Question about Signaling

As most people know, as a train passes a green signal, that signal turns red. I have a very specific question about that. Are there rules dictating how far away from the border of the signal block, the signal itself has to be? In other words, if the border between two signal blocks is here:
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... how far away does the signal have to be? Is that location dictated by rules? Is with within inches of the divide? Feet? Yards? Can the driver see the green light turn red as he's going by?

Since the signal protects the block ahead, it should be located at the insulated joint that divides the blocks. If it weren't, there would exist the possibility of a collision (albeit at slow speed).

No, the locomotive engineer (not “driver” in North America) cannot see the signal change indications, if he is operating from the leading end of the train (which she normally does).

Jim

Since the original post has been answered ...

What was the origin of the "lunar" signal aspect? A restaurant that I dine at regularly has a former switchstand lantern that was once lit using acetylene or perhaps kerosene. The top of the lantern has vents that when the lantern is lit from inside form a circlet of white dots around the top.

It made me wonder if given the frequent use of lunar aspects at interlockings if there was a link of some kind to old switchstand lights.

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It was developed by William Churchill of Corning Glass in the early 1900s: https://www.jonroma.net/media/signaling ... pments.pdf

He was looking to make a standard set of colored glasses that would not be confused, even at varying levels of illumination.

One also has to realize that the current colors used in signals are a "modern" inventions. Up until the early 1900's , red was stop, green was caution and white was clear. The current red/yellow/green/lunar didn't come into use until the early 1900's. If you look at some of the old Edison films of the the LV Black Diamond Express, as the section gang clear for the train, the foreman waves a white "flag" at the train, that's because at the time it was filmed, white was the color for "clear". Today that would be green.