Extent of traffic shockwave propagation induced by midblock U-turn facilities

Abstract

The aim of study is to determine the extent of traffic shockwave propagations induced by midblock U-turn facilities. Based on the hypothesis that shockwave would result from U-turning at midblock facility, 24 hour data were collected which is volume and speed at two sites in FT005 Skudai – Pontian highway, Malaysia. The two sites are denoted as site A and site B. The study of highway capacity is the most important part in the identification of road performance. Any change made at the roadway for example installing a midblock U-turn facilities would result in highway capacity loss.There are mainly three causes of capacity loss which are due to the road condition itself, due to ambient and due to the traffic operation. When capacity loss happen, it would lead to traffic shockwaves. Traffic shockwave is a motion of propagation of a change in density and flow.When shockwaves happen, it would lead to reduction of roadway level of service. Speed, fow and density for with and without midblock U-turn facility are estimated using Greenshields Model. All data was collected using Automatic Traffic Counters (ATC). Shockwave velocity propagation with and without midblock U-turn facility were estimated by determining and comparing the capacity and density of roadway. Direct empirical capacity estimation methods are use to estimate capacity of roadway. Results shows that there is significant shockwave velocity propagation happen on the exit of the U-turn midblock facility which is about -35.1 km/hr. While a minor shockwave happens at the approaching of the U-turn. This study concluded that midblock U-turn facilities will induce traffic shockwave that may lead to road accidents.