"Flashing amber lights are a signal that the school bus is preparing to stop, so drivers need to slow down, pay attention and proceed carefully. Drivers are allowed to pass a moving bus with flashing amber lights, but they should do so cautiously."
Drivers are still prohibited from passing a stopped school bus with red flashing lights (Wis. Stat. 346.48). Watch a DOT video explaining the new regulation or read a brochure for more information about school bus warning lights.
Photo credit: By Dickelbers (Own work) [CC BY-SA 3.0], via Wikimedia Commons