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A General Electric Evolution Series Tier 4 hybrid locomotive before being painted at its factory in Fort Worth, Texas. The Tier 4 series of diesel-electric locomotives are the most efficient in the world with respect to emissions, and can move one ton of freight 500 miles on one gallon of fuel. The 440,000-pound behemoths are designed to transport such heavy loads that aerodynamics would have virtually no impact on increased efficiency. The locomotive incorporates regenerative braking, which captures and stores energy in batteries, along with 8,000 other fuel-saving solutions.

Trains transport 28 billion passengers and more than 12 billion tons of freight annually. Most rely on diesel-burning engines; some tap into the electric grid. Although trains have steadily improved their fuel-use efficiency in recent decades, rail was responsible for 3.5 percent of emissions within the transport sector in 2013.

Railway companies employ a range of technical and operational measures to improve fuel efficiency and reduce costs. As locomotives are retired, more efficient models replace them, many with more aerodynamic designs. In some cases, those models include hybrid diesel-electric engines and batteries, which gain efficiencies similar to those of hybrid cars, saving 10 to 20 percent on fuel.

Better locomotives, more strategically placed, are enhanced by better cars—lighter, more aerodynamic, able to hold more cargo, and equipped with low-torque bearings. The rails themselves can be better lubricated to reduce friction. How a train is driven also remains critical, and software can improve it.

The number of electric trains is increasing. As electricity production shifts to renewables, rail has the potential to provide nearly emissions-free transport.


efficiency [improvements] in recent decades: IEA and UIC. Railway Handbook 2016: Energy Consumption and CO2 Emissions. Paris: International Energy Agency and International Union of Railways, 2016.

rail…emissions: IEA and UIC, Handbook.

8 percent of…passengers and goods: IEA and UIC, Handbook.

hybrid diesel-electric…efficiencies: JR East Group. JR East Group Sustainability Report 2011. Tokyo: East Japanese Railway Company, 2011.

Amtrak…regenerative braking: UIC. World Rail Statistics. Paris: International Union of Railways, 2011.

electric trains [are] increasing: Eom, J., et al. “We Keep on Truckin’: Trends in Freight Energy Use and Carbon Emissions in 11 IEA Countries.” Energy Policy 45 (2012): 327–341.

“electrification…efficiency gain”: IEA. Transport, Energy, and CO2: Moving Toward Sustainability. Paris: International Energy Agency, 2009; Eom et al, “Trends.”

“ton-miles per gallon [vs.] trucks”: RMI. “Fuel Savings Potential Trucks vs. Rail Intermodal.” Rocky Mountain Institute, 2011.

steam locomotive…[vs.] diesel locomotive: Freudenrich, Craig. “How Trains Work.” 2008.

1980…diesel [efficiency]: Palmer, Brian. “Let’s Make an Effort to Move More Freight by Rail and Less by Road. Trains are More Efficient.” Washington Post. March 3, 2014.

[countries driving] rail-sector emissions: IEA and UIC, Handbook.

[volumes of] passengers and…freight: GEA. Global Energy Assessment—Toward a Sustainable Future. Cambridge, UK, New York, and Laxenburg, Austria: Cambridge University Press and the International Institute for Applied Systems Analysis, 2012.

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p. 156

Correction: If that increases to 621,000 miles by 2050, emissions from fuel use for freight operations alone can be reduced by 0.5 gigatons of carbon dioxide.

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