Brake system for a pulling vehicle, in particular a tractor, with a) a trailer control valve which generates a pneumatic brake control pressure for a trailer in dependence on a hydraulic brake pressure and b) an emergency valve arranged between a supply coupling head and a pressurised air source, the emergency valve comprising a first operating position and a second operating position and a throttling cross section of the emergency valve being smaller in the second operating positon than in the first operating position, c) a control unit being provided comprising control logic which generates an electric control signal which controls the emergency valve in an emergency situation into the second operating position, characterised in that d) a sensor is provided which senses the pressure in a hydraulic brake line and a sensor is provided which senses the pressure in a pneumatic brake control line and e) the control unit comprises control logic which ea) detects an emergency situation on the basis of a comparison or the relation of - the signal of the sensor which senses the pressure in the hydraulic brake line, - and the signal of the sensor which senses the pressure in the pneumatic brake control line or eb) for the detection of an emergency situation - analyses a change velocity of the signal of the sensor which senses the pressure in the pneumatic brake control line and/or - analyses a time duration for which the relation of the signal of the sensor which senses the pressure in the hydraulic brake line and the signal of the sensor which senses the pressure in the pneumatic brake control line falls below or exceeds a threshold. a) a trailer control valve which generates a pneumatic brake control pressure for a trailer in dependence on a hydraulic brake pressure and b) an emergency valve arranged between a supply coupling head and a pressurised air source, the emergency valve comprising a first operating position and a second operating position and a throttling cross section of the emergency valve being smaller in the second operating positon than in the first operating position, c) a control unit being provided comprising control logic which generates an electric control signal which controls the emergency valve in an emergency situation into the second operating position, d) a sensor is provided which senses the pressure in a hydraulic brake line and a sensor is provided which senses the pressure in a pneumatic brake control line and e) the control unit comprises control logic which ea) detects an emergency situation on the basis of a comparison or the relation of - the signal of the sensor which senses the pressure in the hydraulic brake line, - and the signal of the sensor which senses the pressure in the pneumatic brake control line or eb) for the detection of an emergency situation - analyses a change velocity of the signal of the sensor which senses the pressure in the pneumatic brake control line and/or - analyses a time duration for which the relation of the signal of the sensor which senses the pressure in the hydraulic brake line and the signal of the sensor which senses the pressure in the pneumatic brake control line falls below or exceeds a threshold. ea) detects an emergency situation on the basis of a comparison or the relation of - the signal of the sensor which senses the pressure in the hydraulic brake line, - and the signal of the sensor which senses the pressure in the pneumatic brake control line or - the signal of the sensor which senses the pressure in the hydraulic brake line, - and the signal of the sensor which senses the pressure in the pneumatic brake control line eb) for the detection of an emergency situation - analyses a change velocity of the signal of the sensor which senses the pressure in the pneumatic brake control line and/or - analyses a time duration for which the relation of the signal of the sensor which senses the pressure in the hydraulic brake line and the signal of the sensor which senses the pressure in the pneumatic brake control line falls below or exceeds a threshold. - analyses a change velocity of the signal of the sensor which senses the pressure in the pneumatic brake control line and/or - analyses a time duration for which the relation of the signal of the sensor which senses the pressure in the hydraulic brake line and the signal of the sensor which senses the pressure in the pneumatic brake control line falls below or exceeds a threshold.