An incredible map can help you work out where you are in the UK with the numbers that appear on motorway signs – with a bit of work.
The allocation of numbers for A-roads is based on a so-called “hub-and-spoke system”, that sees Great Britain divided up into numbered zones from central points, as per Roads.org.uk, a popular blog that untangles the esoteric systems that underpin British travel routes.
Partly because mainland Britain is both long and narrow, there are two “hubs” with lines spreading out across the island from London and Edinburgh.
From these hubs wind the nine principal A-roads, which have changed slightly over the years, but are broadly described as:
The roads divide up the mainland into nine distinct zones, each of which takes its number from the A-road found anticlockwise along the wheel.
This means that zone six is found between the A6 and A7. However, this is only a broad rule of thumb, as the boundary between zones one and two is formed by the Thames Estuary rather than the A2.
This is so that a small isolated section of zone one doesn’t fall along the bank of the river, and as a result the A2 isn’t a boundary like the others, according to the outlet.
All other A- and B-roads are free from this complication as they get their number from the zone they lie in. This means roads in zone 4 with have a number beginning with four.
However, roads do veer across boundaries into other zones, but a clockwise rule is used to flag this for drivers. If a road does move across a boundary, it takes its first digit from the furthest anticlockwise zone it passes into, the website explains.
The naming system was originally intended to give shorter numbers to important roads, with minor ones getting longer ones. A-roads can have one to four digits, while B-roads can only ever have three or four.
But decades of additions to the road network have changed this, with many short numbers now allocated to that have been bypassed or demoted long ago, creating the peculiar situation of the A66 remaining important but the A32 much less so.
