(1) operates a vehicle on a roadway that is divided into two or more clearly marked traffic lanes & doesn't:

(a) operate the vehicle as nearly as practicable entirely within a single lane AND

(b) refrain from leaving the lane until first making sure that the movement can be made safely.

(2) if operating a commercial motor vehicle within a multilane roundabout that's divided into two or more clearly marked traffic lanes may occupy more than one lane when it's not practicable to remain entirely within one lane.