[notatoad]

what's interesting to me about the single queue that forms at the self checkouts is that there is no explicit instructions to do this. everybody intuitively lines up in a single queue, despite having lined up in separate queues their entire lives until the self checkouts were introduced. i'm sure none of them have read studies telling them that this is the most efficient method, they just do it. and every now and then somebody tries to start a second line and gets glared at.

[heliodor]

It seems to me to be a function of how the machines are spaced. People need a certain amount of personal space. The single line is the only way to provide it given how tightly the self-checkout machines are packed.