Not the global urban myths that everyone's heard of, but just local totally unsubstantiated lore that refuses to die?
For me, there's a T-junction where I live that is at an acute angle. On the road markings a bit beyond the Give Way line, there was an irregular blob of splashed white road-marking paint which my wife insisted was a deliberate marker to help you line your car up to turn right, something which her father had told her years ago. I tried to reason with her that the Highways Department or local Council don't do things like that, and what would even be the point as nobody would know what it was there for, and she did concede I had a point.
Anyway, recently the road was resurfaced and the lines repainted. Then all hell broke loose on the local Facebook page that the 'turning marker' had not been repainted by the incompetent council/contractors and that it needed to be sorted before people were killed etc etc – clearly the legend of the 'white blob' had been deep-rooted!
Edit: most of the replies are far more interesting than my example!