Good point, well made. In reality, the situation in your example of a multi-line queue is not usually as dire as your example portrays, because the delayed peop

Good point, well made. In reality, the situation in your example of a multi-line queue is not usually as dire as your example portrays, because the delayed people in queue #1 are likely to jump ship sometime after the other two queues. have cleared. Nonetheless, this queue-jumping behaviour confuses the circulation pattern and causes congestion in the vicinity of the tills, which itself slows down the throughput. There's no doubt that a single-file call-forward queue is more efficient for both the customers and the shop. One point I didn't see made in the article: single-file queues are also a fair amount more space-efficient, which has value to retailer that is separate from the issue of throughput. This spatial opportunity cost is something that also needs to be considered when designing a queuing system. I've seen subtle & sophisticated studies which do say that customers prefer multi-line queues to single-line queues, but I rarely see any that bring the other factors into play. Retailers really should base their decisions on the following formula: average revenue per customer * (% improved customer throuhgput - % of customers you'll lose because of multi-line queues) + extra retail m^2 * average revenue per m^2 In most cases, you'll find that that the value of a single-line queue is a good deal greater than the value of a multi-line queue. So this is one of those cases where it's likely a good idea to not cater to customer preferences. (I'll also note that single-line queues are much more common here in the UK than in the US; I've become quite accustomed to them and in fact dread multi-line queues and the inevitable idiots that I get stuck behind in them. It seems likely to me that a large part of the American aversion to them is simply a bias against the unfamiliar; this is likely to subside as they become more accustomed to it.)