[kolinko]

This is not it. There must be signs accompanying the light saying that you cannot go straight.

Without the signs, someone would simply arrive at the intersection and wait god-knows-how long for it to turn green, until they gave up and went right :)

The reason for the light is that according to regulations, at an intersection, every road leading to it has to have lights. You cannot have three streets with lights, and one with just a sign saying "stop and yield".

[ryanjmo]

It is definitely true that a sign was improve the drivers understanding and be helpful, however the light is still necessary. Stop and yield is not sufficient... that puts the decision of when to turn on the driver of the car, instead of being dictated by the light as is the desired behavior...

I still see this as the only way to communicate correctly the rules of the intersection. And yes, add a sign as well to let people know they can only turn right.