In:
http://www.straightdope.com/classics/a2_152.html
Cecil discusses the choice of red and green for traffic signals, and the risk of confusion for color-blind people. Cecil asserts that red/green color blindness is not an issue for very bright lights, and that drivers can at least see which light is on top.
Figuring out which light is on top would be very difficult from a distance, or at night (leaving aside the fact that green is on top for traffic signals in some urban Irish neighborhoods in the US). Furthermore, I recall back in the late 70’s, a display in one of the buildings on the campus of the National Bureau of Standards (now National Institute of Standards and Technology) with a modern traffic signal. The display noted that the red and green were actually red/orange and green/blue. The justification for this is that color blindness often manifests itself as an inability to distinguish green from red, or blue from orange, but never both. Therefore, a red/green color-blind person would see enough blue and orange to distinguish the stop and go signals, and vice versa.
Blue and orange may have been added to traffic signals recently, probably in the last 20 years. My personal observations of traffic signals around town are that the older signals seem to be a purer red and green, and the newer signals have the blue and orange added to them.
Some traffic signals here are oriented horizontally, so the red-is-top convention doesn’t help. (There is a standard for which side the red light is on, but although I pass horizontally-mounted signals every day, I don’t remember what it is.) A bigger problem from me has always been telling the red signal from the yellow signal, and the addition of orange to the red has exacerbated the problem. For standard traffic control signals, the sequence and duration allow me to discriminate, but flashing signals – where flashing red means “stop” but flashing yellow doesn’t – are a real challenge.
The increased “greeniness” of the newer signals has been a godsend. As I child, I remember perplexing my mother by asking her why green lights were called green lights and not white lights. I have to be extra careful driving down unfamiliar streetlit roads, because I never know when one of the “street lamps” might turn yellow.
Not never, but they are two different defects, and consequently do not often occur together.
As a parallel thought, yellow lights in Australia are the same colour as sodium vapour streetlamps, so at night, where you have a bunch of these lights togther, you are happily motoring along, and suddenly one of them turns red!
Throw out the anchors to stop in time!
I don’t know about the rest of Canada (I never thought of noticing whether it was the case or not), but in Québec different colours are assigned different shapes.
Red = square
Yellow = diamond
green = circle
I think that makes everyone happy, except maybe people who are completely blind.
See, that’s more like it, though it would seem they’d be a tad too small to really distinguish the shapes from much of a distance.My idea would be to simply have the lights the same colors they are now, but make the green light flicker slightly while lit, so everyone could tell that was the green one. This would in my opinion be better than having the red one be the flickering one, in case certain drivers are sensitive to flickering lights; they would not be exposed to it very long as they drive by.
How would that be?
Currently, at least in Maryland, many red lights have a slow rate Xenon strobe in the light. You see a red circle and every second (or so) a thin horizontal line flashes white. Probably not rapidly enough to trigger epileptic episodes. Further, it is super on a foggy day as one can see the flash of the red light before one can see the red itself.
Damn you, Spritle! I was just going to post that I’ve seen that strobe used on a traffic light here. Hasn’t made it onto all lights yet, but where I saw it was on a busy street that has long uninterrupted streches (no side streets or businesses) and then a busy cross street intersecting at a light. The intersection in question had numerous accidents, including a couple of fatal ones, because of the layout and conditions. So they put the strobe on the red so you can see it from a lot farther away and begin to slow down.
I don’t know statistics on if that’s improved the conditions or not, but makes some sense.