The outbreak of the Great War in 1914 brought work to an abrupt stop. It was only in September 1919, as home affairs were returning to normal, that Sir Henry was invited to resume his classification work, now under the new Ministry of Transport.
Building a system
Setting up the Ministry took time. Once there were enough people working there to make a go of it, Sir Henry and his colleague Colonel Richmond wrote again to County Councils asking them to perform traffic surveys on all their roads and return the data so that classification could begin. The work only really got under way in 1920. The system of Class I and Class II roads was resurrected, but now with a new focus of providing a means of navigation, the idea of duplicating numbers in each county was scrapped.
It's hard to say how influential the Michelin company was in the numbering system that was eventually adopted, but André Michelin himself (founder of the Michelin company) took a great interest and wrote a series of four short papers on the subject of French and British road numbering for the Ministry's attention. He explained the French system, and its disadvantages, and went on to propose a system for Britain:
"A first numbering would include the main roads leaving London and the main transversal roads, such as:-
- Glasgow - Edinburgh
- Stranraer - Newcastle
- Liverpool - Scarborough
- Birkenhead - Newcastle
"We think these might well be lettered "N" (corresponding to National) which would afford an interesting similarity to the classification of the French roads.
- The first numbers would be given to the roads leaving London in a northerly direction and then turning from left to right in the sense of the hands of a watch.
- Transversal roads would be numbered from north to south.
"For the other roads, in order to avoid a change of number for purely artificial reasons (administrative boundary, etc.), we would suggest to divide the country into sectors bounded by the National roads. These sectors would reach a maximum of 24 and would radiate from London in accordance with the scale map attached herewith.
"Each sector would be distinguished by a letter of the alphabet (except the letter "N").
"All the first class roads in a sector would be given a capital letter as allocated to the sector, followed by a number (Example: A49, H54). All the second class roads in the sector would be given a serial number followed by a lower case letter as allocated to the sector (Example: 59a, 54h)."
Sir Henry Maybury thanked Michelin for his trouble and the whole lot was forgotten.
As the surveys came back in, maps were marked up to show which roads carried enough traffic or connected sufficiently important places to be regarded as Class I, and which were Class II. The initial proposal to use the designations T and L for first and second class roads - standing for "Trunk" and "Link" - was soon replaced by the idea of simple A and B designations*. The letters A and B don't stand for anything in particular. It's more like a school report where the best roads are awarded grade A, and the smaller connecting roads dread parents' evening because they only got a B.
But enough letters: it was time to start pencilling in some numbers.
A hub-and-spoke system, loosely modelled on the one used by France, was the intention from the outset. At first the numbering encompassed only England and Wales, with Scotland numbering its own roads shortly afterwards. But exactly what form the system would take, and where the spokes would lie, was more problematic. One document lists the London radials and numbers them from one to five - missing out the London-Dover route and giving England and Wales just five zones. It's not clear whether this is just a mistake in an early draft, though, as there are references on the same page to six zones.
A document from about May 1921 (referring only to England and Wales) refers to the A6 as running to Glasgow, and states that "number 6 sector is bounded on the North by the Carlisle - Berwick-on-Tweed Road to which No. 7 is allotted" (Col. Richmond, "Suggested System of Route Numbering"). Aside from the minor gripe that there is no direct or obvious road along the border from Carlisle to Berwick, this splits the system into two very clear parts, with zone 6 prevented from entering Scotland.
There was also a great deal of interest from members of the public, and archive documents on the subject contain an incredible number of letters asking how road numbers were allocated or how the system worked. Each one got its own reply, individually written but always along the same lines.
In 1941, the Encyclopædia Britannica expressed an interest and the response from the Ministry contained a very helpful (and, for once, concise) outline of their intentions for the different classes of road.
"Under this scheme the most important roads connecting large centres of population and other roads of outstanding importance from the point of view of through traffic were classified as Class I roads. Roads forming important links between Class I roads and between the smaller centres of population were classified as Class II roads. Roads of purely local importance were not classified."
Local authorities were actively encouraged to put numbers on new signs and to begin appending them to existing ones as soon as the first batch of numbers were made public in summer 1921. The Ministry of Transport covered all such costs, and once the first 99 A-roads were covered they were keen to see the signposting applied to progressively smaller and smaller routes.
There was a simple reason for the numbers not being made public. In mid-1937 it was suddenly realised that the Ordnance Survey provided a cunning new way of locating points on their maps by use of the National Grid - so any point could be located to within a few yards by a string of co-ordinates.
It was discovered quite by accident, when a senior cartographer at the Ordnance Survey was enlisted to write a leaflet explaining the system, and sent his draft text to an old friend to get his comments on it. The old friend happened to be a senior Ministry of Transport civil servant working on the new Trunk Roads. He then realised that it was possible to send work crews out with a map and a set of co-ordinates, and to keep the whole messy business of Trunk Road numbers secret.
If it wasn't for the old school tie network, we might even today be driving on T-roads.
The history of how motorways came to be numbered is every bit as interesting, and slightly more panicked, than this one. The full story is over at Pathetic Motorways.
* In 1922 Ireland declared its independence from the UK, inheriting classification data but no road numbers. Until 1977, its roads carried T and L numbers, not A and B.
** This plan isn't very well thought-out: there is an arc drawn showing how road numbers should increase as they progress clockwise around Edinburgh, but the ones labelled on the map do the opposite, with A81 on the east coast and A87 in the west.
With thanks to Brian Rolph and Nevis Hulme for information on this page.