| As urbanization accelerates,existing roads are unable to meet the growing travel needs of residents,and traffic congestion is becoming increasingly serious.Expressways,as an important part of the urban road network,carry large traffic flows over medium and long distances and play a key role in improving the efficiency of urban transportation.Due to terrain constraints,there are short-distance continuous diverging ramp settings in the expressway system of mountainous cities.Vehicles frequently experience lane changes,deceleration diverging,and interweaving conflicts within a short distance,which can easily form bottlenecks and cause traffic congestion,resulting in the expressways being unable to function normally.Therefore,analyzing the traffic characteristics of short-distance continuous diverging areas of expressways in mountainous cities and constructing a traffic capacity calculation model is of great significance for ensuring the safe and efficient operation of the expressway system.This thesis selects the short-distance continuous diverging areas of expressways in mountainous cities as the research object.By extracting vehicle trajectory data from aerial videos,the road characteristics,traffic flow characteristics,and vehicle behavior characteristics in the research areas are analyzed.A micro-simulation model is constructed and the main factors affecting the traffic capacity of the diverging areas are determined.A traffic capacity calculation model suitable for short-distance continuous diverging areas of expressways in mountainous cities is proposed.The specific research content is as follows:(1)Definition of short-distance continuous diverging areas of expressways in mountainous cities.The road network structure and continuous diverging areas types of mountainous cities and plain cities are analyzed,and the research object is determined as the right-side ramp continuous diverging areas.By comparing the road characteristics of continuous diverging areas in mountainous cities and plain cities,and combining with relevant design specifications,a definition of short-distance continuous diverging areas of expressways in mountainous cities is given: In the expressway system of mountainous cities,within a certain range,two consecutive diversions occur and the distance between the diverging points is less than 120 m.(2)Traffic characteristics analysis of short-distance continuous diverging areas of expressways in mountainous cities.Vehicle trajectory data are extracted from drone aerial video and cleaned and filtered.The research scope of short-distance continuous diverging areas is determined,and the traffic volume,vehicle speed and lane-changing behavior are analyzed by dividing lanes and section cross-sections,and their spatial distribution characteristics and variation laws are studied.The analysis results show that the traffic flow characteristics and driving behavior vary under different traffic operation states.(3)Construction of simulation model for short-distance continuous diverging areas of expressways in mountainous cities.Using traffic simulation software,a microscopic traffic simulation model for short-distance continuous diverging areas of expressways in mountainous cities is constructed.The key parameters affecting driving behavior of the simulation model are determined by sensitivity analysis.According to the measured data,the key influencing parameters are calibrated to improve the reliability of the simulation model and provide data support for the capacity analysis of short-distance continuous diverging areas.After comparing with measured data,it is determined that the error of the simulation model is within 4%,which can accurately reflect the actual operation situation of short-distance continuous diverging areas.(4)Construction of capacity model for short-distance continuous diverging areas of expressways in mountainous cities.Through simulation experiments,the capacity under different combinations of influencing factors is obtained.The grey correlation analysis method is used to determine that the main influencing factors of capacity are the distance between diverging points,the first diverging ratio and the second diverging ratio.Based on simulation data,considering the main influencing factors,a capacity calculation model suitable for short-distance continuous diverging areas of expressways in mountainous cities is proposed,and the model parameters are solved by using mathematical statistics methods.After verification by an example,the error between the calculated result of this model and the measured capacity is within 5%. |
