From environmental constraint to strategic fixation: A hierarchical decision model of the Dunhuang–Loulan Silk Road corridor

The Dunhuang–Loulan segment of the Silk Road was a key corridor linking the Hexi Corridor with the Tarim Basin during the Western Han dynasty, yet the mechanisms driving its route formation remain elusive. This study employs a multi-scenario Least cost path (LCP) framework to examine how environmental constraints, subsistence requirements, and state strategies jointly shaped this route. Three sequential scenarios were constructed to represent geography-driven feasibility, resource-oriented adaptation, and strategy-constrained routing, based on terrain, hydrological data, archaeological site distributions, and historically documented control points. The results show that topography and hydrology initially restricted movement to a narrow feasibility corridor centered on the Aqik Valley. Within this corridor, water sources and beacon sites redirected the route toward lower-risk areas, producing systematic deviations from the terrain-optimal path. The final route configuration emerged only after strategic constraints were imposed, closely aligning with historically reconstructed routes. These findings indicate that route formation followed a hierarchical decision process rather than a single-factor optimization, providing a quantitative framework for explaining why ancient routes formed where they did.