The Federal guidelines are not to do less than 3 seconds on the yellow. States are all over the map on how they time everything.
There is a formula for yellow lights
Y = t + V/(2a+2Ag)
Y= Yellow clearance interval in seconds
t= reaction time (use 1 second)
V= 85%percentile approach speed in ft/sec/sec [can use speed limit]
a= deceleration rate of a vehicle(use 10 ft/sec/sec)
A= Acceleration due to gravity (32.2 ft/sec/sec)
g= percent grade in decimal form(+for upgrade,- for downgrade) this is
unknown.
*Calculate the yellow clearance interval to the nearest 0.1 second
I had a ticket dropped because the yellow light was too short for the posted speed of the road and I proved it. :)
It’s true, you at the least want a vehicle with normal stopping ability in normal conditions traveling at normal traffic speed to be able to come to a complete stop between green and red, arriving at the stop line, upon yellow alert. Less yellow is asking for trouble, and why. Unless there is a system of pre-yellow alerting (blinking green?)