A Love Letter to the Link

Want a one-sentence summary of every post in this blog? “Here is some data that argues for a radical change in the policies of public transit agencies.” This theme belies my overall satisfaction with the public transit in my life. Yes, I’d like to get places faster and wait less, especially at night and on weekends. But I don’t feel isolated from the city’s opportunities without a car, and it’s a critical component of how I control my cost of living. My life would be worse without it. I can demand improved transit, while still recognizing the great merit of what exists today.

In that spirit, access measurement can be used to celebrate something good, rather than to denounce detrimental policies. And in Seattle, Sound Transit’s Link 1 Line is good.

How do we know the 1 Line is good? People ride it! This is a case where I’m ok with deferring to the most basic of analyses.

What makes the 1 Line good? This is a far more interesting question, but one that I often hear a simplistic answer to. It’s a train! To me, this answer falls flat. Comparing the varying ridership of light rail service in North America should be enough to deem it insufficient as an explanation.

My answer begins with the fact that, within Seattle, the 1 Line is the leader in 30-minute completed journeys, and it’s not close. Meaning that, of the 129,535,414,343 completed journeys—instances where it is possible to start at an origin sector of the city at a minute of the day, and reach a destination sector within a 30-minute time budget—in 10,154,111,033 of them, or 7.38%, the 1 Line appears in the fastest path that does so. Route 40 has the second most, 5,742,732,408, which is just over half the 1 Line’s contribution. The 1 Line is also over 14 times better than the median. The fundamental purpose of any transportation system is to get individuals from one place to another, quickly and whenever. The Link outshines its peers at this.

This isn’t just a matter of the 1 Line running more service, and thus having more chances to gobble up fastest paths. Within Seattle, route 7, the C Line, route 40, the E Line, and route 60 each consume more hours of service. The G line and the E line make more trips. Dividing journeys by a route’s in-service seconds normalizes for varying levels of investment. With 16,222 journeys per in-service second, it leads all transit routes in Seattle. Route 65 comes closest, achieving around 86% of the 1 Line’s performance with 13,945 journeys per in-service second. The 1 Line isn’t just prolific in its contributions, it’s efficient too.

In theory, a route can achieve a high journeys per-in service second, but only marginally improve access. If the fastest path that it allows is just one second shorter than the next fastest one, it will score a journey, but the benefit to riders will be minimal. That’s not the case for the 1 Line. Of the completed journeys where it appears within the fastest path, only 33.1% would still be possible to make within 30 minutes if the 1 Line didn’t exist. Only one other route performs better, but it’s a school bus route that runs a single trip, and is only nominally open to the public. Compare the 1 Line to the South Lake Union Streetcar—84.4% of the latter’s completed journeys could be covered by other routes and walking in its absence, or to the median route’s figure of 55.2%. The 1 Line provides unique access to opportunities; it makes possible what Seattle’s otherwise bus-based network does not.

Non transit riders in Seattle sometimes tell me that they would use public transit if the Link was expanded to be closer to their home. Implicit in this is a critique that the 1 Line is only useful near its stops. I contend that this represents a fundamental misunderstanding of the 1 Line’s utility. There will never be Link stations everywhere. This would remain true even if the city could be blanketed with many new Link lines. A line with many stops cannot achieve the speeds of one where the stops are spaced out, and speed is, of course, critical to getting to places within a reasonable time budget. With only 17 stops in Seattle, there are many people for whom the 1 Line is outside of a comfortable walking distance. In spite of this, within 84.5% of the land area of Seattle, there is at least one destination and time of day wherein the 1 Line makes up part of the fastest path there. This is best among transit service in Seattle. The second best is route 62—covering 76.7% of the city—but that route has 62 stops in its most common outbound service pattern. Route 62 stops are proximate to far more doorsteps than 1 Line stations are, but the 1 Line still has route 62 comfortably beat. The 1 Line doesn’t need to stop everywhere to be at least a little useful nearly anywhere in the city. I sympathize with those who have soured on transit from interminable bus rides in the past, but the 1 Line’s reach when piggybacked with shortened bus trips makes their dismissal of it ring hollow.

The 1 Line is achieving these top scores in spite of some infrastructural and methodological hinderances. It is operating in a slightly degraded state at the time of this analysis’s calculation; due to work at the in-construction Pinehurst Station, the 1 Line is dropping to 12-minute headways after 5:30 PM. The reduced frequency is likely suppressing its overall journey count, compared to regular operations. In addition, the access calculations only consider service that is run entirely within Seattle. The Shoreline South station may be a short walk or bus ride away from points in northeast Seattle, but in this analysis it might as well not exist. This is also depressing the number of journeys, in a way where all of the derived measurements are understated too.

From an unweighted access perspective, Sound Transit’s Link 1 Line is a thoroughly good piece of transit infrastructure. I’m sure if I dug through all the documents concerning the route’s design and implementation, though, I would see no references to access that comport with the ways that I measure it. And, you know what, that doesn’t matter! Having the mandate to expend the monetary and social capital to build transit largely insulated from automobile traffic, faster than any bus serving the city, not encumbered by frequent stopping, and colocated with transfer opportunities is the access equivalent of playing a game on easy mode. It would be hard to adhere to those principles and still create a low-access route, and there’s nothing wrong with that. Not every project is equally blessed, though. If these guarantees are weakened, it is far more important for the access implications of every choice to be carefully considered, lest things get ugly. Let’s not dwell on that, at least for now. Here’s to the Link, an access superstar that makes it look effortless.