This is the Uni-Signal, or Universal Sign Light. It's here to address a major problem with our old traffic lights: if everyone is supposed to know what a traffic light is trying to tell them, then why isn't it designed so that everyone will be able to read it?
Color blindness, more common in men than women, takes many different forms and is present in a good 10%-15% of the population. With that in mind, you don't have to be able to see the usual red-yellow-green to know whether to stop, yield or go. Now, the redesigned red light will also show up as a triangle, the yield sign is still yellow and green for go will look like a square.
Check out a side-by-side comparison below.
Via Yanko Design