I don't understand how assuming 50 LEDs per tile covers my main concern. Under normal circumstances on a four lane highway you'll have 5 strips of light, assuming a 7 ft lane with a 2 ft shoulder on either side that's 32 ft. Take his 1.5 ft per tile measure and you have 12 tiles which is 600 lights. Figure each strip is two lights thick, 3 for the border strip, and 7 lights per length of tile since 7x7 is the closest even layout for 50 lights, and that is 49 lights for the lanes per 600 lights, or 2% of the lights. Of course in cities it will be more, but a vast majority of US roads are not in the city. Let's just assume 20% of lights need to be on, that's only 2.4 trillion of his 12 trillion figure. Cut that in half to account for day and you get 1.2 trillion. Cut that again to account for the empty nighttime roadways, we'll assume a very generous 40% usage and you get 480 billion which is a far cry from 12 trillion and also probably a significant overstatement. This is also assuming the figures of 109% conversion.