Why do we struggle to densify suburbia?

One of the surprises I had when I first became involved in the built environment sector during the 2010s is that there is far more consensus about good urbanism than most outsiders realise. Pretty much everyone in the sector admires The Death and Life of Great American Cities. Pretty much nobody thinks that car-dependent suburban sprawl is a good idea.

A huge range of scholarly and official documents enjoin mixed use, walkability, public transport access, active frontages, façade continuity, greenery, a dense street network, ‘eyes on the street’, and so on. The folk belief in a Corbusian planning elite, committed to rebuilding cities around the needs of the car, is many decades out of date.

The reason for this misperception is obvious enough: it is that dense, mixed-use, street-based urbanism, though widely admired in theory, remains relatively rare in practice. Greenfield development in particular still tends to be single-use, low density, and car dependent. When a British town expands today, it almost certainly replicates the basic model of suburban expansion dominant in the twentieth century.

Bad urbanism perpetuates itself, and having done urbanism badly for half a century, it is not easy to change course

Why is this, given the overwhelmingly good intentions of the planners, urban designers, architects and local councillors? The answer is complex. But one part of it is that the patterns of urban development that we pursued in the twentieth century tend to be self-perpetuating.

Imagine a medium-sized British town. It has a historic core, with many of the features urbanists admire. But around this is a much larger area – 80% of the town’s overall area – of housing estates, retail strips and business parks. If the local council has to add 80 homes on a marginally viable greenfield site near the ring road, it really is impossible to replicate the urbanism of SoHo, Covent Garden, or the Marais – even with dedicated and well-resourced planning officers and a conscientious developer. There really are few shops in walking distance; there is no existing tram line onto which a stop could be added; maybe people really do need two cars per family home.

That is not to say that no improvements on current practice are possible. But it is to acknowledge some of the constraints facing even the best planners and urban designers. Bad urbanism perpetuates itself, and having done urbanism badly for half a century, it is not easy to change course. It is no coincidence that the countries that do urbanism somewhat better now – the Netherlands, Japan, Spain – are those that never entirely stopped doing it well in the first place.

Is the situation hopeless? Maybe not. One reason for hope is that – to a substantial extent – cities have always had urbanistically fragmented peripheries. Consider this 1855 painting of Paris, carefully generated from contemporary maps by an artist imagining himself in a hot air balloon. Districts whose urbanism is now world-famous, like Montparnasse and Val-de-Grâce, were then ragged ribbon-developments along arterial roads. It might have looked picturesque from above, but it would certainly not be considered good urbanism if it were built today.

Sprawl is not, then, altogether new, though of course the development of the car has aggravated it in some ways. What is perhaps new is that we find it harder to let sprawl evolve into something better. By 1914, the suburban districts in this painting had evolved into the dense urbanism we know today. Storeys had been added and backlands built over.

Something like this process of suburban intensification is visible in virtually all premodern cities. But in almost every economically developed country today, it has become rare. During the course of a century of confident outward expansion, we lost the cultural and institutional mechanisms that made intensification possible.

I think this is one of the underlying forces that makes dense walkable urbanism difficult today. If intensification were easy, the British town imagined above would not be adding 80 homes on a greenfield site by the ring road at all: it would be adding homes to the 80% of its surface area that is currently low-density suburbia. Intensifying would not solve all its problems - the street network would not become more interconnected, for example – but it would help with many of them, gradually making more mixed use and more public transport viable as a greater number of people came to live within walking distance of any potential site for a shop or a bus stop.

For many people in suburban Britain today, permission to intensify would be a huge opportunity

Planners are well aware of these opportunities. Many planners around Britain – and the world – have attempted to plan for greater density in suburbs, aiming for more active travel, more transit, and lower emissions. The draft London Plan Guidance on small sites is a particularly admirable example. But building consensus for these reforms has been difficult, and most have not been able to go as far as they would like.

For many people in suburban Britain today, permission to intensify would be a huge opportunity - just as it was for our ancestors over the centuries. They could add a mansard extension or a mews cottage for adult children, vulnerable elderly relatives, or a lodger. The high uptake of permitted development rights for extensions testifies to an appetite for changes like this, though the results have not always been in the best traditions of British planning.

For many people, indeed, there would be major opportunities in a more fundamental transformation in the character of the neighbourhood. If the residents of a street of suburban semis in Outer London received permission to go up to the densities of, say, Georgian Marylebone, every homeowner might instantly become an asset millionaire.

At the moment, cases like these present a collective action problem. It might be in one resident’s interests to get permission to go up to Georgian densities, but for all of their neighbours that means two years of construction work, loss of sightlines, increased population, and change in the character of the neighbourhood.

Street votes now enjoy a broad coalition of support

So even if it was in every individual’s interests to get planning permission for intensification, it is also in every individual’s interests to oppose such permissions for everyone else. Add to this the fact that objectors probably tend to have more time and resources on their hands than potential supporters, and we start to see why planners are rarely able to build the consensus for intensification they need.

The proposal I have worked on, ‘street votes’, is designed to get around this. In a street vote, residents of a street or block vote on a new ‘street plan’, which could create a presumption or a planning permission to increase densities. The maximum densities streets can go up to are carefully limited to avoid loss of light and other inconveniences for neighbours on other streets or blocks. Any units added are required to be car free and to meet a zero net carbon condition. A generous share of any value uplift is captured by the local authority through a levy, to be spent on local services, infrastructure and affordable housing.

In areas of acute housing scarcity, residents will have a powerful incentive to vote in favour: and if they do so, they could create many new homes, while gradually improving the urban form. Our modelling suggests that if just 2% of eligible streets took advantage of the maximum opportunities available, this would produce tens of thousands of extra homes per year for over a decade. Street votes now enjoy a broad coalition of support, and the Government has announced that it intends to run pilots of them.

The outward sprawl model of urban growth is politically, economically and environmentally unsustainable

Readers of Building Design will have many questions at this point. What about tenants? (They enjoy extensive protections.) What about national parks, areas of outstanding natural beauty, listed buildings and historic areas? (All excluded.) What about residents who don’t want to use the permissions? (They don’t have to, and they too enjoy extensive protections.) What about design? (Street plans must include a strict design code.) Will any streets actually do this? (We can’t be sure in advance, but surely it’s worth trialling.)

A policy like this succeeds or fails on the basis of details like these, which of course we cannot go into adequately here – though I have attempted to do so here and here. What I think we should recognise, though, is that we need something like street votes in the years ahead.

The outward sprawl model of urban growth is politically, economically and environmentally unsustainable: we have to find ways to create homes by improving existing urban areas rather than relying on consuming new ones. The only way to do this at scale is with the support of existing communities.

So we need to look at approaches which empower local communities to opt into sustainable development where they stand to benefit from it. Street votes are only one example of this, but approaches like them are going to be increasingly important in the years ahead.