Since trench drains come in various widths, most authoritative bodies have adopted modified ASSHTO M-306 as the standard for static load testing protocol. Unlike the European standard that some manufactures advertise, Modified AASHTO is true application based standard that has saftey factors built into the classification. European Standards are based around the failure, or ultimate strength of a grate.
Following the test the casting is carefully inspected. Cracks or permanent deformation are cause for rejection. Frequently, ABT Inc grates are tested far beyond the specified proof load, often to destruction
Static Load Classifications