  The lifetime of electrons on edge states of a two-dimensional topological
insulator against the background of an allowed two-dimensional band has been
determined. It has been shown that this time in the case of scattering on
Coulomb impurities can be significantly larger than the mean free time of
two-dimensional electrons. As a result, the conductivity of the metallic
two-dimensional topological insulator strip can be determined primarily by edge
states.
