I worked at a place trying to do roadside LED billboards (~2009 before they were common) and the rules about content (in the UK, at the time) were fairly strict

I worked at a place trying to do roadside LED billboards (~2009 before they were common) and the rules about content (in the UK, at the time) were fairly strict - nothing animated, no cuts only fades even between distinct adverts, etc. From what I've seen of the fancy new ones, those rules seem to be mostly still around (in London anyway.)