dual carriageway

A typical British dual carriageway with central barrier on the A63 near Hull, England Map by Cassius Ahenobarbus, zoomed in to show the Via Portuensis, with the dual carriageway splitting close to the city of Rome. This is a very early (perhaps the first) example of a dual carriageway. Autostrada A20 runs through the island of Sicily in Italy linking Palermo to Messina Clara Barton Parkway outside Washington, D.C. Jersey barriers may be used to separate the carriageways where the space is narrow. See this example near Málaga, Spain. There is also a bus stop in the bottom-right corner of the picture; it would not exist in a motorway.

A dual carriageway (BrE) or a divided highway (AmE) is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation (BrE) or median strip (AmE). Roads with two or more carriageways which are designed to higher standards with controlled access are generally classed as motorways, freeways, etc., rather than dual carriageways.