Alberta is one of the few places that explicitly allows passing on the right.
TRAFFIC SAFETY ACT
USE OF HIGHWAY AND RULES OF
THE ROAD REGULATION:
Overtaking and passing on the right
22(1) A person driving a vehicle may drive the vehicle so as to
overtake and pass on the right of another vehicle
(a) when the vehicle being overtaken is making a left turn or
the person driving the overtaken vehicle has signalled that
person’s intention to make a left turn, or
(b) in the case of a one-way highway, where the roadway
(i) is of sufficient width for 2 or more lines of moving
vehicles, and
(ii) is free from obstructions.
(2) Where a highway has 2 or more traffic lanes on the same side
of the centre line for vehicles travelling in the same direction, a
person driving a vehicle that is
(a) overtaking another vehicle travelling in the same direction
may pass on the right or left of the other vehicle if there is
a traffic lane available for passing to the right or the left of
the traffic lane being used by the vehicle being overtaken,
or
(b) being overtaken by another vehicle travelling in the same
direction shall keep the vehicle being overtaken in the
traffic lane in which that person is driving so as to allow
the overtaking vehicle free passage in the traffic lane to
the right or the left of the traffic lane in which the vehicle
being overtaken is travelling.