One more note about green turn arrows. Some intersections are phased to display simultaneous right and left turn arrows, first for one side of the road, then for the other. This is called "split phase timing." These are really bad for pedestrians, because the pedestrian never gets a green condition where drivers are expected (or expecting) to yield to them. MUTCD requires pedestrian detectors and signals to be installed at such locations, in order to allow pedestrians to trigger a different phasing that gives them a safer trip. However, I've found some intersections that violate this requirement, and I've had only partial success getting the DOT to correct them. I got the intersection of Tryon Road and Kildaire Farm here in Cary fixed, but not an intersection near the Cary Town Center mall.
Green or red turn arrow phasing can also be frustrating for cyclists if the signal does not detect the bike, and the type of signal the cyclist needs (straight or turning) is not provided during the cycle.