The BusGraphs Project

Last August, I presented a map that could quickly show sector-centered access. That is, when considering a single start point and a fixed time budget, how often can one reach all other points within a region, when starting at that point at every minute of the day. This prototype map used reachability data produced by an early version of arf and clumsily combined it with spatial information extracted from running the Access Analyzer. After working on disentangling arf from the Access Analyzer late last year, and focusing on arf’s performance in January, I wanted to spend February expanding its visualization capacities beyond the region-wide access maps shown in the last two posts. The first product of this work expands on the sector-centered approach seen in the August prototype.

I’ve spend much of January improving arf’s performance. The 30-minute time budget access map for Washington state that used to take around 70 minutes now takes approximately 40 on my M1 2020 MacBook Air. A map of Seattle with the same parameters takes around eight. With the performance enhancements in place, I wanted to subject arf to a new trial: creating a 30 minute unweighted access map of New York City.

Arf is a new tool for generating unweighted access analyses, like the ones seen in this blog. Its outputs have the same 80 meter spatial resolution as those generated with my previous access analysis tool, the BusGraphs Access Analyzer, but arf can assess areas of sizes on the order of US states, and runs on conventional personal computers rather than cloud computing infrastructure. This 30-minute transit and walking access map of Washington state took around 70 minutes to generate on a 2020 M1 MacBook Air laptop.

This is a proposal to use Interstate 5 between Northeast Northgate Way and the Spokane Street Viaduct as the “second downtown tunnel” planned for Seattle in the Sound Transit 3 project (ST3). Between these two points, the entire highway would be converted into a transit corridor. This would require a feat of political courage and interagency cooperation, but would provide the exceptional public transit network that ST3 promised, while eliminating costly and disruptive portions of the project.

In Human Transit, Jarrett Walker describes his consulting work as being a domain expert who asks communities questions about the transit networks that they want to build. The questions present two endpoints to a spectrum. Each end has advantages and disadvantages. The position a transit agency takes depends on what the community that it serves values; there are no wrong answers. Walker then can help design a transit network conforming to these positions. There are four overarching questions.

• Ridership or coverage?
• Connections or direct service?
• Peak-first or base-first?
• Exclusive or compromised right of way?

I propose a fifth question: cooperation or insurgence?

I’ve been revisiting Jarrett Walker’s book Human Transit¹. Reading it crystalized the disjointed thoughts that I had as a transit rider into opinions on how public transit networks should operate. It is one of the most important books I have read, and I suspect that is true for many people with a stake in public transit.

I’m revisiting it by way of processing the response to my cost-neutral redesign of King County Metro’s network, which overlaid Seattle with 24/7 frequent service . It appeared in Seattle Transit Blog, where comments on it were more uniformly negative than I anticipated. These commenters are not fools. They recognized that widespread frequent overnight service would involve tradeoffs, like more crowding at rush hours, and fewer one-seat rides to population and activity centers like downtown and the University District. They insisted that riders would not favor this exchange.

A network-wide access map colors sectors, uniform areas of a region, according to an access score. For an unweighted access measurement, the score corresponds to how often a rider originating in that sector can reach others throughout the region. But it doesn’t allow a transit rider with an interest in a specific sector to see exactly which destinations are within reach. The same data can generate a sector-centered access map that reveals this, so my maps allow transitioning between the network-wide and sector-centered modes. Unfortunately, it’s slow to the point of being unusable.

This year, my proposed, in-service time neutral restructure of transit in Seattle is appearing in Seattle Transit Blog. Check it out there!

Even if all King County Metro’s “commuter” bus routes were shunted to Link Stations, downtown Seattle would still teem with buses. Many of the transit routes that run entirely within Seattle serve downtown, converging on Third Avenue to create a transit mall. In this proposal, as with past ones, this stretch of road would go from having the greatest amount of bus traffic in the city to being nearly devoid of it. But why mess with this longstanding feature of Seattle’s transit network?

For the third year, I’m proposing a full network, in-service time neutral restructure of Sound Transit and King County Metro’s public transit service in Seattle. This year, I’m adjusting my approach slightly. Previously, after I established a budget of service hours available, I would test large, wide-ranging batches of changes against it, repeating this until I was close to the line without going over. This time, I’m parceling changes by theme, in hopes of better appreciating the savings and costs of different types of changes.

Also new this year is that I am balancing the service time budget not in terms of expenditure within Seattle, but throughout King County¹. The impetus for this is a change in how I’m computing access², but it’s fundamentally a more accurate assessment of expenditure regardless. The in-service time from segments of transit trips that crossed the Seattle border were unaccounted for in previous attempts. By expanding service-time measurement to the county level, this is only a concern for portions of service that leave the county, of which there are far fewer. This change is particularly germane to the routes featured in this post.