I thought I moved out of the countryside

I was in downtown Stuttgart and saw a very strange sight:

Yes, there are ATVs in the city. I've seen people driving around on ATVs, just like they would ride a motorcycle. I've even seen them on the highway! They are actually street legal, provided they have the proper equipment, such as turn signals, etc.

Somehow, I feel as if I haven't left my previous home in the country behind; however, I never saw people riding ATVs on the main roads in the US.