(USA specific) When a traffic light turns green and there’s a left turn lane, why does the light need the blinking yellow arrow? Isn’t it already implied that you can turn left as long as you yield to oncoming traffic? I understand why a red and green arrow are necessary for a turning lane, but the yellow seems redundant.
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Because the green usually indicates there is no oncoming traffic or the oncoming traffic has a red light and you have the right of way, the yellow blinking indicates that you will now have to yield to oncoming traffic and longer have the right of way…. At least in Canada.
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A green arrow for you means that cross-traffic on the other side has a red light still – they are not allowed to go forward yet.
A steady red arrow for you means that you are not allowed to turn yet and must wait.
Those are pretty clear. What becomes less clear is when you have a situation where you *are* allowed to turn *but* the cross-traffic has a green light and has the right-of-way to go through the intersection.
There are lots of different ways to represent that. It could be a flashing red arrow, except some people might not read the sign that says “left turn permitted on flashing red arrow after stopping” (that is a pretty long message to read when driving). It could just be that there’s *no* arrow, but then you might wonder if a left turn is actually permitted at all because there’s no signal to indicate what you’re doing (also another sign you have to read).
So, a yellow blinking yellow is just *one* of the ways you can communicate that a left turn is allowed, but that you don’t have the right-of-way.
Generally you will see a blinking yellow arrow at an intersection where sometimes there is a green arrow. The green arrow indicates you have right of way to make a turn, while the blinking yellow means you have to yield. The blinking yellow is there as an additional warning that you no longer have right of way to turn.
Part of the reason for the layout of lights is behavioral. If they observe certain bad behaviors are common at an intersection, they may add an extra light as warning against that behavior. A blinking yellow light for a turn might be the result of a history of accidents at that light due to failure to yield while turning.
Arrows are intended to protect very specific movements at intersections. An orb controls all traffic coming from a particular approach. The arrow takes precedence over an orb for a very specific movement as indicated by the arrow. Solid red arrows obviously mean stop. Solid yellow arrows are warnings that the signal is changing to red and green arrows mean that a driver has a protected turn and there will be ZERO conflicting movements allowed while the green arrow is illuminated. A flashing yellow arrow was invented to solve a specific problem. As you mentioned a flashing yellow instructs the turning movement to yield to other traffic but allows them to make the movement if it is clear. A green orb would mean the same thing except that a green orb also implies that everyone else from that approach can proceed as well. So what happens when you want certain traffic to stop (straight traffic) but still allow turning movements? You can’t display both a red orb and a green orb to the same approach because that would be confusing. Which one applies to which movement? Thus enters the flashing yellow that can be displayed at the same time as a green orb or a red orb and removes the ambiguity. Yes a flashing yellow arrow can be displayed at the same time as a red orb which is something that can never happen with just a green orb and red orb because of the conflicting meaning. This allows the turning traffic a longer opportunity to complete the turn.
The blinking yellow is redundant. It functionally means the same thing as if it were just green and none of the arrow lights were lit.
But from a practical sense, it reminds people that they *can* go, but should maybe be a bit more careful about it. So this is done where the traffic control folks want you to be more deliberate about it.
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