What is the purpose of a vehicle's brake lights?

The purpose of a vehicle's brake lights is to inform other drivers that you are slowing down or stopping. Brake lights are crucial for communicating your actions to those driving behind you. When you press the brake pedal, the brake lights illuminate to signal to other road users that your vehicle is reducing speed or coming to a stop. This warning allows following drivers to prepare to slow down or stop themselves, thus preventing potential rear-end collisions.

While signaling turns is important in driving, that is specifically the function of turn signals, not brake lights. Indicating a vehicle's speed is typically done via speedometers and speed limit signs, while showing your location on the road is generally accomplished through other vehicle lights or road signs. Therefore, the primary and most essential function of brake lights is to enhance safety by alerting others on the road about your intended actions concerning speed changes.