Also, the biggest caravan advantage is the outdoorsman. It doesn't increase travel speed, but it has the outdoorsman of a car so you won't hit very many encounters. Also, as the above poster said, brahmins, mercs and slaves are all the same. They do have a lower carry weight, but you can load them past it. They just become encumbered. It doesn't matter much with the cow though because they can't run to begin with, but your mercs and slaves won't be able to run after loaded past the limit.