Another reason I love this shot is that it mirrors Mike Sullivan's final scene: the dusty light sweeping in the windows, the camera, the rush of the train and water, someone leaning over a dead/dying man...
And finally, you could easily take any shot/frame from this film and it'd be worthy of discussion and admiration. Conrad Hall was a master of photography and his collaborations with Sam Mendes will stand the test of time as examples of how to shoot a movie. American Beauty was gorgeous, but the palette was expanded with Road to Perdition.
The whole film is poetry in motion.