Around here there are some pretty confusing roundabouts. Some have seven exits, each with their own set of traffic lights and when you're driving through it, it can be very confusing which lights apply to you. To make it easier, many lights have big black hoods over them so they can only be seen, supposedly, from one direction. This helps, but it's far from perfect.
I propose ditching the hoods, and placing a clear plastic lenticular-style covering over the light. A lenticular coating is a series of thin prisms made from moulding the plastic so that light is sent in a specific direction. It's used in simple "holograms" you sometimes get on bookmarks and the like, where more than one image has been printed in columns lining up with the prisms, so it appears as a different image from different points of view.
Most new traffic lights use an array of LEDs instead of a bulb, so these could quite easily line up with the lenticular cover. The green light would only be seen from the direction chosen when the cover was designed, and all of the light would go in that direction, instead of being absorbed by a black hood.
If every other column of LEDs were wired differently, combined with the lenticular design, it would be possible for the traffic light to appear in a different state from different directions. A single unit could send different instructions to different lanes of traffic easily, cutting costs and confusion.