How school buses became yellow, and some of the safest vehicles on the road

In the early days of busing kids to school, buses were painted all sorts of colors, and built to different specs. But in the late 1930s, education expert Frank Cyr started agitating for a national standard -- so manufacturers could mass-produce to one spec, making buses cheaper.

In 1939, Cyr met for one week with school-transportation officials from across the country, and they hammered out a spec. One key decision? Setting the official color of school buses. They hung "hung strips of different paint colors from the wall, in '50 shades ranging from lemon yellow to deep orange-red'", as Smithsonian writes -- and the winner was an orangish-yellow.

Why that color? Because it's easy to see, making buses readily identifiable on the road, very useful for safety. What's more, the particular shade of yellow they picked has some cool spectral qualities that make our perceptual apparatuses jump to attention, notes Ivan Schwab, clinical spokesperson at the American Academy of Ophthalmology:

The wavelength of the popular school-bus color is right smack in the middle of the peak wavelengths that stimulate the photoreceptor cells our eyes use to perceive red and green. The red and green photoreceptor cells, or cones as they are commonly known, are the two most predominant cones in our eyes. Schwab says, If you get a pure wavelength of one colorand you hit just one cone with it, youre going to have x amount of transmission of signal to the brain. But if that [wavelength] were to stimulate two cones, youll get double the amount of transmission to the brain. Remarkably, That color that we are calling school bus yellow hits both peaks equally. So although they may not have fully comprehended the science behind it, the color Cyr and his colleagues chose at the 1939 conference makes it hard for other drivers to miss a school bus, even in their peripheral vision.