This is a post by Abigail Roberts. See her bio at the bottom of this post.

This past spring, hundreds of bright yellow bicycles showed up on campus at Vanderbilt University. All you had to do was unlock the bike with your phone, ride it across campus, and lock it at your destination. Although I personally prefer walking over cycling, I became intrigued by the idea of bicycle sharing. Why is the idea spreading so quickly? Are these systems making a difference?

In a bicycle sharing system, a fleet of bicycles are made available in a city or neighborhood, and users can check out a bike, ride it across town, and leave it at their destination. By a recent estimate there are now over 14 million shared bicycles in cities around the world. With an explosion of companies in the last 10 years, bike sharing is quickly spreading with a goal of mitigating the environmental and economic impacts of traffic congestion in urban areas.

The 4 Generations of Bike Sharing

First Generation: Free Bikes

The first bicycle sharing program started in Amsterdam in 1965 as a grassroots solution to the pollution caused by cars. A group called Provo painted a bunch of bicycles white, and left them around the city to be used by anyone, for free. However, the anarchist political leanings of Provo caused the police to remove the bikes from the streets shortly after.

Second Generation: Coin Deposit

The next wave of bicycle sharing took off in the 1990s in Denmark. The rides were free, but users had to deposit a coin at a station in order to unlock a bicycle, and only got the coin back upon returning the bicycle. The coin system incentivized the return of bicycles, but since a user could not be identified, there were still issues of theft and vandalism.

Third Generation: Paid Access and Technology

Starting in 1998 in France, bike sharing systems began using technology at the docking stations to associate users with bicycles, and most systems began charging usage fees. As technology has improved, it has been integrated into bike sharing systems to allow GPS tracking of the bicycles and access via smartphone. Since 1998, these systems have had the data to tackle the problem of “rebalancing,” which is optimizing the distribution of bicycles across docking stations so that users will not find themselves in an area without any available bicycles.

Fourth Generation: Dockless and Electric Systems

In the last few years, the industry has begun to evolve again with the introduction of dockless bike systems that aren’t tied to specific docking stations, as well as electric bikes that make travel more efficient and accessible to more users. These trends introduce new problems of optimizing the distribution of bicycles without the anchors of specific stations, and in the case of electric bikes, providing places for the bicycles to be recharged becomes necessary.

Research and Bike Sharing

Researchers from Cornell University who participate in the Computational Sustainability Network have been working on ways to optimize operations for one particular bike sharing company, Citi Bike, which operates in New York City. In 2016, Nanjing Jian, Daniel Freund, Holly M. Wiberg, and Shane G. Henderson tackled the problem of optimizing allocation of bicycles at docks across the city. They were able to use heuristic methods to demonstrate a simulation-optimization approach that is computationally feasible for real-life data. In 2018, Hangil Chung, Daniel Freund, and David B. Shmoys analyzed various incentive programs that could be used to encourage users to help with balancing the distribution of bicycles throughout the city; Citi Bike ended up using one of the incentive programs in practice.

Research has also looked at the benefits of increased access to cycling. A 2014 study in London found overall health benefits from bike sharing, though the benefits were greater for men and for older users. This recent paper found a noticeable decrease in carbon dioxide emissions in Shanghai, China due to bicycle sharing. In Barcelona in 2011, this study found reduced carbon dioxide emissions due to cycling, as well as finding that the health benefits of increased physical activity outweigh any potential negatives of traffic fatalities or air pollution inhalation while cycling.

In the rapidly growing industry of bicycle sharing, there will continue to be opportunities for research with applications to these systems, whether examining the benefits and results of these programs, or using computational methods to solve the logistical challenges these systems face. As bicycle systems continue to evolve, research can be extended to emerging Fourth Generation systems. For example, consider how the Cornell work on the rebalancing problem is impacted by dockless systems: instead of centering analysis around fixed docking stations, the analysis might focus on areas with clusters of pick-up and drop-off activity, as well as taking into account situations where a bike is left isolated somewhere for an extended time. Dockless systems also introduce new possibilities for incentive programs that exploit the flexible nature of these new systems. Though there are still many questions to answer with regards to bicycle sharing, the research consensus seems clear: bicycle sharing systems are a benefit to both personal health and local sustainability efforts.

Abigail Roberts is a Computer Science  undergraduate at Vanderbilt University supported by NSF Grant 1521672. The opinions expressed herein are Abbey’s and not necessarily those of Cornell University. or NSF You can reach Abbey at abigail.k.roberts@vanderbilt.edu.