Main takeaways
- Traffic-sign research has long found that a glance takes in three or four short words. We write windshield headlines to that.
- Sign-industry guidance keeps lettering to about 40% of the face. The open space is what makes it read.
- In an eye-tracking study, busier signs got more attention, but at the same level of attractiveness they made people less likely to say they’d buy.
- So we keep the glass simple and put the detail behind the QR.
The banners we print say three things, not eight. Three findings from sign research back that up, and none of them is about cars.
What a glance takes in
Traffic-sign research has long found that a glance takes in three or four short words. It’s an old finding, from a 1965 review of traffic-sign studies, and it’s the rule we write windshield headlines to.
Here’s how that looks on real jobs. Each headline below is read off an install photo in our gallery; the facts line under each one is set smaller.
| Store | Headline on the glass | Words |
|---|---|---|
| MINI of St. Louis | 2021 Hardtop Cooper S | 4 |
| Suntrup Ford Kirkwood | 2021 Explorer XLT | 3 |
| Joe Machens Toyota | Fresh Trade | 2 |
| Joe Machens Toyota | Manager Special | 2 |
Leave the face open
Sign-industry guidance keeps lettering to about 40% of the face. The open space is what makes it read. On a windshield that means the year and the model get room around them, and nothing fills a corner just because the corner is empty.
Busier signs held the eye but lowered intent to buy
In a 2018 eye-tracking study, published in 2020, 85 adults looked at photos of garden-center signs. Moderate and complex signs held the eye longer than simple ones, and the complex ones were rated the most attractive. But at the same level of attractiveness, more complexity lowered how likely people said they were to buy. The study didn’t find a sweet spot.
We read that as a reason to keep the glass simple and put the detail behind the QR, not as proof that simple signs sell more. Nobody has measured that on a car lot.
Where the rest of the detail goes
The facts that don’t fit the headline go on one smaller line under it: 27 MPG, 4WD, third row. Everything after that goes behind a ShortCut on the door glass, which opens the car’s own page on your website.
Sources
Bullough, Illuminated Sign Conspicuity, Lighting Research Center (RPI) for the Sign Research Foundation: three or four words a glance, citing a 1965 review of traffic-sign research (p. 21).
United States Sign Council, Sign Legibility Rules of Thumb (Bertucci, 2006): lettering at about 40% of the face (pp. 8–9).
Knuth, Behe & Huddleston, “Simple or complex? Consumer response to display signs,” Interdisciplinary Journal of Signage and Wayfinding (2020): the eye-tracking study of 85 adults (pp. 10–11).
More Field Notes
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Letters sized for the drive aisle
How tall the letters on a windshield banner need to be, and the sign research behind the sizes.
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One mark, one message
Why every mini-mark we print says one thing, and how the small marks stack on the glass.
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Contrast beats color
Why the key word on our designs sits on the plainest, highest-contrast ground, and what a border is for.