In the workshop in Duisburg, we got an interesting site which owned by private but used as public space. In order to prevent anything a private owner wants to prevent, a street sign was built at the entrance, saying:
Privatweg, Betreten und Befahren auf eigene Gefahr.
(private land, entering at your own risk.)
Following the nature of the site, I added the other sign, “public”, together with the “private” tag, as a more friendly gesture to the public who want to enter at their own risk.
(It was a proposal during brainstorming, however I think it is an plausible idea to be shared here :)