Abstract: A device for detecting the amount of splash water to which a brake pad is subjected on a wet roadway. The device includes a test brake pad, whose friction lining is hygroscopically designed so that it can absorb at least 5%, preferably at least 10% water. In a test phase, vehicles can be easily tested by replacing their stock brake pads with test brake pads. By virtue of the fact that the inventive friction lining is hygroscopic, a direct correlation exists between the water absorption of the friction lining and the amount of moisture led to the friction lining in the form of splash water and air humidity.