No smoke without ire

Published on 27 October 2021

On Monday 25 October, London's Ultra Low Emission Zone (ULEZ) expanded to cover the whole inner city. Across the UK, other cities are implementing their own Clean Air Zones too. Is this the future of urban motoring?

To see the grumbling online and in some corners of the media, you'd think it had come as a complete surprise and that the change was being jumped on an unsuspecting city by a Mayor acting on a particularly cruel whim. But anyone claiming to be caught out by the expansion of London's ULEZ clearly hasn't been paying attention. The date of 25 October 2021 has been fixed since at least spring 2018, so this change has been coming for almost three and a half years.

London is just one of the cities across the UK that are now getting increasingly tough on polluting vehicles. Many refer to theirs as a Clean Air Zone rather than an Ultra Low Emission Zone, but the effect is much the same. The expansion of London's ULEZ on 25 October seems like a good time to take stock of where we are with all these schemes, so before we dip a toe into the controversy, let's take a tour of the LEZ, ULEZ and CAZ projects appearing nationwide.

London ULEZ

This already existed, but on 25 October its scope widened to cover a massive area. Previously it was aligned with the Congestion Charge, covering an area of about 22km² within the Inner Ring Road. Now its boundaries are the North and South Circular Roads, meaning it's now more than fifteen times larger, covering an area of 380km². You could comfortably fit most of Birmingham into that sort of space. City Hall's prediction is that it will have an effect equivalent to taking 60,000 cars off the road, cutting harmful NOx emissions by 30% within its boundaries.

A new sign for London's expanded ULEZ, unveiled on 25 October. Click to enlarge
A new sign for London's expanded ULEZ, unveiled on 25 October. Click to enlarge

It applies to vehicles driving anywhere within the zone, whether or not they cross the zone boundary, though its boundaries do not appear to be completely watertight. There are simply too many streets and lanes crossing the North and South Circulars to feasibly cover with cameras, so the system seems to rely on covering main entrances and exits, and additional cameras doing spot checks at various undisclosed locations within the zone.

Notably, heavy goods vehicles (over 3.5 tonnes) and larger buses (over 5 tonnes) are exempt from the ULEZ - instead, they must observe the even larger Low Emission Zone (LEZ) which covers all of Greater London and has been running since 2008.

Active Now (since 25 October 2021)
Vehicles affected Cars, motorcycles, vans (up to and including 3.5 tonnes) and minibuses (up to and including 5 tonnes)
Exempt vehicles HGVs, buses and coaches are exempt but subject instead to the LEZ
Petrol vehicles that meet Euro 4 standards
Diesel vehicles that meet Euro VI standards
Daily charge £12.50
How to pay Transport for London’s website
TfL Pay to Drive app
Phone 0343 222 2222
More information Transport for London

Bath CAZ

Clean Air Zone class C logo

Bath's scheme has been up and running since March and is a Class C scheme, meaning it charges buses, coaches, taxis, vans and lorries but not private cars or motorbikes. That means, perhaps a little strangely, that if you're delivering essential goods to businesses in Bath, you're liable to pay the charge, but if you commute into the city every day by private car, you won't pay a thing.

Being a small city in a valley without any sort of bypass, the CAZ covers the A4 and A36, and there's no straightforward route to avoid it without diverting via the M4 or other roads far from Bath itself. However, realistically, the traffic in Bath was always bad enough that few people would have been trying to drive from one side to the other via the city centre before the charge came in.

Active Now (since 15 March 2021)
Vehicles affected Buses, coaches, taxis, private hire vehicles, heavy goods vehicles, vans, minibuses
Exempt vehicles All cars and motorbikes
Petrol vehicles that meet Euro 4 standards
Diesel vehicles that meet Euro VI standards
Daily charge Varies from £9 to £100 depending on vehicle
How to pay website
More information Bath & North East Somerset Council

Birmingham CAZ

Clean Air Zone class D symbol

Launched this summer to much fanfare, Birmingham's CAZ is promoted under the cheery "Brum Breathes" slogan, and covers the whole area within the A4540 Middleway. It is a Class D scheme, meaning it covers all vehicles except motorcycles, and private motorists will have to pay if their vehicle doesn't meet the emissions standards.

Unlike Bath, and indeed unlike London, Birmingham is blessed with a well-developed road network and the boundary for the CAZ is a ring road worthy of the name. Even so, the A38 forms a non-stop through route through the city centre and by design is a quick and easy way to get between the north and south of Birmingham by passing right through the middle. People used to making that journey may now be diverting onto the much slower ring road.

Active Now (since 1 June 2021)
Vehicles affected Buses, coaches, taxis, private hire vehicles, heavy goods vehicles, vans, minibuses, cars
Exempt vehicles Motorbikes
Petrol vehicles that meet Euro 4 standards
Diesel vehicles that meet Euro VI standards
Daily charge Cars, taxis and vans: £8
Coaches, buses and HGVs: £50
How to pay website
More information Brum Breathes

Portsmouth CAZ

Clean Air Zone class B symbol

Arriving at the end of next month, Portsmouth's scheme is a bit smaller in scope, covering a tightly-defined area of the city around the main railway station and the historic streets of Portsea. It's a Class B scheme, meaning it affects buses, coaches, taxis and HGVs, but not cars, vans or motorbikes.

The outline of Portsmouth's charging zone is hard to understand, but it appears to be defined by the need to exclude the Navy's operations to the north of Portsea and the suburbs of Southsea to the south east. The result is a zone that won't be easy to navigate around if you're trying to avoid it, but since Portsmouth has no through traffic that might not be a problem for very many people.

Active Starts on 29 November 2021
Vehicles affected Buses, coaches, taxis, private hire vehicles, heavy goods vehicles
Exempt vehicles All vans, minibuses, cars and motorbikes
Petrol vehicles that meet Euro 4 standards
Diesel vehicles that meet Euro VI standards
Daily charge Taxis and private hire vehicles: £10
Buses, coaches and HGVs: £100
How to pay website
More information Cleaner Air Portsmouth

More on the way

London, Bath, Birmingham and Portsmouth won't be the only places you'll have to pay to drive older vehicles. Their clean air zones are a response to an identifiable air quality problem, where motor traffic contributes a significant proportion of the pollution. And this isn't a case of local authorities coming up with some one-off scheme, either: a framework for operating Clean Air Zones has been set up by the Department for Transport, with the intention that they'll all work the same way and be recognisable no matter where you go.

In Wales, similar schemes are being developed for cities, and even for towns, some as small as Cwmbran. In Scotland, the approach is even more brutal; the forthcoming Low Emission Zone (LEZ) schemes in many Scottish cities are an outright ban on vehicles whose engines don’t meet emissions standards, and if you drive one in, you don’t pay a charge, you simply get hit with a large fine.

England’s CAZ schemes will all fit into one of four classes, they will all offer exemptions for the same engine types, they will all use the same signs, and they will all offer payment through the same central Government website. In this way the CAZ system is similar to the clean air schemes that have been operating in cities in Europe for some years now: in Germany, Umweltzonen cover most major cities, and motorists need to buy and display a nationally-accepted sticker indicating their emissions status to be let in; in France, Crit'Air stickers must be displayed to enter many big cities.

Similarly, the DfT (and the Government) want more of these across the country, they want them to be easy to set up, and if necessary, they will force the hand of local authorities who are reluctant to join in. This, for example, is from the website explaining the forthcoming scheme in Portsmouth:

"Portsmouth City Council was identified by central government as one of over 60 local authorities that had air pollution levels in excess of legal limits. As such, we've been told to make an improvement as soon as possible.

"Our technical work shows that a package of non-charging measures, even with the natural reduction in polluting vehicles over time, will still not be enough to achieve the necessary level of improvement in air quality. Therefore central government requires us to implement a charging Clean Air Zone."

It wasn't an option. Air quality in Portsmouth is unacceptably poor, and a Clean Air Zone was required.

The 60+ local authorities who have air pollution levels that breach legal limits will all be required to do something to tackle the problem. Not all will need a Clean Air Zone, and a few will already have them: Bath and Birmingham, for two, plus the London Boroughs that fall within the ULEZ. But it's certain that more CAZ projects are in the pipeline. Here's a summary of some of the cities talking about Clean Air projects (known as Low Emission Zones or LEZ projects in Scotland). This list is just for illustration and it's not exhaustive.

City Proposal Start date More information
Bradford Class C CAZ covering the whole area inside the Outer Ring Road, plus the Aire Valley, Shipley and Saltaire January 2022 Bradford Metropolitan District Council
Bristol Class D CAZ covering the city centre Summer 2022 Bristol City Council
Cambridge Class C CAZ under consideration   Cambridge City Council
Cardiff City centre CAZ being investigated   Cardiff Council
Derby Rejected in favour of "traffic management measures"   FleetWorld
Edinburgh Consultation happening for city centre LEZ   City of Edinburgh Council
Glasgow City centre LEZ in place for buses and coaches; expands to all vehicles in 2023 June 2023 Glasgow City Council
Greater Manchester Class C CAZ covering all of Greater Manchester, excluding M60, M61, M62, M66, M67, M56, A627(M) and A555 May 2022 Clean Air Greater Manchester
Leeds Proposed CAZ cancelled in 2020 due to improvements in air quality   Leeds City Council
Leicester Proposed CAZ cancelled earlier this year due to improvements in air quality   Air Quality News
Liverpool CAZ under consideration but no decision made   Liverpool City Council
Newcastle Class C CAZ being considered, starting Summer 2022, but no final decision yet   Newcastle City Council
Oxford Zero Emission Zone (ZEZ) pilot scheme starts next year in the city centre, expanding to cover more of the city later February 2022 Oxfordshire County Council
Sheffield Class C CAZ covering the city centre within the Inner Ring Road, plus a short length of Sheffield Parkway. Due to start in late 2022 but currently under review   Sheffield City Council
Southampton Proposed CAZ cancelled in 2019 in favour of other measures to improve air quality   Southampton City Council
Stoke-on-Trent Class C CAZ under consideration   City of Stoke-on-Trent

Of these, the Greater Manchester scheme is perhaps the most ambitious - it'll cover the whole of the Greater Manchester conurbation, from Bury in the north to Wythenshawe in the south, excluding only the motorway network and a couple of other major road links. Other cities have gone to some real trouble to avoid having to put a CAZ in place; Southampton, for example, has thrown money at taxi drivers and bus operators to upgrade their vehicles, and built a new distribution facility for the city centre to coordinate and consolidate deliveries into fewer, cleaner lorries. Other cities have cleaned things up quickly enough that their CAZ plans were no longer needed.

But this isn't an end of it, by any means - clean air standards will keep getting cleaner, and just because a city has air pollution at acceptable levels now doesn't mean it will always remain so. If, for example, Leicester's air pollution levels worsen again, or if they aren't able to keep ahead of legal limits for air pollution, it's possible that a CAZ will one day be mandated.

The good news for the private motorist is that only class D, the strictest type of CAZ, levies a charge on cars and motorbikes (and even then, motorbikes are optional and up to the discretion of the local authority). It's worth knowing which categories might affect you, so in full, here are the four types of CAZ.

  A B C D
Buses CAZ class A CAZ class B CAZ class C CAZ class D
Coaches CAZ class A CAZ class B CAZ class C CAZ class D
Taxis CAZ class A CAZ class B CAZ class C CAZ class D
Private Hire vehicles CAZ class A CAZ class B CAZ class C CAZ class D
HGVs   CAZ class B CAZ class C CAZ class D
Vans     CAZ class C CAZ class D
Minibuses     CAZ class C CAZ class D
Cars and motorbikes       CAZ class D

All Clean Air Zones in England will use the same signs, with a cloud symbol containing the letter A, B, C or D to indicate the class. Signs in Scotland and Wales will differ but the principle will be broadly the same, while London's LEZ and ULEZ boundaries will be marked with their own signs since they've been in use since before the CAZ symbol was devised.

The smog of war

It would be wrong to discuss Ultra Low Emission Zones, Zero Emission Zones and Clean Air Zones without mentioning the controversy that surrounds them.

We all want to breathe clean, healthy air, of course, and we all understand that a lungful of tailpipe emissions will no nobody any good. But not everyone agrees that a charging scheme is the way to fix an air pollution problem.

This way to the ULEZ. Click to enlarge
This way to the ULEZ. Click to enlarge

For one thing, these schemes target older cars that are generally on their way to the scrapheap anyway; for another, they target and penalise people who are unlikely to be able to afford a new car or van. Sole traders on low incomes are the hardest hit when their second-hand white van is suddenly subject to a daily pollution charge, and it's hard to argue that's fair when a wealthy person in a newer car can drive to work every day and be unaffected.

It's also fair to ask whether a CAZ is going to do enough to clean up a city. Portsmouth's new CAZ scheme covers most of the city centre, but carefully excludes the Naval facilities along the waterfront and the ferry port, for example - will reductions in pollution from private vehicles visiting city centre shops and offices do anything to offset the damage done by the military vehicles and diesel-powered cross-Channel ferries that will continue to operate right alongside it?

All the same, it's hard to argue that we should stand by and accept the world as it is: air pollution is better understood today than it was even a decade or two ago, and even in a world that has eliminated visible smog from our cities, people are still falling ill and dying from the noxious particulates in our air. A Clean Air Zone might not be the total answer to that, but nobody is claiming that it is - it's one possible tool that can be deployed to address a big and complex problem.

Will they work as well as their proponents hope? It's too early to say, with any of these schemes. But let's hope they do. We'll certainly have the opportunity to find out, because more of them will be appearing across the country before you know it.

Clean Air Zone ends sign


Brandon 27 October 2021

Lovely read, I would like to see CAZs as a social barrier, one that allows posh people living in the suburban remote towns to drive their electric Land Rover and get a boba tea downtown, while the self-emplyed Amazon drivers have to take out a second mortgage to replace their 03 reg Fiesta van just to get by.

It's also important to point out that many of these councils have no proper infrastructures in place for communters to even think about switching to bikes. I am not saying that there are no plans at all, but it just seems that their bike or cycle-to-work initiatives are not as enthusiastic as their CAZ, which is frustrating.

Simon Morgan 28 October 2021

The LEZs in Scotland will be different. They impose a total ban on the more polluting vehicles (but with various exemptions). There's no option to make a modest payment on line; if you get caught in one, it will be the full civil penalty charge.

Martyn Clapham 29 October 2021

I think you need to expand the exempt vehicle sections as not all diesel vehicles are regulated by the Euro regulations with Roman numerals ( They are for heavy-duty engines only ).

My car is Euro 4 but I get told by the CAZ checker on that I need to pay. That's because my car is diesel and I believe the CAZ limits are Euro 6 for diesels.

One other thing. It seems odd that a diesel car with a particulate filter has to pay but a petrol car without one doesn't. Wasn't there some research showing that petrol cars produced the 2.5 micron sized particles that are worse as they get deeper into the lungs?

Gareth J. Thomas 30 October 2021

“This list is just for illustration and it's not exhaustive.”

Pun intended? Haha.

An interesting article, and I am glad that the same standards will be applying to all of them. I checked my car and it is OK to drive it into any of these zones.

I have also had a slight chuckle at the “FURY” and “OUTRAGE” in the papers about the ULEZ expansion, because as you say it is not as if the date hasn’t been known about for many years.....

Peter 31 October 2021

“since Portsmouth has no through traffic that might not be a problem for very many people”.

WRONG! The city forms one of only three access routes from the Isle of Wight to the mainland.

Michael Johnson 2 November 2021

More vehicles are exempt from the London LEZ/ULEZ than the examples given above.

Vehicles in the Historic tax bracket (over 40 years old) are exempt - although it's not quite as simple as that.

Vehicles in the Historic tax bracket built before January 1 1973 are exempt under all circumstances; vehicles in the Historic tax bracket built after January 1 1973 are exempt only if they are not in commercial use.

I think this slightly odd stipulation is to capture fees from the Citroen HY coffee vans in London. All of these are old enough to fall into the Historic tax bracket, but most are post-1973. Rather incredibly, Citroen built the HY van - introduced 1n 1947 but essentially a 1930s design - right up to 1981.

It may seem strange to exempt the oldest vehicles from the ULEZ charge - after all, they're the dirtiest ones, right? But in reality there are so few old vehicles in use they don't make any measurable difference to air quality. After all, it's not like London's roads are choked with 1950s Morris Minors and 1960s Ford Cortinas.

The Historic exemption is a bit academic, really, since the vehicles that benefit are virtually non-existent anyway. But it does mean that traders at the Classic Car Boot Sale, held twice a year in Kings Cross, can drive to the site.

Showman's vehicles are also exempt, regardless of age - so the travelling fair can come to town. There is a requirement to be genuinely involved in the trade, though. You can't just go out and buy an old Foden generator truck and use it as your daily driver. You'll be expected to prove you really are the fairground sparky.

Agricultural vehicles are also exempt, although in this case I can't find any requirement to prove you are actually a farmer. So buy that combine harvester today!

Lucas Blake "B… 2 November 2021

This is a smart idea, but it is beginning to look overused due to many cities introducing them in recent years.
(this is just my opinion)

Carole Newman 2 November 2021

Trying to leave politics aside, it's strange to see that the leader of Portsmouth City Council seems to be against the scheme. Might be interesting to see what happens after the 'two years' he mentions, runs out.

Thomas 16 December 2021

My car is a 2004 petrol produced in fairly small numbers (about 1500 UK registrations). This predates the Euro 4 standard, and yet the government's checker claims I do not need to pay CAZ/ULEZ charges. I'm worried that at some point in the future some computer or person will "realise the mistake" and back-bill me and maybe even levy penalty charges. Am I at risk of such back-billing?

No you're not, only if they re-classify the vehicle and you then go into the ULEZ. Using ANPR, they'll capture your car's reg number, and check to see if payment has been made, (you have until midnight of the third day after the day ouf the journey to pay the tll (£12.50). If you don't pay they'll issue a Penalty Charge Notice to the keeper as recorded on the V5 for the vehicle. If you get one, you can appeal it, (you weren't in the zone), or pay. There is a discount option (50%) for early payment of the PCN. Remember that there is also the London Congestion Charge. The two schemes are totally separate and paying the ULEZ toll does not cover you for the CC

Peter Nicholls 20 December 2021

What’s interesting is most studies and data shows now that the improvements in air quality begin and are quite well established well before the official start dates of these zones. Simply announcing the intention seems to change behaviour almost immediately.

There’s lots of concerns about the class and social divide here, but Birmingham for example has a fantastic public transport network for a start. Euro 4 emissions were introduced on all new cars from January 2005 and all newly registered cars from January 2006. Most cars on the 2nd hand market would be compliant and exempt

Ben 29 April 2022

There's also another type of restriction being implemented with lower speed limits now appearing on some roads to limit air polution, this can be seen on the M4 between J41 and J42 with the speed limit orginally being 70 now 50 with average cameras and signs stating that's to do with air quality

Add new comment

About text formats

Restricted HTML

  • Allowed HTML tags: <a href hreflang> <em> <strong> <cite> <blockquote cite> <code> <ul type> <ol start type> <li> <dl> <dt> <dd> <h2 id> <h3 id> <h4 id> <h5 id> <h6 id>
  • Lines and paragraphs break automatically.
  • Web page addresses and email addresses turn into links automatically.
All comments posted to are moderated before appearing online. Your comment won't be visible immediately.


What's new

South London's lost motorways

Completing the story of London's epic Ringways, we've just published the Southern Radials, five more motorways that never saw the light of day.

To the north east!

Two new additions to our collection of Opening Booklets take us to Darlington and Middlesbrough.

The ghost junction

The only UK motorway that didn’t connect to ordinary roads finally got its own interchange in 2019. But it's not open, because it still doesn’t touch any ordinary roads.

Share this page

Have you seen...

M1 Architecture

The most unique motorway in Britain owes its identity to its fifties architecture. Much of it is in danger of being removed or irreperably altered. This page documents it in detail.

About this page

Published27 October 2021

Last updated8 November 2021