In order to make warning devices more efficient, it is known to design parameters to be variable and therewith to be adaptable depending upon the state or condition of a user of the warning information. Herein, for example, warning start points are changed or multi-stage warnings are engineered depending upon urgency. The disadvantage of such an adaptive system can however reside therein, that the mechanistic detection of the condition of the operator using various sensor systems and the subsequent output to the operator or the operator assistant system is not always acceptable, which can irritate the vehicle operator or occupants. In order to increase the acceptance by the user of the warning information it is proposed that in the lead-up to a planned change in the mode and manner of the output of the warning information, communication is initiated with at least one of the users. In the framework of this communication a user can indicate his acceptance or declining with respect to the planned change.