These were taken last week at the Chelsea Proving Grounds. From the decals on the rear window, it seems they were doing brake testing on the outer, high speed track, though they were actually going quite slow. Photos are blurred because they were taken while driving higher speeds on the inner test track. My assumption is the thing on the hitch is a weight to simulate towing or load. Also notice all the test equipment on there. Neato.

Enjoy: