The text
Every motor vehicle 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 no horn or other warning device shall emit an unreasonably loud or harsh sound or a whistle. The driver of a motor vehicle shall, when reasonably necessary to ensure safe operation, give audible warning with his/her horn, but shall not otherwise use such horn when upon a highway.
(Code 1971, § 22-139)