Illinois CDL Practice Exam.

Warning signs are typically yellow because this color is universally recognized as a cautionary signal, indicating that drivers should be alert to potential hazards ahead. The use of yellow is designed to attract attention and convey a sense of caution, thereby helping to prevent accidents. These signs can indicate various warnings, such as curves in the road, pedestrian crossings, or animal crossings, all of which require drivers to take notice and possibly adjust their driving behavior. In contrast, red is often used for stop signs and signs that require immediate action, while green is associated with directional signs indicating permissible actions or routes. Blue is typically reserved for informational signs, such as those indicating services or facilities, rather than warnings. This distinction in color coding helps ensure that users of the roadway understand the nature of the information presented.