I used to participate in a chat room that allowed a limited subset of HTML, and one of the tags was <marquee>. I played around with this a lot and discovered that you could nest marquees and make (very) limited ASCIImations. This culminated in someone making a ASCIImation parody of Finding Nemo. Good times.
I didn't know what that did so I googled "marquee html", they have a nice little easter egg for it. It's been a while since I've seen anything like that from google
It seems it isn't just auto drive. Cars with object collision detection are slamming on the brakes when they come near this cattle grid. Signs wouldn't help in that case.