Safety Evaluation And Application Study Of The Truck Escape Ramp In Two-class Highway In Mountainous Area

The long downhill section is an important problem to be considered in the design of mountainous highways,and most of the mountainous road traffic accidents are related to it.When large lorries go downhill,the temperature of the vehicle’s brake hub rises,extremely near the bottom of the highway slope,and when the vehicle brake hub temperature exceeds above 260 ℃,the vehicle brake hub fails,resulting in the death of the car crash tragedy.In order to reduce the accidents,such as the traffic signs,marking,Highway longitudinal slope optimization,vehicle speed limit and other measures are adopted in the long downhill section,meanwhile using water to cool the vehicle brake hub is also effective way.However the design of Truck Escape Ramp is the key measures to prevent vehicle running away and reduce personnel and property loss,so it is the key factor.Based on the analysis of the design method of Truck Escape Ramp in mountainous area,this paper takes the preliminary design of G234 Highway Truck Escape Ramp as the research object,analyzes the runningspeed and the possible location of Truck Escape Ramp,then uses AHP-fuzzy comprehensive evaluation method to establish the safety evaluation model of Truck Escape Ramp design.In the paper,the safety and rationality of the design of Truck Escape Ramp of Da Zhu Shan are evaluated by the model,and some useful suggestions are put forward to the Miao Xia Yuan that is to be designed.The main research results are summarized as follows:1)On the basis of analyzing the design method of Truck Escape Ramp,This paper analyzes the factors affecting the Escape Ramp,and establishes the safety evaluation model of Escape Ramp designed by AHP-fuzzy Mathematics Method.2)Using the running speed model to analyze the safety of G234 highway,The analysis shows that the maximum running speed of the truck is 50km/h on Da Zhu Shan-Miao Xia Yuan Lot,while it is up to58.07km/h in Liu Jia Group in Xijiang village.3)Based on the model of brake hub temperature changing of large truck,This paper analyzes the temperature change of the brake hub of large trucks in long downhill section of Zhu Shan-Miao Xia Yuan Lot,and recommends the design stage of the construction drawing in the k37+500~ k38+000 segment which is the vertical slope of the 3rd Viaduct to set as a reverse slope or a flat slope.The long downhill section is divided into Da Zhu Shan and the Miao Xia Yuan two sections,andcalculate the brake hub temperature of the truck respectively,The analysis shows that the k38+140 and k34+100 locations can be set as the Truck Escape Ramp.4)The change of the temperature of the brake hub shows that it’s up to 291.37 ℃ just in few areas in Liu Jia Group of Xijiang village,and the design plan of the construction drawing is designed to change,therefore,it is suggested that Xijiang village Truck Escape Ramp is unnecessary.5)Based on the model,This paper analyzes the preliminary design of the Truck Escape Ramp in Da Zhu Shan,its comprehensive scoring value is 78.03,which belongs to the basic Safety.In order to improve the design,it is suggested that it should increase the length of Truck Escape Ramp and the approach road,increase the vertical curve radius,and improve the design of the auxiliary and traffic safety facilities during the construction drawing design stage.6)The analysis shows that the terrain factors should be taken into account in the design of the Truck Escape Ramp of Miao Xia Yuan,and it is suggested to reduce the longitudinal slope of Truck Escape Ramp and to increase the length of the braking bed,which can effectively reduce the project cost of the safe lane.