Ill. Admin. Code tit. 92, § 442.455
The bus shall be equipped with at least one horn capable of emitting sound audible under normal conditions from a distance of not less than 200 feet. (Section 12-601 of the Code) The horn shall be conveniently controlled from the operator’s position and tested in accordance with SAE Standard J377.
(Source: Amended at 31 Ill. Reg. 8238, effective May 25, 2007)