Writing a setting where there's access to modern technology from the greater world, but the people of this land haven't really developed yet (Specifically a much less colonized America). There isn't a rail or road network connecting the various settlements, so caravans of camels, donkeys, and horses have been transporting cargo over land. This has me wondering if ATVs or other land vehicles would be more effective and cost effective at moving cargo over uneven, unpaved terrain. 

Can an ATV type vehicle carry much cargo? I imagine just pulling a standard trailer can't be much easier than simply using a truck; could more ATVs or some specialized trailer be linked to carry stuff without each needing a driver for each one? I'm also unsure if ATVs would be as good as horses in navigating difficult terrain. Would an aspiring merchant family be better off sticking to beasts of burden until the highway gets built? Alternatively, could a Boston Dynamics type robot offer the best of both worlds?