(a) The Department shall adopt a State manual and specifications for a uniform system of traffic-control devices consistent with this Chapter for use upon highways within this State. Such manual shall include the adoption of the R 7-8 sign adopted by the United States Department of Transportation to designate the reservation of parking facilities for a person with disabilities. Non-conforming signs in use prior to January 1, 1985 shall not constitute a violation during their useful lives, which shall not be extended by other means than normal maintenance. The manual shall also specify insofar as practicable the minimum warrants justifying the use of the various traffic control devices. Such uniform system shall correlate with and, where not inconsistent with Illinois highway conditions, conform to the system set forth in the most recent edition of the national manual on Uniform Traffic Control Devices for Streets and Highways.
     (b) Signs adopted by the Department to designate the reservation of parking facilities for a person with disabilities shall also exhibit, in a manner determined by the Department, the words “$100 Fine”.
     (c) If the amount of a fine is changed, the Department shall change the design of the signs to indicate the current amount of the fine.