A pneumatic braking system for an axle of a vehicle, comprising: a. a service brake actuator configured for applying a braking force to an axle of the vehicle, b. an electro pneumatic modulator unit configured for: i. Receiving a first air control pressure representative of a vehicle driver's braking request, ii. Receiving an air supply pressure (P_R), and iii. Delivering a first modulated air pressure (P_s) to a service brake chamber to control the braking force applied, the first modulated air pressure (P_s) being delivered by a regulation unit, c. a parking brake actuator, configured for applying a braking force under the action of an elastic spring and of a pneumatic chamber, the pneumatic chamber being configured for applying a force opposed to the force applied by the spring, a total braking force being the sum of service brake actuator force and parking brake actuator force, the pneumatic braking system further comprising: d. a parking brake unit, configured for delivering a second air pressure (P_p) to the parking brake pneumatic chamber to control the braking force applied by the parking brake actuator, characterised by e. an isolation device configured for: i. in a first mode in which the isolation device is electrically energized, preventing the delivery of the first air control pressure to the regulation unit, and ii. in a second mode in which the isolation device is not electrically energized: 1. allowing the delivery of the first air control pressure to the regulation unit so that a braking force is applied by the service brake actuator when the pressure in the parking brake chamber is higher than a first predetermined threshold (Th_1), and 2. preventing the delivery of the first air control pressure to the regulation unit when the pressure in the parking brake chamber is lower than or equal to the first predetermined threshold (Th_1). a. a service brake actuator configured for applying a braking force to an axle of the vehicle, b. an electro pneumatic modulator unit configured for: i. Receiving a first air control pressure representative of a vehicle driver's braking request, ii. Receiving an air supply pressure (P_R), and iii. Delivering a first modulated air pressure (P_s) to a service brake chamber to control the braking force applied, the first modulated air pressure (P_s) being delivered by a regulation unit, i. Receiving a first air control pressure representative of a vehicle driver's braking request, ii. Receiving an air supply pressure (P_R), and iii. Delivering a first modulated air pressure (P_s) to a service brake chamber to control the braking force applied, the first modulated air pressure (P_s) being delivered by a regulation unit, c. a parking brake actuator, configured for applying a braking force under the action of an elastic spring and of a pneumatic chamber, the pneumatic chamber being configured for applying a force opposed to the force applied by the spring, d. a parking brake unit, configured for delivering a second air pressure (P_p) to the parking brake pneumatic chamber to control the braking force applied by the parking brake actuator, characterised by e. an isolation device configured for: i. in a first mode in which the isolation device is electrically energized, preventing the delivery of the first air control pressure to the regulation unit, and ii. in a second mode in which the isolation device is not electrically energized: 1. allowing the delivery of the first air control pressure to the regulation unit so that a braking force is applied by the service brake actuator when the pressure in the parking brake chamber is higher than a first predetermined threshold (Th_1), and 2. preventing the delivery of the first air control pressure to the regulation unit when the pressure in the parking brake chamber is lower than or equal to the first predetermined threshold (Th_1). i. in a first mode in which the isolation device is electrically energized, preventing the delivery of the first air control pressure to the regulation unit, and ii. in a second mode in which the isolation device is not electrically energized: 1. allowing the delivery of the first air control pressure to the regulation unit so that a braking force is applied by the service brake actuator when the pressure in the parking brake chamber is higher than a first predetermined threshold (Th_1), and 2. preventing the delivery of the first air control pressure to the regulation unit when the pressure in the parking brake chamber is lower than or equal to the first predetermined threshold (Th_1). 1. allowing the delivery of the first air control pressure to the regulation unit so that a braking force is applied by the service brake actuator when the pressure in the parking brake chamber is higher than a first predetermined threshold (Th_1), and 2. preventing the delivery of the first air control pressure to the regulation unit when the pressure in the parking brake chamber is lower than or equal to the first predetermined threshold (Th_1).