Road safety

Cover of Road Safety Engineering Risk Assessment Part 1: Relationships between Crash Risk and the Standards of Geometric Design Elements
Road Safety Engineering Risk Assessment Part 1: Relationships between Crash Risk and the Standards of Geometric Design Elements
  • Publication no: AP-T146-10
  • ISBN: 978-1-921709-00-5
  • Published: 15 January 2010

This project forms part of an ongoing Austroads strategic research program to improve the understanding of the relationship between crash risk and road elements. This report provides a summary of the relationship between crash risk, and geometric design elements. As part of the Austroads funded Road Safety Engineering Risk Assessment project, ARRB has undertaken an exhaustive exercise of identifying bibliographic and web sources addressing the relationships between geometric standards and crash risk, and extracting comparing, and interpreting the pertinent information. The information was finally reviewed to derive ‘best’ estimates of the relationships.

  • 1. INTRODUCTION
  • 2. LANES AND SHOULDERS
    • 2.1. Two-lane Rural Roads
      • 2.1.1. Lane and Shoulder Widths
      • 2.1.2. Retrofitting Shoulder Seals
    • 2.2. Other Road Types
      • 2.2.1. Freeways
      • 2.2.2. Urban Roads
  • 3. HORIZONTAL CURVES
    • 3.1. The Studies
      • 3.1.1. US Research
      • 3.1.2. New Zealand Study
      • 3.1.3. Elvik and Vaa
    • 3.2. Assessment of Results
      • 3.2.1. Type of Study
      • 3.2.2. Form of Relation
      • 3.2.3. Graphical Comparison
    • 3.3. Other Contributory Factors
      • 3.3.1. Effect of Overall Alignment Standard
      • 3.3.2. Effect of Cross-section
      • 3.3.3. Grade
    • 3.4. Curve Radius Relative Risk Ratios
    • 3.5. Curves and Cross-section Elements
  • 4. VERTICAL GRADE
    • 4.1. Studies
    • 4.2. Vertical Grade Relative Risk Ratios
  • 5. SIGHT DISTANCE
    • 5.1. Crest Vertical Curves
      • 5.1.1. The Studies
      • 5.1.2. Recommended Risk Ratios
      • 5.1.3. Practical Limitations
    • 5.2. Horizontal Curves
  • 6. ROADSIDES
    • 6.1. The Issue
    • 6.2. Relevant Studies
      • 6.2.1. Methodological Considerations
      • 6.2.2. Overall Rating
      • 6.2.3. Single Physical Measure
      • 6.2.4. Overall Roadside Design Policy
      • 6.2.5. Before and After Studies
    • 6.3. Discussion
  • 7. CONCLUSIONS
    • 7.1. Lanes and Shoulders
    • 7.2. Curve Radius
    • 7.3. Vertical Grades
    • 7.4. Crest Sight Distance
    • 7.5. Roadsides
  • REFERENCES
  • APPENDIX A AUSTROADS ROAD SAFETY ENGINEERING RISK ASSESSMENT PROJECT