I’m probably reading too much into it, but a minimum of three seconds sounds stupid. How about a safety-based formula based on length of the intersection, and the speed limit through that intersection?
And leave the fedguv out of it.
The formula is 1 second for each 5 MPH of the speed limit.
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. :)
“There you go thinking like an engineer again!”