You are correct, I don't know if they controlled for screen glare. :)
The road signs are an interesting question. I know there's a lot of work, and occasional controversy, over the typefaces used. If I had to hazard a guess for the color choices, though, it might be the signs have to be very visible in the dark, too -- that's now generally done by using reflective paint for the light part of the sign, but older highway signs, at least in America, used reflective dots in the letters. So that might be a tradition born less out of legibility studies than practicality.
The road signs are an interesting question. I know there's a lot of work, and occasional controversy, over the typefaces used. If I had to hazard a guess for the color choices, though, it might be the signs have to be very visible in the dark, too -- that's now generally done by using reflective paint for the light part of the sign, but older highway signs, at least in America, used reflective dots in the letters. So that might be a tradition born less out of legibility studies than practicality.