Washington / DC. (gov) Wednesday was «National Drive-Thru Day» in the U.S. – noting the popularity of restaurants that take orders by intercom and then pass the food out a window to the customers wanting to keep on the move. The first such service was the idea of Robert Peterson, at a Jack-in-the-Box restaurant in San Diego in 1951, serving hamburgers for just 0,18 USD. At the time, drive-in restaurants were very popular. The serving staff – some even on roller skates – brought food to people who stayed in their parked cars, with the meal set on a tray attached to the car. Today, drive-throughs are a feature of many of the more than 211’000 fast food restaurants in the U.S., which generate over 151 billion USD in sales each year – according to the U.S. Census Bureau.