Sorry, can't stop - having a wee...

What do you understand by the word "ambulant"? To me it means "walking about" or possibly as a noun "one who is walking about". Apparently in a small Cotswold town, edifices have appeared with the signs "Ambulant urinal" and "Ambulant unisex" on them. One of those words perhaps gives the game away - these are public toilets! But what on earth does "ambulant" have to do with it? Are they toilets specifically for walkers (if you're in a car you have to pee yourself?) or are they toilets to be used whilst walking? Even for us men that would be a bit difficult and messy, but for those of the fairer sex it doesn't bear thinking about! It seems the local council have decided to have the signs changed, but which wally was responsible for them in the first place?