Iowa Code § 327D.75: Joint tariff schedules.

The names of the several common carriers which are parties to any joint tariff shall be specified in the schedule showing the same. Unless otherwise ordered by the department, a schedule showing such joint tariff need be filed with the department by only one of the parties if there is also filed with the department, in such form as the department may require, a concurrence in such joint tariff by each of the other parties thereto.