A dash cam on a vehicle for reading signage and updating navigation of the vehicle. A detour is detected from a route using a navigation system in a vehicle. A video recording from a dash cam on the vehicle which is continuously recording as the vehicle is operated is reviewed, and the reviewing of the video recording is based on a time of the detour from the route. Signage of a road diversion on the video at a location of the detour is detected. The signage is assessed to determine a route change based on the road diversion, and the route change includes avoiding the location of the detour or a detour area. The navigation system is updated with the route change based on the signage and the road diversion. The updated navigation includes the avoiding of the location of the detour or the detour area.