"Man ist unterwegs."
"One is on its way" isn't a translation of "Man ist unterwegs." That implies that the "one" who is en route has no gender. Weird... "One is on its way" implies that some object has been shipped to you, for instance, and it's on its way. "Man ist unterwegs" refers to a person, not an object. "One is on one's way", though stiff, would at least convey the correct meaning.
I would say "People are on the road" is another translation, not necessarily better. Depending on context, this could also mean "We're on the road," "We're traveling", "They're traveling", "One travels." "You (general) travel", etc. In German "man" can be used to make a general statement, and the context determines which specific pronoun "man" is standing for or replacing. Since there's no context here, the only "safe" assumption is the literal one, "One". (Though "People" makes sense, because it's general.) For instance: a person is describing a job (to a potential employee): "Es ist hektisch. Man ist unterwegs. Wir muessen viel Reisen." "Man ist unterwegs" stands in for "We travel (a lot)", and also "One travels", and "You (would) travel (a lot too, if you worked here.)" The general "You" we use in English is another contender, but again feels weird without context. I would suggest that this has so many possible interpretations, that it's hard to come up with a definitive translation independent of context.