Application of the IRAP Method Combined with GIS to Improve Road Safety on New Highway Projects in Algeria

Derras, Abdelhak; Amara, Khaled; Oulha, Ramdane · 2022 · OpenAlex-citations

DOI: 10.3311/pptr.19026

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Summary

This study addresses the critical need for proactive road safety assessment in Algeria, where road accidents remain a significant social and economic burden. While human behavior is often cited as the primary cause of accidents, the authors argue that infrastructure design plays a pivotal role in safety outcomes. The research aims to provide highway planners with a decision-support tool to predict high-risk segments in new highway projects before they are opened to traffic, thereby allowing for cost-effective corrective measures during the design phase rather than after construction. The methodology combines the International Road Assessment Program (IRAP) with Geographic Information Systems (GIS). The study focuses on an 11-kilometer section of a new penetrating highway connecting the port of Ghazaouet to the East-West Highway in Algeria. Data were collected from technical execution files, traffic studies, and OpenStreetMap, including attributes such as lane width, curvature, grade, median type, and traffic speed. The IRAP method was adapted for proactive use, calculating Star Rating Scores (SRS) for 100-meter segments based on crash modification factors (CMFs) for vehicle occupants. The analysis specifically targeted two crash types: loss of control and run-off-road accidents, excluding frontal collisions due to the presence of a central median. GIS was utilized to map these risk scores spatially. The results indicate that 52.8% of the studied segments (58 out of 110) received a 3-star rating, indicating a high risk of death or serious injury for vehicle occupants. The remaining segments received 4 or 5-star ratings, representing low risk. The analysis identified specific geometric and operational factors driving these risks. Segments with tight curvature radii (less than 500 meters) combined with traffic speeds exceeding 80 km/h were found to be the most hazardous. Additionally, segments with moderate curvature but high speeds also presented significant risks. The study highlights that reducing speed to 60 km/h in tight curves significantly lowers the risk rating. Road exits and intersections were also noted as contributing factors to safety concerns. The significance of this work lies in its demonstration of a combined IRAP-GIS approach as an effective, innovative tool for proactive road safety management. By identifying accident-prone sections during the design phase, authorities can implement cheaper and more effective safety interventions, such as speed control measures, before construction is finalized. The findings underscore that technical parameters, particularly the interaction between curvature and speed, are critical determinants of road safety. This approach offers a scalable model for improving road infrastructure safety in Algeria and similar contexts, shifting the focus from reactive accident analysis to preventive design optimization.

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• perceptual countermeasures

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• Empirical Findings: crash risk outcomes