What is a clean air zone?

Updated: 29 August 2023

Clean air zone, Ultra Low Emission Zone, Zero Emission Zone – they go by many names and there’s likely to be one already operating, or coming soon, to a city near you. They’re designed to improve urban air quality by discouraging high-polluting vehicles from entering them. To do this the cities either charge a daily fee to the car’s owner or, as in Scotland, impose a penalty for entering the zone.

Most of these zones target buses, taxis and trucks but a few also target more highly polluting cars including comparatively new diesel models. In most cases, electric cars are exempt. Here’s our guide to where to find clean air zones, which cars attract charges by entering the zones; how much those fees are and whether your car is exempt.

A clean air zone (CAZ) is an area within a city where pollution levels are most severe and where vehicles with high levels of exhaust emissions are charged a fee for entering. By charging fees, local authorities hope to encourage drivers to switch to less-polluting vehicles or to walk, cycle or use public transport.

There are four classes of clean air zones.

• Class A covers buses, coaches, taxis and other private-hire vehicles. Buses and coaches must meet Euro 6 emissions standards to be compliant.  Taxis and private-hire vehicles must meet  Euro 4 for petrol engines and Euro 6 for diesel.

• Class B adds heavy goods vehicles (HGVs) to the above list, which must meet Euro 6 standards to be compliant.

• Class C adds light good vehicles (LGVs) such as vans and minibuses, which must also meet Euro 4 standards for petrol or Euro 6 for diesel. For example, Bradford’s CAZ is described as “Class C+”, meaning that there are charges for all non-compliant vehicle types except for passenger cars and motorcycles.

• Class D is the most common type of CAZ and covers all of the above plus cars, with the option of including motorbikes and mopeds. Cars must meet Euro 4 (petrol) or Euro 6 (diesel) standards, while two-wheeled machines must comply with Euro 3 standards.

You’ll know when you’re about to enter a CAZ due to prominent road signs. The signs may have  a drawing of a camera to remind you that cameras are being used to identify each vehicle entering the zone and whether it should be charged a fee.

The Ultra Low Emission Zone, known as ULEZ, is London’s clean air zone. Before, it covered the same area as the capital’s Congestion Charge Zone, but it expanded in late 2021 to cover the area up to – but not including – the North Circular and South Circular roads. A further ULEZ expansion took place on 29 August 2023. Vehicles that don’t meet the ULEZ emissions standards must pay both the ULEZ charge of £12.50 per day and the congestion charge of £15.

The ZEZ is a scheme in Oxford that goes beyond the standard CAZ restrictions. Introduced as a pilot scheme in early 2022, the Zero Emission Zone covers a small area in the centre of the city. Zero-emission vehicles like electric cars are exempt, but all petrol or diesel vehicles are charged. The local government intends to widen the ZEZ in the future, but no date has been announced.

Ultra-low emission vehicles emitting less than 75g/km of carbon dioxide (CO2) are charged £2 a day, set to rise to £4 a day from August 2025. The same charges apply to motorbikes and mopeds. Vehicles that meet the clean air zone requirements (as described earlier) are charged £4 a day (£8 from August 2025), while vehicles that don’t meet the standards are charged £10 a day, rising to £20 from August 2025.

• What is a ULEZ-compliant car?

• Everything you need to know about the 2023 ULEZ expansion

• Petrol vs diesel cars: which should you buy?

Low Emission Zones (LEZs) are the Scottish equivalent of a CAZ, but operate in a different way. Rather than requiring older cars with higher emissions to pay a fee to enter the zone, LEZs require all cars that enter to be compliant with emission standards, or face a penalty. The standards are identical to a Class D CAZ.

London also has a LEZ, but it’s aimed at heavy diesel vehicles and doesn’t apply to cars or motorbikes.

Air pollution has been shown to be a major contributor to heart and lung disease, strokes and cancers. It’s a complex mix of particles and gases, with particulate matter and nitrogen dioxide being major components of vehicle emissions.

Data from Transport for London suggest that half of the city’s air pollution is caused by road traffic. As part of its clean air strategy, the UK government has set legal pollution limits for particulates and is encouraging councils to establish clean air zones.

There are 14 zones either operating or expected to be operating soon in the UK. Most are Class D zones in which certain cars, buses and commercial vehicles are charged fees, but five are Class B or C zones where fees are not charged on cars.

As of summer 2023, the clean air zones are:

Bath
The Bath CAZ came into force in January 2021. It’s a Class C CAZ that doesn’t include cars or motorbikes.

Birmingham
Birmingham’s scheme started in June 2021. As a Class D CAZ, it includes cars. Non-compliant cars are charged at £8 a day.

Bradford
Bradford’s local authority describes its CAZ as Class C+, which means all non-compliant vehicles are charged except passenger cars and motorbikes. The scheme started in September 2022.

Bristol
Bristol’s Class D CAZ went live in November 2022. Non-compliant cars are charged £9 a day.

London
The ULEZ in London operates under Class D rules and was introduced in 2019. Non-compliant cars are charged £12.50 a day, so making sure your car is ULEZ-compliant could save you money. The boundary of the ULEZ expand on August 29, 2023.

Manchester
Manchester was set to implement a Class C CAZ in 2022, but the scheme was put on hold by the Government and is under review  after a public backlash. 

Newcastle and Gateshead
Tyneside’s Class C CAZ became active in January 2023. Cars are exempt, but non-compliant vans, taxis and minibuses are subject to a £12.50 daily charge.

Sheffield
The Sheffield CAZ went live in February 2023. It’s a Class C zone, which means cars are exempt, but non-compliant vans, minibuses and taxis face a £10 charge per day. 

Oxford
The Zero Emission Zone (ZEZ) in Oxford is active as a pilot scheme in a small area of the city centre, but there are plans to expand it. Only zero-emission cars are exempt, while all other vehicles pay between £2 and £10 a day. Those charges are set to double from August 2025.

Portsmouth
In effect since November 2021, Portsmouth’s Class B CAZ doesn’t apply to private cars and vans. However, non-compliant taxis and private hire vehicles must  pay £10 a day.

Glasgow
Glasgow’s Low Emission Zone (LEZ) went active from June 2023. Non-compliant vehicles are in line with Class D CAZ rules, although residents have a grace period until 31 May 2024 before they’re fined. There are no charges for non-compliant vehicles, just a straight penalty of £60. The charge is doubled for each subsequent offence, capped at £480 for cars and vans.

Dundee
The Dundee LEZ has been active since May 2022, but isn’t being enforced until 30 May 2024. The rules and penalties are the same as for other Scottish LEZs.

Aberdeen
Aberdeen is also not enforcing its LEZ immediately. It went active in May 2022 but no penalties will be issued until 1 June 2024.

Edinburgh
The LEZ in Edinburgh went live in May 2022 and, as with Aberdeen and Dundee, is penalty free until 1 June 2024.

Depending on the city, charges range from £2 to £12.50 per day and are triggered by the vehicle’s emissions standard. This measure of a vehicle’s exhaust emissions was created by the EU in 1970 and the first was called Euro 1. Each new Euro standard is tougher than the last and we’ve now reached Euro 6. Each Euro level sets different emissions limits for petrol and diesel cars, because of  the (usually) higher particulate emissions of diesels.

Generally speaking, Euro 4, introduced in January 2005 but mandatory on all new cars registered from January 2006, is the minimum standard required for a petrol car to enter a Class D clean air zone and London’s Ultra Low Emission Zone without attracting a charge.

A diesel car must comply with Euro 6, which has been in force on all new cars registered from September 2015, although some cars registered before that date are also Euro 6. You can find your car’s emission standard on your car’s V5C registration document or your vehicle manufacturer’s website.

It’s easy to find out whether your car will be charged  to enter a clean air zone by using the checker on the Government website. Enter your car’s registration number and it’ll give you a simple yes or no. The TfL website has a similarly simple checker that allows you to find out whether you need to pay the London ULEZ charge.

It’s important to note that in Scotland no access charge is levied. Instead, a £60 penalty is imposed on non-compliant cars that enter the zone, doubling for each offence.

In Class A, B and C zones, cars are not charged fees. In Class D zones, petrol cars complying with at least Euro 4 and diesel cars complying with at least Euro 6 pay nothing. Oxford is an exception in that only electric cars pay nothing while even low-emission cars pay £2. In most cities, motorcycles and historic vehicles more than  40 years old pay nothing.

Typically, there are discounts for people living within a zone, for Blue Badge holders and for vehicles with a disabled tax class although this is by no means universal, so check before entering.

Most zones operate 24 hours a day all year round, with no exemption for bank holidays other than Christmas Day. Depending on the zone, if you don’t pay the charge you may receive a penalty charge notice which, in London, imposes a fine of £160, or £80 if you pay within 14 days.

In Scotland, non-compliant cars pay a £60 penalty for entering the zone. There are plans to double this with each subsequent breach of the rules.

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