DOT / AAR spec
Tank car specification stencil
The specification stencil, such as a DOT-111 or DOT-117 code, identifies which tank standard the car was built to.
A tank car carries a specification stencil that names the standard it was built to. You will see it near the other technical lettering, often as a code that starts with DOT or AAR. A familiar shape is something like DOT-111A100W or a later DOT-117 code. The code identifies the specification. It is not a sentence, and it is not the placard.
The pieces have usual meanings, and they are worth knowing as a way to start reading. DOT means a U.S. Department of Transportation specification. AAR means an Association of American Railroads specification. The digits that follow are the tank class. A number such as 100, on many of these codes, is a test pressure in pounds per square inch. A trailing W means a fusion-welded tank. Other letters mark features such as insulation or the kind of fittings. Those habits are not a promise that every character means the same thing on every class. The specification document is what defines the car. The stencil points at that document.
Around the spec code you may also see test dates, a station stencil, and notes about the tank's service. Those are maintenance and qualification marks. The commodity, when the car is loaded, is identified by the placard and the shipping papers, not by the specification code alone. A DOT-117 car and a DOT-111 car are different tanks. Either one can carry different commodities over its life, within what that specification and the loading rules allow.
RailcarID explains how to recognize the stencil. It is not a substitute for the regulations, the car's certificate, or the emergency response guidebook. If a tank is leaking or the placard doesn't match what you expected, this page is the wrong tool. Get away and call the local emergency number.
Common questions
- What does a DOT specification stencil tell you?
- It identifies the tank standard the car was built or qualified to, including the class and, on many codes, a test pressure and the fact that the tank is welded. The full meaning lives in that specification.
- Is the specification stencil the same as the hazmat placard?
- No. The specification describes the tank. The placard identifies the hazard of the material in the car on that move.