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.

Realistic Approach for Capacity Estimation of U-Turns Under Heterogeneous Traffic Condition

“…However, they ignored the influence of the approaching through traffic volume and did not consider the influence of the temporal conflict factor for the estimation of conflicting traffic volume. Furthermore, for identifying the zone of safety, the methodology proposed by Mohapatra et al ( 13 ) requires the simultaneous arrival of both a U-turning vehicle and approaching through vehicle at the merging line, which is a demanding task because observation of the simultaneous arrival of both vehicles at an MBMO area requires data collection over a very long period. The methodology for the estimation of conflicting traffic volume proposed by Mohapatra et al ( 13 ) may therefore provide inaccurate results, which could result in incorrect estimation of U-turn capacity.…”

“…Capacity estimation for U-turn requires three important parameters, namely: conflicting flow rate, critical gap, and follow-up time ( 8 , 11 , 12 ). Estimation of conflicting flow rate is most challenging pertaining to the peculiar traffic condition prevailing in developing economies in general and India in particular ( 13 ). Liu et al ( 12 ) carried out a study in the United States of America on a six-lane road and reported conflicting traffic volume as 2.2 times approaching traffic volume in each lane.…”

Traffic Performance of U-Turn Effects at Median Opening on Four-Lane Divided of Urban Street (Study Case: Yogyakarta, Indonesia)

“…A geometrical augmentation required at the median opening was suggested. Mohapatra et al in [5] also said that the conflicting traffic on six-lane roads was found to be relatively low, but on fourlane roads, almost all of the opposing traffic becomes conflicting traffic for U-turns.…”

Comparative Appraisal of Critical Gap Estimation Techniques in the Context of U-turning Vehicles

“…MBMOs are provided in the raised median to vehicles to make a U-turn and reverse their flow direction (6). A U-turn maneuver is possible only if the desired gap of the U-turning driver is available in approaching through traffic (ATT) stream.…”