Imagine you're driving down a freeway, sun shining, favorite playlist cruising, when suddenly—BAM!—a giant rock crashes onto your windshield. Sounds like a scene from an action movie, right? Well, it was chilling reality recently in Las Vegas, where two drivers were seriously injured by massive rocks thrown from a pedestrian overpass onto an interstate highway. The incident has alarmed the public and state police, reminding us all that safety is never guaranteed, not even on well-traveled roads. (You can watch the harrowing footage here.)