Study On Formation Mechanism And Safety Strategy Of Urban Tunnel Traffic Danger Area

The city is densely populated and the traffic flow is large.Urban tunnel,as a special section of urban express road,not only has frequent accidents,but also is difficult to deal with after accidents.In view of the role of urban tunnel as the key node in urban rapid road network,it is necessary to conduct in-depth research on the formation mechanism of urban tunnel driving danger zone under the effect of illumination change and longitudinal slope,in order to ensure the safety and unimpeded of the urban rapid road network,in response to the "transportation power" strategy proposed to establish a convenient and smooth urban traffic network.Based on the experimental data,the visual characteristics of drivers in urban tunnels were analyzed.The two-step clustering algorithm was used to cluster the parameters of drivers’ visual characteristics,and the similar or different behaviors of drivers at different positions in the tunnel were identified.In view of the complex and changeable characteristics of the influencing factors of urban tunnel driving behavior risk,the risk analysis and decision theory are introduced to model the risk degree function of the influencing factors of driving behavior risk,and the quantitative research method of urban tunnel driving behavior risk is sought.The simulation model considering mobile operation area was constructed,and the traffic risk evaluation indexes of urban tunnel were selected to analyze the variation rules of macro traffic flow parameters and micro following risks of each section of urban tunnels under different working conditions.From the perspective of the influence of urban tunnel road environment on drivers,this paper expounds the objectivity of the existence of dangerous areas in urban tunnel driving.Based on the corresponding behavior field,kinetic energy field,potential energy field,driving behavior,vehicle,road environment,the driving safety risk field model of urban tunnel was established,and the formation mechanism of the dangerous area of urban tunnel driving was revealed.On the basis of the above research,referring to the relevant normative documents,this paper discusses the engineering and technical measures to effectively reduce the traffic safety risks of urban tunnels from four aspects: lighting design of urban tunnels,visual inducing facilities of urban tunnels,dividing line of variable lanes of urban tunnels and speed control measures of urban tunnels.Through theoretical and experimental research on urban tunnel traffic safety,the following conclusions are drawn:(1)Short urban tunnels with a length of less than 1km have relatively little influence on drivers’ visual characteristics due to good visibility.When the tunnel length is between 1km and2 km,it has the greatest influence on the visual characteristics of the driver.For urban tunnels with a length of more than 2km,drivers’ dark adaptation time is sufficient and the impact on visual characteristics is reduced.The length of tunnel has a significant effect on the distribution of drivers’ fixation points.The larger the length of tunnel,the lower the percentage of drivers’ fixation points located in the front lane.Based on the two-step clustering algorithm,the similar behaviors of drivers at different positions in the tunnel can be identified.The risk of urban tunnel driving behavior is determined by drivers’ physiological and psychological characteristics,drivers’ risk perception level,tunnel lighting conditions,transitional segment alignment and traffic saturation,etc.The driving behavior risk model based on risk analysis and decision theory can describe the driving behavior risk of urban tunnel well.(2)Both the left lane and the middle lane in the open section of urban expressway were indirectly affected by the moving operation area in the right lane,and the influence was controlled by the road traffic volume and the speed of the moving operation zone.The average driving risk in the longitudinal distance of 200 m behind the moving operation area of the right lane is higher,especially in the distance of 50 m behind the moving operation area.As lane changing overtaking is prohibited in urban tunnel,the backlog vehicles queuing in the rear of the moving operation area on the right lane change lane and overtake after exiting the tunnel exit,causing traffic flow disorder on the left lane and the middle lane.It is suggested that the traffic volume of urban expressway mobile operating vehicles should be controlled below 1200pcu/h,and the driving speed of moving operating vehicles should not be less than 10km/h,and the driving vehicles within a longitudinal distance of 200 m behind moving operating vehicles should be effectively reminded.When there is a moving operation area in the tunnel,the driving risk is higher.It is suggested that the working time of the moving operation vehicles in the tunnel section should be arranged during the closed management period at night or temporarily closed the lane of the moving operation area during the working period,so as to ensure the driving safety of the tunnel section.(3)Under the same conditions,the field intensity of kinetic energy field and behavior field at urban tunnel entrance transition section is greater than that in tunnel interior.Due to the superimposed effects of longitudinal slope and tunnel side wall superimposed,the potential energy field intensity corresponding to the tunnel entrance is the largest.The driving risk field force of vehicles at urban tunnel entrance transition section is obviously greater than that at the tunnel exit transition section,and that at the tunnel exit transition section is greater than that inside of the tunnel.Under the same conditions,the maximum force is generated when the tunnel entrance is running downhill in the same lane,next is up to vehicles on the same lane at the tunnel exit uphill,vehicles in different lanes at the tunnel entrance downhill,vehicles in different lanes at the tunnel exit uphill,and the smallest is vehicles in different lanes inside the tunnel.(4)The existence of low-speed vehicles in urban tunnel sections has an impact on the average speed of traffic flow,average delay time and traffic density.The influence of low speed vehicles on traffic flow in urban tunnel can be effectively alleviated by setting a variable lane boundary in urban tunnel and adjusting the display state of lane boundary in real time.The research results of this paper can provide theoretical support for improving the level of traffic safety management in urban tunnels,further improving the tunnel traffic safety research system,increasing traffic efficiency of urban tunnels and improving the urban traffic environment.