Anomalously numbered roads in Great Britain

In the Great Britain road numbering scheme, Great Britain 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 table lists all British roads which are anomalously numbered. Roads in bold lie completely outside of the "correct" zone; all other roads run for some length in the "correct" zones but trespass into zones anticlockwise of this zone.

Motorways

Road Number	Location	Trespassed zone(s)	Reason/Excuse for this
M48	Gloucestershire, Monmouthshire	Zone 5	*This road was formerly the M4 and links up with the A48* .
M49	Bristol, Gloucestershire	Zone 3	This may be in zone 5 as it's west of the M5, but could also be in zone 3, as it's south of the M4. As the M49 is the first motorway in this area, it has been set in zone 4
M62	Merseyside, Greater Manchester/Lancashire (traditionally)	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
M271	Hampshire	Zone 3	Numbered as a spur of the M27, as opposed to the traditional numbering rules, however M3 to Southampton came after the M271 was built and may not be the zone boundary, which appears to be a straight line from M3 j8 to Exeter in some documentation

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 incorrectly numbered; it proceeds into the A-road 1-zone incorrectly.

A roads

Road Number	Location	Trespassed zone(s)	Reason/Excuse for this
A14	Northamptonshire	Zone 5 & 6	The A14 was chosen as a unique, important number for this crucial cross-country route.
A31	Surrey	Zone 2	A section of the A31 through Guildford was bypassed east by the A3.
A42	Leicestershire	Zone 5	*The A42 is numbered as an extension of the M42.*
A51	Warwickshire	Zone 4
A55	Anglesey	Zone 4	The A55 supersedes the A5 through Angelsey.
A66	Cumbria	Zone 5	The A66 was extended westwards beyond the A6 to make it a cross-country 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 was partly formerly the A8.
A167	Durham	Zone 6	The A167 through Durham was formerly part of the A1.
A168	North Yorkshire	Zone 6	The A168 was formerly part of the A1.
A177	Durham	Zone 6	The A1 was moved east of the A177's start point in Durham City.
A181	Durham	Zone 6	The A1 was moved east of the A181's start point in Durham City.
A199	East Lothian	Zone 6	The A199 was formerly part of the A1.
A282	Thurrock	Zone 1	New road which is important and assigned an A2xx number due to a shortage of A1xx numbers.
A307	Surrey	Zone 2	The A307 was formerly part of the A3.
A320	Surrey	Zone 2	As A307.
A322	Surrey	Zone 2	As A307.
A397	Portsmouth	Zone 2	*The A397 was formerly part of the A3.*
A404	Windsor and Maidenhead	Zone 3	The A404 was formerly part of the A4.
A412	Slough	Zone 3
A427	Northamptonshire	Zone 6	*The A427 was truncated and most of it renumbered as the A14.*
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	Derbyshire	Zone 5	The A624 was formerly part of the A6.
A683	Lancashire	Zone 5	The A683 was extended westwards to Heysham docks.
A720	Edinburgh	Zone 6	The A720 bypasses Edinburgh, a numbering hub, making numbering difficult; A720 was chosen for apparent importance. Most important 6-zone numbers were all used.
A882	Highland	Zone 9	*The A882 was formerly part of the A9.*
A899	West Lothian	Zone 7	The A899 was extended south through Livingston new town, Scotland.
A949	Highland	Zone 8	The A949 was formerly part of the A9.
A1000	Hertfordshire	Zone 6	The A1000 was formerly part of the A1.
A1057	Hertfordshire	Zone 6	*As A1000.*
A1068	Northumberland	Zone 6	The A1068 was formerly part of the A1.
A1081	Hertfordshire	Zone 6	The A1081 was formerly part of the A6.
A1246	Northumberland	Zone 6	*The A1246 was formerly part of the A1.*
A3023	Hampshire	Zone 2
A3100	Surrey	Zone 2	*The A3100 was formerly part of the A3 (and the A31).*
A3400	Warwickshire	Zone 4	*The A3400 was formerly part of the A34.*
A4174	Bristol	Zone 3	The A4174 is part of the Bristol outer ring road.
A4208	London	Zone 3	*Truncation of the A4 left the A4208 out-of-zone.*
A4300	Northamptonshire	Zone 5	*The A4300 was formerly part of the A43.*
A4303	Leicestershire	Zone 5	*The A4303 was formerly part of the A427.*
A4304	Leicestershire	Zone 5	*As A4303.*
A4500	Northamptonshire	Zone 5	*The A4500 was formerly part of the A45.*
A4501	Northamptonshire	Zone 5	*As A4500.*
A4601	Staffordshire	Zone 5	*The A4601 was formerly part of the A460.*
A5127	Staffordshire	Zone 4	The A5127 was extended south when the A38 bypassed Lichfield.
A5140	Bedfordshire	Zone 4
A5153	Anglesey	Zone 4	*The more-important A55, rather than the A5, is taken to be zone boundary.*
A5154	Anglesey	Zone 4	*The more-important A55, rather than the A5, is taken to be zone boundary.*
A5223	Telford	Zone 4
A6004	Leicestershire	Zone 5	The A6004 was formerly 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.*
A8000	Edinburgh	Zone 9	*The A8000 was truncated with the building of the M9 spur halfway to the Forth Road Bridge*.

B roads

Road Number	Location	Trespassed zone(s)	Reason/Excuse for this
B197	Hertfordshire	Zone 6	The B197 was formerly part of the A1
B316	London	Zone 4	*A4 rerouted*
B325	London	Zone 4	*A4 rerouted*
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 Thurso.*
B876	Highland	Zone 9	*The A9 was rerouted west of this road, to end at Thurso.*
B1043	Cambridgeshire	Zone 6	The B1043 was formerly part of the A1.
B1164	Nottinghamshire	Zone 6	The B1164 was formerly part of the A1.
B1217	Leeds	Zone 6	extended along old A642 when M1 extended
B1224	North Yorkshire	Zone 6	The A1 was re-routed, leaving its start-point out of zone.
B1284	Durham	Zone 6	The A1 was re-routed, leaving its start-point out of zone.
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 was formerly part of the A47.*
B4667	Hinckley, Leicestershire	Zone 5	*The B4667 was formerly part of the A447.*
B4668	Hinckley, Leicestershire	Zone 5	*The B4668 was formerly part of the A47.*
B4669	Leicestershire	Zone 5
B5060	Telford	Zone 4
B5061	Shropshire	Zone 4
B5070	Wrexham	Zone 4	*The B5070 was formerly part of the A5.*
B5072	Telford	Zone 4
B5444	Swansea	Zone 4
B6280	Darlington	Zone 1	*The A1 was re-routed, leaving its start-point out of zone.*
B6291	Durham	Zone 1	*The section within Zone 6 was renumbered as the A688.*
B6420	Nottinghamshire	Zone 1	*The A1 was re-routed, leaving its start-point out of zone.*
B6469	Manchester	Zone 5
B6541	Middlesborough	Zone 1	*The B6541 was formerly part of the A66.*
B9080	West Lothian	Zone 8	*The B9080 was formerly part of the A9.*
B9150	Highland	Zone 8	*The B9150 was formerly 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 was formerly part of the A9*
B9177	Highland	Zone 8	*The B9177 was formerly part of the A9*

Irregularities not based on the zoning system

Road Number	Location	Reason for irregularity
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	Essex	The other A17x roads are in North Yorkshire or County Durham.
A180	Grimsby	The A180 is numbered as an extension of the M180.
A594	one in Cumbria, one in Leicester	There are two A594s which are clearly separate roads.
A601(M)	Carnforth, Lancashire	"A601(M)" would be a designation for an upgraded section of the A601. The A601 is a completely different road in Derby.

External links

* Out-of-Zone Roads (where most of the info on this page is taken from)
* SABRE's road lists. A comprehensive database of numbered roads in mainland Britain.