(625 ILCS 5/1-105.4)
    Sec. 1-105.4. Auxiliary power unit, or APU. Small engines used on commercial trucks to provide power for auxiliary loads, such as heating, air conditioning, and lighting in sleeper berths, which allows the operator to shut off the main engine while resting. Auxiliary power units may also be referred to as idle reduction units.
(Source: P.A. 97-201, eff. 1-1-12.)