The closest thing to it in the UK is that traffic police would put "Black Rat" stickers on their personal cars. Of course, it didn't take very long for members

The closest thing to it in the UK is that traffic police would put "Black Rat" stickers on their personal cars. Of course, it didn't take very long for members of the public to find out what the stickers meant and for people who had nothing to do with the police to start making and selling them- by all accounts they don't really work any more, and haven't for years.