Under cover cops or civilian patrol volunteers?

I have been seeing quite a few cars being pulled over in my town and most the vehicles seen pulling people over are regular vehicles, not marked or unmarked squad cars as they say, but they are civilian cars that have 2 flashing lights a red and blue either in front of car or on the dash. The people getting out are in regular clothes also and the people they pull over are submissive like, they seem cooperative, I 've seen one guy that was pulled over and he was sitting on the ground and the other guy standing behind him, they were waiting on someone or something, maybe for an acual officer to come. Anyone have an idea who they are?