Navigation apparatus, navigation system and navigation method providing guidance for lane changes

A navigation system includes an input device for inputting a destination, a current location detector for detecting current location of the vehicle, a camera for imaging an area to the rear of the vehicle, a route search program for searching for a route to the destination and a controller for providing guidance along the route determined by the route search. The controller controls the imaging by the camera according to route guidance information and determines whether a lane change is required in accordance with information obtained from the image. When it is determined that a lane change is required, the traffic situation in the vicinity surrounding the vehicle is recognized and guidance for the lane change is provided.