Cargo is "a wide variety of materials which are supplied and demanded by many of the game's locations and form a complex supply chain". It is grouped by loading type, and players must match the cargo to a compatible trailer or cargo space.
Cargo classes
Flatbed/Box — physical objects like boxes, cabinets, pallets.
Container — 20 ft and 40 ft shipping containers; use a Cotra-20-3 or Cotra-40-3 trailer.
Grain — bulk grain hopper loads.
Dry Bulk — sand, cement, similar dry loose cargo.
Tanker — liquid cargo (fuel, oil, milk).
Weight and overload fines
Weight matters. Overloading triggers automated weight-in-motion fines on the highway. Community reports peg this at roughly $3K tickets when a semi-tanker exceeds 25 "units" of 800 kg each.
The forklift
A Forklift for warehouse-style loading was added in 0.7.12. Use it at warehouses where loose cargo needs to be transferred onto pallets before truck pickup.