All states require the traffic in both directions to stop on undivided highways when students are getting on or off a school bus. While wording varies from state to state, generally the law requires the following: The school bus driver activates flashing yellow lights to indicate the school bus is preparing to stop to load or unload students. At this point, motorists should slow down and prepare to stop. The school bus driver activates flashing red lights and extends the stop arm to indicate the school bus has stopped and students are getting on or off. At this point, motorists should stop.

State law varies in what is required on a divided highway and what constitutes a divided highway. However, in all cases on divided highways, traffic behind the bus must stop.