Improving Safety at Unsignalized Rural Intersections in Kansas

Construction of the bypass lanes at rural intersections has usually been considered as a low cost way to improve safety. Crash Modification Factor (CMF) is an acceptable measure for evaluating the safety effectiveness of a countermeasure, which is defined is the expected number of crashes with a countermeasure divided by the number of crashes expected without the countermeasure. This study evaluates the use of case-control method to estimate CMF for safety effectiveness of construction of bypass lanes at unsignalized rural intersections in the state of Kansas. In addition to looking at number of crashes at each intersection, this study evaluated the changes in crash rate and crash severity at intersections with the bypass lane versus intersections without it. Crash data were obtained for more than 700 rural unsignalized intersections from Kansas Crash Database which is maintained by the Kansas department of Transportation (KDOT) for the years 2009 to 2011. The paper concludes that the expected number of crashes is lower at intersections with bypass lanes in comparison to intersections without bypass lanes, while it has no significant effect on reducing crash severity.