Phil says: ' It's something that is announced at the very beginning, but it has a rolling effect going forward through the rest of the Race.'
It could still be my earlier suggestion, and they could have a 'Long Way Round' on every leg, but this would be expensive and could leave many specially printed clues redundant if the team gets eliminated. So this is unlikely to be the Hazard.
My new guess is this: For the team with the Hazard penalty, every pit stop they reach, they must then wait until one more team checks in before checking in behind them. This means that if they come in second to last, they will be eliminated. They can rid themselves of the Hazard by winning a leg, much the same as the 'Marked for Elimination' penalty.