From Human Transit:
“I think frequency is an overrated thing. Let’s say there’s a 20-minute [wait]. You can look on your phone, wait inside and have a beer.” — Portland Streetcar Citizens Committee member Peter Finley Fry, justifying the 18-minute frequency of the Portland Streetcar’s new Eastside loop, quoted last August in Willamette Week.
I don’t mean to pick on Mr Fry — I’m sure he is a person who sincerely wants to make transit in Portland better, and thinks he is doing so — but this quote is perhaps the crowning example of an incredibly misguided, but surprisingly prevalent strain of thought among the political leaders, advocates and managers of transit systems in the northwest; one which, until we slay it, guarantees we will flail ineffectually (and at potentially great cost) in our efforts to provide an alternative to near-universal car ownership by working-age adults.
The highway engineers, social engineers, and car manufacturers of the 1950s, who overthrew the entrenched dominance of public transit virtually everywhere in the United States, used many different tactics and appeals to do so, but one thing they certainly didn’t do was tell people they would have to wait 15 or 20 minutes before they could start their journey, so they should just cool their heels and read the newspaper for a bit. Quite the opposite: they promised freedom to travel where and when you wanted.
If we wish to emulate their feat, and install transit as the (vehicular) mode of choice in the dense parts of our cities, we need to internalize their language, their promise (go where you want when you want), and a proper understanding of how frequency affects travel time for spontaneous trips within a city. On transit, if you wish to travel spontaneously, or arrive at a particular place at a particular time, the average delay is half the headway. At 18-minute headways, that’s nine minutes of expected delay.
If you are travelling within a small city, and have to wait much more than about ten minutes for your transit vehicle to show up, taking transit has probably lost out to driving no matter how fast the vehicle goes, and can now only compete on the convenience and savings of not having to park, or saving you the cost of a cab if you are unable to drive. If, as is the case with the streetcar, you’re travelling in congested, city-center traffic and for a fairly short distance, the streetcar will need very high frequencies to make using it worth your while, compared to walking. If the goal was to make it easier to get around Portland, the Eastside streetcar wasn’t worth building until enough vehicles and operating funds were available to make it run a whole lot more frequently than every 18 minutes.
We can apply this understanding of frequency and travel time to find some quick, easy and impactful ways to improve transit service in Seattle. As an example, most of the city is consigned to 30-minute headways in the evenings and on Sundays, giving an average wait time of 15 minutes. Improving those routes to 15-minute headways would provide a typical travel-time savings of 7.5 minutes, a speedup which would be hard to match by making the vehicle faster, short of building a subway at tremendous expense. Improving RapidRide C/D to five minute headways would save five minutes per trip, which would almost make it worthy of its name.
In general, increased frequency, rather than increased vehicle speed, is going to have a greater impact on your ability to get around until headways get quite short, and headways in Seattle are mostly so long that the smart way to improve mobility is to run more service, and focus capital money on improving reliability so vehicles don’t bunch together. Conversely, understanding frequency can also tell us when it makes sense to make capital improvements rather than throw more vehicles at the problem.
As an example of that case: throughout the weekday, Routes 3 and 4 together provide 5-7.5 minute service from downtown to Harborview via James St (although they tend to bunch together somewhat). With an average wait of around three minutes, throwing more trolleybuses in there isn’t going to do much to reduce travel times, so it makes sense to look for ways to make those trolleybuses go faster. The problematic part of James St is basically an unfixable car sewer, but nearby Yesler provides a very fast, reliable path to Harborview, saving about three to seven minutes per trip, at the cost of slightly reduced access to First Hill. Building trolleybus wire on Yesler is thus likely to be a very good strategy to improve that corridor, rather than improving frequency.
Not understanding (or not caring) about the fundamental relationships between frequency and vehicle speed and travel time is the equivalent of being a cartographer who believes the world is flat (or that the shape of the world doesn’t matter). If a person don’t understand it, and why it matters, they will not be able to reason usefully about transit; they will spend money to fix problems that don’t exist, while missing problems that do; the people who they wish to serve will suffer for their efforts. For as long as our agencies are lead, advised, or influenced by people like Mr Fry, who don’t get this, we’re going nowhere fast.