When driving at night, when should a driver switch from high beams to low beams?

HIGH BEAM ETIQUETTE AND LAW: ONCOMING TRAFFIC: Dim to low beams when an oncoming vehicle is within 500 feet (varies by state: 300-500 feet) — high beams directly into an oncoming driver's eyes cause temporary blindness (glare); the affected driver cannot see for several seconds after the bright light passes; FOLLOWING TRAFFIC: Dim to low beams when following within 300 feet — high beams reflect in the vehicle's mirrors, blinding the driver ahead; USE HIGH BEAMS: When no vehicles are within range; on dark rural roads; when you can safely see further ahead; AUTOMATIC HIGH BEAMS: Some modern vehicles have auto-dimming systems — these are helpful but not always reliable; manual control remains important; TUNNEL AND FOG: Use LOW beams in fog (high beams reflect off fog droplets, reducing visibility further) and in tunnels per posted requirements.