A process agent is a representative who can receive court papers on behalf of a motor carrier, broker, or freight forwarder. Every motor carrier is required to make a designation for each State in which it is authorized to operate and for each State traveled while conducting business. Brokers are required to list process agents in each state where they have an office and write contracts. FMCSA Regulation 49 CFR Part 366 talks more about The Designation of Process Agents by Motor Carriers and Brokers.

From FMCSA:

Designation of Agent — A motor carrier or broker providing transportation subject to jurisdiction under chapter 135, including a motor carrier or broker operating within the United States while providing transportation between places in a foreign country or between a place in one foreign country and a place in another foreign country, shall designate an agent in each State in which it operates by name and post office address on whom process issued by a court with subject matter jurisdiction may be served in an action brought against that carrier or broker.