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.” HowStuffWorks.com. 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.
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.
Project Drawdown defines the trains solution as: the increased electrification of freight railways. This solution replaces the conventional use of diesel-powered freight trains.
Railways are already efficient modes of transportation, whether for goods or passengers. Historically, they have been the backbone of the transport networks for many countries, and remain a critical part of goods transport worldwide. Due to their nature, railways are limited in destinations and flexibility, but they tend to be very low cost to operate and are often used for transportation of lower-value goods such as coal, oil, and bulk materials.
Freight railways can be made more efficient by a wide variety of approaches, including: lighter trains, which need less energy to move; better braking, often with software that supports the train pilot; and electrification of the traction power. The last alternative allows for lower amounts of energy usage at the point of consumption (onboard the train) since the train doesn’t have to carry the diesel fuel long distances before use. Railway electrification stands at about 27 percent of the global track length (based on International Railway Union [UIC]  data); this percentage has been growing over the last two decades by annual amounts that average 1.4 percent, but vary widely from year to year.  Electrification costs are high, since electrical power has to be supplied all along the length of the tracks so that trains always have access to power, very often through overhead cables. Electrification is promoted by global bodies as a way to reduce operating costs, so a continuation of that growth can be expected.
Total Addressable Market 
The total addressable market for trains is defined as the total number of ton-kilometers of rail freight demand projected to 2050. This analysis compares the financial and climate impacts of electrified freight rail transport to regular tracks needing diesel-powered trains. Current adoption  of electrified tracks is estimated at 27 percent of the market.  The tonnage of freight service using electrified lines was projected from 2020-2050 from several sources.
Adoption Scenarios 
Impacts of increased adoption of trains from 2020-2050 were generated based on three growth scenarios, which were assessed in comparison to a Reference Scenario where the solution’s market share was fixed at the current levels.
- Plausible Scenario: Adoption is estimated using a 2.8 percent annual growth rate to 2050. This rate is based on a doubling of the average rate of electrification over the period 1998-2014. 
- Drawdown Scenario: This scenario assumes that 40 percent of all freight power will be electrified by 2050. A linear growth was assumed to interpolate annual adoption from 2014-2050. The average annual use of electrified tracks also increases by 25 percent, to represent intensified usage of electrified tracks due to the high first costs and very low operating costs.
- Optimum Scenario: Assuming that 100 percent of the railway track ton-kilometers are on electrified tracks in 2050, an annual linear growth rate is used to interpolate adoption to 2050. It is also assumed that electrified track usage is twice the average of 2014 (i.e. a 100 percent increase).
Avoided emissions are based on the reduction in fuel use from replacing conventional trains, as well as on additional grid emissions from electrification.
Estimates of electrification costs per kilometer were used for the solution, and 0 for the conventional first costs. This assumes that the electrification of existing tracks costs about as much as the increase in cost between laying new non-electrified tracks and laying new electrified tracks. Operating costs for non-electrified and electrified freight were obtained from 5 sources, including the International Transport Forum, the International Energy Agency, and the UIC.
The additional demand on the electricity grid resulting from the growth of electrified track usage was accounted for in the integrated total market for electricity. To avoid double-counting emissions benefits, the results presented for electrified trains do not reflect the increasingly cleaner grid; instead, the additional emissions benefits are accounted for directly in the supply-side energy solutions.
The Plausible Scenario estimates emissions reductions of 0.5 gigatons of carbon dioxide-equivalent greenhouse gases, at a cost of US$808 billion.  The net operating savings, however, can be as high as US$313 billion. The Drawdown Scenario results in emissions reductions of 0.8 gigatons, and the Optimum Scenario shows 4.0 gigatons of emissions reduced from 2020-2050.
Our results suggest that the high cost of rail electrification may be difficult to avoid, even in the case of high track usage (the Optimum Scenario), so the electrification of freight tracks may have to be balanced at least in part by government incentives. Unit costs are lower on high usage corridors, however, so these should be the initial targets for electrification. Additionally, we did not include the use of passenger rail services on electrified tracks (i.e. shared-use corridors), nor other efficiency technologies such as lighter trains and better train control technology, which may provide additional financial benefits or challenges. Overall, rail is already an efficient mode of transport, but it too can have an impact on reducing emissions—although there is an overall net cost to this reduction.
 UIC means the Union Internationale de Chemins–de-fer (French).
 Electrified track length has actually decreased in some years.
 For more on the Total Addressable Market for the Transport Sector, click the Sector Summary: Transport link below.
 Current adoption is defined as the amount of functional demand supplied by the solution in the base year of study. This study uses 2014 as the base year due to the availability of global adoption data for all Project Drawdown solutions evaluated.
 Estimated based on UIC data that indicates that 27 percent of tracks were electrified in 2014. It is assumed that implies that 27 percent of railway freight travels on electrified tracks.
 For more on Project Drawdown’s three growth scenarios, click the Scenarios link below. For information on Transport Sector-specific scenarios, click the Sector Summary: Transport link.
 Note that this doubled rate falls below the historical average for 5 of the 17 years of UIC data. Note also that the doubling applies to the ton-kilometers of freight work performed, not necessarily the kilometers of track electrified, so this could also be interpreted as growth in the usage of existing electrified tracks.
 For more on Project Drawdown’s Transport Sector integration model, click the Sector Summary: Transport link below.
 All monetary values are presented in US2014$.