MRLD

MRLD (Required Legibility Distance) is the distance over which a sign must be legible and comprehensible. It is calculated as driving speed × DSD. Example: at 40 mph (59 ft/s) with a DSD of 5.5 s, the MRLD is 59 × 5.5 ≈ 323 ft (≈ 98 m). The required character height follows from MRLD divided by the Legibility Index.