Federal Motor Vehicle Safety Standards; Fuel System Integrity of Compressed Natural Gas Vehicles |
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Topics: National Highway Traffic Safety Administration
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Christopher A. Hart
Federal Register
April 25, 1994
[Federal Register: April 25, 1994]
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DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. 93-02; Notice 4]
RIN 2127-AD48
Federal Motor Vehicle Safety Standards; Fuel System Integrity of
Compressed Natural Gas Vehicles
AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).
ACTION: Final rule.
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SUMMARY: This rule establishes a new Federal motor vehicle safety
standard, Standard No. 303, Fuel System Integrity of Compressed Natural
Gas Vehicles, that specifies vehicle performance requirements for the
fuel system of vehicles fueled by compressed natural gas (CNG). The
Standard enhances the fuel system integrity of CNG vehicles by
subjecting the vehicles to crash testing and placing a limit on the
post-crash pressure drop in the fuel system. The Standard specifies
frontal, rear, and lateral barrier crash tests for light vehicles and a
moving contoured barrier crash test for school buses with a GVWR over
10,000 pounds. The purpose of this new standard is to reduce deaths and
injuries caused by fires resulting from fuel leakage during and after
crashes involving vehicles fueled by CNG.
This is the first final rule in the agency's comprehensive effort
to regulate alternative fueled vehicles. In addition to this final
rule, NHTSA anticipates issuing another final rule that will specify
performance requirements addressing the strength, durability, and
venting of CNG fuel containers. In addition, as a result of public
comments on the CNG notice of proposed rulemaking (NPRM), the agency
anticipates issuing a supplemental notice of proposed rulemaking
(SNPRM) proposing performance requirements that would evaluate a CNG
fuel container's internal corrosion, brittle fracture under low
temperatures, external damage, and fragmentation.
DATES: Effective Date: The Standard becomes effective on September 1,
1995.
Petitions for Reconsideration: Any petition for reconsideration of
this rule must be received by NHTSA no later than May 25, 1994.
ADDRESSES: Petitions for reconsideration of this rule should refer to
Docket 93-02; Notice 3 and should be submitted to: Administrator,
National Highway Traffic Safety Administration, 400 Seventh Street SW.,
Washington, DC 20590.
FOR FURTHER INFORMATION CONTACT: Mr. Gary R. Woodford, NRM-01.01,
Special Projects Staff, Office of Rulemaking, National Highway Traffic
Safety Administration, 400 Seventh Street SW., Washington, DC 20590
(202-366-4931).
SUPPLEMENTARY INFORMATION:
Outline
I. Background
A. General Information
B. Advance Notice of Proposed Rulemaking
C. Notice of Proposed Rulemaking
II. Comments on the Proposal
III. Agency's Decision
A. Overview
B. Vehicles Subject to the Performance Requirements
1. Gross Vehicle Weight Ratings
2. Terminology
C. Performance Requirements
1. Allowable Pressure Drop
a. Regulatory Background
b. Problems with Measuring Small Pressure Drops
c. Test Time
d. Test Temperature
e. Leakage from Fuel System Components
f. Bi-Fuel and Dual Fuel Applicability
D. Test Conditions
1. Test Pressure
2. Test Gas
3. Electric Shutoff Valves
E. Requirements Not Adopted
1. Static Rollover
2. Refueling connections
3. Venting
4. Leak detection
5. Retention of Fuel Storage Containers
F. Other Considerations
1. Vehicles manufactured in more than one stage
2. Benefits
3. Costs
4. Leadtime
VI. Rulemaking Analyses
A. Executive Order 12688 and DOT Regulatory Policies and
Procedures
B. Regulatory Flexibility Act
C. Executive Order 12612 (Federalism)
D. National Environmental Policy Act
E. Civil Justice Reform
I. Background
A. General Information
At standard temperature and pressure, natural gas is a gas that is
lighter than air.\1\ When used as a vehicle fuel, natural gas is
typically stored on-board a vehicle in cylindrical containers at a
pressure of approximately 20,684 kPa pressure (3,000 psi). Natural gas
is kept in this compressed state to increase the amount that can be
stored on-board the vehicle. This serves, in turn, to increase the
vehicle's driving range. Since natural gas is flammable and is stored
under high pressure when used as a vehicle fuel, it poses a potential
risk to motor vehicle safety.
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\1\Standard temperature is 0 deg. Celsius or 32 deg. Fahrenheit
and standard pressure is 101.4 kiloPascals (kPa) or 14.7 pounds per
square inch (psi).
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Alternative fuel vehicles powered by CNG have not been numerous to
date. The number of CNG vehicles in the United States has more than
doubled from 10,300 in 1990 to 23,800 at the end of 1992. The number of
CNG vehicles is projected to again double to an estimated 50,800
vehicles in 1994.
However, Federal legislation, as well as the need to meet
environmental and energy security goals, will lead to increased
production and use of these vehicles. Among the items of Federal
legislation encouraging the use of alternative fuels in general are:
(1) The Alternative Motor Fuels Act of 1988, (2) the Clean Air Act
Amendments of 1990, and (3) the Energy Policy Act of 1992. The
Alternative Motor Fuels Act of 1988 directs the Department of Energy to
conduct demonstration programs to encourage the use of alternative
motor fuels, including natural gas. As a further encouragement, this
Act also specifies that new passenger automobiles will have their fuel
economy calculated according to a special mileage enhancing procedure.
The Clean Air Act Amendments of 1990 establish the clean fuel
requirements that treat fuel type and content, along with vehicle
technology, as a potential source of emission reductions. These
Amendments call for programs that will substantially increase the
number of low-polluting vehicle/fuel combinations in use. The Energy
Policy Act of 1992 directs the Department of Transportation to issue
safety standards applicable to vehicle conversions.
Executive branch initiatives will also encourage the increased use
of alternative fueled vehicles. Executive Order 12844 increased by 50
percent the number of alternative fueled vehicles to be acquired by the
Federal Government from 1993 through 1995. (April 21, 1993) In
addition, in 1993, the President established the Federal Fleet
Conversion Task Force to accelerate the commercialization and market
acceptance of alternative fueled vehicles throughout the country.
B. Advance Notice of Proposed Rulemaking
On October 12, 1990, NHTSA published an advance notice of proposed
rulemaking (ANPRM) to explore whether the agency should issue Federal
motor vehicle safety standards (FMVSSs) to promote the fuel system
integrity of motor vehicles using CNG or liquefied petroleum gas (LPG)
as a motor fuel. (55 FR 41561) The ANPRM sought comment about the crash
integrity of vehicle fuel systems, the integrity of fuel storage
containers, and pressure relief for such containers.
C. Notice of Proposed Rulemaking
On January 21, 1993, NHTSA published a notice of proposed
rulemaking (NPRM) in which the agency proposed to establish a new FMVSS
specifying performance requirements for vehicles fueled by CNG (58 FR
5323). The proposal was based on comments received in response to the
ANPRM and other available information. The NPRM was divided into two
segments: (1) Vehicle requirements that addressed the integrity of the
entire fuel system, and (2) equipment requirements that addressed the
safety of the fuel containers themselves.
NHTSA decided to model the proposed requirements for CNG fueled
motor vehicles on Standard No. 301, Fuel System Integrity. Standard No.
301 specifies performance requirements for vehicles that use fuel with
a boiling point above 32 deg.F (i.e., liquid fuels under standard
temperature and pressure). Both gasoline and diesel fuel have a boiling
point above that temperature. Since CNG has a boiling point below 32
deg.F, vehicles manufactured to use only CNG are not subject to
Standard No. 301. Standard No. 301 limits the amount of fuel spillage
from ``light vehicles''\2\ during and after frontal, rear, and lateral
barrier crash tests and a static rollover test. The Standard also
limits fuel spillage from school buses with a GVWR over 10,000 pounds
after being impacted by a moving contoured barrier at any point and any
angle. By adopting a CNG rule based on Standard No. 301, the agency
would afford passengers of CNG vehicles a level of safety comparable to
that provided passengers of vehicles fueled by gasoline or diesel fuel.
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\2\Light vehicles include passenger cars, multipurpose passenger
vehicles (MPV's), trucks, and buses with a gross vehicle weight
rating (GVWR) of 10,000 pounds or less.
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NHTSA proposed that the fuel system integrity requirements for CNG
vehicles would include frontal, rear, and lateral barrier crash tests
for light vehicles, and a moving contoured barrier crash test for large
school buses. The agency proposed that fuel system integrity would be
assessed by measuring the fuel system's post-crash pressure drop,
instead of fuel spillage as under Standard No. 301, since CNG is a gas.
The allowable pressure drop for CNG fueled vehicles would be
equivalent, as measured by the energy content of fuel, to the allowable
spillage of fuel during Standard No. 301 compliance testing.
With respect to the ``equipment'' requirements applicable to CNG
containers, NHTSA proposed a definition for ``CNG fuel tank'' and
performance requirements for such fuel containers manufactured for
motor vehicles, including aftermarket containers.\3\ The Agency
proposed that the CNG containers would be subject to a pressure cycling
test to evaluate durability and a pressure burst test to evaluate
strength. In addition, the NPRM proposed equipment requirements to
regulate how the container may ``vent'' its contents under specified
conditions of elevated temperature and pressure.
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\3\Among the terms used to describe CNG fuel tanks are tanks,
containers, cylinders, and high pressure vessels. The agency will
refer to them as ``containers'' throughout this document.
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II. Comments on the Proposal
NHTSA received a large number of comments addressing the CNG
proposal. The commenters included manufacturers of CNG containers,
vehicle manufacturers, trade associations, other CNG-oriented
businesses, research organizations, State and local governments, the
United States Department of Energy, and energy companies. In addition,
NHTSA met with the Compressed Gas Association (CGA) and the Natural Gas
Vehicle Coalition (NGVC) and had telephone conversations and meetings
with some of the commenters. A record of each of these contacts may be
reviewed in the public docket.
The commenters generally believed that a Federal safety standard
regulating the integrity of CNG fuel systems and fuel containers was
necessary and appropriate. In fact, some commenters, including the CGA,
the NGVC, and CNG container manufacturers stated that NHTSA needs to
issue a Federal standard as soon as possible to facilitate the safe and
expeditious introduction of CNG fueled vehicles. The commenters
generally agreed with most of the vehicle-oriented proposals including
those related to the standard's applicability, the formula used to
determine the allowable amount of CNG leakage, and the barrier crash
tests. Nevertheless, commenters were concerned with the inability of
commercially available measuring devices to measure what they viewed as
the extremely small pressure drops allowed by the proposal.
III. Agency's Decision
A. Overview
In today's final rule, NHTSA is issuing a new Federal motor vehicle
safety standard, Standard No. 303, Fuel System Integrity of Compressed
Natural Gas Vehicles. It specifies vehicle performance requirements
applicable to the fuel system of a CNG fueled vehicle. As explained in
the NPRM, and summarized above, the fuel system integrity requirements
are comparable to those requirements in Standard No. 301. Like those
requirements, the CNG requirements specify frontal, rear, and lateral
barrier crash tests for light vehicles and a moving contoured barrier
crash test for school buses with a GVWR over 10,000 pounds.
There are, however, some differences between Standard No. 301 and
Standard No. 303. For instance, as noted above, CNG fuel leakage is
determined by the post-crash pressure drop in the fuel system instead
of by fuel spillage. The amount of allowable pressure drop is to be
based on the volume of the CNG leakage that either (1) is equivalent in
energy content to the amount of gasoline leakage permitted by Standard
No. 301, as calculated by the pressure drop formula\4\ or (2) 1062 kPa
(154 psi), whichever volume is greater. Another difference with
Standard No. 301 is that a static rollover provision has not been
included in the CNG Standard because while such a procedure can affect
the leakage of a liquid fuel, it has no affect on the leakage of a
lighter-than-air gaseous fuel.
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\4\The formula is set forth in S5.2(a)(2) and discussed in the
sections titled ``Problems with measuring small pressure drops,''
``Test temperatures,'' and ``Test pressures.''
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Each specific issue about the fuel system integrity requirements
for CNG vehicles will be discussed later in this notice. These issues
include the applicability of the vehicle requirements, the
practicability of measuring small pressure drops, the test time, the
test temperature, leakage from components in the fuel system,
evaluating vehicles that have more than one fuel system, and the test
conditions including the test pressure and test gas. The notice also
discusses the agency's decision not to adopt requirements regarding
certain matters, including static rollover, refueling connections, fuel
storage retention, venting, leakage detection, and warning devices.
This rule assures crash integrity of the vehicle which is
comparable to that required in Standard No. 301. In addition, NHTSA
recognizes that additional safety precautions may be required because
of the unique concerns with high pressure fuel containers and the
failure modes to which they may be subject. Thus, in addition to this
final rule, NHTSA has issued a supplemental notice of proposed
rulemaking (SNPRM) addressing the burst test for CNG containers (58 FR
68846, December 29, 1993). Based on comments to that notice and
comments to the January 1993 NPRM, the agency anticipates issuing
another final rule in the near future that will specify requirements
regulating a CNG container's strength, durability, and venting.
Moreover, based on comments to the NPRM and other available
information, the agency anticipates issuing a supplemental notice of
proposed rulemaking (SNPRM) that would propose performance requirements
addressing a CNG fuel container's internal corrosion, brittle fracture
under low temperature conditions, external damage, and fragmentation.
B. Applicability of the Vehicle Requirements
1. Gross Vehicle Weight Ratings
NHTSA proposed to apply the CNG Standard to passenger cars,
multipurpose passenger vehicles, trucks, and buses with a GVWR of
10,000 pounds or less, and to school buses, regardless of their GVWR.
This applicability is identical to the applicability of Standard No.
301. In the NPRM, the agency tentatively stated that it would be
inappropriate to apply the fuel leakage limits to CNG vehicles that
have a GVWR greater than 10,000 pounds other than school buses, because
barrier crash tests are not currently required for liquid-powered
vehicles that have a GVWR over 10,000 pounds other than school buses.
Navistar, Amoco, Transportation Manufacturing Corporation (TMC),
Chrysler, Thomas Built, and Flxible agreed with the agency's proposal
to apply the CNG vehicle requirements to light vehicles and school
buses. Washington State and Blue Bird commented that non-school buses
should be treated the same as school buses and thus be subject to the
new CNG Standard.
After reviewing the comments, NHTSA has decided to apply Standard
No. 303 to light vehicles and to all school buses. The agency's
objective in regulating the fuel system integrity of CNG vehicles is to
provide the same level of safety as that provided by Standard No. 301
for liquid fueled vehicles. Accordingly, the agency has decided to
specify the same applicability for CNG vehicles as Standard No. 301
specifies for gasoline and diesel vehicles. The agency disagrees with
comments favoring the application of the CNG standard to non-school
buses with a GVWR over 10,000 pounds. As explained in the NPRM, NHTSA
does not currently include any vehicle over 10,000 pounds, other than
school buses, in its crash test requirements. NHTSA further notes that
because the anticipated requirements for CNG fuel containers will apply
to containers equipped on all vehicles regardless of GVWR, CNG-fueled
heavy vehicles will be equipped with fuel containers that have been
certified to comply with that equipment standard.
2. Terminology
NHTSA proposed that the vehicle requirements be applicable to
vehicles manufactured to operate on CNG-only (``dedicated'') vehicles
and to vehicles manufactured to operate on two fuels, CNG and either
gasoline or diesel fuel. The agency referred in the NPRM to this latter
type of vehicle as a ``dual fuel'' CNG vehicle.
The American Automobile Manufacturers Association (AAMA), Blue
Bird, Oklahoma Gas, and the NGVC commented that the agency used the
term ``dual fuel vehicle'' incorrectly. These commenters explained that
the industry's generally understood meaning of ``dual fuel vehicle'' is
a vehicle that uses a mixture of two fuels simultaneously, in this case
CNG and another fuel such as gasoline or diesel. A vehicle that is
capable of operating either on CNG and another fuel such as gasoline or
diesel, but not a mixture of both, is referred to as a ``bi-fuel''
vehicle. A vehicle equipped with one fuel system and designed to
operate on CNG is referred to as a ``dedicated CNG vehicle.''
NHTSA has decided to adopt the generally accepted terminology used
in the alternative fuel industry for vehicles that operate on more than
one fuel. Accordingly, the final rule includes definitions for ``Bi-
fuel CNG vehicle,'' ``Dedicated CNG vehicle,'' and ``Dual-fuel CNG
vehicle.'' The agency notes that these definitions are generally
consistent with the statutory terms in the Energy Policy Act. Section
403 of that Act amended certain provisions in Title V of the Motor
Vehicle Information and Cost Savings Act, including definitions for
``dedicated vehicle'' and ``dual fueled vehicles.'' The definitions of
these terms in this notice are consistent with the statutory
provisions. The one difference between the agency's definitions and the
statutory definitions is that the agency's definition of ``bi-fuel''
vehicle also falls under the Act's definition of ``dual fueled
automobile'' (i.e., ``an automobile which is capable of operating on an
alternative fuel [such as CNG] and on gasoline or diesel)''.
Nevertheless, the agency believes that it is necessary that its
definition of ``bi-fuel'' vehicle include the greater specificity
provided by the industry's definition of this term.
C. Performance Requirements
1. Allowable Pressure Drop
a. Regulatory background. In the ANPRM, NHTSA discussed the
possibility of proposing a prohibition against any fuel leakage during
the crash test and for up to 30 minutes after the vehicle's motion had
ceased. A number of commenters to the ANPRM objected to a no-leakage
requirement, claiming that any pressurized gaseous fuel system will
produce a minimal amount of leakage from fittings and valves. Along
with their concerns about practicability, commenters further stated
that a no-leakage requirement would be overly restrictive in comparison
to Standard No. 301. That standard permits a minimal amount of leakage.
After considering the comments on the ANPRM, NHTSA decided that
instead of proposing a no-leakage requirement, it would propose
allowing not more than a minimal level of leakage for a specified time
period. The allowable leakage provision was patterned after Standard
No. 301 and was intended to avoid the practicability problems
associated with a no-leakage requirement. The agency believed that the
allowable amount of leakage is equivalent in energy content to the
leakage allowed for gasoline in Standard No. 301.
Under the proposal, CNG leakage from the vehicle's entire fuel
system would have been measured for a 15-minute period following a
barrier crash test. The proposal discussed two alternatives related to
measuring the allowable leakage: (1) Leakage would be measured through
incremental measurements from the time of impact until the vehicle
ceased motion, for the subsequent five-minute period, and every minute
in the next 10-minute period, or (2) the cumulative leakage would be
measured only once, at the end of the 15-minute test period. With
either measurement, the total gas permitted to leak at the end of the
test period would have been the same. The agency requested comment on
the feasibility and practicability of specifying gaseous leakage
measurements at specific time intervals and about devices that are
capable of measuring incremental pressure changes.
NHTSA received many comments about the proposal to evaluate a CNG
vehicle's fuel system integrity through an allowable pressure drop
requirement. Among the issues addressed by commenters were (1)
practicability problems with measuring small levels of pressure drop,
(2) the appropriate length of time necessary to evaluate pressure drop,
(3) the effect of temperature variations on pressure drop, (4) leakage
from fuel system components, (5) and evaluating bi-fuel and dual fuel
vehicles. Each of these issues will be addressed below, along with the
agency's response to the comments.
b. Problems with measuring small pressure drops. AAMA, Thomas,
Navistar, TMC, NGVC, Minnesota Gas, and Flxible stated that the
proposal about allowable pressure drop would result in manufacturers
trying to measure amounts of gas leakage too small to be measured by
existing technology. They stated that presently manufactured measuring
devices known as pressure transducers do not have the capability to
measure the proposed amounts of pressure drop, even if only one
cumulative measurement is taken after 15 minutes. AAMA stated that a
state-of-the-art capacitance type pressure transducer has an accuracy
of 0.11 percent. Therefore, it believed that if this pressure
transducer has a range of measurement of 0 to 20,685 kPa (0 to 3000
psi), the error associated with any measurement would be
22.8 kPa (3.3 psi). AAMA further stated that a
variation in 5.6 deg. Celsius (10 deg. Fahrenheit) could result in
errors of 41.4 kPa and 31.0 kPa
(6.0 and 4.5 psi) from thermal zero shift and
thermal coefficient sensitivity, respectively. Finally, AAMA stated
that the conversion of analog data to digital form would introduce an
error of 0.056 percent or 11.0 kPa (1.6 psi).
Aggregating all these alleged measurement errors would result in a
potential error of 106.1 kPa (15.4 psi). AAMA
further stated that it is contrary to accepted engineering measurement
practice to accurately measure data that are of the same order of
magnitude as known transducer data system errors. Thus, it stated that
the total measurement error should not exceed 10 percent of the value
being measured and that given the above mentioned errors, pressure
drops under 1062 kPa (154 psi) should not be measured with a
capacitance type transducer. AAMA evaluated the error estimates for a
less accurate type of pressure transducer than the capacitance
transducer (the strain gage transducer) and obtained a maximum error of
328.2 kPa (47.6 psi).
Based on these comments about the accuracy and practicability of
using measurement transducers, NHTSA has independently determined that
current pressure transducers are not able to measure the relatively
small pressure drops that would have been allowed to occur after 15
minutes for a container with a 3000 psi service pressure. The agency
found that most pressure transducers have an accuracy of approximately
0.1 percent, and now concludes that it would have been impracticable to
measure the proposed pressure drop levels.
In view of the problems in measuring small pressure drops, NHTSA
has modified the allowable pressure drop requirement so that the
pressure drop of a CNG vehicle must not exceed the amount calculated by
the pressure drop formula or a pressure drop level of 1062 kPa (154
psi), whichever is greater. As noted above, 1062 kPa (154 psi) is the
cumulative potential error (106.1 kPa (15.4
psi)) of a capacitance type transducer, multiplied by 10 (i.e.,
22.8 kPa (3.3 psi) associated with measurement
error, 72.4 (10.5 psi) associated with
temperature variation, and 11.0 kPa (1.6 psi)
associated with data conversion). Both a 22.8 kPa (3.3 psi) and a 72.4
kPa (10.5 psi) range would result in a significant percentage of the
allowable amount of leakage during a 15-minute period, particularly for
vehicles with large fuel systems. The agency believes that by modifying
the requirement to specify a floor under the amount of permissible
pressure drop determined using the pressure drop formula, the agency
will be able to regulate pressure loss from CNG vehicles to the extent
permitted by existing pressure drop measurement technology.
NHTSA notes that establishing a floor under the amount of
permissible pressure drop is especially important for vehicles with
large fuel systems, such as school buses, because they will experience
extremely small pressure drops. This is so because in the formula for
calculating the allowable pressure drop, pressure drop equals the
ambient temperature divided by the volume of the fuel system. Since the
fuel system volume is the denominator, the allowable pressure drop
decreases as the vehicle's fuel system volume increases. Without the
floor, the formula would yield pressure drops potentially too small to
be measured.
In response to Blue Bird's recommendation that the regulation allow
a five percent drop after the barrier crash test, NHTSA is concerned
that this approach would allow varying amounts of fuel leakage from
different vehicles depending on the fuel system's size. Therefore, the
agency has decided to reject Blue Bird's recommendation.
c. Test time. NHTSA received nine comments addressing the
appropriate test time for the pressure drop requirement. Of the nine
commenters, Washington, NGV Systems, Navistar, and NGVC stated that a
cumulative measurement should be taken after 15 minutes because the
amount of gas leaking each minute would be too small to measure
accurately. They believed that taking incremental measurements within
the 15 minute period would not be acceptable. Other commenters,
including AAMA, Thomas, TMC, and Blue Bird stated that even the
cumulative leakage over 15 minutes would be too small to measure in
some cases. Blue Bird stated that the proposed leakage limit was
``totally unacceptable'' because it would be necessary to detect a
pressure drop of 0.6 psi in a 3000 psi fuel system. AAMA stated that
measurement of the pressure drop 60 minutes after impact would be
reasonable and should be adopted by the agency based on the limitations
of available measurement equipment, since the proposed leakage rate
would result in a total pressure drop of 211 psi for a 3000 psi, 170
liter (45 gallon) fuel system.
Given the problems with measuring the proposed levels of allowable
pressure drop, NHTSA has decided to change the pressure drop
requirement to make it more measurable while keeping it as close to a
no-leakage requirement as practicable. The agency considered two
alternative changes to the proposal to ensure that the level of
pressure drop was practicable to measure: (1) Increase the amount of
CNG leakage allowed during the proposed 15 minute test period or (2)
increase the test time period. The agency has decided to reject the
option of increasing the level of allowable leakage to the point that
even marginal violations of the leakage limit could be reliably
measured at the end of a 15 minute period. Such an increase might be
unsafe and would be inconsistent with the agency's goal of establishing
a minimum leakage requirement that is as close to a no-leakage
requirement as possible while still being readily measurable.
Instead, to accomplish its goal of establishing a safe and
practicable requirement, NHTSA has decided to increase the test time
from 15 minutes to 60 minutes. The agency has determined that it is
necessary to lengthen the test period to permit measurement of safe
levels of leakage. To illustrate, a container with a service pressure
of 3000 psi and an allowable pressure drop of approximately 50 psi
after 15 minutes, would have an allowable pressure drop of 200 psi
after 60 minutes. Since the agency has determined that it is not
possible to reliably measure a pressure drop of less than 154 psi
within a 10 deg.F temperature variation, then the agency's original
goal of prohibiting a pressure drop of more than 50 psi in 15 minutes
would not be practicable. Accordingly, the agency determined that it is
necessary to lengthen the test period or else the only detectable
violations would be gross violations of the pressure drop limit. Small
violations of the limit would not be detectable. Moreover, while a
pressure drop of 50 psi in 15 minutes could not be reliably measured, a
pressure drop of 200 psi (4 x 50 psi=200 psi in 60 minutes (4 x 15
minutes=60 minutes) is readily measurable. While those two pressure
drops are equally stringent since the leakage rate is essentially
constant for a marginal violation, only the 60 minute period would
permit measurable results.
By increasing the test time to 60 minutes, the agency believes that
the requirement will allow only readily measurable and safe amounts of
leakage. The agency believes that increasing the test time from 15
minutes to 60 minutes will not result in an increase in leakage rate.
As explained above, if the limit and the time are proportionately
increased the same extent, the stringency is maintained. Increasing the
test time will not increase the safety risk since the rate of CNG
leakage is still equivalent, in terms of energy content, to that
allowed of liquid fuels in Standard No. 301. In addition, the leakage
rate is more critical than the total level of leakage over an extended
period of time, since CNG dissipates rapidly because it is lighter than
air.
d. Test temperature. In the NPRM, NHTSA proposed a formula in which
the volume of allowable CNG leakage would translate into certain
allowable pressure drops in units of kPa for CNG fuel systems, as
follows:
------------------------------------------------------------------------
Volume of CNG leakage Allowable pressure drop
------------------------------------------------------------------------
39.8 liters CNG.................... 13.72 (T/VFS).
199.0 liters CNG................... 68.6 (T/VFS).
------------------------------------------------------------------------
where
T=Temperature of the test gas in degrees Kelvin, stabilized to
ambient temperature prior to testing.
VFS=The internal volume in liters of the fuel system from
which CNG is leaked.
In the NPRM, NHTSA also considered but decided not to propose
specifying an ambient temperature. The agency believed that not
specifying an ambient temperature would not affect a vehicle's
compliance with the standard and would facilitate the combining of
tests for various standards. The agency requested comments about its
tentative decision not to specify an ambient temperature.
Several commenters, including AAMA, NGVC, Navistar, Blue Bird,
Minnesota Gas, Flxible, and Thomas, addressed the issue of ambient
temperature variability. NGVC, Minnesota Gas, Thomas, and Blue Bird
agreed with the agency that no ambient temperature should be specified.
Nevertheless, all the commenters, except for Thomas, stated that
temperature variations should be compensated for when conducting the
crash test. AAMA stated that temperature variations that occur over the
course of the testing would change the pressure of the test gas. It
stated that a 5.6 deg.C (10 deg.F) variance in the test temperature
would result in a 413.7 kPa (60 psi) change in the pressure of the test
gas in a 170 liter (45 gallon) fuel container. AAMA stated that a
pressure change due to a temperature change could mask or intensify the
actual pressure drop measurement. However, AAMA did not suggest any
method to correct for the temperature.
After reviewing the comments, NHTSA continues to believe that no
ambient temperature should be specified for the reasons set forth in
the NPRM. However, the agency also believes that the test procedure and
formula should control for temperature variations. Without such
control, a large change in temperature could artificially affect the
test results. NHTSA has decided to specify that the maximum ambient
temperature variation over the 60-minute test period cannot exceed
5.6 deg.C (10 deg.F). A temperature variation exceeding this amount
will invalidate the test results. The agency believes that this test
condition will minimize changes in test gas temperature and
instrumentation accuracy during the 60-minute period, without placing
an unreasonable burden on those performing the test.
In addition, NHTSA has decided to include in the pressure drop
formula a provision to calculate the average ambient temperature by
measuring the ambient temperature at the test's start and then every 15
minutes until 60 minutes has elapsed. The sum of these temperatures is
then divided by five (the number of measurements taken) to yield the
average ambient temperature. This calculation will be used for the
term, ``T,'' in the agency's pressure drop formula. NHTSA believes that
including a calculation for the average ambient temperature in the
formula will directly control for fluctuations in pressure due to
temperature variations, because pressure and temperature are linearly
related in the formula (i.e., pressure equals temperature multiplied by
a constant, where the constant includes the volume of the system and
the compressibility factor).
AAMA recommended that testing be conducted between 60 deg. and 70
deg.F. Blue Bird commented that the test conditions specify a
permissible temperature range of between 0 deg.C and 32 deg.C
(32 deg. to 90 deg.F) to eliminate testing at unusually low or high
temperatures. It believed that controlling such temperature extremes
could reduce variables that affect vehicle and fuel system reactions to
crash tests.
After reviewing the comments and other available information, NHTSA
has decided that prohibiting ambient temperature variation by more than
10 deg.F during the 60-minute period after testing will be sufficient
to minimize pressure drop variability due to temperature change.
However, the agency has decided not to specify a minimum or maximum
temperature for the 60-minute period after testing. This will
facilitate the combining of tests for various standards. In addition,
specifying a range like the one recommended by AAMA would be
inappropriate for those vehicle manufacturers that conduct their
compliance crash testing outdoors throughout the year.
e. Leakage from fuel system components. In the NPRM, NHTSA
discussed two alternatives regarding measurement of CNG leakage after a
barrier crash test. Under the first alternative, the allowable CNG
leakage level would apply to the vehicle's entire fuel system, instead
of the fuel storage containers only. The agency proposed that the term
``fuel system'' be defined as ``all components used to store or supply
CNG to the vehicle's engine.'' This approach would have required a
manufacturer to measure the internal volume of the vehicle's entire
fuel system, including the lines, components, and fuel storage
containers as the basis for evaluating allowable leakage. Under the
second alternative, the allowable CNG leakage would only apply to the
CNG fuel container or containers. This approach would have required a
manufacturer to measure the volume of the fuel storage containers only.
The agency tentatively preferred the first alternative, believing that
it would more closely reflect a real world crash. The agency was
concerned that the second alternative would permit unlimited leakage
from the vehicle's plumbing system including fuel lines and other
components downstream from the fuel containers during a crash test.
Nine commenters addressed the issue of what components of a fuel
system should be evaluated for leakage. Navistar, NGV Systems, Flxible,
CNG Pittsburgh, Washington, and Amoco supported measuring leakage from
the entire fuel system. AAMA, Thomas, and Minnesota Gas stated that
leakage should be measured from the fuel containers to the first
pressure regulator, an area which is known as the high pressure side of
the fuel system. Minnesota Gas stated that, while the fuel lines,
connections, and valves may be the most vulnerable part of a fuel
system, the volume of gas in these parts is small when compared to the
gas volume stored in the fuel containers. Thomas stated that the volume
of the gas in the fuel lines and valves between the containers and
engine is negligible. AAMA stated that adding pressure transducers to
points in the fuel lines solely for purposes of conducting the test
would produce points of potential leakage that would not exist on a
non-test vehicle. This would make the test vehicles potentially
unrepresentative of the vehicle population. AAMA recommended that to
minimize the potential leakage points, one pressure check point be used
immediately upstream from the high pressure regulator, or at a location
specified by the manufacturer.
After reviewing the comments and other information, NHTSA has
decided to measure leakage only from the high pressure portion of the
fuel system. By ``high pressure portion'' of a CNG fuel system, the
agency means all the components from and including the CNG fuel
container or containers up to, but not including, the first pressure
regulator. The agency notes that as CNG flows from the vehicle fuel
containers to the engine, it passes through one or two pressure
regulators that reduce the pressure of the gas before it enters the
engine. On a carbureted type vehicle, there may be one or two pressure
regulators. For systems with two pressure regulators, the first
pressure regulator typically reduces service fuel line pressure from
3000 psi to approximately 300 psi, while the second regulator reduces
pressure from this level to approximately ambient pressure.
When the agency proposed to regulate leakage from the entire fuel
system, it was not aware of the significant difficulty involved in
accurately measuring small amounts of leakage. In addition, the volume
of gas in the fuel lines and valves is very small when compared to the
volume of the fuel containers. For instance, Thomas stated that a
school bus with six CNG fuel containers has 822 liters of CNG (137
liters per container x 6). By comparison, the volume of that bus'
plumbing system (e.g., fuel lines, valves, etc.) is 0.62 liters. Thus,
the volume of CNG in the plumbing system is approximately 0.075 percent
of the entire fuel system. Therefore, possible leakage from the
plumbing system would be minimal and therefore not a significant safety
concern. Thus, contrary to the agency's belief in the NPRM, measuring
the entire fuel system would not be much more representative of real
world crashes than measuring the fuel system's high pressure portion.
Another reason that the agency decided not to measure leakage from the
entire fuel system is that using additional transducers would have
resulted in the test vehicles having more points of potential leakage
than non-test vehicles, as pointed out by AAMA.
f. Bi-fuel and dual fuel applicability. In the ANPRM, NHTSA
discussed whether dual-fuel vehicles should be treated differently than
dedicated CNG vehicles. Some commenters recommended that dual-fuel
vehicles have separate fuel system integrity tests based on each of the
fuels used in the particular vehicle. Under this approach, dual-fuel
vehicles would be tested twice: once under current Standard No. 301 as
though they operated only on gasoline or diesel fuel and a second time
under the proposed CNG standard as though they operated only on CNG.
In the NPRM, NHTSA proposed that the energy equivalency of the
allowable fuel leakage from dual-fuel vehicles be the same as that for
dedicated vehicles. The agency disagreed with commenters to the ANPRM
that recommended running two separate tests. The agency believed that
approach would result in an allowable level of total fuel leakage for
dual-fuel vehicles that is twice what is currently permitted under
Standard No. 301 or what the agency proposed to establish for CNG
vehicles. In the NPRM, the agency explained that since a real world
crash could cause both fuel systems to leak, safety concerns associated
with dual-fuel vehicles would be best addressed by establishing a
single, overall fuel leakage limit applicable to the combined energy
equivalency of the amount of both types of fuel leaked in a single
crash test.
Six commenters addressed the most appropriate way to regulate the
safety of dual-fuel and bi-fuel vehicles. While NFPA, CNG Pittsburgh,
and NYCFD agreed with the proposal to require that dual-fuel vehicles
comply with a single overall fuel leakage limit based on the combined
energy level of both fuel types, AAMA, Blue Bird, and Brunswick
disagreed. AAMA, Blue Bird, and Brunswick theoretically agreed with the
concept of establishing a combined energy level. However, they stated
that because the allowable leakage would be cut in half if the agency
adopted the proposal, applying this criterion would make both CNG and
liquid fuel leakage unmeasurable.
After reviewing the comments, NHTSA has decided to require only one
test on dual-fuel and bi-fuel vehicles that permits the amount of
gaseous leakage specified in the CNG standard plus the amount of liquid
leakage specified in Standard No. 301. Ideally, the agency would have
preferred to adopt the proposed approach that would have kept the
combined energy equivalency at an amount consistent with dedicated
vehicles. However, as discussed in an earlier section, the
practicability problems with measuring low levels of CNG leakage using
current technology makes that approach impracticable. Along with being
practicable, the requirement, as adopted, will reduce the test costs
incurred by manufacturers since only one test will have to be run. In
addition, NHTSA notes that the allowable leakage levels for liquid
fuels under Standard No. 301 and CNG each approximate a ``no leakage''
condition.
D. Test Conditions
1. Test Pressure
In the NPRM, NHTSA proposed that CNG fuel storage containers be
tested at 100 percent of service pressure. The agency believed that
this test condition would be consistent with Transport Canada's fuel
system integrity standard for CNG vehicles. In addition, this is the
pressure at which the container is designed to operate when filled with
the gaseous fuel at 20 deg.C (68 deg.F).
The proposal to specify 100 percent of service pressure level
departed from the requirement in Standard No. 301 specifying that
gasoline fueled vehicles be tested at a level of between 90 to 95
percent of capacity. In the proposal, the agency noted that unlike
gaseous fuels, gravity and vehicle attitude play important roles in
determining the amount of leakage experienced by a liquid fuel. The
fuel fill level is not as critical a test condition for liquid fuels.
In contrast, while leakage of gaseous fuels is influenced by the level
of pressure inside a ruptured fuel system, it is not influenced by the
vehicle's attitude or gravity. Based on these considerations, NHTSA
decided to propose that the containers be tested at the maximum fill
level (i.e., 100 percent of service pressure) to simulate a worst case
accident situation for CNG vehicles.
Six commenters addressed the appropriate service pressure at which
the CNG containers would be tested. Minnesota Gas, CNG Pittsburgh, and
Washington agreed with the agency's proposal to test at 100 percent of
service pressure. Minnesota Gas agreed with the proposal because it
would be consistent with Transport Canada. AAMA, Navistar, and Thomas
stated that some tolerance should be allowed, given practicability
concerns. Thomas recommended that a tolerance range of about three
percent should be allowed (i.e., 90 psi on a container with
a 3000 psi service pressure.) AAMA recommended a range for fill level
between 95 percent to 100 percent, because it believed that temperature
in a CNG container may rise significantly as it is filled and that some
time would be required for pressure and temperature to stabilize.
NHTSA has decided to specify the fill level to be at 100 percent of
the service pressure. After reviewing the comments, the agency
considered allowing a fill level of between 95 percent to 100 percent
of service pressure. However, allowing a fill level of 95 percent of
the service pressure (i.e., 2850 psi for a 3000 psi container) would
result in a less stringent condition before the crash test. Thus, the
agency would no longer be testing a worst case situation. The agency
acknowledges that a container will need additional time to stabilize
when achieving a 100 percent fill condition. However, the agency
believes that it is necessary to allow for this additional time since
including a testing tolerance would affect the requirement's
stringency. The agency further notes that including a 100 percent fill
condition is consistent with Transport Canada's standard for fuel
system integrity.
2. Test Gas
In the NPRM, NHTSA proposed to specify nitrogen (N2) as the
test gas. In determining the appropriate test gas, NHTSA sought one
that adequately represents CNG, is safe during crash tests and provides
a common baseline from which to derive all leakage measurements. The
agency decided to propose using nitrogen as the test gas because both
nitrogen and CNG are lighter than air and thus would disperse upward
into the air through any rupture in the fuel system instead of pooling
in cavities of the fuel system or falling to the ground. The agency
believed that a volume of nitrogen that is leaked as a test gas would
be equal to the same volume of CNG that leaks. In addition, nitrogen is
readily available and is safer than CNG for crash tests because it is
neither flammable nor toxic.
Seven commenters addressed the issue of test gas. Of those
commenters, six agreed with the agency's proposal to specify nitrogen
as a test gas. Thomas Built requested that dry air be used as a test
gas but offered no rationale. NGV Systems stated that the vehicles
should be tested with the fuel with which it will operate.
After reviewing the comments and other available information, NHTSA
has decided to specify that nitrogen be the test gas during crash tests
of CNG vehicles. Notwithstanding Thomas Built's request to allow dry
air, the agency has decided not to specify dry air as an alternative
test gas, even though it has properties similar to nitrogen. The agency
believes that the test results will be more consistent and enforcement
will be facilitated by permitting only one test gas. As indicated by
the majority of commenters addressing this issue, NHTSA believes that
nitrogen is stable and readily available and therefore should be
specified in the Standard. This decision is consistent with Standard
No. 301 which specifies the use of Stoddard Solvent as the single test
liquid, and Transport Canada's standard for CNG fuel system integrity
which specifies the use of nitrogen as a test gas.
The type of test gas is relevant to calculating the allowable
pressure drop, since the compressibility factor, ``Z,'' is included in
the formula. In the NPRM, NHTSA estimated that the compressibility of
nitrogen is 1.00. However, AAMA commented that a compressibility of
1.05 is more accurate for the conditions the test gas will be under
when tested in the fuel containers (approximately 20,685 kPa (3,000
psi) and 21.1 deg.C (70 deg.F)). Upon further review, NHTSA agrees with
AAMA that the appropriate compressibility factor is 1.05.
3. Electric Shutoff Valves
In the NPRM, NHTSA proposed that ``if the vehicle has an
electrically driven fuel pump that normally runs when the vehicle's
electrical system is activated, it is operated at the time of the
barrier crash.'' The agency also proposed that ``Any shutoff valve at
the fuel tank is in the open position.'' In this latter statement, the
agency was referring to manual shutoff valves, and not those which may
be electrically operated.
AAMA commented that requiring the crash test to be conducted with
shutoff valves held open would be incompatible with the vehicle's
normal operation during a crash sequence and with the intent of the
standard. AAMA stated that vehicles equipped with manual shutoff valves
at each fuel tank should have these valves in the fully open position
during vehicle testing. However, electric shutoff valves should be
handled in a manner consistent with other electrical devices such as an
electric fuel pump.
After reviewing the comment, NHTSA concurs and believes that if the
vehicle has electrically operated shutoff valves that are normally open
when the electrical system is activated, then they must be open at the
time of the crash test. The agency believes that the vehicle test
conditions should simulate, to the extent practicable, the conditions
present in a real world crash. This is the same rationale used in
having electrically activated fuel pumps in operation, before the crash
test in Standard No. 301.
E. Requirements Not Adopted
1. Static Rollover
In the NPRM, NHTSA decided not to propose a static vehicle rollover
test for dedicated CNG vehicles. The agency explained that a rollover
requirement is only needed for liquid fuel vehicles (including dual-
fuel and bi-fuel vehicles) because leakage is a function of gravity and
the location of the rupture relative to the fuel. Without a rollover
test, a rupture in the fuel system above the level of the liquid fuel
would not be detected. In contrast, CNG is pressurized and would
quickly escape upon rupture of the fuel system. Thus, for a CNG fuel
system, any leakage would be unaffected by vehicle attitude or gravity.
NHTSA received three comments addressing whether to include a
static vehicle rollover requirement. Navistar and Washington State
agreed with the agency's proposal that such a test was not needed. The
New York City Fire Department (NYFD) believed that a rollover
requirement was necessary since some CNG containers may be mounted on
the vehicle's roof.
NHTSA continues to believe that a static rollover test is not
needed for the reasons set forth in the NPRM. The agency notes that
NYFD may have misinterpreted the rollover requirement that was under
consideration. The agency was considering a static rollover requirement
like the one in Standard No. 301 in which after crash testing, the
vehicle is rotated on its axis to determine leakage. The agency was not
considering a dynamic rollover test in the context of the CNG
rulemaking.
2. Refueling Connections
In the NPRM, NHTSA decided not to propose requirements regarding
the standardization of refueling connections, notwithstanding comments
to the ANPRM advocating such an approach. These commenters believed
that specifying certain connector sizes would prevent over-
pressurization during refueling. NHTSA believed that it was not
necessary to regulate this area because the potential safety risks
associated with over-pressurization of the fuel storage containers are
addressed through the proposed container venting requirements (bonfire
test) discussed above. NHTSA further believed that voluntary actions by
industry will address most, if not all, of the problems raised by
commenters. The agency also believed that the issues raised by
commenters to the ANPRM, with the exception of overfilling the fuel
storage containers, did not present significant safety concerns.
NHTSA received 12 comments addressing the need to standardize the
refueling connections. EDO, Flxible, and Tecogen agreed with the
agency's rationale for not including requirements for refueling
connections. Nine commenters believed that NHTSA should adopt a
requirement for refueling connections. AAMA, NGVC, and several natural
gas companies believed that NHTSA should adopt NGV-1. NGV-1 is a
voluntary standard being developed by the American National Standards
Institute (ANSI)/Canadian Gas Association Standard for Compressed
Natural Gas Vehicle Fueling Connection Devices. Ontario recommended
that the agency should specify the universal use of a single maximum
filling pressure of 20,685 kPa (3000 psi). It believed that such
standardization would reduce the safety risk and promote international
harmonization.
After reviewing the comments, NHTSA continues to believe that
Federal regulation is not needed with respect to the refueling
connection devices. As explained in the NPRM, the agency continues to
believe that problems associated with filling fuel containers do not
present significant safety concerns. Moreover, the agency continues to
believe that the proposed bonfire test, which the agency is considering
for CNG containers, addresses potential safety risks associated with
over-pressurization. In addition, the agency believes that refueling
connections present an issue that is peripheral to the agency's focus
of fuel system integrity as determined by crashes. Notwithstanding this
decision, the agency will continue to monitor the safety of refueling
connections to determine if future agency action is needed.
3. Venting
In the ANPRM, the agency discussed requiring that all pressure
relief mechanisms be vented to the outside of the vehicle, away from
the passenger, luggage, or other compartments that could expose vehicle
occupants to the gaseous fuel. However, after considering comments to
the ANPRM, NHTSA decided not to propose a venting requirement. The
agency believed that such a requirement would be unnecessarily design
restrictive in view of the wide variations among vehicle designs and
models. In addition, the agency noted that CNG used in motor fuel
applications would have an odor that would warn vehicle occupants of
the presence of escaping gas.
NHTSA received comments from the California Highway Patrol (CHP)
and Washington State about venting requirements. CHP stated that
venting is necessary to ensure safety, but did not elaborate.
Washington State stated that gaseous fuels could accumulate when a
school bus is parked or when air circulation is inadequate. While it
believed that such accumulation could be explosive, the commenter
provided no data to indicate the extent of the alleged safety problem.
After reviewing the comments, NHTSA continues to believe that it is
not necessary or appropriate to specify venting requirements in the CNG
vehicle standard. The agency notes that there are no data to verify
that gases accumulate under vehicles or otherwise pose a safety problem
that could be alleviated if a venting requirement were adopted. In
addition, the agency believes that exposure to an ignition source would
be unlikely for a parked vehicle.
4. Leak Detection
In the NPRM, NHTSA requested comments about whether to require a
sensing device to detect unacceptable levels of gaseous leakage from
the fuel system and to provide a warning to vehicle occupants. The
notice posed questions about the need for and types of warning devices,
the amount of fuel in the air that would activate a warning device, and
the availability, cost, and reliability of such a device.
NHTSA received 11 comments about warning or leakage detection
devices. EDO, CNG Pittsburgh, Oklahoma Gas, Minnesota Gas, Navistar,
Thomas, Brooklyn Union Gas, Flxible, and NGVC stated that no
requirement was necessary. Several commenters stated that a detection
device was not needed because CNG is odorized and thus readily detected
by the human nose. Therefore, according to these commenters, a
vehicle's occupants or bystanders would be able to detect any CNG
leakage. Two commenters, Washington State and the Metropolitan Suburban
Bus Authority (MSBA), favored a requirement for the detection and
warning of fuel leakage. However, neither commenter elaborated about
the need for such a requirement.
After reviewing the comments, NHTSA has determined that a
requirement applicable to detecting or warning about fuel leakage is
not necessary. The agency agrees with those commenters who noted that
CNG is odorized and thus is readily detectable.
5. Retention of Fuel Storage Containers
In the NPRM, NHTSA decided not to propose a specific requirement
for container retention. This decision was based on the agency's belief
that manufacturers would need to design container retention
characteristics in order for their CNG vehicles to meet the allowable
leakage limits specified for the crash tests.
Nine commenters addressed whether the agency should specify a
container retention requirement. Of the commenters, AAMA, Navistar, and
NGV Systems agreed with the agency's decision not to include a
container retention requirement. Manchester commented that such a
requirement would pose problems. Five commenters, the General Services
Commission (GSC), the National Fire Protection Association (NFPA),
Flxible, NGVC, and CNG Pittsburgh, disagreed with the agency's decision
not to include a container retention requirement. GSC stated that CNG
fuel containers should be surrounded by a strong metal cage to prevent
the container from breaking loose. Alternatively, GSC recommended that
the agency require an internal excess-flow shutoff valve that would
prevent loss of fuel if the external valving ruptured. Several
commenters stated that container detachment was important and could be
prevented by adopting NFPA 52.\5\ NFPA further stated that fuel
container breakaway could occur without fuel leakage if an excess flow
valve or an automatic shutoff valve were actuated during a crash. The
container could then cause injury to the occupants or damage the
vehicle.
---------------------------------------------------------------------------
\5\NFPA 52 is a voluntary standard issued by the National Fire
Protection Association that applies to the design and installation
of CNG engine fuel systems including aftermarket and OEMs and their
associated fueling systems.
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After reviewing the comments, NHTSA has decided not to adopt a
requirement regulating the retention of fuel storage containers. The
agency believes that fuel container retention does not pose a safety
problem, as long as a manufacturer produces its vehicles to comply with
the standard's leakage requirements. If a CNG fuel container did break
away from the vehicle, NHTSA believes that it is highly likely there
would be a fuel leak which would not be able to comply with the barrier
crash test's leakage requirement.
F. Other Considerations
1. Vehicles Manufactured In More Than One Stage
In the NPRM, NHTSA tentatively concluded that it would be
practicable for final stage manufacturers of multi-stage vehicles to
comply with this proposed rule. The agency reasoned that because the
vehicle requirements in the proposed rule only involve those vehicles
currently covered under Standard No. 301, final stage manufacturers are
already subject to similar dynamic crash test requirements. NHTSA
requested comment on the agency's tentative conclusion that final stage
manufacturers could comply with the proposed requirements and provide
the requisite level of safety. NHTSA requested comments about the
effect of this rule on final stage manufacturers.
Twelve commenters addressed the issue of how this rule would affect
vehicles manufactured in more than one stage. Blue Bird, Thomas,
Navistar, Washington State, CNG Pittsburgh, CHP, and Chrysler stated it
would be appropriate for the proposed requirements to apply to multi-
stage vehicles. In contrast, four commenters--the National Truck
Equipment Association (NTEA), NGV Systems, Ontario, and Niagara Mohawk
Power Company--believed that the new standard should not apply to
vehicles manufactured in more than one stage. These commenters were
most concerned about how a final stage manufacturer could certify
compliance to the Standard without performing crash tests.
NHTSA is aware of the concerns of final stage and intermediate
stage manufacturers about crash testing their vehicles. The agency
notes that its regulations already provide that certification of an
incomplete vehicle can pass through to the final stage manufacturer,
provided that the final stage manufacturers take the necessary
precautions to ensure they do not invalidate the certification. More
specifically, the final stage manufacturers must ensure that they
complete the vehicle without exceeding the GAWRs, altering any fuel
system component, moving the center of gravity of the completed vehicle
with the body installed outside the envelope of specifications provided
by the chassis manufacturer, or otherwise violating that envelope. If
the final stage manufacturer takes care to comply with all of the
chassis manufacturer's specifications, the final stage manufacturer
will not have to recertify the vehicle.
If the final stage manufacturer decides not to comply with the
specifications to the extent that the vehicle, in its final form,
differed significantly from what was anticipated by the chassis
manufacturer in specifying the envelope, and the basis for the
incomplete vehicle manufacturer's certification was thus no longer
valid, then the final stage manufacturer will have to accept the
responsibility for certification.
Pass-through certification is also not available for vehicles built
on chassis lacking sufficient components to be certified as an
incomplete vehicle. Some of the manufacturers that build these vehicles
may be small businesses that may be unable to conduct their own crash
tests.
NHTSA notes that while manufacturers must certify that their
vehicles meet all applicable safety standards, this does not
necessarily mean that a manufacturer must conduct the specific tests
set forth in an applicable standard. Certifications may be based on,
among other things, engineering analyses, actual testing, and computer
simulations.
Moreover, a manufacturer need not conduct these operations itself.
Manufacturers can utilize the services of independent engineers and
testing laboratories. They can also join together through trade
associations to sponsor testing or analysis. Finally, they can rely on
testing and analysis performed by other parties, including the CNG
container manufacturers. The container manufacturers typically perform
extensive analyses and tests of their products and, in order to sell
those products, will have a strong incentive to provide their
customers, the vehicle manufacturers, with information that can be used
to certify the vehicle to the applicable standard. Based on the above
discussion, NHTSA does not believe that the requirements pose any
significant certification burdens for the final stage manufacturers or
other small manufacturers.
2. Benefits
In the NPRM, NHTSA estimated the benefits from a CNG vehicle
standard by comparing them to the benefits from Standard No. 301. The
proposal referred to a NHTSA technical report on Standard No. 301's
effect on motor vehicle fires in traffic crashes. That report estimated
that Standard No. 301 has reduced fires in all passenger car crashes by
14 percent. (``Motor Vehicle Fires in Traffic Crashes and the Effects
of Fuel System Integrity Standard,'' DOT HS 807 675, November 1990.)
The NPRM also discussed information submitted by NFPA about 1984-1988
annual average automobile fire rates to the docket (Docket No. 73-20-
N15-027). These data contain information on the number of fires in
passenger cars by type of material first ignited (gasoline, LP-gas, or
natural gas). However, the agency stated that there were limitations
with using these data, and thus they could not be used to enable the
agency to determine the fire rate of CNG and LPG vehicles in comparison
to gasoline fueled vehicles.
Notwithstanding these limitations, NHTSA estimated in the NPRM the
number of fires in CNG vehicles, assuming they have the same fire rate
as gasoline powered vehicles. Based on Standard No. 301 fire rates and
on one Department of Energy scenario of projected on-road alternative
fuel vehicles, by fuel type, the agency estimated that there could be
1,690 fires in CNG vehicles in the year 2010.
NHTSA received only two specific comments about the benefits of the
proposed rulemaking to establish requirements for CNG vehicles. Both
Atlantic Research Corporation and NGVC commented that the agency's
assumption about estimating future CNG vehicle fires is flawed because
it assumes that CNG vehicles will have the same fire rate as gasoline
powered vehicles. Both commenters stated that the fuel systems and the
fuel flammability characteristics are completely different and thus
would result in much lower fire rates for CNG vehicles.
NHTSA acknowledges the favorable flammability characteristics of
CNG relative to gasoline. CNG is lighter than air, and therefore should
quickly dissipate upward. At the same time, however, CNG is under high
pressure onboard the vehicle in contrast to conventional fuels. This
high pressure could make a crash situation more volatile. However,
without real-world crash data on CNG vehicles, no conclusions can be
drawn. In assuming that CNG vehicles had the same fire rate as gasoline
vehicles, the agency wished to provide some estimate of benefits, given
the lack of real world accidents because of the relatively few CNG
vehicles on the road.
NHTSA analyzed data submitted by the American Gas Association (AGA)
on 8,000 natural gas fleet vehicles. Based on vehicle miles travelled
(VMT) during a three-year period, the fire rate for CNG vehicles is
2.52 per 100 million VMT, compared with a gasoline vehicle fire rate of
1.87, or 35 percent higher. However, the agency notes that the small
sample does not allow a reliable analysis of the crash fire potential
in CNG vehicles. With seven fires, the standard errors or the fire
rates for these CNG vehicles are too big to make meaningful comparisons
between CNG-equipped vehicles and their gasoline counterparts. While
the agency does not have the data to determine comparable fire rates
between gasoline and CNG vehicles, the benefits of this final rule are
obtained by ensuring at least equivalent safety with gasoline vehicles.
3. Costs
In the NPRM, NHTSA estimated that testing associated with the
proposed vehicle requirements would cost approximately $58,530-$63,080
per CNG body style. The agency estimated that the cost to perform a
frontal, lateral or rear impact test would be $5,000 (with a total cost
of $15,000 for three tests). The cost of the vehicle, which is
destroyed during the test, is approximately $13,160 ($39,480 for the
three vehicles to be used in the three tests). Thus, the total vehicle
testing costs would be approximately $54,480. The agency requested
comments about the costs of complying with the proposed requirements.
NHTSA received two comments that addressed the cost of implementing
fuel system integrity requirements for CNG vehicles. Navistar and Blue
Bird stated that the agency underestimated the costs associated with
testing school buses to the new CNG standard. Each stated that the cost
associated with purchasing and testing school buses was substantially
higher than the NPRM's estimate. Navistar estimated that for a six fuel
tank design school bus, the costs would be as follows: chassis--
$35,000, six fuel containers at $1,200 each--$7,200; six fuel container
cages at $150 each--$900; associated valves, tubes, fittings, etc.
$1,000; crash testing at $12,000 per test ($36,000 for three tests).
Navistar stated that a minimum of two school buses and six crash tests
would be needed for a total of at least $160,000. Blue Bird estimated
that vehicle costs are in the range of $75,000 to $85,000 and each test
costs approximately $15,000. It further stated that test costs could be
several hundred thousand dollars per vehicle configuration given that
multiple impact tests are often necessary to document conformance to a
standard that requires impacts at any point and angle. If Blue Bird
performed six tests on two school buses, the total cost would range
from $240,000 to $260,000.
After reviewing the comments, NHTSA believes that the cost
estimates provided by Navistar and Blue Bird are reasonable. Thus, the
total cost of testing school buses would be $160,000 per chassis and
$260,000 for a school bus. NHTSA continues to believe that its estimate
of $54,480 for light vehicles is still appropriate.
4. Leadtime
In the NPRM, NHTSA proposed to make the vehicle requirements
effective on September 1, 1994. The agency believed that this would
provide a reasonable time period for manufacturers to make any vehicle
modifications required by the rulemaking. Nevertheless, the agency
stated that the proposed dynamic vehicle crash test requirements could
make it necessary for vehicle manufacturers to make significant design
modifications in order to comply with the proposal, especially since
most CNG vehicles are currently manufactured in accordance with NFPA
Standard 52. That standard specifies design-oriented requirements and
does not specify a barrier crash test. The agency requested comment on
the feasibility of this effective date.
NHTSA received nine comments about the proposed effective date.
Blue Bird, Flxible, and Navistar agreed with the proposed effective
date of September 1, 1994. Flxible's agreement with the agency's
proposed effective date was contingent upon the agency adopting its
recommendations in the final rule. Navistar believed that the effective
date should be earlier if possible.
AAMA, the United States Department of Energy, NGV Systems, Volvo
GM, and CNG Pittsburgh did not agree with the effective date proposed
by the agency. NGV Systems, Volvo GM, and CNG Pittsburgh stated that
the proposed effective date would be difficult to meet but did not
recommend a specific date. AAMA and the U.S. Department of Energy
recommended an effective date of September 1, 1995. However, AAMA's
recommendation was contingent upon its recommendations being
incorporated in the final rule. AAMA further stated that an earlier
effective date would not be reasonable or practicable.
In contrast, the NGVC, the CGA, and CNG container manufacturers
have informed the agency that they want a CNG fuel integrity standard
to be effective as quickly as possible. In addition, they favor having
an opportunity to ``voluntarily certify compliance'' to the standard
once the final rule is published. The CNG industry groups believe that
it is necessary for a Federal standard to be in place as soon as
possible given the expected increased demand for CNG vehicles in light
of Federal and State fleet programs for clean fuel vehicles. They also
favor quick adoption of a Federal standard to preempt state regulations
that otherwise may be promulgated and to ensure that substandard CNG
vehicles are not marketed.
After reviewing the comments, NHTSA has decided to set an effective
date of September 1, 1995. NHTSA is fully aware that the NGVC and CGA,
which represent the natural gas industry, favor what amounts to an
immediate effective date. Nevertheless, the agency believes that a
leadtime of at least one year is necessary given that vehicle
manufacturers will be required to certify compliance to an entirely new
set of dynamic crash requirements. In the meantime, prior to the
standard's effective date, the industry is free to market vehicles as
meeting the CNG vehicle standard that takes effect in 1995.
Manufacturers have taken this approach with respect to the agency's
side impact requirements and air bag requirements. Therefore, to the
extent feasible, the agency encourages manufacturers to manufacture
their CNG vehicles to meet these new requirements before the date the
standard takes effect.
V. Rulemaking Analyses
A. Executive Order 12866 and DOT Regulatory Policies and Procedures
NHTSA has considered the impact of this rulemaking action under
Equal Opportunity 12866 and the Department of Transportation's
regulatory policies and procedures. This rulemaking document was
reviewed under Equal Opportunity 12866, ``Regulatory Planning and
Review.'' This action has been determined to be ``significant'' under
the Department of Transportation's regulatory policies and procedures
because of the significant public and Congressional interest in the
rulemaking. NHTSA has estimated the costs of the amendments in a Final
Regulatory Evaluation (FRE) which is included in the docket for this
rulemaking. As discussed in that document, NHTSA estimates that testing
associated with the vehicle requirements will cost approximately
$54,480 for light vehicles. More generally, the agency believes that
the cost of the final rule is mostly testing costs and the benefits are
derived by ensuring an equivalent level of safety with gasoline
vehicles.
B. Regulatory Flexibility Act
NHTSA has also considered the effects of this rulemaking action
under the Regulatory Flexibility Act. Based upon the agency's
evaluation, I certify that this rule will not have a significant
economic impact on a substantial number of small entities. Information
available to the agency indicates that currently there are very few
businesses manufacturing passenger cars or light trucks for CNG use.
The agency further believes that as the market expands for CNG
vehicles, original vehicle manufacturers will begin to produce CNG
vehicles because they will be able to do so at less expense than final
stage manufacturers and alterers. Few, if any, original vehicle
manufacturers which manufacture CNG vehicles are small businesses.
C. Executive Order 12612 (Federalism)
NHTSA has analyzed this rulemaking action in accordance with the
principles and criteria contained in Executive Order 12612. NHTSA has
determined that the rule will not have sufficient Federalism
implications to warrant the preparation of a Federalism Assessment.
Nevertheless, the agency wishes to elaborate about its preemptive
authority with respect to Federal motor vehicle safety standards given
comments on the NPRM about potentially inconsistent State law.
The AAMA and the NGVC/AGA stated that a Federal standard was
necessary to preempt possible State and local regulations addressing
CNG vehicles. AAMA stated that--
Because the U.S. Energy Policy Act will require that both
Federal and state governments become mandated ``fleet customers'' of
alternative fuel vehicles, AAMA is apprehensive about the potential
promulgation of a plethora of state alternate fueled vehicle
regulations, each slightly different from one another, with an
imposed standard or an alleged higher standard than the finalized
applicable federal safety standard. In such a circumstance, there
would appear to be no federal preemption protection for the vehicle
manufacturer. It is, therefore, conceivable that to market these
mandated alternate fuel vehicles, numerous vehicle versions would
have to be designed, manufactured, and certified.
Similarly, NGV/AGA expressed concern that State authorities may
initiate different or more stringent standards for CNG systems. It was
particularly concerned that NHTSA cannot preempt separate regulation of
vehicles procured by State governmental agencies.
As both commenters are aware, section 103(d) of the National
Traffic and Motor Safety Act sets forth NHTSA's preemptive authority as
follows: Whenever a Federal motor vehicle safety standard established
under this title is in effect, no State or political subdivision of a
State shall have any authority either to establish, or to continue in
effect, with respect to any motor vehicle or item of motor vehicle
equipment any safety standard applicable to the same aspect of
performance of such vehicle or item of equipment which is not identical
to the Federal standard. Nothing in this section shall be construed as
preventing any State from enforcing any safety standard which is
identical to a Federal safety standard. Nothing in this section shall
be construed to prevent the Federal Government or the government of any
State or political subdivision thereof from establishing a safety
requirement applicable to motor vehicles or motor vehicle equipment
procured for its own use if such requirement imposes a higher standard
of performance than that required to comply with the otherwise
applicable Federal standard.
Pursuant to this statutory provision, once Standard No. 303 takes
effect, no State or local government can have a standard in effect
addressing the fuel integrity of CNG vehicles unless that standard is
identical to Standard No. 303. Nevertheless, the statute permits a
State to issue higher performance standards for CNG vehicles procured
for the State's own use, notwithstanding AAMA's desire for the Federal
government to preempt States from doing so. In other words, NHTSA has
no authority to prevent States from issuing more stringent standards
for vehicles procured for their own use.
D. National Environmental Policy Act
In accordance with the National Environmental Policy Act of 1969,
NHTSA has considered the environmental impacts of this rule. The agency
has determined that this rule will have no adverse impact on the
quality of the human environment. On the contrary, because NHTSA
anticipates that ensuring the safety of CNG vehicles will encourage
their use, NHTSA believes that the rule will have positive
environmental impacts since CNG vehicles are expected to have near-zero
evaporative emissions and the potential to produce very low exhaust
emissions as well.
E. Civil Justice Reform
The rule will not have any retroactive effect. Under section 103(d)
of the National Traffic and Motor Vehicle Safety Act (15 U.S.C.
1392(d)), whenever a Federal motor vehicle safety standard is in
effect, a state may not adopt or maintain a safety standard applicable
to the same aspect of performance which is not identical to the Federal
standard. Section 105 of the Act (15 U.S.C. 1394) sets forth a
procedure for judicial review of final rules establishing, amending or
revoking Federal motor vehicle safety standards. That section does not
require submission of a petition for reconsideration or other
administrative proceedings before parties may file suit in court.
List of Subjects in 49 CFR Part 571
Imports, Motor vehicle safety, Motor vehicles.
PART 571--[AMENDED]
In consideration of the foregoing, 49 CFR part 571 is amended as
follows:
1. The authority citation for part 571 continues to read as
follows:
Authority: 15 U.S.C. 1392, 1401, 1403, 1407; delegation of
authority at 49 CFR 1.50.
2. Section 571.303, a new safety standard, Standard No. 303, Fuel
System Integrity of Compressed Natural Gas Vehicles, is added to part
571, to read as follows:
Sec. 571.303 Standard No. 303; Fuel system integrity of compressed
natural gas vehicles.
S1. Scope. This standard specifies requirements for the integrity
of motor vehicle fuel systems using compressed natural gas (CNG),
including the CNG fuel systems of bi-fuel, dedicated, and dual fuel CNG
vehicles.
S2. Purpose. The purpose of this standard is to reduce deaths and
injuries occurring from fires that result from fuel leakage during and
after motor vehicle crashes.
S3. Application. This standard applies to passenger cars,
multipurpose passenger vehicles, trucks and buses that have a gross
vehicle weight rating (GVWR) of 10,000 pounds or less and use CNG as a
motor fuel. This standard also applies to school buses regardless of
weight that use CNG as a motor fuel.
S4. Definitions.
Bi-fuel CNG vehicle means a vehicle equipped with two independent
fuel systems, one of which is designed to supply CNG and the second to
supply a fuel other than CNG.
CNG full container means a container designed to store CNG as motor
fuel on-board a motor vehicle.
CNG fuel system means all components used to store or supply CNG to
a vehicle's engine.
Dedicated CNG vehicle means a vehicle equipped with one fuel system
and designed to operate on CNG.
Dual-fuel CNG vehicle means a vehicle which is fueled by two fuels
simultaneously, one of which is CNG and the second is a fuel other than
CNG.
High pressure portion of a fuel system means all the components
from and including each CNG fuel container up to, but not including,
the first pressure regulator.
Service pressure means the internal pressure of a CNG fuel
container when filled to design capacity with CNG at 20 deg. Celsius
(68 deg. Fahrenheit).
S5. General requirements.
S5.1 Vehicle requirements.
S5.1.1 Vehicles with GVWR of 10,000 pounds or less. Each passenger
car, multipurpose passenger vehicle, truck, and bus with a GVWR of
10,000 pounds or less that uses CNG as a motor fuel and that is
manufactured on or after September 1, 1995 shall meet the requirements
of S6, except S6.4.
S5.1.2 Schoolbuses with a GVWR greater than 10,000 pounds. Each
schoolbus with a GVWR greater than 10,000 pounds that uses CNG as a
motor fuel and that is manufactured on or after September 1, 1995 shall
meet the requirements of S6.4.
S5.2 Fuel system pressure drop: barrier crash.
(a) For all vehicles, the pressure drop in the high pressure
portion of the fuel system, expressed in kiloPascals (kPa), in any
fixed or moving barrier crash from vehicle impact through the 60 minute
period following cessation of motion shall not exceed:
(1) 1062 kPa (154 psi), or
(2) 895 (T/VFS); whichever is higher
where T is the average temperature of the test gas in degrees Kelvin,
stabilized to ambient temperature before testing, where average
temperature (T) is calculated by measuring ambient temperature at the
start of the test time and then every 15 minutes until the test time of
60 minutes is completed; the sum of the ambient temperatures is then
divided by five to yield the average temperature (T); and where
VFS is the internal volume in liters of the fuel container and the
fuel lines up to the first pressure regulator.
(b) For bi-fuel or dual fuel CNG vehicles, the test requirement in
S5.2(a) shall apply to the CNG fuel system, and the test requirement of
Standard No. 301 shall apply to the other fuel system, if that standard
is applicable.
S6. Test requirements: fuel system integrity. Each vehicle with a
GVWR of 10,000 pounds or less shall meet the requirements of any
applicable barrier crash test. A particular vehicle need not meet
further requirements after having been subjected to a single barrier
crash test.
S6.1 Frontal barrier crash. When the vehicle traveling
longitudinally forward at any speed up to and including 30 mph impacts
a fixed collision barrier that is perpendicular to the line of travel
of the vehicle, or at any angle up to 30 degrees in either direction
from the perpendicular to the line of travel of the vehicle, with 50th
percentile test dummies as specified in part 572 of this chapter at
each front outboard designated seating position and at any other
position whose protection system is required to be tested by a dummy
under the provisions of Standard No. 208, under the applicable
conditions of S7, the fuel pressure drop shall not exceed the limits of
S5.2.
S6.2 Rear moving barrier crash. When the vehicle is impacted from
the rear by a barrier moving at any speed up to and including 30 mph,
with test dummies as specified in part 572 of this chapter at each
front outboard designated seating position, under the applicable
conditions of S7, the fuel pressure drop shall not exceed the limits of
S5.2.
S6.3 Lateral moving barrier crash. When the vehicle is impacted
laterally on either side by a barrier moving at any speed up to and
including 20 mph with 50th percentile test dummies as specified in part
572 of this chapter at positions required for testing to Standard No.
208, under the applicable conditions of S7, the fuel pressure drop
shall not exceed the limits of S5.2.
S6.4 Moving contoured barrier crash. When the moving contoured
barrier assembly traveling longitudinally forward at any speed up to
and including 30 mph impacts the test vehicle (schoolbus with a GVWR
exceeding 10,000 pounds) at any point and angle, under the applicable
conditions of S7, the fuel pressure drop shall not exceed the limits of
S5.2.
S7. Test conditions. The requirements of S5 and S6 shall be met
under the following conditions. Where a range of conditions is
specified, the vehicle must be capable of meeting the requirements at
all points within the range.
S7.1 General test conditions. The following conditions apply to
all tests.
S7.1.1 Each fuel storage container is filled to 100 percent of
service pressure with nitrogen, N2. The gas pressure shall
stabilize to ambient temperature before testing may be conducted.
S7.1.2 After each fuel storage container is filled as specified in
S7.1.1, the fuel system other than each fuel storage container is
filled with nitrogen, N2, to normal operating pressures. Any
shutoff valve at the fuel container is in the open position.
S7.1.3 In meeting the requirements of S6.1 through S6.4, if the
vehicle has an electrically driven fuel pump that normally runs when
the vehicle's electrical system is activated, it is operating at the
time of the barrier crash. If the vehicle has any high pressure
electric shutoff valve that is normally open when the electrical system
is activated, it is open at the time of the barrier crash. Furthermore,
if any electric shutoff valve prevents sensing of system pressure by
the pressure transducer when closed, it must be open for both the
initial pressure measurement and the pressure measurement 60 minutes
after the vehicle ceases motion from impact. Any valve shall be open
for a period of one minute to equalize the system pressure.
S7.1.4 The parking brake is disengaged and the transmission is in
neutral, except that in meeting the requirements of S6.4, the parking
brake is set.
S7.1.5 Tires are inflated to manufacturer's specifications.
S7.1.6 The vehicle, including test devices and instrumentation, is
loaded as follows:
(a) A passenger car, with its fuel system filled as specified in
S7.1.1 and S7.1.2, is loaded to its unloaded vehicle weight plus its
rated cargo and luggage capacity weight, secured in the luggage area,
plus the necessary test dummies as specified in S6, restrained only by
means that are installed in the vehicle for protection at its seating
position.
(b) A multipurpose passenger vehicle, truck, or bus with a GVWR of
10,000 pounds or less, whose fuel system is filled as specified in
S7.1.1 and S7.1.2, is loaded to its unloaded vehicle weight, plus the
necessary test dummies as specified in S6, plus 136.1 kilograms (kg.)
(300 pounds (lb.)), or its rated cargo and luggage capacity weight,
whichever is less, secured to the vehicle and distributed so that the
weight on each axle as measured at the tire-ground interface is in
proportion to its GAWR. Each dummy shall be restrained only by means
that are installed in the vehicle for protection at its seating
position.
(c) A schoolbus with a GVWR greater than 10,000 pounds, whose fuel
system is filled as specified in S7.1.1 and S7.1.2, is loaded to its
unloaded vehicle weight, plus 54.4 kg. (120 lb.) of unsecured weight at
each designated seating position.
S7.1.7 The ambient temperature is not to vary more than 5.6 deg.C
(10 deg.F) during the course of the test.
S7.2 Lateral moving barrier crash test conditions. The lateral
moving barrier crash test conditions are those specified in S8.2 of
Standard No. 208, 49 CFR 571.208.
S7.3 Rear moving barrier test conditions. The rear moving barrier
test conditions are those specified in S8.2 of Standard No. 208, 49 CFR
571.208, except for the positioning of the barrier and the vehicle. The
barrier and test vehicle are positioned so that at impact--
(a) The vehicle is at rest in its normal attitude;
(b) The barrier is traveling at any speed up to and including 30
mph with its face perpendicular to the longitudinal centerline of the
vehicle; and
(c) A vertical plane through the geometric center of the barrier
impact surface and perpendicular to that surface coincides with the
longitudinal centerline of the vehicle.
S7.4 Moving contoured barrier test conditions. The moving
contoured barrier crash test conditions are those specified in S7.5 of
Standard No. 301, 49 CFR 571.301.
Issued on April 14, 1994.
Christopher A. Hart,
Deputy Administrator.
[FR Doc. 94-9824 Filed 4-22-94; 8:45 am]
BILLING CODE 4910-59-P