The disclosure relates to a lane detection system for a vehicle, having a camera for sensing the carriageway markings in front of the vehicle, and an evaluation unit for evaluating the data collected by the camera. Geometric data of known types of carriageway markings are stored in the evaluation unit, and the evaluation unit determines the type of sensed carriageway markings by comparing the sensed carriageway markings with the stored carriageway markings. The evaluation unit determines the velocity of the vehicle from the known geometric data of the sensed carriageway markings and their changes over time, which are sensed by the camera. The disclosure also relates to a method for operating a lane detection system.