Abstract: A hydraulic brake valve system for use in a hydraulic circuit consisting of driving and braking fluid lines and including therein at least a hydraulic motor for the actuation of an inertia body such as, for example, a construction vehicle or work implements thereof has a counterbalance valve, a cross-over safety valve, a drain change-over valve and a timer valve. The cross-over safety valve consists of two common relief valves, each having two pressure receiving surfaces and adapted to relieve pressurized fluid acted on one of the pressure receiving surfaces at a low pressure and relieve pressurized fluid acted on the other pressure receiving surface at a high pressure, wherein the first port of one of said relief valves is connected with said driving fluid line and the second port thereof is connected with said braking fluid line, whilst the first port of the other relief valve is connected with said braking fluid line and the second port thereof is connected with said driving fluid line.