Some things are so ubiquitous that it's easy to forget they're designed for a reason. With more than 300,000 traffic lights set up across the United States, it's easy to take how they look for granted ...

Red and green traffic lights have been around since the 1800s, when British traffic officers used to rotate gas lamps that burned red and green to control the movement of mostly horse-drawn vehicles.

Ah, the yellow light. You know, that signal that is supposed to let you know to slow down as you approach the intersection, but makes you speed up instead? You probably take it for granted, but ...