Interchange ideas for freeways arterials
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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

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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


Spi intersection

SPI Intersection


Tight diamond

Tight Diamond


Sylvan interchange tight diamond configuration

Sylvan Interchange Tight Diamond Configuration

US 26 @

Scholls Ferry/Skyline

in Portland


Diverging diamond

Diverging Diamond


Contraflow left

Contraflow Left


Roundabout ramp intersections

Roundabout Ramp Intersections

I-70 in

Avon, CO


3 level stacked diamond

3-Level “Stacked” Diamond

Lubbock, TX

US 82/US 289


Split interchanges

Split Interchanges


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


Intersection grade separation

Intersection Grade Separation


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.

    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!


Interchange ideas for freeways arterials

Q&a

We’re ready for grilling.


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