An emissions zone (also known as a Clean Air Zone) is an area within a city or town that has restrictions on the type of vehicles that are allowed to enter, or the emissions they are allowed to emit. In the UK, emissions zones are being introduced in many cities and towns to help reduce air pollution. The aim is to reduce the number of vehicles with high emissions entering the zone, such as diesel cars and older petrol cars. These vehicles may be charged a fee to enter the zone, or be completely banned from entering. Examples of cities and towns in the UK with emissions zones include London, Birmingham, Manchester, Leeds, Liverpool, Bristol, Sheffield and Newcastle.