In-built network-wide road safety assessment methodologies for rural roads.

Objective: Road traffic crashes are mainly caused by three concurrent factors: infrastructure, vehicle, and human factors. Regarding infrastructure, in recent decades, a series of management tools and procedures called Road Infrastructure Safety Management (RISM) have been proposed. The aim of RISM procedures is to support road authorities in the prevention and mitigation of future road traffic crashes. One of these procedures is the In-built Road Safety Assessment (IRSA) methodology. The peculiarity of an IRSA methodology is the underpinning method used to assign a score to a road section with the aim of identifying those road sections in a network with safety-related infrastructure deficiencies. The objective of this paper is to provide an overall literature review of existing methodologies used worldwide for network-wide road safety assessment for rural road.

Methods: The review was conducted following the guidelines provided by Joanna Briggs Institute (JBI) and the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocols (PRISMA-P) checklist 2020. The characteristics of these methodologies were compared with respect to the following research questions: What are the general characteristics of IRSA methodologies? What risk method/index is applied? Which data collection method/technique is used? What types of road parameters are considered for the assessment? What is the level of expertise needed to implement the methodology? Where and how are the results validated?

Results: As a result, 14 IRSA methodologies were identified. Also, the review showed that similar road parameters were used including: operating speed, road surface, low curve radius, poor sight distance (horizontal and vertical curves), lane width, undivided road (median type), shoulder width, sight obstructions (landscape, obstacles and vegetation), absence of traffic signs and road markings, traffic flow (AADT), intersection quality and density of intersections/lateral accesses.

Conclusions: Despite these similarities, some differences were observed in risk formulation, safety quantities of parameters, level of expertise required, and validation of studies. Researchers may use these findings to develop future road safety assessment methodologies, while road practitioners can make use of this in identifying suitable network-wide assessment methods for safety assessments of road infrastructures. Finally, a series of recommendations for future research work on IRSA methodologies is suggested.