Service at fast-food drive-thrus is slower than ever, according to new study.

Customers' average wait time is now 220 seconds, up from 181 seconds last year, the study by QSR Magazine found. That's the slowest service time in the 17 years that QSR has been conducting the study.

To be fair, QSR expanded its research from seven chains last year to 23 this year. But "the numbers this year were still telling," writes Sam Oches, the editor of QSR.

"Speed used to be a badge of honor for many chains," he writes. "Faster service means happier customers and more cars through the line, both of which can boost perception and sales."

But service times are now suffering because many fast-food chains, in an effort to stem widespread traffic declines, have been rapidly expanding their menus, which slows down workers.



McDonald's executives have acknowledged the adverse effects of their expanded menu on service times. The chain announced plans last year to add a third window to its drive-thru lanes to address complaints about service times.

The company also launched a limited one-minute guarantee program for lunchtime customers at McDonald's locations in South Florida this summer. If customers' food wasn't ready within one minute of ordering, they would be awarded a coupon for a free lunch item.

Taco Bell has also been expanding its offerings, adding a premium Cantina Bell menu in 2012 and launching a breakfast menu this year.

"Consumer needs are changing rapidly," Taco Bell chief operating officer Mike Grams told QSR. "There are going to be more complex products coming in, and we just have to change our training methods, our engagement plans in the restaurant, and how we approach them so that we can execute and still be relatively at a good speed that customers are going to be comfortable with."