A system, a method, and a computer program product for generating updated map data are provided. The method comprises obtaining map data of a speed sign associated with a plurality of parallel roads, determining one or more effective links associated with the speed sign, based on the map data of the speed sign, determining first vehicle sensor data corresponding to the one or more effective links, and generating a speed index for each of the one or more effective links based on the first vehicle sensor data The method further comprises generating the updated map data based on the speed index for each of the one or more effective links.