A Service Life Analysis of Roundabouts Retrofits for Signalized Intersections

Roundabouts have long been regarded as an effective traffic control method. While this method is quite popular in some foreign countries like Australia, there are not as many existing roundabout sites in the U.S. According to foreign experiences and limited experience in the U.S., roundabouts can be good replacement alternatives where signalized intersections no longer function well.This research examined and monetized the potential benefits of converting signalized intersections to roundabouts under three different circumstances. To be specific, the potential benefits included crash reduction, delay time reduction, fuel efficiency improvement and air pollutant reduction. Then a benefit-cost analysis (BCA) was conducted. The monetization of environmental benefits was used to improve the BCA methodology that has been used by others. Three different intersections, that are currently signalized, were studied to determine the BCA. After a systematic evaluation, it was found that a five-way intersection with moderate traffic volume had the best benefit-cost ratio among all three intersections studied.