Semi Trailer

Introduction to Semi Trailer

Semi-trailers, known for their ubiquitous presence on highways and industrial zones, play a crucial role in the global supply chain. These powerful transportation tools allow goods to be moved in large quantities over long distances, effectively supporting economies around the world. But what exactly is a semi-trailer?

What is a Semi-Trailer?

A semi-trailer is a type of freight transport trailer designed to be pulled by a tractor unit, commonly known as a semi-truck or “big rig”. The name “semi-trailer” comes from the fact that the trailer’s weight is supported by its own wheels at the back and by the semi-truck at the front. This design makes semi-trailers distinct from full trailers, where axles are located at both the front and back.
FMCSA article on trailers.

Design and Functionality

The semi-trailer connects to the tractor unit via a hitch known as a fifth wheel coupling, allowing for a degree of movement between the truck and the trailer. This flexibility makes large semi-trucks easier to control than a rigid truck of equivalent length.

Size of a Semi Trailer

Let’s talk about how wide, how long and how tall is a semi trailer.

The dimensions of semi-trailers are regulated to ensure they can safely navigate roads and highways. Here are the typical dimensions:

How Long is a Semi Trailer

Length: The most common length for semi-trailers is 53 feet, although trailers used for less-than-truckload shipments (often called “pup” trailers) can be as short as 28 feet. Some states do allow longer trailers, usually up to 57 feet, but these require special permits and are less common.

How Wide is a Semi Trailer

Width: The standard maximum width for a semi-trailer is 8.5 feet. This is a federal limit and is consistent across all states. This does not include certain safety devices which may extend the width slightly.

How Tall is a Semi Trailer

Height of a Semi Trailer: The maximum height for a semi-trailer is typically 13.5 feet. This is to ensure the trailer can clear bridges, overpasses, and other overhead structures. Some states may have lower maximum height limits, so it’s important for drivers to be aware of the regulations in the states where they’ll be driving.

Weight of a Semi Trailer

The weight of a semi-trailer can vary significantly depending on its size, construction, and specific model.

Dry Van Empty Weight

An empty, standard 53-foot-long dry van semi-trailer typically weighs approximately 13,500 to 14,000 pounds (around 6,100 to 6,350 kilograms).
Learn more about the Dry Van semi-trailer here.

Reefer Empty Weight

A refrigerated trailer, also known as a reefer, usually weighs more due to the additional refrigeration equipment. An empty reefer trailer might weigh around 15,000 to 16,000 pounds.
Learn more about Reefer semi-trailer here.

Keep in mind that the total weight of a loaded semi-trailer must not exceed the federal maximum Gross Vehicle Weight (GVW) of 80,000 pounds in the United States. This weight includes the tractor unit, the trailer, and the cargo.

Trailer Types

We have a dedicated article about different types of semi-trailers here. 
Learn about Power-Only Trucking here.