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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
Interchange Ideas forFreeways & Arterials

ODOT Roadway Conference

April 13, 2010

new interchange ideas
“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 $$$$$

caveat emptor
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!

highway interchanges
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
arterial interchange ideas
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”)
single point
Single Point

I-5 @ Market St. in Salem

sylvan interchange tight diamond configuration
Sylvan Interchange Tight Diamond Configuration

US 26 @

Scholls Ferry/Skyline

in Portland

3 level stacked diamond
3-Level “Stacked” Diamond

Lubbock, TX

US 82/US 289

single loop jug handles
Single Loop/Jug Handles

Greeley Ave @ Going St.

NE Portland

single loop jug handle examples
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)
grade separated roundabouts
Grade Separated Roundabouts

Uncommon in US – Ubiquitous in UK

echelon interchange
Echelon Interchange

Only known example –

US 1 @ Biscayne Blvd.

in Aventura, Florida – near Miami

frontage road systems
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
frontage examples
Frontage Examples

I-35 in San Marcos, TX

frontage examples1
Frontage Examples
  • Detroit, MI Freeways – Incl. a wide variety of U-turn provisions
  • Many Texas Rural Freeways
  • “Texas Turnarounds” another U-turn variation.
and now here s something we hope you ll really like the diverging diamond
And Now Here’s Something We Hope You’ll Really Like… The Diverging Diamond

Watch me pull a rabbit out of my hat.

fern valley interchange i 5 exit 24
Fern Valley Interchange – I-5 Exit 24

Image Stolen From Bob Branch’s Design – March 2010

i 44 @ sr 13 springfield mo
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

i 15 @ main american fork ut
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

diverging diamond the tradeoffs
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.


  • 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!



We’re ready for grilling.