Why are some Motorways numbered similar to A roads the replaced and others not?

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wrinkly
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by wrinkly » Tue Oct 19, 2021 11:37

Motorways were given similar numbers to parallel A roads where the number was free and the rules didn't preclude it.

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Re: Why is the M1 called the M1?

Post by Bryn666 » Tue Oct 19, 2021 11:39

Herned wrote:
Tue Oct 19, 2021 10:54
qwertyK wrote:
Tue Oct 19, 2021 10:42
A third is relatively significant IMO.
If the motorway numbering system is different to the A road numbering system, why does the M11 run parallel to the old A11 for most of its length? Or the M20 with the A20 etc? M23/A23?
I suspect the answer is because even though it is a separate system, the logic is the same. The (English) numbering is based on London, and the most important road is numbered 1 in both systems. Then logically you can either number clockwise or anti-clockwise, and that decision gets you pretty quickly to the numbering system there is. The first motorway east of the M1 is the M10, the second is the M11. As it was decided not to build an entirely new motorway up the A1 corridor, the next long distance route is towards Cambridge.... and so on. I guess logically that would have led to the M23 perhaps being the M21, but there is enough leeway and common sense to number it the same as the a-road it partially replaces. I guess the truth is it is not a purely rule-based system and common sense does come into it
Motorways which generally replaced an existing corridor tended to be numbered in a similar fashion provided it was in zone. The A46 replacement scheme between Coventry and Leicester was of course not in the motorway 4 zone hence the M69. Presumably people today have to park up and have an emotional meltdown over how 'confusing' it all is, whereas once we'd have just got on with it.
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Chris Bertram » Tue Oct 19, 2021 12:08

Let's remember that French and German (just for example) motorways don't necessarily match their national routes number-for-number either. In France it's the A16 that shadows the N1, or what remains of it that hasn't been downgraded, while A1 makes a beeline from Paris to Lille, and I've no idea what N route(s) that has replaced. Meanwhile in Germany, A1 runs from the Saarland to Schleswig-Holstein; B1 runs from near Aachen to a point on the Polish border.

By contrast, the Netherlands seems to align with Ireland, with no separate numbering scheme and motorways being "A" sections of otherwise "N" roads. Sometimes a route is all motorway - there is no N5, but there is an A5.
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Re: Why is the M1 called the M1?

Post by Micro The Maniac » Tue Oct 19, 2021 12:54

qwertyK wrote:
Tue Oct 19, 2021 10:42
If the motorway numbering system is different to the A road numbering system, why does the M11 run parallel to the old A11 for most of its length? Or the M20 with the A20 etc? M23/A23?
Correlation does not mean causation.

Compare:
  • M3 with A30 then A33
  • M5 with A38
  • M6 with A5
  • M27 with A31 (at least, to start with)
  • M53 with A41
  • M62 with A63 (for more than A62)
  • M69 with A46
  • etc

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Re: Why is the M1 called the M1?

Post by KeithW » Tue Oct 19, 2021 13:07

Micro The Maniac wrote:
Tue Oct 19, 2021 09:20
qwertyK wrote:
Mon Oct 18, 2021 13:35
For a large part of its length, the M1 runs parallel to the A5.
For its first 65 miles, the M1 loosely follows the A5... but for its remainder 135 miles it doesn't... so a third which is not "a large part"
The A5, M1, West Coast Main Line and Grand Union Canal all run parallel to each other for the simple reason that they use the Watford Gap which is a flat level area between 2 hills.

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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by crb11 » Tue Oct 19, 2021 18:25

It's interesting to note that in another universe where the M11 got built according to the original plans (west of Harlow then down the Lea Valley) we'd be wondering why a motorway largely in the A10 corridor was called the M11, whereas the London end of the A11 had been replaced by the M12.
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Glenn A » Sat Oct 23, 2021 15:32

The M4 is probably most logical, at least in England, it replaced the A4 from London to Bristol, but the M5 has absolutely nothing to do with the A5 and is a by pass of the A38, but the Mx number was probably chosen as it is a very important motorway, linking the West Midlands with the South West.

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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Steven » Sat Oct 23, 2021 19:18

Glenn A wrote:
Sat Oct 23, 2021 15:32
the Mx number was probably chosen as it is a very important motorway, linking the West Midlands with the South West.
Or of course, people could read and take in the actual evidence as linked to in this thread and not just guess and hope they've got it right in order to just say something.
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Big L » Sat Oct 23, 2021 21:24

Where's the fun in that?
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Steven » Sat Oct 23, 2021 21:35

Big L wrote:
Sat Oct 23, 2021 21:24
Where's the fun in that?
I know. Facts are so boring in this post-truth world...
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by booshank » Sat Oct 23, 2021 22:45

Steven wrote:
Sat Oct 23, 2021 19:18
Glenn A wrote:
Sat Oct 23, 2021 15:32
the Mx number was probably chosen as it is a very important motorway, linking the West Midlands with the South West.
Or of course, people could read and take in the actual evidence as linked to in this thread and not just guess and hope they've got it right in order to just say something.
Well in a sense it is correct, as the M5 forms a zone boundary and so naturally has an Mx number. They wouldn't have chosen, say, M538 as the number. And it would have been chosen as a zone boundary as it is a long/important route.

Personally, I think it's a pretty silly, overcomplicated system, but it's a bit late to do anything about it now. If I were starting from scratch I'd probably number the motorways roughly in order of length and importance say the existing M1-M6-A74(M)-M74 (maybe M73, M80 and M9) as M1, either the rest of the M1 or the A1(M) or the M1 and then A1(M) as M2 etc.

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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Glenn A » Sun Oct 24, 2021 14:26

I think the current system works and renumbering motorways would be pointless. The M5. one of the most important motorways in the country, sounds so much more important than M38 or A38(M), which in the latter's case means Aston Expressway. M2 and M4 are logical, replacing the A2 and A4 respectively.

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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Chris Bertram » Mon Oct 25, 2021 13:23

Glenn A wrote:
Sun Oct 24, 2021 14:26
I think the current system works and renumbering motorways would be pointless. The M5. one of the most important motorways in the country, sounds so much more important than M38 or A38(M), which in the latter's case means Aston Expressway. M2 and M4 are logical, replacing the A2 and A4 respectively.
Well actually M4 also bypasses A48 from Chepstow pretty much all the way to Carmarthen.
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Gareth Thomas » Sun Oct 31, 2021 11:41

I suppose it also depended on where the motorways were in the country and how out of zone the corresponding A- road might be. The motorway built that shadows the A20 could easily have been called M24, it is a valid Motorway Zone 2 number, but it made sense to call it the M20 because it is right by the A20 and meets it at almost every junction.

(Yes, I know it started out as the A20(M) and that’s how the number really came about. 😄)

The motorway from Coventry to Leicester though could not be the M46, even though that number was available, because it was in Motorway Zone 6 and thus the M69 was chosen for that motorway.

It does tend to be the motorways in Zones 5 and 6 that differ greatly from their A-road counterparts, because those zones are completely different. Off the top of my head it is only really the M56 and M62 that shadow their respective A-roads.
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Bryn666 » Wed Nov 03, 2021 18:24

Gareth Thomas wrote:
Sun Oct 31, 2021 11:41
I suppose it also depended on where the motorways were in the country and how out of zone the corresponding A- road might be. The motorway built that shadows the A20 could easily have been called M24, it is a valid Motorway Zone 2 number, but it made sense to call it the M20 because it is right by the A20 and meets it at almost every junction.

(Yes, I know it started out as the A20(M) and that’s how the number really came about. 😄)

The motorway from Coventry to Leicester though could not be the M46, even though that number was available, because it was in Motorway Zone 6 and thus the M69 was chosen for that motorway.

It does tend to be the motorways in Zones 5 and 6 that differ greatly from their A-road counterparts, because those zones are completely different. Off the top of my head it is only really the M56 and M62 that shadow their respective A-roads.
That's because the Lancashire motorway network was always planned to be an major system of roads in their own right instead of this constant SABRE obsession that motorways are just supplementary to A roads, although even here there are exceptions, such as the M66 ending randomly at Edenfield because the Edenfield Bypass had been built as a D2 AP following the 1949 Road Plan whereas the M66 was created when it was realised an A road would not be sufficient for traffic flows past Bury. I can't confirm but everything south of the A58 would have had to be motorway to connect to the Manchester Outer Ring Road regardless.

Equally, there were numerous arguments about the M61 - early proposals had it terminating on the Blackrod Bypass whilst they figured out the rest of the route into Manchester. Thankfully this was nixed and the M61 was instead correctly routed where it now is.

The Stretford-Eccles Bypass was for a short while listed as A575(M) before it became the M62.
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Owain » Sat Nov 06, 2021 09:35

Gareth Thomas wrote:
Sun Oct 31, 2021 11:41

The motorway from Coventry to Leicester though could not be the M46, even though that number was available, because it was in Motorway Zone 6 and thus the M69 was chosen for that motorway.
Actually, it could probably just about get away with it, because it does extend ever so slightly to the south of the M6! :stir:
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Osthagen » Sat Nov 06, 2021 11:10

Gareth Thomas wrote:
Sun Oct 31, 2021 11:41
The motorway from Coventry to Leicester though could not be the M46, even though that number was available, because it was in Motorway Zone 6 and thus the M69 was chosen for that motorway.
Numbering the Coventry-Leicester motorway M46 would be no more illogical than numbering the Aust Severn crossing “M48” or the M5-M4 link the “M49”. The former is in zone 5 and the latter in zone 3., All while a plenteous number of M5x and M3x numbers are available; M51, for example has never been allocated to anything.

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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Steven » Sat Nov 06, 2021 11:50

Osthagen wrote:
Sat Nov 06, 2021 11:10
No M4x roads are actually in the relevant motorway numbering zone
I don't have to go beyond M40 to see that this is false.
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Osthagen » Sat Nov 06, 2021 12:08

Steven wrote:
Sat Nov 06, 2021 11:50
Osthagen wrote:
Sat Nov 06, 2021 11:10
No M4x roads are actually in the relevant motorway numbering zone
I don't have to go beyond M40 to see that this is false.
I will join you in beating me at my own game and mention the M42 and M45, the former of which I’ve used enough and really should have known better.

My main point of numerous M4x routes not conforming to the zoning system remains as strong as it always was.
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Re: Why are some Motorways numbered similar to A roads the replaced and others not?

Post by Micro The Maniac » Sun Nov 07, 2021 07:08

Osthagen wrote:
Sat Nov 06, 2021 11:10
Numbering the Coventry-Leicester motorway M46 would be no more illogical than numbering the Aust Severn crossing “M48” or the M5-M4 link the “M49”. The former is in zone 5 and the latter in zone 3.
M48 is clearly in the 4 zone, as it took over the route of the M4 - thus the zone boundary didn't change and it became M4x.

As it is south of the M4 (3 zone?) and west of the M5 (5 zone?), we can debate the M49 until the cows come home... I've long suggested that this indicates the logical boundary of the Severn (cf Thames and Humber) being used rather than the M5 - but until a new motorway is built between the M5 and the Bristol Channel we will never truly know.

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