What Is the Legal Width of a Trailer?

Author: HALIM
Updated On:

There’s hardly anything you buy at the mall that didn’t make its way there through a trailer. However, that’s only one use out of the many you can get out of trailers.

Trailers come in many different forms and have many other uses, from transportation to residency, so there are lots of laws governing them.

There are laws detailing how much a trailer can carry, where it can carry these loads, along what routes, and at what times. And, of course, there are laws regarding the actual size of the trailer. This begs the question: how wide can a trailer be on the road?

Legal Width of Trailers

Before going into the legal width of trailers, the definition of a trailer and a trailer car must be clear. 

A trailer refers to the vehicles attached to the trucks. Since the trailer is attached to the car, it is commonly known as a trailer car.

The width of a trailer is an indicator of how much stuff can be loaded in it. There isn’t a straightforward answer to the legal width of a trailer, and it varies depending on where you are. However, we can give general numbers based on international definitions of a trailer and car trailer.

The maximum width of a car trailer is 2.55 meters (8.4 feet) on a paved road, whereas, for an unpaved road, the maximum width is 2.20 meters (7.2 feet). The maximum width for trailers behind trucks and semi-trailers is the same as for cars. 

However, transportation statistics show trucks load more than 10 billion tons annually. This leads to problems such as overloading. In these cases, the suitable maximum width can be 2.60 meters (8.5 feet). 

Specifications According to Different CountriesTrailers

As we said above, the legal width of trailers varies from country to country and even from state to state.

According to the US Department of Transportation, the maximum width for commercial autos and semi-trailers is 8.5 feet. So, while traveling on the road, if the width limit is eight feet, the trailer must be thinner than that.

In Europe, since the streets are generally narrow, the legal width of the trailer is about seven feet. Truck drivers are well aware that for traveling purposes, they must keep the width of the trailer and the size of the roads in mind. 

There are various widths allowed for trailers. Currently, the widest width is around 102 inches. The width of an eight-foot-wide trailer is a utility trailer. Utility trailers are a common means for the transportation of equipment or cargo, and you can adjust the trailer width depending on the kind of equipment. 

However, the rules may differ if you’re using another type of trailer.

Common Trailer Types

Today, there are different types of trailers with varying lengths, widths, heights, and maximum load capability. Let’s skim through the common types of trailers and their legal dimensions.

Dry Van Trailers

Dry van trailers are one of the most commonly used trailers in the transportation industry.  

These are the priority when it comes to dock-to-dock shipments or lost commodities. Established industries use dry vans to transport their inventories from one place to another. 

They are up to 53 feet long, and the maximum weight they can legally carry is around 42,000 to 45,000 pounds. They are about 8 feet wide and are unsuitable for carrying massive loads.  

Flatbed Trailers

When it comes to versatility, flatbed trailers are your go-to solution, as you can quickly load stuff in from the sides, thus making versatility its vital feature. They can bear heavy loads because they are not in the shape of a defined container.

They come in different sizes, and you can determine the maximum legal dimensions as per permission by the law, as there are provisions for overloading. The typical dimensions without legal intervention include 8 feet in width and height. Flatbeds come in different lengths, with the 48 feet and 53 feet models being the most popular. The maximum weight capacity of a flatbed is around 48,000 pounds.  

Refrigerated Trailers

Refrigerated trailers, also known as reefers, are used to carry products sensitive to temperature changes, such as seafood. Thus, temperature control is required to maintain the quality of products throughout the journey. 

These trailers are designed to ensure temperature regulation by having insulated walls and other advanced techniques. The products usually transported in reefers include canned food items, dairy goods, medicines, and food from a farm. The maximum weight limit for reefers is about 42,000 to 45,000 pounds and goes up to 63,000 in the case of trailers with tri-axle. 

Due to an extra feature of insulated walls, the length increases compared to the dry vans. It is about 8.2 feet, but it does vary with the thickness of a particular trailer’s walls. 

Step Deck Trailers

Step deck trailers have another name – drop deck trailers. They are more or less just like a standard flatbed trailer. An added height feature makes this type of trailer unique from other kinds.

This type of trailer is usually used when you haul units above 10 feet. In the transportation industry, step deck trailers are typically seen to carry agricultural and building materials or other materials related to the machinery.

The maximum cargo load limit for drop deck trailers is 48000 pounds. They are around 43 to 48 feet in length and 8.5 feet wide.

Reasons for Limits on the Width of a Trailer

There are several reasons why there are limits to trailer sizes. One reason is that overly wide trailers can easily hinder the view of other drivers causing deadly accidents during turning. Furthermore, wide trailers can take on more load.

While this could potentially cut down on travel times, the continual shifting of heavy loads can wear out roads and eventually cause cracks. This will then require the extra expense of fixing the damage to lives and property.


Factors Affecting the Trailer’s Width

Well, different types of trailers have various widths. The width depends upon the trailer category and the road’s width. The road must be wide to support a huge trailer. Wide trailers cannot adjust on narrow streets.

For example, a trailer can be up to 14 feet wide in Utah because the state has roads that can accommodate them and make maneuvering such huge vehicles possible. Trailers that have a width above this need a special permit to drive the equipment on the road. 

Overloading Trailers: Rules and Regulations

You cannot overload most trailers because their sides are enclosed. But when you have a load that extends over the edges of a semi or a flatbed, it is oversized. Of course, if the load surpasses a state’s maximum height and weight, it is also considered oversized, regardless of its positioning. 

Almost all states have laws imposing restrictions on cargo exceeding 102 inches in width. All loads that exceed this measurement have to get permits to be allowed on roads. However, other factors might play a role in whether you’ll be able to gain access to a permit or not. 

Factors Affecting Overloading Permissions

  • Additional Permit: If a load surpasses a width of 144 or 168 inches, most states require additional permits or fees and other special arrangements, including an escort. 
  • Overweight: If a load is overweight and oversized, it may need even more additional permits.
  • Surface Streets: Some streets are incredibly narrow and may require permits for regular loads.
  • Superloads: Any cargo over 192 inches wide is defined as a superload and needs additional permissions and arrangements.

Fees for Permissions

When requesting additional permissions, you will be required to pay some fees. These fees vary from state to state and from load to load. However, you can pay as little as $15 to as much as $80. There may also be fees needed to process the application. 

If you think you may need to purchase these permissions frequently, there are accounts that you can set with your state that may help you reduce these charges. If not, you can get one-time permits to move these loads or even multiple permits to move similar loads.

Permits, Regulations, and Escorts

Although you’ll be required to pay fees for hauling oversized loads, you must also follow some safety regulations. These safety regulations include escort requirements, signage, route and travel limitations, flags, etc.

  • Safety Equipment

The most basic requirement in most states for overloaded trailers is for the vehicle to have a yellow and black sign boldly stating “OVERSIZED LOAD” or something to that effect. You should also attach warning 18-inch flags in red or bright orange at the front and end of the vehicle/load.

If the load has protrusions far from the side of the vehicle, you should also add a flag there. In some states, your vehicle needs to be flagged on all corners.

  • Escorts

Most states do not require escorts for loads under 10 feet wide. However, for loads between 10 and 14 feet, most states do need one to two escorts at the front or back of the vehicle. Some huge loads require law enforcement escorts.

  • Travel Times

Many states have stipulated travel times for overloaded trailers. These times differ from one state to another but are usually not applicable on Interstate roads. You should carefully research what these times are when switching to state highways. 

Frequently Asked Questions (FAQs)

1. What’s the maximum legal width to require a permit?

In some cases, such as in Massachusetts, the most exhaustive load allowed is 24 feet wide. But these extremely rare cases require a permit. Without a permit, it would cause problems for the truck driver. Applying for a permit ensures your safety, and you can apply for it through the States Department of Transportation.

If you’re not sure of what width requires a permit, a good rule of thumb is 10 feet. If your cargo is over 10 feet wide, you’ll probably need at least a single-user permit. However, if you are transporting oversized loads often, getting an account with your state government will help you cut costs in the future.

2. What are side marker lights?

Side marker lights play a significant role in highlighting the contours of your trailer. These lights are tiny orange lights on the sides of your trailer, thus accounting for the name side marker lights.

Just like red and white lights, make sure to enhance the look of your trailer from the back and front sides; these lights are responsible for making your trailer’s width more prominent. Apart from the fancy look, these lights make your trailer look wider than it is. 

3. What is the load limit of a semi-trailer?

The maximum load a semi-trailer can carry differs from state to state. The factors that help determine the maximum weight include the nature of the products in transport, the conditions of the road in that specific area, and the axle. These factors may also change when it comes to other states. The factors mentioned above focus more on North Carolina.


If you are using trailers for transportation, follow the legal guidelines for your safety and avoid future inconveniences. Also, take a look at the legal guidelines of your region and adjust the width of your trailer accordingly, or else you might find yourself in trouble sooner or later.

With the information above, you already have all the details you need to get a good deal on oversized loads if you exceed the legal width of a trailer.


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