Clustering Based Approach to Quantify the Unsafe Driving at Uncontrolled Median Openings due to Forced Deceleration: A Case Study in India

Uncontrolled median openings with no lane discipline lead to complex driving phenomenon since the approaching through vehicles (major traffic stream) generally have to slow down their vehicles due to the presence of U-turns in the opposing traffic stream (minor traffic stream). It is observed that the approaching through vehicles despite being the major stream vehicles are forced to slow their vehicles, which sometimes also leads to evasive deceleration beyond limits of safety. In the present study, field data has been collected and the speed reduction from start of median opening to center of median opening is evaluated. Further, the effect of vehicle category and lane in which they are travelling, on speed reduction is also examined. Linear and quadratic probabilistic models have been developed to estimate the reduction in speed based on speed at the center of median opening, vehicle category, and zone/lane in which the vehicle is travelling. Safe reduction in speed is determined by using the IRC 66-1976 guidelines regarding SSD calculation. Thereafter, an undesirable driving index/safety index is proposed by conducting k-mean clustering utilizing the percentage reduction in speed. If the average reduction in speed increases beyond the proposed index, traffic facilities require deeper analysis for smooth flow of vehicles. The present study shall help in identifying the proportion of safe and unsafe reduction in speeds at median openings and proper steps can be undertaken to improve the safety and comfort of road users.