Study On The Influence Of Truck Escape Ramps Layout On Vehicle System Dynamics

Truck escape ramps,which usually set at the road side of long steep downhill,are special facilities designed to control runaway vehicles by diverting them from the main traffic stream and to achieve the purpose of deceleration in a short distance.Due to the defect of the design of the truck escape ramps,the accident rate of the runaway trucks fail to achieve the deceleration stop and out of the end of the truck escape ramps and rollover is much higher than that of the developed countries,Therefore,it is necessary to put forward the corresponding measures for the design of truck escape ramps.In this paper,the technical parameters of the truck escape ramps and the traffic safety facilities are described.And for the accident type with absolute proportion which the trucks run out of the truck escape ramps and rollover,Combining with the theory of automobile,the accident mechanism is analyzed.In order to reduce the full scale experiment of the real vehicle,the vehicle macro mechanical response of the vehicle under the influence of aggregate is studied.In this paper,A PFC2D micro-simulation model of the interactions between the tire and the aggregate is proposed.The parameters of particle properties are then calibrated by three groups of numerical tests.The calibrated model is verified by full-scale arrester bed testing data to demonstrate its feasibility and accuracy.Based on the simulation model,the influence of different loads on the vehicle's smooth braking is analyzed,and the influence of different aggregate material and gravel particle size on the vehicle speed characteristics and the macro mechanical response are analyzed,we can find that the performance of stopping on gravel bed is better than broken stone bed.And when the radius scope is between 8.3mm and 15.7mm,the stopping performance is the best.At the same time,Combined with the truck escape ramps design technical parameters of recommended values,the road alignment model of truck escape ramps by using TruckSim is established.In this paper,the vehicle system dynamics of the driving lane with a driving angle of 5 degrees,10 degrees and 15 degrees are analyzed when the main line of the vehicle is a straight line,a right turn curve and a left turn curve.and the setting value of the drift angle of truck escape ramps is obtainedFinally,according to the research results of this paper,the reasonable rectification measures are put forward according to the setting of the 3#truck escape ramp in Guangxi.This research has important theoretical significance and engineering application value to enrich and perfect the design specifications and guidelines of truck escape ramps in our country.