Roundabouts are commonly used to regulate traffic at intersections, and their effectiveness depends on factors such as traffic volume, site conditions, and design features. This study is concentrated on Chandigarh, an important city in India as it serves as the capital of two neighbouring states, Haryana and Punjab. In Chandigarh, where most intersections are roundabouts, traffic congestion and smooth mobility have become significant issues, making it essential to manage and regulate traffic efficiently. The purpose of this study is to evaluate the effect of geometric improvements on the level of service (LOS) of roundabouts. The study focuses on two roundabouts at Vikas Marg, which were chosen specifically for their traffic congestion problems caused by the area's escalating traffic volume. The study uses AutoCAD to analyse the geometric features of the roundabouts and examines their viability with respect to IRC:65-(2017) and IRC:SP-41-(1994) guidelines. Based on the analysis of the existing roundabouts, the study proposes recommendations for their improvement, particularly in terms of their design features, to ensure better traffic flow. After implementing the proposed improvements, the study performs a before-and-after analysis using traffic simulation in VISSIM to evaluate the impact of these modifications on the LOS of the roundabouts. The findings of the study show that the proposed modifications significantly improve the LOS of roundabouts, indicating that they are effective in enhancing traffic flow. The study's results provide a useful framework for transportation engineers to enhance the traffic flow and reduce congestion in Chandigarh and other cities facing similar challenges. The abstract should summarize the contents of the paper in short terms, i.e. 150–250 words.