Cars qualify when they incorporate an integral discharge mechanism — such as bottom-dump hoppers, pneumatic discharge systems, or rotary-dump gondolas — that allows unloading without external lifting or scooping equipment. Standard open gondolas that require a crane or excavator to unload do not meet this criterion and classify elsewhere.

Technical drawings, manufacturer specifications, and operational manuals that clearly illustrate the discharge mechanism should accompany the entry. CBP may request this documentation to confirm the car's design meets the self-discharging criterion, particularly for novel or hybrid designs.