By guest blogger Bart Treece

A sky of blue, a sea of green and a river of red brake lights….OK… that’s not how it goes, but that’s what folks could be seeing this weekend, unless they plan ahead  for congestion.

Let me explain. There are so many things to do this weekend in Seattle, and sitting in traffic shouldn’t be one of them when you’d rather be cheering the Sounders on against Sporting KC, enjoying the Seattle Dog Show or watching the women of the Pac-12 battle it out on the hardwood. With so much happening it might be kind of tough to get to where you want to be on time without some preplanning.

What’s going on?

Our contractor crews will be closing all but one lane on the northbound I-5 collector-distributor, which runs parallel to the wider section of I-5 between I-90 and Madison Street. The collector-distributor or “C-D” as it’s known in traffic-talk, helps merge cars from I-90 to I-5 and downtown off- and on-ramps. Here’s some nifty animation that shows how vehicles will navigate through the work zone.

The closure is the fifth of nine in this part of I-5 to replace 26 worn and aging bridge expansion joints before they go bust, which would lead to flat tires, emergency closures and major headaches. It’s happened before, and it ain’t pretty.

Emergency repairs to a damaged expansion joint in Dec. 2013

Traffic tips

Plan your trips ahead of time and know before you go. Carpooling, taking transit, delaying or combining trips will help reduce congestion in the area for everyone. Use alternate routes. If you can, take the backdoor into downtown Seattle on SR 599 to SR 99. We often see free-flowing traffic on this under-utilized route during weekend closures ...just sayin’.

With heavy traffic expected on westbound I-90 into downtown, SR 520 might be a better cross-lake route. The I-90 express lanes will look good westbound, and will be open to all (both carpoolers and solo drivers) during times of high congestion (keep an eye on the highway signs). Sounders fans should expect some delays heading eastbound after the match, so hanging in Pioneer Square for an hour to let traffic settle down would be a good idea. To head north from SoDo, take SR 99 or use surface streets to access the Cherry Street on-ramp to I-5 or the 5th Avenue & Cherry ramp to I-5 express.

You can always see how traffic is or isn’t moving through the area on the Seattle Traffic page or with the WSDOT mobile app for iPhone and Android devices.

There’s really never a “good” time to tighten traffic, but we really appreciate your patience and understanding when we do have closures for construction. Knowing ahead of time and planning for congestion really helps keep people moving, and we appreciate everyone for chipping in.

By Bart Treece

So this weekend, we’re closing lanes on a section of southbound I-5 that’s not quite part of the highway, and not quite a ramp.

The formal name of this thing is the southbound Interstate 5 collector-distributor, and it’s tough to come up with a name that resonates well with folks who aren’t traffic geeks. So what is a collector distributor and how will this affect you this weekend? Good question.  Let’s define collector distributor first. It’s kind of a traffic tweener, meaning it serves many purposes.  This stretch of roadway runs parallel to I-5, and most drivers will recognize it as the southbound I-5 exit to I-90 and the International District. It also connects Spring and James Street on-ramps to southbound I-5, and gives drivers an option to head east to I-90.

Here’s how it works. This animation shows three cars heading south, with the green car peeling off to Airport Way the red car to I-90. The blue car continues south and winds up back on I-5.



Our resident traffic geeks love the collector-distributor as a way to bypass mainline congestion and maximize available roadway. Some folks might be timid to try this (and due to construction this weekend it wouldn’t be a good idea to try it until Monday), because they see the sign and think they’ll end up on Mercer Island instead of points south of downtown. Taking the collector-distributor is totally legal, except for places where it isn’t, like I-405 at NE 85th Street in Kirkland, or anywhere else that is signed exit only. Even the sign on I-405 says it’s verboten, and you could get a ticket.


Back to this weekend, here’s how traffic will move through the construction zone. If this red car is you, don’t let the orange construction stuff scare you, you will still be able to get to I-90 from I-5.


Here’s the details

All but a single lane on the southbound I-5 collector-distributor will close at 10 p.m. Friday, Feb. 21 until 5 a.m. Monday, Feb. 24. At the same time, the on-ramps from Spring and James streets to southbound I-5 will also close. Need to take a downtown ramp to I-90? Try 4th Avenue South and hop on near the Stadiums. There will be marked detours on surface streets in Seattle.

More weekend closure information can be found on our What’s Happening Now page.