Cleaning London's vehicles

To help improve air quality, the world's first 24-hour Ultra Low Emission Zone (ULEZ) was launched in central London on 8 April 2019 and expanded on 25 October 2021 to include the inner London area bounded by the North and South Circular Roads,

Most vehicles now need to meet certain exhaust emission standards (Euro standards) or pay a daily charge to travel within the zone.

Check if your current vehicle complies with the ULEZ standards.

All combustion processes produce nitrogen oxides (NOx). In London, road transport is the main source of these emissions. However, there are technologies available that can nearly eliminate NOx from engine exhaust before it is released from the tailpipe.

NOx emissions need to be tackled immediately because they are harming the health of Londoners.

NOx is primarily made up of two pollutants - nitric oxide (NO) and nitrogen dioxide (NO2). NO2 is of most concern due to its impact on health. However, NO easily converts to NO2 in the air, so to reduce concentrations of NO2 it is essential to control emissions of NOx.

These gases are formed and released into the air when fuel is burned at high temperatures, for example by diesel and petrol cars. Evidence shows breathing in high levels of NO2 can inflame the airways in our lungs and, over a long period, affect how well our lungs work.

Combustion engines also produce emissions of particulate matter (PM) known as primary particulate matter. In addition, NOx can also react with other compounds in the atmosphere to form secondary particulate matter. PM can cause a wide range of health impacts and affect vegetation by reacting to form smog and acid rain.>/p>

Carbon dioxide (CO2) is a greenhouse gas that contributes to climate change, including extreme weather events, sea level rise, floods and drought. The current EU and UK target for CO2 from new passenger cars is 95g/km. Learn more about the CO2 emissions of new and used cars.

Ideally, drivers will choose vehicles that emit low levels of NOx and CO2.

The Mayor's London Environment Strategy includes longer term strategies to tackle CO2 emissions from transport and buildings, all of which will help put London on a path to becoming a zero-carbon city by 2050.

European (Euro) standards set limits on the acceptable amount of harmful air pollutants coming from the exhaust emissions of vehicles sold in the EU.

Before a new vehicle model is approved for sale in Europe, car makers must arrange for emissions tests to show that it meets the current Euro standard. However, results produced in the lab don’t always reflect the emissions produced by vehicles in 'real world' driving scenarios.

The first Euro standard was introduced in 1992. Since then, EU-wide emissions standards have placed ever tighter limits on exhaust emissions. Euro 6 is the current standard in place, but an important upgrade known as Euro 6d began phasing in from late 2017 and has been fully in place since 2021.