New Delhi: The ministry of road transport and highways (MoRTH) has issued a standard operating procedure (SOP) regarding the identification, evaluation, and selection of optimal tunnel alignments for National Highway (NH) projects.
Mandating a structured, data-driven approach for identifying optimal tunnel alignments—particularly for tunnels exceeding 1.5 kilometres in length—the SOP states that authorities must evaluate at least three alignment alternatives based on technical feasibility, environmental compatibility, social impact, and cost-effectiveness before proceeding with a particular alignment.
According to the SOP, the final recommended alignment option should be selected with justification, citing the least environmental and social disruption, optimal tunnel length and gradient, engineering feasibility and constructability, compliance with MoRTH’s guidelines and IRC (Indian Roads Congress) codes, and stakeholder and inter-agency consultations.
The procedures also mandate a Geotechnical Investigation Interpretative Report (GIR), to be prepared after the collection of geological, geotechnical, and hydrogeological data during field investigations, as a prerequisite. This comes two years after a state government panel probing the 2023 Silkyara tunnel collapse in Uttarakhand found that the National Highways Infrastructure Development Corporation Limited, under MoRTH, had designed the tunnel without detailed geotechnical and geophysical investigations.
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{{/usCountry}}The SOP recommends that construction agencies must create a high-resolution Digital Elevation Model (DEM) using high-resolution satellite imagery, Light Detection and Ranging (LiDAR), or drone-based photogrammetry.
All tunnel alignment studies are required to integrate with the PM Gati Shakti portal for spatial transparency and inter-agency coordination, the SOP said.
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The SOP also outlines a 12-step process covering project objective definition, corridor identification, reconnaissance surveys, multidisciplinary data collection, environmental and forest assessments, land acquisition analysis, cost estimation, financial viability studies, and stakeholder consultations.
The ministry, in the SOP, mentioned that tunnels play a pivotal role in improving connectivity—particularly in mountainous and border areas—by reducing travel time, fuel consumption, vehicular emissions, and operating costs, while enhancing safety and year-round accessibility.