CDL General Knowledge TestDriving SafelyMedium
You are driving a commercial vehicle at night on an unlit road. When should you dim your headlights from high beam to low beam?
- AOnly when the oncoming driver flashes their high beams at you.
- BWhen an oncoming vehicle is within 500 feet, or when following another vehicle within 200 feet.
- CWhen an oncoming vehicle is within 100 feet.
- DWhen an oncoming vehicle is within 200 feet, or when following another vehicle within 50 feet.
Show answer & explanationAnswer & explanation
Correct answer: B. When an oncoming vehicle is within 500 feet, or when following another vehicle within 200 feet.
Federal regulations and most state laws require dimming headlights from high to low beams when an oncoming vehicle is within 500 feet, or when following another vehicle within 200 feet. This prevents blinding other drivers and ensures safety.
Why the other options are wrong
- A. Waiting for another driver to flash their lights is reactive and means you've already caused a hazard.
- C. 100 feet is too close; you would have already blinded the other driver.
- D. While better than 'A', these distances (200/50) are still shorter than the legally required and safer distances.
Headlight Dimming Rules (Night Driving)
To prevent blinding other drivers, commercial vehicle operators must dim their high beam headlights to low beams when an oncoming vehicle is within 500 feet or when following another vehicle within 200 feet.
- 500 feet for oncoming traffic.
- 200 feet for following traffic.
- Failure to dim can result in citations and cause accidents.
- Allows other drivers to maintain their night vision.
Memory trick: Five hundred oncoming, two hundred following, keep those beams low and flowing!