At my university there is another method of determining when the urinals flush. There is some sort of circuit that is completed each time the main toilet door closes and the urinals will flush after the circuit has been completed a set number of times. So, for example, the urinals could be set to flush after the main door has been opened and closed 5 times.
I hope you do understand that flushing urine is a huge waste of perfectly good water- water that has been specially treated for dudes to be able to drink it, right?
Urine is sanitary. Although I’ll admit that really stale urine does smell, flushing a few times a day is all that is needed for the smell.
Over all, the USA has a shortage of good fresh water. I know in your childhood you were likely conditioned to think that “pee-pee is bad”, but we are now adults and I hope we can get around that to realize that silly childhood conditioning is not a good reason to waste water.
And that’s why, where I work, we have only urinals that don’t flush at all. Infrared sensors? Bah- who needs that when you can feel the warmth of the last guy’s piss radiating from the back of the urinal?
Some of us have to stand a good distance back in order to use urinals.
Related thread:
http://boards.straightdope.com/sdmb/showthread.php?t=344537&highlight=penis+length