Like the cut of your jib baggydave.

I've seen a fair few fall outs as the result of no sign saying "please form one queue". Some at the station. It invariably gets tricky when you get to the front of a central queue that no one else has joined. Then a new queuer comes along and approaches the cashier who's just finishing with a customer. But you haven't noticed this because you're so distracted by the competing beliefs that a) this new queuer has contemptous diregard for a brilliantly democratic and efficient waiting system - in which case an assertive intervention / early morning row becomes iminent or b) they just think you're queuing for the middle cashier.

A sign saying "please form one queue" would cure my neuroses.