Joe, if you open that .pdf file up, zoom in about 400%, and look at the left rail just past the guard rail and before where the detector starts you can just see where the inside rail cuts out...just barely. Draw a mental line on the inside of the rail and go across the detector, you can see where it bows out.

Also, the width of the rail head doesn't change and looking at the right rail, look at the shadow on the ties, it somewhat lumps out, not linear.