Never really looked into dogman before but this thread caught my eye because I'm more of an earth mysteries / ley lines person and the railway thing jumps out at me straight away.
Old railways in the UK especially were often built along routes that followed much older paths - drove roads, Roman roads, sometimes older than that. So if there's something to the idea that these sightings cluster near rail lines, it might not be the railways themselves that matter, it could be the corridor of land they follow.
Not saying dogman is real tbh, still on the fence with cryptids generally. But the pattern is interesting if the data actually holds up. Anyone got a rough map of where these sightings are reported? Would be curious to see if they line up with anything older than the tracks themselves.