Performance Evaluation of Ramp Metering on Expressway using Microscopic Traffic Simulation Model

Abstract

In the present day, Intelligent Transportation System (ITS) technologies have been widely implemented in various countries to enhance traffic management efficiency and improve safety on expressways. Ramp metering is one notable measure, developed to mitigate traffic congestion at expressway on-ramps, which is often a primary cause of travel delays. This measure facilitates the regulation of vehicle entry from ramps to the mainline at an optimal rate, ensuring continuous traffic flow and minimizing speed reductions on the mainline. Consequently, the road can accommodate a higher volume of vehicles, improving infrastructure utilization and achieving long-term cost savings. This research aims to develop a microscopic traffic simulation model using Aimsun Next software to evaluate the traffic performance of ramp metering compared to a “do nothing” scenario. The study results find that various ramp control measures affect service efficiency. The ramp metering measure using a “one vehicle per green” signal is most effective when mainline traffic volume approaches capacity, specifically in the range of 7,348 to 9,797 vehicles per hour (-10% to +20%). Although this measure may result in increased delays on the ramp, it significantly enhances mainline flow. Conversely, the “Do nothing” scenario—reflecting the current operational condition—is found to perform comparably to other strategies under low traffic volumes, particularly when volumes fall below 6,531 vehicles per hour (-20%). These results can be further refined and adapted for implementation in real scenarios, contributing to improved traffic flow and maximizing benefits for expressway users.