Road vehicles

This page provides background information on the health and environmental impacts of air pollution from road vehicles. It also explains how improving the test procedure for new cars will close the gap between emissions measured in the laboratory and emissions in real-life driving conditions.

What’s the problem?

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). In the air NO is rapidly converted to NO2 which will also react in the air to form nitrate particles and ozone (O3). NO2 is a toxic gas harmful for health. NOx emissions also 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 average contribution of local traffic to urban NO2 and PM10 concentrations is estimated at 46% and 15%, respectively. It is estimated that around 7% of the EU urban population is exposed to NO2 levels above the EU/WHO limit value and that approximately 50% of the urban population is exposed to PM10 levels exceeding the WHO guideline value.

What’s Europe doing?

In order to reduce urban air pollution, 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 before the car can be initially sold to ensure compliance.

However, emissions in real-life driving are much higher than emissions measured in the tests carried out in the laboratory. Passenger cars and vans are tested in a laboratory on a rolling road with the level of emissions measured over a drive cycle that is intended to reproduce real-world driving conditions. Unfortunately, the current test cycle fails to accurately reproduce these conditions and therefore is not representative of how European citizens drive their cars in their everyday lives. This implies a gap between the emissions measured in the laboratory and the emissions in real-life driving conditions of around 500% and therefore non-compliance in the real world with emission limits. The so-called “cycle beating” techniques developed by carmakers enable vehicles to meet the limits during tests, increasing this gap. Recent #dieselgate revelations also point to car makers cheating by fitting defeat devices that sense when vehicles is undergoing testing and adjust the emissions performance accordingly, while emitting significantly more when otherwise driven on the roads.

The only way to avoid optimising and cheating the test cycle is to test vehicles on the road in real-world driving conditions. Since 2011 Europe has been working on the so-called Real-world Driving Emissions (RDE) test to do exactly that. The first step of the test, measuring NOx emissions using a Portable Emissions Measurement System (PEMS), will come into effect in September 2017. However, despite the latest NOx limit being set in 2007, car manufacturers are allowed to miss it by 110% from 2017 until 2020 and 50% continuously after that. Such a lax RDE system will not be fully effective in limiting dangerous effects of NO2 pollution as fast as required.

What should Europe do?

To tackle air pollution by road vehicles, the EU should:

  • Introduce in 2017 an improved laboratory test cycle. It should be based on the Worldwide Harmonized Light vehicles Test Procedures (WLTP), a test cycle being developed by the United Nations Economic Commission for Europe (UNECE).

  • Further improve real-world emissions testing using Portable Emissions Measurement Systems (PEMS) that ensure that vehicles meet the EU standards on the road. In particular, the current flexibility given to the industry should be tightened and Real-world Driving Emissions extended to include other pollutants such as particulate matter from 2017.

  • Make the system of type approval more independent and rigorous through the establishment of an EU-wide type approval authority that would then sub-contract testing services to accredited national organisations. Also, require more testing on the vehicles driven on the road to ensure continued compliance throughout a vehicle’s lifetime.

  • Carefully monitor the implementation of Euro 6 standards – which will introduce a reduction of NOx emission limits for new vehicles from 2017 – to see if they effectively achieve a reduction of emissions in real-world driving and adjust the testing procedures to reflect new evidence.

  • Start developing Euro 7 standards to achieve further reductions of air pollutant emissions in line with WHO guidelines. For example, reduce diesel car emissions and align them with limits for gasoline cars to ensure technology neutrality.

  • Create a European framework to help member states and cities implement non-technical measures – low emission zones (LEZ), congestion charges, etc – to reduce road vehicle pollution and to do so in a harmonised and coherent way across Europe.