I saw some Hell's Angels doing this yesterday and it was impressive. They rode in a tight formation and when the lead guy made sure there was enough room for a lane change for all of them, he'd go, and the rest would instantly follow. The guys in back wouldn't even look to make sure it was clear, because they were trusting to the lead to have made sure there was room. It looked pretty impressive and was very effective because they'd make lightning quick lane changes before traffic could change around them. Looked like a school of fish or a flock of birds. Doubly impressive when you see humans do it.