A trailer braking system

A trailer braking system including:

• a supply line for connection to a continuous source of pressurised fluid;
• a spring brake having an apply position and a release position, where the spring brake moves to the release position when pressurised fluid is provided at or above a threshold;
• a spring brake control valve which controls the flow of fluid to the spring brake;
• an immobiliser having a brake release position and an immobilise position which control the flow of fluid to the spring brake control valve;
• and
• an auxiliary control valve which is electrically operable and has a system enabled configuration and a system disabled configuration, wherein:
• in the system enabled configuration, the immobiliser is operable to move both to the brake release position, in which the immobiliser permits fluid to the spring brake control valve and the spring brake control valve is operable to cause the flow of pressurised fluid into the spring brake or to vent the spring brake, and to the immobilise position, in which fluid is not permitted to the spring brake control valve;
• and
• in the system disabled configuration, the immobiliser is automatically placed in the immobilise position and fluid is not permitted to the spring brake control valve.

A method of controlling a trailer braking system comprising:

• an immobilisation process comprising:
• an electronic control unit (ECU) sending a signal to an auxiliary control valve and causing the auxiliary control valve to depressurise a supply line of pressurised fluid;
• causing a change in a position of an immobiliser to an immobilise position in which the supply line downstream of the immobiliser is depressurized;
• and
• causing a spring brake control valve to vent, and as such a spring brake is moved to an applied position in which an associated wheel is inhibited from rotating;
• and
• a mobilisation process comprising:
• the ECU sending a sending a signal to an override valve and causing the override valve to connect a trailer reservoir to the immobilise;
• and
• allowing fluid in the supply line to reach the spring brake control valve and maintaining the immobiliser in its brake release position;
• and the spring brake are released and the associated wheel is able to rotate.