A brake pressure modulator (110; 106), comprising a relay valve for controlling a supply of pressurized air from a primary source to at least one brake actuator (112a, 112b); a first valve sub-unit configured to be electronically actuated, wherein the first valve sub-unit is configured to receive a primary control pressure from the primary source intended for operating the relay valve; and a second valve unit configured to at least receive a secondary control pressure from a secondary source ('BST') and at least part of the primary control pressure from the primary source and to transmit either the primary control pressure or the secondary control pressure to the relay valve, and wherein, when the secondary control pressure is transmitted to the relay valve, the primary control pressure from the primary source is disconnected, and/or when the primary control pressure is transmitted to the relay valve, the secondary control pressure from the secondary source is disconnected, and the second valve unit is a mechanically operable valve, wherein said mechanically operable valve is a double-sided check valve that is configured so as to selectively transmit the pressure of a higher magnitude among the primary control pressure and secondary control pressure received from the primary source and the secondary source, respectively, and wherein the first valve sub-unit includes at least two solenoid controlled valves (208, 210), wherein an outlet (208.2) of a first one of the at least two solenoid controlled valves (208, 210) leads to an inlet (206.1) of said double-sided check valve and to an inlet (210.1) of a second one of the at least two solenoid controlled valves (208, 210) wherein the first valve sub-unit includes two solenoid controlled 2/2 direction control valves (208, 210) and wherein, based on an actuation state of each of the two direction control valves, the brake pressure modulator (110; 106) is configured to perform at least one of the following functions: - enabling the supply of the primary control pressure from the primary source to actuate the relay valve; - disabling or blocking the supply of the primary control pressure from the primary source to the relay valve; and - releasing the primary control pressure from the primary source to the atmosphere, and wherein the primary control pressure is intended for operating the relay valve, characterized in that, spatial arrangement or spatial requirement of each of the two solenoid controlled 2/2 direction control valves (208, 210) within the brake pressure modulator (110; 106) is same as spatial requirement of the double - sided check valve. a relay valve for controlling a supply of pressurized air from a primary source to at least one brake actuator (112a, 112b); a first valve sub-unit configured to be electronically actuated, wherein the first valve sub-unit is configured to receive a primary control pressure from the primary source intended for operating the relay valve; and a second valve unit configured to at least receive a secondary control pressure from a secondary source ('BST') and at least part of the primary control pressure from the primary source and to transmit either the primary control pressure or the secondary control pressure to the relay valve, and wherein, when the secondary control pressure is transmitted to the relay valve, the primary control pressure from the primary source is disconnected, and/or when the primary control pressure is transmitted to the relay valve, the secondary control pressure from the secondary source is disconnected, and the second valve unit is a mechanically operable valve, wherein said mechanically operable valve is a double-sided check valve that is configured so as to selectively transmit the pressure of a higher magnitude among the primary control pressure and secondary control pressure received from the primary source and the secondary source, respectively, and - enabling the supply of the primary control pressure from the primary source to actuate the relay valve; - disabling or blocking the supply of the primary control pressure from the primary source to the relay valve; and - releasing the primary control pressure from the primary source to the atmosphere, and wherein the primary control pressure is intended for operating the relay valve, characterized in that, spatial arrangement or spatial requirement of each of the two solenoid controlled 2/2 direction control valves (208, 210) within the brake pressure modulator (110; 106) is same as spatial requirement of the double - sided check valve. - releasing the primary control pressure from the primary source to the atmosphere, and wherein the primary control pressure is intended for operating the relay valve, characterized in that, spatial arrangement or spatial requirement of each of the two solenoid controlled 2/2 direction control valves (208, 210) within the brake pressure modulator (110; 106) is same as spatial requirement of the double - sided check valve.