"Bike sharing systems have grown in many cities worldwide From Levinson and Krizek (2015) The End of Traffic and the Future of Transport. http://davidlevinson.org/the-end-of-traffic-and-the-future-of-transport/  Figure 8.3 Source: McCarthy, Niall ""Bike Sharing Takes Off"" Statista http://www.statista.com/chart/1148/bike-sharing-takes-off/ ."