What is the minimum letter height on a portable change message sign (PCMS)?

• A. 12 inches
• B. 18 inches
• C. 24 inches
• D. 30 inches

Answer: (B)

The minimum letter height for a portable changeable message sign (PCMS) is set at 18 inches to ensure optimal readability from a distance. This height is based on guidelines provided by various transportation authorities, which emphasize that text must be legible to drivers traveling at highway speeds. An 18-inch letter height allows for clear visibility and comprehension from a substantial distance, facilitating safe and effective communication of important messages, such as traffic updates or construction information.

Lower letter heights might lead to readability issues, especially for drivers at higher speeds, where clarity and quick understanding of information are crucial for safety. As such, the 18-inch standard strikes a balance between visibility and practicality, ensuring that the signs are effective tools for conveying essential information to motorists.