CDL General Knowledge Practice Test

In limited visibility conditions, such as fog or heavy rain, using low beams is the safest and most effective choice. Low beams produce a wider and shorter light pattern, which helps illuminate the road directly in front of the vehicle without causing glare in the thick moisture or precipitation. This is crucial in foggy conditions, as high beams can reflect off the fog droplets and create a blinding effect, making it even harder to see. Relying solely on daytime running lights is inadequate; they are designed primarily to increase a vehicle's visibility to others during the day and do not provide sufficient illumination in poor weather conditions. Parking lights are also insufficient, as they do not provide enough light for safe navigation. Therefore, using low beams is the best practice in conditions where visibility is compromised due to weather.