Research On The Road Capacity Network Based On Dynamic Simulation

Road net capacity, used to measure the carrying ability of the road net, generally utilizes the peak hour traffic capacity as the measuring standard, but doesn’t take fluctuation differences of road net traffic load into account, which makes it possible that the computation results differ from the critical state of the road net operation.This thesis introduces a dynamic simulation model, uses Euler’s formula to design a PA increasing method, aims to describe the dynamic change characteristics of the road net at peak hour, judges the critical state of road net from the results of road net state changes under different PAs, and takes it as the measuring standard to calculate the maximum PA value. This thesis analyzes route-taking and the determination of the instantaneous position of the vehicle during the dynamic simulation, and designs occupancy rate and the index of the speed standard deviation; Based on PA increasing method and dynamic simulation model, the thesis builds up a PA increasing model and gets five groups of road net state results under different PA values. In the characteristic analysis of road net results, it is found out that when the instantaneous occupancy rate at peak hour ranges between 0.2 and 0.3 or the average speed is approximately equal to 10km/h, the road net occupancy rate, speed, speed standard deviation, delay and others indexes reach their critical values and restore the initial states after the peak hour, and the critical conditions of road net operation are obtained. With the restrictions of such conditions and based on quadratic programming, the PA inversion model is constructed and the PA maximum- road net capacity- is calculated; with the model constructed based on peak hour traffic travel, the capacity and the plot ratio are both calculated. The research shows that the new PA increasing method solves the problem that the differences are big and incoherent of two adjacent road net states after increasing fixed value; indexes in dynamic simulation such as plot ratio and speed standard deviation can be used to analyze the continual changes of road net states and dynamic changes in peak hour during the PA increasing process, which indicates that dynamic simulation can reflect the dynamic changes of road net load. The maximum calculated in the PA inversion model with the restrictions of road net critical state is consistent with the evaluation result of HCM2000 standard, which suggests that the model is scientific.The researching method in this thesis improves the computing accuracy of the road net capacity, and provides references for the urban land utilization and the balance of supply and demand of traffic travel, when the method is applied in assisting in working out plot ratio at regulatory plan stage.