Railcar Load Limit, Route Limit, and Cube

Load limit is what a shipper may put in, and it is a property of the SPECIFIC CAR rather than of its class: light weights differ between cars of the same nominal rating, and a repaired or rebuilt car can be several hundred pounds heavier than its sister and has exactly that much less capacity. Reading the stencil on the car in front of you, rather than the class, is the whole discipline. THE CONSTRAINT THAT GETS MISSED IS THE ROUTE. A 286,000 lb car is not permitted everywhere: bridges and track on light density lines and on many short lines are rated below it, and a car loaded to its own limit can be refused, restricted, or held. The governing gross rail load is the LOWER of the car's and the route's, and a shipper loading to the stencil without checking the route has overloaded the route rather than the car -- a distinction that is completely invisible on the car itself, because the stencil has no idea where the car is going. THE OTHER EVERYDAY QUESTION IS WHETHER WEIGHT OR CUBE GOVERNS. A car has a cubic capacity as well as a weight limit, and light bulky lading fills the car long before it reaches the load limit while dense lading reaches the limit with the car half empty. Which one binds is what sizes a shipment and what decides whether a different car type would carry more, and it changes with the commodity rather than with the car. Common gross rail load classes run 220,000, 263,000, 286,000, and 315,000 lb. This is the load limit arithmetic and the two checks around it. It does not address weight distribution within the car, which has its own limits -- a load concentrated over one truck can overload it while the car's gross is fine -- or eccentric and off-centre loading, load securement, or the AAR loading rules for the commodity. It does not determine whether a specific route accepts a specific car, which is a routing question for the carrier, and it does not address dimensional or excess-height loads, high-wide clearance, or the open-top loading rules. The car's stencil, the AAR loading rules, the carrier's route restrictions, and the shipper's own weighing govern.

load limit = gross rail load - light weight; gross on rail = light weight + lading; the governing limit is the LOWER of the car's and the route's; and the cube check is cubic capacity x lading density against that limit.

The railcar load limit identity by name. Common gross rail load classes are 220,000, 263,000, 286,000 and 315,000 lb. Light weight and load limit come from the car's own stencil, not from its class -- a rebuilt car can be several hundred pounds heavier than its sister. The car's stencil, the AAR loading rules, the carrier's route restrictions, and the shipper's own weighing govern.

Two subtractions and a multiplication on figures read off the car; no AAR loading rule is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: gross_rail_load_lb, light_weight_lb, lading_net_lb, cubic_capacity_ft3, lading_density_pcf, route_gross_rail_load_lb, load_limit_lb, gross_on_rail_lb, utilization_pct, remaining_capacity_lb, route_load_limit_lb, cube_limited_weight_lb

• The stencil, not the class light weights differ between cars of the same ratingthe car's own stencil
• Weight distribution is not checked a load over one truck can overload it while the gross is finethe AAR loading rules
• Route acceptance is a carrier question this compares limits, it does not clear a routingthe carrier's route restrictions