| Studying the evolution mechanism and operation rule of Stop-and-go wave is of great significance to dealing with congestions in expressways."Stop-and-go wave"refers to the phenomenon of frequent acceleration or deceleration in traffic flow,often accompanied by traffic congestion.Deep research on this common phenomenon can help to alleviate urban traffic congestion,reduce the urban traffic accident rate along with vehicle exhaust emissions,which can be instrumental in the construction of green urban traffic.However,at present,the causes and evolution process of this phenomenon has been insufficiently studied in China.Therefore,on the basis of asymmetric driving behavior,a detailed analysis of the phenomenon of stop-and-go wave is presented in this paper.The main contents are as follows:(1)According to the asymmetrical driving behaviors exhibited by the drivers in the actual survey data of the expressway traffic area,further study has been done thoroughly.The influence of vehicle performance and driver characteristics on asymmetric driving behavior is explained.The operation state of the vehicle is divided into free phase,accelerated phase,deceleration phase,uniform phase and stationary phase using the asymmetry of velocity-time,velocity-position,velocity-distance relation graph of typical traffic flow in the confluence area,and the changing process of these 5 stages is analyzed in detail through the velocity-spacing diagram.The acceleration/deceleration curve is therefore derived.(2)On the basis of the theory of asymmetric driving behavior and the route map of typical traffic flow in the expressway junction,the evolution process of stop wave,including generation,growth and dissipation,is analyzed,and the graphic method is used to illustrate the evolution process of the stop wave through the comparison with the actual vehicle trajectory.(3)Taking the North-South entrance ramp confluence area of Wan Jia Li elevated Expressway(Xiang Zhang Road)in Changsha as the research object,the parameters of the VIS SIM are calibrated by the actual survey data,and simulation on the traffic flow in the confluence area is carried out using VII SIM.The simulation effect is proved to be in line with the expected requirements through the two-sample f-test.According to the actual operation condition of the expressway,specific control measures are put forward from the aspects of on-ramp control,off-ramp control and traffic accident. |
