Final answer:
Vehicles must stop and remain stationary when school or shuttle buses are loading or unloading passengers, to ensure the safety of children.
Step-by-step explanation:
When school buses or shuttle buses are loading or unloading passengers, vehicles traveling in either direction must stop and not pass the bus. This is indicated by flashing lights or other signs of loading and unloading activities. Stop moving and become stationary until it is safe to proceed. This rule helps to ensure the safety of children getting on and off the bus and is enforced by law in many jurisdictions.