Even when unplanned simultaneous access occurs, guys always follow the alternate-urinal rule.
Or if it's not possible to simply alternate, here's a handy guide.
Picking the Right Urinal (The Man's Book): https://www.youtube.com/watch?v=IR-qQxA6qoA
Many years ago when my band played in the local country bar, I noted that the men's room had a single stall, and a long slanted stainless steel trough that stretched a good 10 feet down the center of the room. Those who only had to pee used the trough; using the stall to pee was unmanly.
Of course, a similar "don't stand right next to another guy" rule was in force, except when the entire trough was occupied.
And staring across the trough at another man's junk was not just bad form, but could get you knocked out.
I always think of that scene in ALONG CAME POLLY where Alec Baldwin invades Ben Stiller’s space at the urinals.