Great Britain road numbering scheme

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The Great Britain road numbering scheme is a numbering system used to classify and identify all major roads in Great Britain.

Each road is given a single letter, which represents the road's category, and a subsequent number, with a length of between 1 and 4 digits. Similar systems are used in Northern Ireland, the Isle of Man and the Channel Islands. All of these numbering schemes use identical basic conventions and road-sign designs.

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History of road numbering

Great Britain has many ancient roads and trackways dating back not only to the Roman occupation of southern Britain but to much earlier times, including the oldest engineered road to be discovered anywhere in the world: the Sweet Track dating from the 3800s BC.

Following the advent of the motor car around the turn of the 20th century, it was deemed necessary to invest more money in the British road system. This funding was realised through an Act of Parliament in 1919. In order to decide which roads required the most investment, the government invented a system of 'A' and 'B' numbered roads, with the former category receiving more money than the latter.

The first set of numbered roads was finalised in 1923, and was published in a book issued by HMSO. Shortly after this, the numbers started to appear in road atlases and on signs on the roads themselves, converting them into a tool for motorists in addition to their use for determining funding. The numbers of the roads changed quite frequently during the early years of the system as it was a period of heavy expansion of the network and some numbered routes did not follow the most usual routes taken.

With the introduction of motorways in the late 1950s, a new classification 'M' was introduced. In many cases the motorways were replacing existing stretches of A-road, which therefore lost much of their significance and were in some cases renumbered. There was no consistent approach to this renumbering - some retained their existing number as non-primary A roads (e.g. the A40 running alongside the M40), others were given 'less significant' numbers (e.g. the A34 in Warwickshire became the A3400 after the M40 was built) and the remainder were downgraded to B or unclassified roads (e.g. the A38, which has been replaced by the M5 between Bristol and Exeter). Occasionally the new motorway would take the name of the old A-road rather than having its own number. The most notable example of this is the A1(M).

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Important radial roads in England and Wales

Important roads radiating from London have single digit numbers, starting with the A1 which heads due north. The numbering continues sequentially in a clockwise direction, thus:

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Important radial roads in Scotland

Similarly, in Scotland, important roads radiating from Edinburgh have single digit numbers, thus:

While the road numbering system in Scotland centres on Edinburgh, arguably the true "hub" for its road network itself is Broxden Junction in Perth.

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Zoning system

Image:United Kingdom A road zones.jpg

In England and Wales the road numbering system for all-purpose (i.e. non-motorway) roads is based in on a radial pattern centred on London. In Scotland the same scheme is centred on Edinburgh. In both cases the main single-digit roads (largely) define the zone boundaries.

Zone 1: North of the Thames, east of the A1
Zone 2: South of the Thames, east of the A3
Zone 3: North/West of the A3, south of the A4
Zone 4: North of the A4, south/west of the A5
Zone 5: North/East of the A5, west of the A6, south of the Solway Firth/Eden Estuary
Zone 6: East of the A6 and A7, west of the A1
Zone 7: North of the Solway Firth/Eden Estuary, west of the A7, south of the A8
Zone 8: North of the A8, west of the A9
Zone 9: North of the A8, east of the A9

Motorways use a similar zoning system, based on the single-digit motorways, however, as there is no M7, Zone 7 applies to any motorways between the M8 and the English/Scottish border.

The first digit in the number of any road should be the number of the furthest-anticlockwise zone entered by that road. For example, the A38 road, a trunk road running from Bodmin to Mansfield starts in Zone 3, and is therefore numbered with a A3x number, even though it passes through Zones 4 and 5 to end in Zone 6.

To view a list of roads where this does not apply, see Anomalously numbered roads in Great Britain.

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Two-digit "A" roads

These radials are supplemented by two-digit codes which are routes that are slightly less important (but may still be classified as trunk routes), although many of these routes have lost a lot of their significance due to motorway bypasses, or the upgrading of other A-roads. These routes are not all centred on London, but as far as possible follow the general principle that their number locates them radially clockwise from the associated single digit route. For example, the A10 (London to King's Lynn) is the first main route clockwise from the A1, the A11 is the next, and so on:

Note on numbering: These roads have been numbered either outwards from or clockwise around their respective hubs, depending on their alignment.

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Other "A" roads

The system continues to three and four digit numbers which further split and criss-cross the radials. Lower numbers originate closer to London than higher numbered ones. Most roads built or reclassified since road numbers were introduced in 1919 have four-digit numbers. Knowing the number of the road you are on will give you a rough idea of where you are geographically once the system is understood. Below is a rough guide to the numbering series which apply to the various areas of the Great British mainland:

  • 10 and 100 series numbers: Greater London, Essex, Cambridgeshire, East Anglia, Lincolnshire, Pts of Yorkshire, Cleveland, Tyne and Wear, Northumbria, and on up to Edinburgh.
  • 20 and 200-series numbers: Surrey, Sussex and Kent
  • 30 and 300-series numbers: Hampshire, Dorset and South West England
  • 40 and 400-series numbers: Central England and south and Mid Wales
  • 50 and 500-series numbers: North Wales, North Midlands, Cheshire, Southern Lancashire and Cumbria
  • 60 and 600-series numbers: North-East England, Yorkshire and Lancashire
  • 70 and 700-series numbers: Southern and Central Scotland
  • 80 and 800-series numbers: North West Scotland and the Western Isles
  • 90 and 900-series numbers: North East Scotland, Orkney and Shetland

Some of the most important 3-digit "A" roads are:

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Motorway sections of "A" roads

Some sections of "A" roads have been improved to the same level as motorways, while usually remaining dual carriageways. These sections retain the "A" road designation, but are suffixed (M).

Some examples are:

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"B" roads

"B" roads are numbered local routes, which have lower traffic densities than the main trunk roads, or A road. They are typically short, not usually more than 10 miles. The classification has nothing to do with the width or quality of the physical road. B roads follow the same numbering scheme as A roads, but almost always have 3- and 4-digit designations. Many 3-digit B roads outside the London area are former A roads which have been downgraded owing to new road construction; others may link smaller settlements to A roads.

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"C", "D" and "U" roads

Roads and lanes with yet lower traffic densities are designated "C", "D" and "U" roads, but while these are numbered, in general this is done purely for the benefit of the local authorities, etc. who are responsible for maintaining them, and the numbering is arbitrary and does not, or should not, appear on any public signage. Some exceptions to this are known, however. [1]

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Motorways

Main article: List of motorways in the United Kingdom

The first motorway in Britain was the Preston Bypass, opened in December 1958. This is now a section of M6, plus the M55 to junction 1. The M1, M10 and M45 opened together in 1959.

Motorways first came to Britain over three decades after the advent of the A-road numbering event, and as a result required a new numbering system. They were given an M prefix, and a numbering system of their own not conterminous with that of the A-road network.

The most important single-digit motorways were numbered to (loosely) match the existing main roads which the motorway follows or was intended to relieve traffic from. The level of correlation differs; the M4 motorway stays very true to the line of the A4 road throughout England, whereas the M1 motorway meanders a path not too close to the A1 road, although generally north-south like its predecessor.

The rule is followed even more rigidly in Scotland - a motorway must take the number of its predecessor A-road where available. This is the explanation for the lack of an M7 motorway, a number which otherwise may have been assigned quickly.

A very obvious exception to this rule is the M5, which closely mirrors the A38. It was numbered uniquely to give this road perceived importance - it was already known that the A5 road needed no such motorway bypass as this was already the job of the M1.

The single-digit motorways mark out zones or cones, the concept analogous with that of the A-road network. However, due to the difference in position of the A5 vs. the M5, the actual position of these zones varies greatly, especially in the Midlands and South West England.

Shorter motorways typically take their numbers from a parent motorway in violation of the zone system, explaning the apparently anomalous numbers of the M48 and M49 motorways as spurs of the M4, and M271 and M275 motorways as those of the M27. The latter two might be explained by the original plan for the M3 motorway, which was due to head towards Exeter, rather than the Southampton as it does now. The original committee which set up the motorway zones chose the boundary of zones 2 and 3 to be the projected line of the M3 towards Exeter, although it's not currently known whether this is still the case.

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Fictional roads

Fictional numbers are assigned for use on TV and film; such a number that is involved with a serious fictional accident is blacklisted for five years from actual use.<ref>http://www.southerncarclub.com/may99-5.htm</ref>

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Ancient roads

Some ancient routes, such as Roman roads, travel for great distances and have a single modern number for the majority of their length (e.g. the A5 for the Roman road Watling Street). Others, such as the pre-Roman Icknield Way and the Roman Fosse Way are nowadays rather patchy and where a modern road exists, are numbered according to the local scheme.

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See also

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References

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External links

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