Wagons
How many different kinds of wagons do the humans use? There is a one bentar, two wheeled little cart, the two wheeled larger cart pulled by two birds. There is the 4 wheeled wagon pulled by two birds. Smallest cattle wagon pulled by one cattle, medium size cattle wagon pulled by two cattle and the largest farm wagon, used for transporting goods, pulled by two or even four cattle. But there are also the smaller wagons, the ones pulled by humans and dragons as they walk or fly. Basically any conveyance with wheels is a wagon. By the time I realized what was happening, my characters had already sorted it out.