A novel speed prediction model incorporated with changing slope on vertical curve is established in this paper. The speed prediction model was proposed by using higher mathematical calculus and iteration method, considering the variable slope on the vertical curve. The speed-distance curves of trucks on the continuous long uphill section was obtained by inputting the weight-to-power ratio of Trucks and vertical alignment indexes in VB (Visual Basic) programming. The results show that the novel speed model is totally different from that of original speed prediction model (constant vertical slope) on vertical curve sections. Specifically, the speed deviation of the two models reaches the maximum at the gradient change point of slope, and it increases with larger power ratios, larger slope indexes or higher altitude. The proposed speed prediction model can provide an accurate reference for grade length determination and climbing lane design, leading to safe driving and high traffic efficiency.

CICTP