Comparison of Passenger Vehicle and Tmck Crash Rates on Toll Roads

Overall comparisons of crash rates based on mileage indicate that truck crash rates are lower than car crash rates, but that truck crashes are more severe. In 1978 the overall U.S. crash rate for cars was estimated at 8.2 accidents per million vehicle-miles of travel; for large trucks (including combinations) the rate was 4.7 per million vehicle-miles, and for combination trucks (e.g., tractor-trailers, trucktrailers) it was 6.0 per million vehiclemiles.’ However, truck involvement in fatal crashes has been consistently higher than passenger vehicle involvement (see, for example, Jones, et al.’). In 1984, cars were involved in fatal crashes at the rate of 2.8 per 100 million vehiclemiles traveled, as compared with involvement rates of 3.6 per 100 million vehicle-miles for all trucks and 5.2 per 100 million vehicle-miles for combination trucks.’ These overall comparisons are based on total mileage and do not take into account differences in travel characteristics between cars and trucks. For example, in 1985 only 210/. of all passenger vehicle mileage took place on interstate highways, as compared with 43”A of the mileage driven by combination trucks.’ Because crash rates are lower on interstate than on other roadways, such differences in travel strongly influence overall crash rate comparisons. For example, the fatality rate on interstate highways is less than one half that of other roadways, and the nonfatal injury rate is about one quarter.5 One way to obtain comparable mileage-based crash rates is to use vehicle exposure (miles of travel) and crash data for passenger vehicles and trucks using the same roadways. Vehicle mileage data and crash data are routinely collected on the ticket-controlled portions of many turnpikes; thus direct comparisons of passenger vehicle crash rates versus truck crash rates are possible on these roadways. Meyers conducted such a study covering 1976 to 1978 data for 21 turnpikes, parkways, and expressway s.’ He reported that the crash rate for light trucks (10,000 to 26,000 lb.) was 72°A higher than the crash rate for passenger vehicles and the rate for heavy trucks was 58°A higher than the rate for passenger vehicles. Fatal crash rates for trucks were more than double the comparable rates for cars. Similarly, Jovanis and Delleur, using 1978 data from the lndiana Tollway, reported that the mean daily crash rate for “class 1” autos (twoaxles, four-tires) was 1.49 crashes per million vehicle-miles as compared with a rate of 1.75 for trucks defined as “class 3“ (two-axles, six-tires) plus “class 6“ (five-axles).’ Both the Meyers and the Jovanis and Delleur studies covered time periods prior to the Motor Carrier Act of 1980 and the Surface Transportation Assistance Act of 1982.67 These laws specified major changes in the trucking industry, including substantial economic deregulation, and permitted wider use of bigger and heavier trucks. These changes, as well as other events or trends during the intervening years, could have affected passenger vehicle and truck crash rates. The objective of this study was to provide more recent comparative per mile crash rates for both passenger vehicles and large trucks. The ticket-controlled portions of turnpikes were selected as the sampling base because turnpikes routinely collect both mileage and crash data; thus crash rate comparisons for passenger cars and trucks using the same roadway could be calculated.