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Public-images-osm logo.svg carriageway_ref
The carriageway reference used for maintenance and emergency services. Edit this description in the wiki page. Edit this description in the data item.
Group: references
Used on these elements
may be used on nodesmay be used on waysshould not be used on areasshould not be used on relations (except multipolygon relations)
Useful combination
Status: de facto

carriageway_ref is used to distinguish the two separated carriageways of a dual carriageway road. These markers allow emergency services and maintenance agencies to locate where incidents may be occurring, and people calling for breakdown services to locate themselves to their breakdown operator. This is very different from the ref=* tag, which is used to indicate the road number.

This key can be used on ways and nodes:

  • use on way highway=* for the carriageway reference of the road;
  • use on node highway=milestone for the carriageway reference indicated on the highway location marker.

European use


In Flanders, on regional roads (gewestwegen) of operator=Agentschap Wegen en Verkeer, the following carriageway indications are in use on modern distance signs:

  • For the main carriageway of a single-carriageway road:
  • For the main carriageways of a dual-carriageway road:
  • For ramps:


Sign Sign Tag Description
Hectometerbord oud en nieuw BeeldbankVenW.jpg Hectometerpaal N44.jpg carriageway_ref=Re Right/forward main carriageway with ascending distance (hoofdrijbaan rechts).
Hectometerpaal A1 78k1-li met praatpaalwijzer.jpg Hectometerpaal provinciale weg 197.jpg carriageway_ref=Li Left/backward main carriageway with descending distance (hoofdrijbaan links).
A7 hectometerpaal 133.7b.jpg Hectometerpaal A28.jpg carriageway_ref=b Link road[1] or special situation indicated by a lowercase letter. Usually follows the letter assignment scheme from Beschrijvende Plaatsaanduidingsystematiek, e.g. b usually indicates an on-ramp to the right/forward direction. Sometimes mo is used on signs instead of m to avoid confusion with n, in these cases tag with carriageway_ref=mo.

The road number to which the carriageway reference corresponds, is tagged as ref=* or official_ref=* (if both keys exist, the latter takes precedence). In some cases, an administrative road number is tagged with highway_authority_ref=*.

If the carriageway reference is not indicated on a sign, one may try to find it in a road operator database, e.g. Nationaal Wegenbestand. Older signs that omit the road number often also omit the Re/Li indications on the main carriageways.

In rare cases, bidirectional roads are assigned a different carriageway reference on each side. Use the keys carriageway_ref:right=* and carriageway_ref:left=* in these cases. Preferably reverse the way if needed to get the right/forward reference on the right side of the way (e.g. if you have carriageway_ref:left=Re, reverse the way so you get carriageway_ref:right=Re, which avoids a lot of confusion).

United Kingdom

In the United Kingdom the main carriageways of a road are usually designated "A" and "B", with the off sliproad from the "A" side being "J" and the on sliproad being "K", with "L" and "M" being used for corresponding "B" carriageway sliproads. "C" and "D" are used for where motorways or other divided highways have collector/distributor lanes, e.g. the M20 near Maidstone or M60 around Manchester. Some more complicated junctions use other references.

Usual Carriageway Identifiers used on Driver location signs.

The reference values can be considered common knowledge because they are given on wikipedia:Driver location signs signs (e.g. M27 B 2.8, as seen in the image right) and are also printed upon the emergency telephones.

See also

  1. What is a link road according to the road operator is not necessarily always a link road according to OpenStreetMap conventions, and vice versa.