Definition of the Light Vehicle Off-Roadway Crash Problem for the Intelligent Vehicle Initiative

Off-roadway crashes involving light vehicles (passenger cars, sport utility vehicles, vans, and pickup trucks) were analyzed based on the 1998 General Estimates System crash database to support the development of countermeasure systems as part of the U.S. Department of Transportation’s Intelligent Vehicle Initiative. An off-roadway crash occurs when a vehicle in transport departs the road due to loss of control or crossing the edge of the roadway. Approximately 924,000 such crashes occurred in the United States in 1998. These crashes are grouped into six distinct precrash scenarios (3 × 2 matrix) based on vehicle movements (going straight, negotiating a curve, or initiating a maneuver) and critical events (departed roadway edge or lost control). These scenarios are described statistically in terms of their physical setting, which consists of the roadway type, land use, relation to junction, number of travel lanes, and speed limit. Moreover, factors that might have contributed to the cause of these crashes are identified. According to this analysis, 85 percent of these off-roadway crashes occurred on nonfreeways, 64 percent in rural areas, 83 percent away from junctions, 60 percent on two lanes of travel, and 62 percent below the 89-km/h (55-mph) speed limit. In addition, speeding and alcohol were reported in 25 and 20 percent of these crashes, respectively. Finally, inclement environmental conditions or driver inattention or distraction might have contributed to about 42 percent of these crashes.