Some Bib lights came from the factory with dual element bulbs. See the attached pic and you can see the GY wire coming from the Park light that is not connected to anything. Some aftermarket lights also came with two element bulbs.
ERNRAM is correct for an OEM system.
However, just by moving the two Bib light hot wires on the terminal strip to the proper positions, you can make the BIB lights be turn signals or true park lights (on with the Park and the headlights) or they can be both Park and Turn if the bib light socket...