TIL about William Phelps Eno. He invented traffic regulations, the stop sign, the crosswalk, the roundabout, the one-way street and pedestrian safety islands. He never learned how to drive.
He didn't invent the roundabout. It was Eugene Henard in France about 30 years prior. He also didn't invent the stop sign (Harry Jackson). There were also one way streets in England before the US existed.
I was curious about the claims about Eno so I Googled a bit. Eno actually is responsible for a lot of these ideas being put in use, if not inventing them himself. He basically pioneered the concept of standardized traffic rules.
As for the stop sign, Eno proposed the idea in 1900:
The invention of the roundabout is a bit more complicated. Circular intersections of some kind predated Eno, but they wouldn't all be considered roundabouts by our definition today.
Reading the Wikipedia it looks like it's not about the inventions of the individual things, but he utilized them together and potentially further optimized them (round about from 2 lanes to 1 to reduce accidents) and established a rulebook that officers should enforce and the public are expected to know and follow.