Stop-Controlled Intersection Sight Distance: Minor Road on Tangent of Horizontal Curve

Sight distance at the intersection of a minor road (controlled by a stop sign) and a major road is an important element of road safety. Several models have been recently developed for the analysis of sight distance at intersections involving horizontal curves on the major road. All these models assume that the intersection lies within the horizontal curve. There are situations, however, when the intersection lies within one of the tangents of the horizontal curve. This case would adversely affect sight distance, especially when the horizontal curve is sharp and the minor road is close to the horizontal curve. This paper develops a new mathematical model for sight distance analysis that explicitly addresses the case where the intersection lies within the tangents of the horizontal curve. The obstruction may be located within the tangent or within the horizontal curve, or located inside or outside of the horizontal curve. Using the model, graphical aids for the required obstruction distances from the major and minor roads, to satisfy sight distance requirements, are developed. The developed model can be used to evaluate sight distance for existing or new intersections.