I notice that I've recently started to pay more and more attention to the sign vessels of "construction ahead" signs. The signs tend to be official and made on permanent materials, but this is contrasted with their installation. They are by nature quite temporary, and thus are often installed on e.g. concrete blocks or wooden poles attached to scaffolding.
This is very much a natural choice, but somehow the idea of systematically non-permanent official signage piques my interest.