Eugene put some thermoplastic ones down on the river bike paths a decade or so ago. Those were fine. They were basically quarter-mile markers with the path name (west, east, north, south; yes, the river turns ninety degrees) and a different color for each segment.
Then, a few years back, some clown in our police department (yes, I know him and he is a clown) decided to put actual signs up with the same information. That would be fine, except these "signs" are solid steel box-beam construction in concrete with very solid, sharp corners and are placed right on the edge of the path. Such a placement would be illegal in California, which recommends a six-foot clear zone at the edge of bike paths and mandates that the entirety of any sign be six feet from the edge of the path.