ARSRPE Conference Paper Database

Retro-fitting incremental clearzone widths to existing rural roads

Levett, Stephen



The aim of this paper is to outline new alternative and pragmatic incremental clearzone widths that when retrofitted to existing high speed, undivided rural roads are expected to have a significant effect on reducing the road toll. Although the percentage of run off road crashes varies according to individual routes, they usually form the major component of total road crashes on the rural road network. Run off the road crashes on high speed, undivided rural roads cost the NSW community about $360 million per year and result in approximately 80 deaths per year. One cost-effective way to reduce the high number of these types of crashes is to take a more pragmatic view of what is practical and achievable in reconstructing and maintaining the existing alignments and formations on the two lane rural road network. Road Design Guides have tended to concentrated on ?best practice? principles for designing ?greenfield? type road projects. However, they have rarely addressed what was practical and achievable for upgrading existing road alignments and formations. Consequently, the application of full width clearzones of 10 metres to 12 metres are an exception on most existing rural roads throughout NSW. The development of incremental clearzone widths is an attempt to address this lack of design direction when confronted with what is regarded as acceptable and affordable practice on ?brownfield? projects. It concentrates on reducing the severity of run off road crashes into objects as the major concern and not the total elimination of these types of crashes. It tries to achieve this by restricting the design parameters to a practical level of maximum safety benefit return for the minimum cost of construction. This study is consistent with the safe systems approach to road safety which accepts that humans will make mistakes and that the road should be constructed and maintained to ensure these errors don?t result in death or serious injury. Cost effective treatments such as applying incremental clearzones are expected to provide good safety benefits yet be less environmentally destructive than current ?Greenfield? clearzone standards. If they are implemented throughout the NSW road network they will provide a more forgiving roadside environment than presently exists along the edge of most rural roads.