“But that varies from store-to-store,” he said, “and the system’s calculations are unique to each store.”

So how’s QueVision working? Dailey said it has made a big difference in customer wait time – defined as the time between a customer’s arrival at a checkout line and the moment that customer starts putting products on the conveyor belt.

“Before we had the system, the average wait for Kroger was four minutes,” he said. “Now the average is 26 seconds. That’s for all Kroger stores at all times of the day.”

And four minutes is a tipping point for grocery customers, according to a study by M/A/R/C, a Texas-based market-research firm.

First done in 2007 and updated a year later with similar results, the study showed that more than 40 percent of grocery shoppers who had to wait more than four minutes would consider changing stores.

Dailey said customer complaints were what prompted Kroger to pioneer QueVision in the U.S. The system now is in a 32-store grocery chain in Hawaii. Some major European chains use the technology.

“We kept hearing from our customers that they didn’t like waiting,” Dailey said. “We began asking ourselves what we could do to fix this.”