I recently rented an Opel in Spain (have already written what a mediocre car that was) and the navigator kept on saying that the autopista AP7 we were driving or about to take was the autopista apartado postal siete. AP probably means autopista de peaje: toll road or highway. Apartado postal means PO box.
That was as helpful as the recurring warning at irregular intervals that the dead angle warning system did not work right now.