Public Interest Transit Forum -

Alternative North Corridor Alignment for RTA

by Doug Tooley

May 27, 1997




This memo outlines a possible alternative routing for the Regional Transit Authority's North Corridor. The specific proposals herein are largely separable, and are meant to encourage you to think about a variety of modifications to the existing plan. If there is an overall goal it is to encourage an alternative along the lines of the previously developed alternative 2.5, the high bridge over the ship canal. Perhaps, most importantly, I'd also like to encourage you to develop a system that is conceptually more in line with the HOV lane access developments proposed for the remainder of the service area, in advance of the second, successful ballot submittal.

The conceptual approach here is to utilize half of the I-5 express lane right of way for transit usage reducing tunneling/grade separation costs for those segments while accessing all proposed stations via access ramps and bus capable tunnels. Conceptually, this proposal creates a seamless integration between the downtown bus tunnel and the HOV access ramps proposed for outlying, less developed areas. This proposal provides benefits as measured by the proposed evaluation criteria. One significant benefit not listed in the criteria is earlier (5 years?) implementation of a priority segment, specifically the congested University District via a bus tunnel. The bus tunnel approach provides a flexibility for expansion for service in adjoining neighborhoods that greatly exceeds that of the tightly focused light rail exclusive alternative now being proposed.

My background for this preparing this report is as an educated citizen, involved in the process since 1988, before even the formation of the JRPC, when I drafted a response letter to a KIRO-TV editorial, subsequently broadcast, suggesting the University District as a destination for initial light rail developments. I have subsequently attended various meetings on this subject consistently over what is now approaching ten years.


The HOV Access Tunnel Alternative integrates the current system plan with subsequent emphases placed on HOV lane development, continuing, in general, the implementation track originally envisioned in the construction of the Downtown Bus Tunnel.


The initial phase of construction proposed for this alternative is the construction of a University District Bus Tunnel beginning in the general area of the existing express lane off-ramp, serving the currently proposed station areas via a cut and cover tunnel under either Brooklyn or 15th.

This initial tunnel shall continue underground to at least 50th Street. For discussion purposes a tunnel portal is proposed at the University Heights Center grounds with continuing North service along the surface of University Way, connecting back to the Express lanes at Ravenna Boulevard and 65th.

This Bus Tunnel could also serve express cross town service utilizing Northlake Way, as well as routes serving Capitol Hill on the surface and the Eastside. A greater range of North end destinations could be served via the Tunnel as well, maintaining a continuity of service that exists with the various 70 series buses and adding additional frequency to the University District through the addition of the route 40.


The First Hill dog leg/station addition was based on a suggestion from myself to then Council member Jim Street. At this time I would like to put forth a devil's advocate proposal that omits this station for your consideration. There are other alternatives for servicing the First Hill station's service area, which may or may not be within your (or the RTA's) purview. These alternatives might include adding the First Hill area to currently proposed downtown circulator systems or the extension of the downtown pedestrian tunnel between the University Street Station and Rainier Tower to include the Convention Center, Virginia Mason, and Seattle University.

From the Convention Place Station it is proposed to cross I-5 above ground, perhaps with an elevation gaining switchback to gain sufficient elevation. After crossing I-5 a cut and cover tunnel is proposed, climbing the hill, perhaps under Olive Way, to Harvard Street. The cut and cover tunnel is proposed to continue north along Harvard, boring down to exit Capitol Hill with a portal in the hillside above I-5 just to the North of Roy Street.


The proposed Capitol Hill portal is just past the express lane bottleneck. While it would be possible to continue the proposed alignment along the surface to the Ship Canal or even to keep the tunnel underground, a la the high bridge alternative, what is proposed here is to join the express lanes dedicating 2 of the 4 lanes for two way transit usage. The Ship Canal Bridge would require moderate modification, but these modifications could be done at the same time as needed seismic reinforcement.

A freeway lid based station is tentatively proposed at or adjacent to the 520 interchange, providing station service as previously evaluated for both the Eastlake and North Capitol Hill neighborhoods. I make this proposal tentatively for two reasons, it is not worth adding this station if it takes the proposal over budget and the constraints of the site are many, not the least of which is potential future 520 expansion. (A lid at the interchange itself would be a good way to block expansion!).


It is conceivable that this alternative offers significant enough cost savings to fund, in part, the continuation of the line to Northgate. For discussion purposes I would propose that if you address this question to consider utilizing 5th Avenue NE from Ravenna/65th to add useable Greenlake service to the standing plan and the construction of a lid based station at Lake City Way and 80th Avenue NE. A lid based station at Northgate shouldn't be ruled out either.


Although this alternative appears, on the surface to provide greater benefits at a reduced cost, the final evaluation of this approach must be done by credentialed technical and budgetary experts. The benefits of this approach are also delivered sooner, and to a broader portion of the north end population. There is one potential long term drawback regarding total system capacity, when the system is running with buses perhaps reducing the total capacity of the right of way. Emerging intelligent vehicle systems should be available though to mitigate the effects of this success by the use of bus 'platoon' type approaches.

The potential cost savings in this approach are also large enough that the restoration of other transportation demand management approaches previously cut from the Seattle district budget might be restored, or urban area park and rides constructed providing mitigating parking benefits for the minor construction disruption costs. Specific marginal benefits to this approach, as listed in the proposed evaluation criteria include:

Increased Transit Ridership through reduced transfers, increased destinations, and earlier implementation, including new transit trips.

Greater compatibility with plans for the Bus Tunnel and in the utilization of HOV access ramps, a regional focus developed after the current north corridor system plan.

Earlier implementation for University District Segment.

There are also some specific marginal costs to this proposal, which must be justified in terms of cost savings. These include:

Reduced capacity on the express lanes. The current bottleneck entering downtown limits this usage anyway, so taking some of these lanes North of the bottleneck reduces the effect, perhaps to an insignificant amount.

Construction disruption through cut and cover techniques. It should be noted that proposed construction alignments are one block adjacent to business strips, creating some minor access disruption to the Capitol Hill and University District areas, but no disruption to the districts themselves. Bore tunnels through these same right of ways, still connecting to the HOV/Express lanes might still provide cost savings.)

Reprinted with permission of Doug Tooley, who may be reached at e-mail or phone 206-325-8195.

Return to Public Interest Transit Forum home page.

Last modified: February 07, 2011