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Multi-Lane Divided Intersection Design Alternatives

Multi-Lane Divided Intersection Design Alternatives. Introduction to J-Turn and Superstreet Intersections Corey Bogenreif CE 550: Advanced Highway Design October 22, 2010. J-Turn Basics Benefits Design Considerations and Issues Case Study Superstreet 101 Benefits

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Multi-Lane Divided Intersection Design Alternatives

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  1. Multi-Lane Divided Intersection Design Alternatives Introduction to J-Turn and Superstreet Intersections Corey Bogenreif CE 550: Advanced Highway Design October 22, 2010

  2. J-Turn • Basics • Benefits • Design Considerations and Issues • Case Study • Superstreet • 101 • Benefits • Design Issues and Considerations • Signal Phasing • Case Study

  3. J-Turn Basics • Directional median with downstream U-turns • Allows through and left turn movements on expressway • Prohibits left and through movements of side street • Applicable at at-grade expressway intersections Source: NCHRP 650

  4. The most “at-risk” movement (minor road left-turns/through) are eliminated • Replaces right angle conflicts with less severe conflicts • Overall: conflicts from 42 to 24 Safety Benefits Source: NCHRP 650 Source: NCHRP 650

  5. U-Turns • Large vehicles may have difficulty negotiating U-turn • Right-of-Way • Needed for a wider median, loons or jughandles Design Issues and Considerations Source: Green Book Source: NCHRP 650 Source: NCHRP 650

  6. Spacing of U-turns and median • NCDOT: 800-1,000 ft • MODOT: 600-1,000 ft • MSHA: successful at up to 2,500 ft • Sight distance • Breakdown Volume = 44,000 vpd • Driver confusion? Design Issues and Considerations Source: MODOT

  7. Maryland Case Study Source: NCHRP 650

  8. Maryland Case Study Source: NCHRP 650

  9. Superstreets 101 • Urban equivalent of J-Turn • Allows through and left turn movements on expressway • Prohibits left and through movements of side street Source: FHWA

  10. Safety Benefits • Crossing conflicts reduced from 16 to 2 • Replaces right angle conflicts with less severe conflicts Source: FHWA Source: FHWA

  11. Additional Benefits • Cost effective • Simplified signal phasing • Reduces travel time and delay • Increased capacity and flow

  12. Design Issues and Considerations • Median width • Major movements at intersection • Access to adjacent businesses • Additional operating costs Source: FHWA

  13. Signal Phasing Superstreet Simulation Source: http://pinoncreek.com/9.html

  14. Green Time Per Hour San Antonio Case Study Source: Pape-Dawson Engineers US 281 Presentation

  15. Source: Pape-Dawson Engineers US 281 Presentation • http://www.kcrg.com/news/local/84534042.html

  16. References AASHTO Green Book Maze, Thomas H., Joshua L. Hochstein, and Reginal R. Souleyrette. Median Intersection Design for Rural High-Speed Divided Highways. NCHRP 650. Washington, D.C.: Transportation Research Board, 2010. Rodegerdts, Lee A., et al. Signalized Intersections: Information Guide. FHWA-HRT-004-091. Washington, D.C.: Federal Highway Administration, August 2004. http://www.greatercroftoncouncil.org/Superstreet_Presentation.pdf http:// www.modot.mo.gov http://www.pinoncreek.com/9.html

  17. Questions?

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