| Recently, with the rapid development of social economic, land development on both sides of urban road is increasing rapidly. But the unscientific planning, unreasonable design and imperfect management of road access bury a hidden danger for road traffic safety. These problems of urban traffic really need to be solved.Based on the Project supported by the National Natural Science Foundation of China "Study on the mechanism of impact on traffic safety and road traffic operation characteristics based on environmental illumination changes (No.51308177)", traffic safety problems and optimization design method of access system were studied. Firstly, qualitative research of road access traffic was studied. The urban road access system was divided into urban expressway access system, road section traffic access system and slow traffic access system, and the traffic safety problem of access system was expounded. Secondly, safety factors of elevated expressway off ramp were analyzed. Traffic flow characteristics and forms of deceleration lane were studied. The optimization model of deceleration lane length was established. Then recommendation values of deceleration lane length were given. Meanwhile, connection section between off ramp and downstream intersection was analyzed and put forward the problems, the improvement method about planning and management was provided. Thirdly, safety characteristics of access on main road sections were analyzed, the influence relation between access space traffic and three parameters include conflict point, accident rate and main line speed was revealed. According to the positional relation between access road and adjacent intersections, the turning clearance was studied. Then the same side entrance space optimization model and the opposite side entrance space optimization model were established, and the recommendation value of entrance space was obtained. Traffic flow of same side entrance was simulated by using VISSIM. With analysis on the simulation data, the same side entrance space optimization model was evaluated, and the relationship among speed difference, entrance space and traffic delay was revealed. Finally, based on the characteristics of urban traffic in China, and refer to the Access Management strategy, access management methods with Significant improving effect on access traffic safety were given, including access locate method, left-turn control method, right turn guidance method, opposite entrance connect method and entrance geometry design method. By using the optimization design methods and access management methods, ultimately achieve the purpose of improving the road traffic safety and efficiency of access system. |
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