Road map information readout apparatus, recording medium and transmitting method

Road map information used in a vehicle navigation or the like is classified into main road groups comprising roads having a high frequency of utilization for route searching processing or the like and minor street groups comprising roads having a low frequency of utilization. Information relating to the roads belong to the main road group are recorded in such a format that the processing speed precedes reduction of a capacity required for recording. On the contrary, information relating to the roads belonging to the minor street group are recorded in such a format that a reduction of a capacity required for recording precedes the processing speed. The minor street group is divided into a plurality of arbitrary small groups to decrease the range of minor streets requiring information to the utmost in the route searching processing or the like. Further, one road which can be represented with one stroke of the brush and roads branching from the road are recorded upon being integrated as one group. Consequently, it is possible to realize a road map information readout apparatus in which the recording efficiency of the road map information is increased, thereby reducing the amount of information to be recorded.