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Schrodinger’s Vehicles – London has more cars, but car ownership is not changing

Schrodinger’s Vehicles – London has more cars, but car ownership is not changing

Even without the upheaval of a global pandemic, most of us would say there are more cars in London now than there used to be, so it seems logical to assume more cars equals more car ownership. Except this is assuming that ‘car ownership’ is just a gross count of the number of cars in any given area, and as anyone who has dipped a toe in psychology or statistics will tell you, that’s just not how either numbers or people work.

With the new 2021 census results pending, we’re still reliant on the car ownership datasets of the old 2011 census, and increasingly I’m getting comments from officers that the 2011 data doesn’t account for the growth in car ownership and therefore isn’t fit for purpose or should be factored up.  

Well, that’s a fair question. However, my questions in reply are what evidence is there to suggest car ownership has increased since 2011, and, assuming it has, how should the 2011 census be factored up? This isn’t traffic volume flow data, and a Tempro Factor doesn’t make sense. Car ownership isn’t correlated to the number of vehicles passing by on the next road.

Faced with a ringing silence to those questions, I have been doing some digging to satisfy my own curiosity.

Question 1: Is the 2011 baseline car ownership data fit for purpose?

First, the 2011 baseline data gives you lumped areas. You can have a Lower Super Output Area (LSOA) or a Middle Super Output Areas (MSOA), which sometimes (but aggravatingly not always) correlate to wards or electoral districts. Within an MSOA, you can capture a wide range of land uses, housing types, and demographics but it can be hard to tease out the ones which apply to a specific site. For car ownership in general there are variables which are easy to demonstrate – buying a car correlates to having a place to park it; disposable income; personal health; and ease of access to public transport. Even things like community can play a part if your social background, for example, stigmatises cycling as a ‘poor person’s’ activity and considers a vehicle a status symbol. Obviously, some of these are nebulous and hard to measure - the census doesn’t capture attitudinal factors, but it does examine housing types and tenures.

This is important given that most new residential development in London, especially in outer London, is flats. It is also largely accepted that people in affordable or social-rented accommodation own fewer vehicles and rely more on buses.

So, the baseline data can be misleading if you are trying to assess studio flats for affordable rent in an area predominated by large private detached homes.

However, you can order a bespoke tabulation of the census at MSOA level (and we have), which gives you much better baseline that captures tenure, number of habitable rooms (i.e., size of unit) and housing type. Whilst no data set is perfect, this at least refines the proxy, making it ‘truer’ to any given proposal that is being assessed. On that basis, the data is sound, and I have yet to find a more recent alternative data set which can be tabulated in this way to account for local variables. 

Question 2: Has car ownership increased since 2011?

Until the 2021 census data comes forward, it’s hard to say for sure at the LSOA level, but as contradictory as it sounds, an increase in cars does not necessarily equate to an increase in car ownership.

Because car ownership, as I already said, is not the gross total of the number of vehicles in an area. As defined by the Census, it is a ratio. It is how many private vehicles a household has access to or owns. Or indeed, you as an individual. So, what has happened in London, I’d argue, is that the population has increased. And that makes sense, does it not? If one household owns one car, then 100 households will own 100 cars. But the level of car ownership has not by default increased. It’s still one car per household.

And we can examine this ratio at the level of the individual using DfT data on registered cars per year, and ONS population data by London Borough, adults aged 20-75 only. It should also be noted that DfT categorises cars in a way which includes private hire vehicles and there has been a huge surge in private hire since 2011 with app-based hiring such as Uber. 17–19-year-olds were not included due to these ages being in bands which would have included children ineligible to even hold a driving license. Over 75s were not included as this age bracket disproportionately also do not own vehicles. 

So, the data still has some of the same ‘lumping’ issues of the MSOAs in the 2011 baseline – it’s not localised or specific - but it equally gives some insight into the prevailing trends across London. 

Despite all the above, the data sets are informative – but to avoid recounting a long list of numbers, the results are summarised in the infographic below. It is necessarily large, so I suggest zooming in!

Car Ownership Data ver 3

(Click the image above or this link to expand the image in a new tab)

Question 2 again: Has car ownership increased since 2011?

In one word, no. The data strongly indicates that car ownership across London as a ratio of cars per head has remained largely static in the last 10 years.

What should be immediately obvious from the infographic is how the orange bars (2011 cars as a ratio per head) and blue bars (2020 cars as a ratio per head) are identical across most boroughs. Inner London has had the most change, with Westminster, Camden, City of London, and Southwark showing more measurable decrease. In outer London, Hillingdon, Barnet, and Kingston-Upon-Thames likewise show more evident decrease. It should be stressed that most of the decrease is not huge. Levels of 0.1-0.2 cars fewer per adult at the top end of the list. 

A total of six boroughs have shown an increase in car ownership with the highest being Ealing and Hammersmith & Fulham, but with most showing an increase of just 0.01 cars extra per person, you’d need 100 people to club together before you even got a single additional car.

Of course, that’s not exactly what’s happening. There aren’t people in Camden driving 80% less of their car, rolling around on a single axel like a steampunk Segway (though it’s Camden, someone might be), but it does signify that the number of people living without a car, and perhaps more importantly without second cars, is on the rise.

It is also worth noting that, except for the City of London, there have been general population increases in every borough, but despite this adult populations have fallen in some. Ealing, Kensington & Chelsea, and Hammersmith & Fulham all have fewer adults than were recorded in 2011. This might mean that these boroughs have had significant increases in the number of OAPs over 75 years old and/or households with members under the age of 20, or economic reasons have pushed some adults to move away. I need to crunch more numbers to be sure, but if the number of families has risen, unless car-free habits are cemented then these boroughs may see another (small) increase in the car ownership ratio in years to come as this new cohort of children becomes old enough to obtain vehicles, if they become are habituated to the idea of vehicle ownership as a default.

What does it all mean?

Well, it means numerous things. The first is that we still have an awful lot of cars, and a definite issue with parking in many of our London boroughs. Lowering the car ownership rate helps but it won’t solve the parking problem until most people in London live completely free of any car, which is not yet feasible. It means that areas with rapid population increase should be more supported to first deliver high-quality public transport alternatives to car ownership, world-class cycle infrastructure that is safe and accessible to all users, and funding should be allocated to support those efforts accordingly. Areas with growth in families should likewise be targeted as a means of future proofing for a cleaner environment and a healthier adult population.

The second thing this means is that new development could still have an impact on local parking demand and applications will still need to carefully assess existing parking stress through surveys and account for situations where additional demand will be generated, but it also means that a car ownership assessment based on 2011 census data should be acceptable until 2021 data is released. 2021 data may need to be carefully checked for potential bias; however, as it will be a snapshot of a single day during lockdown, and not representative of ‘normal’ conditions for all datasets.

In conclusion, assessing car ownership is about understanding how many cars this group of homes, of this specific type, in this specific place are likely to own, and whether these specific roads can reasonably accommodate any calculated overspill. It should always come in tandem with a view on how car ownership can be reduced through good design and wider mitigation, such as better connections and alternatives such as car clubs. And the 2011 census data is still the best means we have to assess that.

What next?

I’m not done with this data. I am keen to see what the 2021 census shows, and what 2022 ONS and DfT data will show. I want to explore how COVID-19 has impacted on car ownership and if there have been ‘shelves’ where the ratio has suddenly dropped off since 2011 in any particular place and if it’s possible to say why. I want to be rigorous and make sure the conclusions I have come to so far are fair and accurate. There is also National Travel Survey data and New London Plan evidence base which may provide another window onto car ownership, or at least car use in London.

And I want to see what’s going on outside of London in the rest of the UK. How are our other cities faring - Is the same trend true of more rural counties where public transport links are poor, and cars are more essential? Scotland, Northern Ireland, and Wales hold more comprehensive and more focussed travel data sets than England and may indicate a different picture again.

First forays into statistics for Surrey (which has some of the highest rates of car ownership in the country) suggest the downward trend may extend to the home counties, but there’s still a lot of data to wade through. So far, and for now, it’s fair to say that there needs to be more caution in claiming that car ownership is on the rise in London or conflating it with the real issues.

New development will not disproportionately introduce new vehicles into an area – 50 new studio flats will not egregiously generate 200 new cars, even if the houses next door owns 5 each. But the few cars it does generate may still be a problem because what we have is an issue with over-reliance on driving and a lack of appropriate parking in the wake of population increase and rising densities, not necessarily an issue with car ownership itself. 

By Sarah Chapman

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Car Ownership Data ver 3