Pneumatic supply device of a pneumatic braking system for a transport vehicle, such as a railway vehicle, the vehicle comprising a pressure source and a secondary pneumatic suspension supplied by the pressure source, the secondary pneumatic suspension having a suspension element adapted to store a predefined amount of pressurized fluid at a predefined secondary suspension pressure (P SS), the device comprising: - a pneumatic distribution system adapted to be supplied by the pressure source and configured to deliver a supply pressure (P A) as a function of a braking setpoint signal, and - a flow relay comprising a supply inlet pneumatically connected to the pneumatic distribution system and receiving the supply pressure (P A) from the pneumatic distribution system, a control inlet adapted to receive a control pressure (P R), and an outlet for supplying the pneumatic braking system with a braking pressure (P F) as a function of the supply pressure (P A) and the control pressure (P R), characterized in that the device further comprises a safety valve adapted to be pneumatically connected between the control inlet of the flow relay, the pressure source and the suspension element, the safety valve being configured to switch, as a function of the secondary suspension pressure (P SS), between a first configuration in which the control inlet of the flow relay is pneumatically connected to the suspension element, such that the control pressure (P R) is a function of the secondary suspension pressure (P SS), and a second configuration in which the control inlet of the flow relay is pneumatically connected to the pressure source, such that the control pressure (P R) is equal to a pressure supplied by the pressure source. the vehicle comprising a pressure source and a secondary pneumatic suspension supplied by the pressure source, the secondary pneumatic suspension having a suspension element adapted to store a predefined amount of pressurized fluid at a predefined secondary suspension pressure (P SS), the device comprising: - a pneumatic distribution system adapted to be supplied by the pressure source and configured to deliver a supply pressure (P A) as a function of a braking setpoint signal, and - a flow relay comprising a supply inlet pneumatically connected to the pneumatic distribution system and receiving the supply pressure (P A) from the pneumatic distribution system, a control inlet adapted to receive a control pressure (P R), and an outlet for supplying the pneumatic braking system with a braking pressure (P F) as a function of the supply pressure (P A) and the control pressure (P R), - a pneumatic distribution system adapted to be supplied by the pressure source and configured to deliver a supply pressure (P A) as a function of a braking setpoint signal, and - a flow relay comprising a supply inlet pneumatically connected to the pneumatic distribution system and receiving the supply pressure (P A) from the pneumatic distribution system, a control inlet adapted to receive a control pressure (P R), and an outlet for supplying the pneumatic braking system with a braking pressure (P F) as a function of the supply pressure (P A) and the control pressure (P R), characterized in that the device further comprises a safety valve adapted to be pneumatically connected between the control inlet of the flow relay, the pressure source and the suspension element, the safety valve being configured to switch, as a function of the secondary suspension pressure (P SS), between a first configuration in which the control inlet of the flow relay is pneumatically connected to the suspension element, such that the control pressure (P R) is a function of the secondary suspension pressure (P SS), and a second configuration in which the control inlet of the flow relay is pneumatically connected to the pressure source, such that the control pressure (P R) is equal to a pressure supplied by the pressure source.