Why are school buses yellow?

In 1939 Frank W. Cyr, a professor at Columbia University Teachers College, organised a conference of transport officials, engineers and bus makers to standardise school buses. The group agreed 44 standards, including a colour then called National School Bus Chrome and now known as National School Bus Glossy Yellow. The yellow-orange shade was chosen because it stands out in early morning and late afternoon light, and humans detect it well in peripheral vision. Black lettering and trim provide strong contrast, making the bus easy to read at a glance. Today roughly 480,000 yellow school buses carry more than 20 million American children, and they are among the safest ways to travel on the road.