The Interstate Commerce Commission (ICC) was the first transportation surface and sub-surface regulatory agency in the United States created by the Interstate Commerce Act of 1887. The agency's original purpose was to regulate railroads (and later trucking) to ensure fair rates, to eliminate rate discrimination, and to regulate other aspects of common carriers, including interstate bus lines, travel bureaus, and telephone companies.
Congress expanded ICC authority to regulate other modes of commerce beginning in 1906, including freight and passenger brokering, and pipelines. The agency was abolished December 31, 1995, and its remaining functions were transferred to the Surface Transportation Board. The Commission was the first independent regulatory body, as well as the first agency to regulate big business in the U.S.
Eventually, the ICC told the States what transportation the States would regulate. Also, these regulations were primarily written before air transportation. And furtherance of interstate transportation does not include air transportation.
The United States Department of Transportation (USDOT) was established by an act of Congress, signed into law by President Lyndon B. Johnson on October 15, 1966. Its first secretary, Alan S. Boyd, took office on January 16, 1967. The department's first official day of operation was April 1, 1967.
The USDOT primary function is "safety". Just prior to the ICC elimination, the USDOT officials stated that they would not enforce any economic regulations after December 31, 1995. January 1, 1996 the remaining ICC regulations, which were primarily economic regulations, were mingled with the USDOT regulations which are all located in Title 49 of the Code of Federal Regulations Sections 300 – 399. Some intrastate transportation regulations are found within the interstate regulations.
MOST individuals today applying for a USDOT number DO NOT know the difference between interstate and intrastate. The difference between interstate or intrastate TOTALLY depends on the origin and destination of the COMMODITY. It has NOTHING to do with the vehicle.