The student pilot in the left seat and his instructor in the right seat were preparing for a local flight. They estimated that there were about 30 gallons of fuel on board prior to departure; 17 gallons in the left tank and 13 gallons in the right tank. After airwork and emergency procedures practice, they returned to the departure airport for some takeoffs and landings. During the second approach to landing, about two hours into the flight, the student pilot advanced the throttle; however, the engine did not respond. Since they were at low altitude, the instructor took the controls and landed the airplane on a nearby highway. After touchdown, the right wing struck a road sign, partially severing the wing. The pilots egressed the airplane and were not injured. An examination of the wreckage by Federal Aviation Administration inspectors revealed substantial damage to the right wing. The fuel tank selector handle, which was located near the student pilot’s left leg, was found in the LEFT tank position. The left wing fuel tank was uncompromised and contained about ½ gallon of fuel. Although the flight instructor stated that he reminded the student several times to switch tanks, the student did not recall ever switching tanks during the flight. The pilots reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.