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