Do you know what an 18-wheeler is? In fact, people often call it a semi-trailer, because a semi-trailer is composed of a tractor and a trailer, and this combination usually has 18 wheels. In addition, semi-trailers are also called tractor trailers.
We all know that semi-trailers come in different sizes to meet different needs, and because each state has different regulations on semi-trailers, the sizes of semi-trailers will vary. This article will cover the largest sizes and their differences.
How wide is the semi-trailer?
In terms of width, the maximum width of the semi-trailer is 102 inches, or 8.5 feet.
But this measurement does not include load-induced tire bulge, cab handles, mirrors, and other features.
An extension device for a semi-trailer must meet five requirements to be considered an extension device.
- Load and unload functions must not extend beyond 24 inches to the rear of the cab.
- Mirrors can extend up to 10 inches on both sides of the cabin.
- Any aerodynamic devices must be within 5 feet of the rear of the nacelle.
- The elastic bumper assembly must not protrude more than 6 inches from the rear or front of the truck.
- These extensions must be no more than 3 inches wide. For this reason, any tarp systems are generally part of the excluded equipment, as long as they do not protrude more than 3 inches from the side of the cabin.
Each state has different requirements for the width of semi-trailers, check this article:
How long is a semi-trailer?
A semi-trailer can be up to 72 feet long, and this size includes both tractor and trailer.
There are usually some differences in length due to several factors:
- Tractor type: Sleeper cab with a bed inside, usually about 20 feet long, different manufacturers and standards will make this size different.
- Trailer type: A standard dry truck trailer is 53 feet long and overlaps the tractor a few feet, making the combination approximately 70 feet long. Intermodal containers can be 20 or 40 feet, while double or small trailers are typically 28 feet in length.
- State requirements: Manufacturers can often innovate equipment lengths for special freight needs, but are subject to regulations that vary from state to state.
Each state has different requirements for the length of semi-trailers, check this article:
Everything You Need to Know About Semitrailer Length Laws by State
How tall is the semi-trailer?
The average height of a semi-truck trailer is 13′ 5″ to 14′.
There are no federal regulations regarding the height of semitrailers, but each state’s Department of Transportation imposes height restrictions on tractors and trailers. For example, the California Department of Transportation specifies a maximum height of 14 feet for all semi-trailers. However, the Pennsylvania Department of Transportation restricts semitrailers to 13.5 feet or less.
Each state has different height requirements for semi-trailers, check this article:
How heavy is the semi-trailer?
In terms of weight, the combined tractor and trailer weight of the semi-trailer can be up to 80,000 pounds. This is typically divided into 12,000 pounds on the steering axle and 34,000 pounds on the drive axle and trailer tandem axle. This is typically up to 12,000 pounds on the steer axle (the tractor’s front wheel) and up to 34,000 pounds on the drive (the tractor’s rear axle) and the trailer’s tandem axle. The number of axles determines the legal weight. However, the combined tractor and trailer load weight should not exceed 80,000 lbs.
Each state has different weight requirements for semi-trailers, check this article: