An integrated AHP–GIS least-cost path framework with engineering constraints and economic evaluation for optimal route selection of the Iraqi development road

The Iraqi Development Road is one of the largest strategic infrastructure projects in Iraq, and selecting its optimal route requires careful decision-making. Previous studies have focused primarily on spatial suitability or Least Cost Path (LCP) analysis, with limited attention to sensitivity analysis and engineering-economic constraints within a unified framework. This study proposes an integrated decision-making framework that combines the Analytical Hierarchy Process (AHP), LCP analysis in a GIS environment, sensitivity analysis, and engineering-economic evaluation. Expert opinions were sought to weight six spatial criteria—slope, land use/land cover, soil types, distance to main roads, distance to water bodies, and distance to oil and gas facilities—using AHP. The criteria were then integrated with spatial data derived from remote sensing and global geospatial data sources to generate a spatial suitability map. From this map, an initial LCP route was identified, which was subsequently refined using river crossing as an engineering constraint, followed by an economic evaluation to determine the baseline optimal route. The baseline route was 1,095.96 km long, with an accumulated path cost of 2,085,192.4 cost units, and includes 37 river crossings with a total bridge length of 7,673 m, at an estimated construction cost of $6.81 billion. Sensitivity analysis showed that while some scenarios resulted in slightly shorter routes, they resulted in higher accumulated path costs, increased bridge requirements, and higher construction costs, thus confirming the robustness of the baseline route. The proposed framework provides a reliable methodology for strategic transportation planning. Future studies should incorporate updated remote sensing datasets, geotechnical studies, climate-related risks, and life-cycle cost analysis to support future planning of transportation projects.