Yes, it is legal to drive with your interior car light on in the United States. There is no federal or state law that explicitly prohibits it. However, it is generally not recommended for safety reasons, primarily because it can significantly reduce your ability to see outside the vehicle at night.
The core issue is night vision. Car interiors are designed with dark, non-reflective surfaces to minimize distractions. Turning on an interior light creates a bright area inside the cabin, causing your pupils to constrict. This reduces your eyes' sensitivity, making it harder to see darker objects outside, such as pedestrians, animals, or road hazards. This effect, often called compromised peripheral vision, is similar to the difficulty of seeing out a dark window from a brightly lit room.
While experienced drivers on familiar, well-lit roads might manage the distraction, the risk increases dramatically in unfamiliar or dark areas. The light can also create glare and reflections on the windshield and side windows, further obscuring your view.
Practical Scenarios:
- For Passengers: If a passenger needs light, it's safer to use a small, focused reading light or a smartphone light directed only at their area, rather than the main dome light.
- For the Driver: If you need to find something, it is far safer to pull over to a safe, well-lit location (like a parking lot) before turning on the interior light.
The consensus from safety organizations like the National Highway Traffic Safety Administration (NHTSA) is that minimizing distractions and preserving optimal visibility is paramount. Therefore, while not illegal, the safest practice is to keep interior lights off while the vehicle is in motion.
