In most of the EU at least, generally not on roadways I believe. Definitely banned on roadways in my mom's country. In countries where they are more common, it's all stuff like [car brand], [museum/landmark near you], [tv network], [unoffensive mainstream political ad], a lot of which is still annoying but preferable to [strip joint at exit], [call shady lawyer now], [repent or burn], [i'm mclovin' it]

The billboards in this photo would be unthinkable anywhere else