one time i honked at a car that changed lanes into the space i was currently occupying without a signal.
turns out it was an unmarked car and the guy inside told me to settle down.
i asked him to please use a signal so people would know what he's doing. his response "Use a signal? What make the beast with two backsing city did you grow up in?"
honking at police doesn't always work no matter what it was for.
that's too bad. the cops around here obey the law pretty well. it is a big change from nyc where it was a cop every week getting indicted on a felony. i noticed it the first week when i saw a squad car changing lanes -- with turn indicators. total different attitude.