A carriageway (North American English: roadway, informally direction, side and lanes, improperly the singular lane) consists of a width of road on which a vehicle is not restricted by any physical barriers or separation to move laterally. A carriageway generally consists of a number of traffic lanes together with any associated shoulder, but may be a sole lane in width (for example, a highway offramp).
A single carriageway road (North American English: undivided highway) has one carriageway with 1, 2 or more lanes together with any associated footways (North American English: sidewalk) and road verges (North American English: tree lawn, boulevard, etc.). A dual carriageway road (North American English: divided highway) has two roadways separated by a central reservation (North American English: median). A local-express lane system (also called collector-express or collector-distributor) has more than two roadways, typically two 'local lanes' or 'collector lanes' and also two 'express lanes'. High occupancy vehicle lanes may also be physically separated from the rest of the general traffic lanes into a distinct roadway.