An information center generates packets of route guidance information, each corresponding
to a prescribed road length of a recommended route. The information center may
generate major guide point information and guidance information and transmit both
to a vehicular apparatus. The vehicular apparatus provides guidance only for major
guide points based on the received major guide point information if it cannot receive
the guidance information. According to another aspect of the invention, if the
end of a route segment which was the subject of the preceding route guidance information
is on an expressway or toll road, guidance information for a preliminary route
from that end to an escape position ahead on the expressway or toll road is first
transmitted and then information for a remaining route, that is a segment of the
recommended route having the prescribed road length minus the preliminary route,
is then transmitted. If communication with the information center is lost, the
vehicular apparatus performs guidance for the preliminary route to an interchange,
for example, of the expressway using the preliminary route guidance information.
