According to the National Highway Traffic Safety Administration (NHTSA, 2004), approximately 6.3 million motor vehicle crashes occurred in the United States during 2002. Of these, about 38,000 crashes involved fatalities. Thirty percent of all crashes involved only a single vehicle, but among fatal crashes, 58 percent involved a single vehicle.
Single-vehicle crashes often are characterized by a driver losing steering control of the vehicle, often due to excessive speed (Campbell et al., 2003; Najm et al., 2003). Slippery roads, sharp curves, and obstacles in the roadway are factors in many singlevehiclecrashes, as are driver inattention due to distraction, alcohol impairment, or drowsiness. Single-vehicle crashes typicallyare of three types with some overlap: impacts with pedestrians, impacts with fixed objects such as trees, and impacts involving rollover. Because of their high centers of gravity, sport utilityvehicles (SUVs) are involved in many rollovers. Fatal rollover rates of SUVs have been shown to be more than three times those of passenger cars (Deutermann, 2002).
Electronic stability control (ESC) is a vehicle control system comprising sensors, brakes, engine control modules, and a microcomputer that continuously monitors how well the vehicle responds to the driver’s steering input. The computer compares a driver’s commands to the actual behavior of the vehicle. In general, when the sensors indicate the vehicle is leaving the intended line of travel, ESC applies the brake pressure needed at each individual wheel to bring the vehicle back on track. In some cases ESC also reduces the force exerted by the engine. The way ESC systems are programmed to respond to the information from the sensors varies among vehicle models. Some systems intervene sooner and take away more driver control of speed than others.
Per vehicle crash involvement rates were compared for otherwise identical vehicle models with and without electronic stability control (ESC) systems. ESC was found to affect single-vehicle crashes to a greater extent than multiple-vehicle crashes, and crashes with fatal injuries to a greater extent than less severe crashes. Information on all police-reported crashes of these vehicles in Florida, Illinois, Kansas, Maryland, Missouri, New Mexico, and Utah during 2001–2002 was extracted from the State Data System maintained by NHTSA. Information on fatal crashes of these vehicles during 2001–2003 was extracted from the Fatality Analysis Reporting System (FARS), an electronic database of fatal crashes occurring on U.S. public roadways. Based on all police-reported crashes in 7 states over 2 years, ESC reduced single-vehicle crash involvement risk by approximately 41 percent (95 percent confidence limits 33–48) and single-vehicle injury crash involvement risk by 41 percent (27–52). This translates to an estimated 7 percent reduction in overall crash involvement risk (3–10) and a 9 percent reduction in overall injury crash involvement risk (3–14). Based on all fatal crashes in the United States over 3 years, ESC was found to have reduced single-vehicle fatal crash involvement risk by 56 percent (39–68). This translates to an estimated 34 percent reduction in overall fatal crash involvement risk (21–45).
Dang JN. (2004) Preliminary results analyzing the effectiveness of electronic stability control (ESC) systems. Report no. DOT-HS-809-790. U.S. Department of Transportation, Washington, DC.
Campbell B, Smith J, NajmW. (2003) Examination of crash contributing factors using national crash databases. Report no. DOT-HS-809- 664. U.S. Department of Transportation, Washington, DC.
Deutermann W. (2002) Characteristics of fatal rollover crashes. Report no. DOT-HS-809-438. U.S. Department of Transportation, Washington, DC.
Najm W, Sen B, Smith J, Campbell B. (2003) Analysis of light vehicle crashes and pre-crash scenarios based on the 2000 General Estimates System. Report no. DOT-HS-809-573. U.S. Department of Transportation, Washington, DC.
National Highway Traffic Safety Administration. (2004) Traffic Safety Facts 2002. Report no.DOT-HS-809-620. U.S. Department of Transportation,Washington, DC.
Florida, Illinois, Kansas, Maryland, Missouri, New Mexico, and Utah