A Green Vehicle Routing Problem Sevgi Erdog ˘an, Elise Miller-Hooks ⇑ Department of Civil and Environmental Engineering, University of Maryland, 1173 Glenn L. Martin Hall, College Park, MD 20742, United States article info Article history: Received 16 December 2010 Received in revised form 8 May 2011 Accepted 12 July 2011 Keywords: Vehicle routing Alternative-fuel fleet operations Refueling Fuel tank capacity limitation abstract A Green Vehicle Routing Problem (G-VRP) is formulated and solution techniques are devel- oped to aid organizations with alternative fuel-powered vehicle fleets in overcoming diffi- culties that exist as a result of limited vehicle driving range in conjunction with limited refueling infrastructure. The G-VRP is formulated as a mixed integer linear program. Two construction heuristics, the Modified Clarke and Wright Savings heuristic and the Den- sity-Based Clustering Algorithm, and a customized improvement technique, are developed. Results of numerical experiments show that the heuristics perform well. Moreover, prob- lem feasibility depends on customer and station location configurations. Implications of technology adoption on operations are discussed. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction In the United States (US), the transportation sector contributes 28% (US EPA, 2009) of national greenhouse gas (GHG) emissions. This is in large part because 97% of US transportation energy comes from petroleum-based fuels (US DOT, 2010). Efforts have been made over many decades to attract drivers away from personal automobiles and onto public transit and freight from trucks to rail. Such efforts are aimed at reducing vehicle miles traveled by road and, thus, fossil-fuel usage. Other efforts have focused on introducing cleaner fuels, e.g. ultra low sulfur diesel, and efficient engine technologies, leading to reduced emissions for the same miles traveled and greater mileage per gallon of fuel used. While each such effort has its benefits, only a multi-faceted approach can engender the needed reduction in fossil-fuel usage. As part of such a multi-faceted approach, renewed attention is being given to efforts to exploit alternative, greener fuel sources, namely, biodiesel, electricity, ethanol, hydrogen, methanol, natural gas (liquid-LNG or compressed-CNG), and pro- pane (US DOE, 2010). Municipalities, government agencies, nonprofit organizations and private companies are converting their fleets of trucks to include Alternative Fuel Vehicles (AFVs), either to reduce their environmental impact voluntarily or to meet new environmental regulations. This focus on truck conversion is desirable because, while medium- and hea- vy-duty trucks comprise only 4% of the vehicles on the roadways (US FHWA, 2008), they contribute nearly 19.2% of US trans- portation-based GHG emissions (US DOT, 2010). Moreover, truck traffic has had the greatest growth rate of all vehicle traffic, increasing 77% for heavy-duty trucks and 65.6% for light-duty trucks compared with only 3.3% for passenger cars between 1990 and 2006 (US DOT, 2010). The US currently has energy policies in place with the aim of reducing fossil-fuel use so as to reduce GHG emissions, break dependency on foreign oil, increase homeland security and support renewable energy use (e.g. the Energy Policy Act (EPAct), 1992, 2005; Executive Order (EO) 13423 and the Energy Independence and Security Act (EISA), 2007). These policies have led to the creation of regulations, mandates, tax incentives, etc. that motivate or require companies and agencies to use AFVs. In fact, federal agencies with a fleet of 20 motor vehicles or more are required to reduce petroleum consumption by a minimum of 2% per year through the end of fiscal year 2015 from the 2005 baseline usage. These agencies are required by executive 1366-5545/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.tre.2011.08.001 ⇑ Corresponding author. Tel.: +1 301 405 2046; fax: +1 301 405 2585. E-mail addresses: serdogan@umd.edu (S. Erdog ˘an), elisemh@umd.edu (E. Miller-Hooks). Transportation Research Part E 48 (2012) 100–114 Contents lists available at SciVerse ScienceDirect Transportation Research Part E journal homepage: www.elsevier.com/locate/tre