"...the operator of a vehicle may overtake and pass upon the right of another vehicle only under the following conditions: when the vehicle overtaken is making or about to make a left turn; upon a roadway with an unobstructed pavement of sufficient width for 2 or more lines of vehicles moving lawfully in the direction being traveled by the overtaking vehicle. The operator of a vehicle may overtake and pass another vehicle upon the right only under conditions permitting such movements in safety. Such movement shall not be made by driving off the roadway unless passing vehicle comes to a complete stop and such movement may be made safely."