Air Quality

Air Quality expert network, Diesel emissions, CLEANER-D, Biofuels, Electromagnetic fields

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.

Air Quality expert network

The UIC Air Quality Expert Network is responsible for sharing best practice, reporting and identifying upcoming issues and future requirements. It works on a variety of topics, including:

  • airborne particulate matter,
  • air quality requirements.

The network began to work on its “Clean Air Trains” project in 2018. As there is currently no legislation regulating public exposure to the indoor concentrations of air pollutants, this project is aimed at developing a methodology for railway environments to compare measured concentrations with limit values in outdoor air, such as values of particulate matter and nitrogen oxide.

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 CleanER-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:

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)

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