School bus lights are regulated by state and federal law, as well as by the American School Bus Council. Different states have alternate specific requirements for these vehicular safety devices.
All buses must have amber and red flashing lights that alert other traffic of the bus drivers intention to stop at a stop zone. By law, all traffic must stop when a school bus displays these red flashing lights.
The first school bus light warning system was used in Virginia in 1946. When the federal government adopted FMVSS 108, in 1968, amber lights were gradually added to most school buses.