High Quality Content by WIKIPEDIA articles! A dual carriageway (British English) or divided highway (North American English) is a road or highway in which the two directions of traffic are separated by a central barrier or strip of land, known as a central reservation (British English) or median (North American English). This type of road is usually able to carry a great deal more traffic than normal single carriageways (British English) or two-lane roads (North American English) and boulevards.