Study of Sight Distance at Median Opening for U-turn

Abstract

Accident statistics show that the median opening for U-turn is one of the locations with high risk of accidents on the highway. Since there are cross conflicts in this area, an accident would be serious. Allowing U-turn on both directions at this opening, there is a high probability that waiting U-turn vehicles on the other side will obstruct visibility or reduce sight distances at this location. The purpose of this study is to inspect the sight distance at these median openings, and whether it is a sufficient distance compared to the stopping sight distance (SSD). Four types of median opening for U-turns were studied: raised/depressed medians and with/without loons, additional areas for heavy vehicles that require a larger radius for turning. The study found that the sight distance at the median opening is insufficient for a through vehicle to stop, especially when a heavy vehicle is turning or waiting. If there is a high demand for making s, it is recommended that only one side U-turn would be appropriated.