I disagree with alot of the previous posts, in fact all of them. You are all right in the fact that Urban legends are stories that have been passed down from generation to generation. But these 'urban legends' have to start somewhere.... Who says none of these have ever happened? If any of them did actually happen, and someone told you about it, chances are you wouldn't believe it because you would say- Ah, thats just an urban legend..
Think of all the murderers, sickos and psychopaths out there in this world- I believe it's possible for any of these to reinact any of these urban legends.
Take for example- The one about the girl going to the service station and the guy climbing into the back seat, and the service station attendant tells the girl to stay there while he calls the police- This is an Urban Legend right? But it was only a few months ago, I was watching a Real Crime show on tv about this exact crime happening.
So I believe that either:
These Urban Legends did occur at some time in history, and it's just that they are so well known and so often used at kids sleepovers to scare eachother that we tend to think it's just a myth.
OR
These Urban Legends are just stories, but they give ideas to people who are capable of doing such gruesome and terrible things, and so they do these things in reality.
As another example, there is the one about the person in the car that drives around with their headlights off, and when you flash your lights to them to 'warn' them to turn their lights on, they turn their car around and chase you. I am sure that there is at least one person or should I say idiot out there in this world that has done that, therefore this urban legend would be true, wouldn't it?
But it's just my opinion and just my thoughts.....