Navigation systems, methods, and programs

1. A navigation system for a vehicle, comprising:

a controller that:

detects a number of travel lanes available for traveling in a direction that the vehicle is traveling;

detects a lane in which the vehicle is currently located;

determines a congestion degree for each of the available travel lanes;

determines a degree of difficulty of turning right or left at a next intersection that the vehicle is approaching, based on the detected number of available travel lanes, the detected lane in which the vehicle is currently located, and the detected congestion degree;

selects a travel route in accordance with the determined degree of difficulty; and

provides guidance information on the selected travel route.

2. The navigation system claim 1 , wherein the controller:

detects a congestion degree of a lane to which the vehicle can change; and

determines the degree of difficulty of turning right or left based on the detected congestion degree of the lane to which the vehicle can change.

3. The navigation system claim 2 , wherein the controller detects the congestion degree of the lane to which the vehicle can change by determining the speed of another vehicle traveling in the lane to which the vehicle can change.

4. The navigation system claim 1 , wherein the controller:

detects a congestion degree of the lane in which the vehicle is located;

detects a congestion degree of a lane to which the vehicle can change; and

determines the degree of difficulty of turning right or left based on the congestion degree of the lane in which the vehicle is located and the congestion degree of the lane to which the vehicle can change.

5. The navigation system claim 1 , wherein:

the degree of difficulty is expressed in terms of distance; and

the controller excludes from possible routes to be selected a candidate route that requires turning right or left at the next intersection if the degree of difficulty is greater than the actual distance to the next intersection.

6. The navigation system claim 5 , wherein the controller:

selects the excluded candidate route as the travel route if respective lengths of the other possible routes are a predetermined distance longer than the excluded candidate route.

7. The navigation system claim 1 , wherein:

the degree of difficulty is expressed in terms of distance; and

the controller adds the degree of difficulty to the actual length of each candidate route that requires turning right or left at the next intersection.

8. The navigation system claim 1 , wherein the controller determines the congestion degree by communicating with a traffic information center.

9. The navigation system claim 1 , wherein the controller:

detects an number of lane changes required to turn right or left; and

determines the degree of difficulty based on the number of lane changes.

10. A navigation method for a vehicle, comprising:

detecting a number of travel lanes available for traveling in a direction that the vehicle is traveling;

detecting a lane in which the vehicle is currently located;

determining a congestion degree for each of the available travel lanes;

determining a degree of difficulty of turning right or left at a next intersection that the vehicle is approaching, based on the detected number of available travel lanes, the detected lane in which the vehicle is currently located, and the detected congestion degree;

selecting a travel route in accordance with the determined degree of difficulty; and

providing guidance information on the selected travel route.

11. The navigation method claim 10 , wherein:

determining the congestion degree comprises determining a congestion degree of a lane to which the vehicle can change; and

determining the degree of difficulty comprises determining the degree of difficulty of turning right or left based on the detected congestion degree of the lane to which the vehicle can change.

12. The navigation method claim 11 , wherein determining the congestion degree of the lane to which the vehicle can change comprises determining the speed of another vehicle traveling in the lane to which the vehicle can change.

13. The navigation method claim 10 , wherein:

determining the congestion degree comprises determining a congestion degree of the lane in which the vehicle is located;

determining the congestion degree determining a congestion degree of a lane to which the vehicle can change; and

determining the degree of difficulty comprises determining the degree of difficulty of turning right or left based on the congestion degree of the lane in which the vehicle is located and the congestion degree of the lane to which the vehicle can change.

14. The navigation method claim 10 , wherein:

the degree of difficulty is expressed in terms of distance; and

selecting the travel route comprises excluding from possible routes to be selected a candidate route that requires turning right or left at the next intersection if the degree of difficulty is greater than the actual distance to the next intersection.

15. The navigation method claim 14 , wherein:

selecting the travel route comprises selecting the excluded candidate route as the travel route if respective lengths of the other possible routes are a predetermined distance longer than the excluded candidate route.

16. The navigation method claim 10 , wherein:

the degree of difficulty is expressed in terms of distance; and

the method further comprises adding the degree of difficulty to the actual length of each candidate route that requires turning right or left at the next intersection.

17. The navigation method claim 10 , wherein:

determining the congestion degree comprises determining the congestion degree by communicating with a traffic information center.

18. The navigation method claim 10 , further comprising:

detecting a number of lane changes required to turn right or left;

wherein determining the degree of difficulty comprises determining the degree of difficulty based on the number of lane changes.

19. A storage medium storing a set of program instructions executable on a data processing device, the program instructions usable to implement the method of claim 1 .

20. A navigation system for a vehicle, comprising:

means for detecting a number of travel lanes available for traveling in a direction that the vehicle is traveling;

means for detecting a lane in which the vehicle is currently located;

means for determining a congestion degree for each of the available travel lanes;

means for determining a degree of difficulty of turning right or left at a next intersection that the vehicle is approaching, based on the detected number of available travel lanes, the detected lane in which the vehicle is currently located, and the detected congestion degree for each of the available travel lanes;

means for selecting a travel route in accordance with the determined degree of difficulty; and

means for providing guidance information on the selected travel route.