Passing on the left
From New Zealand Motorcycle Wiki
Passing on the left is prohibited in all cases except those specified by the Land Transport (Road User) Rule 2004 (SR 2004/427), section 2.8. This section should be read in conjunction with the general requirements about passing other vehicles. You must comply with all the sections of the act.
(1) A driver must not pass or attempt to pass on the left of another vehicle moving in the same direction except in accordance
with this clause.
(2) In any case in which the movement referred to subclause (1) may be made,—
(a) the 2 vehicles must be in different lanes; or
(b) the overtaken vehicle must be stationary or its driver must have given or be giving the prescribed signal of
that driver's intention to turn right; or
(c) if the overtaken vehicle is a light rail vehicle moving in the same direction, the light rail vehicle must not be—
(i) signalling an intention to turn left or to stop; or
(ii) stationary for the purposes of allowing passengers to alight or board.
(3) If the roadway is marked in lanes, the driver may make the movement referred in subclause (1) only if the driver's vehicle
does not encroach on a lane that is unavailable to a driver.
