The diagram below is a schematic of the Prius powertrain:
Toyota Prius Technical Information
http://www.cleangreencar.co.nz/page/prius-technical-info
thackney WROTE: “Prius sometimes accelerates strictly on the electric drive depending on battery level and other conditions. But it will also use the engine to directly drive transmission in addition to the electric motor.
The diagram below is a schematic of the Prius powertrain:”
ME: Ummm... Did you actually LOOK at the diagram you posted?
The diagram says exactly the opposite.
The diagram shows NO direct connection between the gasoline (petrol) engine and the wheels.
The diagram you posted confirms what I wrote, and disproves what you are saying. The gasoline (petrol) engine generates electricity. The electricity drives the wheels.
Look at your diagram. There is no direct drive between the gas engine and the wheels. There is only one drive train.... electric.