Study On The Applicability Of Grading Speed Limit Programs In The Freeway Exit Ramp Influence Area

Exit ramp influence area as binding portion of the freeway exit ramp and mainline,complex driving operations like decelerating, changing lanes increase significantly, causingspeed dispersion and the number of traffic conflicts increasing, so exit ramp influence area isan accident-prone area. Accordingly, in order to prevent the mutation of speed, reduce thevelocity gradient value of the successive sections, make the vehicle speed be reduced toramp’s speed limit value gradually and improve traffic safety and traffic efficiency of exitramp influence area, the applicability of grading speed limit programs in the exit rampinfluence area is studied systematically in this paper.This paper analyzes traffic characteristics of exit ramp influence areas firstly, the exitramp influence area is divided and dividing ranges are defined based on traffic characteristicsof exit ramp influence areas, then through studying on speed limit values and types of gradingspeed limit programs, position and emplacing of grading speed limit signs, determiningcontrol methods of grading speed limit programs in the exit ramp influence area.According to principles of establishing evaluation index system and screening methodsof evaluation indicators, the coefficient of variation of the speed deviation, trafficcollision rate, average delay time and average queue length are selected as evaluationindicators of the applicability of grading speed limit programs, evaluation index system ofthe applicability of grading speed limit programs in the exit ramp influence area isestablished and the applicability of grading speed limit programs is evaluatedcomprehensively by the selected weighted addition average method.Firstly pivotal operating speed influential factors are selected Initially, and then thosefactors are verified by VISSIM, rational traffic organization simulation environments areformulated, and then grading speed limit simulation programs are determined, grading speedlimit simulation model is established, parameters of simulation software and simulation modelare demarcated, acquisition methods of parameters of the applicability evaluation indicatorsare determined, simulation steps and processes are formulated.Simulation values of the applicability evaluated index of grading speed limit programs are processed in different traffic organization environment simulation programs, and then theapplicability comprehensive evaluation results of grading speed limit programs are comparedand analyzed in different traffic organization environment simulation programs, theApplicability of different Grading Speed Limit Programs are drawn in Different trafficorganizational environment of the Freeway Exit Ramp Influence Area...