Development and Application of a GIS-Based Decision Support System for Turkish Road Restraint System (TR-RRS) Assessments

Run-off-road (RoR) crashes remain a major road safety challenge worldwide due to their high severity and the complex interactions among roadway geometry, roadside conditions and traffic characteristics. Road Restraint Systems (RRS) are widely used to mitigate the consequences of these crashes by protecting roadside hazards and reducing crash severity. Although performance requirements for RRS are defined by standards such as EN 1317 and MASH, countries have developed different roadside safety approaches and decision-making frameworks based on their regulations, roadway characteristics, and safety priorities such as safe zone determination, hazard identification, risk assessment, and containment level selection.This study reviews roadside safety approaches adopted in the United Kingdom, Germany, and the United States to examine the principles underlying roadside safety assessment and RRS applications. The review focuses on safe zone concepts, hazard and risk definitions, roadside safety design principles, and barrier selection procedures. The findings provide the background for understanding the Turkish Road Restraint System (TR-RRS) approach, which integrates roadway geometry, operating speed, traffic volume, heavy vehicle composition, accident history, and roadside hazards within a structured decision-making framework.To support the practical implementation of the TR-RRS methodology, a GIS-based Decision Support System (DSS) was developed by integrating roadway inventory, traffic data, accident records, and roadside information obtained from General Directorate Highways databases. The DSS performs safe zone determination, threat and hazard identification, risk assessment, and containment level selection. Moreoer, applicability of DSS system was evaluated using an 82.66 km intercity road corridor in Zonguldak, Türkiye. The results demonstrate that the GIS-based DSS provides a systematic, and data-driven approach for roadside safety assessments based on TR-RRS methodology. The developed platform offers a practical tool for improving roadside safety management and facilitating future road safety assessment applications in road network.