Why are American and Canadian buses yellow?

It's a Federal regulation.

Safety reasons were the impetuous.

It was especially formulated for use on School buses in North America in 1939.

The color was adopted by the National Bureau of Standards (Now the National Institute of Standards and Technology) as Federal Standard No. 595a, Color 13432.

http://en.wikipedia.org/wiki/School_bus_yellow

School buses are yellow to give them visibility. Where I live, they also have a bright strobe light on them (it is dark here when kids are on the bus, as we are so far north). It is amazing how many drivers ignore flashing red lights, the stop sign, etc., etc. Kids get injured using school buses every year. There isn't a lot more that can be done to keep the kids safe from other drivers, but, the yellow colour, flashing lights, and strict laws do help a bit.

I'm Canadian, and the only yellow buses I've ever seen here, are of some school buses, the rest are not yellow at all...

college buses are oftentimes yellow. the place i'm, they even have strobe lights on them, as that's darkish interior the morning, and afternoon (short days in iciness), while the babies have become picked up/dropped off. Police vehicles have a sort of colorings. RCMP vehicles are customarily white with a blue stripe. OPP vehicles are black with white doorways. different departments variety, yet, maximum have white vehicles these days. Taxis rely on the corporation. Yellow is person-friendly, yet, so are a many different colorings. it particularly relies upon. Many companies have the vehicles being owned via each and every motive force - so, in basic terms the connect up suitable is person-friendly. The vehicles may well be any coloration.

For high visibility. A highly visible school bus helps other drivers see the bus and -- hopefully -- drive safely in its presence.