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Duplication

Road duplication or ‘dualling’ involves changing a single carriageway road to a dual carriageway road by building a second separate carriageway, usually alongside the first.

Road duplication provides a safety benefit through provision of a central median barrier or strip of land (median or central reservation), thereby reducing the chances of head-on crashes.

Divided roads range from high speed, access-controlled roads to moderate speed arterial roads with at-grade intersections. In between, divided roads may consist of a mix of grade-separated and at-grade intersections.

This is costly and requires a large amount of space. Because it is so costly, road duplication projects are often carried out in a staged fashion, in order to make use of limited road funds. Duplication is typically only economically viable at higher traffic flow levels.

The Star Rating Demonstrator is a freely available tool with the iRAP online software, ViDA. With the Star Rating Demonstrator, it is possible to explore the impact that this Safer Roads Treatment has on risk.

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