Right so this is something I've actually been looking into for a few months now after falling down a rabbit hole on the American sightings database. The tunnel connection keeps coming up and I dont think its coincidence. My working theory - and I know this sounds out there - is that the old railway routes follow ley lines or natural geographical corridors that these creatures might use for movement or territory. The tunnels themselves could act as some kind of focal point, almost like the limestone and iron in the infrastructure is amplifying something.
I've been cross-referencing reports from the Pacific Northwest and a few from rural England and the tunnel proximity thing shows up way more than you'd expect by chance. Has anyone actually done a spirit box session near one of these locations? I'd love to compare audio results with the sighting reports to see if theres any overlap in the phenomena. Would be especially interested if anyone has coordinates or specific tunnel names they're willing to share.