Hydropneumatic system for recovering braking energy for a vehicle comprising a power "shunt" transmission, characterized in that it comprises two hydraulic switches (19 and 20) or equivalent devices, the first of which permits two hydraulic machines or sets of machines (3a, 4a) to be combined or opposed and the second of which (20) enables the two-direction lines joining these machines to the hydropneumatic accumulator (17) and a low-pressure reservoir (18) to be connected straight through or crossed-over. Their operation enables the cylinder capacities of the machines to be controlled so as to store or restore the deceleration energy.