  The emergence of controlled, two-dimensional moir\'e materials has uncovered
a new platform for investigating topological physics. Twisted double bilayer
graphene (TDBG) has been predicted to host a topologically non-trivial gapped
phase with Chern number equal to two at charge neutrality, when half the flat
bands are filled. However, it can be difficult to diagnose topological states
using a single measurement because it is ideal to probe the bulk and edge
properties at the same time. Here, we report a combination of chemical
potential measurements, transport measurements, and theoretical calculations
that show that twisted double bilayer graphene can host metallic edge transport
while simultaneously being insulating in the bulk. A Landauer-Buttiker analysis
of measurements on multi-terminal samples allows us to quantitatively assess
edge state scattering. We interpret these results as signatures of the
predicted topological phase at charge neutrality.
