The invention relates to a hydrostatic drive as a whole system, comprising two fluidic displacement units (1, 3), which can be adjusted at least in respect of the volumetric flow and of which one is coupled to an input (9) and the other is coupled to an output (11) and which can be connected to each other in the manner of a closed fluidic circuit, to which a storage circuit (23) is connected, which has at least one storage device (33) and which is divided into a low-pressure side (27) and a high-pressure side (25), and comprising a valve control device (17) for controlling the whole system.

A heavy road vehicle provided with a hybrid propulsion system includes a mechanical propulsion system and a hydraulic propulsion system. The mechanical propulsion system is connected to at least one traction wheel which is powered by an internal combustion engine via a mechanical drive train and a gearbox. The hydraulic propulsion system is connected to at least one other traction wheel including a hydraulic motor powered by a hydraulic pump unit. The hybrid propulsion unit further includes a control unit for at least controlling the hybrid propulsion unit, optionally also controlling the mechanical propulsion system. The hydraulic propulsion system further includes a pressure accumulator which is connected to the hydraulic motor in order to maintain a pressure in the hydraulic motor even if the hydraulic pump unit is switched off.

A heavy road vehicle provided with a hybrid propulsion system includes a mechanical propulsion system and a hydraulic propulsion system. The mechanical propulsion system is connected to at least one traction wheel which is powered by an internal combustion engine via a mechanical drive train and a gearbox. The hydraulic propulsion system is connected to at least one other traction wheel including a hydraulic motor powered by a hydraulic pump unit. The hybrid propulsion unit further includes a control unit for at least controlling the hybrid propulsion unit, optionally also controlling the mechanical propulsion system. The hydraulic propulsion system further includes a pressure accumulator which is connected to the hydraulic motor in order to maintain a pressure in the hydraulic motor even if the hydraulic pump unit is switched off.