Colouring by Numbers

Published: 24 September 2018

A programmer has used GIS data to plot all the numbered roads in Great Britain onto a map and colour them according to the first digit of their number - and the results are surprisingly beautiful.

The resulting graphic appeared in a tweet on Thursday last week, made by Beta Decay. Using GIS data for the British road network, plotted and coloured appropriately, they'd created a map showing just the roads and nothing else - and, rather delightfully, coloured them according to their number, in a living demonstration of the numbering zones.

If you're not familiar with the arcane way that road numbers are allocated in mainland Britain, we have a detailed article on it, but the short version is that Great Britain is divided up into nine sectors by the roads A1 to A9, and within each sector all the roads have numbers with the same first digit. Where roads cross a zone boundary they take their number from the furthest anticlockwise zone on their route. Motorways have a similar but slightly different system.

The result is that, if you colour the roads by their first digit, you get a map showing the UK's numbering zones - and it's amazing.

The shape of Great Britain's numbered roads, colour-coded by their first digit. Click for the full size version
The shape of Great Britain's numbered roads, colour-coded by their first digit. Click for the full size version

The small version in the original tweet was wonderful enough, but click the one above and you'll get the original, full-size graphic - and if you have even a passing interest in the UK road network you'll find it utterly fascinating. The blocks of same-coloured road are obvious enough, and major cities are easily picked out by the clusters of routes all converging on single points.

What stands out next are the roads that don't match all the others - the little splashes of a different colour. Across Norfolk, which is almost exclusively made up of the dark blue lines of the 1-zone, is a single orange line representing the A47 that passes through patches of turquoise and yellow to eventually reach Norwich. To the north, in otherwise all-blue Lincolnshire, yellow tendrils of the 6-zone work their way into the county while a blue-green line around the coast marks the A52, far from its home zone.

Out-of-zone roads are suddenly very easy to spot, like the yellow tendrils of the 6-zone spreading into Lincolnshire

Out-of-zone roads are suddenly very easy to spot, like the yellow tendrils of the 6-zone spreading into Lincolnshire

Roads that are distinctly out of place are also easy to find. The M5 - which, as a motorway, doesn't follow the same numbering rules as A-roads - travels exclusively through the 3- and 4-zones, making a turquoise line through the wash of dark green and orange. And if you look closer, you can even see roads that shouldn't be there, like a surprise dot of something greenish in Swansea, marking the erroneously-numbered B5444.

For more interesting finds like this, you can follow us @roads_uk and Beta Decay @betadecay101.

Comments

Matt 29 September 2018

That's really neat- I wonder if they're doing prints....

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Picture credits

  • Road numbering graphic is by Beta Decay and used here with permission.
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