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SDOT: Weekday biking up 144% after Duwamish Trail connection, freight travel times increased less than 1 second

Before and after photos of W Marginal Way near SW Idaho Street. It's a five-lane street in the before. A two-way bikeway is located in the nearside lane in the after photo with a heavy concrete barrier protecting it.
From the West Marginal Way SW Safety Project Evaluation Report (PDF).

The Freight Advisory Board fought hard against SDOT’s plan to connect the Duwamish Trail to the Alki Trail and Spokane Street Swing Bridge, a connection sorely needed since many sections of the trail opened in the early 1990s. But after Mayor Jenny Durkan delayed the project, safe streets advocates kept pushing. Mayor Bruce Harrell and his then-new SDOT Director Greg Spotts then made the trail link a priority, building a temporary connection during the January 2023 emergency closure of the Spokane Street Swing Bridge that they then kept in place until a permanent trail connection could be completed later that spring.

In response to concerns about the bikeway causing traffic and freight mobility issues, SDOT conducted a study. And the results are in: The trail increased weekday biking by 144%, weekend biking by 53% and walking by 90%. And this all happened while increasing travel times for cars and trucks by less than one second, a literal blink of an eye.

The thing is, these results should not be a surprise to us in 2023. We’ve done this song and dance for more than a decade now. Results like these happen every time the city completes a significant safety project on a fast and over-designed street like W Marginal Way. People worry that the project will increase traffic and complain loudly, unconvinced by assurances from SDOT’s staff that travel times will not increase significantly. Then the city completes the project and finds that, sure enough, SDOT staff was correct all along. It’s almost like the people SDOT has hired to design safer streets know what they’re doing. Here’s a likely non-exhaustive list followed by the date of the study (typically a year later):

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Will the Freight Advisory Board learn from this experience and evolve their understandings of how our streets can be both safer and still support freight movement? I sure hope so, because we’ve got a lot of work to do and could use their help in our city’s fight to reduce our terrifying increases in traffic deaths in recent years, many of which have occurred on major truck streets. My advice for the Freight Board as someone who has observed these advisory boards in action for more than a decade would be that they should focus their efforts on the specific needs of freight movement in city street designs rather than on a misguided idea that more lanes is always better for freight. We know this to be untrue, and holding onto counting lanes as a freight mobility goal makes them look hopelessly outdated. They also do the freight community a disservice when they choose to fight the wrong fights. For example, the Board spent years fighting this trail on W Marginal Way only to discover that they were fighting over travel times equivalent to a blink of an eye. That work did not help the freight community, but it did delay this trail connection for years and alienate a bunch of people who they may want as allies in the future. Going forward, they should be partners in safety by encouraging protection for people walking and biking as well as safer street designs that reduce speeding, make turning movements safer and easier, and improve visibility between all road users. Those goals do help freight operators, and they align with the work of the other advisory boards. The Freight Board could then use their specific expertise and real-world knowledge to help SDOT staffers understand how truck drivers will use their proposed designs and point out potential problem spots that need further analysis.

The controversy surrounding SDOT’s safe streets work should not be the imagined traffic backups in the minds of people who refuse to believe an SDOT safety program that has been exactly correct about the efficacy of their work for more than a decade. The controversy should be that we have all these studies showing that we know what to do to make our streets safer but we aren’t repeating this success on every dangerous street before more people are injured or killed.

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8 responses to “SDOT: Weekday biking up 144% after Duwamish Trail connection, freight travel times increased less than 1 second”

  1. Alden

    But travel time isn’t the valid metric. If half the truckers quit or took other routes, that would account for it. What you need to show is the volume of freight per day is constant. Does the study control for freight volume?

    Otherwise, we’re just crowing that the freight moved somewhere else. Like sweeps.

  2. Alden

    My reading of the report indicates truck volume decreased significantly during the 12 month study period, which seems to me to support the argument that biking has displaced trucking. It also suggests travel time was already at the tolerable maximum, so the only thing that can give is decreasing volume.

    Is this right?

    1. Tom Fucoloro

      No. Volumes are back to where they were before the pandemic. There was a big spike while the West Seattle Bridge was closed, and then volumes were down for a few months after the bridge reopened. But now they seem to have returned to normal.

      1. Alden

        Figure 19 and its text explanation:

        “Overall truck volumes on West Marginal Way SW have decreased significantly since the West
        Seattle High Bridge reopened in September of 2022, falling from a peak of 9,400 per day to a four year low of 2,180.”

      2. Tom Fucoloro

        Yeah, traffic spiked when the nearby freeway bridge closed and this street became a detour route. So when the bridge was fixed and reopened, traffic returned to normal.

      3. Alden

        But this is not what figures 19 and 20 show. Truck volume has steeply declined since reopening the bridge and these bike infrastructure improvements went in. I’m a cyclist and have used those improvements, but on the face of it, it looks like freight has paid the cost. There may be unrelated reasons why freight has abandoned this route, but we would need to know more to rule out the bike improvements. Focusing on transit time is beside the point.

      4. Al Dimond

        Over a period of time where so many big things are changing at the same time it’s rarely going to be possible to isolate or rule out specific causes to any movement in something like traffic or trucking volumes, which depends on a lot of different factors. Closing and reopening of the high bridge looks like a big first-order change. Beyond that it’s hard to say anything with a lot of certainty.

        The world we’re heading towards is one where we’re realizing the effects of climate change. A lot of things are going to change, all at the same time. We’ll be uncertain about the effects of choices we make. The question isn’t, “Can we turn the dials and get the meters reading just like they did in the ‘good times’?” We’ve got to lead with overall vision and values. Volumes of traffic are easy to measure but they only indirectly tell us about something we care about, the viability of industry in this area.

        If industrial businesses sited for unique geography in this corridor are cutting operations because they can’t move products that’s something we care about. If it’s a matter of route choices changing, then the minimal effect on travel times does tell us something: that the alternate routes can’t be catastrophically worse, otherwise they’d stick with the one they’re on that isn’t meaningfully slower than it was before. It’s possible the alternate routes are somewhat worse and volumes will eventually rise on this route. It’s also possible some of the routes taken through here were suboptimal in the first place and the high-bridge closure and re-opening were opportunities for people to re-evaluate them. And, of course, it’s possible that individual businesses in this area are booming or contracting for reasons much bigger than transportation costs.

        If we’re going to say we can’t rule out the bike path having some effect on freight movements… sure, we can’t rule it out. But we also have to be honest that a decline in truck volumes over a very short measurement window doesn’t show that freight has paid a cost.

  3. Breadbaker

    My sense has always been that freight simply will not factor the natural need for pedestrian and cycle existence, let alone safety, into their calculations. You’ll never see a complaint about, say, an on-demand light changing for a single vehicle, but they’ll bitch and moan all day when a pedestrian or bike light affects their run. People travel by means other than motor vehicles. They need to get over it.

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