The standard color of the school bus became yellow since 1939. Frank W. Cyr is known as the father of the yellow school bus. There are two reason for using this color: First, yellow is the most easily seen color at dawn and dusk, so American school bus color is called National School Bus Glossy Yellow. Second, a test shows that people see yellow fastest, which is 1.24 times faster than red. Third, in fog or bad weather, drivers are more likely to see a yellow moving vehicle. Fourth, not only the school bus, a lot of mechanical operations, road construction or other outdoor machine are all yellow, it is a warning color meaning you will be injured if you close to them.