Brake system, vehicle comprising such a brake system, and method for controlling brakes of such a vehicle

A brake system for a vehicle comprising a tractor and a trailer, the brake system including an air production module, a trailer control module, a park brakes relay valve and a supply coupling head for supplying air under pressure to brakes of the trailer, wherein:

• a trailer brakes relay valve, interposed between the trailer control module and the supply coupling head and permanently supplied with air under pressure from the trailer control module, controls supply of air under pressure to the supply coupling head;
• the trailer brakes relay valve has two control input ports, respectively connected to the trailer control module and to the park brake relay valve;
• when control air is applied to either one or both of the control input ports of the trailer brakes relay valve, the trailer brakes relay valve supplies air under pressure to the supply coupling head;
• and
• when no control air is applied on both of the control ports of the trailer brakes relay valve, the trailer brakes relay valve does not supply air under pressure to the supply coupling head.