Algorithm for Analyzing Horizontal Sight Distance from Lane Centerline Coordinates

An algorithm for analyzing the availability of horizontal sight distance on two-lane highways to establish the location of no-passing zones is described. The intent was to incorporate the algorithm into a computer model that could use coordinates of a lane centerline as the input and evaluate the availability of horizontal sight distances. The algorithm was applied to develop a method for locating no-passing zones that was more efficient, accurate, and safe than the current methods that require field measurements. The algorithm uses vector product calculations to derive the geometry of the roadway centerline from spatial coordinates of available data points that represent the center of the travel lane. From the roadway centerline definition, the algorithm defines the location of visual clear zone boundaries on both sides of the roadway. Finally, the algorithm uses the roadway centerline and visual clear zone boundary information to determine whether sufficient passing sight distance exists at each point along the centerline.