Freight Capacity

the capacity of the load space of a railroad car, automobile, vessel, or aircraft. It is one of the fundamental performance criteria of means of transportation. The ratio of occupied load space to the freight capacity is called the freight-capacity use coefficient.

In ships a distinction is made between grain capacity (for bulk cargo) and bale capacity (for piece cargo). Excluding the area in the load space that is not suitable for storage, the bale capacity is 6–10 percent lower than the grain capacity.

An important factor is the specific freight capacity (the volume of load space per unit of freight capacity). The specific freight capacity of present-day covered railroad boxcars is 1.94–2.0 cu m per ton; of half boxcars, 1.08–1.16; and of tank cars, 1.02–1.14. For dump trucks the specific freight capacity is 0.6–0.7 cu m per ton.

Ocean and river vessels have various specific freight capacities, depending on their purpose. For ore carriers it is 0.5–1.0 cu m per ton; for bulk-load vessels and tankers, 1.2–1.4; and for general-cargo vessels, 1.4–2.2. The specific freight capacity of an An-22 airplane is 7.0–7.5 cu m per ton.

For open freight carriers (railroad flatcars and flatbed trucks) the specific freight capacity is expressed as a ratio of the area of load-carrying surface to the freight capacity. This index is 0.58–0.94 sq m per ton for railroad flatcars and 1.2–6.0 sq m per ton for general-purpose motor vehicles.