{i} part of the highway where traffic moves in one direction only generally in two or three lanes (British usage)
one of the two sides of a motorway where traffic travels in one direction only usually in two or three lanes
A carriageway is one side of a road on which traffic travelling in opposite directions is separated by a barrier. one of the two sides of a motorway or main road, for vehicles travelling in the same direction
a highway divided down the middle by a barrier that separates traffic going in different directions; "in England they call a divided highway a dual carriageway"
A dual carriageway is a road which has two lanes of traffic travelling in each direction with a strip of grass or concrete down the middle to separate the two lots of traffic. a main road that has two lines of traffic travelling in each direction, with a narrow part between them that has no traffic American Equivalent: divided highway