FreightViking is reader-supported. We may earn commissions if you buy through our links. Also, as an Amazon Associate we earn from qualifying purchases.

Why Are Semi Trucks So Tall? (15 Facts You Didn’t Know!)

Are you curious as to why semi trucks are so tall? 

Is it because of consumers’ demands? Or is it the result of natural progression? 

If you want to know the reasons, read on to find out more…

Here’s a short summary of why are Semi Trucks so Tall:

Semi trucks are so tall because of their design. They are heavy-duty vehicles that have large components; engines, tires, and axles that sit high above the ground. A truck’s primary function is to transport cargo, which is typically stacked tall in the trailers they pull to optimize load capacity.

How Tall are most Semi Trucks?

The average height of semi trucks is about 9 to 10 feet, while the maximum size is around 13 to 14 feet. 

The federal regulations don’t limit the height of semi trucks. It is the local state law that imposed height restrictions.

In most state laws, a height of 14 feet, loaded or not, is prohibited. The exception is a double-deck bus that can be as tall as 14 feet, 3 inches.

Some state jurisdictions will only allow a height of more than 13 feet when the semi truck operates on open highways. For this reason, most manufacturers build a semi truck with a height of 13 feet.

How Tall is a Box Truck?

Box truck or cube van is typically used for the transport of furniture and appliances.

It has a maximum height of 9 feet, while the dock height is between 48 to 58 inches.

The higher the dock, the easier it would be to load and unload cargoes inside the box truck using a leveler for forklift.

Overall, the height of the box truck is compliant with state regulations. Hence, there’s no need to worry about traveling across the United States to deliver cargoes.

What is the Legal Height for a Semi?

US state laws are not uniform when it comes to the legal height for a semi truck.

The State’s Department of Transportation (DOT) is responsible for setting up height limits in a State’s respective jurisdiction.

In general, the maximum legal height for a semi truck across the United States is 13 feet. Some states like New York, Pennsylvania, and Chicago imposed a legal height of more than 13 feet but less than 14 feet.

There are also states like California having 14 feet height limitations.

Check your state law to determine the legal height of semi trucks imposed in your area.

Why are Semi Trucks so Tall?

Semi trucks are tall because most State laws in the US say so. 

There are no federal regulations that limit a truck’s height. However, every State’s local transport agency imposed height limitations because of lower clearances in their jurisdiction.

The height limitations are means to protect the commercial OTR drivers.

Every State has imposed particular height for their bridges, underpass, or overpass. Their guidelines let the truckers know the maximum height limit of a truck that can safely pass through them.

Once a driver overlooks the “low bridge” clearance sign, it may lead to severe damage to the vehicle, driver, and cargo.

Moreover, another reason why trucks are tall is that they haul freight and travel in distances.

They carry oversized cargo, and the road can be rough and bumpy. It may touch the ground if they are not tall enough. 

So, in general, semi trucks have to be tall for safety.

How Tall is a Semi Truck Suspension Above the Ground?

Suspension height is the term used for ground clearance or rides height. It is the space between the ground and the axle or any part of the semi truck.

The suspension height varies depending on the model of semi truck.

Typically, the suspension height for semi trucks varies between 35 to 50 inches.

You can determine the suspension height of your truck through the vehicle manual. 

The suspension height should not be too high nor too low.

Why do Semi Truck Suspensions Sit High Above the Ground?

Semi truck suspensions are set higher for improved vehicle performance. Since semi trucks are loaded with oversized cargoes, they may hit the ground during the trip if a high suspension height is not observed.

Semi trucks usually travel in far and off-road distances. If the suspension height is low, the components underneath the semi truck may be disturbed.

In this case, the springs and shocks of the suspension are likely to be damaged.

On the other hand, if the suspension height is set too high, it may result in tire wear. It may need great steering effort as the vehicle will be challenging to handle.

How Tall is a Semi Truck Cab?

Typically, a semi truck cab in a semi-truck and trailer configuration is approximately 13 to 14 feet tall from the ground. A semi truck cab in a box truck configuration is approximately 6 feet tall from the ground. The tallness of a semi truck cab vary and will depend on the semi truck design.

If you don’t know which part of a semi truck is the truck cab, it is the part that holds the engine and the driver. The truck cab is where the truck driver is seated.

Why is the Truck Cab so High of the Ground?

As mentioned, the engine of the semi truck is located in the truck cab. It occupies the front area of the semi truck.

There are also huge components mounted in the front part of the truck, e.g., the steering system.

If the truck cab is not high enough, it will be difficult for the driver to see the road.

Even the driver sits in a higher position; it’s still difficult for him to see what’s over the engine. 

Thus, the need for truck drivers to maintain a proper distance from the vehicle in front of them.

But don’t look at this situation as a disadvantage. The higher the truck cab, the more you can see the condition of the traffic or the road as a whole.

How Tall is a Semi Truck Engine Above the Ground?

In general, the engine and other components underneath have a distance of at least 1 feet or 12 inches from the tire.

This means that a semi truck engine will typically be positioned approximately 50 to 60 feet above the ground.

Why does a Semi Truck Engine Sit High Above the Ground?

The semi truck’s engine is enormous, hence the need to be as high as possible to prevent oil dinged up. 

Semi truck engines also have increased horsepower. As such, it needs to be placed in an uplifted position for cooling. 

The more the engine is placed in a higher position, the better the handling of the steering system.

How Tall is a Semi-Trailer from the Ground?

The standard height of a dry van semi trailer is approximately 13.5 feet above the ground. This means that a standard semi trailer can safely go under an overpass on the interstate as the national standard clearance of all overpasses on U.S. Interstates is 13.5 feet.

Here is how tall some of the most popular semi-trailers are from the ground:

Dry van trailer13’6″
Reefer trailer13’6″
Conestoga trailer13’6″
Pup trailer13’6″
Intermodal trailer114″
Hot shot trailer36″ – 42″
Low boy trailer18″ – 24″
Flatbed trailer60″

How Tall is an Underpass?

Under the law, an underpass used by a large or emergency vehicle should be 13 feet and 6 inches.

The standard height of the underpass is not as high as bridges. It can also be smaller than the height limit required by law. The reason for this is the high costs of building an underpass.

As such, a truck of 13 feet tall may not be allowed to cross in some underpass in the US.

Can Semi Trucks Go Under All Underpass?

In general, not all semi trucks can pass through all underpasses in the US. While the required height of the underpass is 13 feet 6 inches, the standard dimension is usually reduced.

However, it is safe to say that a 10 feet semi truck may go under all underpasses.

Thus, a 13 feet truck may not be safe to use the facility.

What is the Standard Height of a Bridge?

The standard height of a bridge in the US is around 14 to 16 feet. In most states, the height limit is 14 feet.

Under the Federal Highway Administration (FHA), bridges in the US should not go lower than 14 feet and not exceed 16 feet. The goal of the regulations is to have at least 1 feet allowance for the bridge and the tallest vehicle allowed by law.

It is meant to avoid the bridge getting struck by a large commercial truck which is the usual implication of low vertical clearance.

Make sure to know the law of the State you’re going to travel to. If you fail to do so, it may result in damage to the vehicle, the bridge, and the safety of the driver and other people around.

Can Semi Trucks Go under All Bridges?

Not all semi trucks can go under all bridges. 

The maximum height of a semi truck is 13 feet. If your semi truck is high as the maximum limit, you can’t pass through the bridges of various states in America.

Although the FHA has set a height limit in bridges, some states like North Carolina have bridges with a height of less than 12 feet.

If this is the case, semi trucks may crash or hit the bridge. It may result in fatal accidents.

It’s extremely important to be wary of the bridge height restriction along your route.