To expedite the settlement of claims between shippers and common carriers, a shipper may join in the same complaint against a common carrier any number of claims for overcharges, or a common carrier may join in the same complaint any number of claims against a shipper for undercharges, whether such claims arose at the same time or in the course of shipments at different times; provided, that each such claim shall be so identified that the same and the allegations with respect thereto may be distinguished from other claims so joined in the complaint, and in cases in which the right of subrogation may be invoked the judgment shall specify the amount of recovery, if any, on each such claim. For the purpose of jurisdiction under this section the aggregate amount set out in the complaint shall be deemed the sum in controversy. Provided, however, that this section shall not apply to motor carriers of passengers. (1947, c. 1008, s. 20; 1963, c. 1165, s. 1.)