The young craftsman assembled the hybrid vehicle by attaching the front part of a moped to the rear part of a Renault Clio, St. Gallen police have said in a statement.
The odd machine braked using a combination of the Renault's handbrake and the front brake of the moped.
The speedometer on the moped indicated that the vehicle could only reach 25 km/h, but police said extra equipment had been attached to the car, enabling it to get to speeds of 80-90 km/h, the statement said.
The 17-year-old driver, who police admitted was 'highly talented', had two passengers in the contraption at the time it was stopped.
Police have now confiscated the vehicle.