When I was a kid growing up in Chicago there was a weatherman on Channel 9 that had a cartoon character titled "The Vice President of Looking Out the Window" I think this applies here. The eyes and ears are a better judge of the "data" outside the window like a tresspasser or any other object that might foul the ROW. What about sudden weather changes or brush fires, failing units? The list goes on. I'm sure the professional railroaders can add to this.