MCLEAN, VA – A new study conducted for QSR Magazine reveals that drive-thru service at QSRs is getting slower due to the growing complexity of new products, USA Today reports.

According to “2013 Drive-Thru Performance Study,” conducted by Insula Research, McDonald’s posted its slowest-ever drive-thru time in the study’s 15-year history, clocking an average 189.5 seconds for the average drive-thru customer to go from order to pickup. That’s roughly nine seconds longer than the industry average.

With major chains recording up to 70% of their business at the drive-thru, the results are significant.

But the extended prep times are not a reflection of a less polished staff. Rather, expanded menus with more complex products take longer to prepare.

"The operational pressures to assemble those items are slowing down the drive-thru," said Sam Oches, editor of QSR.

For instance, Taco Bell’s Cantina Bell bowls include up to 12 ingredients. As a result, they’re more difficult to assemble than a bean burrito.

Additionally, a rededicated effort at getting orders correct is also leading to longer drive-thru times.

"The one thing that angers a customer most is to not get the right food," Oches said. "It's possible to be too fast."

As a result, some chains are slowing down the process or adding order-accuracy checks to ensure correct orders, Oches said. "Customers will be patient if you give them hot, accurate orders.”

Chick-fil-A achieved the industry’s highest percentage in order accuracy at 91.6%, but its customers paid for that with the industry’s longest wait time: 203.9 seconds. That was more than a minute slower than Wendy’s, which recorded the industry fastest average drive-thru time: 133.6 seconds.