Hydraulic brake arrangement for a tractor or a tractor-trailer combination, said hydraulic brake arrangement comprising: - a tractor brake module provided with at least a master brake cylinder configured to provide pressurized fluid to brakes (2a, 2b) of a tractor, - a trailer brake valve module comprising a hydraulically actuated trailer brake valve and a proportional valve, - a coupling module configured to allow the fluidic communication between said trailer brake valve module and trailer's brakes, said coupling module comprising a pair of couplers (23, 24), wherein said trailer brake valve is controlled by a pair of hydraulic pilot signals (L1, L2) acting on one side of its spool, a first pilot signal being generated by said proportional valve by modulating a flow of fluid coming from a source of fluid in pressure and a second pilot signal being picked up via a conduit by said pressurized fluid directed generated by said master brake cylinder to control said brakes (2a, 2b) of said tractor, said trailer brake valve being configured to modulate the fluid coming from said source to said trailer brakes via a trailer brake conduit between zero to a maximum value, characterised in that said proportional valve is electro-actuated, said hydraulic brake arrangement further comprises an electro actuated selection valve configured to allow or deny the fluid passage through said conduit towards said trailer brake valve, said hydraulic brake arrangement further comprises pressure sensor means configured to detect the pressure in said conduit and said trailer brake conduit, switches configured to detect the activation of said at least one master cylinder and sensors (33, 34) configured to detect the coupling status of said couplers (23, 24), said hydraulic brake arrangement comprises an electronic unit electrically connected to said pressure sensor means and to said switches to retrieve their detected values and comprises elaboration means to elaborate such detected values to control said selection valve and said proportional valve. - a tractor brake module provided with at least a master brake cylinder configured to provide pressurized fluid to brakes (2a, 2b) of a tractor, - a trailer brake valve module comprising a hydraulically actuated trailer brake valve and a proportional valve, - a coupling module configured to allow the fluidic communication between said trailer brake valve module and trailer's brakes, said coupling module comprising a pair of couplers (23, 24), wherein said trailer brake valve is controlled by a pair of hydraulic pilot signals (L1, L2) acting on one side of its spool, a first pilot signal being generated by said proportional valve by modulating a flow of fluid coming from a source of fluid in pressure and a second pilot signal being picked up via a conduit by said pressurized fluid directed generated by said master brake cylinder to control said brakes (2a, 2b) of said tractor, said trailer brake valve being configured to modulate the fluid coming from said source to said trailer brakes via a trailer brake conduit between zero to a maximum value, characterised in that said proportional valve is electro-actuated, said hydraulic brake arrangement further comprises an electro actuated selection valve configured to allow or deny the fluid passage through said conduit towards said trailer brake valve, said hydraulic brake arrangement further comprises pressure sensor means configured to detect the pressure in said conduit and said trailer brake conduit, switches configured to detect the activation of said at least one master cylinder and sensors (33, 34) configured to detect the coupling status of said couplers (23, 24), said hydraulic brake arrangement comprises an electronic unit electrically connected to said pressure sensor means and to said switches to retrieve their detected values and comprises elaboration means to elaborate such detected values to control said selection valve and said proportional valve.