Traffic and Geometric Characteristics Affecting the Involvement of Large Trucks in Accidents

About the report:

Recent trends indicate that vehicle miles traveled for large trucks is increasing at a higher rate than for other vehicles. The resulting competition between large trucks and other vehicles for highway space can be expected to result in more multi-vehicle collisions involving large trucks. The likelihood of these collisions causing severe injuries to vehicle occupants will also increase with the trend towards the use of smaller automobiles and heavier and larger trucks. In order to develop countermeasures that will alleviate this problem, it is first necessary to identify the characteristics of large-truck accidents and the role of traffic and geometric variables in such accidents. The major factors associated with large-truck accidents including the effect of highway facility type and highway geometry are investigated. Changes in large-truck accidents for periods before and after 1982 are evaluated by a comparison of pre- and post-1982 accident involvement rates. Factors that might have affected large-truck travel and accident rates include the Surface Transportation Assistance Act of 1982 (STAA), the improvement of the nation's economy, and deregulation of the trucking industry. The results indicate that fatal crashes involving large trucks have been increasing in contrast to all other vehicles, for which the fatality rates are constant for the same period. Driver-related factors are associated with 75 percent of all accidents involving trucks, and driver error is associated with SO percent of all fatal truck accidents. A significant correlation is also observed between driver error and highway alignment in accidents involving trucks. The risk of a fatality in a multi-vehicle accident involving a truck and another vehicle is found LO be highest on two-way undivided facilities. On divided, limited access facilities, this risk is reduced by 50 percent. An unexpected increase in tractor trailer accident involvement rates for non-STAA primary routes is observed and is attributed to incompatibilities between large-truck characteristics and the non-STAA highway environment. This interim report presents the results of the first part of a study, which also involves the development of models relating accident occurrence with geometric and traffic characteristics. The development of these models is now in progress. These models and the information given in this interim report will facilitate the formulation of countermeasures that will reduce accidents involving large trucks in Virginia.

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