| 摘要 |
A navigation system and a program product are provided to determine where there is a passage connected to a main road within the preset range from the current position of a vehicle. A navigation system comprises a detector, a map data acquisition unit, a passage determination unit and a passage guide unit. The detector detects the current position of a vehicle. The map data acquisition unit acquires map data representing information on a road system and roads included in the road system. The passage determination unit determines whether there is a passage based on the acquired map data. The passage guide unit guides a user on the passage according to the determination results. The passage allows a vehicle to drive on a second category road through a first category road. The first category road exists within the preset range. The first and second category roads are created based on road information indicated by the acquired map data.
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