Research On Rationality Of Sectional Speed Limit In Extra Long Tunnel Of Expressway

With the rapid development of highways in China for more than 40 years,provinces in the east and south have formed a perfect highway network.The development of the road network is gradually spreading to the mountainous and hilly areas in the west.In recent years,the number and length have increased significantly.However,at present,there is no comprehensive,scientific and unified method for tunnel speed limit,which has caused the problems of tunnel speed limit to be solved slowly.In order to ensure the safe operation of the super long tunnel of the expressway and improve the efficiency of vehicle traffic,it is very necessary to carry out a feasibility study on the rationality of the tunnel speed control method.This article first explains the speed limit theory and method,puts forward some noun concepts related to speed limit,and analyzes the difference and connection between these speed concepts and speed limit,to provide some theoretical reference for the determination of speed limit value.Then it analyzes and compares several current highway speed limit methods commonly used in China,and proposes a sectional-(speeddividing,vehicle-type)speed-limiting scheme combination form suitable for super-long tunnels of expressways.According to the difference in lighting settings,accident rate and driving speed in the extra-long tunnel,the extra-long tunnel section is roughly divided into the entrance section,the middle section and the exit section,and the maximum speed limit of the entrance and exit section is calculated considering the driver’s visual adaptability,and the The safe stopping sight distance calculates the maximum speed limit value in the middle section and corrects it with the desired speed.Secondly,the concept of speed limit zone and speed limit transition section is proposed.In order to ensure the coordination of vehicle speed,it is necessary to insert a speed limit transition section on the adjacent speed limit road section where the speed limit difference is greater than 20km/h to make the vehicle speed smooth and smooth Suitable for transition.The entrance section,middle section and exit section of the tunnel are further divided according to the driving behavior characteristics,and the length of each small section is preliminarily calculated using the determined maximum speed limit value.The length of each small section is corrected using relevant research and specifications at home and abroad.After the correction,the section is adjusted to obtain the specific setting plan of the location and length of the extra-long tunnel section.The leading distance of each speed limit sign is calculated according to the specifications,and the specific setting positions of each speed limit sign are obtained by referring to the end points of several actions in the section setting scheme.Finally,the vissim simulation software is used to evaluate the rationality of the intermediate speed limit value and the rationality of the section speed limit scheme.Use speed differences to evaluate driving safety,and travel time to evaluate traffic efficiency.The simulation results show that the speed of 100km/h in the middle section is relatively reasonable,and compared with the current domestic tunnel speed limit,the uniform speed limit scheme of the entire tunnel section is adopted.The section speed limit method is used in the super long tunnel section of the expressway.It can improve road traffic efficiency and effectively improve driving safety.This paper comprehensively analyzes the speed control problems of highway sections in my country’s expressways,proposes a speed limit method suitable for the characteristics of my country’s expressway tunnels,and gives specific setting schemes.The research results of the thesis can provide reference for the formulation of speed limit schemes for highway tunnels in my country,and provide a basis and theoretical basis for the establishment of speed limit standards for highways in my country.