It costs around $500 to paint a six-square meter area (65 sq feet), and the paint can lose its hydrophobic quality after a few years. Yet supporters say it’s well worth the investment.

This fall the Southern Pennsylvania Transportation Authority will try out a pee-resistant paint that repels urine and splashes it back on the depositor.

Not just any paint: a high-tech coating that guarantees the urine bounces on to the urinator. “Don’t pee here,” read the warning signs appearing around the district, “we pee back.” ...