How Do Truck Weigh Scales Work?

Truck weigh stations are something you were probably already aware of long before deciding to become a professional truck driver. You see them all the time along the freeways of California. Whether you are just starting your schooling at America Truck Driving School or are a seasoned long hauler, it is good to know why weigh stations exist and how truck weigh scales work.

The Need for Truck Weigh Stations

Vehicles that weigh over 10,000 pounds (5 US tons) are required to stop at weigh stations. There are 65 weigh stations throughout California and hundreds more across the country. They are there to ensure that large commercial trucks and trailers meet state and federal safety standards.

One common concern in trucking is overloading. This means the truck and trailer are filled beyond the recommended weight capacity. This can lead to serious safety issues for the truckers and others on the road. An overloaded truck could be more difficult to control or brake, which increases the likelihood of accidents. Stopping at the weigh stations to confirm the weight of the truck, trailer and cargo is a way to help keep overloaded trucks off the highways. 

How Weigh Scales Work

There are actually several different types of weigh scales, which we will describe later. Most truck weigh scales include the following three features:

Weighbridge—This is the main steel or concrete deck where the truck driver will pull their tractor-trailer. They are designed to fit large commercial trucks with heavy weights.

Load Cells—These are the sensors that actually measure the weight of the trailer. Different types of truck scales may feature different types of load cells to provide the most accurate weight readings. A group of load cells will sit under the weighbridge. As pressure is applied from the tractor-trailer on top, the load cells will compress. Each cell sends out an electrical signal to the junction box. 

Junction Box—All of the load cell readings will be combined in the junction box to provide the scale operator with a single vehicle weight. This data is then run through software to ensure the truck meets the weight requirements. Because the data is measured through individual load cells, the scale may also be looking for weight imbalances. That can be another regulatory concern checked at some weigh stations.

Types of Truck Scales

Below are the most common types of truck weigh scales you will encounter:

Platform Truck Scale—This is a static scale system that uses a weighbridge platform. The driver will enter on a ramp. Once the full truck and trailer are on the platform, the weight can be measured.

Axle Scale—Axle scales are a bit more complex. They are smaller platforms. The driver is required to move the vehicle along and stop on the platform one axle at a time.

Weigh-in-Motion—Some weigh stations will have a weigh-in-motion scale rather than a static platform or axle scale. In this case, the truck driver will move slowly across the scale to determine measurements including gross truck weight, axle spacing and per-axle weight.

Multi-Platform Portable Truck Scale—Portable truck scales are used by many trucking companies that want to have accurate weight readings of their trucks before sending them off. This is a good method to prevent any weight issues or transportation delays at weigh stations. Trucks can be sent out on the road already meeting the weight requirements, making weigh station stops easier for the driver.

This is a basic overview of why we have truck weigh stations and how these truck weigh scales work. If you are interested in becoming a commercial truck driver or looking to further your trucking career with more education and job opportunities, apply for America Truck Driving School. Learn more by visiting our website or contact us with your questions.