus chassis which is easy to identify. In
contrast, identifying load bearing points on a large bus can be
challenging and requires some understanding of its construction. The
location of load bearing points can vary for different designs. In
the two large buses tested, the loads were applied at load bearing
points near the wheel supports.
---------------------------------------------------------------------------

b. Findings of the ECE R.66-Based Tests

Testing of Older Bus Models
    The agency also used one of the MY 1992 MCI buses and one of the MY
1991 Prevost buses to evaluate the ECE R.66 test procedure.
    In the ECE R.66 full vehicle test, the vehicle is placed on a
tilting platform that is 800 mm above a smooth and level concrete
surface. One side of the tilting platform along the length of the
vehicle is raised at a steady rate of not more than 5 degrees/second
until the vehicle becomes unstable, rolls off the platform, and impacts
the concrete surface below. The vehicle typically strikes the hard
surface near the intersection between the sidewall and the roof. The
encroachment of the survival space during and after the rollover
structural integrity test may be assessed using high speed photography,
video, deformable templates, electric contact sensors, or any other
suitable means.
    In our research, high speed video cameras and transfer media were
applied to each survival space template in order to determine if any
portion of the vehicle interior had entered the occupant survival space
during the rollover crash. In addition, two Hybrid III (HIII) 50th
percentile adult male Anthropomorphic Test Devices (ATDs) (test
dummies) were installed in the vehicle to measure injury potential and
seat anchorage performance.
    We observed the following in our tests of the older buses:
--The testing demonstrated that it is practicable to apply the ECE R.66
complete vehicle test to the large buses being considered in today's
NPRM. However, neither of the two buses tested was able to meet the
requirement to maintain the integrity of the survival space during and
after the test. Contact between the front survival space template and
left side window was made on both bus models. As in the FMVSS No. 220-
based tests, the testing indicated that the front sections of these two
models were weaker than the rear. We believe this is because the
windshield and service door are in the front of the bus and offered
little resistance upon impact with the ground.
--On both buses, the windows on the impact side remained intact. The
high speed video footage from both tests indicated that the side
windows located on the far-side of the impact underwent a substantial
amount of flexion during the impact with the ground but remained
intact. The windshield broke from its mounting and fell to the ground.
-- For both buses, the roof emergency exits opened when the bus
impacted the ground. The video footage also indicated that the side
emergency exit windows on the Prevost bus unlatched and opened but
closed when the bus came to its final resting position.
--On the MY 1992 MCI bus, all of the left side overhead luggage rack
inboard hangers (hangers connect the overhead luggage rack to the
ceiling of the vehicle, and are spaced along the length of the rack to
hold it up) rearward of the front two hangers, broke during the impact,
leaving exposed sharp metal edges.
--For the MY 1991 Prevost bus, all the seats on the right side
(opposite the impact side) of the bus detached from their wall mounts
and the seat with the restrained dummy broke completely from its
anchorages.
--The Injury Assessment Reference Values (IARVs) were relatively low
for the ATDs restrained by the seat belts

(even for the seat in the Prevost bus that broke away from its side and
floor anchorages). However, for the ATDs that were unrestrained, the
type and severity of the injury indicated by the dummy IARVs depended
on how they fell from their initial seated position during the rollover
sequence. In the case of the MCI bus, the unrestrained ATD received
only one IARV (neck injury criterion Nij = 1.10) that was over the
performance limit used in FMVSS No. 208, ``Occupant crash protection.''
However, in the case of the MY 1991 Prevost bus, the unrestrained ATD
fell across the bus head-first onto the side window which was in
contact with the ground, resulting in multiple IARVs exceeding the
performance limits specified in FMVSS No. 208. The dummy resulted in
multiple IARVs that were well above the acceptable limits.
Testing of a Newer Bus Model
    NHTSA also conducted the ECE R.66 test on a MY 2000 MCI bus Model
102-EL3 that was 13.7 m (45 foot) in length. This test was conducted to
determine whether the ECE R.66 test protocol could be applied to the
larger and heavier buses sold in the United States and to examine
different ballasting methods. Survival space templates were installed
and the vehicle was placed on a tilting platform that was 800 mm above
a smooth and level concrete surface. One side of the tilting platform
was raised at a steady rate of not more than 5 degrees/second until the
vehicle became unstable, rolled off the platform, and impacted the
concrete surface below. See, ``ECE Regulation 66 Based Research Test of
Motorcoach Roof Strength, 2000 MCI 102-EL3 Series Motorcoach, NHTSA
No.: MY0800,'' October 1, 2009, supra.
    Occupant ballasts were used in the test, as specified in ECE R.66.
ECE R.66 specifies the option of two different methods of securing
occupant ballast to the passenger seats. NHTSA tested both types of
ballasts to determine the feasibility of each and the differences (if
any) that exist between the two. The agency believed that ballasting
was important because it increases the weight and raises the center of
gravity of the vehicle, making the rollover structural integrity test
more stringent and representative of a rollover crash of a fully loaded
bus. In addition, the seat anchorages experience the forces in a
rollover when the seat is occupied by an average sized restrained
occupant.
    NHTSA evaluated the two ballasting methods to assess the
feasibility and merits of the ballast methods. Four anthropomorphic
ballasts, commercially available ``water dummies,'' \39\ were installed
in one full row of seats (four seating positions) and were secured with
ratchet straps that were configured to simulate Type 2 seat belts. The
dimensions of the anthropomorphic ballasts used in this test are shown
in Figures 5(a) and 5(b), below. The water dummies were each filled
with 68 kg (150 lb) of sand. Steel ballasts, 68 kg (150 lb) per seating
position, were installed in a second full row of seats (four seats). In
this row, steel plates were placed on top of each seat cushion and were
secured with bolts that passed through the cushion and attached to a
bar which clamped onto the seat frame. (In the ECE R.66 test, each
designated seating position with occupant restraints would be
ballasted.)
---------------------------------------------------------------------------

    \39\ These water dummies are plastic containers constructed to
simulate the torso shape of a passenger and can be secured in place
using belts. Such water dummies have the capacity to be loaded to a
weight of 176 pounds (80 kg). However, since the GVWR of a vehicle
is typically estimated using an occupant weight of 150 pounds per
seating position and since ECE R.66 specifies ballasts of 150
pounds, the agency only loaded the water dummies to 150 pounds. The
water dummies were filled with sand instead of water because filling
the ballast partially with water would cause the water's mass to
slosh during the rollover test, possibly introducing some
variability.
[GRAPHIC] [TIFF OMITTED] TP06AU14.009

[GRAPHIC] [TIFF OMITTED] TP06AU14.010

    We also seated two 50th percentile adult male ATDs on the opposite
side of the impact. This arrangement was similar to the earlier tests
with the older buses.
    We observed the following in our test of this MY 2000 bus:

--Based on an analysis of image data from the high-speed camera located
outside the vehicle, it appears that a side pillar in the front of the
vehicle along the impact side may have intruded into the survival
space. However, this was not assessed using the survival space
templates since they were not located at the position of the side
pillar during the test, and there was no contact between the survival
space templates and the bus structure.
--During impact, the glazing on five of the seven windows on the right
side of the bus (opposite the impacted side) dislodged from their
window mounting and fell into the occupant compartment during the test.
The glazing in one of the windows was retained by an overhead TV
monitor and prevented the window pane from separating from its mounting
gasket and falling into the bus. The glazing in the last window near
the rear shattered, but was retained and did not fall into the
passenger compartment, apparently because the window was shorter in
length than the other windows. After the bus impacted the ground, both
sides of the windshield lost retention and fell from its supporting
structure.
--All side emergency exit windows remained latched during the test.
However, both roof emergency exits opened when the roof of the bus
impacted the ground.
--The ATD restrained by the seat belt measured forces that were below
the FMVSS No. 208 IARVs. However, the unrestrained ATD had multiple
IARVs that were well above the acceptable limits.
--In terms of the feasibility of the test procedure, the testing showed
that it was possible to ballast the seats with either the
anthropomorphic ballast or steel weights. All of the seats with both
types of ballast remained attached to their original anchorages.

V. Proposed Requirements

a. Overview

    This NPRM proposes performance requirements that the large buses
covered by this rulemaking must meet when tested by NHTSA using a test
substantially modeled after the complete vehicle test of ECE R.66.\40\
In the rollover structural integrity test, the vehicle would be loaded
with up to 68 kg (150 lb) of weight in ballasts at each designated
seating position in order to simulate the load of occupants on both
vehicle structure and the seat anchorages. The following are the
proposed performance requirements when the vehicle is subjected to the
rollover structural integrity test:
---------------------------------------------------------------------------

    \40\ ECE R.66 includes several ``equivalent approval tests,''
including body section testing and computer simulations. In a later
section, we discuss why we believe these alternative compliance
methods would not be suitable for incorporation into today's
proposed Federal motor vehicle safety standard.
---------------------------------------------------------------------------

    (1) Intrusion into the survival space, demarcated in the vehicle
interior, by any part of the bus outside the survival space is
prohibited;
    (2) each anchorage of the seats and interior overhead luggage racks
and compartments shall not completely separate from its mounting
structure;
    (3) emergency exits must remain shut during the test and roof and
rear emergency exits must be operable in the manner required under
FMVSS No. 217 after the test; and
    (4) each side window glazing opposite the impacted side of the
vehicle must remain attached to its mounting such that there is no
opening that will allow the passage of a 102 mm diameter sphere.

b. Applicability

    In this rulemaking, the agency's goal is to apply the proposed
requirements in today's NPRM to generally the same group of vehicles
that are covered by the seat belt final rule. The agency tentatively
believes that it would make sense to apply today's proposed
requirements generally to the same group of vehicles that are covered
by the seat belt final rule. Both rulemakings are intended to address
different facets of occupant harm occurring from the rollover event.
Both standards would apply to the vehicles associated with unreasonable
risk of harm in rollovers. The agency tentatively concludes that this
rollover-specific NPRM should apply to high-occupancy vehicles
associated with unreasonable risk of fatal rollover involvement and
that these vehicles are generally buses with a GVWR greater than 11,793
kg (26,000 lb).
    In order to achieve this, the agency proposes to apply the
requirements to two types of buses: (a) All new over-the-road buses
(regardless of GVWR) and (b) all new buses other than over-the-road
buses, with a GVWR greater than 11,793

kg (26,000 lb).\41\ While the vast majority of over-the-road buses have
a GVWR greater than 11,793 kg (26,000 lb), the agency proposes to take
this two-prong approach towards determining applicability of the
proposed standard in order to cover all of the buses covered by MAP-21
and all of the buses with similar safety risks as the buses covered
under MAP-21.
---------------------------------------------------------------------------

    \41\ Transit buses, school buses, and perimeter-seating buses
would be excluded from the standard under this latter category.
---------------------------------------------------------------------------

MAP-21 and Over-the-Road Buses
    As described above, the large bus rulemaking provisions in MAP-21
apply to ``motorcoaches'' which are defined as ``over-the-road buses.''
An over-the-road bus is, in turn, defined as ``a bus characterized by
an elevated passenger deck located over a baggage compartment.'' In
order to cover this group of vehicles, we propose in this NPRM to use
the language from MAP-21 and apply the proposed requirements to ``over-
the-road buses.'' Further, we propose to adopt the definition
incorporated in MAP-21 and define over-the-road buses as buses that are
characterized by an elevated passenger deck located over a baggage
compartment.\42\
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    \42\ As described further, below, over-the-road buses include
buses operated by public transit agencies so long as they meet the
over-the-road bus definition (buses characterized by an elevated
passenger deck located over a baggage compartment).
---------------------------------------------------------------------------

    The agency believes that the vast majority of ``over-the-road
buses'' are buses with a GVWR greater than 11,793 kg (26,000 lb).
However, rather than simply applying the proposed requirements to buses
(of any type) with a GVWR greater than 11,793 kg (26,000 lb) the agency
tentatively believes that it is necessary to propose a separate
definition for ``over-the-road buses'' and apply the proposed
requirements to all of those buses. While most over-the-road buses have
a GVWR greater than 11,793 kg (26,000 lb), the agency is not aware of
any reason why buses characterized by an elevated passenger deck
located over a baggage compartment (over-the-road buses) must
necessarily have a GVWR greater than 11,793 kg (26,000 lb). As it is
possible to design a bus with an elevated passenger deck located over a
baggage compartment with a GVWR less than 11,793 kg (26,000 lb), the
agency tentatively believes that it is necessary to apply the proposed
requirements to all over-the-road buses (regardless of GVWR) in order
to cover all the buses contemplated by Congress in MAP-21. In addition,
the agency believes that over-the-road buses (as characterized in MAP-
21) are likely to be used for high-speed intercity travel (where
rollover crashes are more likely to occur) regardless of the vehicle's
GVWR.
Buses Other Than Over-the-Road Buses With a GVWR Greater Than 11,793 kg
(26,000 lb)
    However, in addition to the buses contemplated by Congress in MAP-
21, the agency proposed to also cover other types of buses \43\ so long
as those buses have a GVWR greater than 11,793 kg (26,000 lb). As
discussed in the ``Safety Need'' section of this preamble, FARS data
for 2000-2009 show that rollovers constitute a large safety problem for
buses with a GVWR greater than 11,793 kg (26,000 lb). FARS data show
that rollovers (32 crashes, 114 fatalities) accounted for 34 percent of
the fatal crashes yet more than 50 percent of the occupant fatalities.
In these rollover crashes, two-thirds of the fatalities were passengers
who were ejected. The data indicate that, for these vehicles, rollover
crashes and occupant ejections are more likely to cause fatalities than
other types of crashes.
---------------------------------------------------------------------------

    \43\ Except transit buses, school buses, and perimeter seating
buses
---------------------------------------------------------------------------

    As mentioned earlier, NHTSA is proposing to adopt the requirements
in today's NPRM under its authority in both the Motor Vehicle Safety
Act and the relevant provision of MAP-21. While the relevant provisions
of MAP-21 instruct this agency to examine ``over-the-road buses''
(buses characterized by an elevated passenger deck located over a
baggage compartment) in any roof strength and anti-ejection
rulemakings,\44\ no provision in MAP-21 limits the agency's ability to
examine other types of buses pursuant to its existing authority under
the Motor Vehicle Safety Act.
---------------------------------------------------------------------------

    \44\ See Moving Ahead for Progress in the 21st Century Act, Pub.
L. 112-141, Sec.  32703(b).
---------------------------------------------------------------------------

    Given the available data, the agency believes that limiting the
scope of this rulemaking to ``traditional motorcoaches'' (over-the-road
buses) would be only a partial and incomplete response to the safety
problem. As discussed above, the FARS data for 2000-2009 show that
buses other than over-the-road buses were often involved in high speed
crashes involving multiple passenger fatalities. The FARS data show
that 64 percent of the fatalities were in cross-country/intercity buses
(considered traditional over-the-road type buses) and 36 percent were
in the ``other bus'' and ``unknown bus'' categories. While these
``other'' and ``unknown'' buses have a non-traditional (e.g., body-on-
chassis) design and appearance, these buses are of a similar size,
seating configuration, and function as an over-the-road bus type. As a
result, these buses are associated with similar safety risks as over-
the-road buses. Thus, the agency is currently unaware of a rationale
that would support excluding these ``other'' and ``unknown'' buses from
today's proposed requirements.
    As the data indicate, the safety risks associated with rollover
accidents in large buses are not limited to only traditional
motorcoaches (over-the-road buses). Thus, the agency proposes to apply
the proposed requirements in today's NPRM to buses other than those
called ``motorcoaches'' in MAP-21. Beyond the ``over-the-road'' buses
identified by MAP-21, NHTSA proposes to apply the proposed requirements
to generally the same universe of vehicles to which the seat belt final
rule applies. The agency believes that the proposed rule should apply
to all buses with similar rollover crash risks.
Buses Other Than Over-the-Road Buses With a GVWR Between 4,536 and
11,793 kg (10,000 and 26,000 lb)
    On the other hand, buses with a GVWR between 4,536 and 11,793 kg
(10,000 and 26,000 lb) do not have the same rollover crash risks as the
aforementioned bus categories. Thus, while comment is requested on this
subject, this NPRM tentatively has not included these buses in today's
proposal. According to the FARS 2000-2009 data files, there were 42
occupant fatalities in crashes involving cross-country buses, other
buses, and unknown buses with a GVWR between 4,536 and 11,793 kg
(10,000 and 26,000 lb) in this 10-year period (see Table 5, supra).
Among these 42 occupant fatalities in buses with a GVWR between 4,536
and 11,793 kg (10,000 and 26,000 lb), 24 fatalities were a result of 13
rollover crashes. Thus, over the ten year period between 2000 and 2009,
buses with a GVWR between 4,536 and 11,793 kg (10,000 and 26,000 lb)
were associated with an average of 1.3 rollover crashes per year and
2.4 fatalities per year. In contrast, there was an average of 3.2
rollover crashes among buses in these same categories with a GVWR
greater than 11,793 kg (26,000 lb) per year. These crashes resulted in
an average of 11.4 fatalities per year. Among all fatalities occurring
in rollover crashes in cross-country, other, and unknown buses with a
GVWR greater than 4,536 kg (10,000 lb), 83

percent are in buses with a GVWR greater than 11,793 kg (26,000 lb).
    Further, the agency notes that buses with a GVWR between 4,536 and
11,793 kg (10,000 and 26,000 lb) are frequently used for demand-
response transit \45\ services.\46\ These demand-response transit
service vehicles are used in urban areas and rarely operate at highway
speeds, which are the speeds at which the majority of bus rollover
fatalities occur. Compared to the estimated number of large buses sold
annually (approximately 2,200 buses), there are approximately 14,600
buses with a GVWR between 4,536 and 11,793 kg (10,000 and 26,000 lb)
produced annually.\47\ Given that more of the lower weight buses are
manufactured than large buses annually, applying the proposed rule to
buses with a GVWR between 4,536 and 11,793 kg (10,000 and 26,000 lb)
may increase the potential costs of the rule more than the potential
benefits.
---------------------------------------------------------------------------

    \45\ Public transportation characterized by flexible routing and
scheduling of small/medium vehicles operating in shared ride mode
between pickup and drop-off locations according to passenger needs.
It includes transporting persons with special mobility needs.
    \46\ Evaluation of the Market for Small-to-Medium Sized Cutaway
Buses, Federal Transit Administration Project : MI-26-
7208.07.1, December 2007, available at http://www.fta.dot.gov/documents/AnEvaluationofMarketforSmalltoMediumSizedCutawayBuses.pdf.
    \47\ See Id.
---------------------------------------------------------------------------

    However, NHTSA requests comment on the issue and invites useful
data, particularly related to the cost of applying the proposed rule to
buses with a GVWR between 4,536 and 11,793 kg (10,000 and 26,000 lb).
Are there data as to whether the cost of applying the proposed
requirements to buses with a GVWR between 4,536 and 11,793 kg (10,000
and 26,000 lb) will be significantly different when compared to buses
with a GVWR greater than 11,793 kg (26,000 lb)? We request data that
show whether the effectiveness of the countermeasures would be
different between these two bus sizes. Are there data which show how
the impact on small businesses would change if the requirements of
today's proposal were extended to buses with GVWR between 4,536 and
11,793 kg (10,000 and 26,000 lb)?
    Although the aforementioned data show that buses with a GVWR
between 4,536 and 11,793 kg (10,000 and 26,000 lb) have historically
been associated with less fatalities than buses with a GVWR above
11,793 kg (26,000 lb), the agency notes these buses represent a
significant number of bus sales, have a lower price ($50,000--$65,000),
and higher fuel economy.\48\ As smaller buses can also be utilized to
service similar routes as larger buses, it may be possible, in the
future, that more crashes could occur in these types of buses if these
buses experience higher sales volume and begin to service routes that
result in a higher number of vehicles miles traveled. NHTSA recognizes
that this proposal does not cover all the vehicles recommended by the
NTSB in recommendations H-10-3 and H-10-4. As mentioned above, the NTSB
recommended that NHTSA should include all vehicles with a GVWR of 4,536
kg (10,000 lb) or greater in our rulemaking. Thus, the agency is
requesting comment on the above concerns.
---------------------------------------------------------------------------

    \48\ See Id.
---------------------------------------------------------------------------

Transit, School, Perimeter Seating, Prison, and Double-Decker Buses
    While (in general) the agency proposes to apply the requirements in
this NPRM to over-the-road buses (regardless of GVWR) and other buses
with a GVWR greater than 11,793 kg (26,000 lb), the agency has
considered various (more specialized) types of buses and whether or not
these specific types of buses should be covered by the proposed
requirements. Comments are requested on each of the following bus types
and whether or not the agency should apply the proposed requirements in
this NPRM to these bus types.
Transit Buses
    In today's proposal we have not included transit buses as a bus
category that would be subjected to today's proposed requirements. The
data show that the crash risk for transit buses (i.e., buses with a
stop-request system that is sold for public transportation) is much
lower than for the other bus types covered by today's proposal. In
order to exclude transit buses, we propose to utilize the same
definition for transit buses as in the seat belt final rule.\49\ Our
reasoning, like in the seat belt final rule, is that there is a
significantly lower crash risk for passengers of transit buses. We
believe this difference in crash risk is due in part to the stop-and-go
manner of transit bus operation. The FARS data from 2000-2009 show
that, for all bus body types with a GVWR greater than 11,793 kg (26,000
lb), transit buses have the fewest fatalities at 8.2 percent or 23 out
of a total of 281. These same data show that there were 20 fatal
crashes involving occupants of urban transit buses, resulting in
fatalities of 11 drivers and 12 were passengers. Thus, fatal transit
bus crashes involve about one fatality, on average. In summary, there
are many fewer total fatalities and fatalities per crash for transit
buses, and thus a significantly lower risk than in the other buses
covered by today's proposed rule.
---------------------------------------------------------------------------

    \49\ Transit bus means a bus that is equipped with a stop-
request system sold for public transportation provided by, or on
behalf of, a State or local government and that is not an over-the-
road bus.
---------------------------------------------------------------------------

    Like in the seat belt final rule, today's proposal explicitly
states that over-the-road buses cannot qualify as transit buses (and be
exempt from proposed requirements). While the agency acknowledges that
state and local public transit agencies may purchase an over-the-road
bus and equip such buses with a stop-request system, the agency
believes that over-the-road buses used by transit agencies will likely
be used in a similar manner as over-the-road buses purchased by private
companies (i.e., for intercity transport carrying large numbers of
passengers, over long distances, and at highway speeds). It is not
uncommon to see commuter express buses traveling on the highway
alongside privately-operated tour and charter buses of nearly identical
construction. Thus, given the overall similarity of the buses in
construction and use, we cannot distinguish, from a public safety
standpoint, good reasons for distinguishing privately-operated versions
of the over-the-road buses from those operated by state and local
public transit agencies. Comments are requested on this topic.

School Buses

    As described in greater detail below, FMVSS No. 220 establishes
roof strength requirements for school buses. While there are several
reasons why the agency is proposing to use an ECE R.66-based test in
today's NPRM, the agency is not proposing to alter the requirements for
school buses. As further described below, there are various differences
in the operating conditions the large buses covered under today's
proposal and school buses covered under FMVSS No. 220 that make an ECE
R.66-based test more suitable for the buses covered in today's
proposal. As the safety record for school buses demonstrate that FMVSS
No. 220 continues to be appropriate for those buses, the agency is not
proposing to include school buses in today's proposal or to alter the
requirements for school buses under FMVSS No. 220.
Buses With Perimeter Seating
    In the seat belt final rule, the agency did not apply the seat belt
requirements to buses with perimeter seating (unless the bus with
perimeter seating qualifies as an over-the-road bus). We propose to do
the same for the requirements in

today's NPRM. While buses that qualify as over-the-road buses (under
MAP-21) are covered under today's proposal regardless of seating
configuration,\50\ we tentatively believe that it is appropriate to
exclude perimeter buses that are not over-the-road buses because these
buses with perimeter seating are used to carry people for a relatively
short period, typically are meant to transport standees, and are
spacious to accommodate baggage and other carry-on items and to
maximize the speed of passenger boarding and alighting. Under these
conditions, buses with perimeter seating are not expected to transport
passengers for a long distance at relatively high speeds where rollover
crashes are more common. However, the agency requests comment on
whether it is likely that buses with a GVWR greater than 11,793 kg
(26,000 lb) would be configured with perimeter seating and whether such
buses would be used in conditions where rollover crashes are more
likely to occur. We further request comment on whether such buses
should be included as a bus type subject to this proposal.
---------------------------------------------------------------------------

    \50\ In order to cover all the buses that were covered under
MAP-21, this proposal specifically defines ``perimeter seating
buses'' as buses that are not over-the-road buses. Therefore, over-
the-road buses are covered under today's proposal without regard to
their seating configuration.
---------------------------------------------------------------------------

Prison Buses
    While prison buses were excluded from meeting the requirements of
the seat belt final rule, we have tentatively decided not to exclude
prison buses from the proposed requirements of today's NPRM. In the
seat belt final rule, the agency noted in response to comments that
certain structural aspects of prison buses (e.g., fiberglass or
stainless steel low-back seats or benches) are not conducive to install
seat belts. Further, we noted the security concern that lap/shoulder
belt equipment could pose hazards as the buckle hardware and belt
webbing could be used as weapons or tools. However, these similar
concerns are not present when considering the proposed requirements in
today's NPRM.
    Designing the roof of a prison bus to better withstand an impact
during a rollover crash is unlikely to involve any equipment that needs
to be installed on the passenger seats or any equipment that could be
potentially used as weapons/tools. However, the agency requests comment
on whether or not it is reasonable to exclude prison buses from the
proposed requirements in this rulemaking. If the recommendation is to
exclude prison buses, what is the rationale for doing so? Is it
reasonable to exclude prison buses from all of the requirements
proposed in this NPRM or would it be appropriate to apply some--but not
all--of the requirements proposed (e.g., emergency roof exit
requirements but not the survival space requirements)?
Double-Decker Buses
    The agency notes that the requirements of ECE R.66 do not apply to
double-decker buses while NHTSA's proposal does not exclude them from
rollover structural integrity requirements.
    We have tentatively decided that the proposed test procedure is not
appropriate for and should not be applied to the upper/open section of
open-top double-decker buses because there would be no structure to
intrude into any defined survival space in the upper/open level.
However, we believe that lower/enclosed sections of such vehicles (or
the upper/enclosed section of a double-decker bus) can still be tested
under the proposed test procedure for compliance with the requirements
of the proposed rule. In the lower/enclosed or upper/enclosed level,
there would be vehicle structure that could intrude into the survival
space in the same fashion as a traditional bus that does not have an
open-top. Comments are requested on any technical reasons that would
preclude the proposed test from being applied to the enclosed section
of double-decker buses, and on whether additional provisions in the
regulatory text are needed in order to further account for testing of
double-decker buses.

c. Test Procedure

    The agency proposes in today's NPRM that compliance with the
proposed performance requirements will be measured by NHTSA \51\ using
a test substantially patterned after the complete vehicle test of ECE
R.66. Similar to the ECE R.66 complete vehicle test, the proposed test
would specify that the vehicle is placed on a raised platform that is
800 mm (31.50 inches (in)) above a horizontal, dry and smooth concrete
ground surface. The test would allow NHTSA to position the vehicle such
that either side (right and left) of the vehicle may be tested for
compliance. The tilting platform would be raised, on one side, at a
rate not to exceed 5 degrees/sec along an axis no greater than a 100 mm
horizontal distance from the edge of the impact surface closest to the
tilting platform and 100 mm below the top of the platform surface,
until the vehicle becomes unstable and commences the rollover. The
tilting platform would be equipped with wheel supports to maintain the
vehicle's position on the tilting platform before the vehicle becomes
unstable and commences the rollover.
---------------------------------------------------------------------------

    \51\ As with all the FMVSSs, this standard would not require
vehicle manufacturers to use the test to certify their vehicles.
They may certify their vehicles using other means. Manufacturers
must ensure, however, that their vehicles will meet the FMVSS
requirements when tested by NHTSA when we use the test procedure
specified in the FMVSS. If the vehicle does not meet the
requirements when tested by NHTSA, we will ask the manufacturer for
the basis for its certification. If the agency is satisfied that the
manufacturer exercised due care in making the certification, the
agency may decide not to pursue civil penalties against the
manufacturer for the failure of the vehicle to comply. The
manufacturer is still subject to the requirements of the National
Traffic and Motor Vehicle Safety Act to recall the noncomplying
vehicles and remedy the noncompliance free of charge.
---------------------------------------------------------------------------

Ballasts Representing Restrained Occupants
    To simulate a real-world rollover, the agency believes it would be
appropriate to subject the vehicle to the forces resulting from the
mass of restrained occupants. To achieve this, this NPRM proposes that
a mass of 68 kg (150 lb) be secured in each designated seating position
equipped with a seat belt system. The ballast would have to be
restrained in such a manner that the ballast does not break away during
the test. The 150-lb ballast would represent the mass of an ``average''
occupant at each designated seating position. (The 150 lb value is used
in determining the vehicle's gross vehicle weight rating in accordance
with 49 CFR Part 567, ``Certification.'')
    The agency believes that ballasting is important because it
increases the weight and raises the center of gravity of the vehicle to
simulate the forces upon the vehicle structure in a rollover crash when
the seats are occupied by restrained passengers. Also, when occupants
are belted into the vehicle, their mass imparts crash forces to the
seat anchorages during a crash.
    While the agency believes that ballasting is important, we have
tentatively concluded that the method of ballasting and type of ballast
used is not important because these factors will not significantly
alter the forces upon the vehicle structure or the seat anchorages
during compliance testing, so long as the ballast is 150 lb. We note
that ECE R.66 does specify the option of using two different occupant
ballasts: anthropomorphic ballasts (commercially available ``water
dummies''), and fixed steel plates. The ECE regulation stipulates that
if the ballast is an anthropomorphic ballast, it is secured

using a seat belt restraint, and if the ballast is a rigid weight it is
securely attached to the seat frame.
    In its research, NHTSA tested both ballasting methods from ECE R.66
and the results did not show a significant difference between these
methods in terms of the effect on test results. We tentatively believe
that the test results of the complete vehicle rollover test will not be
significantly altered so long as a 150-lb ballast is secured to each
designated seating position equipped with the seat belt system. We
recognize that the center of gravity of the ballast can vary depending
on the manner in which it is secured to the seat and the type of
ballast it is. However, as explained below, the agency tentatively
believes that the difference in the ballasts will not significantly
alter the loads applied to the vehicle structure (as a whole) or to the
seat anchorages.
    We analyzed the effect of the different center of gravity heights
for the anthropomorphic ballasts and the fixed weight ballasts and
found that the overall center of gravity of the vehicle--and,
consequently, the energy absorbed in the rollover structural integrity
test of the fully loaded vehicle--is only slightly higher (less than 3
percent higher) \52\ when using anthropomorphic ballasts as opposed to
when using fixed weights as ballasts positioned on the seat cushion. We
believe that this difference in the stringency of the rollover
structural integrity test using different ballasts is small and within
the overall accepted variability in the test procedure.
---------------------------------------------------------------------------

    \52\ The effect of ballasts (and the type of ballast) is
greatest for the lowest weighing vehicle to which the rollover test
applies, which is, by definition, a vehicle with a GVWR of 26,001
pounds. For determining the effect of the ballasts and type of
ballasts, the following estimations were made: The unloaded weight
of the 55 occupant motorcoach is 26,001 pounds, the center of
gravity of the unloaded motorcoach is 1.22 m (48 in) above ground,
the height of the seat cushion of seats in the bus is 1.5 m (60 in)
above ground, and the height of the center of gravity of a 68 kg
rigid weight and that of an anthropomorphic ballast in the vehicle
seat is 1.57 m (62 in) and 1.7 m (67 in) above ground, respectively.
The addition of a 68 kg ballast at each of the 55 seats increases
the weight of the vehicle by 32 percent. The center of gravity
height above ground of the fully loaded vehicle is higher than that
of the unloaded vehicle by 7 percent when rigid weights are used and
by 9.5 percent when anthropomorphic ballasts are used. Through film
analysis of the motorcoach rollover tests, we estimated that the
center of gravity of the unloaded motorcoach drops approximately
0.85 m during the test. We then estimated that the total energy
absorbed by the fully loaded motorcoach (=9.81 X total mass (kg) X
drop in center of gravity during the rollover test) is 3 percent
greater when anthropomorphic ballasts are used than when rigid
weights are used. Since the effect of ballasts is greatest for the
26,001 lb GVWR motorcoach, the difference in the center of gravity
height and the energy absorbed for different ballast types will be
significantly less than 3 percent for motorcoaches with a GVWR more
than 26,001 lb.
---------------------------------------------------------------------------

    Further, we analyzed the forces and moments generated at the
anchorages due to the ballasts during the rollover impact sequence and
found that the difference in moment at the anchorages due to the
loading from the fixed weight ballast and that from the anthropomorphic
ballast during impact is approximately 350 Nm.\53\ This value is small
in comparison to the moments at the seat anchorages due to the 3,000 lb
loads on the belts in an FMVSS No. 210 test (approximately 20,000 Nm).
Further, the agency tentatively believes that this difference in moment
is small when we consider the racking forces that would be acting upon
the seat anchorages as a result of the vehicle's impact on the impact
surface during the rollover test. During our testing of the 1991
Prevost LeMirage using the ECE R.66 complete vehicle test, all the
seats on the opposite side of impact detached from their wall mounts
due to the racking of the bus side walls, even though the seats were
not ballasted. Therefore, we have tentatively concluded that the type
of ballast does not have significant effect on the performance of the
seat anchorages or the vehicle structure during the rollover structural
integrity test.
---------------------------------------------------------------------------

    \53\ Assuming that the ballast is fully coupled to the seat, the
moment at the seat anchorages generated by the ballast is equal to
the product of the mass of the ballast, its acceleration, and the
height of the ballast center of gravity. In the agency's three ECE
R.66 tests, the peak motorcoach floor acceleration was approximately
4 gs and since the seat is fully coupled to the floor, we estimated
the ballast acceleration to be 4 gs. Thus the moment generated at
the seat anchorages was calculated to be approximately 350 Nm (= 68
kg x 4x9.81 x (1.7m-1.57m)).
---------------------------------------------------------------------------

    Nonetheless, comments are requested on our tentative conclusion.
Should the agency specify a type of ballast? If so, which types of
ballasts should the agency choose and what specifications are
necessary? What repeatable method should the agency establish for
mounting the ballast to each designated seating position? If
anthropomorphic dummies from ECE R.66 are recommended, the agency
requests comment on the availability of the anthropomorphic (water
dummy) ballasts in the U.S. What substances can be used to fill
anthropomorphic ballasts such that the ballast would achieve a weight
of 150 lb with a consistent center of gravity? We note that the
anthropomorphic (water dummy) ballasts specified in ECE R.66 were
plastic containers (constructed to simulate the torso shape of a
passenger) with the capacity to be loaded to a weight of 176 lb (80
kg). Are anthropomorphic ballasts available which are designed to hold
150 pounds?
    Separately, NHTSA has tentatively concluded that two aspects of the
ballasting options allowed in the ECE R.66 complete vehicle test are
not appropriate for application in our proposed test procedure.
    First, we note that ECE R.66 specifies different weights depending
on the type of ballast that is used during the test. The ECE regulation
requires that, when anthropomorphic ballasts are used, the entire
estimated weight of an individual occupant's mass of 68 kg (150 lb) is
required. However, when fixed ballasts are used, only 50 percent of the
estimated individual occupant's mass (34 kg (75 lb)) should be
attached. The agency tentatively concludes that securing only 50
percent of the individual occupant's mass when using rigid weights
would underestimate the load that will be placed on the vehicle and its
seat anchorages during a rollover crash.
    We note that an Australian study \54\ estimated that 93 percent of
a lap/shoulder belt restrained occupant mass, 75 percent of a lap
belted occupant mass, and 18 percent of an unrestrained occupant mass
are effectively coupled to the vehicle structure during rollover. In
addition, a European Commission sponsored study \55\ found that the
percentage of occupant mass coupled to the vehicle structure during
rollover is 90 percent for lap/shoulder belted occupants and 70 percent
for lap belted occupants. Based on the above research findings, the
agency tentatively concludes that the vehicle should be ballasted to
the full weight of 68 kg (150 lb) at all seating positions regardless
of ballast method. Using a lower weight ballast for the fixed ballast
setups does not appear to adequately simulate the loading conditions of
the average restrained occupant.
---------------------------------------------------------------------------

    \54\ Anderson, J., et al., ``Influence of Passengers During
Coach Rollover,'' Cranfield Impact Centre Ltd., ESV Proceedings,
Nagoya, Japan, Paper No. 216, 2003.
    \55\ Enhanced Coach and Bus Occupant Safety (ECBOS), Project No.
1999-RD.11130, European Commission, 5th Framework, August 2003.
---------------------------------------------------------------------------

    Second, ECE R.66 requires the rigid weight be fixed to the seat
such that its center of gravity aligns with that of the anthropomorphic
ballast (approximately 100 mm forward and 100 mm above the seating
reference point). In our research, the agency found it difficult to
position and fix the rigid weights according to this specification in a
consistent and repeatable manner.
    Given that difficulty, we investigated whether affixing the rigid
weights as specified by ECE R.66 is necessary. It

appears that the answer is no. As mentioned above, we analyzed the
effect of the different center of gravity heights for the
anthropomorphic ballasts and the fixed weight ballasts and found that
the difference in center of gravity would not significantly affect the
overall performance of the vehicle in the rollover test. Thus, assuming
that steel ballasts similar to those allowed in ECE R.66 are specified
in the final rule, the agency tentatively concludes that it would be
sufficient to locate the steel ballasts on top of the seat cushion,
since loading fixed ballasts to match the center of gravity of
anthropomorphic ballasts present significant logistical challenges,
without a noteworthy difference in the stringency of the test.
Vehicle Conditions
    To better ensure consistent and repeatable results, the proposed
test procedure also includes specifications for various vehicle
conditions. The proposed test specifies that the vehicle suspension is
blocked to its normal riding position and that the vehicle tires are
inflated to the manufacturer's recommended tire pressure. The proposed
procedure also specifies that vehicle windows, doors, and emergency
exits are fully closed and in the latched but unlocked positions. All
fluids in the vehicle, including fuel, will be at maximum capacity. For
environmental and test personnel safety, substitute fluids would be
permitted provided the weight of the original fluid is maintained.
    The agency recognizes that vehicle fluids have the potential to add
weight to the test specimen. As such, we request comment on whether
there are certain vehicle fluids whose levels should not be included in
the specifications for test conditions.

d. Survival Space

    To reduce unreasonable safety risks due to inadequate structural
integrity during a rollover, the agency is proposing to set minimum
standards for the structural integrity of the occupant compartment. We
are proposing to define a volume of space in the occupant compartment
(called the ``survival space'') and require that there shall be no
intrusion of the survival space by any part of the vehicle or by the
impact surface during movement of the tilting platform or resulting
from impact of the vehicle on the impact surface.
    The agency is concerned that inadequate survival space may result
in restrained occupants being injured by collapsing sidewalls, roof
structure, or other objects. As the agency is currently conducting
rulemaking to potentially require seat belts on the buses covered by
this proposed rulemaking, the agency is also interested in ensuring
that passengers (if belted) will be protected from further danger due
to collapsing vehicle structure that intrudes into the survival space.
Our research of the ECE R.66 test procedure showed that structural
intrusions into the survival space occurred in the MY 1991, MY 1992,
and MY 2000 buses. Our observations showed that the survival space
templates came into contact with the side windows in the rollover
structural integrity tests with the older buses. Further, our review of
the outside high-speed video of the test on the MY 2000 bus indicates
that the side pillars may have collapsed and intruded into the occupant
survival space.
Defining the Survival Space
    The proposed rule defines ``survival space'' in a manner similar to
ECE R.66's ``residual space.'' However, we propose to define the
survival space by establishing the boundaries of the three-dimensional
space, as opposed to the ECE R.66 method of defining the boundaries
through the use of transverse planes which intersect a seat reference
point. Thus, this NPRM proposes to define the survival space as a
three-dimensional volume with a front boundary beginning at the
transverse vertical plane 600 mm in front of the forward-most point on
the centerline of the front surface of the seat back of the forward-
most designated seating position. The rear boundary of the survival
space would be the inside surface of the rear wall of the occupant
compartment of the vehicle. Comments are requested as to whether the
term ``occupant compartment'' is clear.
    The vertical boundaries on both the left and right sides of vehicle
centerline are defined by three line segments (see Figure 6 below).
Segment 1 extends vertically from the floor to an end point that is 500
mm above the floor and 150 mm inboard of the side wall. Segment 2
starts at the end point of Segment 1 and extends to a point 750 mm
above and 250 mm horizontally inboard of the end point of Segment 1.
These values are used in ECE R.66. Segment 3 is a horizontal line
beginning at the end point of Segment 2 and extending to the vertical
longitudinal center plane of the vehicle.
    In proposing this requirement for a survival space, the agency
intends to ensure that the vehicle has sufficient structural strength
to ensure that the survival space during and after the rollover
structural integrity test is maintained. We intend the dimensions of
the survival space to define a volume of space that vehicles with a
minimally acceptable degree of structural integrity should provide. The
survival space requirement would serve as another indicator of the roof
and sidewall strength of the vehicle. The requirement would be a
reasonable proxy through which the agency could assess the adequacy of
the structural integrity of the vehicle.
    The agency tentatively believes that the increased structural
integrity countermeasures should be applied to substantially the entire
length of the vehicle. Thus, this NPRM proposes a survival space volume
which runs the length of the area that can be occupied by the driver
and by the passengers. Therefore, this proposed rule defines the front
boundary of the survival space as 600 mm in front of the forward-most
point on the centerline of the forward-most designated seating
position. Additionally, the proposed rule defines the rear boundary as
the rear inside wall of the occupant compartment.
    The agency proposes to set the vertical boundary of the survival
space using the three line segments outlined above and illustrated in
Figure 6 below. These three line segments mirror the equivalent
vertical boundaries used in the ECE R.66 test. The agency tentatively
believes that the vertical boundaries of the survival space from the
ECE regulation are appropriate for application in this proposed rule
for several reasons. The vertical boundary appears reasonably related
to the occupant space. Photographs from the MY 2000 MCI test report
show the location of the vertical boundary of the survival space as
just about level with the top of the head of the seated HIII 50th
percentile adult male test dummies in the seat. ``ECE Regulation 66
Based Research Test of Motorcoach Roof Strength, 2000 MCI 102-EL3
Series Motorcoach, NHTSA No.: MY0800,'' October 1, 2009, supra. (We
have also placed in the docket for this NPRM other photographs of the
test dummies seated in front of survival space templates.) In addition,
as increasing or decreasing the height of the vertical boundaries of
the survival space could significantly alter the stringency of the
rollover structural integrity test, the agency believes that there is a
strong interest in maintaining similar requirements to ECE R.66 so as
to reduce the regulatory burden on manufacturers having to comply with
different European and U.S. standards.
    Further, as all the older model buses tested by the agency were
unable to

meet the survival space requirements \56\ yet current vehicles in
Europe are approved as meeting the requirements, the agency believes
that setting the same vertical limits of the survival space increases
the likelihood of the practicability of the U.S. standard. Therefore,
the agency tentatively believes that this definition of the survival
space is an appropriate, practical, and practicable proxy for ensuring
that the roof and sidewalls will be able to withstand the racking
forces of rollover crash.
---------------------------------------------------------------------------

    \56\ We note that while the survival space templates in the MY
2000 motorcoach did not come into contact with objects outside of
the survival space during the test, we observed intrusions into the
survival space separate from the survival space templates.
---------------------------------------------------------------------------

    Comment is requested on the need and basis for different boundaries
for the survival space.
[GRAPHIC] [TIFF OMITTED] TP06AU14.011

Determining Intrusions Into the Survival Space
    The NPRM proposes to prohibit any object that is outside the
survival space from entering the survival space. Comments are requested
on the use of survival space templates as tools in helping determine if
there was intrusion into the survival space. Use of templates is
consistent with ECE R.66. The templates are 1,250 mm (50.2 inches) tall
and are tapered from the sidewall a distance of 150 mm (5.9 inches) at
the bottom and 400 mm (15.8 inches) at the top.
    We anticipate using several survival space templates within the
survival space to assist us in determining whether there was intrusion
into the survival space. The templates would

contain a transfer medium (such as chalk or another substance capable
of demonstrating contact between two objects) along the upper edge of
each template. Transfer marks from contact with the survival space
templates would demonstrate that an object intruded into the survival
space during movement of the tilting platform or resulting from impact
of the vehicle on the impact surface.
    We plan on securing the survival space templates to the vehicle
floor such that they remain in their installed location during the
test. We recognize, however, depending on seat placement and
attachment, seats may have to be removed or shifted to accommodate the
placement of the survival space templates or other testing equipment.
Thus, we would move the seats forward or rearwards to make room for the
equipment if the seat spacing is adjustable. If the seat spacing is not
adjustable, we would remove seats from the vehicle and allow ballasts
representing the weight of the seat and its occupants to be secured to
the vehicle floor either forward or rearward of the original seat
placement (within a specified tolerance \57\). Comments are requested
on these procedures.
---------------------------------------------------------------------------

    \57\ The proposed text in this NPRM limit the placement of these
ballasts to no farther forward than the forward-most point of the
motorcoach seat directly in front of the removed seat and no farther
rearward than the rearmost point of the motorcoach seat directly
behind the removed seat.
---------------------------------------------------------------------------

    We emphasize that the templates are simply tools to assist in
determining whether there was intrusion into the survival space. If an
object intruded into the survival space without contacting the
templates--such as if a television monitor fell into the survival
space--that intrusion could be a noncompliance, even if contact with
the templates did not occur. Other tools could also be used to help
determine whether there was intrusion into the survival space, such as
deformable templates, high speed video, photography, or a combination
of means. NHTSA could use templates and/or other means of determining
whether intrusion occurred.

e. Overhead Luggage Rack and Seat Retention

    The agency is proposing a retention requirement for overhead
luggage racks and the passenger seats. The proposed retention
requirement is that each anchorage of an overhead luggage rack or seat
shall not completely separate from its mounting structure during
movement of the tilting platform or resulting from impact of the
vehicle on the impact surface.
    The NTSB identified overhead luggage racks as a safety concern in
its investigation of the Sherman, Texas bus crash. The right side
overhead luggage rack anchorages completely detached from the nine
brackets at the connection points and fell diagonally across the aisle
onto the passengers. NTSB stated that ``several passengers' heads
contacted the overhead luggage rack and, although investigators were
unable to determine exactly when in the accident sequence passenger
injuries took place, it is possible that serious head or neck injury
resulted from the interactions between the passengers and the overhead
luggage rack.''
    Our research confirms the possibility of this danger. In the tests
conducted by the agency, the overhead luggage rack on the older MCI bus
broke, exposing sharp edges that pose a risk of injury to passengers.
The overhead luggage racks did not break during testing of the newer MY
2000 MCI bus. We thus acknowledge that, while this was one test, the
finding indicated a possibility that manufacturers may have made some
improvements to the strength of luggage rack mounts. It also indicates
the practicability of meeting the proposed requirement.
    The overhead luggage rack retention requirement is an additional
way of ensuring that vehicles provide a minimum level of structural
integrity. The vehicle will have to limit its deformation and racking
\58\ in the rollover structural integrity test, to ensure that the
overhead luggage racks meet the retention requirement. The requirement
would also reduce the risk that overhead luggage racks could be
dislodged and injure occupants or block or impede emergency egress.
---------------------------------------------------------------------------

    \58\ The term, ``racking,'' means the tilting of the sides of
the bus relative to the bus floor.
---------------------------------------------------------------------------

    The retention requirement would apply to luggage racks regardless
of their position relative to the survival space. Suppose, in the
rollover structural integrity test, an overhead luggage rack separates
from its mounting structure and one of its anchorages completely
separated from the anchorage's mounting structure but the overhead
luggage rack does not enter the survival space. We would consider that
to be a failure to meet the retention requirement.
    With regard to the seats in these buses, the agency is also
concerned about the strength of the anchorages that secure the seats to
the vehicle. The tests conducted by NHTSA revealed the possibility that
seat anchorages have the potential to break and cause injury to
passengers in these buses. In our test of the MY 1991 Prevost LeMirage
bus, all seat anchorages detached from their sidewall mounting
anchorages and the seat with the restrained occupant completely
separated from its anchorages and fell with the test dummy still
attached to the seat. We acknowledge that manufacturers may have made
improvements since the manufacture of that MY 1991 Prevost bus. Also,
seat anchorages would likely be strengthened if these buses had to meet
the requirements under development for passenger seat belts. However,
the agency believes it is highly important for passenger safety that
the vehicle structure limit deformation and racking of the sidewall,
such that the passenger seats will remain attached to the vehicle in a
rollover (particularly if passengers are restrained to the seat). It is
important to ensure the structural integrity of the bus in a rollover
will enable the seat anchor to withstand the load of the seat and that
of the restrained occupant.
    Compliance would be assessed by inspection of the component's
mounting structure. We propose to permit the anchorage to be damaged or
deformed during the course of the rollover, but we would prohibit any
one anchorage from completely separating with the mounting structure. A
complete separation is indicative of unacceptable structural integrity.
    Comments are requested as to what other items should be covered by
these retention requirements (e.g., television monitors). Please
provide data supporting the safety need for your suggestion. What
methods are available to the agency to objectively and practicably
evaluate the retention of the item?

f. Emergency Exits

    The agency is not only concerned with the protection of belted
occupants, but also with protecting unbelted occupants. The agency
recognizes there is a possibility that not all occupants traveling in
the buses covered by today's proposal will be restrained at all times
during travel. For instance, passengers may need to occasionally move
about the occupant compartment during long, intercity journeys.
Further, MAP-21 directs the agency to consider ``portal improvements to
prevent partial and complete ejection of motorcoach passengers.'' \59\
Thus, the agency is considering--as a part of this rulemaking--
requirements that emergency exits remain latched so as to

avoid becoming an ejection portal for unrestrained occupants.
---------------------------------------------------------------------------

    \59\ See Moving Ahead for Progress in the 21st Century Act, Pub.
L. 112-141, Sec.  32703(b)(2).
---------------------------------------------------------------------------

    In the ECE R.66 tests conducted by the agency in support of this
NPRM, the emergency roof exits of all the tested buses (new and old)
opened upon impact of the bus with the impact surface. The agency is
concerned that emergency roof exits may become ejection portals through
which unrestrained passengers could be ejected during a rollover crash.
Therefore, the agency has proposed a requirement in today's NPRM that
all emergency exits shall not open during the rollover structural
integrity test. While the agency has tentatively determined that this
requirement (remaining closed during and after the rollover test) would
be appropriate for the emergency exits, the agency also requests
comments on whether other similar openings exist in the bus that could
also become ejection portals in a similar fashion to emergency exits
and whether they should also be subject to the proposed requirements.
For example, are there other windows or roof hatches that are designed
to open in buses that are not emergency exits? Do these openings have
similar safety concerns?
    In addition, for emergency exits, NHTSA also seeks to increase the
likelihood that roof and rear door emergency exits are operable after a
rollover crash.\60\ Inoperable emergency exits would impede emergency
egress and emergency rescue efforts. Accordingly, we have proposed to
require that the emergency exits on the roof and at the rear of the bus
(installed to fulfill the emergency exit requirements of FMVSS No. 217)
be able to operate as required under FMVSS No. 217 after the impact.
The agency tentatively concludes that these requirements are necessary
to ensure that these emergency exits are operable after being exposed
to the racking forces of rollover crashes.
---------------------------------------------------------------------------

    \60\ The provisions of MAP-21 also direct the agency to consider
the impact of portal improvement standards on the use of motorcoach
portals as a means of emergency egress. See id.
---------------------------------------------------------------------------

    Note that we have tentatively concluded not to apply the above
requirements (that the emergency exits be operable as required under
FMVSS No. 217) to side emergency exit windows. A requirement that
window exits facing the impact surface must open upon application of