There are three main ways that vehicles pollute the air: carbon pollution, nitrous oxide pollution and particulate matter pollution. The build-up over time of carbon emissions in the atmosphere is one of the main root causes of the climate emergency we now face. Nitrous oxides and particulate matter on the other hand cause local air quality problems, and can be harmful to human health when breathed in by people both inside and outside the vehicle.
These pollutants are produced by all petrol and diesel engines, and emitted into the air from the exhaust pipe. Particulate matter is additionally released from tyres and brakes during their everyday use.
Many petrol and diesel vehicle engines have been getting cleaner in recent years, reducing the amount of carbon, nitrous oxide and particulate matter pollutants they produce. This has been achieved through improvements to engine technology, as well as using ‘hybrid’ technology, where a vehicle runs in electric mode sometimes and petrol or diesel mode at others.
A low emission vehicle (LEV) produces less than 100g of carbon dioxide for every kilometre travelled. An ultra-low emission vehicle (ULEV) produces less than 75g per kilometre. Some modern petrol, diesel and hybrid vehicles are LEVs and ULEVs. A zero-emission vehicle (ZEV) produces no engine emissions at all (but do still produce particulate matter pollution from tyres and brakes). Electric vehicles that are only powered by batteries are ZEVs.
The UK’s Vehicle Certification Agency publish emissions data for makes and models of cars available in the UK.