[Federal Register Volume 81, Number 88 (Friday, May 6, 2016)]
[Proposed Rules]
[Pages 27903-27932]
[FR Doc No: 2016-10418]

Vol. 81

Friday,

No. 88

May 6, 2016

Part III

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 Emergency Exits and Window
Retention and Release, Anti-Ejection Glazing for Bus Portals; Proposed
Rule

Federal Register / Vol. 81 , No. 88 / Friday, May 6, 2016 / Proposed
Rules

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2016-0052]
RIN 2127-AL36

Federal Motor Vehicle Safety Standards; Bus Emergency Exits and
Window Retention and Release, Anti-Ejection Glazing for Bus Portals

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

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This NPRM proposes a new Federal Motor Vehicle Safety Standard
(FMVSS) No. 217a, ``Anti-ejection glazing for bus portals,'' to drive
the installation of advanced glazing in high-occupancy buses
(generally, over-the-road buses (of any weight) and non-over-the-road
buses with a gross vehicle weight rating greater than 11,793 kilograms
(26,000 pounds). The new standard would specify impactor testing of
glazing material. In the tests, a 26 kilogram (57 pound) impactor would
be propelled from inside a test vehicle toward the window glazing at
21.6 kilometers/hour (13.4 miles per hour). The impactor and impact
speed would simulate the loading from an average size unrestrained
adult male impacting a window on the opposite side of a large bus in a
rollover. Performance requirements would apply to side and rear
windows, and to glass panels and windows on the roof to mitigate
partial and complete ejection of passengers from these windows and to
ensure that emergency exits remain operable after a rollover crash.
NHTSA also proposes to limit the protrusions of emergency exit latches
into emergency exit openings of windows to ensure they do not unduly
hinder emergency egress.
    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, to the extent warranted under the National
Traffic and Motor Vehicle Safety Act, establishing advanced glazing
standards for the side and rear portals of the subject buses 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 July 5, 2016.

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>). For legal issues: Ms. Deirdre Fujita, Office of
the Chief Counsel (telephone:<PHONE_NUMBER>) (fax:<PHONE_NUMBER>). The
mailing address for these officials is: National Highway Traffic Safety
Administration, 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 and 2012 Update
    d. NTSB Recommendations
    e. NHTSA's Previous Work on Motorcoach Crashworthiness Standards
    1. Seat Belt Final Rule
    2. Rollover Structural Integrity NPRM
III. Safety Need
    a. Overview
    b. FARS Data
IV. Research
    a. Joint NHTSA and Transport Canada Motorcoach Program (Martec
Study)
    b. NHTSA's Motorcoach Side Glazing Research
    1. Testing on the MCI D-Series Motorcoach Section Emergency Exit
Side Windows
    2. Testing of MCI, Prevost, and Van Hool Emergency Exit Windows
and Latches on Test Frames
    3. Testing of MCI, Prevost, and Van Hool Emergency Exit Windows
With Countermeasure Latches
    4. Pre-Broken Glazing Impact Tests of MCI E/J-Series Emergency
Exit Windows With Countermeasure Latches
    5. Testing of MCI E/J-Series Fixed Windows (Martec Study
Conditions)
    c. NHTSA's Large Bus Rollover Structural Integrity Research
    1. MY 1991 Prevost Bus
    2. MY 1992 MCI Bus
    3. MY 2000 MCI Bus
V. Overview of Proposed Requirements
VI. Test Procedure Specifications
    a. Impactor
    b. Test Speed
    c. ``Portal'' Improvements
    d. Definition of Daylight Opening
    e. Glass Breakage Procedure
VII. Performance Requirements
    a. Unbroken Glazing
    b. Broken Glazing
VIII. Other Proposed Requirements
    a. Latch Protrusions
    b. Latch Workable After Impact
IX. Applicability
X. Retrofitting
XI. Lead Time
XII. Additional MAP-21 Considerations
XIII. Overview of Benefits and Costs
XIV. Regulatory Notices and Analyses
XV. Public Participation

I. Executive Summary

    One of the factors NHTSA considers in determining the priorities of
our rulemaking projects is to ensure the protection of passengers in
high-occupancy vehicles. In 2007, NHTSA published a comprehensive plan
pertaining to improvements in motorcoach safety.\1\ NHTSA developed
this plan in response to several National Transportation Safety Board
(NTSB) recommendations, and also to focus agency resources and research
on improving the safety of these vehicles. NHTSA's motorcoach safety
plan identified four specific areas where we could most effectively
address open NTSB recommendations and most expeditiously achieve our
goals. The four priority areas were: Requiring seat belts (minimizing
passenger and driver ejection from the motorcoach), improved roof
strength, emergency evacuation, and fire safety.\2\
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    \1\ Docket No. NHTSA-2007-28793, NHTSA's Approach to Motorcoach
Safety. In NHTSA's plan, ``motorcoach'' referred to inter-city
transport buses.
    \2\ Motorcoach safety was also the focus of a DOT-wide action
plan. DOT issued a Departmental Motorcoach Safety Action Plan in
2009 which addressed additional factors such as driver fatigue and
operator maintenance schedules. An update to the 2009 plan was
published in December 2012, see http://www.fmcsa.dot.gov/sites/fmcsa.dot.gov/files/docs/Motorcoach-Safety-Action-Plan-2012.pdf.

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    Work on NHTSA's safety plan is ongoing. In 2013, the agency
published a final rule \3\ requiring seat belts for each passenger
seating position in all new over-the-road buses (OTRBs) \4\ regardless
of bus GVWR, and in new ``other'' buses (i.e., large buses other than
OTRBs \5\) with GVWRs greater than 11,793 kilograms (kg) (26,000 pounds
(lb)). In 2014, NHTSA published an NPRM proposing that these buses, and
prison buses, meet increased structural integrity requirements to
protect both restrained and unrestrained occupants in rollover
crashes.\6\ NHTSA also has issued a final rule on electronic stability
control \7\ and has completed research studies on improved motorcoach
emergency evacuation and fire safety.\8\
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    \3\ 78 FR 70416; November 25, 2013.
    \4\ An over-the-road bus is a bus characterized by an elevated
passenger deck located over a baggage compartment. Excluded from the
seat belt requirement are school buses and prison buses.
    \5\ Some buses are also excluded from this latter category, such
as transit and school buses, prison buses, and perimeter seating
buses.
    \6\ 79 FR 46090; August 6, 2014.
    \7\ 80 FR 36050; June 23, 2015.
    \8\ For research reports on emergency evacuation, see Docket No.
NHTSA-2007-28793-22 and -24. For fire safety, Docket No. NHTSA-2007-
28793-0027.
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    Today's NPRM complements the 2014 rollover structural integrity
NPRM to further minimize passenger and driver ejection from
motorcoaches and other large buses. It also enhances emergency
evacuation from the vehicle.
    This advanced glazing NPRM also fulfills a statutory mandate on
motorcoach safety set forth in the ``Moving Ahead for Progress in the
21st Century Act'' (MAP-21). On July 6, 2012, President Obama signed
MAP-21, which incorporated the ``Motorcoach Enhanced Safety Act of
2012'' in subtitle G (sections 32701 et seq.). Among other matters, the
Motorcoach Enhanced Safety Act requires the DOT to ``prescribe
regulations that address the following commercial motor vehicle
standards,'' if the Secretary determines that such standards meet the
requirements and considerations set forth in subsections (a) and (b) of
section 30111 of title 49, United States Code (section 32703(b)).
Section 32703(b)(2) of MAP-21 states that the DOT ``shall consider
requiring advanced glazing standards for each motorcoach portal and
shall consider other portal improvements to prevent partial and
complete ejection of motorcoach passengers, including children.'' \9\
Under MAP-21 (section 32702), ``advanced glazing'' means glazing
installed in a portal on the side or the roof of a motorcoach that is
designed to be highly resistant to partial or complete occupant
ejection in all types of motor vehicle crashes.
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    \9\ Under MAP-21 (sec. 32702), ``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. ``Portal'' is also defined in sec. 32702. The
definitions are discussed further later in this preamble.
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    This NPRM proposes new requirements, in an FMVSS No. 217a, to drive
the installation of advanced glazing in portals \10\ of covered buses
(buses subject to the proposed rollover structural integrity
requirements, except for prison buses).\11\ The tests are based on
procedures developed by NHTSA and Transport Canada to improve
motorcoach glazing and bonding techniques to prevent ejections.
(``Motor Coach Glazing Retention Test Development for Occupant Impact
During a Rollover,'' Martec Technical Report #TR-06-16, Rev 4, August
2006 (``Martec study'').) The proposed test procedures are also based
on a follow-on NHTSA research study.\12\
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    \10\ A portal is an opening that could permit partial or
complete ejection of an occupant from the vehicle in the event of a
crash involving the vehicle.
    \11\ We have proposed these requirements by way of a newly
proposed FMVSS No. 217a. If a final rule is issued, we may keep the
requirements in Standard No. 217a or we may incorporate them into
FMVSS No. 217.
    \12\ ``Motorcoach Side Glazing Retention Research, ``NHTSA
Report DOT HS 811 862, http://www.nhtsa.gov/Research/ci.Defects+Analysis+and+Crashworthiness+Division.print, Last
accessed on December 23, 2015.
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    The glazing types currently used in the motorcoach industry for
side windows are single-pane laminated glass, single-pane tempered (or
``toughened'') glass, or a double-pane of either laminated or tempered
glass or a combination of both. A single-pane laminated glass actually
contains two thin glass layers held together by an interlayer,
typically of polyvinyl butyral (PVB). The interlayer works to keep the
outer layers of glass bonded together in the event they break or crack,
and prevents the formation of large shards of sharp glass. Laminated
glass may crack or splinter upon impact with the ground, but can still
provide a means of keeping passengers within the occupant compartment
of the bus if the glazing is retained within the window frame, the PVB
interlayer is not excessively torn or punctured, and the window latch
remains closed. We believe that laminated glass could meet the
requirements proposed in this NPRM. We consider glass meeting the
requirements to be ``advanced glazing.''
    Tempered glass is glass processed with controlled thermal or
chemical treatments. These treatments increase the strength of the
glass, and also create balanced internal stresses so that when the
glass does break, it breaks or crumbles into smaller granular chunks
instead of large jagged shards. Tempered glass is stronger than
laminated glass, but with tempered glass, occupant loading to the
window during the rollover event and the bus impact with the ground can
potentially shatter tempered glass, causing the glazing to vacate the
window frame and create an ejection portal.
    NHTSA is proposing performance requirements that covered buses
would have to meet by way of anti-ejection safety countermeasures to
prevent partial and complete ejection of passengers. We would adopt a
new FMVSS No. 217a that specifies impactor testing of glazing material.
In the tests, a 26 kg (57 lb) impactor would be propelled from inside
the test vehicle toward the window glazing at 21.6 kilometers per hour
(km/h) (13.4 miles per hour (mph)). Each side and rear window and glass
panel/window on the roof would be subject to any one of three impacts,
as selected by NHTSA in a compliance test: (a) An impact near a
latching mechanism of an intact window \13\; (b) an impact at the
center of the daylight opening \14\ of an intact window; and (c) an
impact at the center of the daylight opening of a pre-broken window.
The impactor and impact speed in these proposed tests, developed in the
Martec study, simulate the loading from an average size adult male
impacting a window on the opposite side of a large bus in a rollover.
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    \13\ For non-emergency exit fixed side and rear windows and
fixed glass panels on the roof, the proposed test would be conducted
at the location of one of the fixed latches or discrete attachment
points. For fully rubber bonded or glued windows with no latch
mechanisms, the test would be conducted along the center of the
lower window edge one inch above the daylight opening periphery.
    \14\ Center of daylight opening is the center of the total
unobstructed window opening that would result from the removal of
the glazing.
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    The proposed performance requirements are as follows:
     In tests described in (a) and (b) in the previous
paragraph, the window would have to prevent passage of a 102 millimeter
(mm) (4 inch) diameter sphere during the impact, and after the test.
The agency would assess the window during the impact by determining
whether any part of the window passes a reference plane defined during
a pre-test set up procedure. These requirements would ensure that
glazing is securely bonded to window frames, no potential ejection
portals are created due to breaking of

the glass, and the windows remain closed when impacted.
     In the test of (c) above, the maximum displacement of the
impactor at the center of daylight opening would be limited to 175 mm
(6.9 inches) for pre-broken glazing. This requirement in particular
would drive the installation of advanced glazing. The requirement would
also help ensure the advanced glazing reasonably retains occupants
within the structural sidewall of the bus even when the glass
surrounding the PVB interlayer is broken. It also ensures that no
potential ejection portals are created during and after impact.
     Emergency exit latch protrusions may not extend more than
one inch into the emergency exit opening of the window when the window
is opened to the minimum emergency egress opening (allowing passage of
an ellipsoid 500 mm (19.7 inches) wide by 300 mm (11.8 inches) high).
This requirement would minimize the potential for the latch plate
protrusions (or other projections) to hinder the emergency egress of
passengers.
     Latches would have to be functional following the impact
test to ensure that occupants can open the emergency exits to egress
the vehicle after the crash.
    The Motorcoach Enhanced Safety Act emphasizes anti-ejection safety
countermeasures, particularly advanced glazing (Sec.  32703(b)(2)).
With regard to advanced glazing standards, NHTSA's strategy has been
first to seek improvements to the rollover structural integrity of
motorcoaches (roof strength and crush resistance) and then to pursue
measures that would drive use of advanced glazing. This ordered
approach is based on findings from the Martec study that found the
integrity of the bus structure has a profound impact on the
effectiveness of glazing as an anti-ejection safety countermeasure.
That is, in the absence of a threshold of requisite performance for bus
structural integrity, a twisting motion of a bus in a rollover could
simply pop out any advanced glazing used in the windows and negate the
potential benefits of the glazing in mitigating occupant ejection.
    To better ensure that the full benefits of anti-ejection
countermeasures such as advanced glazing could be realized, we adopted
a holistic approach. We first focused on improving bus structural
integrity and the strength of side window mountings. The 2014 NPRM on
large bus structural integrity proposed requirements that would
increase the likelihood that bus glazing will be retained in their
mountings in a rollover.\15\ Next in our strategy is issuance of
today's NPRM, which has performance requirements that would increase
use of advanced glazing that prevent partial or complete ejection of
motorcoach passengers and further ensure the integrity of glazing
mounting. Today's NPRM directly addresses the directive in section
32703(b)(2) of the Motorcoach Enhanced Safety Act that NHTSA consider
requiring advanced glazing standards for each motorcoach portal.
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    \15\ The 2014 rollover structural integrity NPRM proposes
performance requirements that must be met when the bus is tipped
over from an 800 mm (31.5 inch) raised platform onto a hard level
surface. Among other requirements, the proposed standard would
require that the occupant ``survival space'' (space around occupant
seating positions) be maintained during and after the dynamic test,
and that side window glazing opposite the impacted side of the
vehicle remain attached to its mounting such that there is no
opening that will allow the passage of a 102 mm (4 inch) diameter
sphere. These proposed requirements would help ensure glazing is
retained in the windows by limiting the twisting motion of a bus and
strengthening window mountings.
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    We have designed this NPRM in furtherance of NHTSA's goal to
enhance the safety of all heavy buses used in intercity bus
transportation, while attending to the Motorcoach Enhanced Safety Act's
focus on over-the-road buses (motorcoaches). Since today's NPRM builds
on the 2014 rollover structural integrity NPRM, we propose to apply
today's advanced glazing proposal to the vehicles subject to the 2014
NPRM.16 17
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    \16\ With the exception of prison buses. We have tentatively
determined that an advanced glazing standard would not be
appropriate for prison buses since these buses typically have bars
over the windows.
    \17\ Note that this NPRM proposes requirements limiting how far
emergency exit latches may protrude into the exit space. We propose
applying the requirement to the buses to which NHTSA proposed would
be subject to the 2014 structural integrity NPRM, except prison
buses. We are also proposing to apply the requirement to school
buses, and are considering applying the proposed maximum emergency
exit latch protrusion requirements to all buses governed under FMVSS
No. 217. Comments are requested on this issue.
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    NHTSA estimates that this rulemaking would be cost beneficial.\18\
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    \18\ 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 the Docket at the address or
telephone number provided at the beginning of this document.
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    The agency estimates an annual incremental material cost for all
new buses covered by this proposed rule to be $0.19 million (see Table
1 below). The countermeasures would likely be advanced glazing and
improved emergency exit latches, resulting in an average incremental
material cost per bus of $87 for buses covered under today's proposed
rule. We estimate the testing cost of $8,700 per bus model. We estimate
there would be no weight increase due to the proposed requirements; in
fact, there could be a weight reduction of approximately 10.5-15 kg
(23-33 lb) per window (125.5-180 kg (276-396 lb) per bus) as glazing
designs change from a double-glazed tempered/tempered configuration to
a single-glazed laminated configuration. We estimate that the proposal
would result in fuel saving of $2.18 million to $2.9 million. This
exceeds the material costs of $0.19 million for the proposal.
    Beyond the benefits attributable to the agency's final rules on
seat belts and ESC and a potential final rule on rollover structural
integrity that also may apply to the subject buses, we estimate that
requiring new subject buses to meet the proposed performance criteria
would save 1.54 lives and prevent 0.4 serious to critical injuries
annually if 15 percent of occupants use seat belts, and save 0.33 lives
and prevent 0.08 serious to critical injuries annually if 84 percent of
occupants use seat belts. Thus, we estimate that this proposal would
save 1.6 equivalent lives annually (undiscounted) if 15 percent of
occupants use seat belts, and 0.34 equivalent lives annually
(undiscounted) if 84 percent of occupants use seat belts (see Table 2,
below).\19\
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    \19\ NHTSA used the same low seat belt usage rate estimate of 15
percent from the November 25, 2013 final rule requiring seat belts
on motorcoaches and other large buses (78 FR 70416). The agency also
utilized the same source of information to establish the high seat
belt usage rate estimate (the National Occupant Protection Use
Survey). Today's NPRM uses the 2009 data which estimates seat belt
use of passenger vehicles to be 84 percent. See 2009 National
Occupant Protection Use Survey. More information at: http://www-nrd.nhtsa.dot.gov/pubs/811100.pdf.
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    Since the fuel savings from the proposed rule would be far greater
than the material costs of this proposal, we did not estimate cost per
equivalent lives saved. The estimated net cost/benefit impact ranges
from a net benefit of $5.87 million to $17.52 million at the 3 percent
discount rate and a net benefit of $4.37 million to $13.15 million at
the 7 percent discount rate (see Table 3, below).

                     Table 1--Estimated Annual Costs
                             [2013 dollars]
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              Potential costs
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Material Costs Per Vehicle................  $87
Material Costs, Total New Fleet...........  $0.19 Million
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                   Table 2--Estimated Annual Benefits
                  [Undiscounted equivalent lives saved]
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15 percent belt usage.....................................          1.6
84 percent belt usage.....................................          0.34
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                                        Table 3--Annualized Net Benefits
                                          [In millions of 2013 dollars]
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                       Discount rate                            Benefits          Net costs       Net benefits
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3%........................................................      $13.22-$2.82     ($4.30-$3.05)      $17.52-$5.87
7%........................................................       $9.95-$2.12     ($3.20-$2.25)      $13.15-$4.37
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    NHTSA has considered retrofit requirements and has made the
following tentative conclusions. The agency does not believe it would
be sensible to apply the requirements proposed today to buses that do
not have sufficient structural integrity to retain the advanced glazing
in a rollover. If the advanced glazing were to pop out in a rollover,
the benefits of the glazing would not be achieved. Yet, Congress was
particularly interested in a possible retrofit requirement for advanced
glazing. 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 section 32703(b)(2),
regarding advanced glazing, to motorcoaches manufactured before the
date on which the requirement applies to new motorcoaches. Thus, NHTSA
is requesting comments on the feasibility, benefits, and costs of any
potential requirement to retrofit existing buses with advanced glazing.

II. Background

a. NHTSA's Statutory Authority

    NHTSA is proposing today's NPRM pursuant to and in accordance with
its authority under the National Traffic and Motor Vehicle Safety Act
and the relevant provisions of MAP-21.
National Traffic and Motor Vehicle Safety Act (Vehicle Safety Act)
    Under 49 United States Code (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 (section 30111(a)). ``Motor vehicle safety'' is defined
in the Vehicle Safety Act (section 30102(a)(8)) 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 standard for motor vehicles or motor vehicle
equipment performance (section 30102(a)(9)). When prescribing such
standards, the Secretary must consider all relevant available motor
vehicle safety information (section 30111(b)(1)). The Secretary must
also consider whether a proposed standard is reasonable, practicable,
and appropriate for the particular type of motor vehicle or motor
vehicle equipment for which it is prescribed (section 30111(b)(3)) and
the extent to which the standard will further the statutory purpose of
reducing traffic accidents and associated deaths and injuries (section
30111(b)(4)). The responsibility for promulgation of FMVSSs is
delegated to NHTSA (49 CFR 1.95).
MAP-21 (Incorporating the Motorcoach Enhanced Safety Act of 2012)
    On July 6, 2012, President Obama signed MAP-21, which incorporated
the ``Motorcoach Enhanced Safety Act of 2012'' into subtitle G. Section
32703(b) of MAP-21 requires the Secretary to prescribe regulations 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 subsections (a) and (b) of section
30111 of the Vehicle Safety Act.
    Section 32703(b)(2) of MAP-21 directs the Secretary to consider
requiring advanced glazing standards for each motorcoach portal and to
consider other portal improvements to prevent partial and complete
ejection of motorcoach passengers, including children. Under section
32702, ``portal'' means any opening on the front, side, rear, or roof
of a motorcoach that could, in the event of a crash involving the
motorcoach, permit the partial or complete ejection of any occupant
from the motorcoach, including a young child. Section 32703(b)(2) also
states that in prescribing such standards, the Secretary shall consider
the impact of such standards on the use of motorcoach portals as a
means of emergency egress.
    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
32702 of MAP-21 excludes transit buses and school buses from the
``motorcoach'' definition.
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    \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.''
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    MAP-21 sets forth compliance dates. It directs the Secretary to
apply any regulation prescribed in accordance with section 32703(b)
(and several other subsections) to all motorcoaches manufactured more
than 3 years after the date on which the regulation is published
(section 32703(e)(1)). In addition, the Secretary may assess the
feasibility, benefits, and costs of applying any requirement
established under section 32703(b)(2) to ``motorcoaches manufactured
before the date on which the requirement applies to new motorcoaches''
(retrofit) (section 32703(e)(2)).
    Finally, MAP-21 also authorizes the Secretary to combine the
required rulemaking actions as the Secretary deems appropriate (section
32706(b)).

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,'' \21\ in which we identified the following areas as the
highest priorities for possible near term regulatory action to enhance
motorcoach safety: (1) Seat belts; (2) improved roof strength; (3)
emergency evacuation; and (4) fire safety. For addressing passenger
ejection (action (1) above), we first pursued the incorporation of
passenger seat belts as the most expeditious way to mitigate ejection.
The agency's seat belt rulemaking, discussed further in subsection (e)
below, began NHTSA's implementation of our Motorcoach Safety Plan.
Today's NPRM further advances the implementation of the plan.
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    \21\ Docket No. NHTSA-2007-28793-001.
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c. DOT's 2009 Task Force Action Plan and 2012 Update

    In 2009, DOT issued a Departmental ``Motorcoach Safety Action
Plan,'' which outlined a Department-wide strategy to enhance motorcoach
safety.\22\ An update of the plan was issued in December 2012.\23\ In
addition to the four priority action items specified in NHTSA's 2007
plan, the DOT plan discussed additional factors for enhancing
motorcoach safety, such as electronic stability control systems, event
data recorders, and driver fatigue and operator maintenance issues.
Departmental agencies continue to work on the motorcoach safety
initiatives related to their administrations.
---------------------------------------------------------------------------

    \22\ https://www.fmcsa.dot.gov/sites/fmcsa.dot.gov/files/docs/MotorcoachSafetyActionPlan_final2009report-508.pdf.
    \23\ http://www.fmcsa.dot.gov/safety/passenger-safety/motorcoach-safety-action-plan-2012.
---------------------------------------------------------------------------

d. NTSB Recommendations

    This NPRM addresses the following NTSB recommendations pertaining
to window glazing and emergency exits.
H-99-049
    NTSB initiated a special investigation reviewing 36 motorcoach
crashes that were investigated from 1968 through 1997.\24\ It found
that of the 168 occupant fatalities, 106 occurred in crashes involving
a rollover. Of those 106 fatalities, 64 were ejected from the bus.
---------------------------------------------------------------------------

    \24\ NTSB/SIR-99/04 PB98-917006; Highway Special Investigation
Report: Bus Crashworthiness Issues; September, 1999.
---------------------------------------------------------------------------

    NTSB also found that glazing composition may mitigate injury during
a rollover event. In one investigation of a 1988 crash,\25\ a 1987
Motor Coach Industries, Inc., intercity-type coach overturned on its
right side and slid 220 feet across the highway before coming to rest.
There was no intrusion into the occupant compartment and no fatalities.
Forty-nine passengers and the driver sustained minor to severe injuries
such as fractured ribs, lacerations, abrasions, and contusions. The 27
passengers on the left side were thrown from their seats and fell on
top of the 22 right side passengers during the overturn sequence;
however, all of the passengers were contained within the coach through
the event. NTSB determined that because the bus's abrasive-resistant,
coated acrylic windows did not break, the passengers may have been
afforded protection from contacting the road surface and possibly
sustaining more serious or even fatal injuries. NTSB concluded that
buses equipped with advanced glazing may decrease the number of
ejections of unrestrained passengers and reduce the risk of serious
injury to restrained passengers during bus crashes, particularly
rollover events. NTSB issued the following recommendation to NHTSA:
---------------------------------------------------------------------------

    \25\ NTSB/HAR-89/01/SUM PB89-916201; Highway Accident Summary
Report: Intercity-Type Buses Chartered for Service to Atlantic City;
April 1989.
---------------------------------------------------------------------------

    ``H-99-049: Expand your research on current advanced glazing to
include its applicability to motorcoach occupant ejection prevention,
and revise window glazing requirements for newly manufactured
motorcoaches based on the results of this research.''
H-11-037
    On August 5, 2010, a multi-vehicle accident occurred in Gray
Summit, Missouri, involving a 2007 Volvo tractor, a 2007 GMC Sierra
extended cab pickup truck, a 2003 Blue Bird 71-passenger bus (``lead
school bus''), and a 2001 Blue Bird 72-passenger bus (``following
school bus''). This multi-vehicle crash was investigated by NTSB in
2011.\26\ In the collision, the lead school bus sustained moderate
front-end damage from colliding into the back of the Sierra pickup and
the rear of the Volvo tractor. Additionally, the rear of the lead
school bus was severely damaged as a result of being impacted and
overridden by the following school bus.
---------------------------------------------------------------------------

    \26\ NTSB/HAR-11/03 PB2011-916203; Multivehicle Collision
Interstate 44 Eastbound Gray Summit, Missouri, August 5, 2010;
December 2011.
---------------------------------------------------------------------------

    The only emergency exits available for egress on the lead school
bus were the rear two emergency exit windows. All but one of the
occupants in the lead bus exited the bus through the left rear
emergency exit window. The remaining entrapped passenger was extricated
by emergency responders and placed on a backboard before being removed
through the right rear emergency exit window.
    Several passengers in the lead school bus, and a witness who
assisted in the evacuation, stated in post-crash interviews that
emergency egress was hindered by the design of the emergency exit
window. Particularly, the 4 inch by 3 inch emergency release latch
plate for the emergency exit window was elevated about 1 inch from the
window base and snagged the clothing of several passengers as they were
exiting through the window opening. In addition, because of the failure
of the emergency exit window to independently remain in the open
position, one individual had to hold the hinged emergency exit window
open so that other individuals could exit the bus unimpeded.
    NTSB made three safety recommendations, including the following:
    ``H-11-037: Modify Federal Motor Vehicle Safety Standard 217 or the
corresponding laboratory test procedure to eliminate the potential for
objects such as latch plates to protrude into the emergency exit window
space even when that protrusion still allows the exit window to meet
the opening size requirements.''

e. NHTSA's Previous Work on Motorcoach Crashworthiness Standards

1. Seat Belt Final Rule
    Section 32703(a) of MAP-21 directs the Secretary to require seat
belts for each designated seating position in motorcoaches. NHTSA
fulfilled this mandate in 2013, issuing a final rule amending FMVSS No.
208, ``Occupant crash protection'' to require lap/shoulder seat belts
for each passenger seating position in: (a) All new OTRBs (except
school buses and prison buses); and (b) in new buses other than
OTRBs,\27\ with a GVWR greater than 11,793 kg (26,000 lb).\28\ 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.
---------------------------------------------------------------------------

    \27\ Except school buses, transit buses, perimeter seating
buses, and prison buses.
    \28\ 78 FR 70416; November 25, 2013.
---------------------------------------------------------------------------

2. Rollover Structural Integrity NPRM
    Section 32703(b)(1) of MAP-21 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'' if such standards meet the requirements and
considerations of subsections (a) and (b) of section 30111 of the
Vehicle Safety Act. In 2014, NHTSA published an NPRM proposing that
OTRBs (except school buses) and buses other than OTRBs \29\ with a GVWR
greater than 11,793 kg (26,000 lb) meet increased structural integrity
requirements to protect both restrained and unrestrained occupants in
rollover crashes. The NPRM was based on a rollover test set forth in
the Economic Commission for Europe (ECE) Regulation No. 66, ``Uniform
Technical Prescriptions Concerning the Approval of Large Passenger
Vehicles with Regard to the Strength of their Superstructure,'' (ECE
R.66).\30\
---------------------------------------------------------------------------

    \29\ Exceptions are transit buses, and perimeter seating buses.
    \30\ Supra. 79 FR 46090; August 6, 2014.
---------------------------------------------------------------------------

    NHTSA proposed performance requirements that each bus must meet
when subjected to a dynamic rollover test. The bus is placed on a
tilting platform that is 800 mm above a smooth and level concrete
surface. One side of the platform is raised at a steady rate until the
vehicle becomes unstable, rolls off the platform, and impacts the
concrete surface below.
    The proposed rollover structural integrity test is illustrated
below in Figure 1.
[GRAPHIC] [TIFF OMITTED] TP06MY16.037

    The following are the main proposed performance requirements that
buses would have to meet when subjected to the rollover structural
integrity test:
    (1) Intrusion into the ``occupant 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 (4 inch) diameter
sphere.

III. Safety Need

a. Background

    Each year, the commercial bus industry transports millions of
people between and in cities, for long and short distance tours, school
field trips, commuting, and entertainment-related trips. According to a
census published by the American Bus Association (ABA) in 2008, there
were approximately 3,400 motorcoach \31\ carriers in the United States
and Canada in 2007.\32\ These motorcoach carriers operated over 33,000
motorcoaches, logged nearly 750 million passenger trips, and traveled
over 1.8 billion miles yearly. Approximately 3,100 of the carriers were
chartered U.S. carriers that operated about 29,000 motorcoaches.
---------------------------------------------------------------------------

    \31\ As used in the ABA census report, ``motorcoach'' refers to
an OTRB. When we discuss this report and use the term motorcoach, we
mean an OTRB.
    \32\ ``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, December 18, 2008.
---------------------------------------------------------------------------

    In an updated 2011 motorcoach census,\33\ the motorcoach industry
had grown to 4,478 carriers and 42,960 motorcoaches in the United
States and Canada by the year 2010. In the U.S. alone, 4,088 carriers
operated 39,324 motorcoaches. Although the number of motorcoaches on
the road increased from 2007, the actual number of passenger trips
logged dropped to 694 million trips, while the amount of vehicle miles
traveled increased to 2.4 billion miles and passenger miles traveled
increased to over 76.1 billion. In essence, the data indicated that the
frequency of passenger trips may have decreased from 2007 to 2010, but
the length or distance of each trip increased.
---------------------------------------------------------------------------

    \33\ ``Motorcoach Census 2011, A Benchmarking of the Study of
the Size and Activity of the Motorcoach Industry in the Unites
States and Canada in 2010,'' John Dunham & Associates, June 18,
2012.
---------------------------------------------------------------------------

    Carriers with a small fleet size (less than 10 motorcoaches) have
older average motorcoach fleet age than carriers with a large fleet
size (more than 50 motorcoaches). In 2007, the small carriers had an
average motorcoach fleet age of 9 years, whereas the large carriers had
an average fleet age of 6 years. In 2010, the small carrier's average
fleet age increased to 10 years, whereas the large carrier's average
fleet age remained the same at 6 years old.

b. FARS Data

    NHTSA's Fatality Analysis Reporting System (FARS) \34\ was analyzed
for a 10 year period from 2004 to 2013 to look at fatal bus crashes
within the United States.\35\ During this period there were 85 fatal
crashes involving all OTRBs regardless of GVWR and other covered non-
OTRBs with a GVWR >11,793 kg (26,000 lb) resulting in a total of 212
occupant fatalities (an average of 21.2 total occupant fatalities per
year). Tables 4 and 5 show the breakdown of the number of crashes and
fatalities by bus body type, GVWR, and crash type, respectively.\36\
Fatalities resulting from other events such as fires or occupants
jumping from a bus were not included.
---------------------------------------------------------------------------

    \34\ NHTSA's FARS contains data on a census of fatal traffic
crashes in the United States and Puerto Rico. Crashes in FARS
involve a motor vehicle traveling on a road customarily open to the
public resulting in a fatality within 30 days of the crash.
    \35\ Over-the-Road Bus (Motorcoach) in the FARS database is
identified by the bus body type category, ``cross-country/intercity
bus,'' and large bus is identified by the bus body categories:
``other bus,'' ``unknown bus,'' and ``van-based bus,'' and by the
vehicle's GVWR greater than 11,793 kg (26,000 lb).
    \36\ The other two bus body types in the FARS database, transit
bus and school bus, were also examined and the safety problem due to
ejections in rollover accidents was found to be significantly lower
than that in OTRBs and large buses. For the 10-year period from 2004
to 2013, 6 passengers (or 0.81 passengers annually on average) were
ejected in rollover crashes of school buses and transit buses with
GVWR >11,793 kg (26,000 lb), but the ejection path was not known.
---------------------------------------------------------------------------

    There were 59 OTRB and 26 large bus crashes. Among these 85 OTRB
and large bus crashes, 40 were rollovers, 41 were frontal crashes, and
4 were side crashes. About 70 percent of the fatal bus crashes involved
OTRBs among which 90 percent had a GVWR greater than 11,793 kg (26,000
lb).

                             Table 4--Over-the-Road Bus and Large Bus Fatal Crashes
                                                (FARS 2004-2013)
----------------------------------------------------------------------------------------------------------------
                                     Rollover          Front           Side            Rear            Total
----------------------------------------------------------------------------------------------------------------
Over-the-road bus...............              33              25               1               0              59
Large bus GVWR >11,793 kg                      7              16               3               0              26
 (26,000 lb)....................
                                 -------------------------------------------------------------------------------
    Total.......................              40              41               4               0              85
----------------------------------------------------------------------------------------------------------------

                                      Table 5--Over-the Road Bus and Other Large Bus Occupant Fatalities in Crashes
                                                                    (FARS 2004-2013)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                Body type                        Over-the-road bus           Large bus GVWR >11,793 kg                         Total
-------------------------------------------------------------------------           (26,000 lb)          -----------------------------------------------
                                                                         --------------------------------
               Crash type                     Driver         Passenger        Driver         Passenger        Driver         Passenger          All
--------------------------------------------------------------------------------------------------------------------------------------------------------
Rollover................................               6             133               1               7               7             140             147
Front...................................              19              19               8              11              27              30              57
Side....................................               1               1               0               6               1               7               8
Rear....................................               0               0               0               0               0               0               0
                                         ---------------------------------------------------------------------------------------------------------------
    Total...............................              26             153               9              24              35             177             212
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The OTRB and large bus fatalities were broken down by separating
the fatalities for drivers and passengers (Table 5). Passenger
fatalities were significantly higher than driver fatalities, accounting
for over 83 percent of the total fatalities, and were particularly
prevalent in the OTRB category. Rollover events accounted for 79
percent of OTRB and large bus passenger fatalities (compared to 21
percent for driver fatalities).
    With the focus on passenger fatalities only, the passenger
fatalities were further broken down based on ejection

status (Table 6). Of the 79 percent of OTRB and large bus passenger
fatalities that were from rollover events, 57 percent of those
passenger fatalities were ejected. One in eight of the passenger
ejections had a documented known ejection portal through the side
window of the bus. Rollovers remain the largest cause of passenger
fatalities, for both ejected and non-ejected, in OTRB and large bus
crashes.

                                  Table 6--OTRB and Large Bus Passenger Fatalities by Ejection Status (FARS 2004-2013)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       OTRB                  Large bus GVWR >26,000 lb                 Total
                       Crash type                        -----------------------------------------------------------------------------------------------
                                                               Eject         No Eject          Eject         No Eject          Eject         No Eject
--------------------------------------------------------------------------------------------------------------------------------------------------------
Rollover................................................              74              59               6               1              80              60
Front...................................................               5              14               2               9               7              23
Side....................................................               1               0               0               6               1               6
Rear....................................................               0               0               0               0               0               0
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................              80              73               8              16              88              89
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The agency is proposing the requirements in today's NPRM to improve
rollover safety in high-capacity 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 nearly 60 percent of rollover
passenger fatalities are associated with occupant ejection.
    In nearly all the recent OTRB and large bus fatal rollover events,
there was a significant amount of structural damage to the roof and
side structure of the vehicles, as well as open window portals. Hence,
NHTSA tentatively believes that the prevention of occupant ejection
through portals is a critical part of mitigating the OTRB and large bus
fatality and injury rate.

IV. Research

    The test procedure and test device proposed in this NPRM were
developed from the findings of several NHTSA research programs
described in this section.

a. Joint NHTSA and Transport Canada Motorcoach Program (Martec Study)

    In 2003, NHTSA and Transport Canada entered into a joint program
that focused on improving glazing and window retention on OTRBs to
prevent occupant ejection. (``Motor Coach Glazing Retention Test
Development for Occupant Impact During a Rollover,'' August 2006.) \37\
Using a combination of crash investigations and numerical simulations,
the study provided the important first steps necessary to develop a
test procedure that realistically represented the impact loads from an
unrestrained occupant on motorcoach glazing during a rollover event.
The program also established the basis of a dynamic test device that
could be used to test glazing materials and bonding techniques to
evaluate their effectiveness in preventing ejections.
---------------------------------------------------------------------------

    \37\ Motor Coach Glazing Retention Test Development for Occupant
Impact During a Rollover, Final Report published on August 2006,
Docket No. NHTSA-2002-11876-15.
---------------------------------------------------------------------------

    In the Martec study, the event chosen for simulation was a
motorcoach rollover with a yaw speed of 30 km/h (18.6 mph) onto a flat
surface, with an unrestrained occupant seated on the far side of the
roll. Through these simulations, the Martec study determined that the
impact velocity of an occupant striking the glazing was as much as 6.0
meters/second (m/s) (21.6 km/h or 13.4 mph). The analysis used a 50th
percentile adult male side impact test dummy (US-SID) numerical model
to determine peak loading and duration. The Martec simulations
(involving a bus rolling over on its side) showed the impact area
between the bus occupant and window glazing was primarily along the
side of the dummy and that the largest load on the glazing was due to
the torso impact. It was this impact that was used as the target load
or load profile in the dynamic impact test device development.
    The impact test device consisted of a guided piston secured to a
platform structure along with an accumulator tank used for powering the
guided piston (Figure 2). The mass of the impactor was 26 kg (57 lb),
representing the effective mass measurements from the numerical
analysis. A spring with the appropriate stiffness (258 N/m) was used to
replicate compression of the thorax and a shoulder foam part from the
SID was affixed to the impactor face to replicate the compression of
the dummy's shoulder and the contact area between the dummy's shoulder
and the glazing during impact (Figure 3).

[GRAPHIC] [TIFF OMITTED] TP06MY16.038

[GRAPHIC] [TIFF OMITTED] TP06MY16.039

    In the Martec study, only limited testing was performed in a test
fixture representing an OTRB side window structure. Only one glazing
composition was tested. No testing was done to establish the motorcoach
fleet performance. The study recommended that further testing be
performed using other configurations (different glazing types such as
laminated glass and polycarbonates and mechanical latching methods)
common in the bus industry. The study concluded that more research was
needed to establish baseline motorcoach fleet performance, determine
the effect of motorcoach structural integrity on window retention and
emergency egress, and identify potential improvements for window
retention purposes.

    NHTSA's follow-on test program, discussed below, was conducted to
obtain data in these areas.

b. NHTSA's Motorcoach Side Glazing Research

    In 2011 and 2013, respectively, we completed a follow-on test
program to the Martec study and a comprehensive test program of bus
models and glazing designs to establish anti-ejection countermeasures
and performance requirements.\38\ The test programs, conducted at
NHTSA's Vehicle Research and Test Center (VRTC), investigated the
performance of bus glazing under passenger loading (simulating a far
side passenger impacting the roll side glazing during a quarter turn
rollover), using standard OTRB side windows (emergency exits and fixed
windows) and different variations of glazing and bonding techniques.
The objectives were: (1) To evaluate the test procedure from the Martec
study; (2) evaluate various types of motorcoach glazing material and
bonding techniques; (3) explore countermeasures for current window
latches that open during such impacts; and, (4) further develop test
procedures to assess the occupant retention provided by different
glazing materials used in bus exits and windows.
---------------------------------------------------------------------------

    \38\ Duffy, S., Prasad, A., ``Motorcoach Side Glazing Retention
Research,'' NHTSA Technical Report DOT HS 811 862, November 2013,
http://www.nhtsa.gov/Research/Defects+Analysis+and+Crashworthiness+Division.
---------------------------------------------------------------------------

    The following is a summary of the different testing conducted and
the test results relevant to this NPRM. Details of the testing and the
results can be found in Duffy et al., ``Motorcoach Side Glazing
Retention Research,'' supra.
1. Testing on the MCI D-Series Motorcoach Section Emergency Exit Side
Windows
    In the first stage of testing, VRTC used a section of a Motor Coach
Industries (MCI) 1993 102D model motorcoach to conduct impact tests at
the center of the window and near the latch. Different types of glazing
material (laminated, tempered), double and single pane glazing, and
different types of bonding of the glazing to the window frame were
evaluated. The windows of the MCI 102D model were 1.5 m (59 inches) in
length and 1 m (39.4 inches) in height and weighed between 25-29 kg
(55-64 lb) for single glazed panes and 42-47 kg (92.5-103.5 lb) for
double glazed panes.
    The center of daylight opening impacts were conducted using the
Martec Study Conditions (26 kg (57 lb) impactor at an impact velocity
of 21.6 km/h (13.4 mph)). The near latch impacts were conducted using
the 26 kg (57 lb) impactor at impact velocities ranging from 10.3 km/h
(6.4 mph) to 21.6 km/h (13.4 mph). Near latch impacts were also
conducted with twist introduced on the bus frame during the impact to
evaluate the effect of torsion of the bus frame on latch opening.\39\
The impact conditions in the tests with twist introduced were in
similar conditions as those without twist.
---------------------------------------------------------------------------

    \39\ The amount of torsion introduced on the bus section frame
was based on the torsion achieved by lifting the left front tire of
a full-sized MCI D-series bus by approximately 1 meter (39 inches)
using a hydraulic wheel lift which resulted in an angle of 4 degrees
about the vehicle's longitudinal axis. Torsion was introduced to the
bus section by applying a 18.9 kilonewton (kN) (4,250 lb) downward
force to one entire end of the bus section and applying a 18.9 kN
(4,250 lb) upward force to one corner of the opposite end of the bus
section.
---------------------------------------------------------------------------

    The results of this first stage of testing are as follows:
    Center of Daylight Opening Impacts on Emergency Exit Windows of the
MCI Bus Section:
     No windows tested opened in the center of daylight opening
impacts under the Martec study conditions.
     Windows with tempered glass produced higher forces and
lower displacement, than those with laminated glass.
     No windows with tempered glass broke in the center of
daylight opening impacts. Single glazed laminated glass broke in the
center of daylight opening impacts but the PVB layer did not tear.
     Polycarbonate windows produced lower resistance forces and
higher displacement compared to laminated glass windows.
     Acrylic windows produced lower resistance forces compared
to most other glazing compositions tested.
     Windows with greater PVB thickness produced reduced
displacements.
    Near-Latch Impacts on Emergency Exit Windows of the MCI Bus
Section:
     Under the Martec Study Conditions (26 kg (57 lb) impactor
and 21.6 km/h (13.4 mph) impact speed), the latches released and the
windows opened, regardless of the type of glazing material. The glazing
material was not damaged in these impacts.
     At impact speeds (10.3 km/h (6.4 mph) to 15.8 km/h (9.8
mph)) that are lower than the Martec Study Conditions the latches near
the impact opened, but the window did not open because the far side
latch remained closed.
     Paired impact tests using the 26 kg (57 lb) impactor at
speeds of 13.9 to 15.5 km/h (8.6 to 9.6 mph) with and without torsion
of the bus frame, showed that torsion in the bus frame either had no
effect on latch opening or made latch opening less likely. In 6 out of
11 pairs of comparison tests, the presence of torsion on the bus
section did not affect whether the struck latch unlatched. In the 5
other tests, the presence of torsion made it harder to open the latch.
2. Testing of MCI, Prevost, and Van Hool Emergency Exit Windows and
Latches on Test Frames
    Next, VRTC expanded testing to windows of other coach series and
those made by other manufacturers to establish fleet baseline
performance. Market share analysis indicated that the fleet would be
well represented by expanding the testing to an MCI E/J-series, a
Prevost model H3-45, and a Van Hool model C2045. Van Hool and Prevost
windows were double glazed tempered glass panes while the MCI E/J-
Series windows were either single glazed laminate glass panes or double
glazed glass panes with tempered glazing on the exterior and laminate
glazing on the interior. The MCI E/J-Series and the Van Hool C2045
windows were 1.74 m (68.5 inches) in length and 1.1 m (43.3 inches) in
height and the Prevost H3-45 model was 1.7 m (66.9 inches) in length
and 1.2 m (47.2 inches) in height.\40\ The glazing was mounted on test
frames that represented the side passenger window frames for each of
the three manufacturers. The mounting methods were in accordance with
the manufacturers' instructions. Impact tests (impacts at the center of
daylight opening and impacts near latches) were conducted under the
Martec Study Conditions (26 kg (57 lb) impactor with 21.6 km/h (13.4
mph) impact speed). The significantly different latching mechanisms in
the emergency exit windows of these three vehicle models allowed for an
evaluation of the different types of latches.\41\ Near latch impact
tests with the 26 kg (57 lb) impactor were also conducted at different
impact velocities to determine the threshold velocity for latch opening
of the different types of windows and latching mechanisms. The results
of this phase of testing are as follows:
---------------------------------------------------------------------------

    \40\ The weight of the MCI E/J single glazed laminated window
was 35 kg (77 lb) while that of the double glazed window was 51 kg
(112.lb). The weight of the Prevost H3-45 was 50 kg (110 lb) and
that of the Van Hool C2045 was 45 kg (99 lb).
    \41\ Details of the testing and the details of the windows and
latching mechanisms in these three bus models are available in the
NHTSA Technical Report DOT HS 811 862, November 2013.
---------------------------------------------------------------------------

    Near-Latch Impacts on Production Emergency Exit Windows:

     Windows from all three manufacturers exhibited latch
openings under the Martec Study Conditions.
     The threshold impact velocity for latch opening was higher
for the MCI E/J-Series windows than the Van Hool and Prevost windows.
    --Van Hool exhibited latch openings in the 9 to 10 km/h (5.6 to 6.2
mph) range.
    --Prevost exhibited latch openings in the 11 to 12 km/h (6.9 to 7.5
mph) range.
    --MCI E/J-series exhibited latch opening in the 18 to 21 km/h (11.2
to 13.1 mph) range.
    Impacts at the Center of the Daylight Opening on Production
Emergency Exit Windows (Martec Study Conditions):
     The MCI E/J-Series single laminate glazing window latches
(primary and secondary) remained closed and the windows did not open.
     The Van Hool latches opened and produced window openings.
The tempered glass panes remained intact.
     The Prevost latches opened and produced window openings.
The tempered glass panes remained intact.
3. Testing of MCI, Prevost, and Van Hool Emergency Exit Windows With
Countermeasure Latches
    Since latches opened in all the near latch impacts on production
windows and in two of the three center of daylight opening impacts of
production windows in the phase 2 tests presented above, VRTC attempted
to modify the latch systems using simple designs to see if the windows
would remain closed during impact under the Martec Study Conditions.
    The latching mechanism of the MCI E/J-Series production windows
includes a lever that latches around a striker post that is press fit
into a latch plate. Unlatching occurred in near-latch impacts by one of
two modes: 1. The striker plate deformed and the striker post rotated
in the direction of impact allowing the lever to slide over the striker
post, and 2. the latch bar rotated upward during impact which opened
the detent lever.\42\ Modifications to the MCI E/J-series latches
involved the simplest modification to improve its performance such that
the latch and glass remained intact. No simple countermeasures were
identified by VRTC for the Van Hool and Prevost latches.
---------------------------------------------------------------------------

    \42\ Latching mechanisms for Prevost and Van Hool windows and
the failures modes observed during testing are provided in detail in
the NHTSA Technical Report DOT HS 811 862, November 2013.
---------------------------------------------------------------------------

    Center of daylight opening and near latch impacts under the Martec
Study Conditions were conducted on the production windows with the
countermeasure latches on the test frame. The results of this phase of
testing are as follows:
    Near-Latch Impacts (Martec Study Conditions) on Production
Emergency Exit Windows With Countermeasure Latches:
     The MCI I/J-series countermeasure latch and glass remained
intact in the near-latch impacts under the Martec Study Conditions.
     The Van Hool primary countermeasure latch opened, but the
secondary latch did not under the near-latch Martec Study Conditions.
Only a partial window opening occurred, as the tempered glass remained
intact.
     The Prevost countermeasure latches opened in near-latch
impacts under the Martec Study Conditions and the window opened.
    Center of Daylight Opening Tests on Emergency Exit Windows With
Countermeasure Latches (Martec Study Conditions):
     MCI E/J-series latches remained intact. The laminated
inside pane broke.
     Van Hool latches remained intact. The tempered glass panes
shattered.
     Prevost latches remained intact. The window bowed outward
during the impact, but the tempered glass panes did not break.
4. Pre-Broken Glazing Impact Tests of MCI E/J-Series Emergency Exit
Windows With Countermeasure Latches
    As part of the test program, VRTC conducted impact tests under the
Martec Study Conditions on pre-broken glazing to assess glazing
strength in the event the window is broken in a rollover prior to
occupant loading. The objective of these tests was to develop an
objective test procedure for pre-breaking the glazing before the impact
tests. Various methods of pre-breaking the glazing were evaluated.
These methods included pummeling the glazing with a hammer and punching
holes in the glazing in specific grid patterns using an unloaded
electric staple gun. The hole punch patterns evaluated were a 75 mm (3
inch) diagonally offset pattern, a 50 mm (2 inch) diagonally offset
pattern, and a 75 mm (3 inch) horizontally offset pattern. The MCI E/J-
Series was chosen to conduct pre-broken glazing impacts since the MCI
E/J-Series model included laminated glazing that would still offer
resistance to impact when the glass was pre-broken. To evaluate the
strength and retention capabilities of pre-broken glazing, it was
important that the windows did not unlatch or open during the impact.
Therefore, NHTSA used modified MCI E/J-Series countermeasure latches in
these tests to ensure the windows did not unlatch.
    After pre-breaking the glazing, the window was mounted on the test
frame and the pre-broken glazing was impacted at the center of daylight
opening in accordance with the Martec Study Conditions. Displacement of
the impactor during the impact was measured. The results of the center
of daylight opening impact tests under the Martec Study conditions on
the MCI E/J-Series windows (double-glazed laminated and single-glazed
laminated windows) with countermeasure latches for the different pre-
breaking methods are as follows:
     The windows remained latched in all the tests and there
was no tearing in the PVB layer.
     Average maximum displacement of the impactor in center of
daylight opening impacts were:
    --214 mm (8.4 inches) for fully pummeled pre-broken glazing.
    --184 mm (7.2 inches) (86 percent of fully pummeled glazing) for 50
mm (2 inch) diagonally offset breakage pattern.
    --175 mm (6.9 inches) (82 percent of fully pummeled) for 75 mm (3
inch) diagonally offset breakage pattern.
    --151 mm (5.9 inches) (71 percent of fully pummeled) for 75 mm (3
inch) horizontally offset breakage pattern.
     The 50 (2 inch) and 75 mm (3 inch) breakage pattern
methods are more objective than the fully pummeled method.
     There was little difference in maximum impactor
displacements between the 50 (2 inch) and 75 mm (3 inch) diagonally
offset pattern methods.
    --The 75 mm (3 inch) horizontally offset pattern method produced
less maximum impactor displacement than the diagonally offset methods.
     Use of an electric staple gun (without the staples) to
pre-break the glass panes was practical, allowed for single person
operation, and did not produce tears in the PVB layer.
    NHTSA also tested single-glazed laminated windows with a thicker
PVB interlayer to evaluate the impactor displacement as a function of
the PVB interlayer thickness. The PVB thickness chosen for this test
series was 1.52 mm (0.06 inches) (versus the 0.76 mm (0.03 inches)
standard thickness). Center of the daylight opening impact tests under
the Martec Study Conditions to pre-broken glazing (all four breaking
methods: Fully pummeled, 75 mm (3 inch) diagonally offset pattern, 50
mm (2 inch) diagonally offset pattern, 75 mm (3 inch) horizontally
offset pattern) were conducted. The impacts did not produce any tearing
in the PVB layer and the windows remained latched in

all the tests. The pre-broken glazing with the thicker PVB interlayer
produced maximum displacements of the impactor that were on average 14
percent less than similar impacts (center of daylight opening impact
under Martec Study Conditions) into similarly pre-broken glazing
production MCI E/J-series windows with standard thickness PVB
interlayer.
5. Testing of MCI E/J-Series Fixed Windows (Martec Study Conditions)
    VRTC also tested fixed windows from the MCI E/J-series to assess
their performance under the Martec Study Conditions. The fixed windows
were attached to the E/J-series test frame in accordance with
manufacturer's recommendations. Tests were conducted on unbroken
single-glazed and unbroken and pre-broken double-glazed windows.
Impacts were conducted near the primary locking mechanism (retaining
clip) that locks the window to the frame and at the center of daylight
opening.
     For tests conducted on unbroken glazing near the primary
locking mechanism (retaining clip), the retaining clip bent backwards.
The secondary clip bent but did not release, resulting in the window
only partially opening.
     For tests conducted at the center of the daylight opening
on unbroken glazing, the retaining clip bent, but the window opening
result depended on the type of glazing impacted.
    --The single-glazed window fully opened.
    --The double-glazed window did not open.
     For tests conducted at the center of the daylight opening
on pre-broken double-glazed windows, there was no damage to the
retaining clips, and the windows did not open.

c. NHTSA's Large Bus Rollover Structural Integrity Research

    In support of the agency's proposal to improve the rollover
structural integrity of motorcoaches and other large buses, among other
things NHTSA evaluated ECE R.66 \43\ to see if the standard would
address the safety needs NHTSA identified in that rulemaking.
---------------------------------------------------------------------------

    \43\ 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.)
---------------------------------------------------------------------------

    In the ECE R.66 full vehicle test, the vehicle is placed on a
tilting platform that is 800 mm (31.5 inches) 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 structures into a designated ``occupant survival
space'' (defined by use of a survival space template) during and after
the rollover structural integrity test is assessed.
    NHTSA evaluated several different models of OTRBs. 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) (ft) long model year (MY) 1992 MCI model MC-12,
and two 12.2 m (40 ft) long MY 1991 Prevost model (Prevost) LeMirage
buses. The most discernible difference between the MCI and Prevost
models was that the Prevost had smaller side windows and more roof
support pillars.
    NHTSA also tested a MY 2000 MCI bus, Model 102-EL3, that was 13.7 m
(45 ft) in length. The agency tested this model because it was
representative of many buses newer than the MCI and Prevost models.
Newer buses are 13.7 m (45 ft) in length instead of 12.2 m (40 ft). The
newer buses also tend to have larger windows than the earlier models.
    A detail report of the test program of the older buses is available
in the docket.\44\ A report on the test of the newer bus can be found
on NHTSA's Web site.\45\
---------------------------------------------------------------------------

    \44\ Docket No. NHTSA-2007-28793-0019.
    \45\ ``ECE Regulation 66 Based Research Test of Motorcoach Roof
Strength, 2000 MCI 102-EL3 Series Motorcoach, NHTSA No.: MY 0800,''
October 1, 2009, Report No.: ECE 66-MGA-2009-001, http://www-nrd.nhtsa.dot.gov/database/aspx/searchmedia2.aspx?database=v&tstno=6797&mediatype=r&r_tstno=6797,
Report 8. http://www-nrd.nhtsa.dot.gov/database/VSR/veh/QueryTest.aspx, Report 8. Step-by-step instructions on accessing the
research report can be found in a memorandum in Docket No. NHTSA-
2007-28793-0025.
---------------------------------------------------------------------------

    In our research, high speed video cameras were used and transfer
media were applied to each survival space template to determine if any
portion of the vehicle interior had entered the occupant survival space
during the rollover test. In addition, two Hybrid III (HIII) 50th
percentile adult male anthropomorphic test devices (ATDs) (test
dummies) were placed in the vehicle, on the opposite side of the
impacted side of the bus, to measure injury potential and seat
anchorage performance. One of the ATDs was belted and the other was
unbelted. For the purposes of this advanced glazing NPRM, NHTSA
reviewed the results from the evaluation to understand better the dummy
occupant interaction with the windows during an elevated one-quarter
turn roll event.
    The following summarizes the findings of the ECE R.66-based tests
that are especially relevant to today's NPRM.
1. MY 1991 Prevost Bus
    The Prevost bus was equipped with ten laminated windows on each
side of the bus. The windows were 815 mm (32 in) in width and 1,040 mm
(41 in) in height. Four of the left windows and three of the right
windows were designated emergency exit windows. The emergency exit
windows were hinged at the top and latched at the bottom.
    Upon impact with the ground (left side of the bus), contact between
the front survival space template and the left side window was made.
The glass panes of the laminated glazing showed cracking and
splintering. All of the glazings on the impact side (left) were
retained in the windows. Three of the four left side emergency exit
windows unlatched and lost retention during the impact but were held in
the closed position by contact with the ground. The remaining left side
emergency exit window remained latched during the impact with the
ground.
    High speed film from the test indicated that the side windows
located on the far side of the impact (right) underwent a substantial
amount of flexion during the impact with the ground but remained
intact. The flexion along with the inertia of the latching bar
mechanism for this particular Prevost bus caused all three of the right
side emergency exit windows to unlatch and open slightly. However, they
were closed by gravity following the impact when the Prevost bus came
to its final resting position. The two roof emergency exits also opened
during the impact.
    The left pelvis of the unrestrained ATD seated far-side of the
impact interacted with the inboard armrest prior to the bus impacting
the ground. After the bus made contact with the ground, the top of the
dummy's head made contact with the left window and the ATD came to rest
straddling the third and fourth left windows from the front of the bus.

2. MY 1992 MCI Bus
    The MCI bus was equipped with seven laminated windows on each side.
All of the windows were designated emergency exit windows with the
exception of the right rearmost window. The windows were 1,310 mm (52
in) in width and 685 mm (27 in) in height. The emergency exit windows
were hinged at the top and latched at the bottom.
    Upon impact with the ground (left side of the bus), contact between
the front survival space template and the left side window was made.
The glass panes of the laminated glazing showed cracking and
splintering. All of the glazings on the bus were fully retained in the
windows.
    None of the emergency exit windows unlatched or opened during or
after the ground impact. The roof emergency exits opened during the
impact and a gap was visible between the roof panel and the emergency
exit frame after the test.
    The left pelvis of the unrestrained ATD interacted with the inboard
armrest during the bus impact with the ground. The top and back of the
ATD head struck the left window as the bus impacted the ground, and the
dummy came to rest on its head over the window.
3. MY 2000 MCI Bus
    The 2000 MCI 102-EL3 bus was equipped with seven laminated glass
windows on each side. The front windows were fixed windows and the
remaining windows were emergency exit windows. The majority of the
windows were 1,564 mm (62 in) in width and 894 mm (35 in) in height,
which is substantially larger than the previous two older buses (a 55
percent increase in window area compared to the 1992 MCI model). The
larger front windows were 1,564 mm (62 in) in width with a maximum of
1,257 mm (50 in) in height, and the smaller rear windows were 1,042 mm
(41 in) in width and 894 mm (35 in) in height.
    During the left-side impact with the ground, five of the seven
right side glazings (toward the front of the bus) cracked and broke,
and the window glazings fell into the occupant compartment during the
test. The glazing from one of the right side front windows was retained
by an overhead TV monitor and prevented the window pane from separating
from its mounting gasket and falling into the bus. We believe that the
glazing fell into the bus in this test, and not in the previous tests,
because glazings on this bus are significantly larger, and presumably
heavier, than the glazings used on the two older buses tested. The
glazing in the last window near the rear cracked and broke but the
window was retained and did not fall into the passenger compartment,
possibly because the window was shorter in width than the other
windows.
    The emergency exit window release handles for four of the right
side windows rotated approximately 90 degrees; however, all emergency
exit windows on both sides remained latched during the test. Both of
the roof emergency exits opened during the test.
    All seven of the left side (impacted side of the bus) glazings
remained fully retained in the windows after the rollover test.
    The unrestrained dummy's head first struck the luggage rack above
the left side seats, and then the dummy's head hit the glazing of the
third window from the front (left side of the bus). The dummy's left
and right knees hit the seat back of the left side seats before hitting
the center of the window. Its final resting position was on top of this
window. The glazing remained intact and retained in the window.

V. Overview of Proposed Requirements

    In the 2013 seat belt final rule,\46\ NHTSA determined that a
significant majority of fatalities in vehicles subject to the rule were
attributable to rollovers and that more than three-quarters of rollover
fatalities were attributable to ejections. In crashes in which the roof
and bus structure remain intact, the main ejection portal for
passengers was through the side windows.
---------------------------------------------------------------------------

    \46\ 78 FR 70416, November 25, 2013, supra.
---------------------------------------------------------------------------

    NHTSA is proposing performance requirements that the subject buses
would have to meet by way of anti-ejection safety countermeasures. We
are proposing to issue an FMVSS No. 217a to specify an impactor test of
glazing material used in side and rear windows.\47\ In the tests, a 26
kg (57 lb) impactor would be propelled from inside a test vehicle
toward the window glazing at 21.6 km/h (13.4 mph). Each window would be
subject to any one of three impacts, as selected by NHTSA in a
compliance test: (a) An impact near a latching mechanism of an intact
window; \48\ (b) an impact at the center of the daylight opening of an
intact window; and (c) an impact at the center of the daylight opening
of a pre-broken window. The impactor and impact speed in these proposed
tests simulate the loading from an average size adult male impacting a
window on the opposite side of a large bus in a rollover.
---------------------------------------------------------------------------

    \47\ A final rule could incorporate the proposed requirements
into FMVSS No. 217, rather than in a separate FMVSS No. 217a. This
NPRM shows the proposed requirements separately in FMVSS No. 217a
for plain language purposes and the reader's convenience.
    \48\ For non-emergency exit fixed windows, the proposed test
would be conducted at the location of one of the fixed latches or
discrete attachment points. For fully rubber bonded or glued windows
with no latch mechanisms, the test would be conducted along the
center of the lower window edge one inch above the daylight opening
periphery.
---------------------------------------------------------------------------

    The proposed performance requirements are as follows:
     In tests described in (a) and (b) in the above paragraph,
the window would have to prevent passage of a 102 mm (4 inch) diameter
sphere during the impact, and after the test. The agency would assess
the window during the impact by determining whether any part of the
window passes a reference plane defined during a pre-test set up
procedure. These requirements would ensure that glazing is securely
bonded to window frames, no potential ejection portals are created due
to breaking of glass, and windows remain closed when impacted.
     In the test of (c) above, the maximum displacement of the
impactor at the center of the daylight opening would be limited to 175
mm (6.9 inches) for pre-broken glazing. This requirement in particular
would drive the installation of advanced glazing. The requirement would
also help ensure the advanced glazing reasonably retains occupants
within the structural sidewall of the bus even when the glass
surrounding the PVB interlayer is broken and ensures that no potential
ejection portals are created during and after impact.
     Emergency exit latch protrusions may not extend more than
one inch into the emergency exit opening of the window when the window
is opened to the minimum emergency egress opening (allowing passage of
an ellipsoid 500 mm (19.7 inches) wide by 300 mm (11.8 inches) high).
This requirement would minimize the potential for the latch plate
protrusions (or other projections) to hinder the emergency egress of
passengers.
     Latches would have to remain functional following the
impact test to ensure that occupants can open the emergency exits to
egress the vehicle after a crash.
    Current regulations and industry standards for large buses do not
adequately address window retention or ejection mitigation through
glazing under dynamic occupant loading in rollovers.\49\ FMVSS No. 205,
``Glazing

materials,'' industry standards,\50\ and various international
regulations \51\ address the minimum strength and mechanical properties
that certain safety glass (test samples) must possess, but they do not
address window retention as a whole. FMVSS No. 217 has an ejection
mitigation requirement by way of a quasi-static load application test
(S5.1), but the test is not representative of the dynamic loading on
glazing from an unrestrained adult male occupant during an OTRB
rollover. The proposed FMVSS No. 227 requirements for bus structural
integrity would require that windows (on the non-roll side) remain
intact in their framing during the quarter turn, do not open up during
the quarter turn, and have no openings large enough to admit passage of
a 102 mm (4 inch) diameter sphere after the quarter turn. However, the
forces that would be experienced by the windows in the proposed FMVSS
No. 227 test are purely inertial and are not representative of any
direct occupant loading from within the bus.
---------------------------------------------------------------------------

    \49\ On January 19, 2011, NHTSA issued a final rule (76 FR 3212)
establishing a new FMVSS No. 226, ``Ejection mitigation,'' to reduce
the partial and complete ejection of vehicle occupants through side
windows in crashes, particularly rollover crashes. The standard
applies to the side windows next to the first three rows of seats,
and to a portion of the cargo area behind the first or second rows,
in motor vehicles with a GVWR of 4,536 kg (10,000 lb) or less.
    \50\ ANSI Z26.1, ``Safety glazing materials for glazing motor
vehicles and motor vehicle equipment operating on land highways,''
specifies performance tests and requirements for different types of
glazing material regarding visibility, strength, and abrasion
resistance. The specified tests do not evaluate the entire window
for retention under loading conditions representing an unrestrained
occupant impacting a window in a rollover event.
    \51\ European regulation, ECE R.43, ``Uniform provisions
concerning the approval of safety glazing materials and their
installation on vehicles,'' Australian Design rule, ADR 8/01,
``Safety glazing material,'' and Japanese Industrial Standards, JI R
3211, ``Safety glazing materials for road vehicles,'' are similar to
FMVSS No. 205 and ANSI Z26.1. These standards only specify
requirements on glazing characteristics but do not specify
requirements for window retention under occupant loading.
---------------------------------------------------------------------------

    Thus, the requirements proposed in today's NPRM would fill a gap
currently existing in NHTSA's motorcoach and large bus safety
regulations. NHTSA recently issued a seat belt requirement \52\ to
mitigate the risk of ejection. However, seat belt usage rates by
motorcoach occupants are uncertain, and even if occupants are belted,
there are risks associated with partial ejections. Advanced glazing in
window openings and improved mountings would mitigate the risk of
ejection of occupants who may not be restrained at the time of the
crash, and the risk of partial ejections of both restrained and
unrestrained occupants. Today's NPRM proposes requirements that would
result in portal improvements by way of advanced glazing, consistent
with the goals of the Motorcoach Safety Enhancement Act of MAP-21.
---------------------------------------------------------------------------

    \52\ 78 FR 70416 (November 25, 2013), supra.
---------------------------------------------------------------------------

    This NPRM is based on a number of research studies.
    NHTSA formulated this NPRM based on findings from the Martec study.
Through computer simulation using the ECE R.66 rollover test, the
Martec study established the forces that motorcoach occupants exert on
the side window during rollover events, and the impact forces applied
to the roof of the motorcoach. The Martec study also established the
basis for the dynamic test procedure proposed today to test glazing
materials and bonding techniques.
    NHTSA also designed this NPRM based on the findings of our 2011 and
2013 follow-on testing of real-world motorcoach windows. The later
study examined the exact failure mechanism(s) for side windows in a
rollover event. We used the dynamic impactor device developed in the
Martec study, along with its prescribed impact speed 21.6 km/h (13.4
mph) and impactor mass 26 kg (57 lb), to evaluate modern bus windows
that were representative of the fleet population. We obtained data
about fleet baseline performance and the performance of various bonding
methods and glazing materials, such as laminated glass and
polycarbonates, tested on test frames representing side passenger
window frames of actual motorcoaches.
    We also found in our 2013 testing that latch mechanisms on
emergency windows routinely failed when the glazing near them was
struck with the impactor. Failure of the latch caused the exit to open,
posing an unreasonable risk of ejection in a rollover. These results
indicated there is a safety need for a test that assesses the ability
of the latches to remain closed when subjected to impactor loading. We
were also able to modify some of the latch systems with simple designs,
enabling the latch to stay closed when struck. This showed the
practicability of meeting an ejection mitigation requirement when
glazing is struck near the latch.
    NHTSA also based this NPRM on the findings from NHTSA's large bus
structural integrity research program.\53\ In that program, NHTSA
conducted ECE R.66 tests of a 1991 Prevost bus, a 1992 MCI bus and a
2000 MCI bus. The 1991 Prevost and the 1992 MCI motorcoaches were able
to retain the glazings on both the side of the bus impacting the ground
and on the far side, showing the practicability of producing sufficient
bonding techniques for glazing materials in motorcoaches.
---------------------------------------------------------------------------

    \53\ Supra.
---------------------------------------------------------------------------

    Additionally, the structural integrity test program showed that bus
design can influence glazing retention. In the test of the 2000 MCI
bus, during the left-side impact with the ground five of the seven
glazings on the right side of the bus cracked and broke, and the window
glazings fell into the occupant compartment during the test. We believe
that the glazing fell into the bus in this test, and not in the
previous tests of the 1991 Prevost and the 1992 MCI, because glazings
on the 2000 MCI bus were significantly larger, and presumably heavier,
than the glazings used on the two older buses tested. The bonding
technique was not strong enough to support the heavier glazings. The
glazing in the last window near the rear of the 2000 MCI bus cracked
and broke but the window was retained and did not fall into the
passenger compartment, possibly because the window was shorter in width
than the other windows.
    NHTSA's structural integrity testing showed good performance by
laminated glazing. The 1991 Prevost bus was equipped with ten laminated
windows on each side of the bus. In the ECE R.66 test, upon impact with
the ground (left side of the bus), the glass panes of the laminated
glazing on the left side showed cracking and splintering but were
retained in the windows. The 1992 MCI bus was equipped with seven
laminated windows on each side. Upon impact with the ground (left side
of the bus), the glass panes of the laminated glazing on the left side
showed cracking and splintering. All of the glazings on the bus were
fully retained in the windows.
    Studies show that bus glazings are exposed to multiple and chaotic
impacts in a rollover. In the Martec study, the simulation showed
glazing struck by the unbelted passenger occupant before the bus was
completely on its side. In NHTSA's structural integrity tests, the
unrestrained ATD was basically freefalling from the seat as the bus
tipped over, and did not contact the side windows until after the bus
had already impacted and made contact with the ground surface. In the
test of the 1992 MCI bus, the top and back of the restrained ATD head
struck the third window from the front of the bus on the left side as
the bus impacted the ground. The window glazing cracked and splintered
as the laminated glazing hit the ground. The test dummy came to rest on
its head over this window which remained intact after the test.

    Because glazings are subject to multiple, unpredictable impacts
from occupant and/or ground contact in a rollover, NHTSA has
tentatively determined that the dynamic impact test proposed today
should include a test set-up specification and method that involves
pre-breaking the glazing prior to the impactor test. Pre-breaking the
glazing mimics a real-world condition, as the side window glazing is
often broken when the bus contacts the ground. With advanced glazing,
the procedure would likely result in the outside glass breaking without
deforming the laminate. With tempered (non-advanced) glazing, the
procedure would likely result in the glazing shattering into fragments.
As a result, to meet a final rule resulting from this NPRM, buses
covered by the rule would likely use laminated glazing, and not
tempered glazing, to meet the requirements proposed today.

VI. Test Procedure Specifications

a. Impactor

    NHTSA proposes to use the impact test device developed in the
Martec study, supra. That study determined that a mid-size adult male
would strike the glazing with his head, followed closely by his
shoulder/torso. Simulations also showed that the impact area between
the bus occupant and the window glazing was primarily along the side of
the occupant.
    The proposed impactor design is as outlined in Figure 3,
representing the torso of the SID. The mass of the impactor is 26 kg
(57 lb), representing the effective mass measurements from the
numerical analysis of the Martec study. A spring with the appropriate
stiffness (258 N/m) was used to replicate compression of the thorax.
The impactor face is a rectangle measuring 177 mm x 212 mm (7 inch x
8.3 inch) with rounded corners. A shoulder foam part from the SID is
affixed to the impactor face to replicate the compression of the foam
located beneath the dummy's chest jacket (Figure 3).

b. Test Speed

    The impact speed in these proposed tests simulates the loading from
an average size adult male impacting a window on the opposite side of a
large bus in a rollover. In the Martec study, computer modeling of a
bus rollover predicted the loads on the bus windows from a mid-size
adult male occupant. The Martec study found that the impact velocity of
the occupant striking the glazing with his head, followed closely by
his shoulder/torso, could be as high as 6.0 m/s (21.6 km/h or 13.4
mph). We propose to use this impact speed of 21.6 km/h (13.4 mph) for
each of the proposed dynamic impact tests.

c. ``Portal'' Improvements

    The Motorcoach Enhanced Safety Act directs the agency to consider
requiring advanced glazing standards for ``each motorcoach portal''
(section 32703(b)(2)). The Act defines ``portal'' as ``any opening on
the front, side, rear, or roof of a motorcoach that could, in the event
of a crash involving the motorcoach, permit the partial or complete
ejection of any occupant from the motorcoach, including a young child''
(section 32702(9)).
    We have considered requiring advanced glazing standards for each
motorcoach portal in accordance with the Act, and have decided, based
on accident data, to apply this NPRM to the bus side and rear windows
and to glass panels/windows on the roof. We are not applying the
proposed requirements to the front windshield, or to emergency exit
doors, service doors, or roof hatches. Accident data of real world
rollover incidents indicate that passenger ejections are not occurring
from the front windshield or emergency or service doors. We are aware
of only one incident of a real world rollover crash involving a front
windshield ejection, and that was a non-fatality.\54\
---------------------------------------------------------------------------

    \54\ The crash occurred in Victory, NY. The front right occupant
was ejected only after the windshield had broken out during a
frontal collision.
---------------------------------------------------------------------------

    To the extent emergency roof exits are opening during the impact
with the ground, NHTSA's rulemaking on large bus rollover structural
integrity will address that ejection risk. NHTSA has proposed in that
rulemaking to require emergency exits to remain shut during the
rollover test, and to be operable in the manner required under FMVSS
No. 217 after the test. Those proposed requirements would ensure that
roof hatches do not open during a quarter-turn rollover, at minimum,
from the inertial loading of its own weight.
    We have applied the proposed advanced glazing requirements to the
portals we believe pose a valid risk of ejection. We estimate that side
bus windows account for about 80 percent of portals (potential ejection
routes) on buses, which presents a high exposure risk to potential
ejection. Given this exposure, this NPRM will focus advanced glazing
and other ejection mitigation efforts on the bus side and rear windows
(emergency and non-emergency exits). In addition, we have recently
become aware of some motorcoaches equipped with glass roofs or glass
panel ceilings to provide an enhanced view for bus passengers. These
glass panels/windows on roofs can become ejection portals if advanced
glazing is not used. Therefore, we propose to apply this NPRM to roof
glass panels/windows as well, assuming they are of a minimum size.
    We also propose to apply this NPRM to rear windows. We recognize
that OTRBs typically have the bus engine in the rear, and therefore
usually have no window on the rear of the bus. However, nothing
precludes bus designs from having windows in the rear of the bus that
could be potential ejection portals. However, to be subject to the
proposed requirements, the windows would have to be a minimum size.
    A minimum size criterion would thus apply to side and rear windows,
and to roof glass panels/windows. The criterion would address
limitations of testing with the impactor. The window would be tested if
it is large enough to fit the impactor face plus a 25 mm (1 inch)
border around the impactor face plate edge without contact with the
window frame. The dimensions of the dynamic impactor we propose to use
are 177 mm by 212 mm (7 inches by 8.3 inches). Using the 8.3 inches
dimension of the dynamic impactor, the proposed dynamic test procedure
would be applicable to a side window whose minimum dimension measured
through the center of its area is (280 mm) (11 inches) or greater. (The
rationale for the 280 mm (11 inches) is provided below in the next
paragraph.) The 25 mm (1 inch) clearance is needed to make sure we are
testing the strength of the glazing and bonding in retaining the
impactor and that of the latches withstanding the impact, and not the
strength of the window frame. If the impactor were to strike the window
frame structure, the impactor could be partially restrained by the
window frame structure and the performance of the glazing and bonding
would not be fully assessed.
    The proposed exclusion is consistent with FMVSS No. 217, which
currently excludes from S5.1's window retention requirements ``a window
whose minimum surface dimension measured through the center of its area
is less than 8 inches'' (S5.1.2). FMVSS No. 217 uses a head form with a
76 mm (3 inch) spherical radius (152 mm (6 inch) diameter) to apply the
quasi-static force application (S5.1). We are proposing that the new
dynamic test be applicable only to bus windows with a proportional
minimum surface dimension. That is, using the wider 212 mm (8.3 inch)
dimension of the dynamic impactor, the proposed dynamic test procedure
would be

applicable to a side window whose minimum dimension measured through
the center of its area is 280 mm (11 inch) or greater.\55\
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    \55\ (6 inch/8 inch) = (8.3 inch/X inch), therefore (X = 11
inch).
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d. Definition of Daylight Opening

    This NPRM proposes a procedure for testing glazing in each side and
rear window opening and roof glass panels/windows. To describe
precisely where the impactor would be targeted on the glazing, we would
first define how the ``daylight opening'' (window opening) would be
determined. For side windows, the ``daylight opening'' would be the
locus of all points where a horizontal line, perpendicular to the
vehicle longitudinal centerline, is tangent to the periphery of the
opening. For rear windows, the ``daylight opening'' would be the locus
of all points where a horizontal line, parallel to the vehicle
longitudinal centerline, is tangent to the periphery of the opening.
For roof glass panels/windows, the ``daylight opening'' would be the
locus of all point where a vertical line is tangent to the periphery of
the opening. The periphery would include surfaces 100 mm (3.94 inches)
inboard of the inside surface of the window glazing and 25 mm (0.98
inches) outboard of the outside surface of the window glazing. The
periphery would exclude any flexible gasket material or weather
stripping, grab handles, and any part of a seat.
    This definition of daylight opening would be similar to the
definition of ``side daylight opening'' in FMVSS No. 226, ``Ejection
mitigation.'' As explained in the FMVSS No. 226 rulemaking, flexible
gasket material, weather stripping and the like are excluded from the
``daylight opening'' definition because the flexible material is
unlikely to impede occupant ejection through the opening.\56\ The
glazing underlying the flexible material should be considered part of
the daylight opening for testing purposes, thus subject to impactor
testing. The exclusion results in keeping the glazing area that NHTSA
may test as large as possible.
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    \56\ 74 FR 63180, 63205 (December 2, 2009).
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    Grab handles would be excluded from the definition for the same
reasons explained in the FMVSS No. 226 rulemaking.\57\ In a rollover,
grab handles are unlikely to have any effect mitigating the likelihood
of ejection since occupants will move toward the daylight opening from
many different angles. Grab handles are unlikely to contribute toward
lowering the risk of occupant ejection through the window (i.e., they
do not lower the chance of ejection because they would block the
opening). Thus, we believe it would not make sense for the test
procedure to allow grab handles to define the area of glazing tested.
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    \57\ Final rule; response to petitions for reconsideration, 78
FR 55138, 55152 (September 9, 2013).
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    We note that there currently is a definition of the term ``daylight
opening'' in FMVSS No. 217 (S4). The term is defined as: ``the maximum
unobstructed opening of an emergency exit when viewed from a direction
perpendicular to the plane of the opening.'' The term was inadvertently
added to the standard by a May 9, 1995 final rule (60 FR 24562); the
term is not used in any other part of the regulatory text. We propose
to delete the term in S4.

e. Glass Breakage Procedure

    NHTSA is proposing a breaking specification and method that
involves punching holes in the glazing, to simulate the damage the
glazing could experience in a rollover prior to impact by an
occupant.\58\ The holes would be punched at set distances on both the
interior and exterior glass plies of the laminated glazing. The window
breaking procedure would damage but not destroy laminated glazing,
while it would obliterate tempered glazing. Since tempered glazing
would be obliterated, a final rule resulting from this proposal would
have the effect of prohibiting manufacturers from having bus windows
made solely from tempered glazing.
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    \58\ In NHTSA's developmental testing, the agency found that
using an electric staple gun without any staples worked well. Holes
punched with the unloaded electric staple gun did not penetrate
through the PVB interlayer. See ``Motorcoach Side Glazing Retention
Research,'' November 2013, supra.
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    NHTSA studied various methods to break the glazing prior to the
impact tests, including impacts with a hammer (pummeled), using an
automatic center punch, and an unloaded electric staple gun.\59\ The
agency also studied several patterns of breakage (75 mm (3 inch)
diagonally offset, 75 mm (3 inch) horizontally offset, and 50 mm (2
inch) diagonally offset grids).\60\ The study is discussed in NHTSA's
``Motorcoach Side Glazing Retention Research,'' November 2013, supra.
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    \59\ A Duo Fast Model EWC electric staple gun without staples
was used. With the front nose opening of the staple gun normal to
the glazing, the staple gun applied a 12.7 mm (0.5 inch) line load
with an average force of 4,200 Newton (N) (994 lb) (standard
deviation = 850 N (191 lb)) when fired. This force was sufficient to
break the glass without any damage to the inner laminate layer.
    \60\ The breakage pattern developed in the ejection mitigation
regulation (FMVSS No. 226) where the 75 mm (3 inch) pattern is
``horizontally offset'' was also studied. NHTSA found that the
automatic center punch used in FMVSS No. 226's procedure was not
practical for large bus windows.
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    In NHTSA's study, the Martec study impact tests were performed on
broken glazing with the impactor striking the window at the center of
the daylight opening, as measured on the interior window frame. Not
surprisingly, the results showed that more glass breakage (maximum
breakage was achieved in the pummeled test) yields more peak impactor
displacement. However, the 75 and 50 mm (3 and 2 inch) diagonally
offset matrix hole punching methods were found to be more controllable
and objective than the pummeling method, while also creating extensive
breakage patterns. Thus, NHTSA decided to incorporate the hole punching
method rather than the pummeling method in the proposed test procedure.
    Results also indicated that there does not appear to be a
significant difference in displacement of the impactor between the 75
and 50 mm (3 and 2 inch) diagonally offset patterns. Yet, the 75 mm (3
inch) diagonally offset grid pattern has 53 percent fewer punch holes
compared to the 50 mm (2 inch) diagonally offset grid pattern, i.e.,
the 75 mm (3 inch) diagonally offset pattern would require less than
half the number of hole punches compared to the 50 mm (2 inch) pattern.
Additionally, the 75 mm (3 inch) diagonally offset pattern resulted in
glazing performance that was closer to the 50 mm (2 inch) diagonally
offset and pummeled glazing tests, compared to the 75 mm (3 inch)
horizontally offset grid pattern. For these reasons, NHTSA has chosen
the 75 mm (3 inch) diagonally offset grid pattern to incorporate into
the proposed test procedure.
    The first step in the test procedure would be to mark the glazing
surface on the occupant interior glass in a horizontal and vertical
grid of points separated by 75 mm (3 inches), with the first point
coincident with the geometric center of the daylight opening. Next, the
grid on the opposite side of the glazing would be marked. For most
glazing, the grid on the opposite side of the glazing would be
staggered to avoid tearing the PVB interlayer. For laminates, ``the
opposite side of the glazing'' means the opposing glass ply directly
opposite of the PVB interlayer. ``Staggered'' means that the 75 mm (3
inch) offset pattern has a 75 mm x 75 mm (3 inch x 3 inch) pattern on
the occupant interior glass and the same pattern, offset by 37.5 mm
(1.5 inch) horizontally and vertically, on the outside exterior glass
surface.
    For windows that are a single-pane unit, we would use the grid
pattern on the occupant space interior surface and

the staggered grid pattern on the outside exterior surface of the glass
pane.
    For double-glazed windows, we would use a grid pattern on the
occupant space side of the interior pane and on the outside of the
exterior pane. For double-glazed windows that consist of one pane of
tempered glass, that pane would be broken and removed, and the
remaining glass pane (that is not of tempered glass) would be pre-
broken on both sides (occupant interior and outside exterior) with the
grid and staggered grid patterns, respectively. For double-glazed
windows that do not consist of any tempered glass pane, it would not be
practical to apply the 75 mm (3 inch) pre-break pattern to the
insulated surface (inside the air gap) of the individual glass panes.
In these cases in which neither pane is tempered glass, both the
occupant space side of the interior pane and the outside of the
exterior pane would be broken in the grid pattern, but the patterns
would not be offset (one side would not use the staggered pattern) due
to a lack of need. That is, for those windows there would be little
likelihood of tearing the PVB interlayer even when the patterns are not
offset.
    The agency envisions breaking the defined grid points using an
unloaded electric staple gun, since the device worked well for that
purpose in our developmental testing. The staple gun we use would apply
12.7 mm (0.5 inch) line load (with a thickness of 1.3 mm (0.05 inches))
(the size of a standard staple) on the glazing with a force in the
range of 3,500 Newtons (N) (787 lb) to 5,000 N (1,124 lb) when the
front nose opening of the staple gun is held normal to the glazing.
These staple gun specifications are designed so as to break the glass
with a single punch without producing tears in the PVB interlayer.
Holes would be punched in the glazing starting with the inside surface
of the glazing, and starting with the forward-most, lowest hole in the
pattern. We would continue punching holes 75 mm (3 inches) apart,
moving rearward on the bus. When the end of a row is reached, we would
move to the most forward hole in the next higher row, 75 mm (3 inches)
from the punched row. After completing the holes on the inside surface,
we would repeat the process on the outside surface.
    When punching a hole, we would place a 100 mm (4 inch) by 100 mm (4
inch) piece of plywood on the opposite side of the glazing as a
reaction surface against the punch. If a particular window were
constructed such that the inner laminated material is penetrated or
damaged, the procedure would not be halted or invalidated. The impactor
test would be conducted at the conclusion of the glazing breakage
procedure. If punching a hole causes the glazing to disintegrate, as
would occur when testing tempered glazing, the procedure would be
halted for that item of glazing and the impactor test would be
conducted on what glazing, if any, remains. If there is no glazing
remaining after the hole-punching procedure, there would be a failure
to comply since the window would not be able to restrain the impactor
or prevent passage of the 102 mm (4 inch) diameter sphere.

VII. Performance Requirements

    NHTSA proposes to specify performance requirements for windows
comprised of unbroken and broken glazing when the glazing is subjected
to impactor testing. The impactor would be propelled along a horizontal
plane for side and rear windows and would be propelled along a vertical
plane for roof glass panels/windows.

a. Unbroken Glazing

    The amendments proposed by this NPRM would require buses to meet
performance requirements during and after the impactor test. Each
unbroken window would be subject to either of the following two
impacts, as selected by NHTSA in a compliance test: (a) An impact near
a latching mechanism,\61\ and (b) an impact at the center of the
daylight opening. The tests would ensure that glazing is securely
bonded to window frames and that glass breakage during impact does not
result in a potential ejection portal. In addition, the test near a
latching mechanism would ensure that the latch system is able to keep
the window closed when subjected to direct occupant loading, so as not
to become a potential ejection portal. In NHTSA's motorcoach side
glazing retention research program, production windows from all three
manufacturers resulted in window opening during the impact.
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    \61\ For non-emergency exit fixed windows, the proposed test
would be conducted at the location of one of the fixed latches or
discrete attachment points. For fully rubber bonded or glued windows
with no latch mechanisms, the test would be conducted along the
center of the lower window edge one inch above the daylight opening
periphery.
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    We are proposing that windows (a) prevent passage of a 102 mm (4
inch) diameter sphere during the impact, and (b) be sturdy enough such
that there are no openings after the test that allow the passage of the
sphere when a force of no more than 22 N (5 lb) is applied with the
sphere at any vector in a direction from the interior to the exterior
of the vehicle. The requirement described in (b) is a simple one based
on a longstanding requirement currently in S5.1 of FMVSS No. 217. The
compliance test for S5.1 of Standard No. 217 involves a compliance
technician probing the window with the sphere. NHTSA would assess
compliance with the requirement in (b) above using the same basic
procedure.
    However, the requirement in (a) is more challenging. Because it is
impractical to probe for openings with the 102 mm (4 inch) sphere
during a dynamic test, NHTSA is proposing a requirement that is
premised on the concept of passage of the sphere, but is one that can
be more easily assessed in a dynamic test. This requirement would be
that during the impactor test, no portion of the window (excluding
glazing shards) may displace past a specified reference plane that is
determined in a pre-test procedure. The procedure is explained below.
Ejection Reference Plane
    In NHTSA's impactor test of glazing near a latching mechanism and
in the impactor test of glazing at the center of daylight opening, an
``ejection reference plane'' would be determined prior to the test. The
plane would be based on the passage of a 102 mm (4 inch) diameter
sphere through a potential ejection portal of the window. We would
require that no part of the window (excluding glazing shards) may pass
this ``ejection reference plane'' during the dynamic impact test. If
any part of the window frame passes the plane, there would be a failure
to comply.
    For side windows, the ``ejection reference plane'' is a vertical
plane parallel to the longitudinal vertical center plane of the bus
passing through a point located at a lateral distance of 102 mm (4
inches) from the lateral most point on the glazing and surrounding
frame, with the window in the closed position.
    For rear windows, the ``ejection reference plane'' is a vertical
plane perpendicular to the longitudinal vertical center plane of the
bus passing through a point located at a longitudinal distance of 102
mm (4 inches) from the rear most point on the glazing and surrounding
frame, with the window in the closed position.
    For roof glass panels/windows, the ``ejection reference plane'' is
a horizontal plane passing through a point located at a vertical
distance of 102 mm (4 inches) from the highest point on the glazing and
surrounding frame, with the window/panel in the closed position.

Displacement Limit of 102 mm (4 inches)
    The proposed performance requirements are built on preventing
passage of a 102 mm (4 inch) diameter sphere. The principle underlying
the 102 mm (4 inch) displacement limit is to prevent gaps or openings
to form in advanced glazing through which occupants (``including
children,'' states MAP-21 at Sec.  32703(b)(2)) can be partially or
totally ejected. A 100 mm (3.94 inch) performance limit is used in
several regulations relating to occupant retention. FMVSS No. 217
already requires manufacturers to ensure that each piece of glazing and
each piece of window frame be retained by its surrounding structure in
a manner that prevents the formation of any opening large enough to
admit the passage of a 102 mm (4 inch) diameter sphere under a
specified force. The 102 mm (4 inch) value is also used in FMVSS No.
206, ``Door locks and door retention components'' (49 CFR 571.206). In
FMVSS No. 206, the door is loaded with 18,000 N (4,047 lb) and the
space between the interior of the door and the exterior of the door
frame must be less than 100 mm (3.94 inches).
    In addition, the 102 mm (4 inch) limit is used in FMVSS No. 226,
``Ejection mitigation'' (49 CFR 571.226). It was noteworthy to NHTSA
when developing the NPRM proposing the standard that a value of
approximately 100 mm is used by the International Code Council (ICC) in
developing building codes used to construct residential and commercial
buildings. The ICC 2006 International Building Code and 2006
International Residential Code require guards to be placed around areas
such as open-sided walking areas, stairs, ramps, balconies and
landings. The guards must not allow passage of a sphere 102 mm (4
inches) in diameter up to a height of 864 mm (34 inches). NHTSA noted
that the ICC explains in the Commentary accompanying the Codes that the
102 mm (4 inch) spacing was chosen after considering information
showing that the 102 mm (4 inch) opening will prevent nearly all
children 1 year in age or older from falling through the guard. That
information helped NHTSA decide on a 100 mm (3.94 inch) limit for the
displacement of the head form impactor used in FMVSS No. 226.
    NHTSA requests comment on the linear displacement limit of 100 mm
(3.94 inch) as an appropriate value.

b. Broken Glazing

    Under this NPRM, each window would have to meet performance
requirements during and after an impact while pre-broken prior to the
test. The impact would be at the center of the daylight opening of the
window. The maximum displacement of the impactor would be limited to
175 mm (6.89 inches). The 75 mm (3 inch) diagonally offset pattern
would be used to pre-break the glazing with an unloaded electric staple
gun.
    This proposed test is to better simulate a real-world test
condition. As explained above in this preamble, the proposed dynamic
test simulates the loading of an unrestrained far-side 50th percentile
adult male passenger falling onto and loading the roll-side window. The
roll-side glazing may not always be intact prior to this occupant
loading. For instance, the glazing could break or shatter from objects
interior or exterior to the bus, torsion or deformation of the bus
structure, or even from the roll-side seated passenger loading prior to
the far-side occupant loading. This proposed test would evaluate the
strength and retention capabilities of pre-broken glazing (particularly
the plastic interlayer of laminated glass) to ensure that there is
enough strength left in the glazing to withstand the loading of the
occupant and to retain the occupant within the bus. In addition, the
window would be prohibited from having any opening after the test that
would allow passage of the 102 mm (4 inch) diameter sphere.
    NHTSA requests comments on the proposed 175 mm (6.9 inch) impactor
displacement value. The proposed 175 mm (6.9 inch) limit was chosen in
the interest of practicability, potential costs, and safety need. The
175 mm (6.9 inch) value is the average displacement from the two tests
of single-glazed laminated windows (standard thickness PVB laminates
0.76 mm (0.03 inch) layer), that were pre-broken using the 75 mm (3
inch) diagonally offset grid. However, the MCI E/J-series was the only
bus model tested at VRTC that offered production windows with a
laminated glass configuration. Therefore, the proposed requirement is
based solely on the MCI E/J windows that were tested. We seek comments
on whether 175 mm (6.9 inch) maximum impactor displacement is an
appropriate value for other bus window designs and window dimensions.
    Comments are also requested on the practicability, costs and
benefits of a lower impactor displacement limit, such as 146 mm (5.75
inches). One hundred forty-six (146) mm (5.75 inches) is the average
displacement of the impactor in the center of daylight opening impacts
under the Martec Study Conditions of pre-broken (using the 75 mm (3