Europe’s railway sysstem is fragmented, unlike those on other continents. Out of 36 European railways, 21 are classified as small railways. Many of these small railways are located on key European railway corridors, making them crucial for achieving seamless international traffic within the Single European Railway Area (SERA) that the EU aims to create. The clustering of some of these railway networks in specific regions further complicates the challenge of ensuring seamless traffic flow. Despite their strategic importance, small railways are not receiving adequate research attention at the EU level. Existing scientific literature includes some case studies and a few papers addressing common issues faced by small railways. This paper hypothesizes that small railways share certain characteristics, financial and expert resources, network capacity, and constraints in accounting, maintenance, and cost allocation, that require a specific approach in modeling the Track Access Charge (TAC) structure. By comparing large and small railway networks, we aim to establish a foundation for SERA, and developing a reliable and resilient algorithm for TAC which is essential to address these unique challenges and ensure fair and efficient use of the rail network across both.