NHTSA Report Number DOT HS 807 675 November 1990

Motor Vehicle Fires in Traffic Crashes and the Effects of the Fuel System Integrity Standard

Glenn G. Parsons


Abstract

To reduce fatalities and injuries due to fire in motor vehicle crashes, Federal Motor Vehicle Safety Standard 301 was issued. This Standard, which applies to passenger cars, light trucks, school buses, prescribes impact test requirements aimed at reducing the chances of fuel-fed fires caused by fuel system breaching in vehicle crashes. This study is an evaluation of the effectiveness, benefits, and costs of fuel system improvements made in response to the Standard. It is based on analysis of on-road crash data from 5 States, FARS, and on information supplied by automobile manufacturers. The study found that:


Executive Summary

Introduction

The National Highway Traffic Safety Administration (NHTSA) is required, under Executive Order 12291, to conduct periodic reviews of the regulations it has issued. The purpose of these reviews is to measure the impact of those regulations in terms of both the benefits and costs to the American public.

This study is a review of Federal Motor Vehicle Safety Standard 301 - Fuel System Integrity (FMVSS 301). The Fuel System Integrity Standard is intended to reduce the chances of injury and fatality due to fires which result from motor vehicle crashes.

Though crashes with fires are relatively rare, fires in motor vehicle crashes have long been a topic of interest and concern. By its very nature, the occurrence of fire can significantly increase the risk of injury in motor vehicle crashes. Fire is of particular concern in crashes where entrapment of the vehicle occupants has occurred, due to jammed doors, or other collapsed vehicle structures that may have pinned the occupants inside the vehicle. Fire is also of concern in crashes where the nature or extent of injury prohibits occupants from extricating themselves. In both of these instances, the presence of fire has the significant potential for increasing injury beyond that caused by crash impact forces.

Due to the hazard it creates, and the speed with which it can spread, it is obviously preferable to attempt to reduce the risk of crash fires occurring rather than to rely on potential rescue efforts, once a fire has started. This is the aim of FMVSS 301. The requirements of this Standard are intended to strengthen and protect the vehicle's fuel system, so that in a crash event, the chances of fuel leakage, and consequently the chances of fire and occupant injury, will be reduced. Because of the highly flammable properties of gasoline, it is an obvious first choice as the source of combustible material in motor vehicle crash fires.

FMVSS 301 was first issued by the National Highway Traffic Safety Administration in 1967. In its initial version, the Standard applied only to passenger cars, manufactured after January 1, 1968, and the fuel system requirements covered only impacts to the front of the vehicle.

Subsequently, the Standard was revised, both to increase the individual performance requirements, and to extend the requirements to other classes of vehicles. In 1975, protection against rollover crashes was added to the frontal requirements for passenger cars. In 1976, these requirements were further increased to include protection against rear and side impacts. In 1976 and 1977, the requirements for cars were extended to light trucks (pickups, vans, multipurpose passenger vehicles, and buses) with gross vehicle weight ratings of 10,000 pounds or less. Finally, in 1977, a fuel system integrity requirement was established for Type I (large) school buses which included frontal, rear, and side protection.

In order to comply with the FMVSS 301 requirements, vehicles must withstand certain specified impact tests ranging from 20 to 30 miles per hour, without leaking fuel in excess of one ounce per minute following the tests.

Study Approach

This study is a statistical evaluation of the effectiveness of the 1975 through 1977 (upgrade) versions of FMVSS 301 in reducing vehicle crash fires, and associated injuries and fatalities. Descriptions of vehicle modifications resulting from the Standard are also included together with estimates of the consumer costs of the these modifications. Thirdly, selected statistics which portray the magnitude and nature of fires in motor vehicle crashes are presented.

The effectiveness analyses are based on the police reported motor vehicle crash files from five States, plus the files of NHTSA's Fatal Accident Reporting System (FARS). Multiple years of data from both sources are used, providing a total of over 14.5 million police-reported crashes from the States and approximately 700,000 fatal vehicle crashes from FARS. Thus, the data represent real-world traffic crashes, and the primary basis for estimating effectiveness is the statistical comparison of fire rates for vehicles manufactured after Standard 301 went into effect, as compared with the fire rates for vehicles produced before the Standard.

Estimates of the costs of Standard 301 are based on information obtained from the motor vehicle manufacturers. Both vehicle modification costs, and fuel penalty costs to cover the added weight of the vehicle modifications are considered.

In most of its evaluation projects, NHTSA develops cost information through independently conducted vehicle teardown studies. These studies disassemble affected components from actual production vehicles, and estimate the costs of the component changes by comparison with baseline components produced prior to the issuance of the Federal standard. Due to the more subtle and varied nature of the vehicle modifications made in response to FMVSS 301, the vehicle teardown approach to cost estimation was not practicable.

Data Limitations

While police reported accident files are considered the best source of data on motor vehicle crash fires, they are nonetheless subject to certain limitations.

First, fires in traffic crashes include both those that result from the crash (post-crash fires) as well as those that are initiated prior to the crash (pre-crash fires). While it is not possible to reliably distinguish between post-crash and pre-crash fires, limited data indicate that pre-crash fires could approach 1/2 of all fires reported in police reported traffic crash data. The proportion of total fires that are post-crash would be expected to increase as the severity of the crash impact increases. FMVSS 301 is primarily designed to affect post-crash fires.

Secondly, in police reported accident data. it is not possible to distinguish between injuries caused by fire and injuries caused by crash impact forces. Since both injury severity and the likelihood of vehicle fire increase with increasing crash severity (i.e., impact force)., delineating the role of fire in injury causation is further compounded.

Lastly, the data obtained from motor vehicle manufacturers concerning the cost and type of vehicle modifications made in response to FMVSS 301 was less complete than desirable. While some companies supplied quite detailed data, other firms were able to provide only limited, or in some instances, no data. One of the hindrances to providing information was the span of several years between the time FMVSS 301 was issued and the time the information was requested from the manufacturers.

Prior Studies

Several prior studies have dealt with fires in motor vehicle crashes and the effects of FMVSS 301 in reducing these fires. Primarily, these earlier efforts studied only fires in passenger car crashes, and all were conducted several years ago when both the available sources and quantity of fire data were much more limited than today. One of the reasons for lack of data at the time the earlier studies were made was that insufficient time had elapsed, following the issue of FMVSS 301, to permit the accumulation of a large sample of on-road accident experience for vehicles incorporating FMVSS 301 modifications.

Generally, the safety effects of Standard 301 found in this study, for passenger cars, are in agreement with those found in the earlier studies, with one principal exception. This study finds no significant reduction for fatalities in fire crashes whereas an earlier (1983) NHTSA evaluation estimated a substantial reduction in fatalities. The principal reason for this difference in findings for fatalities is the limited amount of data used in the earlier study. The study was based on only three years of data from one State and did not analyze data on fatal passenger car crashes.

Principal Findings


The Frequency of Fires in Motor Vehicle Crashes

Casualties in Fire Crashes

The Effectiveness of FMVSS 301

Passenger Cars:

Light Trucks:

School Buses:

The Costs of Modifications Made for FMVSS 301:


Other Findings

The Age Factor The Severity of Fire Crashes

Fire Crashes by Direction of Impact



Conclusions




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