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Road numbering in Great Britain

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1323103.  Fri May 31, 2019 10:24 am Reply with quote

I launch into this subject with some trepidation, because I know that once I start I won't stop. It has been an obsession of mine since I was a small child, and I still don't pretend to know how it all works...

But before starting I thought it would be good manners to check what had already been posted on the subject. Big mistake. I came across this thread from 2007 and now feel impelled to comment on a number of inaccuracies and misapprehensions. (I won't embarrass the original contributors by naming them!)

The M1 was the second motorway constructed in Britain. The first was the Preston Bypass, which later became part of the M6.

Sort of right. The first section of motorway to open was indeed the Preston Bypass in December 1958, though as far as I know it bore the number M6 from its opening. The second section is said by the Motorway Archive to be the Chiswick Flyover on the M4, but it formed part of the A4 when opened and didn't become part of the M4 until later. So the Berrygrove to Crick section of the M1 (plus the M10 and M45 spurs) is properly the second designated section of motorway to be opened.

It stems from an attempted system (pre-motorway) of numbering roads around the compass points with N=1 E=2 S=3 and W=4 hence the A1, A2, A3 etc. being the main arteries in those directions. Further, more minor (major) roads that spin off them try to follow the same 'logic' e.g the A12, A40.

True but in only a very vague sense. The clearest exposition of the numbering system for A-roads and B-roads is probably here on Chris Marshall's site (which I thoroughly recommend).

According to Mr Husband, it's because the M1 more or less duplicates the route of the A1, as does the M6 that of the A6.

This is probably one of the commonest fallacies about the British road numbering system! The numbering system for motorways is here. Only in Scotland is there a general principle that the Mx follows the route of the Ax. The original section of the M1 in fact follows the route of the A5, not the A1 - the sections of motorway along the A1 route were given the number A1(M). The M6 runs parallel to the A6 between Preston and Carlisle, but not elsewhere.

That's not to say that there aren't a significant number of motorway numbers in England and Wales that match the number of the corresponding A-road (e.g. M20 and A20) but they were allocated in spite of the system, not because of it. The best that can be said is that if the numbering system allows a number that matches a parallel A-road number, then it's usually allocated.

If this is right though, they must have soon given upon the scheme - the M5 doesn't duplicate the A5, any more than does the M25 the A25.

Actually the M25 does run alongside the A25 between junctions 5 and 8, and there are suggestions that this may have influenced the eventual choice of number.

Totally trivial fact: I'm told that the M25 was originally meant to be called the M16.

More accurate to say that "parts of what was intended to be the M16 ended up being subsumed into the M25". More on this in another post.

When it opened, the Preston Bypass was only 8 miles long, linking Bamber Bridge and Broughton. All the references to it call it the "Preston Bypass which later became part of the M6." So I'd imagine they didn't really want to call 8 miles of dual-carriageway "the M1", and waited until the 72 mile stretch of road from St Albans to Rugby opened the following year before using that epithet.

Believe it or not, when the Preston Bypass opened the national system for numbering motorways hadn't yet been decided. The excellent feature on motorway numbering at the Pathetic Motorways site reveals that all sorts of conflicting plans were mooted during 1958-9, and that the final decision on what to call the new 72-mile stretch of motorway was made barely a month before it opened.

Why isn't the A282 called the M25?

Because it predates the M25, and it's never been upgraded to motorway. The single-carriageway Dartford Tunnel opened in 1963 with that number. A second bore opened in 1980, and the QEII bridge opened in 1991 after the tunnels started to become congested with the volume of traffic from the new M25 joining at each end. It has never been part of the M25, and as far as I know was never planned to be.

But more on the M25 in a separate post soon (which also conveniently fits under "R")...

1329148.  Sun Sep 01, 2019 9:42 am Reply with quote

the first numbering system in the uk was in 1913 all the other facts that need to be said (apart from that the number after m,a etc. refers to a section of Britain) has been said by barry end of subject(for now)


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