Emergency means any hurricane, tornado, storm (e.g. thunderstorm, snowstorm, icestorm, blizzard, sandstorm, etc.), high water, wind-driven water, tidal wave, tsunami, earthquake, volcanic eruption, mud slide, drought, forest fire, explosion, blackout or other occurrence, natural or man-made, which interrupts the delivery of essential services (such as, electricity, medical care, sewer, water, telecommunications, and telecommunication transmissions) or essential supplies (such as, food and fuel) or otherwise immediately threatens human life or public welfare, provided such hurricane, tornado, or other event results in:
(1) A declaration of an emergency by the President of the United States, the Governor of a State, or their authorized representatives having authority to declare emergencies; by the FMCSA Field Administrator for the geographical area in which the occurrence happens; or by other Federal, State or local government officials having authority to declare emergencies, or
(2) A request by a police officer for tow trucks to move wrecked or disabled motor vehicles.
49 CFR § 390.5
Unless specifically defined elsewhere, in this subchapter: