Study On Speed Limit Regulation Scheme For Typical Maintenance Operation Areas Of Expressway Facing Traffic Flow Stability

After more than 30 years of construction and development,the total mileage of the expressway has been increased year by year,accompanied by the damage of roadbed,pavement and buildings,thus bringing serious hidden danger to highway traffic and transportation.At present,maintenance management is an important means to eliminate the hidden dangers of highway safety,and different forms of maintenance operation areas will be formed in the process of maintenance management.For the maintenance operation area where the lane is closed,because of the reduction of road capacity,there are a large number of hidden dangers for the vehicle to drive.Therefore,it is urgent to strengthen the safety of vehicles in the maintenance operation area of expressway.To strengthen the stability of traffic flow in the maintenance operation area and ensure the traffic safety of the maintenance operation area in the case of increasing demand for transportation,this paper takes the maintenance operation area as the research object and carries out the following research.(1)The traffic flow data of four maintenance operation areas that the lane was closed were investigated,and the traffic flow characteristics in traffic volume,traffic composition and speed distribution were analyzed,which provided the basis for the speed limit values of the speed limit control scheme and other parameters setting's including the expected speed in the VISSIM simulation model and the rate of speed limit compliance.(2)The information entropy was used as a measure of traffic flow stability.The determining method of the optimal grouping number of speed frequency distribution histogram was developed by gain principle of histogram based on conditional entropy and the quantitative comprehensive index judging standard that obeys statistical distribution law,and the problem of quantitative uncertainty of information entropy was solved.Which was easy to compare the traffic flow stability of each section in the operation area.By analyzing the traffic flow law of typical maintenance operation area,it was found that the traffic flow stability in the operation area was present basically: basic section in downstream > work area > warning section > transition section in upstream.For the different operation area,the traffic flow of the warning section is more easily disturbed which locates in the continuous curved slope section compared with the continuous straight slope section.And the traffic flow of the warning section is more chaotic which locates in the continuous uphill section than in the continuous downhill section.(3)Based on the principle of automobile dynamics,the force forms of vehicle braking was analyzed under different road alignment conditions.Then based on the conservation of energy,the first,second and third speed limiting control methods were proposed.The setting position model of speed limit sign was established.Finally the design scheme of speed limit regulation and control in the warning section of typical maintenance operation area was designed,and the specific setting position of speed limit sign was determined.(4)The microscopic simulation model VISSIM was established for the step speed limit control scheme,and the results showed that the two-stage speed limit design scheme is the best method to improve the traffic flow stability under the measured traffic flow in each typical operation area.Based on the simulation,the method of determining the optimal speed limit scheme of warning section in each typical section was obtained considering traffic volume,traffic composition,working area length and speed limit compliance rate.