In this column, Cecil talks about how the colors for traffic lights were selected and how color blind people are able to realize what the lights mean, even if they can’t see the colors. It turns out that in the early days of the traffic light, people were concerned about this and made glasses so the color blind could see the lights.
I like traffic lights, but only when they’re green.
How hard is it for the color-blind to distinguish between the top light and the bottom light? How about different shapes for red, yellow and green? I know they do that somewhere like Iceland or something.
My dad’s red green colorblind, and he tells me that it’s not that he can’t tell the colors apart if they’re side by side in big patches, but if one is present in a small amount inside the other, he can’t see it.
As for stop lights, he says that most of the time it’s not a big deal; in the city, you can see the position of the light and you’re not going more than 35 miles an hour, so you’ve just got to pay attention. In the country where you’re driving at higher speeds, he slows down a bit when coming up to a light, but usually the actions of the other drivers give him a good clue, even before he can see the light.
The only time it’s a real worry is when there’s a storm, and visibility is so limited that he can’t see the position of the light in the fixture. In such cases, he just tries to find someone else to drive behind - if they stop, he stops.
The last time I was in Montreal, in 1972, they had different shaped lenses for the different colors.
I wonder how color blind people handle taffic lights that are horizontal instead of vertical? (I’ve seen this in a few places in the US and it throws me off and I’m not color blind!)
There is a protocol for where the red and the green are on laid over lights, IIRC. I could swear that the California Drivers Manual used to have that protocol in it, but it doesn’t any more. My recollection is that the red is to the left. I also have a hazy memory of driving somewhere (Texas?) where the lights, when they are laid on their side, have two reds and only one green.
Red-at-the-left is certainly usual.
My SO is red-green color blind. Yep, I’ve asked him this questions.
At a standard vertical light, it’s no big deal. Horizontal lights (they are pretty darn rare around here), he watches around him much more closely and tries to get clues from others around him and from the lights for the side roads. It’s the single blinking stand alone lights that cause the most problems. Is that a blinking yellow light, meaning caution/yield, or is it a blinking red light, meaning stop.
The real neat trick is when he manages to lose a red stop sign in the green corn fields.
I’m color blind, very color blind (This is bringing back memories from my Ask a guy who’s color blind thread.) and usually have little difficulty figuring out red & green at stop lights. The main reason is that the red is on the top. For me, the shade of the red light tends to be deeper in comparison to the green…the green is ‘brighter’.
Seeing the green as brighter helps when I come across the rare intersection governed by those crazy horizontal traffic signals. I came across some anti-glare horizontal traffic signals in my area years ago, and I couldn’t tell the difference at all. Fortunately, those were replaced after a short amount of time. On normal, glare-allowing lights, it’s pretty easy to tell the difference, and is usually not a problem.
A nifty site which shows you what it’s like for the color blind. Even has a traffic light on it.
Thanks for the link Tuckerfan. I sent it to almost everyone I know with the statement, “This is how I see the world. Each side-by-side picture looks exactly the same.” Now maybe this year at Xmas I won’t have to play non-stop rounds of “What color’s this? What color’s that? What color…what color…what col…what c…AAARGH”
Now if someone only had a link to the opposite page, where pictures are shifted the opposite way (so I could see two pics; one the normal way and the other shifted to correct for my RG colorblindness.)
In my personal experience, traffic lights have never been much of a problem. The red and amber lights look much the same, so occasionally I have to slow down when coming to a single blinking light until I can see if the light is on the top (red / full stop) or in the middle (amber / yeild). The bottom (green) light is obviously not red or amber. (It’s blue.)
Horizontal Lights (like I’ve seen in Dallas) are really no different, just sideways. Red is at one end, blue at the other and amber in the middle.
BTW, both traffic light pics linked to above look the same as one another, but don’t look like real traffic lights (to me). Especially the green lights (which actually appear to be green, unlike in real life where they are a lot more blueish- green).
Now imagine how great traffic lights would be if we humans could see a fourth color.
(P.S. I don’t like that ‘what it’s like’ website, because looking at pictures doesn’t tell you much at all. But finding out what being colorblind like is easy, you can just wear filtered glasses. You even get to experience getting used to it after a while, which is a pretty weird feeling.)
Actually, it appears to be the case that a good many women may be tetrachromats. I know a couple, in fact.
I am not aware of any kind of filtered glasses that make white look white. To the best of my knowledge, these pictures are as close as you can get.
Most of what you might want to know about traffic signal standards (federal law, subject to interpretation by each state)-see section 4D.16 for position of lenses:
http://mutcd.fhwa.dot.gov/htm/2003r1r2/part4/part4d.htm
I’m mildly red-green color-blind, but I’ve never had a problem distinguishing between red and green traffic lights. I do have some difficulty distinguishing between the yellow and red lights in isolation, but since red follows yellow so closely, it’s not a problem.
The funny thing is, if I look at the glass on the traffic devices with the bulbs shut off, the colours green and red are obvious to me. But when they are lit up, the green looks whitish and the red looks yellowish.
I’m red-green colour blind and I live in a city where most of the signals are horizontal, so I ought to be qualified to answer this question.
Mostly, the signals are well over the street–sometimes each lane has its own set if the intersection is complicated somehow. Anyway, it’s pretty obvious when you have a signal in front of you. It helps that the three-signal sets are in bright yellow boxes, with a reflective border that helps at night.
Many years ago, when I lived in Toronto, it was damn hard to drive at night because the signals were vertical (but that wasn’t the problem) and hung at the side of the road (which was the problem). I don’t see the green light as green–I see it as white, generally, and the height at which the signals were mounted meant that, to me, the green lights looked like regular streetlights. You can imagine my shock and distraction when what I thought was a streetlight suddenly turned yellow. In those situations, I’d generally find another car to drive behind, and do what it did: slow down, stop, and so on.
On recent visits to Toronto, I’m pleased to see that the lights (while still vertical) are positioned differently than they used to be, and they no longer blend into the streetlights at night. And here in Calgary, with the horizontal array right in front of you, they’re not a problem at all.