Ill. Admin. Code tit. 92, § 442.715
a) The warning devices must be securely stored. The warning devices required for use when lighted lamps are required (see Section 12-201(b) of the Code) shall consist of:
3) Three portable red emergency reflectors that meet FMVSS 125.
b) In addition, the following warning devices are also required for use when lighted lamps are not required (see Section 12-201(b) of the Code):
AGENCY NOTE: School buses weighing more than 8,000 pounds and operated upon any highway outside an urban district must carry warning devices, but the bus purchaser may elect to install the warning devices after the bus is purchased.
(Source: Amended at 31 Ill. Reg. 8238, effective May 25, 2007)