as you hear people say.

I have an idea.

Fit cameras to unmarked cars, which members of the public drive.

When the driver sees a particularly horrible traffic offense, they hit the record button.  This causes the video camera to dump the last 60 seconds of (buffered) video to disk, and causes the camera to record for the next minute.

At the end of the day, the recorded offenses are uploaded to the camera office.  Then reviewed, and tickets issued.

I reckon it would sharpen up people’s driving skills pretty damn quick.  Or, at least, take the numpties off the road.