Simulation Of Ramp Control And Variable Speed Control On Urban Expressway

Urban expressway is consisted of mainline road, entrance ramp and weaving area. As in the morning and evening rush hour, the traffic flow in mainline is heavy, making the on-ramp traffic flow cannot enter into the weaving area smoothly, which may result in congestion at weaving area. To relieve traffic jam in urban expressway during peak hours effectively, this work by analyzing the actual vehicle operating characteristics and combining with the expressway traffic control strategy, the simulation study on the expressway traffic at peak is done based on the vehicle run model, which verify the validity of the expressway traffic control strategy.For the study of relieving traffic congestion at weaving area of urban expressway, this paper mainly focuses on the following researches:(1) The expressway ramp controller and the main variable speed control strategy are designed respectively. By using the improved ALINEA algorithm adopt into ramp controller, which can control the on-ramp traffic flow rate and traffic. The main variable speed control is that after determining the weaving area traffic conditions are saturated, the speed limit value of the mainline traffic flow can be obtained by using the fuzzy theory, such that the weaving area upstream traffic wave propagation speed can be controlled.(2) Aim at the questions that the ramp control may cause too long queues and the main line control may pose a great impact on the traffic flow, ramp and main variable speed coordination control strategies are proposed. By testing weaving area space occupancy, parameters such as speed and queue length, the double control strategy for traffic congestion is adopted, and the ramp control strategy is applied on the main line running if the vehicles run smoothly and the queue is too long.(3) During the running process, considering the vehicles’lane changing behavior in the mixed area, this work establishes the improved vehicles’lane changing model by basing on NaSch model. Furthermore, a dual strategy control simulation analysis is done. Take Guangzhou Tianhe district expressway as an example, by using the improved cellular automaton model to simulate the running state of the expressway in peak time, single and double strategies coordinating control strategy are used respectively to simulate the traffic flow condition. By comparing the changes the two strategies taken, such as the vehicle speed in the mainline upstream, the queue length on the on-ramp and the change in the weaving area share, this work verifies that the double strategy can ease the traffic condition in the weaving zone, and meanwhile, can balance the exiled line flow rate between the main and the on-ramp traffic.