Operating Speed Prediction Model Based on Highway Alignment Spacial Geometric Properties

Speed is the key parameter of road alignments design. The alignments design and evaluation based on operating speed is an effective way to solve safety design problems. According to the geometric properties of road alignments, the compound curvature of the alignments in highway's horizontal and vertical curve combination was calculated, and modified by gradient and section width in this article. According to the road alignment evaluation index, which was composed by the modified compound curvature, the relationship between the index and the operating speed was analyzed and the operating speed prediction was established. The prediction model was proved of high reliability through the contrast between the observed and predicted values. This kind of prediction model, which combines the horizontal with the vertical alignments, provided a new thought for the operating speed prediction. This will apply calculating reference to the highway`s design and management based on the operating speed in future.