1. a) Except as specified in subsection (b), letters and other characters used to comply with the carrier identification requirements of Section 18c-4701 of the Law must be at least 2 inches high and ½ inch wide. Such characters must be in a color contrasting with the background color of the vehicle so as to be distinguishable during daylight at a distance of 50 feet while the vehicle is not in motion.
2. b) Letters and other characters used to comply with the carrier identification requirements of Section 18c-4701(5) of the Law for vehicles under 9,000 pounds gross vehicle weight must be at least ½ inch high and ⅛ inch wide. Such characters must be in a color contrasting with the background color of the vehicle so as to be distinguishable during daylight at a distance of 25 feet while the vehicle is not in motion.
3. c) It is a violation of this Part to display more than one identifier on the power unit of a vehicle. Identifier is defined as the information used to comply with the carrier identification requirements set forth in the Law and this Part.

(Source: Amended at 14 Ill. Reg. 13138, effective August 15, 1990)