Any religious organization bus may be equipped with a four-lamp flashing signal system having unison flashing amber lamps, two at the front and two at the rear of the bus, mounted as high and as widely spaced laterally on the same level as is practicable.  If this equipment is installed, each lamp must be a sealed beam at least five and one-half inches in diameter and have sufficient intensity to be visible at 500 feet in normal sunlight; the system shall be actuated only by means of a manual switch; and there shall be a device for indicating to the driver that the system is operating properly or is inoperative.
(ILCS Ch. 625, Act 5, § 12-901)  Penalty, see § 70.999