On the rear covers of April, 2008 (and other issues) there is an ad for MTU Series 4000.
The photo depicts a single line signaled track at MP40 with a curve to the left. The area is hardwoods and in the distant there appears to be a whistle board for opposite moving trains.
Notice the lack of a signal in the opposite direction–suggests that this may be a distant signal on an otherwise non-signaled line. The use of a telephoto lens is making the curve appear much sharper than it actually is, and I’d suspect that if that is a whistle post the photographer is on the grade crossing.
I’d guess somewhere in the lower Mississippi basin. There are probably lots of Milepost 40s to choose from!