Here's what I think, FWIW: The eastbound cop may have looked in his mirror and seen a speck of light (Clayton's headlight) very far behind him. Or maybe he didn't see it.
The latter is quite possible as there's a substantial depression in the topography, just west of the new overpass. Its deep enough and long enough to hide a vehicle for a few seconds.
The former is also possible, but a single light half a mile away could be perceived as a pair of lights (car) much farther away. And no one could be expected to presume that a vehicle in the far distance might be travelling at over twice the speed limit.
I know that on several occasions over decades of driving professionally, I have had my eyes play tricks on my brain when trying to discern a light at a distance. One normally expects to be looking at a car with 2 headlights. Sometimes when the approaching vehicle doesn't fit that pre-supposed description one can get momentarily confused. A car with a headlight out, or a motorcycle, can sometimes be perceived as a car much farther away under the right set of conditions. Usually this happens at night, or when there is fog or rain or snow.
There's also the issue of the road diversion. That was a real dumb place to turn around, even if he was certain there was no one behind him.
Had he drove another couple hundred feet he would have had 4 lanes and 2 shoulders all to himself to do a continuous non-stopping turn.
I'd like to know if he activated his roof lights prior to initiating his turn.
Its too bad the cop didn't have to testify as to what he was doing and thinking. One might think that he chose not contribute to the investigation because doing so would not reflect upon him favourably.
carboncat: There's no possible way a cop in a cruiser with the windows up and his attention focused on, among other things, an ongoing radio conversation about a developing situation, is going to be able to hear a speeding motorcycle far behind him on the other side of an overpass.