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Distances and routing directions are calculated by first determining which roads a vehicle will travel over to get between two points, and then adding up the distances over each section of road to arrive at a total distance (similar to the manual task that one might follow if using an atlas).
Exact distances and driving instructions are generated if both origin and destination points are Key Cities on the ALK Highway Network. If one of the points is not a Key City, then the nearest Key City, in the direction of the other point, is selected to calculate the exact portion of the trip using actual roads. A distance estimation for the local portion of the route is then calculated. This distance is generated from the chosen Key City to the geographic center of the non-Key City point and added to the total distance. Due to the large number of Key Cities (at least one per county), the local portion of any mileage calculation is usually a very small percentage of the total distance.