1. A computer-implemented method for recognizing road signs in a vicinity of a vehicle and for synchronizing to road sign information from a digital map, comprising: generating road-sign recognition data that indicates whether a road sign exists; providing navigation data for localizing the vehicle in digital map data; synchronizing the road-sign recognition data to the map data; deciding, in the case of a discrepancy between road-sign data derived from the map data and the road-sign recognition data, whether to output in the vehicle the road-sign data from the digital map or the road-sign recognition data in the vehicle, with the aid of at least one reliability factor, wherein the reliability factor is independent of the discrepancy between the road-sign data derived from the map data and the road-sign data recognition data, and provides a reference point for the recognition probability of the road-sign recognition data; and outputting road-sign data in the vehicle based on the deciding, wherein road-sign data derived from the road-sign recognition data is output irrespective of the road-sign data derived from the map data when a reliability factor of the road-sign recognition data is high; wherein at least one of the operations is performed by a processor; and wherein when there exists a discrepancy between the road-sign data derived from the map data and the road-sign recognition data, and both the reliability factor of the road-sign recognition data and a reliability factor of the map data are low, the road-sign data is output based on whichever one of the map data and the road-sign recognition data indicates an existence of a road sign.