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[1] are different from the A-road boundaries shown below.

Road number Location Trespassed zone Reason
M48 Gloucestershire, Monmouthshire Zone 5 This 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.[2][3]
M49 Bristol, Gloucestershire Zone 3 This motorway lies entirely within zone 3.[4] The motorway was constructed at the same time as the Second Severn Crossing, and it is likely that the sequential M48 and M49 were used for the old M4 and the new motorway respectively.
M62 Merseyside, Greater Manchester Zone 5 The section from Liverpool to Manchester was planned as M52, but was added to the M62 to make a cross-country route.
M65 Lancashire Zone 5 The 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 (and should therefore begin with a 1). 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
The numbering zones for all-purpose roads in Great Britain
Road number Location Trespassed zone(s) Reason
A14 Northamptonshire Zone 5 & 6 The A14 was chosen as a unique, important number for this crucial cross-country route.
A31 Surrey Zone 2 Formerly north-east of the A3 before the Guildford Bypass.
A42 Leicestershire Zone 5 The A42 is numbered as an extension of the M42.
A51 Warwickshire Zone 4 Extended over an orphaned section of the A423 when part of that road NW of Coventry was downgraded to B class.
A55 Anglesey Zone 4 The A55 supersedes the A5 through Anglesey.
A66 Cumbria Zone 5 The A66 was extended westwards beyond the A6 to make it a coast-to-coast route.
A88 Falkirk Zone 9 Planned to extend westwards to form the A80 to Kincardine Bridge road - this instead became the M876.
A89 Glasgow Zone 7 The A89 through Glasgow used to be partly the A8.
A167 Durham Zone 6 The A167 through Durham used to be part of the A1.
A168 North Yorkshire Zone 6 The 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.
A177 Durham Zone 6 In County Durham the original A1 route (now A167), not the A1(M) motorway, forms the zone boundary.
A181 Durham Zone 6 In County Durham the original A1 route (now A167), not the A1(M) motorway, forms the zone boundary.
A199 East Lothian Zone 6 The A199 used to be part of the A1.
A282 Thurrock Zone 1 New road which is important and assigned an A2xx number as most A1xx numbers were already used (as zone 1 is far larger than zone 2). Could be A108 or A122, both unused numbers at present.
A307 Surrey Zone 2 The A307 used to be part of the A3.
A320 Surrey Zone 2 Formerly north-east of the A3 before the Guildford Bypass.
A322 Surrey Zone 2 Formerly north-east of the A3 before the Guildford Bypass.
A397 Portsmouth Zone 2 The A397 used to be part of the A3.
A404 Windsor and Maidenhead Zone 3 The A404 used to be part of the A4.
A412 Slough Zone 3
A427 Northamptonshire Zone 6 The 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 (pre-c.1960s) heading south from North Kilworth as far as the A45 is now an unclassified road (formerly B5414) and A4071.
A505 Bedfordshire Zone 4 The A505 was extended to become a cross-country route.
A601 Derby Zone 5 Chosen as a unique number for the Derby inner ring road.
A620 Nottinghamshire Zone 1 The A620 was truncated and left east of the A1.
A624 Chapel-en-le-Frith, Derbyshire Zone 5 The A624 was part of the A6 for a short stretch in Chapel-en-le-Frith before the Chapel By-pass was built.
A683 Lancashire Zone 5 The A683 was extended westwards to Heysham docks.
A689 Cumbria Zone 5 The A689 was extended south-westwards around Carlisle from M6 J44 to the A595 in the 5 zone. (It passes through the 7 zone as well between the A7 and River Eden, but the actual boundary between the 5 and 7 zones is undefined, and a road crossing the A7 would be correctly numbered starting 6, as zone 6 is anticlockwise of zone 7 as viewed from the numbering hub of Edinburgh.)
A720 Edinburgh Zone 6 The A720 bypasses the numbering hub of Edinburgh, making numbering difficult; A720 was chosen for apparent importance. Most important 6-zone numbers were all used. Also notably distant from all other A72- roads.
A882 Highland Zone 9 The A9 was rerouted to terminate at Scrabster rather than John O'Groats, leaving the A882 in zone 9.
A899 West Lothian Zone 7 The A899 was extended south through Livingston new town, Scotland.
A949 Highland Zone 8 The A949 used to be part of the A9.
A1000 Hertfordshire Zone 6 The A1000 used to be part of the A1.
A1057 Hertfordshire Zone 6 The A1057 used to be part of the A1.
A1068 Northumberland Zone 6 The A1 was rerouted around Alnwick, leaving the end of A1068 out-of-zone.
A1081 Hertfordshire Zone 6 The A1081 used to be part of the A6.
A1246 North Yorkshire Zone 6 The A1246 used to be part of the A1.
A3023 Hampshire Zone 2
A3100 Surrey Zone 2 The A3100 used to be part of the A3.
A3400 Warwickshire Zone 4 The road was numbered to reflect its history as the old A34.
A4174 Bristol Zone 3 The 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.
A4208 London Zone 3 Truncation of the A4 left the A4208 out-of-zone.
A4300 Northamptonshire Zone 5 The A4300 used to be part of the A43.
A4303 Leicestershire Zone 5 The A4303 used to be part of the A427.
A4304 Leicestershire Zone 5 The A4304 used to be part of the A427.
A4500 Northamptonshire Zone 5 The A4500 used to be part of the A45.
A4501 Northamptonshire Zone 5 The A4501 used to be part of the A45.
A5127 Staffordshire, West Midlands Zone 4 The A5127 was extended south when the A38 bypassed Sutton Coldfield. The entire A5127 was part of the original route of the A38.
A5140 Bedfordshire Zone 4  
A5153 Anglesey Zone 4
A5154 Anglesey Zone 4
A5223 Telford Zone 4
A6004 Leicestershire Zone 5 The A6004 used to be part of the A6.
A6010 Manchester Zone 5 The A6010 is part of the Manchester ring road.
A6143 Manchester Zone 5
A6144 Trafford Zone 5
A6182 Doncaster Zone 1 The A1 was rerouted leaving the A6182 out-of-zone.

B roads
Road number Location Trespassed zone Reason
B197 Hertfordshire Zone 6 The B197 used to be part of the A1
B316 London Zone 4 A4 rerouted
B325 London Zone 4 A4 rerouted
B384 West Midlands Zone 4 Used to be part of the A38, and numbered to match.
B455 London Zone 3
B470 Windsor and Maidenhead Zone 3
B576 Northamptonshire Zone 6 A6 rerouted
B645 Northamptonshire Zone 5 A6 rerouted
B855 Highland Zone 9 The A9 was rerouted west of this road, to end at Scrabster.
B876 Highland Zone 9 The A9 was rerouted west of this road, to end at Scrabster.
B1043 Cambridgeshire Zone 6 The B1043 used to be part of the A1.
B1164 Nottinghamshire Zone 6 The B1164 used to be part of the A1.
B1198 Durham Zone 6 In County Durham the original A1 route (now A167), not the A1(M) motorway, forms the zone boundary.
B1217 Leeds Zone 6 extended along old A642 when M1 extended
B1224 North Yorkshire Zone 6 In County Durham the original A1 route (now A167), not the A1(M) motorway, forms the zone boundary.
B1284 Durham Zone 6 In County Durham the original A1 route (now A167), not the A1(M) motorway, forms the zone boundary.
B1350 Edinburgh Zone 9 Although the B1350 is a continuation of London Road the remaining mile of the A1 is to the south at this point.
B3000 Surrey Zone 2 A3 rerouted
B3004 Hampshire Zone 2
B3006 Hampshire Zone 2
B4640 West Berkshire Zone 3
B4666 Hinckley, Leicestershire Zone 5 The B4666 used to be part of the A47.
B4667 Hinckley, Leicestershire Zone 5 The B4667 used to be part of the A447.
B4668 Hinckley, Leicestershire Zone 5 The B4668 used to be part of the A47.
B4669 Leicestershire Zone 5
B5060 Telford Zone 4
B5061 Shropshire Zone 4
B5070 Wrexham Zone 4 The B5070 used to be part of the A5.
B5072 Telford Zone 4
B5444 Swansea Zone 4
B5477 Shropshire Zone 4 This was, until renumbered in 2004, the northern section of the B4370 (Little Stretton - Church Stretton - All Stretton); additionally the number was (and remains) in separate use in Wallasey.
B6241 Preston, Lancashire Zone 5 The B6241 was extended west of the A6.
B6280 Darlington Zone 1 In County Durham the original A1 route (now A167), not the A1(M) motorway, forms the zone boundary.
B6291 Durham Zone 1 The original section within Zone 6 was renumbered to become an extension of the A688.
B6420 Nottinghamshire Zone 1 The A1 was re-routed, leaving its start-point out of zone.
B6430 Lancashire Zone 5
B6469 Manchester Zone 5
B6541 Middlesbrough Zone 1 The B6541 used to be part of the A66.
B7201 Dumfries and Galloway Zone 6 The B7201 was part of the A7 before bypass of Canonbie; was B720 beforehand.
B9080 West Lothian Zone 8 The B9080 used to be part of the A9.
B9150 Highland Zone 8 The B9150 used to be part of the A9.
B9163 Highland Zone 8 A9 rerouted
B9164 Highland Zone 8 A9 rerouted
B9169 Highland Zone 8 A9 rerouted
B9176 Highland Zone 8 The B9176 used to be part of the A9
B9177 Highland Zone 8 The B9177 used to be part of the A9

Irregularities not based on the zoning system
Road number Location Reason
A135 Stockton-on-Tees The other A13x roads are in southern England.
A139 Stockton-on-Tees The other A13x roads are in southern England.
A176 Basildon, Essex The other A17x roads are in North Yorkshire or County Durham.
A180 Grimsby The other A18x roads are in the North-east. The A180 is numbered as an extension of the M180.
A249 Maidstone - Sheerness, Kent The other A24x roads are in Surrey.
A403 Avonmouth, South Gloucestershire The other A40x roads are in or around Greater London
A437 Hillingdon, Greater London The other A43x roads are in Gloucestershire, Oxfordshire or Warwickshire.
A491 Bromsgrove - Stourbridge The other A49x roads are in North Wales.
A500 Stoke-on-Trent "D"-road The other A50x roads are in London, southern England and Northamptonshire
A506 Liverpool The other A50x roads are in London, southern England and Northamptonshire
A598 Barnet, Greater London The other A59x roads are in Cumbria (but see A594 below)
A601(M) Carnforth, Lancashire "A601(M)" would be expected to be a designation for an upgraded section of the A601. The A601 is in Derby.
A720 Edinburgh City Bypass, Edinburgh The other A72x roads are to the south of Glasgow.

Two clearly separate roads with the same number
Road number Locations Notes
A594 Cumbria Leicester The Cumbria version predates the Leicester version.
A1042 Redcar Norwich The Redcar version predates the Norwich version.
A1114 Chelmsford Gateshead
A1199 Islington Woodford Both are in Greater London.
A1243 Great Yarmouth Grimsby
A5271 Stoke-on-Trent Keswick, Cumbria

References
  1. "How the Motorways were Numbered". Pathetic Motorways. Retrieved 12 May 2010.
  2. "Motorway Database - M48". CBRD. Retrieved 26 October 2007.
  3. http://pathetic.org.uk/features/numbering/maps/sectors.shtml
  4. "How the Motorways were Numbered". Pathetic Motorways. Archived from the original on 2 September 2006. Retrieved 1 September 2006.
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