Impact Analysis of Traffic Management with Alternating Traffic Stoppage: A Microscopic Traffic Simulation Case Study of Phaya Thai Interchange

Abstract

The Phaya Thai Interchange on the Si Rat Expressway is a critical traffic bottleneck with frequent congestion and accidents, particularly during the evening peak hours (16:00–19:00), due to conflicting traffic movements between flows from the Rama IX and Bangklo directions. To alleviate the situation, the Expressway Authority of Thailand (EXAT) has implemented a manual control measure that stops traffic from Bangklo every five minutes, which has partially mitigated congestion. This study employs a microscopic traffic simulation to compare three traffic management strategies: selective closure of Bangklo direction, alternating closure of both directions, and implementation of a ramp metering system. A total of 12 simulation scenarios were evaluated based on traffic performance indicators, including delay time, travel time, average speed, and queue length, with calibration and validation of the model. The results indicate that the application of ramp metering to control traffic from the Rama IX direction, combined with the addition of a supplementary traffic lane by widening the shoulder for 200 meters before the merging area to accommodate a flow rate of 2,500–3,000 vehicles per hour, and the closure of the rightmost lane from the Bangklo direction for approximately 800 meters (Scenario 3.4), provides the most effective overall performance. This approach achieves an 83.7% reduction in delay time, a 61.4% reduction in travel time, a 53.1% increase in average speed, and a significant reduction in queue length when compared with the current traffic management measures (Scenario 1.3).