At most of the large suburban supermarkets I’ve shopped at, there’s a small army of check-out cashiers. Long lines can scare away customers, so supermarkets use lots of cashiers—as it turns out, overstaffing— so that individual lines won’t appear crowded.

When Whole Foods came to New York City, high-density apartment buildings and expensive real-estate posed a problem: how do you staff a space-constrained store to handle the hordes of Manhattan gourmets? Going against conventional wisdom, this popular organic grocer adopted bank-style queuing--a single line and a dispatcher that sent customers to the next free cashier. Sound familiar? It’s the call center model where the supermarket dispatcher is the ACD, the cashiers are agents, and waiting customers with their shopping carts are callers.

In fact, the science part of queuing—the classic Erlang C model-- tells us that Whole Food’s “ACD” approach achieves lower average waiting time with the same number of agents. Intuition behind the science: with a single line, the omniscient dispatcher always insures that cashiers are never idle, but when you pick the wrong line at a multi-line supermarket, you invariably end up watching a cashier open up…at the other end of the store. More advanced ACDs go one better than the supermarket dispatcher by predicting waiting times and then routing those callers who’ll have excessive waits to special reserve agents.

There’s more to customer experience than low average speed of answer. Psychologists tells us that occupied time feels shorter than unoccupied time. Translation: time flies when your mind is active. My solution to reducing perceived waiting time on a slow-moving supermarket line is to reach over and grab one of the conveniently located cooking magazines. For news starved customers, several chains have even added kiosks running CNN feeds. Keeping waiting customers mentally involved improves customer experience with no extra staffing.

Back at the call center, music-on-hold helps to engage waiting callers while location information—“you’re number three in the queue”—removes wait uncertainty. There’s research that shows that customer who are given an expected wait time will remain on the line 25% longer. Makes sense: when you know service is in progress, you’re more likely to stay put.

On the horizon, blended reality and IVVR technology has the potential to make waiting on your iPhone for an agent more like watching previews at the movies. Pushed music, video, and other content will keep us entertained and better informed, and virtual interactions with other waiting customers will add the human element. With all this stimulation, it’s just possible that we may look forward to being number ten in the ACD queue.