Two large Australian department stores implemented single global queueing for non-self-serve when they introduced self-serve. Its a mixed bag because they also reduced staff on the line to match maximal delay for minimum fuss: ie, they don't aim to serve this line any faster than the worst-case single line instance.
It doesn't invalidate the single global line theory: it points out that the qui bono moment in a queue is not you the customer: its the profit centre. They do anything to maximise profit absent a strong signal they went too far.
its morally akin to basic time-and-motion/taylorism.
The signal I usually give is that when I arrive at a line of (understaffed) counters, with all of them having long queues, I turn around with my basket or cart, put everything back on the shelves, and leave. I do that if I it's clear that I have to wait more than a few minutes.
It doesn't invalidate the single global line theory: it points out that the qui bono moment in a queue is not you the customer: its the profit centre. They do anything to maximise profit absent a strong signal they went too far.
its morally akin to basic time-and-motion/taylorism.