Departure Angle and Approach Length of Truck Escape Ramps Locating in Right Turning Circular Curve

Abstract:

As an important safety measurement for longitudinal steep slope, truck escape ramps are widely used in China. Limited to complex terrain of mountainous highway, truck escape ramps will be inevitably built in the horizontal curve. In this paper, UC-win Road 9.0 driving simulation was selected to study the departure angle and approach length of the truck escape ramps locating in the right-turning circular curve. Four indexes, adjusting time, minimum turning radius, steering wheel angle amplitude and frequency, were selected and analyzed by regression analysis using the data of 16 drivers entering the truck escape ramps. Then the quantitative model of each index with the circular curve radius and the departure angle was established. Through the second order clustering method, the setting range of the departure angle and approach length was narrowed. Finally, considering the lateral stability of errant vehicle, the design parameters of truck escape ramps were determined. It was recommended to set truck escape ramps at the main line with radius no less than 1000m, and the departure angle was 0°-5° while the approach length was 6s design speed travelling length. With the restricted condition, the truck escape ramps could be set at the horizontal curve radius of 600m-1000m, and the departure angle was 0°-5° while the approach length was 9s design speed travelling distance. The departure angle was 5 °-10 ° and the approach length was 12s design speed travelling distance.