Abstract
The primary goal of the research presented in this thesis is to mitigate passing lane crash risks on two-lane rural highways. Medium-fidelity driving simulators are normally used to examine the potential safety and operational benefits of several measures aimed at reducing the speed of drivers in the right lane while being passed and reducing the incidence of late, high-speed passes at the end of the passing lane. Alternatives considered in this study include a mix of explicit behavioral interventions, such as regulation (enforcing lower speed limits) and advanced warning (advisory signage upstream from and at the passing lane) as well as passive speed reduction measures such as alternative striping and pavement marking. Results from the driver simulator experiments suggest that regulatory speed reduction signs result in slower speeds for vehicles driving in the right lane. The results also show that passive speed reduction measures have little or no impact on the speed of the drivers. The research shows that the presence of surrounding traffic seems to have no impact on the effectiveness of passive speed resection alternatives. Finally, an analysis of the 2008-2012 state of Idaho reported crashes indicates that, while crash rates at the passing lane merging segments (0.5-mile downstream from the passing lane) are higher than that for the passing lane and for the two-lane highway segments, these differences are not statistically significant at the 95% confidence level.