What is a placard on a hazmat vehicle?

Placards are diamond-shaped (square turned on point) signs attached to the outside of vehicles carrying hazardous materials. They communicate the hazard class to anyone in proximity to the vehicle: other drivers, emergency responders, inspectors, and the public. Placards must be displayed on all four sides of the vehicle (front, rear, both sides), must be at least 10.75 inches square, and must be visible from the direction they face. The placard's color, symbol, and class number identify the hazard: a red flame for flammable liquids/gases, a yellow ball for oxidizers, a white skull and crossbones for poisons, etc. Most hazmat loads above 1,001 pounds require placards; some materials require placards at any quantity.