Data mining in a digital map database to identify decreasing radius of curvature along roads and enabling precautionary actions in a vehicle

Disclosed is a feature for a vehicle that enables taking precautionary actions in response to conditions on the road network around or ahead of the vehicle, in particular, a curved portion of a road where the curvature increases between adjacent curved sections. A database that represents the road network is used to determine locations where curvature between adjacent curved sections increases. Then, precautionary action data is added to the database to indicate a location at which a precautionary action is to be taken about the location where curvature increases. A precautionary action system installed in a vehicle uses this database, or a database derived therefrom, in combination with a positioning system to determine when the vehicle is at a location that corresponds to the location of a precautionary action. When the vehicle is at such a location, a precautionary action is taken by a vehicle system as the vehicle is approaching a location where the curvature increases.