This is an example of symmetry. I really like this photo because it is in black and white the fog in the background adds some depth to the picture. The arch of the bridge is symmetrical on both sides and creates a frame around the picture.
He set his camera to snap a set of three brackets to which he walked in front of the camera, but he had walked out of the frame prior to the final (longest exposure) finishing. The result a ghostly transparent version of him staring out over the river.