UC Irvine Institute of Transportation Studies

Trucks are a major contributor to non-recurrent congestion in the region that comprises Los Angeles, Ventura, and Orange Counties of California. In 1987, for example, a total of 5,203 mainline freeway collisions (i.e., no ramp or connector collisions) involving trucks were reported (according to the state-maintained records of California Highway Patrol field investigations) in this tri-county region. Approximately 91 percent of all mainline truck incidents on Southern California freeways occur on weekdays (Monday through Friday) and 95 percent of these weekday freeway incidents occur during the period of heavy freeway usage (6:00 a.m.--6:00 p.m.) with approximately 56 percent occurring during the morning (6:00 a.m.-- 9:00 a.m.) and evening (3:00 p.m.-- 7:00 p.m.) peak periods. This amounts to an average of approximately 19 truck incidents per weekday on the tri-county freeway system, the majority of which (15 per day) occur 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 impact of truck-related incidents on the freeway system, and to seek ways to mitigate this impact. The research reported here 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. (Non-collision incidents, such as stalls and spilled loads, are not included in this analysis.)