The colour was chosen because of its attention - grabbing qualities. It gets noticed faster than any other colour.  For instance, in one’s peripheral vision, studies have shown that humans notice the colour yellow 1.24 times faster than another eye-catching colour, red. Yellow is also particularly visible in the early morning and evening light, when school buses usually operate. The hope was that people would see the colour of the bus quickly and know to slow down and be mindful of the children on board.