Here's a story about how a little coat of paint save thousands of lives (and probably many more). Before World War II, there weren't too many automobiles in Britain. But after the war, when cars started taking over the world, things started getting unacceptably fatal. Scientists had to invent a new kind of crosswalk.
In post-war England, crossings were marked by little metal bumps. People could see them. They could even feel them under their feet. The problem was, people weren't the ones causing fatalities at crosswalks - cars were. Inside a car, it was nearly impossible to see small metal bumps.
Something had to be done, so the Transport Research Laboratory stepped up. They started with different designs on tiny models (that I would love to see) and then painted all kinds of different designs on real roads. And then they tested which ones drivers found most noticeable. They almost immediately narrowed it down to zebra crossings, whose bold white stripes marked the crosswalk. Drivers found the black and white stripes easy to spot. And the rest is urban design history.
Unfortunately, drivers always find new ways to ignore the road, so signs are in a kind of arms race with inattention. Now we get distracted by mobile phones. And stop signs, red lights to stop traffic, and little island refuges with rectangular "don't mow down the pedestrian" guards have become the norm. Still, it's interesting that the black and white lines we thoughtlessly cross (both on foot and in cars) weren't just a signal put up without thought. They were the result of actual scientific testing.