No person shall place anything on a sidewalk that would obstruct
safe passage thereon unless such placement is temporary, unavoidable,
the obstruction is clearly marked and visible at nighttime, and a
safe path around the obstruction is provided not requiring travel
into the roadway. Any substance or thing that through force of nature
or man falls upon the surface of any sidewalk and presents a tripping
or slipping hazard shall be removed as soon as is practicable.