[throwaway2016a]

That's interesting. Here if I'm waiting in line it's usually in a situation where the human checkout counters have lines as well. I like the Walmart model... here they have six self-checkouts but one line. So if you're first in line you go to the first one that frees up. Very much superior to having one line per self-checkout.

And in those situations if one backs up you still have at least one alternative that is faster.