Speed-Based Proximal Indicator for Right-Turn Crashes at Unsignalized Intersections in India

Unsignalized intersections in India essentially function as uncontrolled ones due to the high prevalence of indisciplined traffic maneuverability. Right-turning vehicles from major and minor roads undertake risky crossing maneuvers in front of right-of-way vehicles by disobeying the priority rules. At such situations, nonprioritized vehicles hinder the movements of the right-of-way vehicles. Because of this, a through moving vehicle plying on the major road needs to take any evasive action to avoid an imminent collision. When the through traffic on the major road has high conflicting speed, the criticality of conflict increases, resulting into a potential crash. This study is an attempt to develop a new proximal indicator by incorporating the conflicting speed of through moving vehicle with a conventional time-proximity conflict indicator postencroachment time. Four unsignalized intersections have been selected from the National Capital Region of India. A speed parameter termed as critical speed is calculated based on the concept of braking distance and used to identify the critical conflicts. More critical conflicts are observed when the conflicting speed of through vehicles is high. Among various crossing situations, the maximum proportions of critical conflicts are found between through moving powered two wheelers (PTWs) along the major road and right-turning heavy vehicles. The conflicting speed of through moving PTW is observed to be the highest among all vehicle categories. The appropriateness of the proposed method is verified using 5 years' crash data for right-turn right angle and right-turn head-on collisions and finding a statistically significant relationship between these right-turn-related crashes and critical crossing conflicts. (C) 2018 American Society of Civil Engineers.