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Junction numbers

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Junction numbers
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The last junction on the M6 - Coppermine - 20959.jpg
Junction number 45 on an Advance Direction Sign on the M6 in Cumberland
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Motorway junctions in Great Britain and Ireland are typically numbered (although this was not the case in the earliest days of British motorways). Some motorway strip maps produced by the AA used numbers or letters to refer to the junctions, but these were entirely unofficial. Official junction numbering began in August 1966 for most motorways in Great Britain. Junctions on some shorter motorways that "do not form parts of the continuous system" initially remained numberless, but some were given numbers later. Numbering in the UK and Ireland is almost always incremental, with a sequence (e.g. 1, 2, 3...) beginning with the junction at the start point. The policy was that, on motorways which radiate from London, the London end would be J1. Other motorways do not have a consistent policy.

Junctions are normally numbered consecutively. Gaps in the sequence are sometimes deliberately left to allow for planned future junctions. New junctions not provided for in the original numbering scheme can be indicated by numbers with appended letters A, B etc. – though such appended letters are also sometimes used for junctions on spurs, or for other purposes, as in the case of the A55. In the latter instance, the numbering suggests that consecutive numbers were first assigned to those junctions which allow all movements, and numbers with appended letters were then used later to label limited-movement junctions.

Junction numbering on a route normally starts from 1. When, as with the M62, it starts at a higher number, this is normally an indication that an extension of the road was originally planned at the low-numbered end.

Junction numbers usually increase in the same direction as the numbers on marker posts and driver location signs, but there are some exceptions, as on the M55.

Junction numbers are shown on direction signage addressed to traffic already on the road in question. In a few cases, junction numbers are also shown on signage seen when joining the road in question.

Junction numbers are normally shown on road maps, though some maps such as OS Landranger show only those on motorways.

A potential problem with junction numbers is that in some areas a journey may involve short stretches on two or three different motorways, leading to forward and backward jumps in the junction numbering, or a switch between increasing and decreasing numbers.

In several cases, the junction numbering on a stretch of road has been changed at some time. In some cases, such as that of the M74, this has happened twice.

The M62 Stretford-Eccles Bypass was unusual in that although it had no official junction numbers (shown on signs) until 1971 when most of it became the M63, maps by several publishers showed its junctions as numbered 1 to 6 from south to north. It is now part of the M60, junction 7 to junction 13.

On the A1(M), junction numbering was introduced in the 1990s, first for the southernmost section, later for the rest. Gaps were left in the numbering to allow for possible future upgrade of the intervening sections of the all-purpose A1. However, junction numbers for all-purpose sections were not shown on maps or signs until about 2014, and then only on Tyneside, where the numbering was extended to Seaton Burn. With the upgrade of some intermediate sections of the A1 to motorway it has become apparent that on some stretches too many or too few junctions were originally allowed for.

Numbers were later assigned to the junctions on some long-distance all-purpose trunk roads. These include the A14 and A55, the trunk section of the A12, and selected sections of the A45, A50, and A483. The numbering used on the M25 was extended onto the A282, and that on the M42 onto the A42.

Some urban areas also have junction numbers applied to central ring roads to aid navigation. These include Birmingham, Blackburn, Coventry, Derby, Dublin, Leeds, Redditch, and Sheffield. In Peterborough there is a junction numbering system that applies to several major roads in the city, equipping main junctions with numbers which are unique over the city area rather than just along a particular road.

Non-motorway roads with junction numbers

Routes that do not start with Junction 1

This list ignores spur junctions, named off a main route, and situations like Peterborough where several routes share a single junction numbering system. It also ignores routes that count from an unsigned 'junction 0'.

'Skipped' junction numbers

This ignores routes that don't start with 1, places where junction numbers are shared with other route and places where there's gaps in the route.

  • M1 (GB) J3 – unfinished junction
  • M1 (NI) J4 – junction renumbered as junction 3 which was to be an unbuilt junction.
  • M1 (NI) J5 – unbuilt junction
  • M2 (NI) J3 – unbuilt junction
  • M4 (GB) J31 – unbuilt junction
  • M7 (RoI) J20 – unbuilt junction
  • M8 (RoI) J2 – unbuilt junction
  • M27 J6 – unbuilt junction
  • M50 (RoI) J8 – unbuilt junction
  • M55 J2 – unbuilt junction
  • M56 J13 – unbuilt junction?
  • M58 J2 – unbuilt junction
  • M61 J7 – unbuilt junction
  • A1(M) J54, J55 – numbers not required (plans for where junctions were changed)
  • A14 J48 – junction replaced with the A14 realigned
  • A14 J26-J30 – the A14 near Huntingdon was rerouted onto a new route with considerably fewer junctions, leading to a large gap in the numbering

Other systems

Other (not always mutually exclusive) systems for junction identification, include:

Named junctions

This system was principally adopted in Germany, although motorways in the UK also use junction names, which are sometimes signposted, in addition to numbering. Every junction in Germany has a name, and is referred to as such on signposts and in traffic reports. In the last 20 years, junction numbers have also been assigned to many German motorways.

Junction numbers based on distance markers

In some countries, junctions are numbered by their kilometre or mile markers. This is the case on Spain's autovías and in the US. This has the advantage that a junction can simply be added between two others, without having to append a suffix (e.g. A) and that it is always apparent how far away the next junction is. It has the disadvantage that multiple junctions in a short space are not easily signed (and may need to use a suffix). Note that parts of Spain and some US states still use consecutive junction numbering on some routes, although they are planned to be converted.

Numerical suffixes

In some countries, the junction suffix, rather than being an alphabetic character appended is a numeric, e.g junction numbers like 12.1 are sometimes used.

Exits only

The distinction between 'exit' and 'interchange' is common in continental Europe, marked with different symbols. Several countries (eg France, Belgium, The Netherlands) typically give numbers only to junctions that allow exit from the motorway network (though exceptions exist). This can be confusing for British drivers. For instance, the A26 in France has, heading south, the following sequence of junctions:

  • exit 7 for the N17,
  • the interchange with the A1,
  • exit 8 for the D939,
  • the interchange with the A2,
  • exit 9 for the D917,
  • exit 10 for the A1029,
  • the interchange with the A29,
  • exit 11 for the D1.

One might initially expect that, after exit 7, exit 11 would be the 4th junction; however, it is the 7th.

Germany numbers its interchanges and exits alike, but interchanges may not be with an autobahn, making the difference between the two not clear from a map.

Junction numbers
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