INFLUENCE OF SIGHT DISTANCE CHARACTERISTICS ON SAFETY OF INTERSECTIONS USING SURROGATE SAFETY MEASURES

Abstract

Recent road accident statistics indicate that more than 30% of accidents occur at intersections. Whereas, total percentage of intersections present in the entire road network is less than 2%. From design point of view, one way to ensure reduction of accidents at intersections is to provide sufficient sight distance and clear sight triangles. However, it was observed that even when minimum sight distance is provided, it does not ensure non-occurrence of accidents because available sight distance at intersection changes with time. Hence there is a need to understand the effect of sight distance characteristics on safety at uncontrolled intersections. From safety studies, it was observed that crash data is highly unreliable as it is generally underreported.  Hence in the present study, surrogate safety measures were used instead of crash data. To accomplish the study objectives, six uncontrolled three-legged intersections were selected. Geometric data such as sight distance was measured as per IRC SP 41 (1994) guidelines. Traffic data collection at each intersection was carried out using videography method. From the recorded videos, volume data, speed data, and Post Encroachment Time (PET) data were extracted manually. The effect of various geometric and traffic factors on the critical conflict rate was studied using correlation and regression analysis. From the models developed, it is observed that for every 1 unit increase in logarithm of major and minor road sight distance, critical conflict rate decreased by 18.14% and 33.56%, respectively. Also, it was found that, the available sight distance is far shorter than the design/minimum sight distance specified by IRC SP 41 (1994).