Comparing Methods of Ramp Metering for On-Ramps to Improve the Operational Conditions at Peak Hours

This paper aims to evaluate and compare the effects of different methods of ramp metering on the operational conditions of traffic flow at three levels: the network level (including the freeway and its connected ramps), the entrance ramp, and the upstream segment of the entrance. To achieve this aim, one of the most important urban freeways in the metropolis of Isfahan was selected. The traffic volume passing through this freeway and its connected ramps were determined during peak hours (7 to 9 am), and the south band flows were simulated using microscopic analysis in AIMSUN software. After calibration and validation of the model, a specific on-ramp (the entrance ramp of Samadiyeh) was reviewed as the selected ramp, by using the fixed-time plan and ALINEA algorithm at demand levels of 100%, 110% and 80%. The results indicate that for normal demand level (100% demand), ramp metering does not have a significant effect on traffic flow. Further, ramp metering significantly improved upstream traffic flow in the freeway at high demand levels (110% demand), indicating its usefulness at high demand levels. At this demand level, ramp metering leads to traffic flow deviation. At low demand (80% demand), ramp metering increased the delay time of both the freeway and the ramp, indicating the ineffectiveness of ramp metering at low demands.