When is it illegal to use your high beam headlights?

Answer: B — When there is oncoming traffic

Using high beam headlights is illegal when there is oncoming traffic because high beams can cause glare and visibility issues for other drivers. The purpose of high beam headlights is to illuminate the road beyond the reach of regular headlights, but this increased brightness can temporarily blind oncoming drivers, increasing the risk of accidents. To ensure safety for all road users, it is required to switch to low beam headlights when you are within a certain distance of oncoming vehicles. In contrast, the other scenarios have specific considerations. Driving on dark roads may be a suitable time to use high beams if no other vehicles are present. In fog, high beams can reflect off the moisture in the air and actually reduce visibility, which is why low beams are recommended instead. During the day, the use of high beams can be inappropriate but is not necessarily illegal, given that daylight conditions typically provide adequate visibility.