Single Carriageway
A road consisting of one carriageway with traffic in one or both directions. There may be more than one lane in either direction.
Dual Carriageway
A road consisting of two separate carriageways with separate flow directions. The carriageways are partitioned by physical features, such as a barrier and/or verge.
Slip Road
A link that provides exit from or entry to another link.
Roundabout
A method of controlling traffic flow by allowing vehicles from a particular direction priority.
Collapsed Dual Carriageway
The geometry of the dual carriageway has collapsed; this occurs where they run parallel and are less than a defined distance apart, resulting in a single line representing both carriageways of a dual carriageway.
Guided Busway
A specially-constructed or modified route for passenger road vehicles that have been built or adapted to be steered by external means. Typically, along guided busways there is a raised kerb with a track along which small wheels protruding from the sides of the modified vehicle run. This classification is only for specific cases where buses run along specifically-designed tracks or channels that remove the need for steering.
Shared Use Carriageway
Roads that have been altered for use principally by pedestrians, but may also provide some access for certain types of vehicles.