Readability is how easily a person can read and understand a message as a whole, while legibility is how easily they can tell individual letters and words apart.
The two are related but not the same. Legibility belongs to the letterforms: typeface, size, weight, spacing, and contrast against the background. Readability belongs to the message: how many words it uses, how they are ordered, and whether the layout lets the eye find what matters first. A sign can be perfectly legible and still unreadable if it says too much.
Three signs, one glance each, then a question. A test of what drivers can actually take in while they are moving.
Wordy sign: seven lines of rules about permits, visitor levels, compact rows, height, overnight parking, EV charging and payment. Edited sign: two lines: “VISITORS: LEVELS 3 TO 5” and “EV CHARGING: LEVEL 4.” Drivers glancing for a second and a half usually miss what they need on the first and catch it on the second.
Signs are illustrative. Use the “take my time” option to read without a timer.
Readability vs legibility at a glance
- Legibility asks: can a driver make out the characters from this distance and in this light?
- Readability asks: can a driver understand what to do in the second or two they have to look?
- Legibility levers: letter height, clear typefaces, strong contrast, glare control, lighting.
- Readability levers: fewer words, one decision per sign, consistent symbols, and a predictable order of information.
In parking facilities
- Drivers read garage signs while moving and while also watching for pedestrians, so every extra word costs attention.
- Entry, level and exit signs work best when each answers one question: where to go next.
- Live space counts and arrows on a guidance system are readable because they replace sentences with a number and a direction.
The Parkonomics view
Most bad parking signage is legible and unreadable: clear letters carrying too many rules. The fix is editing, not a bigger font. Decide the one decision a driver must make at each point in the wayfinding sequence, put that on the sign, and move everything else to the place where people stand still.
Related terms: Wayfinding, Parking Guidance System, MUTCD, Trip Segment Approach to Wayfinding Design