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Comment by stretchwithme | Hacker News Reader

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stretchwithme·

"Red and green are the colors most affected by color-vision deficiency."

So maybe not the best choice for traffic lights. How did that happen?

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This is a decent explainer:

http://www.todayifoundout.com/index.php/2012/03/the-origin-o...

Red is associated with danger so it was stop. Go was original white. This causes problems because if the lens falls off, stop looks like go.

I guess blue is probably hard to make out in daytime against the sky, or if it's raining. Not a whole lot of colors left after that.

It's probably a reason to continue maintaining a distinct position for each color in the traffic light.

There's one stretch of road in southern Quebec that has horizontal traffic lights that always throw me for a loop, despite not being colorblind. They flash in odd (to me) patterns and have two red lights: http://i.imgur.com/i7jCi.jpg

Two red lights... which are also square (other lights are still round). It's actually a pretty good design.

I'm good with the layout, but if I remember correctly the turn arrows flash in the middle while the outer red lights are still lit. So if I've got the green light to turn left, it's flashing in between two red lights, which I think is what made me kind of wary.

But how do you determine the position at night?

Also FTA: "So it made sense to choose a color that everyone could see and not mistake for black."

That's not how colorblindness works.

This is also not how it works: "Almost no one has a blue deficiency. Accordingly, nearly everyone can see blue, or, more accurately, almost everyone can distinguish blue as a color different from others."

People with "red-green colorblindness" usually have difficulty telling purple from blue.

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