Calculation and assessment technique of highway 3D dynamic sight distance

A method of using Highway 3D Dynamic Sight Distance (H3DSD) to represent the available sight distance was proposed. The geometric data was used as the main data source for H3DSD calculation. The data was used to fit the highway alignment with cubic B-spline curves. Considering the influencing factors of combination of horizontal and vertical alignment, the driver's dynamic visual field, and the illumination angle of the vehicle head lamps, the H3DSD of each point along the centerline roadway could be calculated with spatial geometry. The most important constraint during the calculation was the relationship between the computed angle composed by the line from the position of driver's eyes to the sight distance checking point and the centerline of the driver's visual field, and the driver's maximum dynamic visual angle. Moreover, the criterion of H3DSD was proposed in order to identify the segments with poor sight distance. Also the main factors restricting sight distance were analyzed. A case study was carried out and the results show that the proposed method has the advantages of easy to get the source data and good prospect of application. It can provide significant technique support to highway safety design.