Air Quality

The Challenge

Nitrogen dioxide (NO2) is an air pollutant associated with urban areas. It is strongly linked with traffic emissions. High levels affect our lung health. A move towards more sustainable transport modes is essential to see improvement in this area.

The World Health Organisation (WHO) has found that ambient air pollution accounts for an estimated 4.2 million deaths per year due to stroke, heart disease, lung cancer and chronic respiratory diseases. 

Graphic illustrating outdoor air pollution caused by the following factors; Industry and energy supply, Dust, Transport, Agricultural Practices, Waste and Household Energy

Around 91% of the world’s population lives in places where air quality levels exceed WHO limits. Ambient air pollution can affect developed and developing countries alike.

The WHO states that policies and investments supporting cleaner transport, energy-efficient housing, power generation, industry and better municipal waste management can effectively reduce key sources of ambient air pollution

Graphic illustrating solutions for air pollution e.g invest in energy-efficient power generation
Air quality indicator

Back home, in 2019 the Environmental Protection Agency issued a report covering Air pollution in Dublin and found:

  • that many areas in Dublin have high levels of the air pollutant Nitrogen Dioxide.
  • levels are highest at urban traffic locations with some locations at risk of exceeding the statutory EU limit for Nitrogen Dioxide.
  • if further studies confirm that the levels of Nitrogen Dioxide have been exceeded, local authorities in Dublin and its suburbs will be required to prepare air quality action plans for the Dublin area.


On a European level, according to Eurostat figures, Ireland had the fourth highest levels of CO2 equivalent emissions per capita in the European Union in 2016 with the transport sector directly responsible for almost 20% of these emissions.

What CIÉ are doing

Fuel consumption continues to fall year-on-year with the continued renewal of our bus fleet and increased operational efficiency across our operations. Commuter CO2 emissions are generally up to 80% lower, on a per seat basis when compared with private car use.

Through the National Transport Authority (NTA), a procurement process has commenced for up to 600 double-deck hybrid buses, as a key element of the BusConnects programme.

This process is part of the transition to low emission buses, including electric buses, for the urban public bus fleet, as provided for in Project Ireland 2040 and the Climate Action Plan. The first delivery could take place before the end of 2020.

Hybrid Dublin Bus in O'Connell Street

While the EU’s revised Directive on the promotion of clean and energy-efficient road transport vehicles (a.k.a. the ‘Clean Vehicles Directive’) is not expected to enter into force until sometime in 2021, the NTA’s aim is to ensure compliance with the directive for all new city buses delivered from 2020 onwards.  

The new buses will be capable of zero-tailpipe-emissions operation. This capability, combined with the overall reduction in energy consumption, will contribute to an improvement in air quality in the Irish cities that will be served by these buses.

Poster that reads; We're driving change with our new hybrid buses
Hybrid Dublin Bus in O'Connell Street
  1. This electric hybrid Dublin Bus saves up to 35% fuel
  2. The electric hybrid Dublin Bus vehicle will save 27 tonnes of carbon dioxide in one year
  3. The electric hybrid Dublin Bus vehicle will save up to 33% on air quality emissions
  4. The electric hybrid Dublin Bus vehicle is Ultra low Emissions Zone (ULEZ) certified
  5. The electric hybrid vehicles our next step toward zero emission vehicles in the Dublin Bus fleet

​The DART expansion programme

The DART expansion programme, supported by Project Ireland 2040, includes the expansion of the DART fleet by 300 carriages envisaged to be electric or battery-electric hybrid.  This will result in 80% of all journeys on the network being made on non-diesel services. Based on the current energy supply profile, this would see an estimated 40% reduction in emissions from rail services on the Drogheda, Maynooth and M3, and Hazelhatch lines. 

DART at landsdowne road train station

However, as electricity supply sources become more sustainable, ultimately it sets the Greater Dublin Area rail services on course for a potentially emissions-free future, as well as generating reductions in noise, and cost savings in train operations.

The DART Underground project, yet to receive Government funding, will produce a change in rail efficiency, accessibility and quality within the Greater Dublin Area, as well as more travel options for rail users. The project comprises a tunnel linking the Northern line to the Heuston mainline with new underground stations at Docklands, Pearse, St Stephens Green, Christchurch and Heuston and a surface station at Inchicore.

Improved rail access and relief of capacity constraints to the centre of Dublin are crucial to the cities future growth and prosperity. DART Underground provides an efficient and environmentally sustainable alternative to road transport and the capacity to enable growth within an otherwise constrained city centre. DART Underground is consistent with local, national and regional plans and strategies. DART Underground will improve travel in Dublin by:

  • Reducing the need to interchange by providing direct routes for many trips whilst at the same time providing new interchange opportunities, linking the disparate rail lines into a network;

  • Providing additional capacity, thereby reducing crowding, improving journey quality and enabling new development, especially in the Central Business District (CBD);

  • Enabling higher frequencies and improved reliability; and

  • Switching trips from car to rail thereby speeding up remaining road traffic.