Modelling the operational effects of unconventional U-turns at a highway intersection

Abstract

Conventional solutions for congested urban arterials have been exhausted. Recently, some signalised intersections have been replaced with unconventional unsignalised U-turns along six-lane divided arterials. In order to evaluate the new intersection design, it was necessary to quantify impacts of U-turns on movements through modelling. Some models exist for this purpose. However, these models seemed unlikely to be applicable for the unconventional U-turns. Hence, their impacts on travel time and speed of movements were modelled during a study project. Comparisons of the new and previous models affirm that previous models cannot predict the travel time and other variables as well as new models. Two useful applications of these models regarding the feasibility studies and determining optimal location of the U-turns are also presented. This article also outlines that the vehicles, which need to access specific lanes, are the source of turbulence observed in weaving sections of U-turns. Therefore, a new definition of volume ratio is introduced.