Green road index development: policy implications and strategic prioritization for sustainable transportation infrastructure

The sustainable management of road infrastructure has become a critical challenge for transportation agencies due to growing safety requirements, environmental pressures, and financial constraints. While several sustainability assessment frameworks exist, there is still a lack of an integrated and quantitative index that systematically prioritizes key sustainability criteria for roadway infrastructure while accounting for uncertainty in expert judgment. This study addresses this gap by developing a Green Road Index (GRI) to support informed decision-making in sustainable transportation planning and policy. The proposed GRI is developed using the Fuzzy Analytic Hierarchy Process (FAHP), which enables the integration of qualitative and quantitative indicators and effectively manages the uncertainty inherent in subjective evaluations. A structured questionnaire was administered to 30 experts from academia, industry, and public agencies to evaluate four main sustainability criteria include safety, geometric design, cost, and environmental impact, along with their associated sub-criteria through fuzzy pairwise comparisons. The results reveal that safety is the most influential criterion in sustainable roadway development, with a global weight of 0.343, followed by geometric design (0.315), environmental impact (0.182), and cost (0.160). High-priority sub-criteria include enforcement and regulations, pedestrian facilities, traffic control devices, slope reduction, renewable energy use, and promotion of public transportation. These findings emphasize the dominant role of safety and geometric design while highlighting the need to balance economic and environmental considerations. The proposed GRI offers a transparent and adaptable decision-support tool for evaluating and prioritizing roadway projects. By consolidating multiple sustainability dimensions into a single index, the study provides practical insights for planners and policymakers and contributes to advancing sustainable transportation infrastructure assessment.