A number of research studies have shown the significance of considering truck and combination vehicle performance in the geometric design of interchange ramps. The greater potential these vehicles have for offtracking and loss of control as well as rollover plays an important role in determining the safe speed of a ramp. The analysis procedure described provides highway engineers with a method, first, to determine the critical speed of a ramp for such heavy vehicles. The PHASE-4 computer model is used to simulate the dynamic behaviour of the vehicle for a specified ramp geometry. The complete procedure is computerised with a user friendly interface for specifying ramp parameters and built-in data sets of vehicle parameters. Then, a method to convert the critical speed to a safe operating speed for the ramp is presented. Input parameters and results for an example ramp consisting of one simple horizontal curve are included as a demonstration. The ramp is analysed with two types of combination vehicles. The method for estimating the safe operating speed is then demonstrated by converting the critical speeds to safe operating speeds.
Samenvatting