I would say they look like grounding straps, to ensure a good electrical connection between the body and doors, but I don't understand why they would be fitted because the doors contain no electricals.
The blue colour tells it all, I have those grounding straps in my blue gendarmerie ( france police) R4 too. I donot know for sure, but I would say, because of the police communication-installation that time, it had to prevent static electricty.