System-wide Safety Treatments and Design Guidance for J-Turns

In an effort Toward Zero Deaths (TZD) the Missouri Department of Transportation (MoDOT) initiated this research project to develop guidance on treatments that can reduce crashes and fatalities. The project first synthesized the literature and state of practice on system-wide safety treatments and documented their effectiveness. In particular, the objective was to examine those treatments that have not been already implemented in Missouri. The safety effectiveness, implementation guidelines, limitations, costs, and concerns of the treatments were documented. The identified safety treatments work in conjunction with the ‘Necessary Nine’ strategies identified in Missouri’s Blueprint. Accordingly, the synthesis covered three areas: 1) Horizontal curves, 2) Intersections, and 3) Wrong way crashes. The reviewed treatments included signing, geometric and access management, Intelligent Transportation Systems (ITS), pavement markings, and signal control enhancements to improve safety. In the last few years, MoDOT has replaced several high crash intersections on rural highways in the state with J-turns. Given their safety effectiveness and low cost the J-turn has become a preferred alternative to replace high crash two-way stop-controlled intersections on high speed highways. Unfortunately, national guidance on the design of J-turns is very limited. This project addresses this gap in practice by developing guidance on spacing and acceleration lanes. A thorough examination of crashes that occurred at twelve existing J-turn sites in Missouri was conducted. The crash review revealed the proportions of five crash types occurring at J-turn sites: 1) major road sideswipe (31.6%), 2) major road rear-end (28.1%), 3) minor road rear-end (15.8%), 4) loss of control (14%), and 5) merging from U-turn (10.5%). The crash rates decreased with the increase in the spacing to the U-turn, for both sideswipe and rear-end crashes; J-turns with a spacing of 1500 feet or greater experienced the lowest crash rates. A calibrated simulation model was used to study various volume scenarios and design variables. For all scenarios, the presence of acceleration lane resulted in significantly fewer conflicts. Thus, acceleration lanes were recommended for all J-turn designs, including lower volume sites. Second, while spacing between 1000 feet and 2000 feet was found to be sufficient for low volume combinations, spacing of 2000 feet was recommended for medium to high volume conditions.

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  • Supplemental Notes:
    • This document was sponsored by the U.S. Department of Transportation, University Transportation Centers Program. Report Date: May 2016; Published: June 2016. This report is also available at:, with a Report Date of January 2017.
  • Corporate Authors:

    University of Missouri, Columbia

    Department of Civil and Environmental Engineering
    Columbia, MO  United States  65211-2200

    Missouri Department of Transportation

    Construction and Materials Division
    P.O. Box 270
    Jefferson City, MO  United States  65102

    Midwest Transportation Center

    2711 South Loop Drive, Suite 4700
    Ames, IA  United States  50010-8664

    Department of Transportation

    Office of the Assistant Secretary for Research and Technology
    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    Research and Innovative Technology Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
  • Publication Date: 2016-5


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 76p

Subject/Index Terms

Filing Info

  • Accession Number: 01603604
  • Record Type: Publication
  • Report/Paper Numbers: cmr 16-013, MoDOT cmr 16-013
  • Contract Numbers: MoDOT project # TR201510
  • Created Date: Jun 2 2016 1:33PM