STARTED PIAGGO BV 500; ENGAGED THROTTLE, THROTTLE WOULD NOT DISENGAGE; AS A RESULT SCOOTER RAN AWAY; BEFORE LOSS OF CONTROL, KILL-SWITCH WOULD NOT ENGAGE; BRAKES WERE APPLIED TO AVOID FURTHER ACCELERATION AND THE SCOOTER DUMPED... TEMPERATURE OUTSIDE WAS IN THE LOW 20'S, AND THERE MAY HAVE BEEN FROZEN CONDENSATION ON BOTH THE THROTTLE BODY AND THE KILL SWITCH; AFTER SCOOTER WAS AT REST, KILL SWITCH DID ENGAGE AFTER OPERATOR MADE MULTIPLE ATTEMPTS TO ENGAGE/DISENGAGE WHILE THE REAR-TIRE WAS STILL SPINNING; SUSTAINED INJURY TO LEFT LEG, LEFT HIP, AND POSSIBLE NECK INJURY... HAVE CONTACTED PIAGGIO CORPORATE AND LOCAL AUTHORIZED DEALER... CURRENTLY WORKING TO RESOLVE THIS MATTER. *TR