Bridging the Topographic Fortress with a Trail

As promised in the “SR-520 Design Will Discourage Walking and Biking to the UW and University Link” post, here is some further elaboration on the value of a Portage Bay Bridge Trail. Currently the idea is bouncing around the halls of Seattle City government – stayed tuned to see if the trail makes it into an official recommendation to WSDOT.  

The glaciers did not have walking and biking in mind when they sculpted Seattle, and north Capitol Hill in particular. This geological heritage is part of what gives Seattle its character. North-South elongated hills, hidden valleys, and numerous glacially carved bodies of water. As beautiful as it is, this natural character poses serious challenges to creating an interconnected system of family-friendly walking and biking infrastructure.

It would not be hyperbole to think of north Capitol Hill as a topographic fortress. It is surrounded to the east, north, and west by very steep slopes. To the best of our knowledge, there is no ADA accessible route for walking or biking off of north Capitol Hill (check out the map below – compiled from city data and our measurements). Complicating the situation, the streets that were slightly less steep were cherry picked to be arterials for car traffic. As a result, creating an all-ages-and-abilities friendly route between the “urban centers” of Capitol Hill and the University District, and further to neighborhoods in N.E. Seattle and to the Central District, is quite a challenge.

A Portage Bay Bridge Trail would bridge this topographic fortress. According to WSDOT, the Portage Bay Bridge Trail (PBBT) would have less than a 5% grade, be well lit, and be considerably more direct in getting to the “Montlake Hub” of regional trails and to Husky Stadium side of the UW campus. It would be the most direct and family-friendly route from the Montlake Hub to Capitol Hill by far.

Even in terms of getting between Capitol Hill and the East UW Campus, taking the PBBT would only be slightly longer than a Harvard Ave E route (1.89 versus 1.63 miles), but would be significantly less steep (4.5% versus 8.7% grade), and much better protected from traffic. Even amongst experienced cyclists, research has found that “cyclists are willing to go considerably out of their way to use a bike boulevard or bike path rather than an arterial bike lane,” and that people will go over three times more out of their way to avoid routes with slopes of over 6% grade compared to those with 4-6% grade (click here find the full article). This effect would likely be more pronounced in people who are willing-but-wary. In other words, since the PBBT will be better separated and less steep than other options, people will choose to use it over routes that currently exist even if they are shorter. Let’s look at a few of the existing alternatives.

What about alternative streets?

Currently many people cross the notoriously dangerous Eastlake Ave E at/to Harvard Ave E, crossing 4 very busy arterial lanes. Harvard Ave E has a 8.7% grade and also serves bus routes and is used by I-5 and 520 traffic. Creating a family-friendly connection across the extremely busy Eastlake Ave E and up the very steep Harvard Ave E to E Shelby St is no small task. Eastlake Greenways and Central Seattle Greenways are working together to determine whether this connection could ever be made accessible for people of all-ages-and-abilities. Don’t hold your breath.

Another route that people sometimes use if they are coming from NE Seattle is Delmar Drive East. Delmar has a number of problems:

  1. Its arterial designation combined with the lack of separation for the bike lanes mean that according to Seattle Neighborhood Greenway guidelines (drawn from the Mineta report) it is not suitable for people of all-ages-and-abilities.
  2. It’s 8.5% grade means that it is very steep.
  3. The bike lanes are narrow and act as gutters due to the large amount of debris that collects in the roadway.
  4. A curvy road and numerous driveways create the very real possibility for conflicts.
  5. In order to access Delmar, it is necessarily to wind your way through the non-intuitive and disjointed Montlake street grid.

What about bridge width?

Even though the vast majority of community members and groups (including the Montlake Community Club and the Capitol Hill Community Council) support a Portage Bay Bridge Trail regardless of how the bridge is built, there is still interest in making the bridge as narrow as it can be without sacrificing its utility. Here are a few ideas that have been floating around:

  • Use steel rather than concrete for the bridge – this allows the bridge to have less visual bulk
  • Remove the planted median from the middle of the bridge
  • Reduce any unnecessary gusset space (the concrete webbing between lanes)
  • Decrease the lane width – the bridge is slated to be restricted to 45 mph, meaning that lanes can be an urban width rather than suburban freeway sized.
  • Finally it may be worth considering how hanging the Portage Bay Bridge Trail in different manners (underneath, partially offset, raised, etc) affects the light situation.

How will the PBBT connect through the Montlake 520 interchange?

In short, the Montlake interchange needs to be redesigned to make it functional for people of all-ages-and-abilities. Click the PDF below for a quick visual rundown of the top issues:

Toward a Connected Montlake Lid

8 responses to “Bridging the Topographic Fortress with a Trail

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