The Federal Highway Administration estimates that the signals — which allow drivers to make a left turn after yielding, even when the light is red for traffic going straight and opposing traffic has a green light — are in use at more than 1,000 intersections, and the number is rising, spokeswoman Cathy St. Denis says.That description is imprecise. The Michigan version, in which a flashing yellow arrow replaces a flashing red arrow (Rule 245N), stipulates that oncoming traffic has the green. The national Department of Transportation has done some research, concluding that a more permissive aspect expedites traffic flow.
First you create channels at crossroads, and set up traffic lights that permit left turns only on arrows, and then make people wait for the light to cycle, and then you conclude that all those constraints on motion impede motion. Duh.
Those signals still will be holding traffic going straight for the duration of the left turn arrow, and if those signals are not synchronized with neighboring signals, there's still a greater waste of time and gas in those queues that take so long to clear out as the lights change.