Brake system of a commercial vehicle comprising a) a first control unit which is connected by a bus system (45, 46) to an electro-pneumatic wheel brake unit which is connected to a service brake chamber of a combination brake cylinder, and which electrically controls the wheel brake unit via the bus system (45, 46) in order to control a pneumatic brake pressure for the service brake chamber of the combination brake cylinder to correspond to a brake demand, b) a second control unit which is connected via the bus system (45, 46) to the electro-pneumatic wheel brake unit and which electrically controls the wheel brake unit via the bus system (45, 46) in order to control a pneumatic brake pressure for the service brake chamber of the combination brake cylinder to correspond to a brake demand, the second control unit also electrically controlling an electro-pneumatic parking brake valve device for generating a parking brake pressure to correspond to a brake demand, wherein the parking brake valve device is connected via a pneumatic parking brake line to a spring brake chamber of the combination brake cylinder for transmitting the parking brake pressure, c) wherein ca) a service brake unit is connected via brake demand signaling lines (26, 28, 32, 33) both to the first control unit as well as to the second control unit for transmitting a brake demand and/or cb) a parking brake actuation unit is connected by parking brake demand signaling lines (39, 40, 41, 42) both to the first control unit as well as to the second control unit for transmitting a parking brake demand. a) a first control unit which is connected by a bus system (45, 46) to an electro-pneumatic wheel brake unit which is connected to a service brake chamber of a combination brake cylinder, and which electrically controls the wheel brake unit via the bus system (45, 46) in order to control a pneumatic brake pressure for the service brake chamber of the combination brake cylinder to correspond to a brake demand, b) a second control unit which is connected via the bus system (45, 46) to the electro-pneumatic wheel brake unit and which electrically controls the wheel brake unit via the bus system (45, 46) in order to control a pneumatic brake pressure for the service brake chamber of the combination brake cylinder to correspond to a brake demand, the second control unit also electrically controlling an electro-pneumatic parking brake valve device for generating a parking brake pressure to correspond to a brake demand, wherein the parking brake valve device is connected via a pneumatic parking brake line to a spring brake chamber of the combination brake cylinder for transmitting the parking brake pressure, c) wherein ca) a service brake unit is connected via brake demand signaling lines (26, 28, 32, 33) both to the first control unit as well as to the second control unit for transmitting a brake demand and/or cb) a parking brake actuation unit is connected by parking brake demand signaling lines (39, 40, 41, 42) both to the first control unit as well as to the second control unit for transmitting a parking brake demand. ca) a service brake unit is connected via brake demand signaling lines (26, 28, 32, 33) both to the first control unit as well as to the second control unit for transmitting a brake demand and/or cb) a parking brake actuation unit is connected by parking brake demand signaling lines (39, 40, 41, 42) both to the first control unit as well as to the second control unit for transmitting a parking brake demand.