PBOT signage specifiers chose something based on normal applications and they were not selecting fasteners and securing methods that are appropriate for crime infested Portland environment. These signs are usually attached with a hex bolt that can easily be removed with a common store bought/store shoplifted tools.
Moreover, those poles are purposely made frail so they snap when hit by a vehicle, or intentionally kicked over hard.
I am having to report vandalism to sign maybe once or twice a month. Criminals can easily undo the signs, then simply slide your bike off the top. This creates two issues. Bicycle theft, and inability to have unwanted persons’ illegally parked derelict vehicles cited as violation of posted signage is required to establish parking violation.
So. . . by not locking your bike to these, bike thefts can be reduced as well as minimizing damage to signs caused by bike thieves.
This shows a stripped down pole:
This shows possession of stolen property/PBOT signage by an unknown individual who is not the rightful owner.