Tracking Clean Energy Progress

On track

Rail is one of the most energy-efficient transport modes, accounting for 8% of global motorised passenger movements and 7% of freight but only 2% of transport energy use. Urban and high-speed rail infrastructures have scaled up rapidly over the past decade, laying the foundation for convenient, low-emissions transport within and between cities. China is leading the way with unprecedented expansion in high-speed rail: passenger activity grew nearly 20% in 2018, more than twice as fast as domestic aviation. Further rail investments in India and South East Asia in particular can help get the transport sector on track with the SDS by displacing more intensive modes such as cars, trucks and airplanes and reducing net energy use and emissions.

Jacob Teter
Lead author
Contributors: Pierpaolo Cazzola, Jacopo Tattini, Till Bunsen

Energy intensity of passenger transport modes

	Average	Blank	Variability at country level
Rail	0.17	0.06	0.72
Two/three-wheelers	0.45	0.35	0.42
Buses and minibuses	0.66	0.43	0.67
Cars	1.78	0.83	2.06
Aviation	1.80	1.04	2.02
Large cars	2.68	1.02	2.63
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Back to Transport sector | TCEP overview 🕐 Last updated Wednesday, May 29, 2019

Tracking progress

While the share of rail passenger-km travelled has been a steady 8% since 2000 despite rapid rail infrastructure expansion, rail operations account for only 2% of transport sector energy use.

Rail services consume less than 0.6 million barrels per day of oil (about 0.6% of global oil use), around 290 terawatt hours (TWh) of electricity (more than 1% of global consumption) and are responsible for 0.3% of direct CO2 emissions.

The low energy and CO2 intensities of rail transport make promoting rail a promising strategy to diversify energy sources and reduce emissions. Shifting passenger and freight services from more intensive modes such as cars, trucks and airplanes would substantially reduce net energy use and emissions and make the Sustainable Development Scenario (SDS) more achievable.


As with all other transport infrastructure, rail investment is expensive. High passenger or freight throughput (i.e. high infrastructure utilisation) is necessary for a rail construction project to pay off, both economically and environmentally. Shifting considerable transport away from cars, trucks and planes also has very important societal and environmental benefits that cannot be fully captured in conventional commercial pricing.

Costs and throughput capacities of urban transport infrastructure

Urban rail is ideally suited to high passenger throughput, and although per-kilometre capital costs are high, costs per throughput capacity are lower than for urban road infrastructure.

Source: IEA analysis based on Rode et al. (2014).

Rail infrastructure investment increased nearly threefold between 2005 and 2015, with most of this growth in China (OECD, 2018), whose share within a group of more than 40 countries has grown from less than 20% to more than half in the past decade.

Urban and high-speed rail infrastructure have expanded with this investment increase, and China leads the way in both categories.

Passenger rail

Passenger rail travel is the least energy- and CO2-intensive of all motorised transport modes. It is also the least oil-reliant by far: globally, about three-quarters of conventional passenger rail activity uses electricity, and the remaining one-quarter relies on diesel.

Furthermore, virtually all urban and high-speed rail networks are electric, and electrification of conventional rail is expected to continue at a rapid pace.

Classification of various railway services and infrastructure

Rail services can be broadly grouped into passenger and freight, then into specific categories based on operational characteristics.

Passenger rail networks are concentrated in a handful of regions – China, the European Union, India, Japan and Russia – that together register 90% of global passenger rail activity.

Despite rapid metro and high-speed rail system expansions in the past ten years, the rail share in global motorised passenger transport has remained roughly constant at 8% over the past two decades.

However, the share remained unchanged because these high rail investments happened during a decade of unprecedented growth in motorised mobility, proving that rail can keep pace in providing affordable, convenient mass transit even as incomes rise in emerging economies.

Using the full potential of rail transport to meet climate targets and Sustainable Development Goals (SDGs) means capitalising on the competitive advantages it has over other modes to raise passenger usage – even as rising incomes spur greater private car ownership and air travel.

Global line-km of rail, 2000‑18

High-speed and metro rail infrastructure is being built at an unprecedented rate; further strategic investment could contribute substantially to SDS goals.

	 Metro	 Light rail	 High-speed rail
2000	5.657	4.199	4.617
2001	5.781	4.273	4.963
2002	5.904	4.348	5.527
2003	6.027	4.422	6.028
2004	6.151	4.497	6.028
2005	6.274	4.571	6.396
2006	6.346	4.641	8.136
2007	6.418	4.711	8.713
2008	6.490	4.781	11.495
2009	6.562	4.851	14.046
2010	6.634	4.921	16.159
2011	6.726	4.994	18.498
2012	6.818	5.067	20.789
2013	6.910	5.139	26.409
2014	7.003	5.212	29.829
2015	7.095	5.285	31.811
2016	7.414	5.326	34.171
2017	8.053	5.367	36.595
2018	9.508	6.336	38.735
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	 Conventional rail
2000	1071.239732
2001	1069.652089
2002	1064.762946
2003	1062.870704
2004	1053.004044
2005	1051.825385
2006	1051.806658
2007	1046.111267
2008	1041.16695
2009	1043.619337
2010	1046.429991
2011	1041.886105
2012	1044.278412
2013	1046.67072
2014	1049.063027
2015	1051.455335
2016	1049.076269
2017	1055.04152
2018	1061.006771
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Note: Conventional rail includes infrastructure used both by conventional passenger and freight rail.

Source: IEA assessments based on UIC (2018a); UITP (2018a); UITP (2017); ITDP (2018); AAR (2017); Eurostat (2018); Indian Railways (2018a); Japan Ministry of Land, Infrastructure and Tourism (2018); National Bureau of Statistics of China (2018); and Russian Federation State Statistics Service (2018).

High-speed rail

Today, around 600 billion passenger-km are travelled by high-speed rail every year, compared with 3 100 billion passenger-km by conventional rail.

More than two out of three high-speed rail tracks are in China: starting from virtually none only a decade ago, the country now has over 41 000 km. The rapidity and magnitude of this achievement make it one of the largest infrastructure projects of recent history, and total high-speed rail activity in China is catching up with passenger aviation.

Long-distance domestic passenger activity in China

High-speed rail passenger activity growth recently outpaced that of domestic aviation travel in China, reducing fuel consumption for aviation, the fastest-expanding mode of transport.

	Conventional rail	Domestic aviation	High-speed rail
2005	0.6062	0.1666	0
2006	0.6622	0.1874	0
2007	0.7216	0.2082	0.0123
2008	0.7779	0.2289	0.0166
2009	0.7879	0.2794	0.0425
2010	0.8762	0.3271	0.0729
2011	0.9612	0.3654	0.0959
2012	0.9812	0.4031	0.1194
2013	1.0596	0.4508	0.1706
2014	1.1242	0.5013	0.2363
2015	1.1961	0.5559	0.3139
2016	1.2579	0.6216	0.3782
2017	1.301	0.7035	0.4641
2018	1.3627	0.7534	0.5501
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Note: Conventional rail includes both commuter and intercity rail services.

Owing largely to China’s commitment to high-speed rail, global high-speed rail infrastructure expanded 3.4 times between 2008 and 2018.

The rate of annual average growth (13%) is historically unprecedented, but continuing investments can contribute substantially to attaining the SDS. Moreover, high-speed rail infrastructure growth – and the investments needed to realise it – will need to spread from China to other densely populated emerging economies such as India.

Urban rail: metros and light rail

Nearly 200 cities worldwide have metro systems, their combined length exceeding 32 000 km; light rail systems add another 21 000 km of track across more than 220 cities.

China’s metro network extensions since 1990 have outpaced the global average, raising the country’s share of global metro networks from less than 10% in 1990 to more than 30% in 2017. Only three Chinese cities had metro services before 1990, compared with 33 in 2018.

New metro systems have opened in 46 cities since 2010, 34 of which are in Asia. In addition, new light rail transit systems have been launched in 65 cities – 28 in Europe, and the rest dispersed roughly equally among North America, Asia and the Middle East, and North Africa – for a total of 400 cities with light-rail systems (some have both metro and light rail).

The length of urban rail lines, which comprise both metro and light rail, has expanded 3.5% per year in the past decade, but even faster growth would help to get on track with the SDS. Not only do urban rail systems help mitigate CO2 emissions and local air pollution, they also provide wider economic benefits to the cities they serve.

Freight rail

About 7% of global freight transport activity (measured in tonne-kilometres) uses rail.

Transporting cargo by rail has the potential to provide the least energy- and CO2-intensive way to move freight of any land-based transport mode, but as with passenger rail, its economic and environmental benefits depend upon the long-term certainty of high throughput volumes on certain routes.

Given that rising demand for rapid delivery of high-value and lighter goods has led to an ongoing shift from rail to road, it will be a challenge for rail to maintain its current share of freight transport.

Benefits of rail

Beyond CO2 emissions reduction potential, many benefits recommend rail as a choice mode of sustainable transport. 

  • In urban environments, rail is unparalleled in its throughput capacity (i.e. the potential to move large volumes of passengers). Its use can therefore reduce congestion, save valuable and scarce space, and generate wider economic benefits such as agglomeration effects. Urban rail is also far safer than road transport and better for local air quality.
  • High-speed rail is the only established low-carbon alternative to aviation for short-distance trips, and freight rail the only alternative to long-distance inland road freight transport. Aviation and long-haul road freight account for large, rapidly growing shares of transport-related energy demand and emissions, and alternative technology options are currently limited.

Exploiting rail potential fully will require supportive government policies and long-term investments, accompanied by strategic market-oriented business decisions by companies that build, operate and integrate rail with other transport modes. Consequently, there are opportunities for many stakeholders.

Rail project planners, operators and technology providers should focus on minimising costs and maximising revenues.

Governments must ensure that all transport modes pay for both infrastructure use and any adverse impacts, for example through road pricing and congestion charges.

Strategic investments

Conventional rail companies will need to upgrade their rolling stock and further electrify services, starting with the most heavily utilised routes. Introducing energy efficiency measures would both reduce environmental impacts and improve economic viability.

The adoption of digital technologies could optimise rail operations and integrate rail more comprehensively with other mobility services, making rail more accessible, convenient and attractive. Digital tools are therefore important for improving operational and energy efficiency, cutting costs and increasing revenues.

Capturing added land value

Monetising the commercial benefits of new rail is central to the economic viability of rail infrastructure projects, especially since average annual rail infrastructure investments will have to continue to grow for passenger rail to retain its current modal shares.

Securing favourable terms for renewable electricity

In this way, some companies may be able to strengthen their environmental credentials and make their operations more sustainable.

Improving the regulatory environment

A regulatory environment that prices transport according to the "user pays" and "polluter pays" principles is critical to provide a level economic playing field across modes of transport, and to unlocking to the significant sustainability benefits of rail.

Innovation gaps

Expanding high-quality urban rail transport depends on political champions, thorough project viability and costs assessments and effective funding, as much as it does on technical issues. Equally important are sound construction, installation of the necessary equipment and hardware, and well-managed operations.

Digital technologies can be used to help integrate rail with other transport modes, provide superior service and increase utilisation to raise revenues and reduce costs.

Digitalization of rail: automation, management and control systems

By reducing the time and distance between trains, digital technologies can facilitate more intensive use of rail infrastructure, which increases capacity and boosts investment returns while improving user convenience and maintaining high safety standards.

Read more about this innovation gap →

Establishing and expanding urban rail networks in existing and future large cities

A rich literature finds that the provision of reliable, convenient, and affordable public transit, and in the case of large cities, metro and light rail, not only reduces the per capita transport emissions in these cities, but can also contribute substantially to reducing levels of pollutants associated with road vehicles, and also enables reductions in the macro- and micro-economic costs of providing urban mobility.

Other studies identify economic and equity benefits that come from urban rail systems.

Read more about this innovation gap →


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  7. National Bureau of Statistics of China (2018), China Statistical Yearbook 2017, , https://www.stats.gov.cn/tjsj/ndsj/2017/indexeh.htm.
  8. OECD (Organisation for Economic Co-operation and Development) (2017), "OECD Data, Infrastructure Investments", , https://data.oecd.org/transport/infrastructureinvestment.htm.
  9. Rode et al (2014), "Accessibility in cities: Transport and urban form", LSE Cities, NCE Cities – Paper 03, , https://files.lsecities.net/files/2014/11/LSE-Cities-2014-Transportand-Urban-Form-NCE-Cities-Paper-03.pdf.
  10. Russian Federation State Statistics Service (2018), "Russia in Figures - Transport", , https://www.gks.ru/wps/wcm/connect/rosstat_main/rosstat/en/figures/transport/.
  11. UIC (International Union of Railways) (2018), "Railway Statistics – Database", UIC, Paris, https://uic.org/IMG/pdf/uic-statistics-synopsis-2017.pdf.
  12. UITP (2017), "Light Rail Transit World Statistics Database", UITP.
  13. UITP (2018a), "World Metro Figures 2018", , https://www.uitp.org/sites/default/files/cckfocus-papers-files/Statistics%20Brief%20- %20World%20metro%20figures%202018V4_WEB.pdf.
  14. UITP (2018b), "Automated Metro Reaches 1 000 km Milestone", Automated Metros Observatory, , http://metroautomation.org/automated-metro-reaches-1000-kmmilestone/#more-4510.


Many thanks to Laurent Dauby of the UITP for providing valuable input and feedback on this section.