The BusGraphs Project

The contention that the average commute duration has remained constant over time, and is independent of cultural differences and the built environment, underlies Marchetti’s constant. Technological changes might determine how far one can go, but the time allotted remains the same. That allotment is thought to be an hour total, or 30 minutes each way. I came across Marchetti’s constant early in my exploration of transit planning, and my analyses typically use a time budget of 30 minutes. That being said, I never made an explicit decision that I would use that time budget because it’s Marchetti’s constant. That 30 minutes seemed like a reasonable amount is probably influenced by having encountered it, though.

In spite of that choice, I simply don’t like the idea of assessing the quality of transit using a parameter justified by Marchetti’s constant. That a preferred amount of commuting time is built into human nature seems preposterous. While it’s interesting that this average value shows a persistence over circumstance and time, is there any merit to the average value itself? It feels like the sort of average that folds a diversity of individual preferences into a single, flawed description of a human stripped of agency. There are plenty of people who will tolerate longer commutes, and plenty who would balk at devoting an hour per day to it, and plenty whose tolerance varies depending on the current priorities in their lives. There are trips that people need and want to take that are not part of commutes. How long should be considered tolerable for those? Contemplating what people collectively “prefer”, “are like”, or “will do” seems to inform decision making in the transit planning field, but individuals, not populations, make the choice to board a transit vehicle.

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I grew up in Massachusetts. When I go back and spend a day in “Boston”, it might actually involve being in Brookline, Cambridge, Medford, Somerville, Chelsea, Everett, and Revere. That is not my relationship with Seattle and the municipalities around it. Sometimes I don’t leave its boundaries for months at a time. Much of what I need and want to do is located within the city limits. That’s not true all the time, but it’s true often enough that it heavily influences the way that I think about measuring transit access in Seattle. I presuppose that a person in Seattle mostly cares about getting around Seattle. The access analyses of the city that I produce measure the ability to do that.

Making trips within Seattle is, of course, not everyone’s priority all of the time. Looking at access at the city level is also a somewhat awkward way to analyze transit in this area. Seattle does not run or plan the transit service located within it. It provides some funding and participates in the planning process, but most transit in the city is under the purview of King County. Sound Transit, operating the Link Light Rail, exists at the level of a multi-county consortium. City-level access analysis feels like the most instructive tool for evaluating everyday transit quality, but it’s unlikely to be the most relevant tool for the agencies making the decisions. Recognizing that, I produced a thirty-minute transit and walking access analysis for King County. I feared this would be impractically slow and expensive—a fear that was neither entirely born out nor totally meritless. There are caveats to calculating and considering access for the county that are not exposed at the city level.

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Due to a computational error, the data and conclusions in this post may not be accurate.

On September 2nd, King County Metro enacted its plan to suspend or reduce the frequency of 20 routes. Faced with a shortage of operators and mechanics, it could not reliably operate its existing service. Meanwhile, I proposed a reimagined transit network for Seattle, subject to the same service hour constraints. In contrast to Metro’s plan, it achieved greater access than Metro’s pre-reduction network. With schedules for the reduced service now available and running, it’s possible to analyze the exact access implications of the service reductions.

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Due to a computational error, the data and conclusions in this post may not be accurate.

In the last post, I presented a restructured transit network for Seattle. Overall, the new network, versus that of an existing weekday, improves access by 19.7%, while reducing the amount of service by 13.9%. In theory, this would allow King County Metro to operate transit service at least every 15 minutes, on nearly all the current transit corridors in Seattle, 24 hours per day, seven days per week, while still accounting for its current labor shortage. To accomplish this, the restructure eliminates service that appears duplicative. Most notably, rather than having many bus lines go through a downtown already served by the Link 1-Line, routes are altered to serve Link stations that would allow the trip to continue there. It would be an adjustment for transit riders in Seattle, but one that would improve the ability to use transit to reach destinations throughout the city.

The 19.7% access increase throughout Seattle is an average, and those can hide information. It would be hard to accept a network restructure that concentrated all the improvement in one area, at the expense of many others. A positive change in average could indicate that is happening, instead of a more desirable across the board increase. The access map is useful to see that spatial distribution, but it’s hard to look at two different maps and make comparisons. I wanted to look at the restructure in a different way. In previous posts, I have constructed a variety of measurements based on access. This post applies them to the restructured transit network.

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Due to a computational error, the data and conclusions in this post may not be accurate.

King County Metro is facing a labor shortage. Due to a lack of operators and mechanics, on September 2nd, 20 routes will be either suspended or modified to run less frequently. Routes have been chosen based on low ridership or already-high frequency, with the rationale that this will negatively impact the fewest riders. Service hours will be reduced by 3.8%.

Canceling and lowering the frequency of routes is a pragmatic way for King County Metro to decisively deal with a labor shortage. It’s also an approach that necessarily reduces the ability to access destinations via transit. I’m considering a different one. My previous examination of access across cities has convinced me that Metro’s allocation of transit service hours is subpar. By considering options beyond cancelations and frequency reductions, there could be a way to reduce the amount of service that doesn’t negatively impact overall access. This is an experiment in completely restructuring King County Metro’s transit routes in Seattle.

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Due to a computational error, the data and conclusions in this post may not be accurate.

After I posted A Journey on the Seven Seats, a reader noted that while the post acknowledged that some multi-seat journeys would be infeasible if any transit vehicle were running slightly late, the methodology used to count these journeys did nothing to exclude them. Since I stated that a transit rider wouldn’t typically consider such a risky itinerary, I should have found a way to model what a rider would consider, incorporating information like the variability of actual arrival times. I understand the reader’s point. If I were building a trip planning tool, like the transit directions feature of Google Maps, I know that it would frustrate users if it suggested itineraries that were regularly undone by minor lateness.

Trip planning is not the purpose of these access analyses, though. My goal in conducting them is to highlight ways in which transit is, and isn’t, effective in connecting origins and destinations. This is done with the thought that the results can inform attempts to restructure public transit networks, allowing access to more destinations more often. When the matter of what some hypothetical normal rider is willing to do creeps into access measurement, I believe that its efficacy in guiding restructures is actually diminished.

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Transfers have been on my mind. To me, they’re just a normal part of the transit rider’s experience—no different than taking an unprotected left turn when driving a car. I’m not going to go out of my way to make one if I don’t have to, but if it’s part of the fastest path to my destination, I’m not going to give it a second thought. I won’t deny there is some risk and inconvenience, but those do not override the desire to reach the destination as soon as possible.

When I talk to occasional transit riders, I often experience a type of culture shock about transfers. They’ll mention, at times apologetically¹, driving or taking an Uber to some place because there’s no bus route or train line that could get them there. That they refer to a singular one of these is weird to me. A public transit system is a network of interconnected routes; it’s unreasonable to expect all origin destination pairs to have a single route connecting them.

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Last week, there was a two-day stretch of summer-like weather in Seattle, and all I could think about was the beach. Swimming has always been one of my favorite summer activities. I grew up spending parts of the summer on Massachusetts’s South Shore, swimming in temperate water on sandy ocean beaches. When I moved to Seattle, I knew I was giving up convenient access to beaches like that. In the last few years, I’ve adjusted my expectations and come to appreciate the rocky shores of Lake Washington and the exhilarating cold of Puget Sound. I no longer let the comparison to the beaches of my childhood impede my enjoyment of the beaches of Seattle. A second impediment remains, this one in the built environment, rather than the natural one. Serving the beaches of Seattle does not appear to be a priority for the agencies that operate transit in the city.

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Nearly 12 years ago, I sat at a table near the front windows of Pazzo’s in Seattle’s Eastlake neighborhood and confirmed plans to tour some nearby apartments. As I ate my calzone, I noted the route 70 buses that passed by on Eastlake Avenue East. I considered living near a bus route to be a necessity, but I thought of this requirement in unsophisticated terms. Any bus line would do. At the time, I didn’t fully appreciate that the transit service running through Eastlake was frequent. One’s proximity to frequent transit service is typically a reasonable heuristic for assessing one’s ability to use transit as a primary means of travel; it’s one that I learned to employ as my use of transit grew. From the perspective of proximity to frequent transit, Eastlake seems like a good place to be a transit rider. The problem is that from a more sophisticated transit access standpoint, Eastlake is below average in Seattle.

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Whenever I talk about the way that I measure transit access, I run into a problem. The numbers are horrendous. Their magnitudes don’t line up with human-scale quantities. Consider some examples from the analysis in the last post. The number of possible journeys is in the low trillions. The total composite score works out to be a hair over 20 sextillion, a number that sounds fake. It doesn’t get better when expressing access as a ratio between the number of completed and possible journeys. Sectors around the Madison Park terminal of route 11—a reasonably frequent route—have ratios with three zeroes to the right of the decimal point. The purpose of the last two access analyses has been to evaluate whether the transit service of a sector is exceptionally good relative to the entire region. Numbers like these lack the innate sense of scale to communicate that assessment clearly.

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