Urban legend. But it does make for a good campfire story.
My recent favorite was the poor guy they found hanging under the interstate bridge near here a few years ago. Mob snitch, drug deal gone bad, saw something he shouldn't have, etc.......
Turns out he was a postman from upstate New York. Never did hear why he was hung under the bridge. I suppose by the time they figured it out the local press had moved on to more important issues.
Or maybe we were just not meant to know. To add fuel to the fire, someone spray painted "so long snake" on the side of the bridge a week after the body was found.
As kids we were told a troll like creature lived in the Shawville tunnel. Found out that is was a story made up to keep us kids away from it.
I like urban legends though. Cool stuff.