Abstract: A fluid pressure relay valve particularly for the electro-pneumatic control of vehicle brakes has a piston displaceable within a valve housing to define a control chamber on one side of the piston and on the other side of the piston there is a second chamber which is connected to the braking device. The pressure within the control chamber is controlled by inlet and outlet solenoid valves. The piston actuates valve means for controlling the pressure in the second chamber by venting the chamber or by connecting the chamber to a source of fluid pressure. An additional volume of pressure medium is connected to the control chamber for the purpose of increasing the pressure in the control chamber subsequently to the release of the signal "hold the pressure." The increase in pressure is to a predetermined level which is a function of a controlled lowering of pressure in the additional volume.