Saturday, January 9, 2010

Road diets and bridge capacity

A solution has been proposed for the existing Johnson Street Bridge to make it more bike friendly in particular. This is a critical issue driving the design (though only one of several elements of the replacement decision checklist), and supporters of preservation have been claiming that there is an easy fix to provide space for cyclists.

The idea is to close one lane of two for outbound traffic and turn the space over to cyclists. There are numbers of other reasons why this won't work, but firstly, the traffic demand on the bridge is beyond the design capacity that would work with the proposed lane reduction.

I'll put more up on the "tangled octopus" of trails and other design issues that challenge the old bridge, but for now, there's a link at the end of this post to a paper on "road diets", put together by Pete Lagerwey, who recently retired from his position as Seattle's bicycle and pedestrian coordinator, and Dan Burden, who runs Walkable Communities from his home in Florida. Keep in mind that they are both advocates for sustainable transportation design and walking and cycling in particular and, given the numbers on our bridge, their work indicates that the proposed lane reduction would be unworkable.

I've made the point with my council colleague who has raised the issue more than once and suggested it to campaigners for saving the old bridge, but thus far none have even acknowledged that this might be a problem. They continue to promote the idea as an easy fix and, notwithstanding their insistence that we employ the expertise of bridge structural engineers, refuse to consider the expertise offered on other serious issues of bridge design and operation as far as it conflicts with their agenda.

The paper is at:

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