As I understand it, color blindness means the inability to distinguish only a few colors, perhaps most often red and green. All my life I've heard comments as to the trouble this can cause at traffic lights. And recently I've seen figures suggesting that up to one-fifth of all adult American males are color blind. Could this explain the time I almost got creamed by someone running a red light?
Why not add shapes to colors at traffic lights? Already we see directional arrows in many of the green and yellow (a.k.a. "amber" or "orange") lights. Why not use arrows in all of them -- pointing up for "straight ahead"? The green lights could have the same three-line arrows currently in use, while in the yellow lights the shaft might be eliminated, leaving only a directional "V." Red lights could use either an "X" or an octagon shape or both combined.
Might this help cut down on accidents at traffic lights?