Operational Effects of U-Turns as Alternatives to Direct Left-Turns

This study analyzed the operational effects of a widely used access management treatment: using U-turns as alternatives to direct left-turns from driveways. Data were collected at 34 selected roadway segments in central Florida. Delay and travel time were compared for various driveway left-turn alternatives under different levels of driveway volume and major road through traffic volume. The left-turn alternatives considered include direct left-turns (DLT), right-turns followed by U-turns (RTUT) at median openings, and right-turns followed by U-turns at signalized intersections. A binary logit model was developed to estimate how many drivers would like to make a RTUT instead of a DLT under different traffic and roadway geometric conditions. It was found that vehicles making RTUT at a downstream median opening before a signalized intersection have comparable total travel time as compared with those making DLT at a driveway; and the percentage of drivers selecting RTUT increases with the upstream through traffic volume, left-turn volume from major road into the driveway, and the total left-turn traffic demand at a driveway.