8 Q&A Facts on the Significance of Placard Usage in Rail Transportation 1. WHAT ARE PLACARDS? By Federal Code, the definition and identification of hazardous material being transported by any mode requires that they be marked in a manner that is easily observed. The “marking” is called a “placard”. 2. WHEN ARE PLACARDS USED? Hazmat carriers, including railroads, are required to ensure hazmat cars are accurately marked, and hazmat railcar content documents are in the possessi