Necessity is the mother of invention, yes? Here, that applies to potty training in a weird sort of way.

The Philadelphia transit system is preparing to apply a urine-repelling paint to its surfaces in an attempt to stop people from peeing on their walls! The coating is called Ultra-Ever-Dry, and we mean literally a repellent, as in making pee spray back off the walls onto the offenders. Now that's weird science!

Apparently the $300 public-urination fine that is in existence just doesn't matter to the inconsiderate bladder.   DB