Numbering our motorway network went right down to the wire. 

Despite years of agonising (no, seriously) Government had not decided how best to number these new-fangled roads even as our first stretch of motorway opened in 1958.

Those around back then will now immediately understand why talk in the press, on the wireless and TV at the time was of the “Preston bypass” and grandiose plans for the “London to Yorkshire motorway” – without mention of the M6 or M1.

Arguments had raged over whether to number motorways as A routes –  apparently A50 was seriously proposed for what became the M1 – adopt a ‘zone’ system like existing roads, or use “tree and branch” numbering. Road users were ‘consulted’ only at the last moment, by requesting comments from the RAC and AA. In all, its a story which veers from comedy to tragedy and back again, largely detailed in documents in the National Archives. 

A fudged six-zone plan was eventually decided upon for England and Wales, developed from the A and B road original, but including more limited caveats. Its big inconvenience was that not all motorways were planned radiating out from London like A roads, which demanded more flexibility and lateral – now sometimes unfathomable – thinking compared to the original.

The map shows the 1960’s plan, with M1 to M4 radiating from London, forming “clockwise” zone boundaries. With M1 joining the A1 north of Leeds, zone 1 was quite similar to its A road equivalent. The Thames estuary again forms Zone 2’s boundary, while the M3 is the Zone 3 border on its way to, er, somewhere west of Basingstoke, only recently extended to the outskirts of Southampton. The M4 is zone 3’s northern boundary: continuing clockwise, Zone 4 begins. 

After this it gets interesting… The M6 leaves the M1 at Rugby, running via Birmingham to beyond Carlisle, putting everything north of M4 and south and west of that midlands M6 section into a very large Zone 4. Clockwise, the area north and east of M6 to the Solway Firth, across to Edinburgh and west of A1 (neé M1 remember…) becomes Zone 6.

Exactly what happened next seems rather lost in the mist of time, but someone seems to have spotted that zone 5 was missing – and zone 4 was far too big for comfort. Numerical and practical logic seem to have played no further part here, but broadly the plan was manoeuvred like this.

The M5 was originally conceived as “bypassing” the long distance A38 Bodmin to Birmingham route, and was now in tandem with M6 heading north used to conveniently divide zone 4. Everything south and west of the line of M6 and M5 from the Solway Firth to the south Wales coast was placed into a new Zone 5. 

Where the M5 and M4 cross near the Severn Estuary, a grey area was created.

In the 1960’s this was zone 3 and 5 territory, but later the M5 continued south (picture shows Clevedon cutting) to Exeter – raising questions about how new motorways south of M4 in Wales, and west of the M5 to Exeter might be numbered?

Its perhaps rather academic, since all-new British motorways currently rate in rarity value along with hens’ teeth… but slavish obeyance of old rules can sometimes be overridden by outbreaks of common sense – and there’s a precedent hereabouts. 

Motorways west of Bristol saw some changes when the second Severn Crossing opened: these were in ‘old’ Zones 3 and 5… but zone 4 M48 allocations went to the original Severn bridge and its approaches, while a new M5 to M4 link became the M49.

This wasn’t the first time common sense prevailed, though these allocations broke the system-wide principle that motorways always carry originating zone numbers in their first digit, and can extend only into higher numbered zones. Incidentally this is why the Bristol urban motorway is designated M32, despite linking to M4 – and being many miles from M3. Interestingly M32 was once suggested for the M4 Heathrow tunnel link.

A secondary motorway numbering pattern introduced very early on is now used extensively for new bypasses, links and spur roads. Where existing A roads are improved to motorway standards, they frequently retain their original road number, but gain an ‘M’ suffix. If the original road still exists, sometimes its re-numbered, sometimes not.

This will also raise an issue about the numbering of the proposed Newport relief road sweeping south of the M4 from Magor to Caselton (above) and avoiding the Brynglas tunnels bottleneck and earmarked for completion by 2020. 

There’s history here: the early plan was to build and link lots of (M) bypasses, eventually creating “proper” longer motorways. Some northern parts of M6 were constructed like this – but we all know about the best laid plans involving road transport in Britain. The clearest surviving incomplete example of the policy is the A1(M), with long stretches of this historic route upgraded over (many) years… but still bypasses and sections of “ordinary” A1 road remain unlinked.


Scotland’s A route zones are also used for motorways, allowing a straightforward numbering system. Motorways were routed as close as practical to the most heavily trafficked A roads, allowing existing A road numbers to also be used as motorway M numbers. Thus the M8 parallels A8; and the M9 at least part of the A9. The snappily titled M74 is an unavoidable aberration linking Glasgow to the English M6… but it effectively replaces the A74.

There’s much more to motorway numbering than is covered here, and 60 years on – with some founding rules now distinctly bent – the original plan looks frayed around the edges, but still keeps Britain on the move. Now you’re in the know, try spotting some of the many off-plot motorway numbering anomalies when you’re out and about.  


Some of the civil service memos on motorway numbering ideas and related dialogue from the early 1950’s are here:

The archive relating to this topic is, perhaps regrettably, not online. Its held at and for Scotland at 

An official region-by-region, section by section story of building Britain’s original motorway network is here

A list of road numbers that have either never been allocated or are not currently in use is here:

Books and publications

Motorways – Drake, Yeadon and Evans (Faber and Faber, 1969)

A History of British Motorways – George Charlesworth (Thomas Telford, 1984)

The Motorway Achievement Volume 1, edited by Sir Peter Baldwin and Robert Baldwin (Thomas Telford, 2004)

Roads for the Future – Department of Transport, 1969

Roads for Prosperity – Department for Transport, 1989

A brochure issued at the opening of the Preston bypass in December 1958 is here:

Dave Moss
Dave Moss

Dave Moss has a lifetime connection with the world of motoring. His father was a time-served skilled engineer from an age when car repairs really meant repairs: he ran his own garage from the 1930’s to the 60’s, while Mum was the boss’s secretary at a big Austin distributor. Both worked their entire lives in the motor trade, so if motor oil’s not in Dave’s blood, its surely a very close thing.

Though qualified in Electronics, for Dave it seemed a natural step into restoring a succession of classic cars, culminating in a variety of Minis. Writing and broadcasting about these, and a widening range of motoring matters ancient and modern, gathered pace in the 1970’s and has taken over since. Topics nowadays range across the modern motoring mainstream to the offbeat and more arcane aspects of motoring history, and outlets embrace books, websites national and international magazines, newspapers, radio programmes, phone-ins and guest appearances. Spare time: hard graft on the garage floor attending to vehicles old and new. Latest projects: that 1968 Mini Cooper S has finally moved again after 30 years, and when the paint is finished, the 1960 Morris Mini 850 will also soon be ready for the road again…

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