Regulations

• In the United States, the Department of Labor regulates safety and hazard warning signs at workplaces, through the Occupational Safety and Health Administration (OSHA). The federal Department of Transportation (DOT) regulates road and vehicle warning signs. Safety signs must be uniform in design and these standards are developed and published by the American National Standards Institute (ANSI).
  
  

Design

• OSHA mandates the design and coloration of all types of workplace safety and hazard warning signs. All types of safety signs are associated with certain colors, and the signal words on each type of sign, such as "caution," must contrast with their background; for example, light on dark colors. The corners on all signs must be rounded and blunt.
  
  

Types

• There are two main types of safety and hazard warning signs: "caution" and "danger." According to OSHA, danger signs are to be used in situations where there is an immediate risk of serious physical injury or death, and they must use the standard white letters on a red background with a black border. Caution signs are to be used in situations where the potential for minor physical injury is possible, and include yellow letters on a black background. A third type of sign, "warning," may also be used when the risk level falls between these two main types.
  
  

Images

• Often, safety and hazard warning signs incorporate more than the simple signal words caution, danger and warning, and are accompanied by a pictograph which may depict the nature of the risk, or safety precautions that are necessary. This may also include a brief message such as "hardhats required." The image is designed to be nearly universally understandable. As with the signal words, the image and accompanying text are designed to stand out, typically in black on a white or yellow background.
  
  

Hazardous Materials

• The safety and hazard warning signs regulated by the DOT are less often seen but are present on most large vehicles used for shipping. United States federal law requires that vehicles used to carry dangerous goods must have hazardous materials placards attached to them. These diamond-shaped signs warn of flammable, radioactive or toxic materials and often have a numerical value allocated according to the severity of the danger. They are typically brightly colored and include a pictograph.