Capacity and Performance Analysis of 3 Roundabouts in Sunyani

Nowadays traffic congestion at intersections is one of the main societal, economic and environmental problems in urban areas which particularly becomes severe during peak hours. Roundabouts are being weigh up as substitute for traffic control device capable of improving safety and effective functioning at nodes. This study analyzed capacity and performance of 3 major roundabouts (Jubilee Park, Cocoa House and Post Office) in Sunyani, Ghana. Traffic data were collected manually at the roundabouts during peak hours in the interval of 15 minutes. Also, as-built geometric data of the roundabouts were measured in the field. Synchro plus SimTraffic 7 softwares were used to run computer simulations to estimate the capacities and performances of the roundabouts. Results showed that the Jubilee Park and Post Office roundabouts were performing above capacities based on the overall volume to capacity ratios of 0.78 and 1.13 respectively, with intersection capacity utilization (ICU) level of service H. The roundabouts were at least 9 % above capacity and were being subjected to congestion periods in excess of 120 minutes per day. Similarly, the Cocoa House roundabout with volume to capacity ratio of 0.51 and ICU level of service G was 9 % above the traffic-carrying ability and undergoing successive congestion periods of 60 to 120 minutes. The 3 roundabouts should be signalized to improve on vehicular movement.