Road vehicles and air quality

Find out more about the health and environmental impacts of road vehicles on air quality, and see how improving the test procedure for new cars will help.

What impact do road vehicles have on air quality?

Road transport is a major source of air pollution that harms human health and the environment. Vehicles emit a range of pollutants including nitrogen oxides (NOx) and particulate matter (PM). The EU has set limit values for the maximum amount of air pollution citizens should breathe but urban populations are still exposed to levels of NO2 and PM above these limits, mainly due to passenger cars and vans circulating in these areas.

What’s happening?

NOx comprises a mixture of nitric oxide (NO) and nitrogen dioxide (NO2). NO2 is a toxic gas that causes 79,000 premature deaths in Europe per year. In the air, NO is also converted to NO2 in a process that forms ozone (O3). NOx emissions also form secondary particles in the air and contribute to acidification and eutrophication, causing serious damage to ecosystems. Road transport accounts for a third of NOx emissions and is the dominant source in urban, heavily-trafficked areas.

The European Environment Agency estimates that road transport contributes to excessive concentrations about 70% for nitrogen dioxide (NO2) and about 30% for particulate matter (PM). It is estimated that around 7% of the EU urban population is exposed to NO2 levels above the EU/WHO limit value and that more than three-quarters of the urban population is exposed to PM2.5 levels exceeding the WHO guideline value.

Cars in towns and cities are major cause of degrading air quality

How good are Europe’s rules for emissions from cars? 

In order to improve urban air quality, the EU has set limits for the maximum amount of pollution that can be emitted from vehicles. To be driven in the EU, vehicles must meet these standards. Vehicles are therefore tested in a laboratory and on the road to ensure compliance before the car can be initially sold.

The exposure of Dieselgate in 2015 accelerated the development and implementation of a new laboratory test procedure (called Worldwide Harmonised Light Vehicle Test Procedure or WLTP) and, for the first time, a complementary on-road test called Real Driving Emissions or RDE, for which emissions are measured with an on-board Portable Emissions Measurement System (PEMS). As of September 2019, both of these tests are used for the approval of all new cars sold in the EU. This will come into force for all new vans a year later.

In the aftermath of Dieselgate, several national investigations showed that cars and vans emitted much more NOx emissions once driven on the road compared to the official limit. This gap was around 500% on average for Euro 6 diesel vehicles. The use of an on-road test that includes a broader range of driving and testing conditions, coupled with the very recent introduction of third party testing that will enter into force in September 2019 should force car manufacturers to genuinely reduce pollutant emissions from vehicles in real-life conditions.

However, despite the latest Euro 6 NOx limit being set in 2007, car manufacturers are allowed to exceed it by 110% in on-road tests until the end of 2020 and 43% afterwards. 

The current boundary limits for tests don’t capture all driving conditions and it is too soon to tell how carmakers will use these possible loopholes. Moreover, not all regulated pollutants are currently measured by PEMS and further pollutants may be regulated by the future Euro 7/VII standard on which work has begun. Moreover, in-service conformity checks will be crucial to make sure vehicles respect emission limits over the whole duration of use, so that their impact on air quality does not increase over time.

What should Europe do to improve air quality?

To reduce the impact of road vehicles on air quality, the EU should:

  • Tackle the existing fleet of 43 million very dirty diesel cars and vans, namely by making sure recalls are mandatory and not limited to a few member states only. 
  • Use the new type-approval system for cars that enters into force in September 2020 to issue EU-wide recalls where necessary, scrutinise decisions by national authorities, support third-party testing and make sure member states comply with their obligations when it comes to market surveillance of cars already on the road.
  • Develop stringent Euro 7/VII emissions standards for light and heavy duty vehicles to achieve further reductions of air pollutant emissions in line with WHO guidelines. For example: reduce and align diesel and gasoline car emission limits, increase emission durability requirements and increase the amount of regulated pollutants.
  • With the introduction of the Euro 7 regulation, real-world emissions testing using Portable Emissions Measurement Systems (PEMS) should be extended further and improved to ensure that vehicles meet the EU standards on the road under all driving conditions. In particular, the current driving and testing boundaries should be removed, the current flexibility given to the industry should be tightened and all currently regulated as well as unregulated pollutants should be included such as the smallest particles, nitrogen dioxide, ammonia or hydrocarbons.
  • Create a European framework to help member states and cities take necessary measures – namely low emission zones (LEZ) and the gradual phase-out of all internal combustion engines – to improve air quality and tackle climate change.