A grievance arbitration tribunal formed by the National Mediation Board (NMB) to resolve minor disputes between an individual railroad and union covered under the Railway Labor Act (RLA). Public Law 89-456 authorizes the NMB to set up a PLB on the written request of either party. That law also authorizes parties to form a special board of adjustment to arbitrate minor disputes about specific types of grievances that the parties designate.

For more information, see Practice Note, Railway Labor Act: Overview.