Cal. PEN § 369h

Any person, partnership, firm or corporation installing, setting up, maintaining or operating upon public or private property, any sign or light in line of vision along any main line track of any railroad in this State of such type or in such form or manner that it may be mistaken for any fixed or standard railroad signal when viewed from an approaching locomotive cab, railway car, or train, by the operators or employees upon such locomotive cab, railway car or train, so as to hinder the safe and efficient operation of such locomotive, railway car or train, and endanger the safety of persons or property upon such locomotive, railway car, or train, shall be guilty of maintaining a public nuisance. No sign, signal, flare or light placed within the right of way of any street or highway by public authorities in charge thereof, considered necessary by them to direct or warn highway traffic, shall be deemed to violate this section.