The requisite one urinal minimum you put between you and any other men who
may be pissing at a row of urinals. It's a courtesy thing, and it'
s about proximity more than
line of sight:
shame shields don't obviate the need for a buffer urinal.
Of course, when you're in a situation where the buffer is impossible because there are more men than there are urinals (sporting events, concerts, etc.), the buffer urinal no longer applies.