What is the minimum legibility distance for DMS messages at night?

The minimum legibility distance for Dynamic Message Sign (DMS) messages at night is 600 feet. This standard is established to ensure that messages displayed on DMS can be easily read by drivers from a safe distance, allowing for adequate time to respond to the information provided. At night, visibility conditions change due to reduced light, and therefore the distance was set at 600 feet instead of longer distances that might be more suitable during daylight. Ensuring that messages can be read from this distance enhances safety by allowing drivers enough time to make decisions based on the displayed information, such as warnings, directions, or alerts regarding road conditions.