An investigation on traffic issues at Getambe roundabout

Abstract

Getambe roundabout is vulnerable to traffic congestions causing a bottleneck for the vehicles entering and leaving through Western Approach to Kandy city. The aim of this study is to identify the traffic issues at Getambe Roundabout and provide suitable mitigation measures to overcome the problem. The scope of the study is to propose a suitable method to increase the capacity level of the roundabout for traffic in thirty years of time period. According to the traffic flow data, the level of service of A1 road on which the roundabout is located is ‘F’ based on AUSTROADS Standards. It is the worst scenario. In the meantime the capacity of the roundabout was not adequate according to Federal Highway Administration criteria. Collision diagram was developed based on accident records and it is revealed that roundabout is one of the most severely vulnerable place in Kandy. Location of the nearby railway crossing causes long queues of vehicle quite often. Considering all the traffic issues, four combinations were analysed to find out the suitable solution along with the option of widening the roundabout into two lanes, which is a part of each combination. Four combinations; (1) Tunnel between A1 road and Sirimavo Bandaranayake Mawatha, (2) bypass road from William Gopallawa Mawatha (WPM) to Galaha road parallel to the railway track, (3) two way flyover from A1 road to William Gopallawa Mawatha and (4) improvement of access roads to the Getambe Roundabout were analysed to come up with the suitable solution. Second and forth combinations were rejected based on the volume to capacity ration of the roundabout. Out of the remaining, Analytical Hierarchy Process (AHP) was followed to select the best combination, which is the construction of a two way flyover from A1 road to WGM along with the widening of the roundabout into two lanes. Further Benefit/Cost analysis was performed to justify the selective alternative over the others.