Everything in this rulebook hangs off a phrase that sounds self-explanatory and is not. Under § 390.5T, interstate commerce means trade, traffic, or transportation in the United States in one of three situations: between a place in a State and a place outside that State, including a place outside the United States; between two places in a State but passing through another State or a place outside the country; or between two places in a State as part of trade, traffic, or transportation originating or terminating outside the State or the United States. Intrastate commerce is then defined purely by exclusion — § 390.5T calls it any trade, traffic, or transportation in a State which is not described in the interstate term. There is no positive test for intrastate; a movement is intrastate precisely when it fails to be interstate.

The third branch is where the real work happens, and it is the one that surprises drivers. It attaches the test to the journey of the FREIGHT, not the route of the driver. A leg that begins and ends inside one State is interstate commerce when it forms part of a movement that originated or will terminate somewhere else — so a short local run can sit inside the federal rules while a much longer one, wholly self-contained, does not. Distance is irrelevant. Crossing a State line is not required. What matters is whether the load you are carrying is partway through a longer trip.

That has a practical consequence worth fixing now, because it decides which rulebook you are reading. The same truck, the same driver and the same road can be in interstate commerce on Monday and intrastate commerce on Tuesday, purely because the freight changed. Applicability is a question you answer per movement, not once per career — and it is answered from the shipment’s paperwork rather than from the odometer.