I may have to try this; this past Sunday the family & I are cruising the MUP by one of my kids' campus and come upon a young woman/girl happily riding along right in the middle of the path. From a fair ways off I say "on your left" No reaction. I repeat it again as I get closer (and louder, too). Nuthin' Finally I'm right next to her (I kid you not) and I'm yelling at the top of my lungs "HELLLOOOOO!!!!!" right at the side of her head. Nuthin...

It's the few times that I encounter folks like this that I refuse to ride on MUPs unless coerced to by TOWMBO.