Density Models and Safety Analysis for Rural Unsignalised Restricted Crossing U-turn Intersections

Abstract

The first objective of this study was to provide designers with a model that would help them assess the suitability of implementing an unsignalized restricted crossing U-turn (RCUT) based on the traffic volume arriving to a given rural intersection. Specifically, this study identified the zones that were most susceptible to bottlenecks and provided regression models that calculate the traffic density as a function of the traffic volume. In addition, the second objective of this study was to look at how the number of traffic conflicts varied with the traffic volume. Two geometric design cases were studied: four-lane and six-lane arterials using 1000 foot long (305 m long) weaving sections. VISSIM traffic simulations were used to identify the critical zones, and calculate the traffic density for different traffic flows. Volumes and densities allowed the development of regression models. Two critical zones were identified: where vehicles coming from the minor road merge to enter the U-turn and where vehicles exiting the U-turn merge to the multilane arterial. Also, based on the classification given by this study to the traffic volumes, a sensitivity analysis determined which of them had the greatest impact on the level of service. For the number of traffic conflicts from simulation, the Surrogate Safety Analysis Model was applied to measure them. This study found that at certain traffic volumes, traffic conflicts rise sharply. © 2011 Published by Elsevier Ltd.