1. A navigation device comprising: a route calculation module operable to calculate a route from a start location to a destination location; a rendering module configured to use digital map data to generate images of said route for display to a user; and a route preview module operable to provide the user with a preview of the calculated route, wherein: the route preview module is operable to divide said calculated route into junction segments and road segments, calculate a length of each said road segment of the calculated route, and is configured to control said rendering module to display images representative of locations within said road segments at a higher display speed than images representative of locations within said junction segments and vary the display speed of road segments based on the calculated lengths of road segments.