On-vehicle map display apparatus, map display method

1. An on-vehicle map display apparatus, comprising:

a map scale setting unit that sets a map scale;

a summary map generation unit that generates a summary map by abbreviating shapes of road links, if a map scale that is less than a predetermined scale is set by the map scale setting unit;

a summary map display control unit that displays the summary map generated by the summary map generation unit upon a display monitor;

a congestion information acquisition unit that acquires a plurality of congestion information for each of the road links;

a combination unit that combines together a plurality of congestion information that satisfies a predetermined combination condition among the congestion information that has been acquired for each of the road links by the congestion information acquisition unit, the plurality of congestion information including congestion information for a first road link and a second road link, the first and second road links being separated from each other by an intervening road link whose congestion information is not combined in the plurality of congestion information; and

a congestion information display control unit that displays the congestion information that has been acquired by the congestion information acquisition unit and combined by the combination unit as superimposed upon the summary map displayed upon the display monitor by the summary map display control unit.

2. An on-vehicle map display apparatus according to claim 1 , further comprising a conversion unit that converts the congestion information that has been acquired by the congestion information acquisition unit to match the road shape in the summary map, and wherein:

the congestion information display control unit displays the congestion information that has been converted by the conversion unit along the road upon the summary map when displaying the congestion information as superimposed upon the summary map.

3. An on-vehicle map display apparatus according to claim 1 , further comprising:

a conversion unit that converts the congestion information that has been combined by the combination unit to match the abbreviated shapes of the road links in the summary map, and wherein:

the congestion information display control unit displays the congestion information that has been converted by the conversion unit along the road links upon the summary map when displaying the congestion information as superimposed upon the summary map.

4. An on-vehicle map display apparatus according to claim 3 , wherein:

the congestion information indicates congestion levels and congested distances for each of the road links; and

the combination unit determines the display format of the congestion information after conversion that is to be displayed by the congestion information display control unit based upon proportions of total congested distances for each congestion level in the congestion information before combination.

5. An on-vehicle map display apparatus according to claim 4 , wherein the combination unit combines together congestion information that has been set for each of a plurality of road links between specified intersections, as being congestion information that satisfies the predetermined combination condition.

6. An on-vehicle map display apparatus according to claim 3 , wherein the combination unit combines together congestion information that has been set for each of a plurality of road links between specified intersections, as being congestion information that satisfies the predetermined combination condition.

7. An on-vehicle map display apparatus according to claim 1 , wherein:

the congestion information indicates congestion levels and congested distances for each of the road links; and

the combination unit determines the display format of the congestion information after conversion that is to be displayed by the congestion information display control unit based upon proportions of total congested distances for each congestion level in the congestion information before combination.

8. An on-vehicle map display apparatus according to claim 7 , wherein the combination unit combines together congestion information that has been set for each of a plurality of road links between specified intersections, as being congestion information that satisfies the predetermined combination condition.

9. An on-vehicle map display apparatus according to claim 1 , wherein the combination unit combines together congestion information that has been set for each of a plurality of road links between specified intersections, as being congestion information that satisfies the predetermined combination condition.

10. A map display method, comprising:

a step of an on-vehicle map display apparatus setting a map scale;

a step of the on-vehicle map display apparatus generating a summary map by abbreviating shapes of road links, if a map scale that is less than a predetermined scale is set;

a step of the on-vehicle map display apparatus displaying the generated summary map upon a display monitor;

a step of the on-vehicle map display apparatus acquiring a plurality of congestion information for each of the road links;

a step of the on-vehicle map display apparatus combining together a plurality of congestion information that satisfies a predetermined combination condition among the congestion information that has been acquired for each of the road links, the plurality of congestion information including congestion information for a first road link and a second road link, the first and second road links being separated from each other by an intervening road link whose congestion information is not combined in the plurality of congestion information; and

a step of the on-vehicle map display apparatus displaying the acquired and combined congestion information as superimposed upon the summary map displayed upon the display monitor.