Abstract: A method and device for determining the freezing temperature of an ice-water mixture on a road surface. Reference measurements of ice-to-water ratios in dependence on road temperatures for different salt contents of reference ice-water mixtures are provided to the device. The thickness of a water layer on the road surface is detected and the thickness of an ice layer of the road surface is detected by the device and method. From the detected thickness of the water layer and the detected thickness of the ice layer, an ice-to-water ratio of the ice-water mixture is determined. The temperature of the road surface is also detected. The freezing temperature of the ice-water mixture is determined by the device and method from the determined ice-to-water ratio and the detected temperature by means of the provided reference measurements.