A navigation system which includes a central processing unit; a nonvolatile storage for storing digitized map data; a road sinuosity S(R) of a route including a plurality of digitized road segments calculated from a starting point to a destination point to be traveled by a user by summing the rotation angle of each of the road segments divided by the distance of each of the road segments; a module to determine an estimated travel time of the route; a module to determine a corrected travel time using the road sinuosity S(R); and a display to display the corrected travel time.