This report presents the results from an analysis of off-roadway crashes and proposes a set of crash-imminent scenarios to objectively test countermeasure systems for light vehicles (passenger cars, sport utility vehicles, vans, and pickup trucks) based on crash statistics. This analysis was conducted in support of the roadway departure research area of the U.S. Department of Transportation's Intelligent Vehicle Initiative. The first harmful event in target off-roadway crashes occurs off the roadway after a vehicle departs the road due to loss of control or crossing the edge of the roadway. Approximately 992,000 such crashes occurred in the U.S. in 1998 based on the National Automotive Sampling System (NASS) General Estimates System (GES) crash database -- 93% of these crashes involved light vehicles. These crashes were grouped into six pre-crash scenarios based on vehicle movements and critical events and were described in terms of their physical settings, contributing factors, and post-roadway departure events. Based on 1998 GES statistics, 85% of these off-roadway crashes occurred on non-freeways, 66% in rural areas, 82% away from junctions, 59% on two lanes of travel, and 61% below 55 mph speed limit. Speeding was cited as a contributing factor to the cause of the crash in 24% of these crashes, whereas alcohol was reported in 19% of these crashes. Moreover, inclement weather conditions or driver inattention/distraction might have contributed to about 44% of these crashes. After leaving the roadway, vehicles struck other parked vehicles (21%) and signposts (14%); some form of injury resulted in about 37% of off-roadway crashes. Finally, eight test scenarios were proposed and described in terms of roadway type, junction, number of lanes, curvature, shoulder, travel speed, and environmental conditions.
Abstract