Semi Trailer Dimensions, Length & What Can You Haul

While the term semi trailer is used by the public to refer to the common box trailer-tractor cab combinations seen driving down the highway, the reality is that this word encompasses a vast array of trailer types. For those who work in the industry, understanding the specifics of semi trailer dimensions and what each style of trailer can haul is key.

The following guide will walk through common trailer styles, their dimensions, including length, width, and height, as well as what capacity loads they can haul. Additionally, a few key regulations around semi trailer dimensions and load weights will be outlined, helping operators understand when specialized permits are required by state. 

Dimensions, Length, and Freight Weight by Trailer Type

Not all semi trailers are designed with the same use case in mind. For this reason, their dimensions and load weight vary based on what they are intended to haul. The following list curated from Paige Ltd. quickly breaks down some of the most common semi trailer dimensions.

Flatbed Trailers

Flatbed trailers can haul a maximum weight of 48,000 pounds. However, tri-axle trailers can haul up to 65,000 pounds, making them ideal for heavy cargo. 

Common dimensions for flatbeds are as follows:

• Length- 48 ft – 53 ft
• Width- 8.5 ft
• Height- 8.5 ft

Dry Vans

Dry vans boast a freight weight of 42,000 pounds to 45,000 pounds, depending on the specific van. A dry van with a tri-axle, however, can haul up to 63,000 pounds. 

Common dry van dimensions are as follows:

• Length- 48 ft – 53 ft
• Width- 8.2 ft
• Height- 8 ft

Refrigerated Trailers

Refrigerated trailers are designed to transport temperature-sensitive items, such as produce, dairy goods, and other foods. Their max freight weight is 42,000 to 45,000 pounds for a standard refrigerated trailer and 63,000 pounds for a tri-axle.

Common refrigerated trailer dimensions are as follows:

• Length- 48 ft – 53 ft
• Width- 8.2 ft
• Height- 8 ft

Lowboys

Lowboys offer a maximum cargo weight of 40,000 pounds for a standard two-axle trailer. You can add on an additional trailer and cargo combination weight of up to 95,000 pounds depending on the number of axles used.

Common lowboy trailer dimensions are as follows:

• Length- 24 ft – 29.6 ft
• Well Height- 18 in – 24 in
• Width- 8.5 ft
• Legal Freight Height- 11.5 ft – 12 ft
• Legal Overall Load Height- 14 ft

Step Decks

Step decks are designed with a maximum freight weight of 48,000 pounds for a standard trailer. A tri-axle offers a freight weight of 65,000 pounds.

Common step deck trailer dimensions are as follows:

• Length- 48 ft – 53 ft
• Width- 8.5 ft
• Height- 10 ft

Federal Regulations for Interstates

When operating a semi trailer, it’s not just about how the trailer itself was designed to carry loads or how large a manufacturer can create the trailer to be. More importantly, it is also about following the legal regulations surrounding trailers. According to the U.S. Department of Transportation Federal Highway Administration, the following are the mandated maximum weights for the National System of Interstate and Defense Highways:

• 80,000 pounds gross vehicle weight

• 20,000 pounds single axle weight

• 34,000 pounds tandem axle weight

Interestingly, a key consideration for semi operators is the spacing of axles. The Federal Highway Administration looks to protect bridges by calculating the number and spacing of axles carrying the load weight. This is called a bridge formula and is applied to commercial vehicles to ensure compliance. 

The specific formula from the Federal Highway Administration is as follows:

W=500(LN/N-1 + 12N + 36); where W=overall gross weight on any group of 2 or more consecutive axles to the nearest 500 pounds. L=distance in feet between the extreme of any group of 2 or more consecutive axles, and N=number of axles in the group under consideration

When it comes to hauling oversize loads, the federal government is not the one to issue permits to operators. Instead, this is handled on a state-by-state basis. 

Regulations by State

When hauling cargo across state lines, it is critical to understand what semi trailer dimensions are allowed and what requires additional permitting. 

Different states have their own regulations for oversize load permitting, which can make the matter even more complex. The following information gathered from Coast to Coast Trucking Permits extensive state-by-state list helps to highlight the exceptions of which trailer operators should be aware. 

Single Axle Restrictions

The majority of states allow you to haul 20,000 pounds on a single axle trailer without a permit. However, this is not the case for every state. The following list breaks down states that do not adhere to this regulation, including information about what necessitates permitting. (Note: in some cases, state’s will allow for heavier loads than the standard):

• Connecticut: Single axle trailers are allowed up to 22,400 pounds if spaced over 6 feet apart
• Florida: Single axle trailers are allowed up to 22,000 pounds
• Georgia: Single axle trailers are allowed up to 20,340 pounds
• Idaho: Single axle trailers are allowed up to 24,000 pounds
• Iowa: Single axle trailers are allowed up to 20,000 pounds with pneumatic tires and 14,000 pounds with solid rubber tires
• Louisiana: Single axle trailers are allowed up to 20,000 pounds on designated highways, and 22,000 pounds on all other roads
• Massachusetts: Single axle trailers are allowed up to 24,000 pounds
• New Hampshire: Single axle trailers are allowed up to 20,000 pounds or 22,400 pounds if the gross weight is under 73,280 pounds
• New Jersey: Single axle trailers are allowed up to 22,400 pounds
• New Mexico: Single axle trailers are allowed up to 21,600 pounds
• New York: Single axle trailers are allowed up to 22,400 pounds
• Rhode Island: Single axle trailers are allowed up to 22,400 pounds

Gross Weight Restrictions

When it comes to hauling heavy cargo, gross weight is an important consideration beyond just cargo weight. The majority of states follow the regulation of 80,000 pounds gross weight. However, certain states have different allowances as outlined below (Note: in some cases, states will allow for heavier gross weight allowances than the standard):

• Alaska: Not specified
• Colorado: Gross weight equals 80,000 pounds on interstates and 84,000 pounds on non-interstate roads
• Kansas: Gross weight equals 80,000 pounds on interstates and 85,500 pounds on other routes
• Maine: Gross weight equals 80,000 pounds on interstates and 100,000 pounds on other highways
• New Mexico: Gross weight equals 86,400 pounds
• Oklahoma: Gross weight equals 80,000 pounds on state and interstate highways and 90,000 pounds on other roads
• Washington: Gross weight equals 105,500 pounds
• West Virginia: Gross weight equals 80,000 pounds except on local roads with a gross weight limit of 65,000 pounds
• Wyoming: Gross weight on interstates is 117,000 pounds, while the gross weight on other routes is 80,000 pounds

Width Restrictions

In general, states abide by the width restriction of 8 feet 6 inches. However, in some states there are exceptions based on the road or load type:

• Arkansas: 8'6", except for manufactured homes which have an 8’ limit
• Florida: 8'6", except for on roads less than 12’ wide which have an 8' limit
• Kentucky: 8'6" on national networks and 8' on other highways
• Michigan: 8'6" on designated highways and 8' on non-designated highways
• New York: 8'6" except on highways with a pavement width of less than 10’ in which case it is an 8’ limit
• West Virginia: 8'6" except on local service routes less than 10’ wide where an 8’ limit is in place

Height Restrictions

The majority of states allow for a standard height of 13 feet and 6 inches before necessitating special permitting. The following are states that operate with different regulations: 

• Alaska: 15'
• Arizona: 14'
• California: 14'
• Colorado: 13'
• Idaho: 14'
• Kansas: 14'
• Louisiana: 14' on designated highways and 13'6" on all other roads
• Maine: 14', 13'6" on Maine turnpike
• Missouri: 13'6", 14' on designated highways
• Montana: 14'
• Nebraska: 14'6"
• Nevada: 14'
• New Mexico: 14'
• North Dakota: 14'
• Oregon: 14'
• South Dakota: 14'
• Texas: Height 14'
• Utah: 14'
• Washington: 14'
• Wyoming: 14'

Your Partner for Semi Trailer Acquisition

When it comes to choosing a semi trailer, the right dimensions and load capabilities are critical to getting the job at hand done. Whether you are hauling goods around town or across the country, at Transwest, we are here to help you acquire the trailers you need to get the job done. Talk to our knowledgeable staff today about purchasing additional trailers for your fleet.