Why Do Some (But Not All) Escalators Glow Green From Underneath?

This is a question that comes up from time to time and has been discussed elsewhere on the internet, too...

  / what_is_the_green_light_in_escalators  

  / eli5_why_do_the_insides_of_escalators_glow...  

https://www.candlepowerforums.com/thr...

https://konespares.com/escalator-part...

https://duckduckgo.com/?q=escalator+D...

... in short, the green glowing light you often see beneath the treads of an escalator (or moving walkway, as you'll see in some of the clips in this video) is meant to indicate to the rider that they are approaching a zone of embarkation or disembarkation and that they should be alert. Known in the industry as a "Demarcation Light" they are no longer officially required by code, but when they were obligatory they were always green. Originally this was achieved with a filter over top of an intense incandescent or halogen lamp, but nowadays green LEDs are typical on most installs.

As Howard Payne pointed out to me when I discussed this with him: "Demarc light is easy to remember... 777. They required it in '77 and deleted it from the code in '07." I think it's neat that these are always installed in a way that is meant to alert escalator passengers that they are approaching a danger point by emitting bright points of green light directed toward the passenger's eyes. The light is quite distinct and noticeable but only from a very specific and often narrow angle, making it only briefly visible at exactly the moment when riders must be alert. Isn't that neat? I think so. Enjoy! 👍😁👍

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