Department of Transportation, an executive department of the U.S. federal government, created by law in October 1966 and officially established in April 1967 by the combination of transportation agencies or functions formerly dispersed throughout the government. The purpose of the department is to promote and develop rapid, safe, efficient, and convenient transportation in the United States. It is administered by a secretary appointed by the president of the United States and approved by the United States Senate.

The department is divided into a number of major divisions. The Federal Aviation Administration regulates air traffic and commerce in the United States (see Air Traffic Control). The Federal Highway Administration is responsible for highway construction, administration, and safety. The Federal Railroad Administration consolidates government support of rail transportation activities and advises the secretary on matters relating to rail transportation. The Surface Transportation Board has jurisdiction over railroad rate and service issues and reviews proposed railroad mergers (Government Regulation of Railroads). The Saint Lawrence Seaway Development Corporation oversees activities relating to the St. Lawrence Seaway. The National Highway Traffic Safety Administration determines the causes of motor-vehicle accidents and makes recommendations to promote highway safety. The Federal Transit Administration assists in the planning and development of improved mass transportation facilities and equipment. The Maritime Administration carries out programs to aid in the development and operation of the U.S. merchant marine. The Research and Innovative Technology Administration is responsible for rules governing pipeline safety and the safe transportation of hazardous materials, and it also conducts transportation research. The Federal Motor Carrier Safety Administration works to prevent accidents related to commercial motor vehicles, such as trucks and buses. The Pipeline and Hazardous Materials Safety Administration governs the safe movement of hazardous goods by all modes of transportation.