But wait, there's more: when the elevator arrives until it leaves, the button should flash or change to a more prominent color. Why? Because imagine someone presses up and someone else presses down, and the elevator arrives going up. If the up button switches off at this point, now only the down button is lit which clearly signals the elevator is going down, which is wrong.
Let's say you tell someone to do something, and they say "ok". But when you ask them later whether they did, they say "oh no, I just said ok to indicate that I heard you, not that I was going to do something about it." That doesn't make any sense. The indicator light has the same function. Going on and then off again is a violation of basic communication protocol.
The more complex the intersection, the more controls I can watch, to get a feel for the rhythm, patterns, and triggers that influence the cue to activate my “WALK” signal.
I’m also watching the cars to see when the flows slow down or stop. I should perhaps pay more attention to the signal that pertains to me as a pedestrian or motorist...
I guess you might want to fade it from red to green (red being "this works" and green being "it'll do what I want"), but I don't mind the holding-down behaviour. The only problem is that you can never know how long you need to hold it down for unless you stop holding it.