Motor Insurance

Scoreboard | Which local areas have fewer polluting diesel cars, and which don't? See how LEZs are working.

The UK wants to reduce traffic-related pollution, with some cities introducing low emission zones to keep out the worst-polluting vehicles. How have these efforts affected the number of heavily-polluting vehicles in different areas? NimbleFins takes an in-depth look at data from the Department for Transport to find out.

Low emission zones (LEZs) discourage drivers with the worst polluting vehicles from entering certain areas. Drivers with vehicles that do not meet certain standards for exhaust emissions will receive a fine if they drive into an LEZ.

The penalties make driving a polluting vehicle quite costly. For example, in London, the daily ULEZ charge for entering the expanded ULEZ is now £12.50. Failure to pay results in a penalty charge of £160 (reduced to £80 if paid within 14 days). And these ULEZ charges are on top of congestion charges of £15.00 a day in central London.

How have these zones and penalties impacted the number of non-compliant diesel cars in different areas of the UK? Let's take a deeper look at the figures by UK region, as well as the cities that have implemented or proposed a low emission zone. We'll also identify the local areas where there's been the biggest improvement in the UK—and even identify some local areas where we suspect used diesel cars are ending up after being sold from areas with low emission towns.

Comparing polluting diesel cars by regions of the UK

By a mile, London is the region of the UK that has done the best at reducing heavily-polluting, non-compliant diesel cars. This is not a surprise given the ULEZ initially imposed on central London in April 2019 and subsequently expanded on 25 October 2021. By end of June 2021, the number of diesel cars in London not meeting Euro 6 emission standards had dropped 41.6% from the end of 2017.

The new London low emission zone is 18 times the size of the original central London zone and covers 3.8 million people across one quarter of London. In fact, it's the largest low emission zone in all of Europe.

After London, Scotland has seen the most marked reduction in heavily-polluting diesel cars, with a 28.7% reduction from year-end 2017 to the end of the second quarter in 2021.

The worst region of the UK for reducing the number of non-compliant diesel cars is Northern Ireland, which has only seen a 13.6% drop in registered diesel cars that do not meet Euro 6 standards since 2017.

Drop in pre-Euro 6 diesel cars by UK regionQ4 2017Q2 2021Change
3West Midlands968,336754,076-22.1%
4South East1,453,7071,151,850-20.8%
6North East376,986310,288-17.7%
7Yorkshire and The Humber834,639689,876-17.3%
8North West995,810823,541-17.3%
9South West1,024,496855,345-16.5%
11East Midlands803,827684,091-14.9%
12Northern Ireland455,917393,856-13.6%
United Kingdom10,223,5818,112,272-20.7%

How have LEZs impacted the number of polluting cars locally?

Let's look more carefully at how the introduction of low emission zones in specific areas has affected the number of polluting cars in a local area.

In April 2019, a central London ULEZ covering all or part of 7 boroughs (that is, 7 of the 14 "inner London" boroughs) was introduced. These 14 inner London boroughs all fall within the expanded ULEZ zone effective 25 October 2021. Consequently, there's been a 53.6% drop in non-compliant diesels in inner London since 2017.

Outer London, which has 9 boroughs falling within the expanded zone, now has 37% fewer non-compliant diesel cars than in 2017, bringing the overall London average to -41.6%.

Birmingham also introduced a low emission zone that has been effective for cars since 14 June 2021. This has also had a remarkable impact on the number of non-compliant cars in the area. As of 30 June 2021, there were 46.3% fewer diesel cars registered that did not meet Euro 6 standards compared to 2017.

As you can see in the table below, low emission zones work. Cities that have implemented or have a planned low emission zone have seen the biggest drop in heavily-polluting cars. Cities where zones are simply being considered or where zones do not cover private cars have not seen significant drops in non-compliant cars.

City AreaChangeRegarding How LEZ Covers Cars
Inner London-53.6%Cars in central London ULEZ zone from April 2019
Birmingham-46.3%Cars from 14 June 2021
London-41.6%Cars in central London ULEZ from April 2019; expanded ULEZ from 25 October 2021
Outer London-37.0%Cars in expanded ULEZ zone from 25 October 2021
Aberdeen City-30.1%Cars from 2022, but only enforced from spring of 2024
City of Edinburgh-26.3%Cars from 31 May 2022, but only enforced from 01 June 2024
Glasgow City-25.0%Cars from 01 June 2023
Dundee City-23.1%Cars from spring of 2022, but only enforced from spring of 2024
Bath and North East Somerset-20.6%LEZ zone and charges don't apply to private cars
Newcastle upon Tyne-16.4%LEZ zone and charges don't apply to private cars
Liverpool-16.3%Zones currently being assessed
Sheffield-12.7%LEZ zone and charges don't apply to private cars
Bradford-9.2%LEZ zone and charges don't apply to private cars
Manchester-4.1%LEZ zone and charges don't apply to private cars

20 Best UK Local Areas for Reducing Non-Compliant Diesels

Looking at the data on a local level (e.g. local authorities, unitary authorities), it's perhaps not surprising that 17 of the 20 best areas for reducing heavily-polluting cars are in London. Camden tops the charts, with a 64.3% reduction in non-compliant diesel cars from 2017 to Q2 2021. Islington and Tower Hamlets tied for 2nd place, each with a 58.3% drop.

There were 3 local areas outside of London that made the top 20: Slough in the South East (54.1% drop), Swindon in the South West (49.5% drop) and Renfrewshire in Scotland (47.3% drop).

Rank (1=best)Local AuthorityRegionQ4 2017Q2 2021Change
1CamdenLondon (Inner)12,5464,475-64.3%
2IslingtonLondon (Inner)9,2993,878-58.3%
3Tower HamletsLondon (Inner)13,3425,567-58.3%
4City of LondonLondon (Inner)645276-57.2%
5WestminsterLondon (Inner)12,9975,605-56.9%
6HackneyLondon (Inner)11,5495,138-55.5%
7Kensington and ChelseaLondon (Inner)10,9814,945-55.0%
8SloughSouth East43,41019,921-54.1%
9Hammersmith and FulhamLondon (Inner)12,4805,778-53.7%
10SouthwarkLondon (Inner)14,5946,859-53.0%
11Waltham ForestLondon (Outer)22,53810,596-53.0%
12NewhamLondon (Inner)22,84310,760-52.9%
13HaringeyLondon (Inner)17,4138,216-52.8%
14LambethLondon (Inner)16,7338,374-50.0%
15SwindonSouth West60,95530,798-49.5%
16LewishamLondon (Inner)18,7779,619-48.8%
17WandsworthLondon (Inner)22,22711,555-48.0%
18RedbridgeLondon (Outer)31,43916,536-47.4%
20BrentLondon (Outer)27,56114,759-46.4%

20 Best UK Local Areas Outside of London

As mentioned above, the top 3 local areas outside of London were Slough in the South East (54.1% drop), Swindon in the South West (49.5% drop) and Renfrewshire in Scotland (47.3% drop).

Birmingham ranked 4th, with a 46.3% drop, followed by Peterborough with a 42.8% drop. The table below shows the rest of the best 20 local areas in the UK outside of London.

Overall outside of London, Scotland dominates with 8 of the top 20 best local areas for reducing non-compliant diesels.

Rank (1=best)Local AreaRegionQ4 2017Q2 2021Change
1SloughSouth East43,41019,921-54.1%
2SwindonSouth West60,95530,798-49.5%
4BirminghamWest Midlands189,289101,597-46.3%
7Milton KeynesSouth East58,59334,254-41.5%
8West BerkshireSouth East37,38023,204-37.9%
9South GloucestershireSouth West59,31337,196-37.3%
10East RenfrewshireScotland13,0948,363-36.1%
11Epping ForestEast19,22412,308-36.0%
12SolihullWest Midlands37,86924,466-35.4%
13East DunbartonshireScotland15,34310,018-34.7%
14Shetland IslandsScotland4,6433,063-34.0%
18South LanarkshireScotland45,85930,630-33.2%
19ElmbridgeSouth East20,94214,184-32.3%
20North LanarkshireScotland46,05331,653-31.3%

20 Worst UK Local Areas for Reducing Non-Compliant Diesels

There are many local areas where there are essentially the same number of heavily-polluting vehicles now as there were 3.5 years ago. How is this possible? It could be simply a shift of vehicles, where motorists living in low emission areas are selling their cars to those living in areas without these restrictions.

In London there were 296,368 fewer non-compliant diesel cars in June 2021 compared to 2017; and in Birmingham there were 87,692 fewer. Where did all these cars go? While some older cars get scrapped or are sent abroad, many of these likely were sold on as used cars to motorists living in areas without low emission zones.

In fact, the two local areas with the smallest drop in non-compliant diesels in all of the UK are located just outside of Birmingham (which, as discussed above, saw a drop in non-compliant diesel cars of 46.3% due to the LEZ that came into effect on 14 June 2021): Corby (-1.7%) and Leicester (-2.1%).

20 Worst UK Councils for Reducing Pre-Euro 6 Diesels (1=worst)Local AuthorityRegionQ4 2017Q2 2021Change
1CorbyEast Midlands11,46811,272-1.7%
2LeicesterEast Midlands39,50638,662-2.1%
3ManchesterNorth West45,75443,897-4.1%
4NottinghamEast Midlands29,67628,442-4.2%
5Isle of WightSouth East16,70116,003-4.2%
7PlymouthSouth West37,12635,220-5.1%
8WolverhamptonWest Midlands35,26133,362-5.4%
10BlackpoolNorth West15,47514,605-5.6%
11TorbaySouth West19,43118,274-6.0%
12BostonEast Midlands13,05912,270-6.0%
13Great YarmouthEast15,41914,470-6.2%
15Kingston upon Hull, City ofYorkshire and The Humber29,33527,407-6.6%
17HastingsSouth East10,3379,611-7.0%
18North DevonSouth West17,71816,433-7.3%
19ThanetSouth East18,79817,363-7.6%
20Blackburn with DarwenNorth West21,07219,420-7.8%


We analysed data obtained from the Department for Transport (DfT) on the number of licensed diesel cars (first registered before September 2015) at the end of the quarter by local authority, United Kingdom, 2017 Q4 to 2021 Q2.

Diesel cars must have declared emissions of "Euro 6" to meet the minimum emission standards to avoid being charged when entering the ULEZ. While ULEZ charges are based on the declared emissions (e.g. Euro 6) rather than the age, it's generally true that diesel cars meet the standards if they were first registered with the DfT from September 2015. This is because every new car built since September 2015 must meet the Euro 6 emission standard.

We compared the number of non-compliant diesels (estimated by age of registration) in each area from the end of 2017 to the end of June 2021, which is the most recently available data from the DofT as of December 2021.

Erin Yurday

Erin Yurday is the Founder and Editor of NimbleFins. Prior to NimbleFins, she worked as an investment professional and as the finance expert in Stanford University's Graduate School of Business case writing team. Read more on LinkedIn.


Car Insurance

  • You could save up to £530*
  • 4.8 out of 5 stars**
  • Quotes from 100+ providers

Motor Insurance Reviews

NimbleFins Newsletter

Get deals, tips, news, and more!