  We demonstrate that the one-dimensional (1D) transport channels that appear
in the gap when graphene nanoroads are embedded in boron-nitride (BN) sheets
are more robust when they are inserted at AB/BA grain boundaries. Our
conclusions are based on ab-initio electronic structure calculations for a
variety of different crystal orientations and bonding arrangements at the BN/C
interfaces. This property is related to the valley-Hall conductivity present in
the BN band structure and to the topologically protected kink states that
appear in continuum Dirac models with position dependent masses.
