Wow Mike, I don't think your question is silly...in fact, it's great.
I have been intersested in traffic lights ever since I was little and still am.
Here in the city of Dallas, the designs used to vary greatly (and still do somewhat), but now most of the lights are horizontal-mounted lights on mast-arms like in the picture below.
(Picture is from Google.)EDIT: As I went to school today, I realized that we still have a lot of vertically mounted lights on smaller poles with the turn signal on a separate pole. (See
traffic light 2 picture below...Courtesy: Google Maps)
As for LED, all red and green lights have been replaced but most yellows have not. Does anyone know why this is?