“When you put hot food in a closed container, moisture becomes a problem,” Burke says. “The [Denny’s Grand Slam container] has venting holes in the top lid. Heat can rise from the bottom, moisture can leave out the top—it’s a work of engineering genius.”

Another consideration, says Bruce Harte, a professor at the Michigan State University School of Packaging, is reheatability. If the food gets cold before the customer reaches his destination, you should at least make sure he can warm it up without dirtying a dish.

Avoid Fender Benders

Customers choose the drive thru because it’s cheap and fast, but the meal can get a lot more expensive and time-consuming if they lose a rear-view mirror or scratch their car’s paint trying to make it through the lane.

“One mistake we make is we assume everyone is a wonderful driver,” says John Miologos, executive vice president of architecture and engineering for WD Partners. “Not everybody is a wonderful driver, and people are distracted when they’re going through the drive thru.”

Though most drive-thru lanes are built on a curve around the building, it’s easier on the driver if they can straighten out at the points of engagement, says Miologos, who previously worked in McDonald’s Worldwide Architecture, Design, and Construction Group. Turning radiuses also shouldn’t be too tight. Confinement isn’t a good idea either. Nobody likes driving down the highway sandwiched in by those concrete barriers, and the drive-thru equivalent is the double curb. Instead of having raised curbs on both sides, opt instead for only one, on the left. On the right, mark off the lane with a painted line or surface change, Miologos says.

With the diversity of cars on the road today, from Smart Cars to Hummers, deciding on proper clearance heights and widths can be a challenge. Miologos recommends doing some demographic research.

“What I’ve done in the past is design geographically,” he says. “If I know the drive thru is in an area where trucks and SUVs are more the norm, I’ll adjust clearances for that.”

Treat Them Right

If speed is the only thing you’re focusing on at the drive thru, you’re forgetting the very principle on which the restaurant industry was founded: hospitality.

“Some places are focused so much on speed that they’ve been reduced to an arm with a bag hanging out the open window, ready to collect the money,” Schier says.

But a little customer service can go a long way toward pleasing guests. Remembering to ask if they want condiments as well as straws and napkins and making friendly conversation can really make a customer’s day.

“It can be as simple as acknowledging if someone has a dog or a kid in the car,” Schier says. “That four or five seconds of idle chatter shows you care.” The challenge is to do it within the confines of a quick transaction.

“You have to take a cue from the customer,” Lynch says. “If the customer is in a hurry, you can sense that. You have to balance everything, but first and foremost, we want to be courteous to our customers.”