Anyone who has ever driven in japan knows that the country has no modern highway system. its roads still follow the paths laid down for—or by—oxcarts in the tenth century. what makes the system work for automobiles and trucks is an adaptation of the reflector used on american highways since the early 1930s. the reflector lets each car see which other cars are approaching from any one of a half-dozen directions. this minor invention, which enables traffic to move smoothly and with a minimum of accidents, exploited a process need.