Study of Accident Experience of Large Trucks and Combination Vehicles.

The safety of large trucks and combination vehicles is a subject of great concern for the public, the government and the trucking industry. Specific issues of interest include their accident frequency, severity and rate as well as the countermeasures to reduce the accident toll. Three truck-accident characteristics were investigated in this research: accident involvements, collision types, and accident severity. Discrete-multivariate models were used to study these characteristics. The model for accident involvements accounted for the differences in the usage and in the mileage of different truck types. The model for accident severity estimated the probabilities of both fatal and nonfatal injury accidents. The model for accident types estimated the probability of single-truck accidents, collisions with passenger cars, and collisions with commercial vehicles. The analyses were based on the Bureau of Motor Carrier Safety and the Highway Cost Allocation Study data bases. The truck types studied were large single-unit trucks (over 10,000 pounds), singles (tractors pulling one trailer) and doubles (tractors pulling two trailers), which were Interstate Commerce Commission authorized and not carrying farm products. For the accident involvement rate, vehicle configuration, trailer style, trip length, and number of axles of power unit were found to be significant variables; so were road class, road surface condition, day/night, load status, and driver experience. Single-unit trucks showed the lowest accident involvement rate, followed by van singles, tanker singles, flatbed singles, van doubles, tanker doubles and flatbed doubles. The variables that significantly affected accident severity include vehicle configuration, trailer style, accident type, road class, road surface condition, day/night, and load status. Large trucks and combination vehicles on undivided rural roads showed a very high severity level of truck-car collisions, especially at night. Doubles showed very high severity on both divided highways and undivided rural roads, when colliding with cars. Accident type was found to be affected by vehicle configuration, trailer style, road surface condition, day/night, load status, and driver experience. Doubles, loaded tankers and loaded flatbeds showed very high proportions of single-truck accidents. Most loaded singles and doubles showed higher proportions of single-truck accidents on undivided rural than on divided rural roads.PhDCivil engineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160279/1/8502780.pd