Very cool illusion. If I unfocus my eyes and look at only one of the buses, I can see that it is moving at a constant rate across the stripes. But the moment I

Very cool illusion. If I unfocus my eyes and look at only one of the buses, I can see that it is moving at a constant rate across the stripes. But the moment I try to look at both, the illusion takes over. I can sort of get half the illusion by focusing my attention on one of the buses, but still 'noticing' the movement of the other: in that case I will see the bus I am paying attention to move at a constant rate and the other bus move in a stepping motion.