With SDOT kicking off its public outreach effort on the First Hill streetcar line next week, I wanted to outline why we believe that the 12th Ave couplet is a bad idea. The 12th Ave alignment has four major flaws, all of which indicate that the Broadway or Boren alignments (or some variation of these two) is the best option. I have heard many impassioned arguments for the 12th Ave alignment from people that have the same core beliefs as myself but the facts simply make too strong of a case.
Reduced Area with Quality Service
The first and most fundamental problem with the 12th Ave alignment is the couplet. While the couplet increases total coverage of the streetcar, it dramatically reduces the quality of that coverage. By separating the northbound and southbound travel by 3 blocks, the area that is close to both a northbound and southbound station is reduced significantly. To prove my point I spent the day working on ArcGIS to give you the graphics above. Rather than using a 5 minute euclidean circular walking buffer, I used a technique that shows the actual “walk shed” experienced in real life (i.e you can’t walk straight through a building, you have to walk around both sides). This creates a walking shed based on Manhattan distance (this could be a whole other post).
As you can see, I mapped the walking shed of each alternative for 3, 5 and 7 minutes. These are the areas where users have access to both directions. Looking closely at the 12th Ave couplet, you can see how the coverage of the three middle stations is much smaller and of lower quality compared to both of the other alternatives. As I said before, this is an fundamental and intractable flaw of the idea that can’t be overcome.
More after the jump
One of the most commonly cited reasons for the 12th Ave couplet is that it will support new TOD. I agree it would, but this argument is actually much more valid for the Boren alignment. 12th Ave has relatively modest height limits of 40′-60′ feet or less compared to First Hill’s 160′-240′ feet height limit, as well as the major institution overlays for the hospitals. Not to be outdone, the Yesler Terrace redevelopment plans by Seattle Housing Authority could adding up to 5,000 housing units and 1.2 million sq feet of offices space on the existing site. Simply put, the development potential along a Broadway or Boren alignment is an order of magnitude higher than along 12th Ave.
Hospitals, universities, senior housing and low income housing are just about the most transit friend land uses possible. The 12th Ave alignment provides worse service for almost all of these except for Seattle University, which under both the 12th Ave alignment and the Broadway alignment would have similar service quality.
Loss of First Hill Station
Finally, lets not also forget the reason, the only reason, there is money to build this streetcar. Due to the complexity, risk, and cost of building a First Hill station, Sound Transit dropped that station but promised the community to link it better to the Capitol Hill and ID stations. This is how the First Hill streetcar was born. If the streetcar was built only along 12th Ave as proposed in the middle graphic here few could claim that this streetcar in any way serves First Hill. Also as someone who deeply values planning, violating the agreement that Sound Transit made with the First Hill community is foolhardy.
Trips to First Hill from Sounder and Link would be overwhelmingly from International District, in the northbound direction – far from the hospitals. Not only does the 12th Ave couplet completely miss these transit users that demanded its funding in the first place, it provides poor quality of service to all the users in the corridor.