Grids! What are they good for? Basic urban planning, it turns out: take a look at how a US city is laid on a map, and often you’ll be looking at a grid of streets criss-crossing at exactly 90 degrees.

This is not strictly speaking an American phenomenon – similar systems have been used across the world for thousands of years because, well, it’s an easy way to divide up land. Fans of Worthing in West Sussex may be excited to learn that it owes some of its street layout to ‘centuriation’ – the grid system used by the Roman Empire.

But the US has really taken the idea and run with it, as you can see from these charts, which show the most common road orientations within a given city – the closer the chart is to a cross over the centre, the more closely aligned the city is to a grid. Just look at how dead on most of them are:

The street orientations of 25 US cities. Image: Geoff Boeing.

These charts are the work of urban planning researcher Geoff Boeing, who’s put together some software that can analyse the layout of the roads within a city, or any other geographical space, using data from OpenStreet Maps.

The streets of Manhattan, in map and polar histogram form. Image: Geoff Boeing.

Here he’s used the same process on 25 cities from around the world, which tend to be a lot less carefully laid out:

Image: Geoff Boeing.

Even where there isn’t a strict grid system, you can still usually make out an overall orientation if you squint – look at London, for instance.

London with some highly scientific lines drawn on it. Image: author’s own work.

When the City of London burned down in the great fire, the suggestions for how to rebuild it actually included various ideas for grid systems. It came to nothing, and the city ended up with broadly the same layout it had before it burned down – but if we use Boeing’s method, we can there is a pattern to the street orientation:

The City of London as a histogram. Image: author’s own work.

Which does make sense when you think about it – the roads either tend to follow the line of, or run down to, the river, thus: a grid.

Here’s the City together with the London boroughs:

The London boroughs as polar histograms of street orientation. Maps are so last year! Image: author’s own work.

What this doesn’t account for is size. Perhaps the larger the borough, the less likely it is to have a clear pattern – whether that be because it has several ‘competing’ grids or just is not going to be tied down with geometry, man. If we compare the City (1.12 square miles) and Bromley, the largest London borough (57.97 square miles), that seems plausible.

But that’s not necessarily true, because here are the boroughs in size order:

The London boroughs, now in size order. Image: author’s own work.

Lambeth is noticeably more of a jumble than its ‘size-neighbours’ Southwark and Camden, for instance.

And for that one guy who complains on Facebook that I only ever write about London, here are 25 UK towns and cities:

London plus 24 other weird places that aren’t London. Image: author’s own work.

But what about the most famous grid system in the UK, in Milton Keynes? Well, erm:

The Milton Keynes ‘grid system’. Image: author’s own work.

So does Milton Keynes have a grid system or not? Well, yes, but isn’t that strict.

Firstly, that’s because not every road is part of the grid – the ‘squares’ of the grid are the main roads and the smaller roads within don’t necessarily conform to any particular layout. And secondly, because it was deliberately designed not be as rigid as an American-style grid. In the words of David Lock, a planner who’s worked in Milton Keynes since the 1970s:

“The designers decided that the grid concept should apply but should be a lazy grid following the flow of land, its valleys, its ebbs and flows. That would be nicer to look at, more economical and efficient to build, and would sit more beautifully as a landscape intervention.”

Don’t worry though, grid fans, they did stick to a proper grid for the town centre.

Grids! Grids! Grids! Image: author’s own work.

Right, now for a rousing singalong of that classic post-war planning anthem: “You’ve never seen anything like it: Central Milton Keynes!”

Altogether now:

Ed Jefferson works for the internet and tweets as @edjeff.

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