A navigation system and method factors into its routing decisions information pertaining to transient delays encountered from time to time, one example of such a transient delay is accident information obtained from currently available broadcast traffic flow sources. The system can also factor in historically available traffic delay data based on time of day or other parameters. The navigation system keeps track of the routes traveled by the vehicle (or user) and the times of transit of such routes. When a user requests a route based upon given end-points, the navigation system can use its own stored historical data, as well as currently available traffic delay data, to calculate and announce a given route.