New Vehicle Weighing Laws - Mettler-Toledo

How is Handbook 44 amended? Handbook 44 is published with additions, deletions and revisions every year. Proposed amendments are submitted to the NCWM. These proposals may come from consumers, manufacturers, W&M officials or other interested par- ties. The NCWM carefully considers each amendment since it will affect weighing and measuring devices used in commercial transactions across the country. Amendments are developed and voted on by the NCWM membership, which consists of representatives from every US state. If an amendment is adopted, the changes are implemented into the next edition of Handbook 44. METTLER TOLEDO proposed amendment SCL-20.12 to add single draft weigh-in-motion vehicle scales to Handbook 44 in 2019. The amendment allowed vehicles to be weighed in motion as long as the scales still met existing ac- curacy requirements. After careful consideration and a demonstration of the new technology, the NCWM voted to adopt the SD-WIM amendment into the 2022 edition of Handbook 44.

This amendment allows vehicles to be weighed in-motion, as long as scales still meet existing accuracy requirements.

What are the Handbook 44 vehicle scale requirements? Handbook 44 defines requirements for vehicle scales to ensure they are accurate enough to provide fair commer- cial transactions. First, design requirements are defined for vehicle scales to ensure they will produce repeatable and accurate weighments with precautions against fraud. Indications and recorded information must follow stan- dard protocols for consumer clarity. Second, tests and their associated tolerances are defined. These tests include: increasing load tests, decreasing load tests, shift tests, sensitivity tests, discrimination tests, radio frequency interference tests, zero load balance change tests, temperature tests and permanence tests. These tests are either completed as part of the NTEP test or in the field using certified test weights. Finally, there are user requirements directed towards device owners and operators that apply to the selection, installation, use, and maintenance of ve- hicle scales. Vehicle scales must be single draft scales, meaning all axles of the vehicle must be on the platform simultaneously during a weighment. Installation requirements also define the appropriate approach lengths for vehicle scales, minimum/maximum loads, and concentrated loads. Prior to 2022, the HB44 requirements applied to static ve- hicle weighing only, meaning vehicles were required to come to a complete stop on the scale during a weighment. Starting in 2022, HB44 also allows dynamic vehicle weighing, meaning the vehicle may be in motion on the scale during a weighment. All requirements that applied to static vehicle scales also apply to dynamic scales with a few new requirements added for dynamic testing and fault detection.



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