The natural shape of the network is a grid, not a tree. Trees focus on singular points – grids share the burden.
The natural shape of the city is a grid, not a tree. The evidence of history tells us as much. Rectilinear grids pervade the historic record – in the Middle East, Latin America, East Asia. The gridiron is not then a modern creation – it would seem we have always built grids.
Why should grids be as important – indeed fundamental – as they are?
One key aspect of their performance is that grids provide variety: a choice of routes from A to B. It means you don’t have to come back the way you went. Think about how you walk around the city – if you make a trip out from where you’re based, do you take the same route home? The chances are that you don’t – if you live or work in a grid that is.
And because they provide choice, grids are resilient to everyday disruptions – temporary road closures or even permanent outages. Look at the grid of Christchurch in New Zealand after the earthquakes there two years ago – the entire city centre was closed and has only recently reopened. There has been massive disruption but the city hasn’t ground to a halt. Grids are remarkably able to adapt.
People understand grids. Indeed it seems that the rectilinear shape of the grid is highly memorable. Grids can be moulded to fit natural contours and property boundaries. They can bend and twist and still be both navigable and memorable. It is a oft-cited myth that grids are boring. Who thinks Barcelona is boring? Or the West End of London? They are both grids.
There is even evidence to suggest that the cerebral cortex of the brain is wired as a grid. Grids, it would seem, are even more natural than we might imagine.
But every grid is not the same. Suzhou is not the same as Milton Keynes. Kyoto is not the same as LA. Some grids work better than others.
Why should this be?
First, the physical scale of the grid matters. Are the blocks small enough to encourage walking and riding as well as driving? If not then we are consigned to the car.
Second, the design of buildings that occupy grid blocks matters: do these buildings face onto the street, providing doors and windows at ground level? Or are they anti-street and inward-looking? The difference matters. Too many new grids are being built to the latter formula – developers and their architects, it would seem, fear the street.
Third, and most importantly, the geometry of the grid matters. Most cities are made up of a small number of long, linear streets and a large number of shorter ones. This simple, geometrical fact is often overlooked. Long, continuous streets are essential for the effective performance of city networks. And, in line with the previous point, these longer streets should be the most densely fronted by commercial uses – this is what we see in the historic record: high streets, souks, boulevards – all continuously linear and packed with street-fronting uses. Turning the city’s main streets over to the car and withdrawing commercial uses to the secondary streets of the grid – as has happened in cities worldwide, and continues to do so – goes against the grain of historic evolution.