Data mining in a digital map database to identify unusually narrow lanes or roads and enabling precautionary actions in a vehicle

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, an unusually narrow road width or lane width. A database representing the road network is used to determine locations where an unusually narrow road or lane width exists. Then, precautionary action data is added to the database indicating locations at which a precautionary action is to be taken. 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 unusually narrow road width or lane width exists.