LOS ANGELES — The fastest form of fast food is getting even more popular, with 12.4 billion trips made last year to the nation's drive-through windows — a 2 percent increase from the year before.

LOS ANGELES — The fastest form of fast food is getting even more popular, with 12.4 billion trips made last year to the nation's drive-through windows — a 2 percent increase from the year before.

At quick-service hamburger restaurants, the drive-through is responsible for 57 percent of all visits, beating out dine-in and carry-out options.

The window draws 40 percent of visitors at Mexican fast-food joints and 38 percent of chicken-based chains, according to research company NPD Group.

"Drive-through customers' expectations are straightforward — take down my order accurately and give me my food fast," Bonnie Riggs, NPD's restaurant analyst, said in a statement. "To address consumer needs by having a drive-through operation requires ample real estate and a complex mix of technology, logistics and time management principles. It is really a very well-orchestrated dance."

Some 70 percent of fast-food sales happen at drive-through windows, according to the National Restaurant Association.

They're a constant point of innovation for chains, which in recent years have adopted high-tech ordering systems, multiple lanes, 24-hour windows and more.

Other innovations include certification programs for drive-through cashiers, canopies and landscaping to make the drive-through more attractive, menu boards that allow customers to mull over their choices and order confirmation boards, according to a study last year from QSR magazine.

In 1998, the fastest drive-through was Long John Silvers', which averaged 159.1 seconds.

Whataburger had the best accuracy rating, with 86.7 percent.

Last year, Wendy's was speediest, with 145.5 seconds (slower than the industry record of 116.2 seconds it set in 2003).

Del Taco was most accurate, getting 96.5 percent of orders correct.

Added efficiency helps boost turnover; it also keeps fast-food companies competitive with the convenience stores that are heavily moving into the food-service industry.