International sight distance design practices

This paper reviews the geometric design practices related to sight distance of a number of countries. The purpose of this paper is to present the sight distance design practices of a variety of countries as a resource to highway agencies in any country that may be considering possible modifications and updates to their own policies and practices. It is hoped that this paper will serve as a resource presenting ideas and concepts that may be new to some, but are in actual use elsewhere in the world. International exchanges of this type of information are valuable in that they provide practicing engineers and researchers with a perspective that goes beyond their own country and their own part of the world. The ability to see ahead and observe potentially conflicting traffic is critical to safe highway operations. Sight distance, an important element in the geometric design of highways, refers to the length of roadway over which a driver has an unobstructed view. This paper deals with the criteria used in geometric design for three key aspects of sight distance: (1) stopping sight distance; (2) passing sight distance; and (3) intersection sight distance. Each of these types of sight distance is discussed in this paper.