Abstract
Passing maneuvers on rural two-lane highways are complex maneuvers requiring drivers to enter the opposing traffic lane to overtake an impeding vehicle. A successful maneuver requires correctly judging the distance to the oncoming vehicle, speed of the oncoming vehicle, and the time it will take to complete the maneuver. Previous studies have shown that the type and speed of impeding vehicle, traffic volume, road cross-section, horizontal curvature, and driver characteristics influence passing behavior. This study expands on the previous research by investigating the effects of vertical curvature and guardrail on passing behavior as well as distinguishing between left- and right-direction horizontal curvature. The study was conducted by designing and conducting two driving simulation experiments based on two-lane rural highways in the state of Alaska. Data from the first experiment were analyzed to infer the effects of curvature on driver choice to pass, characterize passing maneuvers under different geometric configurations, and compare safety outcomes of pass attempts under different geometric configurations. Horizontal and vertical curvature had significant effects on driver choice to pass but no effects on safety outcomes of pass attempts. Data from the second experiment were analyzed to infer the effects of guardrail on passing behavior and collision avoidance. The presence of guardrail did not have significant effects on driver passing choice or safety outcomes of pass attempts. The presence of guardrail was found to significantly decrease the likelihood that drivers would avoid a head-on collision. The results of this study have implications for capacity and safety analysis of rural two-lane highways.