(i) for a given network, the number of IPW is limited [20], but the number of APWs is likely to be very large.
When a large number of pathways all share common links, the number of APWs between an O–D pair
can be overly sensitive to
the damage to those commonly shared links,
therefore is not a stable metric of the overall network performance;
and (ii) finding APWs between two nodes is NP-Hard, and therefore is impractical for decision making practice.