Design Puzzles II
| Steven Postrel |
When I last posted on whether apparent inefficiencies in the design of objects and institutions were real opportunities or only mirages, there were many well-informed and thoughtful comments. One of the issues I addressed was the use of multiple queues at checkout counters, despite their theoretical inferiority to a single queue where the next available checker gets the next customer in line.
Many readers explained why it wouldn’t be possible to have a single queue — not enough room at the front of the store, long lines scare off shoppers even if they’re fast, less impulse buying, etc. Now comes an article describing the wonders of single-queue checkout at Whole Foods in Manhattan. Apparently, none of these postulated problems is an insuperable barrier to creating an efficient checkout system consistent with theory. (In fact, Whole Foods put in the single queue partly to save space in the store.) So we know at least that there is no show-stopping reason why single queues can’t be used.
It should be noted that Whole Foods also put on a lot of extra checkers, which contaminates measurement of the speed effect of single queues. And of course, basket size may differ across chains. In fact, the article goes on to make an admirable stab at empiricism, measuring a small sample of checkout times at various grocery stores in the city. Interestingly, the fastest checkout (2:46) was at a store with a hybrid system of one line per two registers, but the sample was pretty small there (only 8 people in line). Trader Joe’s, which had a single queue for all of its registers, was a painful, tortoise-like 26:19 (n=81 people in line), whereas Whole Foods blazed away at 3:47 (n=51). So the number of checkers and other factors are likely to be at least as important as the organization of queues.