Truck and trailer rules in Illinois: commercial vehicle line, trailer brakes, size and weight limits

This page reports what the official source says. It is not legal advice: ask the office named here. All of the sources are sections of the Illinois Vehicle Code, 625 ILCS 5, published on the Illinois General Assembly website. Federal background and the other places are on the parent page, trucks and trailers for tree work.

At a glance

Item	What the sources say
Commercial motor vehicle	Gross combination weight rating or weight of 26,001 pounds or more including a towed unit over 10,000 pounds; or a vehicle rated 26,001 pounds or more
Licence rule	No one may drive a commercial motor vehicle without a CDL or commercial learner's permit of the proper class and endorsements
Trailer brakes	Required on a trailer over 3,000 pounds gross; automatic application on breakaway for a towed vehicle over 5,000 pounds
Safety chain	Outside business, residential and suburban districts and on controlled access highways, a towed vehicle other than a pole trailer or a fifth wheel semitrailer is coupled with 2 safety chains or cables
Width, height	8 feet 6 inches wide on most highways; 13 feet 6 inches high
Length	42 feet for a single vehicle, with listed exceptions
Weight	20,000 pounds single axle; 34,000 pounds tandem axle; 80,000 pounds gross for combinations of five or more axles

The commercial vehicle line and licences

Section 6-500 of the Uniform Commercial Driver's License Act part of the Code defines a commercial motor vehicle as a motor vehicle or combination used in commerce to carry passengers or property that has a gross combination weight rating or weight of 11,794 kilograms or more (26,001 pounds or more) including a towed unit with a rating or weight of more than 4,536 kilograms (10,000 pounds), or a gross vehicle weight rating or weight of 11,794 kilograms or more. A vehicle designed to carry 16 or more persons including the driver, and a vehicle of any size carrying hazardous materials as defined in 49 CFR 383.5, also count. The definition leaves out recreational vehicles operated primarily for personal use and vehicles operated by non-civilian military personnel, among others. See 625 ILCS 5/6-500 on definitions.

Section 6-507 says that, except as the Act expressly permits, or when driving on a commercial learner's permit accompanied by a CDL holder valid for the vehicle, no person may drive a commercial motor vehicle on the highways without a CDL in the driver's possession, without having obtained a permit or CDL, without the proper class of permit or CDL or endorsements for the vehicle group, passengers or cargo, or without a copy of a medical variance document where one exists. See 625 ILCS 5/6-507 on the CDL requirement.

Trailer brakes

Section 12-301 covers brakes. Paragraph 4 of subsection (a) says every trailer or semitrailer with a gross weight over 3,000 pounds must be equipped with brakes adequate to control, stop and hold it, designed to be operated by the driver of the towing vehicle from the cab. The brakes must be designed and connected so that on an accidental breakaway of a towed vehicle over 5,000 pounds they are applied automatically. Paragraph 5 says vehicles must have service brakes on all wheels, but that a trailer, pole trailer or semitrailer of up to 3,000 pounds gross weight needs no brakes, and one over 3,000 pounds but under 5,001 pounds needs brakes on only one wheel on each side. For every motor vehicle, paragraph 1 requires brakes adequate to control, stop and hold it, with two separate means of applying them. Section 15-110 on towed vehicles says that outside a business, residential or suburban district, and on any controlled access highway, a towed vehicle other than a pole trailer or a semitrailer on a fifth wheel is towed by drawbar and coupled with 2 safety chains or cables. Its paragraph (c) leaves out a second division vehicle of a person registered with the Bureau of Motor Carrier Safety of the Federal Highway Administration who has complied with its rules. See 625 ILCS 5/15-110 on towed vehicles. See 625 ILCS 5/12-301 on brakes.

Width, height and length

Section 15-102 sets 8 feet 6 inches as the most a vehicle or its load may measure across on Class III and non-designated State and local highways. It lists exceptions for hay loads up to 12 feet wide in daylight and for implements of husbandry on another vehicle, and says a vehicle and load on the interstate or a Class I or Class II highway designated by the Department may also have a total outside width of 8 feet 6 inches, with certain safety devices left out of the measurement. Section 15-103 says the height of a vehicle including load may not exceed 13 feet 6 inches on any highway in the State. Section 15-107 says a single vehicle may not exceed 42 feet in length, except semitrailers, charter or regulated route buses up to 45 feet and motor homes up to 45 feet, and that combinations may not exceed two vehicles except a truck tractor semitrailer drawing one trailer, one converter dolly or one semitrailer, and other listed cases. See 625 ILCS 5/15-102 on width, 5/15-103 on height and 5/15-107 on length.

Weight

Section 15-111 sets limits for a vehicle or combination on pneumatic tires, laden or unladen, measured as weight on the road surface: 20,000 pounds on a single axle, 34,000 pounds on a tandem axle with no axle of the tandem over 20,000 pounds, and 80,000 pounds gross for combinations of five or more axles. A group of two or more consecutive axles is held to the result of a bridge formula, set out in the section as a table by the distance between the extreme axles. See 625 ILCS 5/15-111 on wheel and axle loads and gross weights.