The A167(M) is a little fragment of urban motorway in Newcastle upon Tyne, originally called the "Central Motorway East", indicating the intention that it would form one side of a network of similar routes.
The other sections and connecting roads of the planned network were never built, so it was renamed the Newcastle Central Motorway, reflecting the fact that it is now - and is certain to remain - the only motorway in the city centre. There are no plans to do anything to complete the rest of the routes; indeed, the land reserved for the parallel western side of the motorway box has now been used to build a surface-level boulevard.
The reason for this was a shift in transport policy that occurred just after Newcastle had started building its motorway network, and indeed by the time the Central Motorway East had opened it was almost certain that the rest of the routes that were supposed to accompany it would never be built. In the mid-1970s, the creation of the new Tyne and Wear metropolitan region caused a change in priorities and money that had been earmarked for roadbuilding was diverted to begin work on the Tyne and Wear Metro system; today Newcastle and Gateshead don't have an extensive urban motorway network but they do have one of the best light rail systems in the UK outside London.
When this route first opened it was classified A1(M) - and, since the A1 then passed through the centre of Newcastle, it was literally designed for long-distance traffic to pass through Newcastle itself. The A1 was then rerouted to pass through the Tyne Tunnel east of the city, and then moved again to the new Western Bypass in the 1980s. Each move caused a reshuffle of road numbers, so during the Tyne Tunnel days the Central Motorway was called the A6127(M), and since the Western Bypass opened it has been A167(M). It looks like it might now be settled on this number for the time being.
The road makes an effective bypass for the city centre, though its unconventional junctions make any journey an exhilerating drive, with entries and exits bombarding the driver from all sides. Between the B1318 and the next junction south from the A1058, the southbound carriageway runs underneath the northbound one to save space, and thus forms the UK's only double-deck motorway. The most alarming section, where an entrance from an unclassified road joined the northbound carriageway on the right-hand side at a Give Way line immediately before another exit, was eliminated in about 2008 by permanently closing the little-used sliproad.
Never boring and always evolving, the Newcastle Central Motorway is one of the liveliest but most overlooked corners of the motorway network.