1. A route search apparatus comprising: search means for searching a database to determine a guidance route; a receiver for receiving information as to an impedance to travel on a road within a local area; present location detection means for detecting the present location of the apparatus; first comparison means for comparing the received information, inclusive of location of an impedance to travel, with said guidance route to determine if the impedence to travel is located ahead on the guidance route; search estimation means, responsive to a determination that the location of the impedence to travel is located ahead on the guidance route, for determining a necessary time or distance required for a new route search to determine a new guidance route by-passing the impedence to travel and for preparation to initiate guidance based on the new guidance route; prediction means for determining a predicted travel time or predicted travel distance between the detected present location and a specified location in advance of the impedance to travel; second comparison means for comparing the necessary time with the predicted travel time or the necessary distance with the predicted travel distance; and judgement means for deciding, based on the comparison by said second comparison means, whether or not the new route search is to be conducted.