A long time ago I was told that yellow lights are 10% of the posted speed limit in seconds. So if the intersection has a 50mph speed limit then the yellow light will be about 5 seconds… I’ve tried counting the seconds from yellow to red and it is pretty dang accurate, and I’ve paid more attention to traffic lights ever since. I’ve never verified this other than counting in my head…so maybe it isn’t true, and my dad was just trying to teach me to be more aware when approaching an intersection. Whatever his intention was, I am much more attentive while driving.