Truck and trailer rules in Kentucky: licence classes, brakes, size and weight limits

This page reports what the official source says. It is not legal advice: ask the office named here. The sources are sections of the Kentucky Revised Statutes published by the Kentucky Legislature: chapter 281A on commercial driver's licenses and chapter 189 on traffic regulations and vehicle equipment. 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	A vehicle used in commerce with a federal gross vehicle weight rating adopted by the cabinet; 16 or more passengers; placarded hazardous materials
Class A	Combination rated 26,001 pounds or more, towed vehicle rated over 10,000 pounds
Class B	Single vehicle rated 26,001 pounds or more, or towing a vehicle not over 10,000 pounds
Brakes	Two means of applying; commercial vehicle over 10,000 pounds declared gross weight must meet 49 CFR part 393
Basic width, height	96 inches wide; 11 feet 6 inches high
Basic length, weight	26 1/2 feet motor truck; 30 feet semitrailer truck; 36,000 pounds gross
Designated highways	13 feet 6 inches high; 20,000 pounds single axle; 80,000 pounds gross

The commercial vehicle line and licence classes

KRS 281A.010 defines a commercial motor vehicle as a motor vehicle or combination used in commerce that is designed to carry property and has a gross vehicle weight rating set by federal regulation adopted into cabinet regulations, is designed to carry 16 or more passengers including the driver, carries placarded hazardous materials, or is any other vehicle that cabinet regulation says must be driven by a licensed commercial driver. KRS 281A.170 sets the classes. Class A is any combination of vehicles with a gross vehicle weight rating of 26,001 pounds or more if the rating of the vehicle being towed is more than 10,000 pounds, and a Class A licensee may drive Class B and C vehicles with the proper endorsement. Class B is any single vehicle rated 26,001 pounds or more and any vehicle towing a vehicle not over 10,000 pounds. Class C is a single vehicle rated under 26,001 pounds, or one towing a vehicle not over 10,000 pounds, that is built for 16 or more passengers or carries placarded hazardous materials. See KRS 281A.010 on definitions and KRS 281A.170 on the form of licenses and classes.

Brakes

KRS 189.090 says a motor vehicle other than a motorcycle must have brakes adequate to control, stop and hold it, with two separate means of applying them, each effective on at least two wheels. For a vehicle that is not a commercial motor vehicle over 10,000 pounds declared gross weight, the service brakes must stop it from 20 miles per hour within 40 feet on dry level pavement, and the hand brake within 55 feet. Those distances apply loaded to the maximum the law allows. No one may operate a commercial motor vehicle with a declared gross weight over 10,000 pounds on a highway unless it has efficient brakes that meet the federal motor carrier safety standards in 49 CFR part 393 and can be operated by the driver. The section reads give no separate trailer brake weight line and no safety chain rule. See KRS 189.090 on brakes.

Basic size and weight limits

KRS 189.221 sets the limits on highways other than those designated under KRS 189.222. A truck, semitrailer, trailer, manufactured home or other vehicle may not exceed 11 feet 6 inches in height or 96 inches in width, including body or load. A motor truck other than a semitrailer truck may not exceed 26 1/2 feet in length, and a semitrailer truck 30 feet. A truck, semitrailer truck or truck and trailer unit may not exceed 36,000 pounds gross weight, and may not exceed 600 pounds per inch of the combined width of its tires, up to the same 36,000 pounds. A truck hauling building materials, or hauling to a road construction project on a highway rated lower, may haul up to 80,000 pounds without a permit. The statute lists this text as effective July 15, 2026.

Designated highways

KRS 189.222 lets the secretary of the Transportation Cabinet raise those limits on designated state-maintained highways, within caps the statute names. The caps are 14 feet in height for vehicles transporting motor vehicles and 13 feet 6 inches for all others, and in length 53 feet for semitrailers, 28 feet for trailers and 45 feet for motor trucks, with no more than two trailers per truck tractor. Weight is capped at 20,000 pounds on a single axle (axles under 42 inches apart count as one), 34,000 pounds on two axles in tandem and 48,000 pounds on three axles, with a gross weight of 80,000 pounds. Except on the interstate, a 5 percent tolerance per axle load is allowed. A vehicle 102 inches wide or less and not over 80,000 pounds may be driven on any state highway for up to 15 miles from an interstate or parkway exit.

The same section lists vehicles that may carry up to 80,000 pounds on any state highway without a special permit when transporting named loads. One of those is primary forest products, including sawdust, wood chips, bark, slabs or logs, from the point of origin to first market. Vehicles registered under KRS 186.050(3)(b) that carry primary forest products may exceed the axle or gross weight caps by a 10 percent tolerance, except on the interstate. Refuse collection vehicles are excluded from the axle provisions except on the interstate. See KRS 189.221 on basic limits and KRS 189.222 on designated highways.