In a method for determining the spatial extent of a free queue, proceeding from position information, firstly a monitoring region comprising the free queue is subdivided into a plurality of positions. Proceeding from the position information, objects assigned to the free queue are identified and tracked. A current position of at least a portion of the tracked objects is periodically stored. An average speed of at least a portion of the objects is determined, wherein the average speed of an object is determined on the basis of a plurality of the stored positions of the respective object. Finally, a first map is created, which records, in relation to the positions in the monitoring region, an occurrence density of objects at the corresponding positions, Objects having an average speed outside a predefined range are not taken into account when creating the first map. Proceeding from a predefined exit region of the free queue, a flood fill method is carried out for generating a continuous region corresponding to the extent of the free queue. The first map is used for a validity check.