And Now For Something Completely Mundane
1: Billboards are effective (else businesses wouldn't use them).
2: Being effective, they necessarily divert peoples' attention.
Conclusion: They should be illegal where they would be visible to drivers.
The fact that billboards are not illegal where they would be visible to drivers, that nobody would ever seriously consider making them so, demonstrates that we are stupid or bat shit insane.
And forget about "that would be social engineering." Billboards are social engineering. We allow them to do it to us just because they have the money.
And forget about "that would be infringing free speech." It's a stretch to define companies as people and advertising as protected speech, but even if you do then the public has a right to limit the where and when of it.
Oh, and think how much more pleasant our cities would be without them. Just sayin'.