The Science (and Maps) Behind Finding Available Citi Bikes and Docks

Columbia University researchers have turned their attention to how Citi Bike can improve the availability of bikes and open docks.
Columbia University researchers have turned their attention to how Citi Bike can improve the availability of bikes and open docks. Image: GSAPP Spatial Information Design Lab

Coming across an empty bike-share station when you need a bike — or a full one, when you need a dock — is a disappointing experience, to say the least. While Citi Bike’s rebalancing efforts try to keep up by shuttling bikes around town, the company is working against a tide that shifts demand unevenly across its service area.

Juan Francisco Saldarriaga, a researcher at Columbia University’s Spatial Information Design Lab, mapped those demand imbalances as part of a project the lab is working on. “Origins and destinations of Citi Bike trips are not necessarily symmetrical during the day,” he wrote. To untangle the patterns of bike-share riders, the team used weekday data from last October to create a matrix showing imbalances at every station by hour of day.

There are predictable patterns: Between 10 a.m. and midnight, stations around Union Square act as the center of much of the system’s activity. Not surprisingly, Penn Station and Grand Central become hotspots during peak hours. The worst imbalances occur from 6 to 10 a.m. and again from 4 to 8 p.m., though there a handful of outlier stations that either don’t experience major imbalances or see capacity problems outside those hours.

Imbalances at busier stations affect more people than imbalances at out-of-the-way stations, so the group isolated the highest-impact problem spots by creating a chart that overlays the severity of imbalances with total activity at each station by hour.

Finally, there are some stations that are surrounded by a sea of imbalanced stations, but seem to experience relatively few problems of their own. For one reason or another, something is going right at these locations. “These stations have been outlined on the maps and should be further studied,” Saldarriaga wrote.

There are more maps, as well as charts and animated GIFs to see how bikes move across the Citi Bike network, at the Spatial Information Design Lab website. The data could be used to produce more than just neat maps and animations: Citi Bike is a participant in this year’s Big Apps challenge, an effort led by EDC to use open data to create useful tools for New Yorkers. Now, if only there were an app to fix those broken docks.

  • BBnet3000

    “Finally, there are some stations that are surrounded by a sea of imbalanced stations, but seem to experience relatively few problems of their own. For one reason or another, something is going right at these locations.”

    That makes it sound like people arent finding those stations, which is to say that something ISNT going right at them (and is exacerbating the problems of nearby stations).

  • com63

    More stations and more bikes will fix everything!

  • Ian Turner

    Isn’t that the same line of reasoning that leads people to say that more highways and lanes will fix everything?

  • com63

    don’t forget about more tax cuts too!
    In all honesty though, I think citibike needs to reach a critical mass where all types of people use it for all types of trips and then the rebalancing issue will be less extreme due to more turnover at stations and more stations nearby if one if full.
    Popular locations like Penn Station in the AM/PM will still have trouble in the commute direction but maybe reverse commuters will figure out that they can always have a bike and always have a free dock and they will help to automatically rebalance.

  • ohhleary

    If Citibike was actually capable of using data to fix problems, they would have made some sort of attempt to fix the fact that every station in Midtown is empty by 5:30pm every weekday after a year of this very clear and obvious pattern.

    As long as they’re the only bike share program in the country whose host city refuses to give it a subsidy to operate properly, Citibike will continue to tread water and won’t be able to solve the problems that come as a result of these usage patterns.

  • Joe

    The constant station imbalances are a serious problem–one that is compounded by an even bigger problem: THE REAL-TIME DATA CITIBIKE PROVIDES IS INACCURATE.

    On more than one occasion, mindful of the risk of imbalanced stations, I have carefully planned my Citibike trips by checking online first and finding suitable stations with available bikes to leave from, and docks to arrive at….only to find that the bikes and/or docks that the app reports (even at that moment) as “available” are actually broken and unusable.

    When I have called Citibike to report the problem, the representatives have indicated that yes,they know this station/docks/bikes are broken, and point me to another nearby station. Which is all well and good…except why should people at Citibike headquarters have this information and yet NOT MAKE IT PART OF THE REAL-TIME DATA FEED so I could have made appropriate plans in the first place, and not waste 20 minutes going from dock to dock?

    This kind of incident is very discouraging. If the information I get from the Citibike app and website is inaccurate (yes even real time), how can I trust Citibike? Not only does it force me to waste valuable time searching for free docks, it throws off all the careful plans I made based on the (false) information the app provided me.

    Honestly, what’s the point of even having apps and websites if the data provided is wrong? I’d rather have NO information rather than misinformation.

    I have a suspicion (though no evidence) that Citibike may purposely not report non-functioning docks/bikes on the data feed to keep their stats looking better than they really are…but it could very well be simple incompetence, combined with a desire to keep problems hidden away under the rug.

    In any case, the FIRST priority should be the get the data feed cleaned up and report ACCURATE DATA, warts and all, so people can make good decisions about when and where to use Citibike!

  • Kevin Love

    We don’t have the real estate to build enough highways and lanes to satisfy demand. We do have the capability of manufacturing enough bicycles to meet demand.

  • Emmily_Litella

    Yeah, it ain’t perfect. Pretty good for 15 cents a ride (2 rides every day for a year).

  • Lacking CitiBikes

    I wholeheartedly agree about the inaccurate app info. I can be standing at an empty station that the app says has a single bike. And when I call, the customer person sees no bikes on her map. It’s gotten to the point where if I see one bike at a nearby station and 2+ bikes at a further station, I will go to the further station since I don’t trust the info on the app and rather make the safer choice.

  • Lacking CitiBikes

    There is a serious, 24/7 lack of bikes at the station at West 54th and 9th Ave. If you look at the O’Brien “24 hour” map at any time of day, you will see that the station fluctuates from 0 to maybe 4 bikes at most. But the default is 0 bikes, especially during the morning rush.

    This station falls under the “W” in “Weekday” in the map above and you will see that this black area is a no-man’s land between blue and orange throughout the day since there are so few bikes there (no one is parking there for some reason – perhaps because it’s near the northern edge of the Citibike area but too far from a subway station)

    What I don’t understand is why Citibike doesn’t do more rebalancing between full stations along Broadway to the empty stations in Hell’s Kitchen just 1 avenue block away. They could kill two birds with one stone with very little (time) effort. Here’s an illustration:

  • Lacking CitiBikes

    I think people are just giving up on some stations because they are consistently disappointing in their emptiness or fullness, and relying on the ones that are more consistent in providing the needed bikes or empty docks, despite being further away. I, for one, don’t even worry if I will find a bike outside Trader Joe’s in Chelsea because during store hours, there is high turnover and you never have to wait more than 3 minutes for a bike to materialize.

    One beef I have is that CitiBike is not being very smart or flexible with their rebalancing. Last week I saw a rebalancer add bikes to a station that was almost full while stations a few blocks away were completely empty. It’s like they have been told to focus their efforts on one station (whether it needs the attention or not) and ignore the other nearby stations.

    It’s like CitiBike is trying minimize their work and simply make users walk further to the few designated stations rather than making the system more convenient by distributing bikes to stations that need them.

  • Anxiously Awaiting Bikeshare

    I’d like to promote a new workout:

    Jog to full dock, bikeshare to empty dock. Jog to full dock, bikeshare to empty dock. Repeat 12 times per day 3 days per week. Good for your heart and good for the world.

  • qrt145

    Good training for practicing the bike-to-run transition in triathlons. 😉

    My only objection is that at least in Midtown, where many of the unbalanced stations are, it’s practically impossible to run…

  • ohhleary

    Citibike may purposely not report non-functioning docks/bikes on the
    data feed to keep their stats looking better than they really are

    This is something I’ve been pondering lately. One of Citibike’s performance metrics is “Peak Hours Bicycle Rebalancing.” That’s defined as any instance when a station is empty or full. But if the system shows a station as having one bike available or one dock open and the dock is non-functional, that station still appears (at least in the app) as not empty or full.

    Coincidentally, one of Citibike’s worst performance metrics is “Operational Docks,” which is defined as repairs to non-functional docks made within 48 hours. In May, that was at 29%, versus a performance goal of 99%.

    Could it be that Citibike isn’t being prompt in one metric because it would bring down another metric.


The Spatial Payoff of NYC Bike-Share

Last night’s Brooklyn Community Board 2 hearing on bike-share was hardly the “battle” anticipated by the Brooklyn Eagle. About 20 people testified after DOT presented the draft station maps for the district [PDF, pages 10-15], and almost all of them supported the bike-share program in general, with several residents expressing delight at the prospect of […]

Using Citi Bike Data to Figure Out Where Cyclists Ride

It’s been a week since Citi Bike released a trove of data on bike-share trips, and the public is already using the information to pick out patterns in ridership and glean new details about the demographics of Citi Bike riders. In addition to identifying the busiest late-night stations to map nightlife hotspots, statistician Ben Wellington at […]

5 Highlights From Last Night’s Bike-Share vs. Parking Meeting

Last night’s Brooklyn Community Board 6 bike-share forum lacked the fireworks of previous meetings — no physical threats this time. While the tone was civil, the demands from the anti-bike-share crowd weren’t exactly reasonable. So far, Citi Bike has proven incredibly popular in CB 6, with some stations getting as much as seven rides per dock each day. That’s […]