Truck and trailer rules in Iowa: licence classes, trailer brakes, size limits and the motor carrier safety rules

This page reports what the official source says. It is not legal advice: ask the office named here. The statute text is from the Iowa Code 2026 as published by the Iowa Legislature, and the permit page is from the Iowa Department of Transportation. 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
Class A	Combination rated 26,001 pounds or more with a towed unit rated 10,001 pounds or more; also lower-rated vehicles
Class B	Vehicle rated 26,001 pounds or more, or a combination with a towed unit rated under 10,001 pounds
Class C	A combination under 26,001 pounds, or a heavier combination only when the towing vehicle is under 26,001 pounds and each towed unit under 10,001 pounds
Trailer brakes	Trailer, semitrailer or travel trailer of 3,000 pounds gross weight or more: brakes, a separate auxiliary means from the cab or self-actuating brakes, and a weight equalizing hitch with sway control
Width, height	8 feet 6 inches wide; 13 feet 6 inches high, unladen or with load
Length	45 feet for a single truck; 70 feet for a combination of three vehicles with a non-tractor motor vehicle; 53 feet for a tractor-semitrailer trailer
Carrier safety rules	Federal parts 385 and 390 to 399 adopted by rule; driver rules do not apply to intrastate drivers of vehicles rated 26,000 pounds or less
Permit lines	A permit is typically required above the legal width, height, length and 80,000 pounds gross
State carrier number	Not published in the pages read

Licence classes

Section 321.189 of the Iowa Code sets five classes. Class A covers a combination with a gross combination weight rating of 26,001 pounds or more when the towed vehicle or vehicles are rated 10,001 pounds or more, and also lower-rated vehicles except motorcycles. Class B covers a vehicle rated 26,001 pounds or more, or a combination rated 26,001 pounds or more when the towing vehicle is rated 26,001 pounds or more and the towed vehicle or vehicles are rated under 10,001 pounds. Class C covers a combination rated under 26,001 pounds, and a heavier combination only where the towing vehicle is under 26,001 pounds and each towed vehicle under 10,001 pounds. Class A and B licences are issued only as commercial licences. Section 321.1 defines a commercial motor vehicle as one used to transport passengers or property that has a gross vehicle weight rating or weight of 26,001 pounds or more, or a combination of 26,001 pounds or more with a towed unit of 10,001 pounds or more, with two further limbs for vehicles built for 16 or more people and for placarded hazardous materials. See Iowa Code section 321.189 and section 321.1 on definitions.

Trailer brakes, hitch and braking distance

Section 321.430 is the trailer rule. Every trailer, semitrailer or travel trailer with a gross weight of 3,000 pounds or more must have brakes adequate to control the movement of and to stop and hold it. The same section says such a trailer must also have a separate auxiliary means of applying its brakes from the cab of the towing vehicle, or self-actuating brakes, and a weight equalizing hitch with a sway control. Trailers or semitrailers behind a truck or truck tractor need only comply with the brake requirements. A trailer or semitrailer under 3,000 pounds gross weight need not have brakes. Section 321.431 sets the performance test on dry level pavement at 20 miles per hour: a vehicle or combination under 5,000 pounds gross weight must stop within 30 feet, and one over 5,000 pounds within 45 feet, with the hand brake able to hold on any grade where it is used. The text read does not use the words safety chain. See Iowa Code section 321.430 and section 321.431.

Width, height and length

Section 321.454 says the total outside width of a vehicle or its load may not exceed 8 feet 6 inches, with a wider allowance for divisible loads of hay, straw, stover or bagged livestock bedding. Section 321.456 sets height at 13 feet 6 inches unladen or with load, and says the section does not require railroads or public authorities to provide enough vertical clearance; damage to structures or underpasses caused by a vehicle's height is borne by the operator or owner. Section 321.457 sets length: a single truck may not exceed 45 feet overall including bumpers, a combination of three vehicles that includes a motor vehicle other than a truck tractor may not exceed 70 feet, a trailer or semitrailer in a truck tractor combination may not exceed 53 feet, and a combination of four vehicles is not allowed except for saddle-mounted power units. See Iowa Code section 321.457 on length.

Motor carrier safety rules and permits

Section 321.449 says no one may operate a commercial vehicle on Iowa highways except in compliance with rules of the Department of Public Safety, which must be consistent with the federal motor carrier safety regulations in 49 CFR parts 385 and 390 to 399. The section carves out drivers who work only inside the state: the driver rules do not apply to a driver of a commercial vehicle engaged exclusively in intrastate commerce when its gross vehicle weight rating is 26,000 pounds or less, unless it carries placarded hazardous materials or is designed to carry more than 15 passengers. Separate exemptions cover public utility trucks, construction trucks and trucks hauling gravel on some of the driver rules. The Iowa Department of Transportation permit page says a permit is typically required above 8 feet 6 inches wide, 13 feet 6 inches high, a 45-foot single vehicle, a 53-foot trailer, and 80,000 pounds gross weight, and that city and county roads need separate permits. See Iowa Code section 321.449 and the Iowa DOT oversize and overweight permit requirements.