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Build now, pay (a lot) later: the hidden cost of car-centric development

Schemes such as Garden Towns require expensive off-site road infrastructure and a huge amount of on-site space for cars, says Martina Juvara. It’s time for cost effective alternatives that will help achieve net zero, she argues

Martina Juvara
05 October 2021
Marmalade Lane in Cambridge, where car space makes way for better houses and larger communal space. PIC: David Butler
Marmalade Lane in Cambridge, where car space makes way for better houses and larger communal space. PIC: David Butler


This is a decade of innovation: big change is awaiting us as technology continues to evolve and the response to climate change starts to gather momentum. Yet most housebuilding companies shy away from trumpeting innovation. They clearly rise to meet challenging government targets, but they do not make their customers aware of the innovation they are providing; energy efficient appliances are often disguised as chandeliers or Victorian-looking A-rated stoves, in developments reassuringly named like aristocratic parks or farmhouses.

Housebuilding companies will not be the ones fighting for change, proposing new ways to live and a different relationship with our cars. In doing so, they may be perpetuating a status quo where not enough questions are asked about the real costs of car-centric development. Unfortunately, they are not the only ones.

Mixed messages

The Government, with all its ambition for a Better Greener Britain, still sends plenty of mixed messages about the role of cars in our future. On one hand, it acknowledges that transport is responsible for 27% of greenhouse gas emissions (even excluding aviation and shipping) and that cars are the largest emitters by far1. 

On the other hand, the Government also encourages driving by investing £27bn in road schemes predicated on astonishing traffic growth (29-59% by 2050) and justified by the need to ‘unlock’ housing development2. 

There are multiple reasons why the Government keeps championing driving and the car industry. One is the massive tax contribution we make as road users: between fuel duties, vehicle excise duties, VAT, tolls etc we contribute between £50-70bn every year, which is approximately an essential 8% of total tax revenues for the country. This roughly equates to £1,000 in extra taxes for each UK resident: not a small amount!

Cars will continue to add unnecessary costs on houses and take space that could be otherwise given to people, social interaction or landscape

There is also a powerful narrative at play about needing to support jobs in the UK, with taxpayers’ millions handed out to companies like Nissan, Hyundai and Land Rover. While it is true that car manufacturing provides many skilled jobs (156,000 people were employed directly in the UK3 last year) this is only 0.5% of total jobs and 5% of manufacturing jobs4. By comparison, much less supported SMEs (those with less than 50 employees) employ over 13 million people and have a turnover 26 times larger. Clearly, the automotive lobby punches well above its weight with the Government, the press and the public.

‘Developers will pay’

But the cost of a car-centric society does not stop with helping manufacturing and taxing the operation of cars. It also requires land and roadbuilding, adding significant financial costs to new housing and preventing the construction of beautiful places.  

Road infrastructure is consistently the largest share of costs in all major new developments. As an example, for one of the Garden Towns near London, road infrastructure requirements ‘off site’ (excluding road building as part of the development) were estimated to cost around £700m for 23,000 homes, effectively adding £31,000 to the price of each new home. To put this in perspective, new schools and other social infrastructure will receive less than half that money. This is not unique; large-scale developments elsewhere posted off-site road infrastructure costs adding 10-20% to the price of each house. 

Also, it is a myth that ‘the developers will pay’. This bill is typically split between government grants and market homes for sale, effectively footed by taxpayers and homebuyers.

The unfairness of low density

Car-based mobility not only comes with significant off-site costs. It also makes a huge demand on land on-site; circulation, parking and, more recently, segregated bus lanes and cycle routes. This has budgetary implications (cost of the land plus construction and maintenance) but also affects what people get.

In a quick exercise of master planning by ratios and numbers, in a typical development with an average density of 33dph (dwellings per hectare), roads, parking, garages and verges take up about 30-35% of the land. This means that, on average, when each person gets 30sqm of housing space and a little garden, each car gets 78sqm6! I wonder how many people realise that their small accommodation makes room for car space; how many would trade off some of the land allocated to cars for a larger house and bigger bedrooms. 

The experience of co-housing development, such as the award-winning Marmalade Lane in Cambridge, is that when homebuyers are also the design decision-makers, car space is swapped for better houses and larger communal space.

Housing densities are directly linked to the car, and that in turn is closely related to the quality and beauty of the places we create. At very low densities (below 30dph), for example in rural villages, house plots are large and traffic generation is relatively low. Cars are necessary because public transport is unviable, but house plots are large and vehicles can easily be parked in a planted forecourt. Narrow lanes ensure that traffic remains slow and drivers aware of cyclists and horse riders. 

At higher densities, those of much-loved market towns or the Georgian districts of London, Bath or Edinburgh (roughly equivalent to the 45-70dph developments of today), all sorts of transport options become available. Services can be within walking distance, employment within cycling distance, while buses can be frequent and trams become a possibility. The one mode of transport that needs management is the car: a market town is based on a spatial proportion of 4sqm of living space for every 1sqm of parking space (for example, only one car for a four-bedroom dwelling) and parking is not necessarily available in front of the unit. This is only possible with an integrated mobility approach that puts quality of life and beauty first. 

Current car use patterns and parking standards prevent the creation of developments we generally associate with beauty, flexibility of use and human scale.

So, what happens in developments between 30 and 45dph, which are now the majority of allocated sites? From a spatial and mathematical perspective, they are a grey zone, which is the hardest to devise; too dense to accommodate all the cars needed and not dense enough to allow transport choices and proximity services. They can only be made to work through artificial enforcement, involving subsidies to public transport, travel planning with incentives and penalties, parking restrictions at key destinations, and so on. This is what we are building right now and for the future.

Perpetuating car lifestyles

By 2035, when the world will be different and the 78% emission reduction is set to be target reached, we will have built around 3m new homes in the UK. Unless we change course, this will be equivalent to building over 80% of the Peak District or an area three times the size of Birmingham. In the same period many more developments will be planned. Unless we do something, these developments will perpetuate car lifestyles, which cost us as car users and taxpayers. Car manufacturing will ‘green-wash’ their credentials and continue to get over-scaled attention and funding. Cars will continue to add unnecessary costs on houses and take space that could be otherwise given to people, social interaction or landscape. Beauty will continue to be impossible and home buyers will be none the wiser.

These are exceptional times, and they demand development of exceptional quality. We should not be wasting time with a model that is expensive and cannot work. 

To start making some progress, why not try what the Decarbonising Transport Plan actually suggests? This would mean half of all journeys in towns and cities by walking and cycling, embedding transport decarbonisation in spatial planning, fewer cars through increased occupancy or sharing systems, communication campaigns to change behaviours and ‘commute zero’ models of employment. Moreover, people should be made aware of the reality of the hidden costs of relying on cars. 

The policies are there, the motives too. We just need more courage.

Martina Juvara is director at consultancy URBAN Silence

  1. Decarbonising Transport, A Better, Greener Britain, DfT, July 2021
  2. Road Investment Strategy 2:2020-2025, DfT April 2020
  3. SMMT Motor Industry Facts, Society of Motor Manufacturers and Traders Sept 2021
  4. Employment by Sector Statistics, gov.uk 2018 
  5. UK Small Business Statistics 2020, Federation of Small Businesses
  6. This is estimated based on 160sqm per housing plot, 15% of housing land for green space and 33dph resulting in average occupation of 72 people/ha and 43 cars/ha.

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