| With the high-intensity development of the surrounding urban roads,the number of access points on both sides of urban roads is increasing.Vehicles in shopping malls,parking lots,residential areas and office areas need access to urban roads from access points.More access points will increase road accessibility and make it more convenient for vehicles to reach both sides of the road.However,the increase of access points will greatly affect the operational efficiency of urban roads,that is,mobility.Urban road traffic network is a dynamic and complex system,and minor changes in traffic status will have a greater impact on the transmission of urban road traffic network.Near the entrance of urban roads,the original stable traffic flow becomes disordered due to the influence of the interweaving of the access vehicles and the main road vehicles on the interweaving section of the access roads.Such disturbances will be transmitted on urban roads,which will eventually lead to a decrease in road safety near urban road access points,an increase in vehicle delays and a decrease in traffic efficiency.Therefore,it is of great significance to study the entrances on both sides of urban roads.Firstly,this paper summarizes and analyses the research methods of access points at home and abroad and the research methods of delays in urban roads affected by special factors,especially puts forward some suggestions on improving the basic assumptions of the more popular gap theory.On the basis of the improved basic assumptions,the running state of the traffic flow at the access port and the mechanism of the delay are analyzed.Then,typical factors affecting access delay are extracted,such as steering type,main road traffic volume,number of main road lanes,main road lane width,access traffic volume and main road speed.Then,the single access delay model is established by using probability model and queuing theory under the condition of low density of main road traffic flow;the single access delay model is established by using traffic wave theory under the condition of high density of main road traffic flow;and based on the idea of expectation,the combined impact modeling method of multiple access is put forward,and finally the urban road affected by access delay under different conditions is established.False model.Then a typical field access port is investigated,and the results of the investigation are compared with those of the model.It is found that the error between the field survey results and the model results is 7.3%,which shows that the established access delay model has high accuracy.Finally,the influence rules of some influencing factors are analyzed and discussed by theoretical analysis method,and the superposition effect of access volume and the minimum benefit of critical speed delay of main road are obtained.The existence of these two effects is verified by VISSIM simulation.The innovation of this paper lies in: through the analysis of influence mechanism and the basic theory of traffic flow,the delay at the junction is quantitatively modeled and calculated;secondly,the basic hypothesis of gap theory is revised,assuming that the driver of the access vehicle does not access the main road strictly according to the gap that makes the main road unaffected,so that the main road vehicle will be affected by the delay of the access vehicle,and then the main road vehicle will be affected by the delay of the access vehicle.A more practical access delay model is obtained. |
