Those who are not familiar with the terminology used in the roads fraternity may be easily confused by the use of abbreviations and odd names. Originally devised by engineers, they have spread their wings and become an everyday part of the enthusiast's language.
One of these common cases is where the formation of a road is described. This is because the road is described using a mixture of letters and numbers - it isn't formal, but once you've figured it out, it is easy to interpret!
Here is a quick guide to the formation code:
Single carriageway formations
|The standard single carriageway road, usually consisting of one lane in either direction. However, as this only describes the formation of the road, it could be a two-lane one way street.|
|A single carriageway road that is
wider than normal, meaning overtaking can
be carried out without the need to completely cross into the opposite
This is common where three-lane roads have been relined, or a new rural road has been built to a higher standard.
|A three lane road with two lanes in one direction, and a single lane
in the other. This could be to provide a crawler lane in hilly areas, or
the approach to a junction.
There is also a WS2+1 formation, which is where the middle lane switches direction every so often, so traffic on both sides get chances to overtake.
|This is a single carriageway road which comes with an extra lane
down the middle, often known as the "suicide lane". The idea of the
additional lane is to provide overtaking opportunities in both
directions, with neither direction taking priority.
They are now rare as most S3 roads have become WS2 or had their middle lane hatched.
|A four-lane road that still manages to remain a single carriageway. Traffic in either direction is usually - but not always - separated by double white lines.|
|Dual carriageway formations|
|The standard dual carriageway road, usually consisting of two lanes in either direction.|
|Where a dual carriageway has a different number of lanes on either side, both lane allocations are shown in the style Dx+y. For example, a dual carriageway with two lanes on one side and three in the other direction will be shown as D2+3.|
|A wider dual carriageway, consisting of three lanes in either direction.|
|An "M" after the formation indicates that the road
possesses motorway characteristics. It may not be an actual motorway,
but is built like one - it has hard shoulders and full grade separation
(for example, the A2 near Bean).
For example, D3M means a three-lane motorway-style dual carriageway.
|A "H" after the formation indicates that the road has hard strips at
the edge of each carriageway. A hard strip is narrower than a hard
shoulder, typically around a metre wide.
For example, D2H means a two-lane dual carriageway with hard strips.