How the Motorways were Numbered

Where do we start?

The earliest form of numbering related to "Motor Road" project numbers. "Motor Roads" being an early name for motorways.

This was a system that was completely divorced from the all-purpose system, and the motorways would be allocated numbers based on a big list held at the Ministry and the next one in the list handed out. There would be no geographical basis to the numbers, unlike for the all-purpose system.

Motor Road project numbers were developed in the late 1940's as a shorthand for the motorway alignments county surveyors were asked to fix for planning purposes.

The major drawback with this system was the lack of systematic numbering, so that the final motorway network would consist of completely random numbers.

In true Ministry fashion, it was intended solely as an internal system. Mind you, as we've seen, that was the original idea behind numbering roads in the first place!

Some examples of numbers assigned using this scheme are:
M1 London - Yorkshire Motorway
M2 Birmingham - Lancaster Motorway
M5 Birmingham - Exeter Motorway

Oddly, the scheme appears to lapse in the mid-1950s - just at the point where motorway construction is starting.

Map of proposals

Things move on - 17th April, 1958.

Construction on the Preston Bypass is well under way, and work has started on several other early motorways, including what is now the M1.

No decision has been made yet, and so memos are being written regarding suggestions.

W. Hadfield at the Ministry sits down and starts to dictate. These are some extracts from that very memo, held in the National Archives in Kew, London.

"With a view to continuing this [the in-place] system, the number A.50 has in fact been reserved in anticipation for the London - Birmingham Motorway, with the idea that it would form a parallel to A.5, and again largely on the clockwise side of it, but we have not equivalent reservations for all the other routes; some would need to go into three figures e.g. A.200, and we run into difficulties where the motorways may be said to radiate from Birmingham rather than London.

In respect of the possibility of our including European numbers on some of these motorways, it is thought that as such numbers would be in special colours, namely, white on green, and that so far there are only eight of them, we might introduce a new system of numbers for the motorways with the letter M, giving for home travellers three systems, namely M, A and B. The distinctive letter will have a particular advantage, in that it will immediately tell drivers who see a signpost to an M route that it will be subject to motorway conditions, so that drivers can choose or reject it purely on that account."

This is an early mention of the use of the M prefix that we know today. Another interesting thing about this section of the memo is the way that it talks about the possibility of using European "E" numbers on signs. Whilst the thought of white on green signs seems perfectly normal to us today, back in 1958, the modern white on green signage was still nearly ten years away. And of course, "E" numbers have never made it onto UK signage.

The memo continues:

When we have short spurs on roads, they are sometimes given separate numbers, but occasionally the the same number is used for both arms of the spur. This latter alternative has both advantages and disadvantages, and I think it should only be adopted when the spurs are quite short, so that a driver who might choose the wrong arm is not taken far out of his way. Clearly the forked junction planned for the southern end of the Preston Bypass would have the same number, though drivers approaching it should take the right hand fork for Wigan, and the left hand fork for Manchester. However, if a driver wanting Wigan happens to take the left hand fork, he has not gone far from the shortest route.

This therefore lays the groundwork for the modern approach of short spurs not getting their own number, for example the Gatwick Airport Spur from the M23, the Heathrow Airport spur from the M4 and the Manchester Airport spur from the M56.

Now, let's get on to the meaty parts:

With these principles in mind, let us try to apply them to the projected motorways. The London - Birmingham - Doncaster one at its southern end might be more properly labelled as M.5 at its southern part, and M.1 north of Birmingham. However, the system is not applied inflexibly without regard to common sense, and that suggests that this route should be M.1 between London and Doncaster, with the branch to Birmingham M.5. As regards the spurs, I think we would run into difficulty if we tried to number them seriatim starting from London. Clearly the addition of spurs subsequently would upset such numbering, and M.5 would then not be appropriate for the Birmingham Branch as a parallel to A.5. The alternative is to number the spurs in relation to the equivalent A routes, which suggests that the southern spur near London be numbered M.41, that going north to Sheffield M.57 and that south of Doncaster M.60.

Continuing this system the Medway Towns Bypass would be M.2, and the sections bypassing Slough and Maidenhead and going north of Bristol to South Wales M.4. The northern one from Birmingham might conveniently be called M.6, and the Birmingham - South Wales one M.38 terminating at the Severn Bridge, with M.40 for the Ross Spur.

The Hull - East Lancs. route could be M.63, the Droitwich - Leicester route M.46. The London Orbital Road is not immediately obvious, the present north orbital number being 405, and we might have to compromise with the system, for example to call this M.45.

It will readily be appreciated that short numbers will help with the size of signs, and hence it is suggested that we should never have more than two digits.

My life, there's a lot there. Some will be familiar-sounding, some not. The most stark difference is that one of the most-often asked questions about motorway numbering has an answer. That question is, of course, "Why isn't the M5 called the M38?". Well, under this suggested system, it was!

Map of proposals

The plan gathers pace - 8 June 1959

The Preston Bypass, Britain's first motorway has been open some months now, and still the Ministry are dithering.

A. W. Lovett, Road Traffic Division.

Mr. Hadfield has set out some ideas about this system (Doc. 1). I think we should accept his suggestion that all the motorway should have the distinguishing prefix M and that they should be numbered in accordance with the existing zoning system for trunk and classified roads. The M will give travellers an immediate indication (not only on signposts but on maps) that the road is subject to motorway regulations and it is difficult to see how any other but the existing system (which is widely understood and approved) could be used for the numbering without appearing illogical and confusing.

To carry this argument a stage further, it would be clearly logical so far as possible to give each motorway an M number the same as the A number of the main route it doubles or parallels. Thus, as Mr. Hadfield suggests, the Medway Towns Bypass might be M.2, the Slough and Maidenhead Bypass M.4, the Birmingham - Preston M.6, the Birmingham - South Wales M.38 and the Ross Spur M.40.

With regard to the London - Birmingham, Mr. Hadfield suggests M.1 (since this motorway, when eventually extended into Yorkshire, will duplicate the Great North Road), with M.5 for the spur to Birmingham. But this suggestion leaves out of account the question of by-passes built to motorway standards along e.g. the Great North Road. I understand that the Stevenage, Biggleswade, Stamford and Doncaster Bypasses are all to be built to motorway standards and will be subject to motorway regulations. I have discussed this question with Mr. Huddy, who feels that for the sake of continuity the whole road, including bypasses, should have the same number (A.1) all the way from London to Edinburgh. We must respect this view but it seems to me essential that the bypasses should have M numbers to give the indication, referred to above, that motorway restrictions are in force. The continuity would be preserved by the numeral - thus all the bypasses along the Great North Road would be M.1. This being so, we still have to find a number for the London - Birmingham and I would recommend endorsement of Mr. Hadfield's earlier suggestion that it should be M.5, since it takes off from the A.5 at Park Street and the A.5 is the chief route from London to the Midlands. I would suggest M.50 for the eventual extension into Yorkshire - this a motorist travelling from London to say north of Doncaster might take the M.5 to Watford Gap, M.50 to the Doncaster Bypass and M.1 along the Doncaster Bypass. This strikes me as an easily memorised sequence and Mr. Hadfield, with whom I have discussed the suggestion, thinks there is a lot to be said for it.

On some of the points of detail raised by Mr. Hadfield in Doc. 1, I agree that we cannot rely solely on the European E numbers since there will be many motorways that will not have E numbers. As to spurs, I think that whether these should have separate numbers should depend entirely on the length and importance of each. The Anderson Committee have decided that for signposting purposes the half-mile spur from Kidney Wood at the northern end of the St. Albans Bypass to Pepperstock on the A.6 should be treated as a long slip road; I think this is right and that for traffic purposes it need therefore have no number. The western arm at the southern end of the St. Albans Bypass joining A.41 at Aldenham is, however, a different matter and I agree with Mr. Hadfield that this should be M.41.

I do not think that there would be any insuperable difficulties involved in three figure numbers like M.405 for the London North Orbital Motorway. The Anderson Committee have already been apprised of this possibility.

That's fairly similar to that seen above, with one or two detail changes regarding the London - Yorkshire Motorway, and the suggestion that three-digit numbers could be used.

There are also handwritten notes at the bottom of this memo, that suggest that not everyone agrees with the plan. The most interesting one is from a person who will soon come to the forefront of the debate - C. H. Wykes.

Thank you. I have dispatched the minutes proposed but I am retaining an open mind on what system we should adopt until the pattern can be seen. I am not very happy about a system which might result in say, 40 motorways being given numbers in such a large range as from M.1 to M.405 nor am I entirely convinced that much is to be gained by having numbers which correspond with roughly parallel A routes. Would it not be better to have an M numbering system which is coherent in itself? After all, they are to be the country's most important routes rather than mere alternatives to existing A routes.

Map of proposals


Part 2 - Panic Stations! >>

How the Motorways were Numbered


Part 1

Part 2

Part 3

Part 4

Part 5


Thanks to Jonathan Winkler, Chris Marshall and Mark Dillon for their help towards the production of this feature.