Study On Traffic Congestion Of Urban Tunnel Entrance And Exit

Urban tunnel has an important traffic function on the urban roads. It has played a positive part in reducing the ground of city road, cutting vehicle mileage, and leading city traffic. The road conditions and traffic environment changed a lot at the entrances or exits of tunnels and driving behaviors were in dynamic changes in such sections. Especially during peak hours and in the condition of unstable traffic flow, the traffic condition at tunnel entrances and exits had a great influence on the whole tunnel traffic efficiency. Therefore, it is necessary to study the urban tunnel traffic flow in order to analyze the problem of heavy traffic at urban tunnel entrances and exits. Accordingly, the research can be provided as an analysis reference for the traffic design, organization and management of urban tunnels.This paper was based on traffic flow theory, traffic engineering and traffic management and control measures, researches on relationship between the lane-changing and traffic jams were analyzed. The specific content as follows:Firstly, the paper described the main factors of influencing traffic flow from the aspect in characteristics of drivers, vehicles and road. It analyzed the behavior characteristics influenced by different factors. The root causes of oversize vehicles affecting the traffic statement based on the analysis of traffic characteristics at the entrances and exits of urban tunnels and the classification of traffic states.Through video observation method, investigation and analysis of the urban tunnel traffic flow at the exit of the microscopic parameters were conducted. With the traffic wave model the relationship between vehicle lane-changing and the traffic congestion were analyzed. Meanwhile, the urban tunnel traffic flow states were divided into discrete, following and crowded states using fundamental diagram of traffic flow. Based on the headway method to calculate the vehicle conversion coefficient and combined vehicle conversion coefficient with the free stream velocity analysis of the two parameters. The most important effect on traffic flow was bus ratio.By using safety distance formula and traffic wave model, the driveway transform queue or congestion probability were calculated when a car arrived at the tunnel portal. Using multivariate linear regression model, this paper analyzed the bus lane-changing of specific influence factors on traffic flow, founding that in the different factors, bus ratio influence on urban tunnel traffic flow is more obvious.By using the model of acceleration noise, an investigation of the dynamic acceleration of Xuanwuhu tunnel, Gulou tunnel and Jiuhuashan tunnel traffic was conducted by experimental vehicle. Urban tunnel traffic flow state and acceleration interference diagram were got with simulation. According to the diagram which showed the running characteristics of different vehicles in urban tunnels, the single two-lane service levels were divided into four levels. The scope of the average velocity was provided. The results give out the quantitative between lane-changing and traffic jams with the evaluation of acceleration noise.By the research of this paper, the congestion and disappearance of speed, the range of time headway and the probability of traffic congestion due to the lane-changing were obtained by calculation. The multiple linear regression model was established. It was pointed out that bus ratio was the biggest influence on tunnel entrance traffic flow. The acceleration noises of different tunnel traffic flow were calculated based on the acceleration noise model. The traffic flow states and the diagram of acceleration noise were obtained. The service level was divided into four ranks.