Encumberance is a vital part of travel. Travel is normal if all party members are only lightly encumbered, however, for each character who is either Moderately or Heavily encumbered, travel requires an additional day's provisions between hexes, this is doubled if the person in question is Heavily encumbered.
Campaign Specific Feats (Weight)
Quartermastery (feat) (req. 4 ranks profession: quartermaster): Allies are considered to have two additional strength when determining encumberance.