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How Wide Is a Tractor Trailer? (US Semi Trailers Dimensions)

Tractor trailers are a common sight. It doesn't matter where you travel, you're likely to see several of them in a single day being pulled by a semi truck tractor. There are many different kinds out there; Dry Vans, Reefers, Flatbeds, Lowboy trailers just to name a few. Have you ever wondered how wide a tractor trailer is? Maybe you've wondered about other things such as the different types of trailers and what they're used for. Perhaps you're more interested in knowing the exact dimensions of the most popular trailers and the types of permits required to operate them. You probably already know that it's vitally important for operators to know everything there is to know about the trailer that they are hauling from a safety standpoint, but why is this so crucial? Today's tractor trailers are used to transport all types of products around the country. In fact, they're used all over the world. Without a Refrigerated trailer, it would be almost impossible to purchase something as basic as a gallon of milk, without a flatbed truck bringing supplies to your local Home Depot, it would be hard to purchase supplies for your home project and without car haulers it would be difficult to move stock of regular passenger cars to your local dealer... But no matter the trailer type, almost everything we use in our daily lives is delivered by commercial vehicles.


Tractor Trailer Dimensions


When referring to a standard semi trailer, it's important to remember that dimensions such as height and length can vary to some degree. However, federal government stipulates maximum length, max width, legal height and weight limit for commercial motor vehicles.


Although there are more readily accepted dimensions for these types of measurements. When it comes to the maximum width of the trailer, it's almost always the same, 8.5 feet (102 inches).


Why does the overall width almost never vary? It all comes down to a matter of safety. It's crucial for tractor trailer operators to know all of the dimensions involved with the particular trailer in question. You can incorporate more axles on a longer trailer and you can certainly make trailers stand taller (within reason, of course). However, you can't really make the axles wider so the trailer width can be increased. By the same token, you don't want the trailer to be too wide because the roads are only so big. Make them any larger (in this case, any wider) and they're not going to fit on the road. Whenever cargo is wider than trailer, such cargo would be considered an oversized load and would require special permits. Another thing to consider is a turning radius. Making turns with a wider trailer can endanger passenger vehicles.


Just in case you're curious, the more widely accepted dimensions as far as total length and height are concerned are anywhere from 48 to 53 feet long and 13.5 feet tall. Also, maximum weight of a loaded tractor trailer per federal regulations is set at 80,000 lb. also known as maximum gross weight. As previously mentioned, there can be a number of variations here, so it's imperative that the individual operating that particular trailer know its overall length limit and legal weight before selecting the route they're taking. It is equally important to realize that each state within the United States sets their own regulations when it comes to maximum dimensions. As a result, there is no real maximum when it comes to height nor length. However, it's highly uncommon to see a tractor trailer that's more than 14 feet tall. In most states, anything that is above the aforementioned 53 feet long and 13.5 feet tall will require a special permit to be operated in the area. More will be discussed about the importance of knowing trailer dimensions from a safety standpoint later.




Different Types of Tractor Trailers


There are many different types of trailers that you can expect to see on the road. In order to keep things as orderly as possible, let's break each one of them down individually.

Dry Van Trailers

The most commonly used trailers are the dry vans. This is the one that you're likely to see nine times out of 10, the standard enclosed trailer that has an almost constant presence on the road. It's dimensions are usually quite standard, as follows:

Height: 13.5 - 14 ft

Length: 48 - 53 ft

Width: 8.5 ft

Flatbed Trailers

The next is the flatbed trailer, and exactly as the name implies, it is an open trailer. These trailers are typically used to haul construction materials and other types of equipment that can't be transported in an enclosed trailer.

Height: 13.5 - 14 ft

Length: 48 - 53 ft

Width: 8.5 ft

Step Deck Trailers

A variation of the flatbed trailer are various step deck trailers, a flatbed that has an elevated surface, or upper deck, that is approximately 10 to 11 fet long. The remainder of the trailer sits lower than a typical flatbed trailer. More often than not, the lower deck length is anywhere from 37 to 43 feet.

Height: 13.5 - 14 ft

Length: 10 - 11 ft (Upper Deck ); 37 -43 ft (Lower Deck)

Width: 8.5 ft

Double Drop Trailers

A third variation on this is the double drop trailer, which has an elevated surface on both the front and rear of the trailer, each of them approximately 8 to 10 feet in length. The remainder of the trailer sits much lower and is anywhere from 26 to 30 feet long.

Height: 13.5 - 14 ft

Length: 8 10 ft (Both Rear and Front Decks); 26 - 30 (Main Well)

Width: 8.5 ft

RGN Trailers

Another trailer known as the RGN trailer has an elevated rear deck and is attached with a fifth wheel. The rear deck is 8 to 10 feet in length while the main well of the trailer is anywhere from 26 to 30 feet long.

Height: 13.5 - 14 ft

Length: 8 - 10 ft (Rear Well); 26 - 30 ft (Main Well)

Width: 8.5 ft

Hot Shot Trailers

Similarly, you might see what is known as a hot shot trailer. This is essentially a flatbed trailer that is about 20-40 feet long and attaches with a fifth wheel.

Height: 13.5 - 14 ft

Length: 20-40 ft

Width: 8.5 ft

Cattle Trailers

The standard cattle trailer incorporates the same dimensions as the dry van trailer, only with openings that are designed to create air movement in order to transport livestock.

Height: 13.5 - 14 ft

Length: 53 ft

Width: 8.5 ft

Pup Trailers

Its smaller cousin, the pup trailer, is much shorter. As a matter of fact, it's only about 28 feet long.

Height: 13.5 - 14 ft

Length: 28 ft

Width: 8.5 ft

Reefer Trailers

These trailers are used to transport cargo requiring refirgiration. A lot of produce, meet and other food products are transported by Reefer trailers. This trailer is of standard height and width, with the length maxing out between 48 and 53 feet.

Height: 13.5 ft

Length: 48 - 53 ft

Width: 8.5 ft

Straight Truck

Last but not least, you have a special kind of truck referred to as a straight truck. These look a lot like tractor trailers (without sleeper cab) with pup trailers attached to them, but they're actually a completely different animal. That's because the entire vehicle is attached to a single chassis. The power plant, cab and trailer are all made into one piece. These types of vehicles are frequently used to transport smaller amounts of goods or even used by local or regional companies to deliver products.

Height: 13.5 - 14 ft

Length: Approx. 28 ft

Width: 8.5 ft

Special Permits and Safety Concerns


It's obvious why it's so important for truck drivers to know the exact dimensions of the trailer they are transporting. Being unaware could mean inadvertently getting on a road that isn't large enough to support one of these trailers or even encountering a low bridge that the trailer simply cannot fit under. That's why it's so important to plan the route ahead of time. What happens if a trailer's legal length is longer than usual? A special permit must be obtained in order for that particular trailer to be operated. It depends on the state in which the trailer is being operated which agency you have to go through in order to get that permit. For example, different states have different regulations and someone driving a trailer of this type in Texas will go through the Texas Department of Transportation. In California, it would be Caltrans. If you're operating the trailer in multiple states, you will have to get permission from each state that the trailer will be traveling through. These permits are typically only good for seven days and the trailer must follow an exact, predetermined route. In almost every case, escort cars are provided in order to ensure the overall safety of the general public and of the individual who is operating the tractor trailer.

As you can see, there is a lot that must be considered when operating any tractor trailer. The individuals who do so on a daily basis are truly experts in the matter. There is nothing particularly easy about operating something so large, but a skilled driver is capable of doing so and making it look like there's nothing to it. It all starts with knowing trailer dimensions, safety protocols and the different types of trailers that are commonly operated.


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