| 摘要 |
A road map display system mounted on a vehicle for navigation guidance is arranged to discriminate monitored roads in which traffic conditions are monitored, from unmonitored roads, and to provide reliable information on traffic congestion to a driver of the vehicle. The road map display system includes a display device and a map image processor which controls the display device to display a road map image of the monitored roads distinguished from the unmonitored roads. Preferably, the display system includes a selector switch for selecting one of a normal display mode in which all roads are displayed around a current vehicle position, and a second display mode in which only the monitored roads are displayed with stepwise gradation to indicate degrees of congestion.
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