Traffic Light Puzzler

Last week’s Car Talk puzzler was about traffic lights. Old-style traffic lights use a light bulb behind a green, yellow, or red lens. New traffic lights use LEDs instead. Each has an array of LEDs that light up. The LED traffic lights are cheaper and much brighter. But some of the old lights still around. In fact, where they’ve put new ones in, they’ve replaced the green and red lights, but not the yellow lights. So the puzzler question is: why aren’t the yellow lights being replaced?

Think about how the lights are used. Check your answer here. Since hearing this one, I’ve been noticing which towns have been switching to the newer lights and which ones still use the older lights. More details on the new LED traffic lights can be found here.