Data mining in a digital map database to identify traffic signals, stop signs and yield signs at bottoms of hills and enabling precautionary actions in a vehicle

1. A method for making an augmented version of a database that can be used as a component in a vehicle system that provides a precautionary action in a vehicle when the vehicle approaches a potentially hazardous location, wherein the potentially hazardous location is one in which two conditions are present at a same location along a road network in a geographic region, wherein one of the two conditions comprises presence of a traffic light, stop sign or yield sign and another of the two conditions comprises a bottom of a hill, the method comprising:

using data contained in a first version of the database to identify traffic lights, stop signs or yield signs located at the bottoms of hills throughout the geographic region; and

forming the augmented version of the database by adding precautionary action data to the first version of the database to indicate locations at which a precautionary action is to be taken by the vehicle system.

2. The method of claim 1 further comprising:

selecting from the first version of the database a data record that represents a road segment;

upon determining that the road segment is part of a hill, obtaining data that represent traffic lights stop signs or yield signs along the road segment; and

upon determining that the road segment is part of a hill and that a traffic light, stop sign or yield sign is located at a bottom of the hill, adding the precautionary action data to the first version of the database to indicate the presence of a condition for which a precautionary action is to be taken.

3. The method of claim 2 further wherein the road segment is determined to be part of a hill by comparing the altitudes at the endpoints of the road segment.

4. The method of claim 2 further comprising:

continuing to select from the first version of the database data records that represent road segments to identify all locations of traffic lights, stop signs or yield signs located at bottoms of hills throughout the geographic region.

5. The method of claim 2 further comprising:

continuing to select from the first version of the database data records that represent road segments until all data records that represent road segments have been selected.

6. The method of claim 1 further comprising:

compiling the augmented version of the database into a format suitable for use in a navigation system.

7. The method of claim 1 wherein the step of using data contained in the first version of the database comprises evaluating at least two items of data contained in the first version of the database to determine whether a traffic light, stop sign or yield sign is located at a bottom of a hill.

8. A database stored on a computer-readable medium, wherein the database includes data that represents a road network in a geographic region, wherein the database comprises:

data records that represent road segments that make up the road network;

data that indicates altitude of the road segments; and

data that indicates precautionary action locations, wherein a precautionary action location is associated with a location where two conditions are present at a same location, wherein one of the two conditions comprises a traffic light, stop sign or yield sign and another of the two conditions is a bottom of a hill.

9. The database of claim 8 wherein the precautionary action data further includes data that indicates a location along a road segment at which a precautionary action is to be taken by a vehicle system.

10. The database of claim 8 wherein the precautionary action data further includes data that indicates a direction along a road segment at which a precautionary action is to be taken.

11. The database of claim 8 wherein the precautionary action data further includes data that refers to the location of the actual traffic light, stop sign or yield sign located at the bottom of the hill.

12. The database of claim 8 further comprising data that indicates permitted directions of travel along road segments, speed limits along road segments, classifications of road segments, and locations of road segments.

13. The database of claim 8 further comprising data that identifies successor road segments of each road segment, wherein successor road segments are those road segments that connect to a road segment at each end thereof.

14. A vehicle system comprising:

a database that contains data representing a geographic region in which a vehicle is being operated, wherein the data includes data that represents a road network located in the geographic region and precautionary action data that indicates precautionary action locations associated with locations where traffic lights, stop signs or yield signs are located at bottoms of hills;

a positioning system that determines a current location of the vehicle relative to the data representing a geographic region; and

a precautionary action application responsive to the positioning system and the database that provides a precautionary action when the positioning system determines that the current location of the vehicle is approaching a traffic light, stop sign or yield sign located at a bottom of a hill.

15. The system of claim 14 wherein the precautionary action data further includes data that indicates a location along a road segment at which a precautionary action is to be taken by a vehicle system.

16. The system of claim 14 wherein the precautionary action data further includes data that indicates a direction along a road segment at which a precautionary action is to be taken.

17. The system of claim 14 wherein the precautionary action data further includes data that refers to the location of the actual traffic light, stop sign or yield sign located at the bottom of a hill.

18. A method for providing precautionary actions in a vehicle comprising:

accessing a database that represents a road network,

determining a current position of the vehicle relative to the road network represented by the database;

upon determining that data representations of a part of the road network around the current position of the vehicle include precautionary action data, taking a precautionary action as the vehicle is approaching a traffic light, stop sign or yield sign located at a bottom of a hill.

19. The method of claim 18 further comprising:

building an electronic horizon after accessing the database; and

using the electronic horizon to determine whether precautionary action data is included therein.

20. The method of claim 18 wherein the precautionary action is provided via a user interface of the vehicle.