Capacity of U-Turn Movement at Median Openings on Multilane Highways

Abstract

The goal of this study is to develop a procedure for estimating the capacity of U-turn movement at median openings on multilane highways. Data were collected at six selected median openings in the Tampa Bay area of Florida. The critical gap for U turns was estimated by using the maximum likelihood method. The follow-up time for U turns was determined by using a linear regression model developed in this study. With the estimated critical gaps and follow-up times, Harders model was used to estimate the capacity of U-turn movement. It was found that the median width at median openings greatly impacts the capacity of U-turn movement. Vehicles making U turns at median openings with wide medians (median nose width >=6.4 m) have larger potential capacity than those making U turns at median openings with narrow medians (median nose width <6.4 m). The results of Harders model were tested against the capacity data measured in the field using Kyte's method. It was found that Harders model provided reasonable capacity estimate for U-turn movement at median openings.