Analyzing the Relationship Between Crash Risk Based on iRAP Criteria and Road Accident Statistics

Abstract

Road traffic accidents are a major global issue that cause extensive loss of life and property. Different road hierarchy levels serve distinct purposes: levels 1 and 2 prioritize traffic mobility, while levels 3 and 4 emphasize local accessibility. However, safety challenges remain across all levels due to
substandard physical road conditions. This study employs data from the International Road Assessment Programme (iRAP), which evaluates crash risk based on road infrastructure and environmental features, generating a risk score converted into a Star Rating. The dataset, collected by the Department of Highways in 2020, covers 6,361.2 kilometers of Thailand’s national highways. The objective is to analyze the relationship between iRAP risk scores and actual crash statistics using linear regression and correlation analysis. Results show a positive correlation between iRAP scores and run-off-road crashes on the driver’s side across all road levels, with the most significant relationships found in level 1 roads (p = 0.008 for car users and p = 0.03 for motorcycle users). The findings suggest that higher iRAP risk scores are associated with a greater likelihood of certain crash types and can serve as a basis for prioritizing safety improvements on high-risk road segments. This research supports the use of iRAP data in planning and upgrading highway infrastructure to meet safety standards and reduce crash risk