Optimization approach to depot location and trip selection in one-way carsharing systems Gonçalo Homem de Almeida Correia ⇑ , António Pais Antunes Department of Civil Engineering, University of Coimbra, Portugal article info Article history: Received 15 December 2010 Received in revised form 4 April 2011 Accepted 19 May 2011 Keywords: One-way carsharing Transport demand management Location model Integer programming abstract In this paper, we present an optimization approach to depot location in one-way carsharing systems where vehicle stock imbalance issues are addressed under three trip selection schemes. The approach is based on mixed-integer programming models whose objective is to maximize the profits of a carsharing organization considering all the revenues and costs involved. The practical usefulness of the approach is illustrated with a case study involving the municipality of Lisbon, Portugal. The results we have obtained from this study provided a clear insight into the impact of depot location and trip selection schemes on the profitability of such systems. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Carsharing systems are an alternative to private vehicle ownership. Instead of owning one or more vehicles, a household or business accesses a fleet of shared-use automobiles, benefiting from choosing the one that best fits its needs for a specific purpose (Shaheen et al., 1999). The first experiments with carsharing systems were made in Europe, in the 1940s, mainly motivated by economic rea- sons. One of the best known is the Sefage cooperative, established in Zurich, Switzerland, in 1948 (Shaheen and Cohen, 2007). In the United States, these systems appeared much later, in 1983, within the Mobility Enterprise program. In contrast to Europe early users, US first adopters were motivated more by convenience than by affordability, possibly due to the lower costs of driving in the US (Lane, 2005). More recently there have been carsharing initiatives in Asia, primarily in Japan and Singapore. The main focus in Japan has been on business use, while household use has been dominant in Singapore. ‘‘This is likely because of limited vehicle licensing and high car-ownership costs in Singapore’’ (Barth et al., 2006). Today, carsharing systems exist in 18 countries and show enormous growth potential (Shaheen and Cohen, 2007). Carsharing systems can be classified with respect to organization goals, geographic scope, depot location, and trip con- figuration. As regards the organization goals, some systems are run by volunteers and are non-profit making, while others are commercial ventures run by international companies. The geographic scope may span from a community-level operation with only one or two vehicles, to national organizations with many thousands of members in several major cities. In relation to depot location, there are systems with depots placed only at transit stations mainly to serve commuter trips, designated as station-car systems, and systems with depots scattered around a city independently of transit stations (Shaheen, 2001; Barth and Shaheen, 2002). Finally, with respect to trip configuration, it is usual to distinguish between one-way systems and round-trip (or two-way) systems. The former are by far the most common, being in particular adopted by the three largest organizations that account for 94% of the North America carsharing membership (Shaheen et al., 2006). 1366-5545/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.tre.2011.06.003 ⇑ Corresponding author. E-mail addresses: gcorreia@dec.uc.pt (G.H.A. Correia), antunes@dec.uc.pt (A.P. Antunes). Transportation Research Part E 48 (2012) 233–247 Contents lists available at ScienceDirect Transportation Research Part E journal homepage: www.elsevier.com/locate/tre