Concerned about traffic signals with short yellow light

schlep1967 wrote:
Depending on the state you are in your DOT most likely has standards for how long the yellow needs to be. But as a traffic engineer I can tell you there are a lot of variables across the states. There are recommended formulas to follow but they do not work in all situations. And our fellow human beings add to the problems. A few years back signals were pretty straight forward. They stayed green for a certain time, then yellow for a couple seconds then at the instant the yellow turned to red the other directions green would turn on. This caused problems as larger intersections could still have vehicles crossing when the other direction got the green. The answer is to add clearance time. The width of an intersection can be rather large so extra time would be built into the yellow time to allow vehicles to clear before the opposing light turns green. So we add in clearance time and then we have our fellow humans that are always in a hurry. Humans are smart. They learn quickly that the other side will not get the green light right away as they now have 5 seconds of yellow so why stop? So what the smart DOT people came up with was an all Red time. Take 2 of those 5 seconds of yellow time and make it an all red time. So you have 3 seconds of yellow and 2 seconds of all red. Same clearance time but humans are less likely to run the all red making the interesection safer. So there is your signal light lesson for the day.
Now to your "can't get stopped in 3 seconds" problem. It is my understanding that it is only illegal to enter the intersection after the light is red. If you are entering when yellow you are legally entering the intersection. And if you legally entered it you can legally exit it. Personally as I approach an intersection I pick a point of no return. Once I get to that point and the light has not turned yellow, I am going through the intersection. Most Officers understand that a large truck and trailer can not stop on a dime and that it is safer to continue through the intersection than it is to jam on the brakes.