🛣️ AusRAP Star Rating vs IRR Score

Understanding the two key road safety assessment methodologies used in Australia

⭐ AusRAP Star Rating

The Australian Road Assessment Program (AusRAP) is a globally recognised risk-rating system designed by the International Road Assessment Programme (iRAP). It assesses the inherent safety of road infrastructure.

  • Scale: 1 to 5 stars (1 = least safe, 5 = safest)
  • Focus: Road infrastructure safety features
  • What it measures: Protection offered to road users by the road itself
  • Key factors: Median barriers, guardrails, crash cushions, road width, signage
  • Result: A simple star rating showing overall road safety

📊 IRR Score

Infrastructure Risk Rating (IRR) is a quantitative risk assessment methodology that calculates a numerical score based on multiple risk factors. It provides a more detailed, data-driven risk profile.

  • Scale: Numerical score (typically 0-100+)
  • Focus: Comprehensive risk calculation
  • What it measures: Probability and severity of crashes
  • Key factors: Speed, traffic volume, road geometry, infrastructure, user mix
  • Result: Detailed risk score for prioritisation

🔗 The Relationship Between Star Rating and IRR

⭐⭐⭐⭐⭐
AusRAP Star Rating
Simplified visual rating
Based on infrastructure protection
→
Score: 78
IRR Score
Detailed numerical score
Based on comprehensive risk factors

🔄 They are related but distinct methodologies

Star Rating provides a quick visual indicator, while IRR provides detailed risk quantification

📋 Key Differences at a Glance

Aspect AusRAP Star Rating IRR Score
Purpose Quick visual assessment of road safety Detailed risk quantification for prioritisation
Output Format 1-5 star scale (simple, intuitive) Numerical score (detailed, analytical)
Primary Focus Infrastructure protection features Comprehensive risk factors (including exposure)
Use Case Public communication, quick comparisons Technical analysis, funding prioritisation
Complexity Low - easy to understand High - requires detailed data
Data Requirements Infrastructure attributes Infrastructure + traffic + speed + exposure
Similarity Both assess road safety risk
Both use iRAP methodology (AusRAP is the Australian implementation)
Both aim to identify high-risk roads for intervention

💡 Key Takeaway

Think of it this way:
AusRAP Star Rating is like a "safety grade" (A-F or 1-5 stars) that tells you how safe the road infrastructure is at a glance.

IRR Score is like a detailed risk report that calculates the actual risk level considering all factors including traffic volume and speed.

They serve different purposes but complement each other - use Star Rating for quick communication and IRR for detailed technical analysis and funding decisions.