[Federal Register Volume 60, Number 6 (Tuesday, January 10, 1995)]
[Rules and Regulations]
[Pages 2539-2543]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-464]



=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. 93-02; Notice 07]
RIN 2127-AF42


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; response to petitions for reconsideration.

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

SUMMARY: On April 25, 1994, NHTSA published a new Federal motor vehicle 
safety standard, Standard No. 303, Fuel System Integrity of Compressed 
Natural Gas Vehicles. The standard limits the amount of allowable CNG 
leakage after a crash test by limiting the post-crash pressure drop of 
the fuel system. Ford Motor Company, Chrysler Corporation, and the 
American Automobile Manufacturers Association, submitted petitions for 
reconsideration of the final rule. The issues raised in the petitions 
include the allowable pressure drop limit, submitted by Ford and 
Chrysler, and other pre-crash test conditions and procedures, submitted 
by AAMA. NHTSA is denying the petitions of Ford and Chrysler concerning 
pressure drop limit, and denying in part and granting in part the 
requests by AAMA.

DATES: Effective Date: The amendments made in this rule are effective 
September 1, 1995.
    Petitions for Reconsideration: Any petition for reconsideration of 
this rule must be received by NHTSA no later than February 9, 1995.

ADDRESSES: Petitions for reconsideration should refer to the docket and 
notice number of this notice and be submitted to: Administrator, 
National Highway Traffic Safety Administration, 400 Seventh Street, SW, 
Washington, DC 20590.

[[Page 2540]] 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: On April 25, 1994, NHTSA published a new 
Federal motor vehicle safety standard (FMVSS) for the fuel system 
integrity of compressed natural gas (CNG) vehicles (59 FR 19648). The 
new standard, FMVSS No. 303, Fuel System Integrity of Compressed 
Natural Gas Vehicles, limits the amount of allowable CNG leakage after 
a crash test. This is done by placing a limit on the post-crash 
pressure drop of the fuel system. Vehicles with a gross vehicle weight 
rating (GVWR) of 10,000 pounds or less are subject to front, rear, and 
side impact crash tests. Schoolbuses with a GVWR greater than 10,000 
pounds are subject to moving contoured barrier crash at any point and 
angle on the vehicle. The purpose of the new standard, which becomes 
effective September 1, 1995, is to reduce deaths and injuries caused by 
fires resulting from fuel leakage during and after crashes involving 
CNG vehicles.
    Ford Motor Company (Ford), Chrysler Corporation (Chrysler), and the 
American Automobile Manufacturers Association (AAMA) submitted 
petitions for reconsideration of the final rule. The issues raised in 
the petitions include the post-crash pressure drop limit of the fuel 
system, and procedures and test conditions prior to crash testing. A 
discussion of each issue and the agency's response follows.

Pressure Drop Limit

    The final rule, as specified in S5.2(a), sets the allowable 
pressure drop in the CNG fuel system one hour after any crash test as 
follows:
    (1) 1062 kPa (154 psi), or
    (2) 895 (T/V<INF>FS), whichever is higher.
    T is the average temperature of the test gas in degrees Kelvin, 
stabilized to ambient temperature before testing. Average temperature T 
is determined by measuring ambient temperature at the start of the 
test, and then every 15 minutes until the test time of 60 minutes is 
completed. The sum of the five ambient temperatures is then divided by 
five to yield average temperature T. S7.1.7 of the final rule specifies 
that ambient temperature is not to vary more than 5.6  deg.C (10 
deg.F) during the course of the test. V<INF>FS is the internal volume 
of the high pressure portion of the vehicle fuel system.
    The other allowable pressure drop, 1062 kPa (154 psi), represents 
the smallest pressure drop measurable using existing pressure drop 
measurement technology is test gas temperature varies no more than 5.6 
deg.C (10  deg.F). The agency established this level based on comments 
from AAMA and others in response to the agency's January 21, 1993 
notice of proposed rulemaking (NPRM) (58 FR 5323). In its comments on 
that notice, AAMA stated that using a state-of-the-art capacitance type 
pressure transducer could still result in pressure drop measurement 
error of <plus-minus>106.1 kPa (<plus-minus>15.4 psi) if test gas 
temperature varied no more than <plus-minus>5.6  deg.C (<plus-minus>10 
deg.F). This is due to the cumulative errors attributable to pressure 
transducer accuracy, thermal zero shift, thermal coefficient 
sensitivity, and analogue-digital conversion. These factors, coupled 
with the accepted engineering practice that measurement error should 
not exceed ten percent of the value being measured, led to the 
conclusion that pressure drops less than 1062 kPa (154 psi) should not 
be measured.
    The above pressure drop established in the final rule represents 
the maximum allowable CNG leakage, 895 (T/V<INF>FS), within the limits 
of current pressure drop measurement technology, 1062 kPa (154 psi).
    Both Ford and Chrysler petitioned the agency for reconsideration of 
the above pressure drop limits in S5.2(a). Ford stated that it believes 
the agency erred by disregarding certain information provided by AAMA 
in its response to the January 1993 NPRM (58 FR 5323). Specifically, 
AAMA stated that ``* * * a 10  deg.F change in the temperature of the 
test gas would result in a 60 psi change in the pressure of the test 
gas.'' Noting that the final rule allows the ambient temperature to 
vary as much as 5.6  deg.C (10  deg.F) during the test, Ford stated 
that a 10  deg.F drop in temperature could result in a 60 psi pressure 
drop even with zero leakage. Thus, according to Ford, the pressure drop 
limits in the final rule are, in effect, reduced by 60 psi when the 
ambient temperature drops 10  deg.F and increased by 60 psi when the 
ambient temperature increases 10  deg.F during the test. Ford asserted 
that the pressure drop limits are, therefore, not reasonable, 
practicable, or stated in objective terms as required by statute, 
because they present arbitrary limits that vary depending on whether 
ambient temperature decreases or increases. Ford further stated that an 
appropriate corrective action would be to amend S5.2(a) so that it 
states, ``For all vehicles, the pressure drop in the high pressure 
portion of the fuel system, excluding pressure changes due to changes 
in the temperature of the test gas, expressed in * * *.'' Ford's 
recommended language is underlined. Thus, Ford's alternative would 
eliminate that component of any pressure drop which is due to test gas 
temperature change.
    Chrysler, in its petition, provided an almost identical rationale 
to that of Ford, stating that the pressure drop limits specified in the 
final rule do not accurately measure fuel leakage when the internal 
temperature of the gas causes change to the pressure within the fuel 
system. However, Chrysler's suggested corrective action differs from 
that of Ford. Chrysler requested that the agency amend the pressure 
drop limits in the final rule to incorporate the 60 psi adjustment 
needed to compensate for the possible change in gas temperature. Under 
Chrysler's request, the amended pressure drop limits in S5.2(a) would 
be:
    (1) 1476 kPa (214 psi), or
    (2) 895 (T/V<INF>FS) + 414 kPa (60 psi), whichever is higher.

Chrysler stated that ``[t]his would provide the needed compensation 
without the added difficulty of measuring gas temperature within the 
high pressure fuel system, which is difficult, impracticable, and risks 
compromising the fuel system integrity.''
    After reviewing Ford's and Chrysler's petitions for reconsideration 
about permissible pressure drop, NHTSA has determined that the 
requested modifications to S5.2(a) would be inappropriate. NHTSA 
continues to believe that the pressure drop limits and test procedure 
established in the final rule are the most appropriate and feasible, 
and that they provide a relatively simple and accurate method to 
determine CNG fuel leakage. The agency believes that under real world 
test conditions, any variation in test gas temperature will not 
significantly affect test results.
    NHTSA notes that because CNG is a gas, and not a liquid, measuring 
a safe level of allowable leakage after a crash test is much more 
complex than measuring similar levels for liquid fuels. This is because 
of the relationship between the temperature and pressure of a gas. The 
two are directly proportional. A change in either, pressure or 
temperature, directly affects the other.
    In arriving at the allowable pressure drop limit and test procedure 
established in the final rule, NHTSA addressed the issue of temperature 
and pressure, along with other related issues [[Page 2541]] raised by 
commenters on the January 1993 NPRM. These included whether to measure 
test gas temperature during the 60-minute period following barrier 
impact, whether to specify an ambient test temperature, the accuracy of 
available pressure drop measurement technology, and the time period 
over which pressure drop is measured. These, along with commenters' 
concerns, presented complex, and, in some cases, competing issues to 
resolve. There were a variety of possible solutions, some more feasible 
than others, to the problem of measuring CNG fuel system leakage.
    Contrary to the assertion made by Ford in its petition, the agency 
considered the information provided by AAMA about the effect of 
temperature on pressure. That information is specifically referenced in 
the preamble to the final rule (59 FR 19652). In addition, the agency 
noted in the preamble that several commenters, including AAMA, stated 
that temperature variations should be compensated for when conducting 
the crash test. However, neither AAMA nor other commenters suggested 
any method to correct for this. After reviewing the components, NHTSA 
decided not to specify an ambient test temperature, but to limit the 
amount of ambient temperature variation during the 60-minute test 
period to 5.6  deg.C (10  deg.F). A temperature variation exceeding 
this amount will invalidate the test results. The agency noted that, 
``Without such control, a large change in temperature could 
artificially affect the test results.'' NHTSA continues to believe that 
this test condition will sufficiently minimize changes in test gas 
temperature, as well as pressure drop measurement accuracy.
    NHTSA appreciates the concerns expressed by Ford and Chrysler in 
their petitions. However, as noted above, under real world test 
conditions, any variation in test gas temperature will not 
significantly affect test results. The agency believes there are three 
leakage scenarios that could potentially occur during the 60-minute 
test period following barrier impact: No leak, a large leak, and a 
small or marginal leak condition. In the case of no leak, Ford and 
Chrysler stated in their petitions that a 5.6  deg.C (10  deg.F) drop 
in ambient temperature could result in a 60 psi pressure drop even 
though there is no leakage. However, since the allowable pressure drop 
established in the final rule is at least 1062 kPa (154 psi), a 60 psi 
pressure drop will not affect compliance test results since it is well 
below the amount allowed in the final rule. Similarly, in the case of a 
large leak, any change in test gas temperature should not influence 
compliance test results, since all or most of the gas will leak out 
during the 60-minute test period, thereby making a non-compliance 
obvious. Based on supplemental information which the agency obtained by 
telephone from Ford and Blue Bird Body Company on the NPRM, the agency 
believes these two conditions, no leak or a large leak, will account 
for most of the leakage scenarios after real world CNG vehicle crash 
tests. However, in the event there is a slow leak, NHTSA believes that 
here, too, test gas temperature will remain relatively constant during 
testing, due to thermal contact between the test gas and fuel container 
walls. Any change in test gas temperature will tend to be offset by the 
temperature or thermal energy of the surrounding container walls, which 
along with the test gas have been stabilized to ambient temperature 
prior to testing.
    NHTSA rejects Ford's recommendation that the final rule exclude 
pressure changes due to test gas temperature changes, because it would 
require that test gas temperature be measured. NHTSA believes that this 
would unnecessarily result in a more costly and complex test procedure. 
Further, it could make the fuel system more vulnerable to leakage in a 
crash, since an additional fuel system measurement fitting may be 
required. In its petition for reconsideration, Chrysler referred to 
this as ``* * * the added difficulty of measuring gas temperature 
within the high pressure fuel system, which is difficult, 
impracticable, and risks compromising the fuel system integrity.'' In 
addition, supplemental information which the agency obtained by 
telephone from Ford indicates that measuring gas temperature in a CNG 
fuel system is not always accurate.
    NHTSA also rejects Chrysler's recommendation that an additional 60 
psi be added to the allowable pressure drop in the final rule. In the 
case of an allowable pressure drop of 1062 kPa (154 psi), adopting 
Chrysler's request would have raised this level by approximately 40 
percent. The agency believes that that addition could make the 
allowable pressure drop levels unsafe, since it would allow more fuel 
leakage. This would be clearly 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.
    For the above reasons, NHTSA denies the requests of Ford and 
Chrysler regarding pressure drop.

Fill Condition

    As part of the test conditions prior to CNG vehicle crash testing, 
S7.1.1 of Standard No. 304 specifies that, ``Each fuel storage 
container is filled to 100 percent of service pressure with nitrogen, 
N<INF>2.'' S4 states that, ``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).''
    In its petition, AAMA stated that since the final rule places no 
absolute limits on the ambient temperatures at which testing may be 
performed, but merely requires that ambient temperature not change more 
than 10  deg.F during the course of the test, fuel storage containers 
will not always be filled at and stabilized to a temperature of 20 deg. 
Celsius (68 deg. Fahrenheit). According to the petitioner, the fill 
pressure to be used for ambient temperatures other than 20 deg. Celsius 
(68 deg. Fahrenheit) is unclear and therefore not reasonable, 
practicable, or stated in objective terms. AAMA further stated that an 
appropriate corrective action would be to amend S7.1.1 of the Standard 
to state that, ``Each fuel storage container is filled with nitrogen, 
N<INF>2, to 100 percent of service pressure adjusted for ambient 
temperature.'' AAMA's suggested language is italicized.
    After reviewing AAMA's petition for reconsideration about fill 
pressure, NHTSA has determined that that organization's requested 
modification to S7.1.1 would be inappropriate.
    The agency's purpose in specifying that CNG containers be filled to 
100 percent of service pressure in S7.1.1 is to provide a reference 
point for the fill condition from which crash tests are performed, 
e.g., 20,684 kPa (3000 psi) at 20  deg.C (68  deg.F). NHTSA recognizes 
that since the final rule does not specify an ambient temperature at 
which crash testing is performed, fuel containers will not always be 
filled and stabilized to 20  deg.C (68  deg.F). This will result in CNG 
container pressures which are different than if testing were performed 
at 20  deg.C (68  deg.F), because of the relationship between gas 
temperature and pressure. Thus, manufacturers may fill and stabilize 
the CNG containers prior to testing to a pressure that is adjusted for 
ambient temperature. The final rule does not prohibit this. However, 
that pressure, which is adjusted for ambient temperature, must be such 
that if ambient temperature were 20  deg.C (68  deg.F), pressure in the 
CNG containers would be equal to service pressure. Since the final rule 
does not prohibit this adjustment for ambient temperature prior to 
testing, NHTSA sees no need to [[Page 2542]] adopt the revised language 
suggested by AAMA. Therefore, AAMA's petition concerning fill condition 
is denied.

Pressurizing the High Pressure Side

    S7.1.2 of the final rule states that, ``Any shutoff valve at the 
fuel container is in the open position.'' AAMA states in its petition 
that some CNG fuel systems include additional manual shutoff valves in 
the high pressure side of the fuel system, and that these valves must 
also be open so that pressure is distributed to the entire high 
pressure side of the fuel system. If these valves are closed, the 
vehicle test conditions would not simulate, to the extent practicable, 
conditions present in a real world crash. These observations led that 
organization to conclude that the final rule is not reasonable or 
practicable. In addition, AAMA stated that this aspect of the final 
rule does not meet the need for motor vehicle safety. This is because 
manual valves located downstream from the pressure measurement point, 
if closed, would seal off part of the high pressure side of the fuel 
system. Thus, pressure measurement upstream of the closed valve would 
not detect a leak in the sealed off, high pressure portion of the fuel 
system.
    AAMA stated that an appropriate corrective action would be to amend 
S7.1.2 to state that ``* * * normal operating pressures. All manual 
shutoff valves are to be left in the open position.'' AAMA's suggested 
language is underlined.
    After reviewing AAMA's recommendation about shutoff valves, NHTSA 
has decided to amend S7.1.2 to state ``All manual shutoff valves are to 
be in the open position.''
    The agency believes that this change is consistent with the goal in 
S7.1.2 which is to have the vehicle test conditions be representative 
of real world crash test conditions and to meet the need for motor 
vehicle safety. The agency was not aware that there may be manual 
shutoff valves within the high pressure portion of the fuel system 
other than those located at the fuel containers. In addition, the 
phrase in S7.1.2 stating ``Any shutoff valve * * *'' was meant to refer 
to manual shutoff valves. Based on the above consideration, NHTSA has 
decided to adopt AAMA's request concerning pressurizing the high 
pressure side.

Pressure Measurement Location

    AAMA stated that the final rule does not specify how fuel system 
pressure is to be accessed for measurement. In its response to the 
January 1993 NPRM, AAMA stated that it

    * * * is concerned about adding pressure transducers to points 
in the fuel line solely for purposes of conducting the test. Doing 
so creates a point of potential leakage where a fitting joint does 
not exist in a non-test vehicle.

AAMA stated that if a NHTSA contractor were to test for compliance by 
creating such a pressure measurement point, AAMA member companies 
likely would object, pointing out that the fuel system on the vehicle 
has been disrupted and therefore would not be representative of the 
vehicle as manufactured. AAMA stated that it is not reasonable, 
practicable, or appropriate to have a final rule that is silent on 
where the pressure is to be measured, thereby leaving its selection to 
the discretion of a NHTSA test contractor.
    AAMA stated that an appropriate corrective action would be to add a 
new S7.1.8, which states, ``The pressure drop measurement specified in 
S7.2 (sic) is to be made using a location recommended by the vehicle 
manufacturer.'' AAMA's proposed language is underlined. (Note: NHTSA 
has verified with AAMA that it intended to reference S5.2 rather than 
S7.2 in this statement.)
    NHTSA agrees with AAMA's assessment. Based on additional comments 
obtained from AAMA in response to the January 1993 NPRM, the agency 
understands that vehicle manufacturers will be providing a tap point on 
the vehicle's fuel system where pressure measurement is to be obtained. 
It would be consistent with the intent of Standard 304 if that pressure 
measurement of the fuel system were made at the location specified by 
the vehicle manufacturer. Accordingly, AAMA's petition concerning 
pressure measurement location is granted.

Miscellaneous Correction

    NHTSA is also making a word correction to one of the definitions in 
S4, which AAMA pointed out in its petition. The definition for CNG fuel 
container currently reads CNG full container. Therefore, the word full 
is changed to fuel.

Rulemaking Analyses

A. Executive Order 12866 and DOT Regulatory Policies and Procedures

    NHTSA has considered the impact of this rulemaking action under 
Executive Order 12866 and the Department of Transportation's regulatory 
policies and procedures. This rulemaking document was reviewed under 
E.O. 12866, ``Regulatory Planning and Review.'' This action has been 
determined to be ``non-significant'' under the Department of 
Transportation's regulatory policies and procedures.

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.

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

    This final rule does not have any retroactive effect. Under 49 
U.S.C. 30103, 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, except to the extent that the State requirement imposes a 
higher level of performance and applies only to vehicles procured for 
the State's use. 49 U.S.C. 30161 sets forth a procedure for judicial 
review of final rules establishing, amending or revoking Federal motor 
vehicle safety standards. That section does not require 
[[Page 2543]] 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.

    In consideration of the foregoing, 49 CFR part 571 is amended as 
follows:

PART 571--[AMENDED]

    1. The authority citation for part 571 continues to read as 
follows:

    Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegations of authority at 49 CFR 1.50.

    2. Section 571.303 is amended by revising the definition of CNG 
fuel container in S4, revising S7.1.2, and adding S7.1.8 to read as 
follows:


Sec. 571.303  Standard No. 303; Fuel system integrity of compressed 
natural gas vehicles.

* * * * *
    S4. Definitions.
* * * * *
    CNG fuel container means a container designed to store CNG as motor 
fuel onboard a motor vehicle.
* * * * *
    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, N<INF>2, to normal operating pressures. All 
manual shutoff valves are to be in the open position.
* * * * *
    S7.1.8  The pressure drop measurement specified in S5.2 is to be 
made using a location on the high pressure side of the fuel system in 
accordance with the vehicle manufacturer's recommendation.
* * * * *
    Issued on: January 4, 1994.
Ricardo Martinez,
Administrator.
[FR Doc. 95-464 Filed 1-9-95; 8:45 am]
BILLING CODE 4910-50-M