Road Caution Signs and the Rules of the Road
The Manual on Uniform Traffic Control Devices (MUTCD) is the standard used for all public street signs in the United States. The MUTCD insures that signs use the right colors, shapes, and sizes to notify drivers and pedestrians of traffic rules and hazards.
Diamond shaped yellow road signs are specifically made this way to display the warnings. Yellow is the official color of caution or warning, and the diamond shape is also reserved only for warning signs. These yellow road signs are made to alert you of a specific hazard, such as a dead end, merging lane, or stop ahead.
Yellow road signs are highly visible, and explain to you why you should slow down and proceed with caution.
Pedestrian crossing signs are the most commonly seen yellow road signs. Deer crossing symbols, farm machinery like tractors, and fire trucks are also often found on these road caution signs, alerting drivers to these potential road hazards.