Cal. Vehicle Code § 27001 : California Vehicle Code — Equipment Of Vehicles — Other Equipment — Horns, Sirens And Amplification Devices — Audible warning with horn Date: 7 Sep 2016 TEXT PDF Current through the 2016 Legislative Session (a) The driver of a motor vehicle when reasonably necessary to insure safe operation shall give audible warning with his horn. (b) The horn shall not otherwise be used, except as a theft alarm system which operates as specified in Article 13 (commencing with Section 28085) of this chapter. Ca. Veh. Code § 27001