During a routine drive home, i drove over rail road tracks and the car began to accelerate without my foot on the gas pedal. the car continued to accelerate with both feet on the break. i verified that the floor mat was not stuck on the pedal. i placed the car in neutral and the engine was still pegging. i also tried to depress and release the gas pedal several times and that did not stop the acceleration. in order to keep from crashing, i had to keep my feet firmly on the break. this unintended acceleration was occurring for about a quarter mile. i attempted one final cycle of the gas pedal (depress and release) and that finally stopped the acceleration. *js