Volvo’s hybrid bus is a so-called parallel hybrid for diesel and
electric power where both powerplants can operate independently
of one another. In normal circumstances the electric
motor is used when moving off from standstill and for accelerating
to speeds of up to about 20 km/h, which promotes
considerable fuel savings. At higher speeds, the diesel engine
takes over propulsion of the bus and at the same time charges
the electric motor’s batteries.