The impact of road shoulders on urban freeways: a case study in durban, south africa

Abstract

The growing need to improve transport systems and maximise traffic-flow, efficiency and capacities, particularly those of mobility routes such as urban freeways, has seen some innovations and new trends in terms of urban freeway design in South Africa. They have all aimed at seeking more efficient means of moving passengers, reducing travel and delay time, and improve safety by introducing one or a combination of transport operating strategies such as Bus Rapid Transport (BRT’s), Integrated Rapid Transport (IRT’s), High Occupancy Vehicle lanes (HOV’s), among others. The majority of metropolitan cities have adopted these strategies through a combination of features such as physical transport infrastructure restructuring, together with technologies such as Intelligent Transport Systems (ITS), Variable Message Signs (VMS) and Closed-Circuit Television (CCTV), among others. The study aims to evaluate the impact of this growing trend of restructuring urban freeways, thereby reducing or totally removing road shoulders for the purpose of introducing public transport lanes. Through the static experiment, “before-and-after” analysis, “with-and-without” analysis and other analytical studies and observational methods, a number of interesting findings were concluded. Study results have shown a 4% decline in crash rates after the restructuring of urban freeways. However, in terms of efficiency and traffic flow, major delays are evident when there are minor incidents or crashes on the freeway. It was concluded that while non-shoulder urban freeways do not have the worst crash rates, they also vulnerable to challenges in terms of efficiency, travelling costs, time lost and vehicle operating costs.