The Effect of Trailer Width and Length on Large-truck Accidents

About the report:

In 1982, Congress passed the Surface Transportation Assistance Act (STAA), which authorized the use of longer (14.63 m, or 48.0 ft) trailers and wider (2.6 m, or 102 in) trucks. In addition, it proposed a network of STAA-designated highways on which these larger vehicles would be allowed access. The use of the wider and longer trucks on primary and secondary routes is questioned due to the lower geometric standards of such routes compared to those of interstate highways, particularly lane width and curvature. The purpose of this study was to develop guidelines for state and local governments to determine the lane-width requirements for primary roads to allow the safe operation of different sizes of trucks. Data on truck size collected at permanent and temporary weigh stations along various primary routes in Virginia were used with accident data to compute truck accident rates by type and size. The rates were analyzed using the t test at (a = .05 and analysis of variance to determine whether significant differences among accident rates existed for different sizes of trucks on different lane widths. The rates were higher on roads with lane widths of 3.05 m (10.0 ft) and 3.20 m (10.5 ft) than on roads with lane widths of 3.35 m (11.0 ft) and 3.51 m (11.5 ft). Also, rates were higher on roads with lane widths of 3.05 m (10 ft) and 3.20 m (10.5 ft) than on roads with lane widths =3.66 m (12.0 ft). In addition, trucks with widths >2.44 m (8 ft) had higher accident rates on roads with lane widths of 3.35 m (11 ft) and 3.51 m (11.5 ft) and on roads with lane widths =3.66 m (12 ft); however, these rates were not significantly different than those for trucks with widths =2.44 m (8 ft). Overall, trailers with a length of 14.63 m (48 ft) had significantly higher accident rates than trailers with lengths <14.63 m (48 ft). Single-unit trucks had a significantly higher accident rate than passenger cars for all lane widths. Although the accident rate for tractor-trailers was higher than that for passenger cars, the difference was not significant.

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