You probably didn’t mean to look.

But something landed anyway.

In this special episode of Curious by Design, we explore why billboards look the way they do, and how they became one of the most effective attention-capture systems ever created.

Unlike street signs, billboards don’t guide or instruct. They interrupt. They live in shared space, competing for a fraction of your attention while you’re driving, thinking, or simply passing through. And they do it using principles discovered more than a century ago.

From painted ads along railroad lines to massive displays on interstate highways, billboards evolved alongside predictable movement. As trains, then cars, created steady streams of passing eyes, advertisers learned a critical lesson: at speed, people don’t read, they sample. Design shifted accordingly. Fewer words. Bigger shapes. High contrast. Faces. Repetition.

This episode breaks down the biology behind billboard design, why contrast grabs attention, why faces are impossible to ignore, why motion triggers awareness, and why familiarity often works better than persuasion. We look at how digital billboards borrowed the brain’s sensitivity to movement, why cities regulate how fast they can change, and why some places decided the tradeoff simply wasn’t worth it.

Billboards don’t wait for permission.

They rely on proximity.

And they work because attention doesn’t need consent, just exposure.

The next time something sticks in your mind long after you’ve passed it, remember: the most effective billboard isn’t the one you recall seeing. It’s the one that feels familiar later.

That’s Curious by Design.

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