THE ROUNDABOUT: A DIFFERENT MODE OF MANAGEMENT

The Québec road system was primarily developed in the 60s and 70s. This system has now reached maturity. The constant increase in trips and the number of vehicles on Québec roads and highways has led to saturation of part of the road system, reducing traffic flow and increasing delays at certain intersections and interchanges. In the road traffic management field, the roundabout concept has resurfaced as a solution to this type of problem, in a more modern version that can be adapted to the setting. Based on the experience of several road administrations and numerous exhaustive studies, a guide entitled Le carrefour giratoire: un mode de gestion différent, was published in 2002 by the Ministère des Transports du Québec. This guide brings together all the necessary information for designing a roundabout. Based on the elements of this guide, a ten-stage design method has been produced to standardize the study of projects and the preparation and development of roundabouts in Québec. These stages successively cover the selection of the main design criteria, the determination of the physical features, the location and dimensions of the roundabout, the design of the splitter islands, the estimation of vehicle transit and speed, sight distances, the capacity and saturation study, road markings, traffic control devices, and lighting as needed. Obviously, the case studies and experience in the field should help improve the guide and eventually lead to its standardization.