Road design

Cover of Understanding and Improving Safe System Intersection Performance
Understanding and Improving Safe System Intersection Performance
  • Publication no: AP-R556-17
  • ISBN: 978-1-925671-21-6
  • Published: 13 December 2017

Intersection crashes account for approximately 30% of severe injuries in Australia and New Zealand. This study sought to improve understanding of the key factors in intersection severe injury crashes, and to develop initiatives to improve the design of intersections for better alignment with the Safe System objective of minimising death and serious injury.

The study reviewed recent literature and data to synthesise the following Safe System intersection design principles: minimise conflict points, remove/simplify road user decisions, minimise impact angles, and minimise entry and impact speeds.

Using inputs from literature and data findings, a new safety analytical method, and practitioners, the study proposed nine innovative intersection design concepts seeking to increase Safe System alignment across a wide range of scenarios (urban/rural, new/retrofit). These design concepts form a starting point for practitioners’ trials and refinement.

The study concluded that achievement of Safe System for intersections requires significant supporting contributions from emerging transport disciplines such as C-ITS, autonomous vehicles, and Movement and Place.

  • Summary
  • 1. Introduction
    • 1.1. Background and Study Objectives
    • 1.2. Outline of Work Undertaken
  • 2. Safe System Performance of Intersections
    • 2.1. Review of Research on Safe System Performance of Conventional Intersections
      • 2.1.1. Road Environment and Intersection Type
      • 2.1.2. Intersection Geometry
      • 2.1.3. Traffic Volumes
      • 2.1.4. Key Crash Types
      • 2.1.5. Vulnerable Road Users
    • 2.2. X-KEMM-X Method – Estimation of Severe Injury Probability in the Event of a Crash
    • 2.3. Conventional Intersection Design Case Studies
    • 2.4. Recent Innovations in Safe System-focussed Intersection Design
      • 2.4.1. Literature Summary
      • 2.4.2. Innovative Intersection Designs
      • 2.4.3. Knowledge Gaps
  • 3. Safe System Intersection Design Principles
    • 3.1. High-level Safe System Intersection Design Principles
    • 3.2. Proposed Design-level Guidance
  • 4. Innovative Safe System Intersection Design Concepts
    • 4.1. Signalised Intersection with Safety Platforms
      • 4.1.1. Description and Design Intent
      • 4.1.2. Application, Design Considerations and Costs
      • 4.1.3. Safe System Alignment
      • 4.1.4. Practice Readiness
      • 4.1.5. Knowledge Gaps and Concerns
      • 4.1.6. Further Design Improvements
    • 4.2. Signalised Roundabout
      • 4.2.1. Description and Design Intent
      • 4.2.2. Application, Design Considerations and Costs
      • 4.2.3. Safe System Alignment
      • 4.2.4. Practice Readiness
      • 4.2.5. Knowledge Gaps and Concerns
      • 4.2.6. Further Design Improvements
    • 4.3. Urban Compact Roundabout with Safety Platforms
      • 4.3.1. Description and Design Intent
      • 4.3.2. Application, Design Considerations and Costs
      • 4.3.3. Safe System Alignment
      • 4.3.4. Practice Readiness
      • 4.3.5. Knowledge Gaps and Concerns
      • 4.3.6. Further Design Improvements
    • 4.4. Rural Compact Roundabout with Safety Platforms
      • 4.4.1. Description and Design Intent
      • 4.4.2. Application, Design Considerations and Costs
      • 4.4.3. Safe System Alignment
      • 4.4.4. Practice Readiness
      • 4.4.5. Knowledge Gaps and Concerns
      • 4.4.6. Further Design Improvements
    • 4.5. Urban Signalised Intersection Retrofit Combination Treatment
      • 4.5.1. Description and Design Intent
      • 4.5.2. Application, Design Considerations and Costs
      • 4.5.3. Safe System Alignment
      • 4.5.4. Practice Readiness
      • 4.5.5. Knowledge Gaps and Concerns
      • 4.5.6. Further Design Improvements
    • 4.6. Rural Priority-controlled Intersection with Safety Platforms and Reduced Speed Limits
      • 4.6.1. Description and Design Intent
      • 4.6.2. Application, Design Considerations and Costs
      • 4.6.3. Safe System Alignment
      • 4.6.4. Practice Readiness
      • 4.6.5. Knowledge Gaps and Concerns
      • 4.6.6. Further Design Improvements
    • 4.7. Cut-through Signalised Intersection
      • 4.7.1. Description and Design Intent
      • 4.7.2. Application, Design Considerations and Costs
      • 4.7.3. Safe System Alignment
      • 4.7.4. Practice Readiness
      • 4.7.5. Knowledge Gaps and Concerns
      • 4.7.6. Further Design Improvements
    • 4.8. Urban Priority-controlled Raised Intersection
      • 4.8.1. Description and Design Intent
      • 4.8.2. Application, Design Considerations and Costs
      • 4.8.3. Safe System Alignment
      • 4.8.4. Practice Readiness
      • 4.8.5. Knowledge Gaps and Concerns
      • 4.8.6. Further Design Improvements
    • 4.9. Rural Priority-controlled Intersection with Vehicle Activated Speed Limit
      • 4.9.1. Description and Design Intent
      • 4.9.2. Application, Design Considerations and Costs
      • 4.9.3. Safe System Alignment
      • 4.9.4. Practice Readiness
      • 4.9.5. Knowledge Gaps and Concerns
      • 4.9.6. Further Design Improvements
    • 4.10. Further Design Innovation
  • 5. Summary and Discussion
  • References
  • Appendix A Safe System Assessment Framework (Summary)
  • A.1 Assessment Objectives
  • A.2 Scale and Depth of Assessment
  • A.3 Setting the Context
  • A.4 Applying the ‘Safe System Matrix’
  • A.4.1 Safe Roads and Roadsides, Safe Speeds
  • A.4.2 Other Safe System Pillars
  • Appendix B X-KEMM-X Method Development
  • B.1 Background
  • B.2 Estimating Probability of an Intersection FSI Crash Outcome
  • B.3 Impact Speeds and Crash Angles
  • B.4 Method for Assessing Intersection Designs
  • B.5 Assumptions and Limitations