Biohazard or biological hazard signs have black abstract figures on a black or yellow background. These signs caution the viewer that a substance is present which presents a danger to living things. Frequently you will see biohazard signs on needle-disposal bins at your doctor's office and tattoo parlors, and near chemical plants.
The internationally recognized symbol for poisonous or toxic substances is a skull and crossbones. Many household cleaners bear this symbol due to the inclusion of dangerous poisons in solvents and detergents. Many automobile maintenance products also contain poisons.
Dozens of road signs exist, some common enough to be seen every day, while others are reserved for more rare situations. Several common road safety signs are the red and white "Do Not Enter" signs denoting one way traffic, the railroad crossing sign with a large black "X" in the middle, the red and white "yield" sign instructing drivers to yield the right-of-way and the "Slippery When Wet" sign, with swerving lines trailing behind a vehicle.
Several road signs focus less on drivers and more on the rest of the community. Yield to pedestrians and pedestrian-crossing signs are fluorescent yellow, while regulatory signs, like "Sidewalk Closed Ahead" notices are typically white. Signs that account for blind or deaf residents are typically text based, rather than symbol based.
