How Heavy Duty Trucks Carry The Weight – Understanding Vehicle Systems

When you’re on the highway, you’re bound to see a number of semis and heavy-duty trucks transporting goods across the country. These vehicles are an essential part of the transportation industry and supply chain. In fact, according to the American Trucking Associations, nearly 71% of all freight tonnage moved in the U.S. goes on trucks!

The trucking industry is responsible for transporting everything from consumer goods and raw materials to medical supplies and food products. To that end, they are designed to operate in a way that allows them to transport large amounts of cargo over long distances both safely and efficiently.

Heavy trucks need to be able to support the weight of the load in tow. But it has been said that semi trucks help support the weight of an entire economy. Let’s take a look at how these machines are designed and operate.

Design Features of a Semi Truck

The design of heavy-duty trucks and semi-trucks is optimized for the unique challenges of long-haul trucking. For example, these trucks typically have large, powerful diesel engines and transmissions that can handle heavy loads and long distances. The engines are optimized for torque rather than speed, allowing them to move heavy loads with relative ease. To achieve this, the transmissions often have multiple gears to allow the driver to find the optimal gear for the current load and terrain.


Heavy-duty trucks also have specialized suspension systems that help absorb the shocks and vibrations of the road. This can include air suspension systems, which use compressed air to provide a smoother ride. Additionally, trucks use shock absorbers designed to handle heavy loads.

The brakes on these trucks are also designed to handle the increased weight and momentum of a fully loaded trailer. Many trucks have air brakes, which use compressed air to actuate the brakes. In turn, this provide a more powerful and reliable stopping force.

Semi Truck Cab View


Aerodynamics is an important consideration for heavy-duty trucks. This is because reducing wind resistance can improve fuel efficiency. It can also reduce wear and tear on the vehicle. Many trucks have sloping fronts and other design features to reduce wind resistance and improve fuel economy.

Since heavy-duty trucks are designed to haul large amounts of cargo, there are also considerations in the engineering. Most often hauling occurs in the form of trailers. When fully loaded, the trucks must endure several tons of weight. However, they must remain maneuverable and fuel efficient. Yet, they must remain comfortable to the operator. This is a delicate balancing act the engineers must maintain when designing semis.

All of these influence the considerations influence the design of the semi in use. Let’s start by taking a closer look at the main workspace of the driver: the Cab.

Semi Truck Cab Designs

Semi truck cabs come in various designs, each with its own set of advantages and disadvantages. Understanding these designs can help truckers make the best choice for their needs. One common example is the difference between a driver with a local route and another driver hauling goods across country. Clearly, the daily needs of each driver are going to be different. With that in mind, below are some descriptions of the different semi truck cab designs.

Conventional Cab

The conventional cab design is one of the most common cab styles for semi trucks. Many Freightliner trucks are commonly associated with this design. This conventional design features a long hood and a separate cab that is mounted behind the engine.

The hood allows for greater engine cooling and a larger engine. The separate cab provides more spacious living quarters for the driver and passenger, with greater headroom and improved visibility. However, this design choice makes the truck longer and less maneuverable in tight spaces. This design is popular for long-haul truckers who spend extended periods traveling on the road.

Cabover Cab (COE)

The cabover, also known as a COE (cab over engine) or flat nose design, has the cab mounted directly above the engine. Kenworth and Peterbilt are commonly known for their COE semi truck designs. The COE allows for a shorter overall length and much better maneuverability in tight spaces.

The cabover design also provides better visibility and easier access to the engine for maintenance and semi truck repairs. However, cabover cabs are typically smaller and can be less comfortable for long-haul trips due to limited headroom and cramped sleeping quarters.

Heavy Duty Trucks from above

Mid-Roof Cab

The mid-roof cab design features a slightly shorter height than a full-height cab. This design offers some of the advantages of a full-height cab, such as greater headroom and storage space, while providing improved fuel efficiency and a more aerodynamic profile. Mid-roof cabs are often used for regional hauling or urban delivery routes.

High-Rise Cab

The high-rise cab design provides additional headroom for standing up inside the cab. This design is popular for drivers who spend a lot of time in the cab and prefer a more spacious and comfortable living area. Kenworth trucks are often focused on this design in modern-day machines. The high-rise cab also offers additional storage space and amenities. Some examples include a refrigerator or microwave, making it an excellent choice for drivers that cover long extreme distances.

Overall, the choice of cab design will depend on the specific needs and preferences of the driver and the type of driving and hauling they will be doing. Each design has its own unique advantages and disadvantages. Understanding these differences can help drivers make an informed decision when choosing a semi truck.

Heavy Cargo and Freight Hauling

As heavy-duty trucks are designed to carry large amounts of cargo, the item being hauled is almost as important of a tool as the tractor itself. Most often, this comes in the form of trailers that are up to 53 feet long. The trailers may be refrigerated or have specialized compartments for carrying specific types of cargo, such as livestock or hazardous materials.

Finally, heavy-duty trucks are equipped with a range of safety features to protect the driver, other motorists, and the cargo. This can include systems like collision avoidance, lane departure warnings, and automatic emergency braking. Many trucks also have cameras and other sensors to help the driver monitor blind spots and other potential hazards.

How a Service Manual Can be Helpful

A service manual or repair manual can be an invaluable resource for the operator of a semi-truck, especially in the event of a breakdown on the road. These manuals provide detailed information on how to diagnose and repair common issues with the vehicle, allowing the driver to quickly and efficiently get back on the road.

In many cases, a service manual will include step-by-step instructions on how to troubleshoot various systems in the vehicle, such as the engine, transmission, brakes, and suspension. This can help the driver quickly pinpoint the source of the problem and determine the appropriate course of action. The manual may also include information on common causes of breakdowns and tips for preventing future issues.

In addition to providing troubleshooting and repair information, a semi truck repair manual can also be helpful for routine maintenance tasks, such as oil changes and tire rotations. These tasks are essential for keeping the vehicle in good working order and preventing breakdowns on the road. The manual may include recommended maintenance schedules and instructions for performing these tasks, helping the driver stay on top of routine maintenance even when they are away from a service center.

Classic Heavy Duty Truck Models

It’s hard to talk about trucking today without looking at the classic designs of the past. Semi trucks have been supporting the economy for many decades, so let’s take a look a few of these hard working machines of yesterday – some of which remain on the road today!

Peterbilt Model 359

The Peterbilt Model 359 was first introduced in 1967 and quickly became one of the most iconic and recognizable semi trucks in history. Known for its distinctive long-nose design and powerful diesel engine, the 359 was a favorite of long-haul truckers for decades. The truck was also known for its reliability and durability, with many models still in use today as show trucks and working vehicles.

Kenworth W900A

The Kenworth W900A was another classic semi truck model that was first introduced in the 1960s. The truck was known for its powerful diesel engine and rugged construction, making it a popular choice for heavy-duty applications. The W900A was also notable for its classic styling. This is a result of a long-nose design and chromed accents that made it stand out on the road.

Freightliner FLB Cabover

The FLB was a popular long-haul truck model introduced during the 1980s. It was known for its compact design and maneuverability that made it ideal for navigating tight city streets and highways.

Equipped with a range of driver-centric amenities, including a comfortable sleeper berth and easy-to-use controls, the FLB provided ample power for hauling heavy loads over long distances with its diesel engines, including the Detroit Diesel Series 60 and Cummins N14.

With its sturdy chassis and reliable performance, the Freightliner FLB Cabover remains a popular choice among truckers today.

Recent Heavy Duty Truck Models

Of course, like all things, semi trucks have progressed with the times. New models include features like GPS, satellite television, internet and collision avoidance. Let’s take a peek at some top models from recent years.

Volvo VNL Service Manual Set
Volvo Truck Service Manuals

Volvo VNL Series

The Volvo VNL Series, also introduced in 2017, is another modern semi truck designed for long-haul applications. The VNL Series features a comfortable and spacious cab designed to maximize driver comfort and productivity. Equipped with advanced technologies, including fuel-efficient engines, aerodynamic design, and advanced safety systems, the VNL Series is engineered to provide drivers with a superior driving experience.

International LT Series

The International LT Series is a modern semi truck that was also introduced in 2017. The truck is designed for long-haul applications and is equipped with a range of advanced features. The LT Series is also notable for its driver-centric design, with a spacious and comfortable cab that is designed to reduce driver fatigue and improve productivity.

Heavy Duty Trucks Carry A Supply Chain

Overall, heavy-duty trucks and semi-trucks are designed to operate in a way that allows them to move large amounts of cargo over long distances safely, efficiently, and reliably. These impressive vehicles play an essential role in keeping goods flowing across the country. Consequently, their design is a testament to the ingenuity and innovation of the transportation industry.