Ask a Trooper

Posted: Monday, December 10, 2001

Question: What is the law regarding headlights on automobiles used on state roads? How powerful can they be and how many can be used? Express the power in watts rather than candlepower or provide a conversion. What are the rules on mounting?

Answer: There are many strange interpretations of headlight requirements out there. The federal codes define manufacturing specifications and national Department of Transportation standards. There is not enough space in this paper to get into those. I'll try to summarize the state codes. Alaska Administrative Code 13.04.020 states "a motor vehicle must be equipped with at least two headlights, one on each side of the front ... must emit white light to the front ... and must be mounted at a height of not more than 54 inches from the ground, or less than 24 inches. Extra lights such as spotlights and "moose lights" can be used, but not when other traffic is approaching.

But wait, there's more!

Candlepower defines brightness, watts is the power draw. The state codes don't define wattage, but the federal standard is a 55-watt maximum for highway use. State codes list a 300-candlepower limit on headlights and is within the specs of original equipment and standard headlight replacements. Under the "Restrictions on Lighting Equipment section (13 AAC 04.145)" it explains "no more than a total of four lights on the front of a vehicle may be illuminated at any time when there is approaching traffic." You must also dim your brights when approaching another vehicle head on within 500 feet, and within 300 feet from behind.

Equally important is the aim of your headlights, low and high beams. When you pack that cord of firewood in the trunk of your 1972 Dodge Dart, you might as well have your bright beams on. If other drivers are flashing their high beams at you, there must be a problem.

All this can be made simple. Use not more than four standard factory white headlights, mounted and aimed correctly, and dim those brights.

For more details on vehicle lighting requirements visit

If you have questions that you would like to ask a trooper, please send them to: Alaska State Troopers, 4060 Heath St., Homer, AK 99603. Or you can e-mail them to The Alaska State Troopers remind you to always wear your seat belt. It's the law.

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