Regulations governing the dimensions of commercial motor vehicles and semi-trailers have been in place across the U.S. since first being enacted in 1956. Requirements on the length of semi-trailers date back to 1982 under the Surface Transportation Act (STAA).
The federal government has set the standards for semi-trailer dimensions used on Interstates and national highways. However, individual states have enacted various laws regulating vehicle height and width. As such, while the length will ideally be standardized, variations may be allowed and will differ from State to State.
You’ve likely come across several types of semi-trailers, all used in different ways depending on size and structure. Some of the most common trailers you’ll see on the national highways and Interstates are dry van trailers, refrigerated trailers (also called “reefers”) and petroleum tank trailers.
Each of these trailers takes on different functions according to the type of cargo they haul. But if you are looking to have a given trailer, then knowing its dimensions could help you understand if that trailer would suit your needs.
What is the Size of the Standard Semi-Trailer?
The standard semi-trailer dimensions as set by the U.S. Department of Transportation allow for lengths of 48 to 53 feet. That is the standard length the federal government has set for use on highways across the country.
Commercial motor vehicles, semi-trailers or tractor-hauled trailers also have a maximum width of 102.36 inches, while height is between 13 and 14 feet.
Standard trailer lengths in North America
Note that the federal government hasn’t set any limit on what a state can allow in terms of the height of semi-trailers.
Variations in length and height are common, but width is more standardized. The exception comes in situations like when a trailer truck needs a special rear-view mirror, which may extend the width of the tractor.
The standard dimensions of semi-trailers therefore are:
- length: 48 feet
- height: 13 feet 6 inches
- width: 102 inches
If a truck is hauling a double trailer, then each trailer will be 28 feet long.
In North America, the standard lengths of semi-trailers are 28 ft, 32 ft, 34 ft, 36 ft, 40 ft, 45 ft, 48 ft, and 53 ft. Some states also allow trailer lengths of 57 ft and above, though most have no minimum trailer length for state-wide roads.
For example, Arizona allows a maximum trailer length of 57′ 6″ on its highways and 53 feet on non-Interstate roads. Most other states allow semi-trailers with a maximum length of 53 feet on Interstate highways and a maximum of 48 feet on non-designated state roads.
Different states have specific laws regulating the height at which commercial vehicles and trailers are allowed to use highways.
What are the Semi-Trailer Dimensions of a 53' Trailer?
While trailer lengths vary- from a 28′ High Cube (HCs) to a 53 ft dry van, widths are more or less standardized. If we look at a 53 feet semi-trailer, dimensions vary ever so slightly between the overall and the interior.
Overall length is 53 feet; overall width is 102″; and overall height is 13ft 6 inches. On the inside, semi-trailers are 47′ 6″ long, 98.5″ wide and 108 inches high. The rear door opening is 94″ in width and 102″ in height.
53 ft semi-trailers have a capacity of 3,489 cu ft (cubic feet) and weigh 13, 500 lbs.
Dimensions of a 48 ft Semi-Trailer
Overall length is 48 feet; overall width is 102″; and overall height is 13ft 6 inches. Interior length is similar to a 53 ft trailer at 47′ 6″ and so is the interior width at 98.5″. Interior height is 100.6 inches while the rear door opens 98″ wide and 100.6″ high.
48 ft semi-trailers have a capacity of 3,465 cu ft (cubic feet) and weigh 13, 500 lbs.
Dimensions of a 45 ft Semi-Trailer
Overall length is 45 feet; overall width is 96″; and overall height is 13ft 6 inches. Interior length is 44′ 1.5″ and has an interior width of 93″. Interior height is 100.5 inches while the rear door opens 87″ wide and 98″ high.
45 ft semi-trailers have a capacity of 3,086 cu ft (cubic feet) and weigh 11, 900 lbs.
Dimensions of a 43 ft Semi-Trailer
Overall length is 43 feet; overall width is 96″; and overall height is 13ft 0 inches. 43 ft semi-trailers are 41′ 6″ long on the inside and 92.5″ wide. Interior height is 100.5 inches while the rear door opens 92″ wide and measure 98″ high.
43 ft semi-trailers have a capacity of 2,711 cu ft (cubic feet) and weigh 11, 900 lbs.
How Long is a Semi-Trailer?
Trailers have all sorts of names that describe their usage, size, and length. You probably have used tractor-trailer, semi-trailer, semi, and trailer interchangeably.
Other terms are big rig or 18-wheeler- all of which are used in freight transport or some cases, as storage trailers (or storage on wheels).
When we talk about trailers, we refer to the cargo-carrying part of a semi-trailer that is attached to a towing engine.
According to the Federal Highway Administration (FHWA), the minimum length allowed on highways is 48 ft. The most common trailer length is 53 feet, though this is its length without the truck tractor.
If you add the length of a truck tractor, then the overall length of a semi-trailer could reach 80′.
What the FHWA says
The FHWA allows States not to limit how long a truck tractor-semitrailer could be when combined. That includes even in cases where the trailer ends up being longer than is allowed under the law.
Different states allow for different lengths for truck tractors or cabs, and this means the overall length of a semi-trailer/cab combination varies.
If you use a straight truck to tow a trailer or semitrailer, then the overall length of the two or three should not exceed 65 feet.
If the overall lengths of the trailers go beyond this limit, then the law allows States to impose a maximum limit based on the Intermodal Surface Transportation Efficiency Act (ISTEA).
Summary of standard dimensions
- Standards lengths: 28-53 feet
- Width: 96 – 102 inches
- Height: 12.6 – 13.6 feet
- Door types: Swing /Roller doors
- Capacity: 2,089 cu ft to 3,489 cu ft
- Max weight: 53 ft trailer can haul a maximum of 45,000 lbs
- Max pallets: 26 pallets for a 53 ft trailer
- Max Overall length: 80′
- Max Total Weight: 80,000 lbs.
How Wide is a Trailer on an 18 Wheeler?
18-Wheeler trailers have a maximum width limit of 102 inches (or 2.6 meters), which is the standard width measurements for commercial motor vehicles (CMVs).
The 102-inch standard (also 102.36 inches) is the international limit currently in use for all trailers. However, that is in reference to the big rig’s body or chassis.
In the U.S., various states have local rules that can take the overall width beyond the 102″ standard.
When we add specialized equipment like rear-view mirrors, strap winches, and lights, the width of the rig could reach over 110 inches. Mirrors especially stick out as a driver must have a clear view of the highway to the rear of their trailers.
An 18-wheeler that is 8′ 6″ wide uses most of the lane width on 12 feet Interstate, the same width on most national highways.
How Much Weight Can a Semi-Trailer Carry in North Carolina?
Various states have laws in place regarding how much weight trailers can carry on state roads and interstate highways.
In North Carolina, such laws provide for limits based on axles, what commodities the trailer is transporting and the road network in use. That also depends on the limits allowed for bridges.
The State allows a legal maximum of 20,000 lbs for single axle trailers and 34,000 lbs for a trailer with a tandem axle.
The maximum Gross Vehicle Weight allowed for trailers in North Carolina is 80,000 lbs.
Vehicles other than those with single axle, tandem axle, or GVW limits or those using interstate highways have access to a 10 percent extra weight tolerance
Information on the fhwa.dot.gov website shows that single axle trailers are exempt up to 22,000 lbs when they transport certain commodities within distances of150 miles on non-Interstate highways. Tandem axle trailers get up to 42,000 lbs and Gross Vehicle Weight (GVW) can go up to 90,000 lbs.
Maximum weights per axle
The state also allows an annual permit of up to 90,000 lbs for trailers with a wheelbase of 51 ft at the minimum. But these vehicles cannot use posted roads or bridges that are likely to collapse under their weight.
The gross weight for a semi-trailer with 5 axles is 94,500 lbs; 108,000 lbs for 6 axles; and 122,000 lbs for a 7-axle engine.
How Many Trailers Can a Semi-Trailer Haul in North Carolina?
North Carolina truck and trailer laws allow for the hauling of two trailers behind a semi-truck. The regulations stipulate that a truck tractor can haul the two units only on interstate highways and designated State roads.
- The semi-trailer or trailer towed in such a manner cannot exceed 28 feet.
- The exception is there for trailer models from 1982, or older, whose length is 28.5 feet.
- North Carolina laws allow trucks to haul 53 ft semi-trailers or less on all primary highways in the state. However, the combination must meet state and federal length requirements.
Among requirements is that the combination complies with weight restrictions concerning axles. For one, the distance between a trailer’s kingpin and the rearmost axle must not be more than 41 feet. Likewise, that distance should be 41 feet or less in case of a tandem axle.
Restrictions on trailers in North Carolina
You may be restricted from using truck-trailer or semitrailer combinations in the state if the trailer fails to meet one key requirement: the trailer and the semi-truck needs to be firmly attached. This is to ensure that hauling vehicles and the trailer do not snake when on the highways.
Trailer dimension laws in North Carolina put the overall semi-trailer length at 60 feet, with the standard trailer length being 48 feet. The overall width is 102 inches or 96 inches without mirrors and other specialized equipment.
A truck hauling a trailer attached to it using a hitch must also use safety chains to increase the hold on the cargo-carrying vehicle. This requirement applies to all trailers unless the connection to the semi-truck is via a fifth wheel.
Why Should You Know About Trailer Dimensions?
You might be looking for a trailer to rent or buy or you need one for storage. Whatever the reason, it pays to know the standard dimensions of trailers as allowed on U.S. highways and designated state roads. You don’t want to get into sticky situations with highway patrol or end up on a bridge too weak for your 53 ft trailer.
But perhaps the most important reason is to know what semi-trailer suits your needs.
If you have any questions about semi-trailers or their dimensions, please call B&W Trailer Rental at 1-800-227-5134. We would be more than happy to help you.