  Direct transitions, driven by disorder, from several integral quantum Hall
states to an insulator have been observed in experiment. This finding is
enigmatic in light of a theoretical phase diagram, based on rather general
considerations, that predicts a sequence of transitions in which the integer
$n$ characterizing the Hall conductivity is reduced successively by unity,
eventually going from $n=1$ into an insulator. In this work, we suggest that
the direct transition occurs because, in certain parameter regime, the edge
states of different Landau levels are strongly coupled and behave as a single
edge state. It is indicated under what conditions successive transitions may be
seen.
