Did you ever get a compelling suggestion for this request?
I listened to the minicast last year when it was first posted, but it occurs to me now that the term is commit point. The idea is that if the light turns amber before you reach that point, you have to abandon your original commitment to proceed through the light and brake instead. Once you're past the commit point, it doesn't matter if the light changes because you're committed and you're going through.
Whenever my momentum is such that I go through the intersection on an amber light, I say "sure, I could have hit the brakes, but I still would have gone through, and probably sideways."
When the city where I work debated red-light cameras, I copyrighted and tried to get accepted a caution line. It was a yellow line across the lane that traffic beyond it and traveling at posted speed would make it through the intersection before the yellow (caution) light changed to red (stop). It was a passive version of the active "'RED' SIGNAL AHEAD" signs which are posted in some nearby high-speed signal lights ('RED' indicates that it flashes before yellow and throughout red; SIGNAL AHEAD is always displayed). Multiple lines could indicate different speeds.
I would post images of an intersection and accompaning signage, but they are on my hard drive and do not have an URL.
Emmett
These are all interesting ideas, but doesn't the average human reaction time, as well as the mechanical response time of the vehicle, complicate any attempt to define where the commit point is effectively located? Same with the caution line suggested by Emmett.
Add to that the fact that many drivers accelerate when they see the light turn amber, and the reaction distances increase proportionally. See: http://www.visualexpert.com/Resources/reactiontime.html
Been many years since I had to attend traffic class for a "rolling right turn" I did at a red light. If I recall correctly, in Arizona anyway, if the vehicle breaks the plane of the far crosswalk line (thus entering the intersection) before the light turns red, you did not run that light.
Heimhenge said
Been many years since I had to attend traffic class for a "rolling right turn" I did at a red light. If I recall correctly, in Arizona anyway, if the vehicle breaks the plane of the far crosswalk line (thus entering the intersection) before the light turns red, you did not run that light.
Maybe I'm misunderstanding. I would have said "near crosswalk" to define entering the intersection. Wait, I just read it again and I see you said, "far crosswalk line" not "far crosswalk". Anyway, that's the rule in Texas. If you actually enter the intersection before the light is red, you're okay.
Heimhenge said
These are all interesting ideas, but doesn't the average human reaction time, as well as the mechanical response time of the vehicle, complicate any attempt to define where the commit point is effectively located? Same with the caution line suggested by Emmett.
Add to that the fact that many drivers accelerate when they see the light turn amber, and the reaction distances increase proportionally. See: http://www.visualexpert.com/Resources/reactiontime.html
Yes, the yellow light time should (and does) take into account human reaction time. And, different people would have different commit points, that is not really the definition of the caution line.
The caution line is determined only by the yellow light time and the speed limit. Then, someone who was traveling at the speed limit and already past the caution line when the yellow illuminated would be guaranteed to enter the intersection before the light became red. They would not have to worry about the commit point. Anyone behind the caution line entering the intersection would be guilty of some infraction, i.e. already speeding, speeding up to beat the red, or running red. If the caution line is not far enough away for someone to safely stop, then the yellow light time is too short already. The physics allows nothing else.
Emmett