The invention relates to a driver assistance system for a vehicle, in particular commercial vehicle, wherein the driver assistance system (14) has: a detection system which has at least one sensor (15-1, 15-2, 15-3) for issuing measuring signals (S5-1, S5-2, S5-3), a control unit (16) for receiving the measuring signals (S5-1, S5-2, S5-3) and for determining the probability of a critical situation or critical state of the vehicle (1), wherein, when a critical state or sufficient probability of a critical state is identified, the control unit (16) of the driver assistance system (14) outputs a signal (S6) for priming a brake system (4) to a brake control device (6) of the brake system (4) of the vehicle (1), and wherein the control unit (16) outputs an external brake request signal (S6) for initiating braking operations to the brake control device (6) of the brake system (4). According to the invention, in order to prime the brake system (4), the control unit (16) outputs an external brake request signal (S6) which has a desired acceleration value signal (S6-3) with a higher desired acceleration value (a-des) than a current actual acceleration value (a-act).