carriermeans an express company, sleeping-car company, or carrier by railroad, subject to part I of the Interstate Commerce Act.
employermeans any carrier (as defined in subsection (b) of this section), and any company which is directly or indirectly owned or controlled by one or more such carriers or under common control therewith, and which operates any equipment or facility or performs any service (except trucking service, casual service, and the casual operation of equipment or facilities) in connection with the transportation of passengers or property by railroad, or the receipt, delivery, elevation, transfer in transit, refrigeration or icing, storage, or handling of property transported by railroad, and any receiver, trustee, or other individual or body, judicial or otherwise, when in the possession of the property or operating all or any part of the business of any such employer: Provided, however, That the term “employer” shall not include any street, interurban, or suburban electric railway, unless such railway is operating as a part of a general steam-railroad system of transportation, but shall not exclude any part of the general steam-railroad system of transportation now or hereafter operated by any other motive power.