Alaskan Way Viaduct: Transit & Streets: Flip Side
From More Perfect
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Alternative Viewpoints on the Transit & Streets Proposal
There are many flaws in the current proposal, none of them necessarily fatal, but there is need for more work.
1. The report understates the impact on traffic of these changes. One suggestion is reconfiguring I-5 to handle more through traffic, at the expense of traffic going to Seattle. So what do you do to accommodate the traffic you displace from I-5? Send some to I-405, which is even more congested? Send it to the downtown grid, which you were counting on to take the extra viaduct traffic? Also, there is not as much extra capacity on the street grid as is implied. Basically a route only has as much capacity as its narrowest bottleneck, and there are only a few routes that provide continuous north/south capacity through downtown. They are:
Alaskan Way -- 2 lanes south, one north, plan calls for adding a second northbound lane
1st Ave -- narrows to one lane each way in Pioneer Square, heavily congested
2nd/4th Ave (3rd too?) Merge into 4th Ave at south end of town, 3 lanes each way between Jackson Street and Airport Way.
5th Ave -- southbound only through downtown, becomes two-lane two-way in International District, so it only provides for one lane worth of southbound through traffic. Making it a couplet with sixth would help, but this would require reconfiguring the James street exit from I-5. Come up with how to do that, and then I'll be convinced you're getting somewhere.
So the challenge is to come up with new routes that could serve take the extra traffic. Pick any point west of I-5 and north of Denny Way, and another point west of I-5 south of the stadiums... What continuous route from point A to point B has extra capacity to carry viaduct traffic?
2. How do you distribute Elliot/Western traffic? You've worked on the other routes, but this route supplies 40% of viaduct traffic, so it is important to have a plan for where this traffic goes. It brings 3 lanes of traffic into Seattle, at the viaduct this drops to one lane, and then the street ends in Pioneer square. We can't divert the traffic to Denny as this street is congested already and we need to slow it down to allow more traffic to cross Denny. Alaskan is the only other place to send the traffic, and this is a smaller road. Much of the strategy of this proposal is to remove capacity and count on a reduction in traffic to match, but what are the consequences of providing a large amount of capacity for traffic coming toward downtown and have that capacity disappear at downtown? Downtown is now a major bottleneck in our road system.
3. There isn't that much to gain from signal retiming. In general, if you can't fix where things are bottlenecked, there's little point in fixing elsewhere, and the main bottleneck will be downtown. Right now the lights downtown are very well optimized for north/south traffic. We could get a little more north/south capacity by reducing the signal time given to east/west routes, but how exactly do we redirect east/west routes?
4. The columns supporting I-5 through downtown are hollowing out. Some time after the current round of megaprojects are complete, we will need to look into how to go about replacing this. We will need some spare capacity to redirect its traffic.
