Any vehicle carrying a package with a radioactive Yellow-III label is required to bear a radioactive placard. Certain other vehicles, such as those carrying "strong tight" LSA packages, must also be placarded.

The RADIOACTIVE placard must be yellow on the top half with the black trefoil symbol. The bottom half must be white with the word RADIOACTIVE inscribed in black.

The DOT hazard class 7 denotes radioactive materials. 

Vehicle placards can help a great deal following an accident, particularly for a closed vehicle where the packages have remained in the vehicle.