So, I have a good story on this topic that combines two of our favorite things here on NES, talking smack about idiots and trashing d***head cops (disclaimer not all cops are jerks, but some are, it's true I swear).
I am waiting in my car with my wife in a line of about 30 cars to get through a toll booth type thing. Traffic is moving very slowly (this isn't a road more of a driveway), I have waited 10 mins or so and moved 10-15 cars so I was about halfway to the tollbooth. A guy in a big truck pulls up beside me (he's in the exit/oncoming lane), the traffic in front of me starts to move, I snub up to the bumper of the vehicle in the front of me when he tries to pull in front of me. The guy pulls off to the side of the road (he's still in the middle of the oncoming lane) jumps out of his vehicle and runs over to my window waving a badge. Turns out he was either an off duty or just plain clothes LEO of some sort (transit police or some garbage), starts hollering at me for not letting him in and what the hell was I thinking and it was stupid for me to do that over 6 ft etc. etc.
I kept myself sane, handed him my license and registration, he looks at my license and sees I'm from NH and makes some wisecrack about being from out of state. He comes back 5 mins later or so, hands me all my stuff and says he's not going to give me a ticket because he was taught not to react to a situation when he's emotionally involved in the situation.
Needless to say I was a bit freaked out/pissed/annoyed/angry that this guy had the nerve to drive up in the oncoming lane of traffic, try to cut me off then threaten to give me a ticket.
I still don't know what he would have written the ticket "not letting in an unmarked off duty police officer who was breaking the law" I guess I didn't realize that had been passed as a ticketable offense in MA.
</rant>
Oh, and I agree with most of the other people, if it had gotten physical intervene, otherwise either call the police or stay out of it.