This subtitle does not apply to the erection or maintenance of any school bus waiting shelter displaying outdoor signs if: The advertising does not exceed 32 square feet; The shelter has no more than one sign facing in any one direction; and The shelter has no more than two signs in all. All outdoor signs on school bus waiting shelters are subject to applicable local zoning regulations and standards approved by the State Highway Administration and, in an area to which Part IV of this subtitle applies, that are consistent with the Code of Federal Regulations regarding national standards for outdoor signs on interstate and federal–aid primary highways.