{HEAD ~ A database} that represents {TAIL ~ the road network} is used to determine locations where an intersection of roads is located at the bottom of a hill and then, precautionary action data is added to the database to indicate such locations 
represents
{ HEAD ~ A database } that represents { TAIL ~ the road network } is used to determine locations where an intersection of roads is located at the bottom of a hill and then , precautionary action data is added to the database to indicate such locations
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