Graphic showing that NOx emissions from diesel and petrol cars have regularly breached limits

Cleaning London's vehicles

Driving a less polluting vehicle helps reduce London’s toxic air. The Mayor wants to help Londoners choose cleaner vehicles and encourage manufacturers to build them sooner.

With our Cleaner Vehicle Checker tools, you can find out which cars and vans emit the least amount of poisonous gas - nitrogen oxides (NOx).

  • Newer Vehicle Checker - shows independent, real-world emissions ratings for newer cars and vans
  • Used Vehicle Checker - will show how some older vehicles perform on London's roads. We plan to launch this in 2019
  • Cleaner Fleet Checker - fleet operators can use this service to improve their fleet emissions by identifying and replacing their most polluting vehicles

Damage from NOx and CO2


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

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 NOx can inflame the airways in our lungs and, over a long period, affect how well our lungs work.


The greenhouse gas CO2 contributes to climate change, including extreme weather events, sea level rise, floods and drought. The current EU target for CO2 from new passenger cars is 130g/km, but this will drop to 95 g/km by 2021. We have included official CO2 emissions in the Cleaner Vehicle Checker to help people make the greenest choice possible.

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.

Help phase out fossil fuels - go electric

The Mayor wants all new cars driven in London to be zero emission by 2040. Find out how you can save money today by going ultra low with an electric vehicle. Electric vehicles do not produce NOx or CO2 from the tailpipe.

Real-world tests and Euro standards

Real-world vs laboratory tests

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, especially in dense urban environments like London.

On average, new Euro 6 diesel cars emit around four times more NOx when driven on roads, outside of the lab testing environment.

What are Euro standards?

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

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.

Who we're working with

C40 Cities Climate Leadership Group

C40 is a network of the world’s megacities committed to addressing climate change. We're working with them to develop the Cleaner Vehicle Checker as well as a global car rating system building upon the Airvolution announcements in Paris in March 2017.

Emissions Analytics

This independent vehicle testing company created the EQUA index. The EQUA index is a database of ‘real-world’ emissions from a wide range of cars and vans sold in the UK, France and other European countries. The Newer Vehicle Checker will pull NOx information from the EQUA Index.

Emissions Analytics actively tests new vehicles and will keep ratings for the Newer Vehicle Checker up to date. More than 900 vehicles have been tested so far, covering a range of makes, models and engine types.

If a specific model has not been tested, Emissions Analytics can show results for the nearest equivalent model. Find out how the company works out its EQUA Index.

TRUE Initiative

We are also working in partnership with the TRUE Initiative to develop a Used Vehicle Checker. The TRUE Initiative is a group of experts and interested parties, including the FIA Foundation and ICCT (International Council on Clean Transportation), which tries to show the gap between emissions tested in real-world conditions rather than in labs. ICCT will be carrying out a roadside emissions testing programme at London sites in late 2017. 

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