Extent of roadway capacity shif resulting from midblock U-turn facilities

Abstract

Midblock U-turn facilities are a one of the highway facilities that constructed to provide the U-turn movement for the driver to change the direction. In Malaysia, it is generally constructed at federal multilane highway. Introducing of roadway facilities such as midblock U-turn along the highway segment will give the benefits and at the same time give the risk to the road user. U-turning movements at the midblock U-turn facilities can cause the road safety problem due to the vehicle movement in order to make a U-turn. The aim of study is to determine the extent of road capacity shift resulting from midblock U-turn facilities. In order to know the condition and operational performance of the roadway, the traffic flow need to analysed for the road segment consist of midblock U-turn Facilities at Skudai – pontian Highway. Based on the hypothesis that capacity loss would result from U– turning at midblock U-turn facilities; 24 hours data were collected as volume and speed at two sites in Skudai Town, Malaysia. Automatic traffic counter was used to collect the traffic data such as volume and speed of the road section with and without influence by midblock U-turn facilities. The analyses of traffic data are continued by using fundamental relationship of speed and density to estimate the roadway capacity value. Results show that there is a difference in capacity between carriageway lane affected by midblock U-turn facilities and carriageway lane no affected by midblock U-turn facilities. The study concluded that capacity loss is about 28.3% for Site A and 8.1 % for Site B would occur. It is correct to conclude that the hypothesis that the capacity loss would result from U turning at midblock U-turn facilities is valid.