Official Advice About When to Use Headlights is Nonsense!

In many states in the USA and in certain countries around the world, dreadfully unsafe guidelines still exist which say that headlights need not be switched on until half an hour after sunset and can be turned off again half an hour before sunrise.  This so-called advice is — and always has been — dangerous garbage.

Photo of two pedestrians dangerously standing half way across a road in very low light.
Two darkly-clothed pedestrians dangerously standing in the middle of the road (in the center, left-turn-only lane) in dawn light. Technically — because it was after dawn on this very gloomy winter morning and it wasn’t raining, vehicle drivers were not obliged by law to be using headlights, so imagine these cold, wind-blown pedestrians trying to get to work and not noticing an approaching vehicle with no lights. Not using headlights in low light is insanity but many drivers do it, and even more stupidly, the law allows it (in this case, in New York State)! Copyright image

It is also at least partially to blame for the fact that many drivers wrongly believe that as long as they can see where they are going, in low-light conditions, that is all that matters, but again this is dangerous.  A crucial part of the purpose of headlights is to more easily let other road users see you approaching.

Photograph of the speedometer and other dashboard dials, lit up at night.
If you are accidentally driving on your Daytime Running Lights [DRLs] your dashboard instrument lights will *probably* not be lit (to give you a clue) but check your own vehicle to find out if that is the case for you. Copyright image.
And it’s not just dawn and dusk that matter, either.  Some very important research, from various countries, has shown that driving with low beam headlights on at all times, reduces your chances of being in collision with a vehicle or person who — because they didn’t see you coming — drives or walks out in front of you, by between 14% and 28% (depending on the exact research criteria).  Does it need to be said that reducing the risk of T-boning another vehicle, or perhaps of you killing a pedestrian or bicyclist, by such a significant percentage is a really good thing?

Photograph of a pick-up trucke waiting to turn out of a side road, and in which the driver might be dazzled by sunshine when he looks to see if it is safe to proceed.
When the waiting driver checks to his left, towards our approaching vehicle, he may well be dazzled by the low sun, behind us, so this is just one example of times when headlights help your conspicuity greatly, even in bright sunshine. Copyright image.

So when should you use your headlights?

In terms of safety, Sweden was a long way ahead of the rest of the world on this subject — something which will not surprise true road safety experts around the world, because Sweden has long been one of the two best performing countries worldwide (along with Britain).

Back in 1977, it was made law in Sweden that all drivers must use headlights all the time, 24 hours a day, no matter what the weather… Period! Relevantly, this safety function is known as varselljus (“perception light” or “notice light”).  [My thanks to Barry Kenward for this useful insight.]

Photograph of a car in the foreground with no lights on, compared to vehicles in the distance which do have headlights on.
The vehicles in the distance are more conspicuous then the nearer vehicle because they have their headlights on but it doesn’t. Remember, conspicuity is at least as important even at a significant distance because it can persuade an oncoming driver not to commence a risky passing maneuver. Copyright image.

Eventually — meaning in the last 20-or-so years — some other countries belatedly started to realize the safety benefits of keeping headlights on, even on bright sunny days.  However, as it is a fact that vehicles do consume extra fuel — even though it is only a tiny fraction more — whenever additional electrical demands are placed on the vehicles, such as air conditioning or headlights, some conservation-minded people protested that using headlights at all times would increase the production of greenhouse gases and add to the pollution problem.

Photograph of a moving car's headlight beam at night, from the side.
The beam from Daytime Running Lights [DRLs] is typically not as powerful as that from your low beam headlights — one of the two safety reasons never to drive in poor light with only the DRLs. Copyright image.
As a result, Daytime Running Lights [DRL] were invented, and these used a bit less power on the headlights, to help reduce emissions.  So far, so good.  But some countries and automakers then very stupidly made a bad decision, which was that DRLs did not need to operate the rear lights as well, just the headlights on lower-than-usual power, because omitting the rear lights would save even more electrical power and the resultant but tiny amount of additional emissions.  The ongoing result of this is that drivers in such vehicles are commonly seen, driving around at night with no back lights at all and with DRL front lights which are not as bright as proper, low-beam headlights, so there is extra risk up front and significant danger from behind, especially in poor weather conditions.

I would stress at this point that I have always been a keen naturalist and now an enthusiastic conservationist, and I am by no means averse to cutting harmful emissions.  However, given the direct and undeniable risk to people which occurs when vehicles are driven without adequate lights and are therefore not seen until too late, which issue has to take priority?

Tongue-in-cheek, you should note that no automakers have decided to devote less power to their in-vehicle air conditioning — something that certainly would save more power and therefore more emissions.  In other words, the hypocrisy from automakers is that they will reduce the safety of road users but they will not consider reducing the comfort of their customers, even though environmentally it would do more good.  Putting comfort (and, of course, profits) before safety!

Photo of a road sign requiring "headlights on at all times for safety.
Even though signs like this are typically only used on certain roads and in only a few of the states, this sign actually says it all: Headlights on at ALL times for safety! Copyright image.

So what IS the best advice, in terms of greatest safety?

Here’s a list:

  1. Do NOT rely on Daytime Running Lights [DRL].  We are all human and if something else is on your mind it is all too easy to forget that in low light or poor weather you have no back lights to protect the rear of your vehicle.  Many people undoubtedly have been killed or seriously hurt as a result;
  2. Do NOT rely on automatic headlamps that switch themselves on when a light sensor tells them to.  As with many automatic things, circumstances can sometimes create the wrong outcome and you wont have lights when they really are needed;
  3. IGNORE any rules or guidelines that mention sunrise and sunset.  Even the bright, low sunshine and contrasty shadows that occur before some sunsets and after some sunrises can create situations where vehicles are hard to see;
  4. The common rule about “Wipers On, Lights On” is also INADEQUATE — written, as is so often the case, by somebody with inadequate knowledge who merely thought it was a good idea.  The fact is that many weather conditions such as heavy cloud, mist or lightly falling snow can easily take the light down below the sensible threshold at which lights definitely should be used, even if wipers are not needed! (See the photographs.)
  5. NEVER drive with just the front sidelights (a.k.a. position or parking lights) illuminated, even where there is good street-  or road-lighting.  Sidelights are not adequate for your conspicuity.
  6. What do we do at Advanced Drivers of North America?  That’s easy to answer.  We use at least low-beam headlights, and therefore rear lights too, 24/7.  Does that increase our vehicle emissions?  Yes, undeniably, but by a miniscule amount.  And is the safeguarding of human lives more important?  We think the last question answers itself.

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Author: EddieWren

Eddie Wren is the CEO and Chief Instructor at Advanced Drivers of North America. His driver safety background is given at: http://www.advanceddrivers.com/ceochief-instructors-resumecvbio/

18 thoughts on “Official Advice About When to Use Headlights is Nonsense!”

  1. I drove a big rig for over 2,000,000 safe miles and we were told that headlights( and therefore all other lights!), should be on 24-7. No complaint from me! Did I burn out a few more bulbs? Oh well…

    1. Thanks for that, Raymond. I know that some fleets and trucking companies have “headlights 24/7” as a strict rule — I suppose Walmart’s trucks might be the best known because they have a sign to that effect on the back of every trailer (which is great to see)!

  2. Of course not 24/7, but vehicle lights need to be on at all times the vehicle is driving (and then some).

    Now to get folks to dim their headlights when approaching other vehicles…

    1. My apologies if you thought I meant anything other than when vehicles are being driven. That was not the intended message. 24/7 ***if being driven!***

  3. I agree with the comments that the common legal requirement for headlights in the U.S. of 30 minutes after sunset/30 minutes before sunrise is not as safe as headlights required from sunset to sunrise. However, I have noticed that most “automatic” headlights on most cars and light trucks that I see operating in Georgia, and I assume they are representative of the entire country, come on when ambient illuminance is in the vicinity of 200 footcandles–a ridiculously high level of ambient illuminance for even low-beam headlights in cars with DRLs, in my opinion. I recently measured ambient illuminance on a state highway in Rockdale County, Georgia, at sunset on a day with a clear sky, and it was 35 foot-candles. There was plenty of light to see other motorists, with or without their headlamps being illuminated. Thirty minutes after sunset, the ambient illuminance was one foot-candle, and I’m not sure I would have been able to observe an oncoming vehicle with no exterior lighting. My primary purpose in writing this was to complain about the very high threshold of illumnance at which automatic low-beam headlights are energized–approximately 200 foot-candles. One can even read the fine print on a legal document with that much light! In my opinion, if a person can’t see DRLs in broad daylight, he shouldn’t be driving, period. Just my US$0.02 from north Georgia, USA.

    1. Ralph, thank you for your comments. Given the research I mentioned in the main article, showing that 14-28 percent of a particularly dangerous type of crash can be avoided by the simple expedient of keeping low-beam headlights turned on at all times that a vehicle is being driven, 24/7 and no matter how sunny and bright the weather, I cannot see why anyone would want those lights not to be on or would think — as you put it — that any conditions represent a “ridiculously high level of ambient illuminance for even low-beam headlights”. My counter-question would be: Why would anyone NOT want low-beam headlights to be on? After all, it certainly isn’t costing us anything as drivers, and I for one would certainly argue that my loved ones’ lives are worth far more than the miniscule amount of additional pollution that has previously been mentioned.

  4. With the availability of LED lights the electrical draw should not be an issue. Life safety should trump other concerns.

  5. I’m not sure if made you point or not Eddie. Maybe now more drivers may be able to “see the light”.
    It is pretty simple, if the driver is not going to drive with them on 24/7 and the jurisdiction is thinking the usual 20-30 years behind, just teach or mandate if the “orange ball is not visible” full headlights must be turned on. The KISS method.

    1. Bud, it’s good to hear from you; thanks for your reply. I would suggest that drivers in the USA cannot be expected to yet understand the need for low-beam headlights at all times when driving because the accuracy and (lack of) depth of the information they have so far received via state drivers manuals is utterly appalling. The case for using headlights at all times — per the research I mentioned in the article — is frankly unarguable. A 14-28 percent reduction in a particularly dangerous type of collision cannot be ignored. As implied, Sweden is half-a-century ahead of American thinking on this topic and I would respectfully suggest to anyone that the vast difference between Sweden’s world-leading annual road casualty rates and the said regrettable rates here in the USA is far more than enough to make a serious point about listening to and learning from the leading nations. If we are to use the KISS principle on this issue, the safest solution also represents the simplest message: “Low-beam headlights on at all times the vehicle is being driven,” no matter what the time of day and no matter how nice & sunny the weather may be. Bearing in mind that this is why Daytime Running Lights were invented, then if ever the stupid design fault is rectified so that the rear lights will also be on at all times, not just the front lights, then clearly that would be acceptable, too. (Incidentally, I have plenty photographs showing that even in bright sunlight there are times when approaching vehicles can be hard to see. Conspicuity is everything.)

  6. Dear Eddie, thanks for the tips using Low beam or DRL, we here in Holland train International Executive Chauffeurs, we hate automatic headlamps, every time lichts goes on and off.
    Drivers rely to much to this systems.
    We are making a masterclass Risk Awareness, if you are interested you can contact me.
    Regards, Hans-Peter Woznitza Trainer VIP Drivers

    1. Thank you for your comments, Hans-Peter. I hope you find plenty of interest among our existing ~150 blog posts and the many more that will be published/posted at every opportunity.

  7. I’m from a country in East Africa where the variations in weather and natural lighting conditions are fairly routine.
    During the month of December 2017, we observed an unusually high number of RTAs. These were concentrated in some high altitude areas where fog is not unusual. The discussion on using vehicle head lamps at all times could be introduced here as nobody has raised the issue of visibility/conspicuity in the discussions.

  8. Just an update on DRL’s.
    Here in the UK Vauxhall cars now have rear DRL’s, though these are only on the newer models, including the new Astra.

    1. Thanks, Roy. Car makers have had a couple of decades to recognise and rectify this stupid situation. It beggars belief that it has taken this long. I wonder how many people around the developed world (DRLs probably aren’t fitted in poorer countries) have been killed or seriously injured as a result of this!

      1. Fully agree Eddie and as your previous posts it is all too common to follow a car with no rear lights at all, due to DRL’S being used. I also think that as modern cars have illuminated instrument panels then the driver may not be aware that they are driving without lights – this was a dead giveaway in the “good old days” when you could not read the speedometer etc. if you had not switched on your lights.

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