Junction performance : a study of the main junctions on the local road network with proposals for improvements from a road engineering perspective

Abstract

The main purpose of road junctions is to transfer road users from one section of the network to another in a safe and efficient manner. However, an overview of the local arterial and distributor road network indicates that junctions are the most critical areas both from a capacity and a safety aspect: they are the major cause of delay and the locations with the highest number of traffic accidents, thus hindering the overall efficiency of the local road network. The main causes of this situation are: - junctions having wrong geometric designs/alignments (sight distances, waiting areas, turning radii, intersecting angles and so on); large vehicles making use of junctions that were not designed to cater for them; - control systems that are inappropriate for the volume of traffic or the type of vehicular movement that exist at that particular location; - controls that do not take into consideration the variations in the traffic flow between different times of the day; - inadequate signage and road markings; - inadequate lighting levels; and - lack of adequate facilities for pedestrians and cyclists. The aim of this study is to analyse the existing junctions from a road engineering perspective, commenting on the existing deficiencies and proposing possible solutions. The road engineer's objective in the design of junctions is to reduce the possibility and the severity of potential conflicts between the different users while providing maximum convenience and ease of movement for all. This dissertation is divided into five chapters. The first chapter gives a general overview of the principal junction types, the local traffic situation and the main junctions on the arterial and distributor road network. The next two chapters analyse the local situation with respect to the capacity and safety design criteria of junctions. Chapter four deals with pedestrian and cyclist facilities at junctions while the final chapter includes a number of case studies.