A “star code” indicates that a car is not capable of carrying the maximum load that would otherwise be permitted by the truck design.
AAR Field Manual Rule 70 describes the standard Gross Rail Loads that would typically apply, given the number of axles on the car and the size of the roller bearings used. The Load Limit is typically this value minus the light weight of the car.
However, if a car owner chooses to reduce the load limit then they must stencil a 3-inch star immediately to the left of the load limit stencil.
One reason this could occur is if the car has been outfitted for a particular dedicated service, the car owner may choose to “light spring” the car to provide a softer ride (such as in autoracks, intermodal cars, and box cars), and another is that the body simply is not rated to carry more weight (such as tank cars and covered hopper cars).
Star coding is most frequently seen on autoracks, articulated intermodal flats, tank cars, and covered hoppers.