Cyclists on a London street; Cyclists on a London street;

Streets: the best use of public space?

In London, streets make up 80% of public space. As our rapidly urbanising cities face gridlock, I think we’re going to see some of this space reallocated to more people-centred and sustainable uses.

In London, as in many cities, the typical street is an asphalt paved surface with buried utilities and pedestrian footpaths on both sides, separated from the carriageway by parallel parking and loading bays. Now two forces are driving us to reconsider this particular use of public space.

The first is sustainability. Car use is discouraged by the congestion charge and by petrol taxes. Cycle use is actively promoted, with cars excluded from new cycle lanes and superhighways, and cycle hire stands replacing on-street parking spaces.

Sustainable utilities are also looking a bit different from the grids we’re used to. Power, heating and cooling can all be provided onsite or with local networks. Rain and grey water are being captured and reused. Large-scale regional utility grids won’t go away, but in time they may become less critical and voluminous – needing less of our street space.

We’re also starting to include green infrastructure: the public realm should incorporate surfaces that absorb storm water, planting that mitigates pollution, and routes for wildlife.

Second, the faster-than-expected population growth in cities means that a finite space needs to be shared by more people. The 2011 census showed that London, at 8.2 million, is 400000 people bigger than we realised.

Public transport is a far more efficient use of space than individual cars: one double-decker London bus holds around 80 people. Even so, the kind of significant capacity increases we need can only really be delivered underground – Crossrail, for example, will add 10% to the capacity of London’s underground network.

Public transport concentrates people, bringing them to stations and bus stops. So higher-capacity transport systems will need a larger public realm to disperse arriving passengers: you can’t just dump larger numbers of people onto existing footpaths. More people also need more parks (an additional 9000ha of accessible green space in London by 2050) and more leisure spaces. These three uses – pedestrian, leisure and green – complement each other.

It’s hard to escape the conclusion that streets just aren’t the best use of the vast area of public space they currently consume. Does this mean streets will disappear? I doubt it. But they will be transformed. I predict that networks – roads as well as metros and utilities – will continue to move underground. Streets will increasingly be redesigned for last-mile journeys (particularly those on foot), leisure uses and green infrastructure.

Indeed, this transformation is happening already. The new Crossrail station and expanded Underground station at Tottenham Court Road will be complemented by new public spaces, created by closing underused streets. And boulevards will replace the existing one-way street system. At King’s Cross, over a third of the 67 acre regeneration site has been set aside for public space. And of this, more than 60% is parks, squares and pedestrian priority routes, with servicing to the commercially led southern part of the site provided underground.

These two examples – one the incremental transformation of an existing urban fabric, the second a masterplanned new development – illustrate two approaches to creating a more people-centred city. London’s transformation, incremental and planned, matters, because it’s a transformation that growing cities worldwide are going to need to make.