The American Association of State Highway and Transportation Officials is a nonprofit, nonpartisan association representing highway and transportation departments throughout the United States. It represents all five transportation modes that include air, highways, public transportation, rail and water. It advocates transportation-related policies and provides technical services to support states in their efforts to efficiently and safely move people and goods. Its accreditation program recognizes the competency of a testing laboratory in construction materials testing and is available to all laboratories, including independent laboratories, manufacturers' in-house laboratories, and university and government laboratories. The program utilizes laboratory assessment and proficiency sample services provided by the its AASHTO Materials Reference Laboratory and the Cement and Concrete Reference Laboratory. It is located in Washington, D.C.