There are two pair of sides on a bus: the front and the rear, and the left side and the right side. The question is how do you specify which pair of sides you are talking about without sounding like an alien from Mars? I am thinking "short side", but I am not sure if that's any good. It sounds horribly vague and I am not even sure you can call it the short side, or short sides.
He was looking at the guy on the other side of him, on the short side of the bus.