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.
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.
- Separation of the opposing traffic flows, and therefore reduced head-on crashes.
- Simpler traffic movements leading to less opportunity for conflict.
- Redirection of turning movements to safer locations.
- Protection for turning traffic.
- Reduced traffic congestion.
- This treatment is costly, and other lower cost treatments (such as median barrier installation) should also be considered.
- Requires a large amount of land.
- Community acceptance of the medians that restrict turning movements or restrict pedestrian movements may be an issue.
Benefits
- Separation of the opposing traffic flows, and therefore reduced head-on crashes.
- Simpler traffic movements leading to less opportunity for conflict.
- Redirection of turning movements to safer locations.
- Protection for turning traffic.
- Reduced traffic congestion.
Implementation issues
- This treatment is costly, and other lower cost treatments (such as median barrier installation) should also be considered.
- Requires a large amount of land.
- Community acceptance of the medians that restrict turning movements or restrict pedestrian movements may be an issue.
Did you know?
Unexpectedly tight horizontal bends can lead to crashes when drivers try to negotiate them at high speed.
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