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Headlights: Is It Before or after Sunset?

After sunset - Wikimedia Commons

Turn on Headlights When It Gets Dark.

You must turn on your headlights at night and when it is dark. Nighttime is a period that most of us define as the time after sunset and before sunrise.

In the vehicle code or state statutes you will most likely see it defined as 30 minutes after sunset and 30 minutes before sunrise.

Why is it 30 minutes after sunset and not before? Wouldn’t it be more logical to turn on your headlights before sunset? I mean, isn’t it dark as soon as the sun sets?

It may come as a surprise to you, but no, it isn’t. Not just yet.

Manhattan in twilight - Credit: Dschwen

The Sun is Below the Horizon – But it is Still Light Outside

The period immediately after sunset is known as civil twilight. During this period the sky is still bright enough, even if you cannot see the sun. Streetlights are still off and, normally, you can see the road without using headlights. This period is roughly half an hour after sunset and half an hour before sunrise.

Lawmakers use the civil twilight to define points in time when it is necessary for all drivers to use headlights. Civil twilight is also found in laws and rules related to aviation and hunting.

The real length of the twilight depends on your latitude and the time of the year. The higher the latitude, the more is the slope of the setting sun, and the longer it takes for the sun to reach a certain degree beneath the horizon. This calculator will tell you the length of the civil twilight right now.

Civil twilight occurs when the Sun is less than 6 degrees below the horizon. In the morning, civil twilight begins when the Sun is 6 degrees below the horizon and ends at sunrise. In the evening, it begins at sunset and ends when the Sun reaches 6 degrees below the horizon.

Twilight description - TWCarlson

When the sun is 12 degrees beneath the horizon, most of us will say that it is dark outside. At this point the sky is dark enough for some stars to be visible. This period is known as nautical twilight.

Note that civil twilight can last much longer than the half-hour, but the law still requires you to turn on headlights 30 minutes after sunset and keep them on until 30 minutes before sunrise.

Remember Before Sunrise and After Sunset

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Remember, headlights must be on 30 minutes BEFORE sunrise and 30 minutes AFTER sunset. This question may appear on your written DMV test. You must also know when to use low beam headlights and when to use high beams for your DMV test.

When driving, there is nothing wrong in turning on your headlights long before the sunset and keep them on long after sunrise. In the European Community and many other countries, the laws require you to have daytime running lights or keep your headlights on at all times.

If you don’t have them on all the time, turn them on whenever it is difficult to see others or when you think that others may have difficulties seeing you.


Photo Credits:
Manhattan in Twilight: Dschwen – wikimedia, Twilight Full Day: TWCarlson

About Mark
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3 Comments

  1. I believe the law should read turn your headlights on “one half hour BEFORE sunset and one half hour before sunrise” because if the sunrise or sunset is directly behind you the oncoming traffic can see you better if your lights are ON. Then again, I have my lights on all the time. The thing I hate are these new super bright LED (or whatever) lights that almost blind you when you approach them and they don’t dim them.

    • Yes, you should always turn on your headlights when there is a rising or setting sun behind you – even if it is not required by law. It is one of these things that makes you a really good and considerate driver!

  2. Okay that makes sense after 60 years of driving and thinking the answer was 1/2 hour before and after I stand corrected.
    I’m glad I’ve been taking your free tests, they’ve been very beneficial.

    Thanks Ron S.

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