MODEL FOR CALCULATING SAFE PASSING DISTANCES ON TWO-LANE RURAL ROADS

A model describing the kinematics of vehicle trajectories during the passing maneuver on two-lane rural roads is presented. This model is based on the hypothesis that there exists a point in the passing maneuver that can be identified as a critical position. At this point, the decision to complete the passing maneuver will provide the same factor of safety relative to an oncoming vehicle as will the decision to abort the maneuver. The model locates the critical position in terms of exogenous parameters. The results of a series of sensitivity studies conducted with the model are also presented. These results provide insight into those parameters that strongly influence the required sight distances. It is shown that the current sight-distance specifications of the American Association of State Highway and Transportation Officials may be inadequate from a safety standpoint, particularly for high-speed passing maneuvers and for passing vehicles that are low-powered subcompacts. (Author)