>>3022157 We know who you are too, Harrison Ford. Vacuous minded simpleton. Sock puppet raver on demand. Wild eyed loser.
Easy answer in Wikipedia.
The National Transportation Safety Board is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and incidents, certain types of highway crashes, ship and marine accidents, pipeline incidents, and railroad accidents.
Probably historical. Historically many pipelines are on railroad rights of way.
Pipeline is def part of their mission.