Conflicting volume for U-turns at uncontrolled median openings

Abstract

This paper proposes a practical approach to estimate the conflicting traffic volume caused by U-turns at uncontrolled median openings under mixed traffic conditions. Data were collected at 21 median openings on multi-lane divided roads in India (i.e. 13 on six-lane and eight on four-lane). The road width at the median opening is divided into three parts: zone of severe conflict, zone of safety and unaffected zone based on the placement of the left wheel of U-turning vehicles (left-hand drive rule followed in India). The first two zones together are considered as the conflicting zone for calculating the conflicting traffic. The proportion of opposing through traffic within the conflicting zone is considered as the conflicting traffic volume for U-turns. The conflicting volume at all the sections is estimated based on placement of through traffic across the width of the road and it is found to be dependent on the size of the U-turning vehicle. An equation is suggested to calculate the conflicting traffic based on the composition of U-turning traffic. The conflicting traffic on six-lane roads is found to be relatively, low but on four-lane roads, almost all of the opposing traffic becomes conflicting traffic for U-turns.