These groups took it upon themselves to mark their local sections of highway with signs to warn and direct drivers. This scattered effort resulted in a wide variety of sign designs and messages in different sections of highway, which caused confusion among motorists. In 1924, the first steps toward national uniformity in road signs were taken by the Bureau of Public Roads. Designers were faced with developing signs to guide a largely illiterate population of motorists. As a result, color and shape were especially important components of signs from the beginning.
Early signs lacked the reflectorizen technology prevalent in signs today. In 1924 bright yellow was chosen as the background color for all warning signs, and white was the background color for all remaining signs. These lighter colors provided the greatest contrast with black lettering, especially when the signs were seen with the aid of headlights at night. Later signs used glass beads to produce a reflectorize effect at night. Beads—approximately 0.75 inch (20 mm) in diameter—were glued on the signs in the shape of numbers (such as the speed limit) or symbols to inform and warn nighttime drivers.
