Final answer:
Accident prevention signs with black lettering on a white background are regulatory signs, conveying rules that must be followed for safety on roads.
Step-by-step explanation:
A type of accident prevention sign that generally features black lettering on a white background on the lower panel is known as a regulatory sign.
These signs are designed to convey rules and instructions that must be followed. For example, a speed limit sign would typically have a white rectangular background with black lettering stating the legal maximum speed you are permitted to travel in that area. Regulatory signs are crucial for maintaining safety and order on the roads, and their universal design ensures that they are easily recognizable by all drivers, regardless of where they are.