Anomalously numbered roads in Great Britain


In the Great Britain road numbering scheme, the country is divided into numbered zones, the boundaries of which are usually defined by single-digit roads. The first digit of a road's number should be the number of the zone it occupies. If the road occupies multiple zones, then the furthest-anticlockwise zone is the correct one. The following tables list all British roads which are anomalously numbered. Roads in bold lie completely outside their "correct" zone; all other roads run for some length in their "correct" zones but trespass into zones anticlockwise of this zone. A further table lists duplicated road numbers.

Motorways

Note: The motorway zone boundaries are different from the A-road boundaries shown below.
Road numberLocationTrespassed zoneReason
M48Gloucestershire, MonmouthshireZone 5This road used to be the M4, and as it lies to the north of the current M4 and to the west of the M5, it is in the Motorway Zone 5.
M49Bristol, GloucestershireZone 3This motorway lies entirely within zone 3. The motorway was constructed at the same time as the 2nd Severn Crossing, and it is likely that the sequential M48 and M49 were used for the old M4 and the new motorway respectively.
M62Merseyside, Greater ManchesterZone 5The section from Liverpool to Manchester was planned as M52, but was added to the M62 to make a cross-country route.
M65LancashireZone 5The short link to the A582 is out of zone

While the M25 may appear to contradict these rules as it runs through all the London-bound zones, it in fact does not; it does not run in a complete circle, starting in Zone 2, and proceeding clockwise through zones 3, 4 and 1. The A282, which completes the circle mostly formed by the M25, is anomalously numbered; as it proceeds into the A-road 1-zone.
The M271 is numbered as a spur of the M27, as opposed to the traditional numbering rules, however the M3 to Southampton came after the M271 was built and is not the zone boundary, which appears to be a straight line from M3 J8 to Exeter in some documentation.

A roads

Road numberLocationTrespassed zoneReason
A14NorthamptonshireZone 5 & 6The A14 was chosen as a unique, important number for this crucial cross-country route.
A31SurreyZone 2Formerly north-east of the A3 before the Guildford Bypass.
A42LeicestershireZone 5The A42 is numbered as an extension of the M42.
A51WarwickshireZone 4Extended over an orphaned section of the A423 when part of that road NW of Coventry was downgraded to B class.
A55AngleseyZone 4The A55 supersedes the A5 through Anglesey.
A66CumbriaZone 5The A66 was extended westwards beyond the A6 to make it a coast-to-coast route.
A88FalkirkZone 9Planned to extend westwards to form the A80 to Kincardine Bridge road - this instead became the M876.
A89GlasgowZone 7The A89 through Glasgow used to be partly the A8.
A167DurhamZone 6The A167 through Durham used to be part of the A1.
A168North YorkshireZone 6The A168 originally only went from Northallerton to Dishforth, and was extended by the former A1 when it was upgraded in 1994, changing the most westerly point to a different zone.
A177DurhamZone 6In County Durham the original A1 route, not the A1 motorway, forms the zone boundary.
A181DurhamZone 6In County Durham the original A1 route, not the A1 motorway, forms the zone boundary.
A199East LothianZone 6The A199 used to be part of the A1.
A282ThurrockZone 1New road which is important and assigned an A2xx number as most A1xx numbers were already used. Could be A108 or A122, both unused numbers at present.
A307SurreyZone 2The A307 used to be part of the A3.
A320SurreyZone 2Formerly north-east of the A3 before the Guildford Bypass.
A322SurreyZone 2Formerly north-east of the A3 before the Guildford Bypass.
A397PortsmouthZone 2The A397 used to be part of the A3.
A404Windsor and MaidenheadZone 3The A404 used to be part of the A4.
A412SloughZone 3
A427NorthamptonshireZone 6The A427 previously ran from Coventry to Oundle, and was truncated west of Market Harborough, when the new A14 opened. This section was renumbered as the B4027, A4303 and A4304. An even older alignment heading south from North Kilworth as far as the A45 is now an unclassified road and A4071.
A505BedfordshireZone 4The A505 was extended to become a cross-country route.
A601DerbyZone 5Chosen as a unique number for the Derby inner ring road.
A620NottinghamshireZone 1The A620 was truncated and left east of the A1.
A624Chapel-en-le-Frith, DerbyshireZone 5The A624 was part of the A6 for a short stretch in Chapel-en-le-Frith before the Chapel By-pass was built.
A683LancashireZone 5The A683 was extended westwards to Heysham docks.
A689CumbriaZone 5The A689 was extended south-westwards around Carlisle from M6 J44 to the A595 in the 5 zone.
A720EdinburghZone 6The A720 bypasses the numbering hub of Edinburgh, making numbering difficult; A720 was chosen for apparent importance. Most important 6-zone numbers were all used.
A882HighlandZone 9The A9 was rerouted to terminate at Scrabster rather than John O'Groats, leaving the A882 in zone 9.
A899West LothianZone 7The A899 was extended south through Livingston new town, Scotland.
A949HighlandZone 8The A949 used to be part of the A9.
A1000HertfordshireZone 6The A1000 used to be part of the A1.
A1057HertfordshireZone 6As A1000.
A1068NorthumberlandZone 6The A1 was rerouted around Alnwick, leaving the end of A1068 out-of-zone.
A1081HertfordshireZone 6The A1081 used to be part of the A6.
A1246North YorkshireZone 6The A1246 used to be part of the A1.
A3023HampshireZone 2
A3100SurreyZone 2The A3100 used to be part of the A3.
A3400WarwickshireZone 4The road was numbered to reflect its history as the old A34.
A4174BristolZone 3The A4174 is part of the Bristol outer ring road. It was entirely in zone 4 but has been extended to the A4 and then south of it.
A4208LondonZone 3Truncation of the A4 left the A4208 out-of-zone.
A4300NorthamptonshireZone 5The A4300 used to be part of the A43.
A4303LeicestershireZone 5The A4303 used to be part of the A427.
A4304LeicestershireZone 5As A4303.
A4500NorthamptonshireZone 5The A4500 used to be part of the A45.
A4501NorthamptonshireZone 5As A4500.
A5127Staffordshire, West MidlandsZone 4The A5127 was extended south when the A38 bypassed Sutton Coldfield.
A5140BedfordshireZone 4
A5153AngleseyZone 4
A5154AngleseyZone 4
A5223TelfordZone 4
A6004LeicestershireZone 5The A6004 used to be part of the A6.
A6010ManchesterZone 5The A6010 is part of the Manchester ring road.
A6143ManchesterZone 5
A6144TraffordZone 5
A6182DoncasterZone 1The A1 was rerouted leaving the A6182 out-of-zone.

B roads

Irregularities not based on the zoning system

Two clearly separate roads with the same number