Optimizing the position of bike sharing stations. The Milan case.

Bike Sharing systems are rapidly spreading around in European cities. Bike sharing is a new type of public transportation based on the use of public bikes to cover relatively short distances in urban areas. It is used both in conjunction with traditional public transport to complete the ???last mile???, or in alternative for its flexibility. Usage fees are usually very low, compared to other means of transport, as costs of service are often covered by advertising. In this work we will focus on the case of Milan where the bike sharing system, called "BikeMi", was introduced in 2008 and has already reached over 200 stations and 3.000 bikes with 1.8 million travels in 2013. The aim of the paper is to assess which attractors influence the use of bike sharing stations. The paper also examines the different effect of proximity and visibility of bike sharing stations from attractors. An econometric analysis is performed, based on the data set of use of the system and on GIS information on the position of bike sharing stations and attractors. The main results suggest that the presence of metro and train stations, universities, museums, cinema and restricted traffic areas in correspondence of bike sharing stations significantly increase use. On the other hand the presence of tram and bus stops and theatres does not and has an opposite influence. With respect to visibility, there is a positive effect for tram, bus and metro stops, theatres and cinemas. On the other hand, universities and museums show a negative correlation. The results appear robust to the inclusion of time and other possible confounding variables, such as weather conditions. The analysis supports the relevance of the role of urban planning for the best positioning of bike sharing stations and the need to carefully consider the features of surrounding environment to optimise the distribution of bike sharing stations in a territory