The issue of emissions is a quite large subject and concerns all emissions from the railways operations (i.e. diesel, EMF...), but also other topics dealing with infrastructure (herbicides, creosote, Electromagnetic fields), maintenance and indoor air quality.

Diesel emissions

The rail sector is a minor contributor to air pollution, yet railways are constantly working to reduce their air pollution. In Europe, the rail sector’s share of total Nitrogen Oxide (NOx) emissions of transport is only 3% today, as efforts from the rail sector have reduced its NOx emissions by 35% since 1990. The same is true for Particulate Matter (PM), where the rail’s share is 4.5% only and rail’s PM emissions have also been reduced by 35% since 1990.

The UIC coordinates research and information sharing on the reduction of diesel emissions along with partners in the rail supply industry. Key documents and projects are listed below.


The ClearER-D project was launched to find technical solutions to the challenges faced in complying with this new regulation framework. The project also anticipates that further regulation is likely and seeks to provide the sector with dynamic and innovative solutions for future applications should new limits be instituted.

CLEANER-D project website: http://www.cleaner-d.eu/

The UIC Diesel Action Plan in 2003 advocating pro-active measures to reduce diesel exhaust emissions. This Action Plan led to the initiation of the “Rail Diesel Study” which is summarised in the document below. Results have also been presented in the Rail Diesel Study Workshop - Paris, 16th March 2006.

UIC and CER also published a report on "rail diesel emissions - facts & challenges".

In April 2009, the UIC emission network organised a day on particle filters in rail applications, to have an updated view on their possible use in railways.


Biofuel is one discussed solution to greening the transport sector by reducing the amount of CO2 produced by engine fuel combustion.

As shown in the UIC ‘Railways & Biofuel’ report (UIC 2007), test results from railways in Europe and India reveal that biodiesel is technical feasible for use in railway traction units engines in lower blends. However, there are potential disadvantages of using higher blends, e.g. increased fuel consumption and lower engine power. The report was elaborated in co-operation with ATOC.

Biofuel offers potential to lower the carbon footprint of conventional diesel traction. It is possible to reduce CO2 emissions from well to wheel by up to 80% compared to conventional diesel. But recent public discussion on biofuel (fuel vs. food) has shown that it is vital biodiesel meets sustainability criteria and delivers reasonable greenhouse gas emissions, taking into account the production process.

Workshop on biofuels

UIC organised the first Railways and Biofuel Workshop in July 2007 at UIC Headquarters.

The workshop analysed in detail the existing practical experience on biofuel use by railways (as presented by SNCF, Virgin Trains, and Indian Railways), as well as the stakeholders views on sustainability with speakers from United Nations Environmental Program and European Environment Agency.

On the the Workshop the UIC Report ‘Railways and Biofuel’ was presented. The report shows the state of the art of the biofuel tests in railways, with data collected from all over the world, as well as the regulatory framework and the different visions on sustainability concerns.

Electromagnetic fields

Modern society is dependent on the use of electricity. This results in an accumulating exposure to electric, magnetic and electromagnetic fields (EMF). The rapid development of the telecommunications industry requires the placement of new transmitter masts for use as radiotelephone base stations, which often end up being located close to houses, business premises or schools and emit low level non-ionising radiation on a permanent basis. In addition to this ‘passive environmental exposure’ emissions are absorbed from handsets by the head when in use.

Concerning railways the discussion about extreme low frequency electromagnetic fields emitted from overhead lines or catenaries is normally more important than the radio telephony.

UIC has coordinated two research projects on this topic, and has produced leaflets for members with an introduction to the topic; potential health impacts; and mitigation options. These are available to members on our Extranet site (Sustainability section, in the Emissions folder) http://extranet.uic.org

Vegetation management

Vegetation control along railway lines should not harm the environment. This and the increasing pressure to cut costs for vegetation control motivated several railway companies to start various activities to reduce the amount of herbicides used.

The UIC commissioned research in 2003 on the reduction of herbicides in railways, and launched another project in 2011 to update this information. The UIC also published a more general report on soil pollution in 2009.

There is also available UIC Leaflet 723 on vegetation control which is available to UIC members or can be purchased by the general public here: http://www.shop-etf.com

These reports are available to UIC members on our Extranet, http://extranet.uic.org in the Sustainable Land use section in the Sustainability workspace.