What is the maximum speed limit on the interstate if it is posted as 70 MPH?

In South Carolina, if the posted speed limit on the interstate is 70 MPH, then the maximum speed limit is indeed 70 MPH itself, as the posted limit indicates the maximum lawful speed at which vehicles may travel under ideal conditions. The posted speed limits are determined by traffic regulations to ensure safety and efficiency on the highways.

Other choices represent lower speeds that are not the legal maximum under these conditions. Such limits, like 60 MPH, 65 MPH, or 55 MPH, could potentially represent default speed limits in absence of posted speeds, or might be applicable in specific circumstances or zones, like urban areas or construction zones. However, in the context of a posted limit of 70 MPH, that specific number becomes the authoritative maximum speed, making it clear that any lower limits are not the correct interpretation of the situation.