A navigation system for a vehicle is disclosed, where the navigation system operates in a route planning mode and a route guidance mode. The navigation system employs an interface device that provides route guidance information to a user during the route guidance mode. The route guidance information provided through the interface device may be audible and/or visual, as through a voice and/or visual indicia on a display screen. The navigation system also comprises a voice control system that responds to vocal commands issued by the user. In response to user vocal commands, the navigation system uses the interface device to provide the user with secondary information relating to a planned route. This secondary information may include, for example, locations and items that are ancillary to principal route guidance functions, such as special locations, map topography, environmental information, and the like.