REVIEW OF THE EFFECTIVENESS, LOCATION, DESIGN, AND SAFETY OF PASSING LANES IN KANSAS

Existing passing lanes in place on Kansas highways were studied from an operational and safety perspective. It was found that they generally operated well, improved operational efficiency and were well liked by the public. Determination of highway segments that would need passing lane(s) to improve their operational performance should be accomplished in a two-level process; i.e., Network and Project Level. At the Network Level, two-lane rural highway segments that operate at a level-of-service below a predefined acceptable level are identified. At the Project Level, highway segments identified at the network level are ranked for the purpose of prioritization. The number of highway segment passing lane projects to be implemented will depend on the funding level. At the project level, a detailed economic analysis of different passing lane lengths, spacing, and configurations can be undertaken to set parameters with an objective of minimizing percent time delay. Computer simulation using TWOPAS is a valuable tool to use at this level. The location of passing lanes should be planned along with their spacing. The location guidelines are based in part on the results of field studies, engineering judgement, and common sense. The location guidelines can be grouped into four main considerations: safety, improved traffic performance, a design consistent with driver's expectation, and minimized construction costs. Spacing between any two successive passing lanes is intended to make the passing lanes function as a coordinated system. The effective length of a passing lane depends on traffic volume and composition, passing lane length, and downstream passing opportunities. The report also addresses the geometric elements relating to passing lanes, including lane and taper length and cross sections, and pavement marking and signing. Passing lanes in Kansas are too new to make any statistically significant conclusions regarding safety. However, available statistics show a downward trend in crashes and subjectively, the authors believe that improved operational efficiency should provide safer traffic flow.