How to make a billboard readable at 100 km/h

A roadside board is read in seconds, at an angle, by someone whose main job is driving. Most designs that fail on the road were fine on a laptop screen. Three rules do most of the work.

1. Letter height: 1 inch per 10 feet

The long-standing outdoor rule of thumb is about 1 inch (2.5 cm) of letter height for every 10 feet (3 m) of viewing distance. Put another way, text stays legible up to roughly 120 times its height.

• 15 cm letters read to about 18 m: fine for a mall screen, useless on a highway.
• 50 cm letters read to about 60 m.
• 1.25 m letters read to about 150 m, which is the kind of distance a driver first sees a large highway face.

Measure your smallest important text (the offer, the web address), not the headline.

2. Time in view: seven words or fewer

At 100 km/h a car covers almost 28 metres every second. If a board is visible from 200 m, the driver has around 7 seconds, and only part of that is spent looking at it. That is why outdoor designers aim for seven words or fewer in total, plus a logo.

• One message per board. If you need two, book two boards.
• Drop the phone number: nobody can write it down while driving. A short web address or a brand name people can search later works better.

3. Contrast and simplicity

• High contrast between text and background (dark on light or light on dark), no text over busy photos.
• Bold, simple sans-serif type; avoid thin weights and script fonts.
• Large product or face images read from further away than words do.
• Leave margins: edges of a face are often partly hidden by frames or trees, so keep text inside a safe area.

Check before you print

Our free billboard previewer shows your design at 50, 100 and 200 m and checks text size, time in view and word count. Every listing on Averta also states its exact creative specifications: sizes, formats and artwork deadlines.