Final answer:
The convoy approval authority for all DOD highway movements in each State is typically a high-ranking military official designated by the state's National Guard or other military authorities, whose role has been facilitated by the infrastructure created by the Federal Highway Act of 1956.
Step-by-step explanation:
The military official within each State who is the convoy approval authority for all Department of Defense (DOD) highway movements, both Active and Reserve components, is typically designated by the respective state's National Guard Bureau or by other military authorities within the state.
This position is often held by a high-ranking military officer, who may be supported by a team that helps manage the coordination and approval of military convoys utilizing the highway systems. The Federal Highway Act of 1956 played a significant role in creating the interstate system that these military movements rely upon, facilitating faster and more efficient travel for both military and civilian purposes.
The Act, passed during a period of reconstruction, established federal oversight of the reconstruction states and military districts which underscores how military authority can be structured on a state and federal level.
While the U.S. President holds the official title of Commander in Chief of the military, the actual management of specific tasks such as convoy approvals on highways is delegated to appropriate military officials at the state level.