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Ultra Low Emissions Zone and Clean Air Zone explained

Learn all there is to know about ULEZ and the newer CAZ across the UK

A green ULEZ sign outside of a block of flats

What is ULEZ?

The Ultra Low Emission Zone (ULEZ) was introduced in London in 2019 to discourage high-pollution vehicles from travelling in the centre of London.

In 2008, London introduced the first Low Emissions Zone (LEZ) for large vehicles like buses, lorries and coaches, and the zone has gradually expanded over the years.

It was hoped that the ULEZ zone would lower pollution in the area and improve the air quality, and the zone has had a positive effect, with studies into the results of ULEZ showing that levels of toxic air have been reduced.

In October 2021, the zone was expanded across the North and South Circular Roads (but not to include the roads themselves), and August 2023 saw yet another ULEZ expansion, with all London boroughs now being included.

The ULEZ is applied at all times, 24 hours a day. The only exception at the time of writing is Christmas Day.

How has ULEZ expanded?

The continued expansion of London’s ULEZ means that as of August 2023, the full city of London and all boroughs are included.

This means anyone with a non-ULEZ-compliant car will have to pay £12.50 to drive within London at any time.

That toll isn’t the same as the existing Congestion Charge cost, however – that's a separate £15 fee, which would bring the daily cost of driving into central London up to £27.50. Ouch.

The move is designed to take older, higher-polluting cars out of already congested urban areas in Greater London.

This is either by encouraging people to use cars with low emissions, or – at the very least – shift heavy pollution away from the most densely populated regions.

Transport for London (TfL) makes no bones about its belief that those wanting to drive through London should switch to a greener car that’s certified to at least Euro 4 emissions standard (more on that below) if it’s a petrol car, or Euro 6 standard if it’s diesel.

The reason for the difference in required standards between petrol and diesel relates to nitrogen oxide (NOx).

Diesel cars typically produce more emissions, so stricter limits are enforced. TfL does, however, believe that four out of five cars in the zone are already ULEZ-compliant.

An updated version of the ULEZ map for 2024

TfL states that petrol cars that meet ULEZ standards are usually those registered with the DVLA after 2005. Some models, however, have been compliant since 2001.

Diesel models usually have to be registered after September 2015 to be compliant.

What are the Euro emissions standards that London uses?

The European Union introduced emissions limits in 1992, and these have been getting increasingly stricter over the years, meaning Euro 4 and Euro 6 have tight limits for how much NOx and CO2 cars can produce.

Due to Euro limits, newer cars don’t smoke or smell anything like their predecessors.

If you’re wondering why the UK – and specifically London and its ULEZ – still use the EU’s emissions limits, it’s because they work.

Is my car ULEZ-compliant?

The rules for the expanded Ultra Low Emissions Zone are unchanged from the current area’s restrictions, which means petrol cars of Euro 4 status and diesel cars of Euro 6 status are exempt from the charge.

You might have heard that almost all petrol cars produced after 2011 are ULEZ-compliant, or that diesel cars from after 2015 are also fine.

Unfortunately, it’s not quite as simple as that, because some cars were produced to a higher Euro emissions level before the laws were passed.

To save the headache of diving into the paperwork, you can find out if your car is ULEZ-compliant on TfL's checker.

What are Clean Air Zones (CAZ)?

Clean Air Zones (also referred to as Low Emissions Zones or LEZ) are areas that have restrictions on emissions much like the ULEZ.

There are four types of CAZ in the UK:

  • Class A: buses, taxis, coaches, or other private hire vehicles

  • Class B: the same as above, plus heavy goods vehicles

  • Class C: all the above, plus vans and minibuses

  • Class D: all the above, plus cars, and motorcycles at the discretion of local authorities

Which cities have Clean Air Zones?

There are a fair few Clean Air Zones across the UK now, as well as LEZs in the Scottish cities of Aberdeen, Dundee, Edinburgh and Glasgow.

You can currently find Clean Air Zones in Bath, Birmingham, Bristol, Bradford, Newcastle and Gateshead, Portsmouth, Sheffield, Southampton and York.

All of these locations fall into a different class of CAZ, so it's best to look into the area you're driving through before setting off on your journey.

You'll need to pay a charge for each area, or a penalty in some cases.

Take a look at the government website to see the exact area, class and charge for each type of vehicle.

Are there any exemptions to the CAZ?

There are a few exemptions from the charges that you might be able to benefit from. These include:

  • driving an ultra-low-emissions car

  • driving a disabled tax class vehicle or a disabled passenger tax class vehicle

  • driving a military or historic vehicle

  • some types of agriculture vehicles

  • a vehicle that's been fitted with technology accredited by the CVRAS (Clean Vehicle Retrofit Accreditation Scheme)

Is a non-compliant car really that bad for the environment?

As is often the case with this kind of thing, many variables determine how 'clean' a used car is.

A car that was listed as a low NOx emitter when new can easily become an inefficient, ‘dirty’ car with poor maintenance.

London’s ULEZ rules don’t take into account the life of a car or the driving style of a motorist, but for a scheme of this scale, a line must be drawn.

So, even if you have the best-maintained non-compliant car, it’ll still be considered too highly polluting to enter without paying the £12.50 ULEZ charge for each day in the zone.

Will a low emissions-compliant car remain so forever?

No, current compliant cars are not guaranteed to be compliant in the future.

TfL has stated that it’ll review the rules in the coming years, and it seems at least plausible that in an increasingly electrified automotive world, there will be increased efforts to limit the numbers of petrol and diesel cars in urban areas.

Cities in China have already developed plans for electric-only zones to cut health-affecting pollution in dense areas, and it’s not hard to see similarly strict restrictions coming into place here one day, especially after 2035, when much of Britain’s road traffic will be electric.

That said, the UK approach has typically been different from other countries because instead of amounting to a full ban on certain vehicles, the rules are more stick than carrot, with drivers of older vehicles having to pay charges.

There are few signs of that changing, so in theory, you could drive through London even if your car eventually becomes non-compliant with ULEZ limits – but it’ll cost you.

Are classic cars exempt?

Interestingly, cars that are more than 40 years old are exempt from the rules, despite coming from an era when emissions limits were practically non-existent.

The reason is that these cars are considered to be historically significant – or classics – and the number of them on the roads is tiny.

Not only that, most classic car owners do very few miles per year, so their contribution to NOx and CO2 emissions is considered to be negligible.

London wouldn’t be the same without the odd classic Mini or Jaguar E-Type darting through its streets, would it?

Does ULEZ actually work?

TfL certainly reckons so. It states that around 4,000 Londoners died prematurely in 2019 because of long-term exposure to air pollution, and that 99% of Londoners live in areas that exceed World Health Organization guidelines for the most dangerous toxic particles.

TfL also claims that since ULEZ was introduced in April 2019, nitrogen dioxide (which, along with nitric oxide, makes up London’s NOx emissions) has been reduced by 44%.

This is the stuff that causes respiratory illnesses and, according to some studies, can impact the development of children’s lungs.

TfL also states that “the number of state primary and secondary schools in areas exceeding legal limits for NO2 fell from 455 in 2016 to 14 in 2019, a reduction of 97%”.

It’s hard to argue with that.

Find a ULEZ-compliant car

All of the cars on our site are ULEZ-compliant, so you can take your pick of the bunch.

Take a look at our full range of used cars, or choose an electric car.

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