German residents have been warned that "the walls pee back", as the Deutsche Bahn railway company coats walls in a special kind of paint to deter "wildpinklers", or "freepee-ers", from taking a piddle in public.
Residents hope to prevent public urination
A 30-metre stretch of wall at a railway station in Cologne, frequently abused by people who urinate in public, has been coated with hydrophobic, liquid-repelling paint of the variety originally used by Nissan to keep cars clean.
"It means any stream of liquid aimed at the wall will bounce back off at roughly the same angle," a spokesperson for the railway company told local newspaper Kölner Stadt-Anzeiger.
Earlier this year, similar measures were employed in Hamburg's nightclub district St Pauli, with signs declaring in German and English: "Hier nicht pinkeln! Wir pinkeln zurueck" (Do not pee here! We pee back!).
The paint is very expensive, costing about €700 (£490) to cover six sq metres, but Julia Staron, who organised the community group responsible for the project in Hamburg, told Reuters that it is worth the cost.
"If you compare the work involved for daily cleaning of the mess and the awful smell, as well as all the collateral damage involved, it has definitely been well worth it," she said.
The project's promotional video has since had more than 5m views on YouTube, and other cities, such as San Francisco, have considered using the paint technology to deter "wildpinklers".