This is 99% invisible. I'm Roman Mars.

If you listen to the show for a while, you know that we're big fans of icons and symbols

and signage. And one of the main places you encounter those is on the road.

So in our ongoing ubiquitous icon series, we're taken to the highways.

I'm thinking we should call this one Highways 101.

You know, I like it. I like it. Highways 101. That's Kurt Coles' studies, our digital director

and co-author of the book, the 99% visible city. One of the things Kurt does is he checks

our inbox for listener submitted ideas, combs to all of them. And earlier this summer,

a 99-Pi fan named Daniel wrote us about a strange stop sign that he encountered while traveling

and you started digging into this story. Yeah. So his email started like this.

A couple of years ago, we took a trip to Hawaii and my wife became obsessed over a few blue

stop signs we saw in parking lots. The signs were the size and shape and use the same lettering

as normal red stop signs, but they were bright blue. So I don't think I've ever seen that before.

I had never seen this either. Either in images or in real life. So I started looking into

why some were blue. And that turned out to be pretty easy to figure out. But it got me wondering

something a lot more fundamental, which is why are the rest of the red? All red, right?

Exactly. Why is that such a thing in the first place? Totally.

Yeah. And that got me into, of course, digging into the whole history of stop signs.

Of course, of course, that's the only way this is going to go with you.

Yeah, it's just my nature. And as I was looking into this, this one figure kept popping up everywhere

I looked. A guy named William Phelps, you know, who in the early 1900s became known as the Father

of Traffic Safety. Okay. So what do you have to do to earn that title, the Father of Traffic Safety?

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