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.
Technical summaries for each solution will be available May 1, 2017.