Analyzing dynamic curve widening on forest roads

Forest roads require important design specifications to ensure all-season access for various vehicles. Long and heavy log trucks can face serious maneuvering problems on forest roads due to insufficient amount of area to the left for road widening on horizontal curves. In order to provide safe and continuous shipment and transportation, appropriate curve widening areas should be provided for long vehicles along horizontal curves. In this study, a statistical model was developed to provide curve-widening solutions for long trucks (e.g., those with 18 wheels) considering various curve radius and deflection angles. The dynamic curve widening feature of Plateia 2013 program was employed to calculate curve widening for the specified vehicle. During the solution process, nine different horizontal curve diameters from 10 to 50 m (by 5 m intervals) and 17 different deflection angles from 90° to 170° (by 5° intervals) were evaluated to run horizontal curve-widening analysis. Using a multiple regression model, we made suitable predictions about curve widening. The curve-widening areas decrease as the horizontal curve radius increases, while increasing the deflection angle on horizontal curves increases curve widening areas. Clearly, the computer-based dynamic curve widening model developed in this study can be effectively used in determining optimum widening for horizontal curves by evaluating the number of alternatives that fit geometrical specifications and vehicle types.