Anti-pee wall in San Francisco makes a splash

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Media captionTesting the anti-pee paint in San Francisco

San Francisco has a problem you notice almost immediately once you arrive: some areas stink of urine.

The problem is most noticeable, and pungent, around the city's metro stations.

And it's at one station - 16th & Mission - where an interesting experiment is taking place.

San Francisco's Department of Public Works (DPW) is trying out a new idea that was and announced last week to much intrigue.

They've coated some walls with a special type of paint that would make urine splash wildly up at the perpetrator - over his shoes, legsā€¦ even, as you can see in the video above, even their face.

Image caption Signs in the area don't explicitly state that the anti-pee paint has been applied

The superhydrophobic coating costs about $200 to apply to each wall, and it essentially gives the concrete a waterproof layer.

The effectiveness of the splashing is unquestionable. When Mohammed Nuru from the DPW gave me a demonstration (with a water bottle, I'll add), it splashed everywhere before trickling away.

But the bigger picture isn't quite so clear. Many people urinate in public out of what they see as a necessity. A 30-minute train journey could spell disaster for a bladder, far better to pee outside than on the train, they argue.

And what of the city's homeless who have no toilet of their own to use?

Closing time

Mr Nuru told me that significant effort has gone into making toilets more appealing to all.

There is a public toilet just a few feet away from the painted walls - but it is not open 24 hours a day.

The DPW also brings in additional facilities to certain areas, much like they do in many cities in the UK in preparation for weekend Friday and Saturday night's drinkers.

The department is monitoring how successful the paint is by keeping tabs on 16th & Mission, and seven other locations around the city.

Image caption There are public toilets - with attendants - but they're not open 24 hours a day

The near-term goal, Mr Nuru said, is to limit the number of times specialist teams need to clean areas because of the problem. That would mean saving money and, just as importantly, water: California is in the grip of a troubling drought.

Mr Nuru said there had been much interest from other US cities about the idea.

He first saw it on a viral video shot in Hamburg, Germany, where similar paint was used to deter people leaving bars and urinating in the street.

While I was packing up my camera equipment, a local man approached the DPW team with well-mannered criticism. This is a gimmick, he suggested - doing nothing to solve the real problem of people simply having nowhere else to go.

The San Francisco Chronicle calls homelessness the "shame of the city".

Hundreds of millions of dollars are spent every year trying to solve the problem, but the homeless population is rising, bucking a nationwide trend of decline.

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