A method for validating an illumination-range test value of a light cone of at least one headlight of a vehicle. The method includes reading in a reflection intensity of a point on at least one road marking illuminated by the light cone; generating a reflection intensity model for the road marking, based on the obtained reflection intensity and a particular distance of the point from the vehicle, the reflection intensity model being designed to assign different reflection intensities to different positions on the road marking in front of the vehicle; determining an illumination-range plausibility value, at which, according to the reflection intensity model, a reflection intensity is reached, which corresponds to a reflection-intensity threshold value; and comparing the illumination-range plausibility value to the illumination-range test value, to validate the illumination-range test value, if the illumination-range plausibility value is inside a tolerance range around the illumination-range test value.