Talk:1116: Traffic Lights

Explain xkcd: It's 'cause you're dumb.
Revision as of 08:04, 5 October 2012 by (talk) (Red and yellow)
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I doubt that this comic carries any deeper meaning. 16:29, 4 October 2012 (UTC)

Traffic signals really are one of the most inscrutable inventions to ever be made. I mean, red means stop, yellow means caution, green means go. Unless you're in a turn lane, which means you have to watch for the green arrow, if there is one, or wait for an opening. Unless you're turning right, which is permitted to turn at any time providing there aren't any cars. Unless there's a sign that says "No Right Turn On Red". There's also the crazy cities that have special right turn lights. Then there's the intersections that have a sign for each lane telling what can and cannot be done. Or, if you're really lucky one of those intersections that has the LED screen that dynamically changes what the lane can and cannot do. And to top it all off, the Colorado Department of Transportation (as well as a few other states I'm sure) are testing out a 4-stage left turn light to increase the safety of drivers. [1] Yes, you read that pamphlet correctly. There is a special 4th light, just to blink yellow, because you couldn't just make the yellow light blink, like it does anyway after 9pm. No. There has to be a whole special light that indicates when a left-turn-er must use special caution to turn.

Nope. I'm done driving. Bring on the self-driving cars, people are officially idiots. lcarsos (talk) 16:52, 4 October 2012 (UTC)

There is a problem with a blinking yellow arrow. Blinking yellow is already used. It means you have the right of way, but the other direction may proceed as well. What is wanted here is blinking red, which means that you stop, but may proceed, as someone else has the right of way. As for adding a fourth light, this just confuses things even more, particularly with respect to color blind individuals. Having said that, Virginia's variant is to have lights with both left arrows and solid greens. If it is green arrow, you have the right of way, while solid green means the other direction also has a green. There is almost always a sign reading "left turn yield on <solid-green-circle>" Divad27182 (talk) 18:19, 4 October 2012 (UTC)
so the blinking yellow left arrow generally means the same as a round green light - you can go when it's clear, but the opposite traffic has a green light too. I love this idea because a lot of the time where there is a separate left-turn signal, there are advanced lefts for both ways, and then left turners get a red left arrow and have to stop while people going straight get a green - so even where there's no oncoming traffic, you can't turn. this way, you just lose your "advance" status and go back to the regular rule of "turn if you can, otherwise you end up turning as the lights go yellow"
I think what Lcarsos is pointing out if you check the PDF link, is that the new left-turn lane has 4 lights, all of which are left-arrow shaped. Thus, his point is why couldn't they make the 2nd light (yellow left arrow) blink, instead of installing a third light which is also a yellow left arrow whose job is to blink?
I can think of a few possible reasons - first, perhaps an all-blinking light has different bulbs which are more efficient for blinking and won't burn out as much; second, because they want to distinguish between the two lights more strongly (i.e. if you glance over between blinks, you don't have to wait a moment to see if it will blink - if you see the 3rd light up, you know it's going to blink without waiting for it to actually blink); similarly, I suppose there could be colour blindness issues where they want to make it clear which light is which.
PS: Right on Red is more common in north america than other places, but even here there are a few exceptions that do not allow right turns on red lights. New York City is one. Montreal is another. Most of Mexio is a third. TheHYPO (talk) 21:19, 4 October 2012 (UTC)

Hmm... not one to do the actual analysis, I still wonder whether there could be some message encoded in the pattern of lights -- in binary ASCII, baudot, Morse, or something. Hmm... 19:12, 4 October 2012 (UTC)

Red and yellow

In Poland you can sometimes stumble upon red and yellow -- while yellow alone means that there shortly would be a red, and you can proceed if you are at or almost at crossing, but stop otherwise, red and yellow is to mean that there shortly would be green (go), and to prepare oneself. But it is quite rare. JakubNarebski (talk) 06:45, 5 October 2012 (UTC)

In Germany all traffic lights behave this way. (talk) 07:45, 5 October 2012 (UTC)
At least some lights in Czech behave this way too. -- 08:04, 5 October 2012 (UTC)


It's how traffic engineers troll you when you are going the wrong way on a one-way. Learn to read signs!