Optimising Layout of a Left-Turn Bypass Intersection under Mixed Traffic Flow using Simulation: A Case Study in Pulau Pinang, Malaysia

Various unconventional arterial intersection designs (UAIDs) have been proposed as novel approaches to alleviate congestion at signalised intersections. However, little research has focused on the UAIDs under mixed traffic flow. In Malaysia, a type of unconventional arterial intersection, i.e., the left-turn bypass intersection, is very common. Hence, an alternative two-lane left-turn bypass intersection layout is proposed and compared with two other layouts under mixed traffic flow. An existing intersection in Pulau Pinang, Malaysia is selected as the location of our case study. To compare the three layouts, the state-of-the-art traffic micro-simulation software SUMO is used to model, analyse and estimate operational performances of the studied intersection layouts. To make simulation results more reliable, the simulation model is validated using the GEH empirical test. The performance indicators delay, travel time, speed, and number of stops are used to evaluate the three layouts for low, medium and high traffic volumes. The simulation results show that the left-turn bypass intersection outperforms the intersection without any bypasses, and the proposed intersection performance is better than the two other considered intersections. More specifically, the average delay of the proposed intersection is lower by 2.54s and 4.4s compared to the two other considered intersections in high traffic volume, respectively. Thus, this proposed intersection could be used in urban cities with traffic demand and congestion issues similar to those in this study.