Sunday Video: Diverging Diamond Interchange Comes To Washington


The Washington State Department of Transportation has announced that they are planning on introducing the first Diverging Diamond Intersection (DDI) on I-5 at Marvin Road in Lacey. The DDI was first introduced in 2009 in Springfield, MO and helps improve traffic flow through complex interchanges by minimizing traffic signal phases, shortening wait times, and improving traffic throughput. In addition, this intersection design cuts in half the number of potential conflict points while purportedly improving safety for pedestrians, cyclists, and other road users.

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Gordon is a native New Yorker who wisely chose to leave the Northeast in the early 1990s. A past resident of Belltown, and Queen Anne, he currently calls First Hill home. He is a board member of the First Hill Improvement Association (FHIA) as well as the FHIA Transportation Committee Chair and is constantly looking for ways to improve transportation up the hill.

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Jared Reabow

Could you just use a roundabout.
they have been proven to work in the whole of europe, asia and australia.


I encountered one of these while on vacation in Utah recently. A little disconcerting to be on the “wrong” side of traffic on the overpass. Am glad I didn’t subconsciously revert to my British driving experience.

Erik Nordheim

Why this over a roundabout at each end of the overpass?

Al Dimond

It’s an interchange, it’s gotta move traffic, seems to be pretty efficient at that. The problem is building your town around it! The most walkable places aren’t defined by the most-walkable interchanges and the most-walkable stroads…

Walter Crunch

We have them here.They are a little weird….but folks will get used to them.


This should be on your other blog – ” The Suburbanist” where auto oriented sprawl continues to destroy the planet and make it impossible for pedestrians and bike riders to exist.