A method for determining, dependent on safety levels, spatial regions that are impassable by a vehicle includes: capturing sensor signals and evaluating the captured signals with respect to the spatial position of an obstacle and the effect of the obstacle on the passability of the area surrounding the obstacle; and providing at least two grid structures assigned to different safety levels, each having spatial regions of substantially constant size. The size of the spatial regions is dependent on the safety level of the respective grid structure. The obstacles are entered in the spatial regions of the at least two grid structures. A safety level matching the current state of the vehicle is selected. A grid structure belonging to the selected safety level is selected. All spatial regions of the selected grid structure having an entry exceeding a minimum value are marked as regions impassable by the vehicle.