carriageways

A carriageway is a portion of a road intended for vehicle traffic. It is the part of the roadway allocated to moving vehicles, and is distinct from adjacent footways or cycle tracks. The term is common in road engineering and is used in many Commonwealth and European countries. A road may consist of one or more carriageways.

Carriageways are generally classified as single or dual. A single carriageway carries traffic in both directions on the same roadway, typically with no physical separation between opposing streams. A dual carriageway has two separate roadways for opposite directions, divided by a central reservation or median. Some high-speed or controlled-access roads are built as divided carriageways with additional safety features.

Design and safety features vary by jurisdiction, but common elements include lane markings, hard shoulders or breakdown lanes, and a central reserve on divided roads. Lane widths, shoulder widths, and sightlines influence safety and capacity. On motorways and divided highways, crash barriers or median rails reduce cross-over crashes, while entry and exit ramps enable grade-separated junctions.

Usage and terminology differ by country. In the United Kingdom, 'carriageway' is the standard term for a distinct stream of traffic within a road and distinguishes from footways and cycle tracks; 'dual carriageway' denotes two separated carriageways. In other countries, terms like 'roadway' or simply 'carriageway' may be used less consistently but convey a similar concept.