Bit outside my usual patch but this caught my eye because the pattern actually makes sense if you think about it. Old railway corridors are basically wildlife motorways - dense vegetation, minimal human foot traffic, running through areas that haven't changed much in decades. If something large and semi-nocturnal exists it would absolutely use those routes.
I've seen similar clustering in US sighting reports, particularly around disused lines in the midwest, and the terrain logic holds up. The Lincolnshire Wolds have a few old trackbeds and I've never personally encountered anything but the area does have a weird reputation locally that predates the whole dogman narrative coming over from America.
What I'd want to know before drawing any conclusions is whether the sightings near railway lines are genuinely overrepresented statistically or whether its just that railway lines are where people walk at dusk and dawn, which is obviously a confounding factor. Has anyone actually mapped this properly rather than just noting the anecdotes? Because without that its just pattern matching on incomplete data and we've all seen where that leads.