Monday, March 4, 2013

The Capital Bikeshare Data-set

The Capital Bikeshare Data-set

Capital Bikeshare (also abbreviated CaBi) is a bicycle sharing system that serves Washington, D.C.; Arlington County, Virginia; and the city of Alexandria, Virginia. At the time of this writing (Feb 26th 2013), the network contains 1,670+ bicycles serving 175+ stations.

Station Map (Feb 26th 2013)

I really like Capital Bikeshare, not because I love cycling (I do) or because I live in Washington D.C. (I don't) but because of the data. Capital Bikeshare releases all of its historical data on system usage in quarterly data dumps. At the time of this writing, 9 quarters of data have been released the last quarter of 2010; all of 2011; and all of 2012.

The 9 quarters of Capital Bikeshare data

I've been studying this data for the past few months now. The main purpose of this blog post is to share some of my work with you. After all, whats the point in doing something cool if you don't share it.

The effects of weather on bike rentals

The following is a screenshot of an interactive calendar I developed. This calendar displays a square for each day in the Capital Bikeshare data set. The squares are grouped by day, week and month to produce a beautiful mosaic describing bike rentals. The color of each square represents the number of bikes rented from the system on that day. Dark Red means few rentals, Dark Green means lots of rentals. Hovering over any square will display all of the corresponding weather information for that day in the table below the mosaic.

What does this interactive calendar teach us? Well firstly, if we forget about the weather information for a moment, we see some general trends. In 2011 and 2012, the bulk of renting happens in the summer months with reduced activity on either side. We also see that the system is increasing in popularity with time, all of the dark green is in 2012.

More interestingly I think are the oddly colored squares. A red square surrounded by green squares indicates lower than expected rentals, the more contrast the more peculiar. The highest contrast square is Saturday Aug 27th 2011, this was the day of Hurricane Irene. Other days of high contrast (to choose but a few) include

Sat Oct 29th 2011: 29.97mm of rain.
Sun Apr 22th 2012: 32.26mm of rain.
Mon Oct 29th 2012: 97.79mm of rain.
Tue Oct 30th 2012: 21.34mm of rain.

Federal holidays also cause a disruption of normal bike rental usage. Most notably "Thanksgiving, Christmas and New Years".

Click here to view the interactive calendar for yourself. If you find anything interesting that you would like to share, please post it as a comment.


In conclusion weather has a rather dramatic effect on bike rentals. Thorough exploration of the calendar above shows that rain fall is the largest dampening factor (no pun intended) on rentals. This is followed closely by low temperature and then high wind speed. Also most federal holidays appear to have an effect on usage, some positive, some negative, the most influential are of course Thanksgiving, Christmas and New Years. 

So a note to CapitalBikeshare: if you need to do maintenance or upgrades on your network, please, please wait until a rainy day.

About the visualization

The calendar layout I used was created by the seriously talented Mike Bostock. I simply re-purposed it for my own needs. The weather data was downloaded from wunderground.

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