It's the same reason why headlights are white and taillights are not (unless reversing, in which case the tail becomes the head temporarily, and thus white reversing lights.)
I know Technology Connections complains about it all the time, but I don’t feel like he’s even made a case, he just asserts over and over “and we ALL agree it’s awful” as if he asserts it strongly enough it will become true.
Why is it a problem? How is a red blinker actually measurably worse than an amber one?
I have never had any sort of issue interpreting a blinking red taillight as turning? With red, you can more easily tell the direction of travel and the aesthetics of a single color are far nicer. I frankly don’t see the problem.
Commenter a couple levels up says you can’t see red blinkers in the sunlight? I don’t think that’s true on any measurable level, amber is a far closer match in hue to sunlight than red.
"A 2008 US study by the National Highway Traffic Safety Administration suggests vehicles with amber rear signals rather than red ones are up to 28% less likely to be involved in certain kinds of collisions,[81] a followup 2009 NHTSA study determined there to be a significant overall safety benefit to amber rather than red rear turn signals,[82] US studies in the early 1990s demonstrated improvements in the speed and accuracy of drivers' reactions to the stop lights of vehicles ahead when the turn signals were amber rather than red,[76][83][84][85][86]"
Whoever wrote that section of the Wikipedia page either didn’t read the cited documents or heavily cherry-picked.
The cited document for that “up to 28%” actually states that a first analysis found amber lights leading to a reduction in being struck “between 3 and 28%” Quite a range of uncertainty.
The very same document also states that in their second analysis they found no correlation between signal color and odds of being struck.
Another one of the cited documents goes so far as to say
> Richard Van Iderstine: We have studied the crash involvement of vehicles having yellow rear turn signal lights versus red ones. With our data, we have found it challenging to prove that yellow is better than red.
Based on the actual text of the citations I’m inclined to believe there’s very little difference.
And I don’t see how there could be. The only practical difference I see between a red signal and amber signal is that the signal might ever so briefly interpreted as a brake light activating before the first cycle completes. The course of action of the driver behind in either case is to slow down, so it’s a distinction without a difference in action.
So a red light turns on. What does it mean? For the next 0.5 s you don't know. Maybe it will turn off, maybe it won't. In the meantime, you have delayed your braking action and decreased your margin of safety. Or you have started braking for no reason, endangering people behind you (and yourself).
Technology Connections channel had a video about that a while back:
https://youtu.be/O1lZ9n2bxWA?si=xKRgMFK1DFBrB3i0