Framework for selecting centre median opening locations

Abstract

Currently, many urban roadways in Sri Lanka are being rehabilitated and improved to multi-lane facilities with introducing raised road centre medians. Therefore, the provision of centre median openings for right turns, cross traffic movement & “U” turns is essential. The study attempts to give a broad framework to adopt in making decisions with regarding to provision of centre median openings by identifying the relevant parameters that should be incorporated and evaluating the impact on traffic operations due to various configurations of centre median openings. Road network connectivity, road safety, right turning traffic volume density, positioning of road side developments are some of the factors which influence the decision for selecting a proper location for median opening. A microscopic traffic simulation model developed with PTV VISSIM was used to optimize the selected median opening locations with respect to travel time and total delay of the road network. A major urban road corridor was modelled in VISSIM as a case study. The study found that the median opening spacings are site specific and recommending a general spacing value may not be practical with regard to Sri Lankan Road network. Median opening closure will result to increase the delay to local traffic largely and cannot expect a significant travel time reduction in the main road corridor in the absence of turning/storage areas. It is envisaged that this study would provide a more logical framework for practitioners to adopt in making decisions with regard to centre median opening in urban highway planning