Verifying the connection between road design and road safety

16 May 2017

Austroads has published a compendium of recent evidence on the relationships between 20 key geometric road design criteria and safety outcomes.

The project reviewed quality research sources such as Austroads, National Cooperative Highway Research Program (NCHRP) and American Association of State Highway and Transportation Officials (AASHTO) programs, and selected references based on the robustness of their methods and their applicability to the project.

The authors selected and reviewed crash modification factors for road design criteria such as horizontal curvature, lane and sealed shoulder widths, sag and crest design values and various longitudinal sight distance requirements.

The review of findings by the Project Advisory Group largely verified the current design criteria values as published in the Guide to Road Design Part 3: Geometric Design.

The report highlights areas for further investigation to refine the current understanding or to enable economic appraisal of potential future changes including economic analysis of the provision of wider shoulders on curves, values of the sideways friction coefficient for curves, and human factors associated with longitudinal sight distance.

The study reviewed potential for detailed design applications of the Australian National Road Assessment Model (ANRAM) and Interactive Highway Safety Design Model (IHSDM) in Australia and New Zealand. The review found both to be feasible but would require further adaptations.

The project will contribute to Austroads’ strategic Road Safety priority by providing quality safety evidence to the Austroads Road Design Task Force on the relationships between geometric parameters and crash rates.

The findings will help the Task Force to make recommendations on geometric standards throughout Australia and New Zealand. It will also assist in determining the validity and suitability of design exceptions associated with the selected geometric design criteria.

Report link:Verification of Austroads Road Design Criteria Based on Objective Safety Evidence




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