Newcomer

[Kilkakon]

You're right, upon further inspection it seems it convoys just a single resource - utterly useless. I wonder why they put that in the game, then.

My guess would be leftovers from Civ 2. In that game it was possible to make "Food" caravans, which would transfer 1 food from city of origin to destination per turn, as well as fill up the granary completely. In a mod I made for Civ 2 they became quite important when trying to settle in Food-poor areas.