American Association of State Highway and Transportation Officials

AASHTO means American Association of State Highway and Transportation Officials. It is a standards setting body which publishes specifications, quality control protocols and guidelines which are used in highway design and construction throughout the United States. Despite its name, the association represents not only highways but air, rail, water, and public transportation as well.
Though AASHTO is not a government body, it possesses quasi-governmental powers in the sense that the organizations that supply its members customarily obey most AASHTO decisions. 
Besides its publications, AASHTO performs or cooperates in research projects.