Florida uses restrictive medians and directional median openings to manage left turns and crossing movements on multilane highways. Left turn egress movements from driveways or side streets are replaced by turning right onto the major road and then making U-turns at downstream median openings or signalised intersections. One of the public concerns regarding this treatment is that drivers making a right-turn followed by a U-turn (RTUT) could experience much longer delay and travel time than those who would otherwise make a direct left turn (DLT). This study analysed the operational effects of this widely used access management treatment. Data were collected on eight selected street segments in the Tampa Bay area in Florida. A total of more than 300 hours of traffic data were collected using video cameras. Empirical models were developed based on the collected field data to quantitatively evaluate the operational impacts. Delay and travel time models provided a tool to help address public concerns related to the operational impacts of U-turns and were particularly helpful in identifying the circumstances in which the RTUT takes less time than the DLT. Additionally, a ratio model was developed to estimate how many drivers would like to make a RTUT instead of a DLT under specific traffic volume and roadway geometric conditions. The findings of this study are helpful in providing local and state transportation agencies with recommendations for the design and selection of median treatments in six- to eight-lane urban or suburban arterial roads.
Abstract