Weekend Alert: 520, Mercer, STP

A Closed SR520 – Photo by WSDOT

A quick reminder that numerous closures this weekend will snarl regional travel.  From Friday at 11pm to Monday at 5am, both SR 520 (Montlake to I-405) and the I-5/Mercer interchange will close completely.  SR520 buses will be rerouted to I-90, and expect backups in and around downtown Seattle all weekend.

Saturday is also the 32nd annual Seattle to Portland Bicycle Classic (STP).  10,000 cyclists (including yours truly) will make the 204-mile trek to Portland.  For our mutual sanity and safety, you would do well early Saturday morning to avoid Montlake, the University Bridge, Lake Washington from Madrona to Renton, West Valley Highway, Puyallup, Pacific Avenue/SR7, and SR 507.

In addition, I-5 northbound around Joint Base Lewis McChord will be restricted to a single lane (9pm Friday to 5am Monday), and WSDOT is predicting an 11-mile backup just as STPers drive and bus back from Portland.  If planning on traveling to Portland, Amtrak Cascades is your ticket out of congestion (ok, Horizon too).

Though these closures will frustrate motorists and transit riders alike, I would suggest making the best of a bad situation either by kayaking/canoeing in Union Bay or by visiting the Arboretum (walk, or take the #11 or #8).  The sunny and mild weather, combined with the tranquility afforded by a closed SR 520, should provide a lovely glimpse into the sights and sounds of pre-highway Union Bay.  (Each time I visit the Arboretum I’m grateful anew that the R.H. Thompson was never built.)   During the last viaduct closure I discovered that it’s really quite stunning to be near a major highway without the attendant white noise; one doesn’t internalize the scale of roadway noise until graced with its absence.  So take advantage of it!


  1. Anthony says

    Yes indeed, many thanks and good luck on your ride. I guess we’ll have to take either I-90 or the Bothell way to get to Stevens Pass, we’ll be hillclimbing on our off-road rides from Scenic all the way to the top via the old road. For anyone who isn’t aware of the old road, its a fantastic lil’ road ride combined with some gravel, and totally doable on a road bike if you have decent bike handling skills.

  2. Casey says

    Buses will also be effected in Ballard, for the Seafood Festival. Also, rerouted at Alaska Junction, for the West Seattle Summerfest. Not going to be a very good weekend for buses staying on schedule.

  3. says

    It will be very curious to once again look at how I-5 through Downtown operates without the “Mercer/520 Weave” or “left-hand exit” that many of us suggest contributes to congestion on I-5.

  4. says

    Great opportunity to see what the effects would be of simply removing the 520 for good (my suggestion).

    Brings up an idea I had…with Android GPS location services, wouldn’t it be cool to create an application for drivers that would feed their data back to WADOT and let them see first hand where people are driving to and from? It would be a voluntary thing…not big brother. Start off registering and offering some stats about the person (age, income) and then switch on the the tracker and have it upload driving data for summarization.

    Have we really ever looked at where people are driving? And why?

  5. Alex Francis Burchard says

    the not having a giant freeway running thing is cool, and you don’t notice how loud it is until it’s gone. The 15 minutes that the Lake Shore Drive Drawbridge goes up some days are pure heaven. Suburban Silence. Its amazing.

    • Jeremy says

      Yeah, or the snow disasters, those are a blessing. Noise from I-5 virtually eliminated for a day or two, and Eastlake no longer a grim miasma of car fug.


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