Analyzing the factors affecting the crash severity level at urban roundabouts in non-lane-based heterogeneous traffic.

Pivotal crash factors are investigated, and crash-severity model for the safety assessment at roundabouts and its vicinity in non-lane based heterogenous traffic is developed. An ordered-probit model was developed using crash-data collected between 2015-2019 for 20 roundabouts in India. The analysis revealed critical influencing parameters for determining the severity-level of crash outcomes at roundabouts, namely, inscribed-circle diameter, height of central island, number of circulatory lanes, presence of splitter island and median, posted-speed limit, type of collision, type of violation behaviour, collision partner, the pattern of collision, presence of road lane-marking, presence of street-light and age of victims. To precisely quantify the impact of each significant factor, marginal effects analysis was also carried out. The results show that the probability of fatal-injuries increased by 14.28% due to angle-collision, 15% for hit-pedestrians, 20.6% due to the pattern of collision and 15.60% due to the collision-partner, Whereas the probability of occurrence of grievous injury was the highest for rear-end with 17%, followed by sideswipe collision with 16% respectively. This study's findings can aid in developing effective remedies to reduce the crash severity for roundabouts road-users and updating the roundabout design standards, considering the safety perceptive.