Red Light Green Light

I heard other parents talk about their kids having conversations with them in the car about stop lights while they are driving. I thought - Carson will never get to that stage. . . but alas he has. Just since last week he started noticing when cars are stopped at lights and when we stop and go at lights. But it's not as simple a concept as I thought it would be!!!! I have never heard other parents talk about this - but I'm wondering if anyone else has had this problem.
I started out explaining - "see the light is red, so we stop, when it turns green then we can go" then I realize we are in the turning lane, so we just get a tiny arrow that he probably can't see.
Other scenario - we are going straight - so our light turns green, but he can see out the side and notices the red light for the other direction as we drive by, and is wondering why we are going if he sees the red light.
or a different scenario - we are going right and turn when there is no traffic coming even though our light is still red.
How do you explain all these concepts? I always thought it would be so simple - but it's really not! He yells everytime we come to a stop - "Car stop, Car Stop!!!!" And I say "when it turns green then we can go - oh wait, can you see that tiny arrow?" or "make sure you look straight ahead through daddy's head to see our green light".
Oh well, i guess by the time he's 16 he will understand the concept. . .