EVALUATING TRAFFIC OPERATIONS AT AN URBAN ROUNDABOUT IN A DEVELOPING CITY: EVIDENCE FROM GAA AKANBI, NIGERIA

Efficient operation of urban roundabouts is critical for managing traffic flow, particularly in rapidly growing cities characterized by heterogeneous traffic conditions. This study evaluates the operational performance of Gaa Akanbi Roundabout using established traffic engineering metrics, including average control delay, queue length, and Level of Service (LOS), in accordance with Highway Capacity Manual (HCM) standards. Field data were obtained through direct geometric measurements and video-based traffic surveys conducted during peak periods over seven consecutive days. Traffic volumes and turning movements were manually extracted from recorded footage, while performance indicators such as delay and queue length were computed using standard analytical procedures. The results indicate that the roundabout operates at an overall average delay of 34.5 seconds per vehicle, corresponding to LOS C, which reflects stable but moderately delayed traffic conditions. However, significant disparities were observed across individual approaches. The western approach exhibited the poorest performance, with a delay of 46.2 seconds per vehicle (LOS E), indicating oversaturation largely due to limited entry capacity and inadequate geometric design. The southern and northern approaches recorded delays of 38.5 seconds and 30.2 seconds per vehicle, respectively, both operating at LOS D, suggesting moderate congestion with relatively stable flow conditions. In contrast, the eastern approach demonstrated comparatively efficient operation, with a delay of 23.1 seconds per vehicle (LOS C), characterized by lower conflict levels and shorter queues.