Green means the restaurant is serving a full menu, a signal that damage in an area is limited and the lights are on. Yellow means a limited menu, indicating power from a generator, at best, and low food supplies. Red means the restaurant is closed, a sign of severe damage in the area or unsafe conditions.

“If you get there and the Waffle House is closed?” FEMA Administrator Craig Fugate has said. “That’s really bad. That’s where you go to work.”

Waffle House Inc. has 1,600 restaurants stretching from the mid-Atlantic to Florida and across the Gulf Coast, leaving it particularly vulnerable to hurricanes. Other businesses, of course, strive to reopen as quickly as possible after disasters. But the Waffle House, which spends almost nothing on advertising, has built a marketing strategy around the goodwill gained from being open when customers are most desperate.