The degree of control needed when transporting radioactive materials is called the _________.

Some packages of Class 7 (radioactive) materials bear a number called the transport index. The shipper labels these packages Radioactive II or Radioactive III, and prints the package's transport index on the label. Radiation surrounds each package, passing through all nearby packages.
To deal with this problem, the number of packages you can load together is controlled. Their closeness to people, animals and unexposed film also is controlled. The transport index tells the degree of control needed during transportation. The total transport index of all packages in a single vehicle must not exceed 50.