The effectiveness, location, design and safety of passing lanes in Kansas (USA)

A passing lane is an added lane in one or more directions of travel on a two-lane highway to improve passing opportunities in level or rolling terrain and thus decrease delay, increase traffic flow and improve safety. Passing lanes are differentiated from climbing lanes which are used where there are slow vehicles on unsustainable grades. Some states in the USA and countries like Canada and Australia have used passing lanes. The Kansas (USA) Department of Transportation (KDOT) started constructing them in 1994 as an alternative to providing more expensive four-lane sections. Kansas highways are comprised of a dense grid system with crossroads averaging one every 1.12 miles on state highways, and these crossroads could affect passing lanes. The KDOT sponsored a study to evaluate the effectiveness of the state's existing passing lanes to provide guidelines for planning, location, design, signing and construction of future passing lanes to promote both improved operations and safety. This paper presents a review of key considerations of passing lanes from a review of worldwide literature. A summary of the key findings on passing rates, speed, delay, platooning, lane utilization, spacing, configuration length and signing, and marking are presented. The paper concludes with a discussion of preliminary results and conclusions from the current Kansas study. The paper concludes that when properly located and designed, passing lanes can be an effective means to improve traffic flow and safety on high-volume, two-lane highways, even where crossroads are present.