  Electrical control of spin signals and long distance spin transport are major
requirements in the field of spin electronics. Here we report the efficient
guiding of spin currents at room temperature in high mobility hexagonal boron
nitride encapsulated bilayer graphene using carrier drift. Our experiments,
together with modelling, show that the spin relaxation length can be tuned from
2 to 88 micrometers when applying a DC current of $\mp$40 uA respectively. Our
model predicts that, extending the range up to $\mathrm{I_{dc}}=\mp$150 uA, the
spin relaxation length can be tuned from 0.6 to 320 um respectively, indicating
that spin relaxation lengths in the millimeter range are within scope in near
future with moderate current densities. Our results also show that we are able
to direct spin currents on either side of a spin injection contact. 98% of the
injected spins flow to the left when $\mathrm{I_{dc}}$= -40 uA and 65% flow to
the right when the drift current is reversed. Our model shows that, for
$\mathrm{I_{dc}}=\mp$150 uA the numbers reach 99.8% and 95% respectively
showing the potential of carrier drift for spin-based logic operations and
devices.
