Apparently his feet get the priority ride.
There's a big message at the top with signs pointing to each seat, in case you weren't sure.
So go ahead and claim the priority seats when you want them, but keep an eye on fellow riders and be prepared to offer it to someone more needy than yourself.
First photo: http://www.flickr.com/photos/alykat/ / CC BY-NC 2.0
Second photo by the author's obviously sub-par camera phone.