Scale test car
Type of railroad car in service
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A scale test car is a type of railroad car in maintenance of way service. Its purpose is to calibrate the weighing scales used to weigh loaded railroad cars. Scale test cars are of a precisely known weight so that the track scale can be calibrated against them.[1]


Purposes
Cars are weighed for various purposes. These include:
Axle load limits
Cars are weighed to ensure they are within the axle load limits of the railroad.
Customer billing
Cars are weighed to determine (by subtracting the car's unloaded, or tare weight from the total weight) the amount of cargo loaded. This is used to bill the railroad's customers for the carriage of bulk commodities, so it is essential that the track scales be accurate.