Operational Evaluation of Right Turns Followed by U-Turns (4-Lane Arterials) as an Alternative to Direct Left Turns

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 would be replaced by turning right onto the major road and then making U-turns at downstream median openings or signalized 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 analyzed the operational effects of a widely used access management treatment: Right turns followed by U-turns as an alternative to direct left turns. The focus of this research was on the operational effects of U-turns on 4-lane arterials. Data were collected on sixteen selected street segments in the Tampa Bay area in Florida. A total of more than 600 hours of traffic data were collected. 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 would be particularly helpful in identifying the circumstances in which the RTUT takes less time than the DLT. Additionally, in order to determine the minimum turning radius required by U-turning vehicles, from the operations point of view, an empirical model was developed to estimate the relationship between the turning radius and the average turning time required by each U-turning vehicle. This model can be directly used in estimating the average turning time required by U-turning vehicles under restricted 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 on four-lane urban or suburban arterial roads.


  • English

Media Info

  • Media Type: Web
  • Edition: Final Technical Report
  • Features: Figures; Photos; References; Tables;
  • Pagination: 121p

Subject/Index Terms

Filing Info

  • Accession Number: 01002809
  • Record Type: Publication
  • Contract Numbers: BC 353-39
  • Created Date: Aug 3 2005 9:13AM