  The Citi Bike deployment changes the landscape of urban mobility in New York
City and provides an example of a scalable solution that many other large
cities are already adopting around the world. Urban stakeholders who are
considering a similar deployment would largely benefit from a quantitative
assessment of the impact of bike sharing on urban transportation, as well as
associated economic, social and environmental implications. While the Citi Bike
usage data is publicly available, the main challenge of such an assessment is
to provide an adequate baseline scenario of what would have happened in the
city without the Citi Bike system. Existing efforts, including the reports of
Citi Bike itself, largely imply arbitrary and often unrealistic assumptions
about the alternative transportation mode people would have used otherwise
(e.g. by comparing bike trips against driving). The present paper offers a
balanced baseline scenario based on a transportation choice model to describe
projected customer behavior in the absence of the Citi Bike system. The model
also acknowledges the fact that Citi Bike might be used for recreational
purposes and, therefore, not all the trips would have been actually performed,
if Citi Bike would not be available. The model is trained using open Citi Bike
and other urban transportation data and it is applied to assess direct benefits
of Citi Bike trips for the end users, as well as for urban stakeholders across
different boroughs of New York City and the nearby Jersey City. Besides
estimating the travel time and cost savings, the model also reports the
associated gas savings, emissions cut and additional exercise for the
customers, covering all three areas of anticipated impacts - economic, social
and environmental.
