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March 05, 2007

Vancouver, Land of the SPUI

We went down to Portland last weekend. Actually we stayed in Vancouver, Washington, which is just across the (Columbia) river from Portland.

In Vancouver we had the pleasure (or annoyance, if it's nighttime and the lane markings are unclear) of driving through several SPUIs. What is a SPUI, you ask? Ahhh, it's a Single Point Urban Interchange. In short, it's a highway exit where instead of two sets of traffic lights, one on either side of the highway, you have a single traffic light in the middle. The diagram on the Wikipedia page hopefully makes this clear.

Vancouver has several SPUIs. The ones we visited were on S.R. 500 at the Thurston and Andresen exits (the first two exits west of Interstate 205) and on Interstate 5 at the NE 99th Ave exit.

The Kurumi page on SPUIs promises a link to a complete list of known ones, but the link is dead, so I can't check if the Vancouver ones are listed. I also saw a SPUI in Fairbanks, Alaska about 10 years ago--presumably holding the title of "world's northernmost SPUI".

Posted by AdamBa at March 5, 2007 09:56 PM

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Did they suck? Because I think that's what they are making under 405 at 116th St in Kirkland.

Posted by: Laurie at March 6, 2007 05:38 PM

I actually drove by there today to check it out. I think they are just widening the highway (that intersection actually doesn't even have a light on the side where traffic enters the freeway). If they DID make a SPUI it wouldn't be as bad since it is only a T intersection, so there wouldn't be the same effect of uncontrolled traffic crossing such a wide area. But, at the same time, with a T intersection the benefit of a SPUI (the two traffic flows exiting the freeway can proceed at the same time, as can the two flows entering the freeway) would be less pronounced.

- adam

Posted by: Adam Barr at March 7, 2007 11:29 AM