Comparative Analysis of Railway Alignment and Station Modification Options in Historic Areas (Case Study: Tappeh Hesar, Damghan)

The passage of the Tehran–Mashhad railway corridor from the vicinity of the historic site of Tappeh Hesar near the city of Damghan has necessitated the examination of route modification alternatives from technical, economic, and conservation perspectives. In this study, different options—including station relocation, track geometry improvement, and the construction of grade-separated structures—were evaluated using indicators such as attainable train speed, curve radius, construction cost, operational interference, and maintenance expenses. The results indicate that some alternatives lack practical feasibility due to the need for extremely high capital investment and the significant disruption they would cause to operations on this heavily trafficked corridor between Tehran and Mashhad. In contrast, options based on geometric alignment improvements or limited station relocation, requiring substantially lower investment levels, were able to satisfy the functional requirements of the line. Cost estimates show that full station relocation would require far greater expenditure than alignment modification options, while certain geometric corrections can be implemented at considerably lower and more manageable costs. Furthermore, increasing curve radii from small to larger values improves train operational efficiency, reduces maintenance costs, and results in travel time savings. Accordingly, the selection of an optimal alternative depends on decision-making priorities among high-speed rail development goals, required investment levels, existing operational conditions, and cultural heritage protection requirements. The findings of this study can serve as a decision-support framework for railway projects located near historical and archaeological sites.