Life cycle environmental assessment of state and national highways in India: Evaluating impact reduction potential of sustainable measures

The present study assessed the environmental impacts of State Highways (SH) and National Highways (NH) in India and assessed the potential for impacts reduction through sustainable interventions. This study is one of the first efforts to assess environmental impacts throughout the pavement life cycle in India along with the identification of sustainable measures. The life cycle impact analysis was performed using LCA for Experts software, with a functional unit of 1 km of road pavement, 7.0 m wide. The LCA was performed as per the ISO 14040, ISO 14044, and ISO 21931-2. The results revealed that NH exhibits higher impacts than SH, with flexible pavements having 20-61 % higher impacts and rigid pavements showing a 5-9 % increase. The use phase (50-67 %) dominated the impact of both flexible and rigid pavements, primarily due to street lighting and fuel consumption, followed by the materials extraction and construction phase (27-46 %) and the end-of-life phase (2-3 %). Improvement scenarios demonstrated significant impact reduction potential. The suggested measures showed impacts reduction potential ranging from 19 % to 152 % on different impact categories for flexible pavements. Similarly, for rigid pavements, the suggested measures were found to reduce impacts by 24 % to 44 %. The green highways with tree plantations will directly reduce 22 t of CO2/km/year. Furthermore, the green hydrogen vehicles achieved reductions of 48-152 % (flexible) and 44-73 % (rigid), while solar-powered electric vehicles yielded the highest benefits, with reductions of 59-160 % (flexible) and 49-83 % (rigid). The findings provide insights for transport planners and a policy for integrating sustainable materials and technologies to minimize the environmental impacts and promote sustainable road transportation.