THE CONGESTION EFFECTS OF TRUCK-INVOLVED URBAN FREEWAY COLLISIONS

Trucks are a major contributor to non-recurrent congestion in the region that comprises Los Angeles, Ventura, and Orange Counties of California. In 1983, for example, 5,060 collisions involving trucks were reported in this tri-county region. It is estimated that these figures include virtually all fatal collisions involving trucks, 80 to 90% of all injury collisions, and perhaps only half of all property-damage-only collisions. Approximately 86% of these truck incidents occur on the freeway system. These truck incidents are a major contributor to non-recurrent congestion which, in sum, may be comparable in magnitude to the total recurrent congestion on the region's freeways. Approximately 90% of all truck incidents on Southern California freeways occur on weekdays, and 85% of these occur during the morning and evening peak periods. This amounts to an average of approximately 15 truck incidents per weekday on the tri-county freeway system, with 12 per day occurring on the heavily traveled freeways of Los Angeles County. With congestion increasing on this and other metropolitan freeway systems, it is important to determine the magnitude of truck-related incidents on the freeway system, and to seek ways to cope with problems uncovered. The research reported in this paper focuses on a particular aspect of the truck incident problem: Estimation of the impact of truck-involved collisions on the operation of the freeway system in terms of total delay.