Motor homes, travel trailers, and campers may exceed the maximum width established under RCW 46.44.010 if the excess width is attributable to appurtenances that do not extend beyond the body of the vehicle by more than four inches, or if an awning, by more than six inches. As used in this section, "appurtenance" means an appendage that is installed by a factory or a vehicle dealer and is intended as an integral part of the motor home, travel trailer, or camper. "Appurtenance" does not include an item temporarily affixed or attached to the exterior of a vehicle for the purpose of transporting the item from one location to another. "Appurtenance" does not include an item that obstructs the driver's rearward vision.