Exhaust Emissions

Reducing emissions from road transport is seen as an important factor in the improvement of air quality

Testing of Emissions at the NCT  & CVT

All cars undergoing the National Car Test (NCT) or Commercial Vehicles Test (CVT) are subjected to exhaust emissions testing measuring the levels of certain gases or of particulates (in the case of diesel engines) emitted by the vehicle under defined test conditions. Vehicles may be tested at varying engine RPM depending on the year of manufacture, the manufacturer’s specifications and the type of engine.

You can learn more about emissions testing requirements in our Vehicle testing section.

How do emissions affect the rate of motor tax payable?

The payment of motor tax on new cars registered from 1st July 2008 is determined on the basis of seven CO2 emissions bands. The rates range from around €100/yr for the ‘greenest’ cars to €2,000/yr for cars with the highest emissions ratings. New cars registered between 1 January 2008 and 30 June 2008 initially had their motor tax charged on the basis of engine size. If it was beneficial for these cars to switch to the CO 2 based motor tax system, this was effected on the first renewal of motor tax after 1 July 2008. New cars which were registered in the first six months of 2008 whose tax would be more under the CO 2 based system will continue to pay motor tax on the basis of engine size. If you know its registration number, you can quickly find out the motor tax rate of a vehicle using the Department of Transport’s motor tax calculator. Further information on motor tax is available from the Department of Environment and Local Government.

Emissions Standards

European emission standards define the acceptable limits for exhaust emissions of new vehicles sold in EU member states. The emission standards are defined in a staged series of EU directives of increasingly stringent standards. Non-compliant vehicles cannot be sold in the EU, but new standards do not apply to vehicles already on the roads.

Different standards apply for each vehicle type. Manufacturers must demonstrate compliance with these standards by running the engine at a standardised test cycle. The use of specific technologies is not mandated, though available technology is considered when setting the standards. New vehicle models introduced must meet current or planned standards, but minor lifecycle model revisions may continue to be offered with pre-compliant engines.

We have prepared information notes on Euro IV, Euro V and Euro VI emissions regulations for heavy duty vehicles (PDF) and Euro 5 and Euro 6 emissions regulations for light passenger commercial vehicles (PDF)