A method and apparatus are provided for calculating potential paths between source and destination locations. First and second map databases are provided that are indicative of roadway networks for geographic regions bounded by region edges and containing source and destination locations. The first and second map databases are non-adjacent, non-contiguous such that the region edges of the first map database are separate and distinct from region edges of the second map database. Potential paths are calculated through the roadway network of the first map database up to a node or segment at which each potential path intersects a region edge of the first map database, thereby defining a node/edge coordinate. A transition location is obtained in the second map database that geographically corresponds to the node/edge coordinate at which a given potential path intersected the region edge of the first map database. The calculation continues from the transition location through the roadway network of the second map database. The method and apparatus may include organizing the map databases into a map hierarchy to define tiers for the map databases. The calculation process searches potential paths utilizing the tier-one map databases until each potential path intersects a map edge of the tier-one map databases. Thereafter, the search through potential paths continues automatically based on the lower tier map databases.