Hazardous Materials Safety Act of 1979 - Prohibits the operation of any locomotive which controls a train carrying hazardous materials if such locomotive is not equipped with a device which records and shows the locomotive's speed within six months of the enactment of this Act.

Directs each railroad subject to this Act to: (1) notify the Administrator of the Federal Railroad Administration (FRA) of the date on which such devices are installed; (2) maintain a schedule of the locomotives required to be equipped; and (3) provide the FRA or the National Transportation Safety Board with such device and any required records in the event of an accident or disciplinary action in which a railroad employee is charged with excessive speed.

Sets forth civil and criminal penalties for violations of provisions of this Act.

Amends the Independent Safety Board Act of 1974 to stipulate that any investigation conducted by the National Transportation Safety Board shall have priority over all other investigations of Federal or State agencies. Prohibits agencies participating in such an investigation from participating in the Board's determination of the cause of any accident. Authorizes members of the Board to take custody of any vehicle, rolling stock, track, or pipeline facility for examination necessary for a proper investigation.