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Essential Traffic Routes

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Essential Traffic Routes
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Essential Traffic Routes was a British road numbering system used during World War 2. Very little evidence of this classification has survived, almost certainly due to its original security classification of Secret, and its lack of requirement in peacetime. Mapping showing the routes was declassified during the 1970s.

There were two levels of classification:

  • Main Essential Traffic Routes
  • Local Essential Traffic Routes

Mapping evidence

Whilst there is a suggestion that small-scale mapping (probably at the One Inch scale) was issued out to troops, none seem to have survived.

Instead, the only mapping evidence currently available is a single edition of a single sheet of a Ten Mile Map of Great Britain that was issued in 1943 preserved by the National Library of Scotland; and a copy of both 1943 sheets held in the British Library. Documentary evidence[1] from the Charles Close Society suggests that at least five editions of Sheet 1 were published, of which they found four editions from various sources. However, they were not successful in locating any copies of Sheet 2 at all, but since publication a copy of Sheet 2 has been found in the British Library.

The fact that (at least) five editions were printed, and specifically labelled as First Edition, Second Edition and so on implies that the numbering system was not static throughout World War 2. However, with only a single edition available, it cannot be conclusively answered.


Perhaps surprisingly, Essential Traffic Routes were signed in the style of the time, but in red signs containing only the route number, and no destinations.

It has been speculated that this use of red signage has been effectively preserved in modern military signage, which uses red as its accent colour.


The two types of route are differently numbered, with Main Essential Traffic Routes carrying three digit numbers in the range 200-225 with no prefix, whilst Local Essential Traffic Routes carried one, two or three digit numbers prefixed with a regional identifier letter. All three digit Local Essential Traffic Routes have the first digit of "1". This is probably to ensure that no LETR has the same numeric component as an METR.

Multiplexes existed within the system, and most METRs and LETRs terminated on either other ETRs, or at the coast.

Main ETRs

Main Article: Essential Traffic Routes/Main Routes

Local ETR prefixes

Local ETRs are prefixed with a regional identifier letter based on each Command area:

Prefix Command Areas covered
S Scottish Scotland
N Northern Northumberland • County Durham • Yorkshire • Derbyshire • Nottinghamshire • Lincolnshire • Leicestershire
W Western Cumberland • Westmorland • Lancashire • Cheshire • Staffordshire • Shropshire • Warwickshire • Herefordshire • Worcestershire • Wales
E Eastern Northamptonshire • Buckinghamshire • Hertfordshire • Bedfordshire • Norfolk • Suffolk • Essex
S Southern Gloucestershire • Oxfordshire • Berkshire • Wiltshire • Hampshire • Somerset • Cornwall • Devon • Dorset
- South-Eastern Surrey • Sussex • Kent • London

Whilst both Scottish and Southern Command areas used the prefix "S", and numbers were repeated within the two areas (for example, the Scottish S7 ran from Glasgow to Stranraer; whilst the Southern S7 ran from Stow-on-the-Wold to Cirencester), it was presumably not seen as an issue due to the distance between the areas.

In addition, whilst LETR routes within South-Eastern Command are shown on the mapping evidence, no numbering is shown for these routes. It is mostly likely that either South-Eastern Command did not number their LETRs, or that the numbers were withheld on mapping due to their location covering the most likely invasion sites.

Local ETR numbering

Whilst each Command area has its own set of numbering, it appears to have been the case that for several routes that crossed the boundary between each area that the numeric component was kept, and just the prefix changed.

Examples of this include:

There were some exceptions to the main system in the Eastern Command area, specifically in Essex and eastern Suffolk, where some LETRs seemingly split into "sub-routes" with a lettered suffix. For example, E4 split at Ipswich into E4A and E4B as it approached the coast, whilst E2 arrived into Colchester from the west, and then split into E2A, E2B, E2C, E2D and E2E. However, E1 behaves differently, as E1A crosses E1, whilst E1B runs parallel to E1. These anomolies are yet to be explained.

Relationship to civilian all-purpose numbering

Whilst many of the Essential Traffic Routes followed the same routes as all-purpose A and B roads, it was not in a 1:1 relationship; and nor was there a relationship between the civilian and military numbers. For example, Route 202 at least partly followed the A1.

It's also clear that in some cases Essential Traffic Routes did not follow the obvious civilian route along an individual number. The reason is not known for certain at the time of writing, but a possible reason would be that for some reason the route was considered less suitable for military convoys - for example, where an urban area could be avoided or where there was an unsuitable bridge.

External links


  1. The Ten Mile Maps of the Ordnance Surveys - Roger Hellyer (1992) page: 126

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