(625 ILCS 5/1-204.4)
Any commercial motor vehicle that is designed
to transport any liquid or gaseous material within a tank or tanks having an individual rated capacity of more than 119 gallons and an aggregate rated capacity of 1,000 gallons or more that is either
permanently or temporarily attached to the vehicle or the chassis. A commercial motor vehicle transporting an empty storage container tank, not designed for transportation, with a rated capacity of 1,000 gallons or more that is temporarily attached to a flatbed trailer is not considered a tank vehicle.
(Source: P.A. 98-176 (see Section 10 of P.A. 98-722 and Section 10 of P.A. 99-414 for the effective date of changes made by P.A. 98-176).)