Yeah, he likes to get moving back there. He definitely has his road legs, though! Whenever I hauled him home from the vet after his accident, I let him loose without the divider in my trailer as usual. He was doing circles in the trailer as we were driving down the highway!
The vet said whenever they get excited it irritates the head injury and they get to moving quite a bit. I don't have any breakaway halters but I do have an old nylon halter that may break if he panics.