The Prius is a very technologically advanced machine that employs a 1.5-liter gasoline engine rated at 76 horsepower and a battery-powered electric motor that generates 50 kilowatts (67 horsepower). The...
... Prius emits no sound when started. One simply pushes the start button, selects D from the dash-mounted shifter and depresses the accelerator. The Prius moves forward in utter silence because initially the electric motor is doing all the work.
As the Prius gets up to speed, the car's computer brain signals the gasoline engine to switch on, at which point the electric motor surrenders control in a seamless operation that is virtually undetectable. The differences between driving the Prius and a conventional gasoline-engine car are very subtle -- silent acceleration from rest and gasoline-engine shutdown at stops.