Hell on the Highway

The tow dogs who work California's Donner Pass brave the elements and the competition. Towing is a cut-throat business here, with more than ten local companies fighting for financial survival. In this Hell on the Highway best-of episode, the extremely competitive side of towing in the Sierras is revealed, as tow dogs are pitted against one another in a race for rescues that only the best will win. (National Geographic)