Document Type : Research Paper
Authors
1
, Department of Civil Engineering, Faculty of Engineering, University of Ferdowsi
2
Department of Civil Engineering, Engineering Faculty,Ferdowsi University of Mashhad, Mashhad, Iran And School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran
3
Department of Civil Engineering, Faculty of Engineering, University Babol Noshirvani
Abstract
In recent years, the increase in traffic volume within urban freeway networks has led to intensified merging and weaving interactions in the areas of on-ramps and off-ramps. This phenomenon has had a significant impact on traffic performance, including increased delay, reduced speed, and higher traffic density. The objective of this study is to investigate the effects of geometric improvement of on-ramps and off-ramps on traffic flow performance in the Hemmat Highway in Tehran. In this research, the microscopic traffic simulation software AIMSUN Next 22 was used for modeling and analyzing traffic conditions. Field data, including traffic volume, speed, and ramp geometric characteristics, were collected. After model calibration, five selected ramps were evaluated under two scenarios: the “existing condition” and the “geometric improvement based on AASHTO standards.” Performance evaluation criteria included delay time, average traffic speed, traffic density, and CO emissions. Simulation results indicated that the implementation of geometric improvements led to a significant enhancement in traffic performance across all ramps. Specifically, the average delay time decreased by approximately 40% to 75%, traffic speed increased by 2 to 3 times, and traffic density experienced a noticeable reduction. In addition, CO emissions also decreased in the improved scenarios. Finally, the results demonstrate that improving ramp geometry can play an effective role in reducing traffic weaving and enhancing the overall performance of the highway network. Furthermore, the developed simulation model is capable of being applied to analyze similar scenarios in other urban roadways. It should be noted that the observed improvements are solely based on traffic performance indicators, and a direct safety assessment (based on accident data) was not conducted in this study.
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