The invention relates to methods in a driver assistance system (104) of a vehicle (100) for sensing wet on a carriageway (110), and to a corresponding driver assistance system with a reverse travel camera (106). A method according to the invention has the following steps: recording an image of a region (118) located to the rear of the vehicle (100) with the reverse travel camera (106); evaluating the recorded image for the presence of a spray trail (116) caused by the vehicle; and selectively outputting, on the basis of the evaluation, a wet signal for triggering an automatic reaction of the driver assistance system (104) to the wet carriageway (110).