Legibility is the ease with which individual letters and numbers can be recognized and told apart. It depends mainly on the typeface and how it is set: letter shapes, stroke width, spacing, size and contrast.
Readability is related but broader: how easily a whole message can be read and understood, which depends on wording, length, layout and context. A sign can use a perfectly legible typeface and still be unreadable because it says too much. See readability.
Legibility in parking signage
- Size for distance. Letter height must suit the viewing distance and the speed of the reader, larger for drivers than for pedestrians.
- Contrast. High contrast between letters and background, and lighting or retroreflective materials for night.
- Distinct characters. Typefaces that keep 1, l and I, and 0 and O, clearly different, which matters for level and space numbers.
- Placement. Mounted where drivers look, clear of columns, pipes and glare.
Readability for drivers
- Few words, one decision per sign, consistent terms across the facility. See wayfinding.
The Parkonomics view
A driver has a second or two to read a sign. Legibility gets the characters across; readability gets the decision across. Design for both, and test signs from the driver’s seat.
Related terms: Readability, Wayfinding, Dynamic Signage, Retroreflective Lettering