My first wife lived in Florida (St. Pete) for a few years in the early 70's. She said they had the longest yellows she had ever experienced.
She found out it was because of all the old geezers driving down there. They had to lengthen the yellows because the geezers would go sailing through the intersection on the red otherwise... their reaction times were so slow.
So the longer yellows were begun to save lives. And it worked.
Shortening them makes no sense. People are gonna die.
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But there are few tangible safety benefits to short yellow lights. In fact, they appear to have the opposite effects; according to the USDOT and FHA, short yellow lights raise crash rates.
"A one second increase in yellow time results in 40 percent decrease in severe red light related crashes," the report said.
Jim Walker said shortening a driver's window for reacting to a yellow light creates more difficult split-second decisions, which can lead to more rear end collisions too. And he contends most serious accidents aren't coming from the "innocent driver" who gets caught by a short yellow. They're caused by blatant red light runners who will run a light regardless of yellow light length.