Research On Ramp Metering Method And Optimization Algorithm In Urban Expressway

With the quick development of economy and society in our country, the traffic problems have become even worse in urban area, especially in some large cities, the road capacity is not able to satisfy the request of the traffic. The urban expressway is the road of fast, comfortable and safe, and it plays a very important role in providing long distant traffic service, connecting the main districts closely in urban area, relieving the pressure in the city road capacity. But because of the urbanization process and rapidly increasing in the traffic demand, the urban expressway also has its problem in the traffic safety and traffic jam. As we all know, the ramp metering method is one of the best way to solve the traffic problems in the urban expressway. So it is necessary to further study the ramp metering technology, optimize the ramp metering algorithm.This article is based on the analysis of the ramp metering strategies in the freeway. According to the distribution types of the ramp in our urban expressway, we provide the design principle, the structure, and the divide of the control area for our ramp metering system in the urban expressway. Then we have studied the short term traffic flow prediction method for the lining vehicles at the entrance of ramp in the expressway. This prediction method raises the rapidity and accuracy in the lining vehicles’ rate arrived. It also gives the basic prediction information of lining vehicles for the single on-ramp responsive optimized metering and the multiple on-ramp coordinated optimized metering which have been studied in the chapters behind.According to the arrangement of the sensors on the urban expressway in the ramp metering system, we analyze detector’ type, function and the foundation for the arrangement, and provide a optimized metering method for the single on-ramp. The method takes the speed and the occupy as the control parameters, calculates the real adjustments in the way of taking care of the whole parameters which give their own adjustments. We further provide anther coordinated metering method for multiple on-ramp metering system. This method takes care of multiple on-ramps, establishes a continuity equation using grand fluid theory on the main road, builds a lining vehicles model at the entrance of on-ramp, solves the models above using particle swarm optimization algorithm. The method we give can efficiently improve the effects for the control strategy.Simulations are carried out for the short term traffic flow prediction model, the single on-ramp metering model and the multiple on-ramp metering model. The test results tell that all the three models go well with their own control system.