Section 257.706 - Horn or other warning device; siren, whistle, air horn, or bell; theft alarm signal device(a) A motor vehicle, including a motorcycle or moped, when operated upon a highway shall be equipped with a horn in good working order and capable of emitting sound audible under normal conditions from a distance of not less than 200 feet but a horn or other warning device shall not emit an unreasonably loud or harsh sound or a whistle. The driver of a motor vehicle shall when reasonably necessary to insure safe operation give audible warning with his horn but shall not otherwise use the horn when upon a highway.(b) A vehicle shall not be equipped with nor shall a person use upon a vehicle a siren, whistle, or bell, except as otherwise permitted in this section.(c) A commercial vehicle may be equipped with a theft alarm signal device which is so arranged that it cannot be used by the driver as an ordinary warning signal.(d) An authorized emergency vehicle may be equipped with a siren, whistle, air horn, or bell capable of emitting sound audible under normal conditions from a distance of not less than 500 feet, but the siren shall not be used except when the vehicle is operated in response to an emergency call or in the immediate pursuit of an actual or suspected violator of the law. In those cases the driver of the vehicle shall sound the siren when necessary to warn pedestrians and other drivers of the approach of the vehicle.(e) A motor vehicle licensed as an historic vehicle may be equipped with a siren, whistle, or bell which may be used when participating in a parade, exhibition, tour, or similar event.1949, Act 300, Eff. 9/23/1949 ;--Am. 1969, Act 134, Imd. Eff. 6/1/1970 ;--Am. 1975, Act 100, Eff. 7/1/1976 ;--Am. 1976, Act 439, Imd. Eff. 1/13/1977 ;--Am. 1978, Act 55, Imd. Eff. 3/10/1978 .