ARSRPE Conference Paper Database

The application of asymmetrical design principles to rural roads

Levett, Stephen

Road Environment


The aim of this paper is to introduce alternative and pragmatic ?brownfield? design principles that when retrofitted to existing high speed, undivided rural roads are expected to have a significant effect on reducing the road toll, yet also provide considerable savings in ongoing road maintenance costs.

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.  The only way to reduce the high number of these type of crashes is to take a more pragmatic view of what is practical and achievable in reconstructing and maintaining the existing rural two lane road network in a safe but affordable way.

Previously, Road Design Guides concentrated on ?best practice? principles for designing ?greenfield? type road projects and rarely addressed what was practical and achievable for existing road alignments and formations.  The implementation of asymmetrical design principles is aimed at addressing this lack of design direction when confronted with what is regarded as acceptable practice on ?brownfield? projects.  It concentrates on reducing crashes as the major concern and achieves maximum impact by focusing scarce road safety and road maintenance funding resources towards those sections of rural road that have the most off road crashes and that will return the most safety benefits.  It also has the extra benefit of curbing the over-design of ?brownfield? maintenance and reconstruction projects by restricting the design parameters to a practical level of maximum benefit return for a minimum construction cost.

Most of the effective behavioural and driver-focused crash reduction programs have been in place for a number of years and have had their maximum impact.  The continuation of these programs will only have a holding effect on reducing the NSW road toll and it is now expected that most road toll reduction will have to be achieved by safety engineering works that make the existing road network safer.

The application of Asymmetrical design principles is seen as a more practical and economical alternative in applying safety engineering on two lane rural roads and could be expected to have a major long-term impact on reducing casualty crashes in NSW.