Final answer:
When needing to stop or slow down unexpectedly, it's safest to tap your brake pedal quickly several times to flash your brake lights and warn drivers behind you.
Step-by-step explanation:
If you are going to stop or slow down when others might not expect it, you should tap your brake pedal three or four times quickly to warn those behind you. This action will cause your brake lights to flash, signaling to drivers that you are decelerating. Quick lane changes or using your horn may not effectively communicate your intention to slow down and could startle other drivers, potentially causing an accident. Emergency flashers are typically used when you are already stopped or if you are driving significantly slower than the flow of traffic due to an emergency or vehicle problem, not when you are about to slow down. Always ensure to use your signals in a manner that clearly communicates your actions to other motorists to maintain safety on the road.