OPERATIONAL IMPACTS OF WIDER TRUCKS ON NARROW ROADWAYS

A study was conducted to determine the differences in performance between 102-in.-wide and 96-in.-wide trucks and the impact that these trucks have on other traffic. Trucks that were studied primarily included random trucks in the traffic stream, although some control truck data were also collected to account for driver differences. Truck data were collected on rural two-lane and multilane roads that included curve and tangent sections and a variety of roadway widths and traffic conditions. The data collection effort resulted in approximately 100 hr of videotape and 9,000 slides from which various measures of effectiveness (MOEs) were extracted. Several MOEs were used to test for the operational effects of differential truck widths, lengths, and configurations. Such measures included (a) lateral placement of the truck and the opposing or passing vehicle, (b) lane encroachments by the truck or opposing vehicle, and (c) edgeline encroachments by the truck or opposing vehicle. Analysis of variance and regression analysis techniques were used to determine the significance of and the relationship among the variables used. The results revealed that the wider trucks had significantly higher rates of edgeline encroachments and tended to drive closer to the centerline than the narrower trucks. The wide ranges for a number of the operational measures for a given route and truck type also revealed the importance of driver influence on truck operations.