Development and Comparative Evaluation of Ramp Metering Algorithms Using Microscopic Traffic Simulation

Freeway ramp metering is an efficient freeway control that can ameliorate freeway congestion by limiting the number of vehicles entering the freeway. This study presents development and comparative evaluation of five ramp controls including no control, time-of-day plan, and three well-known ramp metering algorithms; ALINEA, FLOW and Stratified Zone through the use of microscopic traffic simulation. In this paper, ramp controls were developed and evaluated using Microscopic Traffic Simulation, AIMSUN NG. The simulation model of the Pacific Motorway in Queensland, Australia was used as a test-bed model. The results from the study indicated that ramp metering was basically found to be able to improve network performances up to 40% compared to no control. In terms of network and freeway mainline performance, ALINEA was superior to other algorithms under both normal and high traffic demand, whereas, Stratified Zone was the best algorithm for on-ramp performance. In terms of on-ramp performance, ALINEA was found to generate the lowest on-ramp performance. FLOW was found to be slightly superior to Stratified Zone. However, the trend was opposite for on-ramp performance. Gini coefficient was applied to measure the road user equity under the implementation of different algorithms. The results showed that FLOW was the most equitable algorithm, whereas, ALINEA was the worst. The results also indicated that network performance and on-ramp performance were trade-off in the presence of ramp metering operation.     

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高速公路匝道控制是一种通过限制进入高速公路车辆数来有效改善高速公路拥堵的交通控制方法。本文通过微观交通仿真对无匝道控制、定时控制及三种广泛应用的匝道控制算法（ALINEA、FLOW、Stratified Zone）进行比较评价。仿真采用AIMSUN NG软件，以澳大利亚昆士兰州太平洋快速路的仿真模型为基础测试模型。研究结果表明，基本的匝道控制可使路网能力比无控制时提高40%。就路网和高速公路主要线路能力而言，在正常的和高的交通需求条件下，ALINEA算法优于其他算法，Stratified Zone在提高入口匝道能力方面最优。就匝道入口能力而言，ALINEA算法的匝道入口能力最低，FLOW算法比Stratified Zone算法略优。本文用基尼系数（Gini coefficient）评价不同算法的道路使用者效用。结论还表明，匝道控制可使高速公路路网和入口匝道能力达到平衡。