Patent Number: 
Section: claims

1. A navigation system comprising:a map information acquiring unit for acquiring map information;an HOV lane decision unit for deciding whether an HOV lane is included in a road represented by the map information acquired by the map information acquiring unit or not;an HOV lane entrance/exit extracting unit for extracting, when the HOV lane decision unit decides that the HOV lane is included, an entrance/exit section between a lane other than the HOV lane and the HOV lane;a following vehicle detecting unit for detecting presence or absence of a following vehicle traveling in a lane which is adjacent to a current lane and to which a lane change is to be made; anda guidance unit for giving information in accordance with the presence or absence of the following vehicle detected by the following vehicle detecting unit in the HOV lane entrance/exit section extracted by the HOV lane entrance/exit extracting unit. 2. A navigation system comprising:a map information acquiring unit for acquiring map information;an HOV lane decision unit for deciding whether an HOV lane is included in a road represented by the map information acquired by the map information acquiring unit or not;a vehicle information extracting unit for extracting vehicle information including information indicating a type or a size of a vehicle;a control unit for making a passable/impassable decision of the HOV lane from the vehicle information extracted by the vehicle information extracting unit when the HOV lane decision unit decides that the HOV lane is included; anda guidance unit for giving information in accordance with the passable/impassable decision about the HOV lane made by the control unit.