Abstract—Passing zones are primary operational features of two-lane rural highways where fast vehicles pass slow vehicles using a lane reserved for traffic in opposing direction. The operation of these zones has an effect on the overall safety of two-lane rural highways especially when passing opportunities reduce considerably at higher flows. This paper presents a review on capacity and safety of passing zones on two-lane rural highways. Despite stated importance of passing zones to the operational performance of two-lane rural highways, passing zone capacity has not been estimated and its impact on safety is still not known. Safety evaluations mainly compare adequacy of design and marking passing sight distances to complete passing maneuvers as well as parameters derived from the passing process namely; passing duration, speed difference between passing and passed vehicles, and clearance between passing and opposing vehicle at the end of the maneuver. There is need for further research to address gaps in current capacity and safety evaluation methods of two-lane rural highways with focus on; (a) development of robust passing rate models for individual passing zones based on geometric, environmental and traffic factors, (b) estimation of passing zone capacity, (c) development of criteria to evaluate capacity and safety of passing zones for use by policy makers, planners and transportation engineers and (d) application of passing zone capacity to evaluate rural highway sections with several passing zones.

Index Terms—capacity, safety, passing zones, two-lane highways

Cite: Godfrey Mwesige, Haneen Farah, Umaru Bagampadde, and Haris N. Koutsopoulos, "Capacity and Safety of Passing Zones on Two-Lane Rural Highways: A Review of Theory and Practice," Journal of Traffic and Logistics Engineering, Vol. 2, No. 2, pp. 156-163, June 2014. doi: 10.12720/jtle.2.2.156-163