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Federal Motor Vehicle Safety Standards; Fuel System Integrity of Compressed Natural Gas Vehicles Over 4536 Kilograms Gross Vehicle Weight Rating

American Government Special Collections Reference Desk

American Government Topics:  National Highway Traffic Safety Administration, Federal Motor Vehicle Safety Standards

Federal Motor Vehicle Safety Standards; Fuel System Integrity of Compressed Natural Gas Vehicles Over 4536 Kilograms Gross Vehicle Weight Rating

Barry Felrice
Federal Register
May 6, 1994

[Federal Register: May 6, 1994]


National Highway Traffic Safety Administration

49 CFR 571

[Docket No. 94-31; Notice 01]
RIN 2127-AF29

Federal Motor Vehicle Safety Standards; Fuel System Integrity of 
Compressed Natural Gas Vehicles Over 4536 Kilograms Gross Vehicle 
Weight Rating

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

ACTION: Request for comments.


SUMMARY: The purpose of this notice is to assess the need to regulate 
the fuel system integrity of vehicles with a gross vehicle weight 
rating (GVWR) of greater than 4536 kilograms that are fueled with 
compressed natural gas (CNG). Comments are requested regarding the need 
for fuel system integrity standards for CNG-powered vehicles with a 
GVWR of greater than 4536 kilograms, including transit buses, intercity 
buses, trucks, and other heavy vehicles.

DATES: Comments must be received by July 5, 1994.

ADDRESSES: Comments should refer to the docket and notice numbers set 
forth above and be submitted to the Docket Section, NHTSA, room 5109, 
400 Seventh Street SW., Washington, DC 20590 (Docket hours are from 
9:30 a.m. to 4 p.m., Monday through Friday).

FOR FURTHER INFORMATION CONTACT: Mr. Gary Woodford, General Engineer, 
Special Projects Staff, Office of Rulemaking, National Highway Traffic 
Safety Administration, 400 Seventh Street SW., Washington, DC 20590. 
Telephone: (202) 366-4931.

SUPPLEMENTARY INFORMATION: The National Highway Traffic Safety 
Administration (NHTSA) anticipates a significant increase in the number 
of alternatively fueled motor vehicles in the United States. This 
expectation stems from initiatives by the President, Congress, State 
and local governments, and private interest, since these vehicles will 
help reduce air pollution and conserve petroleum fuel. NHTSA has 
undertaken a comprehensive program to address the safe performance of 
these vehicles on the road and in crashes. Further, because the Clean 
Air Act specifies that vehicle fleets in non-attainment areas (mostly 
large cities) must be converted to clean burning fuels, many city 
transit bus fleets are being converted to run on fuels such as 
compressed natural gas (CNG). As NHTSA has become more aware of these 
fleets of heavy vehicles powered by CNG, the agency believes that their 
safe performance merits examination.
    On January 21, 1993, NHTSA published a notice of proposed 
rulemaking (NPRM) which proposed requirements for CNG fuel system and 
fuel container integrity (58 FR 5323). The vehicle fuel system 
requirements were proposed to apply to vehicles with a GVWR of 4536 
kilograms or less, and all school buses. The container requirements 
were proposed to apply to CNG fuel containers for any vehicle.
    On April 25, 1994, the agency published a final rule (59 FR 19648), 
which addresses the fuel system integrity of CNG vehicles. The new 
regulation, Federal Motor Vehicle Safety Standard (FMVSS) No. 303, 
applies to all passenger cars, trucks, buses, and multipurpose 
passenger vehicles with a GVWR of 4536 kilograms of less, and all 
school buses regardless of weight. FMVSS No. 303 sets allowable leakage 
limits for the vehicle fuel system after a barrier crash test. With 
regard to the fuel container requirements, NHTSA anticipates issuing 
another final rule that will specify performance requirements 
addressing the strength, durability, and pressure relief of CNG fuel 
containers. In addition, as a result of public comments on the January 
1993 NPRM, the agency anticipates issuing a supplemental notice of 
proposed rulemaking for CNG fuel containers addressing internal 
corrosion, brittle fracture under low temperatures, environmental 
degradation, external damage, and fragmentation.
    The January 1993 NPRM briefly discussed the issue of whether 
vehicles with a GVWR of over 4536 kilograms, other than school buses, 
should be included in the vehicle requirements. The agency believes 
that an opportunity should be provided for a more focused view on this 
issue. This request for comment will serve that purpose.
    A total of 58 comments were received on the NPRM, of which six 
addressed CNG safety for vehicles over 4536 kilograms GVWR other than 
school buses. Four of the six commenters, Navistar, Chrysler, Flexible, 
and Amoco, believed that federal safety requirements should not apply 
to CNG-powered heavy vehicles. The main reason given by the commenters 
was that the vehicle applicability of the CNG fuel system integrity 
standard should be the same as that for NHTSA's liquid fuel system 
integrity standard, FMVSS No. 301, ``Fuel System Integrity.'' The 
latter only applies to vehicles with a GVWR of 4536 kilograms or less, 
and school buses. However, two commenters believed that the 
requirements should apply to heavier vehicles. The Transportation 
Manufacturing Company, a bus manufacturer, believed that heavy vehicles 
should have requirements that are comparable to those for smaller 
vehicles. No rationale was provided. The Washington Superintendent for 
Public Instruction (WSPI), also believed that these vehicles should be 
regulated. WSPI stated that the agency should consider including these 
vehicles in the proposed rule, but did not offer a rationale.
    Because of the lack of accident data indicating a fuel system 
integrity problem for CNG-powered heavy vehicles, and the lack of 
rationale from the two supporters, the agency concluded that FMVSS No. 
303 should not apply to heavy vehicles. However, because of the 
increasing number of CNG-powered transit buses, the agency seeks 
information by which to consider whether federal safety action is 
desirable, for both transit buses and or other heavy vehicles. It may 
be that action is merited with regard to buses, which carry many 
occupants and can have high traffic exposure, but not other heavy 
vehicles with only one or two occupants.

Current and Proposed Regulations

    As part of NHTSA's inquiry in this notice, the agency seeks 
comments on the desirability of actions which would be harmonized with 
those of Canada.

United States Requirements

    FMVSS No. 303 requires that school buses, regardless of weight, 
must comply with a moving contoured barrier crash test. In this test, a 
barrier traveling longitudinally at 48 kilometers per hour impacts the 
bus at any point and angle. During and after the impact, the fuel 
pressure drop must not exceed a specified limit. The final rule 
contains no requirements for heavy vehicles other than school buses 
with a GVWR of over 4536 kilograms.

Canada's Existing and Proposed Requirements

    Currently, Canadian motor vehicle safety standard No. 301.2, ``CNG 
Fuel System Integrity,'' requires that all vehicles with a GVWR of more 
than 4536 kilograms be subjected to a 48 kilometers per hour contoured 
barrier crash test. This is similar to the test NHTSA requires for 
school buses in FMVSS No. 303. On December 11, 1993, Canada proposed an 
amendment to its standard. Under the amendment, the current requirement 
would apply to vehicles with containers mounted lower than 183 
centimeters from the ground. If the fuel containers are mounted 183 
centimeters or more above the ground, the vehicle would need to meet 
the requirements of the National Standard of Canada CAN/CGA-B149.4-M91 
Natural Gas for Vehicles Installation Code, dated January 1991 (copy 
available in the docket). This is a design standard which specifies in 
great detail the method for building a CNG vehicle.

Request for Comments

    NHTSA seeks two types of information in this notice. First, the 
agency seeks information regarding the current and projected population 
size and vehicle type (transit bus, intercity bus, heavy truck, or 
other heavy vehicle) for CNG vehicles with a GVWR of over 4536 
kilograms. Second, NHTSA seeks information about the potential safety 
problems of these vehicles. When appropriate, please comment by vehicle 
type, i.e., transit bus, intercity bus, heavy truck, or other type of 
heavy vehicle.

CNG Heavy Vehicle Population: Current and Projected

    1. The agency requests information on how many CNG transit buses, 
intercity buses, heavy trucks, and other heavy vehicles of over 4536 
kilograms GVWR are in service or are planned to be placed in service in 
the United States. How many of these vehicles are made by an original 
equipment manufacturer (OEM) and how many are aftermarket vehicles that 
are converted from a vehicle powered by gasoline, diesel, or other 
    2. How many entities manufacture heavy CNG vehicles by type, i.e., 
transit bus, intercity bus, heavy truck, or other type of heavy 
vehicle? How many convert them from other fuels, by type, if 
appropriate? What specifications are used for converting these 
vehicles? Do voluntary industry guidelines exist? Please describe and 
provide the guidelines or citations.
    3. How long have heavy CNG vehicles (by type) been used in this 
country? What are the projections for their future use, in terms of 
numbers and in type of usage?
    4. What are the various locations for mounting CNG containers on 
heavy vehicles? Which are more common; less common? Why? At what height 
are the CNG containers mounted? Are they typically protected by 
shielding or cages? What factors go into deciding where to mount the 
container on the vehicle? How many CNG containers are typically placed 
on a heavy vehicle, and how much do the containers weigh? Does the 
number of containers vary, depending upon the type of vehicle, i.e., 
transit bus, intercity bus, heavy truck, or other type of heavy 

CNG Heavy Vehicle Safety Problems

    The agency foresees four potential areas for examination with 
regard to these vehicles:

--Performance in Crashes
--Leakage Detection

Performance in Crashes

    The agency is interested in obtaining specific information about 
crashes involving these heavy vehicles. General information about the 
number of accidents as well as information regarding specific issues 
such as container detachment would be helpful.
    5. Have there been any CNG fuel container or fuel system failures 
in these types of vehicles? If so, describe the failure, e.g., sequence 
of events, what failed, and how it failed. If the failure occurred as 
the result of a crash, was another vehicle involved? Please describe 
the other vehicle.
    6. Was the vehicle a transit bus, intercity bus, heavy truck, or 
some other type of heavy vehicle? Was it an OEM vehicle or a 
conversion? Who was the manufacturer of the vehicle? If it was a 
conversion, who did the conversion? Was the conversion done before or 
after the vehicle's first consumer purchase?
    7. Please identify and describe any situations where a container 
became detached in a crash situation? Did the container leak? If 
crashes occurred, were they reported to a policy agency, hazardous 
materials agency, or other State/local agency?
    8. Should the agency specify how the fuel containers should be 
attached to the vehicles? Should a requirements apply to all vehicles 
or just for those with containers mounted greater than 183 centimeters 
above the ground (such as referenced in the Canadian proposal)? Are CNG 
tanks rigidly mounted or are they mounted so as to be isolated from 
shock in a crash, permitting some allowable design movement? What is 
the typical orientation of the CNG tank with respect to the 
longitudinal axis of the vehicle? Does a CNG tank's mounting 
orientation and method affect its useful life?
    9. Were there any injuries to the vehicle occupants, pedestrians, 
emergency personnel, or other individuals? What was the type and 
seriousness of the injury?
    10. What type (steel, aluminum, fiberglass wrap, carbon fiber wrap, 
hoop wrap, full wrap, all composite, or other) was the fuel container? 
What were the dimensions of the container? What was the service 
pressure of the container? Who manufactured the container? How long had 
it been in service? To which design specification or standard were the 
tanks built?
    11. Should any Federal standard include a labeling requirement to 
address the periodic reinspection of fuel systems on alternatively 
fueled vehicles? Should States establish guidelines to address the 
periodic reinspection or recertification of such fuel systems? Should 
these schedules be set at specified time or mileage intervals? After a 
vehicle is involved in an accident?
    12. Should CNG heavy vehicles, which are not school buses, be crash 
tested for fuel system integrity in the same way as heavy school buses 
under FMVSS No. 303, i.e., a contoured barrier traveling at 48 
kilometers per hour striking the test vehicle at any point and angle? 
If so, which types of CNG heavy vehicle should be included, i.e., 
transit bus, intercity bus, heavy truck, or other type? Are there other 
tests or guidelines which would be more appropriate to assure the fuel 
system integrity of such vehicles? If so, what are they?


    Because of the size of these vehicles, there may be large enclosed 
areas in which natural gas could accumulate if there is a slow leak in 
the CNG fuel system.
    13. Are there instances where gas accumulated? Did any of them 
result in explosions?
    14. Should venting of the container away from possible areas of 
accumulation and potential ignition sources be required to address 
leakage accumulation?
    15. What experimental or observed data are available regarding the 
dispersion behavior that results from a CNG fuel system leak? Will the 
gas rise or remain near the ground? If the gas remains near the ground, 
how long will it remain there?

Leakage Detection and Warning

    If there is a leak in the fuel system, there would be little or no 
visible evidence of the gas accumulation. If persons nearby could not 
smell the gas, it could accumulate in an area near them without notice, 
which would increase the potential for an explosion.
    16. Are there instances where CNG leaked out of a vehicle fuel 
system and caused a safety problem before the natural gas was detected? 
Describe how the situation occurred.
    17. Should a leakage detection/warning system be required in 
vehicles with a GVWR of over 4536 kilograms to detect leakage of CNG as 
well as to warn persons nearby of the potential hazard? What type of 
system? Is it commercially available? What would be the cost? Would the 
leakage detection/warning system, including its power source, become a 
potential ignition sources when activated?


    NHTSA seeks information on potential safety hazards associated with 
the refueling of heavy CNG vehicles.
    18. Are manufacturers or fleet operators aware of safety hazards or 
accidents that have occurred during refueling operations? If so, please 
provide information on them.
    19. What items are included in current guidelines or procedures for 
CNG refueling, such as the need for grounding straps, operator 
protective clothing, etc.?
    20. Is a small amount of CNG normally released during connecting/
disconnecting of the refueling equipment? If so, how much? Are devices, 
such as excess flow valves, used in refueling equipment to prevent 
excess CNG leakage in the event of a refueling line rupture? To what 
extent are such devices used?
    21. What standards or guidelines currently exist for refueling 
couplers and related equipment?

Submission of Comments

    The agency invites written comments from all interested parties. It 
is requested that 10 copies of each written comment be submitted.
    No comment may exceed 15 pages in length. (49 CFR 553.21). 
Necessary attachments may be appended to a comment without regard to 
the 15-page limit. This limitation is intended to encourage commenters 
to detail their primary arguments in a concise fashion.
    If a commenter wishes to submit specified information under a claim 
of confidentiality, three copies of the complete submission, including 
purportedly confidential business information, should be submitted to 
the Chief Counsel, NHTSA, at the street address given above and seven 
copies from which the purportedly confidential information has been 
deleted should be submitted to the Docket Section. A request for 
confidentiality should be accompanied by a cover letter setting forth 
the information specified in the agency's confidential business 
information regulation, 49 CFR part 512.
    All comments received before the close of business on the comment 
closing date indicated above will be considered, and will be available 
for examination in the docket at the above address both before and 
after the closing date.
    To the extent possible, comments filed after the closing date will 
also be considered. NHTSA will continue to file relevant information as 
it becomes available in the docket after the closing date, and it is 
recommended that interested persons continue to examine the docket for 
new material.
    Those persons desiring to be notified upon receipt of their 
comments in the rules docket should enclose a self-addressed, stamped 
postcard in the envelope with their comments. Upon receiving the 
comments, the docket supervisor will return the postcard by mail.

    Authority: 15 U.S.C. 1392, 1401, 1403, 1407, 1417; delegations 
of authority at 49 CFR 1.50 and 49 CFR 501.8.

    Issued on May 2, 1994.
Barry Felrice,
Associate Administrator for Rulemaking.
[FR Doc. 94-10897 Filed 5-5-94; 8:45 am]

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