Friday, September 27, 2013

Citi Bike at Age 4 (Months): More Numbers, More Bikes

Today marks the four-month anniversary of the introduction of Citi Bike. This is as good a time as any for me to revisit the program's ridership data, as I promised in my original post from the four-week mark. Long story short: the system is thriving.

Since my last post, NYC Bike Share has rolled out a System Data webpage, on which you can view and download substantial data on the system's usage thus far. The data is stored and displayed via Datawrapper; I'm not thrilled with the presentation (particularly the absence of tooltips to display exact values), but I'm surely grateful not to have to manually transcribe another three months' data off of blog posts. Data is available through Tuesday 9/24, so we have just over 17 weeks (and just under four months) to play around with.

Of course, the first step is to validate all this new data. I was dismayed to identify several glaring inconsistencies within the provided numbers. The System Data page includes both daily and total counts for trips taken, miles traveled, and annual memberships sold, plus daily sales of 24-hour and 7-day memberships – but on numerous occasions, adding a day's trips taken to the cumulative total thus far yields a number different than the next day's cumulative total. (Similar problems abounded for miles traveled and annual memberships sold.) Most egregiously, the cumulative numbers for July 18 reflect an additional 12,666 trips and 317,494 miles (= a highly unlikely 25 miles per trip!) beyond the provided daily figures. So I've used the numbers I'd collected from the blog, along with simple arithmetic and common sense, to reconcile the conflicting values; all my data is available here for the curious.

Having massaged our data into some semblance of consistency and plausibility, let's take another look at the key charts from my first post. (If you haven't read it, click here for background on why these figures are important.) It turns out that my first post, dated June 25, occurred right at the beginning of a substantial slide in membership sales. Around 6/23, users were purchasing nearly 2700 daily passes; by 7/10 that number had dropped 45% to under 1500. But at the same time, 7-day and annual membership sales made a comeback; since then, weekly memberships have continued to putter along (this is, perhaps, a category with limited demand; the new Bay Area Bike Share instead offers a three-day pass) while annual sales remain surprisingly robust for a system now beyond its infancy, and daily membership sales have stabilized around the 1500 mark. All in all, sales remain sizeable; when more information on the system's operating costs becomes available, I'll be able to assess whether they're bringing in enough business to cover costs.
System use is extremely strong. The 7-day average "high" of 29,091 trips on 6/24 has turned out to be a "low" in comparison with the system's subsequent performance: Since July 14, the average daily ridership has not dropped below 30,000. At the same time, though, the continued growth in active members has kept the "trips per active member" ratio in check. I had hoped to see that figure continue its dramatic mid-June climb, but no such luck thus far; it's hovering around 0.45 as peak cycling season comes to a close. (Expect that number to drop come winter.) If the system does expand as promised and hoped, active members across the city would be able to use Citi Bike for more trips in more areas, likely leading to a rise in the trips-per-active-member ratio. The unsmoothed data remain noisy, but there is at least one important trend they reveal. It is easy to pick out weekends – when 24-hour membership sales explode – and Mondays, when satisfied 24-hour pass buyers seal the deal by purchasing an annual membership. But in late June, the daily trip count, which had up to that point been closely correlated with 24-hour pass sales, decouples from short-term memberships and begins to stay high throughout the week. My surmise (and hope) is that by the end of the program's first month, annual members began figuring out how to integrate Citi Bike more fully into their daily transportation routines. In any case, daily trips have continued to rise even as sales of short-term passes decline with the end of peak tourist season.

(I promised earlier that I'd investigate the impact of weather on daily ridership; I've now made a preliminary survey and found that impact to be quite limited. I collected daily mean temperature, mean humidity, and total precipitation data from Weather Underground, then exported my data to run some linear regression and correlation analysis on it in R. I found that a simple linear model with total active members as the independent variable and daily trips as the dependent variable accounted for (i.e. adjusted R-squared = ) 76% of the variance in daily trips. Although correlation analysis indicated a weak negative relationship between humidity and precipitation and daily trips, a multivariate model incorporating the three weather measurements accounted for only 5% more of the variance – not a substantial increase in the model's predictive power.)

(If any readers with a strong statistics background want to chime in with a more nuanced analysis of the data, I'm all ears. The comments section is below and here's the spreadsheet.)

It's quite clear from these charts and figures that Citi Bike has been performing excellently over its first four months when compared with its first four weeks. But that is probably not a very useful context. (In the United States' first four Presidential elections, the runner-up became the Vice President.) Instead, let's see how New York's system usage stacks up against a successful and established program across the Atlantic.

London, population 8.3 million, has had Barclays Cycle Hire1 since 2010. With 8,000 bikes and 570 stations in operation, that three-year-old system logged 904,155 rides this August, split 50-50 between short-term riders and annual members; its all-time peak thus far was 47,105 rides in one day, during the 2012 Olympics. Meanwhile, a three-month-old Citi Bike, comprising 6,000 bikes and 330 stations2 in a city of the same population as London, recorded 1,115,340 rides in August, representing a whopping 6.0 trips per bike per day, 64% higher than London's usage levels. NYC's peak thus far was 44,083 rides on Saturday, August 18 – 94% of London's peak, which is not bad given the absence of any Olympic Games.

Data isn't yet available on the percentage of Citi Bike rides taken by annual members vs. temporary members (a division roughly equivalent to "locals vs. tourists" or "work vs. play"), but we can approximately assess the proportions of utility trips vs. recreational trips by examining how many trips occur on weekdays vs. weekends. (This is imperfect, of course – many locals make utility trips on weekends, and most tourists' weekday trips are still recreational in nature – but bear with me.) In May and June, weekends saw substantially more use than weekdays, but in the months since, weekday usage has equalled and often exceeded weekend ridership. Combined with the decoupling of daily rides and 24-hour pass sales we saw above, this leads me to conclude that Citi Bike is less and less dominated by joyriding out-of-towners. Will Citi Bike, having attracted more than 84,000 annual members in its first four months, manage to equal the Boris Bikes' three-year sales figure (186,762)? Almost certainly. About 250 people per day are currently purchasing new annual memberships, a rate that, if sustained, would push total membership sales past the 100,000 mark in just over two months; and when those annual memberships begin to expire next summer, count on the vast majority of users to re-up. Indeed, I am predicting here and now that by June 1, 2015, Citi Bike will have sold more than 200,000 annual memberships.

So: given Citi Bike's burgeoning ridership, its favorable performance compared to London's longer-established system, and the strong support/warm acceptance shown it by New York's mayoral candidates, it looks like bike share is here to stay.

How has bike share been treating you so far? Are there any other bits of analysis you'd like to see in future updates?


1 I always find it so funny that "bike share" has exactly zero words in common with the British English equivalent, "cycle hire." I'm also amused that what we Americans call a "system" the British call a "scheme," which always sounds slightly sinister. ("Cycle to Work Scheme: brought to you by the All-Powerful Bike Lobby")

2 Officially, the system has 6,000 bikes. However, a fabulous visualization by Jehiah Czebotar suggests the true number is currently closer to 4,100 – which would mean that New Yorkers put in almost nine trips per day on every Citi Bike this August.

Tuesday, September 24, 2013

Going Dutch: Is Boston on board?

Stasha recently called my attention to a lengthy and thoughtful article by Martine Powers in the Boston Globe, examining the components of the Netherlands' successful mainstreaming of utility cycling and considering how the techniques might be brought to America. Go read it. I'll wait.

OK, back? Good. I mostly want to talk about the diagram, reproduced in teensy size to the right. Notes:
  • 2 and 3 are the same thing.
  • In Manhattan, the 1st/2nd and 8th/9th Avenue bike lanes have features 1-4 (and cyclists love 'em!). Those lanes are among the best cycling infrastructure in the United States, and their appeal to novice cyclists is a testament to the effectiveness of the "Dutch" approach.
  • I'm ambivalent about 6, unless the cyclists get the light slightly before drivers (allowing them to safely establish a presence before right-turners cut them off). Berlin has bike-specific signals, too, and the timing is staggered in this fashion at major intersections, and it works; but it's important to remember that Germany and the Netherlands are fundamentally more law-abiding cultures than the US, and that American cycling is still seen as something of a Wild West, so it may be quite some time before cycle-specific signalization gains traction, but I guess you have to start somewhere, if you want the American endgame to look like the Netherlands.
  • 7 is not a feature of Dutch cycling infrastructure but rather a byproduct (and partial enabler?) of the ubiquity of utility cycling in the country. It was perhaps unwise for the Globe to bring up this issue, one of the most contentious* in the bike advocacy world. Shall we dismiss Australian utility cycling as doomed to fail, given that country's universal helmet requirement?
  • The real game-changer, as far as infrastructure goes, is 5, which could greatly diminish the incidence of right hooks. (One of the strongest arguments advanced by vehicular cyclists* is that separating bikes and cars using cycletracks actually decreases cyclists' safety at intersections, when they "suddenly appear" from directions drivers aren't expecting.) 5 is an elegant physical solution to that problem.
Of course, the true core component of Dutch bike safety is the high-awareness, cars-last culture they enjoy. Since virtually everyone rides a bike at least some of the time, virtually everyone is very attuned to the presence of bikes on the roads; and the law holds drivers at fault in most collisions. Even the small things matter - American drivers open their door (into the bike lane) with their left hand, but Dutch drivers are trained to turn and open the door with their right hand, forcing them to look out and confirm that the adjacent lane is clear. (Powers covers all these cultural factors well in the article.)

Oh, and - there's parking in the upper diagram, but none in the lower one. How nice! (Realistically, yes, some street parking should remain in cities, but eliminating parking at intersections is a huge boon to safety. Neckdowns help enormously; the protected bike path can curve along the curb extension to approach the intersection more alongside the car lanes as per the illustration.)

I knew most of the facts from the article already, but a couple stood out for me:
  1. A key moment in the Dutch adoption of utility cycling was a nationwide moratorium on Sunday driving caused by the 1973 oil shortages. I've long admired the collectivist spirit of northern European democratic socialist societies; the last time the American government mandated consumption reductions was the rationing during World War II. (Some municipalities, like the Bay Area, now have voluntary air-quality improvement programs, but voluntary just isn't enough for the vast, silent majority of the population.) In the US, the approach is to gently change the market and societal incentives to encourage a transition to cycling, an approach that appears to be working. But it's fairly slow, and I have a hunch that a lot of people out there would take to utility riding if given the nudge. ("A transportation liberal is a conservative who's taken one ride on a Citi Bike.")
  2. The Dutch system of school-based cycling instruction and a "bike diploma" at around age 12 is wonderful. I had the good fortune of being raised by a mobility specialist, so had a very strong grounding from a young age in matters of street safety. I think such pedestrian/bicyclist education is very important, but I also feel strongly that there should be no legal licensing requirement for bicyclists. (They just don't pose enough danger to merit such a requirement.) But formalizing the education and training process - and making it as integral to primary school as driver's education was at my high school - is such a good way to disseminate life-saving information throughout society.
The question that Powers' well-informed article raises, of course, is whether American cities in general - and Boston in particular - can or will go Dutch. It's a crucial question, because adopting and adapting a Dutch street model is about much more than widespread bike use: it's about street safety for all users, smart use of limited space, fostering walkable, human-scale communities, and adjusting our carbon footprint in the face of climate change.

Perhaps simply because of its scale, but also doubtless due to the unparalleled intensity of its land use (and its citizens' resultant reluctance to cede any portion of that land or its use), New York has been a center of attention in the American livable-streets movement. But let us not ignore Boston! Boston beat NYC to bike share; Boston has about 9.7 miles of bike lanes/sharrows per 100,000 population, more than NYC's roughly 6.6 miles per 100,000 citizens. (But, again - scale. New York has more than 500 miles of bike lanes to Boston's 62. Hubway is celebrating two years and 1 million rides; Citi Bike is currently seeing nearly a million rides every month.)

I'd love to hear from some Bostonians about how street safety and bike infrastructure are coming along in their neighborhoods; I'm planning to visit in November and will take the pulse myself. But in the meantime, this article and the progress it reports are heartening for me. Keep up the good work!

* I don't want to get into the vehicular cycling debate, or the helmet debate, at least not here. But I surely will, down the road.