Traffic calming on higher order roads: a case study

Abstract

Paper presented at the 22nd Annual Southern African Transport Conference 14 - 16 July 2003 "National issues affecting the movement of people and goods - strategic approaches", CSIR International Convention Centre, Pretoria, South Africa. ABSTRACT:The use of the more commonly used traffic calming measures, such as speed humps and mini-circles, has mostly been restricted to Class 4 and 5 streets. Inappropriate high speeds and driver behaviour, which cannot fully be addressed by law enforcement, do however also often occur on higher order roads. Application of traffic calming measures suitable to higher order urban roads or even rural roads is not addressed in existing guideline documents, and research and investigation into this issue is required. The case of Tafelberg Road in Middelburg, Mpumalanga has offered the opportunity to investigate and implement traffic calming on a higher order road. The two-lane road is constructed to very high standards, almost completely straight over more than 2 kilometres, with pavement width in excess of 11 metres and wide verges. Tafelberg Road has multiple functions in the road network - it has a through traffic function, connecting regional roads, while also serving as an access road for an adjacent residential area. The road also carries relative high volumes of heavy vehicle traffic. High speeds and perceived high noise levels lead to numerous complaints from the public. This paper describes the traffic study that was done to quantify problem areas, including speed, volumes and noise measurements and the methodology used to identify and refine measures to address the problem and an after study that was done, and its results. The implemented solutions consisted of introducing median islands, road signs and a series of chicanes. A design speed of 80km/h was applied to all elements. The measures were aimed at reducing the sense of openness created by the road environment, which encouraged high speeds. The principal objective was to reduce speed and effect constant speeds, i.e. not to encourage speed change cycles, which are often associated with conventional traffic calming measures, and which could be a source of increased noise levels. Preliminary results indicate that the project was highly successful in reducing speed, speed differential and noise levels, without noticeably inhibiting mobility.