A1 and A1(M)

The A1 is the UK's longest numbered road and probably its most famous. The numbering system for A-roads, devised in the early 1920s, was based around patterns of roads radiating from two hubs at London and Edinburgh. The first number in the system, A1, was given to the most important part of that system: the road from London to Edinburgh, joining the two central points of the system and linking the UK's (then) two mainland capital cities.

Today, the ancient Great North Road has been substantially altered. To some the changes were upgrades, and to others they were bastardisation. Either way there's no escaping the fact that the modern A1 only spends part of its time on the ancient road north, and between London and Newcastle at least, spends most of its time elsewhere running on new bypasses and bits of motorway.

It is probably the most varied and fascinating route on the Motorway Database: there are, if you're sufficiently interested, whole books and websites solely about the A1's history and place in British culture. In terms of highway engineering that variety translates into inconsistency, running the whole way from the single-carriageway rural highway along the Scottish coast to the choked dual carriageway of the Newcastle Western Bypass and the eerily quiet eight-lane motorway that slices incongruously across the Cambridgeshire countryside.

It was always this way. As far back as the 1960s there was strong criticism of the Ministry of Transport's road programme because of the inconsistency with which it chose to make road schemes motorways or normal dual carriageways. Nowhere was this more evident than on the A1, which today is littered with occasional bursts of motorway. In Yorkshire there has been steady progress over the last decade to fill in the gaps and create a continuous and modern motorway route, and works now in progress are pushing the blue line north towards Tyneside. But a few miles south and there have been incredibly budget-conscious works to replace six roundabouts with flyovers at the absolute minimum cost. Inconsistent as ever, in policy as well as appearance.

There is, in short, no single identity to the A1, no one thing that you can say that describes the whole of it, except the glib observation that it's incredibly varied and it always has been. And it's all the more wonderful and fascinating for it.