  We theoretically calculate the impurity-scattering induced resistivity of
twisted bilayer graphene at low twist angles where the graphene Fermi velocity
is strongly suppressed. We consider, as a function of carrier density, twist
angle, and temperature, both long-ranged Coulomb scattering and short-ranged
defect scattering within a Boltzmann theory relaxation time approach. For
experimentally relevant disorder, impurity scattering contributes a resistivity
comparable to (much larger than) the phonon scattering contribution at high
(low) temperatures. Decreasing twist angle leads to larger resistivity, and in
general, the resistivity increases (decreases) with increasing temperature
(carrier density). Inclusion of the van Hove singularity in the theory leads to
a strong increase in the resistivity at higher densities, where the chemical
potential is close to a van Hove singularity, leading to an apparent
density-dependent plateau type structure in the resistivity, which has been
observed in recent transport experiments. We also show that the Matthissen's
rule is strongly violated in twisted bilayer graphene at low twist angles.
