my cousin's husband is a cop in Philadelphia. my cousin has a "courtesy card", signed by him, declaring that she's family. she shows it along with her license when she gets pulled over for speeding, and they let her off with a warning.
Can confirm, NYPD has these as well. Between this and the ghost cars they drive, the illegal parking, flouting traffic laws, use of their law enforcement function as a political cudgel to be deployed and withheld on demand depending on the prevailing political climate - it is hard to see them as anything but an occupying gang.
it's a literal get out of jail free card.