WoW:API TaxiNodeGetType

The best way to "map" out a taxi map in code. Returns a string telling the status of the node. Known strings are "CURRENT" for the green "you are here" node slot, "REACHABLE" for a valid slot that can be taken, and "NONE" for an invalid slot. The slots appear to start at the bottom and move in a general bottom-to-top, left-to-right fashion with precedence being given to left-right.

Example: On the complete taxi map at the Ironforge Gryphon Master, Stormwind is slot 1, Ironforge slot 2, Menethil Harbor slot 3, Thelsamar is slot 4, Southshore slot 5, Refuge Pointe slot 6, and Aerie Peak slot 7.
-Moof