49 CFR 105.50 - Serving a subpoena.
(a) Personal service. Anyone who is not an interested party and who is at least 18 years of age may serve you with a subpoena and fees by handing the subpoena and fees to you, by leaving them at your office with the individual in charge, or by leaving them at your house with someone who lives there and is capable of making sure that you receive them. If PHMSA issues a subpoena to an entity, rather than an individual, personal service is made by delivering the subpoena and fees to the entity's registered agent for service of process or to any officer, director or agent in charge of any of the entity's offices.
(b) Service by mail. You may be served with a copy of a subpoena and fees by certified or registered mail at your last known address. Service of a subpoena and fees may also be made by registered or certified mail to your agent for service of process or any of your representatives at that person's last known address.
(c) Other methods. You may be served with a copy of a subpoena by any method where you receive actual notice of the subpoena and receive the fees before leaving the hearing at which you testify.
(d) Filing after service. After service is complete, the individual who served a copy of a subpoena and fees must file the original subpoena and a certificate of service with the PHMSA official who is responsible for conducting the hearing.