Yes, yes it is.
"No U Turn" signs are made to be ignored. Usually when they're telling you not to make a u turn that's when you need to make it most. However, there are some situations where you should respect what the aforementioned sign is saying, such as when you're driving a bus on the highway. This Polish bus driver obviously didn't do that. A charter bus takes forever to do anything. A freeway u turn needs to be executed quickly. Is it that hard to see what the issue is?
As you'd expect traffic backs up and horns are honked. Hopefully the bus driver never lives this one down. Seriously, what the hell was this guy thinking?