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Interchange Ideas for Freeways & Arterials

Interchange Ideas for Freeways & Arterials. ODOT Roadway Conference April 13, 2010. “New” Interchange Ideas. Many aren’t actually new – ODOT just hasn’t used them up until now. Nor have many others. Sometimes for good reasons.

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Interchange Ideas for Freeways & Arterials

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  1. Interchange Ideas forFreeways & Arterials ODOT Roadway Conference April 13, 2010

  2. “New” Interchange Ideas • Many aren’t actually new – ODOT just hasn’t used them up until now. Nor have many others. Sometimes for good reasons. • Some ideas are appropriate for freeways only, some for arterial roadways only, and some might work in either context. If the stars are properly aligned. • It’s always necessary to look at the specifics of your situation… a “reasonable” idea plopped down in an inappropriate spot will likely not work well. • Many of these ideas are basically an attempt to squeeze more out of the ramp intersections. And stretch $$$$$

  3. Caveat Emptor Not every innovation works out. Sometimes we learn from our mistakes. It’s wiser to learn from the ones already made than to create a bunch of new ones trying to be “clever”. Never stop thinking!

  4. Highway Interchanges • Single Point (SPI or SPUI) • Tight Diamond (TDI) • Diverging Diamond – DDI (aka “Crossing” or “Double Crossover”) • Contraflow Left • Roundabout Ramp Intersections • 3-Level “Stacked” Diamond – Freeway Only • Split Interchanges

  5. Arterial “Interchange” Ideas • Single Loops & Jug Handles • Grade Separated Roundabouts • Partially Grade Separated Intersections • Echelon Interchange • Frontage Systems – Usually include U-Turn Provisions (Such as “Texas Turnarounds”)

  6. Single Point I-5 @ Market St. in Salem

  7. SPI Intersection

  8. Tight Diamond

  9. Sylvan Interchange Tight Diamond Configuration US 26 @ Scholls Ferry/Skyline in Portland

  10. Diverging Diamond

  11. Contraflow Left

  12. Roundabout Ramp Intersections I-70 in Avon, CO

  13. 3-Level “Stacked” Diamond Lubbock, TX US 82/US 289

  14. Split Interchanges

  15. Single Loop/Jug Handles Greeley Ave @ Going St. NE Portland

  16. Single Loop/Jug Handle Examples • Greeley Ave @ Going St. (Portland)-☺ • East End of Ross Isl. Br. (Portland)- <☺ • OR 11 @ OR 204 (near Weston) • US 97 @ Colorado Ave. (Bend) • OR 62 @ Biddle Rd. (Medford) • OR 214 @ N. Front St. (Woodburn)

  17. Grade Separated Roundabouts Uncommon in US – Ubiquitous in UK

  18. Intersection Grade Separation

  19. Echelon Interchange Only known example – US 1 @ Biscayne Blvd. in Aventura, Florida – near Miami

  20. Frontage Road Systems • Fairly common in Texas & some major Midwest cities – mostly on freeways – both rural and urban • ODOT stuff tends to be connections or extensions of cut-off roadways, not directly integrated to the mainline, except for a few spots in Portland • AASHTO Chapters 7 & 8 (Arterials & Freeways) have some discussions on frontage systems

  21. Frontage Examples I-35 in San Marcos, TX

  22. Frontage Examples • Detroit, MI Freeways – Incl. a wide variety of U-turn provisions • Many Texas Rural Freeways • “Texas Turnarounds” another U-turn variation.

  23. And Now Here’s Something We Hope You’ll Really Like… The Diverging Diamond Watch me pull a rabbit out of my hat.

  24. Fern Valley Interchange – I-5 Exit 24 Image Stolen From Bob Branch’s Design – March 2010

  25. I-44 @ SR 13 – Springfield, MO First Completed DDI in the US – Opened to Traffic in Late June 2009 (Before Construction was completed in July) Photos Courtesy of Don Saiko, MoDOT

  26. I-15 @ Main – American Fork, UT Currently Under Construction – North of Ogden Rendering of Final Product February 2010 Const. Photo Photos from UDOT Project Website

  27. Diverging Diamond – The Tradeoffs Advantages include: • Very effective in moving heavy LT demands - esp. compared to other diamond types – Two phase signals at intersections – Less vehicle queuing. • Usually has a narrower X-Section on X-Road – extra LT lanes, etc. not needed – but the median area may be fairly wide anyway (for other reasons). • Probably will work for either Freeways or Arterials – assuming that downstream intersections don’t back up to the ramps. Disadvantages • No “up and over” movement is possible at the ramp intersections – U-turns necessary on X-Road. • When LT and Opposing thru movements are both very heavy, TPAU analysis has shown some operational issues that crop up. • Extensive channelization, signing, markings are required for the ramp intersections – the intersection geometry can be tricky, esp. when the underlying roadway is in a horizontal curve. • Access Management is just as necessary as with any other idea - Don’t overlook it!

  28. Q&a We’re ready for grilling.

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