Yellow traffic light lengths are based on "average" reaction times (average will be different for young vs. elderly). I'd like to see a reaction time test include multiple cars (both directions), cross traffic, motorcycles, bicycles, pedestrians, and traffic lights ... all occurring simultaneously ... plus additional time for a human to hit the brakes. ------ This is to determine if the National NCHRP Report 731 Guidelines for Timing Yellow and All-Red Intervals at Signalized Intersections to be a valid or invalid result. ------ Extending the yellow light time by one second would fix most of the current problems, plus cost no money to implement.