Effect of Vehicle Length on Passing Operations

The maximum permitted length of trucks on Canadian roads has increased significantly over the past 20 years. This has led to concern regarding the interaction of trucks with other elements in the traffic stream. This paper presents a summary of the effect of increased vehicle length on passing operations and, specifically, it looks at the effect on passing‐sight‐distance requirements of increasing the overall maximum vehicle lengths from 23 m to 25 m. Passing‐sight‐distance requirements were calculated based on generalized versions of models developed by Lieberman, in 1982, and Glennon, in 1988. The inherent random nature of vehicle and driver characteristics were incorporated into the passing model by conducting a discrete stochastic simulation of the passing maneuver. The results of the modeling exercise indicate that passing‐sight distances are considerably greater when passing a long truck than when passing a car. However, whether the truck is 23 m or 25 m long does not have a significant impact on the passing‐sight‐distance requirements.