  We identify the physics behind the results of recent measurements [W. Kang et
al., Nature 403, 59 (2000)] of electron transfer between the edges of two
two-dimensional electron systems (2DES). We find that a consistent explanation
of all of the observed phenomena is possible if the barrier between the 2DES is
surrounded by a strong potential well that supports quantum railroads of edge
channels that, in the presence of disorder, exhibit directed localization.
