Prime Minister, please don’t re-open the debate about ULEZ

I had to sigh heavily when I saw this tweet from Prime Minister Rishi Sunak with its pledge to “End Labour’s unfair ULEZ Expansion”.

Just last month, Sadiq Khan won a resounding victory in the Mayor of London elections, an election that had come to be seen as a referendum on ULEZ.

At the time, I revisited the Department for Transport data for the third time and established that between March 2022 and September 2023 there was a 40% reduction in the most problematic private cars. To my mind that makes ULEZ a successful policy intervention. It also means that the incumbent government is campaigning on the basis of something that affects just 331,632 private cars in London, a city of 9 million.

Well, it affected 331,632 private cars by the end of September 2023. I asked ChatGPT to help me with the linear regression and it told me this month, June 2024, the figure will probably be 230,000.

I wonder how many policies have generated so much airtime for such a small proportion of the population. It is deeply perplexing that ULEZ has worked its way into our national psyche (not to mention the time I’ve spent looking at it myself!)

Does the latest dataset support that projection?

We can’t get real-time figures so we don’t know with accuracy how many households voting in the general election are directly wrestling with ULEZ but happily the veh9901 dataset has recently been updated through to the end of December 2023¹.

As always this analysis is caveated with three methodological notes:

• only privately owned cars (so not company cars and not goods vehicles, vans, etc)
• focusing on diesel and petrol
• assuming the cut-off years are 2005 for petrol and 2014 for diesel, even though I know this marks cars that are exempt, like our 2004 Ford Focus, as chargeable.

We can now access 21 months of data from my baseline data of March 2022. In the three months from September 2023 to December 2023, there has been a further fall of 9,000 private cars registered to London addresses. That running total is now a net loss of 58,707.

The total of petrol and diesel private cars has fallen by 22,000, more than double the overall numbers, continuing to indicate the transition away from the internal combustion engine.

The most polluting diesels keep on showing the greatest falls. This time a reduction of their proportion to 4.2% from 4.9% compares to a drop of 0.4% in older petrols (to 8.5% from 8.9%).

Inner London saw a further fall in the number of private cars of 3,000 (to 19,027 from 15,952). The proportion of private cars exempt from paying ULEZ has risen to 86.9% (an increase from 86.3% in September 2023). This means that out of the 628,161 private cars in Inner London, 81,976 of them were non-compliant in December 2023. 21 months previously, the figure was over 120,000.

In Outer London the December 2023 dataset now reflects almost 6 months since the ULEZ expansion came into effect.

And it shows that car ownership habits in the expanded ULEZ are outpacing the behaviour of Inner London. A greater proportion of private cars in Outer London are now exempt from paying ULEZ than Inner London. In March 2022 23.8% of private cars would have had to pay ULEZ but by December 2023 that had fallen to 12.6%. This means 87.3% of private car owners in Outer London are unaffected by ULEZ.

Out of 1,769,800 private cars in Outer London, 223,033 have been paying the ULEZ charge up to the end of December 2023. In March 2022 that would have been 431,272.

It is beyond time for opponents of ULEZ to get over it.

The Prime Minister has made a big deal about the importance of maths. It’s disappointing, really, that (at least) one of the planks he’s building his re-election campaign on is so mathematically illiterate.

Almost a year on from the Uxbridge and South Ruislip by-election there’s been an almost 50% reduction in the number of private cars registered in London that have to pay ULEZ. There is an important discussion to be had about whether those remaining vehicles belong to households that are stuck with cars they cannot afford to replace.

However, the purpose of the policy has always been to remove the most polluting vehicles from the streets.

So if the government really wanted to address what they call the ‘unfairness’ of ULEZ, it would be by acknowledging that they’ve got this argument wrong. Instead of all the time and energy spent antagonising, vandalising, and attempting to frustrate ULEZ, they could have been working to improve air quality around the country. After all, it’s quite stark when you compare the number of private cars with poor quality emissions in London with the rest of the UK:

• 12.7% of private cars in London have to pay ULEZ
• 26.5% of private cars in the rest of the UK would have to pay ULEZ if it was extended nationally

Urban environments with higher concentrations of vehicles are obviously motivated to improve air quality more than other parts of the country so policy interventions may not be required everywhere. But in March 2022 the figure of non-ULEZ-compliant private cars across the whole of London was 22.5%, and by December 2023 it wasn’t. Today it will be even less. I asked ChatGPT to predict when the number of non-ULEZ-compliant private cars reaches 0 – put December 2025 in your diaries.

One day ULEZ may actually come to be seen as a highly effective piece of public policy. Certainly it doesn’t need the Prime Minister to re-open the debate.

1. There is a temporary issue with the file posted to GOV.UK so I’m using a version that I received by email from the team and will update the link to the correct file in the Web Archive when that is resolved ↩︎

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