Cost-Effectiveness of Lane and Shoulder Widening of Rural, Two-Lane Roads in Kentucky

The purpose of the study was to determine the cost-effectiveness of widening lanes and shoulders on rural, two-lane roads. Information concerning geometries, accidents, and traffic volumes was obtained for over 15,000 miles (25,000 km) of roads. Reductions in accident rates occurred as lane and shoulder widths increased. Run-off-road and opposite direction accidents were the primary accident types associated with narrow lanes and shoulders. Reductions in accidents ranged from 10 to 39 percent for lane widening and 6 to 21 percent for shoulder widening. Priority listings were prepared for 531 projects based on critical rate factor. Priority listings were also prepared for tbe top 120 lane widening projects and the top 36 shoulder-widening projects based on benefit-cost ratios.