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NHTSA says "NO" to DRLs

Big news: The National Highway Traffic Safety Administration has recently released a technical report finds DRLs are of practically no use, and further admits that DRLs have negative safety consequences. In NHTSA’s own words:

"The analysis found that DRLs have no statistically significant overall effect on the three target crashes. When combining these three target crashes into one target crash, the drl effects were also not statistically significant. When examined separately for passenger cars and light trucks / van (LTVs) , drls in LTVs significantly reduced LTVs involvement in the target two vehicle by 5.7 percent. However, the remaining drl effects on these three target crashes were not statistically significiant. Although not statistically significant, drls might have unintended consequences for pedestrains and motorcycles. Particularly, the estimated negitive effects for LTV’s were relatively large and cannont be completely ignored.

“Currently the NHTSA is in the rulemaking process in response to General Motors (GM) petition to mandate DRLs. This report will affect the rulemaking decision. Therefore the report is considered to contain ‘highly influential scientific information’.”

The document can be found at and entering 2008-0153-0004 in the Search field.

It does saves lives! Every car is equipped with DRL in Canada since the mid 80"s.

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what european car has rear red drl’s? is it audi? maybe volvo? quite annoying as they are definitely brighter than the running lights/brake lights. they are in separate housings so its not like a string of wide lights. funny, i saw a car this week with 1 of the lights burned out. bet that light module is pricey at the audi dealer

The study was very limited in its scope and was published in 2008.

How can that be fairly called “Big news”?


I will be interested to see how this develops, because the biggest danger I see is people who drive at night with the tail lights and front parking lights off because they don’t realize they only have the DRLs on. Having said that, I wonder if getting rid of DRLs would fix that situation or make it worse, because now some of those idiots might drive with no lights at all at night.

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Back in the late 1970’s the USAF tried going the DRL route. After a year or so they switched back to the regular headlight mode because their studies showed that it had little impact on safety but had a large impact on the cost of operating motor vehicles. Lights burned out constantly and battery life was cut in half. I don’t think safety is improved in the civilian world either. DRL’s are just about worthless in my mind.

To see an analysis of many DRL studies, including the 2008 one referred to in this discussion:

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I find fault with the matched pair analysis they employed. Sure, on the surface it seems like looking at accident rates for the new car with DRLs vs accident rates for the old car without would yield pertinent results.

But what other changes were made to the car when they put DRLs in it? Better handling? Better braking? Better visibility?

And how were the cars maintained? A brand new car which has had no maintenance is just a brand new car. A 4 year old car which has had no maintenance may be running on bald tires and shot front brake pads.

The old car is more likely to be dirty than the new car because you stop caring about keeping it bright and shiny after the newness wears off. Maybe it’s the highly reflective, clean, fresh paint on the new car that makes it more visible.

Additionally, where are the controls for type of accident? I see that they threw out single vehicle crashes, but did they also throw out rear-end collisions? If I’m at a stoplight with a car in front of me, and the guy behind me has DRLs, that’s not going to help much if he’s not paying attention and plows into me.

And then there’s the common sense aspect - if I’m driving along and fail to notice the 15 foot long shiny thing coming at me, adding a couple of dim little lights to it probably wont’ help much.

It reminds me of the fad where fire departments started painting their trucks that highlighter green-yellow color. Why? Because a study came out that showed there weren’t as many crashes involving yellow fire trucks as there were involving red ones. Then someone figured out - that’s because there aren’t as many yellow fire trucks, so naturally there are fewer crashes for that group.

There’s also the prevalence question. Sure, maybe during the changeover when hardly anyone had DRLs you’d notice a car with DRLs because you’re not used to seeing cars with their lights on in the middle of the day. Now that a large number of cars are DRL-equipped, it won’t register as prominently.

Bottom line for me is that I don’t know if DRLs enhance safety during the day. I suspect that even if they did when first introduced, the benefits will fall off as the number of cars equipped with them approaches 100%. If everyone’s got DRLs, no one’s going to notice DRLs.

I do suspect that they decrease safety at night, because oftentimes people who forget to turn their headlights on are reminded to do so as soon as they get to a dark section of road and discover they can’t see. But with DRLs, they can see, and so they keep driving with no side or tail illumination.

I have talked to a lot of people who don’t know that their headlights don;t come on automatically, they think that because their DRLs are on, everything is on.

In MY we have had a law for many years now that you have to have your headlights on in the rain. More than half the people think the DRLs satisfy the law, they don’t. Because the taillights don;t come on, these people become almost invisible from behind in a good rain esp. in a gray, tan or silver car.

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Good points, all. Where is the scientific study of DRL use that will properly answer these questions? I haven’t seen one yet.

---- shadowfax wrote:

I remember my parents Volvo Wagon (an XC70 maybe?) had a button for poor visibility conditions that lit up a separate section of the left tail light brighter than the rest of the tail light. It was supposed to aid rear visibility in foggy/rainy/snowy conditions. I don’t recall it being a separate housing…I think it was just a different bulb in that section of the tail light

Could part of the issue of whether there is any benefit to DRL be related to the fact that in winter it’s usually darker/grayer/rainier in Canada than in, say, Texas?

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All I know is that there have been times that I would have not noticed a vehicle had it not been for the DRL’s.


DRLs saving lives is going to be just about as hard to prove or disprove as loud pipes saving lives in my opinion.

What is interesting is that my Chevy Prizm 2001 has DRL - AND - a sensor that turns on the headlights when it gets too dark. This is on a car that isn’t noted for its high cost (originally).

My only issue with automating that system is: How long will it take you to notice if/when the sensor or another part of the automation system fails? The average Joe doesn’t do routine pre-trip inspections, so the odds are it will be on the road in traffic when the driver notices he or she is driving at night with no lights. Hopefully, a sensor failure would lead to the lights being on all the time as a fail-safe measure, like thermostats that are designed to open up when they fail.

Working in facilities maintenance, we constantly have to replace malfunctioning optical sensors on appliances like automatically-flushing toilets and building automation systems, so I’d rather not rely on an optical sensor for something this important.

One reason I dislike automatic headlights is that people get used to them, and then get into a car that doesn’t have them and forget that they need to turn the lights on themselves, and then drive around all night with no lights.

Another reason I dislike them is because they shorten the lives of headlight bulbs, especially if you have HID lights. They’ll flick on when you start the car in your garage because there isn’t enough light to convince the sensor it’s day. Then 10 seconds later when you pull out into the sunshine, they flick off again. Brief on-off cycles kill HID lights. I never use the auto-lights in my car, and I’ve got 10 years and 120k on the original lights. I know a bunch of people with the same car who do use them, and have already replaced them once or twice.

I believe it was in '74 that Kawasaki introduced a new motorcycle, a 400 cc twin. This bike had no headlight switch, if the ignition was on, so was the headlight and taillight. It actually made the bike less expensive to manufacture by eliminating the headlight switch, and a couple of years later, the government issued a ruling that mandated this in all new motorcycles. How many lives it actually save is hard to prove, but why can’t cars just have full time headlights instead of DRLs. Turn on the ignition and the lights come on, eliminates a headlight switch and actually simplifies instead of complicates cars.

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If I understand them, DRLs do not burn as brightly as headlights on; that provides longer life of the headlight bulbs.

People have such a hard time seeing motorcycles. When I road in the late 1970s, I wore a bright orange jacket with reflective strips and the lights were always on. Still, people missed seeing me. Even with a 400cc engine, I at least had the power to get out of the way of any car or truck that looked like trouble.

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