This is a point of law that everyone should exploit.
When faced with the dilemma of recording without the consent of others, remember that traffic police are already recording their own dashcam recordings, so there is no presumption of privacy on their part. They have already consented to being recorded by virtue of their own dashcam recorders.
Now that you have your own recording to show them, that's a game-changer. In the past, they could go back to the station and have a "hard drive crash" that wipes out that officer's recording of that day only. Now, not only is there a back-up recording, it has already passed the acknowledgement test, because once a person gives their consent to being recorded, it's not clear that the consent is only limited to their own recording devices. If you have a recording device, too, then it is valid because the officer already does not have an expectation of privacy because he knows that he's being recorded by his own dashcam device.
Start recording everything on the road. Hold the police accountable to the laws, too.
-PJ
I wonder - if you got into a dicey situation with a LEO, and you asked him “is this being recorded?” without revealing that you were recording it also, would his positive reply be considered consent to be recorded...
We call that "IRS-style".
Someone needs to record a "Gangnam Style" video with Lois Lerner & John Koskinen "trashing a hard-drive" - "IRS Style".