page_title: Dual carriageway
section_title: Singapore
hierarchical_section_title: Dual carriageway / Other regional implementations / Singapore
caption_attribution_description: Singapore's Pan Island Expressway after Nanyang Flyover
context_page_description: A dual carriageway or divided highway is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation. 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.
  A road without a central reservation is a single carriageway regardless of the number of lanes. Dual carriageways have improved road traffic safety over single carriageways and typically have higher speed limits as a result. In some places, express lanes and local/collector lanes are used within a local-express-lane system to provide more capacity and to smooth traffic flows for longer-distance travel.
context_section_description: A high proportion of roads in Singapore are dual carriageways with central reservations; examples include Clementi Road, Commonwealth Avenue and Holland Road.  Often there might be railings erected on the central reservation to prevent pedestrians from dashing across the road.  These usually have traffic lights along the way but flyovers and road tunnels (or 'underpasses') can be built to minimise the use of traffic lights; for example, at the Holland Road-Farrer Road-Queensway junction there are three levels of roads.  Before the 1980s roundabouts were popular but since then many have been changed to traffic-light controlled junctions.
  These dual carriageways are to be distinguished from motorways, known in Singapore as expressways such as the Pan-Island Expressway (PIE) and Ayer Rajah Expressway (AYE) where no traffic lights are used.
caption: Pan Island Expressway in Singapore.
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