Research On Layout Optimization Of Maintenance Operation Area Of Eight-lane Expressway

With the rapid increase of eight-lane expressways and the rapid growth of traffic volume in China,eight-lane expressways will face more and more heavy maintenance tasks in the future,and road users and maintenance workers have put forward higher expectations on the service level and safety in the maintenance stage.Eight-lane highway maintenance project,the traffic environment is complicated,influencing factors,existing to layout is difficult to complete specifications and standards are applicable to the actual demand,need to build a comprehensive evaluation system,bring about various closed form to evaluate traffic organization scheme and maintenance layout optimization,more detailed guidance to an eight-lane highway maintenance work.First of all,on the basis of the layout of each part of the maintenance operation area,all 27 kinds of maintenance traffic organization forms of different closed lane positions of eight-lane expressway are summarized and classified.A Bayesian network model was constructed to theoretically study the influencing factors of traffic conflicts in the confluence area within the scope of maintenance operation area.The results showed that the position of closed lane and traffic saturation had a significant impact on the types of traffic conflicts,and it was necessary to take control measures such as speed limit before the upstream transition area.Then,the sample expressways were selected for field research to obtain the scene data related to maintenance operations.The Vissim simulation software was selected to build the simulation model and design the simulation scheme.The optimal traffic organization scheme under different closed conditions and the length optimization of the maintenance operation area were studied.In order to meet the service level and safety level of the expressway,the average vehicle delay,average travel time,average speed,average number of stops and average queue length are selected as the service level evaluation indexes,and the number of conflicts is selected as the safety level evaluation indexes.All traffic organization schemes under different closed conditions are simulated,and the single index schemes of various simulations are found to have their own advantages and disadvantages,requiring comprehensive evaluation.Based on this,principal component analysis method was used to analyze the internal structure mechanism of each indicator.The results showed that: when evaluating the maintenance organization form under different vehicle flow saturation,the evaluation index of average number of vehicle stops should be taken into account under low saturation.Under medium saturation,average travel time and average delay should be considered.Under high saturation,the evaluation indexes of average parking times and average queue length should be considered.At the same time,with the increase of saturation,more attention should be paid to the impact of vehicle average conflict on traffic travel.In order to find the most suitable evaluation method,the objective and subjective comprehensive evaluation methods are compared and analyzed.Objective method of principal component analysis model was used to construct the main composition is rated as a comprehensive index is calculated,a subjective method using analytic hierarchy model for comprehensive evaluation of different maintenance organization form,through the contrast found that two methods on the evaluation results are basically identical,the optimal traffic organization was obtained under the condition of different closed form.Finally,according to the evaluation index data of each part of the simulation,the key areas affecting the operation of the traffic flow in the maintenance section are the warning zone and the upstream transition zone by using the fast clustering and systematic clustering analysis methods.For the warning zone and upstream transition zone respectively,with the length of the region as a single variable,the simulation models of various maintenance organization forms obtained from the previous research were constructed,and the simulation indicators were compared.The objective evaluation method of principal component analysis was used to comprehensively evaluate and score each scheme.The results showed that the length of warning zone under low saturation traffic flow should be set to 2000 m,and that under medium and high saturation traffic flow should be set to 2400 m.The length of upstream transition zone should be set at 250 m in the case of closed single and double lane maintenance,375 m in the case of closed three lane maintenance,and 500 m in the case of closed half lane maintenance.