Method for warning a driver of a motor vehicle about a collision, having the steps of: - using a sensor device: ascertaining an actual trajectory of the motor vehicle; - using a computing device: ascertaining a target trajectory of the motor vehicle; - using the computing device: ascertaining a variance of the actual trajectory from the target trajectory; - using the computing device: ascertaining a future collision event with an object categorized as relevant to a collision on the actual trajectory; - using an output device: outputting a warning in the interior of the motor vehicle on the basis of the ascertained future collision event and the ascertained variance, wherein an avoidance point on the actual trajectory is ascertained that characterizes a latest possible starting time for an avoidance manoeuvre to circumvent the collision event with predefined driving parameters relating to the motor vehicle, and the warning is output on the basis of the ascertained avoidance point, characterized in that the target trajectory is ascertained on the basis of a road profile, the road profile being ascertained on the basis of a lane that the motor vehicle is in and the road profile being defined as a target trajectory, wherein the warning is output in the interior of the motor vehicle from a defined minimum driver reaction time before the ascertained avoidance point will probably be reached, wherein ascertainment of the object categorized as relevant to a collision in a second lane, which is different from a first lane of the motor vehicle, results in the minimum driver reaction time being adapted, as a result of which a later warning time compared with the driver reaction time before the adaptation is achieved for output of the warning. - using a sensor device: ascertaining an actual trajectory of the motor vehicle; - using a computing device: ascertaining a target trajectory of the motor vehicle; - using the computing device: ascertaining a variance of the actual trajectory from the target trajectory; - using the computing device: ascertaining a future collision event with an object categorized as relevant to a collision on the actual trajectory; - using an output device: outputting a warning in the interior of the motor vehicle on the basis of the ascertained future collision event and the ascertained variance, wherein an avoidance point on the actual trajectory is ascertained that characterizes a latest possible starting time for an avoidance manoeuvre to circumvent the collision event with predefined driving parameters relating to the motor vehicle, and the warning is output on the basis of the ascertained avoidance point, characterized in that the target trajectory is ascertained on the basis of a road profile, the road profile being ascertained on the basis of a lane that the motor vehicle is in and the road profile being defined as a target trajectory, wherein the warning is output in the interior of the motor vehicle from a defined minimum driver reaction time before the ascertained avoidance point will probably be reached, wherein ascertainment of the object categorized as relevant to a collision in a second lane, which is different from a first lane of the motor vehicle, results in the minimum driver reaction time being adapted, as a result of which a later warning time compared with the driver reaction time before the adaptation is achieved for output of the warning. wherein an avoidance point on the actual trajectory is ascertained that characterizes a latest possible starting time for an avoidance manoeuvre to circumvent the collision event with predefined driving parameters relating to the motor vehicle, and the warning is output on the basis of the ascertained avoidance point, characterized in that the target trajectory is ascertained on the basis of a road profile, the road profile being ascertained on the basis of a lane that the motor vehicle is in and the road profile being defined as a target trajectory, wherein the warning is output in the interior of the motor vehicle from a defined minimum driver reaction time before the ascertained avoidance point will probably be reached, wherein ascertainment of the object categorized as relevant to a collision in a second lane, which is different from a first lane of the motor vehicle, results in the minimum driver reaction time being adapted, as a result of which a later warning time compared with the driver reaction time before the adaptation is achieved for output of the warning.