A method for detecting an operating state of a vehicle, includes selecting the operating state from at least a first or a second operating state for a vehicle that includes a pneumatic brake system and a pneumatic control connection for connecting the pneumatic brake system to a further pneumatic brake system of a trailer. The method includes the following steps: applying pressure to the control connection until a starting pressure in the control connection is set; opening the control connection such that a pressure between the control connection and an environment is equalized; detecting a temporal pressure pattern during the pressure equalization; comparing the temporal pressure pattern to a reference pressure pattern; determining an evaluation result based on the comparison of the temporal and the reference pressure pattern; and assigning the evaluation result to the first or the second operating state of the vehicle.