Final answer:
The Department of Transportation is responsible for overseeing the construction and maintenance of interstate highways, a role stemming from the Federal Highway Act of 1956 which initiated the federal interstate system.
Step-by-step explanation:
One role of the Department of Transportation is overseeing the building and maintenance of interstate highways. This role has been evident since the Federal Highway Act of 1956, which led to the construction of the federal interstate system and its 40,000 miles of highways. The Act was a national defense initiative that also facilitated private and commercial transportation. It received strong support from automobile and oil companies but had mixed effects on smaller cities and towns.
Additionally, the federal government exercises power over the states by way of Fiscal Federalism, using federal highway funds to influence state laws and policies, including the coordination of a national transportation system. This collaboration between the federal and state governments reflects their shared responsibility for building and maintaining the network of interstates and highways.