Adopting a Safe System Approach to Determine Safer Speed Limits: A Case Study from Iran

Abstract

Speed management is one of the main dimensions of the Safe System Approach for reducing both the risk of crash involvement as well as injury severity. This study proposes a practical framework for setting safer speed limits on duplicated rural highways that has been applied to six pilot corridors (total carriageway length of approximately 1,250 km) in Iran. The safer speed limits determined from the proposed framework have been compared with the currently posted speed limits using several indicators and showed a considerable reduction in the total number of changes in speed limits while having very limited impact on reducing the mean travel speed and increase travel time along the study corridors. The study of the pilot corridors establishes that a clear approach and documented guidelines for setting speed limits provides a basis for quantifying engineering judgments about road hazards and determining more consistent speed limit values for similar conditions across Iran’s rural highway network, legitimising speed limit reductions aimed at saving lives.