Lights are an important safety feature. Without them we could not see at night or notice when someone is braking, turning, or changing lanes. Some lights are controlled by sensors so they automatically illuminate in low-light conditions. Other lights are turned on by manual switches. As a safety feature, daytime running lights (DRL) make it easier for approaching drivers to see each other. Lights burn out with age. When replacing bulbs, use the number on the bulb as a guide. This is not true for most automotive replacement parts, but it is true for headlights and other bulbs. It is recommended to replace blown out headlights in pairs. This section focuses on: