Traffic Flow Model And Simulation Implementation Based On Long Tunnel Environment

With the development of the economy and the prosperity of the market,in order to cope with the complex transport environment brought about by the rapid growth of all kinds of vehicles,the mileage of motorway construction and the number of tunnels built has been steadily increasing,while at the same time placing higher demands on the traffic safety monitoring and management of bottleneck sections of tunnels.The use of computer simulation is an economical and effective way to monitor the microscopic and macroscopic traffic operation of tunnels in a more efficient way.Firstly,a traffic flow model adapted to the long tunnel environment was developed.Based on the characteristic that the speed of traffic flow at the entrance section of a long tunnel is significantly influenced by the change of the brightness reduction coefficient at the entrance section,the brightness reduction coefficient is introduced into the traffic flow model of the entrance section of a long tunnel,while different types of vehicles have different model parameters,according to which the basic map of traffic flow in a long tunnel with multiple sections and vehicles is established.A conversion method from Eulerian to Lagrangian coordinates is used to convert the macroscopic basic diagram to a microscopic speed-head spacing relationship,and a conservation equation is established in Lagrangian coordinates to derive the discretization simulation calculation solution steps.Secondly,the model parameters were calibrated and the validity of the long tunnel multisection and multi-model simulation model was verified.A grid search method is used to calibrate all the parameters of the microscopic simulation model according to the calibration process of determining the calibration parameters,establishing the evaluation index,finding the best model parameters,analysing the calibration results and correcting the parameters theoretically.In order to investigate the extensive adaptability of the microscopic traffic model for long tunnels with multiple road sections and multiple vehicles under high,medium and low traffic inputs,this paper also compares and analyses the model with a meta-cellular automaton model to verify the consistency of the congestion and dissipation waves under high starting traffic inputs.Finally,in accordance with the concept of layered design,a program was written to implement an integrated microscopic traffic simulation environment for long tunnels and to design the interactive interface.The computational layer uses a browser-server architecture to decouple the computational layer and the presentation layer.The computational layer calculates the microscopic vehicle location and macroscopic traffic flow parameters through the microscopic simulation model of multiple road sections and vehicles in the long tunnel,while the presentation layer integrates the microscopic and macroscopic aspects to achieve a real-time dynamic display and historical reproduction of the traffic operation of the long tunnel.From the validation of the model and the application results,it can be seen that the multisection and multi-vehicle microscopic traffic flow simulation model built in the long tunnel environment can more accurately describe the characteristics of the traffic flow state changes within the long tunnel and upstream and downstream sections under various traffic input changes,reproduce the traffic flow operation law of each road section,and provide an auxiliary experimental means and analytical tool for the monitoring and control of the tunnel management system.