Study On Traffic Operation Characteristics And Optimal Control Method For Ramp’s Diverging And Merging Areas In Urban Expressway

In recent years, traffic congestion has gradually become a critical problem neededto be resolved in the world. Urban expressway system, as the aorta of city traffic,performs significant support and protection functions in city traffic operation, operationquality of which directly affects the operation efficiency of urban road network. Ramp’sdiverging and merging areas, as the interaction link between internal and external trafficof expressway system, are the key nodes of the cross correlation between expresswaymainline and urban road network, the traffic operating conditions of which play a directimpact on the effective expressway system functions.Researches at home and abroad have shown that it only relying on accelerating thespeed of road construction, especially for traffic congestion of expressway is difficult toease urban road traffic congestion problems, which must rely on advanced trafficmanagement and control measures to ease traffic pressure. Taking the expresswaynetwork of Qingdao as research object, for road network state, traffic conditions andtraffic scenes, this paper analyzes the traffic flow characteristics of ramp’s diverging andmerging areas in urban expressway, explores the approaches to solve the trafficcongestion of urban expressway, establishes an effective system of ramp optimal controlmethod in expressway, which provides theoretical basis and technical support for trafficmanagement and control systems of urban expressway. The content of the paper brieflyas follows:The first part analyzes the spatial and temporal characteristics of traffic flow oframp’s diverging and merging areas in urban expressway. Through traffic surveys,spatial and temporal variation laws of traffic flow characteristics (flow, speed, density)of ramp’s diverging and merging areas in urban expressway are conducted a detailedanalysis, and interference of the pulse, volatility and speed discreteness in on-ramp onthe mainline traffic flow is in-depth probed, which provides basis for ramp control.The second part studies vehicle operation interaction characteristics of ramp’sdiverging and merging areas in urban expressway. Game Theory is applied foranalyzing the interaction mechanism among vehicles in ramp’s diverging and mergingareas, including the car-following interaction behavior, lane-changing behavior and thedynamic game characteristics of vehicles interactions, and using traffic simulation andnumerical statistical analysis validates the accuracy and practicality the models.The third part is the stability analysis for traffic flow of ramp’s diverging and merging areas in urban expressway. Based on research of vehicle interaction behaviorcharacteristics in diverging and merging areas, macroscopic characteristics and stabilityof traffic flow in ramp’s diverging and merging areas are in deep studied. By revealingthe generation, dissemination mechanism of traffic flow disturbance, the transverse andlongitudinal stability analysis for expressway mainline is conducted, the correspondingmodels are established. Through6-DOF automobile driving simulation platform andVissim, the traffic flow instability mechanism is verified from the micro and macroaspects.The fourth part elaborates urban expressway ramp control methods. Based on theanalysis for vehicle interaction characteristics and traffic flow stability mechanism oframp’s diverging and merging areas in urban expressway, this paper regards activeguided traffic control as the concept, proposes a guided real-time dynamic coordinatedcontrol strategy with the expressway as the mainline; based on iterative adaptive controlmethods, dynamic coordinated control methods considering share, vehicle speed andlane-change safe distance are performed and quantitative models are developed.The fifth part illustrates the ramp traffic system simulation for urban expressway.Using Vissim to implement the traffic simulation for the urban expressway on-ramp andoff-ramp control, and making the mathematical statistics analysis with the obtained data,comparing the parameter values before and after the control method optimization, thepracticality and accuracy of optimal control method is validated, and ultimately asuitable optimization algorithm for our urban expressway ramp control is acquired.