At a complete stop for a red traffic light and after about 30 miles of highway driving the truck began accelerating itself to somewhere between 1500 and 2000 rpm's i immediately depressed the accelerator and as the truck passed slowly through the intersection, i shifted the automatic transmission into neutral. the truck returned to a normal (idle) rpm. i got back into the flow of traffic and proceeded. i called a toyota dealer and described the problem. the next day, i drove the truck to the dealership without any further problems. the dealership was approximately 40 miles away from my home and most of that driving was highway driving. the dealership service staff and a toyota service person from another city all inspected the truck and test drove it. they found nothing. after several days, it was returned to me. the weather at the time of the incident was partly cloudy, dry and the outside air temp. was in the low 90's. the toyota service people told me that although nothing was found wrong, the floor mat was suspect. it was not involved in any way. *tr