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1 - Truck Types and Volume The truck scale is mechanically and structurally designed to support the volume, gross vehicle weight (GVW), and axle group weight of the trucks that will be weighed. Two truck types often weighed by truck scales are over-the-road trucks and off-road trucks. Trucks that are designated to travel over roads must adhere to federal transportation weight and load restrictions. For example, the U.S. Federal Highway Administration (FHWA) of the Department of Transportation sets GVW and axle load limits based on the length of the vehicle. Bridge formula weight calculations set truck weight limits to protect roads and bridges from premature wear and failure.
Important Operational Considerations
• Scale traffic flow: Whether traffic is unidirectional or bidirectional, both will affect truck queuing, traffic control systems, and scoreboards. • One-pass or two-pass weighing: Capturing empty and full truck weights versus using stored tare weights can double scale house weighments per truck but provides a more accurate net weight per truckload. • Scale house and after-hours operation: Processing trucks after normal operational hours may require duplicating scale house systems. • Target truck processing time: Typical manual scale house processing can take up to 5 minutes per truckload. This can create a bottleneck with inbound and outbound trucks causing inefficiency and lines. Automating scale house operations can reduce truck processing to <1 minute. 2 - Configuring and Sizing the Weighbridge The most common truck scale configuration is a full-length scale which provides a single, legal-for-trade weight per truckload. Multi-axle truck scales provide legal-for-trade gross truck weight, as well as separate legal-for-trade sectional axle group weights to ensure proper distribution of loads. Axle scales check axle group loads as a non-legal-for-trade load compliance check. Axle scales can be used as static weighments or in-motion at lower speeds, typically <5 to 8 mph (8 to 12 kph). The deck of your weighbridge needs to physically accommodate the footprint of the largest truck you plan to weigh. It is recommended to size the truck scale by adding 10 feet to the length of the largest truck you plan to weigh. This allows faster and easier positioning on the scale for each driver. Many scale manufacturers will offer standard-sized weighbridges, but will also accept custom dimensions. If you are replacing a pre-existing scale and utilizing an existing foundation, you will need your new scale to fit those dimensions.
Truck Traffic Type
A fundamental determination for selecting the correct truck scale is determining traffic type: • Over-the-road vehicles • Off-road vehicles • Combination over-the-road and off-road vehicles Truck scales for off-road vehicles are designed to the specifications of the vehicle. For example, a CAT 797B off-road vehicle has a gross vehicle weight of 1.375M pounds or 687 tons on a 23.5-ft wheelbase, requiring a highly specialized weighing structure.
Single-Axle Truck Scale
Full-Length Truck Scale
Truck Volume
Scale weighbridge structures are designed for the average loads that will be applied over the life of the structure, which is typically 20 years. High volume loads can prematurely wear out the mechanical structure.
The typical truck scale processes <100 trucks per day on average and is considered low volume (<25,000 per year). High volume operations processing 200 to 500 trucks per day (50,000 to 125,000 trucks per year) may require heavier duty weighbridge structural designs. Seasonal operations may see high truck volumes during harvest or construction seasons, but on average may have lower annual truck volumes.
Multi-Axle Truck Scale
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