A Study Of Trffic Light Control Model Based On Petri Nets

With the progress of science and technology,the rapid development of social economic,and the continuous expansion of city size,making the number of motor vehicles increase quickly.Which not only lead to the rapid growth of traffic volume,but also further intensify the traffic congestion.Traffic congestion will cause of frequent accidents,energy consumption,vehicle delay,economic losses,environmental pollution and other issues.In addition,in the case of emergencies,ambulance should send the injured to hospital with the fastest speed,to ensure that the injured receive timely treatment.And intersection is an important part of urban traffic network,where is the major place of occurs traffic accidents,traffic jams and ambulance delay.Therefore,scientific management and control of intersection signal,as well as establish efficient traffic signal control system,is an important method to ensure smooth traffic and rapid passage of emergency vehicles.The characteristic of urban traffic system is the share of roads,signal lights and other resources,and the urban traffic system has a high degree of concurrency,conflict,dynamic and resource sharing.Petri net is a graphical tool which can visualize the description of the system,and is very useful to simulate the dynamic and concurrent activities of system.In addition,Petri net also has strong plasticity and flexibility,which can be expanded,according to the characteristic of different systems,based on ordinary Petri nets.So far,there have been many scholars studied the intersection signal control problem by using the theory of Petri nets,but there are still many problems need to be improved and perfected.For example,although there have been many scholars research about intersection congestion problems,but few consider both congestion,and pedestrian waiting problems.This article focuses on the problem of intersection signal control,specific work and research results are as follows:1.According to the problem that emergency vehicles may be affected by the ordinary vehicles in the process of driving,especially in the road of traffic congestion,an ambulance is hard to implement priority to surpass the vehicles in front of it.This paper based on the Timed Synchronized Petri Net to build the two phase intersection emergency vehicles priority model.This model can timely adjust the status of the signal lights,make sure the evacuation of the congestion vehicles before the emergency vehicle arrives,achieve the purpose of that emergency vehicle pass through the intersection quickly and safety.2.Most intersections in our country use the fixed time control scheme,but the actual change of traffic flow is random.Therefore when the traffic flow is very large,it will lead to traffic congestion;and when the traffic flow is few,it may make pedestrians have to wait for green light all though there is no vehicle in green light direction.To this regard,this paper proposes an adaptive traffic light control strategy,and establish a two phase intersection signal control model based on theTimed Synchronized Petri.Net.This model can detect the current situation of road traffic by using sensors,and judged by computer controller,real-time control the change of signal lights,according to the current traffic flow conditions.Finally,on the basis of summarizing the full text,this paper discuss the future work of solving traffic control problem based on Petri net.