Assessing Level of Service, Capacity and Future Optimization of Roundabouts in Rajshahi City Using Sidra Intersection

Abstract

This study investigates traffic flow challenges at the bustling Mintu Chattar roundabout Situated in Laxmipur Mor, Rajshahi, Bangladesh. Located in close proximity to a hub of hospitals and medical establishments, this intersection routinely witnesses traffic congestion, becoming a familiar occurrence in the area. From dawn to dusk, traffic officers are required to step in to manage the traffic flow of countless individuals commuting to hospitals, workplaces, educational institutions, and other destinations. Our capacity analysis using Sidra Intersection software reveals significant bottlenecks, particularly during peak hours, necessitating traffic police intervention due to inadequate control measures. The research identifies key contributing factors: insufficient entry and circulatory lanes, uneven traffic distribution, and high overall traffic volume. A detailed case study of the south leg highlights the severity of the situation, with Level of Service (LOS) dropping to F during evening hours, resulting in long queues (over 61 vehicles) and delays exceeding 82 seconds per vehicle. The integration of the design life model from SIDRA software has also illustrated the correlation between Level of Service (LOS) and capacity with the projected rise in traffic volume for the next five years. In order to improve traffic flow efficiency, the study proposes exploring design optimization of the roundabout. This includes investigating the impact of geometric redesigning, such as gradual expansion of approach lanes width, on capacity at the roundabout leg, considering both existing and future traffic scenarios.