A. The provisions of this Chapter governing size and weight do not apply to:
1. Any vehicle, combination of vehicles, article, machine, or other equipment in use by the Federal Government, the State of Oregon, or any county or city while in the immediate vicinity of and involved with the construction, maintenance, or repair of public highways;
2. Any vehicle in use by a mass transit district for the purposes authorized under ORS 267.010 to ORS 267.390, provided the size or weight of the vehicle is approved by the City for that route; or
3. Any vehicle, combination of vehicles, article, machine, or other equipment operated under a permit issued by the Traffic Engineer and in compliance with the conditions and restrictions thereof.
B. None of the size limits described in ORS 818, except the maximum limit of allowable extension beyond the last axle of a combination of vehicles, apply to agricultural equipment hauled, towed, or moved upon any street if the movement is incidental to the farming operations of the owner of the agricultural equipment.