Ill. Admin. Code tit. 92 § 562.20
The following definitions have been adopted by the Department of Transportation for the purpose of administering the provisions of the Freeway Act.
"Freeway." A freeway is defined as a public highway especially designed for through traffic and to or from which owners of or persons having an interest in abutting property, or other persons, have no right of direct access or only limited right of direct access by reason of the fact that the said property abuts upon such highway, or for any other reason. On freeways to be constructed with complete control of access the physical means of access shall be limited to ramps, approaches or other facilities located, designed and constructed by the Department for entrance to and exit from the freeway by the general public.
"Local Service Drives." Local service drives, commonly called frontage roads, are roads located generally parallel and adjacent to the freeway traffic lanes. Their purpose is to provide means of indirect access to and from the freeway by the owners of, or persons having interests in the properties abutting the freeway, or any other persons. These local service drives or frontage roads may be either roads constructed by the Department on the freeway right of way or existing roads or streets adjacent to the freeway which shall be or have been designated as such local service drives or frontage roads by the Department.
Ill. Admin. Code tit. 92, § 562.20