A hydraulic system for utility vehicles includes an auxiliary drive, a hydraulic pump and a first valve arrangement, wherein, in an operating mode, the auxiliary drive is supplied with hydraulic energy by the hydraulic pump via the first valve arrangement, wherein, in addition to the auxiliary drive, the hydraulic pump supplies at least one further hydraulically operated system with hydraulic energy, wherein the hydraulic pump is arranged on a tractor vehicle, and wherein the auxiliary drive is arranged on a trailer, which is able to be coupled to the tractor vehicle.