Strange Things are Afoot on Clarksville Pike

I drive this particular stretch of Clarksville Pike twice a day every day on weekdays and at least once a day on weekends. It is the main street through my part of town. So, on Saturday, I was grabbing lunch at Sonic and I'm coming back up Clarksville Pike and I cross the Whites Creek Bridge and stop at the stop light, as I have done approximately eleven billion times before. To my right is South Hamilton. To my left is an overgrown field.

So, imagine my surprise when I notice a turn arrow...