Fail to yield to oncoming vehicle (21803a).. on a roundabout

[I_Got_Banned]

I thought they were always running..

I don't know how the camera goes on and off.

Generally, the camera goes on when the emergency lights/sirens are activated. But that is assuming that the officer's vehicle has a camera to begin with.

 

[HighwayMan]

Most digital video systems have pre-event recording. They are constantly recording to a circular buffer and once the camera is activated 30 seconds or so of pre-event video is committed to the recording media and stored.