PASSING SIGHT DISTANCE REQUIREMENTS FOR CURRENT AND PROJECTED TRAFFIC OPERATIONS

Adequate passing sight distances as provided in current geometric design standards are based on studies of passing behaviour in the period 1938 to 1940. The purpose of this study is to determine whether these standards are adequate for present day and future design practice in the light of changing vehicle and traffic characteristics. Employing a recently developed mathematical passing model, results show that current designs are inadequate for safe passing, given the higher mean traffic velocities in evidence today. It is recommended that design standards be modified to account for the current and projected sight distance requirements. For the covering abstract of the conference see IRRD 286189. (TRRL)