92 Ill. Adm. Code 449.20
Application
Section 449
Section 449.20 Application
a) This Part applies to any school bus which is equipped to use
any liquefied petroleum gas or compressed natural gas as a fuel propellant and
began operation on or after February 26, 1990.
b) This Part does not apply to any school bus which was equipped
to use any liquefied petroleum gas or compressed natural gas as a fuel
propellant before February 26, 1990.