What is the requirement for opening the entrance door of a school bus to activate the warning lights?

Opening the door slightly activates the warning lights on a school bus. This safety feature is crucial as it alerts surrounding drivers that the bus is preparing to pick up or drop off students. The activation of warning lights serves as a visual cue that signals drivers to slow down and be cautious, ensuring student safety as they enter or exit the bus.

The requirement to open the door slightly is designed to provide a balance between ensuring the bus is ready for student loading or unloading while also keeping the bus operator in control of the door. A slight opening is sufficient to activate the lights without fully unveiling the entrance or compromising the security of the bus—this is essential in maintaining an organized and safe environment for students.