Lately I’ve been noticing that where traffic signals have two green lights side by side, the greens are different shades. One seems to be much bluer than the other, but the contrast between the pairs is not consistent. Some are really close, some are very different. I can only imagine two explanations: The city does it so that color-blind folks can see them (but I thought that’s why they consistenly put them in the same order top to bottom or right to left). They replace burnt bulbs at different times, so the new ones are different because they are made by a different company or because they haven’t aged into the other color yet.
Has anyone else noticed this? Can anyone else explain it?? I swear I’m not crazy (yet!).
It’s about as annoying as two out-of-tune violins…
I believe the colour-blind explanation is the valid one. There are two common forms of colour blindness: red-green and blue-green. Someone with red-green blindness has difficulty telling red from green. Some blue tint is therefore added to the green, allowing the red-green colour-blind viewer to perceive the difference. The order of the signals is important as well, but a) is not consistent (some signals are hung sideways over intersections) and b) may not be seen from a distance or under adverse weather conditions.
Adding blue to the green does not affect the perception of those who have blue-green colour blindness, since both colours will be perceived the same anyhow.
BTW, I seem to recall the scientific names for these conditions are “protanopia” and “deuteranopia”, but I can’t find them in my dictionary, and don’t recall which is which.
That’s just it- I CAN detect the difference and it’s irritating to me. (Waah!) If it causes me to have an accident I’m really going to bear a grudge against the colorblind!!
protanopia: red-blindness – (inability to distinguish red and purplish blue)
deuteranopia: green-blindness – (inability to distinguish green and purplish-red), also known as daltonism www.onelook.com
I have a bit of experience with color blindness. My dads family was pretty extensively studied in the 50’s and 60’s because they seemed to be unique.
The most common form of color blindness is called red/green color deficiency. My dad had this. He could not distinguish a red light from a green light at an intersection, but since the red light is always on top, this was not a problem (except in Snyder OK where they had an upside down light.) His problem was that unless he was looking for the light, he wouldn’t see it. This was mainly a problem in small towns where they put the lights on poles on the side of the road. We kids were trained to look for traffic lights when we rode with Dad. To this day, if I am riding shotgun, I will say there’s a green light ahead, there’s a red light ahead… It drives people nuts, but I don’t even realize I am doing it until I get yelled at.
A very rare type of color blindness is blue/yellow. My uncle had this.
An extremely rare type of color blindness is total inability to distinguish colors. Two of my uncles had this. At that time they were thought to be two of the total of 10 in the US. Genetic theory at that time said my dads family was impossible, so they were studied quite a bit.
For more information, you can go to: http://www.cimmerii.demon.co.uk/colourblind/
it is a pretty good sight.
“You can be smart or pleasant. For years I was smart.
I recommend pleasant.”
Elwood P. Dowd