SPR 20-596: Right Shoulder Passing Blisters versus Left Turn Lanes

Since the implementation of KYTC's auxiliary turn lanes policy, Highway Districts have experienced some locations that do not experience safety related impacts, but have significant queuing and delays from left turning volumes that do not meet the left turn lane threshold. Other states, notably Indiana, have used Passing Blister designs, which provide wider areas of full depth pavement to accommodate passing on the shoulder under these conditions. The overall effectiveness of such design has not been fully evaluated though the reduced cost and potential for an effective solution as demonstrated by other states points to this as a potential solution for low volume left turn lane blockages. The objective of this research is to evaluate the cost-effectiveness of passing blister design on reducing delay and improving safety as compared to traditional left turn lane designs.