When stopping a school bus to load or unload passengers, you should turn on your upper alternating red signal lights...?

Answer: D — Before you stop

When approaching a school bus to safely load or unload passengers, it is important to activate your upper alternating red signal lights before you come to a complete stop. This action serves several purposes: it alerts other drivers well in advance that the bus is stopping to pick up or drop off children, thereby increasing safety for both the passengers and the other vehicles on the road. By using the lights beforehand, you provide clear and visible warnings, which is essential in preventing accidents and ensuring that other drivers are prepared to stop. This detail is critical for compliance with traffic laws designed to protect students at school bus stops.