Modern vehicles have an assortment of lights, both interior and exterior. When these lights are on while the engine is off, they switch to battery power. Many cars have a delay for some lights after the car is shut off.
When the car is running, all lighting is powered by the engine, which produces energy to spare. When the engine is not running, any lights still on draw power from the vehicle's 12-volt battery.
Headlights, taillights, brake lights and hazard lights are very bright when the car's engine is running. For safety, these lights can stay on when the engine is shut off, though they may be dimmer due to the battery's limited power supply.
The dome light or courtesy light usually has three settings: on, door, off. "On" and "off" mean on or off all the time, respectively; "door" means the light will be on if and only if a door is open, even when the car is shut off.
Some cars leave the dome light on for a period of time, even if all the doors are closed, when the engine is off. This allows occupants to find seat belts, personal items, etc.; the light switches off or fades out after a few minutes.
