¥There is a statistical curve of probability around the
average time a driver needs to respond to a yellow signal, and the goal
is to make sure that virtually ALL of the curve is accommodated before the opposing
signal turns green (97th-99th percentile). Using the all red as the
safety cushion.
¥The kinematic formula is the tool for doing this; itÕs only
a MODEL of real-world response. It does not CONTROL driver response. If it takes 6 seconds to get all the traffic
stopped, including heavy vehicles, buses with standees, old people, distracted
drivers, drivers with poor vision, in all lighting conditions, then that is what it takes, and there's
nothing anyone can do about it.
¥The engineer only has one duty, to make sure the traffic control devices are set to safely manage and guide traffic to meet the trafficÕs requirements.