Right so this is actually something I've been sitting on for a while. The railroad correlation keeps cropping up in case files and I don't think it's coincidence. Old lines in particular - pre-1950s infrastructure. My working theory is that the rail corridors created long undisturbed strips of land that essentially became wildlife corridors, and whatever these things are they've been using them as travel routes for generations now.
The Rendlesham area has old military and industrial trackways that most people don't even know exist and I've picked up some deeply unsettling EVP material near two of them over the past three years. Whether that's related to cryptid activity or something else entirely I genuinely can't say.
What I will say is that the electromagnetic properties of certain older rail infrastructure - particularly lines with wooden sleepers and corroded iron - might be relevant here if you're thinking along interdimensional lines. Iron has a long folkloric history as a boundary material.
Anyone else actually cross-referencing sighting reports against historical rail maps? Because that feels like the obvious next step and I'm surprised nobody's published anything serious on it yet.