The panning does not appear to have really worked here. It would have been better if more of the vehicles were sharper - though I imagine that if they're all travelling at different speeds that would be tricky!
Pretty good attempt at a difficult challenge. Would be better if subject were sharper, try matching the motion more exactly and/or slightly faster shutter speed.
It's hard to tell which vehicle is the focal point. The cars do appear more "stationary" against the moving background, but none of them is particularly crisp. My guess is that this type of shot is very hard to do from so far away.