It is most important to flash your brake light when:

If a tailgater is following you too closely, it is advisable to flash your brake light before you begin to decelerate. The tailgater may be concentrating on you and may not be aware of hazards farther down the road that you are slowing to avoid.

• Switching into a neutral gear.
• You will be slowing suddenly.
• There is a stop sign ahead.
• Your signals are not working.