A study on the capacity assessment of turbo roundabouts and the applicability in Vietnam

Abstract

A turbo roundabout (or Turbine) is an improvement from conventional roundabouts with lanes running in a spiral shape, helping vehicles to enter the intersection smoothly and eliminate conflicts, reducing traffic congestion as well as the risk of traffic accidents. The turbo roundabout is a modern intersection, newly developed around 1996, initially in the Netherlands, then expanded to many European countries, Russia, and North America. In Vietnam, this type of intersection is still a novelty and requires more scientific exploration. Based on research from developed countries and through the use of Vissim traffic simulation software, the paper presents an analysis and evaluation of the effectiveness of Turbo roundabouts compared to conventional roundabouts. The study also proposed and developed shifted exponential models, capable of well describing the nonlinear relationship between capacity of entry roadway with circular flow. Results show that the turbo roundabout is a potential solution for Vietnamese traffic. The study's evaluation using a basic layout of a two-lane turbo roundabout with only automobile traffic composition limits its applicability to mixed traffic environments. Initially, the study proposes the installation of turbo roundabouts on access roads of freeways, or motor highways with low-to-medium traffic volume