The only studies that show that an increased amber length decrease fatalities have a study period of less than 10 years. Other studies have shown that the effect dissipates after 10 years as drivers adjust to the longer yellow by driving through them.
I hate long yellows, and even worse is the "all red" period some cities have added between the yellow and the next light turning green. It makes traffic inefficient for people who follow the law (which says you must stop at yellow lights) and it vastly increases the number of people who blow late yellows and even reds.
Yellow lights (and all-red periods) are useful because drivers need a transition time between "go" and "stop" to allow them to react safely. Demanding that all drivers always stop at all yellow lights effectively turns the yellow light into a red light, and drivers are forced to switch instantaneously between "go the speed limit" and "stop."
All-red periods are also useful at intersections where traffic backs up and blocks the intersection for a few seconds, not because drivers entered the intersection when traffic was stopped, but because events down the street or at an adjacent light may cause traffic to stop suddenly with drivers already in the intersection.
Demanding that all drivers always stop at all yellow lights effectively turns the yellow light into a red light, and drivers are forced to switch instantaneously between "go the speed limit" and "stop."
I don't know about where you are, but here amber lights mean "Stop if it's safe to do so", i.e. if the choices are go through the junction or slam on the breaks, you should go through the junction. If the choices are to stop smoothly and safely or go through the junction, you should stop.
From what I understand, this is true in most states in the U.S. -- you're considered to have run the red light if you haven't exited the intersection by the time it turns red.
There seems to be some confusion about this. Most people I've talked to think that if you make it past the intersection entrance line before the light turns red, you're fine.
Yellow lights are useful, for the reasons you mentioned. My beef is with long yellow lights.
And I disagree with your justification for all-red periods. If you're stopped in the middle of an intersection because of a blockage, it usually takes a lot longer than 1-2 seconds to clear the intersection.
I hate long yellows, and even worse is the "all red" period some cities have added between the yellow and the next light turning green. It makes traffic inefficient for people who follow the law (which says you must stop at yellow lights) and it vastly increases the number of people who blow late yellows and even reds.