Modern Roundabout or Signalized and Stop-Controlled Intersections? Case Studies of At-Grade Intersections on Alberta and Saskatchewan Rural Highways

摘要

In order to demonstrate the analysis procedures for feasibility study of roundabouts, five case studies on Alberta and Saskatchewan rural arterial highways, including signalized and stop-controlled intersections as well as an interchange ramp terminal were analyzed. They all have either long delays or operational and safety concerns that improvements are required. In the case studies, future intersection turning volumes were predicted to evaluate traffic operations and capacity of each alternative. Cross comparison of traffic operations was made between stop-controlled intersections, signal controls, single-lane and two-lane roundabouts. Detailed traffic analysis was carried out for different alternatives using several software packages, including Synchro, SIDRA and VISSIM. Economic analysis and rating matrix methods were used in alternative evaluation. These case studies demonstrated intersections where roundabout is a good solution and locations where roundabout is not the best choice. Based on the study, it is concluded that in order for a roundabout to be feasible for an intersection, it should have adequate capacity, expected safety performance and superior economic value than other competing alternatives. The capacity of single-lane roundabouts is higher than all-way-stop controlled intersections but lower than signalized intersections with properly designed through and turning lanes. The capacity of two-lane roundabouts is usually lower than channelized intersections with two through lanes in each direction and exclusive left-turn lanes. Innovative use of roundabouts at some interchange terminals can not only provide safety benefits, but also offer operational advantages that were otherwise unavailable with conventional stop-controlled intersections.