That's been around for decades. With newer technology, they could lock on to a specific car; the older stuff just identified the speed of the fastest car and the cop would then pick the winner from those in the oncoming lanes.
Mississippi has the least competent state troopers that I've ever run across.
I had a collision with a bicycle last summer. I was driving to work-I didn’t get cited, and the thing that was odd was that they never asked me for my license and registration.
I offered it and the officer said “We don’t need it”.
First time that happened to me. One of the worst days of my life, but that was an odd detail.