Something I picked up from a friend is when a high five is imminent, to feign the high five then give a pound with a thumbs-up to their palm, or when a pound is imminent, feign that then grab their fist. Bonus points for staring straight through them all the while.
The victim is often so confused that they're left speechless. It may have been awkward for them, but for me, everything went according to plan.
I've been looking at that and you can definitely see where the line is that ties him. The question is whether he is tied to the car that goes by, or tied to some other line-pulling device. It doesn't quite look like the line is being pulled by the car to me.