It is becoming clearer that Sound Transit 3 (ST3) will not provide Seattle (‘North King’) with the approximately $7B needed to fund a true subway from Ballard to West Seattle. At currently proposed ST3 funding levels – $11B in the Senate and $15B in the House for all regional projects– Seattle’s shortfall could be roughly $2-4B. This presents a dilemma: should we build the high quality segments we can afford (and risk alienating the neighborhoods we pass over), or give in to the political temptation to dilute the quality of the lines (surface running, stub lines, etc) to serve more neighborhoods at once? At Seattle Subway we believe we cannot let today’s funding constraints forever dampen the quality of our transit service. So what investments could we make with an ST3-sized budget that would provide high quality (and highly upgradeable) transit?

There is a single project that rises above all the others: The Westside Transit Tunnel (WSTT). For general readers who have heard of Ballard to West Seattle rail for years, proposing a new bus tunnel may seem to come out of nowhere. But let us show you why this is so important for ST3.

What is it?

The WSTT is a new rail convertible bus tunnel through downtown designed to serve Ballard, West Seattle, the Aurora corridor, and South and East King County. The route and features you see in our diagram did not come out of thin air, but are a combination of routing seen in Sound Transit’s Ballard to Downtown Corridor Study and the Downtown portion of the West Seattle & Burien (“South King County”) Corridor Study. We took these studies and enhanced them with a couple of our own ideas: the addition of a Battery Street fork to serve Aurora and bus improvements to the Spokane Street Viaduct to create a direct connection to the E3 busway and improve the connection to West Seattle.

Just like the current Downtown Seattle Transit Tunnel, the WSTT will start with bus service and switch to rail over time as we expand our subway system. This new bus tunnel would have two important features from opening day: 1) tracks and power systems for rail and 2) separate stubs and portals for rail expansions. This project is a major step in the building of a true Seattle Subway.

Why is the WSTT important?

Mitigates the closing (for buses) of the current Downtown Seattle Transit Tunnel

Sometime before 2021 the Downtown Seattle Bus Tunnel will close completely to bus traffic. Very few additional routes can move to city streets and those that do will be moving much slower than they do now. This will also mean more forced transfers from the suburbs.

Solves mobility issues not addressed by Viaduct Replacement Tunnel and mitigates impact of a possibly failed Viaduct Replacement Tunnel Project.

If Bertha is a success, the WSTT will solve serious mobility problems not addressed by a bypass road that skips downtown. If Bertha fails, the WSTT project will be an essential lifeline to central and western Seattle neighborhoods.

Speeds commutes for a great many people living west of I-5

An average commuter using the WSTT will save 10 minutes per day round trip. That time really adds up — that’s 41 hours per year — like getting a whole work week of your life back each year. About 60,000 people ride the buses that will be in this tunnel each weekday. That means daily commuters would collectively save 142 years of commute time each year the tunnel is open.

Better connections

West Seattle: This project provides West Seattle with exclusive lanes in and out of downtown and fast direct connections to growing employment centers like South Lake Union, Pioneer Square, and Belltown.

Ballard: Avoids major choke points in North Downtown, around Denny, and through Lower Queen Anne that greatly improves on current local and RapidRide service.

Aurora Corridor: Extends exclusive lane access through downtown and avoids major choke points through north downtown and around Denny.

South and East King County: We didn’t represent it on this map, however, South and East King will see an immense benefit even if they don’t directly use the WSTT. A lot of space in downtown Seattle will be freed up by moving buses that are currently on the surface into the WSTT. This will mean less bus congestion and could mean fewer forced transfers. There is also capacity to add South and East King routes to the WSTT.

Solves immediate mobility issues while setting up for long term rail investments

Just as the Downtown Seattle Transit Tunnel–which has served buses for years and is now shifting to rail as more rail is built–the WSTT will do the same. The WSTT is a critical step in later rail extensions to Ballard, West Seattle, the Aurora Corridor, and express to the Airport via Georgetown. Seattle is a pioneer in this strategy and it has worked — let’s take our lessons learned from the current DSTT and improve upon that success.

Save Metro money in operations

All of that time costs a Metro lot of money. We estimate that Metro could save about 72,000 service hours a year which translates to a savings of $3.5M/year even when considering the added operating costs of the new tunnel.

The best thing about the WSTT is that we can get an immense benefit the day it opens while making an incremental step towards a Seattle Subway. This is not a one-off project that doesn’t connect to the regional vision. The WSTT is the single improvement with the greatest geographic impact of the projects considered so far for ST3.

The WSTT is just one of multiple investments that North King and the entire region will make as part of ST3. We will get into the full details of what we think should be in ST3 for each subarea in our upcoming ST3 system planning series. If ST3 funding fails at the state level, this project is a must for a local funding option.

Building the WSTT ensures that there is maximum use of the system until we have the money to build out the subway and the demand to use the tunnel to capacity. For these reasons, the WSTT is the most important component in any North King package we pass.

The estimates we used above are conservative. We added existing buses with existing ridership to a tunnel, as is, and made some assumptions about speed improvements. This method misses many positive impacts such as the induced demand that comes with better service. We explain our math in this document of assumptions. For this post, discussions of local funding options are off topic and will be covered in a later post.

Maps by Oran Viriyincy