Resource allocation approaches for improving safety and operations at level crossings: State of the art, existing challenges, and future research needs

Level crossings (LCs) present substantial safety challenges due to their unique role as intersections where road and rail traffic meet at the same elevation. This study provides a comprehensive review and analysis of resource allocation studies aimed at enhancing safety and operational efficiency at LC locations. The collected studies are categorized into three main groups, including resource allocation for countermeasure implementation, resource allocation for crossing closures, and resource allocation for constructing grade separations. Each group of studies is systematically reviewed focusing on the evaluated fields, countermeasure considerations, sustainability considerations, sustainability dimensions, methodologies used, and case studies. By synthesizing the current literature, this study highlights the strengths and weaknesses of various strategies, emphasizing the need for a holistic framework that integrates safety, economic, and environmental sustainability dimensions. The key contributions include a detailed evaluation of mathematical optimization models for selecting LCs for resource allocation, consideration of important practical factors associated with resource allocation decisions, safety enhancement costs, collision risk levels, and community engagement. The findings suggest that safety performance, design, and upgrades are the most common fields evaluated by the existing studies. A substantial number of studies on LC closures and grade separations also capture traffic delays in decision making. Moreover, essential future research directions for countermeasure implementation, crossing closures, and grade separations are presented as well. This study can serve as a valuable point of reference for researchers and practitioners in the field of LC safety and operational enhancement by consolidating diverse findings and methodologies from the existing research.