AASHTO - American Association of State Highway and Transportation Officials
From the AASHTO website:
"AASHTO is a nonprofit, nonpartisan association representing highway and transportation departments in the 50 states, the District of Columbia and Puerto Rico. It represents all five transportation modes: air, highways, public transportation, rail and water. Its primary goal is to foster the development, operation and maintenance of an integrated national transportation system. . . the mission of AASHTO is to advocate transportation policies, provide technical services, demonstrate the contributions of transportation and facilitate institutional change."
Please refer to the 'Approvals' page of the listed locations for the exact scope of the approvals.
Related standards and specifications: